Lowering Miners' Exposure to Respirable Crystalline Silica and Improving Respiratory Protection, 44852-45019 [2023-14199]
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Federal Register / Vol. 88, No. 133 / Thursday, July 13, 2023 / Proposed Rules
DEPARTMENT OF LABOR
Mine Safety and Health Administration
30 CFR Parts 56, 57, 60, 70, 71, 72, 75,
and 90
[Docket No. MSHA–2023–0001]
RIN 1219–AB36
Lowering Miners’ Exposure to
Respirable Crystalline Silica and
Improving Respiratory Protection
Mine Safety and Health
Administration (MSHA), Department of
Labor.
ACTION: Proposed rule; request for
comments; notice of public hearings.
AGENCY:
The Mine Safety and Health
Administration (MSHA) proposes to
amend its existing standards to better
protect miners against occupational
exposure to respirable crystalline silica,
a carcinogenic hazard, and to improve
respiratory protection for all airborne
hazards. MSHA has preliminarily
determined that under the Agency’s
existing standards, miners at metal and
nonmetal mines and coal mines face a
risk of material impairment of health or
functional capacity from exposure to
respirable crystalline silica. MSHA
proposes to set the permissible exposure
limit of respirable crystalline silica at 50
micrograms per cubic meter of air (mg/
m3) for a full shift exposure, calculated
as an 8-hour time-weighted average, for
all miners. MSHA’s proposal would also
include other requirements to protect
miner health, such as exposure
sampling, corrective actions to be taken
when miner exposure exceeds the
permissible exposure limit, and medical
surveillance for metal and nonmetal
miners. Furthermore, the proposal
would replace existing requirements for
respiratory protection and incorporate
by reference ASTM F3387–19 Standard
Practice for Respiratory Protection. The
proposed uniform approach to
respirable crystalline silica occupational
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SUMMARY:
exposure and improved respiratory
protection for all airborne hazards
would significantly improve health
protections for all miners and lower the
risk of material impairment of health or
functional capacity.
DATES: Written comments. Written
comments, including comments on the
information collection requirements
described in this preamble, must be
received or postmarked by midnight
Eastern Time on August 28, 2023.
Public Hearings. MSHA will hold two
public hearings on August 3, 2023 in
Arlington, Virginia and August 21, 2023
in Denver, Colorado. For more
information on the public hearings, see
SUPPLEMENTARY INFORMATION.
ADDRESSES: All submissions must
include RIN 1219–AB36 or Docket No.
MSHA–2023–0001. You should not
include personal or proprietary
information that you do not wish to
disclose publicly. If you mark parts of
a comment as ‘‘business confidential’’
information, MSHA will not post those
parts of the comment. Otherwise, MSHA
will post all comments without change,
including any personal information
provided. MSHA cautions against
submitting personal information.
You may submit comments and
informational materials, clearly
identified by RIN 1219–AB36 or Docket
Id. No. MSHA–2023–0001, by any of the
following methods:
Federal E-Rulemaking Portal: https://
www.regulations.gov. Follow the online
instructions for submitting comments.
Email: zzMSHA-comments@dol.gov.
Include ‘‘RIN 1219–AB36’’ in the
subject line of the message.
Regular Mail: MSHA, Office of
Standards, Regulations, and Variances,
201 12th Street South, Suite 4E401,
Arlington, Virginia 22202–5450.
Hand Delivery or Courier: MSHA,
Office of Standards, Regulations, and
Variances, 201 12th Street South, Suite
4E401, Arlington, Virginia, between
9:00 a.m. and 5:00 p.m. Monday through
Friday, except Federal holidays. Before
visiting MSHA in person, call 202–693–
9440 to make an appointment. Special
health precautions may be required.
Facsimile: 202–693–9441. Include
‘‘RIN 1219–AB36’’ in the subject line of
the message.
Information Collection Requirements.
Comments concerning the information
collection requirements of this proposed
rule must be clearly identified with
‘‘RIN 1219–AB36’’ or ‘‘Docket No.
MSHA–2023–0001,’’ and sent to MSHA
by one of the methods previously
explained.
Docket. For access to the docket to
read comments and background
documents, go to https://
www.regulations.gov. The docket can
also be reviewed in person at MSHA,
Office of Standards, Regulations, and
Variances, 201 12th Street South,
Arlington, Virginia, between 9 a.m. and
5 p.m. Monday through Friday, except
Federal holidays. Before visiting MSHA
in person, call 202–693–9440 to make
an appointment. Special health
precautions may be required.
Email Notification. To subscribe to
receive an email notification when
MSHA publishes rulemaking documents
in the Federal Register, go to https://
public.govdelivery.com/accounts/
USDOL/subscriber/new.
S.
Aromie Noe, Director, Office of
Standards, Regulations, and Variances,
MSHA, at: silicaquestions@dol.gov
(email); 202–693–9440 (voice); or 202–
693–9441 (facsimile). These are not tollfree numbers.
FOR FURTHER INFORMATION CONTACT:
SUPPLEMENTARY INFORMATION:
MSHA will hold two public hearings
to provide industry, labor, and other
interested parties with an opportunity to
present oral statements, written
comments, and other information on the
proposed rule. The public hearings will
begin at 9 a.m. local time and end after
the last presenter speaks on the
following dates:
Date
Location
Contact
number
August 3, 2023 ...
August 21, 2023
Mine Safety and Health Administration, 201 12th Street South, Room 7W202, Arlington, VA 22202 .............
Denver Federal Center, Building 25 Lecture Hall, West 6th Avenue and Kipling Street, Denver, CO 80225 ..
202–693–9440
202–693–9440
The public hearings will begin with
an opening statement from MSHA,
followed by an opportunity for members
of the public to make oral presentations.
Speakers and other attendees may
present information to MSHA for
inclusion in the rulemaking record. The
hearings will be conducted in an
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informal manner. Formal rules of
evidence or cross examination will not
apply.
A verbatim transcript of each of the
proceedings will be prepared and made
a part of the rulemaking record. Copies
of the transcripts will be available to the
public. MSHA will make the transcript
of the hearings available at https://
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www.regulations.gov and on MSHA’s
website at https://arlweb.msha.gov/
currentcomments.asp.
MSHA will accept post-hearing
written comments and other appropriate
information for the record from any
interested party, including those not
presenting oral statements, received by
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midnight (Eastern Time) on August 28,
2023.
Pre-registration is not required to
attend the hearings. Interested parties
may attend the hearings virtually or in
person. Interested parties who intend to
present testimony at the hearings are
asked to register in advance on MSHA’s
website (https://www.msha.gov).
Speakers will be called in the order in
which they signed up. Those who do
not register in advance will have an
opportunity to speak after all those who
pre-registered have spoken. You may
submit hearing testimony and
documentary evidence, identified by
docket number (MSHA–2023–0001), by
any of the methods previously
identified. Additional information on
how to access the public hearings will
be posted when available at https://
www.msha.gov/regulations/rulemaking.
The preamble to the proposed
standard follows this outline:
I. Introduction
II. Request for Comments
III. Background
IV. Existing Standards and Implementation
V. Health Effects Summary
VI. Preliminary Risk Analysis Summary
VII. Section-by-Section Analysis
VIII. Technological Feasibility
IX. Summary of Preliminary Regulatory
Impact Analysis and Regulatory
Alternatives
X. Initial Regulatory Flexibility Analysis
XI. Paperwork Reduction Act
XII. Other Regulatory Considerations
XIII. References Cited in the Preamble
XIV. Appendix
Acronyms and Abbreviations
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COPD chronic obstructive pulmonary
disease
ESRD end-stage renal disease
FEV forced expiratory volume
FVC forced vital capacity
L/min liter per minute
mg milligram
mg/m3 milligrams per cubic meter
mL milliliter
mg/m3 micrograms per cubic meter
MNM metal and nonmetal
NMRD nonmalignant respiratory disease
PEL permissible exposure limit
PMF progressive massive fibrosis
RCMD respirable coal mine dust
REL recommended exposure limit
SiO2 silica
TB tuberculosis
TLV® Threshold Limit Value
TWA time-weighted average
I. Introduction
With the passage of the Federal Mine
Safety and Health Act of 1977 (Mine
Act), Congress declared that ‘‘the first
priority and concern of all in the coal
or other mining industry must be the
health and safety of its most precious
resource—the miner[.]’’ 30 U.S.C.
801(a). In furtherance of that clear
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guiding principle, this proposed rule
promotes MSHA’s mission and statutory
mandate to prevent death, illness, and
injury from mining and promote safe
and healthful workplaces for U.S.
miners. This proposal provides the
public with the opportunity to comment
on the Agency’s proposed uniform and
streamlined regulatory approach to
lowering miners’ exposure to respirable
crystalline silica and improving
respiratory protection.
Exposure to silica dust causes adverse
health effects, including silicosis (acute
silicosis, accelerated silicosis, simple
chronic silicosis, and progressive
massive fibrosis (PMF)), nonmalignant
respiratory diseases (NMRD) (e.g.,
emphysema and chronic bronchitis),
lung cancer, and renal diseases. Each of
these effects is chronic, irreversible, and
potentially disabling or fatal. Silica dust
is generated in most mining activities,
including cutting, sanding, drilling,
crushing, grinding, sawing, scraping,
jackhammering, excavating, and hauling
materials that contain silica, and is
found in all mines—underground and
surface metal and nonmetal (MNM) and
coal mines. In a mining context, silica
exposures may occur in respirable dust
together with exposures to other
airborne contaminants and combustion
biproducts.
MSHA’s existing standards,
established in the early 1970s, help
protect miners from the most dangerous
levels of exposure to respirable
crystalline silica. However, since their
promulgation, scientific understanding
of respirable crystalline silica toxicity
has advanced, and the National Institute
for Occupational Safety and Health
(NIOSH) has recommended a respirable
crystalline silica exposure level of 50
mg/m3 for workers. In 2016, the
Occupational Safety and Health
Administration (OSHA) established a
permissible exposure limit (PEL) of 50
mg/m3 in many industry sectors that it
regulates.
To provide miners with exposure
limits consistent with workers in other
industries and NIOSH’s
recommendation, and to improve
miners’ health, MSHA proposes to
lower its existing exposure limits to 50
mg/m3 for respirable crystalline silica in
MNM and coal mines. MSHA
considered exposure limits below 50 mg/
m3. However, MSHA believes, based on
a review of the Agency’s available silica
sample data, that an exposure limit of
25 mg/m3 may not be achievable for all
mines. The proposed PEL would be
expressed as a full-shift exposure,
calculated as an 8-hour time-weighted
average (TWA). Importantly, a uniform
proposed PEL for all mines would make
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compliance simpler—especially for coal
mines by eliminating the existing
respirable dust standard when quartz is
present.
To meet the requirements of the
proposed PEL, mine operators would
have to implement engineering controls,
followed by administrative controls if
supplementary protection is needed.
Engineering controls, which are most
effective, are designed to remove or
reduce the hazard at the source and
could include the installation of proper
ventilation systems, use of water sprays
or wetting agents to suppress airborne
contaminants, installation of machinemounted dust collectors to capture
respirable crystalline silica and other
contaminants, and the installation of
control booths or environmental cabs to
enclose equipment operators.
Administrative controls, which are often
less effective than engineering controls,
are designed to change the way miners
work. One example would be ensuring
that miners safely clean dust off their
work clothes so that they are not
exposed to respirable dust after their
shift ends.
MSHA’s proposed rule would further
protect all miners by requiring exposure
sampling and corrective actions when
miners’ exposures exceed the proposed
PEL, as well as periodic sampling when
miners’ exposure levels meet or exceed
the proposed action level. The proposed
rule also includes medical surveillance
requirements for MNM miners (medical
surveillance requirements already exist
for coal miners). Proposed medical
examinations would include chest Xrays, spirometry, symptom assessment,
and occupational history and would be
provided at no cost to the miner.
Finally, the proposed rule would
incorporate by reference an updated
respiratory protection standard, ASTM
F3387–19, ‘‘Standard Practice for
Respiratory Protection’’ (ASTM F3387–
19), for respirable crystalline silica and
all other regulated airborne
contaminants. This voluntary consensus
standard represents up-to-date
advancements in respiratory protection
technologies, practices, and techniques,
including proper selection, use, and
maintenance of respirators. The
proposed incorporation of ASTM
F3387–19 by reference would better
protect all miners from airborne
hazards. However, respiratory
protection should only be relied upon as
an exposure control measure in limited
situations and on a temporary basis, and
to supplement engineering controls,
followed by administrative controls.
Taken together, all elements of the
proposed rule are technologically and
economically feasible. MSHA’s 2014
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final rule, Lowering Miners’ Exposure to
Respirable Coal Mine Dust, Including
Continuous Personal Dust Monitors
(Coal Dust Rule) improved health
protections for coal miners by lowering
exposure limits to respirable coal mine
dust and establishing sampling
requirements that included the use of a
Continuous Personal Dust Monitor (79
FR 24813, May 1, 2014). Coal mine
operators have generally achieved
compliance with the respirable dust
standards primarily by implementing or
adjusting existing engineering controls.
Coal mine operators’ sampling data and
MSHA’s compliance data show that
operators have lowered coal miners’
exposures to respirable coal mine dust
and to respirable crystalline silica. Data
show that average exposures in coal
mines are below the proposed PEL of 50
mg/m3, and therefore, corrective
measures would often not be needed.
Similarly, for MNM miners, MSHA data
also show that most exposures to
respirable crystalline silica are below
the proposed PEL. However, at MNM
and coal mines where elevated
exposures are found, operators will be
able to reduce exposures to the
proposed PEL through some
combination of properly maintaining
existing engineering controls,
implementing new engineering controls,
and requiring safe work practices. Mines
and laboratories will be able to meet
exposure monitoring requirements with
existing validated and widely used
sampling and analytical methods. The
proposed revision to the respiratory
protection standard is technologically
feasible because MSHA’s existing
respiratory protection requirements for
selecting, fitting, using, and maintaining
respiratory protection include similar
requirements.
MSHA’s Preliminary Risk Analysis
(PRA) suggests that exposure consistent
with a lower proposed PEL of 50 mg/m3
would deliver many health benefits to
miners who currently experience
exposures above the proposed PEL by
reducing the likelihood of respirable
crystalline silica-related diseases. For
those miners working only under the
proposed PEL, MSHA estimates that the
proposed rule would result in a total of
799 lifetime avoided deaths (63 in coal
and 736 in MNM mines) and 2,809
lifetime avoided morbidity cases (244 in
coal and 2,566 in MNM mines) over a
60-year period. MSHA expects full
implementation and compliance to
reduce lifetime mortality risk due
specifically to silica exposures by 9.5
percent and to reduce silicosis
morbidity risk by 41.9 percent. The
latter statistic is particularly important
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to coal miners given surveillance
findings noted by the National
Academies of Sciences, Engineering,
and Medicine that severe
pneumoconiosis where respirable
crystalline silica is likely an important
contributor is presenting in relatively
young miners, sometimes in their late
30’s and early 40’s.
MSHA’s economic analysis estimates
that the proposed respirable crystalline
silica rule would cost an average of
$56.1 million per year in 2021 dollars at
an undiscounted rate, $57.6 million at a
3 percent discount rate, and $59.9
million at a 7 percent discount rate.
Based on the results of the Preliminary
Regulatory Impact Analysis (PRIA),
MSHA estimates that the proposed
rule’s benefits would exceed its costs,
with or without discount rates.
Monetized benefits are estimated from
avoidance of 410 deaths related to
NMRD, silicosis, ESRD, and lung cancer
and 1,420 cases of silicosis associated
with silica exposure over the first 60year period after the promulgation of the
final rule. The estimated annualized net
benefit is approximately $212.8 million
at an undiscounted rate, $118.2 million
at a 3 percent discount rate, and $36.3
million at a 7 percent discount rate.
A rule is significant under Executive
Order 12866 Section 3(f)(1), as amended
by E.O. 14094, if it is likely to result in
‘‘an annual effect on the economy of
$200 million or more or . . . adversely
affect in a material way the economy, a
sector of the economy, productivity,
competition, jobs, the environment,
public health or safely, or State, local,
or tribal governments or communities.’’
The Office of Management and Budget
has determined that the proposed rule is
significant within the meaning of E.O.
12866 Section 3(f)(1).
The proposed rule would strengthen
MSHA’s existing regulatory framework.
It would establish a uniform proposed
PEL that provides all MNM and coal
miners with the same exposure limits
for respirable crystalline silica
consistent with exposure limits that
other U.S. workers currently receive in
non-mining industries. It would update
the existing respiratory protection
standard to require mine operators to
provide miners with NIOSH-approved
respiratory equipment that has been
fitted, selected, maintained, and used in
accordance with recent consensus
standards. The proposed rule would
also include requirements for all MNM
operators to provide medical
surveillance in the form of a medical
examination regime similar to what coal
miners already receive. Cumulatively,
the proposed provisions would lower
miners’ risk of developing chronic,
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irreversible, disabling, and potentially
fatal health conditions, consistent with
MSHA’s mission and statutory mandate
to prevent occupational diseases and
protect U.S. miners from suffering
material health impairments.
II. Request for Comments
MSHA requests comments on the
proposed rule and all relevant issues,
including the review and conclusions of
the health effects discussion,
preliminary risk analysis, feasibility
analysis, preliminary regulatory impact
analysis and regulatory alternatives, and
preliminary regulatory flexibility
analysis. While MSHA invites
comments on any aspect of its proposed
rule and related documents, the Agency
particularly seeks information and data
in response to questions posed in this
section and any other aspect of this
proposed rule. Instructions for
submitting and viewing comments are
provided under the DATES heading.
MSHA will consider all timely
comments and may change the
proposed rule based on such comments.
MSHA requests that commenters
organize their comments, to the extent
possible, around the following
numbered questions. The Agency is
interested in receiving responses to the
listed questions and any information or
data supporting the responses.
Health Effects
1. In the standalone, background
document entitled ‘‘Health Effects of
Respirable Crystalline Silica’’ and as
summarized in Section V. Health Effects
Summary of this preamble, MSHA has
made a preliminary determination that
miners’ exposure to respirable
crystalline silica presents a risk of
material health impairment due to the
risk of developing silicosis, NMRD, lung
cancer, and renal disease, based on its
extensive review of the health effects
literature. MSHA requests comments on
this preliminary determination and its
literature review, which draws heavily
from the review conducted by OSHA for
its 2016 rulemaking. Are there
additional adverse health effects that
should be included or more recent
literature that offers a different
perspective? MSHA requests that
commenters submit information, data,
or additional studies or their citations.
Please be specific regarding the basis for
any recommendation to include
additional adverse health effects.
Preliminary Risk Analysis
2. In the standalone, background
document entitled ‘‘Preliminary Risk
Analysis’’ and as summarized in Section
VI. Preliminary Risk Analysis Summary
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of this preamble, MSHA relied on risk
models that OSHA used in support of its
2016 respirable crystalline silica final
rule. Does the context of the MSHA rule
suggest that the model would benefit
from changes? If so, please describe both
the justification for those changes and
the likely impact on the final risk
estimates. Are there additional studies
or sources of data that MSHA should
consider? What is the rationale for
recommending the use of these
additional studies or data?
3. MSHA’s risk analysis of lung
cancer mortality uses the exposureresponse model from Miller and
MacCalman (2010) instead of Steenland
et al. (2001a), on which OSHA’s risk
assessment of lung cancer mortality was
based. MSHA uses Miller and
MacCalman (2010) for several reasons.
First, it covers coal mining-specific
cohort large enough (with 45,000
miners) to provide adequate statistical
power to detect low levels of risk, and
it covers an extended follow-up period
(1959–2006). Second, the study
provided data on cumulative exposure
of cohort members and adjusted for or
addressed confounders such as smoking
and exposure to other carcinogens.
Finally, it developed quantitative
assessments of exposure-response
relationships using appropriate
statistical models or otherwise provided
sufficient information that permitted
MSHA to do so. The Agency is
requesting comment on MSHA’s
reliance on the Miller and MacCalman
(2010) study in assessing lung cancer
mortality. Please provide any other
studies or information that MSHA
should take into account in determining
the risk of lung cancer mortality among
miners.
Technological Feasibility of the
Proposed Rule
4. As discussed in Section VIII.
Technological Feasibility of this
preamble, MSHA has preliminarily
determined that it is technologically
feasible for mine operators to conduct
air sampling and analysis and to achieve
the proposed PEL using commercially
available samplers. MSHA has also
determined that these technologically
feasible samplers are widely available,
and a number of commercial
laboratories provide the service of
analyzing dust containing respirable
crystalline silica. In addition, MSHA
has determined that technologically
feasible engineering controls are readily
available, can control crystalline silicacontaining dust particles at the source,
provide reliable and consistent
protection to all miners who would
otherwise be exposed to respirable dust,
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and can be monitored. MSHA has also
determined that administrative controls,
used to supplement engineering
controls, can further reduce and
maintain exposures at or below the
proposed PEL. Moreover, MSHA has
preliminarily determined the proposed
respiratory protection practices for
respirator use are technologically
feasible for mine operators to
implement. MSHA requests comments
on these preliminary conclusions. What
methods have you used that proved
effective in reducing miners’ exposure
to respirable crystalline silica in mining
operations? Please explain how those
methods were effective in reducing
miners’ exposures. To what extent do
existing controls that reduce exposure to
other airborne hazards (e.g., coal dust,
diesel particulate matter) already reduce
exposures to respirable crystalline silica
below the proposed PEL? To what
extent does the proposed rule including
the PEL facilitate MSHA’s workplace
health and safety goals? Please provide
supporting information, such as
quantitative data if available.
5. MSHA has determined that the
proposed medical surveillance
requirements for MNM are
technologically feasible. MSHA requests
comments on this preliminary
conclusion. Please provide supporting
information, such as quantitative data if
available.
on these and other regulatory
alternatives and information on any
other alternatives that the Agency
should consider, including different
average working-life spans and different
average shift lengths. Please provide
supporting information about how these
alternatives could affect miners’
protection from respirable crystalline
silica exposure and affect mine
operators’ costs.
Preliminary Regulatory Impact Analysis
and Regulatory Alternatives
6. In the standalone background
document entitled ‘‘Preliminary
Regulatory Impact Analysis’’ and as
summarized in Section IX. Summary of
Preliminary Regulatory Impact Analysis
and Regulatory Alternatives of this
preamble, MSHA developed estimated
costs of compliance with the proposed
rule and estimated monetized benefits
associated with averted cases of
respirable crystalline silica-related
diseases. MSHA requests comments on
the methodologies, baseline,
assumptions, and estimates presented in
the Preliminary Regulatory Impact
Analysis. Please provide any data or
quantitative information that may be
useful in evaluating the estimated costs
and benefits associated with the
proposed rule.
7. MSHA considered two regulatory
alternatives in developing the proposed
rule discussed in Section IX. Summary
of Preliminary Regulatory Impact
Analysis and Regulatory Alternatives. In
the regulatory alternatives presented,
MSHA discussed alternatives to the
proposed PEL, action level, sampling
requirements, and semi-annual
evaluations. MSHA requests comments
Scope and Effective Date
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Initial Regulatory Flexibility Analysis
8. As summarized in Section X. Initial
Regulatory Flexibility Analysis of this
preamble, MSHA examined the impact
of the proposed rule on small mines in
accordance with the Regulatory
Flexibility Act. MSHA estimated that
small-entity controllers would be
expected to incur, on average,
additional regulatory costs equaling
approximately 0.122 percent of their
revenues (or $1,220 for every $1 million
in revenues). MSHA is interested in
how the proposed rule would affect
small mines, including their ability to
comply with the proposed
requirements. Please provide
information and data that supports your
response. If you operate a small mine,
please provide any projected impacts of
the proposal on your mine, including
the specific rationale supporting your
projections.
9. MSHA is proposing a unified
regulatory and enforcement framework
for controlling miners’ exposures to
respirable crystalline silica for the
mining industry. MSHA requests
comments on this unified regulatory
and enforcement framework. MSHA
requests the views and
recommendations of stakeholders
regarding the scope of proposed part 60,
which would include all surface and
underground MNM and coal mines.
MSHA requests comments on whether
separate standards should be developed
for the MNM mining industry and the
coal mining industry. Please provide
supporting information.
10. MSHA is proposing that the final
rule would be effective 120 days after its
publication in the Federal Register.
This period is intended to provide mine
operators time to evaluate existing
engineering and administrative controls,
update their respiratory protection
programs, and prepare to comply with
other provisions of the rule including
recordkeeping requirements. Please
provide your views on the proposed
effective date. In your response, please
include the rationale for your position.
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Definitions
11. MSHA requests comments on the
proposed action level. Stakeholders
should provide specific information and
data in support of or against a proposed
action level. Stakeholders should
include a discussion of how the use of
a proposed action level would impact
their mines, including the cost of
monitoring respirable crystalline silica
above the proposed action level, and
other relevant information. Please
provide supporting information.
12. MSHA requests comments on the
proposed definition for ‘‘objective data.’’
Is it appropriate to allow mine operators
to use objective data instead of a second
baseline sample? Please provide
supporting information.
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Proposed Permissible Exposure Limit
13. MSHA is proposing a PEL for
respirable crystalline silica of 50 mg/m3
for a full-shift exposure, calculated as an
8-hour TWA for MNM and coal miners.
MSHA has made a preliminary
determination that the proposed PEL
would reduce miners’ risk of suffering
material impairment of health or
functional capacity over their working
lives. MSHA seeks the views and
recommendations of stakeholders on the
proposed PEL. MSHA solicits comments
on the approach of having a standalone
PEL and whether to eliminate the
reduced standard for total respirable
dust when quartz is present at coal
mines. Please provide evidence to
support your response.
14. MSHA is proposing a PEL of 50
ug/m3 and an action level of 25 mg/m3
for respirable crystalline silica exposure.
Which proposed requirements should
be triggered by exposure at, above, or
below the proposed action level? Please
provide supporting information.
Methods of Compliance
15. MSHA requests comments on the
proposed prohibition against rotation of
miners as an administrative control.
Please include a discussion of the
potential effectiveness of this nonexposure approach and its impact on
miners at specific mines. Please provide
supporting information.
16. MSHA requests comments on the
proposed requirement that mine
operators must install, use, and
maintain feasible engineering and
administrative controls to keep miners’
exposures to respirable crystalline silica
below the proposed PEL. Please provide
supporting information.
Proposed Exposure Monitoring
17. MSHA requests comments and
information from stakeholders
concerning the proposed approaches to
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monitoring exposures, and other
approaches to accurately monitor miner
exposure to respirable crystalline silica
in MNM and coal mines. Please provide
supporting information and data.
18. MSHA proposes to require mine
operators to collect a respirable
crystalline silica sample for a miner’s
regular full shift during typical mining
activities. Many potential sources of
respirable crystalline silica are present
only when the mine is operating under
typical conditions. MSHA requests
comments on this requirement and
whether to specify environmental
conditions under which samples should
be taken to ensure that samples
accurately reflect actual levels of
respirable crystalline silica exposure. In
MSHA’s experience, for example,
environmental conditions such as
precipitation (e.g., rain or snow) or wind
could affect the actual levels of
respirable crystalline silica exposure at
miners’ normal or regular workplaces
throughout their typical workday.
Please provide supporting information
and data.
19. MSHA recognizes that some
mining facilities operate seasonally or
intermittently and that cumulative
exposures for miners at these facilities
may be lower than that of miners
working at year-round operations.
MSHA requests comments on the
exposure monitoring approach under
proposed § 60.12, including the
frequency of exposure monitoring
necessary to safeguard the health of
miners at seasonal or intermittent
operations. Please provide supporting
information and data.
20. MSHA is proposing that each
mine operator perform baseline
sampling within 180 days after the rule
becomes effective to assess the
respirable crystalline silica exposure of
each miner who is or may reasonably be
expected to be exposed to respirable
crystalline silica. MSHA requests
comments on this proposed baseline
sampling requirement. MSHA also
requests comment on the ability of
service providers used by mines such as
industrial hygiene suppliers and
consultants, and accredited laboratories
that conduct respirable crystalline silica
analysis, to meet the demand created by
the baseline sampling requirements
within the proposed timeline. Please
include alternative approaches that
might be equally protective of miners
that should be implemented for
assessing a miner’s initial exposure to
respirable crystalline silica.
21. MSHA is proposing a requirement
that mine operators qualitatively
evaluate every 6 months any changes in
production, processes, engineering
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controls, personnel, administrative
controls, or other factors, beginning 18
months after the effective date. MSHA
requests comments on the timing of the
proposed semi-annual evaluation
requirements, and in particular, whether
miners would possibly be exposed
unnecessarily to respirable crystalline
silica levels above the PEL due to the
gap between the effective date and the
proposed requirements. Please provide
supporting information.
22. MSHA has determined that most
occupations related to extraction and
processing would meet the ‘‘reasonably
be expected’’ threshold for baseline
sampling. MSHA recognizes that some
miners may work in areas or perform
tasks where exposure is not reasonably
expected, if at all. MSHA solicits
comments on the assumption that most
miners are exposed to at least some
level of respirable crystalline silica, and
on the proposed requirement that these
miners should be subject to baseline
sampling. Please provide supporting
information.
23. MSHA is proposing that mine
operators would not be required to
conduct periodic sampling if the
baseline sampling result, together with
another sampling result or objective
data, as defined in proposed § 60.2,
confirms miners’ exposures are below
the proposed action level. MSHA seeks
comments on this proposal. Please
provide supporting information and
data.
24. MSHA is proposing that mine
operators conduct periodic sampling
within 3 months where the most recent
sampling indicates miner exposures are
at or above the proposed action level but
at or below the proposed PEL and
continue to sample within 3 months of
the previous sampling until two
consecutive samplings indicate that
miner exposures are below the action
level. MSHA solicits comments on the
proposed frequency for periodic
sampling, including whether the
consecutive samples should be at least
7 days apart. Please provide supporting
information and data.
25. MSHA is proposing that mine
operators may discontinue periodic
sampling when two consecutive
samples indicate that miner exposures
are below the proposed action level.
MSHA requests comments on this
proposal. Please provide supporting
information and data.
26. MSHA is proposing that mine
operators conduct semi-annual
evaluations to evaluate whether any
changes in production, processes,
engineering controls, personnel,
administrative controls, or other factors
may reasonably be expected to result in
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new or increased respirable crystalline
silica exposures. Please provide
comments on this proposal, as well as
alternative approaches that would be
appropriate for evaluating any potential
new or increased respirable crystalline
silica exposures. Please provide
supporting information and data.
27. MSHA is proposing that miners’
exposures are measured using personal
breathing-zone air samples for MNM
operations and occupational
environmental samples collected in
accordance with §§ 70.201(c), 71.201(b),
or 90.201(b) for coal operations. MSHA
requests comments on this proposal.
Please provide supporting information
and data.
28. MSHA is proposing the use of
representative sampling. Where several
miners perform the same task on the
same shift and in the same work area,
the mine operator may sample a
representative fraction of miners to meet
the proposed exposure monitoring
requirements. MSHA seeks comments
on the use of representative sampling.
Please provide supporting information
and data.
29. MSHA is proposing that mine
operators use laboratories accredited to
ISO/IEC 17025 ‘‘General requirements
for the competence of testing and
calibration laboratories,’’ where the
accreditation has been issued by a body
that is compliant with ISO/IEC 17011
‘‘Conformity assessment—requirements
for accreditation bodies accrediting
conformity assessment bodies.’’ MSHA
solicits comments on this proposal. Are
there additional requirements that
should be incorporated into this
proposal to ensure accurate sample
analysis methods? Please provide
supporting information and data.
30. MSHA seeks comments on the
proposal that mine operators ensure that
laboratories evaluate all respirable
crystalline silica samples using
respirable crystalline silica analytical
methods specified by MSHA, NIOSH, or
OSHA. Are there additional
requirements that should be
incorporated into this proposal to
ensure accurate sample analysis? Please
provide supporting information and
data.
31. MSHA seeks comments and
information on mine operator and
stakeholder experience using NIOSH’s
rapid field-based quartz monitoring
(RQM) monitors for determining miners’
exposures to respirable crystalline
silica. Please provide any information
and data.
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Proposed Medical Surveillance for Metal
and Nonmetal Miners
32. MSHA is proposing to require
medical surveillance for MNM miners.
Medical surveillance is already required
for coal miners under 30 CFR 72.100
and has played an important role in
tracking the burden of pneumoconiosis
in coal miners but is not currently
required for MNM miners. MSHA’s
proposal would require MNM mine
operators to provide each miner new to
the mining industry with an initial
medical examination and a follow-up
examination no later than 3 years after
the initial examination, at no cost to the
miner. It would also require MNM mine
operators to provide examinations for
all miners at least every 5 years, which
would be voluntary for miners. Is there
an alternative strategy or schedule, such
as voluntary initial or follow-up
examinations, tying the medical
surveillance requirement to miners
reasonably expected to be exposed to
any level of silica or to the action level
that would be more appropriate for new
MNM miners? Should the rule make
each 5-year examination mandatory?
Should the 5-year examination be
mandatory for coal mine operators as
well? Please provide data or cite
references to support your position.
33. MSHA’s proposed medical
surveillance requirements for MNM
miners do not include some
requirements that are in MSHA’s
existing medical surveillance
requirements for coal mine operators in
30 CFR 72.100. For example, § 72.100
requires coal mine operators to use
NIOSH-approved facilities for medical
examinations. Should MNM operators
be required to use NIOSH-approved
facilities for medical examinations? Coal
mine operators also are required to
submit for approval to NIOSH a plan for
providing miners with the examinations
specified. This is because NIOSH
administers medical surveillance for
coal miners with requirements for coal
operators, but not MNM operators, in
NIOSH standards (42 CFR part 37).
Should the plan requirements be
extended to MNM operators? However,
the proposed requirements also include
some requirements for MNM operators
that are not included for coal operators.
For example, the proposed provisions
require operators of MNM mines to
provide MNM miners with periodic
medical examinations performed by
physicians or other licensed health care
professionals (PLHCP) or specialists
including a history and physical
examination focused on the respiratory
system, a chest X-ray, and a spirometry
test. The proposed rule also requires a
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written medical opinion be provided by
the PLHCP or specialist to the mine
operator regarding the miner’s ability to
wear a respirator. MSHA seeks comment
on the differences between the medical
surveillance requirements for MNM
operators in this proposed rule and the
existing medical surveillance
requirements for coal mine operators in
§ 72.100. MSHA also seeks comment on
how best to collect health surveillance
data from PLHCPs and specialists to
track MNM miners’ health, for example
how to know when pneumoconiosis
cases occur. MSHA seeks comments on
alternative approaches to scheduling
periodic medical surveillance. MSHA
proposes to require operators to keep
medical surveillance information for the
duration of a miner’s employment plus
6 months. The Agency seeks comments
on this proposed requirement and on
any alternative recordkeeping schedules
that would be appropriate. Please
provide supporting information.
34. MSHA’s proposed medical
surveillance requirements for MNM
miners would require operators of MNM
mines to provide miners with periodic
medical examinations performed by
PLHCP or specialists, including a
history and physical examination
focused on the respiratory system, a
chest X-ray, and a spirometry test.
MSHA seeks comment on whether use
of any new diagnostic technology (e.g.,
high-resolution computed tomography)
for the purposes of medical surveillance
should be used.
35. MSHA’s proposed medical
surveillance requirements would
require that the MNM mine operator
provide a mandatory follow-up
examination to the miner no later than
3 years after the miner’s initial medical
examination. If a miner’s 3-year followup examination shows evidence of a
respirable crystalline silica-related
disease or decreased lung function, the
operator would be required to provide
the miner with another mandatory
follow-up examination with a specialist
within 2 years. For examinations that
show evidence of disease or decreased
lung function, MSHA seeks comment on
how, and to whom, test results should
be communicated.
36. MSHA requests comments as to
whether the proposed provisions should
include a medical removal option for
MNM miners who have developed
evidence of silica-related disease that is
equivalent to the transfer rights and
exposure monitoring provided to coal
miners in 30 CFR part 90 (part 90).
Under part 90, any coal miner who has
evidence of the development of
pneumoconiosis based on a chest X-ray
or other medical examinations has the
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option to work in an area of the mine
where the average concentration of
respirable dust in the mine atmosphere
during each shift to which that miner is
exposed is continuously maintained at
or below the applicable standard. Under
part 90, coal miners are entitled to
retention of pay rate, future actual wage
increases, and future work assignment,
shift and respirable dust protection.
MSHA seeks comment on whether this
medical removal option should be
provided to MNM miners. What would
be the economic impact of providing
MNM miners a medical removal option?
Please provide supporting information
and data.
Proposed Respiratory Protection
Standard
37. MSHA requests comments
concerning the temporary, non-routine
use of respirators and whether there are
other instances or occupations in which
the Agency should allow the use of
respirators as a supplemental control.
Please discuss any impacts on particular
mines and mining conditions and the
cost of air-purifying respirators, if
applicable. MSHA also solicits
comments on the proposed requirement
that affected miners wear respiratory
protection to maintain protection during
temporary and non-routine use of
respirators. Please provide supporting
information.
38. MSHA is proposing to incorporate
by reference ASTM F3387–19,
published in 2019. Whenever
respiratory protective equipment is
needed, mine operators would be
required to follow practices for program
administration, standard operating
procedures, medical evaluations,
respirator selection, training, fit testing,
and maintenance, inspection, and
storage in accordance with the
requirements of ASTM F3387–19.
Beyond these elements, MSHA is
proposing to provide operators the
flexibility to select the elements in
ASTM F3387–19 that are applicable to
their practices of respirator use at their
mines. Should mine operators have the
flexibility to choose the ASTM F3387–
19 elements that are appropriate for
their mine-specific hazards because the
need for respirators may vary due to the
variability of mining processes,
activities, airborne hazards, and
commodities mined? What, specifically,
do you think should factor into the
determination of what is applicable?
MSHA seeks comments on its proposed
approach and the impact it would have
on mine operators and on miners’ life
and health.
39. ASTM F3387–19 identifies a
variety of respiratory protection practice
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elements. MSHA proposes to require
certain minimally acceptable program
elements: program administration;
standard operating procedures; medical
evaluations; respirator selection;
training; fit testing; and maintenance,
inspection, and storage. Please comment
on whether these are the appropriate
elements to require, or if there are any
other elements of ASTM F3387–19 that
should be minimally included in any
respiratory protection program. MSHA
also welcomes comments on whether it
would be appropriate to require the
standard in its entirety. Please identify
those elements that would ensure that
approved respirators are selected, fitted,
used, cleaned, and maintained so that
the life and health of miners are
safeguarded. MSHA also seeks data and
information on the impact these changes
would have on mine operators,
especially smaller operators. What
would be the economic impact if all or
parts of ASTM F3387–19 were required
respirator program elements? Please be
specific with your response and provide
details on respirator use at your mine to
include information and data on mining
processes and environmental
conditions; level of exposures to
airborne contaminants; frequency and
duration of exposures; type and amount
of work or physical labor, including
frequency and duration; and medical
evaluation on respirator use, if
applicable.
Recordkeeping Requirements
40. MSHA is proposing to require
recordkeeping for records of
evaluations, records of samplings,
records of corrective actions, and
written determination records received
from a PLHCP. The proposed rule’s
recordkeeping requirements are
discussed in the Section-by-Section
Analysis section of this Preamble.
MSHA seeks comment on the utility of
these recordkeeping requirements as
well as the costs of making and
maintaining these records. Please
provide supporting information.
Training Requirements
41. MSHA requests the views and
recommendations of stakeholders
regarding whether training requirements
for miners should be included in
proposed part 60. Please provide
supporting information and data.
Conforming Changes
42. MSHA requests comments on the
proposed conforming changes to remove
the reduced coal dust standard from 30
CFR and the potential impact on coal
mines and miners and on whether to
retain the reduced standard for part 90
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miners. Please provide supporting
information.
43. MSHA is not proposing to adopt
a similar approach as the OSHA Table
1 for the construction industry, where
MSHA would prescribe specific
exposure control methods for task-based
work practices when working with
materials containing respirable
crystalline silica. See 29 CFR
1926.1153(c)(1). MSHA requests
comments on specific tasks and
exposure control methods appropriate
for a Table 1-approach for the mining
industry that also would adequately
protect miners from risk of exposure to
respirable crystalline silica. Please
provide specific rationale and
supporting information, including data
on how such an approach would be
implemented.
III. Background
The purpose of this proposed rule is
to reduce miners’ risk of developing
occupational lung disease and other
diseases caused by exposure to
respirable crystalline silica and to better
protect all miners from occupational
exposure to airborne hazards. In
promulgating mandatory standards
dealing with toxic materials or harmful
physical agents, MSHA is required to
‘‘set standards which most adequately
assure on the basis of the best available
evidence that no miner will suffer
material impairment of health or
functional capacity . . .’’ 30 U.S.C.
811(a)(6)(A).
A. Statutory Authority
The statutory authority for this
proposal is provided by the Mine Act
under sections 101(a), 103(h), and 508.
30 U.S.C. 811(a), 813(h), and 957.
MSHA implements the provisions of the
Mine Act to prevent death, illness, and
injury from mining and promote safe
and healthful workplaces for miners.
The Mine Act requires the Secretary of
Labor (Secretary) to develop and
promulgate improved mandatory health
or safety standards to prevent hazardous
and unhealthy conditions and protect
the health and safety of the nation’s
miners. 30 U.S.C. 811(a).
Congress passed the Mine Act to
address these dangers, finding ‘‘an
urgent need to provide more effective
means and measures for improving the
working conditions and practices in the
Nation’s coal or other mines in order to
prevent death and serious physical
harm, and in order to prevent
occupational diseases originating in
such mines.’’ 30 U.S.C. 801(c). Congress
concluded that ‘‘the existence of unsafe
and unhealthful conditions and
practices in the Nation’s coal or other
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mines is a serious impediment to the
future growth of the coal or other
mining industry and cannot be
tolerated.’’ 30 U.S.C. 801(d).
Accordingly, ‘‘the Mine Act evinces a
clear bias in favor of miner health and
safety.’’ Nat’l Mining Ass’n v. Sec’y, U.S.
Dep’t of Lab., 812 F.3d 843, 866 (11th
Cir. 2016).
Section 101(a) of the Mine Act gives
the Secretary the authority to develop,
promulgate, and revise, as appropriate,
mandatory health standards to address
toxic materials or harmful physical
agents. Under Section 101(a), standards
must protect lives and prevent injuries
in mines and be ‘‘improved’’ over any
standard that it replaces or revises.
Moreover, ‘‘the Mine Act does not
contain the ‘significant risk’ threshold
requirement . . . from the OSH Act.’’
Nat’l Mining Ass’n v. United Steel
Workers, 985 F.3d 1309, 1319 (11th Cir.
2021); see also Nat’l Min. Ass’n v. Mine
Safety & Health Admin., 116 F.3d 520,
527–28 (D.C. Cir. 1997) (contrasting the
OSH Act at 29 U.S.C. 652 with the Mine
Act at 30 U.S.C. 811(a) and noting that
‘‘[a]rguably, this language does not
mandate the same risk-finding
requirement as OSHA’’ and holding that
‘‘[a]t most, . . . . [MSHA] was required
to identify a significant risk associated
with having no oxygen standard at all’’
(emphasis in original)).
The Secretary must set standards to
assure, based on the best available
evidence, that no miners will suffer
material impairment of health or
functional capacity from exposure to
toxic materials or harmful physical
agents over their working lives. 30
U.S.C. 811(a)(6)(A). In developing
standards that attain the ‘‘highest degree
of health and safety protection for the
miner,’’ the Mine Act requires that the
Secretary consider the latest available
scientific data in the field, the feasibility
of the standards, and experience gained
under the Mine Act and other health
and safety laws. Id. However, MSHA’s
‘‘duty to use the best evidence and to
consider feasibility . . . cannot be
wielded as counterweight to MSHA’s
overarching role to protect the life and
health of workers in the mining
industry.’’ Nat’l Mining Ass’n, 812 F.3d
at 866. Instead, ‘‘when MSHA itself
weighs the evidence before it, it does so
in light of its congressional mandate.’’
Id.
Section 103(h) of the Mine Act gives
the Secretary the authority to
promulgate standards involving
recordkeeping and reporting. 30 U.S.C.
813(h). In general, section 103(h)
requires that every mine operator
establish and maintain records, make
reports, and provide this information, if
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required by the Secretary. Id. Also,
section 508 of the Mine Act gives the
Secretary the authority to issue
regulations to carry out any provision of
the Mine Act. 30 U.S.C. 957.
MSHA’s proposal to lower the
exposure limits for respirable crystalline
silica and adopt an integrated
monitoring approach across all mining
sectors and to update the existing
respiratory protection requirements
would fulfill Congress’ direction by
preventing miners from suffering
material impairment of health or
functional capacity caused by exposure
to respirable crystalline silica and other
airborne contaminants.
B. Respirable Crystalline Silica Hazard
and Mining
Silica is a common component of rock
composed of silicon and oxygen
(chemical formula SiO2), existing in
amorphous and crystalline states. Silica
in the crystalline state is the focus of
this rulemaking. Respirable crystalline
silica consists of small particles of
crystalline silica that can be inhaled and
reach the alveolar region of the lungs,
where they can accumulate and cause
disease. In crystalline silica, the silicon
and oxygen atoms are arranged in a
three-dimensional repeating pattern.
The crystallization pattern varies
depending on the circumstances of
crystallization, resulting in a
polymorphic state—several different
structures with the same chemical
composition. The most common form of
crystalline silica found in nature is
quartz, but cristobalite and tridymite
may also be found in limited
circumstances. Quartz accounts for the
overwhelming majority of naturally
occurring crystalline silica. In fact,
quartz accounts for almost 12 percent of
the earth’s crust by volume. All soils
contain at least trace amounts of quartz
and it is present in varying amounts in
almost every type of mineral. Quartz is
also abundant in most rock types,
including granites, sandstones, and
shale. Moreover, quartz is commonly
found in limestone formations, although
limestone itself does not contain quartz.
Because of its abundance, crystalline
silica in the form of quartz is present in
nearly all mining operations.
Cristobalite and tridymite are formed
at very high temperatures and are
associated with volcanic activity.
Naturally occurring cristobalite and
tridymite are rare, but they can be found
in volcanic ash and in a relatively small
number of rock types limited to specific
geographic regions. Although rare,
exposure to cristobalite occurs when
volcanic deposits are mined. In
addition, when other materials are
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mined, miners can potentially be
exposed to cristobalite during certain
processing steps (e.g., heating silicacontaining materials) and contact with
refractory materials (e.g., replacing fire
bricks in mine processing facility
furnaces). Tridymite is rarely found in
nature and miner exposure to tridymite
is much more infrequent.
Most mining activities generate silica
dust because silica is often contained in
the ore being mined or in the
overburden (i.e., the soil and surface
material surrounding the commodity
being mined). Such activities include,
but are not limited to, cutting, sanding,
drilling, crushing, grinding, sawing,
scraping, jackhammering, excavating,
and hauling materials that contain
silica. These activities can generate
respirable crystalline silica and may
therefore lead to miner exposure.
Inhaled small particles of silica dust
can be deposited throughout the lungs.
A large number of crystalline silica
particles can reach and remain in the
deep lung (i.e., alveolar region),
although some small particles are
cleared from the lungs. Because
respirable crystalline silica particles are
not water-soluble and do not undergo
metabolism into less toxic compounds,
those particles remaining in the lungs
for prolonged periods result in a variety
of cellular responses that may lead to
pulmonary disease. The respirable
crystalline silica particles that are
cleared from the lungs can be
distributed to lymph nodes, blood, liver,
spleen, and kidneys, potentially
accumulating in those other organ
systems and causing renal disease and
other adverse health effects.
In the U.S. in 2021, a total of 12,162
mines produced a variety of
commodities. As shown in Table III–1,
of those 12,162 total mines, 11,231
mines were MNM mines and 931 mines
were coal mines. MNM mines can be
broadly divided into five commodity
groups: metal, nonmetal, stone, crushed
limestone, and sand and gravel. These
broad categories encompass
approximately 98 different
commodities.1 Table III–1 shows that a
majority of MNM mines produce sand
and gravel, while the largest number of
MNM miners work at metal mines (not
1 Commodities such as sand, gravel, silica, and/
or stone for example are used in road building,
concrete construction, manufacture of glass and
ceramics, molds for metal castings in foundries,
abrasive blasting operations, plastics, rubber, paint,
soaps, scouring cleansers, filters, hydraulic
fracturing, and various architectural applications.
Some commodities naturally contain high levels of
crystalline silica, such as high-quartz industrial and
construction sands and granite dimension stone and
gravel (both produced for the construction
industry).
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including MNM contract workers (i.e.,
independent contractors and employees
of independent contractors who are
engaged in mining operations)).
The 931 coal mines—underground
and surface—produce bituminous,
subbituminous, anthracite, and lignite
coal. Coal mining activities generate
mixed coal mine dust that contains
respirable silicates such as kaolinite,
oxides such as quartz, as well as other
components (IARC, 1997). These
activities include the general mining
activities previously mentioned (e.g.,
cutting, sanding, drilling, crushing, and
hauling materials), as well as roof bolter
operations, continuous mining machine
operations, longwall mining, and other
activities. Table III–1 shows that there
are more surface coal mines than
underground coal mines, but more
miners are working in underground coal
mines than surface coal mines (not
including coal contract workers).
or diverting dust generated by mining
activities. They also require mine
operators to provide respiratory
protection in limited situations and on
a temporary basis. The existing
standards for MNM and coal mines
differ in some respects, including
exposure limits and monitoring. This
section describes MSHA’s existing
standards for respirable crystalline silica
and presents respirable crystalline silica
sampling data to show how MNM and
coal mine operators have complied with
them in recent years.
IV. Existing Standards and
Implementation
MSHA has maintained health
standards to protect MNM and coal
miners from excessive exposure to
respirable crystalline silica for decades.
MSHA’s existing standards, established
in the early 1970s, limit miners’
exposures to respirable crystalline
silica. These standards require mine
operators to monitor occupational
exposures to respirable crystalline silica
and to use engineering controls as the
primary means of suppressing, diluting,
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A. Existing Standards—Metal and
Nonmetal Mines
MSHA’s existing standards for
exposure to airborne contaminants,
including respirable crystalline silica, in
MNM mines are found in 30 CFR part
56, subpart D (Air Quality and Physical
Agents), and 30 CFR part 57, subpart D
(Air Quality, Radiation, Physical
Agents, and Diesel Particulate Matter).
These standards include PELs for
airborne contaminants (§§ 56.5001 and
57.5001), exposure monitoring
(§§ 56.5002 and 57.5002), and control of
exposure to airborne contaminants
(§§ 56.5005 and 57.5005).
Permissible Exposure Limits. The
existing PELs for the three polymorphs
of respirable crystalline silica are based
on the TLVs® Threshold Limit Values
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for Chemical Substances in Workroom
Air Adopted by the American
Conference of Governmental Industrial
Hygienists (ACGIH) for 1973,
incorporated by reference in 30 CFR
56.5001 and 57.5001 (ACGIH, 1974).
The 1973 TLV® establishes limits for
respirable dust containing 1 percent
quartz or greater and is calculated in
milligrams per cubic meter of air (mg/
m3) for each respirable dust sample. The
TLV® for quartz is calculated by
dividing the percent of respirable quartz
plus 2, into the number 10. The TLV®
for cristobalite and the TLV® for
tridymite, respectively, are calculated
by multiplying the same mass formula
by one-half using the percentages of
either cristobalite or tridymite found in
the sample. Thus, the resulting TLVs®
for respirable dust containing 1 percent
respirable crystalline silica or greater are
designed to limit exposures to less than
0.1 mg/m3 or 100 mg/m3 for quartz, to
less than 0.05 mg/m3 or 50 mg/m3 for
cristobalite, and to less than 0.05 mg/m3
or 50 mg/m3 for tridymite. Throughout
the remainder of this preamble, the
concentrations of respirable dust and
respirable crystalline silica are
expressed in mg/m3.
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Exposure Monitoring. Under 30 CFR
56.5002 and 57.5002, MNM mine
operators must conduct respirable dust
‘‘surveys . . . as frequently as necessary
to determine the adequacy of control
measures.’’ Mine operators can satisfy
the survey requirement through various
activities, such as respirable dust
sampling and analysis, walk-through
inspections, wipe sampling, examining
dust control system and ventilation
system maintenance, and reviewing
information obtained from injury,
illness, and accident reports.
MSHA encourages MNM mine
operators to conduct sampling for
airborne contaminants to ensure a
healthy and safe work environment for
miners because sampling provides more
accurate information about miners’
exposures to harmful airborne
contaminants and the effectiveness of
existing controls in reducing such
exposures. When a mine operator’s
respirable dust survey indicates that
miners have been overexposed to any
airborne contaminant, including
respirable crystalline silica, the operator
is expected to adjust its control
measures (e.g., exhaust ventilation) to
reduce or eliminate the identified
hazard. After doing so, the mine
operator is expected to conduct
additional surveys to determine whether
these efforts were successful. Resurveying should be done as frequently
as necessary to ensure that the
implemented control measures remain
adequate. MSHA’s determination of
whether a mine operator has surveyed
frequently enough is based on several
factors, including whether sampling
results comply with the permissible
exposure limit, whether there have been
changes in the mining operation or
process, and whether controls such as
local exhaust ventilation systems need
routine or special maintenance.
Exposure Controls. MSHA’s existing
standards for controlling a miner’s
exposure to harmful airborne
contaminants (§§ 56.5005 and 57.5005)
require, if feasible, prevention of
contamination, removal by exhaust
ventilation, or dilution with
uncontaminated air. The use of
respiratory protective equipment is also
allowed under specified circumstances
such as when engineering controls are
being developed or are not feasible.
When respiratory protective equipment
is used, the operator must have a
respiratory protection program
consistent with the requirements of
American National Standards Practices
for Respiratory Protection ANSI Z88.2–
1969.
Consistent with widely accepted
industrial hygiene principles and
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NIOSH’s recommendations, MSHA
requires the use of engineering controls,
supplemented by administrative
controls, in its enforcement for the
control of occupational exposure to
respirable crystalline silica and other
airborne contaminants (NIOSH, 1974).
Engineering controls designed to
remove or reduce the hazard at the
source are the most effective. Examples
of engineering controls include the
installation of proper ventilation
systems, use of water sprays or wetting
agents to suppress airborne
contaminants, installation of machinemounted dust collectors to capture
respirable crystalline silica and other
contaminants, and the installation of
control booths or environmental cabs to
enclose equipment operators.
Although considered a supplementary
or secondary measure to engineering
controls, mine operators may use
administrative controls to further reduce
miners’ exposures to respirable
crystalline silica and other airborne
contaminants. In applying
administrative controls, mine operators
can direct miners to perform certain
activities in specific manners. For
instance, as an administrative control,
operators can specify adequate
housekeeping procedures for miners to
clean spills or handle contaminated
clothing which could reduce
occupational exposure to airborne
contaminants, including respirable
crystalline silica.
In addition, respiratory protective
equipment can be used in controlling
miners’ exposures to airborne
contaminants, including respirable
crystalline silica, on a temporary basis
or under non-routine, limited
conditions. The use of respiratory
protection is, however, considered to be
a supplement, not an alternative to any
engineering or administrative control, in
reducing or eliminating a miner’s
exposure to airborne contaminants
including respirable crystalline silica.
Under the existing standards in
§§ 56.5005 and 57.5005, in
circumstances where engineering
controls are not yet developed or where
it is necessary for miners to enter
hazardous atmospheres to establish
controls or to perform non-routine
maintenance or investigation, a miner
using appropriate respiratory protection
‘‘may work for reasonable periods of
time’’ in concentrations of airborne
contaminants which exceed exposure
limits. Respirators approved by NIOSH
and suitable for their intended purpose
must be provided by mine operators at
no cost to the miner and must be used
by miners to protect themselves against
the health and safety hazards of airborne
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contaminants. Whenever respiratory
protection is used, MNM mine operators
are required to have a respirator
program consistent with the
requirements specified in ANSI Z88.2–
1969.
B. Existing Standards—Coal Mines
Under existing standards, there is no
separate standard for respirable
crystalline silica for coal mines.
MSHA’s existing standards for exposure
to respirable quartz in coal mines, found
in 30 CFR 70.101 and 71.101, establish
a respirable dust standard when quartz
is present for underground and surface
coal mines, respectively. Under 30 CFR
part 90 (Mandatory Health Standards—
Coal Miners Who Have Evidence of the
Development of Pneumoconiosis),
§ 90.101 also sets the respirable dust
standard when quartz is present for coal
miners. Under these respirable dust
standards, coal miners’ exposures to
respirable quartz are indirectly
regulated through reductions in the
overall respirable dust standard.
Under its existing respirable coal
mine dust standards, MSHA defines
quartz as crystalline silicon dioxide
(SiO2), which includes not only quartz
but also two other polymorphs,
cristobalite and tridymite.2 Therefore,
quartz and respirable crystalline silica
are used interchangeably in the
discussions of MSHA’s existing
standards for controlling exposures to
respirable crystalline silica in coal
mines.
Exposure Limits. The exposure limit
for respirable crystalline silica during a
coal miner’s shift is 100 mg/m3, reported
as an equivalent concentration as
measured by the Mining Research
Establishment (MRE) instrument. This
equivalent concentration of respirable
crystalline silica must not be exceeded
during the miner’s entire shift,
regardless of duration. When the
equivalent concentration of respirable
quartz exceeds 100 mg/m3, under
§§ 70.101, 71.101, and 90.101, MSHA
imposes a reduced respirable dust
standard designed to ensure that
respirable quartz will not exceed 100
mg/m3. The applicable dust standard,
when the equivalent concentration of
respirable crystalline silica exceeds 100
mg/m3, is computed by dividing the
percent of quartz into the number 10.
2 Quartz is defined in 30 CFR 70.2, 71.2, and 90.2
as crystalline silicon dioxide (SiO2) not chemically
combined with other substances and having a
distinctive physical structure. Crystalline silicon
dioxide is most commonly found in nature as
quartz but sometimes occurs as cristobalite or,
rarely, as tridymite. Quartz accounts for the
overwhelming majority of naturally occurring
crystalline silica and is present in varying amounts
in almost every type of mineral.
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The result of this calculation becomes
the exposure limit for respirable coal
mine dust (RCMD), for the sections of
the mine represented by the sample.
Various sections within a mine may
have different reduced RCMD exposure
limits. Therefore, when a respirable dust
sample collected by MSHA indicates
that the average concentration of
respirable quartz dust exceeds the
exposure limit, the mine operator is
required to comply with the applicable
dust standard. By reducing the amount
of respirable dust to which miners are
exposed during their shifts, the miners’
exposures to respirable crystalline silica
are reduced to a level at or below the
exposure limit of 100 mg/m3.
Exposure Monitoring. Under
§§ 70.208, 70.209, 71.206, and 90.207,
coal mine operators are required to
sample for respirable dust on a quarterly
basis for specified occupations and
work areas. The occupations and work
areas specified in the existing coal
standards are the occupations and work
areas at a coal mine that are expected to
have the highest concentrations of
respirable dust—typically in locations
where respirable dust is generated. In
addition, respirable dust sampling must
be representative of respirable dust
exposures during a normal production
shift. Also, sampling must occur while
miners are performing routine, day-today activities. Part 90 miners must be
sampled for the air they breathe while
performing their normal work duties,
from the start of their work day to the
end of their work day, in their normal
work locations.3
Exposure Controls. Under §§ 70.208,
70.209, 71.206, and 90.207, coal mine
operators are required to use
engineering or environmental controls
as the primary means of complying with
the respirable dust standards. Similar to
the MNM standards, engineering and
environmental controls include the use
of dust collectors, water sprays, and
ventilation controls. For many
underground coal mines, providing
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3A
‘‘Part 90 miner’’ is defined in 30 CFR 90.3 as
a miner employed at a coal mine who shows
evidence of having contracted pneumoconiosis
based on a chest X-ray or based on other medical
examinations, and who is afforded the option to
work in an area of a mine where the average
concentration of respirable dust in the mine
atmosphere during each shift to which that miner
is exposed is continuously maintained at or below
the applicable standard.
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adequate ventilation is the primary
engineering control for respirable dust,
ensuring that dust concentrations are
continuously diluted with fresh air and
exhausted away from miners.
When a respirable dust sample
exceeds the exposure limit of 100 mg/m3
for respirable quartz, the operator must
reduce the average concentration of
RCMD to a level designed to maintain
the quartz level at or below 100 mg/m3.
If operators exceed the reduced RCMD
standard, they are required to take
corrective action to reduce exposure and
comply with the reduced standard.
Corrective actions that lower respirable
coal mine dust, thus lowering respirable
quartz exposures, are selected after
evaluating the cause or causes of the
overexposure. Corrective actions can
include increasing air flow, improving
ventilation controls, repairing and
maintaining existing dust suppression
controls, adding water sprays or other
controls, cleaning dust filters or
collectors more frequently, or
repositioning the miner away from the
dust source.
When taking corrective actions to
reduce the exposure to respirable dust,
coal mine operators must make
approved respiratory equipment
available to miners under §§ 70.208 and
71.206. Whenever respiratory protection
is used, § 72.700 requires coal mine
operators to comply with requirements
specified in ANSI Z88.2–1969.
C. MSHA Inspection and Respirable
Dust Sampling
MSHA collects respirable dust
samples at mines and analyzes them for
respirable crystalline silica to determine
whether the respirable crystalline silica
exposure limits are met and whether
exposure controls are adequate. This
section describes the respirable dust
samples collected at MNM and coal
mines in recent years and presents the
results of the sample data analyses.
1. Respirable Dust Sample Collection
This subsection offers a brief
description of how MSHA samples for
respirable crystalline silica under the
existing standards. Upon their arrival at
mines, MSHA inspectors determine
which areas of the mine and which
miners to select for respirable dust
sampling. At MNM mines, the MSHA
inspector often determines sampling
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locations based on sample results from
previous inspections and on the
inspector’s onsite observations of work
practices and work areas. At coal mines,
the MSHA inspector conducts sampling
among the occupations or from the work
areas that are specified for operator
sampling under 30 CFR parts 70, 71,
and 90. Generally speaking, MSHA
inspectors collect respirable dust
samples from the common occupations
during typical and normal activities at
the mine and from the positions that are
commonly known to have the highest
concentration of respirable dust.
After identifying which miners and
which areas at the mine will be sampled
for respirable dust, MSHA inspectors
place gravimetric samplers on the
selected miners or at the selected
locations. Gravimetric samplers consist
of a portable air-sampling pump
connected to a particle-size separator
(i.e., cyclone) and collection medium
(i.e., filter). MSHA inspectors use DorrOliver 10-mm nylon cyclones operated
at a 1.7 liters per minute (L/min) flow
rate for MNM mine sampling and at a
2.0 L/min flow rate (reported as MREequivalent concentrations) for coal mine
sampling.4 For the entire duration of the
work shift, the gravimetric sampler
captures air from the breathing zone of
each selected miner or occupation and
from each selected work area.
MSHA inspectors use the full-shift
sampling approach. When miners work
longer than an 8-hour shift, which is
common, those miners are sampled
continuously throughout the extended
work shifts. Full-shift sampling is used
to minimize errors associated with
fluctuations in airborne contaminant
concentrations during the miners’ work
shifts and to avoid any speculation
about the miners’ exposures during
unsampled periods of the work shift.
Once sampling is completed, the
inspectors send the cassettes containing
the full-shift respirable dust samples to
the MSHA Laboratory for analysis.
4 This type of sampling equipment was developed
to separate the airborne particles by size in a
manner similar to the size-selective deposition and
retention characteristics of the human respiratory
system. It is important to note that size-selective
sampling does not measure the deposition of
respirable particles in the lung. Rather, it provides
a measure of the particulate mass available for
deposition to the deep lung during breathing (Raabe
and Stuart, 1999).
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2. Respirable Dust Sample Analysis
The MSHA Laboratory analyzes
inspectors’ respirable dust samples,
following its standard operating
procedures (SOPs) summarized below.5
Any samples that are broken, torn, or
visibly wet are voided and removed
before analysis. Once weighing of the
samples is completed, samples are again
screened based on mass gain and
examined for validity. All valid samples
that meet the minimum mass gain
criteria per the associated MSHA
analytical method are then analyzed for
respirable crystalline silica and for the
compliance determination.6
The MSHA Laboratory uses two
analytical methods to determine the
concentration of quartz (and cristobalite
and tridymite, if requested): X-ray
diffraction (XRD) for respirable dust
samples from MNM mines, and Fourier
transform infrared spectroscopy (FTIR)
for respirable coal mine dust samples.7
The XRD method uses X-rays to
distinguish and measure the structure,
composition, and physical properties of
a sample. The FTIR method relies on the
absorption of infrared light to determine
the composition of a sample. The
percentage of silica in the MNM mine
dust sample is calculated using the mass
of quartz or cristobalite determined from
the XRD analysis and the measured
mass of respirable dust. The percentage
of silica is used to calculate MSHA’s
PELs for quartz and cristobalite, in
accordance with §§ 56.5001 and
57.5001. Similarly, in the respirable coal
mine dust sample, the percentage of
quartz is calculated using the quartz
mass determined from the FTIR analysis
and the sample’s mass of dust. Current
FTIR methods, however, cannot
quantify quartz and cristobalite, and/or
tridymite, in the same sample. For coal
mines, the percentage of quartz is used
to calculate the reduced dust standard
when the quartz concentration exceeds
100 mg/m3 (MRE).
It is worth noting how MSHA
calculates full-shift exposure to
respirable crystalline silica (and other
airborne contaminants). When a miner
who works an 8-hour shift is sampled,
the miner’s 8-hour TWA exposure is
calculated as follows:
However, for work shifts that last
longer than 8 hours, a coal miner’s fullshift exposure is calculated differently
than an MNM miner’s full-shift
exposure. In accordance with § 70.2, the
coal miner’s extended full-shift
exposure has, since 2014, been
calculated in the following way:
For respirable dust samples from
MNM mines, 480 minutes is used in the
denominator regardless of the actual
sampling time. Contaminants collected
over extended shifts (e.g., 600–720
minutes) are calculated as if they had
been collected over 480 minutes. MSHA
has used this calculation approach (also
known as ‘‘shift-weighted average’’)
since the 1970s.
Under the shift-weighted average
approach, exposures for work schedules
greater than 8 hours are proportionately
adjusted to allow direct comparison
with the 8-hour PEL. The ACGIH TLVs®
adopted by MSHA are based on
exposure periods of no more than 8
hours per day and 40 hours per week,
with 16 hours of recovery time between
shifts.
D. Respirable Crystalline Silica
Sampling Results—Metal and Nonmetal
Mines
5 The MSHA Laboratory has fulfilled the
requirements of the AIHA Laboratory Accreditation
Programs (AIHA–LAP), LLC accreditation to the
ISO/IEC 17025:2017 international standard for
industrial hygiene.
6 The minimum mass gain criteria used by the
MSHA Laboratory for the different samples are:
• MNM mine respirable dust samples: greater
than or equal to 0.100 mg;
• Underground coal mine respirable dust
samples: greater than or equal to 0.100 mg; and
• Surface coal mine respirable dust samples:
greater than or equal to 0.200 mg.
Exception: For six surface occupations that have
been deemed ‘‘high risk,’’ the laboratory uses a
minimum mass gain criterion of greater than or
equal to 0.100 mg.
If cristobalite analysis is requested for MNM mine
respirable dust samples, filters having a mass gain
of 0.05 mg or more are analyzed. In the rare
instance when tridymite analysis is requested, a
qualitative analysis for the presence of the
polymorph is conducted concurrently with the
cristobalite analysis.
7 Details on MSHA’s analytical procedures for
respirable crystalline silica analysis can be found in
‘‘MSHA P–2: X-Ray Diffraction Determination of
Quartz and Cristobalite in Respirable Metal/
Nonmetal Mine Dust’’ and ‘‘MSHA P–7:
Determination of Quartz in Respirable Coal Mine
Dust by Fourier Transform Infrared Spectroscopy.’’
Department of Labor, Mine Safety and Health
Administration, Pittsburgh Safety and Health
Technology Center, X-Ray Diffraction
Determination of Quartz and Cristobalite in
Respirable Metal/Nonmetal Mine Dust. https://
arlweb.msha.gov/Techsupp/pshtcweb/MSHA
%20P2.pdf. Department of Labor, Mine Safety and
Health Administration, Pittsburgh Safety and
Health Technology Center, MSHA P–7:
Determination of Quartz in Respirable Coal Mine
Dust By Fourier Transform Infrared Spectroscopy.
https://arlweb.msha.gov/Techsupp/pshtcweb/
MSHA%20P7.pdf.
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This section presents the results of
respirable dust samples that were
collected by MSHA inspectors at MNM
mines from 2005 to 2019. From January
1, 2005, to December 31, 2019, a total
of 104,354 valid samples were collected.
Of this total, 57,769 samples that met
the minimum mass gain criteria were
analyzed for respirable crystalline silica.
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For the MNM miner, MSHA
calculates extended full-shift exposure
according to the following formula:
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m3 for a full-shift exposure, calculated
as an 8-hour TWA, while the existing
PELs for cristobalite and tridymite,
respectively, are approximately
equivalent to 50 mg/m3 for a full-shift
exposure, calculated as an 8-hour
TWA.8
The vast majority of the 46,585 valid
samples that were excluded from the
analysis in this rulemaking did not meet
the mass gain criteria described earlier
and therefore the lab did not determine
their silica concentration. Further
information on the valid respirable dust
samples that are excluded from the
analysis in this rulemaking can be found
in Appendix A of the preamble.
The respirable crystalline silica
concentration is calculated using the
measured mass of each of the
polymorphs and the air sampling
volume. As discussed above, the
existing PEL for quartz in MNM mines
is approximately equivalent to 100 mg/
1. Annual Results of MNM Respirable
Crystalline Silica Samples
Table IV–1 below shows the variation
between 2005 and 2019 in: (1) the
numbers of MNM respirable dust
samples analyzed for respirable
crystalline silica; and (2) the number
and percentage of samples that had
concentrations of respirable crystalline
silica greater than 100 mg/m3. Of the
8 If more than one polymorph is present the
equation used to calculate the TLV® for respirable
dust containing quartz is modified per Appendix C
of the 1973 ACGIH TLV® Handbook, and the
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57,769 MNM respirable dust samples
analyzed for respirable crystalline silica
over the 15-year period, about 6 percent
(3,539 samples) had respirable
crystalline silica concentrations
exceeding the existing PEL of 100 mg/
m3. The average annual rates of
overexposure ranged from a maximum
of approximately 10 percent in 2006
(the second year) to a minimum of
approximately 4 percent in 2019 (the
last year of the time series). Compared
with the rates in 2005–2008,
overexposure rates were substantially
lower in 2009–2017, with a further drop
in 2018–19.
BILLING CODE 4520–43–P
equation is modified as follows: 10/[(% quartz + 2)
+ 2 (% cristobalite + 2)].
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2. Analysis of MNM Respirable
Crystalline Silica Samples by
Commodity
Because the MNM mining industry
produces commodities that contain
varying degrees of respirable crystalline
silica, it is important to examine each
commodity separately. MNM mines can
be grouped by five commodities: metal,
sand and gravel, stone, crushed
limestone, and nonmetal (where
nonmetal includes all other materials
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3. Analysis of MNM Respirable
Crystalline Silica Samples by
Occupation
To examine how miners who perform
different tasks differ in occupational
exposure to respirable crystalline silica,
MSHA grouped MNM mining jobs into
11 occupational categories. These
categories include jobs that are similar
in terms of tasks performed, equipment
used, and engineering or administrative
controls used to control miners’
exposure. For example, backhoe
operators, bulldozer operators, and
tractor operators were grouped into
‘‘operators of large powered haulage
equipment,’’ whereas belt crew, belt
cleaners, and belt vulcanizers were
grouped into ‘‘conveyer operators.’’ The
121 MNM job codes used by MSHA
inspectors were grouped into the
following occupational categories: 9
9 For a full crosswalk of job codes included in
each of these 11 Occupational Categories, please see
Appendix C of the preamble. Also, note that the
order of the presentation of the 11 Occupational
Categories here follows the general sequence of
mining activities: first development and
production, then ore/mineral processing, then
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that are not metals, besides sand, gravel,
stone, and limestone). This grouping is
based on the mine operator-reported
mining products and the North
American Industry Classification
System (NAICS) codes. (Appendix B of
the preamble provides a list of the
NAICS codes relevant for MNM mining
and how each code is assigned to one
of the five commodities.)
Table IV–2 shows the distribution of
the respirable dust samples analyzed for
respirable crystalline silica by mine
commodity. The percentage of samples
with respirable crystalline silica
concentrations greater than the existing
exposure limit of 100 mg/m3 varies
across the different commodities. It is
highest for the metal, sand and gravel,
and stone commodities (at
approximately 11, 7, and 7 percent,
respectively), and lowest for the
nonmetal and crushed limestone
commodities (at approximately 4 and 3
percent, respectively).
(1) Drillers (e.g., Diamond Drill
Operator, Wagon Drill Operator, and
Drill Helper),
(2) Stone Cutting Operators (e.g.,
Jackhammer Operator, Cutting Machine
Operator, and Cutting Machine Helper),
(3) Kiln, Mill, and Concentrator
Workers (e.g., Ball Mill Operator,
Leaching Operator, and Pelletizer
Operator),
(4) Crushing Equipment and Plant
Operators (e.g., Crusher Operator/
Worker, Scalper Screen Operator, and
Dry Screen Plant Operator),
(5) Packaging Equipment Operators
(e.g., Bagging Operator and Packaging
Operations Worker),
(6) Conveyor Operators (e.g., Belt
Cleaner, Belt Crew, and Belt
Vulcanizer),
(7) Truck Loading Station Tenders
(e.g., Dump Operator and Truck Loader),
(8) Operators of Large Powered
Haulage Equipment (e.g., Tractor
Operators, Bulldozer Operator, and
Backhoe Operators),
(9) Operators of Small Powered
Haulage Equipment (e.g., Bobcat
Operator, Scoop-Tram Operator, and
Forklift Operator),
(10) Mobile Workers (e.g., Laborers,
Electricians, Mechanics, and
Supervisors), and
(11) Miners in Other Occupations
(e.g., Welder, Dragline Operator,
Ventilation Crew and Dredge/Barge
Operator).
Table IV–3 shows sample numbers
and overexposure rates by MNM
occupation. Operators of large powered
haulage equipment accounted for the
largest number of samples analyzed for
silica (17,016 samples), whereas
conveyor operators accounted for the
fewest (215 samples). Table IV–3 also
shows the number and percentage of the
samples exceeding the existing
respirable crystalline silica PEL of 100
mg/m3. In every occupational category,
some MNM miners were exposed to
respirable crystalline silica levels above
the existing PEL. In 9 out of the 11
occupational categories, the percentage
of samples exceeding the existing PEL is
less than 10 percent, although two have
loading, hauling, and dumping, and finally all
others.
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higher rates, ranging up to more than 19
percent (in the case of stone cutting
operators).
4. Conclusion
nevertheless, this occupation continues
to experience the highest overexposures
relative to other MNM occupations. For
the categories of drillers, miners in other
occupations, and operators of large
powered haulage equipment,
approximately 5 percent or less of the
respirable dust samples showed
concentrations over the existing
exposure limit.
MSHA believes that improved
technology, engineering controls, and
better training contributed to the
reductions in exposures for miners who
work in occupations exposed to the
highest levels of respirable crystalline
silica. In summary, the analysis of
MSHA inspector sampling data
indicates that the controls that MNM
mine operators are using, together with
This analysis of MSHA inspector
sampling data shows that MNM
operators have generally met the
existing standard. Of the 57,769
respirable dust samples from MNM
mines, approximately 6 percent
exceeded the existing respirable
crystalline silica PEL of 100 mg/m3,
although there are several outliers with
much higher overexposures. For 9 of the
11 occupational categories, less than 10
percent of the respirable dust samples
had concentrations over the existing
PEL of 100 mg/m3 for respirable
crystalline silica. In addition, about 80
percent of samples taken from stone
cutting operators did not exceed the
existing PEL, which historically has had
high exposures to respirable dust and
respirable crystalline silica; 10
10 Analysis
of MSHA respirable dust samples
from 2005 to 2010 showed that stone and rock saw
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operators had approximately 20 percent of the
sampled exposures exceeding the PEL. Watts et al.
(2012).
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MSHA’s enforcement, have generally
been effective in keeping miners’
exposure at or below the existing limit
of 100 mg/m3.
E. Respirable Crystalline Silica
Sampling Results—Coal Mines
To examine coal mine operators’
compliance with existing respirable
crystalline silica standards, MSHA
analyzed RCMD samples collected by
MSHA inspectors from 2016 to 2021.
(The data analyses for this rulemaking
do not include any respirable dust
samples collected by coal mine
operators.) The analysis below is based
on the samples collected by inspectors
starting on August 1, 2016, when Phase
III of MSHA’s 2014 Lowering Miners’
Exposure to Respirable Coal Mine Dust,
Including Continuous Personal Dust
Monitors (Coal Dust Rule) (79 FR 24813,
May 1, 2014) went into effect. At that
time, the exposure limits for RCMD
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overexposure than underground mines
(2.4 percent versus 1.0 percent,
respectively).
were lowered from 2.0 mg/m3 to 1.5 mg/
m3 (MRE equivalent) at underground
and surface coal mines, and from 1.0
mg/m3 to 0.5 mg/m3 (MRE equivalent)
for intake air at underground coal mines
and for Part 90 miners. From August 1,
2016, to July 31, 2021, MSHA inspectors
collected a total of 113,607 valid RCMD
samples. Of these valid samples, only
those collected from the breathing zones
of miners were used in the analysis for
this rulemaking; no environmental dust
samples were included.11 Of those
samples, 63,127 samples that met the
minimum mass gain criteria and had no
other disqualifying issues were analyzed
for respirable quartz and quartz
concentrations were determined. The
majority of the non-environmental valid
samples excluded from this rulemaking
analysis were excluded due to
insufficient mass. Further information
on the valid respirable dust samples that
are not included in the rulemaking
analysis can be found in Appendix A of
the preamble.
Of the 63,127 valid samples analyzed
for respirable crystalline silica and used
for this analysis, about 1 percent (777
samples) were over the existing quartz
exposure limit of 100 mg/m3 (MRE
equivalent) for a full shift, calculated as
a TWA.12 Overexposure rates (the
percent of samples above the exposure
limit, on average across all coal mining
occupations) decreased by nearly a
quarter between the first half and the
second half of the 2016–2021 period. As
in MNM mines, different miner
occupations had different overexposure
rates. Using broader groupings, surface
mines experienced higher rates of
2. Analysis of Coal Respirable
Crystalline Silica Samples by Location
to extract coal, whereas miners at
surface coal mines remove topsoil and
layers of rock to expose coal seams. Due
to these differences, it is important to
examine the respirable crystalline silica
data by location to determine how
underground and surface coal miners
differ in occupational exposure to
respirable crystalline silica.
Table IV–5, which presents the
overexposure rate by type of mine
where respirable coal mine dust
samples were collected, shows that
samples from surface coal mines
reflected higher rates of overexposure
than samples from underground mines.
In the 1995b Criteria Document, NIOSH presented
an empirically derived conversion factor of 0.857
for comparing current (MRE) and recommended
(ISO) respirable dust sampling criteria using the 10
mm Dorr-Oliver nylon cyclone operated at 2.0 and
1.7 L/min, respectively (i.e., 1.5 mg/m3 BMRC–MRE
= 1.29 mg/m3 ISO).
13 The coal samples for 2016 begin in August of
that year and the coal samples for 2021 end in July
of that year.
Coal mining activities differ
depending on the characteristics and
locations of coal seams. When coal
seams are several hundred feet below
the surface, miners tunnel into the earth
and use underground mining equipment
11 Environmental samples were not included in
the analysis to be consistent with the proposed
sampling requirements to determine individual
miner exposure.
12 The conversion between ISO values and MRE
values uses the NIOSH conversion factor of 0.857.
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1. Annual Results of Coal Respirable
Crystalline Silica Samples
In examining trends from one year to
the next, the discussion below focuses
on the samples collected in the 6
calendar years from 2016 to 2021. The
number of samples per year was stable
from 2017 to 2019 before decreasing in
2020.13 The overexposure rate
decreased across the entire 2016 to 2021
period, from 1.41 percent in 2016 to
0.95 percent in 2021. As shown in Table
IV–4, a review of the 6 calendar years
reveals that the overexposure rate
decreased by nearly a quarter from
2016–2018 (1.38 percent) to 2019–2021
(1.07 percent).
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Out of the 53,095 respirable coal mine
dust samples from underground mines,
1 percent (537 samples) were over the
existing exposure limit. By contrast,
there were 10,032 samples from surface
coal mines, and approximately 2.4
percent (240 samples) of those samples
were over the existing exposure limit.
3. Analysis of Coal Respirable
Crystalline Silica Samples by
Occupation
whether they are working at the surface
of a mine or underground.
Of the nine occupational categories
used for coal miners, the five
underground categories are:
(1) Continuous Mining Machine
Operators (e.g., Coal Drill Helper and
Coal Drill Operator),
(2) Longwall Workers (e.g., Headgate
Operator and Jack Setter (Longwall)),
(3) Roof Bolters (e.g., Roof Bolter and
Roof Bolter Helper),
(4) Operators of Large Powered
Haulage Equipment (e.g., Shuttle Car
Operator, Tractor Operator/Motorman,
Scoop Car Operator), and
(5) All Other Underground Miners
(e.g., Electrician, Mechanic, Belt Cleaner
and Laborer, etc.).
The four surface occupational
categories are:
(1) Drillers (e.g., Coal Drill Operator,
Coal Drill Helper, and Auger Operator),
(2) Crusher Operators (e.g., Crusher
Attendant, Washer Operator, and
Scalper-Screen Operator),
(3) Operators of Large Powered
Haulage Equipment (e.g., Backhoe
Operator, Forklift Operator, and
Bulldozer Operator), and
(4) Mobile Workers (e.g., Electrician,
Mechanic, Blaster, Laborer, etc.).
The most sampled occupational
category was operators of large powered
haulage equipment (underground),
representing approximately 34 percent
of the samples taken. The least sampled
occupational category was crusher
operators (surface), consisting of 1
percent of the samples taken. Table IV–
6 displays the number and percent of
respirable coal mine dust samples with
quartz greater than the existing exposure
limit for each occupational category.
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To assess the exposure to respirable
crystalline silica of miners in different
occupations, MSHA has consolidated
the 220 job codes for coal mines into 9
occupational categories (using a similar
process to the one it used for the MNM
mines, but with different job codes and
categories). For the coal mine
occupational categories,14 a distinction
is made between occupations based on
whether the job tasks are being
performed at the surface of a mine or
underground. For example, bulldozer
operators are assigned to the operators
of large powered haulage equipment
grouping and then sorted into separate
occupational categories based on
14 For a full crosswalk of which job codes were
included in each of these nine Occupational
Categories, please see Appendix C of the preamble.
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IV–1. Most of the nine categories had
lower rates of overexposure in the 2019–
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period.
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Looking at trends, every occupational
category shows a decrease in
overexposure rates over time. See Figure
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In all occupational categories, coal
miners were sometimes exposed to
respirable crystalline silica levels above
the existing exposure limit. But the
sampling data showed that coal mine
operators can generally comply with the
existing exposure limit. For example,
although mining tasks performed by the
occupational category of roof bolters
(underground) historically resulted in
high levels of overexposure to quartz,
the low levels of overexposure for that
occupation in 2016–2021 (i.e., 1
percent) suggest that roof bolters now
benefit from the improved respirable
dust standard, improved technology,
and better training.15 Over the 2016–
2021 period, coal miners in the
occupational category drillers (surface)
were the most frequently overexposed,
with approximately 6 percent of
samples over the existing quartz limit;
15 The drilling operation in the roof bolting
process, especially in hard rock, generates excessive
respirable coal and quartz dusts, which could
expose the roof bolting operator to continued health
risks (Jiang and Luo, 2021).
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they were followed by longwall workers
(underground) (about 4 percent),
operators of large powered haulage
equipment (surface) (about 3 percent),
and continuous mining machine
operators (underground) (about 2
percent). For all other occupational
categories, the overexposure rate was
less than 1 percent.
4. Conclusion
This analysis of MSHA inspector
sampling data shows that coal mine
operators can generally comply with the
existing standards related to quartz. Of
the 63,127 valid respirable dust samples
from coal mines over the most recent 5year period, 1.2 percent had respirable
quartz over the existing exposure limit
of 100 mg/m3 (MRE equivalent) for a
full-shift exposure, calculated as a
TWA. Seven of the nine occupational
categories had overexposure rates of 2.5
percent or less. Roof bolters
(underground), which historically have
had high exposures to respirable dust
and respirable crystalline silica, had
overexposure rates of 1 percent over this
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recent period. The data demonstrates
that the controls that coal mine
operators are using, together with
MSHA’s enforcement, have generally
been effective in keeping miners’
exposure to respirable crystalline silica
at or below the existing exposure limit.
V. Health Effects Summary
This section summarizes the health
effects from occupational exposure to
respirable crystalline silica. MSHA’s full
analysis is contained in the standalone
document, entitled Effects of
Occupational Exposure to Respirable
Crystalline Silica on the Health of
Miners (Health Effects document),
which has been placed in the
rulemaking docket for the MSHA silica
rulemaking (RIN 1219–AB36, Docket ID
no. MSHA–2023–0001) and is available
on MSHA’s website.
The purpose of the Agency’s scientific
review is to present MSHA’s
preliminary findings on the nature of
the hazards presented by exposure to
respirable crystalline silica and to
present the basis for the Preliminary
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Risk Analysis (PRA) to follow. (A PRA
summary is presented in Section VI of
this preamble and a standalone
document entitled Preliminary Risk
Analysis has been placed in the
rulemaking docket for the MSHA silica
rulemaking (RIN 1219–AB36, Docket ID
no. MSHA–2023–0001) and is available
on MSHA’s website.) MSHA reviewed a
wide range of health research literature
that included more than 600 studies
exploring the relationship between
respirable crystalline silica exposure
and resultant health effects in miners
and other workers across various
industries. After discussing the toxicity
of respirable crystalline silica, MSHA’s
review of the literature covers the
following topics:
(1) Silicosis;
(2) NMRD, excluding silicosis;
(3) Lung cancer and cancer at other
sites;
(4) Renal disease; and
(5) Autoimmune diseases.
To develop this literature review,
MSHA expanded upon OSHA’s (2013b)
review of the health effects literature to
support its final respirable crystalline
silica rule (81 FR 16286, March 25,
2016). MSHA also drew upon numerous
studies conducted by NIOSH, the
International Agency for Research on
Cancer (IARC), the National Toxicology
Program (NTP), and other researchers.
These studies provided epidemiological
data, morbidity (having a disease or a
symptom of disease) and mortality
(disease resulting in death) analyses,
progression and pathology evaluations,
death certificate and autopsy reviews,
medical surveillance data, health hazard
assessments, in vivo (animal) and in
vitro toxicity data, and other
toxicological reviews. These sources are
cited throughout this summary and are
listed in the References section of the
Health Effects document. Additionally,
these sources appear in the rulemaking
docket.
MSHA’s literature review is based on
a weight-of-evidence approach, in
which studies are evaluated for their
overall quality. Causal inferences are
drawn based on a determination of
whether there is substantial evidence
that exposure increases the risk of a
particular adverse health effect. Factors
MSHA considered in this weight-ofevidence analysis include: size of the
cohort studied and power of the study
to detect a sufficiently low level of
disease risk, duration of follow-up of the
study population, potential for study
bias (such as selection bias or healthy
worker effects), and adequacy of
underlying exposure information for
examining exposure-response
relationships. Of the studies examined
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in the Health Effects document, studies
were deemed suitable for inclusion in
the PRA if there was adequate
quantitative information on exposure
and disease risks and the study was
judged to be of sufficiently high quality
according to the above criteria.
The understanding of how respirable
crystalline silica causes adverse health
effects has evolved greatly in the more
than 45 years since the Mine Act was
passed in 1977. Based on its extensive
review of health research literature,
MSHA has preliminarily determined
that occupational exposure to respirable
crystalline silica causes silicosis (acute
silicosis, accelerated silicosis, simple
chronic silicosis, and PMF), NMRD
(including COPD), and lung cancer, and
it also causes end-stage renal disease
(ESRD). In addition, MSHA believes that
respirable crystalline silica exposure is
causally related to the development of
some autoimmune disorders through
inflammation pathways. Each of these
effects is exposure-dependent, chronic,
irreversible, and potentially disabling or
fatal. MSHA’s review of the literature
indicates that under the existing
standards found in 30 CFR parts 56, 57,
70, 71, and 90, miners are still
developing preventable diseases that are
material impairments of health and
functional capacity. Based on the
assessment of health effects of respirable
crystalline silica, MSHA preliminarily
concludes that the proposed rule, which
would lower the exposure limits in
MNM and coal mining to 50 mg/m3 and
establish an action level of 25 mg/m3 for
a full-shift exposure, calculated as an 8hour TWA, would reduce the risk of
miners developing silicosis, NMRD,
lung cancer, and renal disease.
A. Toxicity of Respirable Crystalline
Silica
Respirable crystalline silica is
released into the environment during
mining or milling processes, thus
creating an airborne hazard. The
particles may be freshly generated or resuspended from surfaces on which it is
deposited in mines or mills. Respirable
crystalline silica particles may be
irregularly shaped and variable in size.
Inhaled respirable crystalline silica can
be deposited throughout the lungs.
Some pulmonary clearance of particles
deposited in the deep lung (i.e., alveolar
region) may occur, but a large number
of particles can be retained and initiate
or advance the disease process. The
toxicity of these retained particles is
amplified because the particles are not
water-soluble and do not undergo
metabolism into less toxic compounds.
This is important biologically and
physiologically, as insoluble dusts may
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remain in the lungs for prolonged
periods, resulting in a variety of cellular
responses that can lead to pulmonary
disease (ATSDR, 2019). Respirable
crystalline silica particles that are
cleared from the lungs by the lymphatic
system are distributed to the lymph
nodes, blood, liver, spleen, and kidneys,
potentially accumulating in these other
organ systems and causing renal disease
and other adverse health effects
(ATSDR, 2019).
Physical characteristics relevant to the
toxicity of respirable crystalline silica
primarily relate to its size and surface
characteristics. Researchers believe that
the size and surface characteristics play
important roles in how respirable
crystalline silica causes tissue damage.
Any factor that influences or modifies
these physical characteristics may alter
the toxicity of respirable crystalline
silica by affecting the mechanistic
processes (OSHA, 2013b; ATSDR, 2019).
Inflammation pathways affect disease
development in various systems and
tissues in the human body. For instance,
it has been proposed that lung fibrosis
caused by exposure to respirable
crystalline silica results from a cycle of
cell damage, oxidant generation,
inflammation, scarring, and ultimately
fibrosis. This has been reported by
Nolan et al. (1981), Shi et al. (1989,
1998), Lapp and Castranova (1993),
Brown and Donaldson (1996), Parker
and Banks (1998), Castranova and
Vallyathan (2000), Castranova (2004),
Fubini et al. (2004), Hu et al. (2017),
Benmerzoug et al. (2018), and Yu et al.
(2020).
Respirable crystalline silica entering
the lungs could cause damage by a
variety of mechanisms, including direct
damage to lung cells. In addition,
activation or stimulation by respirable
crystalline silica of alveolar
macrophages (after phagocytosis) and/or
alveolar epithelial cells may lead to: (1)
release of cytotoxic enzymes, reactive
oxygen species (ROS), reactive nitrogen
species (RNS), inflammatory cytokines
and chemokines, (2) eventual cell death
with the release of respirable crystalline
silica, and (3) recruitment and
activation of polymorphonuclear
leukocytes (PMNs) and additional
alveolar macrophages. The elevated
production of ROS/RNS would result in
oxidative stress and lung injury that
stimulates alveolar macrophages,
ultimately resulting in fibroblast
activation and pulmonary fibrosis. The
prolonged recruitment of macrophages
and PMN causes a persistent
inflammation, regarded as a primary
step in the development of silicosis.
The strong immune response in the
lung following exposure to respirable
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crystalline silica may also be linked to
a variety of extra-pulmonary adverse
effects such as
hypergammaglobulinemia, production
of rheumatoid factor, anti-nuclear
antibodies, and release of other immune
complexes (Parks et al., 1999, Haustein
and Anderegg, 1988; Green and
Vallyathan, 1996). Respirable crystalline
silica exposure has also been associated
with nonmalignant renal disease
through the initiation of immunological
injury to the glomerulus of the kidney
(Calvert et al., 1997).
Proposed mechanisms involved in
respirable crystalline silica-induced
carcinogenesis have included: direct
DNA damage, inhibition of the p53
tumor suppressor gene, loss of cell cycle
regulation; stimulation of growth
factors, and production on oncogenes
(Brown and Donaldson, 1996;
Castranova, 2004; Fubini et al., 2004;
Nolan et al., 1981; Shi et al., 1989,
1998).
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B. Diseases
1. Silicosis
Silicosis is a progressive occupational
disease that has long been identified as
a cause of lung disease in miners. Based
on its review of the literature, MSHA
has preliminarily determined that
exposure to respirable crystalline silica
causes silicosis (acute silicosis,
accelerated silicosis, simple chronic
silicosis, and PMF) in MNM and coal
miners, which is a significant cause of
serious morbidity and early mortality in
this occupational cohort (Mazurek and
Attfield, 2008; Mazurek and Wood,
2008a, 2008b; Mazurek et al., 2015,
2018).
When respirable crystalline silica
particles accumulate in the lungs, they
cause an inflammatory reaction, leading
to lung damage and scarring. Silicosis
can continue to develop even after silica
exposure has ceased. It is not reversible,
and there is only symptomatic
treatment, including bronchodilators to
maintain open airways, oxygen therapy,
and lung transplants in the most severe
cases (Cochrane et al., 1956; Ng et al.,
1987a; Lee et al., 2001; Mohebbi and
Zubeyri, 2007; Kimura et al., 2010;
Laney et al., 2017; Almberg et al., 2020;
Hall et al., 2022).
Respirable crystalline silica exposure
in MNM miners can lead to all three
forms of silicosis (acute, accelerated,
and chronic). These forms differ in the
rate of exposure, pathology (i.e., the
structural and functional changes
produced by the disease), and latency
period from exposure to disease onset.
Acute silicosis is an aggressive
inflammatory process following intense
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exposure to respirable crystalline silica
for ‘‘periods measured in months rather
than years’’ (Cowie and Becklake, 2016).
It causes alveolar proteinosis
(accumulation of lipoproteins in the
alveoli of the lungs). This restructuring
of the lungs leads to symptoms such as
coughing and difficult or labored
breathing, and it often progresses to
profound disability and death due to
respiratory failure or infectious
complications. In addition, symptoms
often advance even after exposure has
stopped, primarily due to the massive
amount of protein debris and fluid that
collects in the alveoli, which can
suffocate the patient. The radiographic
(X-ray) appearance and results of
microscopic examination of acute
silicosis are like those of idiopathic
pulmonary alveolar proteinosis.
Chronic silicosis is the most
frequently observed form of silicosis in
the United States today (Banks, 2005;
OSHA, 2013b; Cowie and Becklake,
2016). It is also the most common form
of silicosis diagnosed in miners.
Chronic silicosis is a fibrotic process
that typically follows less intense
respirable crystalline silica exposure of
10 or more years (Becklake, 1994;
Balaan and Banks, 1998; NIOSH, 2002b,
Kambouchner and Bernaudin, 2015;
Cowie and Becklake, 2016; Rosental,
2017; ATSDR, 2019; Barnes et al., 2019;
Hoy and Chambers, 2020). It is
identified by the presence of the
silicotic islet or nodule that is an agentspecific fibrotic lesion and is recognized
by its pathology (Balaan and Banks,
1998). Chronic silicosis develops slowly
and creates rounded whorls of scar
tissue that progressively destroy the
normal structure and function of the
lungs. In addition, the scar tissue
opacities become visible by chest X-ray
or computerized tomography (CT) only
after the disease is well established and
the lesions become large enough to
view. As a result, surveys based on
chest X-ray films usually underestimate
the true prevalence of silicosis
(Craighead and Vallathol, 1980; Hnizdo
et al., 1993; Rosenman et al., 1997;
Cohen and Velho, 2002). However, the
lesions eventually advance and result in
lung restriction, reduced lung volumes,
decreased pulmonary compliance, and
reduction in the gas exchange
capabilities of the lungs (Balaan and
Banks, 1998). As the disease progresses,
affected miners may have a chronic
cough, sputum production, shortness of
breath, and reduced pulmonary
function.
Accelerated silicosis includes both
inflammation and fibrosis and is
associated with intense respirable
crystalline silica exposure. Accelerated
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silicosis usually manifests over a period
of 3 to 10 years (Cowie and Becklake,
2016), but it can develop in as little as
2 to 5 years if exposure is sufficiently
intense (Davis, 1996). Accelerated
silicosis may have features of both
chronic and acute silicosis (i.e., alveolar
proteinosis in addition to X-ray
evidence of fibrosis). Although the
symptoms are similar to those of
chronic silicosis, the clinical and
radiographic progression of accelerated
silicosis evolves more rapidly, and often
leads to PMF, severe respiratory
impairment, and respiratory failure.
Accelerated silicosis can progress with
associated morbidity and mortality,
even if exposure ceases.
Among coal miners, silicosis is
usually found in conjunction with
simple coal worker’s pneumoconiosis
(CWP) (Castranova and Vallyathan,
2000) because of their exposures to
RCMD that contains respirable
crystalline silica. Coal miners also face
an added risk of developing mixed-dust
pneumoconiosis (MDP) (includes the
presence of coal dust macules), mixeddust fibrosis (MDF), and/or silicotic
nodules (Honma et al., 2004, see Figure
2, Green 2019). The autopsy studies on
coal miners that MSHA reviewed
support a pathological relationship
between mixed-RCMD or respirable
crystalline silica exposures and PMF,
silicosis, and CWP (Attfield et al., 1994;
Cohen et al., 2016, 2019, 2022; Davis et
al., 1979; Douglas et al., 1986; Fernie
and Ruckley, 1987; Green et al., 1989,
1998b; Ruckley et al., 1981, 1984;
Vallyathan et al., 2011). Autopsy studies
in British coal miners indicated that the
more advanced the disease, the more
mixed coal mine dust components were
retained in the lung tissue (Ruckley et
al., 1984; Douglas et al., 1986). Green et
al. (1998b) determined that of 4,115 coal
miners with pneumoconiosis autopsied
as part of the National Coal Workers’
Autopsy Study (NCWAS), 39 percent
had mixed dust nodules and 23 percent
had silicotic nodules.
PMF or ‘‘complicated silicosis’’ has
been diagnosed in both coal and MNM
miners exposed to dusts containing
respirable crystalline silica. Recent
literature on the pathophysiology of
PMF supports the importance of
crystalline silica as a cause of PMF in
silica-exposed workers such as coal
miners from the United States (Cohen et
al., 2016, 2022), sandblasters (Abraham
and Wiesenfeld, 1997; Hughes et al.,
1982), industrial sand workers (Vacek et
al., 2019), hard rock miners (Verma et
al., 1982, 2008), and gold miners
(Carneiro et al., 2006a; Tse et al.,
2007b).
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a. Classifying Radiographic Findings of
Silicosis
Two classification methods used to
characterize the radiographic findings of
silicosis in chest X-rays are described in
this literature review: the International
Labour Office (ILO) Standardized
System and the Chinese categorization
system.16
To describe the presence and severity
of pneumoconiosis from chest X-rays or
digital radiographic images, the ILO
developed a standardized system to
classify the opacities identified (ILO,
1980, 2002, 2011, 2022). The ILO system
grades the size, shape, and profusion
(frequency) of opacities in the lungs.
The density of opacities is classified on
a 4-point major category scale (category
0, 1, 2, or 3), with each major category
divided into three subcategories, giving
a 12-point scale between 0/¥ and 3/+.
Differences between ILO categories are
subtle. For each subcategory, the top
number indicates the major category
that the profusion most closely
resembles, and the bottom number
indicates the major category that was
given secondary consideration. For
example, film readers may assign
classifications such as 1/0, which means
the reader classified it as category 1, but
category 0 (normal) was also considered
(ILO, 2022). Major category 0 indicates
the absence of visible opacities and
categories 1 to 3 reflect increasing
profusion of opacities and a
concomitant increase in severity of
disease.
MSHA’s analysis of silicosis studies
uses NIOSH’s surveillance case
definition to determine the presence of
silicosis. NIOSH defines the presence of
silicosis in terms of the ILO system and
considers a small opacity profusion
score of 1/0 or greater to indicate
pneumoconiosis (NIOSH, 2014b). This
definition originated from testimony
before Congress regarding the 1969 Coal
Act where the Public Health Service
recommended that miners be removed
from dusty environments as soon as
they showed ‘‘minimal effects’’ of dust
exposure on a chest X-ray (i.e., pinpoint,
dispersed micro-nodular lesions).17
16 The ‘‘Radiological Diagnostic Criteria of
Pneumoconiosis and Principles for Management of
Pneumoconiosis’’ (GB5906–86) (Chen et al., 2001;
Yang et al., 2006).
17 On March 26, 1969, Charles C. Johnson, Jr.,
Administrator, Consumer Protection and
Environmental Health Service, PHS, U.S.
Department of Health, Education, and Welfare,
testified before the General Subcommittee on Labor
and presented remarks of the Surgeon General.
They are referenced in the 91st Congress House of
Representatives Report, 1st Session No. 91–563,
Federal Coal Mine Health and Safety Act, October
13, 1969 (https://arlweb.msha.gov/SOLICITOR/
COALACT/69hous.htm).
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MSHA interprets ‘‘minimal effects’’ to
mean an X-ray ILO profusion score of
category 1/0 or greater.
However, some studies in MSHA’s
literature review use the Chinese
categorization scheme, which includes
four categories of silicosis: a suspected
case (0+), stage I, stage II, or stage III.
The four categories correspond to ILO
profusion category 0/1, category 1,
category 2, and category 3, respectively.
A suspected case of silicosis (0+) in a
dust-exposed worker refers to a dust
response in the lung and its
corresponding lymph nodes, or a scale
and severity of small opacities that fall
short of the level observed in a stage I
case of silicosis (Chen et al., 2001; Yang
et al., 2006). Under this scheme, a panel
of three radiologists determines the
presence and severity of radiographic
changes consistent with
pneumoconiosis.
b. Progression and Associated
Impairment
Progression of silicosis is shown
when there are changes or worsening of
the opacities in the lungs, and
sequential chest radiographs are
classified higher by one or more
subcategories (e.g., from 1/0 to 1/1)
because of changes in the location,
thickness, or extent of lung
abnormalities and/or the presence of
calcifications. The higher the category
number, the more severe the disease.
Due to the uncertainty in scoring films,
some investigators count progression as
advancing two or more subcategories,
such as 1/0 to 1/2.
MSHA reviewed studies referenced by
OSHA (2013b) that examined the
relationship between exposure and
progression, as well as between X-ray
findings and pulmonary function.
Additionally, MSHA considered more
recent literature (Dumavibhat et al.,
2013; Mohebbi and Zubeyri, 2007; Wade
et al., 2011) not previously reviewed by
OSHA (2013b).
Overall, the studies indicate that
progression is more likely with
continued exposure, especially high
average levels of exposure. Progression
is also more likely for miners with
higher ILO profusion classifications. As
discussed previously, progression of
disease may continue after miners are
no longer exposed to respirable
crystalline silica (Almberg et al., 2020;
Cochrane et al., 1956; Hall et al., 2020b;
Hurley et al., 1987; Kimura et al., 2010;
Maclaren et al., 1985). In addition,
although lung function impairment is
highly correlated with chest X-ray films
indicating silicosis, researchers
cautioned that respirable crystalline
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silica exposure could impair lung
function before it is detected by X-ray.
Of the studies in which silicosis
progression was documented in
populations of workers, four included
quantitative exposure data that were
based on either existing exposure levels
or historical measurements of respirable
crystalline silica (Hessel et al., 1988
study of gold miners; Miller and
MacCalman, 2010 study of coal miners;
Miller et al., 1998 study of coal miners;
Ng et al., 1987a study of granite miners).
In some studies, episodic exposures to
high average concentrations were
documented and considered in the
analysis. These exposures were strong
predictors of more rapid progression
beyond that predicted by cumulative
exposure alone. Otherwise, the variable
most strongly associated in these studies
with progression of silicosis was
cumulative respirable crystalline silica
exposure (i.e., the product of the
concentration times duration of
exposure, which is summed over time)
(Hessel et al., 1988; Ng et al., 1987a;
Miller and MacCalman, 2010; Miller et
al., 1998). In the absence of
concentration measurements, duration
of employment in specific occupations
known to involve exposure to high
levels of respirable dust has been used
as a surrogate for cumulative exposure
to respirable crystalline silica. It has
also been found to be associated with
the progression of silicosis (Ogawa et
al., 2003a).
Miller et al. (1998) examined the
impact of high quartz exposures on
silicosis disease progression on 547
British coal miners from 1990 to 1991
and evaluated chest X-ray changes after
the mines closed in 1981. The study
reviewed chest X-rays taken during
health surveys conducted between 1954
and 1978 and data from extensive
exposure monitoring conducted
between 1964 and 1978. For some
occupations, exposure was high because
miners had to dig through a sandstone
stratum to reach the coal. For example,
quarterly mean respirable crystalline
silica (quartz) concentrations ranged
from 1,000 to 3,000 mg/m3 (1–3 mg/m3),
and for a brief period, concentrations
exceeded 10,000 mg/m3 (10 mg/m3) for
one job. Some of these high exposures
were associated with accelerated disease
progression.
Buchanan et al. (2003) reviewed the
exposure history and chest X-ray
progression of 371 retired miners and
found that short-term exposures (i.e., ‘‘a
few months’’) to high concentrations of
respirable crystalline silica (e.g., >2,000
mg/m3, >2 mg/m3) increased the silicosis
risk by three-fold (compared to the risk
of cumulative exposure alone) (see the
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separate Preliminary Risk Analysis
document).
The risks of increased rate of
progression, predicted by Buchanan et
al. (2003) have been seen in coal miners
(e.g., Cohen et al., 2016; Laney et al.,
2010, 2017; Miller et al., 1998), metal
(Hessel et al., 1988; Hnizdo and SluisCremer, 1993; Nelson, 2013), and
nonmetal miners such as silica plant
and ground silica mill workers,
whetstone cutters, and silica flour
packers (Mohebbi and Zubeyri, 2007;
NIOSH 2000a,b; Ogawa et al., 2003a).
Accordingly, it is important to limit
higher exposures to respirable
crystalline silica in order to minimize
the risk of rapid progressive
pneumoconiosis (RPP) in miners.
The results of many surveillance
studies conducted by NIOSH as part of
the Coal Workers’ Health Surveillance
Program indicate that the pathology of
pneumoconiosis in coal miners has
changed over time, in part due to
increased exposure to respirable
crystalline silica. The studies of Cohen
et al. (2016, 2022) indicate that a RPP
develops due to increased exposure to
respirable crystalline silica among
contemporary coal miners as compared
to historical coal miners. Through the
examination of pathologic materials
from 23 contemporary (born in or after
1930) and 62 historical coal miners
(born between 1910 and 1930) with
severe pneumoconiosis, who were
autopsied as part of NCWAS, Cohen et
al. (2022) found a significantly higher
proportion of silica-type PMF among
contemporary miners (57 percent vs. 18
percent, p <0.001). They also found that
mineral dust alveolar proteinosis
(MDAP) was more common in the
current generation of miners and that
the lung tissues of contemporary coal
miners contained a significantly greater
percentage and concentration of silica
particles than those of past generations
of miners.
c. Occupation-Based Epidemiological
Studies
MSHA reviewed the occupation-based
epidemiological literature (i.e., studies
that examine health outcomes among
workers and their potential association
with conditions in the workplace).
MSHA’s review included the
occupation-based literature OSHA cited
in developing its respirable crystalline
silica standard (OSHA, 2013b). Overall,
OSHA found substantial evidence
suggesting that occupational exposure to
respirable crystalline silica increases the
risk of silicosis, and MSHA concurs
with this conclusion. MSHA also
reviewed additional occupation-based
literature specific to respirable
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crystalline silica exposure in MNM and
coal miners and preliminarily concludes
that respirable crystalline silica
exposure increases the risk of silicosis
morbidity and early mortality. One
study examined the acute and
accelerated silicosis outbreak that
occurred during and after construction
of Hawk’s Nest Tunnel in West Virginia
from 1930 to 1931. There, an estimated
2,500 men worked in a tunnel drilling
rock consisting of 90 percent silica or
more. The study later estimated that at
least 764 of the 2,500 workers (30.6
percent) died from acute or accelerated
silicosis (Cherniack, 1986). There was
also high turnover among the tunnel
workers, with an average length of
employment underground of only about
2 months.
In a population of granite quarry
workers (mean length of employment:
23.4 years) exposed to an average
respirable crystalline silica
concentration of 480 mg/m3 (0.48 mg/
m3), 45 percent of those diagnosed with
simple silicosis showed radiological
progression of disease 2 to 10 years after
diagnosis (Ng et al., 1987a). Among a
population of gold miners, 92 percent
showed progression after 14 years
(Hessel et al., 1988). Chinese factory
workers and miners who were
categorized under the Chinese system of
X-ray classification as ‘‘suspected’’
silicosis cases (analogous to ILO 0/1)
had a progression rate to stage I
(analogous to ILO major category 1) of
48.7 percent, with an average interval of
about 5.1 years (Yang et al., 2006).
Strong evidence has shown that lung
function deteriorates more rapidly in
miners exposed to respirable crystalline
silica, especially in those with silicosis
(Hughes et al., 1982; Ng and Chan, 1992;
Malmberg et al., 1993; Cowie, 1998).
The rates of decline in lung function are
greater where disease shows evidence of
radiologic progression (Be´gin et al.,
1987; Ng et al., 1987a; Ng and Chan,
1992; Cowie, 1998). The average
deterioration of lung function exceeds
that in smokers (Hughes et al., 1982).
Blackley et al. (2015) found
progressive lung function impairment
across the range of radiographic
profusion of simple CWP in a cohort of
8,230 coal miners that participated in
the Enhanced Coal Workers’ Health
Surveillance Program from 2005 to
2013. There, 269 coal miners had
category 1 or 2 simple CWP. This study
also found that each increase in
profusion score was associated with
decreases in various lung function
parameters: 1.5 percent (95 percent CI,
1.0 percent–1.9 percent) in forced
expiratory volume in one second (FEV1)
percent predicted, 1.0 percent (95
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percent CI, 0.6 percent–1.3 percent)
forced vital capacity (FVC) percent
predicted, and 0.6 percent (95 percent
CI, 0.4 percent–0.8 FEV1/FVC).
Overall, MSHA preliminarily agrees
with OSHA’s conclusion that
substantial evidence suggests that
occupational exposure to respirable
crystalline silica increases the risk of
silicosis. MSHA also preliminarily
concludes that respirable crystalline
silica exposure increases the risk of
silicosis morbidity and early mortality
among miners.
d. Surveillance Data
In addition to occupation-based
epidemiological studies, MSHA
reviewed surveillance studies, which
provide and interpret data to facilitate
the prevention and control of disease,
and preliminarily finds that the
prevalence of silicosis generally
increases with duration of exposure
(work tenure). However, the available
statistics may underestimate silicosisrelated morbidity and mortality in
miners. For example, the following have
been reported: (1) misclassification of
causes of death (e.g., as TB, chronic
bronchitis, emphysema, or cor
pulmonale); (2) errors in recording
occupation on death certificates; and (3)
misdiagnosis of disease (Windau et al.,
1991; Goodwin et al., 2003; Rosenman
et al., 2003, Blackley et al., 2017).
Furthermore, chest X-ray findings may
lead to missed silicosis cases when
fibrotic changes in the lung are not yet
visible on chest X-rays. In other words,
silicosis may be present but not yet
detectable by chest X-ray, or may be
more severe than indicated by the
assigned profusion score (Craighead and
Vallyathan, 1980; Hnizdo et al., 1993;
Rosenman et al., 1997).
e. Pulmonary Tuberculosis
Finally, in addition to the relationship
between silica exposure and silicosis,
studies indicate a relationship between
silica exposure, silicosis, and
pulmonary TB. OSHA reviewed these
and concluded that silica exposure and
silicosis increase the risk of pulmonary
TB (Cowie, 1994; Hnizdo and Murray,
1998; teWaterNaude et al., 2006). MSHA
agrees with this conclusion.
Although early descriptions of dust
diseases of the lung did not distinguish
between TB and silicosis and most fatal
cases described in the first half of the
20th century were likely a combination
of silicosis and TB (Castranova et al.,
1996), more recent findings have
demonstrated that respirable crystalline
silica exposure, even without silicosis,
increases the risk of infectious (i.e.,
active) pulmonary TB (Sherson and
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Lander, 1990; Cowie, 1994; Hnizdo and
Murray, 1998; teWaterNaude et al.,
2006). These co-morbid conditions
hasten the development of respiratory
impairment and increased mortality risk
even beyond the risk in unexposed
persons with active TB (Banks, 2005).
Ng and Chan (1991) hypothesized that
silicosis and TB ‘‘act synergistically’’
(i.e., are more than additive) to increase
fibrotic scar tissue (leading to massive
fibrosis) or to enhance susceptibility to
active mycobacterial infection. The
authors found that lung fibrosis is
common to both diseases, and that both
diseases decrease the ability of alveolar
macrophages to aid in the clearance of
dust or infectious particles.
These findings are also supported by
new studies (Ndlovu et al., 2019; Oni
and Ehrlich, 2015) published since
OSHA’s review (2013b). Oni and
Ehrlich (2015) reviewed a case of silicoTB in a former gold miner with ILO
category 2/2 silicosis. Ndlovu et al.
(2019) found that in a study sample of
South African gold miners who had
died from causes other than silicosis
between 2005 and 2015, 33 percent of
men (n = 254) and 43 percent of women
(n = 29) at autopsy were found to have
TB, whereas 7 percent of men (n = 54)
and 3 percent of women (n = 4) were
found to have pulmonary silicosis.
Overall, MSHA agrees with OSHA’s
conclusion that silica exposure
increases the risk of pulmonary TB and
that pulmonary TB is a complication of
chronic silicosis.
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2. Nonmalignant Respiratory Disease
(Excluding Silicosis)
In addition to causing silicosis (acute
silicosis, accelerated silicosis, simple
chronic silicosis, and PMF), exposure to
respirable crystalline silica causes other
NMRD. NMRD includes emphysema
and chronic bronchitis, which are both
diagnoses within the category of COPD.
Patients with COPD may have chronic
bronchitis, emphysema, or both (ATS,
2010a).
Based on its review of the literature,
MSHA preliminarily concludes that
exposure to respirable crystalline silica
increases the risk for mortality from
NMRD. The following summarizes
MSHA’s review of the literature.
a. Emphysema
Emphysema involves the destruction
of lung architecture in the alveolar
region, causing airway obstruction and
impaired gas exchange. In its literature
review, OSHA (2013b) concluded that
exposure to respirable crystalline silica
can increase the risk of emphysema,
regardless of whether silicosis is
present. OSHA also concluded that this
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is the case for smokers and that smoking
amplifies the effects of respirable
crystalline silica exposure, increasing
the risk of emphysema. MSHA reviewed
the studies cited by OSHA and agrees
with its conclusion. The studies
reviewed are summarized below.
Becklake et al. (1987) determined that
a miner who had worked in a high dust
environment for 20 years had a greater
chance of developing emphysema than
a miner who had never worked in a high
dust environment. In a retrospective
cohort study, Hnizdo et al. (1991a) used
autopsy lung specimens from 1,553
white gold miners to investigate the
types of emphysema caused by
respirable crystalline silica and found
that the occurrence of emphysema was
related to both smoking and dust
exposure. This study also found a
significant association between
emphysema (both panacinar and
centriacinar emphysema types) and
length of employment for miners
working in high dust occupations. A
separate study by Hnizdo et al. (1994)
on life-long non-smoking South African
gold miners found that the degree of
emphysema was significantly associated
with the degree of hilar gland nodules,
which the authors suggested might serve
as a surrogate for respirable crystalline
silica exposure. While Hnizdo et al.
(2000) conversely found that
emphysema prevalence was decreased
in relation to dust exposure, the authors
suggested that selection bias was
responsible for this finding.
The findings of several cross-sectional
and case-control studies discussed in
the OSHA (2013b) Health Effects
Literature were more mixed. For
example, de Beer et al. (1992) found an
increased risk for emphysema; however,
the reported odds ratio (OR) was smaller
than previously reported by Becklake et
al. (1987).
The OSHA (2013b) Health Effects
Literature also recognized that several of
the referenced studies (Becklake et al.,
1987 Hnizdo et al., 1994) found that
emphysema might occur in respirable
crystalline silica-exposed workers who
did not have silicosis and suggested a
causal relationship between respirable
crystalline silica exposure and
emphysema. Experimental (animal)
studies found that emphysema occurred
at lower respirable crystalline silica
exposure concentrations than fibrosis in
the airways or the appearance of early
silicotic nodules (Wright et al., 1988).
These findings tended to support
human studies that respirable
crystalline silica-induced emphysema
can occur absent signs of silicosis.
Green and Vallyathan (1996) reviewed
several studies of emphysema in
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workers exposed to silica and found an
association between cumulative dust
exposure and death from emphysema.
The IARC (1997) also reviewed several
studies and concluded that exposure to
respirable crystalline silica increases the
risk of emphysema. Finally, NIOSH
(2002b) concluded in its Hazard Review
that occupational exposure to respirable
crystalline silica is associated with
emphysema. However, some
epidemiological studies suggested that
this effect might be less frequent or
absent in non-smokers.
Overall, MSHA agrees with OSHA
that exposure to respirable crystalline
silica causes emphysema even in the
absence of silicosis.
b. Chronic Bronchitis
Chronic bronchitis is long-term
inflammation of the bronchi, increasing
the risk of lung infections. This
condition develops slowly by small
increments and ‘‘exists’’ when it reaches
a certain stage (i.e., the presence of a
productive cough sputum production
for at least 3 months of the year for at
least 2 consecutive years) (ATS, 2010b).
OSHA considered many studies that
examined the association between
respirable crystalline silica exposure
and chronic bronchitis, concluding the
following: (1) exposure to respirable
crystalline silica causes chronic
bronchitis regardless of whether
silicosis is present; (2) an exposureresponse relationship may exist; and (3)
smokers may be at an increased risk of
chronic bronchitis compared to nonsmokers. MSHA has reviewed the
literature and agrees with OSHA’s
conclusions.
Miller et al. (1997) reported a 20
percent increased risk of chronic
bronchitis in a British mining cohort
compared to the disease occurrence in
the general population. Using British
pneumoconiosis field research data,
Hurley et al. (2002) calculated estimates
of mixed-RCMD-related disease in
British coal miners at exposure levels
that were common in the late 1980s and
related their lung function and
development of chronic bronchitis with
their cumulative dust exposure. The
authors estimated that by the age of 58,
5.8 percent of these men would report
breathlessness for every 100 gram-hour/
m3 dust exposure. The authors also
estimated the prevalence of chronic
bronchitis at age 58 would be 4 percent
per 100 gram-hour/m3 of dust exposure.
These miners averaged over 35 years of
tenure in mining and a cumulative
respirable dust exposure of 132 gramhour/m3.
Cowie and Mabena (1991) found that
chronic bronchitis was present in 742 of
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1,197 (62 percent) black South African
gold miners, and Ng et al. (1992b) found
a higher prevalence of respiratory
symptoms, independent of smoking and
age, in Singaporean granite quarry
workers exposed to high levels of dust
(rock drilling and crushing) compared to
those exposed to low levels of dust
(maintenance and transport workers).
However, Irwig and Rocks (1978)
compared symptoms of chronic
bronchitis in silicotic and non-silicotic
South African gold miners and did not
find as clear a relationship as did the
above studies, concluding that the
symptoms were not statistically more
prevalent in the silicotic miners,
although prevalence was slightly higher.
Sluis-Cremer et al. (1967) found that
dust-exposed male smokers had a higher
prevalence of chronic bronchitis than
non-dust exposed smokers in a gold
mining town in South Africa. Similarly,
Wiles and Faure (1977) found that the
prevalence of chronic bronchitis rose
significantly with increasing dust
concentration and cumulative dust
exposure in South African gold miners
of smokers, nonsmokers, and exsmokers. Rastogi et al. (1991) found that
female grinders of agate stones in India
had a significantly higher prevalence of
acute bronchitis, but they had no
increase in the prevalence of chronic
bronchitis compared to controls
matched by socioeconomic status, age,
and smoking. However, the study noted
that respirable crystalline silica
exposure durations were very short, and
control workers may also have been
exposed to respirable crystalline silica.
Studies examining the effect of years
of mining on chronic bronchitis risk
were mixed. Samet et al. (1984) found
that prevalence of symptoms of chronic
bronchitis was not associated with years
of mining in a population of
underground uranium miners, even
after adjusting for smoking. However,
Holman et al. (1987) studied gold
miners in West Australia and found that
the prevalence of chronic bronchitis, as
indicated by ORs (controlled for age and
smoking), was significantly increased in
those that had worked in the mines for
over 1 year, compared to lifetime nonminers. In addition, while other studies
found no effect of years of mining on
chronic bronchitis risk, those studies
often qualified this result with possible
confounding factors. For example,
Kreiss et al. (1989) studied 281 hardrock (molybdenum) miners and 108
non-miner residents of Leadville,
Colorado. They did not find an
association between the prevalence of
chronic bronchitis and work in the
mining industry (Kreiss et al., 1989);
however, it is important to note that the
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mine had been temporarily closed for 5
months when the study began, so
miners were not exposed at the time of
the study.
The American Thoracic Society (ATS)
(1997) published a review finding
chronic bronchitis to be common among
worker groups exposed to dusty
environments contaminated with
respirable crystalline silica. NIOSH
(2002b) also published a review finding
that occupational exposure to respirable
crystalline silica has been associated
with bronchitis; however, some
epidemiological studies suggested this
effect might be less frequent or absent in
non-smokers.
Finally, Hnizdo et al. (1990) found an
independent exposure-response
relationship between respirable
crystalline silica exposure and impaired
lung function. For miners with less
severe impairment, the effects of
smoking and dust together were
additive. However, for miners with the
most severe impairment, the effects of
smoking and dust were synergistic (i.e.,
more than additive).
Overall, MSHA agrees with OSHA’s
conclusion that exposure to respirable
crystalline silica causes chronic
bronchitis regardless of whether
silicosis is present and that an exposureresponse relationship may exist.
c. Pulmonary Function Impairment
Pulmonary function impairment,
generally defined as reduction below
the lower limit of normal predicted by
reference equations (and in older
literature as less than 80 percent
predicted) of diffusion capacity for
carbon monoxide (DLCOcSB), total lung
capacity (TLC), FVC, or FEV1 is also a
common condition of NMRD. Based on
its review of the evidence in numerous
longitudinal and cross-sectional studies
and reviews, OSHA concluded that
there is an exposure-response
relationship between respirable
crystalline silica and the development
of impaired lung function. OSHA also
concluded that the effect of tobacco
smoking on this relationship may be
additive or synergistic, and workers
who were exposed to respirable
crystalline silica but did not show signs
of silicosis may also have pulmonary
function impairment. MSHA has
reviewed the studies cited by OSHA and
agrees with their conclusions.
OSHA reviewed several longitudinal
studies regarding the relationship
between respirable crystalline silica
exposure and pulmonary function
impairment. To evaluate whether
exposure to silica affects pulmonary
function in the absence of silicosis, the
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studies focused on workers who did not
exhibit progressive silicosis.
Among both active and retired
Vermont granite workers exposed to an
average quartz dust exposure level of 60
mg/m3, researchers found no exposurerelated decreases in pulmonary function
(Graham et al., 1981, 1994). However,
Eisen et al. (1995) found significant
pulmonary decrements among a subset
of granite workers who left work and
consequently did not voluntarily
participate in the last of a series of
annual pulmonary function tests
(termed ‘‘dropouts’’). This group
experienced steeper declines in lung
function compared to the subset of
workers who remained at work and
participated in all tests (termed
‘‘survivors’’), and these declines were
significantly related to dust exposure.
Exposure-related changes in lung
function were also reported in a 12-year
study of granite workers (Malmberg et
al., 1993), in two 5-year studies of South
African miners (Hnizdo, 1992; Cowie,
1998), and in a study of foundry
workers whose lung function was
assessed between 1978 and 1992
(Hertzberg et al., 2002). Similar
reductions in FEV1 (indicating an
airway obstruction) were linked to
respirable crystalline silica exposure.
Each of these studies reported their
findings in terms of rates of decline in
any of several pulmonary function
measures (e.g., FEV1, FVC, FEV1/FVC).
To put these declines in perspective,
Eisen et al. (1995) reported that the rate
of decline in FEV1 seen among the
dropout subgroup of Vermont granite
workers was 4 ml per 1,000 mg/m3-year
(4 ml per mg/m3-year) of exposure to
respirable granite dust. By comparison,
FEV1 declines at a rate of 10 ml/year
from smoking one pack of cigarettes
daily. From their study of foundry
workers, Hertzberg et al. (2002) reported
a 1.1 ml/year decline in FEV1 and a 1.6
ml/year decline in FVC for each 1,000
mg/m3-year (1 mg/m3-year) of respirable
crystalline silica exposure after
controlling for ethnicity and smoking.
From these rates of decline, they
estimated that exposure to 100 mg/m3 of
respirable crystalline silica for 40 years
would result in a total loss of FEV1 and
FVC that was less than, but still
comparable to, smoking a pack of
cigarettes daily for 40 years. Hertzberg et
al. (2002) also estimated that exposure
to the existing MSHA standard (100 mg/
m3) for 40 years would increase the risk
of developing abnormal FEV1 or FVC by
factors of 1.68 and 1.42, respectively.
OSHA reviewed cross-sectional
studies that described relationships
between lung function loss and
respirable crystalline silica exposure or
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exposure measurement surrogates (e.g.,
tenure). The results of these studies
were similar to those longitudinal
studies already discussed. In several
studies, respirable crystalline silica
exposure was found to reduce lung
function of:
• White South African gold miners
(Hnizdo et al., 1990),
• Black South African gold miners
(Cowie and Mabena, 1991; Irwig and
Rocks, 1978),
• Respirable crystalline silicaexposed workers in Quebec (Be´gin et
al., 1995),
• Rock drilling and crushing workers
in Singapore (Ng et al., 1992b),
• Granite shed workers in Vermont
(Theriault et al., 1974a, 1974b),
• Aggregate quarry workers and coal
miners in Spain (Montes et al., 2004a,
2004b),
• Concrete workers in the
Netherlands (Meijer et al., 2001),
• Chinese refractory brick
manufacturing workers in an iron-steel
plant (Wang et al., 1997),
• Chinese gemstone workers (Ng et
al., 1987b),
• Hard-rock miners in Manitoba,
Canada (Manfreda et al., 1982) and in
Colorado (Kreiss et al., 1989),
• Pottery workers in France
(Neukirch et al., 1994),
• Potato sorters in the Netherlands
(Jorna et al., 1994),
• Slate workers in Norway (Suhr et
al., 2003), and
• Men in a Norwegian community
with years of occupational exposure to
respirable crystalline silica (quartz)
(Humerfelt et al., 1998).
The OSHA (2013b) Health Effects
Literature recognized that many of these
studies found that pulmonary function
impairment: (1) can occur in respirable
crystalline silica-exposed workers
without silicosis, (2) was still observable
when controlling for silicosis in the
analysis, and (3) was related to the
magnitude and duration of respirable
crystalline silica exposure, rather than
to the presence or severity of silicosis.
Many other studies in the OSHA
(2013b) Health Effects Literature have
also found a relationship between
respirable crystalline silica exposure
and lung function impairment,
including IARC (1997), the ATS (1997),
and Hnizdo and Vallyathan (2003).
MSHA reviewed the studies and
agrees with OSHA’s finding that there is
an exposure-response relationship
between respirable crystalline silica and
the impairment of lung function. MSHA
also agrees with OSHA’s finding that the
effect of tobacco smoking on this
relationship may be additive or
synergistic, and that workers who were
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exposed to respirable crystalline silica,
but did not show signs of silicosis, may
also have pulmonary function
impairment.
3. Carcinogenic Effects
a. Lung Cancer
Lung cancer, an irreversible and
usually fatal disease, is a type of cancer
that forms in lung tissue. Agreeing with
the conclusion of other government and
public health organizations that
respirable crystalline silica is a ‘‘known
human carcinogen,’’ MSHA has
preliminarily found that the scientific
literature supports that respirable
crystalline silica exposure significantly
increases the risk of lung cancer
mortality among miners. This
determination is consistent with the
conclusions of other government and
public health organizations, including
the IARC (1997b, 2012), the NTP (2000,
2016), NIOSH (2002b), the ATS (1997),
and the American Conference of
Governmental Industrial Hygienists
(ACGIH®, (2010)). The Agency’s
determination is supported by
epidemiological literature,
encompassing more than 85 studies of
occupational cohorts from more than a
dozen industrial sectors including:
granite/stone quarrying and processing
(Carta et al., 2001; Attfield and Costello,
2004; Costello et al., 1995; Gue´nel et al.,
1989a,b), industrial sand (Sanderson et
al., 2000; Hughes et al., 2001; McDonald
et al., 2001, 2005; Rando et al., 2001;
Steenland and Sanderson, 2001), MNM
mining (Steenland and Brown, 1995a;
deKlerk and Musk, 1998; Roscoe et al.,
1995; Hessel et al., 1986, 1990; Hnizdo
and Sluis-Cremer, 1991; Reid and SluisCremer, 1996; Hnizdo et al., 1997; Chen
et al., 1992; McLaughlin et al., 1992;
Chen and Chen, 2002; Chen et al., 2006;
Schubauer-Berigan et al., 2009; Hua et
al., 1994; Meijers et al., 1991;
Finkelstein 1998; Chen et al., 2012; Liu
et al., 2017a; Wang et al., 2020a,b; Wang
et al., 2021), coal mining (Meijers et al.,
1988; Miller et al., 2007; Miller and
MacCalman, 2010; Miyazaki and Une,
2001; Graber et al., 2014a,b; Tomaskova
et al., 2012, 2017, 2020, 2022; Kurth et
al., 2020), pottery (Winter et al., 1990;
McLaughlin et al., 1992; McDonald et
al., 1995), ceramic industries
(Starzynski et al., 1996), diatomaceous
earth (Checkoway et al., 1993, 1996,
1997, 1999; Seixas et al., 1997; Rice et
al., 2001), and refractory brick
industries (cristobalite exposures) (Dong
et al., 1995).
The strongest evidence comes from
the worldwide cohort and case-control
studies reporting excess lung cancer
mortality among workers exposed to
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respirable crystalline silica in various
industrial sectors, confirmed by the 10cohort pooled case-control analysis by
Steenland et al. (2001a), the more recent
pooled case-control analysis of seven
European countries by Cassidy et al.
(2007), and two national death
certificate registry studies (Calvert et al.,
2003 in the United States; Pukkala et al.,
2005 in Finland).
Recent studies examined lung cancer
mortality among coal and non-coal
miners (Meijers et al., 1988, 1991;
Starzynski et al., 1996; Miyazaki and
Une, 2001; Tomaskova et al., 2012,
2017, 2020, 2022; Attfield and Kuempel,
2008; Graber et al., 2014a, 2014b; Kurth
et al., 2020; NIOSH, 2019a). These
studies also discuss the associations
between RCMD and respirable
crystalline silica exposures with lung
cancer in coal mining populations.
Furthermore, these newer studies are
consistent with the conclusion of
OSHA’s final Quantitative Risk
Assessment (QRA) (2016a) that
respirable crystalline silica is a human
carcinogen. MSHA preliminarily
concludes that miners, both MNM and
coal miners, are at risk of developing
lung cancer due to their occupational
exposure to respirable crystalline silica.
In addition, based on its review of the
literature, MSHA has preliminarily
determined that radiographic silicosis is
a marker for lung cancer risk. Reducing
exposure to levels that lower the
silicosis risk would reduce the lung
cancer risk to exposed miners
(Finkelstein, 1995, 2000; Brown, 2009).
MSHA has also found that, based on the
available epidemiological and animal
data, respirable crystalline silica causes
lung cancer (IARC, 2012; RTECS, 2016;
ATSDR, 2019). Miners who inhale
respirable crystalline silica over time are
at increased risk of developing silicosis
and lung cancer (Greaves, 2000; Erren et
al., 2009; Tomaskova et al., 2017, 2020,
2022).
Toxicity studies provide additional
evidence of the carcinogenic potential of
respirable crystalline silica. Studies
using DNA exposed directly to freshly
fractured respirable crystalline silica
demonstrate the direct effect respirable
crystalline silica had on DNA breakage.
Cell culture research has investigated
the processes by which respirable
crystalline silica disrupt normal gene
expression and replication. Studies have
demonstrated that chronic inflammatory
and fibrotic processes resulting in
oxidative and cellular damage may lead
to neoplastic changes in the lung
(Goldsmith, 1997). In addition, the
biologically damaging physical
characteristics of respirable crystalline
silica and its direct and indirect
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genotoxicity (Schins et al., 2002; Borm
and Driscoll, 1996) support MSHA’s
preliminary determination that
respirable crystalline silica is an
occupational carcinogen.
MSHA determined these studies were
inconclusive in the context of this
rulemaking.
b. Cancers of Other Sites
In addition to lung cancer, OSHA
reviewed studies examining the
relationship between silica exposure
and cancers at other sites. MSHA notes
that OSHA reviewed these mortality
studies (e.g., cancer of the larynx and
the digestive system, including the
stomach and esophagus) and found that
studies suggesting a dose-response
relationship were too limited in terms of
size, study design, or potential for
confounding variables to be conclusive.
OSHA also pointed to the NIOSH
(2002b) silica (respirable crystalline
silica) hazard review, which concluded
that no association has been established
between respirable crystalline silica
exposure and excess mortality from
cancer at other sites. MSHA has
reviewed these studies and agrees with
OSHA’s conclusion. The following
summarizes the studies reviewed with
inconclusive findings.
OSHA considered several studies that
examined the relationship between
respirable crystalline silica exposures
and esophageal cancer and found that
the studies were limited in terms of size,
study design, or potential for
confounding variables. Three nested
case-control studies of Chinese workers
demonstrated a dose-response
association between increased risk of
esophageal cancer mortality and
respirable crystalline silica exposure
(Pan et al., 1999; Wernli et al., 2006; Yu
et al., 2005). Other studies (Tsuda et al.,
2001; Xu et al., 1996a) also indicated
elevated rates of esophageal cancer
mortality with respirable crystalline
silica exposure. However, OSHA noted
that confounding factors due to other
occupational exposures was possible.
Additionally, two large national
mortality studies in Finland and the
United States did not show a positive
association between respirable
crystalline silica exposure and
esophageal cancer mortality (Calvert et
al., 2003; Weiderpass et al., 2003).
MSHA agrees with OSHA’s conclusion
that the literature does not support
attributing increased esophageal cancer
mortality to exposure to respirable
crystalline silica.
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(1) Laryngeal Cancer
Three lung cancer studies
(Checkoway et al., 1997; Davis et al.,
1983; McDonald et al., 2001) included
in OSHA’s health literature review
suggest an association between
respirable crystalline silica exposure
and increased mortality from laryngeal
cancer. However, a small number of
cases were reported and researchers
were unable to determine a statistically
significant effect. Therefore, there is
little evidence of an association based
on these studies.
(2) Gastric (Stomach) Cancer
OSHA reviewed several studies in its
2013b health literature review to assess
a potential relationship between
respirable crystalline silica exposures
and stomach cancers. OSHA’s literature
review noted observations made
previously by Cocco et al. (1996) and in
the NIOSH respirable crystalline silica
hazard review (2002b), which found
that most epidemiological studies of
respirable crystalline silica and stomach
cancer did not sufficiently adjust for the
effects of confounding factors. In
addition, some of these studies were not
properly designed to assess a doseresponse relationship (e.g., Finkelstein
and Verma, 2005; Moshammer and
Neuberger, 2004; Selikoff, 1978; Stern et
al., 2001) or did not demonstrate a
statistically significant dose-response
relationship (e.g., Calvert et al., 2003;
Tsuda et al., 2001). For these reasons,
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(3) Esophageal Cancer
(4) Other Sites
NIOSH (2002b) conducted a health
literature review of the health effects
potentially associated with respirable
crystalline silica exposure, which
identified only infrequent reports of
statistically significant excesses of
deaths for other cancers. Cancer studies
have been reported in the following
organs/systems: salivary gland, liver,
bone, pancreas, skin, lymphopoietic or
hematopoietic, brain, and bladder (see
NIOSH, 2002b for full bibliographic
references). However, the findings were
not observed consistently among
epidemiological studies, and NIOSH
(2002b) concluded that no association
has been established between these
cancers and respirable crystalline silica
exposure. OSHA concurred with NIOSH
that these isolated reports of excess
cancer mortality were insufficient to
determine the role of respirable
crystalline silica exposure.
Overall, OSHA concluded that
evidence of an association between
silica exposure and cancer at sites other
than the lungs is not sufficient. MSHA
agrees with OSHA’s conclusion.
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4. Renal Disease
Renal disease is characterized by the
loss of kidney function, and in the case
of ESRD, the need for a regular course
of long-term dialysis or a kidney
transplant. MSHA reviewed a wide
variety of longitudinal and mortality
epidemiological studies, including case
series, case-control, and cohort studies,
as well as case reports, and
preliminarily concludes that respirable
crystalline silica exposure increases the
risk of morbidity and/or mortality
related to ESRD. However, MSHA notes
that the available literature on respirable
crystalline silica exposures and renal
disease in coal miners is less conclusive
than the literature related to MNM
miners.
Epidemiological studies have found
statistically significant associations
between occupational exposure to
respirable crystalline silica and chronic
renal disease (e.g., Calvert et al., 1997),
sub-clinical renal changes, including
proteinuria and elevated serum
creatinine (e.g., Ng et al., 1992a; Hotz et
al., 1995; Rosenman et al., 2000), ESRD
morbidity (e.g., Steenland et al., 1990),
ESRD mortality (Steenland et al., 2001b,
2002a), and Wegener’s granulomatosis
(Nuyts et al., 1995) (severe injury to the
glomeruli that, if untreated, rapidly
leads to renal failure). The pooled
analysis conducted by Steenland et al.
(2002a) is particularly convincing
because it involved a large number of
workers from three combined cohorts
and had well-documented, validated job
exposure matrices. Steenland et al.
(2002a) found a positive and monotonic
exposure-response trend for both
multiple-cause mortality and underlying
cause data. MSHA has preliminarily
determined that the underlying data
from Steenland et al. (2002a) are
sufficient to provide useful estimates of
risk.
Possible mechanisms suggested for
respirable crystalline silica-induced
renal disease include: (1) a direct toxic
effect on the kidney, (2) a deposition in
the kidney of immune complexes (e.g.,
Immunoglobulin A (IgA), an antibody
blood protein) in the kidney following
respirable crystalline silica-related
pulmonary inflammation, and (3) an
autoimmune mechanism (Gregorini et
al., 1993; Calvert et al., 1997). Steenland
et al. (2002a) demonstrated a positive
exposure-response relationship between
respirable crystalline silica exposure
and ESRD mortality.
Overall, MSHA preliminarily
determines that respirable crystalline
silica exposure in mining increases the
risk of renal disease.
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5. Autoimmune Disease
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Autoimmune diseases occur when the
immune system mistakenly attacks
healthy tissues within the body, causing
inflammation, swelling, pain, and tissue
damage. Examples include rheumatoid
arthritis (RA), systemic lupus
erythematosus (SLE), scleroderma, and
systemic sclerosis (SSc). Based on its
literature review, MSHA preliminarily
concludes that there is a causal
association between occupational
exposure to respirable crystalline silica
and the development of systemic
autoimmune diseases in miners.
However, no studies are available to
date that can be used to model
respirable crystalline silica-exposure
risk in a formal quantitative risk
analysis.
Wallden et al. (2020) found that
respirable crystalline silica exposure is
correlated with an increased risk of
developing ulcerative colitis, which
increases with duration of exposure
(work tenure) and the level of exposure.
This effect was especially significant in
men. Schmajuk et al. (2019) found that
RA was significantly associated with
coal mining and other non-coal
occupations exposed to respirable
crystalline silica. Finally, Vihlborg et al.
(2017) found a significant increased risk
of seropositive RA with high exposure
(>0.048 mg/m3) to respirable crystalline
silica dust when compared to
individuals with no or lower exposure
by examining detailed exposureresponse relationships across four
different respirable crystalline silica
dose groups (quartiles): <23 mg/m3, 24 to
35 mg/m3, 36 to 47 mg/m3, and >48 mg/
m3. However, these researchers did not
report the risk of sarcoidosis and
seropositive RA in relation to respirable
crystalline silica exposure using logistic
regressions resulting in models that
could be used in the risk assessment. In
addition, the meta-analysis of 19
published case-control and cohort
studies on scleroderma by Rubio-Rivas
et al. (2017) found statistically
significant risks among individuals
exposed to respirable crystalline silica,
solvents, silicone, breast implants,
epoxy resins, pesticides, and welding
fumes, but did not provide detailed
quantitative exposure information.
C. Conclusion
MSHA preliminarily concludes that
occupational exposure to respirable
crystalline silica causes silicosis (acute
silicosis, accelerated silicosis, simple
chronic silicosis, and PMF), NMRD
(including COPD), lung cancer, and
kidney disease. Each of these effects is
exposure-dependent, chronic,
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irreversible, potentially disabling, and
can be fatal. MSHA suspects that
respirable crystalline silica exposure is
also linked to the development of some
autoimmune disorders through
inflammation pathways.
The scientific literature (including
peer-reviewed medical, toxicological,
public health, and other related
disciplinary publications) is robust and
compelling. It shows that miners
exposed to the existing respirable
crystalline silica limit of 100 mg/m3 still
have an unacceptable amount of excess
risk for developing and dying from
diseases related to occupational
respirable crystalline silica exposures
and still suffer material impairments of
health or functional capacity.
VI. Preliminary Risk Analysis
Summary
MSHA’s preliminary risk analysis
(PRA) quantifies risks associated with
five specific health outcomes identified
in the separate, standalone Health
Effects document: silicosis morbidity
and mortality, and mortality from
NMRD, lung cancer, and ESRD. The
standalone document, entitled
Preliminary Risk Analysis (PRA
document), has been placed into the
rulemaking docket for the MSHA
respirable crystalline silica rulemaking
(RIN 1219–AB36, Docket ID no. MSHA–
2023–0001) and is available on MSHA’s
website.
MSHA developed a PRA to support
the risk determinations required to set
an exposure limit for a toxic substance
under the Mine Act. MSHA’s PRA
quantifies the health risk to miners
exposed to respirable crystalline silica
under the existing exposure limits for
MNM and coal miners, at the proposed
PEL of 50 mg/m3, and at the proposed
action level of 25 mg/m3.
This analysis addresses three
questions related to the proposed rule:
(1) whether potential health effects
associated with existing exposure
conditions constitute material
impairment to any miner’s health or
functional capacity;
(2) whether existing exposure
conditions place miners at risk of
incurring any material impairment if
regularly exposed for the period of their
working life; and
(3) whether the proposed rule would
reduce those risks.
To answer these questions, MSHA
relied on the large body of research on
the health effects of respirable
crystalline silica and several published,
peer-reviewed, quantitative risk
assessments that describe the risk of
exposed workers to silicosis mortality
and morbidity, NMRD mortality, lung
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cancer mortality, and ESRD mortality.
These assessments are based on several
studies of occupational cohorts in a
variety of industrial sectors. The
underlying studies are described in the
Health Effects document and are
summarized in Section V. Health Effects
Summary of this preamble.
This summary highlights the main
findings from the PRA, briefly describes
how they were derived, and directs
readers interested in more detailed
information to corresponding sections of
the standalone PRA document.
A. Summary of MSHA’s Preliminary
Risk Analysis Process and Methods
MSHA evaluated the literature and
selected an exposure-response model for
each of the five health endpoints—
silicosis morbidity, silicosis mortality,
NMRD mortality, lung cancer mortality,
and ESRD mortality. The selected
exposure-response models were used to
estimate lifetime excess risks and
lifetime excess cases among the current
population of MNM and coal miners
based on real exposure conditions, as
indicated by the samples in the
compliance sampling datasets.
MSHA’s PRA is largely based on the
methodology and findings from a peerreviewed January 2013 OSHA
preliminary quantitative risk assessment
(PQRA) and associated analysis of
health effects in connection with
OSHA’s promulgation of a rule setting
PELs for workplace exposure to
respirable crystalline silica. OSHA’s
PQRA presented quantitative
relationships between respirable
crystalline silica exposure and multiple
health endpoints. Following multiple
legal challenges, the U.S. Court of
Appeals for the D.C. Circuit rejected
challenges to OSHA’s risk assessment
methodology and its findings on
different health risks. N. Am.’s Bldg.
Trades Unions v. OSHA, 878 F.3d 271,
283–89 (D.C. Cir. 2017).
MSHA’s PRA presents detailed
quantitative analyses of health risks
over a range of exposure concentrations
that have been observed in MNM and
coal mines. MSHA applied exposureresponse models to estimate the
respirable crystalline silica-related risk
of material impairment of health or
functional capacity of miners exposed to
respirable crystalline silica at three
levels—(1) the existing standards, (2)
the proposed PEL, and (3) the proposed
action level. As in past MSHA
rulemakings, MSHA estimated and
compared lifetime excess risks
associated with exposures at the
existing and proposed PEL (and at the
proposed action level) over a miner’s
full working life of 45 years.
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MSHA’s PRA is also based on a
compilation of miner exposure data to
respirable crystalline silica. For the
MNM sector, MSHA evaluated 57,769
valid respirable dust samples collected
between January 2005 and December
2019; and for the coal sector, MSHA
evaluated 63,127 valid respirable dust
samples collected between August 2016
and July 2021. The compiled data set
characterizes miners’ exposures to
respirable crystalline silica in various
locations (e.g., underground, surface),
occupations (e.g., drillers, underground
miners, equipment operators), and
commodities (e.g., metal, nonmetal,
stone, crushed limestone, sand and
gravel, and coal). MSHA enforcement
sampling indicates a wide range of
exposure concentrations. These include
exposures from below the proposed
action level (25 mg/m3) to above the
existing standards (100 mg/m3 in MNM
standards, 100 mg/m3 MRE in coal
standards, which is approximately 85.7
mg/m3 ISO).18
The primary results of the PRA are the
calculated number of deaths and
illnesses avoided assuming full
compliance after implementation of
MSHA’s proposed rule. These
calculations were performed for nonfatal silicosis illnesses (morbidity) and
for deaths (mortality) due to silicosis,
lung cancer, NMRD, and ESRD. For each
health outcome, the reduced number of
illnesses or deaths is calculated as the
difference between (a) the number of
illnesses and deaths currently occurring
in the industry, assuming mines fully
comply with the existing standards (100
mg/m3 for MNM and 85.7 mg/m3 ISO for
coal) and (b) the number of deaths and
illnesses expected to occur following
implementation of the proposed rule,
18 As discussed in the PRA, the existing PEL for
coal is 100 mg/m3 MRE, measured as a full-shift
time-weighted average (TWA). To calculate risks
consistently for both coal and MNM miners, the
PRA converts the MRE full-shift TWA
concentrations experienced by coal miners to ISO
8-hour TWA concentrations. (See Section 4 of the
PRA document for a full explanation.) The equation
used to convert MRE full-shift TWA concentrations
into ISO 8-hour TWA concentrations is:
ISO 8-hour TWA concentration = (MRE TWA) ×
(original sampling time)/(480 minutes) × 0.857
Exposures at TWA 100 mg/m3 MRE and SWA 85.7
mg/m3 ISO are only equivalent when the sampling
duration is 480 minutes (eight hours). However, for
the sake of simplicity and for comparison purposes,
the risk analysis approximates exposures at the
existing coal exposure limit of 100 MRE mg/m3 as
85.7 mg/m3 ISO. Thus, ISO concentration values
(measured as an 8-hour TWA) were used as the
exposure metric when (a) calculating risk under the
assumption of full compliance with the existing
standards and (b) calculating risk under the
assumption that no exposure exceeds the proposed
PEL of 50 mg/m3. To simulate compliance among
coal miners at the existing exposure limit,
exposures were capped at 85.7 mg/m3 measured as
an ISO 8-hour TWA.
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which includes a proposed PEL of 50
mg/m3 for a full shift exposure,
calculated as an 8-hour TWA.
Risks and cases were estimated under
two scenarios: (a) a Baseline scenario
where all exposures were capped at 100
mg/m 3 for MNM miners and at 85.7 mg/
m 3 for coal miners, and (b) a proposed
50 mg/m 3 scenario where all risks were
capped at the proposed PEL of 50 mg/m 3
for both MNM and coal miners. The
difference between the two scenarios
yields the estimated reduction in
lifetime excess risks and in lifetime
excess cases due to the proposed PEL.
To calculate risks, MSHA grouped
MNM miners into the following
exposure intervals: ≤25, >25 to ≤50, >50
to ≤100, >100 to ≤250, >250 to ≤500, and
>500 mg/m 3. MSHA grouped coal
miners into the following exposure
intervals: ≤25, >25 to ≤50, >50 to ≤85.7,
>85.7 to ≤100, >100 to ≤250, >250 to
≤500, and >500 mg/m 3. MSHA
calculated the median of all exposure
samples in each exposure interval and
assumed the population of miners is
distributed across the exposure intervals
in proportion to the number of exposure
samples from the compliance dataset in
each interval. Then, miners were
assumed to encounter constant exposure
at the median value of their assigned
exposure interval. MSHA adjusted the
annual cumulative exposure by a fulltime equivalency (FTE) factor to account
for the fact that miners may experience
more or less than 2,000 hours of
exposure per year. MSHA calculated the
FTE adjustment factor as the weighted
average of the production employee FTE
ratio (0.99 for MNM and 1.14 for coal)
and the contract miner FTE ratio (0.59
for MNM and 0.64 for coal), where the
weights are the number of miners
(150,928 for MNM production
employees, 60,275 for MNM contract
miners, 51,573 for coal production
employees, and 22,003 for coal contract
miners). For example, the weighted
average FTE ratio for MNM is (0.987 ×
150,928 + 0.591 × 60,275)/(150,928 +
60,275) = 0.87 and is (1.139 × 51,573 +
0.636 × 22,003)/(51,573 + 22,003) = 0.99
for coal.
MSHA calculated excess risk, which
refers to the additional risk of disease
and death attributable to exposure to
respirable crystalline silica. For silicosis
morbidity, MSHA used an exposureresponse model that directly yields the
accumulated or lifetime excess risk of
silicosis morbidity, assuming there is no
background rate 19 of silicosis in an
19 Here, the ‘‘background’’ risk (or rate) refers to
the risk of disease that the exposed person would
have experienced in the absence of exposure to
respirable crystalline silica. These background
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unexposed (i.e., non-miner) group. For
the four mortality endpoints (silicosis
mortality, lung cancer mortality, NMRD
mortality, and ESRD mortality), MSHA
used cohort life tables to calculate
excess risks, assuming all miners begin
working at age 21, retire at the end of
age 65, and do not live past age 80.
From the life tables, MSHA acquired the
lifetime mortality risk by summing the
miner cohort’s mortality risks in each
year from age 21 through age 80. Life
tables were also constructed for
unexposed (i.e., non-miner) groups
assumed to die from a given disease at
typical rates for the U.S. male
population. MSHA used 2018 data for
all males in the U.S. (published by the
National Center for Health Statistics,
2020b) to estimate (a) the diseasespecific mortality rates among
unexposed males and (b) the all-cause
mortality rates among both groups
(exposed miners and unexposed nonminers).
For a given scenario (either Baseline
or Proposed 50 mg/m3), MSHA
constructed life tables in the manner
described above, both for a miner cohort
exposed to respirable crystalline silica
and for an unexposed non-miner cohort.
MSHA calculated excess risk of the
disease as the difference between the
two cohorts’ disease-specific mortality
risk (due to silicosis, lung cancer,
NMRD, or ESRD). MSHA determined
the lifetime excess cases by multiplying
the lifetime excess risk by the number
of exposed miner FTEs (including both
production employee FTEs and contract
miner FTEs). Risks and cases were
calculated separately for each exposure
interval listed above. Then, the lifetime
excess cases were aggregated across all
exposure intervals. MSHA calculated
the final lifetime excess risks per 1,000
miners in the full population by
dividing the total number of lifetime
excess cases by the total number of
miners in the population (exposed at
any interval). Finally, to estimate the
risk reductions and avoided cases of
illness due to the proposed PEL, MSHA
compared the lifetime excess risks and
lifetime excess cases across the two
scenarios (Baseline and Proposed 50 mg/
m3).
B. Overview of Epidemiologic Studies
MSHA reviewed extensive research
on the health effects of respirable
crystalline silica and several
quantitative risk assessments published
in the peer-reviewed scientific literature
morbidity and mortality rates are measured using
the disease-specific rates among the general
population, which is not exposed to respirable
crystalline silica.
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many studies evaluated, MSHA believes
that the 13 studies used by OSHA
(2013b) to estimate risks provide
reliable estimates of the disease risk
posed by miners’ exposure to respirable
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crystalline silica. These studies are
summarized in Table VI–1.
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regarding occupational exposure risks of
illness and death from silicosis, NMRD,
lung cancer, and ESRD. The Health
Effects document describes the specific
studies reviewed by MSHA. Of the
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Of these 13 studies, OSHA selected
one per health endpoint for final
modeling and estimation of lifetime
excess risk and cases. Combining the
five selected studies with the observed
exposure data yields estimates of actual
lifetime excess risks and lifetime excess
cases among worker populations based
on real exposure conditions. Table VI–
2 presents the 13 studies from OSHA’s
PQRA, which MSHA has also
considered. MSHA evaluated the
evidence of OSHA’s analysis of the 13
studies and the accompanying risks
associated with exposure at 25, 50, 100,
250, and 500 mg/m3. Thorough
evaluation has led MSHA to determine
that the studies OSHA selected still
provide the best available
epidemiological models. However,
MSHA utilized the Miller and
MacCalman (2010) study to estimate
risks. This study was published after
OSHA completed much of its modeling
for their 2013 PRA (OSHA, 2013b). The
study was included in OSHA’s health
effects assessment and its PQRA. The
following lists the study used by MSHA
for each health endpoint:
Silicosis morbidity: Buchanan et al.
(2003);
Silicosis mortality: Mannetje et al.
(2002b);
NMRD mortality: Park et al. (2002);
Lung cancer mortality: Miller and
MacCalman (2010); and
ESRD mortality: Steenland et al.
(2002a).
MSHA developed its risk estimates
based on recent mortality data and using
certain assumptions that differed from
those used by OSHA, as explained in
the standalone PRA document.
Examples of these MSHA assumptions
include a lifetime that ends at age 80,
updated background mortality data and
all-cause mortality, miner population
sizes, and miner-specific full-time
equivalents (FTEs).20
MSHA’s modeling has been done
using life tables, in a manner consistent
with OSHA’s PQRA. In general, the life
table is a technique that allows
estimation of excess risk of diseasespecific mortality while factoring in the
probability of surviving to a particular
age assuming no exposure to respirable
crystalline silica. This analysis accounts
for competing causes of death,
background mortality rates of the
disease, and the effect of the
accumulation of risk due to elevated
mortality rates in each year of a working
life. For each cause of mortality, the
selected study was used in the life table
analysis to compute the increase in
miners’ disease-specific mortality rates
attributable to respirable crystalline
silica exposure.
MSHA uses cumulative exposure (i.e.,
cumulative dose) to characterize the
total exposure over a 45-year working
life. Cumulative exposure is defined as
the product of exposure duration and
exposure intensity (i.e., exposure level).
Cumulative exposure is the predictor
variable in the selected exposureresponse models.
20 FTEs were used to adjust the cumulative
exposure over a year based on the average number
of hours that miners work.
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For each health endpoint, MSHA
generated two sets of risk estimates—
one representing a scenario of full
compliance with the existing standards
(herein referred to as the ‘‘Baseline’’
scenario) and another representing a
scenario wherein no samples exceed the
proposed PEL (herein referred to as the
‘‘Proposed 50 mg/m3’’ scenario). In the
Baseline scenario, MNM miners in the
>100–250, >250–500, and >500 mg/m3
groups were assigned exposure
intensities of 100 mg/m3 ISO. Coal
miners in the 85.7–100, >100–250,
>250–500, and >500 mg/m3 groups were
assigned exposure intensities of 85.7 mg/
m3 ISO, calculated as an 8-hour TWA.
Exposure intensities were not changed
for miners with lower exposure
concentrations, because their exposures
were considered compliant with the
existing standards. A similar procedure
was used for the Proposed 50 mg/m3
scenario, except that each miner group
whose exposure exceeded the proposed
PEL was assigned a new exposure of 50
mg/m3 ISO (for both MNM and coal).
This process—of creating an exposure
profile based on actual exposure data
and modifying it based on the existing
standards or the proposed PEL—
allowed MSHA to estimate real
exposure conditions that miners would
encounter under each scenario, thereby
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enabling estimates of the actual excess
risks the current population of miners
would experience under each scenario
(Baseline and Proposed 50 mg/m3).
For purposes of calculating risk in the
PRA, both for MNM and coal miners,
MSHA estimated excess risks by using
the concentration collected over the full
shift and calculating it as a full-shift, 8hour TWA expressed in ISO standards.
This metric of exposure intensity—the
8-hour TWA concentration of respirable
crystalline silica in ISO standards—was
used consistently across all sets of
estimates (both MNM and coal sectors,
and both the Baseline and Proposed 50
mg/m3 scenarios), thereby facilitating
meaningful comparison. MSHA
acknowledges that this metric does not
correspond to the manner in which coal
exposure concentrations are calculated
for purposes of evaluating compliance
under the existing standard.
Nonetheless, MSHA believes that a fullshift, 8-hour TWA concentration
accurately represents risks to miners
and thus is the most appropriate
cumulative exposure metric for
computing risk given that FTEs were
used to scale exposure durations
relative to the assumption of 250 8-hour
workdays per year.
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C. Summary of Studies Selected for
Modeling
1. Silicosis Morbidity
Due to the long latency periods
associated with chronic silicosis,
OSHA’s respirable crystalline silica
standard relied on the subset of studies
that were able to contact and evaluate
many workers through retirement.
MSHA agrees that relying on studies
that included retired workers comes
closest to characterizing lifetime risk of
silicosis morbidity.
The health endpoint of interest in
these studies was the appearance of
opacities on chest radiographs
indicative of pulmonary
pneumoconiosis (a group of lung
diseases caused by the lung’s reaction to
inhaled dusts). The most reliable
estimates of silicosis morbidity, as
detected by chest X-rays, come from the
studies that evaluated those X-rays over
time, included radiographic evaluation
of workers after they left employment,
and derived cumulative or lifetime
estimates of silicosis disease risk.
To describe the presence and severity
of pneumoconiosis, including silicosis,
the International Labour Organization
(ILO) developed a standardized system
to classify lung opacities identified on
chest radiographs (X-rays) (ILO, 1980,
2002, 2011, 2022). The ILO system
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grades the size, shape, and profusion of
opacities. Although silicosis is defined
and categorized based on chest X-ray,
the X-ray is an imprecise tool for
detecting pulmonary pneumoconiosis
(Craighead and Vallyathan, 1980;
Hnizdo et al., 1993; Rosenman et al.,
1997; Cohen and Velho, 2002). Hnizdo
et al. (1993) recommended that an ILO
category 0/1 (or greater) should be
considered indicative of silicosis among
workers exposed to high respirable
crystalline silica concentrations. They
noted that the sensitivity of the chest Xray as a screening test increases with
disease severity and to maintain high
specificity, category 1/0 (or 1/1) chest Xrays should be considered as a positive
diagnosis of silicosis for miners who
work in low dust occupations (Hnizdo
et al., 1993). MSHA, consistent with
NIOSH’s use of chest X-rays in their
occupational respiratory disease
surveillance program (NIOSH 2014b),
agrees that a small opacity profusion
score of 1/0 is consistent with chronic
silicosis stage 1. Most of the studies
reviewed by MSHA considered a
finding consistent with an ILO category
of 1/1 or greater to be a positive
diagnosis of silicosis, although some
also considered an X-ray classification
of 1/0 or 0/1 to be positive. The low
sensitivity of chest radiography to detect
minimal silicosis suggests that risk
estimates derived from radiographic
evidence likely underestimate the true
risk of this disease (Craighead and
Vallyathan, 1980; Hnizdo et al., 1993;
Rosenman et al., 1997; Cohen and
Velho, 2002).
OSHA summarized the Miller et al.
(1995, 1998) and Buchanan et al. (2003)
papers in their final respirable
crystalline silica standard in 2016
(OSHA 2016a, 81 FR 16286, 16316).
These researchers reported on a 1991
follow-up study of 547 survivors of a
1,416-member cohort of Scottish coal
workers from a single mine. These men
had all worked in the mine during the
period between early 1971 and mid1976, during which time they had
experienced ‘‘unusually high
concentrations of freshly cut quartz in
mixed coal mine dust.’’ The
population’s exposures to quartz dust
had been measured in unique detail for
a considerable proportion of the men’s
working lives (OSHA 2013b, page 333).
The 1,416 men had previous chest Xrays dating from before, during, or just
after this high respirable crystalline
silica exposure period. Of these 1,416
men, 384 were identified as having died
by 1990/1991. Of the 1,032 remaining
men, 156 were untraced, and, of the 876
who were traced and replied, 711 agreed
to participate in the study. Of these, the
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total number of miners who were
surveyed was 551. Four of these were
omitted, two because of a lack of an
available chest X-ray. The 547 surviving
miners (age range: 29–85 years, average
= 59 years) were interviewed and
received their follow-up chest X-rays
between November 1990 and April
1991. The interviews consisted of
questions on current and past smoking
habits and occupational history since
leaving the coal mine, which closed in
1981. They were also asked about
respiratory symptoms and were given a
spirometry test (OSHA 2013b, pages
333–334).
Exposure characterization was based
on extensive respirable dust sampling;
samples were analyzed for quartz
content by IR spectroscopy. Between
1969 and 1977, two coal seams were
mined. One had produced quarterly
average concentrations of respirable
crystalline silica much less than 1,000
mg/m3 (only 10 percent exceeded 300
mg/m3). The other more unusual seam
(mined between 1971 and 1976) lay in
sandstone strata and generated
respirable crystalline silica levels such
that quarterly average exposures
exceeded 1,000 mg/m3 (10 percent of the
quarterly measurements were over
10,000 mg/m3). Thus, this cohort study
allowed evaluation of the effects of both
higher and lower respirable crystalline
silica concentrations and exposure-rate
effects on the development of silicosis
(OSHA 2013b, page 334).
Three physicians read each chest film
taken during the current survey as well
as films from the surveys conducted in
1974 and 1978. Films from an earlier
1970 survey were read only if no films
were available from the subsequent two
surveys. Silicosis cases were identified
if the median classification of the three
readers indicated an ILO category of 1/
1 or greater (Miller et al, 1995, page 24),
plus a progression from the earlier
reading. Of the 547 men, 203 (38
percent) showed progression of at least
1 ILO category from the 1970s’ surveys
to the 1990–91 survey; in 128 of these
(24 percent) there was progression of 2
or more ILO categories. In the 1970s’
surveys, 504 men had normal chest Xrays; of these 120 (24 percent) acquired
an abnormal X-ray consistent with ILO
category 1/0 or greater at the follow-up.
Of the 36 men whose X-rays were
consistent with ILO category 1/0 or
greater in the 1970s’ surveys, 27 (75
percent) exhibited further progression at
the 1990/1991 follow-up. Only one
subject showed a regression from any
earlier reading, and that was slight, from
1/0 to 0/1. The earlier Miller et al.
(1995) report presented results for cases
classified as having X-ray films
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consistent with either 1/0+ and 2/1+
degree of profusion; the Miller et al.
(1998) analysis and the Buchanan et al.
(2003) re-analyses emphasized the
results from cases having X-rays
classified as 2/1+ (OSHA 2013b, page
334).
MSHA modeled the exposureresponse relationship by using
cumulative exposure expressed as gram/
m3-hours, assuming 2,000 work hours
per year and a 45-year working life (after
adjusting for full-time equivalents,
including production employees and
contract workers). MSHA estimated risk
at the existing standard assuming
cumulative exposure to 100 mg/m3 ISO
for MNM miners and 85.7 mg/m3 ISO
(100 mg/m3 MRE) for coal miners.
Respirable crystalline silica exposures
were calculated by commodity, and
median exposure values were used
within a variety of exposure intervals.
Risks were computed using a life table
methodology which iteratively updated
the survival, risk, and mortality rates
each year based on the results of the
preceding year. Covariates in the
regression included smoking, age,
amount of coal dust, and percent of
quartz in the coal dust during various
previous survey periods.
Both Miller et al. papers (1995, 1998)
presented the results of numerous
regression models, and they compared
the results of the partial regression
coefficients using Z statistics of the
coefficient divided by the standard
error. Also presented were the residual
deviances of the models and the
residual degrees of freedom. In the
introduction to the results section,
Miller et al. (1995) stated that, ‘‘in none
of the models fitted was there a
significant effect of smoking habit
(current, ex-smoker, and never smoker),
nor was there any evidence of any
difference between smoking groups in
their relationship of response with age.’’
They therefore presented the results of
the regression analyses without terms
for smoking effects (i.e., without
including smoking effects as a variable
in the final regression analysis, because
they found that smoking did not affect
the modeling results). The logistic
regression models developed by Miller
et al. (1995) included terms for
cumulative exposure and age. In their
later publication, Miller et al. (1998)
presented models similar to their 1995
report, but without the age variable.
Their logistic regression model A from
Table 7 of their report (page 56)
included only an intercept (¥4.32) and
the respirable crystalline silica (quartz)
cumulative exposure variable (0.416).
They estimated that respirable
crystalline silica exposure at an average
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concentration of 100 mg/m3 for 15 years
(2.6 gram/m3-hr assuming 1,750 hours
worked per year) would result in an
increased risk of silicosis (ILO > 2/1) of
5 percent (OSHA 2013b, page 334).
OSHA had a high degree of
confidence in the estimates of silicosis
morbidity risk from this Scotland coal
mine study. This was mainly because of
highly detailed and extensive exposure
measurements, radiographic records,
and detailed analyses of high exposurerate effects. However, in another paper,
Soutar et al. (2004) noted that: ‘‘If the
effects of silica vary according to the
conditions of exposure, these risks are
probably towards the high end of the
risk spectrum, since the silica was
freshly fractured from massive
sandstone, and not derived from dirt
bands where the quartz grains are aged
and accompanied by clay minerals’’
(OSHA 2013b, page 336). MSHA has
reviewed and agrees with OSHA’s
conclusion.
Buchanan et al. (2003) provided an
analysis and risk estimates only for
cases having X-ray films consistent with
ILO category 2/1+ extent of profusion of
opacities, after adjusting for the
disproportionately severe effect of
exposure to high respirable crystalline
silica concentrations. Estimating the risk
of 1/0+ profusions from the Buchanan et
al. (2003) or the earlier Miller et al.
(1995, 1998) publications can only be
roughly approximated because of the
summary information included. Table 4
of Miller et al. (1998) (page 55) presents
a cross-tabulation of radiograph
progression, using the 12-point ILO
scale, from the last baseline exam to the
1990/1991 follow-up visit for the 547
men at the Scottish coal mine. From this
table, among miners having both early
X-ray films and follow-up films, 44 men
had progressed to 2/1+ by the last
follow-up and an additional 105 men
had experienced the onset of silicosis
(i.e., X-ray films were classified as 1/0,
1/1, or 1/2). Thus, by the time of the
follow-up, there were three times more
miners with silicosis consistent with
ILO category 1 than there were miners
with a category 2+ level of severity ((105
+ 44)/44 = 3.38). This suggests that the
Buchanan et al. (2003) model, which
reflects the risk of progressing to ILO
category 2+, underestimates the risk of
acquiring radiological silicosis by about
three-fold in this population (OSHA
2013b, page 336). This type of analysis
shows that the risk of developing
silicosis estimated from the Buchanan et
al. (2003) and Miller et al. (1998) studies
is of the same magnitude as the risks
reported by Hnizdo and Sluis-Cremer
(1993b) (OSHA 2013b, page 338).
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MSHA estimated silicosis risk by
using the Buchanan et al. (2003) model
that predicted the lifetime probability of
developing silicosis at the 2/1+ category
based on cumulative respirable
crystalline silica exposures. As
discussed previously, MSHA applied
the Buchanan et al. (2003) model,
assuming that miners are exposed for 45
years of working life extending from age
21 through age 65, using a life table
approach. Buchanan et al. provides an
exposure-response model using
cumulative exposure in mg/m3-hours as
the predictor variable and lifetime risk
of silicosis as the outcome variable.
MSHA assumed 45 years of exposure,
each such year having a duration of
2,000 work hours, scaled by a weighted
average FTE ratio that accounts for the
average annual hours worked by
production employees and contract
miners.
2. Accelerated Silicosis and Rapidly
Progressive Pneumoconiosis (RPP)
Study
OSHA concluded in their risk
assessment, and MSHA agrees, that
there is little evidence of a dose-rate
effect at respirable crystalline silica
concentrations in the exposure range of
25 mg/m3 to 500 mg/m3 (81 FR 16286,
16396). OSHA noted that the risk
estimates derived from the Buchanan et
al. (2003) study were not appreciably
different from those derived from the
other studies of silicosis morbidity (see
OSHA 2016a, 81 FR 16286, 16386; Table
VI–1. Summary of Lifetime or
Cumulative Risk Estimates for
Crystalline Silica). However, OSHA also
concluded that some uncertainty related
to dose-rate effects exists at
concentrations far higher than the
exposure range of interest. OSHA stated
that it is possible for such a dose-rate
effect to impact the results if not
properly addressed in study populations
with high concentration exposures.
OSHA used the model from the
Buchanan et al. (2003) study in its
silicosis morbidity risk assessment to
account for possible dose-rate effects at
high average concentrations (OSHA
2016a, 81 FR 16286, 16396 OSHA
2013b, pages 335–342). MSHA has
reviewed and agrees with OSHA’s
conclusions.
NIOSH stated in its post-hearing brief
to OSHA, that a ‘‘detailed examination
of dose rate would require extensive and
real time exposure history which does
not exist for silica (or almost any other
agent)’’ (81 FR 16285, 16375). Similarly,
Dr. Kenneth Crump, a researcher from
Louisiana Tech University Foundation
who served on OSHA’s peer review
panel for the Review of Health Effects
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Literature and Preliminary Quantitative
Risk Assessment, wrote to OSHA that,
‘‘[h]aving noted that there is evidence
for a dose rate effect for silicosis, it may
be difficult to account for it
quantitatively. The data are likely to be
limited by uncertainty in exposures at
earlier times, which were likely to be
higher’’ (OSHA 2016a, 81 FR 16286,
16375). OSHA agreed with the
conclusions of NIOSH and Dr. Crump.
OSHA believed that it used the best
available evidence to estimate risks of
silicosis morbidity and sufficiently
accounted for any dose rate effect at
high silica average concentrations by
using the Buchanan et al. (2003) study
as part of their final Quantitative Risk
Analysis (QRA) (OSHA 2016a, 81 FR
16286, 16396). MSHA has reviewed and
agrees with OSHA’s conclusions.
MSHA is using the Buchanan et al.
(2003) study to explain, in part, the
observed cases of progressive lung
disease in miners, known as RPP in coal
miners (Laney and Attfield, 2010; Wade
et al., 2010; Laney et al., 2012b; 2017;
Blackley et al., 2016b, 2018b; Reynolds
et al., 2018b; Halldin et al., 2019;
Halldin et al., 2020; Almberg et al.,
2018a; Cohen et al., 2022) and
accelerated silicosis in MNM miners
(Dumavibhat et al., 2013; Hessel et al.,
1988; Mohebbi and Zubeyri 2007). The
inclusion of this discussion in the risk
analysis is to describe research that
explains, in part, the progressive disease
observed in shorter-tenured miners.
MSHA believes that the risks estimated
by the Buchanan et al. model can be
applied to all mining populations that
have similar respirable crystalline silica
exposure exceedances. MSHA estimated
the increase of silicosis risk in miners
exposed to extreme respirable
crystalline silica exposures for varying
periods of time ranging from 0 hours to
348 hours per year (i.e., 0.0 percent to
20.0 percent of time at extreme
exposures). This information is
important because MSHA data indicate
that many miners’ respirable crystalline
silica exposure samples over the years
have exceeded the existing exposure
limit(s) of 100 mg/m3. MSHA data also
indicate that a smaller number of MSHA
samples showed respirable crystalline
silica concentrations well above the
existing MSHA standard of 100 mg/m3.
Over the last 15 years of MNM
compliance data, 188 samples (0.3
percent) were over 500 mg/m3; the upper
range of exposure was 4,289 mg/m3 ISO
(see PRA Table 4 of the PRA document).
Over the last 5 years of coal compliance
data, eight samples (<0.1 percent) were
over 500 mg/m3; the upper range of
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exposure was 791.4 mg/m3 MRE (see
PRA Table 7 of the PRA document).
Analysis provided by Buchanan et al.
(2003) provides strong evidence of an
exposure-rate effect for silicosis in a
British Pneumoconiosis Field Research
(PFR) coal mining cohort exposed to
high levels of respirable crystalline
silica over short periods of time (OSHA
2013b, page 335). Exposure was
categorized as pre- and post-1964, the
latter period being that of generally
higher quartz concentrations used to
estimate exposure-rate effects. For the
purpose of this analysis, the results
were presented for the 371 men (out of
the original 547) who were between the
ages of 50 and 74 at the time of the
1990/1991 follow-up, ‘‘since they had
experienced the widest range of quartz
concentrations and showed the
strongest exposure-response relations.’’
Thus, combined with their exposure
history, which went back to pre-1954,
many of these men had 30 to 40+ years
of highly detailed occupational
exposure histories available for analysis.
Of these 371 miners, there were 35 men
(9.4 percent) who had X-ray films
consistent with ILO category 2/1+, with
at least 29 of them having progressed
from less severe silicosis since the
previous follow-up during the 1970s
(from Miller et al., 1998) (OSHA 2013b,
page 335).
The Buchanan et al. (2003) re-analysis
presented logistic regression models in
stages. In the final stage of modeling,
using only the statistically significant
post-1964 cumulative exposures, the
authors separated these exposures into,
‘‘two quartz concentration bands,
defined by the cut-point 2.0 mg/m3.’’
This yielded the final simplified
equation, adapted from Buchanan et al.,
2003, page 162:
where p2 is the probability of profusion
category 2/1 or higher (2/1+) at followup and E is the cumulative exposure.
In this model, both the cumulative
exposure concentration variables were
‘‘highly statistically significant in the
presence of the other’’ (Buchanan et al.,
2003, page 162). Since these variables
were in the same units, mg/m3-hr, the
authors noted that the coefficient for
exposure concentrations >2,000 mg/m3
(≤2.0 mg/m3) was three times that for
the concentrations <2,000 mg/m3 (<2.0
mg/m3). They concluded that their latest
analysis showed that ‘‘the risk of
silicosis over a working lifetime can rise
dramatically with exposure to such high
concentrations over a timescale of
merely a few months’’ (Buchanan et al.,
2003, page 163, OSHA 2013b, page 336).
Buchanan et al. (2003) also used these
models to estimate the risk of acquiring
a chest X-ray classified as ILO category
2/1+, 15 years after exposure ends, as a
function of low <2,000 mg/m3 (<2.0 mg/
m3) and high >2,000 mg/m3 (≤2.0 mg/m3)
quartz concentrations. OSHA chose to
use this model to estimate the risk of
radiological silicosis consistent with an
ILO category 2/1+ chest X-ray for
several exposure scenarios. They
assumed 45 years of exposure, 2,000
hours/year of exposure, and no
exposure above a concentration of 2,000
mg/m3 (2.0 mg/m3) (OSHA 2013b, page
336).
Buchanan et al. (2003) used these
models to estimate the combined effect
on the predicted risk of low quartz
exposures (e.g., 100 mg/m3, equal to 0.1
mg/m3) and short-term exposures to
high quartz concentrations (e.g., 2,000
mg/m3, equal to 2 mg/m3). Predicted
risks were estimated for miners who
progressed to silicosis level 2/1+ 15
years after exposure ended. This
analysis showed the increase in
predicted risk with relatively short
periods of quartz exceedance exposures,
over 4, 8, and 12 months. Buchanan et
al. predicted a risk of 2.5 percent for 15
years quartz exposure to 100 mg/m3 (0.1
mg/m3). This risk increased to 10.6
percent with the addition of only 4
months of exposure at the higher
concentration. The risk increased
further to 72 percent with 12 months at
the higher exposure of 2,000 mg/m3 (2.0
mg/m3).
The results indicate miners exposed
to exceedances above MSHA’s existing
standard could develop progression of
silicosis at an exaggerated rate. The
results of Buchanan et al. also indicated
that miners’ exposure to exceedances at
MSHA’s proposed standard will also
suffer increased risk of developing
progressive disease, though at a reduced
rate (see Buchanan et al. (2003), Table
4, page 163).
MSHA used a life table approach to
estimate the lifetime excess silicosis
morbidity from age 21 to age 80,
assuming exposure from age 21 through
age 65 (45 years of working life) and an
additional 15 years of potential illness
progress thereafter. MSHA used the
Buchanan et al. (2003) model to
estimate the effect of respirable
crystalline silica exposure exceedances
as seen in MSHA’s compliance data on
miners’ silicosis risk at the existing and
proposed standard. The model
predicted the probability of developing
silicosis at the 2/1+ category based on
cumulative respirable crystalline silica
exposures. Age-specific cumulative risk
was estimated as 1/(1 + EXP(¥(¥4.83 +
0.443 * cumulative exposure))). The
model determined that even at 17.4
hours on average per year at an
exposure of 1,500 mg/m3 (1.50 mg/m3),
miners’ risk of developing 2/1+ silicosis
increased from a baseline of 24.8/1,000
to 29.0/1,000 at the existing standard
and 14/1,000 to 16.6/1,000 at the
proposed standard. Of course, the more
hours exposed to these levels of
respirable crystalline silica resulted in
even higher increased risk. It is
important to note that NIOSH’s X-ray
classification of the lowest case of
pneumoconiosis is 1/0 profusion of
small opacities (NIOSH 2008c, page A–
2). Using a case definition of level 2/1+,
the miners studied by Buchanan et al.
(2003) would be more likely to show
clinical signs of disease. MSHA
emphasizes the importance of
maintaining miner exposure to
respirable crystalline silica at or below
the proposed standard to minimize
these health risks as much as possible.
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3. Silicosis and NMRD Mortality
Silicosis mortality was ascertained in
the studies included in the pooled
analysis by Mannetje et al. (2002b).
These studies included cohorts of U.S.
diatomaceous earth workers
(Checkoway et al., 1997), Finnish
granite workers (Koskela et al., 1994),
U.S. granite workers (Costello and
Graham, 1988), U.S. industrial sand
workers (Steenland and Sanderson,
2001), U.S. gold miners (Steenland and
Brown (1995a), and Australian gold
miners (de Klerk et al., 1998). The
researchers analyzed death certificates
across all cohorts for cause of death.
OSHA relied upon the published, peerreviewed, pooled analysis of six
epidemiological studies first published
by Mannetje et al. (2002b) and a
sensitivity analysis of the data
conducted by ToxaChemica,
International, Inc. (2004). OSHA used
the model described by Mannetje et al.
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the silicosis misclassification that
results in underestimation of the
disease. NMRD also includes risks from
other lung diseases associated with
respirable crystalline silica exposures.
OSHA found the risk estimates derived
from Park et al. (2002) were important
to include in their range of estimates of
the risk of death from respirable
crystalline silica-related respiratory
diseases, including silicosis (OSHA
2013b, pages 297–298). OSHA
concluded that the ToxaChemica
International Inc. (2004) re-analysis of
Mannetje et al.’s (2002b) silicosis
mortality data and Park et al.’s (2002)
study of NMRD mortality provided a
credible range of estimates of mortality
risk from silicosis and NMRD across
many workplaces. The upper end of this
range, based on the Park et al. (2002)
study, is less likely to underestimate
risk because of underreporting of
silicosis mortality. However, risk
estimates from studies focusing on
cohorts of workers from different
industries cannot be directly compared
(OSHA 2016a, 81 FR 16286, 16397).
a. Silicosis Mortality: Mannetje et al.
(2002b); ToxaChemica, International,
Inc. (2004)
Mannetje et al. (2002b) relied upon
the epidemiological studies contained
within the Steenland et al. (2001a)
pooled analysis of lung cancer mortality
that also included extensive data on
silicosis. The six cohorts included:
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(1) U.S. diatomaceous earth workers
(Checkoway et al., 1997),
(2) Finnish granite workers (Koskela
et al., 1994),
(3) U.S. granite workers (Costello and
Graham, 1988),
(4) U.S. industrial sand workers
(Steenland and Sanderson, 2001),
(5) U.S. gold miners (Steenland and
Brown, 1995b), and
(6) Australian gold miners (de Klerk
and Musk, 1998).
These six cohorts contained 18,364
workers and 170 silicosis deaths, where
silicosis mortality was defined as death
from silicosis (ICD–9 502, n = 150) or
from unspecified pneumoconiosis (ICD–
9 505, n = 20). Table VI–3 provides
information on each cohort, including
size, time period studied, overall
number of deaths, and number of deaths
identified as silicosis for the pooled
analysis conducted by Mannetje et al.
(2002b). The authors believed this
definition to err on the side of caution
in that some cases of death from
silicosis in the cohorts may have been
misclassified as other causes (e.g.,
tuberculosis or COPD without mention
of pneumoconiosis). Four cohorts were
not included in the silicosis mortality
study. The three Chinese studies did not
use the ICD to code cause of death. In
the South African gold miner study,
silicosis was not generally recognized as
an underlying cause of death. Thus, it
did not appear on death certificates
(OSHA 2013b, page 292).
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(2002b) and the rate ratios that were
estimated from the ToxaChemica,
International Inc. sensitivity analysis to
estimate the risks of silicosis mortality.
This process better controlled for age
and exposure measurement uncertainty
(OSHA 2013b, page 295). MSHA has
reviewed and agrees with OSHA’s
conclusions. These studies are
summarized below, including detailed
discussion and analysis of uncertainty
in the studies and associated risk
estimates.
OSHA found that the estimates from
Mannetje et al. (2002b) and
ToxaChemica Inc. probably understated
the actual risk because silicosis is
underreported as a cause of death since
there is no nationwide system for
collecting silicosis morbidity case data
(OSHA 2016a, 81 FR 16286, 16325). To
help address this uncertainty, OSHA
also included an exposure-response
analysis of diatomaceous earth workers
(Park et al., 2002). This analysis better
recognized the totality of respirable
crystalline silica-related respiratory
disease than the datasets of Mannetje et
al. (2002b) and ToxaChemica
International Inc. (2004). Information
from the Park et al. (2002) study
(described in the next subsection) was
used to quantify the relationship
between cristobalite exposure and
mortality caused by NMRD, which
includes silicosis, pneumoconiosis,
emphysema, and chronic bronchitis.
The category of NMRD captures much of
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Mannetje et al. (2002a) described the
exposure assessments developed for the
pooled analysis. Exposure information
from each of the 10 cohort studies
varied and included dust measurements
representing particle counts, mass of
total dust, and respirable dust mass.
Measurement methods also changed
over time for each of the cohort studies.
Generally, sampling was performed
using impingers in earlier decades, and
gravimetric techniques later. Exposure
data based on analysis for respirable
crystalline silica by XRD (the current
method of choice) were available only
from the study of U.S. industrial sand
workers. To develop cumulative
exposure estimates for all cohort
members and to pool the cohort data, all
exposure data were converted to units of
mg/m3 (mg/m3) respirable crystalline
silica. Cohort-specific conversion factors
were generated based on the silica
content of the dust to which workers
were exposed. In some instances, results
of side-by-side comparison sampling
were available. Within each cohort,
available job- or process-specific
information on the silica composition or
nature of the dust was used to
reconstruct respirable crystalline silica
exposures. Most of the studies did not
have exposure measurements prior to
the 1950s. Exposures occurring prior to
that time were estimated either by
assuming such exposures were the same
as the earliest recorded for the cohort or
by modeling that accounted for
documented changes in dust control
measures.
To evaluate the reasonableness of the
exposure assessment for the lung cancer
pooled study, Mannetje et al. (2002a)
investigated the relationship between
silicosis mortality and cumulative
exposure. They performed a nested
case-control analysis for silicosis or
unspecified pneumoconiosis using
conditional logistic regression. Since
exposure to respirable crystalline silica
is the sole cause of silicosis, any finding
for which cumulative exposure was
unrelated to silicosis mortality risk
would suggest that serious
misclassification of the exposures
assigned to cohort members occurred.
Cases and controls were matched for
race, sex, age (within 5 years), and 100
controls were matched to each case.
Each cohort was stratified into quartiles
by cumulative exposure. Standardized
rate ratios (SRRs) were calculated using
the lowest-exposure quartile as the
baseline. Odds ratios (ORs) were also
calculated for the pooled data set
overall, which was stratified into
quintiles based on cumulative exposure.
For the pooled data set, the relationship
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between the ORs for silicosis mortality
and cumulative exposure, along with
each of the 95 percent confidence
intervals (95% CI), were as follows:
(1) 4,450 mg/m3-years (4.45 mg/m3years), OR=3.1 (95% CI: 2.5–4.0);
(2) 9,080 mg/m3-years (9.08 mg/m3years), OR=4.6 (95% CI: 3.6–5.9);
(3) 16,260 mg/m3-years (16.26 mg/m3years), OR=4.5 (95% CI: 3.5–5.8); and
(4) 42,330 mg/m3-years (42.33 mg/m3years), OR=4.8 (95% CI: 3.7–6.2).
In addition, in seven of the cohorts,
there was a statistically significant trend
between silicosis mortality and
cumulative exposure. For two of the
cohorts (U.S. granite workers and U.S.
gold miners), the trend test was not
statistically significant (p=0.10). An
analysis could not be performed on the
South African gold miner cohort
because silicosis was never coded as an
underlying cause of death, apparently
due to coding practices in that country.
Based on this analysis, Mannetje et al.
(2002a) concluded that the exposureresponse relationship for the pooled
data set was ‘‘positive and reasonably
monotonic.’’ That is, the response
increased with increasing exposure. The
results also indicated that the exposure
assessments provided reasonable
estimates of cumulative exposures. In
addition, despite some large differences
in the range of cumulative exposures
between cohorts, a clear positive
exposure-response trend was evident in
seven of the cohorts (OSHA 2013b, page
271).
Furthermore, in their pooled analysis
of silicosis mortality for six of the
cohorts, Mannetje et al. (2002b) found a
clear and consistently positive response
with increasing decile of cumulative
exposure, although there was an
anomaly in the 9th decile. Overall, these
data supported a monotonic exposureresponse relationship for silicosis. Thus,
although some exposure
misclassification almost certainly
existed in the pooled data set, the
authors concluded that exposure
estimates did not appear to have been
sufficiently misclassified to obscure an
exposure-response relationship (OSHA
2013b, page 271).
As part of an uncertainty analysis
conducted for OSHA, Drs. Steenland
and Bartell (ToxaChemica International,
Inc. 2004) examined the quality of the
original data set and analysis to identify
and correct any data entry,
programming, or reporting errors
(ToxaChemica International, Inc. 2004).
This quality assurance process revealed
a small number of errors in exposure
calculations for the originally reported
results. Primarily, these errors resulted
from rounding of job class exposures
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when converting the original data file
for use with a different statistical
program. Although the corrections
affected some of the exposure-response
models for individual cohorts,
ToxaChemica International, Inc. (2004)
reported that models based on the
pooled dataset were not impacted by the
correction of these errors (OSHA 2013b,
pages 271–272).
Silicosis mortality was evaluated
using standard life table analysis in
Mannetje et al. (2002b). Poisson
regression, using 10 categories of
cumulative exposure and adjusting for
age, calendar time, and cohort, was
conducted to derive silicosis mortality
rate ratios using the lowest exposure
group of 0–100 mg/m3-years (0–0.1 mg/
m3-year) as the referent group. More
detailed exploration of the exposureresponse relationship using a variety of
exposure metrics, including cumulative
exposure, duration of exposure, average
exposure (calculated as cumulative
exposure/duration), and the log
transformations of these variables, was
conducted via nested case-control
analyses (conditional logistic
regression). Each case was matched to
100 controls selected from among those
who had survived to at least the age of
the case, with additional matching on
cohort, race, sex, and date of birth
within 5 years. The authors explored
lags of 0, 5, 10, 15, and 20 years, noting
that there is no a priori reason to apply
an exposure lag, as silicosis can develop
within a short period after exposure.
However, a lag could potentially
improve the model, as there is often a
considerable delay in the development
of silicosis following exposure. In
addition to the parametric conditional
logistic regression models, the authors
performed some analyses using a cubicspline model, with knots at 5, 25, 50, 75,
and 95 percent of the distribution of
exposure. Models with cohort-exposure
interaction terms were fit to assess
heterogeneity between cohorts (OSHA
2013b, page 294).
The categorical analysis found a
nearly monotonic increase in silicosis
rates with cumulative exposure, from
4.7 per 100,000 person-years in the
lowest exposure category (0–990 mg/m3years [0–0.99 mg/m3-years]) to 299 per
100,000 person-years in the highest
exposure category (>28,000 mg/m3-years
[>28 mg/m3-years]). Nested case-control
analyses showed a significant
association between silicosis mortality
and cumulative exposure, average
exposure, and duration of exposure. The
best-fitting conditional logistic
regression model used log-transformed
cumulative exposure with no exposure
lag, with a model c2 of 73.2 versus c2
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values ranging from 19.9 to 30.9 for
average exposure, duration of exposure,
and untransformed cumulative exposure
(1 degree of freedom). No significant
heterogeneity was found between
individual cohorts for the model based
on log-cumulative exposure. The cubicspline model did not improve the model
fit for the parametric logistic regression
model using the log-cumulative
exposure (OSHA 2013b, page 294).
Mannetje et al. (2002b) developed
estimates of silicosis mortality risk
through age 65 for two levels of
exposure (50 and 100 mg/m3 respirable
crystalline silica), assuming a working
life of occupational exposure from age
20 to 65. Risk estimates were calculated
based on the silicosis mortality rate
ratios derived from the categorical
analysis described above. The period of
time over which workers’ exposures and
risks were calculated (age 20 to 65) was
divided into one-year intervals. The
mortality rate used to calculate risk in
any given interval was dependent on the
worker’s cumulative exposure at that
time. The equation used to calculate risk
is as follows:
Where timei is equal to one for every age
i, and ratei is the age-, calendar time-,
and cohort adjusted silicosis mortality
rate associated with the level of
cumulative exposure acquired at age i,
as presented in Mannetje et al. (2002b,
Table 2, page 725). The calculated
absolute risks equal the excess risks
since there is no background rate of
silicosis in the exposed population.
Mannetje et al. (2002b) estimated the
lifetime risk of death from silicosis,
assuming 45 years of exposure to 100
mg/m3, to be 13 deaths per 1,000
workers; at an exposure of 50 mg/m3, the
estimated lifetime risk was 6 per 1,000.
Confidence intervals (CIs) were not
reported (OSHA 2013b, page 295).
In summary, OSHA’s estimates of
silicosis morbidity risks were based on
studies of active and retired workers for
which exposure histories could be
constructed and chest X-ray films could
be evaluated for signs of silicosis. There
is evidence in the record that chest Xray films are relatively insensitive to
detecting lung fibrosis (OSHA 2016a, 81
FR 16286, 16397). MSHA agrees with
OSHA’s estimate of silicosis morbidity
risks.
Hnizdo et al. (1993a) found chest Xray films to have low sensitivity for
detecting lung fibrosis related to initial
cases of silicosis, compared to
pathological examination at autopsy. To
address the low sensitivity of chest Xrays for detecting silicosis, Hnizdo et al.
(1993a) recommended that radiographs
consistent with an ILO category of 0/1
or greater be considered indicative of
silicosis among workers exposed to a
high concentration of respirable
crystalline silica-containing dust. In like
manner, to maintain high specificity,
chest X-rays classified as category 1/0 or
1/1 should be considered as a positive
diagnosis of silicosis in miners who
work in low dust (0.2 mg/m3)
occupations. The studies on which
OSHA relied in its risk assessment
typically used an ILO category of 1/0 or
greater to identify cases of silicosis.
According to Hnizdo et al. (1993), they
were unlikely to have included many
false positives (i.e., assumed diagnosis
of silicosis in a miner without the
disease), but may have included false
negatives (i.e., failure to identify cases of
silicosis). Thus, in OSHA’s risk
assessment, the use of chest X-rays to
ascertain silicosis cases in the morbidity
studies may have underestimated risk
given the X-rays’ low sensitivity to
detect disease. MSHA agrees with
OSHA’s assessment.
To estimate the risk of silicosis
mortality at the existing and proposed
exposure limits, OSHA used the
categorical model described by
Mannetje et al. (2002b) but did not rely
upon the Poisson regression in their
study. Instead, OSHA used rate ratios
estimated from a nested case-control
design implemented as part of a
sensitivity analysis (ToxaChemica,
International, Inc. 2004). The casecontrol design was selected because it
was expected to better control for age.
In addition, the rate ratios derived from
the case control study were derived
from a Monte Carlo analysis to reflect
exposure measurement uncertainty (See
ToxaChemica, International, Inc. (2004),
Table 7, page 40). The rate ratio for each
interval of cumulative exposure was
multiplied by the annual silicosis rate
assumed to be associated with the
lowest exposure interval, 4.7 per
100,000 for exposures of 990 mg/m3years (0.99 mg/m3-years), to estimate the
silicosis rate for each interval of
exposure. The lifetime silicosis
mortality risk is the sum of the silicosis
rate for each year of life through age 85
and assuming exposure from age 20 to
65. From this analysis, OSHA estimated
the silicosis mortality risk for exposure
to the then existing general industry
exposure limit (100 mg/m3) and
proposed exposure limit (50 mg/m3) to
be 11 (95% CI 5–37) and 7 (95% CI 3–
21) deaths per 1,000 workers,
respectively. For exposure to 250mg/m3
(0.25 mg/m3) and 500 mg/m3 (0.5 mg/
m3), the range approximating the then
existing construction/shipyard exposure
limit, OSHA estimated the risk to range
from 17 (95% CI 5–66) to 22 (95% CI
6–85) deaths per 1,000 workers (OSHA
2013b, page 294–295).
In view of the foregoing discussion,
MSHA agrees with OSHA’s analysis,
and MSHA also selected the Mannetje et
al. (2002b) study for estimating silicosis
mortality risks and cases. MSHA used a
life table analysis to estimate the
lifetime excess silicosis mortality
through age 80. To estimate the agespecific risk of silicosis mortality at the
existing standards, the proposed PEL,
and the proposed action level, MSHA
used the same categorical model that
OSHA used in their PQRA (as described
above from Mannetje et al., 2002b;
ToxaChemica International, Inc. 2004)
to estimate lifetime risk following
cumulative exposure of 45 years. MSHA
used the 2018 all-cause mortality rates
(NCHS, Underlying Cause of Death,
2018 on CDC WONDER Online
Database, released in 2020b) as all-cause
mortality rates. As stated previously, the
general (unexposed) population is
assumed to have silicosis mortality rates
equal to zero.
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b. NMRD Mortality: Park et al. (2002)
In addition to causing silicosis,
exposure to respirable crystalline silica
causes increased risks of other NMRD.
These include chronic obstructive
pulmonary disease (COPD), which
includes chronic bronchitis,
emphysema, and combinations of the
two and is a cause of chronic airways
obstruction. COPD is characterized by
airflow limitation that is usually
progressive and not fully reversible.
OSHA reviewed several studies of
NMRD morbidity and used a study by
Park et al. (2002) to assess NMRD risk.
Checkoway et al. (1997) originally
studied a California diatomaceous earth
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cohort for which Park et al. (2002) then
analyzed the effect of respirable
crystalline silica exposures on the
development of NMRD. The authors
quantified the relationship between
exposure to cristobalite and mortality
from NMRD (OSHA 2013b, page 295).
The California diatomaceous earth
cohort consisted of 2,570 diatomaceous
earth workers employed for 12 months
or more from 1942 to 1994. As noted
above, Park et al. (2002) was interested
in the relationship between cristobalite
exposure and mortality from chronic
lung disease other than cancer (LDOC).
LDOC included chronic diseases such as
pneumoconiosis (which included
silicosis), chronic bronchitis, and
emphysema, but excluded pneumonia
and other infectious diseases. The
investigators selected LDOC as the
health endpoint for three reasons. First,
increased mortality from LDOC had
been documented among respirable
crystalline silica-exposed workers in
several industry sectors, including gold
mining, pottery, granite, and foundry
industries. Second, the authors pointed
to the likelihood that silicosis as a cause
of death is often misclassified as
emphysema or chronic bronchitis.
Third, the number of deaths from the
diatomaceous earth worker cohort that
were attributed to silicosis was too
small (10) for analysis. Industrial
hygiene data for the cohort were
available from the employer for total
dust, respirable crystalline silica (mostly
cristobalite), and asbestos. Smoking
information was available for about 50
percent of the cohort and for 22 of the
67 LDOC deaths available for analysis,
permitting Park et al. (2002) to partially
adjust for smoking (OSHA 2013b, pages
295–296).
Park et al. (2002) used the exposure
assessment previously reported by
Seixas et al. (1997) and used by Rice et
al. (2001) to estimate cumulative
respirable crystalline silica exposures
for each worker in the cohort based on
detailed work history files. The average
respirable crystalline silica
concentration for the cohort was 290 mg/
m3 (0.29 mg/m3) over the period of
employment (Seixas et al., 1997). The
total respirable dust concentration in
the diatomaceous earth plant was 3,550
mg/m3 (3.55 mg/m3) before 1949 and
declined by more than 10-fold after
1973, to 290 mg/m3 (0.29 mg/m3) (Seixas
et al., 1997). The concentration of
respirable crystalline silica in the dust
ranged from one to 25 percent and was
dependent on the location within the
worksite. It was lowest at the mine and
greatest in the plant where the raw ore
was calcined into final product. The
average cumulative exposure values for
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total respirable dust and respirable
crystalline silica were 7,310 mg/m3-year
(7.31 mg/m3-year) and 2,160 mg/m3-year
(2.16 mg/m3-year), respectively. The
authors also estimated cumulative
exposure to asbestos (OSHA 2013b, page
296).
Using Poisson regression models and
Cox’s proportional hazards models, the
authors fit the same series of relative
rate exposure-response models that
were evaluated by Rice et al. (2001) for
lung cancer (i.e., log-linear, log-square
root, log-quadratic, linear relative rate, a
power function, and a shape function).
In general form, the relative rate model
was:
Rate = exp(a0) × f(E),
where exp(a0) is the background rate
and E is the cumulative respirable
crystalline silica exposure. Park et al.
(2002) also employed an additive excess
rate model of the form:
Rate = exp(a0) + exp(aE).
Relative or excess rates were modeled
using internal controls and adjusting for
age, calendar time, ethnicity, and time
since first entry into the cohort. In
addition, relative rate models were
evaluated using age- and calendar timeadjusted external standardization to
U.S. population mortality rates for 1940
to 1994 (OSHA 2013b, page 296).
There were no LDOC deaths recorded
among workers having cumulative
exposures above 32,000 mg/m3-years (32
mg/m3-years), causing the response to
level off or decline in the highest
exposure range. The authors believed
the most likely explanation for this
observation (which was also observed in
their analysis of silicosis morbidity in
this cohort) was some form of survivor
selection, possibly smokers or others
with compromised respiratory function
leaving work involving extremely high
dust concentrations. These authors
suggested several alternative
explanations. First, there may have been
a greater depletion of susceptible
populations in high dust areas. Second,
there may have been greater
misclassification of exposures in the
earlier years where exposure data were
lacking (and when exposures were
presumably the highest) (OSHA 2013b,
pages 296–297).
Therefore, Park et al. (2002)
performed exposure-response analyses
that restricted the dataset to
observations where cumulative
exposures were below 10,000 mg/m3years (10 mg/m3-years). This is a level
more than four times higher than that
resulting from 45 years of exposure to
the former OSHA PEL for cristobalite
(which was 50 mg/m3 (0.05 mg/m3)
when cristobalite was the only
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polymorph present). These investigators
also conducted analyses using the full
dataset (OSHA 2013b, page 297).
Model fit was assessed by evaluating
the decrease in deviance resulting from
addition of the exposure term, and
cubic-spline models were used to test
for smooth departures from each of the
model forms described. Park et al.
(2002) found that both lagged and
unlagged models fit well, but unlagged
models provided a better fit. In addition,
they believed that unlagged models
were biologically plausible in that
recent exposure could contribute to
LDOC mortality. The Cox proportional
hazards models yielded results that
were similar to those from the Poisson
analysis. Consequently, only the results
from the Poisson analysis were reported.
In general, the use of external
adjustments for age and calendar time
yielded considerably improved fit over
models using internal adjustments. The
additive excess rate model also proved
to be clearly inferior compared to the
relative rate models. With one
exception, the use of cumulative
exposure as the exposure metric
consistently provided better fits to the
data than did intensity of exposure (i.e.,
cumulative exposure divided by
duration of exposure). As to the
exception, when the highest-exposure
cohort members were included in the
analysis, the log-linear model produced
a significantly improved fit with
exposure intensity as the exposure
metric, but a poor fit with cumulative
exposure as the metric (OSHA 2013b,
page 297).
Among the models based on the
restricted dataset (excluding
observations with cumulative exposures
greater than 10,000 mg/m3-years (10 mg/
m3-years)), the best-fitting model with a
single exposure term was the linear
relative rate model using external
adjustment. Most of the other singleterm models using external adjustment
fit almost as well. Of the models with
more than one exposure term, the shape
model provided no improvement in fit
compared with the linear relative rate
model. The log-quadratic model fit
slightly better than the linear relative
rate model, but Park et al. (2002) did not
consider the gain in fit sufficient to
justify an additional exposure term in
the model (OSHA 2013b, page 297).
Based on its superior fit to the cohort
data, Park et al. (2002) selected the
linear relative rate model with external
adjustment and use of cumulative
exposure as the basis for estimating
LDOC mortality risks among exposed
workers. Competing mortality was
accounted for using U.S. death rates
published by the National Center for
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Health Statistics (1996). The authors
estimated the lifetime excess risk for
white men exposed to respirable
crystalline silica (mainly cristobalite) for
45 years at 50 mg/m3 (0.05 mg/m3) to be
54 deaths per 1,000 workers (95% CI:
17–150) using the restricted dataset, and
50 deaths per 1,000 using the full
dataset. For exposure to 100 mg/m3 (0.1
mg/m3), they estimated 100 deaths per
1,000 using the restricted dataset, and
86 deaths per 1,000 using the full
dataset. The CIs were not reported
(OSHA 2013b, page 297).
The estimates of Park et al. (2002)
were about eight to nine times higher
than those that were calculated for the
pooled analysis of silicosis mortality
(Mannetje et al., 2002b). Also, these
estimates are not directly comparable to
those from Mannetje et al. (2002b)
because the mortality endpoint for the
Park et al. (2002) analysis was death
from all non-cancer lung diseases
beyond silicosis (including
pneumoconiosis, emphysema, and
chronic bronchitis). In the pooled
analysis by Mannetje et al. (2002b), only
deaths coded as silicosis or other
pneumoconiosis were included (OSHA
2013b, pages 297–298).
Less than 25 percent of the LDOC
deaths in the Park et al. (2002) analysis
were coded as silicosis or other
pneumoconiosis (15 of 67). As noted by
Park et al. (2002), it is likely that
silicosis as a cause of death is often
misclassified as emphysema or chronic
bronchitis (although COPD is part of the
spectrum of disease caused by
respirable crystalline silica exposure
and can occur in the absence of
silicosis). Thus, the selection of deaths
by Mannetje et al. (2002b) may have
underestimated the true risk of silicosis
mortality. The analysis by Park et al.
(2002) would have more fairly captured
the total respiratory mortality risk from
all non-malignant causes, including
silicosis and chronic obstructive
pulmonary disease. Furthermore, Park
et al. (2002) used untransformed
cumulative exposure in a linear model
compared to the log-transformed
cumulative exposure metric used by
Mannetje et al. (2002b). This would
have caused the exposure-response
relationship to flatten in the higher
exposure ranges (OSHA 2013b, page
298).
It is also possible that some of the
difference between Mannetje et al.’s
(2002b) and Park et al.’s (2002) risk
estimates reflected factors specific to the
nature of exposure among diatomaceous
earth workers (e.g., exposure to
cristobalite vs. quartz). However, neither
the cancer risk assessments nor
assessments of silicosis morbidity
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supported the hypothesis that
cristobalite is more hazardous than
quartz (OSHA 2013b, page 298).
Based on the available risk
assessments for silicosis mortality,
OSHA believed that the estimates from
the pooled study by Mannetje et al.’s
(2002b) represented those least likely to
overestimate mortality risk. It was
unlikely to have overstated silicosis
mortality risks given that the estimates
reflected only those deaths where
silicosis was specifically identified on
death certificates. Therefore, there was
most likely an underestimate of the true
silicosis mortality risk. In contrast, the
risk estimates provided by Park et al.
(2002) for the diatomaceous earth cohort
would have captured some of this
misclassification and included risks
from other lung diseases (e.g.,
emphysema, chronic bronchitis) that
have been associated with respirable
crystalline silica exposure. Therefore,
OSHA believed that the Park et al.
(2002) study provided a better basis for
estimating the respirable crystalline
silica-related risk of NMRD mortality,
including that from silicosis. Based on
Park et al.’s (2002) linear relative rate
model [RR = 1 + bx, where b = 0.5469
(no standard error reported) and x =
cumulative exposure], OSHA used a life
table analysis to estimate the lifetime
excess NMRD mortality through age 85.
For this analysis, OSHA used all-cause
and cause-specific background mortality
rates for all males (National Center for
Health Statistics, 2009). Background
rates for NMRD mortality were based on
rates for ICD–10 codes J40–J47 (chronic
lower respiratory disease) and J60–J66
(pneumoconiosis). OSHA believed that
these corresponded closely to the ICD–
9 disease classes (ICD 490–519) used by
the original investigators. According to
CDC (2001), background rates for
chronic lower respiratory diseases were
increased by less than five percent
because of the reclassification to ICD–
10. From the life table analysis, OSHA
estimated that the excess NMRD risk
due to respirable crystalline silica
exposure at the former general industry
PEL (100 mg/m3) and at OSHA’s final
PEL (50 mg/m3) for 45 years are 83 and
43 deaths per 1,000, respectively. For
exposure at the former construction/
shipyard exposure limit, OSHA
estimated that the excess NMRD risk
ranged from 188 to 321 deaths per 1,000
(OSHA 2013b, page 298).
Following its own independent
review, MSHA agrees with and has
followed the rationale presented by
OSHA in its selection of the Park et al.
(2002) model to estimate NMRD
mortality risk in miners. Coal miners
were not included in the NMRD
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mortality analysis because the endpoint
was included in the Quantitative Risk
Assessment in Support of the Final
Respirable Coal Mine Dust Rule (Dec.
2013).
MSHA used a life table analysis to
estimate the lifetime excess NMRD
mortality through age 80. MSHA used
the Park et al. (2002) model to estimate
age-specific NMRD mortality risk as 1 +
0.5469 * cumulative exposure. MSHA
used all-cause and cause-specific
background mortality rates for all males
for 2018 (National Center for Health
Statistics, Underlying Cause of Death
2018 on CDC WONDER Online
Database, released in 2020b).
Background rates for NMRD mortality
were based on rates for ICD–10 codes
J40–J47 (chronic lower respiratory
disease) and J60–J66 (pneumoconiosis).
4. Lung Cancer Mortality
Since the publication of OSHA’s final
rule in 2016, NIOSH has published two
documents concerning occupational
carcinogens, Chemical Carcinogen
Policy (2017b) and Practices in
Occupational Risk Assessment (2019a).
NIOSH will no longer set recommended
exposure levels for occupational
carcinogens. Instead, NIOSH intends to
develop risk management limits for
carcinogens (RML-Cas) to acknowledge
that, for most carcinogens, there is no
known safe level of exposure. An RML–
CA is a reasonable starting place for
controlling exposures. An RML–CA
limit is based on a daily maximum 8hour TWA concentration of a
carcinogen above which a worker
should not be exposed (NIOSH 2017b,
page vi). RML-Cas for occupational
carcinogens are established at the
estimated 95% lower confidence limit
on the concentration (e.g., dose)
corresponding to 1 in 10,000 (10¥4)
lifetime excess risk (when analytically
possible to measure) (NIOSH 2019a).
NIOSH stated that in order to
incrementally move toward a level of
exposure to occupational chemical
carcinogens that is closer to background,
NIOSH will begin issuing
recommendations for RML-Cas that
would advise employers to take
additional action to control chemical
carcinogens when workplace exposures
result in excess risks greater than 10¥4
(NIOSH 2017b, page vi).
MSHA used the Miller et al. (2007)
and Miller and MacCalman (2010)
studies to estimate lung cancer mortality
risk in miners. In British coal miners,
excess lung cancer mortality was
studied through the end of 2005 in a
cohort of 17,800 miners (Miller et al.,
2007; Miller and MacCalman, 2010). By
that time, the cohort had accumulated
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516,431 person-years of observation (an
average of 29 years per miner), with
10,698 deaths from all causes. Overall
lung cancer mortality was elevated
(Standard Mortality Ratio (SMR) =
115.7, 95% CI: 104.8–127.7), and a
positive exposure-response relationship
with respirable crystalline silica
exposure was determined from Cox
regression after adjusting for smoking
history. Three strengths of this study
were: 1) the detailed time-exposure
measurements of quartz and total mine
dust, 2) detailed individual work
histories, and 3) individual smoking
histories. For lung cancer, analyses
based on Cox regression provided strong
evidence that, for these coal miners,
although quartz exposures were
associated with increased lung cancer
risk, simultaneous exposures to coal
dust did not cause increased lung
cancer risk (OSHA 2016a, 81 FR 16286,
16308).
Miller et al. (2007) and Miller and
MacCalman (2010) conducted a followup study of cohort mortality, begun in
1970. Their previous report on mortality
presented a follow-up analysis on
18,166 coal miners from 10 British coal
mines followed through the end of 1992
(Miller et al., 1997). The two reports
from 2007 and 2010 analyzed the
mortality experience of 17,800 of these
miners (18,166 minus 346 men whose
vital status could not be determined)
and extended the analysis through the
end of 2005. Causes of deaths that were
of particular interest included
pneumoconiosis, other NMRD, lung
cancer, stomach cancer, and
tuberculosis. The researchers noted that
no additional exposure measurements
were included in the updated analysis,
since all the mines had closed by the
mid-1980s. However, some of these men
might have had additional exposure at
other mines or facilities not reported in
this study (OSHA 2013b, page 287).
This cohort mortality study included
analyses using both external and
internal controls. The external controls
used British administrative regional
age-, time-, and cause-specific mortality
rates from which to calculate SMRs. The
internal controls from the mines used
Cox proportional hazards regression
methods, which considered each
miner’s age, smoking status, and
detailed dust and respirable crystalline
silica (quartz) time-dependent exposure
measurements. Cox regression analyses
were done in stages, with the initial
analyses used to establish what factors
were required for baseline adjustment
(OSHA 2013b, page 287).
For the analysis using external
mortality rates, the all-cause mortality
SMR from 1959 through 2005 was 100.9
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(95% CI: 99.0–102.8), based on all
10,698 deaths. However, these SMRs
were not uniform over time. For the
period from 1990–2005, the SMR was
109.6 (95% CI:106.5–112.8), while the
ratios for previous periods were less
than 100. This pattern of increasing
SMRs in the recent past was also seen
for cause-specific deaths from chronic
bronchitis, SMR = 330.0 (95% CI:268.1–
406.2); tuberculosis, SMR = 193.4 (95%
CI: 86.9–430.5); cardiovascular disease,
SMR = 106.6 (95% CI: 102.0–111.5); all
cancers, SMR = 107.1 (95% CI:101.3–
113.2); and lung cancer, SMR = 115.7
(95% CI: 104.8–127.7). The SMR for
NMRD was 142.1 (95% CI: 132.9–152.0)
in this recent period and remained
highly statistically significant. In their
previous analysis on mortality from
lung cancer, reflecting follow-up
through 1995, Miller et al. (1997) had
not found any increase in the risk of
lung cancer mortality (OSHA 2013b,
page 287).
OSHA reported that Miller and
MacCalman (2010) used these analyses
to estimate relative risks for a lifetime
exposure of 5 gram-hours/m3 (ghm¥3) to
quartz (OSHA 2013b, page 288). This is
equivalent to approximately 55 mg/m3
(0.055 mg/m3) for 45 years, assuming
2,000 hours per year of exposure and/
or 100 ghm¥3 total dust. The authors
estimated relative risks (see Miller and
MacCalman (2010), Table 4, page 9) for
various causes of death including
pneumoconiosis, COPD, ischemic heart
disease, lung cancer, and stomach
cancer. Their results were based on
models with single exposures to dust or
respirable crystalline silica (quartz) or
simultaneous exposures to both, with
and without 15-year lag periods.
Generally, the risk estimates were
slightly greater using a 15-year lag
period.
For the models using only quartz
exposures with a 15-year lag,
pneumoconiosis, RR = 1.21 (95% CI:
1.12–1.31); COPD, RR = 1.11 (95% CI:
1.05–1.16); and lung cancer, RR = 1.07
(95% CI: 1.01–1.13) showed statistically
significant increased risks.
For lung cancer, analyses based on
these Cox regression methods provided
strong evidence that, for these coal
miners, quartz exposures were
associated with increased lung cancer
risk, but simultaneous exposures to coal
dust were not associated with increased
lung cancer risk. The relative risk (RR)
estimate for lung cancer deaths using
coal dust with a 15-year lag in the single
exposure model was 1.03 (95% CI: 0.96
to 1.10). In the model using both quartz
and coal mine dust exposures, the RR
based on coal dust decreased to 0.91,
while that for quartz exposure remained
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statistically significant, increasing to a
RR = 1.14 (95% CI: 1.04 to 1.25).
According to Miller and MacCalman
(2010), other analyses have shown that
exposure to radon or diesel fumes was
not associated with an increased cancer
risk among British coal miners (OSHA
2013b, page 288).
The RRs in the Miller and MacCalman
(2010) report were used to estimate
excess lung cancer risk for OSHA’s
purposes. Life table analyses were done
as in the other studies above. Based on
the RR of 1.14 (95% CI: 1.04–1.25) for
a cumulative exposure of 5 ghm10¥3,
the regression slope was recalculated as
b = 0.0524 per 1,000 mg-years (per mg/
m3-years) and used in the life table
program. Similarly, the 95-percent CI on
the slope was 0.0157–0.08926. From
this study, the lifetime (to age 85) risk
estimates for 45 years of exposure to 50
mg/m3 (0.05 mg/m3) and 100 mg/m3
(0.100 mg/m3) respirable crystalline
silica were 6 and 13 excess lung cancer
deaths per 1,000 workers, respectively.
These lung cancer risk estimates were
less by about 2- to 4-fold than those
estimated from the other cohort studies
described above.
However, three factors might explain
these differences. First, these estimates
were adjusted for individual smoking
histories so any smoking-related lung
cancer risk (or smoking–respirable
crystalline silica interaction) that might
possibly be attributed to respirable
crystalline silica exposure in the other
studies were not reflected in the risk
estimates derived from the study of
these coal miners. Second, these coal
miners had significantly increased risks
of death from other lung diseases, which
may have decreased the lung cancersusceptible population. Of note, for
example, were the higher increased
SMRs for NMRD during the years 1959–
2005 for this cohort (Miller and
MacCalman, 2010, Table 2, Page 7).
Third, the difference in risk seen in
these coal miners may have been the
result of differences in the toxicity of
quartz present in the coal mines as
compared to the work environments of
the other cohorts. One Scottish mine
(Miller et al., 1998) in this 10-mine
study had been cited as having
presented ‘‘unusually high exposures to
[freshly fractured] quartz.’’ However,
this was also described as an atypical
exposure among miners working in the
10 mines. Miller and MacCalman (2010)
stated that increased quartz-related lung
cancer risk in their cohort was not
confined to that Scottish mine alone.
They also stated, ‘‘The general nature of
some quartz exposures in later years
. . . may have been different from
earlier periods when coal extraction was
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largely manual . . .’’ (OSHA 2013b,
page 288).
All these factors in this mortality
analysis for the British coal miner
cohort could have combined to yield
lower lung cancer risk estimates.
However, OSHA believed that these coal
miner-derived estimates were credible
because of the quality of several study
factors relating to both study design and
conduct. In terms of design, the cohort
was based on union rolls with very good
participation rates and good reporting.
The study group also included over
17,000 miners, with an average of nearly
30 years of follow-up, and about 60
percent of the cohort had died. Just as
important was the high quality and
detail of the exposure measurements,
both of total dust and quartz. However,
one exposure factor that may have
biased the estimates upward was the
lack of exposure information available
for the cohort after the mines closed in
the mid-1980s. Since the death ratio for
lung cancer was higher during the last
study period, 1990–2005, this period
contributed to the increased lung cancer
risk. It is possible that any quartz
exposure experienced by the cohort
after the mines had closed could have
accelerated either death or malignant
tumor (lung cancer) growth. By not
accounting for this exposure, if there
were any, the risk estimates would have
been biased upwards. Although the 15year lag period for quartz exposure used
in the analyses provided slightly higher
risk estimates than use of no lag period,
the better fit seen with the lag may have
been artificial. This may have occurred
since there appeared to have been no
exposures during the recent period
when risks were seen to have increased
(OSHA 2013b, page 289).
OSHA believed, as does MSHA, that
this study of a large British coal mining
cohort provided convincing evidence of
the carcinogenicity of respirable
crystalline silica. This large cohort
study, with almost 30 years of followup, demonstrated a positive exposureresponse after adjusting for smoking
histories. Additionally, the authors state
that there was no evidence that
exposure to potential confounders such
as radon and diesel exhaust were
associated with excess lung cancer risk
(Miller and MacCalman (2010), page
270). MSHA is relying on the British
studies conducted by Miller et al. (2007)
as well as Miller and MacCalman (2010)
to estimate the lung cancer risk in all
miners.
MSHA found these two studies
suitable for use in the quantitative
characterization of health risks to
exposed miners for several reasons.
First, their study populations were of
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sufficient size to provide adequate
statistical power to detect low levels of
risk. Second, sufficient quantitative
exposure data were available over a
sufficient span of time to characterize
cumulative respirable crystalline silica
exposures of cohort members. Third, the
studies either adjusted for or otherwise
adequately addressed confounders such
as smoking and exposure to other
carcinogens. Finally, these investigators
developed quantitative assessments of
exposure-response relationships using
appropriate statistical models or
otherwise provided sufficient
information that permits MSHA to do
so.
MSHA implemented the risk model in
its life table analysis so that the use of
background rates of lung cancer and
assumptions regarding length of
exposure and lifetime were consistent
across models. Thus, MSHA was able to
estimate lung cancer risks associated
with exposure to specific levels of
respirable crystalline silica of interest to
the Agency. MSHA used the Miller et al.
(2007) and Miller and MacCalman
(2010) model to estimate age-specific
cumulative lung cancer mortality risk as
EXP(0.0524 * cumulative exposure),
lagged 15 years.
MSHA’s PRA uses risk estimates
derived from 10 coal mines in the U.K.
(Miller et al., 2007; Miller and
MacCalman, 2010). These investigators
developed regression analyses for timedependent estimates of individual
exposures to respirable dust. Their
analyses were based on the detailed
individual exposure estimates of the
PFR programme. To estimate mortality
risk for lung cancer from the pooled
cohort analysis, MSHA used the same
life table approach as OSHA. However,
for this life table analysis, MSHA used
2018 mortality rates for U.S. males (i.e.,
all-cause and background lung cancer).
The 2018 lung cancer death rates were
based on the ICD–10 classification of
diseases, C34.0, C34.2, C34.1, C34.3,
C34.8, and C34.9. Lifetime risk
estimates reflected excess risk through
age 80. To estimate lung cancer risks,
MSHA used the log-linear relative risk
model, exp(0.0524 × cumulative
exposure), lagged 15 years. The
coefficient for this model was 0.0524
(OSHA 2013b, page 290).
5. ESRD Mortality
Several epidemiological studies have
found statistically significant
associations between occupational
exposure to respirable crystalline silica
and renal disease, although others have
failed to find a statistically significant
association. These studies are discussed
in the Health Effects document. Possible
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mechanisms suggested for respirable
crystalline silica-induced renal disease
included a direct toxic effect on the
kidney, deposition of immune
complexes (IgA) in the kidney following
respirable crystalline silica-related
pulmonary inflammation, and an
autoimmune mechanism (Gregorini et
al., 1993; Calvert et al., 1997; Parks et
al., 1999; Steenland 2005b) (OSHA
2016a, 81 FR 16286, 16310).
MSHA, like OSHA, chose the
Steenland et al. (2002a) study to include
in the PRA. In a pooled cohort analysis,
Steenland et al. (2002a) combined the
industrial sand cohort from Steenland et
al. (2001b), the gold mining cohort from
Steenland and Brown (1995a), and the
Vermont granite cohort studies by
Costello and Graham (1988). All three
were included in portions of OSHA’s
PQRA for other health endpoints: under
lung cancer mortality in Steenland et al.
(2001a) and under silicosis mortality in
the related work of Mannetje et al.
(2002b). In all, the combined cohort
consisted of 13,382 workers with
exposure information available for
12,783. The analysis demonstrated
statistically significant exposureresponse trends for acute and chronic
renal disease mortality with quartiles of
cumulative respirable crystalline silica
exposure (OSHA 2016a, 81 FR 16286,
16310).
The average duration of exposure,
cumulative exposure, and concentration
of respirable crystalline silica for the
pooled cohort were 13.6 years, 1,200 mg/
m3-years (1.2 mg/m3-years), and 70 mg/
m3 (0.07 mg/m3), respectively. Renal
disease risk was most prevalent among
workers with cumulative exposures of
500 mg/m3 or more (Steenland et al.,
2002a). SMRs (compared to the U.S.
population) for renal disease (acute and
chronic glomerulonephritis, nephrotic
syndrome, acute and chronic renal
failure, renal sclerosis, and nephritis/
nephropathy) were statistically
significant and elevated based on
multiple cause of death data (SMR 1.28,
95% CI: 1.10–1.47, 194 deaths) and
underlying cause of death data (SMR
1.41, 95% CI: 1.05–1.85, 51 observed
deaths) (OSHA 2013b, page 315).
A nested case-control analysis was
also performed which allowed for more
detailed examination of exposureresponse. This analysis included 95
percent of the cohort for which there
were adequate work history and quartz
exposure data. This analysis included
50 cases for underlying cause mortality
and 194 cases for multiple-cause
mortality. Each case was matched by
race, sex, and age within 5 years to 100
controls from the cohort. Exposureresponse trends were examined in a
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categorical analysis where renal disease
mortality of the cohort divided by
exposure quartile was compared to U.S.
rates (OSHA 2013b, page 315).
In this analysis, statistically
significant exposure-response trends for
SMRs were observed for multiple-cause
(p < 0.000001) and underlying cause (p
= 0.0007) mortality (Steenland et al.,
2002a; Table 1; Page 7).
With the lowest exposure quartile
group serving as a referent, the casecontrol analysis showed monotonic
trends in mortality with increasing
cumulative exposure. Conditional
regression models using log-cumulative
exposure fit the data better than
cumulative exposure (with or without a
15-year lag) or average exposure. Odds
ratios by quartile of cumulative
exposure were 1.00, 1.24, 1.77, and 2.86
(p = 0.0002) for multiple cause analyses
and 1.00, 1.99, 1.96, and 3.93 for
underlying cause analyses (p = 0.03)
(Steenland et al., 2002a; Table 2; Page
7). For multiple-cause mortality, the
exposure-response trend was
statistically significant for cumulative
exposure (p = 0.004) and log-cumulative
exposure (p = 0.0002), whereas for
underlying cause mortality, the trend
was statistically significant only for logcumulative exposure (p = 0.03). The
exposure-response trend was
homogeneous across the three cohorts
and interaction terms did not improve
model fit (OSHA 2013b, pages 216, 315).
Based on the exposure-response
coefficient for the model with the log of
cumulative exposure, Steenland (2005)
estimated lifetime excess risks of death
(age 75) over a working life (age 20 to
65). At 100 mg/m3 (0.1 mg/m3) respirable
crystalline silica, this risk was 5.1
percent (95% CI 3.3–7.3) for ESRD
based on 23 cases (Steenland et al.,
2001b). It was 1.8 percent (95% CI 0.8–
9.7) for kidney disease mortality
(underlying), based on 51 deaths
(Steenland et al., 2002a) above a
background risk of 0.3 percent (OSHA
2013b, page 216).
MSHA notes that these studies added
to the evidence that renal disease is
associated with respirable crystalline
silica exposure. Statistically significant
increases in odds ratios and SMRs were
seen primarily for cumulative exposures
of >500 mg/m3-years (0.5 mg/m3-years).
Steenland (2005b) noted that this could
have occurred from working for 5 years
at an exposure level of 100 mg/m3 (0.1
mg/m3) or 10 years at 50 mg/m3 (0.05
mg/m3).
OSHA had a large body of evidence,
particularly from the three-cohort
pooled analysis (Steenland et al.,
2002a), on which to conclude that
respirable crystalline silica exposure
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increased the risk of renal disease
mortality and morbidity. The pooled
analysis by Steenland et al. (2002a)
involved a large number of workers
from three cohorts with welldocumented, validated job-exposure
matrices. These investigators found a
positive, monotonic increase in renal
disease risk with increasing exposure
for underlying and multiple cause data.
Thus, the exposure and work history
data were unlikely to have been
seriously misclassified. However, there
are considerably less data available for
renal disease than there are for silicosis
mortality and lung cancer mortality.
Nevertheless, OSHA concluded that the
underlying data were sufficient to
provide useful estimates of risk and
included the Steenland et al. (2002a)
analysis in its PQRA (OSHA 2013b,
pages 229, 316).
To estimate renal disease mortality
risk from the pooled cohort analysis,
OSHA implemented the same life table
approach as was done for the
assessments on lung cancer and NMRD.
However, for this life table analysis,
OSHA used 1998 all-cause and
background renal mortality rates for
U.S. males, rather than the 2006 rates
used for lung cancer and NMRD. The
1998 rates were based on the ICD–9
classification of diseases, which was the
same as used by Steenland et al. (2002a)
to ascertain the cause of death of
workers in their study. However, U.S.
cause-of-death data from 1999 to present
are based on the ICD–10, in which there
were considerable changes in the
classification system for renal diseases.
According to CDC (2001), the change in
the classification from ICD–9 to ICD–10
increased death rates for nephritis,
nephritic syndrome, and nephrosis by
23 percent, in large part due to
reclassifying ESRD. The change from
ICD–9 to ICD–10 did not materially
affect background rates for those
diseases grouped as lung cancer or
NMRD. Consequently, OSHA conducted
its analysis of excess renal disease
mortality associated with respirable
crystalline silica exposure using
background mortality rates for 1998. As
before, lifetime risk estimates reflected
excess risk through age 85. To estimate
renal mortality risks, OSHA used the
log-linear model with log-cumulative
exposure that provided the best fit to the
pooled cohort data (Steenland et al.,
2002a). The coefficient for this model
was 0.269 (SE = 0.120) (OSHA 2013b,
page 316). Based on the life table
analysis, OSHA estimated that exposure
to the former general industry exposure
limit of 100 mg/m3 and to the final
exposure limit of 50 mg/m3 over a
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working life would result in a lifetime
excess renal disease risk of 39 (95% CI:
2–200) and 32 (95% CI: 1.7–147) deaths
per 1,000, respectively. OSHA also
estimated lifetime risks associated with
the former construction and shipyard
exposure limits of 250 and 500 mg/m3.
These lifetime excess risks ranged from
52 (95% CI 2.2–289) to 63 (95% CI 2.5–
368) deaths per 1,000 workers (OSHA
2013b, page 316).
MSHA concludes that the evidence
supporting causality regarding renal risk
outweighs the evidence casting doubt
on that conclusion. However, MSHA
acknowledges the uncertainty
associated with the divergent findings
in the renal disease literature. To
estimate renal disease mortality risk
from the pooled cohort analysis, MSHA
implemented the same life table
approach as OSHA. However, MSHA’s
life table analysis used 2018 all-cause
and 1998 background renal mortality
rates for U.S. males. The 1998 renal
death rates were based on the ICD–9
classification of diseases, 580–589. This
is the same classification used by
Steenland et al. (2002a) to ascertain the
cause of death of workers in their study.
Consequently, MSHA conducted its
analysis of excess ESRD mortality
associated with exposure to respirable
crystalline silica using background
mortality rates for 1998. The U.S. causeof-death data from 2018 were used as
well. Lifetime risk estimates reflect
excess risk through age 85. To estimate
ESRD mortality risks, MSHA used the
log-linear model with log-cumulative
exposure that provided the best fit to the
pooled cohort data (Steenland et al.,
2002a), as EXP(0.269 * ln (cumulative
exposure)). The coefficient for this
model was 0.269 (SE = 0.120) (OSHA
2013b, page 316).
6. Coal Workers’ Pneumoconiosis (CWP)
Exposure to respirable coal mine dust
causes lung diseases including CWP,
emphysema, silicosis, and chronic
bronchitis, known collectively as ‘‘black
lung.’’ These diseases are debilitating,
incurable, and can result in disability
and premature death. There are no
specific treatments to cure CWP or
COPD. These chronic effects may
progress even after miners are no longer
exposed to coal dust.
MSHA’s 2014 coal dust rule
quantified benefits among coal miners
related to reduced cases of CWP due to
lower exposure limits for respirable coal
mine dust. In this PRA, MSHA has not
quantified the reduction in risk
associated with CWP among coal
miners. Nonetheless, MSHA believes
that the proposed rule would reduce the
excess risk of this disease. Many coal
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D. Overview of Results
Table VI–4 summarizes the PRA’s
main results: once it is fully effective
(and all miners have been exposed only
under the proposed PEL), the proposed
rule is expected to result in at least 799
avoided deaths and 2,809 avoided cases
of silicosis morbidity among the
working miner population. These
numbers represent the lifetime health
outcomes expected to occur after both
45 years of employment under the
proposed PEL (from 21 through 65 years
of age) and 15 years of retirement (up to
80 years of age). These estimates of the
avoided lifetime excess mortality and
morbidity represent the final
calculations based on the 5 selected
models and the observed exposure data.
The first group of miners that would
experience the avoided lifetime
fatalities and illnesses shown in Table
VI–4 is the population living 60 years
after promulgation of the proposed rule.
In other words, this group would only
contain miners exposed under the
proposed rule. To calculate benefits
associated with the proposed
rulemaking, the economic analysis
monetizes avoided deaths and illnesses
while accounting for the fact that,
during the first 60 years following
promulgation, miners would have fewer
avoided lifetime fatalities and illnesses
because they would be exposed under
both the existing standards and the
proposed PEL.
Table VI–5 summarizes miners’
expected percentage reductions in
lifetime excess risk of developing or
dying from certain diseases due to their
reduced respirable crystalline silica
exposure expected to result from
implementation of the proposed rule.
The lifetime excess risk reflects the
probability of developing or dying from
diseases over a maximum lifetime of 45
years of exposure during employment
and 15 years of retirement. The excess
risk reduction compares (a) miners’
excess health risks associated with
respirable crystalline silica exposure at
the limits included in MSHA’s existing
standards to (b) miners’ excess health
risks associated with exposure at this
standard’s proposed PEL. MSHA
expects full-scale implementation to
reduce lifetime excess mortality risk by
9.5 percent and to reduce lifetime
excess silicosis morbidity risk by 41.9
percent. Excess mortality risk includes
the excess risk of death due to silicosis,
NMRD, lung cancer, and ESRD.
miners work extended shifts, thus
increasing their potential exposure to
respirable crystalline silica. The result
of calculating exposures based on a fullshift 8-hour TWA would be more
protective. Thus, the proposed rule is
expected to provide additional
reductions in CWP risk beyond those
ascribed in the 2014 coal dust rule.
However, exposure-response
relationships based on respirable
crystalline silica exposure are not
available for CWP, so the reductions in
this disease due to reductions in silica
exposure cannot be quantified.
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Table VI–6 presents MSHA’s
estimates of lifetime excess risk per
1,000 miners at exposure levels equal to
the existing standards, the proposed
PEL, and the proposed action level.
These estimates are adjusted for FTE
ratios and thus utilize cumulative
exposures that more closely reflect the
average hours worked per year.21 For an
MNM miner who is presently exposed
at the existing PEL of 100 mg/m3 (and
given the weighted average FTE ratio of
0.87), implementing the proposed PEL
would lower the miner’s lifetime excess
risk of death by 58.8 percent for
silicosis, 45.6 percent for NMRD (not
including silicosis), 52.0 percent for
lung cancer, and 19.9 percent for ESRD.
The MNM miner’s risk of acquiring a
non-fatal case of silicosis (would
decrease by 80.4 percent).
For a coal miner who is currently
exposed at the existing exposure limit of
85.7 mg/m3 (and given the weighted
average FTE ratio of 0.99),
implementing the proposed PEL would
lower the miner’s lifetime excess risk of
death by 42.3 percent for silicosis
mortality, 40.2 percent for NMRD
mortality (not including silicosis), 43.5
percent for lung cancer mortality, and
15.8 percent for ESRD mortality. The
coal miner’s lifetime excess risk of
acquiring non-fatal silicosis would
decrease by 73.8 percent. While even
greater reductions would be achieved at
exposures equal to the proposed action
level (25 mg/m3), some residual risks do
remain at exposures of 25 mg/m3.
Notably, at the proposed action level,
ESRD risk is still 20.7 per 1,000 MNM
miners and 21.6 per 1,000 coal miners.
At the proposed action level, risk of
non-fatal silicosis is 16.3 per 1,000
MNM miners and 16.9 per 1,000 coal
miners.
21 The FTE ratios used in these calculations are
a weighted average of the FTE ratio for production
employees and the FTE ratio for contract miners.
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E. Healthy Worker Bias
MSHA accounted for ‘‘healthy worker
survivor bias’’ in estimating the risks for
coal and MNM miners. The healthy
worker survivor bias causes
epidemiological studies to
underestimate excess risks associated
with occupational exposures. As with
most worker populations, miners are
composed of heterogeneous groups that
possess varying levels of background
health. Over the course of miners’
careers, illness tends to remove the most
at-risk workers from the workforce
prematurely, thus causing the highest
cumulative exposures to be experienced
by the healthiest workers who are most
immune to risk. Failing to account for
this imbalance of cumulative exposure
across workers negatively biases risk
estimates, thereby underestimating true
risks in the population. Keil et al. (2018)
analyzed a type of healthy worker bias
referred to as the healthy worker
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survivor bias in the context of OSHA’s
2016 life table estimates for risk
associated with respirable crystalline
silica exposure. After analyzing data
from 65,999 workers pooled across
multiple countries and industries, Keil
et al. found that the ‘‘healthy worker
survivor bias results in a 28%
underestimate of risk for lung cancer
and a 50% underestimate for other
causes of death,’’ with risk being
defined as ‘‘cumulative incidence of
mortality [at age 80].’’
Given that MSHA has calculated risks
using the same underlying
epidemiological studies OSHA used in
2016, the healthy worker survivor bias
is likely impacting the estimates in
Table VI–6 of lifetime excess risk and
lifetime excess cases avoided.
Accordingly, as part of a sensitivity
analysis, MSHA re-estimated risks for
MNM and coal miners to account for the
healthy worker survivor bias. MSHA
adjusted for this effect by increasing the
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risk estimates of lung cancer risk by 28
percent and increasing the risk of each
other disease by 50 percent. This
produced larger estimates of lifetime
excess risk reductions and lifetime
excess cases avoided, which are
presented in PRA Table 23 through PRA
Table 26 of the PRA document. As these
tables show, when adjusting for the
healthy worker survivor bias, the
proposed PEL would decrease lifetime
silicosis morbidity risk by 20.8 cases per
1,000 MNM miners (compared to the
unadjusted estimate of 13.9 cases per
1,000 MNM miners, see PRA Table 15
of the PRA document) and 5.0 cases per
1,000 coal miners (compared to 3.3
cases per 1,000 coal miners, see PRA
Table 16 of the PRA document). Still
accounting for the healthy worker
survivor bias, the proposed PEL would
decrease total morbidity by 3,848
lifetime cases among MNM miners
(compared to 2,566 cases, see PRA Table
17 of the PRA document) and by 366
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lifetime cases among coal miners
(compared to 244 cases, see PRA Table
18 of the PRA document). Among the
current MNM and coal mining
populations, implementation of the
proposed PEL during their full lives
would have prevented 1,091 deaths and
94 deaths, respectively, over their
lifetimes (compared to unadjusted
estimates of 736 deaths and 63 deaths,
respectively).
MSHA believes adjusted estimates for
the healthy worker survivor bias are
more reliable than unadjusted estimates.
However, given that the literature does
not support specific scaling factors for
each of the health endpoints analyzed,
these adjustments for the healthy
worker survivor bias have not been
incorporated into the final lifetime
excess risk estimates that served as the
basis for monetizing benefits. Because
the monetized benefits do not account
for the healthy worker bias, MSHA
believes the reductions in lifetime
excess risks and lifetime excess cases, as
well as the monetized benefits, likely
underestimate the true reductions and
benefits attributable to the proposed
rule.
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F. Uncertainty Analysis
MSHA conducted extensive
uncertainty analyses to assess the
impact on risk estimates of factors
including treatment of data in excess of
the proposed PEL, sampling error, and
use of average rather than median point
estimates for risk. The impact of
excluding insufficient mass (weight)
samples was also examined.
1. Alternate Treatment of Exposure
Samples in Excess of the Proposed
Exposure Limit
To estimate excess risks and excess
cases under the proposed PEL, MSHA
assumed that no exposures would
exceed the proposed limit, which
effectively reduced any exposures
exceeding 50 mg/m3 to 50 mg/m3.
However, if mines implement controls
with the goal of reducing exposures to
50 mg/m3 on every shift, then some
exposure currently in excess of 50 mg/
m3 would likely decrease below the
proposed PEL. For this reason, the
estimation method of capping all
exposure data at 50 mg/m3 represents a
‘‘lowball’’ estimate of risk reductions
due to the proposed PEL. In this section,
MSHA presents estimates using an
alternate ‘‘highball’’ method wherein
exposures exceeding 50 mg/m3 are set
equal to the median exposure value for
the 25–50 mg/m3 exposure group.
Because this highball method attributes
larger reductions in exposure to the
proposed PEL, it estimates higher
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lifetime excess risk reductions and more
avoided lifetime excess cases.
As with lifetime excess risks, the
highball method also yields larger
reductions in lifetime excess cases.
Using the highball method, MNM
miners are expected to experience 3,111
fewer cases of non-fatal silicosis and
coal miners are expected to experience
344 fewer cases of non-fatal silicosis
over their lifetimes. MNM miners would
experience 1,137 fewer deaths and coal
miners would experience 123 fewer
deaths over their lifetimes. Compared to
the lowball method—which estimates
that the proposed PEL would prevent a
total of 2,809 lifetime cases of non-fatal
silicosis and 799 lifetime excess deaths
(among both MNM and coal miners)—
the highball method estimates totals of
3,445 avoided lifetime cases of non-fatal
silicosis and 1,260 avoided lifetime
excess deaths.
2. Sampling Error in Exposure Data
To quantify the impact of sampling
uncertainty on the risk estimates, 1,000
bootstrap resamples of the original
exposure data were generated (sampling
with replacement). The resamples were
stratified by commodity to preserve the
relative sampling frequencies of coal,
metal, non-metal, sand and gravel,
crushed limestone, and stone
observations in the original dataset. Risk
calculations were repeated on each of
the 1,000 bootstrap samples, thereby
generating empirical distributions for all
risk estimates. From these empirical
distributions, 95 percent confidence
intervals were calculated. These
confidence intervals characterize the
uncertainty in the risk estimates arising
from sampling error in the exposure
data. All lifetime excess risk estimates
had narrow confidence intervals,
indicating that the estimates of lifetime
excess morbidity and mortality risks
have a high degree of precision.
In regard to use of average, rather than
median, point estimates of risk, the
estimates acquired from average
exposures are similar to the estimates
from median exposures, with 95 percent
confidence intervals having similar
widths. However, the 95 percent
confidence intervals are not always
overlapping, and average exposures
tended to yield higher estimates of
reduced morbidity and mortality.
Among MNM miners, MSHA expects
the proposed PEL to produce lifetime
risk reductions of silicosis morbidity of
2,546–2,777 using average exposures
(see PRA Table 41 of the PRA
document), compared to 2,453–2,683
using median exposures (see PRA Table
37 of the PRA document). Among coal
miners, this reduction is expected to be
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246–279 using average exposures (see
PRA Table 42 of the PRA document),
compared to 229–265 using median
exposures (see PRA Table 38 of the PRA
document). The proposed PEL is
estimated to reduce lifetime excess
mortality by 735–791 MNM miner
deaths and 65–73 coal miner deaths
using average exposures (see PRA
Tables 41 and 42 of the PRA document),
compared to 708–764 MNM miner
deaths and 60–69 coal miner deaths
using median exposures (see PRA
Tables 37 and 38 of the PRA document).
3. Samples With Insufficient Mass
The MNM exposure data gathered by
enforcement from January 1, 2005,
through December 31, 2019, contain
samples that were analyzed using the P–
2 method. As discussed, the P–2 method
specifies that filters are only analyzed
for quartz if they achieve a net mass
gain of 0.100 mg or more. If cristobalite
is requested, a mass gain of 0.050 mg or
more is required for a filter to be
analyzed (MSHA 2022a). During the 15year sample period for MNM exposure
data, 40,618 MNM samples were not
analyzed because the filter failed to
meet the P–2 minimum net mass
(weight) gain requirements.
Similarly, the coal exposure data
gathered by enforcement from August 1,
2016, through July 31, 2021, contains
samples that were analyzed using the P–
7 method. The P–7 method requires a
minimum sample mass of 0.100 mg 22 of
dust for the sample to be analyzed for
quartz. During the five-year sample
period for coal exposure data, 63,127
coal samples were not analyzed because
the P–7 method’s minimum mass
requirement was not met.
For samples that do not meet a
minimum threshold for total respirable
dust mass, the MSHA lab does not
analyze these samples for respirable
crystalline silica. These samples were
excluded from the risk analysis because
their concentrations of respirable
crystalline silica are not known.
Nonetheless, the unanalyzed samples all
had very low total respirable dust mass,
making it unlikely that many would
have exceeded the existing standards or
the proposed PEL. Excluding these
unanalyzed samples from the exposure
datasets thus may introduce bias,
potentially causing the Agency to
overestimate the proportion of highintensity exposure values.
22 Often the threshold for analyzing Coal samples
is ≥0.1 mg. There are, however, some exceptions
based on Sample Type and Occupation Code. For
samples with Sample Type 4 or 8, if the sample’s
Occupation Code is not 307, 368, 382, 383, 384, or
386, then the threshold is ≥0.2 mg.
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As a sensitivity analysis, MSHA used
imputation techniques to estimate the
respirable crystalline silica mass for
each sample based on the sample weight
and the median percent silica content
for each commodity and occupation. All
the unanalyzed samples with imputed
concentrations were estimated to be <25
mg/m3, and thus including these
unanalyzed samples in the analysis
leads to lower estimates of estimated
lifetime excess cases for both MNM and
coal miners.
When including the imputed values
for the unanalyzed samples, the
proposed PEL would result in 1,642
fewer cases of non-fatal silicosis among
MNM miners and 128 fewer cases
among coal miners, over their lifetimes.
The proposed PEL would also result in
469 fewer deaths (due to all 4 diseases)
among MNM miners and 34 fewer
deaths among coal miners, over their
lifetimes. This yields a total reduction of
1,770 in lifetime excess morbidity and
of 503 in lifetime excess mortality,
respectively. While these estimates are
lower than those presented in Table VI–
4 (of 2,809 avoided lifetime cases of
non-fatal silicosis and 799 avoided
lifetime excess fatalities), MSHA
nonetheless believes that—even
including these unanalyzed samples—
the proposed PEL would still reduce the
risk of material impairment of health or
functional capacity in miners exposed
to respirable crystalline silica.
Moreover, the possible positive bias that
may arise when excluding these
samples would be offset by other
negative biases discussed herein (e.g.,
the healthy worker survivor bias and the
assumption that full compliance with
the proposed PEL would not produce
any reductions in exposure below 50 mg/
m3).
It should be noted that the imputation
method has some limitations. For
example, the method assumes that, if
the insufficient mass samples had been
analyzed, every sample would have
possessed a percentage of quartz, by
mass, equal to the median percentage
for that sample’s associated commodity
and occupation. (See Section 17.1 of the
PRA document for a full discussion of
the imputation method.) However,
within a given occupation, this
percentage varies substantially and is
positively correlated with exposure
concentration. Suppressing the variation
in this percentage quartz, by mass,
produces less variation in the resulting
imputed concentrations. Consequently,
the imputation method may
underestimate the number of
unanalyzed samples that would truly
exceed 50 mg/m3.
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VII. Section-by-Section Analysis
MSHA proposes to add a new part 60,
titled Respirable Crystalline Silica, to
title 30 CFR, chapter I, subchapter M—
Uniform Mine Health Regulations.
Proposed part 60, which would apply to
all MNM and coal mines, contains
health standards to protect all miners
from adverse health risks caused by
occupational exposure to respirable
crystalline silica (as discussed in the
standalone document entitled Effects of
Occupational Exposure to Respirable
Crystalline Silica on the Health of
Miners and as summarized in Section V.
Health Effects Summary of this
preamble). This proposed part
establishes a new PEL for respirable
crystalline silica for all mines and
includes other ancillary provisions to
improve methods of compliance,
exposure monitoring, corrective actions,
respiratory protection, medical
surveillance for MNM miners, and
recordkeeping. In addition to the new
part 60, MSHA proposes to incorporate
by reference ASTM F3387–19, Standard
Practice for Respiratory Protection, to
replace its respiratory protection
standards under 30 CFR parts 56, 57,
and 72 to better protect all miners from
airborne contaminants. This section-bysection analysis discusses each
provision under the proposed part 60,
the conforming amendments related to
the proposed part, and the updated
respiratory protection standard.
A. Part 60—Respirable Crystalline Silica
MSHA has preliminarily determined
that occupational exposure to respirable
crystalline silica causes adverse health
effects, including silicosis (acute
silicosis, accelerated silicosis, simple
chronic silicosis, and PMF), NMRD (e.g.,
emphysema and chronic bronchitis),
lung cancer, and renal diseases. MSHA
has also preliminarily determined that
under the existing standards, miners
remain at risk of suffering material
impairment of health or functional
capacity from these adverse health
effects. Each of these effects is exposuredependent, chronic, irreversible, and
potentially disabling or fatal. MSHA has
preliminarily concluded that lowering
the PEL for respirable crystalline silica
to 50 mg/m3 would substantially reduce
the health risks to miners.
MSHA proposes to replace its existing
standards for respirable crystalline silica
or respirable dust containing quartz
with a single, uniform health standard
for all miners. The proposed uniform
standard would establish consistent,
industry-wide requirements that
directly address the adverse health
effects of overexposure to respirable
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crystalline silica. This proposal would
also facilitate mining-industry
compliance and help MSHA and other
stakeholders provide consistent
compliance assistance. MSHA believes
this unified regulatory framework for
controlling miner exposure to respirable
crystalline silica would improve
protection for all miners and help the
Agency fulfill its obligations under the
Mine Act to prevent occupational
diseases.
Proposed part 60 includes: Scope and
effective date; Definitions; Permissible
exposure limit (PEL); Methods of
compliance; Exposure monitoring;
Corrective actions; Respiratory
protection; Medical surveillance for
metal and nonmetal miners;
Recordkeeping requirements; and
Severability.
Detailed discussions of the proposed
sections are followed by discussions on
conforming amendments and
discussions of the proposed update to
the respiratory protection standard in
parts 56, 57, and 72.
1. Section 60.1—Scope; Effective Date
This section provides that proposed
part 60 would take effect 120 days after
the final rule is published in the Federal
Register. Mine operators would be
required to comply with the
requirements in this part starting on the
proposed effective date.
MSHA believes that the proposed
120-day period gives operators the
necessary time to plan and prepare for
effective compliance with the new
standards, while also ensuring that
improved protections for miners from
the hazards of respirable crystalline
silica take effect as soon as practically
possible. MSHA believes that it is
important to reduce miner exposure to
respirable crystalline silica promptly
because every exposure at levels above
the proposed PEL imposes adverse
health risks on miners. However, for
implementation to be successful, mine
operators need enough time to
understand the standard and to prepare
for compliance (e.g., by purchasing
gravimetric ISO-conforming samplers
and/or selecting a commercial
laboratory for respirable crystalline
silica analysis, if necessary). MSHA
believes that the proposed effective date
of 120 days would provide enough time
for mine operators to take necessary
steps to achieve successful compliance.
Under the existing standards, both
MNM and coal operators have had many
years of experience with monitoring and
controlling airborne contaminants,
including respirable crystalline silica,
and this experience should facilitate
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implementation of the proposed
standard.
2. Section 60.2—Definitions
This section includes the proposed
definitions of four terms: ‘‘action level,’’
‘‘objective data,’’ ‘‘respirable crystalline
silica,’’ and ‘‘specialist.’’
The term ‘‘action level’’ would mean
an airborne concentration of respirable
silica of 25 micrograms per cubic meter
of air (mg/m3) for a full-shift exposure,
calculated as an 8-hour time-weighted
average (TWA). The action level sets the
level of respirable crystalline silica
concentration at or above which
operators would be subject to periodic
sampling requirements, which are
explained in proposed § 60.12. This
proposed action level is intended to
support operator compliance with the
proposed PEL of 50 mg/m3 by initiating
periodic sampling requirements.
The proposed action level of 25 mg/
m3, one-half of the proposed PEL, is
consistent with NIOSH research
findings and other MSHA standards.
According to NIOSH research, wherever
exposure measurements are above onehalf the PEL, the employer cannot be
reasonably confident that the employee
is not exposed to levels above the PEL
on days when no measurements are
taken (NIOSH 1975). MSHA has
experience with setting an action level
equivalent to 50 percent of the PEL for
occupational noise exposure (30 CFR
62.101), applicable to MNM and coal
mines, and an action level of 50 percent
of the exhaust gas monitoring standards
for underground coal mines (30 CFR
70.1900). Based upon Agency
experience, MSHA believes these action
levels have allowed mine operators to
be more proactive in providing
necessary protection.
The term ‘‘objective data’’ would
mean information such as air
monitoring data from industry-wide
surveys or calculations based on the
composition of a substance that
indicates the level of miner exposure to
respirable crystalline silica associated
with a particular product or material or
a specific process, task, or activity. Such
data must reflect mining conditions
closely resembling, or with a higher
exposure potential than, the processes,
types of material, control methods, work
practices, and environmental conditions
in the operator’s current operations.
Some examples of information that
would qualify as objective data under
this definition include historical MSHA
sampling data, NIOSH Health Hazard
Evaluations and other published
scientific reports, and industry-wide
surveys compiled from mines with
similar mining conditions, geological
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composition, work processes, miner
tasks, and the same commodities.
‘‘Respirable crystalline silica’’ would
mean quartz, cristobalite, and/or
tridymite contained in airborne particles
that are determined to be respirable by
a sampling device designed to meet the
characteristics for respirable-particlesize-selective samplers that conform to
the International Organization for
Standardization (ISO) 7708:1995: Air
Quality—Particle Size Fraction
Definitions for Health-Related
Sampling. These characteristics are
described further below.
First, the proposed definition would
apply to airborne particles that contain
collectively or individually, quartz,
cristobalite, and/or tridymite, three
polymorphs of respirable crystalline
silica that may be encountered in
mining and for which exposures are
addressed in existing MSHA standards.
Quartz is the most common polymorph
and is present in varying amounts in
almost every type of mineral, whereas
naturally occurring cristobalite and
tridymite are rare.
Second, airborne particles determined
to be respirable are those particles
capable of entering the gas-exchange
region (alveolar region) of the lungs.
MSHA’s proposed definition would
harmonize the Agency’s existing
practice with current aerosol science
and be consistent with the nationally
and internationally accepted ISO
definition of ‘‘respirable particulate
mass’’ (i.e., the respirable mass fraction
of total airborne particles that can be
inhaled through the nose or mouth). ISO
7708:1995 defines conventions for the
‘‘inhalable,’’ ‘‘thoracic,’’ and
‘‘respirable’’ fractions of total airborne
particles. The inhalable fraction
represents the fraction of total airborne
particles capable of being inhaled
through the nose or mouth. The thoracic
fraction is the portion of the inhalable
particles that pass the larynx and into
the airways (trachea) and the bronchial
region of the lungs. The respirable
fraction is the portion of inhalable
particles that can enter the gas-exchange
region (alveolar region) of the lungs. The
ISO 7708:1995 definition of ‘‘respirable
particulate mass’’ corresponds to
particulate matter (respirable dust) that
is inhaled and capable of entering the
gas-exchange region (alveolar region) of
the lungs. MSHA considers this
definition to be biologically relevant
because exposures to airborne
contaminants that are respirable can
lead to material impairment of health or
functional capacity.23
23 The gas-exchange region of the human lung is
the region where the exchange of carbon dioxide
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Third, respirable particles are those
particles which can be collected by a
sampling device designed to meet the
characteristics for respirable-particlesize-selective samplers that conform to
the ISO 7708:1995 standard. While
‘‘respirable dust’’ generally refers to
dust particles having an aerodynamic
diameter of 10 micrometers (mm) or less,
ISO 7708:1995 defines the term more
precisely based on the respiratory
system’s efficiency at collecting
different types and sizes of particles.
Collection efficiency is represented by
particle collection efficiency curves
based on the aerodynamic diameter of
particles.24 The ISO 7708:1995 standard
uses particle collection efficiency curves
to approximate the fraction of respirable
particles that can be deposited in the
alveolar region of the human respiratory
tract. A sampling device that conforms
to the ISO 7708:1995 standard would
ensure the collection of only respirable
particles, including crystalline silica
polymorphs.
MSHA believes that the proposed
definition of respirable crystalline silica
has two main advantages. First, because
the ISO 7708:1995 definition of
respirable particulate mass represents
an international consensus, adoption of
the ISO 7708:1995 criterion would
allow harmonization with standards
used by other occupational health and
safety organizations in the U.S. and
internationally, including ACGIH,
OSHA (29 CFR 1910.1053 and 29 CFR
1926.1153), NIOSH (2003b, Manual of
Analytical Methods), and the European
Committee for Standardization (CEN)
(ISO 7708:1995). Second, the proposed
definition would eliminate
inconsistencies in the existing standards
for MNM and coal mines. Under the
proposal, defining respirable crystalline
silica to include quartz, cristobalite,
and/or tridymite and establishing a PEL
for exposure to respirable particles of
any combination of these three
polymorphs would provide consistency
across the different mining sectors.
Using samplers that conform to ISO
7708:1995 would allow for uniform
collection for these three polymorphs.
The proposed streamlined approach
would facilitate compliance and provide
consistency in the development of best
practices and would allow mine
operators and MSHA to better promote
the health and safety of all miners.
and oxygen occurs between the lung and blood and
includes the alveoli and respiratory bronchioles.
24 The ISO 7708:1995 standard defines
aerodynamic diameter as the ‘‘diameter of a sphere
of density 1 g/cm3 with the same terminal velocity
due to gravitational force in calm air as the particle,
under the prevailing conditions of temperature,
pressure, and relative humidity.’’
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existing respirable crystalline silica or
quartz standards, miners are exposed to
respirable crystalline silica at
concentrations that result in a risk of
material impairment of health or
functional capacity; and (2) that
lowering the PEL to 50 mg/m3 would
substantially reduce this risk. According
to the CDC, between 1999 and 2014,
miners died from silicosis, COPD, lung
cancer, and NMRD at substantially
higher rates than did members of the
general population; for silicosis, the
proportionate mortality ratio for miners
was 21 times as high.27 Evidence in the
standalone Health Effects document
demonstrates that exposure to respirable
crystalline silica at levels permitted
under existing standards contributes to
this excess mortality.
In the case of coal mines, the
proposed rule would establish a
separate PEL for respirable crystalline
silica. Under the existing standard,
miners’ exposure to quartz is tied to
exposure to respirable coal mine dust,
making it more difficult to monitor coal
miners’ exposure to respirable
crystalline silica. The proposed separate
standard would be more transparent and
make compliance easier to track,
allowing more effective control of
respirable crystalline silica.
The proposed PEL of 50 mg/m3 applies
to a miner’s full-shift exposure,
calculated as an 8-hour TWA. Under
this proposal, a miner’s work shift
exposure would be calculated as
follows:
Regardless of a miner’s actual working
hours (full shift), 480 minutes would be
used in the denominator. This means
that the respirable crystalline silica
collected over an extended period (e.g.,
a 12-hour shift) would be calculated (or
normalized) as if it were collected over
8 hours (480 minutes). For example, if
a miner was sampled for 12 hours and
55 mg of respirable crystalline silica was
collected on the sample, the miner’s
respirable crystalline silica 8-hour TWA
exposure would be 67.4 mg/m3,
calculated as follows:
25 NIOSH conducted a literature review of studies
containing environmental data on the harmful
effects of exposure to respirable crystalline silica.
Based on these studies, and especially fifty years’
worth of studies on Vermont granite workers during
which time dust controls improved, exposures fell,
and silicosis diagnoses neared zero, NIOSH
recommended an exposure limit of 50 mg/m3 for all
industries. OSHA’s examination of health effects
evidence and its risk assessment led to the
conclusion that occupational exposure to respirable
crystalline silica at the previous PELs, which were
approximately equivalent to 100 mg/m3 for general
industry and 250 mg/m3 for construction and
maritime industries, resulted in a significant risk of
material health impairment to exposed workers,
and that compliance with the revised PEL would
substantially reduce that risk. (81 FR at 16755).
OSHA considered the level of risk remaining at the
revised PEL to be significant but determined that a
PEL of 50 mg/m3 is appropriate because it is the
lowest level feasible.
26 For Part 90 miners, MSHA lowered the
exposure to respirable coal mine dust during a coal
miner’s shift to not exceed 0.5 mg/m3.
27 Data on occupational mortality by industry and
occupation can be accessed by visiting the CDC
website at https://www.cdc.gov/niosh/topics/noms/
default.html. The NOMS database provides detailed
mortality data for the 11-year period from 1999,
2003 to 2004, and 2007 to 2014. https://
;wwwn.cdc.gov/niosh-noms/industry2.aspx;
accessed November 7, 2022.
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3. Section 60.10—Permissible Exposure
Limit (PEL)
This section establishes a single,
uniform PEL of 50 mg/m3 for respirable
crystalline silica for all mines. Under
this proposed provision, mine operators
would be required to ensure that ‘‘no
miner is exposed to an airborne
concentration of respirable crystalline
silica in excess of 50 mg/m3 for a fullshift exposure, calculated as an 8-hour
TWA.’’ For coal mines, this proposal
would establish a separate PEL for
respirable crystalline silica. This
proposed PEL would replace the
Agency’s existing exposure limits for
respirable crystalline silica or respirable
quartz in 30 CFR parts 56, 57, 70, 71,
and 90.
The proposed PEL is consistent with
NIOSH’s recommended exposure limit
for workers and with the PEL for
respirable crystalline silica covering
U.S. workplaces regulated by OSHA.
NIOSH recommended in 1974 that
occupational exposure to crystalline
silica be controlled so that ‘‘no worker
is exposed to a TWA of silica [respirable
crystalline silica] greater than 50 mg/m3
as determined by a full-shift sample for
up to a 10-hour workday over a 40-hour
workweek’’ (NIOSH 1974). In 2016,
OSHA promulgated a rule establishing
that for construction, general industry,
and the maritime industry, workers’
exposures to respirable crystalline silica
must not exceed 50 mg/m3, averaged
over an 8-hour day (29 CFR
1910.1053(c); 29 CFR
1926.1153(d)(1)).25 MSHA’s 2014 rule
on respirable coal mine dust established
that the average concentration of
respirable dust in the mine atmosphere
during each shift to which each miner
is exposed be at or below 1.5 mg/m3,
calculated as a TWA, and that coal
miners’ exposure to respirable
crystalline silica be regulated through
reductions in the overall respirable dust
standard (30 CFR 70.100, 70.101,
71.100, 71.101, 90.100, and 90.101).26
As discussed in the Health Effects
Summary of this preamble, occupational
exposure to respirable crystalline silica
is detrimental to an individual’s health.
Silicosis and other diseases caused by
respirable crystalline silica exposure are
irreversible, disabling, and potentially
fatal. However, these diseases are
exposure-dependent and are therefore
preventable. The lower a miner’s
exposure to respirable crystalline silica,
the less likely that miner is to suffer
from adverse health effects.
As presented in the PRA, MSHA has
preliminarily determined that: (1) under
‘‘Specialist’’ would mean an
American Board-Certified Specialist in
Pulmonary Disease or an American
Board-Certified Specialist in
Occupational Medicine. The proposed
definition is applicable to proposed
§ 60.15, which addresses medical
surveillance for MNM miners. Under
the proposed medical surveillance
requirements, which will be discussed
later, MNM mine operators would be
required to provide miners with medical
examinations performed by a specialist
in pulmonary disease or occupational
medicine or a PLHCP.
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This proposed calculation method is
the one that MSHA uses to calculate
MNM miner exposures to respirable
crystalline silica and other airborne
contaminants; it differs from the
existing method of calculating a coal
miner’s exposure to respirable coal mine
dust. For coal miners, the existing
calculation method uses the entire
duration of a miner’s work shift in both
the denominator and numerator,
resulting in the total mass of respirable
coal mine dust collected over an entire
work shift scaled by the sample’s air
volume over the same period.
MSHA’s proposal to apply the
existing method of calculating MNM
miner exposure to all miners has two
main advantages. First, the proposal
would improve protection for coal
miners who work longer shifts. The goal
of the proposed respirable crystalline
silica PEL is to prevent miners from
suffering a body burden high enough to
cause adverse health effects. If a miner
works longer than 8 hours, the miner’s
body (lungs, in particular) may not have
sufficient time to eliminate the
respirable crystalline silica that enters
the lungs or to reduce the body
burden.28 Coal miners commonly work
extended shifts, with many working 10hour or longer shifts.29 In such cases, a
28 The pulmonary uptake and clearance of
respirable crystalline silica are dependent upon
many factors, including a miner’s breathing
patterns, exposure duration, concentration (dose),
particle size, and durability or bio-persistence of the
particle. These factors will also affect the time to
clear particles, even after exposure ceases. Of
principal concern is the possibility that a
continuous dust exposure over an extended period
of time (or high dust level exposure during a short
exposure period may excessively tax lung defense
mechanisms (Industrial Minerals Association-North
America and Mine Safety and Health
Administration, 2008).
The ACGIH (2022), while not specifically
addressing silica, has stated, ‘‘numerous
mathematical models to adjust for unusual work
schedules have been described. In terms of
toxicologic principles, their general objective is to
identify a dose that ensures that the daily peak body
burden or weekly peak body burden does not
exceed that which occurs during a normal 8-hours/
day, 5-day/week shift.’’ There are associated
concerns with the body burden from an ‘‘unusual
work schedule’’ such as a 10- or a 12- hour shift.
As Elias (2013) stated, ‘‘if the length of the workday
is increased, there is more time for the chemical to
accumulate, and less time for it to be eliminated.
It is assumed that the time away from work will be
contamination free. The aim is to keep the chemical
concentrations in the target organs from exceeding
the levels determined by the TLVs® (8-hour day, 5day week) regardless of the shift length. Ideally, the
concentration of material remaining in the body
should be zero at the start of the next day’s work.’’
29 Sampling hours of coal mine dust samples
approximate the working hours of coal miners who
were sampled. According to the coal mine dust
samples for a 5-year period (August 2016–July
2021), 90 percent of the samples by MSHA
inspectors were from miners working 8 hours or
longer and about 43 percent of the samples from
miners working 10 hours or longer. The dust
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coal miner’s recovery time would be
reduced from 16 hours to 12 to 14
hours. To account for this increased
risk, the proposed calculation (like the
current MNM calculation method)
normalizes to an 8-hour TWA. The
concept of adjusting occupational
exposure limits for ‘‘extended shifts’’
has been addressed by researchers (Brief
and Scala, 1986; Elias, 2013).
Second, applying the proposed
calculation method for all miners would
be more straightforward and easier to
understand for mine operators, miners,
and other stakeholders. The current
calculation method for coal miners
requires first determining the percentage
of quartz in the sample of collected
respirable dust, then dividing the result
into the number 10 to calculate an
exposure limit for respirable dust. The
proposed calculation method requires
only measuring the total mass of
respirable crystalline silica collected
and dividing it by the air volume over
480 minutes.
This proposal would establish a lower
PEL and apply it to all miners using a
consistent method for calculating
exposures. These changes would
improve the health and safety of miners
while making compliance more
straightforward and transparent. The 8hour TWA is the ‘‘gold standard’’ for
exposure assessments, except in
scenarios involving chemical substances
that are predominantly fast-acting (i.e.,
those evoking acute effects). NIOSH has
also supported the use of the TWA and
discussed this term since the
publication of the NIOSH Pocket Guide
to Chemical Hazards (First Edition,
1973) (the ‘‘White Book’’).
4. Section 60.11—Methods of
Compliance
This proposed section would require
mine operators to install, use, and
maintain feasible engineering and
administrative controls to keep each
miner’s exposure to respirable
crystalline silica at or below the
proposed PEL. Mine operators would be
required to use feasible engineering
controls as the primary means of
controlling respirable crystalline silica;
administrative controls would be used,
when necessary, as a supplementary
control. However, under the proposal,
rotation of miners—that is, assigning
more than one miner to a high-exposure
task or location, and rotating them to
keep each miner’s exposure below the
samples by coal mine operators show that over 98
percent of them were from miners working 8 hours
or longer and over 26 percent from the miners
working 10 hours or longer. The coal mine dust
samples are available at Mine Data Retrieval System
| Mine Safety and Health Administration (MSHA).
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PEL—would be prohibited. Under the
proposal, respiratory protection
equipment could be used in specific and
limited situations, as discussed in
§ 60.14—Respiratory Protection, but the
use of respiratory protection equipment
would not be acceptable as a method of
compliance.
This proposed approach to controlling
miners’ exposures is consistent with
MSHA’s existing standards, NIOSH’s
recommendations, and generally
accepted industrial hygiene principles.
The proposal is consistent with MSHA’s
existing respirable dust standards,
which require engineering controls as
the primary means to protect miners.
MSHA’s experience and data show that
engineering controls provide improved,
more consistent, and more reliable
protection for miners than
administrative controls or respirators. In
its recommendations, NIOSH also
stressed the importance of using
engineering controls to control miners’
exposure to respirable crystalline silica.
In 1995, NIOSH recommended that the
dust standard state that ‘‘the mine
operator shall use engineering controls
and work practices [administrative
controls] to keep worker exposures at or
below the REL [recommended exposure
limit]. . .’’ (NIOSH 1995a). In its public
response to MSHA’s 2019 Request for
Information for Respirable Silica
(Quartz) (84 FR 45452, Aug. 29, 2019),
NIOSH also supported the use of
engineering controls as the primary
means of protecting miners from
exposure to respirable crystalline silica,
stating that ‘‘[r]espirators should only be
used when engineering control systems
are not feasible. Engineering control
systems, such as adequate ventilation or
scrubbing of contaminants, are the
preferred control methods for reducing
worker exposures.’’ 30
As discussed in the technological
feasibility and preliminary regulatory
impact analysis sections of the
preamble, MSHA has preliminarily
determined that engineering and
administrative controls are
technologically and economically
feasible, and the use of these controls
would be sufficient to achieve
compliance with the proposed PEL.
After reviewing the effectiveness of
various exposure reduction controls
which are currently available and have
been successfully adopted in various
combinations in mines, MSHA has
concluded that all mine operators can
ensure miners’ exposures are below the
proposed PEL through implementing
some combination of enhanced
30 Comment from Paul Schulte, NIOSH (Oct. 23,
2019) to Docket No. MSHA 2016–0013.
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maintenance of existing engineering
controls, new engineering controls, and
improved administrative controls/work
practices.
a. Engineering Controls
Proposed paragraph (a) would require
mine operators to use feasible
engineering controls as the primary
means of controlling respirable
crystalline silica; administrative
controls would be used, when
necessary, as a supplementary control.
This proposed paragraph would
require engineering controls to be used
as the primary means of controlling
respirable crystalline silica. Engineering
controls can include ventilation systems
(i.e., main, auxiliary, local exhaust),
dust suppression devices (i.e., wet dust
suppression and airborne capture), and
enclosed cabs or control booths with
filtered breathing air, as well as changes
in materials handling, equipment used
in a process, ventilation, and dust
capture mechanisms. Engineering
controls generally suppress (e.g., using
water sprays, wetting agents, foams,
water infusion), dilute (e.g., ventilation),
divert (e.g., water sprays, passive
barriers, ventilation), or capture dust
(e.g., dust collectors) to minimize the
exposure of miners working in the
surrounding areas. The use of
automated ore-processing equipment
and use of video cameras for remote
scanning and monitoring can also help
to reduce or eliminate miners’
exposures to respirable crystalline
silica.
Engineering controls are the most
effective means of controlling the
amount of dust to which miners are
exposed. They have the advantage of
addressing dust at its source, thus
ensuring that all miners in an area are
adequately protected from overexposure
to respirable crystalline silica.
Engineering controls provide more
consistent and more reliable protection
to miners than other interventions
because the controls are not dependent
on an individual’s performance,
supervision, or intervention to function
as intended. In contrast to other controls
and other interventions, engineering
controls can also be continually
evaluated and monitored relatively
easily, allowing their effectiveness to be
assessed regularly.
b. Administrative Controls
Under the proposed rule, mine
operators would be permitted to
supplement engineering controls with
administrative controls as a means of
controlling exposure to respirable
crystalline silica. Administrative
controls include practices that change
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the way tasks are performed to reduce
a miner’s exposure. These practices
would include housekeeping
procedures; proper work positions of
miners; cleaning of spills; and measures
to prevent or minimize contamination of
clothing to help decrease miners’
exposure to respirable crystalline silica.
Administrative controls require
significant effort by mine operators to
ensure that miners understand and
follow the controls. If not properly
implemented, understood, or followed,
or if persons responsible for
administrative controls do not properly
supervise their implementation, they
would not be effective in controlling
miners’ overexposure to respirable
crystalline silica. Therefore,
administrative controls would be
permitted only as supplementary
measures, with engineering controls
required as the primary means of
protection.
Proposed paragraph (b) would
prohibit mine operators from using
rotation of miners—that is, assigning
more than one miner to a high-exposure
task or location, and rotating them to
keep each miner’s exposure below the
PEL—as an acceptable method of
compliance. MSHA does not believe
that rotation of miners is consistent with
the Agency’s regulatory framework or its
mandate under the Mine Act. Based on
MSHA’s experience, rotation of miners
may, if permitted, reduce the amount of
time each miner is exposed to the
hazard by rotating miners out of the task
faster. However, it would increase the
number of miners working in highexposure tasks or areas and would lead
to increased material impairment of
health or functional capacity for the
additional miners.
The concept of miner rotation, which
may be an appropriate control to
minimize musculoskeletal stress, is not
acceptable for work involving
carcinogens. Based on NIOSH’s
publication entitled ‘‘Current
Intelligence Bulletin 68: NIOSH
Chemical Carcinogen Policy,’’ MSHA
believes that the primary way to prevent
occupational cancer is to reduce worker
exposure to chemical carcinogens as
much as possible through elimination or
substitution at the source and through
engineering controls (NIOSH 2017b).
5. Section 60.12—Exposure Monitoring
The proposed section addresses
exposure monitoring, sampling method,
and sample analysis methods. MSHA is
proposing two types of exposure
monitoring: quantitative, through
sampling the air that miners breathe,
and qualitative, through semi-annual
evaluations of how changes in mining
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processes, production activities, and
dust control systems affect exposures.
For the quantitative monitoring, MSHA
is proposing four types of sampling—
baseline, periodic, corrective actions,
and post-evaluation—together with
methods for sampling and analyzing the
samples.
The proposed exposure monitoring
requirements, which include sampling
miners’ exposures, would facilitate
operator compliance with the proposed
PEL, harmonize MSHA’s approach to
monitoring and evaluating respirable
crystalline silica exposures in both
MNM and coal mines, and lead to better
protection of miners’ health. Monitoring
miner exposures to airborne
contaminants is an effective risk
management tool. The sampling and
evaluation requirements of proposed
§ 60.12 are designed to ensure
maximum protection for miners and
prevent them from suffering material
impairment of health or functional
capacity, while providing operators
flexibility to tailor their sampling
program to the miners’ risk of exposure
to respirable crystalline silica at their
mines.
The first type of exposure monitoring
under the proposed rule is quantitative
sampling for miners’ exposures to
respirable crystalline silica. This
sampling would help mine operators
determine the extent and degree of
exposures, identify sources of exposure
and potential overexposure, maintain
updated and accurate records of
exposures, select the most appropriate
control methods, and evaluate the
effectiveness of those controls. The
proposal would require operators to
conduct sampling for a miner’s regular
full shift during typical mining
activities. The second type of exposure
monitoring under the proposed rule
would be qualitative evaluations, which
would help operators identify changes
in mining conditions and processes that
affect the exposure risk to miners.
a. Section 60.12(a)—Baseline Sampling
The first action mine operators would
take to assess miners’ exposures under
the proposed rule would be to conduct
baseline sampling. Baseline sampling
would provide an initial measurement
of respirable crystalline silica exposures
that would be compared to the proposed
action level and the proposed PEL to
determine the effectiveness of existing
controls and the need for additional
controls.
Proposed paragraph (a)(1) would
require mine operators to perform
baseline sampling to assess the fullshift, 8-hour TWA exposure of
respirable crystalline silica for each
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miner who is or may reasonably be
expected to be exposed to respirable
crystalline silica at any level. MSHA
assumes that most mining occupations
related to extraction and processing
would meet the ‘‘reasonably be
expected’’ threshold; however, MSHA
recognizes that some miners may work
in areas or perform tasks where
exposures are not reasonably likely, and
some miners may work in silica-free
environments. Based on the Agency’s
experience, both MNM and coal mine
operators generally know from their
existing sampling data and MSHA’s
sampling data the occupations, work
areas, and work activities where
respirable crystalline silica exposures
occur. The mine operator would be
required to sample only those miners
the operator knows or reasonably
expects to be exposed to respirable
crystalline silica.
The proposed provisions would
require that, within the first 180 days
after the effective date of the final rule,
the mine operator perform the baseline
sampling. During this 180-day period,
mine operators would acquire necessary
sampling devices or sampling services,
sample occupations or areas of known
or reasonably expected exposures,
identify appropriate laboratories, and
arrange for analysis of samples. Given
that the mining industry has experience
with sampling programs for other
airborne contaminants, as well as
respirable crystalline silica, MSHA
anticipates that the proposed 180 days
would provide sufficient time for mine
operators to comply with the proposed
standard.
Under this proposed standard, mine
operators would need to accurately
characterize the exposure of each miner
who is or may reasonably be expected
to be exposed to respirable crystalline
silica. As discussed later in detail, mine
operators would be permitted to use
representative sampling whenever
sampling is required. In some cases,
however, operators may have to sample
all miners to obtain an accurate
assessment of exposures.
This proposed requirement would
ensure that mine operators have the
quantitative information needed to
evaluate miners’ exposure risks,
determine the adequacy of existing
engineering and administrative controls,
and make necessary changes to ensure
miners are not overexposed. In addition,
the results of the baseline sampling
would determine further operator
obligations for periodic sampling. A
baseline sample result at or above the
proposed action level but at or below
the proposed PEL, would require
operators to conduct periodic sampling
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under proposed § 60.12(b). However, if
the baseline sample indicated that
exposures were below the proposed
action level and operators can confirm
those results, mine operators would not
be required to conduct periodic
sampling. The results can be confirmed
in three ways: (1) sample data, collected
by the operator or the Secretary in the
12 months preceding the baseline
sampling, that also shows exposures
below the proposed action level; (2)
objective data (as defined in the
proposal) confirming that a miner’s
exposure to respirable crystalline silica
would remain below the proposed
action level; or (3) another sample taken
within 3 months showing exposure
below the proposed action level.
Proposed paragraph (a)(2) would
allow mine operators to use objective
data to confirm the baseline sample
result. Under this proposal, objective
data must demonstrate that respirable
crystalline silica would not be released
in airborne concentrations at or above
the action level under any expected
conditions. Objective data, as defined in
proposed § 60.2, would include air
monitoring data from industry-wide
surveys that demonstrate miners’
exposure to respirable crystalline silica
associated with a particular product or
material or a specific process, task, or
activity. Objective data must reflect
mining conditions that closely resemble
the processes, material, control
methods, work practices, and
environmental conditions in the mine
operator’s current operations. The mine
operator would have the burden of
showing that the objective data
characterizes miner exposures to
respirable crystalline silica with
sufficient accuracy.
Also, proposed paragraph (a)(2)
would permit mine operators to use
sampling conducted by the Secretary or
mine operator within the preceding 12
months of baseline sampling to confirm
miner exposures below the proposed
action level. The proposed rule would
require mine operator sampling that was
conducted in accordance with sampling
requirements in paragraph (f) and
analyzed according to paragraph (g) of
this section. Under proposed paragraph
(a)(2), any subsequent sampling
conducted by the operator or by the
Secretary, collected within 3 months of
the baseline sample, could also be used
to confirm a baseline sample result.
MSHA believes that before sampling
is discontinued for miners previously
determined to be exposed at or above
the proposed action level, it is necessary
to confirm any sample result that
indicates miner exposures are below the
proposed action level. When such a
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result is confirmed by a second
measurement, an operator could
reasonably expect exposures to remain
below the action level if mining
conditions and practices do not change.
However, as discussed later, under
proposed paragraph (d), if there is any
change in conditions or practices that
could be reasonably expected to result
in exposures at or above the action
level, sampling to assess these
exposures would be required.
b. Section 60.12(b)—Periodic Sampling
Periodic sampling under the proposed
rule would provide mine operators and
miners with regular information about
miners’ exposures. Changes in exposure
levels can be caused by changes in the
mine environment, inadequate
engineering controls, or other changes
in mining processes or procedures.
Periodic sampling would inform mine
operators about increases in exposures
in a timely manner so they can prevent
potential overexposures. In addition,
periodic sampling alerts operators and
miners of the continued need to protect
against the hazards associated with
exposure to respirable crystalline silica.
If a mine operator installs new
engineering controls and/or starts new
administrative control practices,
periodic sampling would show whether
those controls are working properly to
achieve the anticipated health results
and would document their
effectiveness.
Proposed § 60.12(b) would require
periodic sampling of miners’ exposures
to respirable crystalline silica whenever
the most recent sampling indicates that
exposures are at or above the proposed
action level but at or below the
proposed PEL. Whether a mine operator
would have to conduct periodic
sampling under the proposal would
depend on the results of the most recent
sample, which could include a baseline
sample, a corrective actions sample, or
a post-evaluation sample, as well as
samples taken by MSHA during its
inspections. If operators are required to
conduct periodic sampling, and
periodic sampling results indicate that
miner exposures are below the action
level, a mine operator would be
permitted to discontinue periodic
sampling for those miners whose
exposures are represented by these
samples. If the most recent sample
shows exposures at or above the action
level but at or below the proposed PEL,
periodic sampling every 3 months
would continue until two consecutive
sample analyses showed miners’
exposures below the action level. MSHA
believes that two consecutive sample
analyses showing exposures below the
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action level would indicate a low
probability that prevailing mining
conditions would result in
overexposures.
MSHA believes that the proposed
frequency for periodic sampling—
repeating the sampling within 3
months—is practical for mine operators
and protective of the health and safety
of miners. MSHA has preliminarily
concluded that the health risks caused
by respirable crystalline silica
overexposure warrant more regular
sampling when exposure levels
approach the proposed PEL, because
this periodic sampling would provide a
higher level of confidence that miners
would not be overexposed. Due to the
unique conditions of mining
environments, where conditions change
quickly and exposures to respirable
crystalline silica can vary frequently,
MSHA is proposing a three-month
periodic sampling schedule (NIOSH,
2014e). This three-month schedule
would provide a meaningful degree of
confidence that mine operators would
recognize quickly when exposures are
increasing and approaching the
proposed PEL and would respond by
implementing additional controls to
prevent overexposure. Periodic
sampling data would also provide
information that operators could use to
select, implement, and maintain
controls. MSHA has structured the
proposal to balance the costs of periodic
sampling requirements, including when
sampling can be stopped, and the
benefits of additional health protection
for miners. Taking these factors into
consideration, MSHA has preliminarily
determined that the proposed frequency
of periodic sampling is both
economically and technologically
feasible for mine operators. (See Section
VIII. Technological Feasibility and
Section IX. Summary of Preliminary
Regulatory Impact Analysis.)
As with the baseline sampling in
proposed paragraph (a), in meeting the
requirements of this paragraph, mine
operators would be allowed to sample a
representative fraction of at least two
miners. The exposure result would be
attributed to the remaining miners
represented by this sample, as discussed
in more detail below. When miners are
not performing the same job under the
same working conditions, a
representative sample would not
accurately characterize actual
exposures, and individual samples
would be necessary.
c. Section 60.12(c)—Corrective Actions
Sampling
Under the proposed rule, MSHA
would require mine operators to take
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corrective actions when any sampling
shows exposures above the proposed
PEL. After such corrective actions,
proposed § 60.12(c) would require mine
operators to conduct corrective actions
sampling to determine whether the
control measures taken under proposed
§ 60.13 have reduced miner exposures
to respirable crystalline silica to at or
below the proposed PEL. If not, the
mine operator would be required to take
additional or new corrective actions
until subsequent corrective actions
sampling indicates miner exposures are
at or below the proposed PEL.
Once corrective actions sampling
indicates that miner exposures have
been lowered to levels at or below the
proposed PEL, one of two scenarios
could occur. First, if corrective actions
sampling taken under proposed
§ 60.12(c) indicate that miner exposures
are at or below the proposed PEL, but
at or above the proposed action level,
the mine operator would be required to
conduct periodic sampling as described
in proposed § 60.12(b). The periodic
sampling requirements would require
mine operators to continue to conduct
sampling every three months until two
consecutive sampling results indicate
miners’ exposures are below the action
level. Second, if corrective actions
sampling taken under proposed
§ 60.12(c) indicate that miner exposures
are below the proposed action level, the
mine operator would be required to
conduct a subsequent sample within 3
months as described in proposed
§ 60.12(b); if those results show miners’
exposures are below the action level, the
mine operator could discontinue
periodic sampling.
Sampling after corrective actions
would provide operators with specific
information regarding the effectiveness
of the corrective actions for the mine
environment and provide additional
data for use in making decisions about
updating or improving controls. It
would also provide mine operators with
an updated profile of miners’ exposures
against which future samples could be
compared.
d. Section 60.12(d) and (e)—SemiAnnual Evaluation and Post-Evaluation
Sampling
Historically, MSHA has recognized
the importance of qualitatively
evaluating changes in mining conditions
and processes and assessing the effect of
those changes on exposure risk.
Operators have general experience with
these types of evaluations. The
proposed rule would require mine
operators to qualitatively evaluate any
changes in production, processes,
engineering controls, personnel,
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44907
administrative controls, or other factors
including geological characteristics that
might result in new or increased
respirable crystalline silica exposures,
beginning 18 months after the effective
date and every 6 months thereafter.
Such evaluations could identify changes
in miners’ exposures to respirable
crystalline silica.
The proposed semi-annual evaluation,
and post-evaluation sampling, as
appropriate, would help confirm that
the results of baseline and periodic
sampling continue to accurately
represent current exposure conditions.
These proposed semi-annual evaluation
and sampling requirements would also
enable mine operators to take
appropriate actions to protect exposed
miners, such as implementing new or
additional engineering controls, and
would provide information to miners
and their representatives, as necessary.
An evaluation could identify a change
in operation processes or control
measures that might lead to increased
exposures to respirable crystalline silica
which need to be corrected. Under
proposed paragraph (d)(1), the mine
operator would be required to make a
record of the evaluation, including the
date of the evaluation. Under proposed
paragraph (d)(2), the mine operator
would be required to post the record on
the mine bulletin board, and, if
applicable, make the evaluation
available electronically, for the next 31
days.
Once the evaluation is complete, a
mine operator would be required to
conduct post-evaluation sampling under
proposed § 60.12(e) when the results of
the evaluation show that miners may be
exposed at or above the action level.
Post-evaluation sampling would provide
operators with information on whether
existing controls are effective, whether
additional control measures are needed,
and whether respiratory protection is
appropriate. When post-evaluation
samples indicate that miner exposures
are at or above the proposed action
level, the mine operator would be
required to conduct periodic sampling
as described in proposed paragraph (b).
Post-evaluation sampling, however,
would not be required if the mine
operator determines that mining
conditions would not reasonably be
expected to result in exposures at or
above the action level.
e. Section 60.12(f)—Sampling
Requirements
Knowledge of typical respirable dust
exposure levels is critical to protect the
health of miners. The proposed rule
includes certain sampling requirements
that would ensure mine operators’
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respirable crystalline silica monitoring
is representative of miners’ actual
exposures.
(1) Typical Mining Activities and
Sampling Device Placement
Proposed paragraph (f)(1) would
require mine operators to collect a
respirable dust sample for the duration
of a miner’s regular full shift and during
typical mining activities. Many
potential sources of respirable
crystalline silica are present only when
the mine is operating under typical
conditions. If a sample is not taken
during typical mining activities, the
actual risk to the miner may not be
known. This proposed requirement
would ensure that respirable crystalline
silica exposure data accurately reflect
actual levels of respirable crystalline
silica exposure at miners’ normal or
regular workplaces throughout their
typical workday, even if there are
fluctuations in airborne contaminant
concentrations during a work shift. As
discussed in other sections of this
preamble, the sample results from the
full shift would be calculated as an 8hour TWA concentration for
comparison with the proposed action
level and PEL and for compliance
determinations.
This proposed provision is consistent
with existing standards and with
generally accepted industrial hygiene
principles, which recommend taking
into consideration the entire duration of
time a miner is exposed to an airborne
contaminant, even if it exceeds 8 hours.
Based on Agency data and experience,
MSHA anticipates that operators would
not have major challenges in meeting
these sampling requirements.
This proposal would continue
existing procedures for sampling device
placement during sampling. Under
proposed § 60.12(f)(2)(i), for MNM
miners the regular full-shift, 8-hour
TWA exposure would be based on
personal breathing-zone air samples. A
breathing zone sample is an individual
sample that characterizes a miner’s
exposure to respirable crystalline silica
during an entire work shift. More
specifically, the sampler remains with
the miner for the entire shift, regardless
of the task or occupation performed.
For coal miners, under proposed
§ 60.12(f)(2)(ii), the regular full-shift, 8hour TWA exposure would be based on
an occupational environmental sample
collected in compliance with existing
standards found in §§ 70.201(c),
71.201(b), and 90.201(b). Under the
existing standards, the sampling device
would be worn or carried ‘‘portal-toportal,’’ meaning from the time the
miner enters the mine until the miner
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exits the mine. The sampling device
would remain with the miner during the
entire shift. For shifts that exceed 12
hours, the operator would be required to
switch the sampling pump prior to the
13th-hour of operation. However, except
in the case of Part 90 miners, if a miner
who is being sampled changes positions
or duties, the sampling device would
remain with the position or duty chosen
for sampling (rather than the miner). For
Part 90 miners, the sampling device
would be operated portal-to-portal and
would remain operational with the
miner throughout the Part 90 miner’s
entire shift, which would include the
time spent performing normal work
duties and the time spent traveling to
and from the assigned work location.
(2) Representative Sampling
Under the proposed rule, mine
operators must accurately characterize
miners’ exposure to respirable
crystalline silica. In some cases, this
would require sampling all exposed
miners. In other cases, as proposed in
paragraph (f)(3), sampling a
‘‘representative’’ fraction of miners
would be sufficient. Where several
miners perform the same tasks on the
same shift and in the same work area,
the mine operator could sample a
representative fraction of miners. Under
this proposed rule, a representative
fraction of miners would consist of two
or more miners performing the same
tasks on the same shift and in the same
work area and who are expected to have
the highest exposures of all the miners
in an area. For example, sampling a
representative fraction may involve
monitoring the exposure of those miners
who are closest to the dust source. The
sampling results for these miners would
then be attributed to the remaining
miners in the group. When miners are
not performing the same job under the
same working conditions, a
representative sample would not be
sufficient to characterize actual
exposures, and therefore individual
samples would be necessary.
MSHA has determined that requiring
operators to sample at least two miners
as representative, where they perform
the same tasks on the same shift and in
the same work area as the remaining
miners, would be sufficient to ensure
that exposures are accurately
characterized and health protections are
provided. This representative sampling
provision of the proposal is similar to
the approach that OSHA uses for both
general industry (29 CFR
1910.1053(d)(3)) and construction (29
CFR 1926.1153(d)(2)) under the
scheduled sampling options.
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(3) Sampling Devices
Respirable dust sampling assesses the
ambient air quality in mines and
evaluates miners’ exposure to airborne
contaminants. Respirable dust
comprises particles small enough that,
when inhaled, can reach the gas
exchange region of the lung.
Measurement of respirable dust
exposure is based on the collection
efficiency of the human respiratory
system and the separation of airborne
particles by size to assess their
respirable fraction. Proposed paragraph
(f)(4) would require mine operators to
use sampling devices designed to meet
the characteristics for respirableparticle-size-selective samplers that
conform to the ISO 7708:1995, ‘‘Air
Quality—Particle Size Fraction
Definitions for Health-Related
Sampling,’’ Edition 1, 1995–04 to
determine compliance with the
proposed respirable crystalline silica
action level and PEL. MSHA proposes to
incorporate by reference ISO 7708:1995,
which is the international consensus
standard that defines sampling
conventions for particle size fractions
used in assessing possible health effects
of airborne particles in the workplace
and ambient environment. Mine
operators could use any type of
sampling device they wish for respirable
crystalline silica sampling, as long as it
is designed to meet the characteristics
for respirable-particle-size-selective
samplers that conform to the ISO
7708:1995 standard and, where
appropriate, meets MSHA permissibility
requirements.31
Sampling devices, such as cyclones 32
and elutriators,33 can separate the
31 MSHA’s permissibility requirements are
specified in 30 CFR parts 18 and 74. Part 18,
Electric Motor-Driven Mine Equipment and
Accessories, specifies the procedures and
requirements for obtaining MSHA approval,
certification, extension, or acceptance of electrical
equipment intended for use in gassy mines. Part 74,
Coal Mine Dust Sampling Devices, specifies the
requirements for evaluation and testing for
permissibility of coal mine dust sampling devices.
32 A cyclone is a centrifugal device used for
extracting particulates from carrier gases (e.g., air).
It consists of a conically shaped vessel. The
particulate-containing gas is drawn tangentially into
the base of the cone, takes a helical route toward
the apex, where the gas turns sharply back along the
axis, and is withdrawn axially through the base.
The device is a classifier in which only dust with
terminal velocity less than a given value can pass
through the formed vortex and out with the gas. The
particle cut-off diameter is calculable for given
conditions.
33 An elutriator is a device that separates particles
based on their size, shape, and density, using a
stream of gas or liquid flowing in a direction
usually opposite to the direction of sedimentation.
The smaller or lighter particles rise to the top
(overflow) because their terminal sedimentation
velocities are lower than the velocity of the rising
fluid.
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respirable fraction of airborne dust from
the non-respirable fraction in a manner
that simulates the size-selective
characteristics of the human respiratory
tract and that meets the ISO standard.
These devices enable collection of dust
samples that contain only particles
small enough to penetrate deep into the
lungs. Size-selective cyclone sampling
devices are typically used in the U.S.
mining industry. These samplers
generally consist of a pump, a cyclone,
and a membrane filter. The cyclone uses
a rapid vortical flow of air inside a
cylindrical or conical chamber to
separate airborne particles according to
their aerodynamic diameter (i.e.,
particle size). As air enters the cyclone,
the larger particles are centrifugally
separated and fall into a grit pot, while
smaller particles pass into a sampling
cassette where they are captured by a
filter membrane that is later analyzed in
a laboratory to determine the mass of
the respirable dust collected. The pump
creates and regulates the flow rate of
incoming air. As the flow rate of air
increases, a greater percentage of larger
and higher-mass particles are removed
from the airstream, and smaller particles
are collected with greater efficiency.
Adjustment of the flow rate changes the
particle collection characteristics of the
sampler and allows calibration to a
specified respirable particle size
sampling definition, such as the ISO
criterion.
MSHA and many mine operators use
cyclone samplers. A cyclone sampler
calibrated to operate at the
manufacturer’s specified air flow rate
that conforms to the ISO standard can
be used to collect respirable crystalline
silica samples under this proposed rule.
MSHA reviewed OSHA’s feasibility
analysis for its 2016 silica final rule and
agrees with OSHA that there are
commercially available cyclone
samplers that conform to the ISO
standard and allow for the accurate and
precise measurement of respirable
crystalline silica at concentrations
below both the proposed action level
and PEL (OSHA 2016a) Such cyclone
samplers include the Dorr-Oliver 10-mm
nylon cyclone used by MSHA and many
mine operators, as well as the HigginsDewell, GK2.69, SIMPEDS, and SKC
aluminum cyclone. Each of these
cyclones has different operating
specifications, including flow rates, and
performance criteria, but all are
compliant with the ISO criteria for
respirable dust with an acceptable level
of measurement bias. MSHA’s
preliminary determination is that
cyclone samplers, when used at the
appropriate flow rates, can collect a
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sufficient mass of respirable crystalline
silica to quantify atmospheric
concentrations lower than the proposed
action level and would meet MSHA’s
crystalline silica sample analysis
specifications for samples collected at
MNM and coal mines.
MNM mine operators who currently
use a Dorr-Oliver 10 mm nylon cyclone
could continue to use these samplers at
a flow rate of 1.7 L/min, which
conforms to the ISO standard, to comply
with the proposed requirements. For
coal mine operators, the gravimetric
samplers previously used to sample
RCMD (i.e., coal mine dust personal
sampling units (CMDPSUs)) were
operated at a 2.0 L/min flow rate. Those
CMDPSUs could be adjusted to operate
at a flow rate of 1.7 L/min to conform
to the ISO standard.
NIOSH’s rapid field-based quartz
monitoring (RQM) approach is an
emerging technology. It provides a fieldbased method for providing respirable
crystalline silica exposure
measurements at the end of a miner’s
shift. With such an end-of-shift analysis,
mine operators can identify
overexposures and mitigate hazards
more quickly. NIOSH Information
Circular 9533, ‘‘Direct-on-filter Analysis
for Respirable Crystalline Silica Using a
Portable FTIR Instrument’’ provides
detailed guidance on how to implement
a field-based end-of-shift respirable
crystalline silica monitoring program.34
The current RQM monitor, however,
was designed as an engineering tool; it
is not currently designed as a
compliance tool with tamper-proof
components and is susceptible to
interferences which can affect its
accuracy. This means that the integrity
of the sample cannot be guaranteed, and
therefore the monitor cannot be used as
a compliance tool. MSHA continues to
support NIOSH efforts to develop the
RQM monitor for use in mines.
34 National Institute for Occupational Safety and
Health (NIOSH). Direct-on-filter analysis for
respirable crystalline silica using a portable FTIR
instrument. By Chubb LG, Cauda EG. Pittsburgh PA:
U.S. Department of Health and Human Services,
Centers for Disease Control and Prevention,
National Institute for Occupational Safety and
Health, DHHS (NIOSH) Publication No. 2022–108,
IC 9533. https://doi.org/10.26616/NIOSHPUB
2022108. The document is intended for industrial
hygienists and other health and safety mining
professionals who are familiar with respirable
crystalline silica exposure assessment techniques,
but who are not necessarily trained in analytical
techniques. It gives general instructions for setting
up the field-based monitoring equipment and
software. It also provides case studies and examples
of different types of samplers that can be used for
respirable crystalline silica monitoring. Guidance
on the use, storage, and maintenance of portable IR
instruments is also provided in the document.
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f. Section 60.12 (g)—Methods of Sample
Analysis.
Proposed paragraph (g) specifies the
methods to be used for analysis of
respirable crystalline silica samples,
including details regarding the specific
analytical methods to be used and the
qualifications of the laboratories where
the samples are analyzed. Proposed
paragraph (g)(1) would require mine
operators to use laboratories that are
accredited to the International
Organization for Standardization (ISO)
or International Electrotechnical
Commission (IEC) (ISO/IEC) 17025,
‘‘General requirements for the
competence of testing and calibration
laboratories’’ with respect to respirable
crystalline silica analyses, where the
accreditation has been issued by a body
that is compliant with ISO/IEC 17011
‘‘Conformity assessment—Requirements
for accreditation bodies accrediting
conformity assessment bodies.’’
Accredited laboratories are held to
internationally recognized laboratory
standards and must participate in
quarterly proficiency testing for all
analyses within the scope of the
accreditation.
The ISO/IEC 17025 standard is a
consensus standard developed by the
International Organization for
Standardization and the International
Electrotechnical Commission (ISO/IEC)
and approved by ASTM International
(formerly the American Society for
Testing and Materials). This standard
establishes criteria by which
laboratories can demonstrate
proficiency in conducting laboratory
analysis through the implementation of
quality control measures. To
demonstrate competence, laboratories
must implement a quality control
program that evaluates analytical
uncertainty and provides estimates of
sampling and analytical error when
reporting samples. The ISO/IEC 17011
standard establishes criteria for
organizations that accredit laboratories
under the ISO/IEC 17025 standard. For
example, the American Industrial
Hygiene Association (AIHA) accredits
laboratories for proficiency in the
analysis of respirable crystalline silica
using criteria based on the ISO 17025
and other criteria appropriate for the
scope of the accreditation.
Many MNM mine operators currently
use third-party laboratories to perform
respirable crystalline silica sample
analyses, and under the proposed
standard, MSHA anticipates that they
would continue to use third-party
laboratories.
For most coal mine operators, using a
third-party accredited laboratory to
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analyze respirable crystalline silica
samples would be a new requirement
because respirable coal mine dust
samples are currently analyzed only by
MSHA. Under the proposed standard,
all mine operators would have to use
third-party laboratories accredited to
ISO/IEC 17025 to have respirable dust
samples analyzed for respirable
crystalline silica. By requiring all mines
to use third-party laboratories, proposed
paragraph (g)(1) would ensure that
sample analysis requirements and
MSHA enforcement efforts are
consistent across all mines.
Proposed paragraph (g)(2) would
require mine operators to ensure that
laboratories evaluate all samples using
analytical methods for respirable
crystalline silica that are specified by
MSHA, NIOSH, or OSHA. These are
validated methods currently being cited
by third party accredited labs for
measuring respirable crystalline silica in
mine dust matrices. MSHA and NIOSH
have specific FTIR methods for
analyzing quartz in coal mine dust. The
NIOSH 7603 method is based on the
MSHA P–7 method which was
collaboratively tested and specifically
addresses the interference from
kaolinite clay. All three methods,
MSHA P–2, NIOSH 7500, and OSHA
ID–142 for analyzing respirable
crystalline silica using X-ray diffraction
(XRD) have similar procedures for
measuring respirable crystalline silica
and are capable of distinguishing
between the three silica polymorphs.
Additional steps such as acid treatment
can be taken to remove respirable
crystalline silica interferences from
other minerals that can be found in
mine dust sample matrices. Consistent
with MSHA’s current practices for the
analysis of respirable crystalline silica
samples, analytical techniques used for
samples from MNM mines and coal
mines would generally be different due
to potential sources of interference and
cost considerations. Under the proposed
rule, as discussed below, MSHA expects
that samples collected in MNM mines
would continue to be analyzed by X-ray
diffraction (XRD) and samples collected
for coal mines would continue to be
analyzed by Fourier transform infrared
spectroscopy (FTIR).
Coal mine samples are currently
analyzed using the FTIR method
because it is cheaper, faster, and better
suited for the coal mining sector, where
samples contain little or no minerals
that could interfere or confound
respirable crystalline silica analysis
results. Current FTIR methods, however,
cannot quantify quartz if either of the
other two forms of crystalline silica
(cristobalite and tridymite) are present
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in the sample. Unlike coal dust samples,
MNM samples may have a variety of
minerals present, which could cause
interference with respirable crystalline
silica measurements if FTIR were used.
Thus, MNM samples are currently
analyzed by XRD because the XRD
method can distinguish and isolate
respirable crystalline silica for
measurement, thereby avoiding
interference or confounding of
respirable crystalline silica analysis
results. The XRD method could be used
for both MNM and coal samples but
using the XRD method is more time
consuming and more costly, with no
additional benefit for coal mine sample
analysis. For this reason, MSHA does
not expect the use of XRD on samples
from coal mines.
For MNM samples, the methods used
for respirable crystalline silica sample
analysis using XRD include MSHA P–2,
NIOSH 7500, and OSHA ID–142. For
coal samples, the methods used for
respirable crystalline silica sample
analysis using FTIR include MSHA P–
7, NIOSH 7602, and NIOSH 7603.
(OSHA does not currently have an
established FTIR method for analysis of
respirable crystalline silica.)
g. Section 60.12 (h)—Sampling Records
Proposed paragraph (h) would
establish requirements for sampling
records, including what mine operators
would be required to do after receiving
the analytical reports from laboratories.
For each sample taken, this proposed
paragraph would require mine operators
to create a record that includes the
sample date, the sampled occupations,
and the reported concentrations of both
respirable dust and respirable
crystalline silica. After making such a
record, the mine operator would be
required to post the record, together
with the laboratory report, on the mine
bulletin board and, if applicable, make
the record and the laboratory report
available electronically, for the next 31
days upon receipt.
When electronic means are available,
mine operators would be required to use
those electronics means such as
electronic bulletin boards or
newsletters, in addition to physically
posting the sampling record and
laboratory report on the mine bulletin
board. MSHA believes that most mines
have the ability to display this
information electronically. For any
mines where electronic means are not
available, mine operators would only be
required to physically post the sampling
record and laboratory report on the
mine bulletin board. Also, as required in
proposed § 60.16(b), the sampling
records created under this section may
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be requested at any time by, and must
promptly be made available to, miners,
authorized representatives of miners, or
an authorized representative of the
Secretary.
MSHA believes that the posted
information including sampling results
and methodology and other relevant
information would inform miners of the
sampled exposures and would
encourage them to have heightened
awareness of potential health hazards
that could impact not only them but
other miners. It would also provide
them with knowledge to take proactive
actions to protect themselves and fellow
miners through better and safer work
practices and more active participation
in health and safety programs. This is
consistent with the Mine Act which
states that mine operators, with the
assistance of miners, have the
responsibility to prevent the existence
of unsafe and unhealthful conditions
and practices in mines. 30 U.S.C. 801(e).
Making miners aware that respirable
crystalline silica exposures below the
PEL may still pose a health risk could
encourage them to take steps to manage
their health risks.
6. Section 60.13—Corrective Actions
This proposed section includes
several actions a mine operator would
be required to take to protect miners’
health and safety when any sampling
result indicates that a miner’s exposure
to respirable crystalline silica exceeds
the proposed PEL. Proposed paragraph
(a)(1) would require the mine operator
to make NIOSH-approved respirators
available to affected miners before the
start of the next work shift. Proposed
paragraph (a)(2) would require mine
operators to ensure that affected miners
wear respirators for the full shift or
during the period of overexposure to
protect miners until miner exposures
are at or below the PEL.
Proposed paragraph (a)(3) would
require operators to take immediate
corrective actions to lower the
concentration of respirable crystalline
silica to levels at or below the PEL.
Some examples of corrective actions
include increasing air ventilation and/or
water flow rates, adding more water
sprays, and improving maintenance of
the existing engineering controls.
Once corrective actions have been
taken, proposed paragraph (a)(4)(i)
would require the operator to conduct
sampling in accordance with § 60.12(c)
to determine if the corrective actions
have been successful in lowering
exposures to at or below the PEL. If
sampling indicates that the corrective
actions did not reduce miner exposures
to at or below the PEL, proposed
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paragraph (a)(4)(ii) would require the
operator to implement additional or
new corrective actions until sampling
indicates miner exposures are at or
below the PEL.
Proposed § 60.13(b) would require the
mine operator to make a record of
corrective actions required under
proposed paragraph (a) of this section
and the dates of those actions. These
records would help the operator and
MSHA identify whether existing
controls are effective, or whether
maintenance or additional control
measures are needed.
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7. Section 60.14—Respiratory Protection
This proposed provision addresses
the use of respiratory protection
equipment. As noted earlier, the use of
respiratory protection equipment,
including powered air-purifying
respirators (PAPRs), would not be
permitted as a control to achieve
compliance with the proposed PEL
because engineering controls are more
effective than respirators in protecting
miners. However, temporary nonroutine use of respirators would be
allowed under limited circumstances.
Proposed paragraph (a) would require
the mine operator to provide respirators
to miners as a temporary measure in
accordance with proposed paragraph (c)
of this section, when miners are
working in concentrations of respirable
crystalline silica above the PEL under
specific, limited circumstances.
Proposed paragraph (a)(1) would require
the temporary use of respirators when
miners’ exposures exceed the proposed
PEL during the development and
implementation of engineering controls.
Proposed paragraph (a)(2) would
require the use of respirators for
temporary, nonroutine work to prevent
miners’ exposures at levels above the
proposed PEL. Examples include when
a miner is mixing cement to build a
stopping to separate a main intake from
return airways or is engaged in an
unplanned entry into an atmosphere
with excessive respirable crystalline
silica concentrations to perform a repair
or investigation that must occur before
feasible engineering or administrative
controls can be implemented.
The proposal is consistent with
NIOSH’s recommendation in the 1995
Criteria Document (NIOSH 1995a) and
is similar to the existing standards for
MNM and coal mines. NIOSH (1995a)
recommended the use of respirators as
an interim measure when engineering
controls and work practices are not
effective in maintaining worker
exposures for respirable crystalline
silica at or below the proposed PEL.
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MSHA’s existing MNM standards in
parts 56 and 57 permit mine operators
to allow miners to work for reasonable
periods of time protected by appropriate
respiratory protection in locations
where concentrations of contaminants
(including respirable crystalline silica)
exceed permissible levels and where
feasible engineering control measures
have not been developed or where
necessary by the nature of the work
involved (e.g., occasional entry into
hazardous atmospheres to perform
maintenance or investigation). MSHA’s
existing standards for respirable coal
mine dust require the mine operator to
make respiratory protection equipment
available while the operator evaluates
and implements engineering control
measures when a valid sample meets or
exceeds the applicable standard during
operator exposure monitoring. (30 CFR
70.208(e)(1); 30 CFR 71.206(h)(1); 30
CFR 72.700–72.701; 30 CFR
90.207(c)(1)).
Proposed paragraph (b) addresses
situations where miners are not able to
wear a respirator while working.
Proposed paragraph (b) would require
the mine operator, upon written
notification by a PLHCP, to transfer an
affected miner who is unable to wear a
respirator to work in another area of the
same mine, or to another occupation at
the same mine, where respiratory
protection is not required.
The operator must ensure that the
occupation and the area of the mine to
which the miner is temporarily
transferred do not expose the miner to
respirable crystalline silica above the
proposed PEL. Proposed paragraph
(b)(1) would require the mine operator
to continue to compensate the affected
miner at no less than the regular rate of
pay in the occupation held by that
miner immediately prior to the transfer.
Under proposed paragraph (b)(2), the
miner may be transferred back to the
initial work area or occupation when
the temporary, non-routine use of
respirators is no longer required.
MSHA believes that this proposed
provision is consistent with the
mandate in the Mine Act to provide the
maximum health protection for miners.
Also, any effect on miners by this
provision should be temporary since the
concentration of respirable crystalline
silica to which the miner would be
exposed must be controlled through
feasible engineering and administrative
controls on a long-term basis.
Proposed paragraph (c) includes the
respiratory protection requirements that
an operator must address when
providing respirators to miners.
Proposed paragraph (c)(1), like the
existing standards in parts 56, 57, and
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72, would require mine operators to
provide respiratory protection
equipment approved by NIOSH under
42 CFR part 84. Whenever respirators
are used by miners, proposed paragraph
(c)(1) would require the mine operator
to provide miners with NIOSHapproved atmosphere-supplying
respirators or air-purifying respirators.
Atmosphere-supplying respirators
provide clean breathing air from a
separate source (e.g., a self-contained air
tank), whereas air-purifying respirators
use filters, cartridges, or canisters to
remove contaminants from the air.
In mines, commonly used types of airpurifying respirators include
elastomeric respirators, filtering
facepiece respirators (FFRs), and PAPRs.
Elastomeric respirators, such as halffacepiece or full-facepiece tight-fitting
respirators, are made of synthetic or
natural rubber material and can be
cleaned, disinfected, stored, and
repeatedly re-used. FFRs (i.e., dust
masks), designed to cover areas of the
wearer’s face from the bridge of the nose
to the chin, are disposable respirators
composed of a weave of electrostatically
charged synthetic filter fibers and an
elastic head strap. PAPRs utilize a
blower to move ambient air through an
air-purifying filter that removes
particulates and delivers clean air to the
wearer. When air-purifying respirators
(elastomeric respirators, FFRs, and
PAPRs) are used, under proposed
paragraph (c)(1), the mine operator
would be required to select only highefficiency NIOSH-certified particulate
protection (i.e., 100 series or HE filters)
for respirable crystalline silica
protection. A 100 series and high
efficiency filter means that the filter
must demonstrate a minimum efficiency
level of 99.97 percent (i.e., the filter is
at least 99.97 percent efficient in
removing particles of 0.3 mm
aerodynamic mass median diameter).
Under proposed paragraphs (c)(1)(i)
through (c)(1)(ii), air-purifying
respirators would be required to be
equipped with one of the following
three particulate protection types: (1)
particulate protection defined as a 100
series under 42 CFR part 84; or (2)
particulate protection defined as High
Efficiency ‘‘HE’’ under 42 CFR part 84.
MSHA believes that air-purifying
respirators with the highest efficiency
NIOSH classifications for particulate
protection are most suitable in
protecting miners from occupational
exposure to a carcinogen such as
respirable crystalline silica.
Proposed paragraph (c)(2) would
require mine operators to follow the
provisions, as applicable, of ASTM
F3387–19, ‘‘Standard Practice for
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Respiratory Protection,’’ when
respiratory protection equipment is
needed. Under the proposal, MSHA
would require that the respiratory
program would be in writing and would
include the following minimally
acceptable program elements: program
administration; standard operating
procedures; medical evaluations;
respirator selection; training; fit testing;
and maintenance, inspection, and
storage. Beyond the minimally
acceptable program elements, mine
operators would be allowed to comply
with the provisions of the 2019 ASTM
standard that they deem applicable. The
need for temporary non-routine use of
respirators may vary, given the
variability of mining processes,
activities, and commodities that are
mined. MSHA believes that flexibility
afforded to mine operators under this
paragraph may lead mine operators to
focus more appropriately on those
provisions that are relevant to their
mine-specific situations, allowing them
to comply more efficiently and
effectively.
ASTM F3387–19 is a voluntary
consensus standard published by ASTM
International and was approved in 2019.
MSHA proposes to incorporate by
reference this consensus standard for
two reasons.
First, adopting this voluntary
consensus standard is consistent with
OMB Circular A–119, which encourages
Federal agencies to ‘‘minimize reliance
on government-unique standards where
an existing standard would meet the
Federal government’s objective.’’ ASTM
F3387–19 comprehensively addresses
all aspects of establishing,
implementing, and evaluating
respiratory protection programs, and
describes respiratory protection program
elements which include: program
administration; standard operating
procedures; medical evaluation;
respirator selection; training; fit testing;
and respirator maintenance, inspection,
and storage.
Second, ASTM F3387–19 reflects
current respirator technology and an upto-date understanding of effective
respiratory protection. For example,
ASTM F3387–19 provides detailed
information on respirator selection that
are based on NIOSH’s long-standing
experience of testing and approving
respirators for occupational use and
OSHA’s research and rulemaking on
respiratory protection.
More detailed discussion on ASTM
F3387–19 is provided later in C.
Updating MSHA Respiratory Protection
Standards: Proposed Incorporation of
ASTM F3387–19 by Reference.
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8. Section 60.15—Medical Surveillance
for Metal and Nonmetal Miners
This proposed provision would
require MNM mine operators to provide
mandatory medical examinations to
miners who begin in the mining
industry after the effective date of the
rule and offer voluntary periodic
examinations to all other miners. These
medical examinations would be
provided by a PLHCP or specialist. The
proposed requirements in this section
are consistent with the Mine Act’s
mandate to provide maximum health
protection for miners and provide MNM
miners with information needed for
early detection of respirable crystalline
silica-related disease, resulting in
prevention of disabling disease.
The proposed requirements for MNM
mine operators are also generally
consistent with existing medical
surveillance requirements for coal mine
operators under 30 CFR 72.100 although
the requirements differ in some
respects. For example, the proposed
provision specifies that medical
examinations must be provided by a
PLHCP or specialist, while the existing
medical surveillance requirements for
coal miners in § 72.100 coordinate with
the surveillance system managed by
NIOSH’s Coal Workers’ Health
Surveillance Program (CWHSP) which
works with coal mine operators under
NIOSH regulations to provide medical
surveillance. Proposed paragraph
60.15(a) would require that each MNM
mine operator make medical
examinations available to each MNM
miner, at no cost to the miner,
regardless of whether miners are
reasonably expected to be exposed to
any level of respirable crystalline silica.
This proposed requirement is consistent
with section 101(a)(7) of the Mine Act.
Proposed paragraph 60.15(a) would
also require medical examinations to be
performed by a PLHCP or specialist. A
PLHCP is an individual whose legally
permitted scope of practice (i.e., license,
registration, or certification) allows that
individual to independently provide or
be delegated the responsibility to
provide some or all of the required
health services (i.e., chest X-rays,
spirometry, symptom assessment, and
occupational history). A specialist, as
defined in proposed § 60.2, refers to an
American Board-certified specialist in
pulmonary disease or occupational
medicine. The Agency believes it is
appropriate to allow not only a
physician, but also any State-licensed
health care professional, to perform the
required medical examinations. This
would provide operators with the
flexibility needed to use professionals
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with necessary medical skills and
minimize cost and compliance burdens.
Proposed paragraph (a)(1) requires
periodic examinations to be offered to
all MNM miners at the frequencies
specified in this section. Proposed
paragraph (a)(2) specifies the types of
medical examinations and is consistent
with the existing requirements for coal
mine operators under existing § 72.100.
Proposed paragraphs (a)(2)(i) and (ii)
would require MNM operators to
provide each miner with a medical
examination that includes a review of
the miner’s medical and work history
and a physical examination. The
medical and work history would cover
a miner’s present and past work
exposures, illnesses, and any symptoms
indicating respirable crystalline silicarelated diseases and compromised lung
function. The medical and work history
should focus not only on any history of
tuberculosis, smoking, or exposure to
respirable crystalline silica, but also on
any diagnoses and symptoms of
respiratory system dysfunction,
including shortness of breath, coughing,
or wheezing. The physical examination
under (a)(2)(ii) would be focused on the
respiratory tract. For the reasons stated
above, these proposed requirements
differ from the existing requirements for
coal miners. The existing medical
surveillance requirements for coal
miners in 42 CFR 37 specify
standardized data collection elements
for occupational histories and
respiratory symptom assessment while
proposed paragraphs (a)(2)(i) and (ii)
specify a respiratory-focused history
and physical examination by a clinician.
Under proposed paragraph (a)(2)(iii),
MSHA would require all medical
examinations to include a chest X-ray.
The required chest X-ray is a posterior/
anterior view no less than 14 x 17
inches and no more than 16 x 17 inches
at full inspiration, recorded on either
film or digital radiography systems. The
chest X-ray must be classified by a
NIOSH-certified B Reader, in
accordance with the Guidelines for the
Use of the International Labour Office
(ILO) International Classification of
Radiographs of Pneumoconioses. The
ILO recently made additional standard
digital radiographic images available
and has published guidelines on the
classification of digital radiographic
images (ILO 2022). This is a standard
practice in pneumoconiosis surveillance
programs and can potentially detect
other respirable crystalline silica-related
conditions, including lung cancer
(Industrial Minerals Association-North
America and Mine Safety and Health
Administration, 2008). The test would
provide data that can be used to assess
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for progression of silicosis and for other
respirable crystalline silica-related
conditions in MNM miners.
MSHA preliminarily concludes that
the number of B readers in the U.S. is
adequate to classify chest X-rays
conducted as part of the respirable
crystalline silica rule (OSHA 2016a, 81
FR 16286, 16821). As discussed in
OSHA’s 2016 final silica rule, the
number of B Readers is driven by
supply and demand created by a free
market, and many physicians choose to
become B readers based on demands for
such services (OSHA 2016a, 81 FR
16286, 16822). NIOSH is also able to
train enough B readers to handle any
potential increase in demand, providing
several pathways for physicians to
become B readers, such as free selfstudy materials by mail or download
and free B reader examinations (OSHA
2016a, 81 FR 16286, 16822). In addition,
courses and examinations for
certification are periodically offered for
a fee through the American College of
Radiology (OSHA 2016a, 81 FR 16286,
16822). Even if B readers are scarce in
certain geographical locations, digital Xrays can be easily transmitted
electronically to B readers located
anywhere in the U.S. (OSHA 2016a, 81
FR 16286, 16822).
Under proposed paragraph (a)(2)(iv),
MSHA would require that pulmonary
function testing (including spirometry)
be part of every medical examination.
The pulmonary function test must be
administered by a spirometry technician
with a current certificate from a NIOSHapproved Spirometry Training
Sponsorship. The purpose of spirometry
is to measure baseline lung function
followed by periodic tests to detect early
impairment patterns, such as
obstruction of air flow and restriction
caused by underlying respiratory
disease. This measurement can provide
critical information for the primary,
secondary, and tertiary prevention of
workplace-related lung diseases,
including respirable crystalline silicarelated diseases. The use of spirometry
is consistent with recommendations of
the Dust Advisory Committee (U.S.
DOL, 1996) and the NIOSH Criteria
Document (1974). Indeed, NIOSH
(2014a) notes that properly conducted
spirometry should be part of a
comprehensive workplace respiratory
health program. Spirometry and chest
X-rays are complementary examinations
for detecting adverse health effects from
respirable crystalline silica exposures.
In order to maintain a certificate from
a NIOSH-approved course, technicians
must complete an initial training and
then refresher training every five years
(OSHA 2016a, 81 FR 16286, 16825). As
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discussed in OSHA’s 2016 silica final
rule, course sponsors are located
throughout the U.S. and some sponsors
will travel to a requested site to teach a
course (OSHA 2016a, 81 FR 16286,
16825). One NIOSH-approved sponsor
offers instructor-led live virtual initial
training. Several live virtual and webbased refresher training options are also
available. Because the required training
is not too frequent and course sponsors
appear to be widely available
throughout the U.S., MSHA
preliminarily concludes that the
requirement that technicians maintain a
certificate from a NIOSH-approved
course will not impose substantial
burdens on providers of spirometry
testing.
MSHA believes that the proposed
medical examinations consisting of a
medical and work history, a physical
examination, a chest X-ray, and a
spirometry test would help medical
professionals identify early symptoms of
respirable crystalline silica-related
diseases, assist MNM miners in
protecting their health, and lower the
risk that MNM miners become
materially impaired due to occupational
exposure to respirable crystalline silica.
Under proposed paragraph (b), MSHA
would require MNM mine operators to
provide every miner employed at MNM
mines with the opportunity to have
periodic medical examinations. Miner
participation would be voluntary, as in
the case of the examination requirement
for coal miners in 30 CFR 72.100(b).
Starting on the proposed effective date,
mine operators must provide the
opportunity for an examination to MNM
miners no later than 5 years after the
date of their last medical surveillance
examination, and in addition, during a
6-month period that begins no less than
3.5 years and not more than 4.5 years
from the end of the last 6-month period
for medical examinations. Periodic
examinations would allow for
comparisons with a miner’s prior
examination results, help detect
respirable crystalline silica-related
disease including silicosis, and address
further progression of existing
respiratory disease. If a miner has a
positive chest X-ray (ILO category of 1/
0+), it is important to intervene as
promptly as possible for maximum
health protection. In addition, an
interval of 5 years or less between each
miner’s periodic examinations can
ensure detection of declines in a miner’s
lung function due to potential
occupational exposure. MSHA believes
that the proposed schedule, which is
consistent with the periodic
examination for coal miners required
under § 72.100(b), would provide MNM
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44913
mine operators with flexibility in
offering examinations to miners.
Proposed paragraph (c) would require
MNM mine operators to provide a
mandatory initial medical examination
for each MNM miner who is new to the
mining industry. Consequently, if a
miner had previous mining experience
(such as working in a coal mine) and
subsequently came to work in an MNM
mine, MSHA would not require that the
MNM mine operator provide the miner
with an initial examination after the
miner begins employment. Mandatory
initial examinations would be
conducted when miners are first hired
in the mining industry and would
provide an individual baseline of each
miner’s health status. This initial
examination would assist in the early
detection of respirable crystalline silicarelated illnesses and conditions that
may make the miner more susceptible to
the toxic effects of respirable crystalline
silica. The individual baseline would
also be valuable in assessing any future
health changes in each miner. Overall,
the initial examination results would
enable miners to respond appropriately
to information about their health status.
Proposed paragraph (c)(1) would
require that the mandatory initial
medical examination occur no later than
30 days after a miner new to the
industry begins employment. Proposed
paragraphs (c)(2) and (3) would require
MNM mine operators to provide
mandatory follow-up examinations to
new miners who were eligible for an
initial mandatory medical examination
under proposed paragraph (c). MSHA
believes follow-up examinations are
important for assessments of any
changes in a new miner’s health status
and for future diagnoses.
Under proposed paragraph (c)(2),
MSHA would require that the mine
operator provide a mandatory follow-up
examination to the miner no later than
3 years after the miner’s initial medical
examination. Under proposed paragraph
(c)(3), if a miner’s 3-year follow-up
examination shows evidence of a
respirable crystalline silica-related
disease or decreased lung function, the
operator would be required to provide
the miner with another mandatory
follow-up examination with a specialist,
as defined in proposed § 60.2, within 2
years. This proposed requirement is
intended to ensure that any miner
whose follow-up medical examination
shows evidence of silicosis or evidence
of decreased lung function, as
determined by the PLHCP or specialist,
is seen by a professional with expertise
in respiratory disease. This would
ensure that miners would benefit from
not only expert medical judgment but
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also counseling regarding work
practices and personal habits that could
affect the miners’ health. For the reasons
stated above, this proposed requirement
differs from the existing requirements
for coal miners, which provides for
follow up surveillance testing but does
not include interaction with a PLHCP or
specialist.
Proposed paragraph (d) would require
that the results of any medical
examination performed under this
section be kept confidential and
provided only to the miner. The miner
is also entitled to request that the
medical examination results be
provided to the miner’s designated
physician. Based on MSHA’s experience
with coal miners’ medical surveillance,
the Agency believes that confidentiality
regarding medical conditions is
essential and that it encourages miners
to take advantage of the opportunity to
detect early adverse health effects due to
respirable crystalline silica. See 79 FR
24813, at 24928, May 1, 2014.
Under proposed paragraph (e), MNM
mine operators would be required to
obtain a written medical opinion from a
PLHCP or specialist within 30 days of
the medical examination that includes
only the date of a miner’s medical
examination, a statement that the
examination has met the requirements
of this section, and any recommended
limitations on the miner’s use of
respirators. This would allow the mine
operator to verify the examination has
occurred and would provide the mine
operator with information on miners’
ability to use respirators. Proposed
paragraph (f) would require the mine
operator to maintain a record of the
written medical opinions obtained from
the PLHCP or specialist under proposed
paragraph (e).
9. Section 60.16—Recordkeeping
Requirements.
Section 60.16 lists all the proposed
recordkeeping requirements under this
proposed part. To ensure that mine
operators track actual or potential
exposures, risks, and controls and keep
miners, miners’ representatives, and
other stakeholders informed about them,
the proposed part 60 establishes five
recordkeeping requirements. Discussion
of these requirements follow and are
summarized in table 1 to paragraph (a)
in § 60.16 of the rule text.
First, this section would require that,
once mine operators complete the
sampling or semi-annual evaluations
required under proposed § 60.12, the
operators retain the associated exposure
monitoring records for at least 2 years.
Examples of exposure monitoring
records include the date of sampling or
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evaluation, names and occupations of
miners who were sampled, description
of sampling or evaluation method, and
laboratory reports of sampling analysis.
The 2-year period would give mine
operators sufficient exposure
monitoring data to evaluate the
effectiveness of their engineering and
administrative controls over different
mining and weather conditions.
Second, mine operators would also be
required to retain records of corrective
actions made under proposed § 60.13(b)
for at least 2 years from the date when
each corrective action was taken. This
proposed requirement is similar to the
recordkeeping requirements related to
other corrective-action requirements
under parts 56 and 57 (for MNM mines)
and parts 70, 71, and 90 (for coal
mines).
Third, this proposed section would
require mine operators to maintain any
written determination records that they
receive from a PLHCP or specialist.
When a PLHCP or specialist certifies in
writing that a miner cannot wear a
respirator, including a PAPR, that miner
must be temporarily transferred to a
different work area or task where
respiratory protection is not required (or
needed). In such cases, mine operators
would be required to retain the written
determinations by a PLHCP or specialist
for the duration of the miner’s
employment plus 6 months.
Fourth, under this section, MNM
mine operators would be required to
maintain written medical opinion
records that they obtain from a PLHCP
or specialist who conducts medical
examinations of their miners under
proposed § 60.15. This proposed
recordkeeping requirement would apply
only to MNM mine operators. Under
proposed § 60.15, after the examination
has taken place, the MNM mine
operator would receive from the PLHCP
or specialist a written medical opinion
that contains the date of the medical
examination, a statement that the
examination has met the requirements
under this proposed rule, and any
recommended limitations on the
miner’s use of respirators. Upon receipt,
the mine operator would retain the
medical opinion for the duration of the
miner’s employment plus 6 months.
Proposed paragraph (b) would ensure
that all the listed records would be
made available promptly upon request
to miners, authorized representatives of
miner(s), and authorized representatives
of the Secretary of Labor.
any section or provision of the Lowering
Miners’ Exposure to Respirable
Crystalline Silica and Improving
Respiratory Protection rule—including
its conforming amendments in sections
of 30 CFR parts 56, 57, 70, 71, 72, 75,
and 90 that address respirable
crystalline silica or respiratory
protection—is held invalid or
unenforceable or is stayed or enjoined
by any court of competent jurisdiction,
the remaining sections or provisions
should remain effective and operative.
Second, the severability clause
expresses MSHA’s judgment, based on
its technical and scientific expertise,
that each individual section and
provision of the rule can remain
effective and operative if some sections
or provisions are invalidated, stayed, or
enjoined. Accordingly, MSHA’s
inclusion of this severability clause
addresses the twin concerns of Federal
courts when determining the propriety
of severability: identifying agency intent
and clarifying that any severance will
not undercut the structure or function of
the rule more broadly. Am. Fuel &
Petrochem. Mfrrs. v. Env’t Prot. Agency,
3 F.4th 373, 384 (D.C. Cir. 2021)
(‘‘Severability ‘depends on the issuing
agency’s intent,’ and severance ‘is
improper if there is substantial doubt
that the agency would have adopted the
severed portion on its own’ ’’) (quoting
North Carolina v. FERC, 730 F.2d 790,
796 (D.C. Cir. 1984) and New Jersey v.
Env’t Prot. Agency, 517 F.3d 574, 584
(D.C. Cir. 2008)).
Under the principle of severability, a
reviewing court will generally presume
that an offending provision of a
regulation is severable from the
remainder of the regulation, so long as
that outcome appears consistent with
the issuing agency’s intent, and the
remainder of the regulation can function
independently without the offending
provision. See K Mart Corp. v. Cartier,
Inc., 486 U.S. 281, 294 (1988)
(invalidating and severing subsection of
a regulation where it would not impair
the function of the statute as a whole
and there was no indication the
regulation would not have been passed
but for inclusion of the invalidated
subsection). Consequently, in the event
that a court of competent jurisdiction
stays, enjoins, or invalidates any
provision, section, or application of this
rule, the remainder of the rule should be
allowed to take effect.
10. Section 60.17—Severability
The severability clause under
proposed § 60.17 serves two purposes.
First, it expresses MSHA’s intent that if
The proposed rule would require
conforming amendments in 30 CFR
parts 56, 57, 70, 71, 72, 75, and 90 based
on the proposed new part 60.
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B. Conforming Amendments
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1. Part 56—Safety and Health
Standards—Surface Metal and
Nonmetal Mines
a. Section 56.5001—Exposure Limits for
Airborne Contaminants
For respirable crystalline silica,
proposed part 60 would establish
exposure limits and other related
requirements for all mines. Existing
paragraph (a) of § 56.5001 governs
exposure limits for airborne
contaminants, except asbestos, for
surface MNM mines. MSHA is
proposing to amend paragraph (a) of
§ 56.5001 to add respirable crystalline
silica as an exception. The amended
paragraph (a) of § 56.5001 would govern
exposure limits for airborne
contaminants other than respirable
crystalline silica and asbestos for
surface MNM mines.
2. Part 57—Safety and Health
Standards—Underground Metal and
Nonmetal Mines
a. Section 57.5001—Exposure Limits for
Airborne Contaminants
Existing paragraph (a) of § 57.5001
governs exposure limits for airborne
contaminants, except asbestos, for
underground MNM mines. Similar to
the proposed changes discussed above
for § 56.5001, MSHA is proposing to
amend paragraph (a) of § 57.5001 to add
respirable crystalline silica as an
exception. The amended paragraph (a)
of § 57.5001 would govern exposure
limits for airborne contaminants other
than respirable crystalline silica and
asbestos for underground MNM mines.
3. Part 70—Mandatory Health
Standards—Underground Coal Mines
a. Section 70.2—Definitions.
MSHA proposes to remove the Quartz
definition in § 70.2. With the adoption
of an independent respirable crystalline
silica standard in proposed part 60, the
Agency is proposing to remove RCMD
when quartz is present in § 70.101 and
the term quartz would no longer appear
in part 70.
ddrumheller on DSK120RN23PROD with PROPOSALS2
b. Section 70.101—Respirable Dust
Standard When Quartz Is Present
MSHA is proposing to remove the
entire section and reserve the section
number. The RCMD when quartz is
present in § 70.101 would no longer be
needed because MSHA is proposing an
independent respirable crystalline silica
standard in proposed part 60.
MSHA’s proposed independent
standard for respirable crystalline silica
would result in miners’ exposure to
respirable crystalline silica no longer
being controlled indirectly by reducing
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respirable dust. NIOSH, the Secretary of
Labor’s Advisory Committee on the
Elimination of Pneumoconiosis Among
Coal Mine Workers (Dust Advisory
Committee), and the Department of
Labor’s Inspector General 35 have each
recommended the adoption of an
independent standard for respirable
quartz exposure in coal mines. NIOSH
evaluated the effectiveness of the
existing standard and found the
approach of controlling miners’
exposures to respirable crystalline silica
indirectly through the control of
respirable dust did not protect miners
from excessive exposure to respirable
quartz in all cases (Joy GJ 2012). The
study concluded that a separate
respirable quartz standard, as described
by the 1995 NIOSH Criteria Document,
could reduce miners’ risk of
overexposures to respirable quartz and,
by extension, their risk of developing
silicosis. The adoption of a separate
standard would hold operators
accountable, at risk of a citation and
monetary penalty, when overexposures
of the respirable crystalline silica PEL
occur and enhance its sampling program
to increase the frequency of operator
sampling.
c. Section 70.205—Approved Sampling
Devices; Operation; Air Flowrate
MSHA is proposing to amend
paragraph (c) of § 70.205 to remove the
reference to the reduced RCMD
standard. References to the RCMD
exposure limit specified in § 70.100
would replace references to the
applicable standard. The rest of the
section would remain unchanged.
d. Section 70.206—Bimonthly
Sampling; Mechanized Mining Units
MSHA is proposing to amend subpart
C, Sampling Procedures, by removing
§ 70.206 and reserving the section
number. Section 70.206 included
requirements for bimonthly sampling of
mechanized mining units which were in
effect until January 31, 2016, and are no
longer needed.
35 Office of Inspector General Audit 05–21–001–
06–001, MSHA Needs to Improve Efforts to Protect
Coal Miners from Respirable Crystalline Silica
(Nov. 12, 2020). The Inspector General
recommended that MSHA:
1. Adopt a lower legal exposure limit for silica
in coal mines based on recent scientific evidence.
2. Establish a separate standard for silica that
allows MSHA to issue a citation and monetary
penalty when violations of its silica exposure limit
occur.
3. Enhance its sampling program to increase the
frequency of inspector samples where needed (e.g.,
by implementing a risk-based approach).
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e. Section 70.207—Bimonthly Sampling;
Designated Areas
MSHA is proposing to amend subpart
C, Sampling Procedures, by removing
§ 70.207 and reserving the section
number. Section 70.207 included
requirements for bimonthly sampling of
designated areas that were in effect until
January 31, 2016, and are no longer
needed.
f. Section 70.208—Quarterly Sampling;
Mechanized Mining Units
MSHA is proposing to amend § 70.208
to remove references to a reduced
RCMD standard. Paragraph (c) in
§ 70.208 would be removed and the
paragraph designation reserved.
References to the respirable dust
standard specified in § 70.100 would
replace references to the applicable
standard throughout the section.
A new table 1 to § 70.208 would be
added. The table contains the Excessive
Concentration Values (ECV) for the
section based on a single sample, 3
samples, or the average of 5 or 15 fullshift coal mine dust personal sampler
unit (CMDPSU) or continuous personal
dust monitor (CPDM) concentration
measurements. This table contains the
remaining ECV after the removal of the
reduced standard in § 70.101. It was
generated from data contained in
existing Tables 70–1 and 70–2 to
subpart C of part 70. Conforming
changes are made to paragraphs (e) and
(f)(1) and (2) to update the name of the
table to table 1 to § 70.208.
g. Section 70.209—Quarterly Sampling;
Designated Areas
Similar to the proposed changes
discussed above for § 70.208, MSHA is
proposing to amend § 70.209 to remove
references to a reduced RCMD standard.
Paragraph (b) in § 70.209 would be
removed and the paragraph designation
reserved. References to the RCMD
exposure limit specified in § 70.100
would replace references to the
applicable standard.
A new table 1 to § 70.209 would be
added. The table contains the ECVs for
the section based on a single sample, 2
or more samples, or the average of 5 or
15 full-shift CMDPSU/CPDM
concentration measurements. This table
contains the remaining ECV after the
removal of the reduced RCMD standard
in § 70.101. It was generated from data
contained in existing Tables 70–1 and
70–2 to subpart C of part 70.
Conforming changes are made to
paragraphs (c) and (d)(1) and (2) to
update the name of the table to table 1
to § 70.209.
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h. Subpart C—Table 70–1 and Table 70–
2
MSHA is proposing to amend subpart
C, Sampling Procedures, by removing
Table 70–1 Excessive Concentration
Values (ECV) Based on Single, Full-Shift
CMDPSU/CPDM Concentration
Measurements and Table 70–2 Excessive
Concentration Values (ECV) Based on
the Average of 5 or 15 Full-Shift
CMDPSU/CPDM Concentration
Measurements because § 70.101 would
be removed. These tables would be
replaced with new tables added to
§§ 70.208 and 70.209.
its sampling program to increase the
frequency of inspector sampling.
update the name of the table to table 1
to § 71.206.
c. Section 71.205—Approved Sampling
Devices; Operation; Air Flowrate
e. Section 71.300—Respirable Dust
Control Plan; Filing Requirements
MSHA is proposing to amend
paragraph (c) of § 71.205 to remove the
reference to the reduced RCMD
standard. References to the respirable
dust standard specified in § 71.100
would replace the reference to the
applicable standard. The rest of the
section would remain unchanged.
MSHA is proposing to amend § 71.300
to remove references to the reduced
RCMD standard. The respirable dust
standard specified in § 71.100 would
replace references to the applicable
standard. The rest of the section would
remain unchanged.
4. Part 71—Mandatory Health
Standards—Surface Coal Mines and
Surface Work Areas of Underground
Coal Mines
Similar to the analysis of conforming
amendments for §§ 70.208 and 70.209,
MSHA is proposing to amend § 71.206
to remove references to the reduced
RCMD standard. Paragraph (b) in
§ 71.206 would be removed and the
paragraph designation reserved. Other
conforming changes for § 71.206 would
remove references to the applicable
standard and replace them, where
needed, with references to the respirable
dust standard specified in § 71.100
throughout the section.
MSHA is also proposing to amend
paragraph (l) by removing Table 71–1
Excessive Concentration Values (ECV)
Based on Single, Full-Shift CMDPSU/
CPDM Concentration Measurements and
Table 71–2 Excessive Concentration
Values (ECV) Based on the Average of
5 Full-Shift CMDPSU/CPDM
Concentration Measurements since
reference to a reduced RCMD standard
in § 71.101 would be removed. They
would be replaced with a new table
added to § 71.206.
Existing paragraph (m) would be
modified by removing the language, ‘‘in
effect at the time the sample is taken, or
a concentration of respirable dust
exceeding 50 percent of the standard
established in accordance with
§ 71.101,’’ because the reduced standard
in § 71.101 would be removed, as
discussed above, which removes the
reference to the reduced standard and
replaces it with a reference to the
respirable dust standard specified in
§ 71.100.
A new table 1 to § 71.206 would be
added. This table contains the ECV for
the section based on a single sample,
two or more samples, or the average of
five full-shift CMDPSU/CPDM
concentration measurements. This table
contains the remaining ECV after the
removal of the reduced standard in
§ 71.101. It was generated from data
contained in existing Tables 71–1 and
71–2 to subpart C of part 71.
Conforming changes are made to
paragraphs (h) and (i)(1) and (2) to
ddrumheller on DSK120RN23PROD with PROPOSALS2
a. Section 71.2—Definitions
As discussed in the analysis of
conforming amendments for § 70.2,
MSHA also proposes to remove the
Quartz definition in § 71.2 because the
Agency is proposing to remove the
respirable dust standard when quartz is
present in § 71.101. The term quartz
would no longer appear in part 71.
b. Section 71.101—Respirable Dust
Standard When Quartz Is Present
MSHA is proposing to remove the
entire section of § 71.101 and reserve
the section number. Similar to the
proposed conforming amendments for
§ 70.101, the respirable coal mine dust
standard when quartz is present in
§ 71.101 would no longer be needed
because MSHA is proposing an
independent respirable crystalline silica
standard in part 60.
MSHA’s proposal to adopt an
independent standard for respirable
crystalline silica would replace the
existing method of indirectly controlling
miners’ exposure to silica by reducing
respirable coal dust. As stated
previously, NIOSH evaluated the
effectiveness of the existing standard
and found the existing approach of
controlling miners’ exposures to
respirable crystalline silica indirectly
through the control of respirable dust
did not protect miners from excessive
exposure to respirable crystalline silica
in all cases. The study concluded that
a separate respirable crystalline silica
standard, as described by the 1995
NIOSH Criteria Document, could reduce
miners’ risk of overexposures to
respirable crystalline silica and, by
extension, their risk of developing
silicosis. The adoption of a separate
standard would allow MSHA to issue a
citation and monetary penalty when
overexposures of the respirable
crystalline silica PEL occur and enhance
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d. Section 71.206—Quarterly Sampling;
Designated Work Positions
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f. Section 71.301—Respirable Dust
Control Plan; Approval by District
Manager and Posting
MSHA is proposing to amend § 71.301
to remove references to the reduced
RCMD standard. The respirable dust
standard specified in § 71.100 would
replace references to the applicable
standard. The rest of the section would
remain unchanged.
5. Part 72—Health Standards for Coal
Mines
a. Section 72.800—Single, Full-Shift
Measurement of Respirable Coal Mine
Dust
MSHA is proposing to amend § 72.800
in subpart E, Miscellaneous, and remove
references to the reduced RCMD
standard. The proposed section would
also replace references to Tables 70–1,
71–1, and 90–1 with references to tables
in §§ 70.208, 70.209, 71.206, and 90.207.
6. Part 75—Mandatory Safety
Standards—Underground Coal Mines
a. Section 75.350(b)(3)(i) and (ii)—Belt
Air Course Ventilation
MSHA is proposing to update
§ 75.350 by revising paragraph (b)(3)(i)
and removing paragraphs (b)(3)(i)(A)
and (B) and (b)(3)(ii).
Paragraph (b)(3)(i)(A) would be
removed because its provision has not
been in effect since August 1, 2016.
Paragraph (b)(3)(i)(B) would be removed
because the proposed revised language
in paragraph (b)(3)(i) would be
simplified by stating that ‘‘[t]he average
concentration of respirable dust in the
belt air course, when used as a section
intake air course, shall be maintained at
or below 0.5 mg/m3.’’ This would
ensure that miners would be protected
from coal dust overexposures, including
respirable crystalline silica
overexposures, by maintaining the
RCMD PEL in the belt air course at 50
mg/m3. Therefore, paragraph (b)(3)(i)(B)
which sets the PEL for belt course air at
0.5 mg/m3 would be redundant.
Existing paragraph (b)(3)(ii) would be
removed since it refers to a reduced
RCMD standard under § 70.101 that
would also be removed. Existing
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paragraph (b)(3)(iii) would be
redesignated to (b)(3)(ii).
7. Part 90—Mandatory Health
Standards—Coal Miners Who Have
Evidence of the Development of
Pneumoconiosis
a. Section 90.2—Definitions
Similar to the proposed changes for
§§ 70.2 and 71.2, MSHA proposes to
remove the Quartz definition in § 90.2
because the Agency proposes to remove
the respirable dust standard when
quartz is present in § 90.101. The term
quartz would no longer appear in part
90.
In addition, MSHA is revising the
definition of Part 90 miner to remove
references to the reduced RCMD
standard. The respirable dust standard
specified in § 90.100 would replace the
reference to the applicable standard.
The definition of Part 90 miner would
also be updated to define Part 90 miners
as miners who have exercised the
option to work in an area of a mine
where the average concentration of
respirable dust in the mine atmosphere
during each shift to which that miner is
exposed is continuously maintained at
or below the respirable dust standard
specified in § 90.100.
ddrumheller on DSK120RN23PROD with PROPOSALS2
b. Section 90.3—Part 90 Option; Notice
of Eligibility; Exercise of Option
MSHA is proposing to revise
paragraph (a) in § 90.3 to require that
miners diagnosed with pneumoconiosis
must be afforded the option to work in
an area of a mine where the average
concentration of respirable dust is
continuously maintained below the
respirable dust standard specified in
§ 90.100 rather than at or below the
applicable standard. The rest of the
section would remain unchanged.
c. Section 90.101—Respirable Dust
Standard When Quartz Is Present
MSHA is proposing to remove the
entire section and reserve the section
number. The respirable coal mine dust
standard when quartz is present in
§ 90.101 would no longer be needed
because MSHA is proposing an
independent respirable crystalline silica
standard in proposed part 60.
MSHA’s proposal to adopt an
independent standard for respirable
crystalline silica would replace the
existing method of indirectly controlling
miners’ exposure to respirable
crystalline silica by reducing respirable
coal dust. As stated previously, NIOSH
evaluated the effectiveness of the
existing standard and found the existing
approach of controlling miners’
exposures to respirable crystalline silica
indirectly through the control of
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d. Section 90.102—Transfer; Notice
MSHA is proposing to amend § 90.102
to remove references to the reduced
RCMD standard. The respirable dust
standard specified in § 90.100 would
replace references to the applicable
standard. The rest of the section would
remain unchanged.
Concentration Measurements because
§ 90.101 would be removed.
A new table 1 to § 90.207 would be
added to replace the tables removed in
paragraph (g). The table contains the
ECV for the section based on a single
sample, two or more samples, or the
average of 5 full-shift CMDPSU/CPDM
concentration measurements. This table
contains the remaining ECV after the
removal of the reduced standard in
§ 90.101. It was generated from data
contained in existing Tables 90–1 and
90–2 to subpart C of part 90.
Conforming changes are made to
paragraphs (c) and (d)(1) and (2) to
update the name of the table to table 1
to § 90.207.
e. Section 90.104—Waiver of Rights; ReExercise of Option
MSHA is proposing to amend § 90.104
to remove references to the reduced
RCMD standard. The respirable dust
standard specified in § 90.100 would
replace references to the applicable
standard. The rest of the section would
remain unchanged.
i. Section 90.300—Respirable Dust
Control Plan; Filing Requirements
MSHA is proposing to amend § 90.300
to remove references to the reduced
RCMD standard. The respirable dust
standard specified in § 90.100 would
replace references to the applicable
standard. The rest of the section would
remain unchanged.
f. Section 90.205—Approved Sampling
Devices; Operation; Air Flowrate
MSHA is proposing to amend § 90.205
to remove the reference to the reduced
RCMD standard. The respirable dust
standard specified in § 90.100 would
replace the reference to the applicable
standard. The rest of the section would
remain unchanged.
j. Section 90.301—Respirable Dust
Control Plan; Approval by District
Manager; Copy to Part 90 Miner
MSHA is proposing to amend § 90.301
to remove references to the reduced
RCMD standard. The respirable dust
standard specified in § 90.100 would
replace references to the applicable
standard. The rest of the section would
remain unchanged.
respirable dust did not protect miners
from excessive exposure to respirable
quartz in all cases. The study concluded
that a separate respirable quartz
standard, as described by the 1995
NIOSH Criteria Document, could reduce
miners’ risk of overexposures to
respirable quartz and, by extension,
their risk of developing silicosis.
g. Section 90.206—Exercise of Option or
Transfer Sampling
MSHA is proposing to amend § 90.206
to remove references to the reduced
RCMD standard. The respirable dust
standard specified in § 90.100 would
replace references to the applicable
standard. The rest of the section would
remain unchanged.
h. Section 90.207—Quarterly Sampling
Similar to the analysis of conforming
amendments for §§ 70.208, 70.209, and
71.206, MSHA is proposing to amend
§ 90.207 to remove references to the
reduced RCMD standard. Paragraph (b)
in § 90.207 would be removed and the
paragraph designation reserved. The
respirable dust standard specified in
§ 90.100 would replace references to the
applicable standard. The rest of the
section would remain unchanged.
MSHA is proposing to amend
paragraph (g) by removing the Table 90–
1 Excessive Concentration Values (ECV)
Based on Single, Full-Shift CMDPSU/
CPDM Concentration Measurements and
Table 90–2 Excessive Concentration
Values (ECV) Based on the Average of
5 Full-Shift CMDPSU/CPDM
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C. Updating MSHA Respiratory
Protection Standards: Proposed
Incorporation of ASTM F3387–19 by
Reference
MSHA is proposing to update the
Agency’s existing respiratory protection
standard to help safeguard the life and
health of all miners exposed to
respirable airborne hazards at MNM and
coal mines. The proposed rule would
incorporate by reference ASTM F3387–
19, ‘‘Standard Practice for Respiratory
Protection’’ (ASTM F3387–19), as
applicable, in existing §§ 56.5005,
57.5005, and 72.710, as well as in
proposed § 60.14(c)(2). The ASTM
F3387–19 standard includes provisions
for selection, fitting, use, and care of
respirators used to remove airborne
contaminants from the air using filters,
cartridges, or canisters, as well as
respirators that protect in oxygendeficient or immediately dangerous to
life or health (IDLH) atmospheres.
ASTM F3387–19 is based on the most
recent consensus standards recognized
by experts in government and
professional associations on the
selection, use, and maintenance for
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respiratory equipment. The ASTM
Standard would replace American
National Standards Institute’s ANSI
Z88.2–1969, ‘‘Practices for Respiratory
Protection’’ (ANSI Z88.2–1969), which
is incorporated in the existing
standards.
Incorporating this voluntary
consensus standard complies with the
Federal mandate—as set forth in the
National Technology Transfer and
Advancement Act of 1995 and OMB
Circular A119—that agencies use
voluntary consensus standards in their
regulatory activities unless doing so
would be legally impermissible or
impractical. This standard proposed for
incorporation would also improve
clarity because it is a consensus
standard developed by stakeholders.
Under existing standards, whenever
respiratory protective equipment is
used, mine operators are required to
have a respiratory protection program
that is consistent with the provisions of
ANSI Z88.2–1969. At the time of its
publication, ANSI Z88.2–1969 reflected
a consensus of accepted practices for
respiratory protection.
Respirator technology and knowledge
on respiratory protection have since
advanced and as a result, changes in
respiratory protection standards have
occurred. For example, in 2006, OSHA
revised its respiratory protection
standard to add definitions and
requirements for Assigned Protection
Factors (APF) and Maximum Use
Concentrations (MUCs) (71 FR 50121,
50122, Aug. 24, 2006). In addition to
this rulemaking, OSHA updated
Appendix A to § 1910.134: Fit Testing
Procedures (69 FR 46986, 46993, Aug. 4,
2004).
After withdrawing the 1992 version of
Z–88.2 in 2002, ANSI published the
American National Standard, ANSI/
AIHA Z88.10–2010, ‘‘Respirator Fit
Testing Methods,’’ approved in 2010.
These rules and standards addressed the
topics of APFs and fit testing. APFs
provide employers with critical
information to use when selecting
respirators for employees exposed to
atmospheric contaminants found in
industry. Finally, in 2015, ANSI
published ANSI/ASSE Z88.2–2015,
‘‘Practices for Respiratory Protection,’’
which referenced OSHA regulations.
These updates included requirements
for classification of considerations for
selection and use of respirators,
establishment of cartridge/canister
change schedules, use of fit factor value
for respirator fit testing, calculation of
effective protection factors, and
compliance with compressed air dew
requirements, compressed breathing air
equipment, and systems and
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designation of positive pressure
respirators. In July 2017, ANSI/ASSE
transferred the responsibilities for
developing respiratory consensus
standards to ASTM International.
ASTM F3387–19 is based on the most
recent consensus standards recognized
by experts in government and
professional associations on the
selection, use, and maintenance for
respiratory protection equipment. The
standard contains detailed guidance and
provisions on respirator selection that
are based on NIOSH’s long-standing
experience of testing and approving
respirators for occupational use and
OSHA’s research and rulemaking on
respiratory protection. ASTM F3387–19
also addresses all aspects of
establishing, implementing, and
evaluating respiratory protection
programs and establishes minimum
acceptable respiratory protection
program elements in the areas of
program administration, standard
operating procedures, medical
evaluation, respirator selection, training,
fit testing, respirator maintenance,
inspection, and storage. ASTM F3387–
19 comprehensively covers numerous
aspects of respiratory protection and
provides the most up-to-date provisions
for current respirator technology and
effective respiratory protection.
Therefore, MSHA believes that ASTM
F3387–19 would provide mine
operators with information and
guidance on the proper selection, use,
and maintenance of respirators, which
would protect the health and safety of
miners.
Under this proposed rule, MSHA
would require that operators establish a
respiratory protection program in
writing, that includes minimally
acceptable program elements: program
administration; standard operating
procedures; medical evaluations;
respirator selection; training; fit testing;
and maintenance, inspection, and
storage.
Beyond the minimally acceptable
program elements, MSHA proposes to
provide mine operators with flexibility
to select the provisions in ASTM
F3387–19 that are applicable to the
conditions of their mines and respirator
use by their miners. In MSHA’s
experience, the need for and actual use
of respirators varies among mines for
different reasons, including the type of
commodity mined or processed and the
mining method and controls used. At
some mines, miners may not use or may
only rarely use respirators. At other
mines, miners may use respirators more
frequently. Recognizing these
differences, MSHA would allow mine
operators to comply with the provisions
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in ASTM F3387–19 that they deem are
relevant and appropriate for their
mining operations and conditions.
MSHA has observed that many
operators, in particular larger mine
operators, have already implemented in
their respiratory programs many OSHA
requirements, which are substantially
similar to many requirements in ASTM
F3387–19. Indeed, ASTM F3387–19
refers to OSHA’s regulations on
respiratory protection programs, APFs
and MUCs, and fit testing. MSHA
believes that the mining industry is
already familiar with many provisions
in ASTM F3387–19. MSHA anticipates
that for many large mine operators, few
changes to their respiratory protection
program may be warranted, whereas
small mines, or mines that use
respirators intermittently, may need to
revise their respiratory practices in
accordance with the requirements, as
applicable, in ASTM F3387–19.
1. Respiratory Program Elements
Under the proposed rule, MSHA
would require that the respiratory
protection program be in writing and
that it include the following minimally
acceptable program elements: program
administration; standard operating
procedures; medical evaluations;
respirator selection; training; fit testing;
and maintenance, inspection, and
storage.
a. Program Administration
ASTM F3387–19 specifies several
practices related to respiratory
protection program administration,
including the qualifications and
responsibilities of a program
administrator. For example, ASTM
F3387–19 provides that responsibility
and authority for the respirator program
be assigned to a single qualified person
with sufficient knowledge of respiratory
protection. Qualifications could be
gained through training or experience;
however, the qualifications of a program
administrator must be commensurate
with the respiratory hazards present at
a worksite.
This individual should have access to
and direct communication with the site
manager about matters impacting
worker safety and health. ASTM F3387–
19 notes a preference that the
administrator be in the company’s
industrial hygiene, environmental,
health physics, or safety engineering
department; however, a third-party
entity meeting the provisions may also
provide this service. ASTM F3387–19
outlines the respiratory program
administrator’s responsibilities,
specifying that they should include:
measuring, estimating, or reviewing
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information on the concentration of
airborne contaminants; ensuring that
medical evaluations, training, and fit
testing are performed; selecting the
appropriate type or class of respirator
that will provide adequate protection for
each contaminant; maintaining records;
evaluating the respirator program’s
effectiveness; and revising the program,
as necessary.
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b. Standard Operating Procedures (SOP)
SOPs are written policies and
procedures available for all wearers of
respirators to read and are established
by the employer. ASTM F3387–19 states
that written SOPs for respirator
programs are necessary when respirators
are used routinely or sporadically.
Written SOPs should cover hazard
assessment; respirator selection;
medical evaluation; training; fit testing;
issuance, maintenance, inspection, and
storage of respirators; schedule of airpurifying elements; hazard reevaluation; employer policies; and
program evaluation and audit. ASTM
F3387–19 also provides that wearers of
respirators be provided with copies of
the SOP and that written SOPs include
special consideration for respirators
used for emergency situations. The
procedures are reviewed in conjunction
with the annual respirator program
audit and are revised by the program
administrator, as necessary.
c. Medical Evaluation
Medical evaluations determine
whether an employee has any medical
conditions that would preclude the use
of respirators, limitation on use, or other
restrictions. ASTM F3387–19 provides
that a program administrator advise the
PLHCP of the following conditions to
aid in determining the need for a
medical evaluation: type and weight of
the respirator to be used; duration and
frequency of respirator use (including
use for rescue and escape); typical work
activities; environmental conditions
(e.g., temperature); hazards for which
the respirator will be worn, including
potential exposure to reduced-oxygen
environments; and additional protective
clothing and equipment to be worn.
ASTM F3387–19 also incorporates ANSI
Z88.6 Respiratory Protection—
Respirator Use—Physical Qualifications
for Personnel.
d. Respirator Selection
Proper respirator selection is an
important component of an effective
respiratory protection program. ASTM
F3387–19 provides that proper
respirator selection consider the
following: the nature of the hazard,
worker activity and workplace factors,
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respirator use duration, respirator
limitations, and use of approved
respirators. ASTM F3387–19 states that
respirator selection for both routine and
emergency use include hazard
assessment, selection of respirator type
or class that can offer adequate
protection, and maintenance of written
records of hazard assessment and
respirator selection.
ASTM F3387–19 provides specific
steps to establish the nature of
inhalation hazards, including
determining the following: the types of
contaminants present in the workplace;
the physical state and chemical
properties of all airborne contaminants;
the likely airborne concentration of the
contaminants (by measurement or by
estimation); potential for an oxygendeficient environment; an occupational
exposure limit for each contaminant;
existence of an IDLH atmosphere; and
compliance with applicable health
standards for the contaminants.
ASTM F3387–19 includes other
information to support the respirator
selection process, including information
on operational characteristics,
capabilities, and performance
limitations of various types of
respirators. These limitations must be
considered during the selection process.
ASTM F3387–19 also describes types of
respirators and consideration for their
use, including service life, worker
mobility, compatibility with other
protective equipment, durability,
comfort factors, compatibility with the
environment, and compatibility with job
and workforce performance. Finally,
ASTM F3387–19 provides other
essential information regarding
respirator selection such as oxygen
deficiency, ambient noise, and need for
communication.
e. Training
Employee training is essential for
correct respirator use. ASTM F3387–19
provides that all users be trained in
their area of responsibility by a qualified
person to ensure the proper use of
respirators. A respirator trainer must be
knowledgeable in the application and
use of the respirators and must
understand the site’s work practices,
respirator program, and applicable
regulations. Employees who receive
training include the workplace
supervisor, the person issuing and
maintaining respirators, respirator
wearers, and emergency teams. To
ensure the proper and safe use of a
respirator, ASTM F3387–19 also
provides that the minimum training for
each respirator wearer includes: the
need for respiratory protection; the
nature, extent, and effects of respiratory
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hazards in the workplace; reasons for
particular respirator selections; reasons
for engineering controls not being
applied or reasons why they are not
adequate; types of efforts made to
reduce or eliminate the need for
respirators; operation, capabilities, and
limitations of the respirators selected;
instructions for inspecting, donning,
and doffing the respirator; the
importance of proper respirator fit and
use; and maintenance and storage of
respirators. The standard provides for
each respirator wearer to receive initial
and annual training. Workplace
supervisors and persons issuing
respirators are retrained as determined
by the program administrator. Training
records for each respirator wearer are
maintained and include the date, type of
training received, performance results
(as appropriate), and instructor’s name.
f. Respirator Fit Testing
A serious hazard may occur if a
respirator, even though properly
selected, is not properly fitted. For
example, if a proper face seal is not
achieved, the respirator would provide
a lower level of protection than it is
designed to provide because the
respirator could allow contaminants to
leak into the breathing area. Proper fit
testing verifies that the selected make,
model, and size of a respirator
adequately fits and ensures that the
expected level of protection is provided.
ASTM F3387–19 includes provisions for
qualitative and quantitative fit testing to
determine the ability of a respirator
wearer to obtain a satisfactory fit with
a tight-fitting respirator and
incorporates ANSI/AIHA Z88.10,
Respirator Fit Testing Methods, for
guidance on how to conduct fit testing
of tight-fitting respirators and
appropriate methods to be used. ASTM
F3387–19 also provides information on
conducting quantitative and qualitative
fits test to determine how well a tightfitting respirator fits a wearer. This
includes information on the application
of fit factors and assigned protection
factors, and how these factors are used
to ensure that a wearer is receiving the
necessary protection. ASTM F3387–19
provides for each respirator wearer to be
fit tested before being assigned a
respirator (currently at least once every
12 months or repeated when a wearer
expresses concern about respirator fit or
comfort or has a condition that may
interfere with the face piece seal).
g. Maintenance, Inspection, and Storage
Proper maintenance and storage of
respirators are important in a respiratory
protection program. ASTM F3387–19
includes specific provisions for
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decontaminating, cleaning, and
sanitizing respirators, inspecting
respirators, replacing, and repairing
parts, and storing and disposing of
respirators. For example, the
decontamination provisions state that
respirators are decontaminated after
each use and cleaned and sanitized
regularly per manufacturer instructions.
Following cleaning and disinfection,
reassembled respirators are inspected to
verify proper working condition. ASTM
F3387–19 states that employers consult
manufacturer instructions to determine
component expiration dates or end-ofservice life, inspect the rubber or other
elastomeric components of respirators
for signs of deterioration that would
affect respirator performance, and repair
or replace respirators failing inspection.
ASTM F3387–19 also provides that
respirators are stored according to
manufacturer recommendations and in a
manner that will protect against hazards
(i.e., physical, biological, chemical,
vibration, shock, temperature extremes,
moisture, etc.). It also provides that
respirators are stored to prevent
distortion of rubber or other parts.
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2. Section-by-Section Analysis of
Incorporation by Reference—ASTM
F3387–19
a. Part 56—Safety and Health
Standards—Surface Metal and
Nonmetal Mines—Section 56.5005—
Control of Exposure to Airborne
Contaminants
Existing § 56.5005 provides that
whenever respiratory protective
equipment is used, a program for
selection, maintenance, training, fitting,
supervision, cleaning, and use shall
meet the requirements of paragraph (b).
Paragraph (b) requires that mine
operators implement a respirator
program consistent with the
requirements of ANSI Z88.2–1969.
MSHA is proposing to revise paragraph
(b) to remove the incorporation by
reference to ANSI Z88.2–1969 and
incorporate by reference ASTM F3387–
19.
MSHA is proposing to revise
paragraph (b) to state that approved
respirators must be selected, fitted,
cleaned, used, and maintained in
accordance with the requirements of
ASTM F3387–19 ‘‘as applicable.’’ Under
the proposal, MSHA would require that
the respiratory program be in writing
and that it include the following
minimally acceptable program elements:
program administration; standard
operating procedures; medical
evaluations; respirator selection;
training; fit testing; and maintenance,
inspection, and storage.
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Also, MSHA is proposing to change
paragraph (c) to require the presence of
at least one other person with backup
equipment and rescue capability when
respiratory protection is used in
atmospheres that are IDLH. This change
is needed to conform to language in the
proposed incorporation by reference of
ASTM F3387–19, which defines IDLH
as ‘‘any atmosphere that poses an
immediate hazard to life or immediate
irreversible debilitating effects on
health’’ (ASTM International 2019).
b. Part 57—Safety and Health
Standards—Underground Metal and
Nonmetal Mines—Section 57.5005—
Control of Exposure to Airborne
Contaminants
Existing § 57.5005 provides that
whenever respiratory protective
equipment is used, a program for
selection, maintenance, training, fitting,
supervision, cleaning, and use shall
meet the requirements of paragraph (b).
Paragraph (b) requires that mine
operators implement a respirator
program consistent with the
requirements of ANSI Z88.2–1969.
MSHA is proposing to revise paragraph
(b) to remove the incorporation by
reference to ANSI Z88.2–1969 and
incorporate by reference ASTM F3387–
19.
MSHA is proposing to revise
paragraph (b) to state that approved
respirators must be selected, fitted,
cleaned, used, and maintained in
accordance with the requirements of
ASTM F3387–19 ‘‘as applicable.’’ Under
the proposal, MSHA would require that
the respiratory program be in writing
and that it include the following
minimally acceptable program elements:
program administration; standard
operating procedures; medical
evaluations; respirator selection;
training; fit testing; and maintenance,
inspection, and storage.
Also, MSHA is proposing to change
paragraph (c) to require the presence of
at least one other person with backup
equipment and rescue capability when
respiratory protection is used in
atmospheres that are IDLH. This change
is needed to conform to language in the
proposed incorporation by reference of
ASTM F3387–19, which defines the
term IDLH as ‘‘any atmosphere that
poses an immediate hazard to life or
immediate irreversible debilitating
effects on health’’ (ASTM International
2019).
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c. Part 72—Health Standards for Coal
Mines—Section 72.710—Selection, Fit,
Use, and Maintenance of Approved
Respirators
Existing § 72.710 requires approved
respirators be selected, fitted, used, and
maintained in accordance with the
provisions of ANSI Z88.2–1969, which
was incorporated by reference into coal
standards in 1995 (60 FR 30398, June 8,
1995). MSHA is proposing to revise
§ 72.710 by removing the requirement in
the first sentence that coal mine
operators must ensure that the
maximum amount of respiratory
protection is made available to miners
when respirators are used. MSHA
believes that the use of approved
respirators and the proposed
incorporation by reference of ASTM
F3387–19 would ensure that coal
miners’ health is protected. Under the
proposal, MSHA would require that the
respiratory program be in writing and
that it include the following minimally
acceptable program elements: program
administration; standard operating
procedures; medical evaluations;
respirator selection; training; fit testing;
and maintenance, inspection, and
storage.
VIII. Technological Feasibility
This technological feasibility analysis
considers whether currently available
technologies, used alone or in
combination with each other, can be
used by operators to comply with the
proposed standard.
MSHA is required to set standards to
assure, based on the best available
evidence, that no miner will suffer
material impairment of health or
functional capacity from exposure to
toxic materials or harmful physical
agents over his working life. 30 U.S.C.
811(a)(6)(A). The Mine Act also
instructs MSHA to set health standards
to attain ‘‘the highest degree of health
and safety protection for the miner’’
while considering ‘‘the latest available
scientific data in the field, the feasibility
of the standards, and experience gained
under this and other health and safety
laws.’’ 30 U.S.C. 811(a)(6)(A). But the
health and safety of the miner is always
the paramount consideration: ‘‘[T]he
Mine Act evinces a clear bias in favor
of miner health and safety,’’ and ‘‘[t]he
duty to use the best evidence and to
consider feasibility are appropriately
viewed through this lens and cannot be
wielded as counterweight to MSHA’s
overarching role to protect the life and
health of workers in the mining
industry.’’ Nat’l Min. Ass’n v. Sec’y,
U.S. Dep’t of Lab., 812 F.3d 843, 866
(11th Cir. 2016); 30 U.S.C. 801(a).
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The D.C. Circuit clarified the
Agency’s obligation to demonstrate the
technological feasibility of reducing
occupational exposure to a hazardous
substance. MSHA ‘‘must only
demonstrate a ‘reasonable possibility’
that a ‘typical firm’ can meet the
permissible exposure limits in ‘most of
its operations.’’ Kennecott Greens Creek
Min. Co. v. Mine Safety & Health
Admin., 476 F.3d 946, 958 (D.C. Cir.
2007) (quoting American Iron & Steel
Inst. v. OSHA, 939 F.2d 975, 980 (D.C.
Cir. 1991)).
This section presents technological
feasibility findings that guided MSHA’s
selection of the proposed PEL. MSHA’s
technological feasibility findings are
organized into two main sections
covering: (1) the technological
feasibility of proposed part 60; and (2)
the technological feasibility of the
proposed revision to existing respiratory
protection standards. Based on the
analyses presented in the two sections,
MSHA preliminarily concludes that the
Agency’s proposal is technologically
feasible. MSHA’s feasibility
determinations in this rulemaking are
supported by its findings that the
majority of the industry is already using
technology that would be sufficient to
comply with the proposed rule.
First, MSHA has preliminarily
determined that proposed part 60 is
technologically feasible. Many mine
operators already maintain respirable
crystalline silica exposures at or below
the proposed PEL of 50 mg/m3, and at
mines where there are elevated
exposures, operators would be able to
reduce exposures to at or below the
proposed PEL by properly maintaining
existing engineering controls and/or by
implementing new engineering and
administrative controls that are
currently available. In addition, mines
would be able to satisfy the exposure
monitoring requirements of proposed
part 60 with existing, validated, and
widely used sampling technologies and
analytical methods.
Second, the analysis shows that the
proposed update to MSHA’s respiratory
protection requirements is also
technologically feasible. The mining
industry’s existing respiratory
protection practices for selecting, fitting,
using, and maintaining respiratory
protection include program elements
that are similar to those of ASTM
F3387–19, ‘‘Standard Practice for
Respiratory Protection’’ (ASTM F3387–
19), which MSHA is proposing to
incorporate by reference.
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A. Technological Feasibility of
Sampling and Analytical Methods
1. Sampling Methods
MSHA’s proposed rule would require
mine operators in both MNM and coal
mines to conduct sampling for
respirable crystalline silica using
respirable particle size-selective
samplers that conform to the
‘‘International Organization for
Standardization (ISO) 7708:1995: Air
Quality—Particle Size Fraction
Definitions for Health-Related
Sampling’’ standard. The ISO
convention defines respirable
particulates as having a 4 micrometer
(mm) aerodynamic diameter median cutpoint (i.e., 4 mm-sized particles are
collected with 50 percent efficiency),
which approximates the size
distribution of particles that when
inhaled can reach the alveolar region of
the lungs. For this reason, the ISO
convention is widely considered
biologically relevant for respirable
particulates and provides appropriate
criteria for equipment used to sample
respirable crystalline silica. MSHA’s
current sampling method for MNM
mines meets the ISO criteria by using a
10 mm Dorr-Oliver cyclone and a
sampling pump operated at a flow rate
of 1.7 liter per minute (L/min), and
MNM mine operators also already use
this type of sampler for MNM sampling
under existing standards. MSHA’s
current sampling method for RCMD,
including respirable crystalline silica,
uses a 10 mm Dorr-Oliver cyclone but
operated at 2.0 L/min to approximate
the British Mining Research
Establishment (MRE) sampling criteria,
and thus does not meet the ISO criteria.
Although, the existing sampling pumps
can be adjusted to operate at a flow rate
of 1.7 L/min flow rate to meet the ISO
criteria. To comply with this proposed
requirement, coal mine operators that
currently use coal mine dust personal
sampler units (CMDPSU) would need to
adjust their samplers to the flow rate
specified by the manufacturer for
complying with the ISO.
There are a variety of size-selective
samplers on the market that meet the
ISO respirable-particle-size selection
criteria. Examples include Dorr-Oliver
cyclone currently used by MSHA and
OSHA, operated at 1.7 L/min; SKC
aluminum cyclone (2.5 L/min); HD
cyclone (2.2 L/min); SKC GS–3 multiinlet cyclone (2.75 L/min); and BGI GK
2.69 (4.2 L/min). Each cyclone has
different operating specifications and
performance criteria, but they all are
compliant with the ISO criteria for
respirable dust with an acceptable level
of measurement bias. Manufacturers of
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size-selective samplers specify the flow
rates that are necessary to conform to
the particle size collection criteria of the
ISO standard. Samplers used in both
MNM and coal mines can be used to
perform the proposed sampling, and
because other commercially available
(already on the market) samplers
conform to the ISO standard, MSHA
preliminarily finds that sampling in
accordance with the ISO standard is
technologically feasible.
2. Analytical Methods and Feasibility of
Measuring Below the Proposed PEL and
Action Level
After a respirable dust sample is
collected and submitted to a laboratory,
it must be analyzed to quantify the mass
of respirable crystalline silica present.
The laboratory method must be
sensitive enough to detect and quantify
respirable crystalline silica at levels
below the applicable concentration. The
analytical limit of detection (LOD) and/
or limit of quantification (LOQ),
together with the sample volume,
determine the airborne concentration
LOD and/or LOQ for a given air sample.
MSHA proposes a PEL for respirable
crystalline silica of 50 mg/m3 as a full
shift, 8-hour TWA for both MNM and
coal mines. Several analytical methods
are available for measuring respirable
crystalline silica at levels well below the
proposed PEL of 50 mg/m3 and action
level of 25 mg/m3.
MSHA uses two main analytical
methods (1) P–2: X-Ray Diffraction
Determination Of Quartz And
Cristobalite In Respirable Metal/
Nonmetal Mine Dust (analysis by X-ray
diffraction, XRD) for MNM mines and
(2) P–7: Determination Of Quartz In
Respirable Coal Mine Dust By Fourier
Transform Infrared Spectroscopy
(analysis by infrared spectroscopy, FTIR
or IR) for coal mines.36 The MSHA P–
2 and P–7 methods, reliably analyze
compliance samples collected by MSHA
inspectors, including 15 years of MNM
compliance samples and 5 years of coal
industry compliance samples MSHA
used for the exposure profile portion of
this technological feasibility analysis.
These methods are capable of measuring
respirable crystalline silica exposures at
levels below the proposed PEL and
action level.
For an analytical method to have
acceptable sensitivity for determining
36 Other similar XRD methods include NIOSH–
7500 and OSHA ID–142. XRD methods are able to
distinguish between the different polymorphs—
quartz, cristobalite and tridymite. Other IR methods
include NIOSH 7602 and 7603. IR methods are
efficient, but they are more prone to interferences
and should only be used for samples with a wellcharacterized matrix (e.g., coal dust).
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exposures at the proposed PEL of 50 mg/
m3 and action level of 25 mg/m3, the
LOQ must be at or below the amount of
analyte (e.g., quartz) that would be
collected in an air sample where the
concentration of analyte is equivalent to
the proposed PEL or action level. To
determine the minimum airborne
concentration that can be quantified, the
LOQ mass is divided by the sample air
volume, which is determined by the
sampling flow rate and duration. Table
VIII–1 presents minimum quantifiable
quartz concentrations, for various
cyclones and established analytical
methods.
Based on this discussion, MSHA
preliminarily finds that current
analytical methods are sufficiently
sensitive to meet the proposed PEL and
action level.
MSHA interviewed a sample of three
laboratories (one small-capacity
laboratory,37 one medium-capacity
laboratory,38 and one large-capacity
laboratory) 39 to estimate their sampleprocessing capacity. Insights from these
interviews suggest that laboratories have
the ability to provide surge capacity as
the proposed rule is phased in.
Collectively, these three laboratories
could process approximately 33,240
samples by XRD (suitable for MNM
mines) and 1,752 samples by FTIR or IR
(suitable for coal mines) within a 6month period. Extrapolating this across
all laboratories that can analyze
respirable crystalline silica samples,
MSHA estimates that 232,680 samples
for MNM mines and 12,250 samples for
coal mines could be processed in the
phase-in 6-month period. Over the first
12 months after the standard goes into
effect, analysis would be available for
465,360 samples for MNM mines and
24,500 samples for coal mines.
Based on exposure profiles for the
MNM and coal mining industries and
MSHA’s experience and knowledge of
the mining industry, MSHA estimates
that within this first 12-month period,
mines would seek analysis for a total of
172,907 respirable crystalline silica
samples (including 58,126 samples for
MNM mines and 12,373 samples for
coal mines associated with the 6-month
baseline sampling period). In the
subsequent 12-month period, mines
would require analysis for 102,409
samples (includes process/control
measure evaluation samples and
periodic samples associated with the
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3. Laboratory Capacity
MSHA’s proposed standard would
require that mines conduct baseline
sampling, periodic sampling, corrective
actions sampling, and post-evaluation
sampling with analyses conducted by
laboratories that meet ISO 17025,
General Requirements for the
Competence of Testing and Calibration
Laboratories (ISO 17025). The majority
of U.S. industrial hygiene laboratories
that perform respirable crystalline silica
analysis are accredited to ISO 17025 by
the American Industrial Hygiene
Association (AIHA) Laboratory
Accreditation Program (LAP). The AIHA
LAP lists 23 accredited commercial
laboratories nationwide that, as of April
2022, perform respirable crystalline
silica analysis using an MSHA, NIOSH
or OSHA method.
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37 The small capacity laboratory has a maximum
respirable crystalline silica sample analysis
capacity of 300 samples per month (280 additional
samples per month above the current number of
samples analyzed), a level which the laboratory
could sustain for two months.
38 The medium capacity laboratory has a
maximum respirable crystalline silica sample
analysis capacity of 2,025 samples per month. Surge
from the mining industry is considered to replace,
rather than be in addition to the current number of
samples analyzed.
39 The large capacity laboratory has a maximum
respirable crystalline silica sample analysis
capacity of 4,500 samples per month (3,700
additional samples per month above the current
number of samples analyzed).
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proposed action level), a number that
will decline over years 1 through 6 as
the mine operators reduce some miner
exposures below the proposed action
level.40 Comparing these figures with
the surge capacity estimates previously
noted above, MSHA believes that there
would be sufficient processing capacity
to meet the sampling analysis schedule
envisioned in the proposed rule.
a. Baseline Sampling
MSHA’s proposal would require
baseline sampling for each miner who is
or may reasonably be expected to be
exposed to respirable crystalline silica
within 180 days (6 months) of the
standard’s effective date.41 This would
require an initial increase in analytical
laboratory capacity of approximately
70,498 sample analyses over 6 months.
MSHA expects that with months of lead
time during the proposed rule and final
rule stages of the rulemaking,
laboratories would anticipate the initial
baseline period increase in demand and
would respond by increasing their
analytical capacity. For example,
laboratories could acquire additional
instrumentation, train additional
analysts, or add a second or third
operating shift. This is particularly
likely given that demand would be
based on a regulatory requirement and
during the rulemaking process MSHA
would conduct outreach to make all
relevant stakeholders aware of the rule’s
provisions. MSHA is specifically
soliciting comments on the
technological feasibility of laboratory
capability to conduct baseline sampling.
At this point in the rulemaking, MSHA
believes that the proposed rule is
technologically feasible for laboratories
to conduct baseline sampling analyses.
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b. Periodic, Corrective Actions, and
Post-Evaluation Sampling
Under proposed § 60.12 (b)–(e), three
conditions would require mine
operators to conduct additional
sampling after the initial 6-month
40 MSHA anticipates that in the initial six-month
baseline period mine operators will collect 70,498
baseline samples, of which 12,373 will be coal mine
samples. In the 12 months beginning after the initial
baseline period, mines will collect 88,281 samples
for miners who are exposed at or above the
proposed action level (25 mg/m3), but at or below
the proposed PEL, plus 14,128 samples to evaluate
corrective action and process change (i.e., processes
which must be analyzed to determine whether
newly implemented dust control measures are
successful and processes newly identified during
periodic walk-through evaluations), for a total of
102,409 samples per year (including 25,152 coal
mine samples). Estimates are as of December 2022.
41 Where several miners perform similar activities
on the same shift, only a representative fraction of
miners (minimum of two miners) would need to be
sampled, including those expected to have the
highest exposures.
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baseline period. First, when the most
recent sampling indicates that miner
exposures are at or above the proposed
action level (25 mg/m3) but at or below
the proposed PEL (50 mg/m3), the mine
operator would be required to sample
within 3 months of that sampling and
continue to sample within 3 months of
the previous sampling until two
consecutive samplings indicate that
miner exposures are below the action
level. Second, where the most recent
sampling indicates that miner exposures
are above the PEL, the mine operator
would be required to sample after
corrective actions are taken to reduce
overexposures, until sampling results
indicate miner exposures are at or below
the PEL. Third, if the mine operator
determines, as a result of the semiannual evaluation, that miners may be
exposed to respirable crystalline silica
at or above the action level, the mine
operator would be required to perform
sampling to assess the full-shift, 8-hour
TWA exposure of respirable crystalline
silica for each miner who is or may
reasonably be expected to be at or above
the action level.
MSHA estimates that the total number
of analyses (489,860) that laboratories
will be able to perform per year is more
than 2.5 times the total estimated
number of samples for which mines will
seek analyses in the first year (172,907).
Based on the estimated surplus analyses
available beyond baseline sampling
(419,362), MSHA preliminarily finds
that periodic, corrective actions, and
post-evaluation sampling would also be
technologically feasible both in the first
year and in subsequent years.42
B. Technological Feasibility of the
Proposed PEL
1. Methodology
The technological feasibility analysis
for the proposed PEL relies primarily on
information from three key sources:
• MSHA’s Standardized Information
System (MSIS) respirable crystalline
silica exposure data, which includes
57,769 MNM and 63,127 coal mine
compliance samples collected by MSHA
inspectors; these samples were of
sufficient mass to be analyzed for
respirable crystalline silica by MSHA’s
analytical laboratory.43
42 489,860 total annual laboratory analyses
divided by 172,907 mine samples to be analyzed,
equals 2.83 percent surplus sample analyses.
489,860 total analyses¥70,498 baseline analyses =
a surplus of 419,362 analyses available for the
102,409 periodic, corrective actions, and process
change sampling.
43 These respirable crystalline silica exposure
data consist of 15 years of MNM mine samples
(January 1, 2005, through December 31, 2019) and
five years of coal mine samples (August 1, 2016,
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• The National Institute for
Occupational Safety and Health
(NIOSH) series on reducing respirable
dust in mines, including: ‘‘Dust Control
Handbook for Industrial Minerals
Mining and Processing, Second Edition’’
(NIOSH, 2019b) and ‘‘Best Practices for
Dust Control in Coal Mining, Second
Edition’’ (NIOSH, 2021a).44 With
cooperation from the MNM and coal
mining industries, NIOSH has
extensively researched and documented
engineering and administrative controls
for respirable crystalline silica in mines.
• MSHA’s knowledge of the mining
industry. MSHA has over four decades
of experience inspecting surface mines
at least twice per year and underground
mines at least four times per year and
in assisting mine operators and miners
with technological issues, including
control of respirable dust (including
respirable crystalline silica) exposure.
MSHA offers informational programs,
training, publications, onsite
evaluations, and investigations that
document conditions in mines and help
mines operate in a safe and healthy
manner.45
MSHA also consulted other published
reports, scientific journal articles, and
information from equipment
manufacturers and mining industry
suppliers.46
2. The Technological Feasibility
Analysis Process
a. Mining Commodity Categories and
Activity Groups
As described in the Preliminary
Regulatory Impact Analysis (PRIA),
MSHA categorized mine types into six
MNM ‘‘commodity categories’’ (using
through July 31, 2021). These MSHA compliance
samples represent the conditions identified by
MSHA inspectors as having the greatest potential
for respirable crystalline silica exposure during the
periodic inspection when sampling occurred. While
MSHA’s laboratory also analyzes mine operators’
respirable coal mine dust samples containing
respirable crystalline silica, those samples are not
included in the data used for this analysis.
44 Together, these two recent reports provide
more than 500 pages of detailed descriptions,
discussion, and illustrations of dust control
technologies currently used in mines.
45 MSHA also analyzes RCMD samples collected
by mine operators, including those containing
respirable crystalline silica, in addition to the
compliance samples collected by MSHA inspectors
(mentioned in the first bullet of this series).
46 Project personnel reviewed 104,365 samples
collected and analyzed by MSHA for respirable
crystalline silica, plus another 103,745 samples
collected but not analyzed due to insufficient
respirable dust collected in the sample. They
examined over 200 published reports, proceedings,
case studies, analytical methods, and journal
articles, in addition to inspecting more than 200
web page, product brochures, user manuals,
service/maintenance manuals and descriptive
literature for dust control products, mining
equipment, and related services.
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the method of Watts et al., 2012) based
on similarities in exposure
characteristics. MNM mine categories
include metal, nonmetal, stone, crushed
limestone, and sand and gravel. All coal
mines are categorized together as one
commodity category.
Within each commodity, MSHA
further separated mining operations into
the four activity groups widely used by
the industry: (1) development and
production miners (drillers, stone
cutters); (2) ore/mineral processing
miners (crushing/screening equipment
operators and kiln, mill, and
concentrator workers in mine facilities);
(3) miners engaged in load/haul/dump
activities (conveyor, loader, and large
haulage vehicle operators, such as dump
truck drivers); and (4) miners in all
other occupations (mobile and utility
workers, such as surveyors, mechanics,
cleanup crews, laborers, and operators
of compact tractors and utility trucks).
Before determining the feasibility of
reducing miners’ exposure to respirable
crystalline silica, MSHA gathered and
analyzed information to understand
current miner exposures by creating an
‘‘exposure profile,’’ identified the
existing (i.e., baseline) conditions and
the exposure levels associated with
those conditions, and determined
whether mines would need additional
control methods, and if so, whether
those methods were available.
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b. Exposure Profiles
MSHA classified all valid respirable
crystalline silica samples in the
Agency’s MSIS data,47 grouping the data
by commodity category, followed by
activity group.48 MSHA created an
exposure profile to better examine the
sample data for each commodity
category. These profiles include basic
summary statistics, such as sample
count, mean, median, and maximum
values, presented as ISO 8-hour TWA
values. They also show the sample
distribution within the following
exposure ranges: ≤25 mg/m3, >25 mg/m3
to ≤50 mg/m3, >50 mg/m3 to ≤100 mg/m3
(equivalent to 85.7 mg/m3 in coal mines
for a sample calculated as an 8-hour
TWA), >100 mg/m3 to ≤250 mg/m3, >250
mg/m3 to ≤500 mg/m3, and >500 mg/m3.49
47 MSHA removed duplicate samples, samples
missing critical information, and those identified as
invalid by the mine inspector, for example because
of a ‘‘fault’’ (failure) of the air sampling pump
during the sampling period.
48 MSHA MSIS respirable crystalline silica data
for the MNM industry, January 1, 2005, through
December 31, 2019 (version 20220812); MSHA
MSIS respirable crystalline silica data for the Coal
Industry, August 1, 2016, through July 31, 2021
(version 20220617). All samples were collected by
mine inspectors and were of sufficient mass to be
analyzed for respirable crystalline silica by MSHA’s
laboratory.
49 MSHA selected these ranges based on the
proposed PELs under consideration, then multiples
of 100 mg/m3 to show how data are distributed in
the higher ranges. Table VIII–5 also presents
additional exposure ranges corresponding to the
85.7 mg/m3 concentration for coal samples.
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In Table VIII–2, the respirable
crystalline silica exposure data for
MNM miners are summarized by
commodity and for the MNM industry
as a whole, while Table VIII–3 presents
the exposure profile as the percentage of
samples in each exposure range.
Overall, approximately 82 percent of the
57,769 MNM compliance samples were
at or below the proposed PEL (50 mg/
m3). The exposure profile shows
variability between the commodity
categories: approximately 73 percent of
metal miner exposures at or below the
proposed PEL (50 mg/m3) (the lowest
among all MNM mines), compared with
approximately 90 percent of the crushed
limestone miner exposures (the highest
among all MNM mines).
Table VIII–4 and Table VIII–5 present
the corresponding respirable crystalline
silica exposure information for coal
miners by location (underground or
surface). Overall, approximately 93
percent of the 63,127 samples obtained
by MSHA inspectors for coal miners
were at or below the proposed PEL (50
mg/m3). There was little variation
between samples for underground
miners and surface miners (with
approximately 93 and 92 percent of the
samples at or below 50 mg/m3,
respectively). Exposure values from the
coal industry are expressed as ISO 8hour TWAs, compatible with the
proposed PEL.
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c. Existing Dust Controls in Mines
(Baseline Conditions)
MNM and coal mines are controlling
dust containing respirable crystalline
silica in various ways. As shown in
Tables VIII–2 through VIII–5, respirable
crystalline silica exposures exceeded
the proposed PEL of 50 mg/m3 in about
18 percent of all MNM samples
collected. Of all coal samples, exposure
levels exceeded the proposed PEL in
about seven percent of the samples.
Overall, metal mines and sand and
gravel mines had higher exposure levels
than other commodity mines.
Despite the extensive dust control
methods available, dust control
measures have been implemented in
some commodity categories to a greater
degree than in others. This is partly
because some commodity categories
tend to have larger mines. MSHA has
found that the larger the amount
(tonnage) of material a mine moves
(including overburden and other waste
rock), the faster the mine tends to
operate its equipment (i.e., closer to the
equipment capacity), creating more air
turbulence and therefore generating
more respirable crystalline silica. The
amount of material moved also
influences the number of miners
employed at a mine, and therefore, the
number of miners can be indirectly
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correlated to the amount of dust
generated. MSHA has observed that in
large mines, dusty conditions typically
prompt more control efforts, usually in
the form of added engineering controls.
MSHA has also found that metal
mines, which are typically large
operations with higher numbers of
miners, tend to have available
engineering controls for dust
management. On the other hand, sand
and gravel mines, which generally
employ fewer miners and handle
modest amounts of material, have very
limited, if any, dust control measures.
This is because most of the mined
material is a commodity that only
requires washing and screening into
various sizes of product stockpiles,
generating little waste material.
Nonmetal, stone, and crushed limestone
mines occupy the middle range in terms
of employment, existing engineering
controls, and maintenance practices.
Over the years, staff from multiple
MSHA program areas have worked
alongside miners and mine operators to
improve safety and health by inspecting,
evaluating, and researching mine
conditions, equipment, and operations.
These key programs, each of which has
an onsite presence, include (but are not
limited to) Mine Safety and Health
Enforcement; Directorate of Educational
Policy and Development which includes
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the National Mine Health and Safety
Academy and the Educational Field and
Small Mine Services; and the
Directorate of Technical Support, which
is comprised of the Approval and
Certification Center and the Pittsburgh
Safety and Health Technology Center
(including its Health Field Division,
National Air and Dust Laboratory,
Ventilation Division, and other
specialized divisions). Table VIII–6
reflects the collective observations of
these MSHA programs, presented in
terms of existing dust control (baseline
conditions) and the classes of additional
control measures that would provide
those mines with the greatest benefit to
reduce exposures below the proposed
PEL and action level.
Table VIII–6 shows MSHA’s
assessment of existing dust controls in
mines (baseline conditions) and
additional controls needed to meet the
proposed PEL for each commodity
category, including the need for
frequent scheduled maintenance. By
conducting frequent scheduled
maintenance, mine operators can reduce
the concentration of respirable
crystalline silica. Table VIII–6 shows
that metal mines have adopted
extensive dust controls, while sand and
gravel mines tend to have minimal
engineering controls, if any.
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Based on MSHA’s experience, NIOSH
research, and effective respirable dust
controls currently available and in use
in the mining industry, MSHA
preliminarily finds that the baseline
conditions include various
combinations of existing engineering
controls selected and installed by
individual mines to address respirable
crystalline silica generated during
mining operations.
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d. Respirable Crystalline Silica
Exposure Controls Available to Mines
Under the proposal, the mine operator
must install, use, and maintain feasible
engineering controls, supplemented by
administrative controls, when
necessary, to keep each miner’s
exposure at or below the proposed PEL.
Engineering controls reduce or prevent
miners’ exposure to hazards.50
Administrative controls establish work
practices that reduce the duration,
50 Control measures that reduce respirable
crystalline silica can also reduce exposures to other
hazardous particulates, such as RCMD, metals,
asbestos, and diesel exhaust. Operator enclosures
and process enclosures also reduce hazardous
levels of noise by creating a barrier between the
operator and the noise source.
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frequency, or intensity of miners’
exposures (although rotation of miners
would be prohibited under the proposed
rule).
MSHA data and experience show that
mine operators already have numerous
engineering and administrative control
options to control miners’ exposures to
respirable crystalline silica. These
control options are widely recognized
and used throughout the mining
industry. NIOSH has extensively
researched and documented engineering
and administrative controls for
respirable crystalline silica in mines. As
noted previously, NIOSH has published
a series on reducing respirable dust in
mines (NIOSH, 2019b; NIOSH, 2021a).
(1) Engineering controls
Examples of existing engineering
controls used at mines and
commercially available engineering
controls that MSHA considered include:
• Wetting or water sprays that
prevent, capture, or redirect dust;
• Ventilation systems that capture
dust at its source and transport it to a
dust collection device (e.g., filter or bag
house), dilute dust already in the air, or
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‘‘scrub’’ (cleanse) dust from the air in
the work area;
• Process enclosures that restrict dust
from migrating outside of the enclosed
area, sometimes used with an attached
ventilation system to improve
effectiveness (e.g., crushing equipment
and associated dump hopper enclosure,
with curtains and mechanical
ventilation to keep dust inside);
• Operator enclosures, such as mobile
equipment cabs or control booths,
which provide an environment with
clean air for an equipment operator to
work safely;
• Protective features on mining
process equipment to help prevent
process failures and associated dust
releases (e.g., skirtboards on conveyors,
which protect the conveyor system from
damage and prevent material on the
conveyor from falling off, which
generates airborne dust);
• Preventive maintenance conducted
on engineering controls and mining
equipment that can influence dust
levels at a mine, to keep them
functioning optimally; and
• Instrumentation and other
equipment to assist mine operators and
miners in evaluating engineering control
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effectiveness and recognizing control
failures or other conditions that need
corrective action.51
(2) Administrative controls
Administrative controls include
practices that change the way tasks are
performed to reduce a miner’s exposure.
Administrative controls can be very
effective and can even prevent exposure
entirely. MSHA has preliminarily
determined that various administrative
controls are readily available to provide
supplementary support to engineering
controls. Examples of administrative
controls would include housekeeping
procedures; proper work positions of
miners; walking around the outside of a
dusty process area rather than walking
through it; cleaning of spills; and
measures to prevent or minimize
contamination of clothing to help
decrease miners’ exposure to respirable
crystalline silica. However, these
control methods depend on human
behavior and intervention and are less
reliable than properly designed,
installed, and maintained engineering
controls. Therefore, administrative
controls would be permitted only as
supplementary measures, with
engineering controls required as the
primary means of protection.
Nevertheless, administrative controls
play an important role in reducing
miners’ exposure to respirable
crystalline silica.52
(3) Combinations of Controls
Various control options can also be
used in combinations. NIOSH has
documented in detail most control
methods and has confirmed that they
are currently used in mines, both
individually and in combination with
each other (2019b, 2021a).
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e. Maintenance
MSHA preliminarily finds that a
strong and feasible preventive
maintenance program plays an
important role in achieving consistently
lower respirable crystalline silica
exposure levels. MSHA has observed
that when engineering controls are
installed and maintained in working
condition, respirable dust exposures
tend to be below the existing exposure
limits. When engineering controls are
51 These instruments include dust monitors;
water, air, and differential air pressure gauges; pitot
tubes and air velocity meters; and video camera
(NIOSH recommends software that pairs video with
a dust monitor to track conditions that could lead
to elevated exposures if not corrected). These
instruments are discussed in NIOSH’s best practices
guides and dust control handbooks.
52 Proposed paragraph 60.11(b) prohibits the use
of rotation of miners as an administrative control
used for compliance with this part.
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not maintained, dust control efficiency
declines and exposure levels rise. When
engineering controls fail due to a lack of
proper maintenance, a marked rise in
exposures can occur, resulting in
noncompliance with MSHA’s existing
exposure limits. Some examples of the
impact that proper maintenance can
have on respirable dust levels include:
• Water spray maintenance: An
experiment using water spray bars that
could be turned on or off showed that
dust reduction was less effective each
time additional spray nozzles were
deactivated. A 10 percent decrease
occurred when three of 21 sprays were
shut off, but a 50 percent decrease
occurred when 12 out of the 21 sprays
were shut off. Decreased total water
spray volume and gaps in the spray
pattern (due to deactivated nozzles)
were both partially responsible for the
decreased dust control (Seaman et al.,
2020).
• Water added to drill bailing air:
When introduced into the drill hole
(with the bailing air through a hollow
drill bit), water mixes with and
moistens the drill dust ejected from the
hole and can reduce respirable dust by
more than 90% (NIOSH 2021a, 2019b).
NIOSH reports that this same control
measure, and others, are similarly
effective for MNM and surface coal
mine drills preparing the blasting holes
used to expose the material below
(whether ore or coal).
• Ventilation system maintenance:
The amount of air cleaned by an air
scrubber is decreased by up to one-third
(33 percent) after one continuous
mining machine cut. Cleaning the
scrubber screens restores scrubber
efficacy, but this maintenance must be
performed after every cut. Spare
scrubber screens make frequent cleaning
practical without slowing production
(NIOSH, 2021a).
• Operator enclosure maintenance:
Tests with mining equipment showed
that maintenance activities including
repairing weather stripping and
replacing clogged and missing cab
ventilation system filters (intake,
recirculation, final filters) increased
miner protection, by up to 95 percent
(NIOSH 2019b, 2021a).
• Filter selection during maintenance:
Airflow is as important as filtration and
pressurization in operator enclosures;
during maintenance, filter selection can
influence all three factors. Performing
serial end-shift testing of enclosed cabs
(on a face drill and a roof/rock bolter)
at an underground crushed limestone
mine, NIOSH compared installed HEPA
filters and an alternative (MERV 16
filters). The latter provided an equal
level of filtration and better overall
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miner protection by allowing greater
airflow and cab pressurization. As an
added advantage, NIOSH showed that
these filters cost less and required lessfrequent replacement, reducing
maintenance expenses in this mining
environment (Cecala et al., 2016; NIOSH
2021a, 2019b).53 54
• Proper design and installation—
foundation for effective maintenance: A
new replacement equipment operator
enclosure (control booth) installed
adjacent to the primary crusher at a
granite stone quarry initially provided
50 to 96 percent respirable dust
reduction, even with inadequate
pressurization. The protection it offered
miners tripled after the booth’s second
pressurization/filtration unit was
activated (Organiscak et al., 2016).
MSHA has observed that when
engineering controls are properly
maintained, exposure levels decrease or
stay low. Metal mines, which typically
have substantial controls already
installed, primarily need reliable
preventive maintenance programs to
achieve the proposed PEL. It is also
important to repair equipment damage
that contributes to dust exposure (for
example, damage to conveyor
skirtboards that protect the conveyor
system from damage and prevent
spillage which generates airborne dust).
Maintenance and repair programs must
ensure that dust control equipment is
functioning properly.
3. Feasibility Determination of Control
Technologies
MSHA is proposing a PEL of 50 mg/
m3 for MNM and coal mines. As NIOSH
has documented, the mining industry
has a wide range of options for
controlling dust exposure that are
already in various configurations in
mines (2019b; 2021a). NIOSH has
carefully evaluated most of the dust
controls used in the mining industry
and found that many of the controls
may be used in combinations with other
control options. NIOSH has documented
protective factors and exposure
reductions of 30 to 90 percent or higher
for many engineering and
administrative controls.
53 NIOSH believes this study, like many of its
other mining studies on operator enclosures and
surface drill dust controls, is relevant to both MNM
mining and coal mining. NIOSH reports on this
study, conducted at an underground limestone
mine, in detail in both its Dust control handbook
for industrial minerals mining and processing
(second edition) (2019b) and its best practices for
dust control in coal mining (second edition)
(2021a).
54 Acronyms: High efficiency particulate air
(HEPA). Minimum efficiency reporting value
(MERV).
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MSHA also preliminarily finds that
maintaining (including adjusting) or
repairing existing controls would help
achieve exposures at or below 50 mg/m3.
For example, NIOSH found that
performing maintenance on an operator
enclosure can restore enclosure
pressurization and reduce the respirable
dust exposure of a miner by 90 to 98.9
percent (e.g., by maintaining weather
stripping, reseating or replacing leaking
or clogged filters, and upgrading
filtration) (NIOSH, 2019b). When an
equipment operator remains inside a
well-maintained enclosure for a portion
of a shift (for example 75 percent of an
8-hour shift), the cab can reduce the
exposure of the operator proportionally,
to a level of 50 mg/m3 (or lower). This
point is demonstrated by the following
example involving a bulk loading
equipment operator in a poorly
maintained booth, exposed to respirable
crystalline silica near the existing
exposure limit (in the MNM sectors, 100
mg/m3, as ISO 8-hour TWA value; in the
Coal sector, 85.7 mg/m3 ISO, calculated
as an 8-hour TWA). During the 25
percent of their shift (two hours of an
eight-hour shift) that the operator was
working in the poorly maintained
enclosure, their exposure would
continue to be 100 mg/m3, while for the
other six hours (operating mobile
equipment with a fully refurbished
protective cab), the exposure level
would be 90 percent lower, or 10 mg/m3,
resulting in an 8-hour TWA exposure of
33 mg/m3 for that miner’s shift.55 Greater
exposure reductions could also be
achieved by repairing or replacing the
poorly maintained enclosure, or
modifying the miner’s schedule so that
the miner works seven hours, rather
than six, inside of the well-maintained
enclosure.
Other engineering controls (e.g.,
process enclosure, water dust
suppression, dust suppression hopper,
ventilation systems) could reduce dust
concentrations in the area surrounding
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55 Calculating the exposure for the shift: 8-hour
TWA = [(10 mg/m3 × 6 hours) + (100 mg/m3 × 2
hours)]/8 hours = 33 mg/m3.
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the poorly maintained enclosure, which
would reduce the exposure of the
operator inside. For example, if the
poorly maintained enclosure was an
open-air control booth (windows do not
close) at a truck loading station, adding
a dust suppression hopper (which
reduces respirable dust exposure by 39
to 88 percent during bulk loading)
(NIOSH, 2019b), would lead to lower
exposure during the two hours the
miner was inside the open-air booth.
The calculated respirable crystalline
silica 8-hour TWA exposure of that
miner could be reduced from 33 mg/m3
(with improved operator enclosure
alone) to 23 mg/m3 (improved operator
enclosure plus dust suppression
hopper).56 As an added benefit, any
helper or utility worker in the truck
loading area would also experience
reduced exposure.
Similarly, considering an example for
a coal miner helper who spends 90
minutes (1.5 hours) per 8-hour shift
assisting a drilling rig operator (in a
protective operator’s cab) drilling blast
holes. The combination of controls used
to control drilling dust (including water
added to the bailing air, which can
reduce airborne respirable dust
emissions by up to 96 percent) usually
maintain the helper’s respirable
crystalline silica exposure in the range
of 35 mg/m3 (ISO) as an 8-hour TWA. If,
however, the drill’s on-board water tank
runs dry due to poor maintenance, the
respirable crystalline silica
concentration near the drill will rise by
95 percent, meaning that the
concentration is 20 times greater than
the usual level (NIOSH 2021a). If the
drill operator idles the drill and calls for
water resupply, the helper will not
experience an elevated exposure. If
instead the drill is operated dry for
another 30 minutes until water resupply
arrives, the helper will experience a
respirable crystalline silica exposure of
77 mg/m3 (ISO) as an 8-hour TWA. If dry
drilling continued for 1.5 hours, the
helper would have an exposure of 160
mg/m3 ISO as an 8-hour TWA.57 After
water is delivered, drill respirable dust
emissions will return to their normal
level once water is again introduced
into the drill bailing air.
Based on these examples and the
wide range of effective exposure control
options available to the mining
industry, MSHA preliminarily finds that
control technologies capable of reducing
miners’ respirable crystalline silica
exposures are available, proven,
effective, and transferable between
mining commodities; however, they
must be well-designed and consistently
used and maintained.
56 Calculating the exposure with both the wellmaintained operator enclosure (6 hours) and dust
suppression hopper, assuming only the minimum
documented respirable dust concentration
reduction (39 percent): [(10 mg/m3 × 6 hours) + (100
mg/m3 × (1–0.39) × 2 hours)]/8 hours = 23 mg/m3.
57 The 8-hour TWA exposure level of the helper,
including the 30-minute period of elevated
exposure, is calculated as: [(35 mg/m3 × 7.5 hours)
+ (35 mg/m3 × 20 × 0.5 hours)]/8 hours = 77 mg/m3.
Drill bits designed for use with water may need to
be replaced sooner if used dry.
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a. Feasibility Findings for the Proposed
PEL
Based on the exposure profiles in
Table VIII–2 and Table VIII–3 for MNM
mines, and in Table VIII–4 and VIII–5
for coal mines, and the examples in the
previous section that demonstrate the
beneficial effect of combined controls,
MSHA preliminarily finds that the
proposed PEL of 50 mg/m3 is
technologically feasible for all mines.
Table VIII–7 summarizes the
technological feasibility of control
technologies available to the mining
industry, by commodity. MSHA
preliminarily finds that control
technologies are technologically feasible
for all six commodities and their
respective activity groups. Under
baseline conditions, mines in each
commodity category have already
achieved respirable crystalline silica
exposures at or below 50 mg/m3 for most
of the miners represented by MSHA’s
57,769 samples for MNM miners and
63,127 samples for coal miners.
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b. Feasibility Findings for the Proposed
Action Level
MSHA believes that mine operators
can achieve exposure levels at or below
the proposed action level of 25 mg/m3,
for most miners by implementing
additional engineering controls and
more flexible and innovative
administrative controls, in addition to
the existing control methods already
discussed in this technological
feasibility analysis. MSHA notes that
the exposure profiles in Table VIII–2
and Table VIII–3 for MNM mines, and
Table VIII–4 and VIII–5 for coal mines
indicate that mine operators have
already achieved the proposed action
level for at least half of the miners who
MSHA has sampled in each commodity
category. However, to do so reliably for
all miners, operators would need to
upgrade equipment and facility designs,
particularly in mines with higher
respirable crystalline silica
concentrations, that may be due to an
elevated silica content in materials.
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One control option would be
increased automation, such as
expanding the use of existing
autonomous or remote-controlled
drilling rigs, roof bolters, stone cutting
equipment, and packaging/bagging
equipment. This type of automation can
reduce exposures by increasing the
distance between the equipment
operator and the dust source. Other
options include completely enclosing
most processes and ventilating the
enclosures with dust extraction
equipment or controlling the speed of
mining equipment (e.g., longwall
shearers, conveyors, dump truck
emptying) and process equipment (e.g.,
crushers, mills) to reduce turbulence
that increases dust concentrations in air.
Additionally, where compatible with
the material, exposure levels can be
reduced by increased wetting to
constantly maintain the material,
equipment, and mine facility surfaces
damp through added water sprays and
frequent housekeeping (i.e., hosing
down surfaces as often as necessary). In
addition, vacuuming will minimize the
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amount of dust that becomes airborne
and prevent dust that does settle on a
surface from being resuspended in air.
Mines that only occasionally work
with higher-silica-content materials may
not be equipped with the controls
required to achieve the proposed action
level of 25 mg/m3, or they may not
currently have procedures to ensure
miners are protected when they do work
with these materials. Examples of these
activities include cutting roof or floor
rock with a continuous mining machine
in underground coal mines; packaging
operations that involve materials from
an unfamiliar supplier, including
another mine; and rebuilding or
repairing kilns. To address these
activities, under the proposed rule,
mine operators would have to add
engineering controls to address any
foreseeable respirable crystalline silica
overexposures. Examples of additional
controls include pre-testing batches of
new raw materials; improving hazard
communication when batches of
incoming raw materials contain higher
concentrations of crystalline silica, and
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augmenting enclosure and ventilation
(e.g., adding ventilation to all crushing
and screening equipment, increasing
mine facility ventilation to 30 air
changes per hour, and fully enclosing
and ventilating all conveyor transfer
locations). NIOSH (2019b, 2021a)
describes all of the dust control methods
described in this section, which are
already used in mines, although to a less
rigorous extent than would be necessary
to reliably achieve exposure levels of 25
mg/m3 or lower for all miners.
MSHA preliminarily finds that the
proposed action level of 25 mg/m3 is
technologically feasible for most mines.
This finding is based on the exposure
profiles, presented in Table VIII–2 and
Table VIII–3 for MNM mines, and Table
VIII–4 and VIII–5 for coal mines, which
shows that within each commodity
category, the exposure levels are at or
below 25 mg/m3 for at least half of the
miners sampled. MSHA’s finding is also
based on the extensive control options
documented by NIOSH, which can be
used in combinations to achieve
additional control of respirable
crystalline silica. Although most mines
would need to adopt and rigorously
implement a number of the control
options mentioned in this section, the
technology exists to achieve this level
and is already in use in mines.
C. Technological Feasibility of
Respiratory Protection (Within Proposed
Part 60)
Under the proposed rule, respiratory
protection would only be allowed for
temporary, non-routine use. MSHA has
preliminarily determined that it is
technologically feasible to limit
respirator use to temporary, non-routine
activities based on the Agency’s
knowledge of and experience with the
mining industry, evidence presented by
NIOSH (2019b, 2020a), and Tables VIII–
2 through VIII–5 (exposure profiles for
MNM and coal mines). These tables
indicate that the proposed PEL (50 mg/
m3) has already been achieved for
approximately 82 percent of the MNM
miners and approximately 93 percent of
the coal miners sampled by MSHA.
Proposed § 60.14(b) requires that any
miner unable to wear a respirator must
receive a temporary job transfer to an
area or to an occupation at the same
mine where respiratory protection is not
required. The proposed paragraph
would also require that an affected
miner continue to receive compensation
at no less than the regular rate of pay in
the occupation held by that miner
immediately prior to the transfer. MNM
mine operations have complied with the
job transfer provisions under the
existing standard in § 57.5060(d)(7) that
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states miners unable to wear a respirator
must be transferred to work in an
existing position in an area of the mine
where respiratory protection is not
required. Proposed § 60.14(b) is similar
to these existing requirements. MSHA
anticipates that mine operators would
have a similar experience implementing
the job transfer provisions of proposed
§ 60.14(b). Therefore, MSHA
preliminarily finds that the proposed
requirement in § 60.14(b) is
technologically feasible.
For miners who would need to wear
respiratory protection on a temporary
and non-routine basis, proposed
§ 60.14(c)(1) would require the mine
operator to provide NIOSH-approved
atmosphere-supplying respirators or
NIOSH-approved air-purifying
respirators equipped with highefficiency particulate filters in one of
the following NIOSH classifications
under 42 CFR part 84: 100 series or High
Efficiency (HE). As previously
discussed, MSHA preliminarily finds
that particulate respirators meeting
these criteria would offer the best
filtration efficiency (99.97 percent) and
protection for miners exposed to
respirable crystalline silica and are
widely available and used by most
industries. This finding is based on the
suitability of the three particulate
classifications for respirable size
particle filtration and the broad
commercial availability of these NIOSHapproved particulate respirators.58
NIOSH publishes a list of approved
respirator models along with
manufacturer/supplier information. In
November 2022, the NIOSH-approved
list contained 221 records on
atmosphere-supplying respirator
models, 160 records on elastomeric
respirators with P–100 classification,
and 23 records on filtering facepiece
respirators with P–100 classification
(NIOSH, 2022 list P–100 elastomeric, P–
100 filtering facepiece, and atmospheresupplying respirator models).59 Based
on this information, MSHA
preliminarily finds that proposed
§ 60.14(c)(1) is technologically feasible.
Proposed § 60.14(c)(2) would
incorporate the ASTM F3387–19
‘‘Standard Practice for Respiratory
Protection’’ to ensure that the most
current and protective respiratory
58 Class 100 particulate respirators (currently the
most widely used respirator filter specification in
the U.S.) are available from numerous sources
including respirator manufacturers, online safety
supply companies, mine equipment suppliers, and
local retail hardware stores.
59 The NIOSH list of approved models does not
guarantee that each model is currently
manufactured. However, the list does not include
obsolete models, and the more popular models are
widely available, including in bulk quantities.
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protection practices would be
implemented by operators who
temporarily use respiratory protection to
control miners’ exposures to respirable
crystalline silica. The Agency is also
incorporating this respiratory protection
consensus standard under §§ 56.5005,
57.5005, and 72.710. This proposed
update is also addressed in the next
section (see Technological feasibility of
updated respiratory protection
standards). Based on the information
contained in that section, MSHA
preliminarily finds that the proposed
§ 60.14(c)(2) is technologically feasible.
Based on information contained in
this section, MSHA preliminarily finds
that proposed § 60.14 is technologically
feasible.
D. Technological Feasibility of Updated
Respiratory Protection Standards
(Amendments to 30 CFR Parts 56, 57,
and 72)
1. Incorporation by Reference
Respirators are commonly used by
miners as a means of protection against
a multitude of respiratory hazards,
including particulates, gases, and
vapors. Respirators are needed in
immediately life-threatening (i.e., IDLH)
situations as well as operations where
engineering controls and administrative
controls do not provide sufficient
protection against respiratory hazards.
Where respirators are used, they must
seal and isolate the miner’s respiratory
system from the contaminated
environment. The risk that a miner will
experience an adverse health effect from
a contaminant when relying on
respiratory protection is a function of
the toxicity or hazardous nature of the
air contaminants present, the
concentrations of the contaminants in
the air, the duration of exposure, and
the degree of protection provided by the
respirator. When respirators fail to
provide the proper protection, there is
an increased risk of adverse health
effects. Therefore, it is critical that
respirators perform as they are designed.
Accordingly, MSHA is proposing to
incorporate by reference ASTM F3387–
19 under 30 CFR 56.5005, 30 CFR
57.5005, and 30 CFR 72.710. With this
action, the Agency intends to assist
mine operators in developing effective
respiratory protection practices and
programs that meet current industry
standards. This proposed revision
would better protect miners who
temporarily wear respiratory protection.
The American National Standards
Practices for Respiratory Protection
ANSI Z88.2–1969 is currently
incorporated by reference in 30 CFR
56.5005, 30 CFR 57.5005, and 30 CFR
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72.710.60 Since MSHA issued these
standards, respirator technology and
knowledge on respirator protection have
advanced and as a result, changes in
respiratory protection standard practices
have occurred. ASTM F3387–19 is
based on the most recent consensus
standard and provides more
comprehensive and detailed guidance.
MSHA believes that most mines that use
respiratory protection are already
following current respiratory protection
practices and standards such as ANSI/
ASSE Z88.2—2015 ‘‘Practices for
Respiratory Protection’’ standard, its
similar ASTM replacement (the F3387–
19 standard), or OSHA 29 CFR
1910.134—Respiratory protection.
ASTM F3387–19 standard practices are
substantially similar to the standard
practices included in ANSI/ASSE
Z88.2–2015 or OSHA’s respiratory
standards.
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2. Availability of Respirators
The updated respiratory protection
standard reflects current practice at
many mines that currently use
respiratory protection and does not
require the use of new technology.
Thus, MSHA preliminarily finds that
the proposed update is technologically
feasible for affected mines of all sizes.
3. Respiratory Protection Practices
By incorporating the updated
respiratory protection consensus
standard (ASTM F3387–19), MSHA
intends that mine operators would
develop effective respiratory protection
practices that meet the updated
consensus standard and that would
better protect miners from respirable
hazards not yet controlled by other
methods.
MSHA presumes that most mines
with respiratory protection programs,
and particularly those MNM mines that
have operations under both MSHA and
OSHA jurisdiction, are already
following either the ANSI/ASSE
Z88.2—2015 standard, the ASTM
F3387–19 standard, or OSHA 1910.134.
The respiratory protection program
elements under ASTM F3387–19 are
largely similar to those in the existing
standard.
MSHA expects that some operators
may need to adjust their current
respiratory protection practices and
standard operating procedures to reflect
ASTM F3387–19 standard practices.
Examples of adjustments include
formalizing fit testing and respirator
60 ASTM
3387–19 is the revised version of ANSI/
ASSE Z88.2–2015. In 2017, the Z88 respirator
standards were transferred from ANSI/ASSE to
ASTM International (source: F3387–19, Appendix
XI).
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training annually; updating the training
qualifications of respirator trainers,
managers, supervisors, and others
responsible for the respiratory
protection program; reviewing the
information exchanged with the
physician or other licensed health care
professional (PLHCP); and formalizing
internal and external respiratory
protection program reviews or audits.
Overall, MSHA preliminarily finds
that the proposed amendments to
existing parts 56, 57, and 72 are
technologically feasible because the
requirements of ASTM F3378–19 are
already implemented at some mines.
E. Technological Feasibility of Medical
Surveillance (Within Proposed Part 60)
Under the proposed rule, mine
operators would be required to provide
periodic medical examinations for each
MNM miner, at no cost to the miner.
The proposed medical surveillance
standards would extend to MNM miners
similar protections available to coal
miners under 30 CFR 72.100. The
requirements in proposed § 60.15 are
consistent with the Mine Act’s mandate
to provide maximum health protection
for miners.
Under the proposed standards, MNM
miners new to the mining industry
would receive an initial examination,
within 30 days. If they are not new to
mining, they are categorized as
belonging to a group of workers who are
eligible for an examination every 5
years. Workers who are new to mining,
after they have their initial examination,
would be provided another follow-up
examination within 3 years. If the 3-year
follow-up examination indicates any
medical concerns associated with chest
X-ray findings or decreased lung
function, these miners are eligible to
have another follow-up exam in 2 years.
After this additional 2-year follow-up
exam, or if the 3-year follow-up
examination indicates no medical
concerns associated with chest X-ray
findings or decreased lung function,
these miners will enter the category of
miners eligible for periodic 5-year
exams.
MSHA is proposing that medical
examinations would be performed by a
PLHCP or specialist. A medical
examination would include a review of
the miner’s medical and work history
and physical examination. The medical
and work history would cover a miner’s
present and past work exposures,
illnesses, and any symptoms indicating
respirable crystalline silica-related
diseases and compromised lung
function. The medical examination
would include a chest X-ray. The
required chest X-ray would be required
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to be classified by a NIOSH-certified B
Reader, in accordance with the
Guidelines for the Use of the
International Labour Office (ILO)
International Classification of
Radiographs of Pneumoconioses. The
ILO recently made additional standard
digital radiographic images available
and has published guidelines on the
classification of digital radiographic
images (ILO 2022). These guidelines
provide standard practices for detecting
changes of pneumoconiosis, including
silicosis, in chest X-rays. The proposed
rule would also require spirometry test
be part of the medical examination.
MSHA has preliminarily determined
that it is technologically feasible for
MNM mine operators to provide
periodic examinations. The procedures
required for initial and periodic medical
examination are commonly conducted
in the general population (i.e., medical
history, physical examination, chest Xray, spirometry test) by a wide range of
practitioners with varying medical
backgrounds. Because the proposed
medical examinations consist of
procedures conducted in the general
population and because MSHA would
be giving MNM mine operators
maximum flexibility in selecting a
PLHCP who would be able to offer these
services, MSHA anticipates that
operators would not experience
difficulty in finding PLHCPs who are
licensed to provide these services.
In addition, in the case of classifying
chest X-rays, MSHA has preliminarily
determined that the availability of
digital X-ray technology allows for
electronic submission to remotely
located B Readers for interpretation;
therefore, MSHA anticipates that the
limited number of B Readers in certain
geographic locations would not be an
obstacle for MNM operators. Overall,
MSHA preliminarily finds that the
proposed medical surveillance
provisions are technologically feasible.
F. Conclusions
Based on MSHA’s technological
feasibility analysis, MSHA has
determined that all elements of the
proposed rule on Lowering Miners’
Exposure to Respirable Crystalline
Silica and Improving Respiratory
Protection are technologically feasible.
IX. Summary of Preliminary Regulatory
Impact Analysis and Regulatory
Alternatives
A. Introduction
Executive Orders (E.O.s) 12866 and
13563 direct agencies to assess all costs
and benefits of available regulatory
alternatives and, if regulation is
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necessary, to select regulatory
approaches that maximize net benefits
(including potential economic,
environmental, public health and safety
effects, distributive impacts, and
equity). E.O. 13563 emphasizes the
importance of quantifying both costs
and benefits, of reducing costs, of
harmonizing rules, and of promoting
flexibility. E.O.s 12866 and 13563
require that regulatory agencies assess
both the costs and benefits of
regulations.
A regulatory action is considered
‘‘significant’’ if it is likely to ‘‘have an
annual effect on the economy of $200
million or more . . .’’ under E.O. 12866
Section 3(f)(1), as amended by E.O.
14094. The proposed rule ‘‘Lowering
Miners’ Exposure to Respirable
Crystalline Silica and Improving
Respiratory Protection’’ is a significant
rule. To comply with E.O.s 12866 and
13563, MSHA has prepared a
standalone PRIA for this proposed rule.
A summary of the PRIA is presented
below. The standalone PRIA contains
detailed supporting data and
explanation for the summary materials
presented here, including the mining
industry, costs and benefits, and
economic feasibility. The standalone
PRIA can be accessed electronically at
https://www.msha.gov and has been
placed in the rulemaking docket at
www.regulations.gov, docket number
MSHA–2023–0001. MSHA requests
comments on all estimates of costs and
benefits presented in this PRIA and on
the data, assumptions, and
methodologies the Agency used to
develop the cost and benefit estimates.
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B. Miners and Mining Industry
The proposed rule would affect mine
operators and miners. This section
provides information on the structure of
the Metal/Nonmetal (MNM) and coal
mining industries, including the
revenue, number, employment by
commodity and size; economic
characteristics of MNM and coal mines;
and the respirable crystalline silica
exposure profiles for miners across
different occupations in the MNM and
coal industry. The data come from the
U.S. Department of the Interior (DOI),
U.S. Geological Survey (USGS); U.S.
Department of Labor (DOL), Mine Safety
and Health Administration (MSHA),
Educational Policy and Development
and Program Evaluation and
Information Resources; the Statistics of
US Businesses (SUSB); and the Energy
Information Administration (EIA).
1. Structure of the Mining Industry
The mining industry can be divided
into two major sectors based on
commodity: (1) Metal/Nonmetal mines
(hereafter referred to as MNM mines)
and (2) coal mines with further
distinction made regarding type of
operation (e.g., underground coal mines
or surface coal mines). The MNM
mining sector is made up of metal mines
(copper, iron ore, gold, silver, etc.) and
nonmetal mines. Nonmetal mines can
be categorized into four commodity
groups: (1) nonmetal (mineral) materials
such as clays, potash, soda ash, salt,
talc, and pyrophyllite; (2) sand and
gravel, including industrial sand; (3)
stone including granite, limestone,
dolomite, sandstone, slate, and marble;
and (4) crushed limestone.
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MSHA categorizes mines by size
based on employment. For purposes of
this industry profile, MSHA has
categorized mines into the following
four groups for analytical purposes 61—
mines that employ: (1) 1–20 miners
(Emp ≤20); (2) 21 to 100 miners (20<
Emp ≤100); (3) 101 to 500 miners (100<
Emp ≤500); and (4) 501 or more miners
(500< Emp).
MSHA tracks mine characteristics and
maintains a database containing the
number of mines by commodity and
size, number of employees, and
employee hours worked. MSHA also
collects data on the number of mining
contractors, their employees, and
employee hours. While contractors are
issued a unique MSHA contractor
identification number, they may work at
any mine.
Table IX–1 presents an overview of
the mining industry, including the
number of MNM and coal mines, their
employment, excluding contractors, and
revenues by commodity and size. All
data are current in reference to the year
2019. In 2019, the MNM mining sector
of 11,525 mines employed 169,070
individuals, of which 150,928 were
miners and 18,142 were office workers.
There were 1,106 coal mines that
reported production and that employed
52,966 individuals, of which 51,573
were miners and 1,393 were office
workers.
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61 Miner employment is based on the information
submitted quarterly through the MSHA Form 7000–
2, excluding Subunit 99—Office (professional and
clerical employees at the mine or plant working in
an office); https://www.msha.gov/sites/default/files/
Support_Resources/Forms/7000-2_0.pdf.
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a. Metal Mining
There are 24 groups of metal
commodities mined in the U.S. Metal
mines, which represent about 2.4
percent (280 out of 11,525) of all MNM
mines and employ roughly 24.5 percent
of all MNM miners. Of these 280 mines,
157 employ 20 or fewer miners and 22
employ greater than 500 miners.
Additionally, the 2019 MSHA data
show that there are a total of 13,792
contract miners in the metal mining
industry.
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b. Non-Metal (Mineral) Mining
c. Stone Mining
Thirty-five non-metal commodities
are mined in the U.S., not including
stone, and sand and gravel. Non-metal
mines represent about 7.8 percent of all
MNM mines and employ roughly 15
percent of all MNM miners. The
majority of non-metal mines (71.9
percent) employ fewer than 20 miners
and less than 1 percent employ more
than 500 employees. In 2019, there were
11,346 contract miners in the non-metal
mining industry.
The stone mining subsector includes
eight different stone commodities.
Seven of the eight are further classified
as either dimension stone or crushed
and broken stone. Stone mines make up
20.9 percent of all MNM mines and
employ 23.4 percent of all MNM miners.
The majority of these mines (83.1
percent) employ less than 20 miners. In
2019, there were 18,559 contract miners
in the stone mining industry.
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d. Crushed Limestone
Crushed limestone mines make up
16.2 percent of all MNM mines and
employ about the same percentage (16.0
percent) of all MNM miners. Of the
1,862 crushed limestone mines, 83.5
percent employ fewer than 20 miners,
and there are no crushed limestone
mines that employ over 500 miners. In
2019, there were 9,605 contract miners
in the crushed limestone mining
industry.
e. Sand and Gravel Mining
Sand and gravel mines account for
52.7 percent of all MNM mines and
employ 21.1 percent of all MNM miners.
Nearly all (96.7 percent) of these mines
employ fewer than 20 employees. In
2019, MSHA data show that there were
7,512 contract miners in the sand and
gravel mining industry.
f. Coal
In the coal sector, 707 mines (63.9
percent) employed fewer than 20
miners. Overall, coal mine employment
in 2019 was 52,966, of which 51,573
were miners and the remaining 1,393
were office workers. Additionally, there
were a total of 22,003 contract miners in
the coal mining industry in 2019.
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2. Economic Characteristics of the
Metal/Non-Metal Mining Industry
The value of all MNM mining output
in 2019 was estimated at $83.8 billion
(U.S. Department of Interior, 2019).
Metal mines, which include iron, gold,
copper, silver, nickel, lead, zinc,
uranium, radium, and vanadium mines,
contributed $26.9 billion. In the USGS
Mineral Commodity Summaries,
nonmetals, stone, sand and gravel, and
crushed limestone are combined in to
one commodity group called industrial
minerals. MSHA estimated the
production value of each individual
commodity by applying the proportion
of revenues represented by each among
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all commodities in the SUSB and
applying that proportion to the 2019
production value for all industrial
minerals reported by USGS. This
approach yielded the following
estimates: metal production was valued
at $26.9 billion, non-metal production at
$22.3 billion, stone mining at $12.85
billion, sand and gravel at $9.0 billion,
and crushed limestone at $12.7 billion.
Production in the U.S. coal sector
amounted to 706.1 million tons in
2019.62 To estimate coal revenues in
2019, MSHA combined production
estimates with prices per ton. Mine
production data was taken from MSHA
quarterly data and the coal price per ton
was taken from the 2019 EIA Annual
Coal Report. As shown in Table IX–1,
total coal revenues in 2019 equaled
$25.6 billion.
The U.S. coal mining sector produces
three major types of coal: bituminous,
lignite, and anthracite. According to
MSHA data, bituminous operations
account for approximately 92.1 percent
of total coal production in short tons,
and 91.9 percent of all coal miners.
Lignite operations account for roughly
7.5 percent of total coal production and
6.2 percent of coal miners. Anthracite
operations account for 0.4 percent of
coal production and 1.9 percent of coal
miners.
C. Cost-Benefit Analysis
The PRIA is based on MSHA’s
Preliminary Risk Analysis and the
Technological Feasibility analysis. The
PRIA presents estimated benefits and
costs of the proposed rule for
informational purposes only. Under the
Mine Act, MSHA is not required to use
estimated net benefits as the basis for its
decision. MSHA requests comments on
the methodologies, baseline,
assumptions, and estimates presented in
62 Source: MSHA MSIS Data (reported on MSHA
Form 7000–2).
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the PRIA and also asks for any data or
quantitative information that may be
useful in evaluating the estimated costs
and benefits associated with the
proposed rule. The PRIA assesses the
costs and benefits in the MNM and coal
industries of reducing miners’
exposures to silica to 50 mg/m3 for a full
shift, calculated as an 8-hour time
weighted average (TWA) and of
complying with the standard’s ancillary
requirements. The PRIA also assesses
the costs and benefits from requiring
medical surveillance of MNM miners. It
also assesses the costs and benefits from
revising the existing respiratory
protection standards. MSHA is
proposing to incorporate by reference
ASTM F3387–19, ‘‘Standard Practice for
Respiratory Protection’’ (ASTM F3387–
19). ASTM F3387–19 would replace the
1969 American National Standards
Institute (ANSI) ‘‘Practices for
Respiratory Protection.’’
MSHA estimates the proposed rule
would have an annualized cost of $57.6
million in 2021 dollars at a real
discount rate of 3 percent. Of this cost,
over 55 percent is attributable to
exposure monitoring; 30 percent to
medical surveillance; 10 percent to
engineering, improved maintenance and
repair, and administrative controls; 2.4
percent related to the selection, use, and
maintenance of approved respirators in
accordance with ASTM F3387–19,
respiratory protection practices; and 1.8
percent to additional respiratory
protection (e.g., when miners need
temporary respiratory protection from
exposure at the proposed PEL when it
would not have been necessary at the
existing PEL). MSHA further estimates
that the MNM sector will incur $52.7
million (91 percent), and the coal sector
will incur $4.9 million (9 percent) in
annualized compliance costs (see Table
IX–2).
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In its analysis, MSHA annualizes all
costs using 3 percent and 7 percent
discount rates as recommended by
OMB. MSHA bases the annualization
periods for expenditures on equipment
life cycles and primarily uses a 10-year
annualization period for one-time costs
and 20-year for medical surveillance.
However, MSHA annualizes the benefits
of the proposed rule over a 60-year
period to reflect the time needed for
benefits to reach the steady-state values
projected in MSHA’s PRA. Therefore,
MSHA’s complete analysis of this rule
is 60 years (which corresponds to 45
years of working life and 15 years of
retirement for the current miner
population). MSHA holds the
employment and production constant
over this period for purposes of the
analysis.63
For both MNM and coal mines, the
estimated costs to comply with the
proposed PEL (50 mg/m3), assumes that
all mines are compliant with the
existing PEL of 100 mg/m3 for MNM
mines (for a full shift, calculated as an
8-hour TWA) and 85.7 mg/m3 for coal
mines (for a full shift, calculated as an
8-hour TWA).
MSHA estimates that:
D The proposed respirable crystalline
silica rule will result in a total of 799
lifetime avoided deaths (63 in coal and
736 in MNM mines) and 2,809 lifetime
avoided morbidity cases (244 in coal
and 2,566 in MNM mines) once it is
fully effective (i.e., beginning 60 years
post rule promulgation through year 120
such that all miners, working and
retired, have been exposed only under
the proposed PEL) (see Table IX–3).
D Over the first 60 years, annual cases
avoided will increase gradually to the
steady-state values (i.e., long-run peryear averages). Upon reaching the
steady-state values, annual cases
avoided will be constant from year 60
onward because all miner cohorts will
have identical lifetime risks. From Table
IX–4, in the first 60 years, the proposed
rule would result in a total of 410
avoided deaths (377 in MNM and 33 in
Coal) and 1,420 avoided morbidity cases
(1,298 in MNM and 122 in Coal), which
are the benefits MSHA monetized in its
benefits analysis.
D The total benefits of the proposed
respirable crystalline silica rule from
these avoided deaths and morbidity
cases are $175.7 million per year in
2021 dollars.
—The majority (60.7 percent) of these
benefits ($108.0 million) are
attributable to avoided mortality due
to non-malignant respiratory disease
(NMRD) ($52.8 million), silicosis
($28.1 million), and end-stage renal
disease (ESRD) ($19.9 million), and
lung cancer ($7.2 million).
—Benefits from avoided morbidity due
to silicosis are $53.2 million per year:
$48.7 million for MNM mines and
$4.6 million for coal mines (see Table
IX–5).
—Benefits from avoided morbidity that
precedes fatal cases associated with
NMRD, silicosis, renal disease, and
lung cancer, are $14.5 million: $13.3
million for MNM mines and $1.2
million for coal mines (see Table IX–
5).
63 This modeling strategy implicitly assumes that
the ten-year cost annualization repeats five more
times to cover the same 60-year analytic period as
the benefits model. Thus, one-time costs incurred
in the first year implicitly repeat in years 11, 21,
31, 41 and 51. This may introduce a tendency
toward overestimation of compliance costs.
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MSHA acknowledges that its benefit
estimates are influenced by the
underlying assumptions and that the
long-time frame of this analysis (first 60
years) is a source of uncertainty. The
main assumptions underlying these
estimates of avoided mortality and
morbidity include the following:
D Employment and production are
held constant over the 60 years—the
analysis period of the proposed rule.64
D Any miners currently exposed
above the existing PELs are exposed to
levels of respirable crystalline silica at
existing standards (100 mg/m3 for a fullshift exposure, calculated as an 8-hour
TWA at MNM mines and 85.7 mg/m3 for
a full-shift exposure, calculated as an 8hour TWA at coal mines).
D The proposed rule will result in
miners being exposed at or below the
proposed PEL (50 mg/m3).
D Miners have identical employment
and hence exposure tenures (45 years).
The assumptions inherent in developing
the exposure-response functions for the
modeled health outcomes are reasonable
throughout the exposure ranges relevant
to this benefits analysis. In the final
rule, the agency plans to augment the
Regulatory Impact Analysis, for
informational purposes, so as to
incorporate different durations of
working life based on exposure
information, while continuing to also
present calculations based on a 45-year
working life assumption.
64 MSHA recognizes that it is impossible to
predict economic factors over such a long period.
Given known information and forecast limitations,
MSHA believes this is a reasonable assumption.
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In addition to the above quantified
health benefits of the lower PEL, MSHA
projects that there would be additional
benefits from requiring approved
respirators be selected, used, and
maintained in accordance with the
requirements, as applicable, of ASTM
F3387–19. The ASTM standard reflects
developments in respiratory protection
since MSHA issued its existing
standards. These developments include
OSHA’s research and rulemaking on
respiratory protection. Under the
proposed rule, MSHA would require
operators’ respiratory protection plans
to include minimally acceptable
respiratory program elements: program
administration; standard operating
procedures (SOPs); medical evaluation;
respirator selection; training; fit testing;
and maintenance, inspection, and
storage. Given the uncertainty about the
current state of operator respiratory
protection practices, MSHA did not
quantify the benefits that would be
realized by requiring approved
respirators to be selected, used, and
maintained in accordance with ASTM
F3387–19.
MSHA believes the proposed rule
would lower exposures to respirable
crystalline silica and respirable coal
mine dust. The available exposureresponse models do not account for
separate health effects from exposure to
mixed dust that contains both respirable
crystalline silica and coal mine dust.
However, MSHA anticipates that there
would be additional unquantified
benefits provided by the proposed
rule—reduced adverse health outcomes
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attributable to respirable coal mine dust
exposure, such as CWP.65 The proposed
rule does quantify the benefits of
avoided deaths and illnesses from
reducing coal miners’ exposures to
respirable crystalline silica. Among coal
miners, MSHA estimates 35 lifetime
avoided deaths and illnesses from
NMRD (see Table IX–3).
Finally, MSHA also expects that the
proposed rule’s medical surveillance
provisions would reduce mortality and
morbidity from respirable crystalline
silica exposure among MNM miners.
The initial mandatory examination that
assesses a new miner’s baseline
pulmonary status, coupled with
periodic examinations, would assist in
the early detection of respirable
crystalline silica related illnesses. Early
detection of illness often leads to early
intervention and treatment, which may
slow disease progression and/or
65 The following references document miner
exposures that could be simultaneously below the
PEL for RCMD but exceed the PEL for silica:
Rahimi, E., Shekarian, Y., Shekarian, N. et al.
Investigation of respirable coal mine dust (RCMD)
and respirable crystalline silica (RCS) in the U.S.
underground and surface coal mines. Sci Rep 13,
1767 (2023). https://doi.org/10.1038/s41598-02224745-x.
Doney BC, Blackley D, Hale JM, Halldin C, Kurth
L, Syamlal G, Laney AS. Respirable coal mine dust
in underground mines, United States, 1982–2017.
Am J Ind Med. 2019 Jun;62(6):478–485. doi:
10.1002/ajim.22974. Epub 2019 Apr 29. PMID:
31033017; PMCID: PMC6800046.
Doney BC, Blackley D, Hale JM, Halldin C, Kurth
L, Syamlal G, Laney AS. Respirable coal mine dust
at surface mines, United States, 1982–2017. Am J
Ind Med. 2020 Mar;63(3):232–239. doi: 10.1002/
ajim.23074. Epub 2019 Dec 9. PMID: 31820465;
PMCID: PMC7814307.
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improve health outcomes. However, as
noted, MSHA lacks data to quantify
these additional benefits.
The net benefits of the proposed rule
are the differences between the
estimated benefits and costs. Table IX–
6 shows estimated net benefits using
alternative discount rates of 0, 3, and 7
percent for benefits and costs. As is
observed from the table, the choice of
discount rate has a significant effect on
annualized costs, benefits, and hence
net benefits. While the net benefits of
the proposed respirable crystalline silica
rule vary considerably depending on the
choice of discount rate used to
annualize costs and benefits, total
benefits exceed total costs under each
discount rate considered. MSHA’s
estimate of the net annualized benefits
of the proposed rule, using a uniform
discount rate for both costs and benefits
of 3 percent, is $118.2 million a year
with the largest share ($108.8 million;
92.0 percent) attributable to the MNM
sector.
D. Economic Feasibility
annualized compliance costs to
revenues from the screener analysis
should be interpreted with care. If
annualized compliance costs comprise
less than 1 percent of revenue, the
Department of Labor presumes that the
affected entities can incur the
compliance costs without significant
economic impacts.
For the MNM and coal mining sectors,
MSHA estimates the projected impacts
of the rule by calculating the average
annualized compliance costs for each
sector as a percentage of total revenues.
To be consistent with costs that are
calculated in 2021 dollars, MSHA first
inflated mine revenues expressed in
2019 to their 2021 equivalent using the
GDP Implicit Price Deflator. Due to
inflation, the nominal value of a dollar
in 2021 is estimated to be about 5.4
percent higher than in 2019.
To establish economic feasibility,
MSHA uses a revenue screening test—
whether the yearly costs of a rule are
less than 1 percent of revenues, or are
negative (i.e., provide net cost
savings)—to presumptively establish
that compliance with the regulation is
economically feasible for the mining
industry. The resulting ratio of
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Table IX–8 presents the projected
impacts of the proposed rule. The table
compares aggregate annualized
compliance costs for MNM and coal
sectors at a 0 percent, 3 percent, and 7
percent real discount rate to total annual
revenues. At a 3 percent real discount
rate, total aggregate annualized
compliance costs are projected to be
$57.6 million (including both 30 CFR
part 60 and 2019 ASTM Upgrade Costs),
while aggregate revenues are estimated
to be $115.3 billion in 2021 dollars.
Thus, the mining industry is expected to
incur compliance costs that comprise
0.05 percent of total revenues.
For the MNM sector, MSHA estimates
that the annualized costs of the
proposed rule (including ASTM update
costs) would be $52.7 million at 3
percent discount rate, which is
approximately 0.06 percent of total
annual revenue of $88.3 billion ($52.7
million/$88.3 billion) for MNM mine
operators. For the coal sector, MSHA
estimates that the annualized cost of the
proposed rule would also be $4.9
million at 3 percent, which is
approximately 0.02 percent of total
annual revenue of $27.0 billion ($4.9
million/$27.0 billion) for coal mine
operators.
The ratios of screening analysis are
well below the 1.0 percent threshold,
and therefore, MSHA has concluded
that the requirements of the proposed
rule are economically feasible, and no
sector of the industry will likely incur
significant costs.
E. Regulatory Alternatives
processes that would reasonably be
expected to result in new or increased
exposures.
In developing the proposed rule,
MSHA considered two regulatory
alternatives. Both alternatives include
less stringent monitoring provisions
than the proposed monitoring
provisions. One of the alternatives also
combines less stringent monitoring with
a more stringent PEL. MSHA discusses
the regulatory options in the sections
below, from least expensive to most
expensive. Both alternatives would
retain the respiratory protection updates
and medical surveillance from the
proposed rule.
1. Regulatory Alternative #1: Changes in
Sampling and Evaluation Requirements
The proposed rule presents a
comprehensive approach for lowering
miners’ exposure to respirable
crystalline silica. The proposal includes
the following regulatory provisions:
lowering miners’ respirable crystalline
silica exposure to a PEL of 50 mg/m3 for
a full-shift exposure, calculated as an 8hour TWA; initial baseline sampling for
miners who are reasonably expected to
be exposed to respirable crystalline
silica; periodic sampling for miners who
are at or above the proposed action level
of 25 mg/m3 but at or below the
proposed PEL of 50 mg/m3; and semiannual evaluation of changing mining
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Under this alternative, the proposed
PEL would remain unchanged at 50 mg/
m3 and the proposed action level would
remain unchanged at 25 mg/m3. Further,
mine operators would conduct: (1)
baseline sampling for miners who may
be exposed to respirable crystalline
silica at or above the proposed action
level of 25 mg/m3, (2) periodic sampling
twice per year for miners who are at or
above the proposed action level of 25
mg/m3 but at or below the proposed PEL
of 50 mg/m3, and (3) annual evaluation
of changing mining processes or
conditions that would reasonably be
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expected to result in new or increased
exposures.
Mine operators would be required to
undertake sampling under this
regulatory alternative and would thus
incur compliance costs. However,
monitoring requirements under this
alternative are less stringent than the
requirements under the proposed rule
because the number of miners to be
sampled for baseline sampling would be
smaller than in the proposed rule and
the frequency of periodic sampling and
evaluations of changing mining
processes or conditions are set at half
the frequency of the proposed
monitoring requirements. Therefore, the
cost of compliance will be lower under
this alternative. MSHA estimates that
annualized monitoring costs will total
$17.3 million for this alternative (at a 3
percent discount rate), compared to
$32.0 million for the proposed
monitoring requirements, resulting in an
estimated $14.7 million in lower costs
per year (Table IX–9).
Although this alternative does not
eliminate exposure monitoring, the
requirements are minimal relative to the
monitoring requirements under the
proposed rule. However, MSHA
believes it is necessary for mine
operators to establish a solid baseline
for any miner who is reasonably
expected to be exposed to respirable
crystalline silica. In addition, quarterly
monitoring helps mine operators
correlate mine conditions to miner
exposure levels and see exposure trends
more rapidly than would result from
semi-annual or annual sampling. This
would enable mine operators to take
measures necessary to ensure continued
compliance with the PEL. Further, more
frequent monitoring would enable mine
operators to ensure the adequacy of
controls at their mines and better
protect miners’ health. These benefits
cannot be quantified, but they are
nevertheless material benefits that
increase the likelihood of compliance.
MSHA also believes that requiring
more frequent periodic sampling would
provide mine operators with greater
confidence that they are in compliance
with the proposed rule. Because of the
variable nature of miner exposures to
airborne concentrations of respirable
crystalline silica, maintaining exposures
below the proposed action level
provides mine operators with
reasonable assurance that miners would
not be exposed to respirable crystalline
silica at levels above the PEL on days
when sampling is not conducted. MSHA
believes that the benefits of the
proposed sampling requirements justify
the additional costs relative to
Regulatory Alternative 1.
2. Regulatory Alternative #2: Changes in
Sampling and Evaluation Requirements
and the Proposed PEL
would be required to perform semiannual evaluations of changing mining
processes or conditions. Further, mine
operators would be required to perform
post-evaluation sampling when the
operators determine as a result of the
semi-annual evaluation that miners may
be exposed to respirable crystalline
silica at or above proposed PEL at 25 mg/
m3. When estimating the cost of the
proposed monitoring requirements,
MSHA assumes that the number of
samples for corrective action and semiannual evaluation are relatively small
(2.5 percent of miners) because samples
from sampling to determine the
adequacy of controls and from MSHA
can both be used to meet the
requirements. Since this alternative
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Under this regulatory alternative, the
proposed PEL would be set at 25 mg/m3;
mine operators would install whatever
controls are necessary to meet this PEL;
and no action level would be proposed.
Further, mine operators: (1) would not
be required to conduct baseline
sampling or periodic sampling; (2)
would conduct semi-annual evaluations
of changing conditions; and (3) would
sample as frequently as necessary to
determine the adequacy of controls.
Mine operators would not be required
to undertake baseline or periodic
sampling. However, mine operators
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does not require periodic sampling,
MSHA increases samples after each
evaluation to 10 percent of miners to
ensure the monitoring requirements can
be met.
This alternative also sets the proposed
PEL at 25 mg/m3. In addition to the
estimated cost of compliance with a PEL
of 50 mg/m3, mine operators would
incur additional engineering control
costs to meet a PEL of 25 mg/m3. To
estimate these additional engineering
control costs, MSHA largely uses the
same methodology as for mines affected
at the proposed PEL of 50 mg/m3.
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a. Number of Mines Affected Under
Regulatory Alternative 2
MSHA first estimated the number of
mines expected to incur the cost of
implementing engineering controls to
reach the more stringent PEL. After
excluding mines that are affected at the
proposed PEL of 50 mg/m3 (to avoid
double-counting), MSHA finds that
3,477 mines (2,991 MNM mines and 486
coal mines) operating in 2019 had at
least one sample at or above 25 mg/m3
but below 50 mg/m3.66
To this number, MSHA adds the 1,226
affected mines expected to incur costs to
reach the proposed PEL of 50 mg/m3.
Based on its experience and knowledge,
MSHA does not expect the mines that
installed engineering controls to meet
However, the difficulty of meeting a
PEL of 25 mg/m3 is such that MSHA’s
the PEL of 50 mg/m3 will also be able to
comply with a PEL of 25 mg/m3. For
example, to comply with the proposed
PEL of 50 mg/m3, a mine might need to
add the engineering controls necessary
to achieve an additional 10 air changes
per hour over that achieved by existing
controls, which are costed in the
following section. However, such a
mine facility would then need to add an
additional 10 air changes per hour to
meet the more stringent PEL of 25 mg/
m3, which is not costed in the following
section. Thus, MSHA expects that the
1,226 affected mines will incur
additional costs to meet the PEL of 25
mg/m3 specified under this alternative.
MSHA estimates a total of 4,703
mines will incur costs to purchase,
install, and operate engineering controls
to meet the PEL of 25 mg/m3 under this
alternative. MNM mines account for
4,087 (87 percent) and coal mines 616
(13 percent). Further, of the estimated
4,087 MNM mines and 616 coal mines,
1,096 MNM mines (27 percent) and 130
coal mines (21 percent) are also
estimated to incur compliance costs to
reach the proposed PEL of 50 mg/m3.
b. Estimated Engineering Control Costs
Under Regulatory Alternative 2
mines with respirable crystalline silica
dust exposures at or above 25 mg/m3 but
below 50 mg/m3 categories to meet the
PEL of 25 mg/m3 under consideration for
this alternative. While MSHA assumes
that mine operators will base such
decisions on site-specific conditions
such as mine layout and existing
infrastructure, MSHA cannot make
further assumptions about the specific
controls that might be adopted and
instead assumes the expected value of
purchased technologies should equal
the simple average of the technologies
listed in each control category.
Where more precise information is
unavailable, MSHA assumes operating
and maintenance (O&M) costs to be 35
percent of initial capital expenditure
and installation cost, when appropriate,
will be equal to the initial capital
expenditure (Table IX–10). MSHA also
assumes the larger capital expenditure
controls will have a 30-year service life.
MSHA welcomes public comment
concerning the engineering controls
selected for this analysis and the
assumptions used to estimate
installation and O&M costs for these
controls.
MSHA identified potential
engineering controls that would enable
experience suggests a single control
from Table IX–10 will not be sufficient.
For example, respirable crystalline silica
dust exposure at such a stringent limit
66 About 8,053 of mines active in 2019 either did
not have a sample > 25 mg/m3 or did not have a
sample in the last 5 years.
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necessary. Therefore, MSHA assumes
mine operators will purchase and install
at least two of the engineering controls
listed in Table IX–10. This may be a
conservative assumption.
Table IX–11 presents the average
annualized engineering control costs per
mine and total annualized engineering
control costs by mine sector. Because
the service life of nearly all components
is expected to be 30 years, the costs of
all engineering controls are annualized
over 30 years. At a 3 percent real
discount rate, the average annualized
engineering control costs are about
$94,300 per mine, resulting in an
additional cost of $443.6 million if the
PEL is set at 25 mg/m3 instead of 50 mg/
m3.
Table IX–12 summarizes the
estimated annualized cost of this
alternative under consideration. At a 3
percent real discount rate, exposure
monitoring costs less than the proposed
rule; however, this lower cost is more
than offset by the increased control
costs necessitated by the requirement
that mines maintain respirable
crystalline silica exposure levels below
25 mg/m3. At an estimated annualized
cost of $491.2 million, this alternative
would cost nearly eight times more than
the proposed requirements.
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as 25 mg/m3 is likely to occur at more
than one area of the mine; in addition
to increasing ventilation to a crusher/
grinder, enclosing and ventilating the
conveyor belt mine would be necessary
to reduce concentrations below the
limit. Similarly, increasing facility
ventilation from 20 to 30 air changes per
hour may not be adequate to meet the
limit; 40 air changes per hour might be
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This alternative requires exposure
monitoring that is more stringent than
Regulatory Alternative 1, but less
stringent than the proposed
requirements. In addition, Regulatory
Alternative 2 increases miner protection
by proposing to set the PEL at 25 mg/m3,
resulting in measurable avoided
mortality and other health benefits.
Table IX–13 presents the avoided
morbidity and mortality cases over the
60-year regulatory analysis time horizon
under this alternative. Under this
alternative, the avoided 60-year
mortality is expected to be 981, which
is 2.4 times higher than the expected
avoided mortality of 410 under a
proposed PEL of 50 mg/m3. The avoided
60-year morbidity under the regulatory
alternative of 25 mg/m3 is expected to be
1,948, which is 1.4 times higher than
the expected avoided 60-year morbidity
of 1,420 under the proposed PEL of 50
mg/m3.
Table IX–14 presents the benefits
associated with this avoided morbidity
and mortality. The expected total
benefits, discounted at 3 percent, are
$365.5 million, which is twice the
expected total benefits of $175.7 million
under the proposed PEL of 50 mg/m3.
Under this regulatory alternative, these
benefits are made up of $258.0 million
due to avoided mortality, $34.5 million
due to morbidity preceding mortality,
and $73.0 million due to morbidity not
preceding mortality. However, when
compared to the annualized costs, the
net benefits of this alternative are
negative at both a 3 percent and 7
percent real discount rate.
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MSHA solicits further comment on
the extent to which these or other
regulatory alternatives (including
different ways of calculating respirable
crystalline silica concentration) may
change the effects of the proposed rule.
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X. Initial Regulatory Flexibility
Analysis
The Regulatory Flexibility Act (RFA)
of 1980, as amended by the Small
Business Regulatory Enforcement
Fairness Act (SBREFA) of 1996, requires
preparation of an Initial Regulatory
Flexibility Analysis (IRFA) for any rule
that by law must be proposed for public
comment, unless the agency certifies
that the rule, if promulgated, will not
have a significant economic impact on
a substantial number of small entities. 5
U.S.C. 601- 612. Because MSHA’s
proposed rule on respirable crystalline
silica, including the incorporation of
ASTM F3387–19 by reference, would
regulate the mining industry, the
proposed rule falls within the purview
of the RFA. MSHA has evaluated the
impact of the proposed rule on small
entities in this IRFA. MSHA’s analysis
is presented in the following.
Description of the Reasons Why MSHA
is Considering Regulatory Action
Based on its review of the health
effects literature, MSHA has
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preliminarily determined that
occupational exposure to respirable
crystalline silica causes silicosis and
other diseases. Based on its preliminary
risk analysis, MSHA has also
determined that under its existing
standards, miners face a risk of material
impairment of health or functional
capacity from exposures to respirable
crystalline silica.
Based on these preliminary
determinations, MSHA proposes to
amend its existing standards to better
protect miners against occupational
exposure to respirable crystalline silica,
a carcinogen, and to improve respiratory
protection for all airborne contaminants.
The proposed rule would establish for
mines of all sizes, a PEL of 50 mg/m3 for
a full shift, calculated as an 8-hour
TWA, for all miners, and an action level
of 25 mg/m3 for a full-shift exposure,
calculated as 8-hour TWA. MSHA’s
proposal would also include other
requirements to protect miner health,
such as periodic exposure sampling and
corrective actions to be taken when
miners’ exposures exceed the PEL.
MSHA also proposes to replace existing
requirements for respiratory protection
and to incorporate by reference the
ASTM F3387–19 Standard Practice for
Respiratory Protection. MSHA believes
that the proposed changes would
significantly improve health protections
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for all miners over the course of their
working lives.
Objectives of, and Legal Basis for, the
Proposed Rule
The proposed rule would fulfill
MSHA’s statutory obligation to
‘‘promulgate improved mandatory
health . . . standards to protect’’
miners’ health under the Mine Act, as
amended. 30 U.S.C. 801(g). The Mine
Act requires the Secretary of Labor
(Secretary) to develop and promulgate
improved mandatory health or safety
standards to prevent hazardous and
unhealthy conditions and protect the
health and safety of the nation’s miners.
30 U.S.C. 811(a). The Secretary must set
standards to assure, based on the best
available evidence, that no miners will
suffer material impairment of health or
functional capacity from exposure to
toxic materials or harmful physical
agents over their working lives. 30
U.S.C. 811(a)(6)(A). Section 103(h) of
the Mine Act gives the Secretary the
authority to promulgate standards
involving recordkeeping and reporting.
30 U.S.C. 813(h). Additionally, section
508 of the Mine Act gives the Secretary
the authority to issue regulations to
carry out any provision of the Mine Act.
30 U.S.C. 957.
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Description and Estimate of the Number
of Small Entities to Which the Proposed
Rule Would Apply
The proposed rule would affect MNM
and coal mining operations. To
determine the number of small entities
subject to the proposed rule, MSHA
reviewed the North American Industrial
Classification System (NAICS), the
standard used by Federal statistical
agencies in classifying business
establishments, as well as information
from the Office of Advocacy of the
Small Business Administration (SBA).
MSHA used its data from the MSHA
Standardized Information System
(MSIS) to identify the responsible party
for each mine. MSHA then combined
that information with the size
classification information.
First, MSHA determined that mining
operations that fall into 25 NAICS-based
industry classifications may be subject
to the proposed rule. These industry
categories and their accompanying sixdigit NAICS codes are shown in Table
X–1.67
NAICS classifications used in this analysis
are drawn from a recent version of the NAICS
(though, for reasons described below, not the latest
version, which was published in January 2022).
SBA established definitions of small entities for
each of the categories in the earlier version, which
were effective in August 2019. This version of
NAICS categories was needed for this analysis, in
order for MSHA to cross-tabulate (or crosswalk) its
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Second, MSHA matched the NAICS
classifications with SBA small-entity
size standards (based on number of
employees) to determine the number of
small entities within each of the
respective NAICS codes. See Table X–1.
Third, MSHA counted the number of
small-entity controllers in each NAICS
code, after determining that a
‘‘controller’’ who owns and controls a
mine as the appropriate unit of this
IRFA analysis (based on SBA guidance)
(Small Business Administration 2017).
A controller is a parent company
owning or controlling one or more
mines. A controller can also be a firm,
whereas a mine can be an
establishment. Table X–1 shows the
count of all controllers and a count of
small-entity controllers in each NAICS
code. Some ‘‘unique controllers’’ are
included in more than one NAICS code
because they own or control multiple
mines, each producing a different
commodity. For this analysis, however,
MSHA single-counted these unique
data on mines and controllers with Bureau of
Census data on revenues by NAICS codes, where
these Census data were organized by the same
NAICS codes that were in the earlier version. No
comparable revenue data, at this writing, had yet
been revised to the most recent NAICS categories,
which prevented MSHA from using those
categories. MSHA identified 25 NAICS categories
(in the previous system) that accounted for all
mining activities.
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controllers; for example, a controller
who owns three mines in three different
NAICS codes was only counted once.
Based on this methodology, MSHA
estimated that in 2021, there were a
total of 5,879 controllers, 5,007 of which
were small-entity controllers. Many
controllers owned one or two mines,
while some controllers owned hundreds
of mines nationwide (or worldwide).
The 5,007 small-entity controllers
owned a total of 8,240 mines out of
11,791 mines in operation in 2021.68
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68 The number of controllers and mines examined
in this regulatory flexibility analysis are those
specifically known to operate in 2021. The year
2021 is the most current year for which complete
information were available. Such information about
controllers as parent companies might include, for
example, knowledge of whether the parent
company is a large, multinational corporation,
which has bearing on this regulatory flexibility
analysis. Because the benefit-cost analysis
performed on the proposed rule did not need this
kind of detailed information about controllers, it
was able to have a broader scope to include data
from other years besides 2021, which it did. As a
result, the benefit cost analysis included a larger
number of mines (and affected mines) and
controllers. The key factor for this regulatory
flexibility analysis is the estimated ratio of the
regulatory cost per revenue for controllers, as
reflected by the most current data. The estimation
of this ratio is robustly addressed in MSHA’s
analysis of the 5,879 controllers in 2021 (which is
not impacted by the exclusion of other years in this
analyis).
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Description of the Projected Reporting,
Recordkeeping, and Other Compliance
Requirements for Small Entities
As explained earlier, the proposed
rule would establish a PEL of 50 mg/m3
and an action level of 25 mg/m3 for a
full-shift exposure, calculated as 8-hour
TWA. The proposed rule would also
include other requirements. Examples
include baseline, periodic, and
corrective action sampling, semi-annual
evaluations, medical surveillance,
respiratory protection, and
recordkeeping.
With regard to the paperwork burden
on small entities, MSHA’s proposed rule
would create new information
collection requests for the mining
industry. As described in greater detail
in Section XI below, these requirements
include the collection of information
involving: (1) exposure monitoring—
samplings and semi-annual evaluations,
(2) corrective actions taken, (3) miners
unable to wear respirators, and (4)
medical surveillance for MNM miners.
Table XI–2 displays an annual estimate
of information collection burden for the
whole mining industry. Compliance
costs on small entities that include
recordkeeping costs are discussed
below.
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Estimation of the Compliance Costs and
Relative Burden to Small Entities
MSHA estimated the average annual
regulatory cost per small-entity
controller (based on a 3 percent
discount rate), as well as the average
annual revenue per small-entity
controller. MSHA estimated, for each
controller, the additional annual cost of
the proposed regulation as a proportion
of that controller’s annual revenue. The
average of these proportions (weighting
controllers equally) was 0.122 percent,
below a 3 percent threshold used for
significant impact. That is, for every $1
million in revenue earned by a
controller, the average regulatory cost
was estimated to be $1,220.
Total Compliance Cost. MSHA
estimated that the proposed rule would
have an average cost of $60.23 million
per year in 2021 dollars at a real
discount rate of 3 percent. The
estimated costs for the proposed rule
would represent the additional costs
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necessary for mine operators to achieve
full compliance with the proposed rule.
Compliance Costs by Small-Entity
Controllers. Because mines (as well as
controllers) vary in the scale of their
operations, MSHA first estimated
additional regulatory costs on a perminer basis. MSHA anticipated that the
additional regulatory costs per miner
would vary across the six major
commodity categories: coal, metal,
nonmetal, stone, crushed limestone, and
sand and gravel. MSHA analyzed
employment data linked with controller
data. By combining this information
with compliance cost information,
MSHA derived estimates of the
regulatory costs for small-entity
controllers. MSHA then estimated the
regulatory cost for each of the 5,007
small-entity controllers identified in
2021. See the average annual regulatory
cost per controller in Table X–2.
Revenues by Small-Entity Controllers.
MSHA estimated revenues for each
small-entity controller. The Agency
estimated revenues per employee, by
mine, and by controller, using data
published by the U.S. Bureau of Census
in their report, ‘‘Statistics of U.S.
Businesses’’ (SUSB).69 The SUSB data
provided revenue estimates for
enterprises in each NAICS code and for
each ‘‘size category’’ (based on number
of employees) within each NAICS code.
The enterprise data considered
controllers that had operations in more
than one NAICS code. MSHA summed
the estimated revenue for the
establishments within the same NAICS
code to create multiple enterprises with
different NAICS codes and compare
constructed enterprises with the SUSB
69 U.S. Census Bureau, ‘‘Statistics of U.S.
Businesses,’’ released May 2021. https://
www.census.gov/data/tables/2017/econ/susb/2017susb-annual.html. Data in the report were in
reference to the year 2017, which MSHA adjusted
to 2021 dollars. Data on revenues are presented in
the report under the equivalent term ‘‘receipts.’’
MSHA converted the 2017 revenues to 2021 dollars
using the GDP Implicit Price Deflator published by
the Bureau of Economic Analysis October 26, 2022,
Table 1.1.9 Implicit Price Deflators for Gross
Domestic Product, Series A191RD. https://
apps.bea.gov/histdata/fileStructDisplay.cfm?HMI=7
&DY=2022&DQ=Q3&DV=Advance
&dNRD=October-28-2022. The index was 107.749
for 2017 and 118.895 for 2021, creating an
adjustment factor (from 2017 to 2021 dollars) of
118.895/107.749 or 1.103.
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data to estimate the revenue for each of
these size-category-specific enterprises.
This methodology was relevant for the
‘‘largest’’ of small-entity controllers,
which controlled more than one mine,
sometimes operating in different NAICS
categories. Most small-entity controllers
operated only one mine, meaning that
no summation was required because
only the number of employees in a
single mine needed to be counted.
MSHA estimated revenues for each
small-entity controller. Some smallentity controllers had mines belonging
to different NAICS codes. This factor
precluded MSHA from being able to
precisely categorize small-entity
controllers by NAICS code. MSHA
estimated each small-entity controller’s
revenues.70
Some of the small-entity controllers
may also have operations in non-mining
industries. If so, total revenues,
including those from non-mining
operations, would be higher than
estimated here, and the ratios of
regulatory costs to revenues shown in
the summary table may be
overestimated.
MSHA developed estimates of the
number of miners for each small-entity
controller, and for each NAICS category
within each controller’s activities.
MSHA then combined these data with
SUSB data on revenues by NAICS
category and size category to generate
estimated revenues for each small-entity
controller. See the estimated average
annual revenue per controller in Table
X–2.
Ratio of Compliance Cost to Revenue.
From the two sets of estimates described
above—costs and revenues—for each
small-entity controller, MSHA generated
estimates of the ratios of regulatory cost
to revenue, for each controller. Table X–
2 shows the number of controllers,
average annual regulatory costs, average
annual revenue, and average cost as a
percent of revenue.
70 In a small number of cases (in terms of NAICS
codes and size categories) the SUSB data were
incomplete. In these cases, MSHA imputed
revenue/employee ratios based on closely related
data for comparable NAICS-size categories. MSHA
then used these imputed revenue/employee ratios
to estimate the revenues of some small-entity
controllers, by the methodology just described.
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There are no Federal rules that may
duplicate, overlap, or conflict with the
proposed rule.
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Significant Alternatives and Their
Impact on Small Entities
MSHA considered two alternatives in
the proposed rule. Under Alternative 1,
the proposed PEL would remain
unchanged at 50 mg/m3 and the
proposed action level would remain
unchanged at 25 mg/m3. Further, mine
operators would conduct: (1) baseline
sampling for miners who may be
exposed to respirable crystalline silica
at or above the proposed action level of
25 mg/m3, (2) periodic sampling twice
per year, and (3) annual evaluation of
changing mining processes or
conditions that would reasonably be
expected to result in new or increased
exposures. Under Alternative 2, the
proposed PEL would be set at 25 mg/m3;
mine operators would install whatever
controls are necessary to meet this PEL;
and no action level would be proposed.
Further, mine operators would: (1) not
be required to conduct baseline
sampling or periodic sampling, (2)
conduct semi-annual evaluations of
changing conditions, and (3) sample as
frequently as necessary to determine the
adequacy of controls. Additional detail
on the two regulatory alternatives
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MSHA considered can be found in IX.
Summary of Preliminary Regulatory
Impact Analysis and Regulatory
Alternatives and in the standalone PRIA
document.
MSHA believes the proposed rule
would provide improved health
protections for miners and would be
achievable for all mines. In developing
the proposed rule, MSHA has included
flexibilities for operators in the
implementation of updated respiratory
protection standard, which would
reduce the burden on small entities.
MSHA has made the following
determinations regarding the two
alternatives considered:
• Alternative 1, ‘‘Changes in
Sampling and Evaluation
Requirements,’’ would reduce overall
costs to the mining industry by 26.2
percent, for costs calculated at both a 3
percent and 7 percent discount rate.
These reduced costs would be
proportionally experienced by small
entities. The average costs as a percent
of revenues for small entities would
then be reduced (relative to the
proposed rule) from 0.12 percent to 0.09
percent.
• Alternative 2, ‘‘Changes in
Sampling and Evaluation Requirements
and the Proposed PEL,’’ would increase
overall costs to the mining industry by
701.9 percent, for costs calculated at a
3 percent discount rate, and by 930.2
percent for costs calculated at a 7
percent discount rate. The average costs
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as a percent of revenues for small
entities would then rise (relative to the
proposed rule) from 0.12 percent to 0.98
percent, based on a 3 percent discount
rate, and from 0.12 percent to 1.259
percent based on a 7 percent discount
rate.
MSHA is seeking comments or
additional information from
stakeholders on whether there are
alternatives the Agency should consider
that would accomplish the objectives of
this rulemaking while reducing the
impact on small entities.
Conclusion
MSHA estimated that small-entity
controllers would be expected to incur,
on average, additional regulatory costs
equaling approximately 0.122 percent of
their revenues (or $1,220 for every $1
million in revenues).
As required under the RFA, MSHA is
complying with its obligation to consult
with the SBA’s Chief Counsel for
Advocacy on this proposed rule and on
this initial regulatory flexibility
analysis. Consistent with Agency’s
practice, notes of any meetings with the
Chief Counsel for Advocacy’s office on
this proposed rule, or any written
communications, will be placed in the
rulemaking record.
XI. Paperwork Reduction Act
The Paperwork Reduction Act of 1995
(44 U.S.C. 3501–3521) provides for the
Federal Government’s collection, use,
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and dissemination of information. The
goals of the Paperwork Reduction Act
include minimizing paperwork and
reporting burdens and ensuring the
maximum possible utility from the
information that is collected under 5
CFR part 1320. The Paperwork
Reduction Act requires Federal agencies
to obtain approval from the Office of
Management and Budget (OMB) before
requesting or requiring ‘‘a collection of
information’’ from the public.
As part of the Paperwork Reduction
Act process, agencies are generally
required to provide a notice in the
Federal Register concerning each
proposed collection of information to
solicit, among other things, comment on
the necessity of the information
collection and its estimated burden, as
required in 44 U.S.C. 3506(c)(2)(A). To
comply with this requirement, MSHA is
publishing a notice of proposed
collection of information in the
proposed rule titled, Lowering Miners’
Exposure to Respirable Crystalline
Silica and Improving Respiratory
Protection.
This rulemaking would require the
creation of a new information collection
as well as modification to the burdens
for existing collections. As required by
the Paperwork Reduction Act, the
Department has submitted information
collections, including a new
information collection and revisions of
two existing collections, to OMB for
review to reflect new burdens and
changes to existing burdens.
I. New Information Collection Under
Proposed Part 60, Respirable
Crystalline Silica
Under proposed part 60 entitled
‘‘Respirable Crystalline Silica,’’ some
new burdens would apply to all mine
operators, and other burdens would
apply to only some mine operators.
Below, the new information collection
burden that would be created by
proposed part 60 is discussed.
Proposed § 60.16 lists all the
recordkeeping requirements related to
proposed part 60. Each of the
requirements are discussed below:
Proposed § 60.12 would require mine
operators to make a record for each
sampling and each evaluation
conducted pursuant to this section. The
sampling record would consist of the
sample date, the occupations sampled,
and the concentrations of respirable
crystalline silica and respirable dust.
The mine operator would also retain
laboratory reports on sampling results.
The semi-annual evaluation record
would include the date of the evaluation
and a record of the mine operator’s
evaluation of any changes in mining
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operations that may reasonably be
expected to result in new or increased
respirable crystalline silica exposures.
In addition, the mine operator would be
required to post the sampling and
evaluation records and the laboratory
report on the mine bulletin board and,
if applicable, by electronic means, for
the next 31 days, upon receipt. All
records would be retained for at least 2
years from the date of each sampling or
evaluation.
Proposed § 60.13 would require mine
operators to make a record of corrective
actions and the dates of the corrective
actions. The corrective action records
would be retained for at least 2 years
from the date of each corrective action.
Proposed § 60.14 would require mine
operators to retain a record of the
written determination by a PLHCP that
a miner who may be required to use a
respirator is unable to wear a respirator.
The written determination record would
be retained for the duration of a miner’s
employment plus 6 months.
Proposed § 60.15 would require MNM
mine operators to obtain a written
medical opinion from the PLHCP or
specialist within 30 days of a miner’s
medical examination. The written
medical opinion would contain the date
of the medical examination, a statement
that the examination has met the
requirements of this proposed section,
and any recommended limitations on
the miner’s use of respirators. The
written medical opinion record would
be retained for the duration of a miner’s
employment plus 6 months.
II. Changes to Existing Information
Collections
This proposed rulemaking would
result in non-substantive changes to
existing information collection
packages. One change under OMB
Control Number 1219–0011 is to occur
after 1219–0NEW, Respirable
Crystalline Silica Standard, is approved
by OMB. The other change is the
discontinuance of the existing
information collection package under
OMB Control Number 1219–0048 which
is also to occur after OMB approval of
1219–0NEW, Respirable Crystalline
Silica Standard.
OMB Control Number 1219–0011,
Respirable Coal Mine Dust Sampling,
involves records for quarterly sampling
of respirable dust in coal mines. The
supporting statement references quartz
and a reduced standard for respirable
dust when quartz is present; however,
there is no specific recordkeeping
requirement that is associated with
those references. Due to changes in the
proposed rule, MSHA would make a
non-substantive change to the
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supporting statement by removing such
references. However, there would be no
changes in paperwork burden and costs
in this information collection.
OMB Control Number 1219–0048,
Respirator Program Records, involves
recordkeeping requirements under 30
CFR parts 56 and 57 for MNM mines
when respiratory protection is used.
MSHA is proposing to update the
existing respiratory protection standard
and permit mine operators to select the
requirements of the standard that are
applicable to their mines. This proposed
change would eliminate the paperwork
burden associated with respiratory
protection resulting in the request to
discontinue the existing information
collection.
A. Solicitation of Comments
Pursuant to the Paperwork Reduction
Act, MSHA has prepared and submitted
an information collection request (ICR)
to OMB for the collection of information
requirements identified in this proposed
rule for OMB’s review in accordance
with 44 U.S.C. 3507(d). MSHA is
soliciting comments concerning the
proposed information collection related
to respirable crystalline silica. MSHA is
particularly interested in comments
that:
• Evaluate whether the proposed
collection of information is necessary
for the proper performance of the
functions of the agency, including
whether the information will have
practical utility;
• Evaluate the accuracy of the
agency’s estimate of the burden of the
proposed collection of information,
including the validity of the
methodology and assumptions used;
• Suggest methods to enhance the
quality, utility, and clarity of the
information to be collected; and
• Minimize the burden of the
collection of information on those who
are to respond, including through the
use of appropriate automated,
electronic, mechanical, or other
technological collection techniques or
other forms of information technology
(e.g., permitting electronic submission
of responses).
B. Proposed Information Collection
Requirements
I. Type of Review: New Collection.
OMB Control Number: 1219–0NEW.
1. Title: Respirable Crystalline Silica
Standard.
2. Description of the ICR: The
proposed rule on respirable crystalline
silica contains collection of information
requirements that would assist miners
and mine operators in identifying
exposures to respirable crystalline silica
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in order to track actual and potential
occupational exposure and action taken
to control such exposure.
There are provisions of this proposed
rule that would take effect at different
times after the implementation of this
proposed rule, and there are provisions
that would have different burden hours,
burden costs, and responses each year.
Therefore, MSHA shows the estimates
of burden hours, burden costs, and
responses in three separate years.
3. Summary of the Collection of
Information: Highlighted below are the
key assumptions, by provision, used in
the burden estimates in Table XI–1:
Proposed § 60.12—Exposure Monitoring
ICR. Proposed § 60.12 would require
mine operators to make a record for
each baseline sampling, corrective
action sampling, periodic sampling,
semi-annual evaluation, and postevaluation sampling, as previously
described.
Number of respondents. For proposed
§ 60.12, the respondents would consist
of all active mines because operators of
active mines are assumed to perform
baseline sampling and conduct semiannual evaluations.
MSHA counts the number of active
mines in 2019, defining an active mine
as one that had at least 520 employment
hours (equivalent to 1 person working
full time for a quarter) in at least one
quarter of 2019. Using this definition,
MSHA estimates that a total of 12,631
mines (11,525 MNM mines and 1,106
coal mines) would generate sampling
and evaluation records.
Annual number of responses. The
estimated average annual number of
responses would be 142,408, including
24,439 for baseline sampling, 9,237 for
sampling after corrective actions, 64,116
for periodic sampling, 42,103 for semiannual evaluation recording and
posting, and 2,513 for post-evaluation
sampling.
MSHA assumes that all the active
mines (12,631 mines) would conduct
baseline sampling once in the first year.
In succeeding years, about 253 new
mines would conduct baseline sampling
with an average of 5.6 samples per
mine. The estimated number of periodic
samplings is calculated based on the
following factors: the number of miners
with sampling results at or above the
proposed action level (25 mg/m3) but at
or below the PEL (50 mg/m3), the percent
of miners needed for representative
samples, and the number of quarters
mines would be in operation. In year 1,
MSHA expects the sampling to begin in
the second half of the year, thereby
decreasing the number of samples by
half. As a result, MSHA estimates that
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an annual average of 64,116 periodic
samples would be conducted in the first
three years. Furthermore, MSHA
assumes that all 12,631 mines would
record semi-annual evaluation results
twice a year—except in year 1, when it
would be done once—and then post
those results on a mine bulletin board,
or if applicable, by electronic means.
MSHA estimates mines would conduct
sampling as a result of their semi-annual
evaluations and an average of four
miners would be sampled, resulting in
an annual average of 2,513 samples.
MSHA estimates that about 22 percent
of active mines (2,771 mines in total)
would have at least one miner
overexposed to respirable crystalline
silica. MSHA further estimates that the
2,771 mines that would then conduct
corrective action sampling for about
four areas per mine. In year 1, they
would sample in half as many areas.
Estimated annual burden. The
estimated average annual burden would
be 31,392 hours, including 6,110 hours
for baseline sampling, 2,309 for
corrective action sampling, 16,029 hours
for periodic sampling, 6,316 hours for
semi-annual evaluation recording and
posting, and 628 hours for postevaluation sampling. MSHA estimates
that it would take 15 minutes to record
the sampling results, 15 minutes to
record the results of a semi-annual
evaluation, and 3 minutes to post each
of the evaluation results on the mine
bulletin board, and, if applicable, by
electronic means.
Proposed § 60.13—Corrective Actions
ICR. Proposed § 60.13 would require
mine operators to make a record of
corrective actions, as previously
described.
Number of respondents. For proposed
§ 60.13, only those mines with at least
one miner exposure above the proposed
PEL are assumed to carry out the
proposed requirement. MSHA estimates
that about 22 percent of active mines
(2,771 mines in total) would have at
least one miner overexposed to
respirable crystalline silica.
Annual number of responses. The
estimated average annual number of
responses would be 14,922, including
9,237 for corrective action records, and
5,685 for miner respirator records.
MSHA estimates that the 2,771 mines
that will be required to conduct and
record corrective actions will do so for
about four mine areas, except in year 1,
when it would be done in half as many
mine areas. MSHA further estimates this
will affect 6,822 miners per year—
except in year 1, when half as many
miners would be affected—with each
miner requiring a record of the miner
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being given access to a respirator until
the corrective action is taken.
Estimated annual burden. The
estimated average annual burden would
be 1,054 hours, including 769.7 for
corrective action records and 284.3 for
miner respirator records. MSHA
estimates that it takes five minutes to
record a corrective action and the date.
On average, it takes three minutes to
note a miner’s access to a respirator.
Proposed § 60.14—Respiratory
Protection
ICR. Proposed § 60.14 would require
mine operators to retain a record of the
determination by a PLHCP that a miner
who may be required to use a respirator
is unable to wear a respirator, as
previously described.
Number of respondents. For proposed
§ 60.14, MSHA assumes that 33 percent
of mine operators would have their
miners use respiratory protection as a
temporary measure and keep records of
their miners’ ability to wear respirators.
The number of respondents would be,
on average, 603 mines per year, with
each mine assumed to have at least
some miners wearing respirators.
Annual number of responses. The
estimated annual number of responses
would be 1,205, with an average of two
miners for each of the 603 mines.
Estimated annual burden. The
estimated annual burden would be 603
hours. MSHA assumes it takes 30
minutes to record this information for
about two miners for each of the 603
mines.
Proposed § 60.15—Medical Surveillance
for Mental and Nonmetal Miners
ICR. Proposed § 60.15 would require
MNM mine operators to obtain a written
medical opinion from a PLHCP or
specialist regarding any recommended
limitations on a miner’s use of
respirators, as previously described.
Number of respondents. MSHA
assumes that 75 percent of eligible
MNM miners (current MNM miners),
including contract workers, would make
use of the opportunity to receive a
voluntary medical exam that is paid by
their mine operator. As a result, an
average of 25,175 current miners are
estimated to receive voluntary medical
exams per year. This estimate represents
the upper range of the participation rate
of voluntary medical exams by miners.
MSHA is using the upper end of the
range to avoid underestimating
compliance costs.
MSHA further estimates that 8,392
miners in a given year, including
contract workers, would be new miners
and contractors who would undergo
mandatory medical examinations.
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MSHA estimated that the turnover of
MNM miners would be 8,392 miners per
year (1/22 of the estimated total of
184,615 MNM workers with an average
number of 22 years on the job before
leaving the mining industry). The
estimated total respondents per year
therefore would be 33,567 (= 8,392 +
25,175).
Annual number of responses. The
estimated annual number of responses
would be 33,567, including 8,392 new
miners and 25,175 current miners.
Estimated annual burden. The
estimated annual burden would be
8,392 hours, including 2,098 hours for
new MNM miners and 6,294 hours for
current miners. MSHA estimates it takes
15 minutes to record the medical
examination results for each of the
33,567 miners.
As shown in Table XI–1, the total
number of respondents is 46,198: 12,631
mines plus 33,567 miners; the estimated
annual number of responses would be
192,102; and the estimated annual
burden would be 41,440 hours. These
estimates are based on the conservative
assumption that 75 percent of eligible
current miners would take part in
medical surveillance, which could
overestimate the recordkeeping cost and
burden. The following estimates of
information collection burden are
summarized in Table XI–2.
1. Affected Public: Businesses or ForProfit.
2. Estimated Number of Respondents:
47,456 respondents in the first year;
46,198 respondents in the second year;
and 44,939 respondents in the third
year.
3. Frequency: On Occasion.
4. Estimated Number of Responses:
192,990 responses in the first year;
197,021 responses in the second year;
and 186,294 responses in the third year.
5. Estimated Number of Burden
Hours: 44,678 hours in the first year;
41,162 hours in the second year; and
38,480 hours in the third year.
6. Estimated Hour Burden Costs:
$2,843,901 in the first year; $2,558,724
in the second year; and $2,377,996 in
the third year.
7. Estimated Capital Costs to
Respondents: $25,262 in each of the
three years.
Most of the reduction in the number
of responses and burden hours from the
first year to the second year is a result
of baseline sampling being carried out
in all current mines in the first year
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while only being carried out in new
mines starting from the second year.
For a detailed summary of the burden
hours and related costs by provision, see
the Preliminary Regulatory Impact
Analysis (PRIA) accompanying the
proposed rule. The PRIA includes the
estimated costs and assumptions for the
paperwork requirements related to this
proposed rule.
C. Changes to Existing Information
Collection Requirements
I. Type of review: Non-substantive
change to currently approved
information collection.
OMB Control Number: 1219–0011.
1. Title: Respirable Coal Mine Dust
Sampling.
2. Description of the ICR:
Background
In October 2022, MSHA received
OMB approval for the reauthorization of
the Respirable Coal Mine Dust Sampling
under OMB Control Number 1219–0011.
This information collection request
outlines the legal authority, procedures,
burden, and costs associated with
recordkeeping and reporting
requirements for coal mine operators.
MSHA’s standards require that coal
mine operators sample respirable coal
mine dust quarterly and make records of
such samples.
Summary of Changes
This non-substantive change request
is to revise the supporting statement for
this information collection request due
to the proposed PEL for respirable
crystalline silica for all miners in this
proposed rule. These proposed revisions
would remove any reference in the
information collection request to quartz
or the reduction of the respirable dust
standard due to the presence of quartz.
This change does not modify the
authority, affected mine operators, or
paperwork burden.
3. Summary of the Collection of
Information:
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Changes in Burden
The calculated burden including
respondents and responses remain the
same.
Affected Public: Businesses or ForProfit.
Estimated Number of Respondents:
676 (0 from this rulemaking).
Frequency: On occasion.
Estimated Number of Responses:
995,102 (0 from this rulemaking).
Estimated Number of Burden Hours:
58,259 (0 from this rulemaking).
Estimated Hour Burden Costs:
$3,271,611 ($0 from this rulemaking).
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Estimated Capital Costs to
Respondents: $29,835 ($0 from this
rulemaking).
II. Type of Review: Discontinued
information collection request.
OMB Control Number: 1219–0048.
1. Title: Respirator Program Records.
2. Description of the ICR:
Background
Title 30 CFR parts 56 and 57
incorporate by reference requirements of
ANSI Z88.2–1969, ‘‘Practices for
Respiratory Protection.’’ Under this
standard, certain records are required to
be kept in connection with respirators.
The proposed rule would incorporate by
reference ASTM F3387–19, ‘‘Standard
Practice for Respiratory Protection,’’ in
30 CFR parts 56 and 57 to replace the
Agency’s existing respiratory protection
standard. The proposal would require
mine operators’ respiratory protection
plans to include certain minimally
acceptable program elements, but
beyond that, would permit mine
operators to select the requirements of
ASTM F3387–19 that are applicable to
their mines.
Summary of Changes
The proposed rule would remove the
paperwork burden associated with
respiratory protection in the information
collection request.
3. Summary of the Collection of
Information:
Changes in Burden
MSHA has submitted a request to
discontinue OMB Control Number
1219–0048, eliminating all paperwork
burden associated with the information
collection request. It would discontinue
upon the effective date of the final rule.
Affected Public: Businesses or ForProfit.
Estimated Number of Respondents: 0
(¥350 from this rulemaking).
Frequency: On occasion.
Estimated Number of Responses: 0
(¥630 from this rulemaking).
Estimated Number of Burden Hours: 0
(¥3,588 from this rulemaking).
Estimated Hour Burden Costs: $0
(¥$284,084 from this rulemaking).
Estimated Capital Costs to
Respondents: $0 (¥$140,000 from this
rulemaking).
D. Submitting Comments
The information collection package
for this proposal has been submitted to
OMB for review under 44 U.S.C. 3506(c)
of the Paperwork Reduction Act of 1995,
as amended. Comments on the
information collection requirements
should be sent to MSHA by one of the
methods previously explained in the
DATES section of this preamble.
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The information collection request
will be available on https://
www.regulations.gov. MSHA cautions
the commenter against providing any
information in the submission that
should not be publicly disclosed. Full
comments, including personal
information provided, will be made
available on www.regulations.gov and
www.reginfo.gov.
The public may also examine publicly
available documents at the Mine Safety
and Health Administration, 201 12th
South, Suite 4E401, Arlington, VA
22202–5450. Sign in at the receptionist’s
desk on the 4th floor via the East
elevator. Before visiting MSHA in
person, call 202–693–9440 to make an
appointment and determine if any
special health precautions are required
in keeping with the Department of
Labor’s COVID–19 policy.
Questions about the information
collection requirements may be directed
to the contact person listed in the FOR
FURTHER INFORMATION CONTACT section of
this preamble.
E. Docket and Inquiries
Those wishing to download
comments and other materials relating
to paperwork determinations should use
the procedures described in this
preamble. One may also obtain a copy
of this ICR by going to https://
www.reginfo.gov/public/do/PRAMain,
clicking on ‘‘Currently under Review—
Open for Public Comments’’ and
scrolling down to ‘‘Department of
Labor.’’
A Federal agency cannot conduct or
sponsor a collection of information
unless it is approved by OMB under the
Paperwork Reduction Act and displays
a currently valid OMB control number.
The public is not required to respond to
a collection of information unless the
collection of information displays a
currently valid OMB control number.
XII. Other Regulatory Considerations
A. National Environmental Policy Act
The National Environmental Policy
Act (NEPA) of 1969 (42 U.S.C. 4321 et
seq.), requires each Federal agency to
consider the environmental effects of
final actions and to prepare an
Environmental Impact Statement on
major actions significantly affecting the
quality of the environment. MSHA has
reviewed the proposed standard in
accordance with NEPA requirements,
the regulations of the Council on
Environmental Quality (40 CFR part
1500), and the Department of Labor’s
NEPA procedures (29 CFR part 11). As
a result of this review, MSHA has
determined that this proposed rule will
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not have a significant environmental
impact. Accordingly, MSHA has not
conducted an environmental assessment
nor provided an environmental impact
statement.
litigation and avoid undue burden on
the Federal court system. Accordingly,
the proposed rule meets the applicable
standards provided in section 3 of E.O.
12988, Civil Justice Reform.
B. The Unfunded Mandates Reform Act
of 1995
MSHA has reviewed the proposed
rule under the Unfunded Mandates
Reform Act of 1995 (2 U.S.C. 1501 et
seq.). The Unfunded Mandates Reform
Act requires Federal agencies to assess
the effects of their discretionary
regulatory actions. In particular, the Act
addresses actions that may result in the
expenditure by State, local, and Tribal
governments, in the aggregate, or by the
private sector, of $100 million or more
(adjusted annually for inflation) in any
1 year (5 U.S.C. 1532(a)). MSHA has
determined that this proposed rule does
not result in such an expenditure.
Accordingly, the Unfunded Mandates
Reform Act requires no further Agency
action or analysis.
F. Executive Order 13045: Protection of
Children From Environmental Health
Risks and Safety Risks
E.O. 13045 requires Federal agencies
submitting covered regulatory actions to
OMB’s Office of Information and
Regulatory Affairs (OIRA) for review,
pursuant to E.O. 12866, to provide OIRA
with (1) an evaluation of the
environmental health or safety effects
that the planned regulation may have on
children, and (2) an explanation of why
the planned regulation is preferable to
other potentially effective and
reasonably feasible alternatives
considered by the agency. In E.O. 13045,
‘‘covered regulatory action’’ is defined
as rules that may (1) be significant
under Executive Order 12866 Section
3(f)(1) (i.e., a rulemaking that has an
annual effect on the economy of $200
million or more or would adversely
affect in a material way the economy, a
sector of the economy, productivity,
competition, jobs, the environment,
public health or safety, or State, local or
Tribal governments or communities),
and (2) concern an environmental
health risk or safety risk that an agency
has reason to believe may
disproportionately affect children.
Environmental health risks and safety
risks refer to risks to health or to safety
that are attributable to products or
substances that the child is likely to
come in to contact with or ingest
through air, food, water, soil, or product
use or exposure.
MSHA has determined that, in
accordance with E.O. 13045, while the
proposed rule is considered significant
under E.O. 12866 Section 3(f)(1), it does
not concern an environmental health or
safety risk that may have a
disproportionate impact on children.
MSHA’s proposed rule would lower the
occupational exposure limit to
respirable crystalline silica for all
miners, take other actions to protect
miners from adverse health risks
associated with exposure to respirable
crystalline silica, and require updated
respiratory standards to better protect
miners from all airborne hazards.
MSHA is aware of studies which have
characterized and assessed the risks
posed by ‘‘take-home’’ exposure
pathways for hazardous dust particles.
However, the proposed rule’s primary
reliance on engineering and
administrative controls to protect
miners from respirable crystalline silica
exposures helps minimize risks
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C. The Treasury and General
Government Appropriations Act of
1999: Assessment of Federal
Regulations and Policies on Families
Section 654 of the Treasury and
General Government Appropriations
Act of 1999 (5 U.S.C. 601 note) requires
agencies to assess the impact of Agency
action on family well-being. MSHA has
determined that the proposed rule will
have no effect on family stability or
safety, marital commitment, parental
rights and authority, or income or
poverty of families and children, as
defined in the Act. The proposed rule
impacts the mine industry and does not
impose requirements on states or
families. Accordingly, MSHA certifies
that this proposed rule will not impact
family well-being, as defined in the Act.
D. Executive Order 12630: Government
Actions and Interference With
Constitutionally Protected Property
Rights
Section 5 of E.O. 12630 requires
Federal agencies to ‘‘identify the takings
implications of proposed regulatory
actions . . .’’ MSHA has determined
that the proposed rule does not
implement a taking of private property
or otherwise have takings implications.
Accordingly, E.O. 12630 requires no
further Agency action or analysis.
E. Executive Order 12988: Civil Justice
Reform
The proposed rule was written to
provide a clear legal standard for
affected conduct and was carefully
reviewed to eliminate drafting errors
and ambiguities so as to minimize
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associated with ‘‘take-home’’ exposures
by reducing or eliminating silica that is
in the mine atmosphere or the miner’s
personal breathing zone. The risks of
take-home exposures are further
minimized by MSHA’s existing
standards, operators’ policies and
procedures, and operators’ use of
clothing cleaning systems.
MSHA’s existing standards limit
miners’ exposures to respirable
crystalline silica. MSHA also requires
coal mine operators to provide miners
bathing facilities and change rooms.
Miners have access to these facilities to
shower and change their work clothes at
the end of each shift. In addition, some
mine operators provide miners with
clean company clothing for each shift,
have policies and procedures for
cleaning or disposing of contaminated
clothing, and provide a boot wash for
miners to clean work boots during and
after each shift. Moreover, some
operators use clothing cleaning systems
that can remove dust from a miner’s
clothing. Many of these systems include
NIOSH-designed dust removal booths
that use compressed air to remove dust,
which is then vacuumed through a filter
to remove airborne contaminants.
Overall, the Agency’s standards, mine
operators’ policies and procedures, and
other safety practices including the use
of clothing cleaning systems help to
reduce or eliminate the amount of takehome exposure, therefore protecting
other persons in a miner’s household or
persons who come in to contact with the
miner outside of the mine site.
MSHA identified one epidemiological
study (Onyije et al., 2022) that suggests
a possible association between paternal
exposure to respirable crystalline silica
and childhood leukemia. However, this
study does not provide dose-response
data which would be needed to
establish the dose of respirable
crystalline silica which results in a noadverse-effect-level (NOAEL) for
childhood leukemia. This potential
association has not been independently
confirmed by another study. MSHA
invites comment on the identification of
any other scientific or academic study
or information that evaluates the
potential association between paternal
exposure to respirable crystalline silica
and childhood leukemia during the
NPRM’s public comment period.
MSHA also invites comment on the
identification of any scientific or
academic study or information that
evaluates the potential risks to female
workers who are exposed to respirable
crystalline silica during pregnancy.
MSHA has no evidence that the
environmental health or safety risks
posed by respirable crystalline silica,
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including ‘‘take-home’’ exposure to
respirable crystalline silica,
disproportionately affect children.
Therefore, MSHA preliminarily
concludes no further analysis or action
is needed, in accordance with E.O.
13045.
G. Executive Order 13132: Federalism
MSHA has determined that the
proposed rule does not have ‘‘federalism
implications’’ because it will not ‘‘have
substantial direct effects on the States,
on the relationship between the national
government and the States, or on the
distribution of power and
responsibilities among the various
levels of government.’’ Accordingly,
under E.O. 13132, no further Agency
action or analysis is required.
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H. Executive Order 13175: Consultation
and Coordination With Indian Tribal
Governments
MSHA has determined the proposed
rule does not have ‘‘tribal implications’’
because it will not ‘‘have substantial
direct effects on one or more Indian
tribes, on the relationship between the
Federal Government and Indian tribes,
or on the distribution of power and
responsibilities between the Federal
Government and Indian tribes.’’
Accordingly, under E.O. 13175, no
further Agency action or analysis is
required.
result in annualized compliance costs of
$54.23 million using a 3 percent real
discount rate and $55.72 million using
a 7 percent real discount rate for the
metal/nonmetal mine industry relative
to annual revenue of $88.32 billion.
Because it is not ‘‘likely to have a
significant adverse effect on the supply,
distribution, or use of energy’’ including
a ‘‘shortfall in supply, price increases,
and increased use of foreign supplies,’’
it is not a ‘‘significant energy action.’’
Accordingly, E.O. 13211 requires no
further agency action or analysis.
J. Executive Order 13272: Proper
Consideration of Small Entities in
Agency Rulemaking
MSHA has thoroughly reviewed the
proposed rule to assess and take
appropriate account of its potential
impact on small businesses, small
governmental jurisdictions, and small
organizations. MSHA’s analysis is
presented in Section X. Initial
Regulatory Flexibility Analysis.
44957
ethnic distribution of the U.S. workforce
(Table XII–1), and (2) the extent to
which mining may be concentrated
within general mining communities
(Table XII–2).
In 2008, NIOSH conducted a survey of
mines, which entailed sending a survey
packet to 2,321 mining operations to
collect a wide range of information,
including demographic information on
miners. NIOSH’s 2012 report, entitled
‘‘National Survey of the Mining
Population: Part I: Employees’’ reported
the findings of this survey (NIOSH
2012a). Race and ethnicity information
about U.S. mine workers is presented in
Table XII–1. Of all mine workers,
including miners as well as
administrative employees at mines, 93.4
percent of mine workers were white,
compared to 80.6 percent of all U.S
workers.71 There were larger
percentages of American Indian or
Alaska Native and Native Hawaiian or
Other Pacific Islander people in the
mining industry compared to all U.S.
workers, while there were smaller
percentages of Asian, Black or African
American, and Hispanic/Latino people
in the mining industry compared to all
U.S. workers.
Table XII–2 shows that there are 22
mining communities, defined as
counties where at least 2 percent of the
population is working in the mining
industry.72 Although the total
population in this table represents only
0.15 percent of the U.S. population, it
represents 12.0 percent of all mine
workers. The average per capita income
in these communities in 2020,
$47,977,73 was lower than the U.S.
average, $59,510, representing 80.6
percent of the U.S. average. However,
each county’s average per capita income
varies substantially, ranging from 56.4
percent of the U.S. average to 146.8
percent.
The proposed rule would lower
exposure to respirable crystalline silica
and improve respiratory protection for
all mine workers. MSHA determined
that the proposed rule is consistent with
the goals of E.O. 13985 and would
support the advancement of equity for
all workers at mines, including those
who are historically underserved and
marginalized.
I. Executive Order 13211: Actions
Concerning Regulations That
Significantly Affect Energy Supply,
Distribution, or Use
E.O. 13211 requires agencies to
publish a Statement of Energy Effects for
‘‘significant energy actions,’’ which are
agency actions that are ‘‘likely to have
a significant adverse effect on the
supply, distribution, or use of energy’’
including a ‘‘shortfall in supply, price
increases, and increased use of foreign
supplies.’’ MSHA has reviewed the
proposal for its impact on the supply,
distribution, and use of energy because
it applies to the mining industry. The
proposed rule would result in
annualized compliance costs of $4.85
million using a 3 percent real discount
rate and $4.97 million using a 7 percent
real discount rate for the coal mine
industry relative to annual revenue of
$27.03 billion. The proposal would also
K. Executive Order 13985: Advancing
Racial Equity and Support for
Underserved Communities Through the
Federal Government
E.O. 13985 provides ‘‘that the Federal
Government should pursue a
comprehensive approach to advancing
equity for all, including people of color
and others who have been historically
underserved, marginalized, and
adversely affected by persistent poverty
and inequality.’’ E.O. 13985 defines
‘‘equity’’ as ‘‘consistent and systematic
fair, just, and impartial treatment of all
individuals, including individuals who
belong to underserved communities that
have been denied such treatment, such
as Black, Latino, and Indigenous and
Native American persons, Asian
Americans and Pacific Islanders and
other persons of color; members of
religious minorities; lesbian, gay,
bisexual, transgender, and queer
(LGBTQ+) persons; persons with
disabilities; persons who live in rural
areas; and persons otherwise adversely
affected by persistent poverty or
inequality.’’ To assess the impact of the
proposed rule on equity, MSHA
considered two factors: (1) the racial/
ethnic distribution in mining in NAICS
212 (which does not include oil and gas
extraction) compared to the racial/
BILLING CODE 4520–43–P
71 National data on workers by race were not
available for the year 2008; comparable data for
2012 are provided for comparison under the
assumption that there would not be major
differences in distributions between these two
years.
72 Although 2 percent may appear to be a small
number for identifying a mining community, one
might consider that if the average household with
one parent working as a miner has five members in
total, then approximately 10 percent of households
in the area would be directly associated with
mining. While 10 percent may also appear small,
this refers to the county. There are likely particular
areas that have a heavier concentration of mining
households.
73 This is a simple average rather than a weighted
average by population.
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L. Availability of Materials To Be
Incorporated by Reference
The Office of the Federal Register
(OFR) has regulations concerning
incorporation by reference. 5 U.S.C.
552(a); 1 CFR part 51. These regulations
require that information that is
incorporated by reference in a rule be
‘‘reasonably available’’ to the public.
They also require discussion in the
preamble to the rule of the ways in
which materials it proposes to
incorporate by reference are reasonably
available to interested parties or how it
worked to make those materials
reasonably available to interested
parties. Additionally, the preamble to
the rule must summarize the material. 1
CFR 51.5(b).
In accordance with the OFR’s
requirements, MSHA provides in the
following: (a) summaries of the
materials to be incorporated by
reference and (b) information on the
public availability of the materials and
on how interested parties can access the
materials during the comment period
and upon finalization of the rule.
ASTM F3387–19, ‘‘Standard Practice
for Respiratory Protection’’ (ASTM
F3387–19) ASTM F3387–19 is a
voluntary consensus standard that
represents up-to-date advancements in
respiratory protection technologies,
practices, and techniques. The standard
includes provisions for selection, fitting,
use, and care of respirators designed to
remove airborne contaminants from the
air using filters, cartridges, or canisters,
as well as respirators that protect miners
in oxygen-deficient or immediately
dangerous to life or health atmospheres.
These provisions are based on NIOSH’s
long-standing experience of testing and
approving respirators for occupational
use and OSHA’s research and
rulemaking on respiratory protection.
The proposed rule would incorporate by
reference ASTM F3387–19 in existing
§§ 56.5005, 57.5005, and 72.710 and in
proposed § 60.14(c)(2) to better protect
all miners from airborne hazards. MSHA
believes that incorporating by reference
ASTM F3387–19 would provide mine
operators with up-to-date requirements
for respirator technology, reflecting an
improved understanding of effective
respiratory protection and therefore
better protecting the health and safety of
miners. For further details on MSHA’s
proposed update to the Agency’s
existing respiratory protection standard,
please see section VII.C of this
preamble, Updating MSHA Respiratory
Protection Standards by Incorporating
by Reference ASTM F3387–19.
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A paper copy or printable version of
ASTM F3387–19 may be purchased by
mine operators or any member of the
public at any time from ASTM
International, 100 Barr Harbor Drive, PO
Box C700, West Conshohocken, PA
19428–2959; https://www.astm.org/.
ASTM International makes read-only
versions of its standards that have been
referenced or incorporated into Federal
regulation or laws available free of
charge at its online Reading Room,
https://www.astm.org/products-services/
reading-room.html. During the comment
period, a read-only version of ASTM
F3387–19 will be made available free of
charge.74
In addition, during the comment
period and upon finalization of this
rule, ASTM F3387–19 will be available
for review free of charge at MSHA
headquarters at 201 12th Street South,
Arlington, VA 22202–5450 (202–693–
9440).
ISO 7708:1995: Air Quality—Particle
Size Fraction Definitions for HealthRelated Sampling.
ISO 7708:1995 is an international
consensus standard that defines
sampling conventions for particle size
fractions used in assessing possible
health effects of airborne particles in the
workplace and ambient environment. It
defines conventions for the inhalable,
thoracic, and respirable fractions. The
proposed rule would incorporate by
reference ISO 7708:1995 in proposed
§ 60.12(f)(4) to ensure consistent
sampling collection by mine operators
through the utilization of samplers
conforming to ISO 7708:1995.
A paper copy or printable version of
ISO 7708:1995 may be purchased by
mine operators or any member of the
public at any time from ISO, CP 56, CH–
1211 Geneva 20, Switzerland; phone: +
41 22 749 01 11; fax: + 41 22 733 34 30;
website: www.iso.org/. ISO makes readonly versions of its standards that have
been incorporated by reference in the
CFR available free of charge at its online
Incorporation by Reference Portal,
https://ibr.ansi.org/Default.aspx.
In addition, during the comment
period and upon finalization of this
rule, ISO 7708:1995 will be available for
review free of charge at MSHA
headquarters at 201 12th Street South,
Arlington, VA 22202–5450, (202–693–
9440).
TLV’s Threshold Limit Values for
Chemical Substances in Workroom Air
Adopted by ACGIH for 1973.
This material is referenced in the
amendatory text of this document but
74 The read-only version of ASTM F3387–19
available for public review during the comment
period can be accessed using the following link—
https://tinyurl.com/mwk97hjn.
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has already been approved for appendix
A. No changes are proposed.
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Agency for Toxic Substances and Disease
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Almberg, K.S., Friedman, L.S., Rose, C.S., Go,
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MNM Respirable Dust Sample Dataset,
2005–2019
(PEL), and the units of measure for each
contaminant sampled.
The MNM respirable crystalline silica
dataset includes five contaminant codes.
From January 1, 2005, to December 31,
2019, 104,354 valid MNM respirable dust
samples were entered into the MSHA
Technical Support Laboratory Information
Management System (LIMS) database.75 The
dataset includes MNM mine respirable dust
personal exposure samples collected by
MSHA inspectors. A total of 57,824 samples
contained a respirable dust mass of 0.100 mg
or greater (referred as ‘‘sufficient-mass dust
samples’’), while a total of 46,530 samples
contained a respirable dust mass of less than
0.100 mg (referred as ‘‘insufficient-mass dust
samples’’).
Respirable dust samples collected by
MSHA inspectors are assigned a three-digit
‘‘contaminant code’’ based on the
contaminant in the sample. MSHA’s
contaminant codes group contaminants based
on their health effects 76 and are assigned by
the MSHA Laboratory based on sample type
and analysis results. The codes link
information, such as contaminant
description, permissible exposure limit
MNM Respirable Dust Sample Contaminant
Codes
The 57,824 samples that contained at least
0.100 mg of respirable dust were analyzed to
quantify their respirable crystalline silica
content—mostly respirable quartz but also
respirable cristobalite. The respirable
crystalline silica concentrations were entered
into the MSHA Standardized Information
System (MSIS) database (internal facing) and
Mine Data Retrieval System (MDRS) database
(public facing). Those MNM respirable dust
samples with a mass of at least 0.100 mg are
analyzed and contained in MSIS. MSIS and
MDRS differ from LIMS in that some of the
fields associated with a sample can be
modified or corrected by the inspector. These
correctable fields include Mine ID, Location
Code, and Job Code. Inspectors cannot access
or modify the fields in the LIMS database.
75 Only valid (non-void) MNM respirable dust
samples were included in the LIMS dataset. Voided
samples include any samples with a documented
reason which occurred during the sampling and/or
the MSHA’s laboratory analysis for invalidating the
results.
76 For example, contaminant code 523 indicates
that dust from that sample contained 1 percent or
more respirable crystalline silica (quartz). Exposure
to respirable crystalline silica has been linked to the
following health outcomes: silicosis, non-malignant
respiratory disease, lung cancer, and renal disease.
XIV. Appendix
Appendix A
Description of MSHA Respirable Crystalline
Silica Samples
This document describes the respirable
crystalline silica samples used in this
rulemaking. The Mine Safety and Health
Administration (MSHA) collected these
samples from metal/nonmetal (MNM) and
coal mines and analyzed the data to support
MNM Respirable Dust Samples With a Mass
of at Least 0.100 milligram (mg) (SufficientMass Dust Samples)
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this rulemaking. Technical details are
discussed in the following attachments.
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• Contaminant code 521—MNM respirable
dust samples that were not analyzed for
respirable crystalline silica.
• Contaminant code 523—MNM respirable
dust samples containing 1 percent or more
quartz.
• Contaminant code 525—MNM respirable
dust samples containing cristobalite.
• Contaminant code 121—MNM respirable
dust samples containing less than 1 percent
quartz where the commodity is listed as a
‘‘nuisance particulate’’ in Appendix E of the
TLVs® Threshold Limit Values for Chemical
Substances in Workroom Air Adopted by
ACGIH for 1973 (reproduced in Table A–1).
• Contaminant code 131—MNM respirable
dust samples containing less than 1 percent
quartz where the commodity is not listed as
a ‘‘nuisance particulate’’ in Appendix E of
the 1973 ACGIH TLV® Handbook.
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University of Science and Technology.
[Med Sci]. 26: 257–260.
Yu I.T., Tse, L.A., Wong, T.W., Leung, C.C.,
Tam, C.M, and Chan, A. C.K. 2005.
Further evidence for a link between
silica dust and esophageal cancer.
International Journal of Cancer. 114:479–
483.
Yu, Q., Fu, G., Lin, H., Zhao, Q., Liu, Y.,
Zhou, Y., Shi, Y., Zhang, L., Wang, Z.,
Zhang, Z., Qin, L. and Zhou, T. 2020.
Influence of silica particles on
mucociliary structure andMUC5B
expression in airways of C57BL/6 mice.
Experimental Lung Research. 46(7):217–
225. doi: 10.1080/01902148
.2020.1762804.
Federal Register / Vol. 88, No. 133 / Thursday, July 13, 2023 / Proposed Rules
less than 0.100 mg of respirable dust. These
samples did not meet the minimum dust
mass criterion of 0.100 mg and were not
analyzed for respirable crystalline silica by
MSHA’s Laboratory.
From these 46,530 samples, 167 samples 78
were removed because they were erroneous,
had an incorrect flow rate, or had insufficient
sampling time. This resulted in 46,363
remaining MNM samples containing less
than 0.100 mg of respirable dust. These
samples were assigned to contaminant code
521, indicating that the samples were not
analyzed for quartz. Datasets containing the
unanalyzed samples that MSHA removed
and retained can be found in the rulemaking
docket MSHA–2023–0001.
From August 1, 2016, to July 31, 2021,
113,607 valid respirable dust samples from
coal mines were collected by MSHA
inspectors and entered in the LIMS
database.79 For coal mines, the analysis is
based on samples collected by inspectors
beginning on August 1, 2016, when Phase III
of MSHA’s 2014 respirable coal mine dust
(RCMD) standard went into effect. Samples
taken prior to implementation of the RCMD
standard would not be representative of
current respirable crystalline silica exposure
levels in coal mines.
Of these samples collected by MSHA
inspectors, 67,963 samples were analyzed for
respirable crystalline silica; 45,644 samples
77 There were 55 samples removed: 7 samples had
no detected mass gain (denoted as ‘‘0 mg’’);
1 sample was a partial shift that was not originally
marked correctly; 1 sample was removed at the
request of the district; 44 samples had flow rates
outside the acceptable range of 1.616–1.785 L/min;
and 2 samples were duplicates of samples that were
already in the dataset. This resulted in the final
sample size of 57,769 = 57,824¥(7 + 1 + 1 + 44
+ 2).
78 There were 167 samples removed: 75 samples
had a cassette mass less than ¥0.03 mg (based on
instrument tolerances, samples that report a cassette
mass between ¥0.03 mg and 0 mg were treated as
having a mass of 0 mg, samples with masses below
that threshold of ¥0.03 mg were excluded); 52
samples had Mine IDs that did not report
employment for any year from 2005–2019; 31
samples had flow rates outside the acceptable range
of 1.615–1.785 L/min; six samples had sampling
times of less than 30 minutes; and three samples
had invalid Job Codes. This resulted in the final
sample size of 46,363 = 46,530¥(75 + 52 + 31 +
6 + 3).
79 Only valid (non-void) coal respirable dust
samples were included in the LIMS dataset. Voided
samples include any samples with a documented
reason which occurred during the sampling and/or
the MSHA’s Laboratory analysis for invalidating the
results.
MNM Respirable Dust Samples With a Mass
of Less Than 0.100 mg (Insufficient-Mass
Samples)
The LIMS database also included 46,530
MNM respirable dust samples that contained
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Coal Respirable Dust Sample Dataset, 2016–
2021
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All MNM Respirable Dust Samples
After removing the 222 samples mentioned
above (55 sufficient-mass and 167
insufficient-mass), the dataset consisted of
104,132 MNM respirable dust samples:
57,769 sufficient-mass samples and 46,363
insufficient-mass samples. A breakdown of
the MNM respirable dust samples is included
in Table A–2.
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From the database, 55 samples 77 were
removed because they were erroneous, had
an incorrect flow rate, had insufficient
sampling time, or were duplicated. This
resulted in a final dataset of 57,769 MNM
samples that contained a mass of at least
0.100 mg of respirable dust. Datasets
containing the analyzed samples that MSHA
removed and retained can be found in the
rulemaking docket MSHA–2023–0001.
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were not. Respirable dust samples from coal
mines contain the records of the sample type,
and the occupation of the miner sampled. A
coal sample’s type is based on the location
within the mine as well as the occupation of
the miner sampled. Below is a list of coal
sample types and descriptions, as well as the
mass of respirable dust required for that type
of sample to be analyzed for respirable
crystalline silica.
• Type 1—Designated occupation (DO).
The occupation on a mechanized mining unit
(MMU) that has been determined by results
of respirable dust samples to have the
greatest respirable dust concentration.
Designated occupation samples must contain
at least 0.100 mg of respirable dust to be
analyzed for respirable crystalline silica.
• Type 2—Other designated occupation
(ODO). Occupations other than the DO on an
MMU that are also designated for sampling,
required by 30 CFR part 70. These samples
must contain at least 0.100 mg of respirable
dust to be analyzed for respirable crystalline
silica.
• Type 3—Designated area (DA).
Designated area samples are from specific
locations in the mine identified by the
operator in the mine ventilation plan under
30 CFR 75.371(t), where samples will be
collected to measure respirable dust
generation sources in the active workings.
These samples must contain at least 0.100 mg
of respirable dust to be analyzed for
respirable crystalline silica.
• Type 4—Designated work position
(DWP). A designated work position in a
surface coal mine or surface work area of an
underground coal mine designated for
sampling to measure respirable dust
generation sources in the active workings.
Designated work position samples must
contain at least 0.200 mg of respirable dust
to be analyzed for respirable crystalline
silica. There are exceptions for certain
occupations: bulldozer operator (MSIS
general occupation code 368), high wall drill
operator (code 384), high wall drill helper
(code 383), blaster/shotfirer (code 307),
refuse/backfill truck driver (code 386), or
high lift operator/front end loader (code 382).
Samples from these occupations must have at
least 0.100 mg of respirable dust to be
analyzed for respirable crystalline silica.
• Type 5—Part 90 miner. A Part 90 miner
is employed at a coal mine and has exercised
the option under the old section 203(b)
program (36 FR 20601, Oct. 27, 1971) or
under 30 CFR 90.3 to work in an area of a
mine where the average concentration of
respirable dust in the mine atmosphere
during each shift to which a miner is exposed
is continuously maintained at or below the
applicable standard and has not waived these
rights. A sample from a Part 90 miner must
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contain at least 0.100 mg of respirable dust
to be analyzed for respirable crystalline
silica.
• Type 6—Non-designated area (NDA).
Non-designated area samples are taken from
locations in the mine that are not identified
by the operator in the mine ventilation plan
under 30 CFR 75.371(t) as areas where
samples will be collected to measure
respirable dust generation sources in the
active workings. These samples are not
analyzed for respirable crystalline silica.
• Type 7—Intake air samples are taken
from air that has not yet ventilated the last
working place on any split of any working
section or any worked-out area, whether
pillared or non-pillared, as per 30 CFR
75.301. These samples are not analyzed for
respirable crystalline silica.
• Type 8—Non-designated work position
(NDWP). A work position in a surface coal
mine or a surface work area of an
underground coal mine that is sampled
during a regular health inspection to measure
respirable dust generation sources in the
active workings but has not been designated
for mandatory sampling. For the analysis of
respirable crystalline silica, these samples
must have at least 0.200 mg of respirable
dust. There are exceptions for certain
occupations: bulldozer operator (MSIS
general occupation code 368), high wall drill
operator (code 384), high wall drill helper
(code 383), blaster/shotfirer (code 307),
refuse/backfill truck driver (code 386), or
high lift operator/front end loader (code 382).
Samples taken from these occupations must
contain at least 0.100 mg respirable dust to
be analyzed for respirable crystalline silica.
Coal Respirable Dust Samples Analyzed for
Respirable Crystalline Silica
There were 67,963 samples from coal
mines collected by MSHA inspectors from
underground and surface coal mining
operations that were analyzed for respirable
crystalline silica. These results were entered
first into LIMS, and then into MSIS and
MDRS. Results from MSIS were used as they
may be updated by the inspectors at later
dates.80 From those 67,963 samples, 4,836
samples were removed as they were
environmental samples, voided in MSIS, or
had other errors.81 This resulted in a dataset
80 As mentioned in the section concerning
samples for MNM mines, MSIS and MDRS differ
from LIMS in that some data fields can be modified
or corrected by the inspector. These correctable
fields include Mine ID, Location Code, and Job
Code.
81 There were 4,836 samples removed: 4,199
samples were environmental and not personal
samples (see Sample Type explanation for more
detail); 631 samples had been voided after they had
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of 63,127 samples from coal mines that were
analyzed for respirable crystalline silica.
Datasets containing the analyzed samples
that MSHA removed and retained can be
found in the rulemaking docket MSHA–
2023–0001.
Coal Respirable Dust Samples Not Analyzed
for Respirable Crystalline Silica
Similar to MNM respirable dust samples,
the LIMS database includes 45,644 coal
samples that did not meet the criteria for
analysis and were thus not analyzed for
respirable crystalline silica content.82 After
removing 13,243 83 samples that were
environmental samples, erroneous, or had
voided controls, there were 32,401 samples
that were not analyzed for respirable
crystalline silica. Datasets containing the
unanalyzed samples that MSHA removed
and retained can be found in the rulemaking
docket MSHA–2023–0001.
All Coal Respirable Dust Samples
In total, 18,079 respirable dust samples
from coal mines were removed from the
original datasets: 4,836 samples that were
analyzed for respirable crystalline silica and
13,243 samples that were not. This created a
final dataset of 95,528 samples: 63,127
analyzed samples and 32,401 samples that
were not analyzed.84 A breakdown of
respirable dust samples from coal mines is
included in Table A–3.
BILLING CODE 4520–43–P
been entered into MSIS; and 6 had invalid Job
Codes. This resulted in the final sample size of
63,127 = 67,963¥(4,199 + 631 + 6).
82 In addition to the criteria listed above, samples
from Shop Welders (code 319) are not analyzed for
respirable crystalline silica as they are instead
analyzed for welding fumes.
83 There were 13,243 samples removed: 6 samples
had typographical errors; 14 samples had a cassette
mass less than ¥0.03 mg (based on instrument
tolerances, samples that report a cassette mass
between ¥0.03 mg and 0 mg were treated as having
a mass of 0 mg); 92 samples had invalid Job Codes;
12,724 were environmental samples; 44 samples
had an occupation code of 000 despite having a
personal sample ‘Sample Type’; 271 samples had
controls that were voided; and 92 came from Job
Code 319—Welder (see Footnote 82). This resulted
in the final sample size of 32,401 = 50,545¥(6 +
14 + 92 + 12,724 + 44 + 271 + 92).
84 This dataset did not include any other coal
mine respirable dust sample types collected by
MSHA inspectors—i.e., sample types 3 (designated
area samples), types 6 (Non-face occupations) and
7 (Intake air), samples taken on the surface mine
shop welder (n=319), and all voided samples.
Voided samples are any samples that have a
documented reason which occurred during the
sampling and/or laboratory analysis for invalidating
the results.
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While the samples that were analyzed for
cristobalite were assigned to all four
contaminant codes seen in this dataset, the
majority were assigned contaminant code
523.
85 See Attachment 2. Technical Background about
Measuring Respirable Crystalline Silica, for more
information.
86 See Attachment 2. Technical Background about
Measuring Respirable Crystalline Silica, for more
information.
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Of the 57,769 retained MNM samples that
contained at least 0.050 mg of respirable
dust, 0.6 percent (or 359 samples) were
analyzed for cristobalite. Coal respirable dust
samples are not analyzed for cristobalite.86
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Cristobalite is one of the three polymorphs
of respirable crystalline silica analyzed by
MSHA’s Laboratory upon request that is
included in this proposed rule. At the request
of the inspector, MNM 85 respirable dust
samples that contain at least 0.050 mg of
respirable dust are analyzed for cristobalite.
13JYP2
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Attachment 1. MNM Samples Analyzed for
Cristobalite
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dividing the mass of cristobalite by the
volume of air sampled (0.816 m3). The
calculated concentrations ranged from 6 mg/
m3 to 53 mg/m3.88
87 Of the 369 samples that were analyzed for
cristobalite, 334 had a value for cristobalite mass
that was less than the limit of detection (LOD) for
cristobalite, 10 mg. As such these samples were
assigned a value of 5 mg of cristobalite, one half the
LOD. See Attachment 2. Technical Background
about Measuring Respirable Crystalline Silica, for
more information.
88 One sample had a cristobalite concentration of
53 mg/m3. It was sampled in July of 2011 at Mine
ID 4405407 and cassette number 610892. The
commodity being mined was Stone: Crushed,
Broken Quartzite. The occupation of the miner
being sampled was Miners in Other Occupations:
Job Code 513—Building and Maintenance.
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The mass of each sample was then used to
calculate a cristobalite concentration by
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The distribution of the 359 samples by
cristobalite mass can be seen in Table A1–
3.87
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Attachment 2. Technical Background About
Measuring Respirable Crystalline Silica
In the proposed rule, respirable crystalline
silica refers to three polymorphs: quartz,
cristobalite, and tridymite. MSHA’s
Laboratory uses two methods to analyze
respirable crystalline silica content in mine
respirable dust samples. The first method, Xray diffraction (XRD), separately analyzes
quartz, cristobalite, and tridymite contents in
respirable dust samples that mine inspectors
obtain at MNM mine sites (MSHA Method P–
2, 2018a). The second method, Fourier
transform infrared spectroscopy (FTIR), is
used to analyze quartz in respirable dust
samples obtained at coal mines (MSHA
Method P–7, 2018b and 2020). Although the
XRD method can be expanded from MNM to
coal dust samples, MSHA chooses to use the
FTIR method for coal dust samples because
it is a faster and less expensive method.
However, the current MSHA P–7 FTIR
method cannot quantify quartz if cristobalite
and/or tridymite are present in the sample.
The method also corrects the quartz result for
the presence of kaolinite, an interfering
mineral for quartz analysis in coal dust.
ddrumheller on DSK120RN23PROD with PROPOSALS2
Limits of Detection and Limits of
Quantification for Silica Sample Data
The Limits of Detection (LOD) and Limits
of Quantification (LOQ) are the two terms
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used to describe the method capability. The
LOD refers to the smallest amount of the
target analyte (respirable crystalline silica)
that can be detected in the sample and
distinguished from zero with an acceptable
confidence level that the analyte is actually
present. It can also be described as the
instrument signal that is needed to report
with a specified confidence that the analyte
is present. The LOQ refers to the smallest
amount of the target analyte that can be
repeatedly and accurately quantified in the
sample with a specified precision. The LOQ
is higher than the LOD. The values of the
LOD and LOQ are specific to MSHA’s
Laboratory as well as the instrumentation
and analytical method used to perform the
analysis. These values do not change from
one batch to another when samples are
analyzed on the same equipment using the
same method. However, their levels may
change over time due to updated analytical
methods and technological advances. The
values of the LOD and LOQ for the methods
(XRD and FTIR) used in analyzing respirable
crystalline silica samples are explained in
MSHA documents for MNM samples and
coal samples (MSHA Method P–2, 2018a;
MSHA Method P–7, 2018b and 2020). MSHA
periodically updates these values to reflect
progress in its analytical methods. The values
of LOD and LOQ were last updated in 2022
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44975
for MNM samples and in 2020 for coal
samples.
The values of LODs and LOQs for
respirable crystalline silica in samples from
MSHA inspectors depend on several factors,
including the analytical method used (XRD
or FTIR) and the silica polymorph analyzed
(quartz, cristobalite, or tridymite), as
presented in Table A2–1.
For a sample with respirable crystalline
silica content less than the method LOD, the
maximum concentration is calculated as the
respirable crystalline silica mass equivalent
to LOD divided by the volume of air
sampled. For example, if no quartz is
detected by XRD analysis for an MNM
sample, the method LOD is 5 mg. If that
sample is collected at 1.7 L/min air flow rate
for 480 minutes (i.e., 8 hours), the air sample
volume would be 816 L (= 1.7 L/min * 480
minutes), or 0.816 m3. The calculated
maximum concentration associated with a
sample having respirable crystalline silica
mass below the method LOD would be 6 mg/
m3 (= 5 mg/0.816 m3). The ‘‘half maximum
concentration’’ is the midpoint between 0
and the calculated maximum respirable
crystalline silica concentration, which is 3
mg/m3 (= 1⁄2 * 6 mg/m3) in this example.
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The air volume is treated differently for
MNM and coal samples under the existing
standards. In the case of MNM samples, 8hour equivalent time weighted averages
(TWAs) are calculated using 480 minutes (8
hours) and a flow rate of 1.7 L/min, even if
samples are collected for a longer duration.
In contrast, coal TWAs are calculated using
the full duration of the shift and a flow rate
of 2.0 L/min and converted to an MRE
equivalent concentration under existing
standards.
Assumptions for Analyzed Samples
Samples from MNM mines that contain at
least 0.100 mg of dust mass are analyzed for
the presence of quartz and/or cristobalite. For
samples from coal mines, the minimum
amount of respirable dust in a sample to be
89 In its Final Regulatory Economic Analysis
(FREA) for its 2016 silica rule, OSHA observed:
‘‘. . . that XRD analysis of quartz from samples
prepared from reference materials can achieve
LODs and LOQs between 5 and 10 mg was not
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analyzed for respirable crystalline silica is
determined by sample type and the
occupation of the miner sampled. For Sample
Types 1, 2, and 5, the sample must contain
at least 0.100 mg of respirable dust. For
Sample Types 4 and 8, the sample must
contain at least 0.200 mg of respirable dust
unless it comes from one of the following
occupations: bulldozer operator (MSIS
general occupation code 368), high wall drill
operator (code 384), high wall drill helper
(code 383), blaster/shotfirer (code 307),
refuse/backfill truck driver (code 386), and
high lift operator/front end loader (code 382).
Samples taken from these occupations must
contain at least 0.100 mg respirable dust to
be analyzed for respirable crystalline silica.
Samples from Shop Welders (code 319) are
never analyzed for quartz, as they instead are
sent for welding fume analysis.
MSHA makes separate assumptions based
on the mass of respirable crystalline silica for
a sample, whether it is above or below the
method LOD. For all samples reporting a
mass of respirable crystalline silica greater or
equal to the method LOD, MSHA used the
reported values to calculate the respirable
crystalline silica concentration for the
sample. For samples with values below the
method LOD, including samples reported as
containing 0 mg of silica, MSHA used 1⁄2 of
the LOD to calculate the respirable
crystalline silica concentration of the sample.
MSHA understands that its assumptions
regarding samples with respirable crystalline
silica mass below the method LOD will have
a minimal impact on the assessment.89
disputed in the [rulemaking] record.’’ (OSHA,
2016).
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Quartz Mass at or Above the Method LOQ
For MNM and coal samples reporting
quartz mass at or above the method LOQs,
MSHA uses the values reported by the
MSHA’s Laboratory.
Quartz Mass Between Method LOD and LOQ
For MNM and coal samples reporting
quartz mass at or above the method LOD but
below the LOQ, MSHA uses the values
reported by the MSHA’s Laboratory.
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Quartz Mass Between the Method LOD and
0 μg
A review of respirable crystalline silica
samples in LIMS reveals that some samples
had a respirable crystalline silica mass below
the LOD of the analytical methods but greater
than 0 mg. Values in this range (i.e., below the
method LOD but greater than 0 mg) cannot
reliably indicate the presence of respirable
crystalline silica. The mass of silica in these
is too small to reliably detect, but the
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concentration of silica could be up to the
calculated maximum concentration based on
the method LOD. For example, consider a
sample from an MNM mine that was
analyzed for quartz and had a reported quartz
mass of 4 mg. This falls below the LOD of 5
mg but above 0 mg, and as such the sample
could actually contain anywhere from 0 mg of
quartz up to the LOD value of 5 mg of quartz.
In these cases, MSHA used 1⁄2 the LOD
value to calculate respirable crystalline silica
concentration. MSHA explored other options
to treat these samples such as treating the
reported silica mass as 0 mg/m3 (lower
bound) as well as assuming the sample silica
mass is just below the LOD and assigning
each sample a value of the method LOD
(upper bound). The use of the 1⁄2 LOD value
is considered a reasonable assumption since
using either the lower bound of 0 mg/m3 or
the upper bound of the associated method’s
LOD could under or overestimate exposures,
respectively. The assumption is not expected
to impact the assessment of silica
concentration because any sample results
with respirable crystalline silica mass below
the method LODs (between 3–10 mg/m3)
would also have been well below the lowest
exposure profile range (<25 mg/m3).
Quartz Mass of 0 μg
A portion of the MNM and coal samples
below the LOD are listed as having respirable
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crystalline silica (specifically quartz) mass
levels of 0 mg. For these samples, instead of
treating the mass of silica in the sample as
a true zero, MSHA replaced the value with
1⁄2 the LOD of the associated method.
Although the respirable crystalline silica
mass of these samples is less than the LOD,
it is likely that the sample still contains a
small amount of respirable crystalline silica.
Hence, MSHA assumes a value of 1⁄2 LOD in
its calculation of respirable crystalline silica
concentration for these samples. This
assumption is considered to be reasonable
because using the lower bound of 0 mg/m3 for
these samples could underestimate the
respirable crystalline silica concentration
while using the upper bound of method
LODs could overestimate the respirable
crystalline silica concentration.
Table A2–3 presents an example for quartz,
one of the respirable crystalline silica
polymorphs. This table shows the LOD of
quartz mass and the possible range of quartz
concentrations for samples reporting a quartz
mass of 0 mg. These adjusted concentrations
are expected to have a limited impact of the
assessment of respirable crystalline silica
concentration, as supported by MSHA’s
sensitivity analyses.
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The reported value of respirable crystalline
silica mass from an MNM or coal sample can
fall under one of the four groups: (1) at or
above the method LOQ, (2) at or above the
method LOD but below the LOQ, (3) greater
than 0 mg but less than the method LOD, or
(4) equal to 0 mg. MSHA treats these samples
differently based on their respirable
crystalline silica mass.
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Cristobalite Measurement
Respirable dust samples from MNM mines
are rarely analyzed for cristobalite by MSHA,
and respirable coal dust samples are not
analyzed for the presence of cristobalite.
MNM samples are analyzed for the presence
of cristobalite only when requested by MSHA
inspectors because the geological or work
conditions indicate this specific polymorph
may be present. The LIMS database includes
samples for which cristobalite was analyzed,
either with or without quartz analysis. MSHA
uses similar assumptions for cristobalite and
quartz.
The cristobalite LOD for these samples is
10 mg. The MSHA Laboratory-reported values
are used for analyzed dust samples with
cristobalite mass values equal to or above the
method LODs. Samples that were analyzed
for cristobalite and had a cristobalite mass
value below the method LOD were assigned
values of 1⁄2 LOD, or 5 mg. For example, 267
samples, or 74.4 percent of the 359 samples
that were analyzed for cristobalite, reported
a value of 0 mg of cristobalite; these were
assigned a value of 5 mg.
When a sample is analyzed for two
polymorphs (i.e., both quartz and
cristobalite), detectable quartz and
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cristobalite are summed to generate the total
respirable crystalline silica. If only one of
these polymorphs is detected, the sample
concentration is based on the detected
polymorph. If the concentrations of both
polymorphs (quartz and cristobalite) are
reported as 0 mg/m3, 1⁄2 mass LOD is assumed
in calculating the concentrations and the
resulting concentrations are summed.
OSHA, 2016. Final Regulatory Economic
Analysis (FEA) for OSHA’s Final Rule on
Respirable Crystalline Silica, Chapter
IV.3.2.3—Sensitivity of Sampling and
Analytical Methods.
Unanalyzed Samples
There are also samples whose dust mass
fell below their associated mass threshold,
and as such, they were not analyzed for the
presence of quartz and/or cristobalite. The
respirable dust mass for a sample was
considered to be 0 mg when the net mass gain
of dust was 0 mg or less.
For this rulemaking analysis, the mining
industries are grouped into six
commodities—Coal, Metal, Nonmetal, Stone,
Crushed Limestone, and Sand and Gravel.
The table below shows the six commodity
groupings based on the Standard Industrial
Classification (SIC) codes and the North
American Industry Classification System
(NAICS) codes. The SIC system is a
predecessor of NAICS using industry titles to
standardize industry classification. The
NAICS is widely used by Federal statistical
agencies, including the Small Business
Administration (SBA), for classifying
business establishments for the purpose of
collecting, analyzing, and publishing
statistical data related to the U.S. business
economy.
References
MSHA. 2018. P–2: X-Ray Diffraction
Determination of Quartz and Cristobalite
in Respirable Metal/Nonmetal Mine
Dust.
MSHA. 2018a. P–7: Infrared Determination of
Quartz in Respirable Coal Mine Dust.
MSHA. 2020. P–7: Determination of Quartz
in Respirable Coal Mine Dust by Fourier
Transform Infrared Spectroscopy.
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Appendix B
Mining Commodity Groups
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90 For coal mines, the analysis is based on
samples collected by inspectors beginning on
August 1, 2016, when Phase III of MSHA’s 2014
RCMD standard went into effect. Samples taken
prior to implementation of the RCMD standard
would not be representative of current respirable
crystalline silica exposure levels in coal mines.
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‘‘Crusher Operators,’’ ‘‘Continuous Mining
Machine Operators,’’ etc.).
Job Codes and Respirable Dust Sampling
MSHA inspectors use job codes to label
samples of respirable dust when they
conduct health inspections.91 Following the
sampling strategy outlined in the most recent
91 The job codes have been referred to as both job
codes and occupation codes by MSHA. For
example, in the Mine Data Retrieval System, they
are called job codes; in other materials, including
MSHA’s Inspection Application System (IAS), they
are called occupational codes. For the purposes of
this document, the term job code has been used to
clearly differentiate the job codes from the
occupational categories.
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Occupational Categories for Respirable
Crystalline Silica Sample Collection
This Appendix explains how MSHA
categorized MNM and coal samples in
constructing respirable crystalline silica
exposure profile tables for the current
rulemaking. MSHA has developed respirable
crystalline silica exposure profile tables
using its inspectors’ sampling data and
results. One set of exposure profile tables
displays the analysis of 15 years of respirable
crystalline silica sampling data from MNM
mines (Attachment 1), and the other set
displays the analysis of 5 years of respirable
crystalline silica samples collected at coal
mines (Attachment 2).90 In the MNM tables,
the respirable crystalline silica concentration
information is broken out by 5 commodities
(e.g., ‘‘Metal,’’ ‘‘Crushed Limestone,’’ etc.)
and then by 11 occupational categories (e.g.,
‘‘Drillers,’’ ‘‘Stone Cutting Operators,’’ etc.).
The data for coal mining is disaggregated by
2 locations (‘‘Underground’’ and ‘‘Surface’’)
and then by 9 occupational categories (e.g.,
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Appendix C
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MSHA Health Inspection Procedures
Handbook (December 2020; PH20–V–4), the
inspectors determine potential airborne
hazards to which miners may be exposed,
including respirable dust, and then take
samples from the appropriate miners or
working areas at a mine. Using gravimetric
samplers, the inspectors collect respirable
dust samples at MNM and coal mines. When
submitting the collected samples to MSHA’s
Laboratory for analysis, the inspectors label
their samples with the three-digit job code
that best describes the duties that each miner
was performing during the sampling period.
The three-digit job codes are taken from
MSHA’s Inspection Application System
(IAS), which includes 220 job codes for coal
mines and 121 job codes for MNM mines.
Attachments 3 and 4 include the IAS job
codes for coal and MNM operations,
respectively.
Coal Job Codes: The coal job codes have
generally been consistent over time, with
new codes added when needed. For example,
IAS has the same job code for the duties of
a coal ‘‘supervisor/foreman’’ as two
predecessor documents—the ‘‘Job Code
Pocket Cards’’ for coal mining, used by
MSHA’s predecessor, the Mining
Enforcement and Safety Administration
(MESA) (see Attachment 5), and a Fall 1983
Mine Safety and Health publication. An
example is presented below in Table C–1. In
the three-digit coal job code, the first digit
generally identifies where the work is taking
place in the mine: 0 (Underground Section
Workers—Face); 1 (General Underground—
Non-Face); 2 (Underground Transportation—
Non-Face); 3 (Surface); 4 (Supervisory and
Staff); 5 (MSHA—State); and 6 (Shaft and
Slope Sinking). The coal codes starting with
6 were added in 2020 to better delineate the
samples for miners conducting shaft and
slope sinking activities.
MNM Job Codes: Many of the 121 MNM job
codes are similar to the coal job codes, as
noted in Attachment 4. One major difference
is that unlike the coal job codes, MNM job
codes are not based on the location of the
work/job. The first digit of the three-digit
MNM job code does not indicate whether a
job is located at an underground or surface
area of the mine. For example, a ‘‘MNM
Diamond Drill Operator’’ (Job Code 034)
could be working on the surface or
underground, whereas a ‘‘Coal Drill
Operator’’ would have a different job code
based on the miner’s location within a mine
(Job Code 034—underground at the face; Job
Code 334—at the surface).
have differing impacts on coal miners’
exposures to respirable crystalline silica. In
2020, MSHA’s Laboratory used 9 coal and 14
MNM occupational categories for its
respirable crystalline silica data analyses.
For the respirable crystalline silica
exposure profile tables in the proposed
respirable crystalline silica rule, MSHA made
no change to the 9 coal occupational
categories, but condensed the 14 MNM
occupational categories to 11. These
occupational categories are meant to
reasonably group multiple job codes with
similar occupational activities/tasks and
engineering controls. The grouping of job
codes into occupational categories purposely
focused on the occupational activities/tasks
and exposure risk of the miner performing a
particular job rather than the type of mining
equipment utilized by the miner. The
creation of occupational categories based on
the types of equipment utilized by miners
would have failed to accurately characterize
the risk of individual miners.
Coal Occupational Categories
There are 220 job codes for coal miners in
IAS.92 Overall, 209 job codes are included in
the 9 occupational categories. Some job codes
were excluded, primarily because sampling
data were not available for those job codes.
The codes that have been excluded are:
• Job code 0 ‘‘Area,’’ because area samples
are not specific to any one occupation.
• Job code 398 ‘‘Groundman,’’ because
there were no sample data for this code in
the respirable crystalline silica sampling
dataset.
• Job codes 590 ‘‘Education Specialist,’’
591 ‘‘Mineral Industrial Safety Officer,’’ 592
‘‘Mine Safety Instructor,’’ and 594 ‘‘Training
Specialist,’’ because there were no coal
respirable crystalline silica (quartz) data for
these codes for the timeframe selected.
• Job codes 602 ‘‘Electrician,’’ 604
‘‘Mechanic,’’ 609 ‘‘Supply Person,’’ 632
‘‘Ventilation Worker,’’ and 635 ‘‘Continuous
Miner Operator Helper,’’ because there were
no sample data for these codes in the
respirable crystalline silica sampling dataset.
The remaining 209 coal job codes are first
divided by the job location—underground or
surface—because potential respirable
crystalline silica exposures at coal mines can
vary depending on where a miner works at
a given mine. (Three job codes are used in
92 IAS also contains 272 coal job codes that are
used to fill out a Mine Accident, Injury and Illness
Report (MSHA Form 7000–1). These codes were not
included in the respirable crystalline silica
exposure profile tables and are not discussed
further in this document.
Occupational Categories for the Respirable
Crystalline Silica Rulemaking
Some of the original work to group the
MNM job codes into occupational categories
was completed in 2010 in support of earlier
rulemaking efforts. The MNM occupational
categories were developed first and were
later updated with additional sampling data
as it became available. The coal occupational
categories were developed several years later
and were generally modeled after the MNM
tables; however, coal occupational categories
are first divided based on surface and
underground locations because occupational
activities at different locations of a mine can
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both underground and surface locations: job
codes 402 ‘‘Master Electrician,’’ 404 ‘‘Master
Mechanic,’’ and 497 ‘‘Clerk/Timekeeper.’’)
The underground and surface job codes are
further grouped on the basis of the types of
tasks and typical engineering controls. For
example, as shown in Figure 1, the
underground ‘‘Continuous Mining Machine
Operators’’ occupational category includes 14
different occupations that involve drilling
activities—occupations such as ‘‘Coal Drill
Helper,’’ ‘‘Coal Drill Operator,’’ and ‘‘Rock
Driller.’’ The underground ‘‘Operators of
Large Powered Haulage Equipment’’
occupational category has 12 similar
occupations including ‘‘Loading Machine
Operator,’’ ‘‘Shuttle Car Operator,’’ and
‘‘Motorman.’’
There are five categories of underground
occupations and four categories of surface
occupations.
The five underground occupational
categories include:
(1) Continuous Mining Machine Operators
(e.g., Coal Drill Helper and Coal Drill
Operator);
(2) Operators of Large Powered Haulage
Equipment (e.g., Shuttle Car, Tractor, Scoop
Car);
(3) Longwall Workers (e.g., Headgate
Operator and Jack Setter (Longwall));
(4) Roof Bolters (e.g., Roof Bolter and Roof
Bolter Helper); and
(5) Underground Miners (e.g., Electrician,
Mechanic, Belt Man/Conveyor Man, and
Laborer, etc.).
The four surface occupational categories
include:
(1) Drillers (e.g., Coal Drill Operator, Coal
Drill Helper, and Auger Operator);
(2) Operators of Large Powered Haulage
Equipment (e.g., Backhoe, Forklift, and
Shuttle Car);
(3) Crusher Operators (e.g., Crusher
Attendant, Washer Operator, and ScalperScreen Operator); and
(4) Mobile Workers (e.g., Electrician,
Mechanic, Blaster, Cleanup Man, Mine
Foreman, etc.).
Attachments 1 and 3 provide the full lists
of occupational categories and coal job codes.
Workers’’ category. The code that was used
twice is:
• Job Code 388 ‘‘Screen/Scalper
Operators,’’ because MNM job codes do not
indicate the location where the work is
taking place and this work can be conducted
either in a plant or on the surface of the
mine.
The final 121 MNM job codes (with job
code 388 included twice) were first grouped
into 14 occupational categories based on the
types of tasks and typical engineering
controls used. For example, as seen in Figure
2, the ‘‘Drillers’’ occupational category
includes the 20 different occupations that
involve drilling activities, such as ‘‘Diamond
Drill Operator,’’ ‘‘Drill Operator Churn,’’ and
‘‘Continuous Miner Operator.’’ ‘‘Belt
Cleaner,’’ ‘‘Belt Crew,’’ and ‘‘Belt Vulcanizer’’
are included in the occupational category,
‘‘Conveyor Operators.’’ Similar tasks were
grouped together because the work activities
and respirable crystalline silica exposures
were anticipated to be comparable.
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MNM Occupational Categories
From the 121 MNM job codes in IAS, 120
job codes are included in the occupational
categories and 1 job code is excluded. The
code that has been excluded is:
• Job code 413 ‘‘Janitor,’’ because there
were no sample data for this code in the
respirable crystalline silica sampling dataset.
Of the 120 job codes included, 1 job code
was listed in both the ‘‘Crushing Equipment
and Plant Operators’’ occupational category
and the ‘‘Kiln, Mill and Concentrator
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The 14 occupational categories were:
(1) Bagging Machines;
(2) Stone Saws;
(3) Stone Trimmers, Splitters;
(4) Truck Loading Stations;
(5) Mobile Workers (e.g., Laborers,
Electricians, Mechanics, and Supervisors);
(6) Conveyors;
(7) Crushers;
(8) Dry Screening Plants;
(9) Kilns/Dryers, Rotary Mills, Ball Mills,
and Flotation/Concentrators;
(10) Large Powered Haulage Equipment
(e.g., Trucks, FELs, Bulldozers, and Scalers);
(11) Small Powered Haulage Equipment
(e.g., Bobcats and Forklifts);
(12) Jackhammers;
(13) Drills; and
(14) Other Occupations.
After additional consideration, it was
determined that the original 14 categories
could be further condensed into the final 11
categories since some of the occupational
categories contained job codes where the
types of tasks and engineering and
administrative controls were similar enough
to be combined.
The final 11 occupational categories
include:
(1) Drillers (e.g., Diamond Drill Operator,
Wagon Drill Operator, and Drill Helper);
(2) Stone Cutting Operators (e.g.,
Jackhammer Operator, Cutting Machine
Operator, and Cutting Machine Helper);
(3) Operators of Large Powered Haulage
Equipment (e.g., Trucks, Bulldozers, and
Scalers);
(4) Conveyor Operators (e.g., Belt Cleaner,
Belt Crew, and Belt Vulcanizer);
(5) Crushing Equipment and Plant
Operators (Crusher Operator/Worker, Scalper
Screen Operator, and Dry Screen Plant
Operator);
(6) Kiln, Mill, and Concentrator Workers
(e.g., Ball Mill Operator, Leaching Operator,
and Pelletizer Operator);
(7) Operators of Small Powered Haulage
Equipment (e.g., Bobcats, Shuttle Car, and
Forklifts);
(8) Packaging Equipment Operators (e.g.,
Bagging Operator and Packaging Operations
Worker);
(9) Truck Loading Station Tenders (e.g.,
Dump Operator and Truck Loader);
(10) Mobile Workers (Laborers,
Electricians, Mechanics, and Supervisors,
etc.); and
(11) Miners in Other Occupations (Welder,
Dragline Operator, Shotcrete/Gunite Man,
and Dredge/Barge Operator, etc.).
The sampling data for each of the 11
occupational categories were then
summarized by commodity group (‘‘Metal,’’
‘‘Nonmetal,’’ ‘‘Stone,’’ ‘‘Crushed Limestone,’’
and ‘‘Sand and Gravel’’) based on the
material being extracted.93 The available
sampling data were then collated for each
occupation and commodity and summarized
by concentration ranges in the exposure
profile tables for MNM mines.
93 Crushed Limestone and Sand and Gravel were
considered separately because these commodities
make up a large percentage of inspection samples.
Watts et al. (2012). Respirable crystalline silica
[Quartz] Concentration Trends in Metal and
Nonmetal Mining, J Occ Environ Hyg 9:12, 720–
732.
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Attachment 3: Coal Job Codes
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The complete list of job codes that are
found in IAS, as of March 11, 2022, are
included below, with Table C3–1 listing job
codes for coal miners. For coal, the first digit
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of the job code identifies where the work is
taking place. For example, codes starting
with 0 represent jobs that occur at the
underground face of the mine. Job codes that
start with 6 were added in 2020.
0—Underground Section Workers (Face)
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1—General Underground (Non-Face)
2—Underground Transportation (Non-Face)
3—Surface
4—Supervisory and Staff
5—MSHA—State
6—Shaft and Slope Sinking
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included below with Table C4–1 outlining
job codes for MNM miners.
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Attachment 4: MNM Job Codes
The complete list of job codes that are
found in IAS, as of March 11, 2022, are
45003
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45005
EP13JY23.089</GPH>
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Attachment 5. Examples of Job Code Pocket
Cards
Inspectors previously received pocketsized job code cards for use in filling out
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forms with the correct job code. Now, a dropdown menu in IAS is used to select the
codes. Table C5–1 contains Underground
Coal Mining Occupation Codes from Coal Job
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Code Cards used by MESA between 1973 and
1977. Table C5–2 contains Surface
Occupation Codes from Coal Job Codes used
by MESA between 1973 and 1977.
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EP13JY23.090</GPH>
45006
EP13JY23.092</GPH>
45007
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MNM Job Code Cards (1997)
Table C5–3 includes MNM Job Codes from
a MNM Job Code Card printed in 1997 by the
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GPO and which referenced a 1981 MSHA
form (MSHA Form 4000–50, Sept. 1981).
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45010
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List of Subjects
recordkeeping requirements,
Underground mining.
30 CFR Part 56
30 CFR Part 60
Chemicals, Electric power,
Explosives, Fire prevention, Hazardous
substances, Incorporation by reference,
Metal and nonmetal mining, Mine safety
and health, Noise control, Reporting and
recordkeeping requirements, Surface
mining.
Coal, Incorporation by reference,
Metal and nonmetal mining, Medical
surveillance, Mine safety and health,
Respirable crystalline silica, Reporting
and recordkeeping requirements,
Surface mining, Underground mining.
30 CFR Part 70
30 CFR Part 57
Chemicals, Electric power,
Explosives, Fire prevention, Gases,
Hazardous substances, Incorporation by
reference, Metal and nonmetal mining,
Mine safety and health, Noise control,
Radiation protection, Reporting and
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30 CFR Part 71
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30 CFR Part 72
Coal, Health standards, Incorporation
by reference, Mine safety and health,
Training, Underground mining.
30 CFR Part 75
Coal, Mine safety and health,
Reporting and recordkeeping
requirements, Respirable dust,
Underground coal mines.
PO 00000
Coal, Mine safety and health,
Reporting and recordkeeping
requirements, Surface coal mines,
Underground coal mines.
Sfmt 4702
Coal, Mine safety and health,
Reporting and recordkeeping
requirements, Underground coal mines,
Ventilation.
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BILLING CODE 4520–43–C
Federal Register / Vol. 88, No. 133 / Thursday, July 13, 2023 / Proposed Rules
30 CFR Part 90
Coal, Mine safety and health,
Reporting and recordkeeping
requirements, Respirable dust.
Christopher J. Williamson,
Assistant Secretary of Labor for Mine Safety
and Health.
For the reasons discussed in the
preamble, the Mine Safety and Health
Administration is proposing to amend
30 CFR subchapters K, M, and O as
follows:
Subchapter K-Metal and Nonmetal
Mine Safety and Health
PART 56—SAFETY AND HEALTH
STANDARDS—SURFACE METAL AND
NONMETAL MINES
1. The authority citation for part 56
continues to read as follows:
■
Authority: 30 U.S.C. 811.
Subpart D—Air Quality and Physical
Agents
2. Amend § 56.5001 by revising
paragraph (a) to read as follows:
■
§ 56.5001 Exposure limits for airborne
contaminants.
ddrumheller on DSK120RN23PROD with PROPOSALS2
*
*
*
*
*
(a) Except as provided in paragraph
(b) of this section and in part 60 of this
chapter, the exposure to airborne
contaminants shall not exceed, on the
basis of a time weighted average, the
threshold limit values adopted by the
American Conference of Governmental
Industrial Hygienists, as set forth and
explained in the 1973 edition of the
Conference’s publication, entitled
‘‘TLV’s Threshold Limit Values for
Chemical Substances in Workroom Air
Adopted by ACGIH for 1973,’’ pages 1
through 54. This publication is
incorporated by reference into this
section with the approval of the Director
of the Federal Register under 5 U.S.C.
552(a) and 1 CFR part 51. This material
is available for inspection at the Mine
Safety and Health Administration
(MSHA) and at the National Archives
and Records Administration (NARA).
Contact MSHA at: MSHA’s Office of
Standards, Regulations, and Variances,
201 12th Street South, Arlington, VA
22202–5450; 202–693–9440; or at any
MSHA Metal and Nonmetal Mine Safety
and Health District Office. For
information on the availability of this
material at NARA, visit
www.archives.gov/federal-register/cfr/
ibr-locations.html or email
fr.inspection@nara.gov. The material
may be obtained from American
Conference of Governmental Industrial
Hygienists, 1330 Kemper Meadow
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22:10 Jul 12, 2023
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Drive, Attn: Customer Service,
Cincinnati, OH 45240; www.acgih.org.
*
*
*
*
*
■ 3. Amend § 56.5005 by revising the
introductory text and paragraphs (b) and
(c) to read as follows:
§ 56.5005 Control of exposure to airborne
contaminants.
Control of employee exposure to
harmful airborne contaminants shall be,
insofar as feasible, by prevention of
contamination, removal by exhaust
ventilation, or by dilution with
uncontaminated air. However, where
accepted engineering control measures
have not been developed or when
necessary by the nature of work
involved (for example, while
establishing controls or occasional entry
into hazardous atmospheres to perform
maintenance or investigation),
employees may work for reasonable
periods of time in concentrations of
airborne contaminants exceeding
permissible levels if they are protected
by appropriate respiratory protective
equipment. Whenever respiratory
protective equipment is used, its
selection, fitting, maintenance, cleaning,
training, supervision, and use shall meet
the following minimum requirements:
*
*
*
*
*
(b) Approved respirators shall be
selected, fitted, cleaned, used, and
maintained in accordance with the
requirements, as applicable, of ASTM
F3387–19. ASTM F3387–19, Standard
Practice for Respiratory Protection
approved August 1, 2019, is
incorporated by reference into this
section with the approval of the Director
of the Federal Register under 5 U.S.C.
552(a) and 1 CFR part 51. This material
is available for inspection at the Mine
Safety and Health Administration
(MSHA) and at the National Archives
and Records Administration (NARA).
Contact MSHA at: MSHA’s Office of
Standards, Regulations, and Variances,
201 12th Street South, Arlington, VA
22202–5450; 202–693–9440; or any
Mine Safety and Health Enforcement
District Office. For information on the
availability of this material at NARA,
visit www.archives.gov/federal-register/
cfr/ibr-locations.html or email
fr.inspection@nara.gov. The material
may be obtained from ASTM
International, 100 Barr Harbor Drive,
P.O. Box C700, West Conshohocken, PA
19428–2959; www.astm.org/.
(c) When respiratory protection is
used in atmospheres immediately
dangerous to life or health (IDLH), the
presence of at least one other person
with backup equipment and rescue
capability shall be required in the event
of failure of the respiratory equipment.
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45011
PART 57—SAFETY AND HEALTH
STANDARDS—UNDERGROUND
METAL AND NONMETAL MINES
4. The authority citation for part 57
continues to read as follows:
■
Authority: 30 U.S.C. 811.
Subpart D—Air Quality, Radiation,
Physical Agents, and Diesel Particulate
Matter
5. Amend § 57.5001 by revising
paragraph (a) to read as follows:
■
§ 57.5001 Exposure limits for airborne
contaminants.
*
*
*
*
*
(a) Except as provided in paragraph
(b) of this section and in part 60 of this
chapter, the exposure to airborne
contaminants shall not exceed, on the
basis of a time weighted average, the
threshold limit values adopted by the
American Conference of Governmental
Industrial Hygienists, as set forth and
explained in the 1973 edition of the
Conference’s publication, entitled
‘‘TLV’s Threshold Limit Values for
Chemical Substances in Workroom Air
Adopted by ACGIH for 1973,’’ pages 1
through 54. Excursions above the listed
thresholds shall not be of a greater
magnitude than is characterized as
permissible by the Conference. This
publication is incorporated by reference
into this section with the approval of
the Director of the Federal Register
under 5 U.S.C. 552(a) and 1 CFR part 51.
This material is available for inspection
at the Mine Safety and Health
Administration (MSHA) and at the
National Archives and Records
Administration (NARA). Contact MSHA
at: MSHA’s Office of Standards,
Regulations, and Variances, 201 12th
Street South, Arlington, VA 22202–
5450; 202–693–9440; or any MSHA
Metal and Nonmetal Mine Safety and
Health District Office. For information
on the availability of this material at
NARA, visit www.archives.gov/federalregister/cfr/ibr-locations.html or email
fr.inspection@nara.gov. The material
may be obtained from American
Conference of Governmental Industrial
Hygienists by writing to 1330 Kemper
Meadow Drive, Attn: Customer Service,
Cincinnati, OH 45240; www.acgih.org.
*
*
*
*
*
■ 6. Amend § 57.5005 by revising the
introductory text and paragraphs (b) and
(c) to read as follows:
§ 57.5005 Control of exposure to airborne
contaminants.
Control of employee exposure to
harmful airborne contaminants shall be,
insofar as feasible, by prevention of
contamination, removal by exhaust
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Federal Register / Vol. 88, No. 133 / Thursday, July 13, 2023 / Proposed Rules
ventilation, or by dilution with
uncontaminated air. However, where
accepted engineering control measures
have not been developed or when
necessary by the nature of work
involved (for example, while
establishing controls or occasional entry
into hazardous atmospheres to perform
maintenance or investigation),
employees may work for reasonable
periods of time in concentrations of
airborne contaminants exceeding
permissible levels if they are protected
by appropriate respiratory protective
equipment. Whenever respiratory
protective equipment is used, its
selection, fitting, maintenance, cleaning,
training, supervision, and use shall meet
the following minimum requirements:
*
*
*
*
*
(b) Approved respirators shall be
selected, fitted, cleaned, used, and
maintained in accordance with the
requirements, as applicable, of ASTM
F3387–19. ASTM F3387–19, Standard
Practice for Respiratory Protection
approved August 1, 2019, is
incorporated by reference into this
section with the approval of the Director
of the Federal Register under 5 U.S.C.
552(a) and 1 CFR part 51. This material
is available for inspection at the Mine
Safety and Health Administration
(MSHA) and at the National Archives
and Records Administration (NARA).
Contact MSHA at: MSHA’s Office of
Standards, Regulations, and Variances,
201 12th Street South, Arlington, VA
22202–5450; 202–693–9440; or any
Mine Safety and Health Enforcement
District Office. For information on the
availability of this material at NARA,
visit www.archives.gov/federal-register/
cfr/ibr-locations.html or email
fr.inspection@nara.gov. The material
may be obtained from ASTM
International, 100 Barr Harbor Drive,
P.O. Box C700, West Conshohocken, PA
19428–2959; www.astm.org/.
(c) When respiratory protection is
used in atmospheres immediately
dangerous to life or health (IDLH), the
presence of at least one other person
with backup equipment and rescue
capability shall be required in the event
of failure of the respiratory equipment.
ddrumheller on DSK120RN23PROD with PROPOSALS2
Subchapter M-Uniform Mine Health
Regulations
7. Add part 60 to subchapter M to read
as follows:
■
PART 60–RESPIRABLE CRYSTALLINE
SILICA
Sec.
60.1 Scope; effective date.
60.2 Definitions.
60.10 Permissible exposure limit (PEL).
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60.11 Methods of compliance.
60.12 Exposure monitoring.
60.13 Corrective actions.
60.14 Respiratory protection.
60.15 Medical surveillance for metal and
nonmetal miners.
60.16 Recordkeeping requirements.
60.17 Severability.
Authority: 30 U.S.C. 811, 813(h) and 957.
§ 60.1
Scope; effective date.
This part sets forth mandatory health
standards for each surface and
underground metal, nonmetal, and coal
mine subject to the Federal Mine Safety
and Health Act of 1977, as amended.
Requirements regarding medical
surveillance for metal and nonmetal
miners are also included. The
provisions of this part are effective [date
120 days after publication of the final
rule].
§ 60.2
Definitions.
The following definitions apply in
this part:
Action level means an airborne
concentration of respirable crystalline
silica of 25 micrograms per cubic meter
of air (mg/m3) for a full-shift exposure,
calculated as an 8-hour time-weighted
average (TWA).
Objective data means information,
such as air monitoring data from
industry-wide surveys or calculations
based on the composition of a
substance, demonstrating miner
exposure to respirable crystalline silica
associated with a particular product or
material or a specific process, task, or
activity. The data must reflect mining
conditions closely resembling or with a
higher exposure potential than the
processes, types of material, control
methods, work practices, and
environmental conditions in the
operator’s current operations.
Respirable crystalline silica means
quartz, cristobalite, and/or tridymite
contained in airborne particles that are
determined to be respirable by a
sampling device designed to meet the
characteristics for respirable-particlesize-selective samplers that conform to
the International Organization for
Standardization (ISO) 7708:1995: Air
Quality—Particle Size Fraction
Definitions for Health-Related
Sampling.
Specialist means an American BoardCertified Specialist in Pulmonary
Disease or an American Board-Certified
Specialist in Occupational Medicine.
§ 60.10
Permissible exposure limit (PEL).
The mine operator shall ensure that
no miner is exposed to an airborne
concentration of respirable crystalline
silica in excess of 50 mg/m3 for a full-
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shift exposure, calculated as an 8-hour
TWA.
§ 60.11
Methods of compliance.
(a) The mine operator shall install,
use, and maintain feasible engineering
controls, supplemented by
administrative controls when necessary,
to keep each miner’s exposure at or
below the PEL, except as specified in
§ 60.14.
(b) Rotation of miners shall not be
considered an acceptable administrative
control used for compliance with this
part.
§ 60.12
Exposure monitoring.
(a) Baseline sampling. (1) The mine
operator shall perform baseline
sampling within the first 180 days after
[date 120 days after publication of the
final rule] to assess the full shift, 8-hour
TWA exposure of respirable crystalline
silica for each miner who is or may
reasonably be expected to be exposed to
respirable crystalline silica.
(2) The mine operator is not required
to conduct periodic sampling under
paragraph (b) of this section if the
baseline sampling indicates that miner
exposures are below the action level and
if the conditions in either paragraph
(a)(2)(i) or (ii) of this section are met:
(i) One of the following sources from
within the preceding 12 months of
baseline sampling indicates that miner
exposures are below the action level:
(A) Sampling conducted by the
Secretary; or
(B) Mine operator sampling
conducted in accordance with
paragraphs (f) and (g) of this section; or
(C) Objective data.
(ii) Subsequent sampling that is
conducted within 3 months after the
baseline sampling indicates that miner
exposures are below the action level.
(b) Periodic sampling. Where the most
recent sampling indicates that miner
exposures are at or above the action
level but at or below the PEL, the mine
operator shall sample within 3 months
of that sampling and continue to sample
within 3 months of the previous
sampling until two consecutive
samplings indicate that miner exposures
are below the action level.
(c) Corrective actions sampling.
Where the most recent sampling
indicates that miner exposures are
above the PEL, the mine operator shall
sample after corrective actions taken
pursuant to § 60.13 until the sampling
indicates that miner exposures are at or
below the PEL.
(d) Semi-annual evaluation. At least
every 6 months after [date one year after
the effective date of the final rule], mine
operators shall evaluate any changes in
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production, processes, engineering or
administrative controls, or other factors
that may reasonably be expected to
result in new or increased respirable
crystalline silica exposures. Once the
evaluation is completed, the mine
operator shall:
(1) Make a record of the evaluation
and the date of the evaluation; and
(2) Post the record on the mine
bulletin board and, if applicable, by
electronic means, for the next 31 days.
(e) Post-evaluation sampling. If the
mine operator determines as a result of
the semi-annual evaluation under
paragraph (d) of this section that miners
may be exposed to respirable crystalline
silica at or above the action level, the
mine operator shall perform sampling to
assess the full shift, 8-hour TWA
exposure of respirable crystalline silica
for each miner who is or may reasonably
be expected to be at or above the action
level.
(f) Sampling requirements. (1)
Sampling shall be performed for the
duration of a miner’s regular full shift
and during typical mining activities.
(2) The full-shift, 8-hour TWA
exposure for such miners shall be
measured based on:
(i) Personal breathing-zone air
samples for metal and nonmetal
operations; or
(ii) Occupational environmental
samples collected in accordance with
§ 70.201(c) or (b) or § 90.201(b) of this
chapter for coal operations.
(3) Where several miners perform the
same tasks on the same shift and in the
same work area, the mine operator may
sample a representative fraction (at least
two) of these miners to meet the
requirements in paragraphs (a) through
(e) of this section. In sampling a
representative fraction of miners, the
mine operator shall select the miners
who are expected to have the highest
exposure to respirable crystalline silica.
(4) The mine operator shall use
respirable-particle-size-selective
samplers that conform to ISO 7708:1995
to determine compliance with the PEL.
ISO 7708:1995, Air Quality—Particle
Size Fraction Definitions for HealthRelated Sampling, Edition 1, 1995–04, is
incorporated by reference into this
section with the approval of the Director
of the Federal Register under 5 U.S.C.
552(a) and 1 CFR part 51. This material
is available for inspection at the Mine
Safety and Health Administration
(MSHA) and at the National Archives
and Records Administration (NARA).
Contact MSHA at: MSHA’s Office of
Standards, Regulations, and Variances,
201 12th Street South, Arlington, VA
22202–5450; 202–693–9440; or any
Mine Safety and Health Enforcement
VerDate Sep<11>2014
22:10 Jul 12, 2023
Jkt 259001
District Office. For information on the
availability of this material at NARA,
visit www.archives.gov/federal-register/
cfr/ibr-locations.html or email
fr.inspection@nara.gov. The material
may be obtained from the International
Organization for Standardization (ISO),
CP 56, CH–1211 Geneva 20,
Switzerland; phone: + 41 22 749 01 11;
fax: + 41 22 733 34 30; website:
www.iso.org.
(g) Methods of sample analysis. (1)
The mine operator shall use a laboratory
that is accredited to ISO/IEC 17025
‘‘General requirements for the
competence of testing and calibration
laboratories’’ with respect to respirable
crystalline silica analyses, where the
accreditation has been issued by a body
that is compliant with ISO/IEC 17011
‘‘Conformity assessment—Requirements
for accreditation bodies accrediting
conformity assessment bodies.’’
(2) The mine operator shall ensure
that the laboratory evaluates all samples
using respirable crystalline silica
analytical methods specified by MSHA,
the National Institute for Occupational
Safety and Health (NIOSH), or the
Occupational Safety and Health
Administration (OSHA).
(h) Sampling records. For each sample
taken pursuant to paragraphs (a)
through (e) of this section, the mine
operator shall make a record of the
sample date, the occupations sampled,
and the concentrations of respirable
crystalline silica and respirable dust,
and post the record and the laboratory
report on the mine bulletin board and,
if applicable, by electronic means, for
the next 31 days, upon receipt.
§ 60.13
Corrective actions.
(a) If any sampling indicates that a
miner’s exposure exceeds the PEL, the
mine operator shall:
(1) Make approved respirators
available to affected miners before the
start of the next work shift in
accordance with § 60.14;
(2) Ensure that affected miners wear
respirators properly for the full shift or
during the period of overexposure until
miner exposures are at or below the
PEL; and
(3) Immediately take corrective
actions to lower the concentration of
respirable crystalline silica to at or
below the PEL.
(4) Once corrective actions have been
taken, the mine operator shall:
(i) Conduct sampling pursuant to
§ 60.12(c); and
(ii) Take additional or new corrective
actions until sampling indicates miner
exposures are at or below the PEL.
(b) The mine operator shall make a
record of corrective actions and the
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45013
dates of the corrective actions under
paragraph (a) of this section.
§ 60.14
Respiratory protection.
(a) Temporary non-routine use of
respirators. The mine operator shall use
respiratory protection as a temporary
measure in accordance with paragraph
(c) of this section. Miners must use
respirators when working in
concentrations of respirable crystalline
silica above the PEL while:
(1) Engineering control measures are
being developed and implemented; or
(2) It is necessary by the nature of
work involved.
(b) Miners unable to wear respirators.
Upon written determination by a
physician or other licensed health care
professional (PLHCP) that an affected
miner is unable to wear a respirator, the
miner shall be temporarily transferred
either to work in a separate area of the
same mine or to an occupation at the
same mine where respiratory protection
is not required.
(1) The affected miner shall continue
to receive compensation at no less than
the regular rate of pay in the occupation
held by that miner immediately prior to
the transfer.
(2) The affected miner may be
transferred back to the miner’s initial
work area or occupation when
temporary non-routine use of respirators
under paragraph (a) of this section is no
longer required.
(c) Respiratory protection
requirements. (1) Affected miners shall
be provided with a NIOSH-approved
atmosphere-supplying respirator or
NIOSH-approved air-purifying
respirator equipped with the following:
(i) Particulate protection classified as
100 series under 42 CFR part 84; or
(ii) Particulate protection classified as
High Efficiency ‘‘HE’’ under 42 CFR part
84.
(2) Approved respirators shall be
selected, fitted, used, and maintained in
accordance with the requirements, as
applicable, of ASTM F3387–19. ASTM
F3387–19, Standard Practice for
Respiratory Protection approved August
1, 2019, is incorporated by reference
into this section with the approval of
the Director of the Federal Register
under 5 U.S.C. 552(a) and 1 CFR part 51.
This material is available for inspection
at the Mine Safety and Health
Administration (MSHA) and at the
National Archives and Records
Administration (NARA). Contact MSHA
at: MSHA’s Office of Standards,
Regulations, and Variances, 201 12th
Street South, Arlington, VA 22202–
5450; 202–693–9440; or any Mine Safety
and Health Enforcement District Office.
For information on the availability of
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this material at NARA, visit
www.archives.gov/federal-register/cfr/
ibr-locations.html or email
fr.inspection@nara.gov. The material
may be obtained from ASTM
International, 100 Barr Harbor Drive, PO
Box C700, West Conshohocken, PA
19428–2959; www.astm.org/.
§ 60.15 Medical surveillance for metal and
nonmetal miners.
(a) Medical surveillance. Each
operator of a metal and nonmetal mine
shall provide to each miner periodic
medical examinations performed by a
physician or other licensed health care
professional (PLHCP) or specialist, as
defined in § 60.2, at no cost to the
miner.
(1) Medical examinations shall be
provided at frequencies specified in this
section.
(2) Medical examinations shall
include:
(i) A medical and work history, with
emphasis on: past and present exposure
to respirable crystalline silica, dust, and
other agents affecting the respiratory
system; any history of respiratory
system dysfunction, including
diagnoses and symptoms of respiratory
disease (e.g., shortness of breath, cough,
wheezing); history of tuberculosis; and
smoking status and history;
(ii) A physical examination with
special emphasis on the respiratory
system;
(iii) A chest X-ray (a single
posteroanterior radiographic projection
or radiograph of the chest at full
inspiration recorded on either film (no
less than 14 x 17 inches and no more
than 16 x 17 inches) or digital
radiography systems), classified
according to the International Labour
Office (ILO) International Classification
of Radiographs of Pneumoconioses by a
NIOSH-certified B Reader; and
(iv) A pulmonary function test to
include forced vital capacity (FVC) and
forced expiratory volume in one second
(FEV1) and FEV1/FVC ratio,
administered by a spirometry technician
with a current certificate from a NIOSHapproved Spirometry Program Sponsor.
(b) Voluntary medical examinations.
Each mine operator shall provide the
opportunity to have the medical
examinations specified in paragraph (a)
of this section at least every 5 years to
all miners employed at the mine. The
medical examinations shall be available
during a 6-month period that begins no
less than 3.5 years and not more than
4.5 years from the end of the last 6month period.
(c) Mandatory medical examinations.
For each miner who begins work in the
mining industry for the first time, the
mine operator shall provide medical
examinations specified in paragraph (a)
of this section as follows:
(1) An initial medical examination no
later than 30 days after beginning
employment;
(2) A follow-up medical examination
no later than 3 years after the initial
examination in paragraph (c)(1) of this
section; and
(3) A follow-up medical examination
conducted by a specialist no later than
2 years after the examinations in
paragraph (c)(2) of this section if the
chest X-ray shows evidence of
pneumoconiosis or the spirometry
examination indicates evidence of
decreased lung function.
(d) Medical examinations results. The
results of medical examinations or tests
made pursuant to this section shall be
provided only to the miner, and at the
request of the miner, to the miner’s
designated physician.
(e) Written medical opinion. The mine
operator shall obtain a written medical
opinion from the PLHCP or specialist
within 30 days of the medical
examination. The written opinion shall
contain only the following:
(1) The date of the medical
examination;
(2) A statement that the examination
has met the requirements of this section;
and
(3) Any recommended limitations on
the miner’s use of respirators.
(f) Written medical opinion records.
The mine operator shall maintain a
record of the written medical opinions
received from the PLHCP or specialist
under paragraph (e) of this section.
§ 60.16
Recordkeeping requirements.
(a) Table 1 to this paragraph (a) lists
the records the mine operator shall
retain and their retention period.
(1) Evaluation records made under
§ 60.12(d) shall be retained for at least
2 years from the date of each evaluation.
(2) Sampling records made under
§ 60.12(h) shall be retained for at least
2 years from the sample date.
(3) Corrective action records made
under § 60.13(b) shall be retained for at
least 2 years from the date of each
corrective action. These records must be
stored with the records of related
sampling under § 60.12(h).
(4) Written determination records
received from a PLHCP under § 60.14(b)
shall be retained for the duration of the
miner’s employment plus 6 months.
(5) Written medical opinion records
received from a PLHCP or specialist
under § 60.15(f) shall be retained for the
duration of the miner’s employment
plus 6 months.
TABLE 1 TO PARAGRAPH (a)—RECORDKEEPING REQUIREMENTS
Record
Section references
Evaluation records ..................................................
Sampling records ....................................................
Corrective action records ........................................
Written determination records received from a
PLHCP.
5. Written medical opinion records received from a
PLHCP or specialist.
ddrumheller on DSK120RN23PROD with PROPOSALS2
1.
2.
3.
4.
(b) Upon request from an authorized
representative of the Secretary, from an
authorized representative of miners, or
from miners, mine operators shall
promptly provide access to any record
listed in this section.
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§ 60.12(d)
§ 60.12(h)
§ 60.13(b)
§ 60.14(b)
Retention period
.......................................
.......................................
.......................................
.......................................
§ 60.15(f) ........................................
§ 60.17
At least 2 years from date of each evaluation.
At least 2 years from sample date.
At least 2 years from date of each corrective action.
Duration of miner’s employment plus 6 months.
Duration of miner’s employment plus 6 months.
Severability.
Each section of this part, as well as
sections in 30 CFR parts 56, 57, 70, 71,
72, 75, and 90 that address respirable
crystalline silica or respiratory
protection, is separate and severable
from the other sections and provisions.
If any provision of this subpart is held
to be invalid or unenforceable by its
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terms, or as applied to any person,
entity, or circumstance, or is stayed or
enjoined, that provision shall be
construed so as to continue to give the
maximum effect to the provision
permitted by law, unless such holding
shall be one of utter invalidity or
unenforceability, in which event the
provision shall be severable from these
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sections and shall not affect the
remainder thereof.
using the full box, open breast, or slant
breast mining method.
Subchapter O—Coal Mine Safety and
Health
§ 70.206
PART 70—MANDATORY HEALTH
STANDARDS—UNDERGROUND COAL
MINES
§ 70.207
8. The authority citation for part 70
continues to read as follows:
■
Authority: 30 U.S.C. 811, 813(h), 957.
Subpart A—General
§ 70.2
[Amended]
9. Amend § 70.2 by removing the
definition of ‘‘Quartz’’.
■
■
[Removed and Reserved]
12. Remove and reserve § 70.206.
[Removed and Reserved]
13. Remove and reserve § 70.207.
14. Amend § 70.208 by:
a. Removing and reserving paragraph
(c);
■ b. Revising paragraphs (d), (e)
introductory text, (e)(2), (f), (g), (h)
introductory text, (h)(2), (i) introductory
text, and (i)(1); and
■ c. Adding table 1.
The revisions and addition read as
follows:
■
■
■
§ 70.208 Quarterly sampling; mechanized
mining units.
Subpart B—Dust Standards
§ 70.101
■
*
[Removed and Reserved]
10. Remove and reserve § 70.101.
Subpart C—Sampling Procedures
11. Amend § 70.205 by revising
paragraph (c) to read as follows:
■
§ 70.205 Approved sampling devices;
operation; air flowrate.
*
*
*
*
*
(c) If using a CPDM, the person
certified in sampling shall monitor the
dust concentrations and the sampling
status conditions being reported by the
sampling device at mid-shift or more
frequently as specified in the approved
mine ventilation plan to assure: The
sampling device is in the proper
location and operating properly; and the
work environment of the occupation or
DA being sampled remains in
compliance with the standard at the end
of the shift. This monitoring is not
required if the sampling device is being
operated in an anthracite coal mine
*
*
*
*
(d) If a normal production shift is not
achieved, the DO or ODO sample for
that shift may be voided by MSHA.
However, any sample, regardless of
production, that exceeds the standard
by at least 0.1 mg/m3 shall be used in
the determination of the equivalent
concentration for that occupation.
(e) When a valid representative
sample taken in accordance with this
section meets or exceeds the ECV in
table 1 to this section that corresponds
to the particular sampling device used,
the operator shall:
*
*
*
*
*
(2) Immediately take corrective action
to lower the concentration of respirable
dust to at or below the respirable dust
standard; and
*
*
*
*
*
(f) Noncompliance with the standard
is demonstrated during the sampling
period when:
(1) Three or more valid representative
samples meet or exceed the ECV in table
1 to this section that corresponds to the
particular sampling device used; or
(2) The average for all valid
representative samples meets or exceeds
the ECV in table 1 to this section that
corresponds to the particular sampling
device used.
(g)(1) Unless otherwise directed by
the District Manager, upon issuance of
a citation for a violation of the standard
involving a DO in an MMU, paragraph
(a)(1) of this section shall not apply to
the DO in that MMU until the violation
is abated and the citation is terminated
in accordance with paragraphs (h) and
(i) of this section.
(2) Unless otherwise directed by the
District Manager, upon issuance of a
citation for a violation of the standard
involving a type of ODO in an MMU,
paragraph (a)(2) of this section shall not
apply to that ODO type in that MMU
until the violation is abated and the
citation is terminated in accordance
with paragraphs (h) and (i) of this
section.
(h) Upon issuance of a citation for
violation of the standard, the operator
shall take the following actions
sequentially:
*
*
*
*
*
(2) Immediately take corrective action
to lower the concentration of respirable
coal mine dust to at or below the
standard; and
*
*
*
*
*
(i) A citation for a violation of the
standard shall be terminated by MSHA
when:
(1) Each of the five valid
representative samples is at or below the
standard; and
*
*
*
*
*
TABLE 1 TO § 70.208—EXCESSIVE CONCENTRATION VALUES (ECV) BASED ON A SINGLE SAMPLE, THREE SAMPLES, OR
THE AVERAGE OF FIVE OR FIFTEEN FULL-SHIFT CMDPSU/CPDM CONCENTRATION MEASUREMENTS
ECV (mg/m3)
Section
Samples
CMDPSU
70.208 (e) ........................................
70.208(f)(1) ......................................
70.208(f)(2) ......................................
ddrumheller on DSK120RN23PROD with PROPOSALS2
70.208(f)(2) ......................................
70.208(i)(1) ......................................
70.100(a)—Single sample .........................................................................
70.100(b)—Single sample .........................................................................
70.100(a)—3 or more samples .................................................................
70.100(b)—3 or more samples .................................................................
70.100(a)—5 sample average ...................................................................
70.100(b)—5 sample average ...................................................................
70.100(a)—15 sample average .................................................................
70.100(b)—15 sample average .................................................................
70.100(a)—Each of 5 samples .................................................................
70.100(b)—Each of 5 samples .................................................................
15. Amend § 70.209 by:
a. Removing and reserving paragraph
(b);
■
■
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b. Revising paragraphs (c)
introductory text, (c)(2), (d), (e), (f)
introductory text, (f)(2), (g) introductory
text, and (g)(1); and
■
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c. Adding table 1.
The revisions and addition read as
follows:
■
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Quarterly sampling; designated
*
*
*
*
*
(c) When a valid representative
sample taken in accordance with this
section meets or exceeds the ECV in
table 1 to this section that corresponds
to the particular sampling device used,
the operator shall:
*
*
*
*
*
(2) Immediately take corrective action
to lower the concentration of respirable
dust to at or below the respirable dust
standard; and
*
*
*
*
*
(d) Noncompliance with the standard
is demonstrated during the sampling
period when:
(1) Two or more valid representative
samples meet or exceed the ECV in table
1 to this section that corresponds to the
particular sampling device used; or
(2) The average for all valid
representative samples meets or exceeds
the ECV in table 1 to this section that
corresponds to the particular sampling
device used.
(e) Unless otherwise directed by the
District Manager, upon issuance of a
citation for a violation of the standard,
paragraph (a) of this section shall not
apply to that DA until the violation is
abated and the citation is terminated in
accordance with paragraphs (f) and (g)
of this section.
(f) Upon issuance of a citation for a
violation of the standard, the operator
shall take the following actions
sequentially:
*
*
*
*
*
(2) Immediately take corrective action
to lower the concentration of respirable
coal mine dust to at or below the
standard; and
*
*
*
*
*
(g) A citation for a violation of the
standard shall be terminated by MSHA
when:
(1) Each of the five valid
representative samples is at or below the
standard; and
*
*
*
*
*
TABLE 1 TO § 70.209—EXCESSIVE CONCENTRATION VALUES (ECV) BASED ON A SINGLE SAMPLE, TWO SAMPLES, OR THE
AVERAGE OF FIVE OR FIFTEEN FULL-SHIFT CMDPSU/CPDM CONCENTRATION MEASUREMENTS
ECV (mg/m3)
Section
Samples
CMDPSU
70.209 (c) .........................................
70.209(d)(1) .....................................
70.209(d)(2) .....................................
70.209(d)(2) .....................................
70.209(g)(1) .....................................
70.100(a)—Single sample .........................................................................
70.100(b)—Single sample .........................................................................
70.100(a)—2 or more samples .................................................................
70.100(b)—2 or more samples .................................................................
70.100(a)—5 sample average ...................................................................
70.100(b)—5 sample average ...................................................................
70.100(a)—15 sample average .................................................................
70.100(b)—15 sample average .................................................................
70.100(a)—Each of 5 samples .................................................................
70.100(b)—Each of 5 samples .................................................................
Table 70—1 to Subpart C of Part 70
[Removed]
Subpart C—Sampling Procedures
Table 70—2 to Subpart C of Part 70
[Removed]
17. Remove table 70–2 to subpart C of
part 70.
PART 71—MANDATORY HEALTH
STANDARDS—SURFACE COAL MINES
AND SURFACE WORK AREAS OF
UNDERGROUND COAL MINES
18. The authority citation for part 71
continues to read as follows:
Authority: 30 U.S.C. 811, 813(h), 957.
ddrumheller on DSK120RN23PROD with PROPOSALS2
Subpart A—General
§ 71.2
[Amended]
19. Amend § 71.2 by removing the
definition of ‘‘Quartz’’.
■
Subpart B—Dust Standards
§ 71.101
■
[Removed and Reserved]
20. Remove and reserve § 71.101.
VerDate Sep<11>2014
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§ 71.205 Approved sampling devices;
operation; air flowrate.
*
■
■
21. Amend § 71.205 by revising
paragraph (c) to read as follows:
■
16. Remove table 70–1 to subpart C of
part 70.
■
*
*
*
*
(c) If using a CPDM, the person
certified in sampling shall monitor the
dust concentrations and the sampling
status conditions being reported by the
sampling device at mid-shift or more
frequently as specified in the approved
respirable dust control plan, if
applicable, to assure: The sampling
device is in the proper location and
operating properly; and the work
environment of the occupation being
sampled remains in compliance with
the standard at the end of the shift.
■ 22. Amend § 71.206 by:
■ a. Removing and reserving paragraph
(b);
■ b. Revising paragraphs (e), (g), (h)
introductory text, (h)(2), (i), (j), (k)
introductory text, (k)(2), and (l);
■ c. Removing tables 71–1 and 71–2;
■ d. Revising paragraphs (m) and (n);
and
■ e. Adding table 1.
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1.58
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0.74
1.70
0.57
1.70
0.57
1.59
0.53
1.56
0.52
1.70
0.57
The revisions and addition read as
follows:
§ 71.206 Quarterly sampling; designated
work positions.
*
*
*
*
*
(e) Each DWP sample shall be taken
on a normal work shift. If a normal work
shift is not achieved, the respirable dust
sample shall be transmitted to MSHA
with a notation by the person certified
in sampling on the back of the dust data
card stating that the sample was not
taken on a normal work shift. When a
normal work shift is not achieved, the
sample for that shift may be voided by
MSHA. However, any sample,
regardless of whether a normal work
shift was achieved, that exceeds the
standard by at least 0.1 mg/m3 shall be
used in the determination of the
equivalent concentration for that
occupation.
*
*
*
*
*
(g) Upon notification from MSHA that
any valid representative sample taken
from a DWP to meet the requirements of
paragraph (a) of this section exceeds the
standard, the operator shall, within 15
calendar days of notification, sample
that DWP each normal work shift until
five valid representative samples are
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taken. The operator shall begin
sampling on the first normal work shift
following receipt of notification.
(h) When a valid representative
sample taken in accordance with this
section meets or exceeds the excessive
concentration value (ECV) in table 1 to
this section that corresponds to the
particular sampling device used, the
mine operator shall:
*
*
*
*
*
(2) Immediately take corrective action
to lower the concentration of respirable
coal mine dust to at or below the
standard; and
*
*
*
*
*
(i) Noncompliance with the standard
is demonstrated during the sampling
period when:
(1) Two or more valid representative
samples meet or exceed the ECV in table
1 to this section that corresponds to the
particular sampling device used; or
(2) The average for all valid
representative samples meets or exceeds
the ECV in table 1 to this section that
corresponds to the particular sampling
device used.
(j) Unless otherwise directed by the
District Manager, upon issuance of a
citation for a violation of the standard,
paragraph (a) of this section shall not
apply to that DWP until the violation is
abated and the citation is terminated in
accordance with paragraphs (k) and (l)
of this section.
(k) Upon issuance of a citation for
violation of the standard, the operator
shall take the following actions
sequentially:
*
*
*
*
*
(2) Immediately take corrective action
to lower the concentration of respirable
coal mine dust to at or below the
standard; and
*
*
*
*
*
(l) A citation for violation of the
standard shall be terminated by MSHA
when the equivalent concentration of
each of the five valid representative
samples is at or below the standard.
(m) The District Manager may
designate for sampling under this
section additional work positions at a
surface coal mine and at a surface work
area of an underground coal mine where
a concentration of respirable dust
exceeding 50 percent of the standard
has been measured by one or more
MSHA valid representative samples.
(n) The District Manager may
withdraw from sampling any DWP
designated for sampling under
paragraph (m) of this section upon
finding that the operator is able to
maintain continuing compliance with
the standard. This finding shall be based
on the results of MSHA and operator
valid representative samples taken
during at least a 12-month period.
TABLE 1 TO § 71.206—EXCESSIVE CONCENTRATION VALUES (ECV) BASED ON A SINGLE SAMPLE, TWO SAMPLES, OR THE
AVERAGE OF FIVE FULL-SHIFT CMDPSU/CPDM CONCENTRATION MEASUREMENTS
ECV (mg/m3)
Section
Samples
CMDPSU
71.206(h) ......................................................................
71.206(i)(1) ...................................................................
71.206(i)(2) ...................................................................
71.206(l) ........................................................................
Subpart D—Respirable Dust Control
Plans
23. Amend § 71.300 by revising
paragraph (a) introductory text to read
as follows:
■
ddrumheller on DSK120RN23PROD with PROPOSALS2
§ 71.300 Respirable dust control plan;
filing requirements.
§ 71.301 Respirable dust control plan;
approval by District Manager and posting.
(a) * * *
(1) The respirable dust control
measures would be likely to maintain
22:10 Jul 12, 2023
Jkt 259001
concentrations of respirable coal mine
dust at or below the standard; and
*
*
*
*
*
PART 72—HEALTH STANDARDS FOR
COAL MINES
25. The authority citation for part 72
continues to read as follows:
■
(a) Within 15 calendar days after the
termination date of a citation for
violation of the standard, the operator
shall submit to the District Manager for
approval a written respirable dust
control plan applicable to the DWP
identified in the citation. The respirable
dust control plan and revisions thereof
shall be suitable to the conditions and
the mining system of the coal mine and
shall be adequate to continuously
maintain respirable dust to at or below
the standard at the DWP identified in
the citation.
*
*
*
*
*
■ 24. Amend § 71.301 by revising
paragraph (a)(1) to read as follows:
VerDate Sep<11>2014
Single sample ...............................................................
2 or more samples .......................................................
5 sample average .........................................................
Each of 5 samples ........................................................
Authority: 30 U.S.C. 811, 813(h), 957.
Subpart E—Miscellaneous
■
26. Revise § 72.710 to read as follows:
§ 72.710 Selection, fit, use, and
maintenance of approved respirators.
Approved respirators shall be
selected, fitted, used, and maintained in
accordance with the provisions of a
respiratory protection program
consistent with the requirements, as
applicable, of ASTM F3387–19. ASTM
F3387–19, Standard Practice for
Respiratory Protection approved August
1, 2019, is incorporated by reference
into this section with the approval of
the Director of the Federal Register
under 5 U.S.C. 552(a) and 1 CFR part 51.
This material is available for inspection
at the Mine Safety and Health
Administration (MSHA) and at the
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1.70
1.70
1.59
1.70
National Archives and Records
Administration (NARA). Contact MSHA
at: MSHA’s Office of Standards,
Regulations, and Variances, 201 12th
Street South, Arlington, VA 22202–
5450; 202–693–9440; or any Mine Safety
and Health Enforcement District Office.
For information on the availability of
this material at NARA, visit
www.archives.gov/federal-register/cfr/
ibr-locations.html or email
fr.inspection@nara.gov. The material
may be obtained from ASTM
International, 100 Barr Harbor Drive,
P.O. Box C700, West Conshohocken, PA
19428–2959; www.astm.org/.
■ 27. Revise § 72.800 to read as follows:
§ 72.800 Single, full-shift measurement of
respirable coal mine dust.
The Secretary will use a single, fullshift measurement of respirable coal
mine dust to determine the average
concentration on a shift since that
measurement accurately represents
atmospheric conditions to which a
miner is exposed during such shift.
Noncompliance with the respirable dust
standard, in accordance with this
subchapter, is demonstrated when a
single, full-shift measurement taken by
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MSHA meets or exceeds the applicable
ECV in table 1 to § 70.208, table 1 to
§ 70.209, table 1 to § 71.206, or table 1
to § 90.207 of this chapter that
corresponds to the particular sampling
device used. Upon issuance of a citation
for a violation of the standard, and for
MSHA to terminate the citation, the
mine operator shall take the specified
actions in this subchapter.
PART 75—MANDATORY SAFETY
STANDARDS—UNDERGROUND COAL
MINES
28. The authority citation for part 75
continues to read as follows:
■
Authority: 30 U.S.C. 811, 813(h), 957.
Subpart D—Ventilation
■
■
■
■
29. Amend § 75.350 by:
a. Revising paragraph (b)(3)(i);
b. Removing paragraph (b)(3)(ii); and
c. Redesignating (b)(3)(iii) as (b)(3)(ii).
The revision reads as follows:
§ 75.350
Belt air course ventilation.
*
*
*
*
(b) * * *
(3) * * *
(i) The average concentration of
respirable dust in the belt air course,
when used as a section intake air
course, shall be maintained at or below
0.5 milligrams per cubic meter of air
(mg/m3).
*
*
*
*
*
PART 90—MANDATORY HEALTH
STANDARDS—COAL MINERS WHO
HAVE EVIDENCE OF THE
DEVELOPMENT OF
PNEUMOCONIOSIS
30. The authority citation for part 90
continues to read as follows:
■
Authority: 30 U.S.C. 811, 813(h), 957.
Subpart A—General
31. Amend § 90.2 by revising the
definition of ‘‘Part 90 miner’’ and
removing the definition of ‘‘Quartz’’.
The revision reads as follows:
■
Definitions.
ddrumheller on DSK120RN23PROD with PROPOSALS2
*
*
*
*
*
Part 90 miner. A miner employed at
a coal mine who has exercised the
option under the old section 203(b)
program (36 FR 20601 preview citation
details, October 27, 1971), or under
§ 90.3 to work in an area of a mine
where the average concentration of
respirable dust in the mine atmosphere
during each shift to which that miner is
exposed is continuously maintained at
or below the standard, and who has not
waived these rights.
*
*
*
*
*
VerDate Sep<11>2014
22:10 Jul 12, 2023
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§ 90.3 Part 90 option; notice of eligibility;
exercise of option.
(a) Any miner employed at a coal
mine who, in the judgment of the
Secretary of HHS, has evidence of the
development of pneumoconiosis based
on a chest X-ray, read and classified in
the manner prescribed by the Secretary
of HHS, or based on other medical
examinations shall be afforded the
option to work in an area of a mine
where the average concentration of
respirable dust in the mine atmosphere
during each shift to which that miner is
exposed is continuously maintained at
or below the standard. Each of these
miners shall be notified in writing of
eligibility to exercise the option.
*
*
*
*
*
Subpart B—Dust Standards, Rights of
Part 90 Miners
§ 90.101
*
§ 90.2
32. Amend § 90.3 by revising
paragraph (a) to read as follows:
■
[Removed and Reserved]
33. Remove and reserve § 90.101.
34. Amend § 90.102 by revising
paragraph (a) to read as follows:
■
■
§ 90.102
Transfer; notice.
(a) Whenever a Part 90 miner is
transferred in order to meet the
standard, the operator shall transfer the
miner to an existing position at the same
coal mine on the same shift or shift
rotation on which the miner was
employed immediately before the
transfer. The operator may transfer a
Part 90 miner to a different coal mine,
a newly created position or a position
on a different shift or shift rotation if the
miner agrees in writing to the transfer.
The requirements of this paragraph do
not apply when the respirable dust
concentration in a Part 90 miner’s work
position complies with the standard but
circumstances, such as reductions in
workforce or changes in operational
status, require a change in the miner’s
job or shift assignment.
*
*
*
*
*
■ 35. Amend § 90.104 by revising
paragraph (a)(2) to read as follows:
§ 90.104
option.
Waiver of rights; re-exercise of
(a) * * *
(2) Applying for and accepting a
position in an area of a mine which the
miner knows has an average respirable
dust concentration exceeding the
standard; or
*
*
*
*
*
Subpart C—Sampling Procedures
36. Amend § 90.205 by revising
paragraph (c) to read as follows:
■
PO 00000
Frm 00168
Fmt 4701
Sfmt 4702
§ 90.205 Approved sampling devices;
operation; air flowrate.
*
*
*
*
*
(c) If using a CPDM, the person
certified in sampling shall monitor the
dust concentrations and the sampling
status conditions being reported by the
sampling device at mid-shift or more
frequently as specified in the approved
respirable dust control plan, if
applicable, to assure: The sampling
device is in the proper location and
operating properly; and the work
environment of the Part 90 miner being
sampled remains in compliance with
the standard at the end of the shift. This
monitoring is not required if the
sampling device is being operated in an
anthracite coal mine using the full box,
open breast, or slant breast mining
method.
■ 37. Amend § 90.206 by revising
paragraphs (b) and (c) to read as follows:
§ 90.206 Exercise of option or transfer
sampling.
*
*
*
*
*
(b) Noncompliance with the standard
shall be determined in accordance with
§ 90.207(d).
(c) Upon issuance of a citation for a
violation of the standard, the operator
shall comply with § 90.207(f).
■ 38. Amend § 90.207 by:
■ a. Removing and reserving paragraph
(b);
■ b. Revising paragraphs (c)
introductory text, (c)(2), (d), (e), (f)
introductory text, (f)(2) introductory
text, (f)(2)(ii), and (g);
■ c. Removing tables 90–1 and 90–2;
and
■ d. Adding table 1.
The revisions and addition read as
follows:
§ 90.207
Quarterly sampling.
*
*
*
*
*
(c) When a valid representative
sample taken in accordance with this
section meets or exceeds the ECV in
table 1 to this section corresponding to
the particular sampling device used, the
mine operator shall:
*
*
*
*
*
(2) Immediately take corrective action
to lower the concentration of respirable
coal mine dust to below the standard;
and
*
*
*
*
*
(d) Noncompliance with the standard
is demonstrated during the sampling
period when:
(1) Two or more valid representative
samples meet or exceed the ECV in table
1 to this section that corresponds to the
particular sampling device used; or
(2) The average for all valid
representative samples meets or exceeds
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the ECV in table 1 to this section that
corresponds to the particular sampling
device used.
(e) Unless otherwise directed by the
District Manager, upon issuance of a
citation for a violation of the standard,
paragraph (a) of this section shall not
apply to that Part 90 miner until the
violation is abated and the citation is
terminated in accordance with
paragraphs (f) and (g) of this section.
(f) Upon issuance of a citation for a
violation of the standard, the operator
shall take the following actions
sequentially:
*
*
*
*
*
(2) Immediately take corrective action
to lower the concentration of respirable
dust to below the standard. If the
corrective action involves:
*
*
*
*
*
(ii) Transferring the Part 90 miner to
another work position at the mine to
meet the standard, the operator shall
comply with § 90.102 and then sample
the affected miner in accordance with
§ 90.206(a).
*
*
*
*
*
(g) A citation for a violation of the
standard shall be terminated by MSHA
when the equivalent concentration of
each of the five valid representative
samples is below the standard.
TABLE 1 TO § 90.207—EXCESSIVE CONCENTRATION VALUES (ECV) BASED ON A SINGLE SAMPLE, TWO SAMPLES, OR THE
AVERAGE OF FIVE FULL-SHIFT CMDPSU/CPDM CONCENTRATION MEASUREMENTS
ECV (mg/m3)
Section
Samples
CMDPSU
90.207(c) .......................................................................
90.207(d)(1) ..................................................................
90.207(d)(2) ..................................................................
90.207(g) ......................................................................
Subpart D—Respirable Dust Control
Plans
39. Amend § 90.300 by revising
paragraphs (a) and (b)(3) to read as
follows:
■
§ 90.300 Respirable dust control plan;
filing requirements.
ddrumheller on DSK120RN23PROD with PROPOSALS2
(a) If an operator abates a violation of
the standard by reducing the respirable
dust level in the position of the Part 90
miner, the operator shall submit to the
District Manager for approval a written
respirable dust control plan for the Part
90 miner in the position identified in
the citation within 15 calendar days
after the citation is terminated. The
respirable dust control plan and
VerDate Sep<11>2014
22:10 Jul 12, 2023
Jkt 259001
Single sample ...............................................................
2 or more samples .......................................................
5 sample average .........................................................
Each of 5 samples ........................................................
revisions thereof shall be suitable to the
conditions and the mining system of the
coal mine and shall be adequate to
continuously maintain respirable dust
below the standard for that Part 90
miner.
(b) * * *
(3) A detailed description of how each
of the respirable dust control measures
used to continuously maintain
concentrations of respirable coal mine
dust below the standard; and
*
*
*
*
*
■ 40. Amend § 90.301 by revising
paragraphs (a)(1) and (b) to read as
follows:
PO 00000
Fmt 4701
Sfmt 9990
0.74
0.74
0.61
0.74
0.57
0.57
0.53
0.57
§ 90.301 Respirable dust control plan;
approval by District Manager; copy to part
90 miner.
(a) * * *
(1) The respirable dust control
measures would be likely to maintain
concentrations of respirable coal mine
dust below the standard; and
*
*
*
*
*
(b) MSHA may take respirable dust
samples to determine whether the
respirable dust control measures in the
operator’s plan effectively maintain
concentrations of respirable coal mine
dust below the standard.
*
*
*
*
*
[FR Doc. 2023–14199 Filed 7–6–23; 11:15 am]
BILLING CODE 4520–43–P
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[Federal Register Volume 88, Number 133 (Thursday, July 13, 2023)]
[Proposed Rules]
[Pages 44852-45019]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-14199]
[[Page 44851]]
Vol. 88
Thursday,
No. 133
July 13, 2023
Part II
Department of Labor
-----------------------------------------------------------------------
Mine Safety and Health Administration
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30 CFR Parts 56, 57, 60, et al.
Lowering Miners' Exposure to Respirable Crystalline Silica and
Improving Respiratory Protection; Proposed Rule
Federal Register / Vol. 88 , No. 133 / Thursday, July 13, 2023 /
Proposed Rules
[[Page 44852]]
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DEPARTMENT OF LABOR
Mine Safety and Health Administration
30 CFR Parts 56, 57, 60, 70, 71, 72, 75, and 90
[Docket No. MSHA-2023-0001]
RIN 1219-AB36
Lowering Miners' Exposure to Respirable Crystalline Silica and
Improving Respiratory Protection
AGENCY: Mine Safety and Health Administration (MSHA), Department of
Labor.
ACTION: Proposed rule; request for comments; notice of public hearings.
-----------------------------------------------------------------------
SUMMARY: The Mine Safety and Health Administration (MSHA) proposes to
amend its existing standards to better protect miners against
occupational exposure to respirable crystalline silica, a carcinogenic
hazard, and to improve respiratory protection for all airborne hazards.
MSHA has preliminarily determined that under the Agency's existing
standards, miners at metal and nonmetal mines and coal mines face a
risk of material impairment of health or functional capacity from
exposure to respirable crystalline silica. MSHA proposes to set the
permissible exposure limit of respirable crystalline silica at 50
micrograms per cubic meter of air ([micro]g/m\3\) for a full shift
exposure, calculated as an 8-hour time-weighted average, for all
miners. MSHA's proposal would also include other requirements to
protect miner health, such as exposure sampling, corrective actions to
be taken when miner exposure exceeds the permissible exposure limit,
and medical surveillance for metal and nonmetal miners. Furthermore,
the proposal would replace existing requirements for respiratory
protection and incorporate by reference ASTM F3387-19 Standard Practice
for Respiratory Protection. The proposed uniform approach to respirable
crystalline silica occupational exposure and improved respiratory
protection for all airborne hazards would significantly improve health
protections for all miners and lower the risk of material impairment of
health or functional capacity.
DATES: Written comments. Written comments, including comments on the
information collection requirements described in this preamble, must be
received or postmarked by midnight Eastern Time on August 28, 2023.
Public Hearings. MSHA will hold two public hearings on August 3,
2023 in Arlington, Virginia and August 21, 2023 in Denver, Colorado.
For more information on the public hearings, see SUPPLEMENTARY
INFORMATION.
ADDRESSES: All submissions must include RIN 1219-AB36 or Docket No.
MSHA-2023-0001. You should not include personal or proprietary
information that you do not wish to disclose publicly. If you mark
parts of a comment as ``business confidential'' information, MSHA will
not post those parts of the comment. Otherwise, MSHA will post all
comments without change, including any personal information provided.
MSHA cautions against submitting personal information.
You may submit comments and informational materials, clearly
identified by RIN 1219-AB36 or Docket Id. No. MSHA-2023-0001, by any of
the following methods:
Federal E-Rulemaking Portal: https://www.regulations.gov. Follow
the online instructions for submitting comments.
Email: [email protected]. Include ``RIN 1219-AB36'' in the
subject line of the message.
Regular Mail: MSHA, Office of Standards, Regulations, and
Variances, 201 12th Street South, Suite 4E401, Arlington, Virginia
22202-5450.
Hand Delivery or Courier: MSHA, Office of Standards, Regulations,
and Variances, 201 12th Street South, Suite 4E401, Arlington, Virginia,
between 9:00 a.m. and 5:00 p.m. Monday through Friday, except Federal
holidays. Before visiting MSHA in person, call 202-693-9440 to make an
appointment. Special health precautions may be required.
Facsimile: 202-693-9441. Include ``RIN 1219-AB36'' in the subject
line of the message.
Information Collection Requirements. Comments concerning the
information collection requirements of this proposed rule must be
clearly identified with ``RIN 1219-AB36'' or ``Docket No. MSHA-2023-
0001,'' and sent to MSHA by one of the methods previously explained.
Docket. For access to the docket to read comments and background
documents, go to https://www.regulations.gov. The docket can also be
reviewed in person at MSHA, Office of Standards, Regulations, and
Variances, 201 12th Street South, Arlington, Virginia, between 9 a.m.
and 5 p.m. Monday through Friday, except Federal holidays. Before
visiting MSHA in person, call 202-693-9440 to make an appointment.
Special health precautions may be required.
Email Notification. To subscribe to receive an email notification
when MSHA publishes rulemaking documents in the Federal Register, go to
https://public.govdelivery.com/accounts/USDOL/subscriber/new.
FOR FURTHER INFORMATION CONTACT: S. Aromie Noe, Director, Office of
Standards, Regulations, and Variances, MSHA, at:
[email protected] (email); 202-693-9440 (voice); or 202-693-9441
(facsimile). These are not toll-free numbers.
SUPPLEMENTARY INFORMATION:
MSHA will hold two public hearings to provide industry, labor, and
other interested parties with an opportunity to present oral
statements, written comments, and other information on the proposed
rule. The public hearings will begin at 9 a.m. local time and end after
the last presenter speaks on the following dates:
------------------------------------------------------------------------
Date Location Contact number
------------------------------------------------------------------------
August 3, 2023.............. Mine Safety and Health 202-693-9440
Administration, 201 12th
Street South, Room 7W202,
Arlington, VA 22202.
August 21, 2023............. Denver Federal Center, 202-693-9440
Building 25 Lecture Hall,
West 6th Avenue and
Kipling Street, Denver,
CO 80225.
------------------------------------------------------------------------
The public hearings will begin with an opening statement from MSHA,
followed by an opportunity for members of the public to make oral
presentations. Speakers and other attendees may present information to
MSHA for inclusion in the rulemaking record. The hearings will be
conducted in an informal manner. Formal rules of evidence or cross
examination will not apply.
A verbatim transcript of each of the proceedings will be prepared
and made a part of the rulemaking record. Copies of the transcripts
will be available to the public. MSHA will make the transcript of the
hearings available at https://www.regulations.gov and on MSHA's website
at https://arlweb.msha.gov/currentcomments.asp.
MSHA will accept post-hearing written comments and other
appropriate information for the record from any interested party,
including those not presenting oral statements, received by
[[Page 44853]]
midnight (Eastern Time) on August 28, 2023.
Pre-registration is not required to attend the hearings. Interested
parties may attend the hearings virtually or in person. Interested
parties who intend to present testimony at the hearings are asked to
register in advance on MSHA's website (https://www.msha.gov). Speakers
will be called in the order in which they signed up. Those who do not
register in advance will have an opportunity to speak after all those
who pre-registered have spoken. You may submit hearing testimony and
documentary evidence, identified by docket number (MSHA-2023-0001), by
any of the methods previously identified. Additional information on how
to access the public hearings will be posted when available at https://www.msha.gov/regulations/rulemaking.
The preamble to the proposed standard follows this outline:
I. Introduction
II. Request for Comments
III. Background
IV. Existing Standards and Implementation
V. Health Effects Summary
VI. Preliminary Risk Analysis Summary
VII. Section-by-Section Analysis
VIII. Technological Feasibility
IX. Summary of Preliminary Regulatory Impact Analysis and Regulatory
Alternatives
X. Initial Regulatory Flexibility Analysis
XI. Paperwork Reduction Act
XII. Other Regulatory Considerations
XIII. References Cited in the Preamble
XIV. Appendix
Acronyms and Abbreviations
COPD chronic obstructive pulmonary disease
ESRD end-stage renal disease
FEV forced expiratory volume
FVC forced vital capacity
L/min liter per minute
mg milligram
mg/m\3\ milligrams per cubic meter
mL milliliter
[micro]g/m\3\ micrograms per cubic meter
MNM metal and nonmetal
NMRD nonmalignant respiratory disease
PEL permissible exposure limit
PMF progressive massive fibrosis
RCMD respirable coal mine dust
REL recommended exposure limit
SiO2 silica
TB tuberculosis
TLV[supreg] Threshold Limit Value
TWA time-weighted average
I. Introduction
With the passage of the Federal Mine Safety and Health Act of 1977
(Mine Act), Congress declared that ``the first priority and concern of
all in the coal or other mining industry must be the health and safety
of its most precious resource--the miner[.]'' 30 U.S.C. 801(a). In
furtherance of that clear guiding principle, this proposed rule
promotes MSHA's mission and statutory mandate to prevent death,
illness, and injury from mining and promote safe and healthful
workplaces for U.S. miners. This proposal provides the public with the
opportunity to comment on the Agency's proposed uniform and streamlined
regulatory approach to lowering miners' exposure to respirable
crystalline silica and improving respiratory protection.
Exposure to silica dust causes adverse health effects, including
silicosis (acute silicosis, accelerated silicosis, simple chronic
silicosis, and progressive massive fibrosis (PMF)), nonmalignant
respiratory diseases (NMRD) (e.g., emphysema and chronic bronchitis),
lung cancer, and renal diseases. Each of these effects is chronic,
irreversible, and potentially disabling or fatal. Silica dust is
generated in most mining activities, including cutting, sanding,
drilling, crushing, grinding, sawing, scraping, jackhammering,
excavating, and hauling materials that contain silica, and is found in
all mines--underground and surface metal and nonmetal (MNM) and coal
mines. In a mining context, silica exposures may occur in respirable
dust together with exposures to other airborne contaminants and
combustion biproducts.
MSHA's existing standards, established in the early 1970s, help
protect miners from the most dangerous levels of exposure to respirable
crystalline silica. However, since their promulgation, scientific
understanding of respirable crystalline silica toxicity has advanced,
and the National Institute for Occupational Safety and Health (NIOSH)
has recommended a respirable crystalline silica exposure level of 50
[micro]g/m\3\ for workers. In 2016, the Occupational Safety and Health
Administration (OSHA) established a permissible exposure limit (PEL) of
50 [micro]g/m\3\ in many industry sectors that it regulates.
To provide miners with exposure limits consistent with workers in
other industries and NIOSH's recommendation, and to improve miners'
health, MSHA proposes to lower its existing exposure limits to 50
[micro]g/m\3\ for respirable crystalline silica in MNM and coal mines.
MSHA considered exposure limits below 50 [micro]g/m\3\. However, MSHA
believes, based on a review of the Agency's available silica sample
data, that an exposure limit of 25 [micro]g/m\3\ may not be achievable
for all mines. The proposed PEL would be expressed as a full-shift
exposure, calculated as an 8-hour time-weighted average (TWA).
Importantly, a uniform proposed PEL for all mines would make compliance
simpler--especially for coal mines by eliminating the existing
respirable dust standard when quartz is present.
To meet the requirements of the proposed PEL, mine operators would
have to implement engineering controls, followed by administrative
controls if supplementary protection is needed. Engineering controls,
which are most effective, are designed to remove or reduce the hazard
at the source and could include the installation of proper ventilation
systems, use of water sprays or wetting agents to suppress airborne
contaminants, installation of machine-mounted dust collectors to
capture respirable crystalline silica and other contaminants, and the
installation of control booths or environmental cabs to enclose
equipment operators. Administrative controls, which are often less
effective than engineering controls, are designed to change the way
miners work. One example would be ensuring that miners safely clean
dust off their work clothes so that they are not exposed to respirable
dust after their shift ends.
MSHA's proposed rule would further protect all miners by requiring
exposure sampling and corrective actions when miners' exposures exceed
the proposed PEL, as well as periodic sampling when miners' exposure
levels meet or exceed the proposed action level. The proposed rule also
includes medical surveillance requirements for MNM miners (medical
surveillance requirements already exist for coal miners). Proposed
medical examinations would include chest X-rays, spirometry, symptom
assessment, and occupational history and would be provided at no cost
to the miner.
Finally, the proposed rule would incorporate by reference an
updated respiratory protection standard, ASTM F3387-19, ``Standard
Practice for Respiratory Protection'' (ASTM F3387-19), for respirable
crystalline silica and all other regulated airborne contaminants. This
voluntary consensus standard represents up-to-date advancements in
respiratory protection technologies, practices, and techniques,
including proper selection, use, and maintenance of respirators. The
proposed incorporation of ASTM F3387-19 by reference would better
protect all miners from airborne hazards. However, respiratory
protection should only be relied upon as an exposure control measure in
limited situations and on a temporary basis, and to supplement
engineering controls, followed by administrative controls.
Taken together, all elements of the proposed rule are
technologically and economically feasible. MSHA's 2014
[[Page 44854]]
final rule, Lowering Miners' Exposure to Respirable Coal Mine Dust,
Including Continuous Personal Dust Monitors (Coal Dust Rule) improved
health protections for coal miners by lowering exposure limits to
respirable coal mine dust and establishing sampling requirements that
included the use of a Continuous Personal Dust Monitor (79 FR 24813,
May 1, 2014). Coal mine operators have generally achieved compliance
with the respirable dust standards primarily by implementing or
adjusting existing engineering controls. Coal mine operators' sampling
data and MSHA's compliance data show that operators have lowered coal
miners' exposures to respirable coal mine dust and to respirable
crystalline silica. Data show that average exposures in coal mines are
below the proposed PEL of 50 [mu]g/m\3\, and therefore, corrective
measures would often not be needed. Similarly, for MNM miners, MSHA
data also show that most exposures to respirable crystalline silica are
below the proposed PEL. However, at MNM and coal mines where elevated
exposures are found, operators will be able to reduce exposures to the
proposed PEL through some combination of properly maintaining existing
engineering controls, implementing new engineering controls, and
requiring safe work practices. Mines and laboratories will be able to
meet exposure monitoring requirements with existing validated and
widely used sampling and analytical methods. The proposed revision to
the respiratory protection standard is technologically feasible because
MSHA's existing respiratory protection requirements for selecting,
fitting, using, and maintaining respiratory protection include similar
requirements.
MSHA's Preliminary Risk Analysis (PRA) suggests that exposure
consistent with a lower proposed PEL of 50 [micro]g/m\3\ would deliver
many health benefits to miners who currently experience exposures above
the proposed PEL by reducing the likelihood of respirable crystalline
silica-related diseases. For those miners working only under the
proposed PEL, MSHA estimates that the proposed rule would result in a
total of 799 lifetime avoided deaths (63 in coal and 736 in MNM mines)
and 2,809 lifetime avoided morbidity cases (244 in coal and 2,566 in
MNM mines) over a 60-year period. MSHA expects full implementation and
compliance to reduce lifetime mortality risk due specifically to silica
exposures by 9.5 percent and to reduce silicosis morbidity risk by 41.9
percent. The latter statistic is particularly important to coal miners
given surveillance findings noted by the National Academies of
Sciences, Engineering, and Medicine that severe pneumoconiosis where
respirable crystalline silica is likely an important contributor is
presenting in relatively young miners, sometimes in their late 30's and
early 40's.
MSHA's economic analysis estimates that the proposed respirable
crystalline silica rule would cost an average of $56.1 million per year
in 2021 dollars at an undiscounted rate, $57.6 million at a 3 percent
discount rate, and $59.9 million at a 7 percent discount rate. Based on
the results of the Preliminary Regulatory Impact Analysis (PRIA), MSHA
estimates that the proposed rule's benefits would exceed its costs,
with or without discount rates. Monetized benefits are estimated from
avoidance of 410 deaths related to NMRD, silicosis, ESRD, and lung
cancer and 1,420 cases of silicosis associated with silica exposure
over the first 60-year period after the promulgation of the final rule.
The estimated annualized net benefit is approximately $212.8 million at
an undiscounted rate, $118.2 million at a 3 percent discount rate, and
$36.3 million at a 7 percent discount rate.
A rule is significant under Executive Order 12866 Section 3(f)(1),
as amended by E.O. 14094, if it is likely to result in ``an annual
effect on the economy of $200 million or more or . . . adversely affect
in a material way the economy, a sector of the economy, productivity,
competition, jobs, the environment, public health or safely, or State,
local, or tribal governments or communities.'' The Office of Management
and Budget has determined that the proposed rule is significant within
the meaning of E.O. 12866 Section 3(f)(1).
The proposed rule would strengthen MSHA's existing regulatory
framework. It would establish a uniform proposed PEL that provides all
MNM and coal miners with the same exposure limits for respirable
crystalline silica consistent with exposure limits that other U.S.
workers currently receive in non-mining industries. It would update the
existing respiratory protection standard to require mine operators to
provide miners with NIOSH-approved respiratory equipment that has been
fitted, selected, maintained, and used in accordance with recent
consensus standards. The proposed rule would also include requirements
for all MNM operators to provide medical surveillance in the form of a
medical examination regime similar to what coal miners already receive.
Cumulatively, the proposed provisions would lower miners' risk of
developing chronic, irreversible, disabling, and potentially fatal
health conditions, consistent with MSHA's mission and statutory mandate
to prevent occupational diseases and protect U.S. miners from suffering
material health impairments.
II. Request for Comments
MSHA requests comments on the proposed rule and all relevant
issues, including the review and conclusions of the health effects
discussion, preliminary risk analysis, feasibility analysis,
preliminary regulatory impact analysis and regulatory alternatives, and
preliminary regulatory flexibility analysis. While MSHA invites
comments on any aspect of its proposed rule and related documents, the
Agency particularly seeks information and data in response to questions
posed in this section and any other aspect of this proposed rule.
Instructions for submitting and viewing comments are provided under the
DATES heading. MSHA will consider all timely comments and may change
the proposed rule based on such comments.
MSHA requests that commenters organize their comments, to the
extent possible, around the following numbered questions. The Agency is
interested in receiving responses to the listed questions and any
information or data supporting the responses.
Health Effects
1. In the standalone, background document entitled ``Health Effects
of Respirable Crystalline Silica'' and as summarized in Section V.
Health Effects Summary of this preamble, MSHA has made a preliminary
determination that miners' exposure to respirable crystalline silica
presents a risk of material health impairment due to the risk of
developing silicosis, NMRD, lung cancer, and renal disease, based on
its extensive review of the health effects literature. MSHA requests
comments on this preliminary determination and its literature review,
which draws heavily from the review conducted by OSHA for its 2016
rulemaking. Are there additional adverse health effects that should be
included or more recent literature that offers a different perspective?
MSHA requests that commenters submit information, data, or additional
studies or their citations. Please be specific regarding the basis for
any recommendation to include additional adverse health effects.
Preliminary Risk Analysis
2. In the standalone, background document entitled ``Preliminary
Risk Analysis'' and as summarized in Section VI. Preliminary Risk
Analysis Summary
[[Page 44855]]
of this preamble, MSHA relied on risk models that OSHA used in support
of its 2016 respirable crystalline silica final rule. Does the context
of the MSHA rule suggest that the model would benefit from changes? If
so, please describe both the justification for those changes and the
likely impact on the final risk estimates. Are there additional studies
or sources of data that MSHA should consider? What is the rationale for
recommending the use of these additional studies or data?
3. MSHA's risk analysis of lung cancer mortality uses the exposure-
response model from Miller and MacCalman (2010) instead of Steenland et
al. (2001a), on which OSHA's risk assessment of lung cancer mortality
was based. MSHA uses Miller and MacCalman (2010) for several reasons.
First, it covers coal mining-specific cohort large enough (with 45,000
miners) to provide adequate statistical power to detect low levels of
risk, and it covers an extended follow-up period (1959-2006). Second,
the study provided data on cumulative exposure of cohort members and
adjusted for or addressed confounders such as smoking and exposure to
other carcinogens. Finally, it developed quantitative assessments of
exposure-response relationships using appropriate statistical models or
otherwise provided sufficient information that permitted MSHA to do so.
The Agency is requesting comment on MSHA's reliance on the Miller and
MacCalman (2010) study in assessing lung cancer mortality. Please
provide any other studies or information that MSHA should take into
account in determining the risk of lung cancer mortality among miners.
Technological Feasibility of the Proposed Rule
4. As discussed in Section VIII. Technological Feasibility of this
preamble, MSHA has preliminarily determined that it is technologically
feasible for mine operators to conduct air sampling and analysis and to
achieve the proposed PEL using commercially available samplers. MSHA
has also determined that these technologically feasible samplers are
widely available, and a number of commercial laboratories provide the
service of analyzing dust containing respirable crystalline silica. In
addition, MSHA has determined that technologically feasible engineering
controls are readily available, can control crystalline silica-
containing dust particles at the source, provide reliable and
consistent protection to all miners who would otherwise be exposed to
respirable dust, and can be monitored. MSHA has also determined that
administrative controls, used to supplement engineering controls, can
further reduce and maintain exposures at or below the proposed PEL.
Moreover, MSHA has preliminarily determined the proposed respiratory
protection practices for respirator use are technologically feasible
for mine operators to implement. MSHA requests comments on these
preliminary conclusions. What methods have you used that proved
effective in reducing miners' exposure to respirable crystalline silica
in mining operations? Please explain how those methods were effective
in reducing miners' exposures. To what extent do existing controls that
reduce exposure to other airborne hazards (e.g., coal dust, diesel
particulate matter) already reduce exposures to respirable crystalline
silica below the proposed PEL? To what extent does the proposed rule
including the PEL facilitate MSHA's workplace health and safety goals?
Please provide supporting information, such as quantitative data if
available.
5. MSHA has determined that the proposed medical surveillance
requirements for MNM are technologically feasible. MSHA requests
comments on this preliminary conclusion. Please provide supporting
information, such as quantitative data if available.
Preliminary Regulatory Impact Analysis and Regulatory Alternatives
6. In the standalone background document entitled ``Preliminary
Regulatory Impact Analysis'' and as summarized in Section IX. Summary
of Preliminary Regulatory Impact Analysis and Regulatory Alternatives
of this preamble, MSHA developed estimated costs of compliance with the
proposed rule and estimated monetized benefits associated with averted
cases of respirable crystalline silica-related diseases. MSHA requests
comments on the methodologies, baseline, assumptions, and estimates
presented in the Preliminary Regulatory Impact Analysis. Please provide
any data or quantitative information that may be useful in evaluating
the estimated costs and benefits associated with the proposed rule.
7. MSHA considered two regulatory alternatives in developing the
proposed rule discussed in Section IX. Summary of Preliminary
Regulatory Impact Analysis and Regulatory Alternatives. In the
regulatory alternatives presented, MSHA discussed alternatives to the
proposed PEL, action level, sampling requirements, and semi-annual
evaluations. MSHA requests comments on these and other regulatory
alternatives and information on any other alternatives that the Agency
should consider, including different average working-life spans and
different average shift lengths. Please provide supporting information
about how these alternatives could affect miners' protection from
respirable crystalline silica exposure and affect mine operators'
costs.
Initial Regulatory Flexibility Analysis
8. As summarized in Section X. Initial Regulatory Flexibility
Analysis of this preamble, MSHA examined the impact of the proposed
rule on small mines in accordance with the Regulatory Flexibility Act.
MSHA estimated that small-entity controllers would be expected to
incur, on average, additional regulatory costs equaling approximately
0.122 percent of their revenues (or $1,220 for every $1 million in
revenues). MSHA is interested in how the proposed rule would affect
small mines, including their ability to comply with the proposed
requirements. Please provide information and data that supports your
response. If you operate a small mine, please provide any projected
impacts of the proposal on your mine, including the specific rationale
supporting your projections.
Scope and Effective Date
9. MSHA is proposing a unified regulatory and enforcement framework
for controlling miners' exposures to respirable crystalline silica for
the mining industry. MSHA requests comments on this unified regulatory
and enforcement framework. MSHA requests the views and recommendations
of stakeholders regarding the scope of proposed part 60, which would
include all surface and underground MNM and coal mines. MSHA requests
comments on whether separate standards should be developed for the MNM
mining industry and the coal mining industry. Please provide supporting
information.
10. MSHA is proposing that the final rule would be effective 120
days after its publication in the Federal Register. This period is
intended to provide mine operators time to evaluate existing
engineering and administrative controls, update their respiratory
protection programs, and prepare to comply with other provisions of the
rule including recordkeeping requirements. Please provide your views on
the proposed effective date. In your response, please include the
rationale for your position.
[[Page 44856]]
Definitions
11. MSHA requests comments on the proposed action level.
Stakeholders should provide specific information and data in support of
or against a proposed action level. Stakeholders should include a
discussion of how the use of a proposed action level would impact their
mines, including the cost of monitoring respirable crystalline silica
above the proposed action level, and other relevant information. Please
provide supporting information.
12. MSHA requests comments on the proposed definition for
``objective data.'' Is it appropriate to allow mine operators to use
objective data instead of a second baseline sample? Please provide
supporting information.
Proposed Permissible Exposure Limit
13. MSHA is proposing a PEL for respirable crystalline silica of 50
[mu]g/m\3\ for a full-shift exposure, calculated as an 8-hour TWA for
MNM and coal miners. MSHA has made a preliminary determination that the
proposed PEL would reduce miners' risk of suffering material impairment
of health or functional capacity over their working lives. MSHA seeks
the views and recommendations of stakeholders on the proposed PEL. MSHA
solicits comments on the approach of having a standalone PEL and
whether to eliminate the reduced standard for total respirable dust
when quartz is present at coal mines. Please provide evidence to
support your response.
14. MSHA is proposing a PEL of 50 ug/m\3\ and an action level of 25
[mu]g/m\3\ for respirable crystalline silica exposure. Which proposed
requirements should be triggered by exposure at, above, or below the
proposed action level? Please provide supporting information.
Methods of Compliance
15. MSHA requests comments on the proposed prohibition against
rotation of miners as an administrative control. Please include a
discussion of the potential effectiveness of this non-exposure approach
and its impact on miners at specific mines. Please provide supporting
information.
16. MSHA requests comments on the proposed requirement that mine
operators must install, use, and maintain feasible engineering and
administrative controls to keep miners' exposures to respirable
crystalline silica below the proposed PEL. Please provide supporting
information.
Proposed Exposure Monitoring
17. MSHA requests comments and information from stakeholders
concerning the proposed approaches to monitoring exposures, and other
approaches to accurately monitor miner exposure to respirable
crystalline silica in MNM and coal mines. Please provide supporting
information and data.
18. MSHA proposes to require mine operators to collect a respirable
crystalline silica sample for a miner's regular full shift during
typical mining activities. Many potential sources of respirable
crystalline silica are present only when the mine is operating under
typical conditions. MSHA requests comments on this requirement and
whether to specify environmental conditions under which samples should
be taken to ensure that samples accurately reflect actual levels of
respirable crystalline silica exposure. In MSHA's experience, for
example, environmental conditions such as precipitation (e.g., rain or
snow) or wind could affect the actual levels of respirable crystalline
silica exposure at miners' normal or regular workplaces throughout
their typical workday. Please provide supporting information and data.
19. MSHA recognizes that some mining facilities operate seasonally
or intermittently and that cumulative exposures for miners at these
facilities may be lower than that of miners working at year-round
operations. MSHA requests comments on the exposure monitoring approach
under proposed Sec. 60.12, including the frequency of exposure
monitoring necessary to safeguard the health of miners at seasonal or
intermittent operations. Please provide supporting information and
data.
20. MSHA is proposing that each mine operator perform baseline
sampling within 180 days after the rule becomes effective to assess the
respirable crystalline silica exposure of each miner who is or may
reasonably be expected to be exposed to respirable crystalline silica.
MSHA requests comments on this proposed baseline sampling requirement.
MSHA also requests comment on the ability of service providers used by
mines such as industrial hygiene suppliers and consultants, and
accredited laboratories that conduct respirable crystalline silica
analysis, to meet the demand created by the baseline sampling
requirements within the proposed timeline. Please include alternative
approaches that might be equally protective of miners that should be
implemented for assessing a miner's initial exposure to respirable
crystalline silica.
21. MSHA is proposing a requirement that mine operators
qualitatively evaluate every 6 months any changes in production,
processes, engineering controls, personnel, administrative controls, or
other factors, beginning 18 months after the effective date. MSHA
requests comments on the timing of the proposed semi-annual evaluation
requirements, and in particular, whether miners would possibly be
exposed unnecessarily to respirable crystalline silica levels above the
PEL due to the gap between the effective date and the proposed
requirements. Please provide supporting information.
22. MSHA has determined that most occupations related to extraction
and processing would meet the ``reasonably be expected'' threshold for
baseline sampling. MSHA recognizes that some miners may work in areas
or perform tasks where exposure is not reasonably expected, if at all.
MSHA solicits comments on the assumption that most miners are exposed
to at least some level of respirable crystalline silica, and on the
proposed requirement that these miners should be subject to baseline
sampling. Please provide supporting information.
23. MSHA is proposing that mine operators would not be required to
conduct periodic sampling if the baseline sampling result, together
with another sampling result or objective data, as defined in proposed
Sec. 60.2, confirms miners' exposures are below the proposed action
level. MSHA seeks comments on this proposal. Please provide supporting
information and data.
24. MSHA is proposing that mine operators conduct periodic sampling
within 3 months where the most recent sampling indicates miner
exposures are at or above the proposed action level but at or below the
proposed PEL and continue to sample within 3 months of the previous
sampling until two consecutive samplings indicate that miner exposures
are below the action level. MSHA solicits comments on the proposed
frequency for periodic sampling, including whether the consecutive
samples should be at least 7 days apart. Please provide supporting
information and data.
25. MSHA is proposing that mine operators may discontinue periodic
sampling when two consecutive samples indicate that miner exposures are
below the proposed action level. MSHA requests comments on this
proposal. Please provide supporting information and data.
26. MSHA is proposing that mine operators conduct semi-annual
evaluations to evaluate whether any changes in production, processes,
engineering controls, personnel, administrative controls, or other
factors may reasonably be expected to result in
[[Page 44857]]
new or increased respirable crystalline silica exposures. Please
provide comments on this proposal, as well as alternative approaches
that would be appropriate for evaluating any potential new or increased
respirable crystalline silica exposures. Please provide supporting
information and data.
27. MSHA is proposing that miners' exposures are measured using
personal breathing-zone air samples for MNM operations and occupational
environmental samples collected in accordance with Sec. Sec.
70.201(c), 71.201(b), or 90.201(b) for coal operations. MSHA requests
comments on this proposal. Please provide supporting information and
data.
28. MSHA is proposing the use of representative sampling. Where
several miners perform the same task on the same shift and in the same
work area, the mine operator may sample a representative fraction of
miners to meet the proposed exposure monitoring requirements. MSHA
seeks comments on the use of representative sampling. Please provide
supporting information and data.
29. MSHA is proposing that mine operators use laboratories
accredited to ISO/IEC 17025 ``General requirements for the competence
of testing and calibration laboratories,'' where the accreditation has
been issued by a body that is compliant with ISO/IEC 17011 ``Conformity
assessment--requirements for accreditation bodies accrediting
conformity assessment bodies.'' MSHA solicits comments on this
proposal. Are there additional requirements that should be incorporated
into this proposal to ensure accurate sample analysis methods? Please
provide supporting information and data.
30. MSHA seeks comments on the proposal that mine operators ensure
that laboratories evaluate all respirable crystalline silica samples
using respirable crystalline silica analytical methods specified by
MSHA, NIOSH, or OSHA. Are there additional requirements that should be
incorporated into this proposal to ensure accurate sample analysis?
Please provide supporting information and data.
31. MSHA seeks comments and information on mine operator and
stakeholder experience using NIOSH's rapid field-based quartz
monitoring (RQM) monitors for determining miners' exposures to
respirable crystalline silica. Please provide any information and data.
Proposed Medical Surveillance for Metal and Nonmetal Miners
32. MSHA is proposing to require medical surveillance for MNM
miners. Medical surveillance is already required for coal miners under
30 CFR 72.100 and has played an important role in tracking the burden
of pneumoconiosis in coal miners but is not currently required for MNM
miners. MSHA's proposal would require MNM mine operators to provide
each miner new to the mining industry with an initial medical
examination and a follow-up examination no later than 3 years after the
initial examination, at no cost to the miner. It would also require MNM
mine operators to provide examinations for all miners at least every 5
years, which would be voluntary for miners. Is there an alternative
strategy or schedule, such as voluntary initial or follow-up
examinations, tying the medical surveillance requirement to miners
reasonably expected to be exposed to any level of silica or to the
action level that would be more appropriate for new MNM miners? Should
the rule make each 5-year examination mandatory? Should the 5-year
examination be mandatory for coal mine operators as well? Please
provide data or cite references to support your position.
33. MSHA's proposed medical surveillance requirements for MNM
miners do not include some requirements that are in MSHA's existing
medical surveillance requirements for coal mine operators in 30 CFR
72.100. For example, Sec. 72.100 requires coal mine operators to use
NIOSH-approved facilities for medical examinations. Should MNM
operators be required to use NIOSH-approved facilities for medical
examinations? Coal mine operators also are required to submit for
approval to NIOSH a plan for providing miners with the examinations
specified. This is because NIOSH administers medical surveillance for
coal miners with requirements for coal operators, but not MNM
operators, in NIOSH standards (42 CFR part 37). Should the plan
requirements be extended to MNM operators? However, the proposed
requirements also include some requirements for MNM operators that are
not included for coal operators. For example, the proposed provisions
require operators of MNM mines to provide MNM miners with periodic
medical examinations performed by physicians or other licensed health
care professionals (PLHCP) or specialists including a history and
physical examination focused on the respiratory system, a chest X-ray,
and a spirometry test. The proposed rule also requires a written
medical opinion be provided by the PLHCP or specialist to the mine
operator regarding the miner's ability to wear a respirator. MSHA seeks
comment on the differences between the medical surveillance
requirements for MNM operators in this proposed rule and the existing
medical surveillance requirements for coal mine operators in Sec.
72.100. MSHA also seeks comment on how best to collect health
surveillance data from PLHCPs and specialists to track MNM miners'
health, for example how to know when pneumoconiosis cases occur. MSHA
seeks comments on alternative approaches to scheduling periodic medical
surveillance. MSHA proposes to require operators to keep medical
surveillance information for the duration of a miner's employment plus
6 months. The Agency seeks comments on this proposed requirement and on
any alternative recordkeeping schedules that would be appropriate.
Please provide supporting information.
34. MSHA's proposed medical surveillance requirements for MNM
miners would require operators of MNM mines to provide miners with
periodic medical examinations performed by PLHCP or specialists,
including a history and physical examination focused on the respiratory
system, a chest X-ray, and a spirometry test. MSHA seeks comment on
whether use of any new diagnostic technology (e.g., high-resolution
computed tomography) for the purposes of medical surveillance should be
used.
35. MSHA's proposed medical surveillance requirements would require
that the MNM mine operator provide a mandatory follow-up examination to
the miner no later than 3 years after the miner's initial medical
examination. If a miner's 3-year follow-up examination shows evidence
of a respirable crystalline silica-related disease or decreased lung
function, the operator would be required to provide the miner with
another mandatory follow-up examination with a specialist within 2
years. For examinations that show evidence of disease or decreased lung
function, MSHA seeks comment on how, and to whom, test results should
be communicated.
36. MSHA requests comments as to whether the proposed provisions
should include a medical removal option for MNM miners who have
developed evidence of silica-related disease that is equivalent to the
transfer rights and exposure monitoring provided to coal miners in 30
CFR part 90 (part 90). Under part 90, any coal miner who has evidence
of the development of pneumoconiosis based on a chest X-ray or other
medical examinations has the
[[Page 44858]]
option to work in an area of the mine where the average concentration
of respirable dust in the mine atmosphere during each shift to which
that miner is exposed is continuously maintained at or below the
applicable standard. Under part 90, coal miners are entitled to
retention of pay rate, future actual wage increases, and future work
assignment, shift and respirable dust protection. MSHA seeks comment on
whether this medical removal option should be provided to MNM miners.
What would be the economic impact of providing MNM miners a medical
removal option? Please provide supporting information and data.
Proposed Respiratory Protection Standard
37. MSHA requests comments concerning the temporary, non-routine
use of respirators and whether there are other instances or occupations
in which the Agency should allow the use of respirators as a
supplemental control. Please discuss any impacts on particular mines
and mining conditions and the cost of air-purifying respirators, if
applicable. MSHA also solicits comments on the proposed requirement
that affected miners wear respiratory protection to maintain protection
during temporary and non-routine use of respirators. Please provide
supporting information.
38. MSHA is proposing to incorporate by reference ASTM F3387-19,
published in 2019. Whenever respiratory protective equipment is needed,
mine operators would be required to follow practices for program
administration, standard operating procedures, medical evaluations,
respirator selection, training, fit testing, and maintenance,
inspection, and storage in accordance with the requirements of ASTM
F3387-19. Beyond these elements, MSHA is proposing to provide operators
the flexibility to select the elements in ASTM F3387-19 that are
applicable to their practices of respirator use at their mines. Should
mine operators have the flexibility to choose the ASTM F3387-19
elements that are appropriate for their mine-specific hazards because
the need for respirators may vary due to the variability of mining
processes, activities, airborne hazards, and commodities mined? What,
specifically, do you think should factor into the determination of what
is applicable? MSHA seeks comments on its proposed approach and the
impact it would have on mine operators and on miners' life and health.
39. ASTM F3387-19 identifies a variety of respiratory protection
practice elements. MSHA proposes to require certain minimally
acceptable program elements: program administration; standard operating
procedures; medical evaluations; respirator selection; training; fit
testing; and maintenance, inspection, and storage. Please comment on
whether these are the appropriate elements to require, or if there are
any other elements of ASTM F3387-19 that should be minimally included
in any respiratory protection program. MSHA also welcomes comments on
whether it would be appropriate to require the standard in its
entirety. Please identify those elements that would ensure that
approved respirators are selected, fitted, used, cleaned, and
maintained so that the life and health of miners are safeguarded. MSHA
also seeks data and information on the impact these changes would have
on mine operators, especially smaller operators. What would be the
economic impact if all or parts of ASTM F3387-19 were required
respirator program elements? Please be specific with your response and
provide details on respirator use at your mine to include information
and data on mining processes and environmental conditions; level of
exposures to airborne contaminants; frequency and duration of
exposures; type and amount of work or physical labor, including
frequency and duration; and medical evaluation on respirator use, if
applicable.
Recordkeeping Requirements
40. MSHA is proposing to require recordkeeping for records of
evaluations, records of samplings, records of corrective actions, and
written determination records received from a PLHCP. The proposed
rule's recordkeeping requirements are discussed in the Section-by-
Section Analysis section of this Preamble. MSHA seeks comment on the
utility of these recordkeeping requirements as well as the costs of
making and maintaining these records. Please provide supporting
information.
Training Requirements
41. MSHA requests the views and recommendations of stakeholders
regarding whether training requirements for miners should be included
in proposed part 60. Please provide supporting information and data.
Conforming Changes
42. MSHA requests comments on the proposed conforming changes to
remove the reduced coal dust standard from 30 CFR and the potential
impact on coal mines and miners and on whether to retain the reduced
standard for part 90 miners. Please provide supporting information.
43. MSHA is not proposing to adopt a similar approach as the OSHA
Table 1 for the construction industry, where MSHA would prescribe
specific exposure control methods for task-based work practices when
working with materials containing respirable crystalline silica. See 29
CFR 1926.1153(c)(1). MSHA requests comments on specific tasks and
exposure control methods appropriate for a Table 1-approach for the
mining industry that also would adequately protect miners from risk of
exposure to respirable crystalline silica. Please provide specific
rationale and supporting information, including data on how such an
approach would be implemented.
III. Background
The purpose of this proposed rule is to reduce miners' risk of
developing occupational lung disease and other diseases caused by
exposure to respirable crystalline silica and to better protect all
miners from occupational exposure to airborne hazards. In promulgating
mandatory standards dealing with toxic materials or harmful physical
agents, MSHA is required to ``set standards which most adequately
assure on the basis of the best available evidence that no miner will
suffer material impairment of health or functional capacity . . .'' 30
U.S.C. 811(a)(6)(A).
A. Statutory Authority
The statutory authority for this proposal is provided by the Mine
Act under sections 101(a), 103(h), and 508. 30 U.S.C. 811(a), 813(h),
and 957. MSHA implements the provisions of the Mine Act to prevent
death, illness, and injury from mining and promote safe and healthful
workplaces for miners. The Mine Act requires the Secretary of Labor
(Secretary) to develop and promulgate improved mandatory health or
safety standards to prevent hazardous and unhealthy conditions and
protect the health and safety of the nation's miners. 30 U.S.C. 811(a).
Congress passed the Mine Act to address these dangers, finding ``an
urgent need to provide more effective means and measures for improving
the working conditions and practices in the Nation's coal or other
mines in order to prevent death and serious physical harm, and in order
to prevent occupational diseases originating in such mines.'' 30 U.S.C.
801(c). Congress concluded that ``the existence of unsafe and
unhealthful conditions and practices in the Nation's coal or other
[[Page 44859]]
mines is a serious impediment to the future growth of the coal or other
mining industry and cannot be tolerated.'' 30 U.S.C. 801(d).
Accordingly, ``the Mine Act evinces a clear bias in favor of miner
health and safety.'' Nat'l Mining Ass'n v. Sec'y, U.S. Dep't of Lab.,
812 F.3d 843, 866 (11th Cir. 2016).
Section 101(a) of the Mine Act gives the Secretary the authority to
develop, promulgate, and revise, as appropriate, mandatory health
standards to address toxic materials or harmful physical agents. Under
Section 101(a), standards must protect lives and prevent injuries in
mines and be ``improved'' over any standard that it replaces or
revises. Moreover, ``the Mine Act does not contain the `significant
risk' threshold requirement . . . from the OSH Act.'' Nat'l Mining
Ass'n v. United Steel Workers, 985 F.3d 1309, 1319 (11th Cir. 2021);
see also Nat'l Min. Ass'n v. Mine Safety & Health Admin., 116 F.3d 520,
527-28 (D.C. Cir. 1997) (contrasting the OSH Act at 29 U.S.C. 652 with
the Mine Act at 30 U.S.C. 811(a) and noting that ``[a]rguably, this
language does not mandate the same risk-finding requirement as OSHA''
and holding that ``[a]t most, . . . . [MSHA] was required to identify a
significant risk associated with having no oxygen standard at all''
(emphasis in original)).
The Secretary must set standards to assure, based on the best
available evidence, that no miners will suffer material impairment of
health or functional capacity from exposure to toxic materials or
harmful physical agents over their working lives. 30 U.S.C.
811(a)(6)(A). In developing standards that attain the ``highest degree
of health and safety protection for the miner,'' the Mine Act requires
that the Secretary consider the latest available scientific data in the
field, the feasibility of the standards, and experience gained under
the Mine Act and other health and safety laws. Id. However, MSHA's
``duty to use the best evidence and to consider feasibility . . .
cannot be wielded as counterweight to MSHA's overarching role to
protect the life and health of workers in the mining industry.'' Nat'l
Mining Ass'n, 812 F.3d at 866. Instead, ``when MSHA itself weighs the
evidence before it, it does so in light of its congressional mandate.''
Id.
Section 103(h) of the Mine Act gives the Secretary the authority to
promulgate standards involving recordkeeping and reporting. 30 U.S.C.
813(h). In general, section 103(h) requires that every mine operator
establish and maintain records, make reports, and provide this
information, if required by the Secretary. Id. Also, section 508 of the
Mine Act gives the Secretary the authority to issue regulations to
carry out any provision of the Mine Act. 30 U.S.C. 957.
MSHA's proposal to lower the exposure limits for respirable
crystalline silica and adopt an integrated monitoring approach across
all mining sectors and to update the existing respiratory protection
requirements would fulfill Congress' direction by preventing miners
from suffering material impairment of health or functional capacity
caused by exposure to respirable crystalline silica and other airborne
contaminants.
B. Respirable Crystalline Silica Hazard and Mining
Silica is a common component of rock composed of silicon and oxygen
(chemical formula SiO2), existing in amorphous and
crystalline states. Silica in the crystalline state is the focus of
this rulemaking. Respirable crystalline silica consists of small
particles of crystalline silica that can be inhaled and reach the
alveolar region of the lungs, where they can accumulate and cause
disease. In crystalline silica, the silicon and oxygen atoms are
arranged in a three-dimensional repeating pattern. The crystallization
pattern varies depending on the circumstances of crystallization,
resulting in a polymorphic state--several different structures with the
same chemical composition. The most common form of crystalline silica
found in nature is quartz, but cristobalite and tridymite may also be
found in limited circumstances. Quartz accounts for the overwhelming
majority of naturally occurring crystalline silica. In fact, quartz
accounts for almost 12 percent of the earth's crust by volume. All
soils contain at least trace amounts of quartz and it is present in
varying amounts in almost every type of mineral. Quartz is also
abundant in most rock types, including granites, sandstones, and shale.
Moreover, quartz is commonly found in limestone formations, although
limestone itself does not contain quartz. Because of its abundance,
crystalline silica in the form of quartz is present in nearly all
mining operations.
Cristobalite and tridymite are formed at very high temperatures and
are associated with volcanic activity. Naturally occurring cristobalite
and tridymite are rare, but they can be found in volcanic ash and in a
relatively small number of rock types limited to specific geographic
regions. Although rare, exposure to cristobalite occurs when volcanic
deposits are mined. In addition, when other materials are mined, miners
can potentially be exposed to cristobalite during certain processing
steps (e.g., heating silica-containing materials) and contact with
refractory materials (e.g., replacing fire bricks in mine processing
facility furnaces). Tridymite is rarely found in nature and miner
exposure to tridymite is much more infrequent.
Most mining activities generate silica dust because silica is often
contained in the ore being mined or in the overburden (i.e., the soil
and surface material surrounding the commodity being mined). Such
activities include, but are not limited to, cutting, sanding, drilling,
crushing, grinding, sawing, scraping, jackhammering, excavating, and
hauling materials that contain silica. These activities can generate
respirable crystalline silica and may therefore lead to miner exposure.
Inhaled small particles of silica dust can be deposited throughout
the lungs. A large number of crystalline silica particles can reach and
remain in the deep lung (i.e., alveolar region), although some small
particles are cleared from the lungs. Because respirable crystalline
silica particles are not water-soluble and do not undergo metabolism
into less toxic compounds, those particles remaining in the lungs for
prolonged periods result in a variety of cellular responses that may
lead to pulmonary disease. The respirable crystalline silica particles
that are cleared from the lungs can be distributed to lymph nodes,
blood, liver, spleen, and kidneys, potentially accumulating in those
other organ systems and causing renal disease and other adverse health
effects.
In the U.S. in 2021, a total of 12,162 mines produced a variety of
commodities. As shown in Table III-1, of those 12,162 total mines,
11,231 mines were MNM mines and 931 mines were coal mines. MNM mines
can be broadly divided into five commodity groups: metal, nonmetal,
stone, crushed limestone, and sand and gravel. These broad categories
encompass approximately 98 different commodities.\1\ Table III-1 shows
that a majority of MNM mines produce sand and gravel, while the largest
number of MNM miners work at metal mines (not
[[Page 44860]]
including MNM contract workers (i.e., independent contractors and
employees of independent contractors who are engaged in mining
operations)).
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\1\ Commodities such as sand, gravel, silica, and/or stone for
example are used in road building, concrete construction,
manufacture of glass and ceramics, molds for metal castings in
foundries, abrasive blasting operations, plastics, rubber, paint,
soaps, scouring cleansers, filters, hydraulic fracturing, and
various architectural applications. Some commodities naturally
contain high levels of crystalline silica, such as high-quartz
industrial and construction sands and granite dimension stone and
gravel (both produced for the construction industry).
[GRAPHIC] [TIFF OMITTED] TP13JY23.000
The 931 coal mines--underground and surface--produce bituminous,
subbituminous, anthracite, and lignite coal. Coal mining activities
generate mixed coal mine dust that contains respirable silicates such
as kaolinite, oxides such as quartz, as well as other components (IARC,
1997). These activities include the general mining activities
previously mentioned (e.g., cutting, sanding, drilling, crushing, and
hauling materials), as well as roof bolter operations, continuous
mining machine operations, longwall mining, and other activities. Table
III-1 shows that there are more surface coal mines than underground
coal mines, but more miners are working in underground coal mines than
surface coal mines (not including coal contract workers).
IV. Existing Standards and Implementation
MSHA has maintained health standards to protect MNM and coal miners
from excessive exposure to respirable crystalline silica for decades.
MSHA's existing standards, established in the early 1970s, limit
miners' exposures to respirable crystalline silica. These standards
require mine operators to monitor occupational exposures to respirable
crystalline silica and to use engineering controls as the primary means
of suppressing, diluting, or diverting dust generated by mining
activities. They also require mine operators to provide respiratory
protection in limited situations and on a temporary basis. The existing
standards for MNM and coal mines differ in some respects, including
exposure limits and monitoring. This section describes MSHA's existing
standards for respirable crystalline silica and presents respirable
crystalline silica sampling data to show how MNM and coal mine
operators have complied with them in recent years.
A. Existing Standards--Metal and Nonmetal Mines
MSHA's existing standards for exposure to airborne contaminants,
including respirable crystalline silica, in MNM mines are found in 30
CFR part 56, subpart D (Air Quality and Physical Agents), and 30 CFR
part 57, subpart D (Air Quality, Radiation, Physical Agents, and Diesel
Particulate Matter). These standards include PELs for airborne
contaminants (Sec. Sec. 56.5001 and 57.5001), exposure monitoring
(Sec. Sec. 56.5002 and 57.5002), and control of exposure to airborne
contaminants (Sec. Sec. 56.5005 and 57.5005).
Permissible Exposure Limits. The existing PELs for the three
polymorphs of respirable crystalline silica are based on the
TLVs[supreg] Threshold Limit Values for Chemical Substances in Workroom
Air Adopted by the American Conference of Governmental Industrial
Hygienists (ACGIH) for 1973, incorporated by reference in 30 CFR
56.5001 and 57.5001 (ACGIH, 1974). The 1973 TLV[supreg] establishes
limits for respirable dust containing 1 percent quartz or greater and
is calculated in milligrams per cubic meter of air (mg/m\3\) for each
respirable dust sample. The TLV[supreg] for quartz is calculated by
dividing the percent of respirable quartz plus 2, into the number 10.
The TLV[supreg] for cristobalite and the TLV[supreg] for tridymite,
respectively, are calculated by multiplying the same mass formula by
one-half using the percentages of either cristobalite or tridymite
found in the sample. Thus, the resulting TLVs[supreg] for respirable
dust containing 1 percent respirable crystalline silica or greater are
designed to limit exposures to less than 0.1 mg/m\3\ or 100 [micro]g/
m\3\ for quartz, to less than 0.05 mg/m\3\ or 50 [micro]g/m\3\ for
cristobalite, and to less than 0.05 mg/m\3\ or 50 [micro]g/m\3\ for
tridymite. Throughout the remainder of this preamble, the
concentrations of respirable dust and respirable crystalline silica are
expressed in [micro]g/m\3\.
[[Page 44861]]
Exposure Monitoring. Under 30 CFR 56.5002 and 57.5002, MNM mine
operators must conduct respirable dust ``surveys . . . as frequently as
necessary to determine the adequacy of control measures.'' Mine
operators can satisfy the survey requirement through various
activities, such as respirable dust sampling and analysis, walk-through
inspections, wipe sampling, examining dust control system and
ventilation system maintenance, and reviewing information obtained from
injury, illness, and accident reports.
MSHA encourages MNM mine operators to conduct sampling for airborne
contaminants to ensure a healthy and safe work environment for miners
because sampling provides more accurate information about miners'
exposures to harmful airborne contaminants and the effectiveness of
existing controls in reducing such exposures. When a mine operator's
respirable dust survey indicates that miners have been overexposed to
any airborne contaminant, including respirable crystalline silica, the
operator is expected to adjust its control measures (e.g., exhaust
ventilation) to reduce or eliminate the identified hazard. After doing
so, the mine operator is expected to conduct additional surveys to
determine whether these efforts were successful. Re-surveying should be
done as frequently as necessary to ensure that the implemented control
measures remain adequate. MSHA's determination of whether a mine
operator has surveyed frequently enough is based on several factors,
including whether sampling results comply with the permissible exposure
limit, whether there have been changes in the mining operation or
process, and whether controls such as local exhaust ventilation systems
need routine or special maintenance.
Exposure Controls. MSHA's existing standards for controlling a
miner's exposure to harmful airborne contaminants (Sec. Sec. 56.5005
and 57.5005) require, if feasible, prevention of contamination, removal
by exhaust ventilation, or dilution with uncontaminated air. The use of
respiratory protective equipment is also allowed under specified
circumstances such as when engineering controls are being developed or
are not feasible. When respiratory protective equipment is used, the
operator must have a respiratory protection program consistent with the
requirements of American National Standards Practices for Respiratory
Protection ANSI Z88.2-1969.
Consistent with widely accepted industrial hygiene principles and
NIOSH's recommendations, MSHA requires the use of engineering controls,
supplemented by administrative controls, in its enforcement for the
control of occupational exposure to respirable crystalline silica and
other airborne contaminants (NIOSH, 1974). Engineering controls
designed to remove or reduce the hazard at the source are the most
effective. Examples of engineering controls include the installation of
proper ventilation systems, use of water sprays or wetting agents to
suppress airborne contaminants, installation of machine-mounted dust
collectors to capture respirable crystalline silica and other
contaminants, and the installation of control booths or environmental
cabs to enclose equipment operators.
Although considered a supplementary or secondary measure to
engineering controls, mine operators may use administrative controls to
further reduce miners' exposures to respirable crystalline silica and
other airborne contaminants. In applying administrative controls, mine
operators can direct miners to perform certain activities in specific
manners. For instance, as an administrative control, operators can
specify adequate housekeeping procedures for miners to clean spills or
handle contaminated clothing which could reduce occupational exposure
to airborne contaminants, including respirable crystalline silica.
In addition, respiratory protective equipment can be used in
controlling miners' exposures to airborne contaminants, including
respirable crystalline silica, on a temporary basis or under non-
routine, limited conditions. The use of respiratory protection is,
however, considered to be a supplement, not an alternative to any
engineering or administrative control, in reducing or eliminating a
miner's exposure to airborne contaminants including respirable
crystalline silica.
Under the existing standards in Sec. Sec. 56.5005 and 57.5005, in
circumstances where engineering controls are not yet developed or where
it is necessary for miners to enter hazardous atmospheres to establish
controls or to perform non-routine maintenance or investigation, a
miner using appropriate respiratory protection ``may work for
reasonable periods of time'' in concentrations of airborne contaminants
which exceed exposure limits. Respirators approved by NIOSH and
suitable for their intended purpose must be provided by mine operators
at no cost to the miner and must be used by miners to protect
themselves against the health and safety hazards of airborne
contaminants. Whenever respiratory protection is used, MNM mine
operators are required to have a respirator program consistent with the
requirements specified in ANSI Z88.2-1969.
B. Existing Standards--Coal Mines
Under existing standards, there is no separate standard for
respirable crystalline silica for coal mines. MSHA's existing standards
for exposure to respirable quartz in coal mines, found in 30 CFR 70.101
and 71.101, establish a respirable dust standard when quartz is present
for underground and surface coal mines, respectively. Under 30 CFR part
90 (Mandatory Health Standards--Coal Miners Who Have Evidence of the
Development of Pneumoconiosis), Sec. 90.101 also sets the respirable
dust standard when quartz is present for coal miners. Under these
respirable dust standards, coal miners' exposures to respirable quartz
are indirectly regulated through reductions in the overall respirable
dust standard.
Under its existing respirable coal mine dust standards, MSHA
defines quartz as crystalline silicon dioxide (SiO2), which
includes not only quartz but also two other polymorphs, cristobalite
and tridymite.\2\ Therefore, quartz and respirable crystalline silica
are used interchangeably in the discussions of MSHA's existing
standards for controlling exposures to respirable crystalline silica in
coal mines.
---------------------------------------------------------------------------
\2\ Quartz is defined in 30 CFR 70.2, 71.2, and 90.2 as
crystalline silicon dioxide (SiO2) not chemically
combined with other substances and having a distinctive physical
structure. Crystalline silicon dioxide is most commonly found in
nature as quartz but sometimes occurs as cristobalite or, rarely, as
tridymite. Quartz accounts for the overwhelming majority of
naturally occurring crystalline silica and is present in varying
amounts in almost every type of mineral.
---------------------------------------------------------------------------
Exposure Limits. The exposure limit for respirable crystalline
silica during a coal miner's shift is 100 [micro]g/m\3\, reported as an
equivalent concentration as measured by the Mining Research
Establishment (MRE) instrument. This equivalent concentration of
respirable crystalline silica must not be exceeded during the miner's
entire shift, regardless of duration. When the equivalent concentration
of respirable quartz exceeds 100 [micro]g/m\3\, under Sec. Sec.
70.101, 71.101, and 90.101, MSHA imposes a reduced respirable dust
standard designed to ensure that respirable quartz will not exceed 100
[micro]g/m\3\. The applicable dust standard, when the equivalent
concentration of respirable crystalline silica exceeds 100 [micro]g/
m\3\, is computed by dividing the percent of quartz into the number 10.
[[Page 44862]]
The result of this calculation becomes the exposure limit for
respirable coal mine dust (RCMD), for the sections of the mine
represented by the sample. Various sections within a mine may have
different reduced RCMD exposure limits. Therefore, when a respirable
dust sample collected by MSHA indicates that the average concentration
of respirable quartz dust exceeds the exposure limit, the mine operator
is required to comply with the applicable dust standard. By reducing
the amount of respirable dust to which miners are exposed during their
shifts, the miners' exposures to respirable crystalline silica are
reduced to a level at or below the exposure limit of 100 [micro]g/m\3\.
Exposure Monitoring. Under Sec. Sec. 70.208, 70.209, 71.206, and
90.207, coal mine operators are required to sample for respirable dust
on a quarterly basis for specified occupations and work areas. The
occupations and work areas specified in the existing coal standards are
the occupations and work areas at a coal mine that are expected to have
the highest concentrations of respirable dust--typically in locations
where respirable dust is generated. In addition, respirable dust
sampling must be representative of respirable dust exposures during a
normal production shift. Also, sampling must occur while miners are
performing routine, day-to-day activities. Part 90 miners must be
sampled for the air they breathe while performing their normal work
duties, from the start of their work day to the end of their work day,
in their normal work locations.\3\
---------------------------------------------------------------------------
\3\ A ``Part 90 miner'' is defined in 30 CFR 90.3 as a miner
employed at a coal mine who shows evidence of having contracted
pneumoconiosis based on a chest X-ray or based on other medical
examinations, and who is afforded the option to work in an area of a
mine where the average concentration of respirable dust in the mine
atmosphere during each shift to which that miner is exposed is
continuously maintained at or below the applicable standard.
---------------------------------------------------------------------------
Exposure Controls. Under Sec. Sec. 70.208, 70.209, 71.206, and
90.207, coal mine operators are required to use engineering or
environmental controls as the primary means of complying with the
respirable dust standards. Similar to the MNM standards, engineering
and environmental controls include the use of dust collectors, water
sprays, and ventilation controls. For many underground coal mines,
providing adequate ventilation is the primary engineering control for
respirable dust, ensuring that dust concentrations are continuously
diluted with fresh air and exhausted away from miners.
When a respirable dust sample exceeds the exposure limit of 100
[micro]g/m\3\ for respirable quartz, the operator must reduce the
average concentration of RCMD to a level designed to maintain the
quartz level at or below 100 [micro]g/m\3\. If operators exceed the
reduced RCMD standard, they are required to take corrective action to
reduce exposure and comply with the reduced standard. Corrective
actions that lower respirable coal mine dust, thus lowering respirable
quartz exposures, are selected after evaluating the cause or causes of
the overexposure. Corrective actions can include increasing air flow,
improving ventilation controls, repairing and maintaining existing dust
suppression controls, adding water sprays or other controls, cleaning
dust filters or collectors more frequently, or repositioning the miner
away from the dust source.
When taking corrective actions to reduce the exposure to respirable
dust, coal mine operators must make approved respiratory equipment
available to miners under Sec. Sec. 70.208 and 71.206. Whenever
respiratory protection is used, Sec. 72.700 requires coal mine
operators to comply with requirements specified in ANSI Z88.2-1969.
C. MSHA Inspection and Respirable Dust Sampling
MSHA collects respirable dust samples at mines and analyzes them
for respirable crystalline silica to determine whether the respirable
crystalline silica exposure limits are met and whether exposure
controls are adequate. This section describes the respirable dust
samples collected at MNM and coal mines in recent years and presents
the results of the sample data analyses.
1. Respirable Dust Sample Collection
This subsection offers a brief description of how MSHA samples for
respirable crystalline silica under the existing standards. Upon their
arrival at mines, MSHA inspectors determine which areas of the mine and
which miners to select for respirable dust sampling. At MNM mines, the
MSHA inspector often determines sampling locations based on sample
results from previous inspections and on the inspector's onsite
observations of work practices and work areas. At coal mines, the MSHA
inspector conducts sampling among the occupations or from the work
areas that are specified for operator sampling under 30 CFR parts 70,
71, and 90. Generally speaking, MSHA inspectors collect respirable dust
samples from the common occupations during typical and normal
activities at the mine and from the positions that are commonly known
to have the highest concentration of respirable dust.
After identifying which miners and which areas at the mine will be
sampled for respirable dust, MSHA inspectors place gravimetric samplers
on the selected miners or at the selected locations. Gravimetric
samplers consist of a portable air-sampling pump connected to a
particle-size separator (i.e., cyclone) and collection medium (i.e.,
filter). MSHA inspectors use Dorr-Oliver 10-mm nylon cyclones operated
at a 1.7 liters per minute (L/min) flow rate for MNM mine sampling and
at a 2.0 L/min flow rate (reported as MRE-equivalent concentrations)
for coal mine sampling.\4\ For the entire duration of the work shift,
the gravimetric sampler captures air from the breathing zone of each
selected miner or occupation and from each selected work area.
---------------------------------------------------------------------------
\4\ This type of sampling equipment was developed to separate
the airborne particles by size in a manner similar to the size-
selective deposition and retention characteristics of the human
respiratory system. It is important to note that size-selective
sampling does not measure the deposition of respirable particles in
the lung. Rather, it provides a measure of the particulate mass
available for deposition to the deep lung during breathing (Raabe
and Stuart, 1999).
---------------------------------------------------------------------------
MSHA inspectors use the full-shift sampling approach. When miners
work longer than an 8-hour shift, which is common, those miners are
sampled continuously throughout the extended work shifts. Full-shift
sampling is used to minimize errors associated with fluctuations in
airborne contaminant concentrations during the miners' work shifts and
to avoid any speculation about the miners' exposures during unsampled
periods of the work shift. Once sampling is completed, the inspectors
send the cassettes containing the full-shift respirable dust samples to
the MSHA Laboratory for analysis.
[[Page 44863]]
2. Respirable Dust Sample Analysis
The MSHA Laboratory analyzes inspectors' respirable dust samples,
following its standard operating procedures (SOPs) summarized below.\5\
Any samples that are broken, torn, or visibly wet are voided and
removed before analysis. Once weighing of the samples is completed,
samples are again screened based on mass gain and examined for
validity. All valid samples that meet the minimum mass gain criteria
per the associated MSHA analytical method are then analyzed for
respirable crystalline silica and for the compliance determination.\6\
---------------------------------------------------------------------------
\5\ The MSHA Laboratory has fulfilled the requirements of the
AIHA Laboratory Accreditation Programs (AIHA-LAP), LLC accreditation
to the ISO/IEC 17025:2017 international standard for industrial
hygiene.
\6\ The minimum mass gain criteria used by the MSHA Laboratory
for the different samples are:
MNM mine respirable dust samples: greater than or equal
to 0.100 mg;
Underground coal mine respirable dust samples: greater
than or equal to 0.100 mg; and
Surface coal mine respirable dust samples: greater than
or equal to 0.200 mg.
Exception: For six surface occupations that have been deemed
``high risk,'' the laboratory uses a minimum mass gain criterion of
greater than or equal to 0.100 mg.
If cristobalite analysis is requested for MNM mine respirable
dust samples, filters having a mass gain of 0.05 mg or more are
analyzed. In the rare instance when tridymite analysis is requested,
a qualitative analysis for the presence of the polymorph is
conducted concurrently with the cristobalite analysis.
---------------------------------------------------------------------------
The MSHA Laboratory uses two analytical methods to determine the
concentration of quartz (and cristobalite and tridymite, if requested):
X-ray diffraction (XRD) for respirable dust samples from MNM mines, and
Fourier transform infrared spectroscopy (FTIR) for respirable coal mine
dust samples.\7\ The XRD method uses X-rays to distinguish and measure
the structure, composition, and physical properties of a sample. The
FTIR method relies on the absorption of infrared light to determine the
composition of a sample. The percentage of silica in the MNM mine dust
sample is calculated using the mass of quartz or cristobalite
determined from the XRD analysis and the measured mass of respirable
dust. The percentage of silica is used to calculate MSHA's PELs for
quartz and cristobalite, in accordance with Sec. Sec. 56.5001 and
57.5001. Similarly, in the respirable coal mine dust sample, the
percentage of quartz is calculated using the quartz mass determined
from the FTIR analysis and the sample's mass of dust. Current FTIR
methods, however, cannot quantify quartz and cristobalite, and/or
tridymite, in the same sample. For coal mines, the percentage of quartz
is used to calculate the reduced dust standard when the quartz
concentration exceeds 100 [micro]g/m\3\ (MRE).
---------------------------------------------------------------------------
\7\ Details on MSHA's analytical procedures for respirable
crystalline silica analysis can be found in ``MSHA P-2: X-Ray
Diffraction Determination of Quartz and Cristobalite in Respirable
Metal/Nonmetal Mine Dust'' and ``MSHA P-7: Determination of Quartz
in Respirable Coal Mine Dust by Fourier Transform Infrared
Spectroscopy.''
Department of Labor, Mine Safety and Health Administration,
Pittsburgh Safety and Health Technology Center, X-Ray Diffraction
Determination of Quartz and Cristobalite in Respirable Metal/
Nonmetal Mine Dust. https://arlweb.msha.gov/Techsupp/pshtcweb/MSHA%20P2.pdf. Department of Labor, Mine Safety and Health
Administration, Pittsburgh Safety and Health Technology Center, MSHA
P-7: Determination of Quartz in Respirable Coal Mine Dust By Fourier
Transform Infrared Spectroscopy. https://arlweb.msha.gov/Techsupp/pshtcweb/MSHA%20P7.pdf.
---------------------------------------------------------------------------
It is worth noting how MSHA calculates full-shift exposure to
respirable crystalline silica (and other airborne contaminants). When a
miner who works an 8-hour shift is sampled, the miner's 8-hour TWA
exposure is calculated as follows:
[GRAPHIC] [TIFF OMITTED] TP13JY23.001
However, for work shifts that last longer than 8 hours, a coal
miner's full-shift exposure is calculated differently than an MNM
miner's full-shift exposure. In accordance with Sec. 70.2, the coal
miner's extended full-shift exposure has, since 2014, been calculated
in the following way:
[GRAPHIC] [TIFF OMITTED] TP13JY23.002
For the MNM miner, MSHA calculates extended full-shift exposure
according to the following formula:
[GRAPHIC] [TIFF OMITTED] TP13JY23.003
For respirable dust samples from MNM mines, 480 minutes is used in
the denominator regardless of the actual sampling time. Contaminants
collected over extended shifts (e.g., 600-720 minutes) are calculated
as if they had been collected over 480 minutes. MSHA has used this
calculation approach (also known as ``shift-weighted average'') since
the 1970s.
Under the shift-weighted average approach, exposures for work
schedules greater than 8 hours are proportionately adjusted to allow
direct comparison with the 8-hour PEL. The ACGIH TLVs[supreg] adopted
by MSHA are based on exposure periods of no more than 8 hours per day
and 40 hours per week, with 16 hours of recovery time between shifts.
D. Respirable Crystalline Silica Sampling Results--Metal and Nonmetal
Mines
This section presents the results of respirable dust samples that
were collected by MSHA inspectors at MNM mines from 2005 to 2019. From
January 1, 2005, to December 31, 2019, a total of 104,354 valid samples
were collected. Of this total, 57,769 samples that met the minimum mass
gain criteria were analyzed for respirable crystalline silica.
[[Page 44864]]
The vast majority of the 46,585 valid samples that were excluded from
the analysis in this rulemaking did not meet the mass gain criteria
described earlier and therefore the lab did not determine their silica
concentration. Further information on the valid respirable dust samples
that are excluded from the analysis in this rulemaking can be found in
Appendix A of the preamble.
The respirable crystalline silica concentration is calculated using
the measured mass of each of the polymorphs and the air sampling
volume. As discussed above, the existing PEL for quartz in MNM mines is
approximately equivalent to 100 [micro]g/m\3\ for a full-shift
exposure, calculated as an 8-hour TWA, while the existing PELs for
cristobalite and tridymite, respectively, are approximately equivalent
to 50 [micro]g/m\3\ for a full-shift exposure, calculated as an 8-hour
TWA.\8\
---------------------------------------------------------------------------
\8\ If more than one polymorph is present the equation used to
calculate the TLV[supreg] for respirable dust containing quartz is
modified per Appendix C of the 1973 ACGIH TLV[supreg] Handbook, and
the equation is modified as follows: 10/[(% quartz + 2) + 2 (%
cristobalite + 2)].
---------------------------------------------------------------------------
1. Annual Results of MNM Respirable Crystalline Silica Samples
Table IV-1 below shows the variation between 2005 and 2019 in: (1)
the numbers of MNM respirable dust samples analyzed for respirable
crystalline silica; and (2) the number and percentage of samples that
had concentrations of respirable crystalline silica greater than 100
[micro]g/m\3\. Of the 57,769 MNM respirable dust samples analyzed for
respirable crystalline silica over the 15-year period, about 6 percent
(3,539 samples) had respirable crystalline silica concentrations
exceeding the existing PEL of 100 [micro]g/m\3\. The average annual
rates of overexposure ranged from a maximum of approximately 10 percent
in 2006 (the second year) to a minimum of approximately 4 percent in
2019 (the last year of the time series). Compared with the rates in
2005-2008, overexposure rates were substantially lower in 2009-2017,
with a further drop in 2018-19.
BILLING CODE 4520-43-P
[GRAPHIC] [TIFF OMITTED] TP13JY23.004
[[Page 44865]]
2. Analysis of MNM Respirable Crystalline Silica Samples by Commodity
Because the MNM mining industry produces commodities that contain
varying degrees of respirable crystalline silica, it is important to
examine each commodity separately. MNM mines can be grouped by five
commodities: metal, sand and gravel, stone, crushed limestone, and
nonmetal (where nonmetal includes all other materials that are not
metals, besides sand, gravel, stone, and limestone). This grouping is
based on the mine operator-reported mining products and the North
American Industry Classification System (NAICS) codes. (Appendix B of
the preamble provides a list of the NAICS codes relevant for MNM mining
and how each code is assigned to one of the five commodities.)
Table IV-2 shows the distribution of the respirable dust samples
analyzed for respirable crystalline silica by mine commodity. The
percentage of samples with respirable crystalline silica concentrations
greater than the existing exposure limit of 100 [micro]g/m\3\ varies
across the different commodities. It is highest for the metal, sand and
gravel, and stone commodities (at approximately 11, 7, and 7 percent,
respectively), and lowest for the nonmetal and crushed limestone
commodities (at approximately 4 and 3 percent, respectively).
[GRAPHIC] [TIFF OMITTED] TP13JY23.005
3. Analysis of MNM Respirable Crystalline Silica Samples by Occupation
To examine how miners who perform different tasks differ in
occupational exposure to respirable crystalline silica, MSHA grouped
MNM mining jobs into 11 occupational categories. These categories
include jobs that are similar in terms of tasks performed, equipment
used, and engineering or administrative controls used to control
miners' exposure. For example, backhoe operators, bulldozer operators,
and tractor operators were grouped into ``operators of large powered
haulage equipment,'' whereas belt crew, belt cleaners, and belt
vulcanizers were grouped into ``conveyer operators.'' The 121 MNM job
codes used by MSHA inspectors were grouped into the following
occupational categories: \9\
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\9\ For a full crosswalk of job codes included in each of these
11 Occupational Categories, please see Appendix C of the preamble.
Also, note that the order of the presentation of the 11 Occupational
Categories here follows the general sequence of mining activities:
first development and production, then ore/mineral processing, then
loading, hauling, and dumping, and finally all others.
---------------------------------------------------------------------------
(1) Drillers (e.g., Diamond Drill Operator, Wagon Drill Operator,
and Drill Helper),
(2) Stone Cutting Operators (e.g., Jackhammer Operator, Cutting
Machine Operator, and Cutting Machine Helper),
(3) Kiln, Mill, and Concentrator Workers (e.g., Ball Mill Operator,
Leaching Operator, and Pelletizer Operator),
(4) Crushing Equipment and Plant Operators (e.g., Crusher Operator/
Worker, Scalper Screen Operator, and Dry Screen Plant Operator),
(5) Packaging Equipment Operators (e.g., Bagging Operator and
Packaging Operations Worker),
(6) Conveyor Operators (e.g., Belt Cleaner, Belt Crew, and Belt
Vulcanizer),
(7) Truck Loading Station Tenders (e.g., Dump Operator and Truck
Loader),
(8) Operators of Large Powered Haulage Equipment (e.g., Tractor
Operators, Bulldozer Operator, and Backhoe Operators),
(9) Operators of Small Powered Haulage Equipment (e.g., Bobcat
Operator, Scoop-Tram Operator, and Forklift Operator),
(10) Mobile Workers (e.g., Laborers, Electricians, Mechanics, and
Supervisors), and
(11) Miners in Other Occupations (e.g., Welder, Dragline Operator,
Ventilation Crew and Dredge/Barge Operator).
Table IV-3 shows sample numbers and overexposure rates by MNM
occupation. Operators of large powered haulage equipment accounted for
the largest number of samples analyzed for silica (17,016 samples),
whereas conveyor operators accounted for the fewest (215 samples).
Table IV-3 also shows the number and percentage of the samples
exceeding the existing respirable crystalline silica PEL of 100
[micro]g/m\3\. In every occupational category, some MNM miners were
exposed to respirable crystalline silica levels above the existing PEL.
In 9 out of the 11 occupational categories, the percentage of samples
exceeding the existing PEL is less than 10 percent, although two have
[[Page 44866]]
higher rates, ranging up to more than 19 percent (in the case of stone
cutting operators).
[GRAPHIC] [TIFF OMITTED] TP13JY23.006
4. Conclusion
This analysis of MSHA inspector sampling data shows that MNM
operators have generally met the existing standard. Of the 57,769
respirable dust samples from MNM mines, approximately 6 percent
exceeded the existing respirable crystalline silica PEL of 100
[micro]g/m\3\, although there are several outliers with much higher
overexposures. For 9 of the 11 occupational categories, less than 10
percent of the respirable dust samples had concentrations over the
existing PEL of 100 [micro]g/m\3\ for respirable crystalline silica. In
addition, about 80 percent of samples taken from stone cutting
operators did not exceed the existing PEL, which historically has had
high exposures to respirable dust and respirable crystalline silica;
\10\ nevertheless, this occupation continues to experience the highest
overexposures relative to other MNM occupations. For the categories of
drillers, miners in other occupations, and operators of large powered
haulage equipment, approximately 5 percent or less of the respirable
dust samples showed concentrations over the existing exposure limit.
---------------------------------------------------------------------------
\10\ Analysis of MSHA respirable dust samples from 2005 to 2010
showed that stone and rock saw operators had approximately 20
percent of the sampled exposures exceeding the PEL. Watts et al.
(2012).
---------------------------------------------------------------------------
MSHA believes that improved technology, engineering controls, and
better training contributed to the reductions in exposures for miners
who work in occupations exposed to the highest levels of respirable
crystalline silica. In summary, the analysis of MSHA inspector sampling
data indicates that the controls that MNM mine operators are using,
together with MSHA's enforcement, have generally been effective in
keeping miners' exposure at or below the existing limit of 100
[micro]g/m\3\.
E. Respirable Crystalline Silica Sampling Results--Coal Mines
To examine coal mine operators' compliance with existing respirable
crystalline silica standards, MSHA analyzed RCMD samples collected by
MSHA inspectors from 2016 to 2021. (The data analyses for this
rulemaking do not include any respirable dust samples collected by coal
mine operators.) The analysis below is based on the samples collected
by inspectors starting on August 1, 2016, when Phase III of MSHA's 2014
Lowering Miners' Exposure to Respirable Coal Mine Dust, Including
Continuous Personal Dust Monitors (Coal Dust Rule) (79 FR 24813, May 1,
2014) went into effect. At that time, the exposure limits for RCMD
[[Page 44867]]
were lowered from 2.0 mg/m\3\ to 1.5 mg/m\3\ (MRE equivalent) at
underground and surface coal mines, and from 1.0 mg/m\3\ to 0.5 mg/m\3\
(MRE equivalent) for intake air at underground coal mines and for Part
90 miners. From August 1, 2016, to July 31, 2021, MSHA inspectors
collected a total of 113,607 valid RCMD samples. Of these valid
samples, only those collected from the breathing zones of miners were
used in the analysis for this rulemaking; no environmental dust samples
were included.\11\ Of those samples, 63,127 samples that met the
minimum mass gain criteria and had no other disqualifying issues were
analyzed for respirable quartz and quartz concentrations were
determined. The majority of the non-environmental valid samples
excluded from this rulemaking analysis were excluded due to
insufficient mass. Further information on the valid respirable dust
samples that are not included in the rulemaking analysis can be found
in Appendix A of the preamble.
---------------------------------------------------------------------------
\11\ Environmental samples were not included in the analysis to
be consistent with the proposed sampling requirements to determine
individual miner exposure.
---------------------------------------------------------------------------
Of the 63,127 valid samples analyzed for respirable crystalline
silica and used for this analysis, about 1 percent (777 samples) were
over the existing quartz exposure limit of 100 [micro]g/m\3\ (MRE
equivalent) for a full shift, calculated as a TWA.\12\ Overexposure
rates (the percent of samples above the exposure limit, on average
across all coal mining occupations) decreased by nearly a quarter
between the first half and the second half of the 2016-2021 period. As
in MNM mines, different miner occupations had different overexposure
rates. Using broader groupings, surface mines experienced higher rates
of overexposure than underground mines (2.4 percent versus 1.0 percent,
respectively).
---------------------------------------------------------------------------
\12\ The conversion between ISO values and MRE values uses the
NIOSH conversion factor of 0.857. In the 1995b Criteria Document,
NIOSH presented an empirically derived conversion factor of 0.857
for comparing current (MRE) and recommended (ISO) respirable dust
sampling criteria using the 10 mm Dorr-Oliver nylon cyclone operated
at 2.0 and 1.7 L/min, respectively (i.e., 1.5 mg/m\3\ BMRC-MRE =
1.29 mg/m\3\ ISO).
---------------------------------------------------------------------------
1. Annual Results of Coal Respirable Crystalline Silica Samples
In examining trends from one year to the next, the discussion below
focuses on the samples collected in the 6 calendar years from 2016 to
2021. The number of samples per year was stable from 2017 to 2019
before decreasing in 2020.\13\ The overexposure rate decreased across
the entire 2016 to 2021 period, from 1.41 percent in 2016 to 0.95
percent in 2021. As shown in Table IV-4, a review of the 6 calendar
years reveals that the overexposure rate decreased by nearly a quarter
from 2016-2018 (1.38 percent) to 2019-2021 (1.07 percent).
---------------------------------------------------------------------------
\13\ The coal samples for 2016 begin in August of that year and
the coal samples for 2021 end in July of that year.
[GRAPHIC] [TIFF OMITTED] TP13JY23.007
2. Analysis of Coal Respirable Crystalline Silica Samples by Location
Coal mining activities differ depending on the characteristics and
locations of coal seams. When coal seams are several hundred feet below
the surface, miners tunnel into the earth and use underground mining
equipment to extract coal, whereas miners at surface coal mines remove
topsoil and layers of rock to expose coal seams. Due to these
differences, it is important to examine the respirable crystalline
silica data by location to determine how underground and surface coal
miners differ in occupational exposure to respirable crystalline
silica.
Table IV-5, which presents the overexposure rate by type of mine
where respirable coal mine dust samples were collected, shows that
samples from surface coal mines reflected higher rates of overexposure
than samples from underground mines.
[[Page 44868]]
Out of the 53,095 respirable coal mine dust samples from underground
mines, 1 percent (537 samples) were over the existing exposure limit.
By contrast, there were 10,032 samples from surface coal mines, and
approximately 2.4 percent (240 samples) of those samples were over the
existing exposure limit.
[GRAPHIC] [TIFF OMITTED] TP13JY23.008
3. Analysis of Coal Respirable Crystalline Silica Samples by Occupation
To assess the exposure to respirable crystalline silica of miners
in different occupations, MSHA has consolidated the 220 job codes for
coal mines into 9 occupational categories (using a similar process to
the one it used for the MNM mines, but with different job codes and
categories). For the coal mine occupational categories,\14\ a
distinction is made between occupations based on whether the job tasks
are being performed at the surface of a mine or underground. For
example, bulldozer operators are assigned to the operators of large
powered haulage equipment grouping and then sorted into separate
occupational categories based on whether they are working at the
surface of a mine or underground.
---------------------------------------------------------------------------
\14\ For a full crosswalk of which job codes were included in
each of these nine Occupational Categories, please see Appendix C of
the preamble.
---------------------------------------------------------------------------
Of the nine occupational categories used for coal miners, the five
underground categories are:
(1) Continuous Mining Machine Operators (e.g., Coal Drill Helper
and Coal Drill Operator),
(2) Longwall Workers (e.g., Headgate Operator and Jack Setter
(Longwall)),
(3) Roof Bolters (e.g., Roof Bolter and Roof Bolter Helper),
(4) Operators of Large Powered Haulage Equipment (e.g., Shuttle Car
Operator, Tractor Operator/Motorman, Scoop Car Operator), and
(5) All Other Underground Miners (e.g., Electrician, Mechanic, Belt
Cleaner and Laborer, etc.).
The four surface occupational categories are:
(1) Drillers (e.g., Coal Drill Operator, Coal Drill Helper, and
Auger Operator),
(2) Crusher Operators (e.g., Crusher Attendant, Washer Operator,
and Scalper-Screen Operator),
(3) Operators of Large Powered Haulage Equipment (e.g., Backhoe
Operator, Forklift Operator, and Bulldozer Operator), and
(4) Mobile Workers (e.g., Electrician, Mechanic, Blaster, Laborer,
etc.).
The most sampled occupational category was operators of large
powered haulage equipment (underground), representing approximately 34
percent of the samples taken. The least sampled occupational category
was crusher operators (surface), consisting of 1 percent of the samples
taken. Table IV-6 displays the number and percent of respirable coal
mine dust samples with quartz greater than the existing exposure limit
for each occupational category.
[[Page 44869]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.009
Looking at trends, every occupational category shows a decrease in
overexposure rates over time. See Figure IV-1. Most of the nine
categories had lower rates of overexposure in the 2019-2021 period than
in the 2016-2018 period.
[[Page 44870]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.010
BILLING CODE 4520-43-C
In all occupational categories, coal miners were sometimes exposed
to respirable crystalline silica levels above the existing exposure
limit. But the sampling data showed that coal mine operators can
generally comply with the existing exposure limit. For example,
although mining tasks performed by the occupational category of roof
bolters (underground) historically resulted in high levels of
overexposure to quartz, the low levels of overexposure for that
occupation in 2016-2021 (i.e., 1 percent) suggest that roof bolters now
benefit from the improved respirable dust standard, improved
technology, and better training.\15\ Over the 2016-2021 period, coal
miners in the occupational category drillers (surface) were the most
frequently overexposed, with approximately 6 percent of samples over
the existing quartz limit; they were followed by longwall workers
(underground) (about 4 percent), operators of large powered haulage
equipment (surface) (about 3 percent), and continuous mining machine
operators (underground) (about 2 percent). For all other occupational
categories, the overexposure rate was less than 1 percent.
---------------------------------------------------------------------------
\15\ The drilling operation in the roof bolting process,
especially in hard rock, generates excessive respirable coal and
quartz dusts, which could expose the roof bolting operator to
continued health risks (Jiang and Luo, 2021).
---------------------------------------------------------------------------
4. Conclusion
This analysis of MSHA inspector sampling data shows that coal mine
operators can generally comply with the existing standards related to
quartz. Of the 63,127 valid respirable dust samples from coal mines
over the most recent 5-year period, 1.2 percent had respirable quartz
over the existing exposure limit of 100 [micro]g/m\3\ (MRE equivalent)
for a full-shift exposure, calculated as a TWA. Seven of the nine
occupational categories had overexposure rates of 2.5 percent or less.
Roof bolters (underground), which historically have had high exposures
to respirable dust and respirable crystalline silica, had overexposure
rates of 1 percent over this recent period. The data demonstrates that
the controls that coal mine operators are using, together with MSHA's
enforcement, have generally been effective in keeping miners' exposure
to respirable crystalline silica at or below the existing exposure
limit.
V. Health Effects Summary
This section summarizes the health effects from occupational
exposure to respirable crystalline silica. MSHA's full analysis is
contained in the standalone document, entitled Effects of Occupational
Exposure to Respirable Crystalline Silica on the Health of Miners
(Health Effects document), which has been placed in the rulemaking
docket for the MSHA silica rulemaking (RIN 1219-AB36, Docket ID no.
MSHA-2023-0001) and is available on MSHA's website.
The purpose of the Agency's scientific review is to present MSHA's
preliminary findings on the nature of the hazards presented by exposure
to respirable crystalline silica and to present the basis for the
Preliminary
[[Page 44871]]
Risk Analysis (PRA) to follow. (A PRA summary is presented in Section
VI of this preamble and a standalone document entitled Preliminary Risk
Analysis has been placed in the rulemaking docket for the MSHA silica
rulemaking (RIN 1219-AB36, Docket ID no. MSHA-2023-0001) and is
available on MSHA's website.) MSHA reviewed a wide range of health
research literature that included more than 600 studies exploring the
relationship between respirable crystalline silica exposure and
resultant health effects in miners and other workers across various
industries. After discussing the toxicity of respirable crystalline
silica, MSHA's review of the literature covers the following topics:
(1) Silicosis;
(2) NMRD, excluding silicosis;
(3) Lung cancer and cancer at other sites;
(4) Renal disease; and
(5) Autoimmune diseases.
To develop this literature review, MSHA expanded upon OSHA's
(2013b) review of the health effects literature to support its final
respirable crystalline silica rule (81 FR 16286, March 25, 2016). MSHA
also drew upon numerous studies conducted by NIOSH, the International
Agency for Research on Cancer (IARC), the National Toxicology Program
(NTP), and other researchers. These studies provided epidemiological
data, morbidity (having a disease or a symptom of disease) and
mortality (disease resulting in death) analyses, progression and
pathology evaluations, death certificate and autopsy reviews, medical
surveillance data, health hazard assessments, in vivo (animal) and in
vitro toxicity data, and other toxicological reviews. These sources are
cited throughout this summary and are listed in the References section
of the Health Effects document. Additionally, these sources appear in
the rulemaking docket.
MSHA's literature review is based on a weight-of-evidence approach,
in which studies are evaluated for their overall quality. Causal
inferences are drawn based on a determination of whether there is
substantial evidence that exposure increases the risk of a particular
adverse health effect. Factors MSHA considered in this weight-of-
evidence analysis include: size of the cohort studied and power of the
study to detect a sufficiently low level of disease risk, duration of
follow-up of the study population, potential for study bias (such as
selection bias or healthy worker effects), and adequacy of underlying
exposure information for examining exposure-response relationships. Of
the studies examined in the Health Effects document, studies were
deemed suitable for inclusion in the PRA if there was adequate
quantitative information on exposure and disease risks and the study
was judged to be of sufficiently high quality according to the above
criteria.
The understanding of how respirable crystalline silica causes
adverse health effects has evolved greatly in the more than 45 years
since the Mine Act was passed in 1977. Based on its extensive review of
health research literature, MSHA has preliminarily determined that
occupational exposure to respirable crystalline silica causes silicosis
(acute silicosis, accelerated silicosis, simple chronic silicosis, and
PMF), NMRD (including COPD), and lung cancer, and it also causes end-
stage renal disease (ESRD). In addition, MSHA believes that respirable
crystalline silica exposure is causally related to the development of
some autoimmune disorders through inflammation pathways. Each of these
effects is exposure-dependent, chronic, irreversible, and potentially
disabling or fatal. MSHA's review of the literature indicates that
under the existing standards found in 30 CFR parts 56, 57, 70, 71, and
90, miners are still developing preventable diseases that are material
impairments of health and functional capacity. Based on the assessment
of health effects of respirable crystalline silica, MSHA preliminarily
concludes that the proposed rule, which would lower the exposure limits
in MNM and coal mining to 50 [micro]g/m\3\ and establish an action
level of 25 [micro]g/m\3\ for a full-shift exposure, calculated as an
8-hour TWA, would reduce the risk of miners developing silicosis, NMRD,
lung cancer, and renal disease.
A. Toxicity of Respirable Crystalline Silica
Respirable crystalline silica is released into the environment
during mining or milling processes, thus creating an airborne hazard.
The particles may be freshly generated or re-suspended from surfaces on
which it is deposited in mines or mills. Respirable crystalline silica
particles may be irregularly shaped and variable in size. Inhaled
respirable crystalline silica can be deposited throughout the lungs.
Some pulmonary clearance of particles deposited in the deep lung (i.e.,
alveolar region) may occur, but a large number of particles can be
retained and initiate or advance the disease process. The toxicity of
these retained particles is amplified because the particles are not
water-soluble and do not undergo metabolism into less toxic compounds.
This is important biologically and physiologically, as insoluble dusts
may remain in the lungs for prolonged periods, resulting in a variety
of cellular responses that can lead to pulmonary disease (ATSDR, 2019).
Respirable crystalline silica particles that are cleared from the lungs
by the lymphatic system are distributed to the lymph nodes, blood,
liver, spleen, and kidneys, potentially accumulating in these other
organ systems and causing renal disease and other adverse health
effects (ATSDR, 2019).
Physical characteristics relevant to the toxicity of respirable
crystalline silica primarily relate to its size and surface
characteristics. Researchers believe that the size and surface
characteristics play important roles in how respirable crystalline
silica causes tissue damage. Any factor that influences or modifies
these physical characteristics may alter the toxicity of respirable
crystalline silica by affecting the mechanistic processes (OSHA, 2013b;
ATSDR, 2019).
Inflammation pathways affect disease development in various systems
and tissues in the human body. For instance, it has been proposed that
lung fibrosis caused by exposure to respirable crystalline silica
results from a cycle of cell damage, oxidant generation, inflammation,
scarring, and ultimately fibrosis. This has been reported by Nolan et
al. (1981), Shi et al. (1989, 1998), Lapp and Castranova (1993), Brown
and Donaldson (1996), Parker and Banks (1998), Castranova and
Vallyathan (2000), Castranova (2004), Fubini et al. (2004), Hu et al.
(2017), Benmerzoug et al. (2018), and Yu et al. (2020).
Respirable crystalline silica entering the lungs could cause damage
by a variety of mechanisms, including direct damage to lung cells. In
addition, activation or stimulation by respirable crystalline silica of
alveolar macrophages (after phagocytosis) and/or alveolar epithelial
cells may lead to: (1) release of cytotoxic enzymes, reactive oxygen
species (ROS), reactive nitrogen species (RNS), inflammatory cytokines
and chemokines, (2) eventual cell death with the release of respirable
crystalline silica, and (3) recruitment and activation of
polymorphonuclear leukocytes (PMNs) and additional alveolar
macrophages. The elevated production of ROS/RNS would result in
oxidative stress and lung injury that stimulates alveolar macrophages,
ultimately resulting in fibroblast activation and pulmonary fibrosis.
The prolonged recruitment of macrophages and PMN causes a persistent
inflammation, regarded as a primary step in the development of
silicosis.
The strong immune response in the lung following exposure to
respirable
[[Page 44872]]
crystalline silica may also be linked to a variety of extra-pulmonary
adverse effects such as hypergammaglobulinemia, production of
rheumatoid factor, anti-nuclear antibodies, and release of other immune
complexes (Parks et al., 1999, Haustein and Anderegg, 1988; Green and
Vallyathan, 1996). Respirable crystalline silica exposure has also been
associated with nonmalignant renal disease through the initiation of
immunological injury to the glomerulus of the kidney (Calvert et al.,
1997).
Proposed mechanisms involved in respirable crystalline silica-
induced carcinogenesis have included: direct DNA damage, inhibition of
the p53 tumor suppressor gene, loss of cell cycle regulation;
stimulation of growth factors, and production on oncogenes (Brown and
Donaldson, 1996; Castranova, 2004; Fubini et al., 2004; Nolan et al.,
1981; Shi et al., 1989, 1998).
B. Diseases
1. Silicosis
Silicosis is a progressive occupational disease that has long been
identified as a cause of lung disease in miners. Based on its review of
the literature, MSHA has preliminarily determined that exposure to
respirable crystalline silica causes silicosis (acute silicosis,
accelerated silicosis, simple chronic silicosis, and PMF) in MNM and
coal miners, which is a significant cause of serious morbidity and
early mortality in this occupational cohort (Mazurek and Attfield,
2008; Mazurek and Wood, 2008a, 2008b; Mazurek et al., 2015, 2018).
When respirable crystalline silica particles accumulate in the
lungs, they cause an inflammatory reaction, leading to lung damage and
scarring. Silicosis can continue to develop even after silica exposure
has ceased. It is not reversible, and there is only symptomatic
treatment, including bronchodilators to maintain open airways, oxygen
therapy, and lung transplants in the most severe cases (Cochrane et
al., 1956; Ng et al., 1987a; Lee et al., 2001; Mohebbi and Zubeyri,
2007; Kimura et al., 2010; Laney et al., 2017; Almberg et al., 2020;
Hall et al., 2022).
Respirable crystalline silica exposure in MNM miners can lead to
all three forms of silicosis (acute, accelerated, and chronic). These
forms differ in the rate of exposure, pathology (i.e., the structural
and functional changes produced by the disease), and latency period
from exposure to disease onset. Acute silicosis is an aggressive
inflammatory process following intense exposure to respirable
crystalline silica for ``periods measured in months rather than years''
(Cowie and Becklake, 2016). It causes alveolar proteinosis
(accumulation of lipoproteins in the alveoli of the lungs). This
restructuring of the lungs leads to symptoms such as coughing and
difficult or labored breathing, and it often progresses to profound
disability and death due to respiratory failure or infectious
complications. In addition, symptoms often advance even after exposure
has stopped, primarily due to the massive amount of protein debris and
fluid that collects in the alveoli, which can suffocate the patient.
The radiographic (X-ray) appearance and results of microscopic
examination of acute silicosis are like those of idiopathic pulmonary
alveolar proteinosis.
Chronic silicosis is the most frequently observed form of silicosis
in the United States today (Banks, 2005; OSHA, 2013b; Cowie and
Becklake, 2016). It is also the most common form of silicosis diagnosed
in miners. Chronic silicosis is a fibrotic process that typically
follows less intense respirable crystalline silica exposure of 10 or
more years (Becklake, 1994; Balaan and Banks, 1998; NIOSH, 2002b,
Kambouchner and Bernaudin, 2015; Cowie and Becklake, 2016; Rosental,
2017; ATSDR, 2019; Barnes et al., 2019; Hoy and Chambers, 2020). It is
identified by the presence of the silicotic islet or nodule that is an
agent-specific fibrotic lesion and is recognized by its pathology
(Balaan and Banks, 1998). Chronic silicosis develops slowly and creates
rounded whorls of scar tissue that progressively destroy the normal
structure and function of the lungs. In addition, the scar tissue
opacities become visible by chest X-ray or computerized tomography (CT)
only after the disease is well established and the lesions become large
enough to view. As a result, surveys based on chest X-ray films usually
underestimate the true prevalence of silicosis (Craighead and
Vallathol, 1980; Hnizdo et al., 1993; Rosenman et al., 1997; Cohen and
Velho, 2002). However, the lesions eventually advance and result in
lung restriction, reduced lung volumes, decreased pulmonary compliance,
and reduction in the gas exchange capabilities of the lungs (Balaan and
Banks, 1998). As the disease progresses, affected miners may have a
chronic cough, sputum production, shortness of breath, and reduced
pulmonary function.
Accelerated silicosis includes both inflammation and fibrosis and
is associated with intense respirable crystalline silica exposure.
Accelerated silicosis usually manifests over a period of 3 to 10 years
(Cowie and Becklake, 2016), but it can develop in as little as 2 to 5
years if exposure is sufficiently intense (Davis, 1996). Accelerated
silicosis may have features of both chronic and acute silicosis (i.e.,
alveolar proteinosis in addition to X-ray evidence of fibrosis).
Although the symptoms are similar to those of chronic silicosis, the
clinical and radiographic progression of accelerated silicosis evolves
more rapidly, and often leads to PMF, severe respiratory impairment,
and respiratory failure. Accelerated silicosis can progress with
associated morbidity and mortality, even if exposure ceases.
Among coal miners, silicosis is usually found in conjunction with
simple coal worker's pneumoconiosis (CWP) (Castranova and Vallyathan,
2000) because of their exposures to RCMD that contains respirable
crystalline silica. Coal miners also face an added risk of developing
mixed-dust pneumoconiosis (MDP) (includes the presence of coal dust
macules), mixed-dust fibrosis (MDF), and/or silicotic nodules (Honma et
al., 2004, see Figure 2, Green 2019). The autopsy studies on coal
miners that MSHA reviewed support a pathological relationship between
mixed-RCMD or respirable crystalline silica exposures and PMF,
silicosis, and CWP (Attfield et al., 1994; Cohen et al., 2016, 2019,
2022; Davis et al., 1979; Douglas et al., 1986; Fernie and Ruckley,
1987; Green et al., 1989, 1998b; Ruckley et al., 1981, 1984; Vallyathan
et al., 2011). Autopsy studies in British coal miners indicated that
the more advanced the disease, the more mixed coal mine dust components
were retained in the lung tissue (Ruckley et al., 1984; Douglas et al.,
1986). Green et al. (1998b) determined that of 4,115 coal miners with
pneumoconiosis autopsied as part of the National Coal Workers' Autopsy
Study (NCWAS), 39 percent had mixed dust nodules and 23 percent had
silicotic nodules.
PMF or ``complicated silicosis'' has been diagnosed in both coal
and MNM miners exposed to dusts containing respirable crystalline
silica. Recent literature on the pathophysiology of PMF supports the
importance of crystalline silica as a cause of PMF in silica-exposed
workers such as coal miners from the United States (Cohen et al., 2016,
2022), sandblasters (Abraham and Wiesenfeld, 1997; Hughes et al.,
1982), industrial sand workers (Vacek et al., 2019), hard rock miners
(Verma et al., 1982, 2008), and gold miners (Carneiro et al., 2006a;
Tse et al., 2007b).
[[Page 44873]]
a. Classifying Radiographic Findings of Silicosis
Two classification methods used to characterize the radiographic
findings of silicosis in chest X-rays are described in this literature
review: the International Labour Office (ILO) Standardized System and
the Chinese categorization system.\16\
---------------------------------------------------------------------------
\16\ The ``Radiological Diagnostic Criteria of Pneumoconiosis
and Principles for Management of Pneumoconiosis'' (GB5906-86) (Chen
et al., 2001; Yang et al., 2006).
---------------------------------------------------------------------------
To describe the presence and severity of pneumoconiosis from chest
X-rays or digital radiographic images, the ILO developed a standardized
system to classify the opacities identified (ILO, 1980, 2002, 2011,
2022). The ILO system grades the size, shape, and profusion (frequency)
of opacities in the lungs. The density of opacities is classified on a
4-point major category scale (category 0, 1, 2, or 3), with each major
category divided into three subcategories, giving a 12-point scale
between 0/- and 3/+. Differences between ILO categories are subtle. For
each subcategory, the top number indicates the major category that the
profusion most closely resembles, and the bottom number indicates the
major category that was given secondary consideration. For example,
film readers may assign classifications such as 1/0, which means the
reader classified it as category 1, but category 0 (normal) was also
considered (ILO, 2022). Major category 0 indicates the absence of
visible opacities and categories 1 to 3 reflect increasing profusion of
opacities and a concomitant increase in severity of disease.
MSHA's analysis of silicosis studies uses NIOSH's surveillance case
definition to determine the presence of silicosis. NIOSH defines the
presence of silicosis in terms of the ILO system and considers a small
opacity profusion score of 1/0 or greater to indicate pneumoconiosis
(NIOSH, 2014b). This definition originated from testimony before
Congress regarding the 1969 Coal Act where the Public Health Service
recommended that miners be removed from dusty environments as soon as
they showed ``minimal effects'' of dust exposure on a chest X-ray
(i.e., pinpoint, dispersed micro-nodular lesions).\17\ MSHA interprets
``minimal effects'' to mean an X-ray ILO profusion score of category 1/
0 or greater.
---------------------------------------------------------------------------
\17\ On March 26, 1969, Charles C. Johnson, Jr., Administrator,
Consumer Protection and Environmental Health Service, PHS, U.S.
Department of Health, Education, and Welfare, testified before the
General Subcommittee on Labor and presented remarks of the Surgeon
General. They are referenced in the 91st Congress House of
Representatives Report, 1st Session No. 91-563, Federal Coal Mine
Health and Safety Act, October 13, 1969 (https://arlweb.msha.gov/SOLICITOR/COALACT/69hous.htm).
---------------------------------------------------------------------------
However, some studies in MSHA's literature review use the Chinese
categorization scheme, which includes four categories of silicosis: a
suspected case (0+), stage I, stage II, or stage III. The four
categories correspond to ILO profusion category 0/1, category 1,
category 2, and category 3, respectively. A suspected case of silicosis
(0+) in a dust-exposed worker refers to a dust response in the lung and
its corresponding lymph nodes, or a scale and severity of small
opacities that fall short of the level observed in a stage I case of
silicosis (Chen et al., 2001; Yang et al., 2006). Under this scheme, a
panel of three radiologists determines the presence and severity of
radiographic changes consistent with pneumoconiosis.
b. Progression and Associated Impairment
Progression of silicosis is shown when there are changes or
worsening of the opacities in the lungs, and sequential chest
radiographs are classified higher by one or more subcategories (e.g.,
from 1/0 to 1/1) because of changes in the location, thickness, or
extent of lung abnormalities and/or the presence of calcifications. The
higher the category number, the more severe the disease. Due to the
uncertainty in scoring films, some investigators count progression as
advancing two or more subcategories, such as 1/0 to 1/2.
MSHA reviewed studies referenced by OSHA (2013b) that examined the
relationship between exposure and progression, as well as between X-ray
findings and pulmonary function. Additionally, MSHA considered more
recent literature (Dumavibhat et al., 2013; Mohebbi and Zubeyri, 2007;
Wade et al., 2011) not previously reviewed by OSHA (2013b).
Overall, the studies indicate that progression is more likely with
continued exposure, especially high average levels of exposure.
Progression is also more likely for miners with higher ILO profusion
classifications. As discussed previously, progression of disease may
continue after miners are no longer exposed to respirable crystalline
silica (Almberg et al., 2020; Cochrane et al., 1956; Hall et al.,
2020b; Hurley et al., 1987; Kimura et al., 2010; Maclaren et al.,
1985). In addition, although lung function impairment is highly
correlated with chest X-ray films indicating silicosis, researchers
cautioned that respirable crystalline silica exposure could impair lung
function before it is detected by X-ray.
Of the studies in which silicosis progression was documented in
populations of workers, four included quantitative exposure data that
were based on either existing exposure levels or historical
measurements of respirable crystalline silica (Hessel et al., 1988
study of gold miners; Miller and MacCalman, 2010 study of coal miners;
Miller et al., 1998 study of coal miners; Ng et al., 1987a study of
granite miners). In some studies, episodic exposures to high average
concentrations were documented and considered in the analysis. These
exposures were strong predictors of more rapid progression beyond that
predicted by cumulative exposure alone. Otherwise, the variable most
strongly associated in these studies with progression of silicosis was
cumulative respirable crystalline silica exposure (i.e., the product of
the concentration times duration of exposure, which is summed over
time) (Hessel et al., 1988; Ng et al., 1987a; Miller and MacCalman,
2010; Miller et al., 1998). In the absence of concentration
measurements, duration of employment in specific occupations known to
involve exposure to high levels of respirable dust has been used as a
surrogate for cumulative exposure to respirable crystalline silica. It
has also been found to be associated with the progression of silicosis
(Ogawa et al., 2003a).
Miller et al. (1998) examined the impact of high quartz exposures
on silicosis disease progression on 547 British coal miners from 1990
to 1991 and evaluated chest X-ray changes after the mines closed in
1981. The study reviewed chest X-rays taken during health surveys
conducted between 1954 and 1978 and data from extensive exposure
monitoring conducted between 1964 and 1978. For some occupations,
exposure was high because miners had to dig through a sandstone stratum
to reach the coal. For example, quarterly mean respirable crystalline
silica (quartz) concentrations ranged from 1,000 to 3,000 [micro]g/m\3\
(1-3 mg/m\3\), and for a brief period, concentrations exceeded 10,000
[micro]g/m\3\ (10 mg/m\3\) for one job. Some of these high exposures
were associated with accelerated disease progression.
Buchanan et al. (2003) reviewed the exposure history and chest X-
ray progression of 371 retired miners and found that short-term
exposures (i.e., ``a few months'') to high concentrations of respirable
crystalline silica (e.g., >2,000 [mu]g/m\3\, >2 mg/m\3\) increased the
silicosis risk by three-fold (compared to the risk of cumulative
exposure alone) (see the
[[Page 44874]]
separate Preliminary Risk Analysis document).
The risks of increased rate of progression, predicted by Buchanan
et al. (2003) have been seen in coal miners (e.g., Cohen et al., 2016;
Laney et al., 2010, 2017; Miller et al., 1998), metal (Hessel et al.,
1988; Hnizdo and Sluis-Cremer, 1993; Nelson, 2013), and nonmetal miners
such as silica plant and ground silica mill workers, whetstone cutters,
and silica flour packers (Mohebbi and Zubeyri, 2007; NIOSH 2000a,b;
Ogawa et al., 2003a). Accordingly, it is important to limit higher
exposures to respirable crystalline silica in order to minimize the
risk of rapid progressive pneumoconiosis (RPP) in miners.
The results of many surveillance studies conducted by NIOSH as part
of the Coal Workers' Health Surveillance Program indicate that the
pathology of pneumoconiosis in coal miners has changed over time, in
part due to increased exposure to respirable crystalline silica. The
studies of Cohen et al. (2016, 2022) indicate that a RPP develops due
to increased exposure to respirable crystalline silica among
contemporary coal miners as compared to historical coal miners. Through
the examination of pathologic materials from 23 contemporary (born in
or after 1930) and 62 historical coal miners (born between 1910 and
1930) with severe pneumoconiosis, who were autopsied as part of NCWAS,
Cohen et al. (2022) found a significantly higher proportion of silica-
type PMF among contemporary miners (57 percent vs. 18 percent, p
<0.001). They also found that mineral dust alveolar proteinosis (MDAP)
was more common in the current generation of miners and that the lung
tissues of contemporary coal miners contained a significantly greater
percentage and concentration of silica particles than those of past
generations of miners.
c. Occupation-Based Epidemiological Studies
MSHA reviewed the occupation-based epidemiological literature
(i.e., studies that examine health outcomes among workers and their
potential association with conditions in the workplace). MSHA's review
included the occupation-based literature OSHA cited in developing its
respirable crystalline silica standard (OSHA, 2013b). Overall, OSHA
found substantial evidence suggesting that occupational exposure to
respirable crystalline silica increases the risk of silicosis, and MSHA
concurs with this conclusion. MSHA also reviewed additional occupation-
based literature specific to respirable crystalline silica exposure in
MNM and coal miners and preliminarily concludes that respirable
crystalline silica exposure increases the risk of silicosis morbidity
and early mortality. One study examined the acute and accelerated
silicosis outbreak that occurred during and after construction of
Hawk's Nest Tunnel in West Virginia from 1930 to 1931. There, an
estimated 2,500 men worked in a tunnel drilling rock consisting of 90
percent silica or more. The study later estimated that at least 764 of
the 2,500 workers (30.6 percent) died from acute or accelerated
silicosis (Cherniack, 1986). There was also high turnover among the
tunnel workers, with an average length of employment underground of
only about 2 months.
In a population of granite quarry workers (mean length of
employment: 23.4 years) exposed to an average respirable crystalline
silica concentration of 480 [micro]g/m\3\ (0.48 mg/m\3\), 45 percent of
those diagnosed with simple silicosis showed radiological progression
of disease 2 to 10 years after diagnosis (Ng et al., 1987a). Among a
population of gold miners, 92 percent showed progression after 14 years
(Hessel et al., 1988). Chinese factory workers and miners who were
categorized under the Chinese system of X-ray classification as
``suspected'' silicosis cases (analogous to ILO 0/1) had a progression
rate to stage I (analogous to ILO major category 1) of 48.7 percent,
with an average interval of about 5.1 years (Yang et al., 2006).
Strong evidence has shown that lung function deteriorates more
rapidly in miners exposed to respirable crystalline silica, especially
in those with silicosis (Hughes et al., 1982; Ng and Chan, 1992;
Malmberg et al., 1993; Cowie, 1998). The rates of decline in lung
function are greater where disease shows evidence of radiologic
progression (B[eacute]gin et al., 1987; Ng et al., 1987a; Ng and Chan,
1992; Cowie, 1998). The average deterioration of lung function exceeds
that in smokers (Hughes et al., 1982).
Blackley et al. (2015) found progressive lung function impairment
across the range of radiographic profusion of simple CWP in a cohort of
8,230 coal miners that participated in the Enhanced Coal Workers'
Health Surveillance Program from 2005 to 2013. There, 269 coal miners
had category 1 or 2 simple CWP. This study also found that each
increase in profusion score was associated with decreases in various
lung function parameters: 1.5 percent (95 percent CI, 1.0 percent-1.9
percent) in forced expiratory volume in one second (FEV1)
percent predicted, 1.0 percent (95 percent CI, 0.6 percent-1.3 percent)
forced vital capacity (FVC) percent predicted, and 0.6 percent (95
percent CI, 0.4 percent-0.8 FEV1/FVC).
Overall, MSHA preliminarily agrees with OSHA's conclusion that
substantial evidence suggests that occupational exposure to respirable
crystalline silica increases the risk of silicosis. MSHA also
preliminarily concludes that respirable crystalline silica exposure
increases the risk of silicosis morbidity and early mortality among
miners.
d. Surveillance Data
In addition to occupation-based epidemiological studies, MSHA
reviewed surveillance studies, which provide and interpret data to
facilitate the prevention and control of disease, and preliminarily
finds that the prevalence of silicosis generally increases with
duration of exposure (work tenure). However, the available statistics
may underestimate silicosis-related morbidity and mortality in miners.
For example, the following have been reported: (1) misclassification of
causes of death (e.g., as TB, chronic bronchitis, emphysema, or cor
pulmonale); (2) errors in recording occupation on death certificates;
and (3) misdiagnosis of disease (Windau et al., 1991; Goodwin et al.,
2003; Rosenman et al., 2003, Blackley et al., 2017). Furthermore, chest
X-ray findings may lead to missed silicosis cases when fibrotic changes
in the lung are not yet visible on chest X-rays. In other words,
silicosis may be present but not yet detectable by chest X-ray, or may
be more severe than indicated by the assigned profusion score
(Craighead and Vallyathan, 1980; Hnizdo et al., 1993; Rosenman et al.,
1997).
e. Pulmonary Tuberculosis
Finally, in addition to the relationship between silica exposure
and silicosis, studies indicate a relationship between silica exposure,
silicosis, and pulmonary TB. OSHA reviewed these and concluded that
silica exposure and silicosis increase the risk of pulmonary TB (Cowie,
1994; Hnizdo and Murray, 1998; teWaterNaude et al., 2006). MSHA agrees
with this conclusion.
Although early descriptions of dust diseases of the lung did not
distinguish between TB and silicosis and most fatal cases described in
the first half of the 20th century were likely a combination of
silicosis and TB (Castranova et al., 1996), more recent findings have
demonstrated that respirable crystalline silica exposure, even without
silicosis, increases the risk of infectious (i.e., active) pulmonary TB
(Sherson and
[[Page 44875]]
Lander, 1990; Cowie, 1994; Hnizdo and Murray, 1998; teWaterNaude et
al., 2006). These co-morbid conditions hasten the development of
respiratory impairment and increased mortality risk even beyond the
risk in unexposed persons with active TB (Banks, 2005).
Ng and Chan (1991) hypothesized that silicosis and TB ``act
synergistically'' (i.e., are more than additive) to increase fibrotic
scar tissue (leading to massive fibrosis) or to enhance susceptibility
to active mycobacterial infection. The authors found that lung fibrosis
is common to both diseases, and that both diseases decrease the ability
of alveolar macrophages to aid in the clearance of dust or infectious
particles.
These findings are also supported by new studies (Ndlovu et al.,
2019; Oni and Ehrlich, 2015) published since OSHA's review (2013b). Oni
and Ehrlich (2015) reviewed a case of silico-TB in a former gold miner
with ILO category 2/2 silicosis. Ndlovu et al. (2019) found that in a
study sample of South African gold miners who had died from causes
other than silicosis between 2005 and 2015, 33 percent of men (n = 254)
and 43 percent of women (n = 29) at autopsy were found to have TB,
whereas 7 percent of men (n = 54) and 3 percent of women (n = 4) were
found to have pulmonary silicosis.
Overall, MSHA agrees with OSHA's conclusion that silica exposure
increases the risk of pulmonary TB and that pulmonary TB is a
complication of chronic silicosis.
2. Nonmalignant Respiratory Disease (Excluding Silicosis)
In addition to causing silicosis (acute silicosis, accelerated
silicosis, simple chronic silicosis, and PMF), exposure to respirable
crystalline silica causes other NMRD. NMRD includes emphysema and
chronic bronchitis, which are both diagnoses within the category of
COPD. Patients with COPD may have chronic bronchitis, emphysema, or
both (ATS, 2010a).
Based on its review of the literature, MSHA preliminarily concludes
that exposure to respirable crystalline silica increases the risk for
mortality from NMRD. The following summarizes MSHA's review of the
literature.
a. Emphysema
Emphysema involves the destruction of lung architecture in the
alveolar region, causing airway obstruction and impaired gas exchange.
In its literature review, OSHA (2013b) concluded that exposure to
respirable crystalline silica can increase the risk of emphysema,
regardless of whether silicosis is present. OSHA also concluded that
this is the case for smokers and that smoking amplifies the effects of
respirable crystalline silica exposure, increasing the risk of
emphysema. MSHA reviewed the studies cited by OSHA and agrees with its
conclusion. The studies reviewed are summarized below.
Becklake et al. (1987) determined that a miner who had worked in a
high dust environment for 20 years had a greater chance of developing
emphysema than a miner who had never worked in a high dust environment.
In a retrospective cohort study, Hnizdo et al. (1991a) used autopsy
lung specimens from 1,553 white gold miners to investigate the types of
emphysema caused by respirable crystalline silica and found that the
occurrence of emphysema was related to both smoking and dust exposure.
This study also found a significant association between emphysema (both
panacinar and centriacinar emphysema types) and length of employment
for miners working in high dust occupations. A separate study by Hnizdo
et al. (1994) on life-long non-smoking South African gold miners found
that the degree of emphysema was significantly associated with the
degree of hilar gland nodules, which the authors suggested might serve
as a surrogate for respirable crystalline silica exposure. While Hnizdo
et al. (2000) conversely found that emphysema prevalence was decreased
in relation to dust exposure, the authors suggested that selection bias
was responsible for this finding.
The findings of several cross-sectional and case-control studies
discussed in the OSHA (2013b) Health Effects Literature were more
mixed. For example, de Beer et al. (1992) found an increased risk for
emphysema; however, the reported odds ratio (OR) was smaller than
previously reported by Becklake et al. (1987).
The OSHA (2013b) Health Effects Literature also recognized that
several of the referenced studies (Becklake et al., 1987 Hnizdo et al.,
1994) found that emphysema might occur in respirable crystalline
silica-exposed workers who did not have silicosis and suggested a
causal relationship between respirable crystalline silica exposure and
emphysema. Experimental (animal) studies found that emphysema occurred
at lower respirable crystalline silica exposure concentrations than
fibrosis in the airways or the appearance of early silicotic nodules
(Wright et al., 1988). These findings tended to support human studies
that respirable crystalline silica-induced emphysema can occur absent
signs of silicosis.
Green and Vallyathan (1996) reviewed several studies of emphysema
in workers exposed to silica and found an association between
cumulative dust exposure and death from emphysema. The IARC (1997) also
reviewed several studies and concluded that exposure to respirable
crystalline silica increases the risk of emphysema. Finally, NIOSH
(2002b) concluded in its Hazard Review that occupational exposure to
respirable crystalline silica is associated with emphysema. However,
some epidemiological studies suggested that this effect might be less
frequent or absent in non-smokers.
Overall, MSHA agrees with OSHA that exposure to respirable
crystalline silica causes emphysema even in the absence of silicosis.
b. Chronic Bronchitis
Chronic bronchitis is long-term inflammation of the bronchi,
increasing the risk of lung infections. This condition develops slowly
by small increments and ``exists'' when it reaches a certain stage
(i.e., the presence of a productive cough sputum production for at
least 3 months of the year for at least 2 consecutive years) (ATS,
2010b).
OSHA considered many studies that examined the association between
respirable crystalline silica exposure and chronic bronchitis,
concluding the following: (1) exposure to respirable crystalline silica
causes chronic bronchitis regardless of whether silicosis is present;
(2) an exposure-response relationship may exist; and (3) smokers may be
at an increased risk of chronic bronchitis compared to non-smokers.
MSHA has reviewed the literature and agrees with OSHA's conclusions.
Miller et al. (1997) reported a 20 percent increased risk of
chronic bronchitis in a British mining cohort compared to the disease
occurrence in the general population. Using British pneumoconiosis
field research data, Hurley et al. (2002) calculated estimates of
mixed-RCMD-related disease in British coal miners at exposure levels
that were common in the late 1980s and related their lung function and
development of chronic bronchitis with their cumulative dust exposure.
The authors estimated that by the age of 58, 5.8 percent of these men
would report breathlessness for every 100 gram-hour/m\3\ dust exposure.
The authors also estimated the prevalence of chronic bronchitis at age
58 would be 4 percent per 100 gram-hour/m\3\ of dust exposure. These
miners averaged over 35 years of tenure in mining and a cumulative
respirable dust exposure of 132 gram-hour/m\3\.
Cowie and Mabena (1991) found that chronic bronchitis was present
in 742 of
[[Page 44876]]
1,197 (62 percent) black South African gold miners, and Ng et al.
(1992b) found a higher prevalence of respiratory symptoms, independent
of smoking and age, in Singaporean granite quarry workers exposed to
high levels of dust (rock drilling and crushing) compared to those
exposed to low levels of dust (maintenance and transport workers).
However, Irwig and Rocks (1978) compared symptoms of chronic bronchitis
in silicotic and non-silicotic South African gold miners and did not
find as clear a relationship as did the above studies, concluding that
the symptoms were not statistically more prevalent in the silicotic
miners, although prevalence was slightly higher.
Sluis-Cremer et al. (1967) found that dust-exposed male smokers had
a higher prevalence of chronic bronchitis than non-dust exposed smokers
in a gold mining town in South Africa. Similarly, Wiles and Faure
(1977) found that the prevalence of chronic bronchitis rose
significantly with increasing dust concentration and cumulative dust
exposure in South African gold miners of smokers, nonsmokers, and ex-
smokers. Rastogi et al. (1991) found that female grinders of agate
stones in India had a significantly higher prevalence of acute
bronchitis, but they had no increase in the prevalence of chronic
bronchitis compared to controls matched by socioeconomic status, age,
and smoking. However, the study noted that respirable crystalline
silica exposure durations were very short, and control workers may also
have been exposed to respirable crystalline silica.
Studies examining the effect of years of mining on chronic
bronchitis risk were mixed. Samet et al. (1984) found that prevalence
of symptoms of chronic bronchitis was not associated with years of
mining in a population of underground uranium miners, even after
adjusting for smoking. However, Holman et al. (1987) studied gold
miners in West Australia and found that the prevalence of chronic
bronchitis, as indicated by ORs (controlled for age and smoking), was
significantly increased in those that had worked in the mines for over
1 year, compared to lifetime non-miners. In addition, while other
studies found no effect of years of mining on chronic bronchitis risk,
those studies often qualified this result with possible confounding
factors. For example, Kreiss et al. (1989) studied 281 hard-rock
(molybdenum) miners and 108 non-miner residents of Leadville, Colorado.
They did not find an association between the prevalence of chronic
bronchitis and work in the mining industry (Kreiss et al., 1989);
however, it is important to note that the mine had been temporarily
closed for 5 months when the study began, so miners were not exposed at
the time of the study.
The American Thoracic Society (ATS) (1997) published a review
finding chronic bronchitis to be common among worker groups exposed to
dusty environments contaminated with respirable crystalline silica.
NIOSH (2002b) also published a review finding that occupational
exposure to respirable crystalline silica has been associated with
bronchitis; however, some epidemiological studies suggested this effect
might be less frequent or absent in non-smokers.
Finally, Hnizdo et al. (1990) found an independent exposure-
response relationship between respirable crystalline silica exposure
and impaired lung function. For miners with less severe impairment, the
effects of smoking and dust together were additive. However, for miners
with the most severe impairment, the effects of smoking and dust were
synergistic (i.e., more than additive).
Overall, MSHA agrees with OSHA's conclusion that exposure to
respirable crystalline silica causes chronic bronchitis regardless of
whether silicosis is present and that an exposure-response relationship
may exist.
c. Pulmonary Function Impairment
Pulmonary function impairment, generally defined as reduction below
the lower limit of normal predicted by reference equations (and in
older literature as less than 80 percent predicted) of diffusion
capacity for carbon monoxide (DLCOcSB), total lung capacity (TLC), FVC,
or FEV1 is also a common condition of NMRD. Based on its
review of the evidence in numerous longitudinal and cross-sectional
studies and reviews, OSHA concluded that there is an exposure-response
relationship between respirable crystalline silica and the development
of impaired lung function. OSHA also concluded that the effect of
tobacco smoking on this relationship may be additive or synergistic,
and workers who were exposed to respirable crystalline silica but did
not show signs of silicosis may also have pulmonary function
impairment. MSHA has reviewed the studies cited by OSHA and agrees with
their conclusions.
OSHA reviewed several longitudinal studies regarding the
relationship between respirable crystalline silica exposure and
pulmonary function impairment. To evaluate whether exposure to silica
affects pulmonary function in the absence of silicosis, the studies
focused on workers who did not exhibit progressive silicosis.
Among both active and retired Vermont granite workers exposed to an
average quartz dust exposure level of 60 [micro]g/m\3\, researchers
found no exposure-related decreases in pulmonary function (Graham et
al., 1981, 1994). However, Eisen et al. (1995) found significant
pulmonary decrements among a subset of granite workers who left work
and consequently did not voluntarily participate in the last of a
series of annual pulmonary function tests (termed ``dropouts''). This
group experienced steeper declines in lung function compared to the
subset of workers who remained at work and participated in all tests
(termed ``survivors''), and these declines were significantly related
to dust exposure. Exposure-related changes in lung function were also
reported in a 12-year study of granite workers (Malmberg et al., 1993),
in two 5-year studies of South African miners (Hnizdo, 1992; Cowie,
1998), and in a study of foundry workers whose lung function was
assessed between 1978 and 1992 (Hertzberg et al., 2002). Similar
reductions in FEV1 (indicating an airway obstruction) were
linked to respirable crystalline silica exposure.
Each of these studies reported their findings in terms of rates of
decline in any of several pulmonary function measures (e.g.,
FEV1, FVC, FEV1/FVC). To put these declines in
perspective, Eisen et al. (1995) reported that the rate of decline in
FEV1 seen among the dropout subgroup of Vermont granite
workers was 4 ml per 1,000 [micro]g/m\3\-year (4 ml per mg/m\3\-year)
of exposure to respirable granite dust. By comparison, FEV1
declines at a rate of 10 ml/year from smoking one pack of cigarettes
daily. From their study of foundry workers, Hertzberg et al. (2002)
reported a 1.1 ml/year decline in FEV1 and a 1.6 ml/year
decline in FVC for each 1,000 [micro]g/m\3\-year (1 mg/m\3\-year) of
respirable crystalline silica exposure after controlling for ethnicity
and smoking. From these rates of decline, they estimated that exposure
to 100 [micro]g/m\3\ of respirable crystalline silica for 40 years
would result in a total loss of FEV1 and FVC that was less
than, but still comparable to, smoking a pack of cigarettes daily for
40 years. Hertzberg et al. (2002) also estimated that exposure to the
existing MSHA standard (100 [micro]g/m\3\) for 40 years would increase
the risk of developing abnormal FEV1 or FVC by factors of
1.68 and 1.42, respectively.
OSHA reviewed cross-sectional studies that described relationships
between lung function loss and respirable crystalline silica exposure
or
[[Page 44877]]
exposure measurement surrogates (e.g., tenure). The results of these
studies were similar to those longitudinal studies already discussed.
In several studies, respirable crystalline silica exposure was found to
reduce lung function of:
White South African gold miners (Hnizdo et al., 1990),
Black South African gold miners (Cowie and Mabena, 1991;
Irwig and Rocks, 1978),
Respirable crystalline silica-exposed workers in Quebec
(B[eacute]gin et al., 1995),
Rock drilling and crushing workers in Singapore (Ng et
al., 1992b),
Granite shed workers in Vermont (Theriault et al., 1974a,
1974b),
Aggregate quarry workers and coal miners in Spain (Montes
et al., 2004a, 2004b),
Concrete workers in the Netherlands (Meijer et al., 2001),
Chinese refractory brick manufacturing workers in an iron-
steel plant (Wang et al., 1997),
Chinese gemstone workers (Ng et al., 1987b),
Hard-rock miners in Manitoba, Canada (Manfreda et al.,
1982) and in Colorado (Kreiss et al., 1989),
Pottery workers in France (Neukirch et al., 1994),
Potato sorters in the Netherlands (Jorna et al., 1994),
Slate workers in Norway (Suhr et al., 2003), and
Men in a Norwegian community with years of occupational
exposure to respirable crystalline silica (quartz) (Humerfelt et al.,
1998).
The OSHA (2013b) Health Effects Literature recognized that many of
these studies found that pulmonary function impairment: (1) can occur
in respirable crystalline silica-exposed workers without silicosis, (2)
was still observable when controlling for silicosis in the analysis,
and (3) was related to the magnitude and duration of respirable
crystalline silica exposure, rather than to the presence or severity of
silicosis. Many other studies in the OSHA (2013b) Health Effects
Literature have also found a relationship between respirable
crystalline silica exposure and lung function impairment, including
IARC (1997), the ATS (1997), and Hnizdo and Vallyathan (2003).
MSHA reviewed the studies and agrees with OSHA's finding that there
is an exposure-response relationship between respirable crystalline
silica and the impairment of lung function. MSHA also agrees with
OSHA's finding that the effect of tobacco smoking on this relationship
may be additive or synergistic, and that workers who were exposed to
respirable crystalline silica, but did not show signs of silicosis, may
also have pulmonary function impairment.
3. Carcinogenic Effects
a. Lung Cancer
Lung cancer, an irreversible and usually fatal disease, is a type
of cancer that forms in lung tissue. Agreeing with the conclusion of
other government and public health organizations that respirable
crystalline silica is a ``known human carcinogen,'' MSHA has
preliminarily found that the scientific literature supports that
respirable crystalline silica exposure significantly increases the risk
of lung cancer mortality among miners. This determination is consistent
with the conclusions of other government and public health
organizations, including the IARC (1997b, 2012), the NTP (2000, 2016),
NIOSH (2002b), the ATS (1997), and the American Conference of
Governmental Industrial Hygienists (ACGIH[supreg], (2010)). The
Agency's determination is supported by epidemiological literature,
encompassing more than 85 studies of occupational cohorts from more
than a dozen industrial sectors including: granite/stone quarrying and
processing (Carta et al., 2001; Attfield and Costello, 2004; Costello
et al., 1995; Gu[eacute]nel et al., 1989a,b), industrial sand
(Sanderson et al., 2000; Hughes et al., 2001; McDonald et al., 2001,
2005; Rando et al., 2001; Steenland and Sanderson, 2001), MNM mining
(Steenland and Brown, 1995a; deKlerk and Musk, 1998; Roscoe et al.,
1995; Hessel et al., 1986, 1990; Hnizdo and Sluis-Cremer, 1991; Reid
and Sluis-Cremer, 1996; Hnizdo et al., 1997; Chen et al., 1992;
McLaughlin et al., 1992; Chen and Chen, 2002; Chen et al., 2006;
Schubauer-Berigan et al., 2009; Hua et al., 1994; Meijers et al., 1991;
Finkelstein 1998; Chen et al., 2012; Liu et al., 2017a; Wang et al.,
2020a,b; Wang et al., 2021), coal mining (Meijers et al., 1988; Miller
et al., 2007; Miller and MacCalman, 2010; Miyazaki and Une, 2001;
Graber et al., 2014a,b; Tomaskova et al., 2012, 2017, 2020, 2022; Kurth
et al., 2020), pottery (Winter et al., 1990; McLaughlin et al., 1992;
McDonald et al., 1995), ceramic industries (Starzynski et al., 1996),
diatomaceous earth (Checkoway et al., 1993, 1996, 1997, 1999; Seixas et
al., 1997; Rice et al., 2001), and refractory brick industries
(cristobalite exposures) (Dong et al., 1995).
The strongest evidence comes from the worldwide cohort and case-
control studies reporting excess lung cancer mortality among workers
exposed to respirable crystalline silica in various industrial sectors,
confirmed by the 10-cohort pooled case-control analysis by Steenland et
al. (2001a), the more recent pooled case-control analysis of seven
European countries by Cassidy et al. (2007), and two national death
certificate registry studies (Calvert et al., 2003 in the United
States; Pukkala et al., 2005 in Finland).
Recent studies examined lung cancer mortality among coal and non-
coal miners (Meijers et al., 1988, 1991; Starzynski et al., 1996;
Miyazaki and Une, 2001; Tomaskova et al., 2012, 2017, 2020, 2022;
Attfield and Kuempel, 2008; Graber et al., 2014a, 2014b; Kurth et al.,
2020; NIOSH, 2019a). These studies also discuss the associations
between RCMD and respirable crystalline silica exposures with lung
cancer in coal mining populations. Furthermore, these newer studies are
consistent with the conclusion of OSHA's final Quantitative Risk
Assessment (QRA) (2016a) that respirable crystalline silica is a human
carcinogen. MSHA preliminarily concludes that miners, both MNM and coal
miners, are at risk of developing lung cancer due to their occupational
exposure to respirable crystalline silica.
In addition, based on its review of the literature, MSHA has
preliminarily determined that radiographic silicosis is a marker for
lung cancer risk. Reducing exposure to levels that lower the silicosis
risk would reduce the lung cancer risk to exposed miners (Finkelstein,
1995, 2000; Brown, 2009). MSHA has also found that, based on the
available epidemiological and animal data, respirable crystalline
silica causes lung cancer (IARC, 2012; RTECS, 2016; ATSDR, 2019).
Miners who inhale respirable crystalline silica over time are at
increased risk of developing silicosis and lung cancer (Greaves, 2000;
Erren et al., 2009; Tomaskova et al., 2017, 2020, 2022).
Toxicity studies provide additional evidence of the carcinogenic
potential of respirable crystalline silica. Studies using DNA exposed
directly to freshly fractured respirable crystalline silica demonstrate
the direct effect respirable crystalline silica had on DNA breakage.
Cell culture research has investigated the processes by which
respirable crystalline silica disrupt normal gene expression and
replication. Studies have demonstrated that chronic inflammatory and
fibrotic processes resulting in oxidative and cellular damage may lead
to neoplastic changes in the lung (Goldsmith, 1997). In addition, the
biologically damaging physical characteristics of respirable
crystalline silica and its direct and indirect
[[Page 44878]]
genotoxicity (Schins et al., 2002; Borm and Driscoll, 1996) support
MSHA's preliminary determination that respirable crystalline silica is
an occupational carcinogen.
b. Cancers of Other Sites
In addition to lung cancer, OSHA reviewed studies examining the
relationship between silica exposure and cancers at other sites. MSHA
notes that OSHA reviewed these mortality studies (e.g., cancer of the
larynx and the digestive system, including the stomach and esophagus)
and found that studies suggesting a dose-response relationship were too
limited in terms of size, study design, or potential for confounding
variables to be conclusive. OSHA also pointed to the NIOSH (2002b)
silica (respirable crystalline silica) hazard review, which concluded
that no association has been established between respirable crystalline
silica exposure and excess mortality from cancer at other sites. MSHA
has reviewed these studies and agrees with OSHA's conclusion. The
following summarizes the studies reviewed with inconclusive findings.
(1) Laryngeal Cancer
Three lung cancer studies (Checkoway et al., 1997; Davis et al.,
1983; McDonald et al., 2001) included in OSHA's health literature
review suggest an association between respirable crystalline silica
exposure and increased mortality from laryngeal cancer. However, a
small number of cases were reported and researchers were unable to
determine a statistically significant effect. Therefore, there is
little evidence of an association based on these studies.
(2) Gastric (Stomach) Cancer
OSHA reviewed several studies in its 2013b health literature review
to assess a potential relationship between respirable crystalline
silica exposures and stomach cancers. OSHA's literature review noted
observations made previously by Cocco et al. (1996) and in the NIOSH
respirable crystalline silica hazard review (2002b), which found that
most epidemiological studies of respirable crystalline silica and
stomach cancer did not sufficiently adjust for the effects of
confounding factors. In addition, some of these studies were not
properly designed to assess a dose-response relationship (e.g.,
Finkelstein and Verma, 2005; Moshammer and Neuberger, 2004; Selikoff,
1978; Stern et al., 2001) or did not demonstrate a statistically
significant dose-response relationship (e.g., Calvert et al., 2003;
Tsuda et al., 2001). For these reasons, MSHA determined these studies
were inconclusive in the context of this rulemaking.
(3) Esophageal Cancer
OSHA considered several studies that examined the relationship
between respirable crystalline silica exposures and esophageal cancer
and found that the studies were limited in terms of size, study design,
or potential for confounding variables. Three nested case-control
studies of Chinese workers demonstrated a dose-response association
between increased risk of esophageal cancer mortality and respirable
crystalline silica exposure (Pan et al., 1999; Wernli et al., 2006; Yu
et al., 2005). Other studies (Tsuda et al., 2001; Xu et al., 1996a)
also indicated elevated rates of esophageal cancer mortality with
respirable crystalline silica exposure. However, OSHA noted that
confounding factors due to other occupational exposures was possible.
Additionally, two large national mortality studies in Finland and the
United States did not show a positive association between respirable
crystalline silica exposure and esophageal cancer mortality (Calvert et
al., 2003; Weiderpass et al., 2003). MSHA agrees with OSHA's conclusion
that the literature does not support attributing increased esophageal
cancer mortality to exposure to respirable crystalline silica.
(4) Other Sites
NIOSH (2002b) conducted a health literature review of the health
effects potentially associated with respirable crystalline silica
exposure, which identified only infrequent reports of statistically
significant excesses of deaths for other cancers. Cancer studies have
been reported in the following organs/systems: salivary gland, liver,
bone, pancreas, skin, lymphopoietic or hematopoietic, brain, and
bladder (see NIOSH, 2002b for full bibliographic references). However,
the findings were not observed consistently among epidemiological
studies, and NIOSH (2002b) concluded that no association has been
established between these cancers and respirable crystalline silica
exposure. OSHA concurred with NIOSH that these isolated reports of
excess cancer mortality were insufficient to determine the role of
respirable crystalline silica exposure.
Overall, OSHA concluded that evidence of an association between
silica exposure and cancer at sites other than the lungs is not
sufficient. MSHA agrees with OSHA's conclusion.
4. Renal Disease
Renal disease is characterized by the loss of kidney function, and
in the case of ESRD, the need for a regular course of long-term
dialysis or a kidney transplant. MSHA reviewed a wide variety of
longitudinal and mortality epidemiological studies, including case
series, case-control, and cohort studies, as well as case reports, and
preliminarily concludes that respirable crystalline silica exposure
increases the risk of morbidity and/or mortality related to ESRD.
However, MSHA notes that the available literature on respirable
crystalline silica exposures and renal disease in coal miners is less
conclusive than the literature related to MNM miners.
Epidemiological studies have found statistically significant
associations between occupational exposure to respirable crystalline
silica and chronic renal disease (e.g., Calvert et al., 1997), sub-
clinical renal changes, including proteinuria and elevated serum
creatinine (e.g., Ng et al., 1992a; Hotz et al., 1995; Rosenman et al.,
2000), ESRD morbidity (e.g., Steenland et al., 1990), ESRD mortality
(Steenland et al., 2001b, 2002a), and Wegener's granulomatosis (Nuyts
et al., 1995) (severe injury to the glomeruli that, if untreated,
rapidly leads to renal failure). The pooled analysis conducted by
Steenland et al. (2002a) is particularly convincing because it involved
a large number of workers from three combined cohorts and had well-
documented, validated job exposure matrices. Steenland et al. (2002a)
found a positive and monotonic exposure-response trend for both
multiple-cause mortality and underlying cause data. MSHA has
preliminarily determined that the underlying data from Steenland et al.
(2002a) are sufficient to provide useful estimates of risk.
Possible mechanisms suggested for respirable crystalline silica-
induced renal disease include: (1) a direct toxic effect on the kidney,
(2) a deposition in the kidney of immune complexes (e.g.,
Immunoglobulin A (IgA), an antibody blood protein) in the kidney
following respirable crystalline silica-related pulmonary inflammation,
and (3) an autoimmune mechanism (Gregorini et al., 1993; Calvert et
al., 1997). Steenland et al. (2002a) demonstrated a positive exposure-
response relationship between respirable crystalline silica exposure
and ESRD mortality.
Overall, MSHA preliminarily determines that respirable crystalline
silica exposure in mining increases the risk of renal disease.
[[Page 44879]]
5. Autoimmune Disease
Autoimmune diseases occur when the immune system mistakenly attacks
healthy tissues within the body, causing inflammation, swelling, pain,
and tissue damage. Examples include rheumatoid arthritis (RA), systemic
lupus erythematosus (SLE), scleroderma, and systemic sclerosis (SSc).
Based on its literature review, MSHA preliminarily concludes that there
is a causal association between occupational exposure to respirable
crystalline silica and the development of systemic autoimmune diseases
in miners. However, no studies are available to date that can be used
to model respirable crystalline silica-exposure risk in a formal
quantitative risk analysis.
Wallden et al. (2020) found that respirable crystalline silica
exposure is correlated with an increased risk of developing ulcerative
colitis, which increases with duration of exposure (work tenure) and
the level of exposure. This effect was especially significant in men.
Schmajuk et al. (2019) found that RA was significantly associated with
coal mining and other non-coal occupations exposed to respirable
crystalline silica. Finally, Vihlborg et al. (2017) found a significant
increased risk of seropositive RA with high exposure (>0.048 mg/m\3\)
to respirable crystalline silica dust when compared to individuals with
no or lower exposure by examining detailed exposure-response
relationships across four different respirable crystalline silica dose
groups (quartiles): <23 [micro]g/m\3\, 24 to 35 [micro]g/m\3\, 36 to 47
[micro]g/m\3\, and >48 [micro]g/m\3\. However, these researchers did
not report the risk of sarcoidosis and seropositive RA in relation to
respirable crystalline silica exposure using logistic regressions
resulting in models that could be used in the risk assessment. In
addition, the meta-analysis of 19 published case-control and cohort
studies on scleroderma by Rubio-Rivas et al. (2017) found statistically
significant risks among individuals exposed to respirable crystalline
silica, solvents, silicone, breast implants, epoxy resins, pesticides,
and welding fumes, but did not provide detailed quantitative exposure
information.
C. Conclusion
MSHA preliminarily concludes that occupational exposure to
respirable crystalline silica causes silicosis (acute silicosis,
accelerated silicosis, simple chronic silicosis, and PMF), NMRD
(including COPD), lung cancer, and kidney disease. Each of these
effects is exposure-dependent, chronic, irreversible, potentially
disabling, and can be fatal. MSHA suspects that respirable crystalline
silica exposure is also linked to the development of some autoimmune
disorders through inflammation pathways.
The scientific literature (including peer-reviewed medical,
toxicological, public health, and other related disciplinary
publications) is robust and compelling. It shows that miners exposed to
the existing respirable crystalline silica limit of 100 [mu]g/m\3\
still have an unacceptable amount of excess risk for developing and
dying from diseases related to occupational respirable crystalline
silica exposures and still suffer material impairments of health or
functional capacity.
VI. Preliminary Risk Analysis Summary
MSHA's preliminary risk analysis (PRA) quantifies risks associated
with five specific health outcomes identified in the separate,
standalone Health Effects document: silicosis morbidity and mortality,
and mortality from NMRD, lung cancer, and ESRD. The standalone
document, entitled Preliminary Risk Analysis (PRA document), has been
placed into the rulemaking docket for the MSHA respirable crystalline
silica rulemaking (RIN 1219-AB36, Docket ID no. MSHA-2023-0001) and is
available on MSHA's website.
MSHA developed a PRA to support the risk determinations required to
set an exposure limit for a toxic substance under the Mine Act. MSHA's
PRA quantifies the health risk to miners exposed to respirable
crystalline silica under the existing exposure limits for MNM and coal
miners, at the proposed PEL of 50 [mu]g/m\3\, and at the proposed
action level of 25 [mu]g/m\3\.
This analysis addresses three questions related to the proposed
rule:
(1) whether potential health effects associated with existing
exposure conditions constitute material impairment to any miner's
health or functional capacity;
(2) whether existing exposure conditions place miners at risk of
incurring any material impairment if regularly exposed for the period
of their working life; and
(3) whether the proposed rule would reduce those risks.
To answer these questions, MSHA relied on the large body of
research on the health effects of respirable crystalline silica and
several published, peer-reviewed, quantitative risk assessments that
describe the risk of exposed workers to silicosis mortality and
morbidity, NMRD mortality, lung cancer mortality, and ESRD mortality.
These assessments are based on several studies of occupational cohorts
in a variety of industrial sectors. The underlying studies are
described in the Health Effects document and are summarized in Section
V. Health Effects Summary of this preamble.
This summary highlights the main findings from the PRA, briefly
describes how they were derived, and directs readers interested in more
detailed information to corresponding sections of the standalone PRA
document.
A. Summary of MSHA's Preliminary Risk Analysis Process and Methods
MSHA evaluated the literature and selected an exposure-response
model for each of the five health endpoints--silicosis morbidity,
silicosis mortality, NMRD mortality, lung cancer mortality, and ESRD
mortality. The selected exposure-response models were used to estimate
lifetime excess risks and lifetime excess cases among the current
population of MNM and coal miners based on real exposure conditions, as
indicated by the samples in the compliance sampling datasets.
MSHA's PRA is largely based on the methodology and findings from a
peer-reviewed January 2013 OSHA preliminary quantitative risk
assessment (PQRA) and associated analysis of health effects in
connection with OSHA's promulgation of a rule setting PELs for
workplace exposure to respirable crystalline silica. OSHA's PQRA
presented quantitative relationships between respirable crystalline
silica exposure and multiple health endpoints. Following multiple legal
challenges, the U.S. Court of Appeals for the D.C. Circuit rejected
challenges to OSHA's risk assessment methodology and its findings on
different health risks. N. Am.'s Bldg. Trades Unions v. OSHA, 878 F.3d
271, 283-89 (D.C. Cir. 2017).
MSHA's PRA presents detailed quantitative analyses of health risks
over a range of exposure concentrations that have been observed in MNM
and coal mines. MSHA applied exposure-response models to estimate the
respirable crystalline silica-related risk of material impairment of
health or functional capacity of miners exposed to respirable
crystalline silica at three levels--(1) the existing standards, (2) the
proposed PEL, and (3) the proposed action level. As in past MSHA
rulemakings, MSHA estimated and compared lifetime excess risks
associated with exposures at the existing and proposed PEL (and at the
proposed action level) over a miner's full working life of 45 years.
[[Page 44880]]
MSHA's PRA is also based on a compilation of miner exposure data to
respirable crystalline silica. For the MNM sector, MSHA evaluated
57,769 valid respirable dust samples collected between January 2005 and
December 2019; and for the coal sector, MSHA evaluated 63,127 valid
respirable dust samples collected between August 2016 and July 2021.
The compiled data set characterizes miners' exposures to respirable
crystalline silica in various locations (e.g., underground, surface),
occupations (e.g., drillers, underground miners, equipment operators),
and commodities (e.g., metal, nonmetal, stone, crushed limestone, sand
and gravel, and coal). MSHA enforcement sampling indicates a wide range
of exposure concentrations. These include exposures from below the
proposed action level (25 [mu]g/m\3\) to above the existing standards
(100 [mu]g/m\3\ in MNM standards, 100 [mu]g/m\3\ MRE in coal standards,
which is approximately 85.7 [mu]g/m\3\ ISO).\18\
---------------------------------------------------------------------------
\18\ As discussed in the PRA, the existing PEL for coal is 100
[mu]g/m\3\ MRE, measured as a full-shift time-weighted average
(TWA). To calculate risks consistently for both coal and MNM miners,
the PRA converts the MRE full-shift TWA concentrations experienced
by coal miners to ISO 8-hour TWA concentrations. (See Section 4 of
the PRA document for a full explanation.) The equation used to
convert MRE full-shift TWA concentrations into ISO 8-hour TWA
concentrations is:
ISO 8-hour TWA concentration = (MRE TWA) x (original sampling
time)/(480 minutes) x 0.857
Exposures at TWA 100 [mu]g/m\3\ MRE and SWA 85.7 [mu]g/m\3\ ISO
are only equivalent when the sampling duration is 480 minutes (eight
hours). However, for the sake of simplicity and for comparison
purposes, the risk analysis approximates exposures at the existing
coal exposure limit of 100 MRE [mu]g/m\3\ as 85.7 [mu]g/m\3\ ISO.
Thus, ISO concentration values (measured as an 8-hour TWA) were used
as the exposure metric when (a) calculating risk under the
assumption of full compliance with the existing standards and (b)
calculating risk under the assumption that no exposure exceeds the
proposed PEL of 50 [mu]g/m\3\. To simulate compliance among coal
miners at the existing exposure limit, exposures were capped at 85.7
[mu]g/m\3\ measured as an ISO 8-hour TWA.
---------------------------------------------------------------------------
The primary results of the PRA are the calculated number of deaths
and illnesses avoided assuming full compliance after implementation of
MSHA's proposed rule. These calculations were performed for non-fatal
silicosis illnesses (morbidity) and for deaths (mortality) due to
silicosis, lung cancer, NMRD, and ESRD. For each health outcome, the
reduced number of illnesses or deaths is calculated as the difference
between (a) the number of illnesses and deaths currently occurring in
the industry, assuming mines fully comply with the existing standards
(100 [mu]g/m\3\ for MNM and 85.7 [mu]g/m\3\ ISO for coal) and (b) the
number of deaths and illnesses expected to occur following
implementation of the proposed rule, which includes a proposed PEL of
50 [mu]g/m\3\ for a full shift exposure, calculated as an 8-hour TWA.
Risks and cases were estimated under two scenarios: (a) a Baseline
scenario where all exposures were capped at 100 [mu]g/m \3\ for MNM
miners and at 85.7 [mu]g/m \3\ for coal miners, and (b) a proposed 50
[mu]g/m \3\ scenario where all risks were capped at the proposed PEL of
50 [mu]g/m \3\ for both MNM and coal miners. The difference between the
two scenarios yields the estimated reduction in lifetime excess risks
and in lifetime excess cases due to the proposed PEL.
To calculate risks, MSHA grouped MNM miners into the following
exposure intervals: <=25, >25 to <=50, >50 to <=100, >100 to <=250,
>250 to <=500, and >500 [mu]g/m \3\. MSHA grouped coal miners into the
following exposure intervals: <=25, >25 to <=50, >50 to <=85.7, >85.7
to <=100, >100 to <=250, >250 to <=500, and >500 [mu]g/m \3\. MSHA
calculated the median of all exposure samples in each exposure interval
and assumed the population of miners is distributed across the exposure
intervals in proportion to the number of exposure samples from the
compliance dataset in each interval. Then, miners were assumed to
encounter constant exposure at the median value of their assigned
exposure interval. MSHA adjusted the annual cumulative exposure by a
full-time equivalency (FTE) factor to account for the fact that miners
may experience more or less than 2,000 hours of exposure per year. MSHA
calculated the FTE adjustment factor as the weighted average of the
production employee FTE ratio (0.99 for MNM and 1.14 for coal) and the
contract miner FTE ratio (0.59 for MNM and 0.64 for coal), where the
weights are the number of miners (150,928 for MNM production employees,
60,275 for MNM contract miners, 51,573 for coal production employees,
and 22,003 for coal contract miners). For example, the weighted average
FTE ratio for MNM is (0.987 x 150,928 + 0.591 x 60,275)/(150,928 +
60,275) = 0.87 and is (1.139 x 51,573 + 0.636 x 22,003)/(51,573 +
22,003) = 0.99 for coal.
MSHA calculated excess risk, which refers to the additional risk of
disease and death attributable to exposure to respirable crystalline
silica. For silicosis morbidity, MSHA used an exposure-response model
that directly yields the accumulated or lifetime excess risk of
silicosis morbidity, assuming there is no background rate \19\ of
silicosis in an unexposed (i.e., non-miner) group. For the four
mortality endpoints (silicosis mortality, lung cancer mortality, NMRD
mortality, and ESRD mortality), MSHA used cohort life tables to
calculate excess risks, assuming all miners begin working at age 21,
retire at the end of age 65, and do not live past age 80. From the life
tables, MSHA acquired the lifetime mortality risk by summing the miner
cohort's mortality risks in each year from age 21 through age 80. Life
tables were also constructed for unexposed (i.e., non-miner) groups
assumed to die from a given disease at typical rates for the U.S. male
population. MSHA used 2018 data for all males in the U.S. (published by
the National Center for Health Statistics, 2020b) to estimate (a) the
disease-specific mortality rates among unexposed males and (b) the all-
cause mortality rates among both groups (exposed miners and unexposed
non-miners).
---------------------------------------------------------------------------
\19\ Here, the ``background'' risk (or rate) refers to the risk
of disease that the exposed person would have experienced in the
absence of exposure to respirable crystalline silica. These
background morbidity and mortality rates are measured using the
disease-specific rates among the general population, which is not
exposed to respirable crystalline silica.
---------------------------------------------------------------------------
For a given scenario (either Baseline or Proposed 50 [mu]g/m\3\),
MSHA constructed life tables in the manner described above, both for a
miner cohort exposed to respirable crystalline silica and for an
unexposed non-miner cohort. MSHA calculated excess risk of the disease
as the difference between the two cohorts' disease-specific mortality
risk (due to silicosis, lung cancer, NMRD, or ESRD). MSHA determined
the lifetime excess cases by multiplying the lifetime excess risk by
the number of exposed miner FTEs (including both production employee
FTEs and contract miner FTEs). Risks and cases were calculated
separately for each exposure interval listed above. Then, the lifetime
excess cases were aggregated across all exposure intervals. MSHA
calculated the final lifetime excess risks per 1,000 miners in the full
population by dividing the total number of lifetime excess cases by the
total number of miners in the population (exposed at any interval).
Finally, to estimate the risk reductions and avoided cases of illness
due to the proposed PEL, MSHA compared the lifetime excess risks and
lifetime excess cases across the two scenarios (Baseline and Proposed
50 [mu]g/m\3\).
B. Overview of Epidemiologic Studies
MSHA reviewed extensive research on the health effects of
respirable crystalline silica and several quantitative risk assessments
published in the peer-reviewed scientific literature
[[Page 44881]]
regarding occupational exposure risks of illness and death from
silicosis, NMRD, lung cancer, and ESRD. The Health Effects document
describes the specific studies reviewed by MSHA. Of the many studies
evaluated, MSHA believes that the 13 studies used by OSHA (2013b) to
estimate risks provide reliable estimates of the disease risk posed by
miners' exposure to respirable crystalline silica. These studies are
summarized in Table VI-1.
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Of these 13 studies, OSHA selected one per health endpoint for
final modeling and estimation of lifetime excess risk and cases.
Combining the five selected studies with the observed exposure data
yields estimates of actual lifetime excess risks and lifetime excess
cases among worker populations based on real exposure conditions. Table
VI-2 presents the 13 studies from OSHA's PQRA, which MSHA has also
considered. MSHA evaluated the evidence of OSHA's analysis of the 13
studies and the accompanying risks associated with exposure at 25, 50,
100, 250, and 500 [mu]g/m\3\. Thorough evaluation has led MSHA to
determine that the studies OSHA selected still provide the best
available epidemiological models. However, MSHA utilized the Miller and
MacCalman (2010) study to estimate risks. This study was published
after OSHA completed much of its modeling for their 2013 PRA (OSHA,
2013b). The study was included in OSHA's health effects assessment and
its PQRA. The following lists the study used by MSHA for each health
endpoint:
Silicosis morbidity: Buchanan et al. (2003);
Silicosis mortality: Mannetje et al. (2002b);
NMRD mortality: Park et al. (2002);
Lung cancer mortality: Miller and MacCalman (2010); and
ESRD mortality: Steenland et al. (2002a).
MSHA developed its risk estimates based on recent mortality data
and using certain assumptions that differed from those used by OSHA, as
explained in the standalone PRA document. Examples of these MSHA
assumptions include a lifetime that ends at age 80, updated background
mortality data and all-cause mortality, miner population sizes, and
miner-specific full-time equivalents (FTEs).\20\
---------------------------------------------------------------------------
\20\ FTEs were used to adjust the cumulative exposure over a
year based on the average number of hours that miners work.
---------------------------------------------------------------------------
MSHA's modeling has been done using life tables, in a manner
consistent with OSHA's PQRA. In general, the life table is a technique
that allows estimation of excess risk of disease-specific mortality
while factoring in the probability of surviving to a particular age
assuming no exposure to respirable crystalline silica. This analysis
accounts for competing causes of death, background mortality rates of
the disease, and the effect of the accumulation of risk due to elevated
mortality rates in each year of a working life. For each cause of
mortality, the selected study was used in the life table analysis to
compute the increase in miners' disease-specific mortality rates
attributable to respirable crystalline silica exposure.
MSHA uses cumulative exposure (i.e., cumulative dose) to
characterize the total exposure over a 45-year working life. Cumulative
exposure is defined as the product of exposure duration and exposure
intensity (i.e., exposure level). Cumulative exposure is the predictor
variable in the selected exposure-response models.
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For each health endpoint, MSHA generated two sets of risk
estimates--one representing a scenario of full compliance with the
existing standards (herein referred to as the ``Baseline'' scenario)
and another representing a scenario wherein no samples exceed the
proposed PEL (herein referred to as the ``Proposed 50 [mu]g/m\3\''
scenario). In the Baseline scenario, MNM miners in the >100-250, >250-
500, and >500 [mu]g/m\3\ groups were assigned exposure intensities of
100 [mu]g/m\3\ ISO. Coal miners in the 85.7-100, >100-250, >250-500,
and >500 [mu]g/m\3\ groups were assigned exposure intensities of 85.7
[mu]g/m\3\ ISO, calculated as an 8-hour TWA. Exposure intensities were
not changed for miners with lower exposure concentrations, because
their exposures were considered compliant with the existing standards.
A similar procedure was used for the Proposed 50 [mu]g/m\3\ scenario,
except that each miner group whose exposure exceeded the proposed PEL
was assigned a new exposure of 50 [mu]g/m\3\ ISO (for both MNM and
coal). This process--of creating an exposure profile based on actual
exposure data and modifying it based on the existing standards or the
proposed PEL--allowed MSHA to estimate real exposure conditions that
miners would encounter under each scenario, thereby enabling estimates
of the actual excess risks the current population of miners would
experience under each scenario (Baseline and Proposed 50 [mu]g/m\3\).
For purposes of calculating risk in the PRA, both for MNM and coal
miners, MSHA estimated excess risks by using the concentration
collected over the full shift and calculating it as a full-shift, 8-
hour TWA expressed in ISO standards. This metric of exposure
intensity--the 8-hour TWA concentration of respirable crystalline
silica in ISO standards--was used consistently across all sets of
estimates (both MNM and coal sectors, and both the Baseline and
Proposed 50 [mu]g/m\3\ scenarios), thereby facilitating meaningful
comparison. MSHA acknowledges that this metric does not correspond to
the manner in which coal exposure concentrations are calculated for
purposes of evaluating compliance under the existing standard.
Nonetheless, MSHA believes that a full-shift, 8-hour TWA concentration
accurately represents risks to miners and thus is the most appropriate
cumulative exposure metric for computing risk given that FTEs were used
to scale exposure durations relative to the assumption of 250 8-hour
workdays per year.
C. Summary of Studies Selected for Modeling
1. Silicosis Morbidity
Due to the long latency periods associated with chronic silicosis,
OSHA's respirable crystalline silica standard relied on the subset of
studies that were able to contact and evaluate many workers through
retirement. MSHA agrees that relying on studies that included retired
workers comes closest to characterizing lifetime risk of silicosis
morbidity.
The health endpoint of interest in these studies was the appearance
of opacities on chest radiographs indicative of pulmonary
pneumoconiosis (a group of lung diseases caused by the lung's reaction
to inhaled dusts). The most reliable estimates of silicosis morbidity,
as detected by chest X-rays, come from the studies that evaluated those
X-rays over time, included radiographic evaluation of workers after
they left employment, and derived cumulative or lifetime estimates of
silicosis disease risk.
To describe the presence and severity of pneumoconiosis, including
silicosis, the International Labour Organization (ILO) developed a
standardized system to classify lung opacities identified on chest
radiographs (X-rays) (ILO, 1980, 2002, 2011, 2022). The ILO system
[[Page 44886]]
grades the size, shape, and profusion of opacities. Although silicosis
is defined and categorized based on chest X-ray, the X-ray is an
imprecise tool for detecting pulmonary pneumoconiosis (Craighead and
Vallyathan, 1980; Hnizdo et al., 1993; Rosenman et al., 1997; Cohen and
Velho, 2002). Hnizdo et al. (1993) recommended that an ILO category 0/1
(or greater) should be considered indicative of silicosis among workers
exposed to high respirable crystalline silica concentrations. They
noted that the sensitivity of the chest X-ray as a screening test
increases with disease severity and to maintain high specificity,
category 1/0 (or 1/1) chest X-rays should be considered as a positive
diagnosis of silicosis for miners who work in low dust occupations
(Hnizdo et al., 1993). MSHA, consistent with NIOSH's use of chest X-
rays in their occupational respiratory disease surveillance program
(NIOSH 2014b), agrees that a small opacity profusion score of 1/0 is
consistent with chronic silicosis stage 1. Most of the studies reviewed
by MSHA considered a finding consistent with an ILO category of 1/1 or
greater to be a positive diagnosis of silicosis, although some also
considered an X-ray classification of 1/0 or 0/1 to be positive. The
low sensitivity of chest radiography to detect minimal silicosis
suggests that risk estimates derived from radiographic evidence likely
underestimate the true risk of this disease (Craighead and Vallyathan,
1980; Hnizdo et al., 1993; Rosenman et al., 1997; Cohen and Velho,
2002).
OSHA summarized the Miller et al. (1995, 1998) and Buchanan et al.
(2003) papers in their final respirable crystalline silica standard in
2016 (OSHA 2016a, 81 FR 16286, 16316). These researchers reported on a
1991 follow-up study of 547 survivors of a 1,416-member cohort of
Scottish coal workers from a single mine. These men had all worked in
the mine during the period between early 1971 and mid-1976, during
which time they had experienced ``unusually high concentrations of
freshly cut quartz in mixed coal mine dust.'' The population's
exposures to quartz dust had been measured in unique detail for a
considerable proportion of the men's working lives (OSHA 2013b, page
333).
The 1,416 men had previous chest X-rays dating from before, during,
or just after this high respirable crystalline silica exposure period.
Of these 1,416 men, 384 were identified as having died by 1990/1991. Of
the 1,032 remaining men, 156 were untraced, and, of the 876 who were
traced and replied, 711 agreed to participate in the study. Of these,
the total number of miners who were surveyed was 551. Four of these
were omitted, two because of a lack of an available chest X-ray. The
547 surviving miners (age range: 29-85 years, average = 59 years) were
interviewed and received their follow-up chest X-rays between November
1990 and April 1991. The interviews consisted of questions on current
and past smoking habits and occupational history since leaving the coal
mine, which closed in 1981. They were also asked about respiratory
symptoms and were given a spirometry test (OSHA 2013b, pages 333-334).
Exposure characterization was based on extensive respirable dust
sampling; samples were analyzed for quartz content by IR spectroscopy.
Between 1969 and 1977, two coal seams were mined. One had produced
quarterly average concentrations of respirable crystalline silica much
less than 1,000 [mu]g/m\3\ (only 10 percent exceeded 300 [mu]g/m\3\).
The other more unusual seam (mined between 1971 and 1976) lay in
sandstone strata and generated respirable crystalline silica levels
such that quarterly average exposures exceeded 1,000 [mu]g/m\3\ (10
percent of the quarterly measurements were over 10,000 [mu]g/m\3\).
Thus, this cohort study allowed evaluation of the effects of both
higher and lower respirable crystalline silica concentrations and
exposure-rate effects on the development of silicosis (OSHA 2013b, page
334).
Three physicians read each chest film taken during the current
survey as well as films from the surveys conducted in 1974 and 1978.
Films from an earlier 1970 survey were read only if no films were
available from the subsequent two surveys. Silicosis cases were
identified if the median classification of the three readers indicated
an ILO category of 1/1 or greater (Miller et al, 1995, page 24), plus a
progression from the earlier reading. Of the 547 men, 203 (38 percent)
showed progression of at least 1 ILO category from the 1970s' surveys
to the 1990-91 survey; in 128 of these (24 percent) there was
progression of 2 or more ILO categories. In the 1970s' surveys, 504 men
had normal chest X-rays; of these 120 (24 percent) acquired an abnormal
X-ray consistent with ILO category 1/0 or greater at the follow-up. Of
the 36 men whose X-rays were consistent with ILO category 1/0 or
greater in the 1970s' surveys, 27 (75 percent) exhibited further
progression at the 1990/1991 follow-up. Only one subject showed a
regression from any earlier reading, and that was slight, from 1/0 to
0/1. The earlier Miller et al. (1995) report presented results for
cases classified as having X-ray films consistent with either 1/0+ and
2/1+ degree of profusion; the Miller et al. (1998) analysis and the
Buchanan et al. (2003) re-analyses emphasized the results from cases
having X-rays classified as 2/1+ (OSHA 2013b, page 334).
MSHA modeled the exposure-response relationship by using cumulative
exposure expressed as gram/m\3\-hours, assuming 2,000 work hours per
year and a 45-year working life (after adjusting for full-time
equivalents, including production employees and contract workers). MSHA
estimated risk at the existing standard assuming cumulative exposure to
100 [micro]g/m\3\ ISO for MNM miners and 85.7 [micro]g/m\3\ ISO (100
[micro]g/m\3\ MRE) for coal miners. Respirable crystalline silica
exposures were calculated by commodity, and median exposure values were
used within a variety of exposure intervals. Risks were computed using
a life table methodology which iteratively updated the survival, risk,
and mortality rates each year based on the results of the preceding
year. Covariates in the regression included smoking, age, amount of
coal dust, and percent of quartz in the coal dust during various
previous survey periods.
Both Miller et al. papers (1995, 1998) presented the results of
numerous regression models, and they compared the results of the
partial regression coefficients using Z statistics of the coefficient
divided by the standard error. Also presented were the residual
deviances of the models and the residual degrees of freedom. In the
introduction to the results section, Miller et al. (1995) stated that,
``in none of the models fitted was there a significant effect of
smoking habit (current, ex-smoker, and never smoker), nor was there any
evidence of any difference between smoking groups in their relationship
of response with age.'' They therefore presented the results of the
regression analyses without terms for smoking effects (i.e., without
including smoking effects as a variable in the final regression
analysis, because they found that smoking did not affect the modeling
results). The logistic regression models developed by Miller et al.
(1995) included terms for cumulative exposure and age. In their later
publication, Miller et al. (1998) presented models similar to their
1995 report, but without the age variable. Their logistic regression
model A from Table 7 of their report (page 56) included only an
intercept (-4.32) and the respirable crystalline silica (quartz)
cumulative exposure variable (0.416). They estimated that respirable
crystalline silica exposure at an average
[[Page 44887]]
concentration of 100 [micro]g/m\3\ for 15 years (2.6 gram/m\3\-hr
assuming 1,750 hours worked per year) would result in an increased risk
of silicosis (ILO > 2/1) of 5 percent (OSHA 2013b, page 334).
OSHA had a high degree of confidence in the estimates of silicosis
morbidity risk from this Scotland coal mine study. This was mainly
because of highly detailed and extensive exposure measurements,
radiographic records, and detailed analyses of high exposure-rate
effects. However, in another paper, Soutar et al. (2004) noted that:
``If the effects of silica vary according to the conditions of
exposure, these risks are probably towards the high end of the risk
spectrum, since the silica was freshly fractured from massive
sandstone, and not derived from dirt bands where the quartz grains are
aged and accompanied by clay minerals'' (OSHA 2013b, page 336). MSHA
has reviewed and agrees with OSHA's conclusion.
Buchanan et al. (2003) provided an analysis and risk estimates only
for cases having X-ray films consistent with ILO category 2/1+ extent
of profusion of opacities, after adjusting for the disproportionately
severe effect of exposure to high respirable crystalline silica
concentrations. Estimating the risk of 1/0+ profusions from the
Buchanan et al. (2003) or the earlier Miller et al. (1995, 1998)
publications can only be roughly approximated because of the summary
information included. Table 4 of Miller et al. (1998) (page 55)
presents a cross-tabulation of radiograph progression, using the 12-
point ILO scale, from the last baseline exam to the 1990/1991 follow-up
visit for the 547 men at the Scottish coal mine. From this table, among
miners having both early X-ray films and follow-up films, 44 men had
progressed to 2/1+ by the last follow-up and an additional 105 men had
experienced the onset of silicosis (i.e., X-ray films were classified
as 1/0, 1/1, or 1/2). Thus, by the time of the follow-up, there were
three times more miners with silicosis consistent with ILO category 1
than there were miners with a category 2+ level of severity ((105 +
44)/44 = 3.38). This suggests that the Buchanan et al. (2003) model,
which reflects the risk of progressing to ILO category 2+,
underestimates the risk of acquiring radiological silicosis by about
three-fold in this population (OSHA 2013b, page 336). This type of
analysis shows that the risk of developing silicosis estimated from the
Buchanan et al. (2003) and Miller et al. (1998) studies is of the same
magnitude as the risks reported by Hnizdo and Sluis-Cremer (1993b)
(OSHA 2013b, page 338).
MSHA estimated silicosis risk by using the Buchanan et al. (2003)
model that predicted the lifetime probability of developing silicosis
at the 2/1+ category based on cumulative respirable crystalline silica
exposures. As discussed previously, MSHA applied the Buchanan et al.
(2003) model, assuming that miners are exposed for 45 years of working
life extending from age 21 through age 65, using a life table approach.
Buchanan et al. provides an exposure-response model using cumulative
exposure in mg/m\3\-hours as the predictor variable and lifetime risk
of silicosis as the outcome variable. MSHA assumed 45 years of
exposure, each such year having a duration of 2,000 work hours, scaled
by a weighted average FTE ratio that accounts for the average annual
hours worked by production employees and contract miners.
2. Accelerated Silicosis and Rapidly Progressive Pneumoconiosis (RPP)
Study
OSHA concluded in their risk assessment, and MSHA agrees, that
there is little evidence of a dose-rate effect at respirable
crystalline silica concentrations in the exposure range of 25 [micro]g/
m\3\ to 500 [micro]g/m\3\ (81 FR 16286, 16396). OSHA noted that the
risk estimates derived from the Buchanan et al. (2003) study were not
appreciably different from those derived from the other studies of
silicosis morbidity (see OSHA 2016a, 81 FR 16286, 16386; Table VI-1.
Summary of Lifetime or Cumulative Risk Estimates for Crystalline
Silica). However, OSHA also concluded that some uncertainty related to
dose-rate effects exists at concentrations far higher than the exposure
range of interest. OSHA stated that it is possible for such a dose-rate
effect to impact the results if not properly addressed in study
populations with high concentration exposures. OSHA used the model from
the Buchanan et al. (2003) study in its silicosis morbidity risk
assessment to account for possible dose-rate effects at high average
concentrations (OSHA 2016a, 81 FR 16286, 16396 OSHA 2013b, pages 335-
342). MSHA has reviewed and agrees with OSHA's conclusions.
NIOSH stated in its post-hearing brief to OSHA, that a ``detailed
examination of dose rate would require extensive and real time exposure
history which does not exist for silica (or almost any other agent)''
(81 FR 16285, 16375). Similarly, Dr. Kenneth Crump, a researcher from
Louisiana Tech University Foundation who served on OSHA's peer review
panel for the Review of Health Effects Literature and Preliminary
Quantitative Risk Assessment, wrote to OSHA that, ``[h]aving noted that
there is evidence for a dose rate effect for silicosis, it may be
difficult to account for it quantitatively. The data are likely to be
limited by uncertainty in exposures at earlier times, which were likely
to be higher'' (OSHA 2016a, 81 FR 16286, 16375). OSHA agreed with the
conclusions of NIOSH and Dr. Crump. OSHA believed that it used the best
available evidence to estimate risks of silicosis morbidity and
sufficiently accounted for any dose rate effect at high silica average
concentrations by using the Buchanan et al. (2003) study as part of
their final Quantitative Risk Analysis (QRA) (OSHA 2016a, 81 FR 16286,
16396). MSHA has reviewed and agrees with OSHA's conclusions.
MSHA is using the Buchanan et al. (2003) study to explain, in part,
the observed cases of progressive lung disease in miners, known as RPP
in coal miners (Laney and Attfield, 2010; Wade et al., 2010; Laney et
al., 2012b; 2017; Blackley et al., 2016b, 2018b; Reynolds et al.,
2018b; Halldin et al., 2019; Halldin et al., 2020; Almberg et al.,
2018a; Cohen et al., 2022) and accelerated silicosis in MNM miners
(Dumavibhat et al., 2013; Hessel et al., 1988; Mohebbi and Zubeyri
2007). The inclusion of this discussion in the risk analysis is to
describe research that explains, in part, the progressive disease
observed in shorter-tenured miners. MSHA believes that the risks
estimated by the Buchanan et al. model can be applied to all mining
populations that have similar respirable crystalline silica exposure
exceedances. MSHA estimated the increase of silicosis risk in miners
exposed to extreme respirable crystalline silica exposures for varying
periods of time ranging from 0 hours to 348 hours per year (i.e., 0.0
percent to 20.0 percent of time at extreme exposures). This information
is important because MSHA data indicate that many miners' respirable
crystalline silica exposure samples over the years have exceeded the
existing exposure limit(s) of 100 [micro]g/m\3\. MSHA data also
indicate that a smaller number of MSHA samples showed respirable
crystalline silica concentrations well above the existing MSHA standard
of 100 [micro]g/m\3\. Over the last 15 years of MNM compliance data,
188 samples (0.3 percent) were over 500 [micro]g/m\3\; the upper range
of exposure was 4,289 [micro]g/m\3\ ISO (see PRA Table 4 of the PRA
document). Over the last 5 years of coal compliance data, eight samples
(<0.1 percent) were over 500 [micro]g/m\3\; the upper range of
[[Page 44888]]
exposure was 791.4 [micro]g/m\3\ MRE (see PRA Table 7 of the PRA
document).
Analysis provided by Buchanan et al. (2003) provides strong
evidence of an exposure-rate effect for silicosis in a British
Pneumoconiosis Field Research (PFR) coal mining cohort exposed to high
levels of respirable crystalline silica over short periods of time
(OSHA 2013b, page 335). Exposure was categorized as pre- and post-1964,
the latter period being that of generally higher quartz concentrations
used to estimate exposure-rate effects. For the purpose of this
analysis, the results were presented for the 371 men (out of the
original 547) who were between the ages of 50 and 74 at the time of the
1990/1991 follow-up, ``since they had experienced the widest range of
quartz concentrations and showed the strongest exposure-response
relations.'' Thus, combined with their exposure history, which went
back to pre-1954, many of these men had 30 to 40+ years of highly
detailed occupational exposure histories available for analysis. Of
these 371 miners, there were 35 men (9.4 percent) who had X-ray films
consistent with ILO category 2/1+, with at least 29 of them having
progressed from less severe silicosis since the previous follow-up
during the 1970s (from Miller et al., 1998) (OSHA 2013b, page 335).
The Buchanan et al. (2003) re-analysis presented logistic
regression models in stages. In the final stage of modeling, using only
the statistically significant post-1964 cumulative exposures, the
authors separated these exposures into, ``two quartz concentration
bands, defined by the cut-point 2.0 mg/m\3\.'' This yielded the final
simplified equation, adapted from Buchanan et al., 2003, page 162:
[GRAPHIC] [TIFF OMITTED] TP13JY23.017
where p2 is the probability of profusion category 2/1 or
higher (2/1+) at follow-up and E is the cumulative exposure.
In this model, both the cumulative exposure concentration variables
were ``highly statistically significant in the presence of the other''
(Buchanan et al., 2003, page 162). Since these variables were in the
same units, mg/m\3\-hr, the authors noted that the coefficient for
exposure concentrations >2,000 [mu]g/m\3\ (>2.0 mg/m\3\) was three
times that for the concentrations <2,000 [mu]g/m\3\ (<2.0 mg/m\3\).
They concluded that their latest analysis showed that ``the risk of
silicosis over a working lifetime can rise dramatically with exposure
to such high concentrations over a timescale of merely a few months''
(Buchanan et al., 2003, page 163, OSHA 2013b, page 336).
Buchanan et al. (2003) also used these models to estimate the risk
of acquiring a chest X-ray classified as ILO category 2/1+, 15 years
after exposure ends, as a function of low <2,000 [mu]g/m\3\ (<2.0 mg/
m\3\) and high >2,000 [mu]g/m\3\ (>2.0 mg/m\3\) quartz concentrations.
OSHA chose to use this model to estimate the risk of radiological
silicosis consistent with an ILO category 2/1+ chest X-ray for several
exposure scenarios. They assumed 45 years of exposure, 2,000 hours/year
of exposure, and no exposure above a concentration of 2,000 [mu]g/m\3\
(2.0 mg/m\3\) (OSHA 2013b, page 336).
Buchanan et al. (2003) used these models to estimate the combined
effect on the predicted risk of low quartz exposures (e.g., 100 [mu]g/
m\3\, equal to 0.1 mg/m\3\) and short-term exposures to high quartz
concentrations (e.g., 2,000 [mu]g/m\3\, equal to 2 mg/m\3\). Predicted
risks were estimated for miners who progressed to silicosis level 2/1+
15 years after exposure ended. This analysis showed the increase in
predicted risk with relatively short periods of quartz exceedance
exposures, over 4, 8, and 12 months. Buchanan et al. predicted a risk
of 2.5 percent for 15 years quartz exposure to 100 [mu]g/m\3\ (0.1 mg/
m\3\). This risk increased to 10.6 percent with the addition of only 4
months of exposure at the higher concentration. The risk increased
further to 72 percent with 12 months at the higher exposure of 2,000
[mu]g/m\3\ (2.0 mg/m\3\).
The results indicate miners exposed to exceedances above MSHA's
existing standard could develop progression of silicosis at an
exaggerated rate. The results of Buchanan et al. also indicated that
miners' exposure to exceedances at MSHA's proposed standard will also
suffer increased risk of developing progressive disease, though at a
reduced rate (see Buchanan et al. (2003), Table 4, page 163).
MSHA used a life table approach to estimate the lifetime excess
silicosis morbidity from age 21 to age 80, assuming exposure from age
21 through age 65 (45 years of working life) and an additional 15 years
of potential illness progress thereafter. MSHA used the Buchanan et al.
(2003) model to estimate the effect of respirable crystalline silica
exposure exceedances as seen in MSHA's compliance data on miners'
silicosis risk at the existing and proposed standard. The model
predicted the probability of developing silicosis at the 2/1+ category
based on cumulative respirable crystalline silica exposures. Age-
specific cumulative risk was estimated as 1/(1 + EXP(-(-4.83 + 0.443 *
cumulative exposure))). The model determined that even at 17.4 hours on
average per year at an exposure of 1,500 [mu]g/m\3\ (1.50 mg/m\3\),
miners' risk of developing 2/1+ silicosis increased from a baseline of
24.8/1,000 to 29.0/1,000 at the existing standard and 14/1,000 to 16.6/
1,000 at the proposed standard. Of course, the more hours exposed to
these levels of respirable crystalline silica resulted in even higher
increased risk. It is important to note that NIOSH's X-ray
classification of the lowest case of pneumoconiosis is 1/0 profusion of
small opacities (NIOSH 2008c, page A-2). Using a case definition of
level 2/1+, the miners studied by Buchanan et al. (2003) would be more
likely to show clinical signs of disease. MSHA emphasizes the
importance of maintaining miner exposure to respirable crystalline
silica at or below the proposed standard to minimize these health risks
as much as possible.
3. Silicosis and NMRD Mortality
Silicosis mortality was ascertained in the studies included in the
pooled analysis by Mannetje et al. (2002b). These studies included
cohorts of U.S. diatomaceous earth workers (Checkoway et al., 1997),
Finnish granite workers (Koskela et al., 1994), U.S. granite workers
(Costello and Graham, 1988), U.S. industrial sand workers (Steenland
and Sanderson, 2001), U.S. gold miners (Steenland and Brown (1995a),
and Australian gold miners (de Klerk et al., 1998). The researchers
analyzed death certificates across all cohorts for cause of death. OSHA
relied upon the published, peer-reviewed, pooled analysis of six
epidemiological studies first published by Mannetje et al. (2002b) and
a sensitivity analysis of the data conducted by ToxaChemica,
International, Inc. (2004). OSHA used the model described by Mannetje
et al.
[[Page 44889]]
(2002b) and the rate ratios that were estimated from the ToxaChemica,
International Inc. sensitivity analysis to estimate the risks of
silicosis mortality. This process better controlled for age and
exposure measurement uncertainty (OSHA 2013b, page 295). MSHA has
reviewed and agrees with OSHA's conclusions. These studies are
summarized below, including detailed discussion and analysis of
uncertainty in the studies and associated risk estimates.
OSHA found that the estimates from Mannetje et al. (2002b) and
ToxaChemica Inc. probably understated the actual risk because silicosis
is underreported as a cause of death since there is no nationwide
system for collecting silicosis morbidity case data (OSHA 2016a, 81 FR
16286, 16325). To help address this uncertainty, OSHA also included an
exposure-response analysis of diatomaceous earth workers (Park et al.,
2002). This analysis better recognized the totality of respirable
crystalline silica-related respiratory disease than the datasets of
Mannetje et al. (2002b) and ToxaChemica International Inc. (2004).
Information from the Park et al. (2002) study (described in the next
subsection) was used to quantify the relationship between cristobalite
exposure and mortality caused by NMRD, which includes silicosis,
pneumoconiosis, emphysema, and chronic bronchitis. The category of NMRD
captures much of the silicosis misclassification that results in
underestimation of the disease. NMRD also includes risks from other
lung diseases associated with respirable crystalline silica exposures.
OSHA found the risk estimates derived from Park et al. (2002) were
important to include in their range of estimates of the risk of death
from respirable crystalline silica-related respiratory diseases,
including silicosis (OSHA 2013b, pages 297-298). OSHA concluded that
the ToxaChemica International Inc. (2004) re-analysis of Mannetje et
al.'s (2002b) silicosis mortality data and Park et al.'s (2002) study
of NMRD mortality provided a credible range of estimates of mortality
risk from silicosis and NMRD across many workplaces. The upper end of
this range, based on the Park et al. (2002) study, is less likely to
underestimate risk because of underreporting of silicosis mortality.
However, risk estimates from studies focusing on cohorts of workers
from different industries cannot be directly compared (OSHA 2016a, 81
FR 16286, 16397).
a. Silicosis Mortality: Mannetje et al. (2002b); ToxaChemica,
International, Inc. (2004)
Mannetje et al. (2002b) relied upon the epidemiological studies
contained within the Steenland et al. (2001a) pooled analysis of lung
cancer mortality that also included extensive data on silicosis. The
six cohorts included:
(1) U.S. diatomaceous earth workers (Checkoway et al., 1997),
(2) Finnish granite workers (Koskela et al., 1994),
(3) U.S. granite workers (Costello and Graham, 1988),
(4) U.S. industrial sand workers (Steenland and Sanderson, 2001),
(5) U.S. gold miners (Steenland and Brown, 1995b), and
(6) Australian gold miners (de Klerk and Musk, 1998).
These six cohorts contained 18,364 workers and 170 silicosis
deaths, where silicosis mortality was defined as death from silicosis
(ICD-9 502, n = 150) or from unspecified pneumoconiosis (ICD-9 505, n =
20). Table VI-3 provides information on each cohort, including size,
time period studied, overall number of deaths, and number of deaths
identified as silicosis for the pooled analysis conducted by Mannetje
et al. (2002b). The authors believed this definition to err on the side
of caution in that some cases of death from silicosis in the cohorts
may have been misclassified as other causes (e.g., tuberculosis or COPD
without mention of pneumoconiosis). Four cohorts were not included in
the silicosis mortality study. The three Chinese studies did not use
the ICD to code cause of death. In the South African gold miner study,
silicosis was not generally recognized as an underlying cause of death.
Thus, it did not appear on death certificates (OSHA 2013b, page 292).
[GRAPHIC] [TIFF OMITTED] TP13JY23.018
[[Page 44890]]
Mannetje et al. (2002a) described the exposure assessments
developed for the pooled analysis. Exposure information from each of
the 10 cohort studies varied and included dust measurements
representing particle counts, mass of total dust, and respirable dust
mass. Measurement methods also changed over time for each of the cohort
studies. Generally, sampling was performed using impingers in earlier
decades, and gravimetric techniques later. Exposure data based on
analysis for respirable crystalline silica by XRD (the current method
of choice) were available only from the study of U.S. industrial sand
workers. To develop cumulative exposure estimates for all cohort
members and to pool the cohort data, all exposure data were converted
to units of [mu]g/m\3\ (mg/m\3\) respirable crystalline silica. Cohort-
specific conversion factors were generated based on the silica content
of the dust to which workers were exposed. In some instances, results
of side-by-side comparison sampling were available. Within each cohort,
available job- or process-specific information on the silica
composition or nature of the dust was used to reconstruct respirable
crystalline silica exposures. Most of the studies did not have exposure
measurements prior to the 1950s. Exposures occurring prior to that time
were estimated either by assuming such exposures were the same as the
earliest recorded for the cohort or by modeling that accounted for
documented changes in dust control measures.
To evaluate the reasonableness of the exposure assessment for the
lung cancer pooled study, Mannetje et al. (2002a) investigated the
relationship between silicosis mortality and cumulative exposure. They
performed a nested case-control analysis for silicosis or unspecified
pneumoconiosis using conditional logistic regression. Since exposure to
respirable crystalline silica is the sole cause of silicosis, any
finding for which cumulative exposure was unrelated to silicosis
mortality risk would suggest that serious misclassification of the
exposures assigned to cohort members occurred. Cases and controls were
matched for race, sex, age (within 5 years), and 100 controls were
matched to each case. Each cohort was stratified into quartiles by
cumulative exposure. Standardized rate ratios (SRRs) were calculated
using the lowest-exposure quartile as the baseline. Odds ratios (ORs)
were also calculated for the pooled data set overall, which was
stratified into quintiles based on cumulative exposure. For the pooled
data set, the relationship between the ORs for silicosis mortality and
cumulative exposure, along with each of the 95 percent confidence
intervals (95% CI), were as follows:
(1) 4,450 [mu]g/m\3\-years (4.45 mg/m\3\-years), OR=3.1 (95% CI:
2.5-4.0);
(2) 9,080 [mu]g/m\3\-years (9.08 mg/m\3\-years), OR=4.6 (95% CI:
3.6-5.9);
(3) 16,260 [mu]g/m\3\-years (16.26 mg/m\3\-years), OR=4.5 (95% CI:
3.5-5.8); and
(4) 42,330 [mu]g/m\3\-years (42.33 mg/m\3\-years), OR=4.8 (95% CI:
3.7-6.2).
In addition, in seven of the cohorts, there was a statistically
significant trend between silicosis mortality and cumulative exposure.
For two of the cohorts (U.S. granite workers and U.S. gold miners), the
trend test was not statistically significant (p=0.10). An analysis
could not be performed on the South African gold miner cohort because
silicosis was never coded as an underlying cause of death, apparently
due to coding practices in that country.
Based on this analysis, Mannetje et al. (2002a) concluded that the
exposure-response relationship for the pooled data set was ``positive
and reasonably monotonic.'' That is, the response increased with
increasing exposure. The results also indicated that the exposure
assessments provided reasonable estimates of cumulative exposures. In
addition, despite some large differences in the range of cumulative
exposures between cohorts, a clear positive exposure-response trend was
evident in seven of the cohorts (OSHA 2013b, page 271).
Furthermore, in their pooled analysis of silicosis mortality for
six of the cohorts, Mannetje et al. (2002b) found a clear and
consistently positive response with increasing decile of cumulative
exposure, although there was an anomaly in the 9th decile. Overall,
these data supported a monotonic exposure-response relationship for
silicosis. Thus, although some exposure misclassification almost
certainly existed in the pooled data set, the authors concluded that
exposure estimates did not appear to have been sufficiently
misclassified to obscure an exposure-response relationship (OSHA 2013b,
page 271).
As part of an uncertainty analysis conducted for OSHA, Drs.
Steenland and Bartell (ToxaChemica International, Inc. 2004) examined
the quality of the original data set and analysis to identify and
correct any data entry, programming, or reporting errors (ToxaChemica
International, Inc. 2004). This quality assurance process revealed a
small number of errors in exposure calculations for the originally
reported results. Primarily, these errors resulted from rounding of job
class exposures when converting the original data file for use with a
different statistical program. Although the corrections affected some
of the exposure-response models for individual cohorts, ToxaChemica
International, Inc. (2004) reported that models based on the pooled
dataset were not impacted by the correction of these errors (OSHA
2013b, pages 271-272).
Silicosis mortality was evaluated using standard life table
analysis in Mannetje et al. (2002b). Poisson regression, using 10
categories of cumulative exposure and adjusting for age, calendar time,
and cohort, was conducted to derive silicosis mortality rate ratios
using the lowest exposure group of 0-100 [mu]g/m\3\-years (0-0.1 mg/
m\3\-year) as the referent group. More detailed exploration of the
exposure-response relationship using a variety of exposure metrics,
including cumulative exposure, duration of exposure, average exposure
(calculated as cumulative exposure/duration), and the log
transformations of these variables, was conducted via nested case-
control analyses (conditional logistic regression). Each case was
matched to 100 controls selected from among those who had survived to
at least the age of the case, with additional matching on cohort, race,
sex, and date of birth within 5 years. The authors explored lags of 0,
5, 10, 15, and 20 years, noting that there is no a priori reason to
apply an exposure lag, as silicosis can develop within a short period
after exposure. However, a lag could potentially improve the model, as
there is often a considerable delay in the development of silicosis
following exposure. In addition to the parametric conditional logistic
regression models, the authors performed some analyses using a cubic-
spline model, with knots at 5, 25, 50, 75, and 95 percent of the
distribution of exposure. Models with cohort-exposure interaction terms
were fit to assess heterogeneity between cohorts (OSHA 2013b, page
294).
The categorical analysis found a nearly monotonic increase in
silicosis rates with cumulative exposure, from 4.7 per 100,000 person-
years in the lowest exposure category (0-990 [mu]g/m\3\-years [0-0.99
mg/m\3\-years]) to 299 per 100,000 person-years in the highest exposure
category (>28,000 [mu]g/m\3\-years [>28 mg/m\3\-years]). Nested case-
control analyses showed a significant association between silicosis
mortality and cumulative exposure, average exposure, and duration of
exposure. The best-fitting conditional logistic regression model used
log-transformed cumulative exposure with no exposure lag, with a model
[chi]\2\ of 73.2 versus [chi]\2\
[[Page 44891]]
values ranging from 19.9 to 30.9 for average exposure, duration of
exposure, and untransformed cumulative exposure (1 degree of freedom).
No significant heterogeneity was found between individual cohorts for
the model based on log-cumulative exposure. The cubic-spline model did
not improve the model fit for the parametric logistic regression model
using the log-cumulative exposure (OSHA 2013b, page 294).
Mannetje et al. (2002b) developed estimates of silicosis mortality
risk through age 65 for two levels of exposure (50 and 100 [mu]g/m\3\
respirable crystalline silica), assuming a working life of occupational
exposure from age 20 to 65. Risk estimates were calculated based on the
silicosis mortality rate ratios derived from the categorical analysis
described above. The period of time over which workers' exposures and
risks were calculated (age 20 to 65) was divided into one-year
intervals. The mortality rate used to calculate risk in any given
interval was dependent on the worker's cumulative exposure at that
time. The equation used to calculate risk is as follows:
[GRAPHIC] [TIFF OMITTED] TP13JY23.019
Where timei is equal to one for every age i, and ratei is the age-,
calendar time-, and cohort adjusted silicosis mortality rate associated
with the level of cumulative exposure acquired at age i, as presented
in Mannetje et al. (2002b, Table 2, page 725). The calculated absolute
risks equal the excess risks since there is no background rate of
silicosis in the exposed population. Mannetje et al. (2002b) estimated
the lifetime risk of death from silicosis, assuming 45 years of
exposure to 100 [mu]g/m\3\, to be 13 deaths per 1,000 workers; at an
exposure of 50 [mu]g/m\3\, the estimated lifetime risk was 6 per 1,000.
Confidence intervals (CIs) were not reported (OSHA 2013b, page 295).
In summary, OSHA's estimates of silicosis morbidity risks were
based on studies of active and retired workers for which exposure
histories could be constructed and chest X-ray films could be evaluated
for signs of silicosis. There is evidence in the record that chest X-
ray films are relatively insensitive to detecting lung fibrosis (OSHA
2016a, 81 FR 16286, 16397). MSHA agrees with OSHA's estimate of
silicosis morbidity risks.
Hnizdo et al. (1993a) found chest X-ray films to have low
sensitivity for detecting lung fibrosis related to initial cases of
silicosis, compared to pathological examination at autopsy. To address
the low sensitivity of chest X-rays for detecting silicosis, Hnizdo et
al. (1993a) recommended that radiographs consistent with an ILO
category of 0/1 or greater be considered indicative of silicosis among
workers exposed to a high concentration of respirable crystalline
silica-containing dust. In like manner, to maintain high specificity,
chest X-rays classified as category 1/0 or 1/1 should be considered as
a positive diagnosis of silicosis in miners who work in low dust (0.2
mg/m\3\) occupations. The studies on which OSHA relied in its risk
assessment typically used an ILO category of 1/0 or greater to identify
cases of silicosis. According to Hnizdo et al. (1993), they were
unlikely to have included many false positives (i.e., assumed diagnosis
of silicosis in a miner without the disease), but may have included
false negatives (i.e., failure to identify cases of silicosis). Thus,
in OSHA's risk assessment, the use of chest X-rays to ascertain
silicosis cases in the morbidity studies may have underestimated risk
given the X-rays' low sensitivity to detect disease. MSHA agrees with
OSHA's assessment.
To estimate the risk of silicosis mortality at the existing and
proposed exposure limits, OSHA used the categorical model described by
Mannetje et al. (2002b) but did not rely upon the Poisson regression in
their study. Instead, OSHA used rate ratios estimated from a nested
case-control design implemented as part of a sensitivity analysis
(ToxaChemica, International, Inc. 2004). The case-control design was
selected because it was expected to better control for age. In
addition, the rate ratios derived from the case control study were
derived from a Monte Carlo analysis to reflect exposure measurement
uncertainty (See ToxaChemica, International, Inc. (2004), Table 7, page
40). The rate ratio for each interval of cumulative exposure was
multiplied by the annual silicosis rate assumed to be associated with
the lowest exposure interval, 4.7 per 100,000 for exposures of 990
[mu]g/m\3\-years (0.99 mg/m\3\-years), to estimate the silicosis rate
for each interval of exposure. The lifetime silicosis mortality risk is
the sum of the silicosis rate for each year of life through age 85 and
assuming exposure from age 20 to 65. From this analysis, OSHA estimated
the silicosis mortality risk for exposure to the then existing general
industry exposure limit (100 [mu]g/m\3\) and proposed exposure limit
(50 [mu]g/m\3\) to be 11 (95% CI 5-37) and 7 (95% CI 3-21) deaths per
1,000 workers, respectively. For exposure to 250[mu]g/m\3\ (0.25 mg/
m\3\) and 500 [mu]g/m\3\ (0.5 mg/m\3\), the range approximating the
then existing construction/shipyard exposure limit, OSHA estimated the
risk to range from 17 (95% CI 5-66) to 22 (95% CI 6-85) deaths per
1,000 workers (OSHA 2013b, page 294-295).
In view of the foregoing discussion, MSHA agrees with OSHA's
analysis, and MSHA also selected the Mannetje et al. (2002b) study for
estimating silicosis mortality risks and cases. MSHA used a life table
analysis to estimate the lifetime excess silicosis mortality through
age 80. To estimate the age-specific risk of silicosis mortality at the
existing standards, the proposed PEL, and the proposed action level,
MSHA used the same categorical model that OSHA used in their PQRA (as
described above from Mannetje et al., 2002b; ToxaChemica International,
Inc. 2004) to estimate lifetime risk following cumulative exposure of
45 years. MSHA used the 2018 all-cause mortality rates (NCHS,
Underlying Cause of Death, 2018 on CDC WONDER Online Database, released
in 2020b) as all-cause mortality rates. As stated previously, the
general (unexposed) population is assumed to have silicosis mortality
rates equal to zero.
b. NMRD Mortality: Park et al. (2002)
In addition to causing silicosis, exposure to respirable
crystalline silica causes increased risks of other NMRD. These include
chronic obstructive pulmonary disease (COPD), which includes chronic
bronchitis, emphysema, and combinations of the two and is a cause of
chronic airways obstruction. COPD is characterized by airflow
limitation that is usually progressive and not fully reversible. OSHA
reviewed several studies of NMRD morbidity and used a study by Park et
al. (2002) to assess NMRD risk. Checkoway et al. (1997) originally
studied a California diatomaceous earth
[[Page 44892]]
cohort for which Park et al. (2002) then analyzed the effect of
respirable crystalline silica exposures on the development of NMRD. The
authors quantified the relationship between exposure to cristobalite
and mortality from NMRD (OSHA 2013b, page 295).
The California diatomaceous earth cohort consisted of 2,570
diatomaceous earth workers employed for 12 months or more from 1942 to
1994. As noted above, Park et al. (2002) was interested in the
relationship between cristobalite exposure and mortality from chronic
lung disease other than cancer (LDOC). LDOC included chronic diseases
such as pneumoconiosis (which included silicosis), chronic bronchitis,
and emphysema, but excluded pneumonia and other infectious diseases.
The investigators selected LDOC as the health endpoint for three
reasons. First, increased mortality from LDOC had been documented among
respirable crystalline silica-exposed workers in several industry
sectors, including gold mining, pottery, granite, and foundry
industries. Second, the authors pointed to the likelihood that
silicosis as a cause of death is often misclassified as emphysema or
chronic bronchitis. Third, the number of deaths from the diatomaceous
earth worker cohort that were attributed to silicosis was too small
(10) for analysis. Industrial hygiene data for the cohort were
available from the employer for total dust, respirable crystalline
silica (mostly cristobalite), and asbestos. Smoking information was
available for about 50 percent of the cohort and for 22 of the 67 LDOC
deaths available for analysis, permitting Park et al. (2002) to
partially adjust for smoking (OSHA 2013b, pages 295-296).
Park et al. (2002) used the exposure assessment previously reported
by Seixas et al. (1997) and used by Rice et al. (2001) to estimate
cumulative respirable crystalline silica exposures for each worker in
the cohort based on detailed work history files. The average respirable
crystalline silica concentration for the cohort was 290 [micro]g/m\3\
(0.29 mg/m\3\) over the period of employment (Seixas et al., 1997). The
total respirable dust concentration in the diatomaceous earth plant was
3,550 [micro]g/m\3\ (3.55 mg/m\3\) before 1949 and declined by more
than 10-fold after 1973, to 290 [micro]g/m\3\ (0.29 mg/m\3\) (Seixas et
al., 1997). The concentration of respirable crystalline silica in the
dust ranged from one to 25 percent and was dependent on the location
within the worksite. It was lowest at the mine and greatest in the
plant where the raw ore was calcined into final product. The average
cumulative exposure values for total respirable dust and respirable
crystalline silica were 7,310 [micro]g/m\3\-year (7.31 mg/m\3\-year)
and 2,160 [micro]g/m\3\-year (2.16 mg/m\3\-year), respectively. The
authors also estimated cumulative exposure to asbestos (OSHA 2013b,
page 296).
Using Poisson regression models and Cox's proportional hazards
models, the authors fit the same series of relative rate exposure-
response models that were evaluated by Rice et al. (2001) for lung
cancer (i.e., log-linear, log-square root, log-quadratic, linear
relative rate, a power function, and a shape function). In general
form, the relative rate model was:
Rate = exp(a0) x f(E),
where exp(a0) is the background rate and E is the cumulative
respirable crystalline silica exposure. Park et al. (2002) also
employed an additive excess rate model of the form:
Rate = exp(a0) + exp(aE).
Relative or excess rates were modeled using internal controls and
adjusting for age, calendar time, ethnicity, and time since first entry
into the cohort. In addition, relative rate models were evaluated using
age- and calendar time-adjusted external standardization to U.S.
population mortality rates for 1940 to 1994 (OSHA 2013b, page 296).
There were no LDOC deaths recorded among workers having cumulative
exposures above 32,000 [micro]g/m\3\-years (32 mg/m\3\-years), causing
the response to level off or decline in the highest exposure range. The
authors believed the most likely explanation for this observation
(which was also observed in their analysis of silicosis morbidity in
this cohort) was some form of survivor selection, possibly smokers or
others with compromised respiratory function leaving work involving
extremely high dust concentrations. These authors suggested several
alternative explanations. First, there may have been a greater
depletion of susceptible populations in high dust areas. Second, there
may have been greater misclassification of exposures in the earlier
years where exposure data were lacking (and when exposures were
presumably the highest) (OSHA 2013b, pages 296-297).
Therefore, Park et al. (2002) performed exposure-response analyses
that restricted the dataset to observations where cumulative exposures
were below 10,000 [micro]g/m\3\-years (10 mg/m\3\-years). This is a
level more than four times higher than that resulting from 45 years of
exposure to the former OSHA PEL for cristobalite (which was 50
[micro]g/m\3\ (0.05 mg/m\3\) when cristobalite was the only polymorph
present). These investigators also conducted analyses using the full
dataset (OSHA 2013b, page 297).
Model fit was assessed by evaluating the decrease in deviance
resulting from addition of the exposure term, and cubic-spline models
were used to test for smooth departures from each of the model forms
described. Park et al. (2002) found that both lagged and unlagged
models fit well, but unlagged models provided a better fit. In
addition, they believed that unlagged models were biologically
plausible in that recent exposure could contribute to LDOC mortality.
The Cox proportional hazards models yielded results that were similar
to those from the Poisson analysis. Consequently, only the results from
the Poisson analysis were reported. In general, the use of external
adjustments for age and calendar time yielded considerably improved fit
over models using internal adjustments. The additive excess rate model
also proved to be clearly inferior compared to the relative rate
models. With one exception, the use of cumulative exposure as the
exposure metric consistently provided better fits to the data than did
intensity of exposure (i.e., cumulative exposure divided by duration of
exposure). As to the exception, when the highest-exposure cohort
members were included in the analysis, the log-linear model produced a
significantly improved fit with exposure intensity as the exposure
metric, but a poor fit with cumulative exposure as the metric (OSHA
2013b, page 297).
Among the models based on the restricted dataset (excluding
observations with cumulative exposures greater than 10,000 [micro]g/
m\3\-years (10 mg/m\3\-years)), the best-fitting model with a single
exposure term was the linear relative rate model using external
adjustment. Most of the other single-term models using external
adjustment fit almost as well. Of the models with more than one
exposure term, the shape model provided no improvement in fit compared
with the linear relative rate model. The log-quadratic model fit
slightly better than the linear relative rate model, but Park et al.
(2002) did not consider the gain in fit sufficient to justify an
additional exposure term in the model (OSHA 2013b, page 297).
Based on its superior fit to the cohort data, Park et al. (2002)
selected the linear relative rate model with external adjustment and
use of cumulative exposure as the basis for estimating LDOC mortality
risks among exposed workers. Competing mortality was accounted for
using U.S. death rates published by the National Center for
[[Page 44893]]
Health Statistics (1996). The authors estimated the lifetime excess
risk for white men exposed to respirable crystalline silica (mainly
cristobalite) for 45 years at 50 [micro]g/m\3\ (0.05 mg/m\3\) to be 54
deaths per 1,000 workers (95% CI: 17-150) using the restricted dataset,
and 50 deaths per 1,000 using the full dataset. For exposure to 100
[micro]g/m\3\ (0.1 mg/m\3\), they estimated 100 deaths per 1,000 using
the restricted dataset, and 86 deaths per 1,000 using the full dataset.
The CIs were not reported (OSHA 2013b, page 297).
The estimates of Park et al. (2002) were about eight to nine times
higher than those that were calculated for the pooled analysis of
silicosis mortality (Mannetje et al., 2002b). Also, these estimates are
not directly comparable to those from Mannetje et al. (2002b) because
the mortality endpoint for the Park et al. (2002) analysis was death
from all non-cancer lung diseases beyond silicosis (including
pneumoconiosis, emphysema, and chronic bronchitis). In the pooled
analysis by Mannetje et al. (2002b), only deaths coded as silicosis or
other pneumoconiosis were included (OSHA 2013b, pages 297-298).
Less than 25 percent of the LDOC deaths in the Park et al. (2002)
analysis were coded as silicosis or other pneumoconiosis (15 of 67). As
noted by Park et al. (2002), it is likely that silicosis as a cause of
death is often misclassified as emphysema or chronic bronchitis
(although COPD is part of the spectrum of disease caused by respirable
crystalline silica exposure and can occur in the absence of silicosis).
Thus, the selection of deaths by Mannetje et al. (2002b) may have
underestimated the true risk of silicosis mortality. The analysis by
Park et al. (2002) would have more fairly captured the total
respiratory mortality risk from all non-malignant causes, including
silicosis and chronic obstructive pulmonary disease. Furthermore, Park
et al. (2002) used untransformed cumulative exposure in a linear model
compared to the log-transformed cumulative exposure metric used by
Mannetje et al. (2002b). This would have caused the exposure-response
relationship to flatten in the higher exposure ranges (OSHA 2013b, page
298).
It is also possible that some of the difference between Mannetje et
al.'s (2002b) and Park et al.'s (2002) risk estimates reflected factors
specific to the nature of exposure among diatomaceous earth workers
(e.g., exposure to cristobalite vs. quartz). However, neither the
cancer risk assessments nor assessments of silicosis morbidity
supported the hypothesis that cristobalite is more hazardous than
quartz (OSHA 2013b, page 298).
Based on the available risk assessments for silicosis mortality,
OSHA believed that the estimates from the pooled study by Mannetje et
al.'s (2002b) represented those least likely to overestimate mortality
risk. It was unlikely to have overstated silicosis mortality risks
given that the estimates reflected only those deaths where silicosis
was specifically identified on death certificates. Therefore, there was
most likely an underestimate of the true silicosis mortality risk. In
contrast, the risk estimates provided by Park et al. (2002) for the
diatomaceous earth cohort would have captured some of this
misclassification and included risks from other lung diseases (e.g.,
emphysema, chronic bronchitis) that have been associated with
respirable crystalline silica exposure. Therefore, OSHA believed that
the Park et al. (2002) study provided a better basis for estimating the
respirable crystalline silica-related risk of NMRD mortality, including
that from silicosis. Based on Park et al.'s (2002) linear relative rate
model [RR = 1 + [beta]x, where [beta] = 0.5469 (no standard error
reported) and x = cumulative exposure], OSHA used a life table analysis
to estimate the lifetime excess NMRD mortality through age 85. For this
analysis, OSHA used all-cause and cause-specific background mortality
rates for all males (National Center for Health Statistics, 2009).
Background rates for NMRD mortality were based on rates for ICD-10
codes J40-J47 (chronic lower respiratory disease) and J60-J66
(pneumoconiosis). OSHA believed that these corresponded closely to the
ICD-9 disease classes (ICD 490-519) used by the original investigators.
According to CDC (2001), background rates for chronic lower respiratory
diseases were increased by less than five percent because of the
reclassification to ICD-10. From the life table analysis, OSHA
estimated that the excess NMRD risk due to respirable crystalline
silica exposure at the former general industry PEL (100 [micro]g/m\3\)
and at OSHA's final PEL (50 [micro]g/m\3\) for 45 years are 83 and 43
deaths per 1,000, respectively. For exposure at the former
construction/shipyard exposure limit, OSHA estimated that the excess
NMRD risk ranged from 188 to 321 deaths per 1,000 (OSHA 2013b, page
298).
Following its own independent review, MSHA agrees with and has
followed the rationale presented by OSHA in its selection of the Park
et al. (2002) model to estimate NMRD mortality risk in miners. Coal
miners were not included in the NMRD mortality analysis because the
endpoint was included in the Quantitative Risk Assessment in Support of
the Final Respirable Coal Mine Dust Rule (Dec. 2013).
MSHA used a life table analysis to estimate the lifetime excess
NMRD mortality through age 80. MSHA used the Park et al. (2002) model
to estimate age-specific NMRD mortality risk as 1 + 0.5469 * cumulative
exposure. MSHA used all-cause and cause-specific background mortality
rates for all males for 2018 (National Center for Health Statistics,
Underlying Cause of Death 2018 on CDC WONDER Online Database, released
in 2020b). Background rates for NMRD mortality were based on rates for
ICD-10 codes J40-J47 (chronic lower respiratory disease) and J60-J66
(pneumoconiosis).
4. Lung Cancer Mortality
Since the publication of OSHA's final rule in 2016, NIOSH has
published two documents concerning occupational carcinogens, Chemical
Carcinogen Policy (2017b) and Practices in Occupational Risk Assessment
(2019a). NIOSH will no longer set recommended exposure levels for
occupational carcinogens. Instead, NIOSH intends to develop risk
management limits for carcinogens (RML-Cas) to acknowledge that, for
most carcinogens, there is no known safe level of exposure. An RML-CA
is a reasonable starting place for controlling exposures. An RML-CA
limit is based on a daily maximum 8-hour TWA concentration of a
carcinogen above which a worker should not be exposed (NIOSH 2017b,
page vi). RML-Cas for occupational carcinogens are established at the
estimated 95% lower confidence limit on the concentration (e.g., dose)
corresponding to 1 in 10,000 (10-4) lifetime excess risk
(when analytically possible to measure) (NIOSH 2019a). NIOSH stated
that in order to incrementally move toward a level of exposure to
occupational chemical carcinogens that is closer to background, NIOSH
will begin issuing recommendations for RML-Cas that would advise
employers to take additional action to control chemical carcinogens
when workplace exposures result in excess risks greater than
10-4 (NIOSH 2017b, page vi).
MSHA used the Miller et al. (2007) and Miller and MacCalman (2010)
studies to estimate lung cancer mortality risk in miners. In British
coal miners, excess lung cancer mortality was studied through the end
of 2005 in a cohort of 17,800 miners (Miller et al., 2007; Miller and
MacCalman, 2010). By that time, the cohort had accumulated
[[Page 44894]]
516,431 person-years of observation (an average of 29 years per miner),
with 10,698 deaths from all causes. Overall lung cancer mortality was
elevated (Standard Mortality Ratio (SMR) = 115.7, 95% CI: 104.8-127.7),
and a positive exposure-response relationship with respirable
crystalline silica exposure was determined from Cox regression after
adjusting for smoking history. Three strengths of this study were: 1)
the detailed time-exposure measurements of quartz and total mine dust,
2) detailed individual work histories, and 3) individual smoking
histories. For lung cancer, analyses based on Cox regression provided
strong evidence that, for these coal miners, although quartz exposures
were associated with increased lung cancer risk, simultaneous exposures
to coal dust did not cause increased lung cancer risk (OSHA 2016a, 81
FR 16286, 16308).
Miller et al. (2007) and Miller and MacCalman (2010) conducted a
follow-up study of cohort mortality, begun in 1970. Their previous
report on mortality presented a follow-up analysis on 18,166 coal
miners from 10 British coal mines followed through the end of 1992
(Miller et al., 1997). The two reports from 2007 and 2010 analyzed the
mortality experience of 17,800 of these miners (18,166 minus 346 men
whose vital status could not be determined) and extended the analysis
through the end of 2005. Causes of deaths that were of particular
interest included pneumoconiosis, other NMRD, lung cancer, stomach
cancer, and tuberculosis. The researchers noted that no additional
exposure measurements were included in the updated analysis, since all
the mines had closed by the mid-1980s. However, some of these men might
have had additional exposure at other mines or facilities not reported
in this study (OSHA 2013b, page 287).
This cohort mortality study included analyses using both external
and internal controls. The external controls used British
administrative regional age-, time-, and cause-specific mortality rates
from which to calculate SMRs. The internal controls from the mines used
Cox proportional hazards regression methods, which considered each
miner's age, smoking status, and detailed dust and respirable
crystalline silica (quartz) time-dependent exposure measurements. Cox
regression analyses were done in stages, with the initial analyses used
to establish what factors were required for baseline adjustment (OSHA
2013b, page 287).
For the analysis using external mortality rates, the all-cause
mortality SMR from 1959 through 2005 was 100.9 (95% CI: 99.0-102.8),
based on all 10,698 deaths. However, these SMRs were not uniform over
time. For the period from 1990-2005, the SMR was 109.6 (95% CI:106.5-
112.8), while the ratios for previous periods were less than 100. This
pattern of increasing SMRs in the recent past was also seen for cause-
specific deaths from chronic bronchitis, SMR = 330.0 (95% CI:268.1-
406.2); tuberculosis, SMR = 193.4 (95% CI: 86.9-430.5); cardiovascular
disease, SMR = 106.6 (95% CI: 102.0-111.5); all cancers, SMR = 107.1
(95% CI:101.3-113.2); and lung cancer, SMR = 115.7 (95% CI: 104.8-
127.7). The SMR for NMRD was 142.1 (95% CI: 132.9-152.0) in this recent
period and remained highly statistically significant. In their previous
analysis on mortality from lung cancer, reflecting follow-up through
1995, Miller et al. (1997) had not found any increase in the risk of
lung cancer mortality (OSHA 2013b, page 287).
OSHA reported that Miller and MacCalman (2010) used these analyses
to estimate relative risks for a lifetime exposure of 5 gram-hours/m\3\
(ghm-3) to quartz (OSHA 2013b, page 288). This is equivalent
to approximately 55 [micro]g/m\3\ (0.055 mg/m\3\) for 45 years,
assuming 2,000 hours per year of exposure and/or 100 ghm-3
total dust. The authors estimated relative risks (see Miller and
MacCalman (2010), Table 4, page 9) for various causes of death
including pneumoconiosis, COPD, ischemic heart disease, lung cancer,
and stomach cancer. Their results were based on models with single
exposures to dust or respirable crystalline silica (quartz) or
simultaneous exposures to both, with and without 15-year lag periods.
Generally, the risk estimates were slightly greater using a 15-year lag
period.
For the models using only quartz exposures with a 15-year lag,
pneumoconiosis, RR = 1.21 (95% CI: 1.12-1.31); COPD, RR = 1.11 (95% CI:
1.05-1.16); and lung cancer, RR = 1.07 (95% CI: 1.01-1.13) showed
statistically significant increased risks.
For lung cancer, analyses based on these Cox regression methods
provided strong evidence that, for these coal miners, quartz exposures
were associated with increased lung cancer risk, but simultaneous
exposures to coal dust were not associated with increased lung cancer
risk. The relative risk (RR) estimate for lung cancer deaths using coal
dust with a 15-year lag in the single exposure model was 1.03 (95% CI:
0.96 to 1.10). In the model using both quartz and coal mine dust
exposures, the RR based on coal dust decreased to 0.91, while that for
quartz exposure remained statistically significant, increasing to a RR
= 1.14 (95% CI: 1.04 to 1.25). According to Miller and MacCalman
(2010), other analyses have shown that exposure to radon or diesel
fumes was not associated with an increased cancer risk among British
coal miners (OSHA 2013b, page 288).
The RRs in the Miller and MacCalman (2010) report were used to
estimate excess lung cancer risk for OSHA's purposes. Life table
analyses were done as in the other studies above. Based on the RR of
1.14 (95% CI: 1.04-1.25) for a cumulative exposure of 5
ghm10-3, the regression slope was recalculated as [beta] =
0.0524 per 1,000 [micro]g-years (per mg/m\3\-years) and used in the
life table program. Similarly, the 95-percent CI on the slope was
0.0157-0.08926. From this study, the lifetime (to age 85) risk
estimates for 45 years of exposure to 50 [micro]g/m\3\ (0.05 mg/m\3\)
and 100 [micro]g/m\3\ (0.100 mg/m\3\) respirable crystalline silica
were 6 and 13 excess lung cancer deaths per 1,000 workers,
respectively. These lung cancer risk estimates were less by about 2- to
4-fold than those estimated from the other cohort studies described
above.
However, three factors might explain these differences. First,
these estimates were adjusted for individual smoking histories so any
smoking-related lung cancer risk (or smoking-respirable crystalline
silica interaction) that might possibly be attributed to respirable
crystalline silica exposure in the other studies were not reflected in
the risk estimates derived from the study of these coal miners. Second,
these coal miners had significantly increased risks of death from other
lung diseases, which may have decreased the lung cancer-susceptible
population. Of note, for example, were the higher increased SMRs for
NMRD during the years 1959-2005 for this cohort (Miller and MacCalman,
2010, Table 2, Page 7). Third, the difference in risk seen in these
coal miners may have been the result of differences in the toxicity of
quartz present in the coal mines as compared to the work environments
of the other cohorts. One Scottish mine (Miller et al., 1998) in this
10-mine study had been cited as having presented ``unusually high
exposures to [freshly fractured] quartz.'' However, this was also
described as an atypical exposure among miners working in the 10 mines.
Miller and MacCalman (2010) stated that increased quartz-related lung
cancer risk in their cohort was not confined to that Scottish mine
alone. They also stated, ``The general nature of some quartz exposures
in later years . . . may have been different from earlier periods when
coal extraction was
[[Page 44895]]
largely manual . . .'' (OSHA 2013b, page 288).
All these factors in this mortality analysis for the British coal
miner cohort could have combined to yield lower lung cancer risk
estimates. However, OSHA believed that these coal miner-derived
estimates were credible because of the quality of several study factors
relating to both study design and conduct. In terms of design, the
cohort was based on union rolls with very good participation rates and
good reporting. The study group also included over 17,000 miners, with
an average of nearly 30 years of follow-up, and about 60 percent of the
cohort had died. Just as important was the high quality and detail of
the exposure measurements, both of total dust and quartz. However, one
exposure factor that may have biased the estimates upward was the lack
of exposure information available for the cohort after the mines closed
in the mid-1980s. Since the death ratio for lung cancer was higher
during the last study period, 1990-2005, this period contributed to the
increased lung cancer risk. It is possible that any quartz exposure
experienced by the cohort after the mines had closed could have
accelerated either death or malignant tumor (lung cancer) growth. By
not accounting for this exposure, if there were any, the risk estimates
would have been biased upwards. Although the 15-year lag period for
quartz exposure used in the analyses provided slightly higher risk
estimates than use of no lag period, the better fit seen with the lag
may have been artificial. This may have occurred since there appeared
to have been no exposures during the recent period when risks were seen
to have increased (OSHA 2013b, page 289).
OSHA believed, as does MSHA, that this study of a large British
coal mining cohort provided convincing evidence of the carcinogenicity
of respirable crystalline silica. This large cohort study, with almost
30 years of follow-up, demonstrated a positive exposure-response after
adjusting for smoking histories. Additionally, the authors state that
there was no evidence that exposure to potential confounders such as
radon and diesel exhaust were associated with excess lung cancer risk
(Miller and MacCalman (2010), page 270). MSHA is relying on the British
studies conducted by Miller et al. (2007) as well as Miller and
MacCalman (2010) to estimate the lung cancer risk in all miners.
MSHA found these two studies suitable for use in the quantitative
characterization of health risks to exposed miners for several reasons.
First, their study populations were of sufficient size to provide
adequate statistical power to detect low levels of risk. Second,
sufficient quantitative exposure data were available over a sufficient
span of time to characterize cumulative respirable crystalline silica
exposures of cohort members. Third, the studies either adjusted for or
otherwise adequately addressed confounders such as smoking and exposure
to other carcinogens. Finally, these investigators developed
quantitative assessments of exposure-response relationships using
appropriate statistical models or otherwise provided sufficient
information that permits MSHA to do so.
MSHA implemented the risk model in its life table analysis so that
the use of background rates of lung cancer and assumptions regarding
length of exposure and lifetime were consistent across models. Thus,
MSHA was able to estimate lung cancer risks associated with exposure to
specific levels of respirable crystalline silica of interest to the
Agency. MSHA used the Miller et al. (2007) and Miller and MacCalman
(2010) model to estimate age-specific cumulative lung cancer mortality
risk as EXP(0.0524 * cumulative exposure), lagged 15 years.
MSHA's PRA uses risk estimates derived from 10 coal mines in the
U.K. (Miller et al., 2007; Miller and MacCalman, 2010). These
investigators developed regression analyses for time-dependent
estimates of individual exposures to respirable dust. Their analyses
were based on the detailed individual exposure estimates of the PFR
programme. To estimate mortality risk for lung cancer from the pooled
cohort analysis, MSHA used the same life table approach as OSHA.
However, for this life table analysis, MSHA used 2018 mortality rates
for U.S. males (i.e., all-cause and background lung cancer). The 2018
lung cancer death rates were based on the ICD-10 classification of
diseases, C34.0, C34.2, C34.1, C34.3, C34.8, and C34.9. Lifetime risk
estimates reflected excess risk through age 80. To estimate lung cancer
risks, MSHA used the log-linear relative risk model, exp(0.0524 x
cumulative exposure), lagged 15 years. The coefficient for this model
was 0.0524 (OSHA 2013b, page 290).
5. ESRD Mortality
Several epidemiological studies have found statistically
significant associations between occupational exposure to respirable
crystalline silica and renal disease, although others have failed to
find a statistically significant association. These studies are
discussed in the Health Effects document. Possible mechanisms suggested
for respirable crystalline silica-induced renal disease included a
direct toxic effect on the kidney, deposition of immune complexes (IgA)
in the kidney following respirable crystalline silica-related pulmonary
inflammation, and an autoimmune mechanism (Gregorini et al., 1993;
Calvert et al., 1997; Parks et al., 1999; Steenland 2005b) (OSHA 2016a,
81 FR 16286, 16310).
MSHA, like OSHA, chose the Steenland et al. (2002a) study to
include in the PRA. In a pooled cohort analysis, Steenland et al.
(2002a) combined the industrial sand cohort from Steenland et al.
(2001b), the gold mining cohort from Steenland and Brown (1995a), and
the Vermont granite cohort studies by Costello and Graham (1988). All
three were included in portions of OSHA's PQRA for other health
endpoints: under lung cancer mortality in Steenland et al. (2001a) and
under silicosis mortality in the related work of Mannetje et al.
(2002b). In all, the combined cohort consisted of 13,382 workers with
exposure information available for 12,783. The analysis demonstrated
statistically significant exposure-response trends for acute and
chronic renal disease mortality with quartiles of cumulative respirable
crystalline silica exposure (OSHA 2016a, 81 FR 16286, 16310).
The average duration of exposure, cumulative exposure, and
concentration of respirable crystalline silica for the pooled cohort
were 13.6 years, 1,200 [micro]g/m\3\-years (1.2 mg/m\3\-years), and 70
[micro]g/m\3\ (0.07 mg/m\3\), respectively. Renal disease risk was most
prevalent among workers with cumulative exposures of 500 [micro]g/m\3\
or more (Steenland et al., 2002a). SMRs (compared to the U.S.
population) for renal disease (acute and chronic glomerulonephritis,
nephrotic syndrome, acute and chronic renal failure, renal sclerosis,
and nephritis/nephropathy) were statistically significant and elevated
based on multiple cause of death data (SMR 1.28, 95% CI: 1.10-1.47, 194
deaths) and underlying cause of death data (SMR 1.41, 95% CI: 1.05-
1.85, 51 observed deaths) (OSHA 2013b, page 315).
A nested case-control analysis was also performed which allowed for
more detailed examination of exposure-response. This analysis included
95 percent of the cohort for which there were adequate work history and
quartz exposure data. This analysis included 50 cases for underlying
cause mortality and 194 cases for multiple-cause mortality. Each case
was matched by race, sex, and age within 5 years to 100 controls from
the cohort. Exposure-response trends were examined in a
[[Page 44896]]
categorical analysis where renal disease mortality of the cohort
divided by exposure quartile was compared to U.S. rates (OSHA 2013b,
page 315).
In this analysis, statistically significant exposure-response
trends for SMRs were observed for multiple-cause (p < 0.000001) and
underlying cause (p = 0.0007) mortality (Steenland et al., 2002a; Table
1; Page 7).
With the lowest exposure quartile group serving as a referent, the
case-control analysis showed monotonic trends in mortality with
increasing cumulative exposure. Conditional regression models using
log-cumulative exposure fit the data better than cumulative exposure
(with or without a 15-year lag) or average exposure. Odds ratios by
quartile of cumulative exposure were 1.00, 1.24, 1.77, and 2.86 (p =
0.0002) for multiple cause analyses and 1.00, 1.99, 1.96, and 3.93 for
underlying cause analyses (p = 0.03) (Steenland et al., 2002a; Table 2;
Page 7). For multiple-cause mortality, the exposure-response trend was
statistically significant for cumulative exposure (p = 0.004) and log-
cumulative exposure (p = 0.0002), whereas for underlying cause
mortality, the trend was statistically significant only for log-
cumulative exposure (p = 0.03). The exposure-response trend was
homogeneous across the three cohorts and interaction terms did not
improve model fit (OSHA 2013b, pages 216, 315).
Based on the exposure-response coefficient for the model with the
log of cumulative exposure, Steenland (2005) estimated lifetime excess
risks of death (age 75) over a working life (age 20 to 65). At 100
[micro]g/m\3\ (0.1 mg/m\3\) respirable crystalline silica, this risk
was 5.1 percent (95% CI 3.3-7.3) for ESRD based on 23 cases (Steenland
et al., 2001b). It was 1.8 percent (95% CI 0.8-9.7) for kidney disease
mortality (underlying), based on 51 deaths (Steenland et al., 2002a)
above a background risk of 0.3 percent (OSHA 2013b, page 216).
MSHA notes that these studies added to the evidence that renal
disease is associated with respirable crystalline silica exposure.
Statistically significant increases in odds ratios and SMRs were seen
primarily for cumulative exposures of >500 [micro]g/m\3\-years (0.5 mg/
m\3\-years). Steenland (2005b) noted that this could have occurred from
working for 5 years at an exposure level of 100 [micro]g/m\3\ (0.1 mg/
m\3\) or 10 years at 50 [micro]g/m\3\ (0.05 mg/m\3\).
OSHA had a large body of evidence, particularly from the three-
cohort pooled analysis (Steenland et al., 2002a), on which to conclude
that respirable crystalline silica exposure increased the risk of renal
disease mortality and morbidity. The pooled analysis by Steenland et
al. (2002a) involved a large number of workers from three cohorts with
well-documented, validated job-exposure matrices. These investigators
found a positive, monotonic increase in renal disease risk with
increasing exposure for underlying and multiple cause data. Thus, the
exposure and work history data were unlikely to have been seriously
misclassified. However, there are considerably less data available for
renal disease than there are for silicosis mortality and lung cancer
mortality. Nevertheless, OSHA concluded that the underlying data were
sufficient to provide useful estimates of risk and included the
Steenland et al. (2002a) analysis in its PQRA (OSHA 2013b, pages 229,
316).
To estimate renal disease mortality risk from the pooled cohort
analysis, OSHA implemented the same life table approach as was done for
the assessments on lung cancer and NMRD. However, for this life table
analysis, OSHA used 1998 all-cause and background renal mortality rates
for U.S. males, rather than the 2006 rates used for lung cancer and
NMRD. The 1998 rates were based on the ICD-9 classification of
diseases, which was the same as used by Steenland et al. (2002a) to
ascertain the cause of death of workers in their study. However, U.S.
cause-of-death data from 1999 to present are based on the ICD-10, in
which there were considerable changes in the classification system for
renal diseases. According to CDC (2001), the change in the
classification from ICD-9 to ICD-10 increased death rates for
nephritis, nephritic syndrome, and nephrosis by 23 percent, in large
part due to reclassifying ESRD. The change from ICD-9 to ICD-10 did not
materially affect background rates for those diseases grouped as lung
cancer or NMRD. Consequently, OSHA conducted its analysis of excess
renal disease mortality associated with respirable crystalline silica
exposure using background mortality rates for 1998. As before, lifetime
risk estimates reflected excess risk through age 85. To estimate renal
mortality risks, OSHA used the log-linear model with log-cumulative
exposure that provided the best fit to the pooled cohort data
(Steenland et al., 2002a). The coefficient for this model was 0.269 (SE
= 0.120) (OSHA 2013b, page 316). Based on the life table analysis, OSHA
estimated that exposure to the former general industry exposure limit
of 100 [micro]g/m\3\ and to the final exposure limit of 50 [micro]g/
m\3\ over a working life would result in a lifetime excess renal
disease risk of 39 (95% CI: 2-200) and 32 (95% CI: 1.7-147) deaths per
1,000, respectively. OSHA also estimated lifetime risks associated with
the former construction and shipyard exposure limits of 250 and 500
[micro]g/m\3\. These lifetime excess risks ranged from 52 (95% CI 2.2-
289) to 63 (95% CI 2.5-368) deaths per 1,000 workers (OSHA 2013b, page
316).
MSHA concludes that the evidence supporting causality regarding
renal risk outweighs the evidence casting doubt on that conclusion.
However, MSHA acknowledges the uncertainty associated with the
divergent findings in the renal disease literature. To estimate renal
disease mortality risk from the pooled cohort analysis, MSHA
implemented the same life table approach as OSHA. However, MSHA's life
table analysis used 2018 all-cause and 1998 background renal mortality
rates for U.S. males. The 1998 renal death rates were based on the ICD-
9 classification of diseases, 580-589. This is the same classification
used by Steenland et al. (2002a) to ascertain the cause of death of
workers in their study. Consequently, MSHA conducted its analysis of
excess ESRD mortality associated with exposure to respirable
crystalline silica using background mortality rates for 1998. The U.S.
cause-of-death data from 2018 were used as well. Lifetime risk
estimates reflect excess risk through age 85. To estimate ESRD
mortality risks, MSHA used the log-linear model with log-cumulative
exposure that provided the best fit to the pooled cohort data
(Steenland et al., 2002a), as EXP(0.269 * ln (cumulative exposure)).
The coefficient for this model was 0.269 (SE = 0.120) (OSHA 2013b, page
316).
6. Coal Workers' Pneumoconiosis (CWP)
Exposure to respirable coal mine dust causes lung diseases
including CWP, emphysema, silicosis, and chronic bronchitis, known
collectively as ``black lung.'' These diseases are debilitating,
incurable, and can result in disability and premature death. There are
no specific treatments to cure CWP or COPD. These chronic effects may
progress even after miners are no longer exposed to coal dust.
MSHA's 2014 coal dust rule quantified benefits among coal miners
related to reduced cases of CWP due to lower exposure limits for
respirable coal mine dust. In this PRA, MSHA has not quantified the
reduction in risk associated with CWP among coal miners. Nonetheless,
MSHA believes that the proposed rule would reduce the excess risk of
this disease. Many coal
[[Page 44897]]
miners work extended shifts, thus increasing their potential exposure
to respirable crystalline silica. The result of calculating exposures
based on a full-shift 8-hour TWA would be more protective. Thus, the
proposed rule is expected to provide additional reductions in CWP risk
beyond those ascribed in the 2014 coal dust rule. However, exposure-
response relationships based on respirable crystalline silica exposure
are not available for CWP, so the reductions in this disease due to
reductions in silica exposure cannot be quantified.
D. Overview of Results
Table VI-4 summarizes the PRA's main results: once it is fully
effective (and all miners have been exposed only under the proposed
PEL), the proposed rule is expected to result in at least 799 avoided
deaths and 2,809 avoided cases of silicosis morbidity among the working
miner population. These numbers represent the lifetime health outcomes
expected to occur after both 45 years of employment under the proposed
PEL (from 21 through 65 years of age) and 15 years of retirement (up to
80 years of age). These estimates of the avoided lifetime excess
mortality and morbidity represent the final calculations based on the 5
selected models and the observed exposure data. The first group of
miners that would experience the avoided lifetime fatalities and
illnesses shown in Table VI-4 is the population living 60 years after
promulgation of the proposed rule. In other words, this group would
only contain miners exposed under the proposed rule. To calculate
benefits associated with the proposed rulemaking, the economic analysis
monetizes avoided deaths and illnesses while accounting for the fact
that, during the first 60 years following promulgation, miners would
have fewer avoided lifetime fatalities and illnesses because they would
be exposed under both the existing standards and the proposed PEL.
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Table VI-5 summarizes miners' expected percentage reductions in
lifetime excess risk of developing or dying from certain diseases due
to their reduced respirable crystalline silica exposure expected to
result from implementation of the proposed rule. The lifetime excess
risk reflects the probability of developing or dying from diseases over
a maximum lifetime of 45 years of exposure during employment and 15
years of retirement. The excess risk reduction compares (a) miners'
excess health risks associated with respirable crystalline silica
exposure at the limits included in MSHA's existing standards to (b)
miners' excess health risks associated with exposure at this standard's
proposed PEL. MSHA expects full-scale implementation to reduce lifetime
excess mortality risk by 9.5 percent and to reduce lifetime excess
silicosis morbidity risk by 41.9 percent. Excess mortality risk
includes the excess risk of death due to silicosis, NMRD, lung cancer,
and ESRD.
[[Page 44898]]
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Table VI-6 presents MSHA's estimates of lifetime excess risk per
1,000 miners at exposure levels equal to the existing standards, the
proposed PEL, and the proposed action level. These estimates are
adjusted for FTE ratios and thus utilize cumulative exposures that more
closely reflect the average hours worked per year.\21\ For an MNM miner
who is presently exposed at the existing PEL of 100 [mu]g/m\3\ (and
given the weighted average FTE ratio of 0.87), implementing the
proposed PEL would lower the miner's lifetime excess risk of death by
58.8 percent for silicosis, 45.6 percent for NMRD (not including
silicosis), 52.0 percent for lung cancer, and 19.9 percent for ESRD.
The MNM miner's risk of acquiring a non-fatal case of silicosis (would
decrease by 80.4 percent).
---------------------------------------------------------------------------
\21\ The FTE ratios used in these calculations are a weighted
average of the FTE ratio for production employees and the FTE ratio
for contract miners.
---------------------------------------------------------------------------
For a coal miner who is currently exposed at the existing exposure
limit of 85.7 [mu]g/m\3\ (and given the weighted average FTE ratio of
0.99), implementing the proposed PEL would lower the miner's lifetime
excess risk of death by 42.3 percent for silicosis mortality, 40.2
percent for NMRD mortality (not including silicosis), 43.5 percent for
lung cancer mortality, and 15.8 percent for ESRD mortality. The coal
miner's lifetime excess risk of acquiring non-fatal silicosis would
decrease by 73.8 percent. While even greater reductions would be
achieved at exposures equal to the proposed action level (25 [mu]g/
m\3\), some residual risks do remain at exposures of 25 [mu]g/m\3\.
Notably, at the proposed action level, ESRD risk is still 20.7 per
1,000 MNM miners and 21.6 per 1,000 coal miners. At the proposed action
level, risk of non-fatal silicosis is 16.3 per 1,000 MNM miners and
16.9 per 1,000 coal miners.
[[Page 44899]]
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BILLING CODE 4520-43-C
E. Healthy Worker Bias
MSHA accounted for ``healthy worker survivor bias'' in estimating
the risks for coal and MNM miners. The healthy worker survivor bias
causes epidemiological studies to underestimate excess risks associated
with occupational exposures. As with most worker populations, miners
are composed of heterogeneous groups that possess varying levels of
background health. Over the course of miners' careers, illness tends to
remove the most at-risk workers from the workforce prematurely, thus
causing the highest cumulative exposures to be experienced by the
healthiest workers who are most immune to risk. Failing to account for
this imbalance of cumulative exposure across workers negatively biases
risk estimates, thereby underestimating true risks in the population.
Keil et al. (2018) analyzed a type of healthy worker bias referred to
as the healthy worker survivor bias in the context of OSHA's 2016 life
table estimates for risk associated with respirable crystalline silica
exposure. After analyzing data from 65,999 workers pooled across
multiple countries and industries, Keil et al. found that the ``healthy
worker survivor bias results in a 28% underestimate of risk for lung
cancer and a 50% underestimate for other causes of death,'' with risk
being defined as ``cumulative incidence of mortality [at age 80].''
Given that MSHA has calculated risks using the same underlying
epidemiological studies OSHA used in 2016, the healthy worker survivor
bias is likely impacting the estimates in Table VI-6 of lifetime excess
risk and lifetime excess cases avoided. Accordingly, as part of a
sensitivity analysis, MSHA re-estimated risks for MNM and coal miners
to account for the healthy worker survivor bias. MSHA adjusted for this
effect by increasing the risk estimates of lung cancer risk by 28
percent and increasing the risk of each other disease by 50 percent.
This produced larger estimates of lifetime excess risk reductions and
lifetime excess cases avoided, which are presented in PRA Table 23
through PRA Table 26 of the PRA document. As these tables show, when
adjusting for the healthy worker survivor bias, the proposed PEL would
decrease lifetime silicosis morbidity risk by 20.8 cases per 1,000 MNM
miners (compared to the unadjusted estimate of 13.9 cases per 1,000 MNM
miners, see PRA Table 15 of the PRA document) and 5.0 cases per 1,000
coal miners (compared to 3.3 cases per 1,000 coal miners, see PRA Table
16 of the PRA document). Still accounting for the healthy worker
survivor bias, the proposed PEL would decrease total morbidity by 3,848
lifetime cases among MNM miners (compared to 2,566 cases, see PRA Table
17 of the PRA document) and by 366
[[Page 44900]]
lifetime cases among coal miners (compared to 244 cases, see PRA Table
18 of the PRA document). Among the current MNM and coal mining
populations, implementation of the proposed PEL during their full lives
would have prevented 1,091 deaths and 94 deaths, respectively, over
their lifetimes (compared to unadjusted estimates of 736 deaths and 63
deaths, respectively).
MSHA believes adjusted estimates for the healthy worker survivor
bias are more reliable than unadjusted estimates. However, given that
the literature does not support specific scaling factors for each of
the health endpoints analyzed, these adjustments for the healthy worker
survivor bias have not been incorporated into the final lifetime excess
risk estimates that served as the basis for monetizing benefits.
Because the monetized benefits do not account for the healthy worker
bias, MSHA believes the reductions in lifetime excess risks and
lifetime excess cases, as well as the monetized benefits, likely
underestimate the true reductions and benefits attributable to the
proposed rule.
F. Uncertainty Analysis
MSHA conducted extensive uncertainty analyses to assess the impact
on risk estimates of factors including treatment of data in excess of
the proposed PEL, sampling error, and use of average rather than median
point estimates for risk. The impact of excluding insufficient mass
(weight) samples was also examined.
1. Alternate Treatment of Exposure Samples in Excess of the Proposed
Exposure Limit
To estimate excess risks and excess cases under the proposed PEL,
MSHA assumed that no exposures would exceed the proposed limit, which
effectively reduced any exposures exceeding 50 [mu]g/m\3\ to 50 [mu]g/
m\3\. However, if mines implement controls with the goal of reducing
exposures to 50 [mu]g/m\3\ on every shift, then some exposure currently
in excess of 50 [mu]g/m\3\ would likely decrease below the proposed
PEL. For this reason, the estimation method of capping all exposure
data at 50 [mu]g/m\3\ represents a ``lowball'' estimate of risk
reductions due to the proposed PEL. In this section, MSHA presents
estimates using an alternate ``highball'' method wherein exposures
exceeding 50 [mu]g/m\3\ are set equal to the median exposure value for
the 25-50 [mu]g/m\3\ exposure group. Because this highball method
attributes larger reductions in exposure to the proposed PEL, it
estimates higher lifetime excess risk reductions and more avoided
lifetime excess cases.
As with lifetime excess risks, the highball method also yields
larger reductions in lifetime excess cases. Using the highball method,
MNM miners are expected to experience 3,111 fewer cases of non-fatal
silicosis and coal miners are expected to experience 344 fewer cases of
non-fatal silicosis over their lifetimes. MNM miners would experience
1,137 fewer deaths and coal miners would experience 123 fewer deaths
over their lifetimes. Compared to the lowball method--which estimates
that the proposed PEL would prevent a total of 2,809 lifetime cases of
non-fatal silicosis and 799 lifetime excess deaths (among both MNM and
coal miners)--the highball method estimates totals of 3,445 avoided
lifetime cases of non-fatal silicosis and 1,260 avoided lifetime excess
deaths.
2. Sampling Error in Exposure Data
To quantify the impact of sampling uncertainty on the risk
estimates, 1,000 bootstrap resamples of the original exposure data were
generated (sampling with replacement). The resamples were stratified by
commodity to preserve the relative sampling frequencies of coal, metal,
non-metal, sand and gravel, crushed limestone, and stone observations
in the original dataset. Risk calculations were repeated on each of the
1,000 bootstrap samples, thereby generating empirical distributions for
all risk estimates. From these empirical distributions, 95 percent
confidence intervals were calculated. These confidence intervals
characterize the uncertainty in the risk estimates arising from
sampling error in the exposure data. All lifetime excess risk estimates
had narrow confidence intervals, indicating that the estimates of
lifetime excess morbidity and mortality risks have a high degree of
precision.
In regard to use of average, rather than median, point estimates of
risk, the estimates acquired from average exposures are similar to the
estimates from median exposures, with 95 percent confidence intervals
having similar widths. However, the 95 percent confidence intervals are
not always overlapping, and average exposures tended to yield higher
estimates of reduced morbidity and mortality. Among MNM miners, MSHA
expects the proposed PEL to produce lifetime risk reductions of
silicosis morbidity of 2,546-2,777 using average exposures (see PRA
Table 41 of the PRA document), compared to 2,453-2,683 using median
exposures (see PRA Table 37 of the PRA document). Among coal miners,
this reduction is expected to be 246-279 using average exposures (see
PRA Table 42 of the PRA document), compared to 229-265 using median
exposures (see PRA Table 38 of the PRA document). The proposed PEL is
estimated to reduce lifetime excess mortality by 735-791 MNM miner
deaths and 65-73 coal miner deaths using average exposures (see PRA
Tables 41 and 42 of the PRA document), compared to 708-764 MNM miner
deaths and 60-69 coal miner deaths using median exposures (see PRA
Tables 37 and 38 of the PRA document).
3. Samples With Insufficient Mass
The MNM exposure data gathered by enforcement from January 1, 2005,
through December 31, 2019, contain samples that were analyzed using the
P-2 method. As discussed, the P-2 method specifies that filters are
only analyzed for quartz if they achieve a net mass gain of 0.100 mg or
more. If cristobalite is requested, a mass gain of 0.050 mg or more is
required for a filter to be analyzed (MSHA 2022a). During the 15-year
sample period for MNM exposure data, 40,618 MNM samples were not
analyzed because the filter failed to meet the P-2 minimum net mass
(weight) gain requirements.
Similarly, the coal exposure data gathered by enforcement from
August 1, 2016, through July 31, 2021, contains samples that were
analyzed using the P-7 method. The P-7 method requires a minimum sample
mass of 0.100 mg \22\ of dust for the sample to be analyzed for quartz.
During the five-year sample period for coal exposure data, 63,127 coal
samples were not analyzed because the P-7 method's minimum mass
requirement was not met.
---------------------------------------------------------------------------
\22\ Often the threshold for analyzing Coal samples is >=0.1 mg.
There are, however, some exceptions based on Sample Type and
Occupation Code. For samples with Sample Type 4 or 8, if the
sample's Occupation Code is not 307, 368, 382, 383, 384, or 386,
then the threshold is >=0.2 mg.
---------------------------------------------------------------------------
For samples that do not meet a minimum threshold for total
respirable dust mass, the MSHA lab does not analyze these samples for
respirable crystalline silica. These samples were excluded from the
risk analysis because their concentrations of respirable crystalline
silica are not known. Nonetheless, the unanalyzed samples all had very
low total respirable dust mass, making it unlikely that many would have
exceeded the existing standards or the proposed PEL. Excluding these
unanalyzed samples from the exposure datasets thus may introduce bias,
potentially causing the Agency to overestimate the proportion of high-
intensity exposure values.
[[Page 44901]]
As a sensitivity analysis, MSHA used imputation techniques to
estimate the respirable crystalline silica mass for each sample based
on the sample weight and the median percent silica content for each
commodity and occupation. All the unanalyzed samples with imputed
concentrations were estimated to be <25 [mu]g/m\3\, and thus including
these unanalyzed samples in the analysis leads to lower estimates of
estimated lifetime excess cases for both MNM and coal miners.
When including the imputed values for the unanalyzed samples, the
proposed PEL would result in 1,642 fewer cases of non-fatal silicosis
among MNM miners and 128 fewer cases among coal miners, over their
lifetimes. The proposed PEL would also result in 469 fewer deaths (due
to all 4 diseases) among MNM miners and 34 fewer deaths among coal
miners, over their lifetimes. This yields a total reduction of 1,770 in
lifetime excess morbidity and of 503 in lifetime excess mortality,
respectively. While these estimates are lower than those presented in
Table VI-4 (of 2,809 avoided lifetime cases of non-fatal silicosis and
799 avoided lifetime excess fatalities), MSHA nonetheless believes
that--even including these unanalyzed samples--the proposed PEL would
still reduce the risk of material impairment of health or functional
capacity in miners exposed to respirable crystalline silica. Moreover,
the possible positive bias that may arise when excluding these samples
would be offset by other negative biases discussed herein (e.g., the
healthy worker survivor bias and the assumption that full compliance
with the proposed PEL would not produce any reductions in exposure
below 50 [mu]g/m\3\).
It should be noted that the imputation method has some limitations.
For example, the method assumes that, if the insufficient mass samples
had been analyzed, every sample would have possessed a percentage of
quartz, by mass, equal to the median percentage for that sample's
associated commodity and occupation. (See Section 17.1 of the PRA
document for a full discussion of the imputation method.) However,
within a given occupation, this percentage varies substantially and is
positively correlated with exposure concentration. Suppressing the
variation in this percentage quartz, by mass, produces less variation
in the resulting imputed concentrations. Consequently, the imputation
method may underestimate the number of unanalyzed samples that would
truly exceed 50 [mu]g/m\3\.
VII. Section-by-Section Analysis
MSHA proposes to add a new part 60, titled Respirable Crystalline
Silica, to title 30 CFR, chapter I, subchapter M--Uniform Mine Health
Regulations. Proposed part 60, which would apply to all MNM and coal
mines, contains health standards to protect all miners from adverse
health risks caused by occupational exposure to respirable crystalline
silica (as discussed in the standalone document entitled Effects of
Occupational Exposure to Respirable Crystalline Silica on the Health of
Miners and as summarized in Section V. Health Effects Summary of this
preamble). This proposed part establishes a new PEL for respirable
crystalline silica for all mines and includes other ancillary
provisions to improve methods of compliance, exposure monitoring,
corrective actions, respiratory protection, medical surveillance for
MNM miners, and recordkeeping. In addition to the new part 60, MSHA
proposes to incorporate by reference ASTM F3387-19, Standard Practice
for Respiratory Protection, to replace its respiratory protection
standards under 30 CFR parts 56, 57, and 72 to better protect all
miners from airborne contaminants. This section-by-section analysis
discusses each provision under the proposed part 60, the conforming
amendments related to the proposed part, and the updated respiratory
protection standard.
A. Part 60--Respirable Crystalline Silica
MSHA has preliminarily determined that occupational exposure to
respirable crystalline silica causes adverse health effects, including
silicosis (acute silicosis, accelerated silicosis, simple chronic
silicosis, and PMF), NMRD (e.g., emphysema and chronic bronchitis),
lung cancer, and renal diseases. MSHA has also preliminarily determined
that under the existing standards, miners remain at risk of suffering
material impairment of health or functional capacity from these adverse
health effects. Each of these effects is exposure-dependent, chronic,
irreversible, and potentially disabling or fatal. MSHA has
preliminarily concluded that lowering the PEL for respirable
crystalline silica to 50 [mu]g/m\3\ would substantially reduce the
health risks to miners.
MSHA proposes to replace its existing standards for respirable
crystalline silica or respirable dust containing quartz with a single,
uniform health standard for all miners. The proposed uniform standard
would establish consistent, industry-wide requirements that directly
address the adverse health effects of overexposure to respirable
crystalline silica. This proposal would also facilitate mining-industry
compliance and help MSHA and other stakeholders provide consistent
compliance assistance. MSHA believes this unified regulatory framework
for controlling miner exposure to respirable crystalline silica would
improve protection for all miners and help the Agency fulfill its
obligations under the Mine Act to prevent occupational diseases.
Proposed part 60 includes: Scope and effective date; Definitions;
Permissible exposure limit (PEL); Methods of compliance; Exposure
monitoring; Corrective actions; Respiratory protection; Medical
surveillance for metal and nonmetal miners; Recordkeeping requirements;
and Severability.
Detailed discussions of the proposed sections are followed by
discussions on conforming amendments and discussions of the proposed
update to the respiratory protection standard in parts 56, 57, and 72.
1. Section 60.1--Scope; Effective Date
This section provides that proposed part 60 would take effect 120
days after the final rule is published in the Federal Register. Mine
operators would be required to comply with the requirements in this
part starting on the proposed effective date.
MSHA believes that the proposed 120-day period gives operators the
necessary time to plan and prepare for effective compliance with the
new standards, while also ensuring that improved protections for miners
from the hazards of respirable crystalline silica take effect as soon
as practically possible. MSHA believes that it is important to reduce
miner exposure to respirable crystalline silica promptly because every
exposure at levels above the proposed PEL imposes adverse health risks
on miners. However, for implementation to be successful, mine operators
need enough time to understand the standard and to prepare for
compliance (e.g., by purchasing gravimetric ISO-conforming samplers
and/or selecting a commercial laboratory for respirable crystalline
silica analysis, if necessary). MSHA believes that the proposed
effective date of 120 days would provide enough time for mine operators
to take necessary steps to achieve successful compliance. Under the
existing standards, both MNM and coal operators have had many years of
experience with monitoring and controlling airborne contaminants,
including respirable crystalline silica, and this experience should
facilitate
[[Page 44902]]
implementation of the proposed standard.
2. Section 60.2--Definitions
This section includes the proposed definitions of four terms:
``action level,'' ``objective data,'' ``respirable crystalline
silica,'' and ``specialist.''
The term ``action level'' would mean an airborne concentration of
respirable silica of 25 micrograms per cubic meter of air ([mu]g/m\3\)
for a full-shift exposure, calculated as an 8-hour time-weighted
average (TWA). The action level sets the level of respirable
crystalline silica concentration at or above which operators would be
subject to periodic sampling requirements, which are explained in
proposed Sec. 60.12. This proposed action level is intended to support
operator compliance with the proposed PEL of 50 [micro]g/m\3\ by
initiating periodic sampling requirements.
The proposed action level of 25 [mu]g/m\3\, one-half of the
proposed PEL, is consistent with NIOSH research findings and other MSHA
standards. According to NIOSH research, wherever exposure measurements
are above one-half the PEL, the employer cannot be reasonably confident
that the employee is not exposed to levels above the PEL on days when
no measurements are taken (NIOSH 1975). MSHA has experience with
setting an action level equivalent to 50 percent of the PEL for
occupational noise exposure (30 CFR 62.101), applicable to MNM and coal
mines, and an action level of 50 percent of the exhaust gas monitoring
standards for underground coal mines (30 CFR 70.1900). Based upon
Agency experience, MSHA believes these action levels have allowed mine
operators to be more proactive in providing necessary protection.
The term ``objective data'' would mean information such as air
monitoring data from industry-wide surveys or calculations based on the
composition of a substance that indicates the level of miner exposure
to respirable crystalline silica associated with a particular product
or material or a specific process, task, or activity. Such data must
reflect mining conditions closely resembling, or with a higher exposure
potential than, the processes, types of material, control methods, work
practices, and environmental conditions in the operator's current
operations. Some examples of information that would qualify as
objective data under this definition include historical MSHA sampling
data, NIOSH Health Hazard Evaluations and other published scientific
reports, and industry-wide surveys compiled from mines with similar
mining conditions, geological composition, work processes, miner tasks,
and the same commodities.
``Respirable crystalline silica'' would mean quartz, cristobalite,
and/or tridymite contained in airborne particles that are determined to
be respirable by a sampling device designed to meet the characteristics
for respirable-particle-size-selective samplers that conform to the
International Organization for Standardization (ISO) 7708:1995: Air
Quality--Particle Size Fraction Definitions for Health-Related
Sampling. These characteristics are described further below.
First, the proposed definition would apply to airborne particles
that contain collectively or individually, quartz, cristobalite, and/or
tridymite, three polymorphs of respirable crystalline silica that may
be encountered in mining and for which exposures are addressed in
existing MSHA standards. Quartz is the most common polymorph and is
present in varying amounts in almost every type of mineral, whereas
naturally occurring cristobalite and tridymite are rare.
Second, airborne particles determined to be respirable are those
particles capable of entering the gas-exchange region (alveolar region)
of the lungs. MSHA's proposed definition would harmonize the Agency's
existing practice with current aerosol science and be consistent with
the nationally and internationally accepted ISO definition of
``respirable particulate mass'' (i.e., the respirable mass fraction of
total airborne particles that can be inhaled through the nose or
mouth). ISO 7708:1995 defines conventions for the ``inhalable,''
``thoracic,'' and ``respirable'' fractions of total airborne particles.
The inhalable fraction represents the fraction of total airborne
particles capable of being inhaled through the nose or mouth. The
thoracic fraction is the portion of the inhalable particles that pass
the larynx and into the airways (trachea) and the bronchial region of
the lungs. The respirable fraction is the portion of inhalable
particles that can enter the gas-exchange region (alveolar region) of
the lungs. The ISO 7708:1995 definition of ``respirable particulate
mass'' corresponds to particulate matter (respirable dust) that is
inhaled and capable of entering the gas-exchange region (alveolar
region) of the lungs. MSHA considers this definition to be biologically
relevant because exposures to airborne contaminants that are respirable
can lead to material impairment of health or functional capacity.\23\
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\23\ The gas-exchange region of the human lung is the region
where the exchange of carbon dioxide and oxygen occurs between the
lung and blood and includes the alveoli and respiratory bronchioles.
---------------------------------------------------------------------------
Third, respirable particles are those particles which can be
collected by a sampling device designed to meet the characteristics for
respirable-particle-size-selective samplers that conform to the ISO
7708:1995 standard. While ``respirable dust'' generally refers to dust
particles having an aerodynamic diameter of 10 micrometers ([mu]m) or
less, ISO 7708:1995 defines the term more precisely based on the
respiratory system's efficiency at collecting different types and sizes
of particles. Collection efficiency is represented by particle
collection efficiency curves based on the aerodynamic diameter of
particles.\24\ The ISO 7708:1995 standard uses particle collection
efficiency curves to approximate the fraction of respirable particles
that can be deposited in the alveolar region of the human respiratory
tract. A sampling device that conforms to the ISO 7708:1995 standard
would ensure the collection of only respirable particles, including
crystalline silica polymorphs.
---------------------------------------------------------------------------
\24\ The ISO 7708:1995 standard defines aerodynamic diameter as
the ``diameter of a sphere of density 1 g/cm\3\ with the same
terminal velocity due to gravitational force in calm air as the
particle, under the prevailing conditions of temperature, pressure,
and relative humidity.''
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MSHA believes that the proposed definition of respirable
crystalline silica has two main advantages. First, because the ISO
7708:1995 definition of respirable particulate mass represents an
international consensus, adoption of the ISO 7708:1995 criterion would
allow harmonization with standards used by other occupational health
and safety organizations in the U.S. and internationally, including
ACGIH, OSHA (29 CFR 1910.1053 and 29 CFR 1926.1153), NIOSH (2003b,
Manual of Analytical Methods), and the European Committee for
Standardization (CEN) (ISO 7708:1995). Second, the proposed definition
would eliminate inconsistencies in the existing standards for MNM and
coal mines. Under the proposal, defining respirable crystalline silica
to include quartz, cristobalite, and/or tridymite and establishing a
PEL for exposure to respirable particles of any combination of these
three polymorphs would provide consistency across the different mining
sectors. Using samplers that conform to ISO 7708:1995 would allow for
uniform collection for these three polymorphs. The proposed streamlined
approach would facilitate compliance and provide consistency in the
development of best practices and would allow mine operators and MSHA
to better promote the health and safety of all miners.
[[Page 44903]]
``Specialist'' would mean an American Board-Certified Specialist in
Pulmonary Disease or an American Board-Certified Specialist in
Occupational Medicine. The proposed definition is applicable to
proposed Sec. 60.15, which addresses medical surveillance for MNM
miners. Under the proposed medical surveillance requirements, which
will be discussed later, MNM mine operators would be required to
provide miners with medical examinations performed by a specialist in
pulmonary disease or occupational medicine or a PLHCP.
3. Section 60.10--Permissible Exposure Limit (PEL)
This section establishes a single, uniform PEL of 50 [mu]g/m\3\ for
respirable crystalline silica for all mines. Under this proposed
provision, mine operators would be required to ensure that ``no miner
is exposed to an airborne concentration of respirable crystalline
silica in excess of 50 [mu]g/m\3\ for a full-shift exposure, calculated
as an 8-hour TWA.'' For coal mines, this proposal would establish a
separate PEL for respirable crystalline silica. This proposed PEL would
replace the Agency's existing exposure limits for respirable
crystalline silica or respirable quartz in 30 CFR parts 56, 57, 70, 71,
and 90.
The proposed PEL is consistent with NIOSH's recommended exposure
limit for workers and with the PEL for respirable crystalline silica
covering U.S. workplaces regulated by OSHA. NIOSH recommended in 1974
that occupational exposure to crystalline silica be controlled so that
``no worker is exposed to a TWA of silica [respirable crystalline
silica] greater than 50 [mu]g/m\3\ as determined by a full-shift sample
for up to a 10-hour workday over a 40-hour workweek'' (NIOSH 1974). In
2016, OSHA promulgated a rule establishing that for construction,
general industry, and the maritime industry, workers' exposures to
respirable crystalline silica must not exceed 50 [mu]g/m\3\, averaged
over an 8-hour day (29 CFR 1910.1053(c); 29 CFR 1926.1153(d)(1)).\25\
MSHA's 2014 rule on respirable coal mine dust established that the
average concentration of respirable dust in the mine atmosphere during
each shift to which each miner is exposed be at or below 1.5 mg/m\3\,
calculated as a TWA, and that coal miners' exposure to respirable
crystalline silica be regulated through reductions in the overall
respirable dust standard (30 CFR 70.100, 70.101, 71.100, 71.101,
90.100, and 90.101).\26\
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\25\ NIOSH conducted a literature review of studies containing
environmental data on the harmful effects of exposure to respirable
crystalline silica. Based on these studies, and especially fifty
years' worth of studies on Vermont granite workers during which time
dust controls improved, exposures fell, and silicosis diagnoses
neared zero, NIOSH recommended an exposure limit of 50 [mu]g/m\3\
for all industries. OSHA's examination of health effects evidence
and its risk assessment led to the conclusion that occupational
exposure to respirable crystalline silica at the previous PELs,
which were approximately equivalent to 100 [mu]g/m\3\ for general
industry and 250 [mu]g/m\3\ for construction and maritime
industries, resulted in a significant risk of material health
impairment to exposed workers, and that compliance with the revised
PEL would substantially reduce that risk. (81 FR at 16755). OSHA
considered the level of risk remaining at the revised PEL to be
significant but determined that a PEL of 50 [mu]g/m\3\ is
appropriate because it is the lowest level feasible.
\26\ For Part 90 miners, MSHA lowered the exposure to respirable
coal mine dust during a coal miner's shift to not exceed 0.5 mg/
m\3\.
---------------------------------------------------------------------------
As discussed in the Health Effects Summary of this preamble,
occupational exposure to respirable crystalline silica is detrimental
to an individual's health. Silicosis and other diseases caused by
respirable crystalline silica exposure are irreversible, disabling, and
potentially fatal. However, these diseases are exposure-dependent and
are therefore preventable. The lower a miner's exposure to respirable
crystalline silica, the less likely that miner is to suffer from
adverse health effects.
As presented in the PRA, MSHA has preliminarily determined that:
(1) under existing respirable crystalline silica or quartz standards,
miners are exposed to respirable crystalline silica at concentrations
that result in a risk of material impairment of health or functional
capacity; and (2) that lowering the PEL to 50 [mu]g/m\3\ would
substantially reduce this risk. According to the CDC, between 1999 and
2014, miners died from silicosis, COPD, lung cancer, and NMRD at
substantially higher rates than did members of the general population;
for silicosis, the proportionate mortality ratio for miners was 21
times as high.\27\ Evidence in the standalone Health Effects document
demonstrates that exposure to respirable crystalline silica at levels
permitted under existing standards contributes to this excess
mortality.
---------------------------------------------------------------------------
\27\ Data on occupational mortality by industry and occupation
can be accessed by visiting the CDC website at https://www.cdc.gov/niosh/topics/noms/default.html. The NOMS database provides detailed
mortality data for the 11-year period from 1999, 2003 to 2004, and
2007 to 2014. https://;wwwn.cdc.gov/niosh-noms/industry2.aspx;
accessed November 7, 2022.
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In the case of coal mines, the proposed rule would establish a
separate PEL for respirable crystalline silica. Under the existing
standard, miners' exposure to quartz is tied to exposure to respirable
coal mine dust, making it more difficult to monitor coal miners'
exposure to respirable crystalline silica. The proposed separate
standard would be more transparent and make compliance easier to track,
allowing more effective control of respirable crystalline silica.
The proposed PEL of 50 [mu]g/m\3\ applies to a miner's full-shift
exposure, calculated as an 8-hour TWA. Under this proposal, a miner's
work shift exposure would be calculated as follows:
[GRAPHIC] [TIFF OMITTED] TP13JY23.023
Regardless of a miner's actual working hours (full shift), 480
minutes would be used in the denominator. This means that the
respirable crystalline silica collected over an extended period (e.g.,
a 12-hour shift) would be calculated (or normalized) as if it were
collected over 8 hours (480 minutes). For example, if a miner was
sampled for 12 hours and 55 [mu]g of respirable crystalline silica was
collected on the sample, the miner's respirable crystalline silica 8-
hour TWA exposure would be 67.4 [mu]g/m\3\, calculated as follows:
[GRAPHIC] [TIFF OMITTED] TP13JY23.024
[[Page 44904]]
This proposed calculation method is the one that MSHA uses to
calculate MNM miner exposures to respirable crystalline silica and
other airborne contaminants; it differs from the existing method of
calculating a coal miner's exposure to respirable coal mine dust. For
coal miners, the existing calculation method uses the entire duration
of a miner's work shift in both the denominator and numerator,
resulting in the total mass of respirable coal mine dust collected over
an entire work shift scaled by the sample's air volume over the same
period.
MSHA's proposal to apply the existing method of calculating MNM
miner exposure to all miners has two main advantages. First, the
proposal would improve protection for coal miners who work longer
shifts. The goal of the proposed respirable crystalline silica PEL is
to prevent miners from suffering a body burden high enough to cause
adverse health effects. If a miner works longer than 8 hours, the
miner's body (lungs, in particular) may not have sufficient time to
eliminate the respirable crystalline silica that enters the lungs or to
reduce the body burden.\28\ Coal miners commonly work extended shifts,
with many working 10-hour or longer shifts.\29\ In such cases, a coal
miner's recovery time would be reduced from 16 hours to 12 to 14 hours.
To account for this increased risk, the proposed calculation (like the
current MNM calculation method) normalizes to an 8-hour TWA. The
concept of adjusting occupational exposure limits for ``extended
shifts'' has been addressed by researchers (Brief and Scala, 1986;
Elias, 2013).
---------------------------------------------------------------------------
\28\ The pulmonary uptake and clearance of respirable
crystalline silica are dependent upon many factors, including a
miner's breathing patterns, exposure duration, concentration (dose),
particle size, and durability or bio-persistence of the particle.
These factors will also affect the time to clear particles, even
after exposure ceases. Of principal concern is the possibility that
a continuous dust exposure over an extended period of time (or high
dust level exposure during a short exposure period may excessively
tax lung defense mechanisms (Industrial Minerals Association-North
America and Mine Safety and Health Administration, 2008).
The ACGIH (2022), while not specifically addressing silica, has
stated, ``numerous mathematical models to adjust for unusual work
schedules have been described. In terms of toxicologic principles,
their general objective is to identify a dose that ensures that the
daily peak body burden or weekly peak body burden does not exceed
that which occurs during a normal 8-hours/day, 5-day/week shift.''
There are associated concerns with the body burden from an ``unusual
work schedule'' such as a 10- or a 12- hour shift. As Elias (2013)
stated, ``if the length of the workday is increased, there is more
time for the chemical to accumulate, and less time for it to be
eliminated. It is assumed that the time away from work will be
contamination free. The aim is to keep the chemical concentrations
in the target organs from exceeding the levels determined by the
TLVs[supreg] (8-hour day, 5-day week) regardless of the shift
length. Ideally, the concentration of material remaining in the body
should be zero at the start of the next day's work.''
\29\ Sampling hours of coal mine dust samples approximate the
working hours of coal miners who were sampled. According to the coal
mine dust samples for a 5-year period (August 2016-July 2021), 90
percent of the samples by MSHA inspectors were from miners working 8
hours or longer and about 43 percent of the samples from miners
working 10 hours or longer. The dust samples by coal mine operators
show that over 98 percent of them were from miners working 8 hours
or longer and over 26 percent from the miners working 10 hours or
longer. The coal mine dust samples are available at Mine Data
Retrieval System [verbar] Mine Safety and Health Administration
(MSHA).
---------------------------------------------------------------------------
Second, applying the proposed calculation method for all miners
would be more straightforward and easier to understand for mine
operators, miners, and other stakeholders. The current calculation
method for coal miners requires first determining the percentage of
quartz in the sample of collected respirable dust, then dividing the
result into the number 10 to calculate an exposure limit for respirable
dust. The proposed calculation method requires only measuring the total
mass of respirable crystalline silica collected and dividing it by the
air volume over 480 minutes.
This proposal would establish a lower PEL and apply it to all
miners using a consistent method for calculating exposures. These
changes would improve the health and safety of miners while making
compliance more straightforward and transparent. The 8-hour TWA is the
``gold standard'' for exposure assessments, except in scenarios
involving chemical substances that are predominantly fast-acting (i.e.,
those evoking acute effects). NIOSH has also supported the use of the
TWA and discussed this term since the publication of the NIOSH Pocket
Guide to Chemical Hazards (First Edition, 1973) (the ``White Book'').
4. Section 60.11--Methods of Compliance
This proposed section would require mine operators to install, use,
and maintain feasible engineering and administrative controls to keep
each miner's exposure to respirable crystalline silica at or below the
proposed PEL. Mine operators would be required to use feasible
engineering controls as the primary means of controlling respirable
crystalline silica; administrative controls would be used, when
necessary, as a supplementary control. However, under the proposal,
rotation of miners--that is, assigning more than one miner to a high-
exposure task or location, and rotating them to keep each miner's
exposure below the PEL--would be prohibited. Under the proposal,
respiratory protection equipment could be used in specific and limited
situations, as discussed in Sec. 60.14--Respiratory Protection, but
the use of respiratory protection equipment would not be acceptable as
a method of compliance.
This proposed approach to controlling miners' exposures is
consistent with MSHA's existing standards, NIOSH's recommendations, and
generally accepted industrial hygiene principles. The proposal is
consistent with MSHA's existing respirable dust standards, which
require engineering controls as the primary means to protect miners.
MSHA's experience and data show that engineering controls provide
improved, more consistent, and more reliable protection for miners than
administrative controls or respirators. In its recommendations, NIOSH
also stressed the importance of using engineering controls to control
miners' exposure to respirable crystalline silica. In 1995, NIOSH
recommended that the dust standard state that ``the mine operator shall
use engineering controls and work practices [administrative controls]
to keep worker exposures at or below the REL [recommended exposure
limit]. . .'' (NIOSH 1995a). In its public response to MSHA's 2019
Request for Information for Respirable Silica (Quartz) (84 FR 45452,
Aug. 29, 2019), NIOSH also supported the use of engineering controls as
the primary means of protecting miners from exposure to respirable
crystalline silica, stating that ``[r]espirators should only be used
when engineering control systems are not feasible. Engineering control
systems, such as adequate ventilation or scrubbing of contaminants, are
the preferred control methods for reducing worker exposures.'' \30\
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\30\ Comment from Paul Schulte, NIOSH (Oct. 23, 2019) to Docket
No. MSHA 2016-0013.
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As discussed in the technological feasibility and preliminary
regulatory impact analysis sections of the preamble, MSHA has
preliminarily determined that engineering and administrative controls
are technologically and economically feasible, and the use of these
controls would be sufficient to achieve compliance with the proposed
PEL. After reviewing the effectiveness of various exposure reduction
controls which are currently available and have been successfully
adopted in various combinations in mines, MSHA has concluded that all
mine operators can ensure miners' exposures are below the proposed PEL
through implementing some combination of enhanced
[[Page 44905]]
maintenance of existing engineering controls, new engineering controls,
and improved administrative controls/work practices.
a. Engineering Controls
Proposed paragraph (a) would require mine operators to use feasible
engineering controls as the primary means of controlling respirable
crystalline silica; administrative controls would be used, when
necessary, as a supplementary control.
This proposed paragraph would require engineering controls to be
used as the primary means of controlling respirable crystalline silica.
Engineering controls can include ventilation systems (i.e., main,
auxiliary, local exhaust), dust suppression devices (i.e., wet dust
suppression and airborne capture), and enclosed cabs or control booths
with filtered breathing air, as well as changes in materials handling,
equipment used in a process, ventilation, and dust capture mechanisms.
Engineering controls generally suppress (e.g., using water sprays,
wetting agents, foams, water infusion), dilute (e.g., ventilation),
divert (e.g., water sprays, passive barriers, ventilation), or capture
dust (e.g., dust collectors) to minimize the exposure of miners working
in the surrounding areas. The use of automated ore-processing equipment
and use of video cameras for remote scanning and monitoring can also
help to reduce or eliminate miners' exposures to respirable crystalline
silica.
Engineering controls are the most effective means of controlling
the amount of dust to which miners are exposed. They have the advantage
of addressing dust at its source, thus ensuring that all miners in an
area are adequately protected from overexposure to respirable
crystalline silica. Engineering controls provide more consistent and
more reliable protection to miners than other interventions because the
controls are not dependent on an individual's performance, supervision,
or intervention to function as intended. In contrast to other controls
and other interventions, engineering controls can also be continually
evaluated and monitored relatively easily, allowing their effectiveness
to be assessed regularly.
b. Administrative Controls
Under the proposed rule, mine operators would be permitted to
supplement engineering controls with administrative controls as a means
of controlling exposure to respirable crystalline silica.
Administrative controls include practices that change the way tasks are
performed to reduce a miner's exposure. These practices would include
housekeeping procedures; proper work positions of miners; cleaning of
spills; and measures to prevent or minimize contamination of clothing
to help decrease miners' exposure to respirable crystalline silica.
Administrative controls require significant effort by mine
operators to ensure that miners understand and follow the controls. If
not properly implemented, understood, or followed, or if persons
responsible for administrative controls do not properly supervise their
implementation, they would not be effective in controlling miners'
overexposure to respirable crystalline silica. Therefore,
administrative controls would be permitted only as supplementary
measures, with engineering controls required as the primary means of
protection.
Proposed paragraph (b) would prohibit mine operators from using
rotation of miners--that is, assigning more than one miner to a high-
exposure task or location, and rotating them to keep each miner's
exposure below the PEL--as an acceptable method of compliance. MSHA
does not believe that rotation of miners is consistent with the
Agency's regulatory framework or its mandate under the Mine Act. Based
on MSHA's experience, rotation of miners may, if permitted, reduce the
amount of time each miner is exposed to the hazard by rotating miners
out of the task faster. However, it would increase the number of miners
working in high-exposure tasks or areas and would lead to increased
material impairment of health or functional capacity for the additional
miners.
The concept of miner rotation, which may be an appropriate control
to minimize musculoskeletal stress, is not acceptable for work
involving carcinogens. Based on NIOSH's publication entitled ``Current
Intelligence Bulletin 68: NIOSH Chemical Carcinogen Policy,'' MSHA
believes that the primary way to prevent occupational cancer is to
reduce worker exposure to chemical carcinogens as much as possible
through elimination or substitution at the source and through
engineering controls (NIOSH 2017b).
5. Section 60.12--Exposure Monitoring
The proposed section addresses exposure monitoring, sampling
method, and sample analysis methods. MSHA is proposing two types of
exposure monitoring: quantitative, through sampling the air that miners
breathe, and qualitative, through semi-annual evaluations of how
changes in mining processes, production activities, and dust control
systems affect exposures. For the quantitative monitoring, MSHA is
proposing four types of sampling--baseline, periodic, corrective
actions, and post-evaluation--together with methods for sampling and
analyzing the samples.
The proposed exposure monitoring requirements, which include
sampling miners' exposures, would facilitate operator compliance with
the proposed PEL, harmonize MSHA's approach to monitoring and
evaluating respirable crystalline silica exposures in both MNM and coal
mines, and lead to better protection of miners' health. Monitoring
miner exposures to airborne contaminants is an effective risk
management tool. The sampling and evaluation requirements of proposed
Sec. 60.12 are designed to ensure maximum protection for miners and
prevent them from suffering material impairment of health or functional
capacity, while providing operators flexibility to tailor their
sampling program to the miners' risk of exposure to respirable
crystalline silica at their mines.
The first type of exposure monitoring under the proposed rule is
quantitative sampling for miners' exposures to respirable crystalline
silica. This sampling would help mine operators determine the extent
and degree of exposures, identify sources of exposure and potential
overexposure, maintain updated and accurate records of exposures,
select the most appropriate control methods, and evaluate the
effectiveness of those controls. The proposal would require operators
to conduct sampling for a miner's regular full shift during typical
mining activities. The second type of exposure monitoring under the
proposed rule would be qualitative evaluations, which would help
operators identify changes in mining conditions and processes that
affect the exposure risk to miners.
a. Section 60.12(a)--Baseline Sampling
The first action mine operators would take to assess miners'
exposures under the proposed rule would be to conduct baseline
sampling. Baseline sampling would provide an initial measurement of
respirable crystalline silica exposures that would be compared to the
proposed action level and the proposed PEL to determine the
effectiveness of existing controls and the need for additional
controls.
Proposed paragraph (a)(1) would require mine operators to perform
baseline sampling to assess the full-shift, 8-hour TWA exposure of
respirable crystalline silica for each
[[Page 44906]]
miner who is or may reasonably be expected to be exposed to respirable
crystalline silica at any level. MSHA assumes that most mining
occupations related to extraction and processing would meet the
``reasonably be expected'' threshold; however, MSHA recognizes that
some miners may work in areas or perform tasks where exposures are not
reasonably likely, and some miners may work in silica-free
environments. Based on the Agency's experience, both MNM and coal mine
operators generally know from their existing sampling data and MSHA's
sampling data the occupations, work areas, and work activities where
respirable crystalline silica exposures occur. The mine operator would
be required to sample only those miners the operator knows or
reasonably expects to be exposed to respirable crystalline silica.
The proposed provisions would require that, within the first 180
days after the effective date of the final rule, the mine operator
perform the baseline sampling. During this 180-day period, mine
operators would acquire necessary sampling devices or sampling
services, sample occupations or areas of known or reasonably expected
exposures, identify appropriate laboratories, and arrange for analysis
of samples. Given that the mining industry has experience with sampling
programs for other airborne contaminants, as well as respirable
crystalline silica, MSHA anticipates that the proposed 180 days would
provide sufficient time for mine operators to comply with the proposed
standard.
Under this proposed standard, mine operators would need to
accurately characterize the exposure of each miner who is or may
reasonably be expected to be exposed to respirable crystalline silica.
As discussed later in detail, mine operators would be permitted to use
representative sampling whenever sampling is required. In some cases,
however, operators may have to sample all miners to obtain an accurate
assessment of exposures.
This proposed requirement would ensure that mine operators have the
quantitative information needed to evaluate miners' exposure risks,
determine the adequacy of existing engineering and administrative
controls, and make necessary changes to ensure miners are not
overexposed. In addition, the results of the baseline sampling would
determine further operator obligations for periodic sampling. A
baseline sample result at or above the proposed action level but at or
below the proposed PEL, would require operators to conduct periodic
sampling under proposed Sec. 60.12(b). However, if the baseline sample
indicated that exposures were below the proposed action level and
operators can confirm those results, mine operators would not be
required to conduct periodic sampling. The results can be confirmed in
three ways: (1) sample data, collected by the operator or the Secretary
in the 12 months preceding the baseline sampling, that also shows
exposures below the proposed action level; (2) objective data (as
defined in the proposal) confirming that a miner's exposure to
respirable crystalline silica would remain below the proposed action
level; or (3) another sample taken within 3 months showing exposure
below the proposed action level.
Proposed paragraph (a)(2) would allow mine operators to use
objective data to confirm the baseline sample result. Under this
proposal, objective data must demonstrate that respirable crystalline
silica would not be released in airborne concentrations at or above the
action level under any expected conditions. Objective data, as defined
in proposed Sec. 60.2, would include air monitoring data from
industry-wide surveys that demonstrate miners' exposure to respirable
crystalline silica associated with a particular product or material or
a specific process, task, or activity. Objective data must reflect
mining conditions that closely resemble the processes, material,
control methods, work practices, and environmental conditions in the
mine operator's current operations. The mine operator would have the
burden of showing that the objective data characterizes miner exposures
to respirable crystalline silica with sufficient accuracy.
Also, proposed paragraph (a)(2) would permit mine operators to use
sampling conducted by the Secretary or mine operator within the
preceding 12 months of baseline sampling to confirm miner exposures
below the proposed action level. The proposed rule would require mine
operator sampling that was conducted in accordance with sampling
requirements in paragraph (f) and analyzed according to paragraph (g)
of this section. Under proposed paragraph (a)(2), any subsequent
sampling conducted by the operator or by the Secretary, collected
within 3 months of the baseline sample, could also be used to confirm a
baseline sample result.
MSHA believes that before sampling is discontinued for miners
previously determined to be exposed at or above the proposed action
level, it is necessary to confirm any sample result that indicates
miner exposures are below the proposed action level. When such a result
is confirmed by a second measurement, an operator could reasonably
expect exposures to remain below the action level if mining conditions
and practices do not change. However, as discussed later, under
proposed paragraph (d), if there is any change in conditions or
practices that could be reasonably expected to result in exposures at
or above the action level, sampling to assess these exposures would be
required.
b. Section 60.12(b)--Periodic Sampling
Periodic sampling under the proposed rule would provide mine
operators and miners with regular information about miners' exposures.
Changes in exposure levels can be caused by changes in the mine
environment, inadequate engineering controls, or other changes in
mining processes or procedures. Periodic sampling would inform mine
operators about increases in exposures in a timely manner so they can
prevent potential overexposures. In addition, periodic sampling alerts
operators and miners of the continued need to protect against the
hazards associated with exposure to respirable crystalline silica. If a
mine operator installs new engineering controls and/or starts new
administrative control practices, periodic sampling would show whether
those controls are working properly to achieve the anticipated health
results and would document their effectiveness.
Proposed Sec. 60.12(b) would require periodic sampling of miners'
exposures to respirable crystalline silica whenever the most recent
sampling indicates that exposures are at or above the proposed action
level but at or below the proposed PEL. Whether a mine operator would
have to conduct periodic sampling under the proposal would depend on
the results of the most recent sample, which could include a baseline
sample, a corrective actions sample, or a post-evaluation sample, as
well as samples taken by MSHA during its inspections. If operators are
required to conduct periodic sampling, and periodic sampling results
indicate that miner exposures are below the action level, a mine
operator would be permitted to discontinue periodic sampling for those
miners whose exposures are represented by these samples. If the most
recent sample shows exposures at or above the action level but at or
below the proposed PEL, periodic sampling every 3 months would continue
until two consecutive sample analyses showed miners' exposures below
the action level. MSHA believes that two consecutive sample analyses
showing exposures below the
[[Page 44907]]
action level would indicate a low probability that prevailing mining
conditions would result in overexposures.
MSHA believes that the proposed frequency for periodic sampling--
repeating the sampling within 3 months--is practical for mine operators
and protective of the health and safety of miners. MSHA has
preliminarily concluded that the health risks caused by respirable
crystalline silica overexposure warrant more regular sampling when
exposure levels approach the proposed PEL, because this periodic
sampling would provide a higher level of confidence that miners would
not be overexposed. Due to the unique conditions of mining
environments, where conditions change quickly and exposures to
respirable crystalline silica can vary frequently, MSHA is proposing a
three-month periodic sampling schedule (NIOSH, 2014e). This three-month
schedule would provide a meaningful degree of confidence that mine
operators would recognize quickly when exposures are increasing and
approaching the proposed PEL and would respond by implementing
additional controls to prevent overexposure. Periodic sampling data
would also provide information that operators could use to select,
implement, and maintain controls. MSHA has structured the proposal to
balance the costs of periodic sampling requirements, including when
sampling can be stopped, and the benefits of additional health
protection for miners. Taking these factors into consideration, MSHA
has preliminarily determined that the proposed frequency of periodic
sampling is both economically and technologically feasible for mine
operators. (See Section VIII. Technological Feasibility and Section IX.
Summary of Preliminary Regulatory Impact Analysis.)
As with the baseline sampling in proposed paragraph (a), in meeting
the requirements of this paragraph, mine operators would be allowed to
sample a representative fraction of at least two miners. The exposure
result would be attributed to the remaining miners represented by this
sample, as discussed in more detail below. When miners are not
performing the same job under the same working conditions, a
representative sample would not accurately characterize actual
exposures, and individual samples would be necessary.
c. Section 60.12(c)--Corrective Actions Sampling
Under the proposed rule, MSHA would require mine operators to take
corrective actions when any sampling shows exposures above the proposed
PEL. After such corrective actions, proposed Sec. 60.12(c) would
require mine operators to conduct corrective actions sampling to
determine whether the control measures taken under proposed Sec. 60.13
have reduced miner exposures to respirable crystalline silica to at or
below the proposed PEL. If not, the mine operator would be required to
take additional or new corrective actions until subsequent corrective
actions sampling indicates miner exposures are at or below the proposed
PEL.
Once corrective actions sampling indicates that miner exposures
have been lowered to levels at or below the proposed PEL, one of two
scenarios could occur. First, if corrective actions sampling taken
under proposed Sec. 60.12(c) indicate that miner exposures are at or
below the proposed PEL, but at or above the proposed action level, the
mine operator would be required to conduct periodic sampling as
described in proposed Sec. 60.12(b). The periodic sampling
requirements would require mine operators to continue to conduct
sampling every three months until two consecutive sampling results
indicate miners' exposures are below the action level. Second, if
corrective actions sampling taken under proposed Sec. 60.12(c)
indicate that miner exposures are below the proposed action level, the
mine operator would be required to conduct a subsequent sample within 3
months as described in proposed Sec. 60.12(b); if those results show
miners' exposures are below the action level, the mine operator could
discontinue periodic sampling.
Sampling after corrective actions would provide operators with
specific information regarding the effectiveness of the corrective
actions for the mine environment and provide additional data for use in
making decisions about updating or improving controls. It would also
provide mine operators with an updated profile of miners' exposures
against which future samples could be compared.
d. Section 60.12(d) and (e)--Semi-Annual Evaluation and Post-Evaluation
Sampling
Historically, MSHA has recognized the importance of qualitatively
evaluating changes in mining conditions and processes and assessing the
effect of those changes on exposure risk. Operators have general
experience with these types of evaluations. The proposed rule would
require mine operators to qualitatively evaluate any changes in
production, processes, engineering controls, personnel, administrative
controls, or other factors including geological characteristics that
might result in new or increased respirable crystalline silica
exposures, beginning 18 months after the effective date and every 6
months thereafter. Such evaluations could identify changes in miners'
exposures to respirable crystalline silica.
The proposed semi-annual evaluation, and post-evaluation sampling,
as appropriate, would help confirm that the results of baseline and
periodic sampling continue to accurately represent current exposure
conditions. These proposed semi-annual evaluation and sampling
requirements would also enable mine operators to take appropriate
actions to protect exposed miners, such as implementing new or
additional engineering controls, and would provide information to
miners and their representatives, as necessary. An evaluation could
identify a change in operation processes or control measures that might
lead to increased exposures to respirable crystalline silica which need
to be corrected. Under proposed paragraph (d)(1), the mine operator
would be required to make a record of the evaluation, including the
date of the evaluation. Under proposed paragraph (d)(2), the mine
operator would be required to post the record on the mine bulletin
board, and, if applicable, make the evaluation available
electronically, for the next 31 days.
Once the evaluation is complete, a mine operator would be required
to conduct post-evaluation sampling under proposed Sec. 60.12(e) when
the results of the evaluation show that miners may be exposed at or
above the action level. Post-evaluation sampling would provide
operators with information on whether existing controls are effective,
whether additional control measures are needed, and whether respiratory
protection is appropriate. When post-evaluation samples indicate that
miner exposures are at or above the proposed action level, the mine
operator would be required to conduct periodic sampling as described in
proposed paragraph (b). Post-evaluation sampling, however, would not be
required if the mine operator determines that mining conditions would
not reasonably be expected to result in exposures at or above the
action level.
e. Section 60.12(f)--Sampling Requirements
Knowledge of typical respirable dust exposure levels is critical to
protect the health of miners. The proposed rule includes certain
sampling requirements that would ensure mine operators'
[[Page 44908]]
respirable crystalline silica monitoring is representative of miners'
actual exposures.
(1) Typical Mining Activities and Sampling Device Placement
Proposed paragraph (f)(1) would require mine operators to collect a
respirable dust sample for the duration of a miner's regular full shift
and during typical mining activities. Many potential sources of
respirable crystalline silica are present only when the mine is
operating under typical conditions. If a sample is not taken during
typical mining activities, the actual risk to the miner may not be
known. This proposed requirement would ensure that respirable
crystalline silica exposure data accurately reflect actual levels of
respirable crystalline silica exposure at miners' normal or regular
workplaces throughout their typical workday, even if there are
fluctuations in airborne contaminant concentrations during a work
shift. As discussed in other sections of this preamble, the sample
results from the full shift would be calculated as an 8-hour TWA
concentration for comparison with the proposed action level and PEL and
for compliance determinations.
This proposed provision is consistent with existing standards and
with generally accepted industrial hygiene principles, which recommend
taking into consideration the entire duration of time a miner is
exposed to an airborne contaminant, even if it exceeds 8 hours. Based
on Agency data and experience, MSHA anticipates that operators would
not have major challenges in meeting these sampling requirements.
This proposal would continue existing procedures for sampling
device placement during sampling. Under proposed Sec. 60.12(f)(2)(i),
for MNM miners the regular full-shift, 8-hour TWA exposure would be
based on personal breathing-zone air samples. A breathing zone sample
is an individual sample that characterizes a miner's exposure to
respirable crystalline silica during an entire work shift. More
specifically, the sampler remains with the miner for the entire shift,
regardless of the task or occupation performed.
For coal miners, under proposed Sec. 60.12(f)(2)(ii), the regular
full-shift, 8-hour TWA exposure would be based on an occupational
environmental sample collected in compliance with existing standards
found in Sec. Sec. 70.201(c), 71.201(b), and 90.201(b). Under the
existing standards, the sampling device would be worn or carried
``portal-to-portal,'' meaning from the time the miner enters the mine
until the miner exits the mine. The sampling device would remain with
the miner during the entire shift. For shifts that exceed 12 hours, the
operator would be required to switch the sampling pump prior to the
13th-hour of operation. However, except in the case of Part 90 miners,
if a miner who is being sampled changes positions or duties, the
sampling device would remain with the position or duty chosen for
sampling (rather than the miner). For Part 90 miners, the sampling
device would be operated portal-to-portal and would remain operational
with the miner throughout the Part 90 miner's entire shift, which would
include the time spent performing normal work duties and the time spent
traveling to and from the assigned work location.
(2) Representative Sampling
Under the proposed rule, mine operators must accurately
characterize miners' exposure to respirable crystalline silica. In some
cases, this would require sampling all exposed miners. In other cases,
as proposed in paragraph (f)(3), sampling a ``representative'' fraction
of miners would be sufficient. Where several miners perform the same
tasks on the same shift and in the same work area, the mine operator
could sample a representative fraction of miners. Under this proposed
rule, a representative fraction of miners would consist of two or more
miners performing the same tasks on the same shift and in the same work
area and who are expected to have the highest exposures of all the
miners in an area. For example, sampling a representative fraction may
involve monitoring the exposure of those miners who are closest to the
dust source. The sampling results for these miners would then be
attributed to the remaining miners in the group. When miners are not
performing the same job under the same working conditions, a
representative sample would not be sufficient to characterize actual
exposures, and therefore individual samples would be necessary.
MSHA has determined that requiring operators to sample at least two
miners as representative, where they perform the same tasks on the same
shift and in the same work area as the remaining miners, would be
sufficient to ensure that exposures are accurately characterized and
health protections are provided. This representative sampling provision
of the proposal is similar to the approach that OSHA uses for both
general industry (29 CFR 1910.1053(d)(3)) and construction (29 CFR
1926.1153(d)(2)) under the scheduled sampling options.
(3) Sampling Devices
Respirable dust sampling assesses the ambient air quality in mines
and evaluates miners' exposure to airborne contaminants. Respirable
dust comprises particles small enough that, when inhaled, can reach the
gas exchange region of the lung. Measurement of respirable dust
exposure is based on the collection efficiency of the human respiratory
system and the separation of airborne particles by size to assess their
respirable fraction. Proposed paragraph (f)(4) would require mine
operators to use sampling devices designed to meet the characteristics
for respirable-particle-size-selective samplers that conform to the ISO
7708:1995, ``Air Quality--Particle Size Fraction Definitions for
Health-Related Sampling,'' Edition 1, 1995-04 to determine compliance
with the proposed respirable crystalline silica action level and PEL.
MSHA proposes to incorporate by reference ISO 7708:1995, which is the
international consensus standard that defines sampling conventions for
particle size fractions used in assessing possible health effects of
airborne particles in the workplace and ambient environment. Mine
operators could use any type of sampling device they wish for
respirable crystalline silica sampling, as long as it is designed to
meet the characteristics for respirable-particle-size-selective
samplers that conform to the ISO 7708:1995 standard and, where
appropriate, meets MSHA permissibility requirements.\31\
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\31\ MSHA's permissibility requirements are specified in 30 CFR
parts 18 and 74. Part 18, Electric Motor-Driven Mine Equipment and
Accessories, specifies the procedures and requirements for obtaining
MSHA approval, certification, extension, or acceptance of electrical
equipment intended for use in gassy mines. Part 74, Coal Mine Dust
Sampling Devices, specifies the requirements for evaluation and
testing for permissibility of coal mine dust sampling devices.
---------------------------------------------------------------------------
Sampling devices, such as cyclones \32\ and elutriators,\33\ can
separate the
[[Page 44909]]
respirable fraction of airborne dust from the non-respirable fraction
in a manner that simulates the size-selective characteristics of the
human respiratory tract and that meets the ISO standard. These devices
enable collection of dust samples that contain only particles small
enough to penetrate deep into the lungs. Size-selective cyclone
sampling devices are typically used in the U.S. mining industry. These
samplers generally consist of a pump, a cyclone, and a membrane filter.
The cyclone uses a rapid vortical flow of air inside a cylindrical or
conical chamber to separate airborne particles according to their
aerodynamic diameter (i.e., particle size). As air enters the cyclone,
the larger particles are centrifugally separated and fall into a grit
pot, while smaller particles pass into a sampling cassette where they
are captured by a filter membrane that is later analyzed in a
laboratory to determine the mass of the respirable dust collected. The
pump creates and regulates the flow rate of incoming air. As the flow
rate of air increases, a greater percentage of larger and higher-mass
particles are removed from the airstream, and smaller particles are
collected with greater efficiency. Adjustment of the flow rate changes
the particle collection characteristics of the sampler and allows
calibration to a specified respirable particle size sampling
definition, such as the ISO criterion.
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\32\ A cyclone is a centrifugal device used for extracting
particulates from carrier gases (e.g., air). It consists of a
conically shaped vessel. The particulate-containing gas is drawn
tangentially into the base of the cone, takes a helical route toward
the apex, where the gas turns sharply back along the axis, and is
withdrawn axially through the base. The device is a classifier in
which only dust with terminal velocity less than a given value can
pass through the formed vortex and out with the gas. The particle
cut-off diameter is calculable for given conditions.
\33\ An elutriator is a device that separates particles based on
their size, shape, and density, using a stream of gas or liquid
flowing in a direction usually opposite to the direction of
sedimentation. The smaller or lighter particles rise to the top
(overflow) because their terminal sedimentation velocities are lower
than the velocity of the rising fluid.
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MSHA and many mine operators use cyclone samplers. A cyclone
sampler calibrated to operate at the manufacturer's specified air flow
rate that conforms to the ISO standard can be used to collect
respirable crystalline silica samples under this proposed rule. MSHA
reviewed OSHA's feasibility analysis for its 2016 silica final rule and
agrees with OSHA that there are commercially available cyclone samplers
that conform to the ISO standard and allow for the accurate and precise
measurement of respirable crystalline silica at concentrations below
both the proposed action level and PEL (OSHA 2016a) Such cyclone
samplers include the Dorr-Oliver 10-mm nylon cyclone used by MSHA and
many mine operators, as well as the Higgins-Dewell, GK2.69, SIMPEDS,
and SKC aluminum cyclone. Each of these cyclones has different
operating specifications, including flow rates, and performance
criteria, but all are compliant with the ISO criteria for respirable
dust with an acceptable level of measurement bias. MSHA's preliminary
determination is that cyclone samplers, when used at the appropriate
flow rates, can collect a sufficient mass of respirable crystalline
silica to quantify atmospheric concentrations lower than the proposed
action level and would meet MSHA's crystalline silica sample analysis
specifications for samples collected at MNM and coal mines.
MNM mine operators who currently use a Dorr-Oliver 10 mm nylon
cyclone could continue to use these samplers at a flow rate of 1.7 L/
min, which conforms to the ISO standard, to comply with the proposed
requirements. For coal mine operators, the gravimetric samplers
previously used to sample RCMD (i.e., coal mine dust personal sampling
units (CMDPSUs)) were operated at a 2.0 L/min flow rate. Those CMDPSUs
could be adjusted to operate at a flow rate of 1.7 L/min to conform to
the ISO standard.
NIOSH's rapid field-based quartz monitoring (RQM) approach is an
emerging technology. It provides a field-based method for providing
respirable crystalline silica exposure measurements at the end of a
miner's shift. With such an end-of-shift analysis, mine operators can
identify overexposures and mitigate hazards more quickly. NIOSH
Information Circular 9533, ``Direct-on-filter Analysis for Respirable
Crystalline Silica Using a Portable FTIR Instrument'' provides detailed
guidance on how to implement a field-based end-of-shift respirable
crystalline silica monitoring program.\34\ The current RQM monitor,
however, was designed as an engineering tool; it is not currently
designed as a compliance tool with tamper-proof components and is
susceptible to interferences which can affect its accuracy. This means
that the integrity of the sample cannot be guaranteed, and therefore
the monitor cannot be used as a compliance tool. MSHA continues to
support NIOSH efforts to develop the RQM monitor for use in mines.
---------------------------------------------------------------------------
\34\ National Institute for Occupational Safety and Health
(NIOSH). Direct-on-filter analysis for respirable crystalline silica
using a portable FTIR instrument. By Chubb LG, Cauda EG. Pittsburgh
PA: U.S. Department of Health and Human Services, Centers for
Disease Control and Prevention, National Institute for Occupational
Safety and Health, DHHS (NIOSH) Publication No. 2022-108, IC 9533.
https://doi.org/10.26616/NIOSHPUB2022108. The document is intended
for industrial hygienists and other health and safety mining
professionals who are familiar with respirable crystalline silica
exposure assessment techniques, but who are not necessarily trained
in analytical techniques. It gives general instructions for setting
up the field-based monitoring equipment and software. It also
provides case studies and examples of different types of samplers
that can be used for respirable crystalline silica monitoring.
Guidance on the use, storage, and maintenance of portable IR
instruments is also provided in the document.
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f. Section 60.12 (g)--Methods of Sample Analysis.
Proposed paragraph (g) specifies the methods to be used for
analysis of respirable crystalline silica samples, including details
regarding the specific analytical methods to be used and the
qualifications of the laboratories where the samples are analyzed.
Proposed paragraph (g)(1) would require mine operators to use
laboratories that are accredited to the International Organization for
Standardization (ISO) or International Electrotechnical Commission
(IEC) (ISO/IEC) 17025, ``General requirements for the competence of
testing and calibration laboratories'' with respect to respirable
crystalline silica analyses, where the accreditation has been issued by
a body that is compliant with ISO/IEC 17011 ``Conformity assessment--
Requirements for accreditation bodies accrediting conformity assessment
bodies.'' Accredited laboratories are held to internationally
recognized laboratory standards and must participate in quarterly
proficiency testing for all analyses within the scope of the
accreditation.
The ISO/IEC 17025 standard is a consensus standard developed by the
International Organization for Standardization and the International
Electrotechnical Commission (ISO/IEC) and approved by ASTM
International (formerly the American Society for Testing and
Materials). This standard establishes criteria by which laboratories
can demonstrate proficiency in conducting laboratory analysis through
the implementation of quality control measures. To demonstrate
competence, laboratories must implement a quality control program that
evaluates analytical uncertainty and provides estimates of sampling and
analytical error when reporting samples. The ISO/IEC 17011 standard
establishes criteria for organizations that accredit laboratories under
the ISO/IEC 17025 standard. For example, the American Industrial
Hygiene Association (AIHA) accredits laboratories for proficiency in
the analysis of respirable crystalline silica using criteria based on
the ISO 17025 and other criteria appropriate for the scope of the
accreditation.
Many MNM mine operators currently use third-party laboratories to
perform respirable crystalline silica sample analyses, and under the
proposed standard, MSHA anticipates that they would continue to use
third-party laboratories.
For most coal mine operators, using a third-party accredited
laboratory to
[[Page 44910]]
analyze respirable crystalline silica samples would be a new
requirement because respirable coal mine dust samples are currently
analyzed only by MSHA. Under the proposed standard, all mine operators
would have to use third-party laboratories accredited to ISO/IEC 17025
to have respirable dust samples analyzed for respirable crystalline
silica. By requiring all mines to use third-party laboratories,
proposed paragraph (g)(1) would ensure that sample analysis
requirements and MSHA enforcement efforts are consistent across all
mines.
Proposed paragraph (g)(2) would require mine operators to ensure
that laboratories evaluate all samples using analytical methods for
respirable crystalline silica that are specified by MSHA, NIOSH, or
OSHA. These are validated methods currently being cited by third party
accredited labs for measuring respirable crystalline silica in mine
dust matrices. MSHA and NIOSH have specific FTIR methods for analyzing
quartz in coal mine dust. The NIOSH 7603 method is based on the MSHA P-
7 method which was collaboratively tested and specifically addresses
the interference from kaolinite clay. All three methods, MSHA P-2,
NIOSH 7500, and OSHA ID-142 for analyzing respirable crystalline silica
using X-ray diffraction (XRD) have similar procedures for measuring
respirable crystalline silica and are capable of distinguishing between
the three silica polymorphs. Additional steps such as acid treatment
can be taken to remove respirable crystalline silica interferences from
other minerals that can be found in mine dust sample matrices.
Consistent with MSHA's current practices for the analysis of respirable
crystalline silica samples, analytical techniques used for samples from
MNM mines and coal mines would generally be different due to potential
sources of interference and cost considerations. Under the proposed
rule, as discussed below, MSHA expects that samples collected in MNM
mines would continue to be analyzed by X-ray diffraction (XRD) and
samples collected for coal mines would continue to be analyzed by
Fourier transform infrared spectroscopy (FTIR).
Coal mine samples are currently analyzed using the FTIR method
because it is cheaper, faster, and better suited for the coal mining
sector, where samples contain little or no minerals that could
interfere or confound respirable crystalline silica analysis results.
Current FTIR methods, however, cannot quantify quartz if either of the
other two forms of crystalline silica (cristobalite and tridymite) are
present in the sample. Unlike coal dust samples, MNM samples may have a
variety of minerals present, which could cause interference with
respirable crystalline silica measurements if FTIR were used. Thus, MNM
samples are currently analyzed by XRD because the XRD method can
distinguish and isolate respirable crystalline silica for measurement,
thereby avoiding interference or confounding of respirable crystalline
silica analysis results. The XRD method could be used for both MNM and
coal samples but using the XRD method is more time consuming and more
costly, with no additional benefit for coal mine sample analysis. For
this reason, MSHA does not expect the use of XRD on samples from coal
mines.
For MNM samples, the methods used for respirable crystalline silica
sample analysis using XRD include MSHA P-2, NIOSH 7500, and OSHA ID-
142. For coal samples, the methods used for respirable crystalline
silica sample analysis using FTIR include MSHA P-7, NIOSH 7602, and
NIOSH 7603. (OSHA does not currently have an established FTIR method
for analysis of respirable crystalline silica.)
g. Section 60.12 (h)--Sampling Records
Proposed paragraph (h) would establish requirements for sampling
records, including what mine operators would be required to do after
receiving the analytical reports from laboratories. For each sample
taken, this proposed paragraph would require mine operators to create a
record that includes the sample date, the sampled occupations, and the
reported concentrations of both respirable dust and respirable
crystalline silica. After making such a record, the mine operator would
be required to post the record, together with the laboratory report, on
the mine bulletin board and, if applicable, make the record and the
laboratory report available electronically, for the next 31 days upon
receipt.
When electronic means are available, mine operators would be
required to use those electronics means such as electronic bulletin
boards or newsletters, in addition to physically posting the sampling
record and laboratory report on the mine bulletin board. MSHA believes
that most mines have the ability to display this information
electronically. For any mines where electronic means are not available,
mine operators would only be required to physically post the sampling
record and laboratory report on the mine bulletin board. Also, as
required in proposed Sec. 60.16(b), the sampling records created under
this section may be requested at any time by, and must promptly be made
available to, miners, authorized representatives of miners, or an
authorized representative of the Secretary.
MSHA believes that the posted information including sampling
results and methodology and other relevant information would inform
miners of the sampled exposures and would encourage them to have
heightened awareness of potential health hazards that could impact not
only them but other miners. It would also provide them with knowledge
to take proactive actions to protect themselves and fellow miners
through better and safer work practices and more active participation
in health and safety programs. This is consistent with the Mine Act
which states that mine operators, with the assistance of miners, have
the responsibility to prevent the existence of unsafe and unhealthful
conditions and practices in mines. 30 U.S.C. 801(e). Making miners
aware that respirable crystalline silica exposures below the PEL may
still pose a health risk could encourage them to take steps to manage
their health risks.
6. Section 60.13--Corrective Actions
This proposed section includes several actions a mine operator
would be required to take to protect miners' health and safety when any
sampling result indicates that a miner's exposure to respirable
crystalline silica exceeds the proposed PEL. Proposed paragraph (a)(1)
would require the mine operator to make NIOSH-approved respirators
available to affected miners before the start of the next work shift.
Proposed paragraph (a)(2) would require mine operators to ensure that
affected miners wear respirators for the full shift or during the
period of overexposure to protect miners until miner exposures are at
or below the PEL.
Proposed paragraph (a)(3) would require operators to take immediate
corrective actions to lower the concentration of respirable crystalline
silica to levels at or below the PEL. Some examples of corrective
actions include increasing air ventilation and/or water flow rates,
adding more water sprays, and improving maintenance of the existing
engineering controls.
Once corrective actions have been taken, proposed paragraph
(a)(4)(i) would require the operator to conduct sampling in accordance
with Sec. 60.12(c) to determine if the corrective actions have been
successful in lowering exposures to at or below the PEL. If sampling
indicates that the corrective actions did not reduce miner exposures to
at or below the PEL, proposed
[[Page 44911]]
paragraph (a)(4)(ii) would require the operator to implement additional
or new corrective actions until sampling indicates miner exposures are
at or below the PEL.
Proposed Sec. 60.13(b) would require the mine operator to make a
record of corrective actions required under proposed paragraph (a) of
this section and the dates of those actions. These records would help
the operator and MSHA identify whether existing controls are effective,
or whether maintenance or additional control measures are needed.
7. Section 60.14--Respiratory Protection
This proposed provision addresses the use of respiratory protection
equipment. As noted earlier, the use of respiratory protection
equipment, including powered air-purifying respirators (PAPRs), would
not be permitted as a control to achieve compliance with the proposed
PEL because engineering controls are more effective than respirators in
protecting miners. However, temporary non-routine use of respirators
would be allowed under limited circumstances.
Proposed paragraph (a) would require the mine operator to provide
respirators to miners as a temporary measure in accordance with
proposed paragraph (c) of this section, when miners are working in
concentrations of respirable crystalline silica above the PEL under
specific, limited circumstances. Proposed paragraph (a)(1) would
require the temporary use of respirators when miners' exposures exceed
the proposed PEL during the development and implementation of
engineering controls.
Proposed paragraph (a)(2) would require the use of respirators for
temporary, nonroutine work to prevent miners' exposures at levels above
the proposed PEL. Examples include when a miner is mixing cement to
build a stopping to separate a main intake from return airways or is
engaged in an unplanned entry into an atmosphere with excessive
respirable crystalline silica concentrations to perform a repair or
investigation that must occur before feasible engineering or
administrative controls can be implemented.
The proposal is consistent with NIOSH's recommendation in the 1995
Criteria Document (NIOSH 1995a) and is similar to the existing
standards for MNM and coal mines. NIOSH (1995a) recommended the use of
respirators as an interim measure when engineering controls and work
practices are not effective in maintaining worker exposures for
respirable crystalline silica at or below the proposed PEL.
MSHA's existing MNM standards in parts 56 and 57 permit mine
operators to allow miners to work for reasonable periods of time
protected by appropriate respiratory protection in locations where
concentrations of contaminants (including respirable crystalline
silica) exceed permissible levels and where feasible engineering
control measures have not been developed or where necessary by the
nature of the work involved (e.g., occasional entry into hazardous
atmospheres to perform maintenance or investigation). MSHA's existing
standards for respirable coal mine dust require the mine operator to
make respiratory protection equipment available while the operator
evaluates and implements engineering control measures when a valid
sample meets or exceeds the applicable standard during operator
exposure monitoring. (30 CFR 70.208(e)(1); 30 CFR 71.206(h)(1); 30 CFR
72.700-72.701; 30 CFR 90.207(c)(1)).
Proposed paragraph (b) addresses situations where miners are not
able to wear a respirator while working. Proposed paragraph (b) would
require the mine operator, upon written notification by a PLHCP, to
transfer an affected miner who is unable to wear a respirator to work
in another area of the same mine, or to another occupation at the same
mine, where respiratory protection is not required.
The operator must ensure that the occupation and the area of the
mine to which the miner is temporarily transferred do not expose the
miner to respirable crystalline silica above the proposed PEL. Proposed
paragraph (b)(1) would require the mine operator to continue to
compensate the affected miner at no less than the regular rate of pay
in the occupation held by that miner immediately prior to the transfer.
Under proposed paragraph (b)(2), the miner may be transferred back to
the initial work area or occupation when the temporary, non-routine use
of respirators is no longer required.
MSHA believes that this proposed provision is consistent with the
mandate in the Mine Act to provide the maximum health protection for
miners. Also, any effect on miners by this provision should be
temporary since the concentration of respirable crystalline silica to
which the miner would be exposed must be controlled through feasible
engineering and administrative controls on a long-term basis.
Proposed paragraph (c) includes the respiratory protection
requirements that an operator must address when providing respirators
to miners. Proposed paragraph (c)(1), like the existing standards in
parts 56, 57, and 72, would require mine operators to provide
respiratory protection equipment approved by NIOSH under 42 CFR part
84. Whenever respirators are used by miners, proposed paragraph (c)(1)
would require the mine operator to provide miners with NIOSH-approved
atmosphere-supplying respirators or air-purifying respirators.
Atmosphere-supplying respirators provide clean breathing air from a
separate source (e.g., a self-contained air tank), whereas air-
purifying respirators use filters, cartridges, or canisters to remove
contaminants from the air.
In mines, commonly used types of air-purifying respirators include
elastomeric respirators, filtering facepiece respirators (FFRs), and
PAPRs. Elastomeric respirators, such as half-facepiece or full-
facepiece tight-fitting respirators, are made of synthetic or natural
rubber material and can be cleaned, disinfected, stored, and repeatedly
re-used. FFRs (i.e., dust masks), designed to cover areas of the
wearer's face from the bridge of the nose to the chin, are disposable
respirators composed of a weave of electrostatically charged synthetic
filter fibers and an elastic head strap. PAPRs utilize a blower to move
ambient air through an air-purifying filter that removes particulates
and delivers clean air to the wearer. When air-purifying respirators
(elastomeric respirators, FFRs, and PAPRs) are used, under proposed
paragraph (c)(1), the mine operator would be required to select only
high-efficiency NIOSH-certified particulate protection (i.e., 100
series or HE filters) for respirable crystalline silica protection. A
100 series and high efficiency filter means that the filter must
demonstrate a minimum efficiency level of 99.97 percent (i.e., the
filter is at least 99.97 percent efficient in removing particles of 0.3
[micro]m aerodynamic mass median diameter).
Under proposed paragraphs (c)(1)(i) through (c)(1)(ii), air-
purifying respirators would be required to be equipped with one of the
following three particulate protection types: (1) particulate
protection defined as a 100 series under 42 CFR part 84; or (2)
particulate protection defined as High Efficiency ``HE'' under 42 CFR
part 84. MSHA believes that air-purifying respirators with the highest
efficiency NIOSH classifications for particulate protection are most
suitable in protecting miners from occupational exposure to a
carcinogen such as respirable crystalline silica.
Proposed paragraph (c)(2) would require mine operators to follow
the provisions, as applicable, of ASTM F3387-19, ``Standard Practice
for
[[Page 44912]]
Respiratory Protection,'' when respiratory protection equipment is
needed. Under the proposal, MSHA would require that the respiratory
program would be in writing and would include the following minimally
acceptable program elements: program administration; standard operating
procedures; medical evaluations; respirator selection; training; fit
testing; and maintenance, inspection, and storage. Beyond the minimally
acceptable program elements, mine operators would be allowed to comply
with the provisions of the 2019 ASTM standard that they deem
applicable. The need for temporary non-routine use of respirators may
vary, given the variability of mining processes, activities, and
commodities that are mined. MSHA believes that flexibility afforded to
mine operators under this paragraph may lead mine operators to focus
more appropriately on those provisions that are relevant to their mine-
specific situations, allowing them to comply more efficiently and
effectively.
ASTM F3387-19 is a voluntary consensus standard published by ASTM
International and was approved in 2019. MSHA proposes to incorporate by
reference this consensus standard for two reasons.
First, adopting this voluntary consensus standard is consistent
with OMB Circular A-119, which encourages Federal agencies to
``minimize reliance on government-unique standards where an existing
standard would meet the Federal government's objective.'' ASTM F3387-19
comprehensively addresses all aspects of establishing, implementing,
and evaluating respiratory protection programs, and describes
respiratory protection program elements which include: program
administration; standard operating procedures; medical evaluation;
respirator selection; training; fit testing; and respirator
maintenance, inspection, and storage.
Second, ASTM F3387-19 reflects current respirator technology and an
up-to-date understanding of effective respiratory protection. For
example, ASTM F3387-19 provides detailed information on respirator
selection that are based on NIOSH's long-standing experience of testing
and approving respirators for occupational use and OSHA's research and
rulemaking on respiratory protection.
More detailed discussion on ASTM F3387-19 is provided later in C.
Updating MSHA Respiratory Protection Standards: Proposed Incorporation
of ASTM F3387-19 by Reference.
8. Section 60.15--Medical Surveillance for Metal and Nonmetal Miners
This proposed provision would require MNM mine operators to provide
mandatory medical examinations to miners who begin in the mining
industry after the effective date of the rule and offer voluntary
periodic examinations to all other miners. These medical examinations
would be provided by a PLHCP or specialist. The proposed requirements
in this section are consistent with the Mine Act's mandate to provide
maximum health protection for miners and provide MNM miners with
information needed for early detection of respirable crystalline
silica-related disease, resulting in prevention of disabling disease.
The proposed requirements for MNM mine operators are also generally
consistent with existing medical surveillance requirements for coal
mine operators under 30 CFR 72.100 although the requirements differ in
some respects. For example, the proposed provision specifies that
medical examinations must be provided by a PLHCP or specialist, while
the existing medical surveillance requirements for coal miners in Sec.
72.100 coordinate with the surveillance system managed by NIOSH's Coal
Workers' Health Surveillance Program (CWHSP) which works with coal mine
operators under NIOSH regulations to provide medical surveillance.
Proposed paragraph 60.15(a) would require that each MNM mine operator
make medical examinations available to each MNM miner, at no cost to
the miner, regardless of whether miners are reasonably expected to be
exposed to any level of respirable crystalline silica. This proposed
requirement is consistent with section 101(a)(7) of the Mine Act.
Proposed paragraph 60.15(a) would also require medical examinations
to be performed by a PLHCP or specialist. A PLHCP is an individual
whose legally permitted scope of practice (i.e., license, registration,
or certification) allows that individual to independently provide or be
delegated the responsibility to provide some or all of the required
health services (i.e., chest X-rays, spirometry, symptom assessment,
and occupational history). A specialist, as defined in proposed Sec.
60.2, refers to an American Board-certified specialist in pulmonary
disease or occupational medicine. The Agency believes it is appropriate
to allow not only a physician, but also any State-licensed health care
professional, to perform the required medical examinations. This would
provide operators with the flexibility needed to use professionals with
necessary medical skills and minimize cost and compliance burdens.
Proposed paragraph (a)(1) requires periodic examinations to be
offered to all MNM miners at the frequencies specified in this section.
Proposed paragraph (a)(2) specifies the types of medical examinations
and is consistent with the existing requirements for coal mine
operators under existing Sec. 72.100.
Proposed paragraphs (a)(2)(i) and (ii) would require MNM operators
to provide each miner with a medical examination that includes a review
of the miner's medical and work history and a physical examination. The
medical and work history would cover a miner's present and past work
exposures, illnesses, and any symptoms indicating respirable
crystalline silica-related diseases and compromised lung function. The
medical and work history should focus not only on any history of
tuberculosis, smoking, or exposure to respirable crystalline silica,
but also on any diagnoses and symptoms of respiratory system
dysfunction, including shortness of breath, coughing, or wheezing. The
physical examination under (a)(2)(ii) would be focused on the
respiratory tract. For the reasons stated above, these proposed
requirements differ from the existing requirements for coal miners. The
existing medical surveillance requirements for coal miners in 42 CFR 37
specify standardized data collection elements for occupational
histories and respiratory symptom assessment while proposed paragraphs
(a)(2)(i) and (ii) specify a respiratory-focused history and physical
examination by a clinician.
Under proposed paragraph (a)(2)(iii), MSHA would require all
medical examinations to include a chest X-ray. The required chest X-ray
is a posterior/anterior view no less than 14 x 17 inches and no more
than 16 x 17 inches at full inspiration, recorded on either film or
digital radiography systems. The chest X-ray must be classified by a
NIOSH-certified B Reader, in accordance with the Guidelines for the Use
of the International Labour Office (ILO) International Classification
of Radiographs of Pneumoconioses. The ILO recently made additional
standard digital radiographic images available and has published
guidelines on the classification of digital radiographic images (ILO
2022). This is a standard practice in pneumoconiosis surveillance
programs and can potentially detect other respirable crystalline
silica-related conditions, including lung cancer (Industrial Minerals
Association-North America and Mine Safety and Health Administration,
2008). The test would provide data that can be used to assess
[[Page 44913]]
for progression of silicosis and for other respirable crystalline
silica-related conditions in MNM miners.
MSHA preliminarily concludes that the number of B readers in the
U.S. is adequate to classify chest X-rays conducted as part of the
respirable crystalline silica rule (OSHA 2016a, 81 FR 16286, 16821). As
discussed in OSHA's 2016 final silica rule, the number of B Readers is
driven by supply and demand created by a free market, and many
physicians choose to become B readers based on demands for such
services (OSHA 2016a, 81 FR 16286, 16822). NIOSH is also able to train
enough B readers to handle any potential increase in demand, providing
several pathways for physicians to become B readers, such as free self-
study materials by mail or download and free B reader examinations
(OSHA 2016a, 81 FR 16286, 16822). In addition, courses and examinations
for certification are periodically offered for a fee through the
American College of Radiology (OSHA 2016a, 81 FR 16286, 16822). Even if
B readers are scarce in certain geographical locations, digital X-rays
can be easily transmitted electronically to B readers located anywhere
in the U.S. (OSHA 2016a, 81 FR 16286, 16822).
Under proposed paragraph (a)(2)(iv), MSHA would require that
pulmonary function testing (including spirometry) be part of every
medical examination. The pulmonary function test must be administered
by a spirometry technician with a current certificate from a NIOSH-
approved Spirometry Training Sponsorship. The purpose of spirometry is
to measure baseline lung function followed by periodic tests to detect
early impairment patterns, such as obstruction of air flow and
restriction caused by underlying respiratory disease. This measurement
can provide critical information for the primary, secondary, and
tertiary prevention of workplace-related lung diseases, including
respirable crystalline silica-related diseases. The use of spirometry
is consistent with recommendations of the Dust Advisory Committee (U.S.
DOL, 1996) and the NIOSH Criteria Document (1974). Indeed, NIOSH
(2014a) notes that properly conducted spirometry should be part of a
comprehensive workplace respiratory health program. Spirometry and
chest X-rays are complementary examinations for detecting adverse
health effects from respirable crystalline silica exposures.
In order to maintain a certificate from a NIOSH-approved course,
technicians must complete an initial training and then refresher
training every five years (OSHA 2016a, 81 FR 16286, 16825). As
discussed in OSHA's 2016 silica final rule, course sponsors are located
throughout the U.S. and some sponsors will travel to a requested site
to teach a course (OSHA 2016a, 81 FR 16286, 16825). One NIOSH-approved
sponsor offers instructor-led live virtual initial training. Several
live virtual and web-based refresher training options are also
available. Because the required training is not too frequent and course
sponsors appear to be widely available throughout the U.S., MSHA
preliminarily concludes that the requirement that technicians maintain
a certificate from a NIOSH-approved course will not impose substantial
burdens on providers of spirometry testing.
MSHA believes that the proposed medical examinations consisting of
a medical and work history, a physical examination, a chest X-ray, and
a spirometry test would help medical professionals identify early
symptoms of respirable crystalline silica-related diseases, assist MNM
miners in protecting their health, and lower the risk that MNM miners
become materially impaired due to occupational exposure to respirable
crystalline silica.
Under proposed paragraph (b), MSHA would require MNM mine operators
to provide every miner employed at MNM mines with the opportunity to
have periodic medical examinations. Miner participation would be
voluntary, as in the case of the examination requirement for coal
miners in 30 CFR 72.100(b). Starting on the proposed effective date,
mine operators must provide the opportunity for an examination to MNM
miners no later than 5 years after the date of their last medical
surveillance examination, and in addition, during a 6-month period that
begins no less than 3.5 years and not more than 4.5 years from the end
of the last 6-month period for medical examinations. Periodic
examinations would allow for comparisons with a miner's prior
examination results, help detect respirable crystalline silica-related
disease including silicosis, and address further progression of
existing respiratory disease. If a miner has a positive chest X-ray
(ILO category of 1/0+), it is important to intervene as promptly as
possible for maximum health protection. In addition, an interval of 5
years or less between each miner's periodic examinations can ensure
detection of declines in a miner's lung function due to potential
occupational exposure. MSHA believes that the proposed schedule, which
is consistent with the periodic examination for coal miners required
under Sec. 72.100(b), would provide MNM mine operators with
flexibility in offering examinations to miners.
Proposed paragraph (c) would require MNM mine operators to provide
a mandatory initial medical examination for each MNM miner who is new
to the mining industry. Consequently, if a miner had previous mining
experience (such as working in a coal mine) and subsequently came to
work in an MNM mine, MSHA would not require that the MNM mine operator
provide the miner with an initial examination after the miner begins
employment. Mandatory initial examinations would be conducted when
miners are first hired in the mining industry and would provide an
individual baseline of each miner's health status. This initial
examination would assist in the early detection of respirable
crystalline silica-related illnesses and conditions that may make the
miner more susceptible to the toxic effects of respirable crystalline
silica. The individual baseline would also be valuable in assessing any
future health changes in each miner. Overall, the initial examination
results would enable miners to respond appropriately to information
about their health status.
Proposed paragraph (c)(1) would require that the mandatory initial
medical examination occur no later than 30 days after a miner new to
the industry begins employment. Proposed paragraphs (c)(2) and (3)
would require MNM mine operators to provide mandatory follow-up
examinations to new miners who were eligible for an initial mandatory
medical examination under proposed paragraph (c). MSHA believes follow-
up examinations are important for assessments of any changes in a new
miner's health status and for future diagnoses.
Under proposed paragraph (c)(2), MSHA would require that the mine
operator provide a mandatory follow-up examination to the miner no
later than 3 years after the miner's initial medical examination. Under
proposed paragraph (c)(3), if a miner's 3-year follow-up examination
shows evidence of a respirable crystalline silica-related disease or
decreased lung function, the operator would be required to provide the
miner with another mandatory follow-up examination with a specialist,
as defined in proposed Sec. 60.2, within 2 years. This proposed
requirement is intended to ensure that any miner whose follow-up
medical examination shows evidence of silicosis or evidence of
decreased lung function, as determined by the PLHCP or specialist, is
seen by a professional with expertise in respiratory disease. This
would ensure that miners would benefit from not only expert medical
judgment but
[[Page 44914]]
also counseling regarding work practices and personal habits that could
affect the miners' health. For the reasons stated above, this proposed
requirement differs from the existing requirements for coal miners,
which provides for follow up surveillance testing but does not include
interaction with a PLHCP or specialist.
Proposed paragraph (d) would require that the results of any
medical examination performed under this section be kept confidential
and provided only to the miner. The miner is also entitled to request
that the medical examination results be provided to the miner's
designated physician. Based on MSHA's experience with coal miners'
medical surveillance, the Agency believes that confidentiality
regarding medical conditions is essential and that it encourages miners
to take advantage of the opportunity to detect early adverse health
effects due to respirable crystalline silica. See 79 FR 24813, at
24928, May 1, 2014.
Under proposed paragraph (e), MNM mine operators would be required
to obtain a written medical opinion from a PLHCP or specialist within
30 days of the medical examination that includes only the date of a
miner's medical examination, a statement that the examination has met
the requirements of this section, and any recommended limitations on
the miner's use of respirators. This would allow the mine operator to
verify the examination has occurred and would provide the mine operator
with information on miners' ability to use respirators. Proposed
paragraph (f) would require the mine operator to maintain a record of
the written medical opinions obtained from the PLHCP or specialist
under proposed paragraph (e).
9. Section 60.16--Recordkeeping Requirements.
Section 60.16 lists all the proposed recordkeeping requirements
under this proposed part. To ensure that mine operators track actual or
potential exposures, risks, and controls and keep miners, miners'
representatives, and other stakeholders informed about them, the
proposed part 60 establishes five recordkeeping requirements.
Discussion of these requirements follow and are summarized in table 1
to paragraph (a) in Sec. 60.16 of the rule text.
First, this section would require that, once mine operators
complete the sampling or semi-annual evaluations required under
proposed Sec. 60.12, the operators retain the associated exposure
monitoring records for at least 2 years. Examples of exposure
monitoring records include the date of sampling or evaluation, names
and occupations of miners who were sampled, description of sampling or
evaluation method, and laboratory reports of sampling analysis. The 2-
year period would give mine operators sufficient exposure monitoring
data to evaluate the effectiveness of their engineering and
administrative controls over different mining and weather conditions.
Second, mine operators would also be required to retain records of
corrective actions made under proposed Sec. 60.13(b) for at least 2
years from the date when each corrective action was taken. This
proposed requirement is similar to the recordkeeping requirements
related to other corrective-action requirements under parts 56 and 57
(for MNM mines) and parts 70, 71, and 90 (for coal mines).
Third, this proposed section would require mine operators to
maintain any written determination records that they receive from a
PLHCP or specialist. When a PLHCP or specialist certifies in writing
that a miner cannot wear a respirator, including a PAPR, that miner
must be temporarily transferred to a different work area or task where
respiratory protection is not required (or needed). In such cases, mine
operators would be required to retain the written determinations by a
PLHCP or specialist for the duration of the miner's employment plus 6
months.
Fourth, under this section, MNM mine operators would be required to
maintain written medical opinion records that they obtain from a PLHCP
or specialist who conducts medical examinations of their miners under
proposed Sec. 60.15. This proposed recordkeeping requirement would
apply only to MNM mine operators. Under proposed Sec. 60.15, after the
examination has taken place, the MNM mine operator would receive from
the PLHCP or specialist a written medical opinion that contains the
date of the medical examination, a statement that the examination has
met the requirements under this proposed rule, and any recommended
limitations on the miner's use of respirators. Upon receipt, the mine
operator would retain the medical opinion for the duration of the
miner's employment plus 6 months.
Proposed paragraph (b) would ensure that all the listed records
would be made available promptly upon request to miners, authorized
representatives of miner(s), and authorized representatives of the
Secretary of Labor.
10. Section 60.17--Severability
The severability clause under proposed Sec. 60.17 serves two
purposes. First, it expresses MSHA's intent that if any section or
provision of the Lowering Miners' Exposure to Respirable Crystalline
Silica and Improving Respiratory Protection rule--including its
conforming amendments in sections of 30 CFR parts 56, 57, 70, 71, 72,
75, and 90 that address respirable crystalline silica or respiratory
protection--is held invalid or unenforceable or is stayed or enjoined
by any court of competent jurisdiction, the remaining sections or
provisions should remain effective and operative. Second, the
severability clause expresses MSHA's judgment, based on its technical
and scientific expertise, that each individual section and provision of
the rule can remain effective and operative if some sections or
provisions are invalidated, stayed, or enjoined. Accordingly, MSHA's
inclusion of this severability clause addresses the twin concerns of
Federal courts when determining the propriety of severability:
identifying agency intent and clarifying that any severance will not
undercut the structure or function of the rule more broadly. Am. Fuel &
Petrochem. Mfrrs. v. Env't Prot. Agency, 3 F.4th 373, 384 (D.C. Cir.
2021) (``Severability `depends on the issuing agency's intent,' and
severance `is improper if there is substantial doubt that the agency
would have adopted the severed portion on its own' '') (quoting North
Carolina v. FERC, 730 F.2d 790, 796 (D.C. Cir. 1984) and New Jersey v.
Env't Prot. Agency, 517 F.3d 574, 584 (D.C. Cir. 2008)).
Under the principle of severability, a reviewing court will
generally presume that an offending provision of a regulation is
severable from the remainder of the regulation, so long as that outcome
appears consistent with the issuing agency's intent, and the remainder
of the regulation can function independently without the offending
provision. See K Mart Corp. v. Cartier, Inc., 486 U.S. 281, 294 (1988)
(invalidating and severing subsection of a regulation where it would
not impair the function of the statute as a whole and there was no
indication the regulation would not have been passed but for inclusion
of the invalidated subsection). Consequently, in the event that a court
of competent jurisdiction stays, enjoins, or invalidates any provision,
section, or application of this rule, the remainder of the rule should
be allowed to take effect.
B. Conforming Amendments
The proposed rule would require conforming amendments in 30 CFR
parts 56, 57, 70, 71, 72, 75, and 90 based on the proposed new part 60.
[[Page 44915]]
1. Part 56--Safety and Health Standards--Surface Metal and Nonmetal
Mines
a. Section 56.5001--Exposure Limits for Airborne Contaminants
For respirable crystalline silica, proposed part 60 would establish
exposure limits and other related requirements for all mines. Existing
paragraph (a) of Sec. 56.5001 governs exposure limits for airborne
contaminants, except asbestos, for surface MNM mines. MSHA is proposing
to amend paragraph (a) of Sec. 56.5001 to add respirable crystalline
silica as an exception. The amended paragraph (a) of Sec. 56.5001
would govern exposure limits for airborne contaminants other than
respirable crystalline silica and asbestos for surface MNM mines.
2. Part 57--Safety and Health Standards--Underground Metal and Nonmetal
Mines
a. Section 57.5001--Exposure Limits for Airborne Contaminants
Existing paragraph (a) of Sec. 57.5001 governs exposure limits for
airborne contaminants, except asbestos, for underground MNM mines.
Similar to the proposed changes discussed above for Sec. 56.5001, MSHA
is proposing to amend paragraph (a) of Sec. 57.5001 to add respirable
crystalline silica as an exception. The amended paragraph (a) of Sec.
57.5001 would govern exposure limits for airborne contaminants other
than respirable crystalline silica and asbestos for underground MNM
mines.
3. Part 70--Mandatory Health Standards--Underground Coal Mines
a. Section 70.2--Definitions.
MSHA proposes to remove the Quartz definition in Sec. 70.2. With
the adoption of an independent respirable crystalline silica standard
in proposed part 60, the Agency is proposing to remove RCMD when quartz
is present in Sec. 70.101 and the term quartz would no longer appear
in part 70.
b. Section 70.101--Respirable Dust Standard When Quartz Is Present
MSHA is proposing to remove the entire section and reserve the
section number. The RCMD when quartz is present in Sec. 70.101 would
no longer be needed because MSHA is proposing an independent respirable
crystalline silica standard in proposed part 60.
MSHA's proposed independent standard for respirable crystalline
silica would result in miners' exposure to respirable crystalline
silica no longer being controlled indirectly by reducing respirable
dust. NIOSH, the Secretary of Labor's Advisory Committee on the
Elimination of Pneumoconiosis Among Coal Mine Workers (Dust Advisory
Committee), and the Department of Labor's Inspector General \35\ have
each recommended the adoption of an independent standard for respirable
quartz exposure in coal mines. NIOSH evaluated the effectiveness of the
existing standard and found the approach of controlling miners'
exposures to respirable crystalline silica indirectly through the
control of respirable dust did not protect miners from excessive
exposure to respirable quartz in all cases (Joy GJ 2012). The study
concluded that a separate respirable quartz standard, as described by
the 1995 NIOSH Criteria Document, could reduce miners' risk of
overexposures to respirable quartz and, by extension, their risk of
developing silicosis. The adoption of a separate standard would hold
operators accountable, at risk of a citation and monetary penalty, when
overexposures of the respirable crystalline silica PEL occur and
enhance its sampling program to increase the frequency of operator
sampling.
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\35\ Office of Inspector General Audit 05-21-001-06-001, MSHA
Needs to Improve Efforts to Protect Coal Miners from Respirable
Crystalline Silica (Nov. 12, 2020). The Inspector General
recommended that MSHA:
1. Adopt a lower legal exposure limit for silica in coal mines
based on recent scientific evidence.
2. Establish a separate standard for silica that allows MSHA to
issue a citation and monetary penalty when violations of its silica
exposure limit occur.
3. Enhance its sampling program to increase the frequency of
inspector samples where needed (e.g., by implementing a risk-based
approach).
---------------------------------------------------------------------------
c. Section 70.205--Approved Sampling Devices; Operation; Air Flowrate
MSHA is proposing to amend paragraph (c) of Sec. 70.205 to remove
the reference to the reduced RCMD standard. References to the RCMD
exposure limit specified in Sec. 70.100 would replace references to
the applicable standard. The rest of the section would remain
unchanged.
d. Section 70.206--Bimonthly Sampling; Mechanized Mining Units
MSHA is proposing to amend subpart C, Sampling Procedures, by
removing Sec. 70.206 and reserving the section number. Section 70.206
included requirements for bimonthly sampling of mechanized mining units
which were in effect until January 31, 2016, and are no longer needed.
e. Section 70.207--Bimonthly Sampling; Designated Areas
MSHA is proposing to amend subpart C, Sampling Procedures, by
removing Sec. 70.207 and reserving the section number. Section 70.207
included requirements for bimonthly sampling of designated areas that
were in effect until January 31, 2016, and are no longer needed.
f. Section 70.208--Quarterly Sampling; Mechanized Mining Units
MSHA is proposing to amend Sec. 70.208 to remove references to a
reduced RCMD standard. Paragraph (c) in Sec. 70.208 would be removed
and the paragraph designation reserved. References to the respirable
dust standard specified in Sec. 70.100 would replace references to the
applicable standard throughout the section.
A new table 1 to Sec. 70.208 would be added. The table contains
the Excessive Concentration Values (ECV) for the section based on a
single sample, 3 samples, or the average of 5 or 15 full-shift coal
mine dust personal sampler unit (CMDPSU) or continuous personal dust
monitor (CPDM) concentration measurements. This table contains the
remaining ECV after the removal of the reduced standard in Sec.
70.101. It was generated from data contained in existing Tables 70-1
and 70-2 to subpart C of part 70. Conforming changes are made to
paragraphs (e) and (f)(1) and (2) to update the name of the table to
table 1 to Sec. 70.208.
g. Section 70.209--Quarterly Sampling; Designated Areas
Similar to the proposed changes discussed above for Sec. 70.208,
MSHA is proposing to amend Sec. 70.209 to remove references to a
reduced RCMD standard. Paragraph (b) in Sec. 70.209 would be removed
and the paragraph designation reserved. References to the RCMD exposure
limit specified in Sec. 70.100 would replace references to the
applicable standard.
A new table 1 to Sec. 70.209 would be added. The table contains
the ECVs for the section based on a single sample, 2 or more samples,
or the average of 5 or 15 full-shift CMDPSU/CPDM concentration
measurements. This table contains the remaining ECV after the removal
of the reduced RCMD standard in Sec. 70.101. It was generated from
data contained in existing Tables 70-1 and 70-2 to subpart C of part
70. Conforming changes are made to paragraphs (c) and (d)(1) and (2) to
update the name of the table to table 1 to Sec. 70.209.
[[Page 44916]]
h. Subpart C--Table 70-1 and Table 70-2
MSHA is proposing to amend subpart C, Sampling Procedures, by
removing Table 70-1 Excessive Concentration Values (ECV) Based on
Single, Full-Shift CMDPSU/CPDM Concentration Measurements and Table 70-
2 Excessive Concentration Values (ECV) Based on the Average of 5 or 15
Full-Shift CMDPSU/CPDM Concentration Measurements because Sec. 70.101
would be removed. These tables would be replaced with new tables added
to Sec. Sec. 70.208 and 70.209.
4. Part 71--Mandatory Health Standards--Surface Coal Mines and Surface
Work Areas of Underground Coal Mines
a. Section 71.2--Definitions
As discussed in the analysis of conforming amendments for Sec.
70.2, MSHA also proposes to remove the Quartz definition in Sec. 71.2
because the Agency is proposing to remove the respirable dust standard
when quartz is present in Sec. 71.101. The term quartz would no longer
appear in part 71.
b. Section 71.101--Respirable Dust Standard When Quartz Is Present
MSHA is proposing to remove the entire section of Sec. 71.101 and
reserve the section number. Similar to the proposed conforming
amendments for Sec. 70.101, the respirable coal mine dust standard
when quartz is present in Sec. 71.101 would no longer be needed
because MSHA is proposing an independent respirable crystalline silica
standard in part 60.
MSHA's proposal to adopt an independent standard for respirable
crystalline silica would replace the existing method of indirectly
controlling miners' exposure to silica by reducing respirable coal
dust. As stated previously, NIOSH evaluated the effectiveness of the
existing standard and found the existing approach of controlling
miners' exposures to respirable crystalline silica indirectly through
the control of respirable dust did not protect miners from excessive
exposure to respirable crystalline silica in all cases. The study
concluded that a separate respirable crystalline silica standard, as
described by the 1995 NIOSH Criteria Document, could reduce miners'
risk of overexposures to respirable crystalline silica and, by
extension, their risk of developing silicosis. The adoption of a
separate standard would allow MSHA to issue a citation and monetary
penalty when overexposures of the respirable crystalline silica PEL
occur and enhance its sampling program to increase the frequency of
inspector sampling.
c. Section 71.205--Approved Sampling Devices; Operation; Air Flowrate
MSHA is proposing to amend paragraph (c) of Sec. 71.205 to remove
the reference to the reduced RCMD standard. References to the
respirable dust standard specified in Sec. 71.100 would replace the
reference to the applicable standard. The rest of the section would
remain unchanged.
d. Section 71.206--Quarterly Sampling; Designated Work Positions
Similar to the analysis of conforming amendments for Sec. Sec.
70.208 and 70.209, MSHA is proposing to amend Sec. 71.206 to remove
references to the reduced RCMD standard. Paragraph (b) in Sec. 71.206
would be removed and the paragraph designation reserved. Other
conforming changes for Sec. 71.206 would remove references to the
applicable standard and replace them, where needed, with references to
the respirable dust standard specified in Sec. 71.100 throughout the
section.
MSHA is also proposing to amend paragraph (l) by removing Table 71-
1 Excessive Concentration Values (ECV) Based on Single, Full-Shift
CMDPSU/CPDM Concentration Measurements and Table 71-2 Excessive
Concentration Values (ECV) Based on the Average of 5 Full-Shift CMDPSU/
CPDM Concentration Measurements since reference to a reduced RCMD
standard in Sec. 71.101 would be removed. They would be replaced with
a new table added to Sec. 71.206.
Existing paragraph (m) would be modified by removing the language,
``in effect at the time the sample is taken, or a concentration of
respirable dust exceeding 50 percent of the standard established in
accordance with Sec. 71.101,'' because the reduced standard in Sec.
71.101 would be removed, as discussed above, which removes the
reference to the reduced standard and replaces it with a reference to
the respirable dust standard specified in Sec. 71.100.
A new table 1 to Sec. 71.206 would be added. This table contains
the ECV for the section based on a single sample, two or more samples,
or the average of five full-shift CMDPSU/CPDM concentration
measurements. This table contains the remaining ECV after the removal
of the reduced standard in Sec. 71.101. It was generated from data
contained in existing Tables 71-1 and 71-2 to subpart C of part 71.
Conforming changes are made to paragraphs (h) and (i)(1) and (2) to
update the name of the table to table 1 to Sec. 71.206.
e. Section 71.300--Respirable Dust Control Plan; Filing Requirements
MSHA is proposing to amend Sec. 71.300 to remove references to the
reduced RCMD standard. The respirable dust standard specified in Sec.
71.100 would replace references to the applicable standard. The rest of
the section would remain unchanged.
f. Section 71.301--Respirable Dust Control Plan; Approval by District
Manager and Posting
MSHA is proposing to amend Sec. 71.301 to remove references to the
reduced RCMD standard. The respirable dust standard specified in Sec.
71.100 would replace references to the applicable standard. The rest of
the section would remain unchanged.
5. Part 72--Health Standards for Coal Mines
a. Section 72.800--Single, Full-Shift Measurement of Respirable Coal
Mine Dust
MSHA is proposing to amend Sec. 72.800 in subpart E,
Miscellaneous, and remove references to the reduced RCMD standard. The
proposed section would also replace references to Tables 70-1, 71-1,
and 90-1 with references to tables in Sec. Sec. 70.208, 70.209,
71.206, and 90.207.
6. Part 75--Mandatory Safety Standards--Underground Coal Mines
a. Section 75.350(b)(3)(i) and (ii)--Belt Air Course Ventilation
MSHA is proposing to update Sec. 75.350 by revising paragraph
(b)(3)(i) and removing paragraphs (b)(3)(i)(A) and (B) and (b)(3)(ii).
Paragraph (b)(3)(i)(A) would be removed because its provision has
not been in effect since August 1, 2016. Paragraph (b)(3)(i)(B) would
be removed because the proposed revised language in paragraph (b)(3)(i)
would be simplified by stating that ``[t]he average concentration of
respirable dust in the belt air course, when used as a section intake
air course, shall be maintained at or below 0.5 mg/m\3\.'' This would
ensure that miners would be protected from coal dust overexposures,
including respirable crystalline silica overexposures, by maintaining
the RCMD PEL in the belt air course at 50 [micro]g/m\3\. Therefore,
paragraph (b)(3)(i)(B) which sets the PEL for belt course air at 0.5
mg/m\3\ would be redundant.
Existing paragraph (b)(3)(ii) would be removed since it refers to a
reduced RCMD standard under Sec. 70.101 that would also be removed.
Existing
[[Page 44917]]
paragraph (b)(3)(iii) would be redesignated to (b)(3)(ii).
7. Part 90--Mandatory Health Standards--Coal Miners Who Have Evidence
of the Development of Pneumoconiosis
a. Section 90.2--Definitions
Similar to the proposed changes for Sec. Sec. 70.2 and 71.2, MSHA
proposes to remove the Quartz definition in Sec. 90.2 because the
Agency proposes to remove the respirable dust standard when quartz is
present in Sec. 90.101. The term quartz would no longer appear in part
90.
In addition, MSHA is revising the definition of Part 90 miner to
remove references to the reduced RCMD standard. The respirable dust
standard specified in Sec. 90.100 would replace the reference to the
applicable standard. The definition of Part 90 miner would also be
updated to define Part 90 miners as miners who have exercised the
option to work in an area of a mine where the average concentration of
respirable dust in the mine atmosphere during each shift to which that
miner is exposed is continuously maintained at or below the respirable
dust standard specified in Sec. 90.100.
b. Section 90.3--Part 90 Option; Notice of Eligibility; Exercise of
Option
MSHA is proposing to revise paragraph (a) in Sec. 90.3 to require
that miners diagnosed with pneumoconiosis must be afforded the option
to work in an area of a mine where the average concentration of
respirable dust is continuously maintained below the respirable dust
standard specified in Sec. 90.100 rather than at or below the
applicable standard. The rest of the section would remain unchanged.
c. Section 90.101--Respirable Dust Standard When Quartz Is Present
MSHA is proposing to remove the entire section and reserve the
section number. The respirable coal mine dust standard when quartz is
present in Sec. 90.101 would no longer be needed because MSHA is
proposing an independent respirable crystalline silica standard in
proposed part 60.
MSHA's proposal to adopt an independent standard for respirable
crystalline silica would replace the existing method of indirectly
controlling miners' exposure to respirable crystalline silica by
reducing respirable coal dust. As stated previously, NIOSH evaluated
the effectiveness of the existing standard and found the existing
approach of controlling miners' exposures to respirable crystalline
silica indirectly through the control of respirable dust did not
protect miners from excessive exposure to respirable quartz in all
cases. The study concluded that a separate respirable quartz standard,
as described by the 1995 NIOSH Criteria Document, could reduce miners'
risk of overexposures to respirable quartz and, by extension, their
risk of developing silicosis.
d. Section 90.102--Transfer; Notice
MSHA is proposing to amend Sec. 90.102 to remove references to the
reduced RCMD standard. The respirable dust standard specified in Sec.
90.100 would replace references to the applicable standard. The rest of
the section would remain unchanged.
e. Section 90.104--Waiver of Rights; Re-Exercise of Option
MSHA is proposing to amend Sec. 90.104 to remove references to the
reduced RCMD standard. The respirable dust standard specified in Sec.
90.100 would replace references to the applicable standard. The rest of
the section would remain unchanged.
f. Section 90.205--Approved Sampling Devices; Operation; Air Flowrate
MSHA is proposing to amend Sec. 90.205 to remove the reference to
the reduced RCMD standard. The respirable dust standard specified in
Sec. 90.100 would replace the reference to the applicable standard.
The rest of the section would remain unchanged.
g. Section 90.206--Exercise of Option or Transfer Sampling
MSHA is proposing to amend Sec. 90.206 to remove references to the
reduced RCMD standard. The respirable dust standard specified in Sec.
90.100 would replace references to the applicable standard. The rest of
the section would remain unchanged.
h. Section 90.207--Quarterly Sampling
Similar to the analysis of conforming amendments for Sec. Sec.
70.208, 70.209, and 71.206, MSHA is proposing to amend Sec. 90.207 to
remove references to the reduced RCMD standard. Paragraph (b) in Sec.
90.207 would be removed and the paragraph designation reserved. The
respirable dust standard specified in Sec. 90.100 would replace
references to the applicable standard. The rest of the section would
remain unchanged.
MSHA is proposing to amend paragraph (g) by removing the Table 90-1
Excessive Concentration Values (ECV) Based on Single, Full-Shift
CMDPSU/CPDM Concentration Measurements and Table 90-2 Excessive
Concentration Values (ECV) Based on the Average of 5 Full-Shift CMDPSU/
CPDM Concentration Measurements because Sec. 90.101 would be removed.
A new table 1 to Sec. 90.207 would be added to replace the tables
removed in paragraph (g). The table contains the ECV for the section
based on a single sample, two or more samples, or the average of 5
full-shift CMDPSU/CPDM concentration measurements. This table contains
the remaining ECV after the removal of the reduced standard in Sec.
90.101. It was generated from data contained in existing Tables 90-1
and 90-2 to subpart C of part 90. Conforming changes are made to
paragraphs (c) and (d)(1) and (2) to update the name of the table to
table 1 to Sec. 90.207.
i. Section 90.300--Respirable Dust Control Plan; Filing Requirements
MSHA is proposing to amend Sec. 90.300 to remove references to the
reduced RCMD standard. The respirable dust standard specified in Sec.
90.100 would replace references to the applicable standard. The rest of
the section would remain unchanged.
j. Section 90.301--Respirable Dust Control Plan; Approval by District
Manager; Copy to Part 90 Miner
MSHA is proposing to amend Sec. 90.301 to remove references to the
reduced RCMD standard. The respirable dust standard specified in Sec.
90.100 would replace references to the applicable standard. The rest of
the section would remain unchanged.
C. Updating MSHA Respiratory Protection Standards: Proposed
Incorporation of ASTM F3387-19 by Reference
MSHA is proposing to update the Agency's existing respiratory
protection standard to help safeguard the life and health of all miners
exposed to respirable airborne hazards at MNM and coal mines. The
proposed rule would incorporate by reference ASTM F3387-19, ``Standard
Practice for Respiratory Protection'' (ASTM F3387-19), as applicable,
in existing Sec. Sec. 56.5005, 57.5005, and 72.710, as well as in
proposed Sec. 60.14(c)(2). The ASTM F3387-19 standard includes
provisions for selection, fitting, use, and care of respirators used to
remove airborne contaminants from the air using filters, cartridges, or
canisters, as well as respirators that protect in oxygen-deficient or
immediately dangerous to life or health (IDLH) atmospheres. ASTM F3387-
19 is based on the most recent consensus standards recognized by
experts in government and professional associations on the selection,
use, and maintenance for
[[Page 44918]]
respiratory equipment. The ASTM Standard would replace American
National Standards Institute's ANSI Z88.2-1969, ``Practices for
Respiratory Protection'' (ANSI Z88.2-1969), which is incorporated in
the existing standards.
Incorporating this voluntary consensus standard complies with the
Federal mandate--as set forth in the National Technology Transfer and
Advancement Act of 1995 and OMB Circular A119--that agencies use
voluntary consensus standards in their regulatory activities unless
doing so would be legally impermissible or impractical. This standard
proposed for incorporation would also improve clarity because it is a
consensus standard developed by stakeholders.
Under existing standards, whenever respiratory protective equipment
is used, mine operators are required to have a respiratory protection
program that is consistent with the provisions of ANSI Z88.2-1969. At
the time of its publication, ANSI Z88.2-1969 reflected a consensus of
accepted practices for respiratory protection.
Respirator technology and knowledge on respiratory protection have
since advanced and as a result, changes in respiratory protection
standards have occurred. For example, in 2006, OSHA revised its
respiratory protection standard to add definitions and requirements for
Assigned Protection Factors (APF) and Maximum Use Concentrations (MUCs)
(71 FR 50121, 50122, Aug. 24, 2006). In addition to this rulemaking,
OSHA updated Appendix A to Sec. 1910.134: Fit Testing Procedures (69
FR 46986, 46993, Aug. 4, 2004).
After withdrawing the 1992 version of Z-88.2 in 2002, ANSI
published the American National Standard, ANSI/AIHA Z88.10-2010,
``Respirator Fit Testing Methods,'' approved in 2010. These rules and
standards addressed the topics of APFs and fit testing. APFs provide
employers with critical information to use when selecting respirators
for employees exposed to atmospheric contaminants found in industry.
Finally, in 2015, ANSI published ANSI/ASSE Z88.2-2015, ``Practices for
Respiratory Protection,'' which referenced OSHA regulations. These
updates included requirements for classification of considerations for
selection and use of respirators, establishment of cartridge/canister
change schedules, use of fit factor value for respirator fit testing,
calculation of effective protection factors, and compliance with
compressed air dew requirements, compressed breathing air equipment,
and systems and designation of positive pressure respirators. In July
2017, ANSI/ASSE transferred the responsibilities for developing
respiratory consensus standards to ASTM International.
ASTM F3387-19 is based on the most recent consensus standards
recognized by experts in government and professional associations on
the selection, use, and maintenance for respiratory protection
equipment. The standard contains detailed guidance and provisions on
respirator selection that are based on NIOSH's long-standing experience
of testing and approving respirators for occupational use and OSHA's
research and rulemaking on respiratory protection. ASTM F3387-19 also
addresses all aspects of establishing, implementing, and evaluating
respiratory protection programs and establishes minimum acceptable
respiratory protection program elements in the areas of program
administration, standard operating procedures, medical evaluation,
respirator selection, training, fit testing, respirator maintenance,
inspection, and storage. ASTM F3387-19 comprehensively covers numerous
aspects of respiratory protection and provides the most up-to-date
provisions for current respirator technology and effective respiratory
protection. Therefore, MSHA believes that ASTM F3387-19 would provide
mine operators with information and guidance on the proper selection,
use, and maintenance of respirators, which would protect the health and
safety of miners.
Under this proposed rule, MSHA would require that operators
establish a respiratory protection program in writing, that includes
minimally acceptable program elements: program administration; standard
operating procedures; medical evaluations; respirator selection;
training; fit testing; and maintenance, inspection, and storage.
Beyond the minimally acceptable program elements, MSHA proposes to
provide mine operators with flexibility to select the provisions in
ASTM F3387-19 that are applicable to the conditions of their mines and
respirator use by their miners. In MSHA's experience, the need for and
actual use of respirators varies among mines for different reasons,
including the type of commodity mined or processed and the mining
method and controls used. At some mines, miners may not use or may only
rarely use respirators. At other mines, miners may use respirators more
frequently. Recognizing these differences, MSHA would allow mine
operators to comply with the provisions in ASTM F3387-19 that they deem
are relevant and appropriate for their mining operations and
conditions.
MSHA has observed that many operators, in particular larger mine
operators, have already implemented in their respiratory programs many
OSHA requirements, which are substantially similar to many requirements
in ASTM F3387-19. Indeed, ASTM F3387-19 refers to OSHA's regulations on
respiratory protection programs, APFs and MUCs, and fit testing. MSHA
believes that the mining industry is already familiar with many
provisions in ASTM F3387-19. MSHA anticipates that for many large mine
operators, few changes to their respiratory protection program may be
warranted, whereas small mines, or mines that use respirators
intermittently, may need to revise their respiratory practices in
accordance with the requirements, as applicable, in ASTM F3387-19.
1. Respiratory Program Elements
Under the proposed rule, MSHA would require that the respiratory
protection program be in writing and that it include the following
minimally acceptable program elements: program administration; standard
operating procedures; medical evaluations; respirator selection;
training; fit testing; and maintenance, inspection, and storage.
a. Program Administration
ASTM F3387-19 specifies several practices related to respiratory
protection program administration, including the qualifications and
responsibilities of a program administrator. For example, ASTM F3387-19
provides that responsibility and authority for the respirator program
be assigned to a single qualified person with sufficient knowledge of
respiratory protection. Qualifications could be gained through training
or experience; however, the qualifications of a program administrator
must be commensurate with the respiratory hazards present at a
worksite.
This individual should have access to and direct communication with
the site manager about matters impacting worker safety and health. ASTM
F3387-19 notes a preference that the administrator be in the company's
industrial hygiene, environmental, health physics, or safety
engineering department; however, a third-party entity meeting the
provisions may also provide this service. ASTM F3387-19 outlines the
respiratory program administrator's responsibilities, specifying that
they should include: measuring, estimating, or reviewing
[[Page 44919]]
information on the concentration of airborne contaminants; ensuring
that medical evaluations, training, and fit testing are performed;
selecting the appropriate type or class of respirator that will provide
adequate protection for each contaminant; maintaining records;
evaluating the respirator program's effectiveness; and revising the
program, as necessary.
b. Standard Operating Procedures (SOP)
SOPs are written policies and procedures available for all wearers
of respirators to read and are established by the employer. ASTM F3387-
19 states that written SOPs for respirator programs are necessary when
respirators are used routinely or sporadically. Written SOPs should
cover hazard assessment; respirator selection; medical evaluation;
training; fit testing; issuance, maintenance, inspection, and storage
of respirators; schedule of air-purifying elements; hazard re-
evaluation; employer policies; and program evaluation and audit. ASTM
F3387-19 also provides that wearers of respirators be provided with
copies of the SOP and that written SOPs include special consideration
for respirators used for emergency situations. The procedures are
reviewed in conjunction with the annual respirator program audit and
are revised by the program administrator, as necessary.
c. Medical Evaluation
Medical evaluations determine whether an employee has any medical
conditions that would preclude the use of respirators, limitation on
use, or other restrictions. ASTM F3387-19 provides that a program
administrator advise the PLHCP of the following conditions to aid in
determining the need for a medical evaluation: type and weight of the
respirator to be used; duration and frequency of respirator use
(including use for rescue and escape); typical work activities;
environmental conditions (e.g., temperature); hazards for which the
respirator will be worn, including potential exposure to reduced-oxygen
environments; and additional protective clothing and equipment to be
worn. ASTM F3387-19 also incorporates ANSI Z88.6 Respiratory
Protection--Respirator Use--Physical Qualifications for Personnel.
d. Respirator Selection
Proper respirator selection is an important component of an
effective respiratory protection program. ASTM F3387-19 provides that
proper respirator selection consider the following: the nature of the
hazard, worker activity and workplace factors, respirator use duration,
respirator limitations, and use of approved respirators. ASTM F3387-19
states that respirator selection for both routine and emergency use
include hazard assessment, selection of respirator type or class that
can offer adequate protection, and maintenance of written records of
hazard assessment and respirator selection.
ASTM F3387-19 provides specific steps to establish the nature of
inhalation hazards, including determining the following: the types of
contaminants present in the workplace; the physical state and chemical
properties of all airborne contaminants; the likely airborne
concentration of the contaminants (by measurement or by estimation);
potential for an oxygen-deficient environment; an occupational exposure
limit for each contaminant; existence of an IDLH atmosphere; and
compliance with applicable health standards for the contaminants.
ASTM F3387-19 includes other information to support the respirator
selection process, including information on operational
characteristics, capabilities, and performance limitations of various
types of respirators. These limitations must be considered during the
selection process. ASTM F3387-19 also describes types of respirators
and consideration for their use, including service life, worker
mobility, compatibility with other protective equipment, durability,
comfort factors, compatibility with the environment, and compatibility
with job and workforce performance. Finally, ASTM F3387-19 provides
other essential information regarding respirator selection such as
oxygen deficiency, ambient noise, and need for communication.
e. Training
Employee training is essential for correct respirator use. ASTM
F3387-19 provides that all users be trained in their area of
responsibility by a qualified person to ensure the proper use of
respirators. A respirator trainer must be knowledgeable in the
application and use of the respirators and must understand the site's
work practices, respirator program, and applicable regulations.
Employees who receive training include the workplace supervisor, the
person issuing and maintaining respirators, respirator wearers, and
emergency teams. To ensure the proper and safe use of a respirator,
ASTM F3387-19 also provides that the minimum training for each
respirator wearer includes: the need for respiratory protection; the
nature, extent, and effects of respiratory hazards in the workplace;
reasons for particular respirator selections; reasons for engineering
controls not being applied or reasons why they are not adequate; types
of efforts made to reduce or eliminate the need for respirators;
operation, capabilities, and limitations of the respirators selected;
instructions for inspecting, donning, and doffing the respirator; the
importance of proper respirator fit and use; and maintenance and
storage of respirators. The standard provides for each respirator
wearer to receive initial and annual training. Workplace supervisors
and persons issuing respirators are retrained as determined by the
program administrator. Training records for each respirator wearer are
maintained and include the date, type of training received, performance
results (as appropriate), and instructor's name.
f. Respirator Fit Testing
A serious hazard may occur if a respirator, even though properly
selected, is not properly fitted. For example, if a proper face seal is
not achieved, the respirator would provide a lower level of protection
than it is designed to provide because the respirator could allow
contaminants to leak into the breathing area. Proper fit testing
verifies that the selected make, model, and size of a respirator
adequately fits and ensures that the expected level of protection is
provided. ASTM F3387-19 includes provisions for qualitative and
quantitative fit testing to determine the ability of a respirator
wearer to obtain a satisfactory fit with a tight-fitting respirator and
incorporates ANSI/AIHA Z88.10, Respirator Fit Testing Methods, for
guidance on how to conduct fit testing of tight-fitting respirators and
appropriate methods to be used. ASTM F3387-19 also provides information
on conducting quantitative and qualitative fits test to determine how
well a tight-fitting respirator fits a wearer. This includes
information on the application of fit factors and assigned protection
factors, and how these factors are used to ensure that a wearer is
receiving the necessary protection. ASTM F3387-19 provides for each
respirator wearer to be fit tested before being assigned a respirator
(currently at least once every 12 months or repeated when a wearer
expresses concern about respirator fit or comfort or has a condition
that may interfere with the face piece seal).
g. Maintenance, Inspection, and Storage
Proper maintenance and storage of respirators are important in a
respiratory protection program. ASTM F3387-19 includes specific
provisions for
[[Page 44920]]
decontaminating, cleaning, and sanitizing respirators, inspecting
respirators, replacing, and repairing parts, and storing and disposing
of respirators. For example, the decontamination provisions state that
respirators are decontaminated after each use and cleaned and sanitized
regularly per manufacturer instructions. Following cleaning and
disinfection, reassembled respirators are inspected to verify proper
working condition. ASTM F3387-19 states that employers consult
manufacturer instructions to determine component expiration dates or
end-of-service life, inspect the rubber or other elastomeric components
of respirators for signs of deterioration that would affect respirator
performance, and repair or replace respirators failing inspection. ASTM
F3387-19 also provides that respirators are stored according to
manufacturer recommendations and in a manner that will protect against
hazards (i.e., physical, biological, chemical, vibration, shock,
temperature extremes, moisture, etc.). It also provides that
respirators are stored to prevent distortion of rubber or other parts.
2. Section-by-Section Analysis of Incorporation by Reference--ASTM
F3387-19
a. Part 56--Safety and Health Standards--Surface Metal and Nonmetal
Mines--Section 56.5005--Control of Exposure to Airborne Contaminants
Existing Sec. 56.5005 provides that whenever respiratory
protective equipment is used, a program for selection, maintenance,
training, fitting, supervision, cleaning, and use shall meet the
requirements of paragraph (b). Paragraph (b) requires that mine
operators implement a respirator program consistent with the
requirements of ANSI Z88.2-1969. MSHA is proposing to revise paragraph
(b) to remove the incorporation by reference to ANSI Z88.2-1969 and
incorporate by reference ASTM F3387-19.
MSHA is proposing to revise paragraph (b) to state that approved
respirators must be selected, fitted, cleaned, used, and maintained in
accordance with the requirements of ASTM F3387-19 ``as applicable.''
Under the proposal, MSHA would require that the respiratory program be
in writing and that it include the following minimally acceptable
program elements: program administration; standard operating
procedures; medical evaluations; respirator selection; training; fit
testing; and maintenance, inspection, and storage.
Also, MSHA is proposing to change paragraph (c) to require the
presence of at least one other person with backup equipment and rescue
capability when respiratory protection is used in atmospheres that are
IDLH. This change is needed to conform to language in the proposed
incorporation by reference of ASTM F3387-19, which defines IDLH as
``any atmosphere that poses an immediate hazard to life or immediate
irreversible debilitating effects on health'' (ASTM International
2019).
b. Part 57--Safety and Health Standards--Underground Metal and Nonmetal
Mines--Section 57.5005--Control of Exposure to Airborne Contaminants
Existing Sec. 57.5005 provides that whenever respiratory
protective equipment is used, a program for selection, maintenance,
training, fitting, supervision, cleaning, and use shall meet the
requirements of paragraph (b). Paragraph (b) requires that mine
operators implement a respirator program consistent with the
requirements of ANSI Z88.2-1969. MSHA is proposing to revise paragraph
(b) to remove the incorporation by reference to ANSI Z88.2-1969 and
incorporate by reference ASTM F3387-19.
MSHA is proposing to revise paragraph (b) to state that approved
respirators must be selected, fitted, cleaned, used, and maintained in
accordance with the requirements of ASTM F3387-19 ``as applicable.''
Under the proposal, MSHA would require that the respiratory program be
in writing and that it include the following minimally acceptable
program elements: program administration; standard operating
procedures; medical evaluations; respirator selection; training; fit
testing; and maintenance, inspection, and storage.
Also, MSHA is proposing to change paragraph (c) to require the
presence of at least one other person with backup equipment and rescue
capability when respiratory protection is used in atmospheres that are
IDLH. This change is needed to conform to language in the proposed
incorporation by reference of ASTM F3387-19, which defines the term
IDLH as ``any atmosphere that poses an immediate hazard to life or
immediate irreversible debilitating effects on health'' (ASTM
International 2019).
c. Part 72--Health Standards for Coal Mines--Section 72.710--Selection,
Fit, Use, and Maintenance of Approved Respirators
Existing Sec. 72.710 requires approved respirators be selected,
fitted, used, and maintained in accordance with the provisions of ANSI
Z88.2-1969, which was incorporated by reference into coal standards in
1995 (60 FR 30398, June 8, 1995). MSHA is proposing to revise Sec.
72.710 by removing the requirement in the first sentence that coal mine
operators must ensure that the maximum amount of respiratory protection
is made available to miners when respirators are used. MSHA believes
that the use of approved respirators and the proposed incorporation by
reference of ASTM F3387-19 would ensure that coal miners' health is
protected. Under the proposal, MSHA would require that the respiratory
program be in writing and that it include the following minimally
acceptable program elements: program administration; standard operating
procedures; medical evaluations; respirator selection; training; fit
testing; and maintenance, inspection, and storage.
VIII. Technological Feasibility
This technological feasibility analysis considers whether currently
available technologies, used alone or in combination with each other,
can be used by operators to comply with the proposed standard.
MSHA is required to set standards to assure, based on the best
available evidence, that no miner will suffer material impairment of
health or functional capacity from exposure to toxic materials or
harmful physical agents over his working life. 30 U.S.C. 811(a)(6)(A).
The Mine Act also instructs MSHA to set health standards to attain
``the highest degree of health and safety protection for the miner''
while considering ``the latest available scientific data in the field,
the feasibility of the standards, and experience gained under this and
other health and safety laws.'' 30 U.S.C. 811(a)(6)(A). But the health
and safety of the miner is always the paramount consideration: ``[T]he
Mine Act evinces a clear bias in favor of miner health and safety,''
and ``[t]he duty to use the best evidence and to consider feasibility
are appropriately viewed through this lens and cannot be wielded as
counterweight to MSHA's overarching role to protect the life and health
of workers in the mining industry.'' Nat'l Min. Ass'n v. Sec'y, U.S.
Dep't of Lab., 812 F.3d 843, 866 (11th Cir. 2016); 30 U.S.C. 801(a).
[[Page 44921]]
The D.C. Circuit clarified the Agency's obligation to demonstrate
the technological feasibility of reducing occupational exposure to a
hazardous substance. MSHA ``must only demonstrate a `reasonable
possibility' that a `typical firm' can meet the permissible exposure
limits in `most of its operations.'' Kennecott Greens Creek Min. Co. v.
Mine Safety & Health Admin., 476 F.3d 946, 958 (D.C. Cir. 2007)
(quoting American Iron & Steel Inst. v. OSHA, 939 F.2d 975, 980 (D.C.
Cir. 1991)).
This section presents technological feasibility findings that
guided MSHA's selection of the proposed PEL. MSHA's technological
feasibility findings are organized into two main sections covering: (1)
the technological feasibility of proposed part 60; and (2) the
technological feasibility of the proposed revision to existing
respiratory protection standards. Based on the analyses presented in
the two sections, MSHA preliminarily concludes that the Agency's
proposal is technologically feasible. MSHA's feasibility determinations
in this rulemaking are supported by its findings that the majority of
the industry is already using technology that would be sufficient to
comply with the proposed rule.
First, MSHA has preliminarily determined that proposed part 60 is
technologically feasible. Many mine operators already maintain
respirable crystalline silica exposures at or below the proposed PEL of
50 [mu]g/m\3\, and at mines where there are elevated exposures,
operators would be able to reduce exposures to at or below the proposed
PEL by properly maintaining existing engineering controls and/or by
implementing new engineering and administrative controls that are
currently available. In addition, mines would be able to satisfy the
exposure monitoring requirements of proposed part 60 with existing,
validated, and widely used sampling technologies and analytical
methods.
Second, the analysis shows that the proposed update to MSHA's
respiratory protection requirements is also technologically feasible.
The mining industry's existing respiratory protection practices for
selecting, fitting, using, and maintaining respiratory protection
include program elements that are similar to those of ASTM F3387-19,
``Standard Practice for Respiratory Protection'' (ASTM F3387-19), which
MSHA is proposing to incorporate by reference.
A. Technological Feasibility of Sampling and Analytical Methods
1. Sampling Methods
MSHA's proposed rule would require mine operators in both MNM and
coal mines to conduct sampling for respirable crystalline silica using
respirable particle size-selective samplers that conform to the
``International Organization for Standardization (ISO) 7708:1995: Air
Quality--Particle Size Fraction Definitions for Health-Related
Sampling'' standard. The ISO convention defines respirable particulates
as having a 4 micrometer ([mu]m) aerodynamic diameter median cut-point
(i.e., 4 [mu]m-sized particles are collected with 50 percent
efficiency), which approximates the size distribution of particles that
when inhaled can reach the alveolar region of the lungs. For this
reason, the ISO convention is widely considered biologically relevant
for respirable particulates and provides appropriate criteria for
equipment used to sample respirable crystalline silica. MSHA's current
sampling method for MNM mines meets the ISO criteria by using a 10 mm
Dorr-Oliver cyclone and a sampling pump operated at a flow rate of 1.7
liter per minute (L/min), and MNM mine operators also already use this
type of sampler for MNM sampling under existing standards. MSHA's
current sampling method for RCMD, including respirable crystalline
silica, uses a 10 mm Dorr-Oliver cyclone but operated at 2.0 L/min to
approximate the British Mining Research Establishment (MRE) sampling
criteria, and thus does not meet the ISO criteria. Although, the
existing sampling pumps can be adjusted to operate at a flow rate of
1.7 L/min flow rate to meet the ISO criteria. To comply with this
proposed requirement, coal mine operators that currently use coal mine
dust personal sampler units (CMDPSU) would need to adjust their
samplers to the flow rate specified by the manufacturer for complying
with the ISO.
There are a variety of size-selective samplers on the market that
meet the ISO respirable-particle-size selection criteria. Examples
include Dorr-Oliver cyclone currently used by MSHA and OSHA, operated
at 1.7 L/min; SKC aluminum cyclone (2.5 L/min); HD cyclone (2.2 L/min);
SKC GS-3 multi-inlet cyclone (2.75 L/min); and BGI GK 2.69 (4.2 L/min).
Each cyclone has different operating specifications and performance
criteria, but they all are compliant with the ISO criteria for
respirable dust with an acceptable level of measurement bias.
Manufacturers of size-selective samplers specify the flow rates that
are necessary to conform to the particle size collection criteria of
the ISO standard. Samplers used in both MNM and coal mines can be used
to perform the proposed sampling, and because other commercially
available (already on the market) samplers conform to the ISO standard,
MSHA preliminarily finds that sampling in accordance with the ISO
standard is technologically feasible.
2. Analytical Methods and Feasibility of Measuring Below the Proposed
PEL and Action Level
After a respirable dust sample is collected and submitted to a
laboratory, it must be analyzed to quantify the mass of respirable
crystalline silica present. The laboratory method must be sensitive
enough to detect and quantify respirable crystalline silica at levels
below the applicable concentration. The analytical limit of detection
(LOD) and/or limit of quantification (LOQ), together with the sample
volume, determine the airborne concentration LOD and/or LOQ for a given
air sample. MSHA proposes a PEL for respirable crystalline silica of 50
[mu]g/m\3\ as a full shift, 8-hour TWA for both MNM and coal mines.
Several analytical methods are available for measuring respirable
crystalline silica at levels well below the proposed PEL of 50 [mu]g/
m\3\ and action level of 25 [mu]g/m\3\.
MSHA uses two main analytical methods (1) P-2: X-Ray Diffraction
Determination Of Quartz And Cristobalite In Respirable Metal/Nonmetal
Mine Dust (analysis by X-ray diffraction, XRD) for MNM mines and (2) P-
7: Determination Of Quartz In Respirable Coal Mine Dust By Fourier
Transform Infrared Spectroscopy (analysis by infrared spectroscopy,
FTIR or IR) for coal mines.\36\ The MSHA P-2 and P-7 methods, reliably
analyze compliance samples collected by MSHA inspectors, including 15
years of MNM compliance samples and 5 years of coal industry compliance
samples MSHA used for the exposure profile portion of this
technological feasibility analysis. These methods are capable of
measuring respirable crystalline silica exposures at levels below the
proposed PEL and action level.
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\36\ Other similar XRD methods include NIOSH-7500 and OSHA ID-
142. XRD methods are able to distinguish between the different
polymorphs--quartz, cristobalite and tridymite. Other IR methods
include NIOSH 7602 and 7603. IR methods are efficient, but they are
more prone to interferences and should only be used for samples with
a well-characterized matrix (e.g., coal dust).
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For an analytical method to have acceptable sensitivity for
determining
[[Page 44922]]
exposures at the proposed PEL of 50 [mu]g/m\3\ and action level of 25
[mu]g/m\3\, the LOQ must be at or below the amount of analyte (e.g.,
quartz) that would be collected in an air sample where the
concentration of analyte is equivalent to the proposed PEL or action
level. To determine the minimum airborne concentration that can be
quantified, the LOQ mass is divided by the sample air volume, which is
determined by the sampling flow rate and duration. Table VIII-1
presents minimum quantifiable quartz concentrations, for various
cyclones and established analytical methods.
[GRAPHIC] [TIFF OMITTED] TP13JY23.025
Based on this discussion, MSHA preliminarily finds that current
analytical methods are sufficiently sensitive to meet the proposed PEL
and action level.
3. Laboratory Capacity
MSHA's proposed standard would require that mines conduct baseline
sampling, periodic sampling, corrective actions sampling, and post-
evaluation sampling with analyses conducted by laboratories that meet
ISO 17025, General Requirements for the Competence of Testing and
Calibration Laboratories (ISO 17025). The majority of U.S. industrial
hygiene laboratories that perform respirable crystalline silica
analysis are accredited to ISO 17025 by the American Industrial Hygiene
Association (AIHA) Laboratory Accreditation Program (LAP). The AIHA LAP
lists 23 accredited commercial laboratories nationwide that, as of
April 2022, perform respirable crystalline silica analysis using an
MSHA, NIOSH or OSHA method.
MSHA interviewed a sample of three laboratories (one small-capacity
laboratory,\37\ one medium-capacity laboratory,\38\ and one large-
capacity laboratory) \39\ to estimate their sample-processing capacity.
Insights from these interviews suggest that laboratories have the
ability to provide surge capacity as the proposed rule is phased in.
Collectively, these three laboratories could process approximately
33,240 samples by XRD (suitable for MNM mines) and 1,752 samples by
FTIR or IR (suitable for coal mines) within a 6-month period.
Extrapolating this across all laboratories that can analyze respirable
crystalline silica samples, MSHA estimates that 232,680 samples for MNM
mines and 12,250 samples for coal mines could be processed in the
phase-in 6-month period. Over the first 12 months after the standard
goes into effect, analysis would be available for 465,360 samples for
MNM mines and 24,500 samples for coal mines.
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\37\ The small capacity laboratory has a maximum respirable
crystalline silica sample analysis capacity of 300 samples per month
(280 additional samples per month above the current number of
samples analyzed), a level which the laboratory could sustain for
two months.
\38\ The medium capacity laboratory has a maximum respirable
crystalline silica sample analysis capacity of 2,025 samples per
month. Surge from the mining industry is considered to replace,
rather than be in addition to the current number of samples
analyzed.
\39\ The large capacity laboratory has a maximum respirable
crystalline silica sample analysis capacity of 4,500 samples per
month (3,700 additional samples per month above the current number
of samples analyzed).
---------------------------------------------------------------------------
Based on exposure profiles for the MNM and coal mining industries
and MSHA's experience and knowledge of the mining industry, MSHA
estimates that within this first 12-month period, mines would seek
analysis for a total of 172,907 respirable crystalline silica samples
(including 58,126 samples for MNM mines and 12,373 samples for coal
mines associated with the 6-month baseline sampling period). In the
subsequent 12-month period, mines would require analysis for 102,409
samples (includes process/control measure evaluation samples and
periodic samples associated with the
[[Page 44923]]
proposed action level), a number that will decline over years 1 through
6 as the mine operators reduce some miner exposures below the proposed
action level.\40\ Comparing these figures with the surge capacity
estimates previously noted above, MSHA believes that there would be
sufficient processing capacity to meet the sampling analysis schedule
envisioned in the proposed rule.
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\40\ MSHA anticipates that in the initial six-month baseline
period mine operators will collect 70,498 baseline samples, of which
12,373 will be coal mine samples. In the 12 months beginning after
the initial baseline period, mines will collect 88,281 samples for
miners who are exposed at or above the proposed action level (25
[micro]g/m\3\), but at or below the proposed PEL, plus 14,128
samples to evaluate corrective action and process change (i.e.,
processes which must be analyzed to determine whether newly
implemented dust control measures are successful and processes newly
identified during periodic walk-through evaluations), for a total of
102,409 samples per year (including 25,152 coal mine samples).
Estimates are as of December 2022.
---------------------------------------------------------------------------
a. Baseline Sampling
MSHA's proposal would require baseline sampling for each miner who
is or may reasonably be expected to be exposed to respirable
crystalline silica within 180 days (6 months) of the standard's
effective date.\41\ This would require an initial increase in
analytical laboratory capacity of approximately 70,498 sample analyses
over 6 months. MSHA expects that with months of lead time during the
proposed rule and final rule stages of the rulemaking, laboratories
would anticipate the initial baseline period increase in demand and
would respond by increasing their analytical capacity. For example,
laboratories could acquire additional instrumentation, train additional
analysts, or add a second or third operating shift. This is
particularly likely given that demand would be based on a regulatory
requirement and during the rulemaking process MSHA would conduct
outreach to make all relevant stakeholders aware of the rule's
provisions. MSHA is specifically soliciting comments on the
technological feasibility of laboratory capability to conduct baseline
sampling. At this point in the rulemaking, MSHA believes that the
proposed rule is technologically feasible for laboratories to conduct
baseline sampling analyses.
---------------------------------------------------------------------------
\41\ Where several miners perform similar activities on the same
shift, only a representative fraction of miners (minimum of two
miners) would need to be sampled, including those expected to have
the highest exposures.
---------------------------------------------------------------------------
b. Periodic, Corrective Actions, and Post-Evaluation Sampling
Under proposed Sec. 60.12 (b)-(e), three conditions would require
mine operators to conduct additional sampling after the initial 6-month
baseline period. First, when the most recent sampling indicates that
miner exposures are at or above the proposed action level (25 [micro]g/
m\3\) but at or below the proposed PEL (50 [micro]g/m\3\), the mine
operator would be required to sample within 3 months of that sampling
and continue to sample within 3 months of the previous sampling until
two consecutive samplings indicate that miner exposures are below the
action level. Second, where the most recent sampling indicates that
miner exposures are above the PEL, the mine operator would be required
to sample after corrective actions are taken to reduce overexposures,
until sampling results indicate miner exposures are at or below the
PEL. Third, if the mine operator determines, as a result of the semi-
annual evaluation, that miners may be exposed to respirable crystalline
silica at or above the action level, the mine operator would be
required to perform sampling to assess the full-shift, 8-hour TWA
exposure of respirable crystalline silica for each miner who is or may
reasonably be expected to be at or above the action level.
MSHA estimates that the total number of analyses (489,860) that
laboratories will be able to perform per year is more than 2.5 times
the total estimated number of samples for which mines will seek
analyses in the first year (172,907). Based on the estimated surplus
analyses available beyond baseline sampling (419,362), MSHA
preliminarily finds that periodic, corrective actions, and post-
evaluation sampling would also be technologically feasible both in the
first year and in subsequent years.\42\
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\42\ 489,860 total annual laboratory analyses divided by 172,907
mine samples to be analyzed, equals 2.83 percent surplus sample
analyses. 489,860 total analyses-70,498 baseline analyses = a
surplus of 419,362 analyses available for the 102,409 periodic,
corrective actions, and process change sampling.
---------------------------------------------------------------------------
B. Technological Feasibility of the Proposed PEL
1. Methodology
The technological feasibility analysis for the proposed PEL relies
primarily on information from three key sources:
MSHA's Standardized Information System (MSIS) respirable
crystalline silica exposure data, which includes 57,769 MNM and 63,127
coal mine compliance samples collected by MSHA inspectors; these
samples were of sufficient mass to be analyzed for respirable
crystalline silica by MSHA's analytical laboratory.\43\
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\43\ These respirable crystalline silica exposure data consist
of 15 years of MNM mine samples (January 1, 2005, through December
31, 2019) and five years of coal mine samples (August 1, 2016,
through July 31, 2021). These MSHA compliance samples represent the
conditions identified by MSHA inspectors as having the greatest
potential for respirable crystalline silica exposure during the
periodic inspection when sampling occurred. While MSHA's laboratory
also analyzes mine operators' respirable coal mine dust samples
containing respirable crystalline silica, those samples are not
included in the data used for this analysis.
---------------------------------------------------------------------------
The National Institute for Occupational Safety and Health
(NIOSH) series on reducing respirable dust in mines, including: ``Dust
Control Handbook for Industrial Minerals Mining and Processing, Second
Edition'' (NIOSH, 2019b) and ``Best Practices for Dust Control in Coal
Mining, Second Edition'' (NIOSH, 2021a).\44\ With cooperation from the
MNM and coal mining industries, NIOSH has extensively researched and
documented engineering and administrative controls for respirable
crystalline silica in mines.
---------------------------------------------------------------------------
\44\ Together, these two recent reports provide more than 500
pages of detailed descriptions, discussion, and illustrations of
dust control technologies currently used in mines.
---------------------------------------------------------------------------
MSHA's knowledge of the mining industry. MSHA has over
four decades of experience inspecting surface mines at least twice per
year and underground mines at least four times per year and in
assisting mine operators and miners with technological issues,
including control of respirable dust (including respirable crystalline
silica) exposure. MSHA offers informational programs, training,
publications, onsite evaluations, and investigations that document
conditions in mines and help mines operate in a safe and healthy
manner.\45\
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\45\ MSHA also analyzes RCMD samples collected by mine
operators, including those containing respirable crystalline silica,
in addition to the compliance samples collected by MSHA inspectors
(mentioned in the first bullet of this series).
---------------------------------------------------------------------------
MSHA also consulted other published reports, scientific journal
articles, and information from equipment manufacturers and mining
industry suppliers.\46\
---------------------------------------------------------------------------
\46\ Project personnel reviewed 104,365 samples collected and
analyzed by MSHA for respirable crystalline silica, plus another
103,745 samples collected but not analyzed due to insufficient
respirable dust collected in the sample. They examined over 200
published reports, proceedings, case studies, analytical methods,
and journal articles, in addition to inspecting more than 200 web
page, product brochures, user manuals, service/maintenance manuals
and descriptive literature for dust control products, mining
equipment, and related services.
---------------------------------------------------------------------------
2. The Technological Feasibility Analysis Process
a. Mining Commodity Categories and Activity Groups
As described in the Preliminary Regulatory Impact Analysis (PRIA),
MSHA categorized mine types into six MNM ``commodity categories''
(using
[[Page 44924]]
the method of Watts et al., 2012) based on similarities in exposure
characteristics. MNM mine categories include metal, nonmetal, stone,
crushed limestone, and sand and gravel. All coal mines are categorized
together as one commodity category.
Within each commodity, MSHA further separated mining operations
into the four activity groups widely used by the industry: (1)
development and production miners (drillers, stone cutters); (2) ore/
mineral processing miners (crushing/screening equipment operators and
kiln, mill, and concentrator workers in mine facilities); (3) miners
engaged in load/haul/dump activities (conveyor, loader, and large
haulage vehicle operators, such as dump truck drivers); and (4) miners
in all other occupations (mobile and utility workers, such as
surveyors, mechanics, cleanup crews, laborers, and operators of compact
tractors and utility trucks).
Before determining the feasibility of reducing miners' exposure to
respirable crystalline silica, MSHA gathered and analyzed information
to understand current miner exposures by creating an ``exposure
profile,'' identified the existing (i.e., baseline) conditions and the
exposure levels associated with those conditions, and determined
whether mines would need additional control methods, and if so, whether
those methods were available.
b. Exposure Profiles
MSHA classified all valid respirable crystalline silica samples in
the Agency's MSIS data,\47\ grouping the data by commodity category,
followed by activity group.\48\ MSHA created an exposure profile to
better examine the sample data for each commodity category. These
profiles include basic summary statistics, such as sample count, mean,
median, and maximum values, presented as ISO 8-hour TWA values. They
also show the sample distribution within the following exposure ranges:
<=25 [mu]g/m\3\, >25 [mu]g/m\3\ to <=50 [mu]g/m\3\, >50 [mu]g/m\3\ to
<=100 [mu]g/m\3\ (equivalent to 85.7 [mu]g/m\3\ in coal mines for a
sample calculated as an 8-hour TWA), >100 [mu]g/m\3\ to <=250 [mu]g/
m\3\, >250 [mu]g/m\3\ to <=500 [mu]g/m\3\, and >500 [mu]g/m\3\.\49\
---------------------------------------------------------------------------
\47\ MSHA removed duplicate samples, samples missing critical
information, and those identified as invalid by the mine inspector,
for example because of a ``fault'' (failure) of the air sampling
pump during the sampling period.
\48\ MSHA MSIS respirable crystalline silica data for the MNM
industry, January 1, 2005, through December 31, 2019 (version
20220812); MSHA MSIS respirable crystalline silica data for the Coal
Industry, August 1, 2016, through July 31, 2021 (version 20220617).
All samples were collected by mine inspectors and were of sufficient
mass to be analyzed for respirable crystalline silica by MSHA's
laboratory.
\49\ MSHA selected these ranges based on the proposed PELs under
consideration, then multiples of 100 [mu]g/m\3\ to show how data are
distributed in the higher ranges. Table VIII-5 also presents
additional exposure ranges corresponding to the 85.7 [mu]g/m\3\
concentration for coal samples.
---------------------------------------------------------------------------
In Table VIII-2, the respirable crystalline silica exposure data
for MNM miners are summarized by commodity and for the MNM industry as
a whole, while Table VIII-3 presents the exposure profile as the
percentage of samples in each exposure range. Overall, approximately 82
percent of the 57,769 MNM compliance samples were at or below the
proposed PEL (50 [mu]g/m\3\). The exposure profile shows variability
between the commodity categories: approximately 73 percent of metal
miner exposures at or below the proposed PEL (50 [mu]g/m\3\) (the
lowest among all MNM mines), compared with approximately 90 percent of
the crushed limestone miner exposures (the highest among all MNM
mines).
Table VIII-4 and Table VIII-5 present the corresponding respirable
crystalline silica exposure information for coal miners by location
(underground or surface). Overall, approximately 93 percent of the
63,127 samples obtained by MSHA inspectors for coal miners were at or
below the proposed PEL (50 [mu]g/m\3\). There was little variation
between samples for underground miners and surface miners (with
approximately 93 and 92 percent of the samples at or below 50 [mu]g/
m\3\, respectively). Exposure values from the coal industry are
expressed as ISO 8-hour TWAs, compatible with the proposed PEL.
BILLING CODE 4520-43-P
[[Page 44925]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.026
[[Page 44926]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.027
[[Page 44927]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.028
[[Page 44928]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.029
c. Existing Dust Controls in Mines (Baseline Conditions)
MNM and coal mines are controlling dust containing respirable
crystalline silica in various ways. As shown in Tables VIII-2 through
VIII-5, respirable crystalline silica exposures exceeded the proposed
PEL of 50 [mu]g/m\3\ in about 18 percent of all MNM samples collected.
Of all coal samples, exposure levels exceeded the proposed PEL in about
seven percent of the samples. Overall, metal mines and sand and gravel
mines had higher exposure levels than other commodity mines.
Despite the extensive dust control methods available, dust control
measures have been implemented in some commodity categories to a
greater degree than in others. This is partly because some commodity
categories tend to have larger mines. MSHA has found that the larger
the amount (tonnage) of material a mine moves (including overburden and
other waste rock), the faster the mine tends to operate its equipment
(i.e., closer to the equipment capacity), creating more air turbulence
and therefore generating more respirable crystalline silica. The amount
of material moved also influences the number of miners employed at a
mine, and therefore, the number of miners can be indirectly correlated
to the amount of dust generated. MSHA has observed that in large mines,
dusty conditions typically prompt more control efforts, usually in the
form of added engineering controls.
MSHA has also found that metal mines, which are typically large
operations with higher numbers of miners, tend to have available
engineering controls for dust management. On the other hand, sand and
gravel mines, which generally employ fewer miners and handle modest
amounts of material, have very limited, if any, dust control measures.
This is because most of the mined material is a commodity that only
requires washing and screening into various sizes of product
stockpiles, generating little waste material. Nonmetal, stone, and
crushed limestone mines occupy the middle range in terms of employment,
existing engineering controls, and maintenance practices.
Over the years, staff from multiple MSHA program areas have worked
alongside miners and mine operators to improve safety and health by
inspecting, evaluating, and researching mine conditions, equipment, and
operations. These key programs, each of which has an onsite presence,
include (but are not limited to) Mine Safety and Health Enforcement;
Directorate of Educational Policy and Development which includes the
National Mine Health and Safety Academy and the Educational Field and
Small Mine Services; and the Directorate of Technical Support, which is
comprised of the Approval and Certification Center and the Pittsburgh
Safety and Health Technology Center (including its Health Field
Division, National Air and Dust Laboratory, Ventilation Division, and
other specialized divisions). Table VIII-6 reflects the collective
observations of these MSHA programs, presented in terms of existing
dust control (baseline conditions) and the classes of additional
control measures that would provide those mines with the greatest
benefit to reduce exposures below the proposed PEL and action level.
Table VIII-6 shows MSHA's assessment of existing dust controls in
mines (baseline conditions) and additional controls needed to meet the
proposed PEL for each commodity category, including the need for
frequent scheduled maintenance. By conducting frequent scheduled
maintenance, mine operators can reduce the concentration of respirable
crystalline silica. Table VIII-6 shows that metal mines have adopted
extensive dust controls, while sand and gravel mines tend to have
minimal engineering controls, if any.
[[Page 44929]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.030
BILLING CODE 4520-43-C
Based on MSHA's experience, NIOSH research, and effective
respirable dust controls currently available and in use in the mining
industry, MSHA preliminarily finds that the baseline conditions include
various combinations of existing engineering controls selected and
installed by individual mines to address respirable crystalline silica
generated during mining operations.
d. Respirable Crystalline Silica Exposure Controls Available to Mines
Under the proposal, the mine operator must install, use, and
maintain feasible engineering controls, supplemented by administrative
controls, when necessary, to keep each miner's exposure at or below the
proposed PEL. Engineering controls reduce or prevent miners' exposure
to hazards.\50\ Administrative controls establish work practices that
reduce the duration, frequency, or intensity of miners' exposures
(although rotation of miners would be prohibited under the proposed
rule).
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\50\ Control measures that reduce respirable crystalline silica
can also reduce exposures to other hazardous particulates, such as
RCMD, metals, asbestos, and diesel exhaust. Operator enclosures and
process enclosures also reduce hazardous levels of noise by creating
a barrier between the operator and the noise source.
---------------------------------------------------------------------------
MSHA data and experience show that mine operators already have
numerous engineering and administrative control options to control
miners' exposures to respirable crystalline silica. These control
options are widely recognized and used throughout the mining industry.
NIOSH has extensively researched and documented engineering and
administrative controls for respirable crystalline silica in mines. As
noted previously, NIOSH has published a series on reducing respirable
dust in mines (NIOSH, 2019b; NIOSH, 2021a).
(1) Engineering controls
Examples of existing engineering controls used at mines and
commercially available engineering controls that MSHA considered
include:
Wetting or water sprays that prevent, capture, or redirect
dust;
Ventilation systems that capture dust at its source and
transport it to a dust collection device (e.g., filter or bag house),
dilute dust already in the air, or ``scrub'' (cleanse) dust from the
air in the work area;
Process enclosures that restrict dust from migrating
outside of the enclosed area, sometimes used with an attached
ventilation system to improve effectiveness (e.g., crushing equipment
and associated dump hopper enclosure, with curtains and mechanical
ventilation to keep dust inside);
Operator enclosures, such as mobile equipment cabs or
control booths, which provide an environment with clean air for an
equipment operator to work safely;
Protective features on mining process equipment to help
prevent process failures and associated dust releases (e.g.,
skirtboards on conveyors, which protect the conveyor system from damage
and prevent material on the conveyor from falling off, which generates
airborne dust);
Preventive maintenance conducted on engineering controls
and mining equipment that can influence dust levels at a mine, to keep
them functioning optimally; and
Instrumentation and other equipment to assist mine
operators and miners in evaluating engineering control
[[Page 44930]]
effectiveness and recognizing control failures or other conditions that
need corrective action.\51\
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\51\ These instruments include dust monitors; water, air, and
differential air pressure gauges; pitot tubes and air velocity
meters; and video camera (NIOSH recommends software that pairs video
with a dust monitor to track conditions that could lead to elevated
exposures if not corrected). These instruments are discussed in
NIOSH's best practices guides and dust control handbooks.
---------------------------------------------------------------------------
(2) Administrative controls
Administrative controls include practices that change the way tasks
are performed to reduce a miner's exposure. Administrative controls can
be very effective and can even prevent exposure entirely. MSHA has
preliminarily determined that various administrative controls are
readily available to provide supplementary support to engineering
controls. Examples of administrative controls would include
housekeeping procedures; proper work positions of miners; walking
around the outside of a dusty process area rather than walking through
it; cleaning of spills; and measures to prevent or minimize
contamination of clothing to help decrease miners' exposure to
respirable crystalline silica. However, these control methods depend on
human behavior and intervention and are less reliable than properly
designed, installed, and maintained engineering controls. Therefore,
administrative controls would be permitted only as supplementary
measures, with engineering controls required as the primary means of
protection. Nevertheless, administrative controls play an important
role in reducing miners' exposure to respirable crystalline silica.\52\
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\52\ Proposed paragraph 60.11(b) prohibits the use of rotation
of miners as an administrative control used for compliance with this
part.
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(3) Combinations of Controls
Various control options can also be used in combinations. NIOSH has
documented in detail most control methods and has confirmed that they
are currently used in mines, both individually and in combination with
each other (2019b, 2021a).
e. Maintenance
MSHA preliminarily finds that a strong and feasible preventive
maintenance program plays an important role in achieving consistently
lower respirable crystalline silica exposure levels. MSHA has observed
that when engineering controls are installed and maintained in working
condition, respirable dust exposures tend to be below the existing
exposure limits. When engineering controls are not maintained, dust
control efficiency declines and exposure levels rise. When engineering
controls fail due to a lack of proper maintenance, a marked rise in
exposures can occur, resulting in noncompliance with MSHA's existing
exposure limits. Some examples of the impact that proper maintenance
can have on respirable dust levels include:
Water spray maintenance: An experiment using water spray
bars that could be turned on or off showed that dust reduction was less
effective each time additional spray nozzles were deactivated. A 10
percent decrease occurred when three of 21 sprays were shut off, but a
50 percent decrease occurred when 12 out of the 21 sprays were shut
off. Decreased total water spray volume and gaps in the spray pattern
(due to deactivated nozzles) were both partially responsible for the
decreased dust control (Seaman et al., 2020).
Water added to drill bailing air: When introduced into the
drill hole (with the bailing air through a hollow drill bit), water
mixes with and moistens the drill dust ejected from the hole and can
reduce respirable dust by more than 90% (NIOSH 2021a, 2019b). NIOSH
reports that this same control measure, and others, are similarly
effective for MNM and surface coal mine drills preparing the blasting
holes used to expose the material below (whether ore or coal).
Ventilation system maintenance: The amount of air cleaned
by an air scrubber is decreased by up to one-third (33 percent) after
one continuous mining machine cut. Cleaning the scrubber screens
restores scrubber efficacy, but this maintenance must be performed
after every cut. Spare scrubber screens make frequent cleaning
practical without slowing production (NIOSH, 2021a).
Operator enclosure maintenance: Tests with mining
equipment showed that maintenance activities including repairing
weather stripping and replacing clogged and missing cab ventilation
system filters (intake, recirculation, final filters) increased miner
protection, by up to 95 percent (NIOSH 2019b, 2021a).
Filter selection during maintenance: Airflow is as
important as filtration and pressurization in operator enclosures;
during maintenance, filter selection can influence all three factors.
Performing serial end-shift testing of enclosed cabs (on a face drill
and a roof/rock bolter) at an underground crushed limestone mine, NIOSH
compared installed HEPA filters and an alternative (MERV 16 filters).
The latter provided an equal level of filtration and better overall
miner protection by allowing greater airflow and cab pressurization. As
an added advantage, NIOSH showed that these filters cost less and
required less-frequent replacement, reducing maintenance expenses in
this mining environment (Cecala et al., 2016; NIOSH 2021a,
2019b).53 54
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\53\ NIOSH believes this study, like many of its other mining
studies on operator enclosures and surface drill dust controls, is
relevant to both MNM mining and coal mining. NIOSH reports on this
study, conducted at an underground limestone mine, in detail in both
its Dust control handbook for industrial minerals mining and
processing (second edition) (2019b) and its best practices for dust
control in coal mining (second edition) (2021a).
\54\ Acronyms: High efficiency particulate air (HEPA). Minimum
efficiency reporting value (MERV).
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Proper design and installation--foundation for effective
maintenance: A new replacement equipment operator enclosure (control
booth) installed adjacent to the primary crusher at a granite stone
quarry initially provided 50 to 96 percent respirable dust reduction,
even with inadequate pressurization. The protection it offered miners
tripled after the booth's second pressurization/filtration unit was
activated (Organiscak et al., 2016).
MSHA has observed that when engineering controls are properly
maintained, exposure levels decrease or stay low. Metal mines, which
typically have substantial controls already installed, primarily need
reliable preventive maintenance programs to achieve the proposed PEL.
It is also important to repair equipment damage that contributes to
dust exposure (for example, damage to conveyor skirtboards that protect
the conveyor system from damage and prevent spillage which generates
airborne dust). Maintenance and repair programs must ensure that dust
control equipment is functioning properly.
3. Feasibility Determination of Control Technologies
MSHA is proposing a PEL of 50 [mu]g/m\3\ for MNM and coal mines. As
NIOSH has documented, the mining industry has a wide range of options
for controlling dust exposure that are already in various
configurations in mines (2019b; 2021a). NIOSH has carefully evaluated
most of the dust controls used in the mining industry and found that
many of the controls may be used in combinations with other control
options. NIOSH has documented protective factors and exposure
reductions of 30 to 90 percent or higher for many engineering and
administrative controls.
[[Page 44931]]
MSHA also preliminarily finds that maintaining (including
adjusting) or repairing existing controls would help achieve exposures
at or below 50 [mu]g/m\3\. For example, NIOSH found that performing
maintenance on an operator enclosure can restore enclosure
pressurization and reduce the respirable dust exposure of a miner by 90
to 98.9 percent (e.g., by maintaining weather stripping, reseating or
replacing leaking or clogged filters, and upgrading filtration) (NIOSH,
2019b). When an equipment operator remains inside a well-maintained
enclosure for a portion of a shift (for example 75 percent of an 8-hour
shift), the cab can reduce the exposure of the operator proportionally,
to a level of 50 [mu]g/m\3\ (or lower). This point is demonstrated by
the following example involving a bulk loading equipment operator in a
poorly maintained booth, exposed to respirable crystalline silica near
the existing exposure limit (in the MNM sectors, 100 [mu]g/m\3\, as ISO
8-hour TWA value; in the Coal sector, 85.7 [mu]g/m\3\ ISO, calculated
as an 8-hour TWA). During the 25 percent of their shift (two hours of
an eight-hour shift) that the operator was working in the poorly
maintained enclosure, their exposure would continue to be 100 [mu]g/
m\3\, while for the other six hours (operating mobile equipment with a
fully refurbished protective cab), the exposure level would be 90
percent lower, or 10 [mu]g/m\3\, resulting in an 8-hour TWA exposure of
33 [mu]g/m\3\ for that miner's shift.\55\ Greater exposure reductions
could also be achieved by repairing or replacing the poorly maintained
enclosure, or modifying the miner's schedule so that the miner works
seven hours, rather than six, inside of the well-maintained enclosure.
---------------------------------------------------------------------------
\55\ Calculating the exposure for the shift: 8-hour TWA = [(10
[mu]g/m\3\ x 6 hours) + (100 [mu]g/m\3\ x 2 hours)]/8 hours = 33
[mu]g/m\3\.
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Other engineering controls (e.g., process enclosure, water dust
suppression, dust suppression hopper, ventilation systems) could reduce
dust concentrations in the area surrounding the poorly maintained
enclosure, which would reduce the exposure of the operator inside. For
example, if the poorly maintained enclosure was an open-air control
booth (windows do not close) at a truck loading station, adding a dust
suppression hopper (which reduces respirable dust exposure by 39 to 88
percent during bulk loading) (NIOSH, 2019b), would lead to lower
exposure during the two hours the miner was inside the open-air booth.
The calculated respirable crystalline silica 8-hour TWA exposure of
that miner could be reduced from 33 [mu]g/m\3\ (with improved operator
enclosure alone) to 23 [mu]g/m\3\ (improved operator enclosure plus
dust suppression hopper).\56\ As an added benefit, any helper or
utility worker in the truck loading area would also experience reduced
exposure.
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\56\ Calculating the exposure with both the well-maintained
operator enclosure (6 hours) and dust suppression hopper, assuming
only the minimum documented respirable dust concentration reduction
(39 percent): [(10 [mu]g/m\3\ x 6 hours) + (100 [mu]g/m\3\ x (1-
0.39) x 2 hours)]/8 hours = 23 [mu]g/m\3\.
---------------------------------------------------------------------------
Similarly, considering an example for a coal miner helper who
spends 90 minutes (1.5 hours) per 8-hour shift assisting a drilling rig
operator (in a protective operator's cab) drilling blast holes. The
combination of controls used to control drilling dust (including water
added to the bailing air, which can reduce airborne respirable dust
emissions by up to 96 percent) usually maintain the helper's respirable
crystalline silica exposure in the range of 35 [mu]g/m\3\ (ISO) as an
8-hour TWA. If, however, the drill's on-board water tank runs dry due
to poor maintenance, the respirable crystalline silica concentration
near the drill will rise by 95 percent, meaning that the concentration
is 20 times greater than the usual level (NIOSH 2021a). If the drill
operator idles the drill and calls for water resupply, the helper will
not experience an elevated exposure. If instead the drill is operated
dry for another 30 minutes until water resupply arrives, the helper
will experience a respirable crystalline silica exposure of 77 [mu]g/
m\3\ (ISO) as an 8-hour TWA. If dry drilling continued for 1.5 hours,
the helper would have an exposure of 160 [mu]g/m\3\ ISO as an 8-hour
TWA.\57\ After water is delivered, drill respirable dust emissions will
return to their normal level once water is again introduced into the
drill bailing air.
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\57\ The 8-hour TWA exposure level of the helper, including the
30-minute period of elevated exposure, is calculated as: [(35 [mu]g/
m\3\ x 7.5 hours) + (35 [mu]g/m\3\ x 20 x 0.5 hours)]/8 hours = 77
[mu]g/m\3\. Drill bits designed for use with water may need to be
replaced sooner if used dry.
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Based on these examples and the wide range of effective exposure
control options available to the mining industry, MSHA preliminarily
finds that control technologies capable of reducing miners' respirable
crystalline silica exposures are available, proven, effective, and
transferable between mining commodities; however, they must be well-
designed and consistently used and maintained.
a. Feasibility Findings for the Proposed PEL
Based on the exposure profiles in Table VIII-2 and Table VIII-3 for
MNM mines, and in Table VIII-4 and VIII-5 for coal mines, and the
examples in the previous section that demonstrate the beneficial effect
of combined controls, MSHA preliminarily finds that the proposed PEL of
50 [mu]g/m\3\ is technologically feasible for all mines.
Table VIII-7 summarizes the technological feasibility of control
technologies available to the mining industry, by commodity. MSHA
preliminarily finds that control technologies are technologically
feasible for all six commodities and their respective activity groups.
Under baseline conditions, mines in each commodity category have
already achieved respirable crystalline silica exposures at or below 50
[mu]g/m\3\ for most of the miners represented by MSHA's 57,769 samples
for MNM miners and 63,127 samples for coal miners.
BILLING CODE 4520-43-P
[[Page 44932]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.031
BILLING CODE 4520-43-C
b. Feasibility Findings for the Proposed Action Level
MSHA believes that mine operators can achieve exposure levels at or
below the proposed action level of 25 [mu]g/m\3\, for most miners by
implementing additional engineering controls and more flexible and
innovative administrative controls, in addition to the existing control
methods already discussed in this technological feasibility analysis.
MSHA notes that the exposure profiles in Table VIII-2 and Table VIII-3
for MNM mines, and Table VIII-4 and VIII-5 for coal mines indicate that
mine operators have already achieved the proposed action level for at
least half of the miners who MSHA has sampled in each commodity
category. However, to do so reliably for all miners, operators would
need to upgrade equipment and facility designs, particularly in mines
with higher respirable crystalline silica concentrations, that may be
due to an elevated silica content in materials.
One control option would be increased automation, such as expanding
the use of existing autonomous or remote-controlled drilling rigs, roof
bolters, stone cutting equipment, and packaging/bagging equipment. This
type of automation can reduce exposures by increasing the distance
between the equipment operator and the dust source. Other options
include completely enclosing most processes and ventilating the
enclosures with dust extraction equipment or controlling the speed of
mining equipment (e.g., longwall shearers, conveyors, dump truck
emptying) and process equipment (e.g., crushers, mills) to reduce
turbulence that increases dust concentrations in air. Additionally,
where compatible with the material, exposure levels can be reduced by
increased wetting to constantly maintain the material, equipment, and
mine facility surfaces damp through added water sprays and frequent
housekeeping (i.e., hosing down surfaces as often as necessary). In
addition, vacuuming will minimize the amount of dust that becomes
airborne and prevent dust that does settle on a surface from being
resuspended in air.
Mines that only occasionally work with higher-silica-content
materials may not be equipped with the controls required to achieve the
proposed action level of 25 [mu]g/m\3\, or they may not currently have
procedures to ensure miners are protected when they do work with these
materials. Examples of these activities include cutting roof or floor
rock with a continuous mining machine in underground coal mines;
packaging operations that involve materials from an unfamiliar
supplier, including another mine; and rebuilding or repairing kilns. To
address these activities, under the proposed rule, mine operators would
have to add engineering controls to address any foreseeable respirable
crystalline silica overexposures. Examples of additional controls
include pre-testing batches of new raw materials; improving hazard
communication when batches of incoming raw materials contain higher
concentrations of crystalline silica, and
[[Page 44933]]
augmenting enclosure and ventilation (e.g., adding ventilation to all
crushing and screening equipment, increasing mine facility ventilation
to 30 air changes per hour, and fully enclosing and ventilating all
conveyor transfer locations). NIOSH (2019b, 2021a) describes all of the
dust control methods described in this section, which are already used
in mines, although to a less rigorous extent than would be necessary to
reliably achieve exposure levels of 25 [mu]g/m\3\ or lower for all
miners.
MSHA preliminarily finds that the proposed action level of 25
[mu]g/m\3\ is technologically feasible for most mines. This finding is
based on the exposure profiles, presented in Table VIII-2 and Table
VIII-3 for MNM mines, and Table VIII-4 and VIII-5 for coal mines, which
shows that within each commodity category, the exposure levels are at
or below 25 [mu]g/m\3\ for at least half of the miners sampled. MSHA's
finding is also based on the extensive control options documented by
NIOSH, which can be used in combinations to achieve additional control
of respirable crystalline silica. Although most mines would need to
adopt and rigorously implement a number of the control options
mentioned in this section, the technology exists to achieve this level
and is already in use in mines.
C. Technological Feasibility of Respiratory Protection (Within Proposed
Part 60)
Under the proposed rule, respiratory protection would only be
allowed for temporary, non-routine use. MSHA has preliminarily
determined that it is technologically feasible to limit respirator use
to temporary, non-routine activities based on the Agency's knowledge of
and experience with the mining industry, evidence presented by NIOSH
(2019b, 2020a), and Tables VIII-2 through VIII-5 (exposure profiles for
MNM and coal mines). These tables indicate that the proposed PEL (50
[mu]g/m\3\) has already been achieved for approximately 82 percent of
the MNM miners and approximately 93 percent of the coal miners sampled
by MSHA.
Proposed Sec. 60.14(b) requires that any miner unable to wear a
respirator must receive a temporary job transfer to an area or to an
occupation at the same mine where respiratory protection is not
required. The proposed paragraph would also require that an affected
miner continue to receive compensation at no less than the regular rate
of pay in the occupation held by that miner immediately prior to the
transfer. MNM mine operations have complied with the job transfer
provisions under the existing standard in Sec. 57.5060(d)(7) that
states miners unable to wear a respirator must be transferred to work
in an existing position in an area of the mine where respiratory
protection is not required. Proposed Sec. 60.14(b) is similar to these
existing requirements. MSHA anticipates that mine operators would have
a similar experience implementing the job transfer provisions of
proposed Sec. 60.14(b). Therefore, MSHA preliminarily finds that the
proposed requirement in Sec. 60.14(b) is technologically feasible.
For miners who would need to wear respiratory protection on a
temporary and non-routine basis, proposed Sec. 60.14(c)(1) would
require the mine operator to provide NIOSH-approved atmosphere-
supplying respirators or NIOSH-approved air-purifying respirators
equipped with high-efficiency particulate filters in one of the
following NIOSH classifications under 42 CFR part 84: 100 series or
High Efficiency (HE). As previously discussed, MSHA preliminarily finds
that particulate respirators meeting these criteria would offer the
best filtration efficiency (99.97 percent) and protection for miners
exposed to respirable crystalline silica and are widely available and
used by most industries. This finding is based on the suitability of
the three particulate classifications for respirable size particle
filtration and the broad commercial availability of these NIOSH-
approved particulate respirators.\58\ NIOSH publishes a list of
approved respirator models along with manufacturer/supplier
information. In November 2022, the NIOSH-approved list contained 221
records on atmosphere-supplying respirator models, 160 records on
elastomeric respirators with P-100 classification, and 23 records on
filtering facepiece respirators with P-100 classification (NIOSH, 2022
list P-100 elastomeric, P-100 filtering facepiece, and atmosphere-
supplying respirator models).\59\ Based on this information, MSHA
preliminarily finds that proposed Sec. 60.14(c)(1) is technologically
feasible.
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\58\ Class 100 particulate respirators (currently the most
widely used respirator filter specification in the U.S.) are
available from numerous sources including respirator manufacturers,
online safety supply companies, mine equipment suppliers, and local
retail hardware stores.
\59\ The NIOSH list of approved models does not guarantee that
each model is currently manufactured. However, the list does not
include obsolete models, and the more popular models are widely
available, including in bulk quantities.
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Proposed Sec. 60.14(c)(2) would incorporate the ASTM F3387-19
``Standard Practice for Respiratory Protection'' to ensure that the
most current and protective respiratory protection practices would be
implemented by operators who temporarily use respiratory protection to
control miners' exposures to respirable crystalline silica. The Agency
is also incorporating this respiratory protection consensus standard
under Sec. Sec. 56.5005, 57.5005, and 72.710. This proposed update is
also addressed in the next section (see Technological feasibility of
updated respiratory protection standards). Based on the information
contained in that section, MSHA preliminarily finds that the proposed
Sec. 60.14(c)(2) is technologically feasible.
Based on information contained in this section, MSHA preliminarily
finds that proposed Sec. 60.14 is technologically feasible.
D. Technological Feasibility of Updated Respiratory Protection
Standards (Amendments to 30 CFR Parts 56, 57, and 72)
1. Incorporation by Reference
Respirators are commonly used by miners as a means of protection
against a multitude of respiratory hazards, including particulates,
gases, and vapors. Respirators are needed in immediately life-
threatening (i.e., IDLH) situations as well as operations where
engineering controls and administrative controls do not provide
sufficient protection against respiratory hazards. Where respirators
are used, they must seal and isolate the miner's respiratory system
from the contaminated environment. The risk that a miner will
experience an adverse health effect from a contaminant when relying on
respiratory protection is a function of the toxicity or hazardous
nature of the air contaminants present, the concentrations of the
contaminants in the air, the duration of exposure, and the degree of
protection provided by the respirator. When respirators fail to provide
the proper protection, there is an increased risk of adverse health
effects. Therefore, it is critical that respirators perform as they are
designed.
Accordingly, MSHA is proposing to incorporate by reference ASTM
F3387-19 under 30 CFR 56.5005, 30 CFR 57.5005, and 30 CFR 72.710. With
this action, the Agency intends to assist mine operators in developing
effective respiratory protection practices and programs that meet
current industry standards. This proposed revision would better protect
miners who temporarily wear respiratory protection.
The American National Standards Practices for Respiratory
Protection ANSI Z88.2-1969 is currently incorporated by reference in 30
CFR 56.5005, 30 CFR 57.5005, and 30 CFR
[[Page 44934]]
72.710.\60\ Since MSHA issued these standards, respirator technology
and knowledge on respirator protection have advanced and as a result,
changes in respiratory protection standard practices have occurred.
ASTM F3387-19 is based on the most recent consensus standard and
provides more comprehensive and detailed guidance. MSHA believes that
most mines that use respiratory protection are already following
current respiratory protection practices and standards such as ANSI/
ASSE Z88.2--2015 ``Practices for Respiratory Protection'' standard, its
similar ASTM replacement (the F3387-19 standard), or OSHA 29 CFR
1910.134--Respiratory protection. ASTM F3387-19 standard practices are
substantially similar to the standard practices included in ANSI/ASSE
Z88.2-2015 or OSHA's respiratory standards.
---------------------------------------------------------------------------
\60\ ASTM 3387-19 is the revised version of ANSI/ASSE Z88.2-
2015. In 2017, the Z88 respirator standards were transferred from
ANSI/ASSE to ASTM International (source: F3387-19, Appendix XI).
---------------------------------------------------------------------------
2. Availability of Respirators
The updated respiratory protection standard reflects current
practice at many mines that currently use respiratory protection and
does not require the use of new technology. Thus, MSHA preliminarily
finds that the proposed update is technologically feasible for affected
mines of all sizes.
3. Respiratory Protection Practices
By incorporating the updated respiratory protection consensus
standard (ASTM F3387-19), MSHA intends that mine operators would
develop effective respiratory protection practices that meet the
updated consensus standard and that would better protect miners from
respirable hazards not yet controlled by other methods.
MSHA presumes that most mines with respiratory protection programs,
and particularly those MNM mines that have operations under both MSHA
and OSHA jurisdiction, are already following either the ANSI/ASSE
Z88.2--2015 standard, the ASTM F3387-19 standard, or OSHA 1910.134. The
respiratory protection program elements under ASTM F3387-19 are largely
similar to those in the existing standard.
MSHA expects that some operators may need to adjust their current
respiratory protection practices and standard operating procedures to
reflect ASTM F3387-19 standard practices. Examples of adjustments
include formalizing fit testing and respirator training annually;
updating the training qualifications of respirator trainers, managers,
supervisors, and others responsible for the respiratory protection
program; reviewing the information exchanged with the physician or
other licensed health care professional (PLHCP); and formalizing
internal and external respiratory protection program reviews or audits.
Overall, MSHA preliminarily finds that the proposed amendments to
existing parts 56, 57, and 72 are technologically feasible because the
requirements of ASTM F3378-19 are already implemented at some mines.
E. Technological Feasibility of Medical Surveillance (Within Proposed
Part 60)
Under the proposed rule, mine operators would be required to
provide periodic medical examinations for each MNM miner, at no cost to
the miner. The proposed medical surveillance standards would extend to
MNM miners similar protections available to coal miners under 30 CFR
72.100. The requirements in proposed Sec. 60.15 are consistent with
the Mine Act's mandate to provide maximum health protection for miners.
Under the proposed standards, MNM miners new to the mining industry
would receive an initial examination, within 30 days. If they are not
new to mining, they are categorized as belonging to a group of workers
who are eligible for an examination every 5 years. Workers who are new
to mining, after they have their initial examination, would be provided
another follow-up examination within 3 years. If the 3-year follow-up
examination indicates any medical concerns associated with chest X-ray
findings or decreased lung function, these miners are eligible to have
another follow-up exam in 2 years. After this additional 2-year follow-
up exam, or if the 3-year follow-up examination indicates no medical
concerns associated with chest X-ray findings or decreased lung
function, these miners will enter the category of miners eligible for
periodic 5-year exams.
MSHA is proposing that medical examinations would be performed by a
PLHCP or specialist. A medical examination would include a review of
the miner's medical and work history and physical examination. The
medical and work history would cover a miner's present and past work
exposures, illnesses, and any symptoms indicating respirable
crystalline silica-related diseases and compromised lung function. The
medical examination would include a chest X-ray. The required chest X-
ray would be required to be classified by a NIOSH-certified B Reader,
in accordance with the Guidelines for the Use of the International
Labour Office (ILO) International Classification of Radiographs of
Pneumoconioses. The ILO recently made additional standard digital
radiographic images available and has published guidelines on the
classification of digital radiographic images (ILO 2022). These
guidelines provide standard practices for detecting changes of
pneumoconiosis, including silicosis, in chest X-rays. The proposed rule
would also require spirometry test be part of the medical examination.
MSHA has preliminarily determined that it is technologically
feasible for MNM mine operators to provide periodic examinations. The
procedures required for initial and periodic medical examination are
commonly conducted in the general population (i.e., medical history,
physical examination, chest X-ray, spirometry test) by a wide range of
practitioners with varying medical backgrounds. Because the proposed
medical examinations consist of procedures conducted in the general
population and because MSHA would be giving MNM mine operators maximum
flexibility in selecting a PLHCP who would be able to offer these
services, MSHA anticipates that operators would not experience
difficulty in finding PLHCPs who are licensed to provide these
services.
In addition, in the case of classifying chest X-rays, MSHA has
preliminarily determined that the availability of digital X-ray
technology allows for electronic submission to remotely located B
Readers for interpretation; therefore, MSHA anticipates that the
limited number of B Readers in certain geographic locations would not
be an obstacle for MNM operators. Overall, MSHA preliminarily finds
that the proposed medical surveillance provisions are technologically
feasible.
F. Conclusions
Based on MSHA's technological feasibility analysis, MSHA has
determined that all elements of the proposed rule on Lowering Miners'
Exposure to Respirable Crystalline Silica and Improving Respiratory
Protection are technologically feasible.
IX. Summary of Preliminary Regulatory Impact Analysis and Regulatory
Alternatives
A. Introduction
Executive Orders (E.O.s) 12866 and 13563 direct agencies to assess
all costs and benefits of available regulatory alternatives and, if
regulation is
[[Page 44935]]
necessary, to select regulatory approaches that maximize net benefits
(including potential economic, environmental, public health and safety
effects, distributive impacts, and equity). E.O. 13563 emphasizes the
importance of quantifying both costs and benefits, of reducing costs,
of harmonizing rules, and of promoting flexibility. E.O.s 12866 and
13563 require that regulatory agencies assess both the costs and
benefits of regulations.
A regulatory action is considered ``significant'' if it is likely
to ``have an annual effect on the economy of $200 million or more . .
.'' under E.O. 12866 Section 3(f)(1), as amended by E.O. 14094. The
proposed rule ``Lowering Miners' Exposure to Respirable Crystalline
Silica and Improving Respiratory Protection'' is a significant rule. To
comply with E.O.s 12866 and 13563, MSHA has prepared a standalone PRIA
for this proposed rule. A summary of the PRIA is presented below. The
standalone PRIA contains detailed supporting data and explanation for
the summary materials presented here, including the mining industry,
costs and benefits, and economic feasibility. The standalone PRIA can
be accessed electronically at https://www.msha.gov and has been placed
in the rulemaking docket at www.regulations.gov, docket number MSHA-
2023-0001. MSHA requests comments on all estimates of costs and
benefits presented in this PRIA and on the data, assumptions, and
methodologies the Agency used to develop the cost and benefit
estimates.
B. Miners and Mining Industry
The proposed rule would affect mine operators and miners. This
section provides information on the structure of the Metal/Nonmetal
(MNM) and coal mining industries, including the revenue, number,
employment by commodity and size; economic characteristics of MNM and
coal mines; and the respirable crystalline silica exposure profiles for
miners across different occupations in the MNM and coal industry. The
data come from the U.S. Department of the Interior (DOI), U.S.
Geological Survey (USGS); U.S. Department of Labor (DOL), Mine Safety
and Health Administration (MSHA), Educational Policy and Development
and Program Evaluation and Information Resources; the Statistics of US
Businesses (SUSB); and the Energy Information Administration (EIA).
1. Structure of the Mining Industry
The mining industry can be divided into two major sectors based on
commodity: (1) Metal/Nonmetal mines (hereafter referred to as MNM
mines) and (2) coal mines with further distinction made regarding type
of operation (e.g., underground coal mines or surface coal mines). The
MNM mining sector is made up of metal mines (copper, iron ore, gold,
silver, etc.) and nonmetal mines. Nonmetal mines can be categorized
into four commodity groups: (1) nonmetal (mineral) materials such as
clays, potash, soda ash, salt, talc, and pyrophyllite; (2) sand and
gravel, including industrial sand; (3) stone including granite,
limestone, dolomite, sandstone, slate, and marble; and (4) crushed
limestone.
MSHA categorizes mines by size based on employment. For purposes of
this industry profile, MSHA has categorized mines into the following
four groups for analytical purposes \61\--mines that employ: (1) 1-20
miners (Emp <=20); (2) 21 to 100 miners (20< Emp <=100); (3) 101 to 500
miners (100< Emp <=500); and (4) 501 or more miners (500< Emp).
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\61\ Miner employment is based on the information submitted
quarterly through the MSHA Form 7000-2, excluding Subunit 99--Office
(professional and clerical employees at the mine or plant working in
an office); https://www.msha.gov/sites/default/files/Support_Resources/Forms/7000-2_0.pdf.
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MSHA tracks mine characteristics and maintains a database
containing the number of mines by commodity and size, number of
employees, and employee hours worked. MSHA also collects data on the
number of mining contractors, their employees, and employee hours.
While contractors are issued a unique MSHA contractor identification
number, they may work at any mine.
Table IX-1 presents an overview of the mining industry, including
the number of MNM and coal mines, their employment, excluding
contractors, and revenues by commodity and size. All data are current
in reference to the year 2019. In 2019, the MNM mining sector of 11,525
mines employed 169,070 individuals, of which 150,928 were miners and
18,142 were office workers. There were 1,106 coal mines that reported
production and that employed 52,966 individuals, of which 51,573 were
miners and 1,393 were office workers.
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a. Metal Mining
There are 24 groups of metal commodities mined in the U.S. Metal
mines, which represent about 2.4 percent (280 out of 11,525) of all MNM
mines and employ roughly 24.5 percent of all MNM miners. Of these 280
mines, 157 employ 20 or fewer miners and 22 employ greater than 500
miners. Additionally, the 2019 MSHA data show that there are a total of
13,792 contract miners in the metal mining industry.
b. Non-Metal (Mineral) Mining
Thirty-five non-metal commodities are mined in the U.S., not
including stone, and sand and gravel. Non-metal mines represent about
7.8 percent of all MNM mines and employ roughly 15 percent of all MNM
miners. The majority of non-metal mines (71.9 percent) employ fewer
than 20 miners and less than 1 percent employ more than 500 employees.
In 2019, there were 11,346 contract miners in the non-metal mining
industry.
c. Stone Mining
The stone mining subsector includes eight different stone
commodities. Seven of the eight are further classified as either
dimension stone or crushed and broken stone. Stone mines make up 20.9
percent of all MNM mines and employ 23.4 percent of all MNM miners. The
majority of these mines (83.1 percent) employ less than 20 miners. In
2019, there were 18,559 contract miners in the stone mining industry.
[[Page 44937]]
d. Crushed Limestone
Crushed limestone mines make up 16.2 percent of all MNM mines and
employ about the same percentage (16.0 percent) of all MNM miners. Of
the 1,862 crushed limestone mines, 83.5 percent employ fewer than 20
miners, and there are no crushed limestone mines that employ over 500
miners. In 2019, there were 9,605 contract miners in the crushed
limestone mining industry.
e. Sand and Gravel Mining
Sand and gravel mines account for 52.7 percent of all MNM mines and
employ 21.1 percent of all MNM miners. Nearly all (96.7 percent) of
these mines employ fewer than 20 employees. In 2019, MSHA data show
that there were 7,512 contract miners in the sand and gravel mining
industry.
f. Coal
In the coal sector, 707 mines (63.9 percent) employed fewer than 20
miners. Overall, coal mine employment in 2019 was 52,966, of which
51,573 were miners and the remaining 1,393 were office workers.
Additionally, there were a total of 22,003 contract miners in the coal
mining industry in 2019.
2. Economic Characteristics of the Metal/Non-Metal Mining Industry
The value of all MNM mining output in 2019 was estimated at $83.8
billion (U.S. Department of Interior, 2019). Metal mines, which include
iron, gold, copper, silver, nickel, lead, zinc, uranium, radium, and
vanadium mines, contributed $26.9 billion. In the USGS Mineral
Commodity Summaries, nonmetals, stone, sand and gravel, and crushed
limestone are combined in to one commodity group called industrial
minerals. MSHA estimated the production value of each individual
commodity by applying the proportion of revenues represented by each
among all commodities in the SUSB and applying that proportion to the
2019 production value for all industrial minerals reported by USGS.
This approach yielded the following estimates: metal production was
valued at $26.9 billion, non-metal production at $22.3 billion, stone
mining at $12.85 billion, sand and gravel at $9.0 billion, and crushed
limestone at $12.7 billion.
Production in the U.S. coal sector amounted to 706.1 million tons
in 2019.\62\ To estimate coal revenues in 2019, MSHA combined
production estimates with prices per ton. Mine production data was
taken from MSHA quarterly data and the coal price per ton was taken
from the 2019 EIA Annual Coal Report. As shown in Table IX-1, total
coal revenues in 2019 equaled $25.6 billion.
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\62\ Source: MSHA MSIS Data (reported on MSHA Form 7000-2).
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The U.S. coal mining sector produces three major types of coal:
bituminous, lignite, and anthracite. According to MSHA data, bituminous
operations account for approximately 92.1 percent of total coal
production in short tons, and 91.9 percent of all coal miners. Lignite
operations account for roughly 7.5 percent of total coal production and
6.2 percent of coal miners. Anthracite operations account for 0.4
percent of coal production and 1.9 percent of coal miners.
C. Cost-Benefit Analysis
The PRIA is based on MSHA's Preliminary Risk Analysis and the
Technological Feasibility analysis. The PRIA presents estimated
benefits and costs of the proposed rule for informational purposes
only. Under the Mine Act, MSHA is not required to use estimated net
benefits as the basis for its decision. MSHA requests comments on the
methodologies, baseline, assumptions, and estimates presented in the
PRIA and also asks for any data or quantitative information that may be
useful in evaluating the estimated costs and benefits associated with
the proposed rule. The PRIA assesses the costs and benefits in the MNM
and coal industries of reducing miners' exposures to silica to 50
[mu]g/m\3\ for a full shift, calculated as an 8-hour time weighted
average (TWA) and of complying with the standard's ancillary
requirements. The PRIA also assesses the costs and benefits from
requiring medical surveillance of MNM miners. It also assesses the
costs and benefits from revising the existing respiratory protection
standards. MSHA is proposing to incorporate by reference ASTM F3387-19,
``Standard Practice for Respiratory Protection'' (ASTM F3387-19). ASTM
F3387-19 would replace the 1969 American National Standards Institute
(ANSI) ``Practices for Respiratory Protection.''
MSHA estimates the proposed rule would have an annualized cost of
$57.6 million in 2021 dollars at a real discount rate of 3 percent. Of
this cost, over 55 percent is attributable to exposure monitoring; 30
percent to medical surveillance; 10 percent to engineering, improved
maintenance and repair, and administrative controls; 2.4 percent
related to the selection, use, and maintenance of approved respirators
in accordance with ASTM F3387-19, respiratory protection practices; and
1.8 percent to additional respiratory protection (e.g., when miners
need temporary respiratory protection from exposure at the proposed PEL
when it would not have been necessary at the existing PEL). MSHA
further estimates that the MNM sector will incur $52.7 million (91
percent), and the coal sector will incur $4.9 million (9 percent) in
annualized compliance costs (see Table IX-2).
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[[Page 44938]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.033
In its analysis, MSHA annualizes all costs using 3 percent and 7
percent discount rates as recommended by OMB. MSHA bases the
annualization periods for expenditures on equipment life cycles and
primarily uses a 10-year annualization period for one-time costs and
20-year for medical surveillance. However, MSHA annualizes the benefits
of the proposed rule over a 60-year period to reflect the time needed
for benefits to reach the steady-state values projected in MSHA's PRA.
Therefore, MSHA's complete analysis of this rule is 60 years (which
corresponds to 45 years of working life and 15 years of retirement for
the current miner population). MSHA holds the employment and production
constant over this period for purposes of the analysis.\63\
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\63\ This modeling strategy implicitly assumes that the ten-year
cost annualization repeats five more times to cover the same 60-year
analytic period as the benefits model. Thus, one-time costs incurred
in the first year implicitly repeat in years 11, 21, 31, 41 and 51.
This may introduce a tendency toward overestimation of compliance
costs.
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For both MNM and coal mines, the estimated costs to comply with the
proposed PEL (50 [mu]g/m\3\), assumes that all mines are compliant with
the existing PEL of 100 [mu]g/m\3\ for MNM mines (for a full shift,
calculated as an 8-hour TWA) and 85.7 [mu]g/m\3\ for coal mines (for a
full shift, calculated as an 8-hour TWA).
MSHA estimates that:
[ssquf] The proposed respirable crystalline silica rule will result
in a total of 799 lifetime avoided deaths (63 in coal and 736 in MNM
mines) and 2,809 lifetime avoided morbidity cases (244 in coal and
2,566 in MNM mines) once it is fully effective (i.e., beginning 60
years post rule promulgation through year 120 such that all miners,
working and retired, have been exposed only under the proposed PEL)
(see Table IX-3).
[ssquf] Over the first 60 years, annual cases avoided will increase
gradually to the steady-state values (i.e., long-run per-year
averages). Upon reaching the steady-state values, annual cases avoided
will be constant from year 60 onward because all miner cohorts will
have identical lifetime risks. From Table IX-4, in the first 60 years,
the proposed rule would result in a total of 410 avoided deaths (377 in
MNM and 33 in Coal) and 1,420 avoided morbidity cases (1,298 in MNM and
122 in Coal), which are the benefits MSHA monetized in its benefits
analysis.
[ssquf] The total benefits of the proposed respirable crystalline
silica rule from these avoided deaths and morbidity cases are $175.7
million per year in 2021 dollars.
--The majority (60.7 percent) of these benefits ($108.0 million) are
attributable to avoided mortality due to non-malignant respiratory
disease (NMRD) ($52.8 million), silicosis ($28.1 million), and end-
stage renal disease (ESRD) ($19.9 million), and lung cancer ($7.2
million).
--Benefits from avoided morbidity due to silicosis are $53.2 million
per year: $48.7 million for MNM mines and $4.6 million for coal mines
(see Table IX-5).
--Benefits from avoided morbidity that precedes fatal cases associated
with NMRD, silicosis, renal disease, and lung cancer, are $14.5
million: $13.3 million for MNM mines and $1.2 million for coal mines
(see Table IX-5).
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[GRAPHIC] [TIFF OMITTED] TP13JY23.035
[[Page 44940]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.036
MSHA acknowledges that its benefit estimates are influenced by the
underlying assumptions and that the long-time frame of this analysis
(first 60 years) is a source of uncertainty. The main assumptions
underlying these estimates of avoided mortality and morbidity include
the following:
[ssquf] Employment and production are held constant over the 60
years--the analysis period of the proposed rule.\64\
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\64\ MSHA recognizes that it is impossible to predict economic
factors over such a long period. Given known information and
forecast limitations, MSHA believes this is a reasonable assumption.
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[ssquf] Any miners currently exposed above the existing PELs are
exposed to levels of respirable crystalline silica at existing
standards (100 [mu]g/m\3\ for a full-shift exposure, calculated as an
8-hour TWA at MNM mines and 85.7 [mu]g/m\3\ for a full-shift exposure,
calculated as an 8-hour TWA at coal mines).
[ssquf] The proposed rule will result in miners being exposed at or
below the proposed PEL (50 [mu]g/m\3\).
[ssquf] Miners have identical employment and hence exposure tenures
(45 years). The assumptions inherent in developing the exposure-
response functions for the modeled health outcomes are reasonable
throughout the exposure ranges relevant to this benefits analysis. In
the final rule, the agency plans to augment the Regulatory Impact
Analysis, for informational purposes, so as to incorporate different
durations of working life based on exposure information, while
continuing to also present calculations based on a 45-year working life
assumption.
In addition to the above quantified health benefits of the lower
PEL, MSHA projects that there would be additional benefits from
requiring approved respirators be selected, used, and maintained in
accordance with the requirements, as applicable, of ASTM F3387-19. The
ASTM standard reflects developments in respiratory protection since
MSHA issued its existing standards. These developments include OSHA's
research and rulemaking on respiratory protection. Under the proposed
rule, MSHA would require operators' respiratory protection plans to
include minimally acceptable respiratory program elements: program
administration; standard operating procedures (SOPs); medical
evaluation; respirator selection; training; fit testing; and
maintenance, inspection, and storage. Given the uncertainty about the
current state of operator respiratory protection practices, MSHA did
not quantify the benefits that would be realized by requiring approved
respirators to be selected, used, and maintained in accordance with
ASTM F3387-19.
MSHA believes the proposed rule would lower exposures to respirable
crystalline silica and respirable coal mine dust. The available
exposure-response models do not account for separate health effects
from exposure to mixed dust that contains both respirable crystalline
silica and coal mine dust. However, MSHA anticipates that there would
be additional unquantified benefits provided by the proposed rule--
reduced adverse health outcomes attributable to respirable coal mine
dust exposure, such as CWP.\65\ The proposed rule does quantify the
benefits of avoided deaths and illnesses from reducing coal miners'
exposures to respirable crystalline silica. Among coal miners, MSHA
estimates 35 lifetime avoided deaths and illnesses from NMRD (see Table
IX-3).
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\65\ The following references document miner exposures that
could be simultaneously below the PEL for RCMD but exceed the PEL
for silica: Rahimi, E., Shekarian, Y., Shekarian, N. et al.
Investigation of respirable coal mine dust (RCMD) and respirable
crystalline silica (RCS) in the U.S. underground and surface coal
mines. Sci Rep 13, 1767 (2023). https://doi.org/10.1038/s41598-022-24745-x.
Doney BC, Blackley D, Hale JM, Halldin C, Kurth L, Syamlal G,
Laney AS. Respirable coal mine dust in underground mines, United
States, 1982-2017. Am J Ind Med. 2019 Jun;62(6):478-485. doi:
10.1002/ajim.22974. Epub 2019 Apr 29. PMID: 31033017; PMCID:
PMC6800046.
Doney BC, Blackley D, Hale JM, Halldin C, Kurth L, Syamlal G,
Laney AS. Respirable coal mine dust at surface mines, United States,
1982-2017. Am J Ind Med. 2020 Mar;63(3):232-239. doi: 10.1002/
ajim.23074. Epub 2019 Dec 9. PMID: 31820465; PMCID: PMC7814307.
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Finally, MSHA also expects that the proposed rule's medical
surveillance provisions would reduce mortality and morbidity from
respirable crystalline silica exposure among MNM miners. The initial
mandatory examination that assesses a new miner's baseline pulmonary
status, coupled with periodic examinations, would assist in the early
detection of respirable crystalline silica related illnesses. Early
detection of illness often leads to early intervention and treatment,
which may slow disease progression and/or
[[Page 44941]]
improve health outcomes. However, as noted, MSHA lacks data to quantify
these additional benefits.
The net benefits of the proposed rule are the differences between
the estimated benefits and costs. Table IX-6 shows estimated net
benefits using alternative discount rates of 0, 3, and 7 percent for
benefits and costs. As is observed from the table, the choice of
discount rate has a significant effect on annualized costs, benefits,
and hence net benefits. While the net benefits of the proposed
respirable crystalline silica rule vary considerably depending on the
choice of discount rate used to annualize costs and benefits, total
benefits exceed total costs under each discount rate considered. MSHA's
estimate of the net annualized benefits of the proposed rule, using a
uniform discount rate for both costs and benefits of 3 percent, is
$118.2 million a year with the largest share ($108.8 million; 92.0
percent) attributable to the MNM sector.
[GRAPHIC] [TIFF OMITTED] TP13JY23.037
D. Economic Feasibility
To establish economic feasibility, MSHA uses a revenue screening
test--whether the yearly costs of a rule are less than 1 percent of
revenues, or are negative (i.e., provide net cost savings)--to
presumptively establish that compliance with the regulation is
economically feasible for the mining industry. The resulting ratio of
annualized compliance costs to revenues from the screener analysis
should be interpreted with care. If annualized compliance costs
comprise less than 1 percent of revenue, the Department of Labor
presumes that the affected entities can incur the compliance costs
without significant economic impacts.
For the MNM and coal mining sectors, MSHA estimates the projected
impacts of the rule by calculating the average annualized compliance
costs for each sector as a percentage of total revenues. To be
consistent with costs that are calculated in 2021 dollars, MSHA first
inflated mine revenues expressed in 2019 to their 2021 equivalent using
the GDP Implicit Price Deflator. Due to inflation, the nominal value of
a dollar in 2021 is estimated to be about 5.4 percent higher than in
2019.
[[Page 44942]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.038
Table IX-8 presents the projected impacts of the proposed rule. The
table compares aggregate annualized compliance costs for MNM and coal
sectors at a 0 percent, 3 percent, and 7 percent real discount rate to
total annual revenues. At a 3 percent real discount rate, total
aggregate annualized compliance costs are projected to be $57.6 million
(including both 30 CFR part 60 and 2019 ASTM Upgrade Costs), while
aggregate revenues are estimated to be $115.3 billion in 2021 dollars.
Thus, the mining industry is expected to incur compliance costs that
comprise 0.05 percent of total revenues.
For the MNM sector, MSHA estimates that the annualized costs of the
proposed rule (including ASTM update costs) would be $52.7 million at 3
percent discount rate, which is approximately 0.06 percent of total
annual revenue of $88.3 billion ($52.7 million/$88.3 billion) for MNM
mine operators. For the coal sector, MSHA estimates that the annualized
cost of the proposed rule would also be $4.9 million at 3 percent,
which is approximately 0.02 percent of total annual revenue of $27.0
billion ($4.9 million/$27.0 billion) for coal mine operators.
The ratios of screening analysis are well below the 1.0 percent
threshold, and therefore, MSHA has concluded that the requirements of
the proposed rule are economically feasible, and no sector of the
industry will likely incur significant costs.
[GRAPHIC] [TIFF OMITTED] TP13JY23.039
E. Regulatory Alternatives
The proposed rule presents a comprehensive approach for lowering
miners' exposure to respirable crystalline silica. The proposal
includes the following regulatory provisions: lowering miners'
respirable crystalline silica exposure to a PEL of 50 [mu]g/m\3\ for a
full-shift exposure, calculated as an 8-hour TWA; initial baseline
sampling for miners who are reasonably expected to be exposed to
respirable crystalline silica; periodic sampling for miners who are at
or above the proposed action level of 25 [mu]g/m\3\ but at or below the
proposed PEL of 50 [mu]g/m\3\; and semi-annual evaluation of changing
mining processes that would reasonably be expected to result in new or
increased exposures.
In developing the proposed rule, MSHA considered two regulatory
alternatives. Both alternatives include less stringent monitoring
provisions than the proposed monitoring provisions. One of the
alternatives also combines less stringent monitoring with a more
stringent PEL. MSHA discusses the regulatory options in the sections
below, from least expensive to most expensive. Both alternatives would
retain the respiratory protection updates and medical surveillance from
the proposed rule.
1. Regulatory Alternative #1: Changes in Sampling and Evaluation
Requirements
Under this alternative, the proposed PEL would remain unchanged at
50 [mu]g/m\3\ and the proposed action level would remain unchanged at
25 [mu]g/m\3\. Further, mine operators would conduct: (1) baseline
sampling for miners who may be exposed to respirable crystalline silica
at or above the proposed action level of 25 [mu]g/m\3\, (2) periodic
sampling twice per year for miners who are at or above the proposed
action level of 25 [mu]g/m\3\ but at or below the proposed PEL of 50
[mu]g/m\3\, and (3) annual evaluation of changing mining processes or
conditions that would reasonably be
[[Page 44943]]
expected to result in new or increased exposures.
Mine operators would be required to undertake sampling under this
regulatory alternative and would thus incur compliance costs. However,
monitoring requirements under this alternative are less stringent than
the requirements under the proposed rule because the number of miners
to be sampled for baseline sampling would be smaller than in the
proposed rule and the frequency of periodic sampling and evaluations of
changing mining processes or conditions are set at half the frequency
of the proposed monitoring requirements. Therefore, the cost of
compliance will be lower under this alternative. MSHA estimates that
annualized monitoring costs will total $17.3 million for this
alternative (at a 3 percent discount rate), compared to $32.0 million
for the proposed monitoring requirements, resulting in an estimated
$14.7 million in lower costs per year (Table IX-9).
Although this alternative does not eliminate exposure monitoring,
the requirements are minimal relative to the monitoring requirements
under the proposed rule. However, MSHA believes it is necessary for
mine operators to establish a solid baseline for any miner who is
reasonably expected to be exposed to respirable crystalline silica. In
addition, quarterly monitoring helps mine operators correlate mine
conditions to miner exposure levels and see exposure trends more
rapidly than would result from semi-annual or annual sampling. This
would enable mine operators to take measures necessary to ensure
continued compliance with the PEL. Further, more frequent monitoring
would enable mine operators to ensure the adequacy of controls at their
mines and better protect miners' health. These benefits cannot be
quantified, but they are nevertheless material benefits that increase
the likelihood of compliance.
[GRAPHIC] [TIFF OMITTED] TP13JY23.040
MSHA also believes that requiring more frequent periodic sampling
would provide mine operators with greater confidence that they are in
compliance with the proposed rule. Because of the variable nature of
miner exposures to airborne concentrations of respirable crystalline
silica, maintaining exposures below the proposed action level provides
mine operators with reasonable assurance that miners would not be
exposed to respirable crystalline silica at levels above the PEL on
days when sampling is not conducted. MSHA believes that the benefits of
the proposed sampling requirements justify the additional costs
relative to Regulatory Alternative 1.
2. Regulatory Alternative #2: Changes in Sampling and Evaluation
Requirements and the Proposed PEL
Under this regulatory alternative, the proposed PEL would be set at
25 [mu]g/m\3\; mine operators would install whatever controls are
necessary to meet this PEL; and no action level would be proposed.
Further, mine operators: (1) would not be required to conduct baseline
sampling or periodic sampling; (2) would conduct semi-annual
evaluations of changing conditions; and (3) would sample as frequently
as necessary to determine the adequacy of controls.
Mine operators would not be required to undertake baseline or
periodic sampling. However, mine operators would be required to perform
semi-annual evaluations of changing mining processes or conditions.
Further, mine operators would be required to perform post-evaluation
sampling when the operators determine as a result of the semi-annual
evaluation that miners may be exposed to respirable crystalline silica
at or above proposed PEL at 25 [mu]g/m\3\. When estimating the cost of
the proposed monitoring requirements, MSHA assumes that the number of
samples for corrective action and semi-annual evaluation are relatively
small (2.5 percent of miners) because samples from sampling to
determine the adequacy of controls and from MSHA can both be used to
meet the requirements. Since this alternative
[[Page 44944]]
does not require periodic sampling, MSHA increases samples after each
evaluation to 10 percent of miners to ensure the monitoring
requirements can be met.
This alternative also sets the proposed PEL at 25 [mu]g/m\3\. In
addition to the estimated cost of compliance with a PEL of 50 [mu]g/
m\3\, mine operators would incur additional engineering control costs
to meet a PEL of 25 [mu]g/m\3\. To estimate these additional
engineering control costs, MSHA largely uses the same methodology as
for mines affected at the proposed PEL of 50 [mu]g/m\3\.
a. Number of Mines Affected Under Regulatory Alternative 2
MSHA first estimated the number of mines expected to incur the cost
of implementing engineering controls to reach the more stringent PEL.
After excluding mines that are affected at the proposed PEL of 50
[mu]g/m\3\ (to avoid double-counting), MSHA finds that 3,477 mines
(2,991 MNM mines and 486 coal mines) operating in 2019 had at least one
sample at or above 25 [mu]g/m\3\ but below 50 [mu]g/m\3\.\66\
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\66\ About 8,053 of mines active in 2019 either did not have a
sample > 25 [mu]g/m\3\ or did not have a sample in the last 5 years.
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To this number, MSHA adds the 1,226 affected mines expected to
incur costs to reach the proposed PEL of 50 [mu]g/m\3\. Based on its
experience and knowledge, MSHA does not expect the mines that installed
engineering controls to meet the PEL of 50 [mu]g/m\3\ will also be able
to comply with a PEL of 25 [mu]g/m\3\. For example, to comply with the
proposed PEL of 50 [mu]g/m\3\, a mine might need to add the engineering
controls necessary to achieve an additional 10 air changes per hour
over that achieved by existing controls, which are costed in the
following section. However, such a mine facility would then need to add
an additional 10 air changes per hour to meet the more stringent PEL of
25 [mu]g/m\3\, which is not costed in the following section. Thus, MSHA
expects that the 1,226 affected mines will incur additional costs to
meet the PEL of 25 [mu]g/m\3\ specified under this alternative.
MSHA estimates a total of 4,703 mines will incur costs to purchase,
install, and operate engineering controls to meet the PEL of 25 [mu]g/
m\3\ under this alternative. MNM mines account for 4,087 (87 percent)
and coal mines 616 (13 percent). Further, of the estimated 4,087 MNM
mines and 616 coal mines, 1,096 MNM mines (27 percent) and 130 coal
mines (21 percent) are also estimated to incur compliance costs to
reach the proposed PEL of 50 [mu]g/m\3\.
b. Estimated Engineering Control Costs Under Regulatory Alternative 2
MSHA identified potential engineering controls that would enable
mines with respirable crystalline silica dust exposures at or above 25
[mu]g/m\3\ but below 50 [mu]g/m\3\ categories to meet the PEL of 25
[mu]g/m\3\ under consideration for this alternative. While MSHA assumes
that mine operators will base such decisions on site-specific
conditions such as mine layout and existing infrastructure, MSHA cannot
make further assumptions about the specific controls that might be
adopted and instead assumes the expected value of purchased
technologies should equal the simple average of the technologies listed
in each control category.
Where more precise information is unavailable, MSHA assumes
operating and maintenance (O&M) costs to be 35 percent of initial
capital expenditure and installation cost, when appropriate, will be
equal to the initial capital expenditure (Table IX-10). MSHA also
assumes the larger capital expenditure controls will have a 30-year
service life. MSHA welcomes public comment concerning the engineering
controls selected for this analysis and the assumptions used to
estimate installation and O&M costs for these controls.
[GRAPHIC] [TIFF OMITTED] TP13JY23.041
However, the difficulty of meeting a PEL of 25 [mu]g/m\3\ is such
that MSHA's experience suggests a single control from Table IX-10 will
not be sufficient. For example, respirable crystalline silica dust
exposure at such a stringent limit
[[Page 44945]]
as 25 [mu]g/m\3\ is likely to occur at more than one area of the mine;
in addition to increasing ventilation to a crusher/grinder, enclosing
and ventilating the conveyor belt mine would be necessary to reduce
concentrations below the limit. Similarly, increasing facility
ventilation from 20 to 30 air changes per hour may not be adequate to
meet the limit; 40 air changes per hour might be necessary. Therefore,
MSHA assumes mine operators will purchase and install at least two of
the engineering controls listed in Table IX-10. This may be a
conservative assumption.
Table IX-11 presents the average annualized engineering control
costs per mine and total annualized engineering control costs by mine
sector. Because the service life of nearly all components is expected
to be 30 years, the costs of all engineering controls are annualized
over 30 years. At a 3 percent real discount rate, the average
annualized engineering control costs are about $94,300 per mine,
resulting in an additional cost of $443.6 million if the PEL is set at
25 [mu]g/m\3\ instead of 50 [mu]g/m\3\.
[GRAPHIC] [TIFF OMITTED] TP13JY23.042
Table IX-12 summarizes the estimated annualized cost of this
alternative under consideration. At a 3 percent real discount rate,
exposure monitoring costs less than the proposed rule; however, this
lower cost is more than offset by the increased control costs
necessitated by the requirement that mines maintain respirable
crystalline silica exposure levels below 25 [mu]g/m\3\. At an estimated
annualized cost of $491.2 million, this alternative would cost nearly
eight times more than the proposed requirements.
[GRAPHIC] [TIFF OMITTED] TP13JY23.043
[[Page 44946]]
This alternative requires exposure monitoring that is more
stringent than Regulatory Alternative 1, but less stringent than the
proposed requirements. In addition, Regulatory Alternative 2 increases
miner protection by proposing to set the PEL at 25 [mu]g/m\3\,
resulting in measurable avoided mortality and other health benefits.
Table IX-13 presents the avoided morbidity and mortality cases over the
60-year regulatory analysis time horizon under this alternative. Under
this alternative, the avoided 60-year mortality is expected to be 981,
which is 2.4 times higher than the expected avoided mortality of 410
under a proposed PEL of 50 [mu]g/m\3\. The avoided 60-year morbidity
under the regulatory alternative of 25 [mu]g/m\3\ is expected to be
1,948, which is 1.4 times higher than the expected avoided 60-year
morbidity of 1,420 under the proposed PEL of 50 [mu]g/m\3\.
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Table IX-14 presents the benefits associated with this avoided
morbidity and mortality. The expected total benefits, discounted at 3
percent, are $365.5 million, which is twice the expected total benefits
of $175.7 million under the proposed PEL of 50 [mu]g/m\3\. Under this
regulatory alternative, these benefits are made up of $258.0 million
due to avoided mortality, $34.5 million due to morbidity preceding
mortality, and $73.0 million due to morbidity not preceding mortality.
However, when compared to the annualized costs, the net benefits of
this alternative are negative at both a 3 percent and 7 percent real
discount rate.
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BILLING CODE 4520-43-C
MSHA solicits further comment on the extent to which these or other
regulatory alternatives (including different ways of calculating
respirable crystalline silica concentration) may change the effects of
the proposed rule.
X. Initial Regulatory Flexibility Analysis
The Regulatory Flexibility Act (RFA) of 1980, as amended by the
Small Business Regulatory Enforcement Fairness Act (SBREFA) of 1996,
requires preparation of an Initial Regulatory Flexibility Analysis
(IRFA) for any rule that by law must be proposed for public comment,
unless the agency certifies that the rule, if promulgated, will not
have a significant economic impact on a substantial number of small
entities. 5 U.S.C. 601- 612. Because MSHA's proposed rule on respirable
crystalline silica, including the incorporation of ASTM F3387-19 by
reference, would regulate the mining industry, the proposed rule falls
within the purview of the RFA. MSHA has evaluated the impact of the
proposed rule on small entities in this IRFA. MSHA's analysis is
presented in the following.
Description of the Reasons Why MSHA is Considering Regulatory Action
Based on its review of the health effects literature, MSHA has
preliminarily determined that occupational exposure to respirable
crystalline silica causes silicosis and other diseases. Based on its
preliminary risk analysis, MSHA has also determined that under its
existing standards, miners face a risk of material impairment of health
or functional capacity from exposures to respirable crystalline silica.
Based on these preliminary determinations, MSHA proposes to amend
its existing standards to better protect miners against occupational
exposure to respirable crystalline silica, a carcinogen, and to improve
respiratory protection for all airborne contaminants. The proposed rule
would establish for mines of all sizes, a PEL of 50 [micro]g/m\3\ for a
full shift, calculated as an 8-hour TWA, for all miners, and an action
level of 25 [micro]g/m\3\ for a full-shift exposure, calculated as 8-
hour TWA. MSHA's proposal would also include other requirements to
protect miner health, such as periodic exposure sampling and corrective
actions to be taken when miners' exposures exceed the PEL. MSHA also
proposes to replace existing requirements for respiratory protection
and to incorporate by reference the ASTM F3387-19 Standard Practice for
Respiratory Protection. MSHA believes that the proposed changes would
significantly improve health protections for all miners over the course
of their working lives.
Objectives of, and Legal Basis for, the Proposed Rule
The proposed rule would fulfill MSHA's statutory obligation to
``promulgate improved mandatory health . . . standards to protect''
miners' health under the Mine Act, as amended. 30 U.S.C. 801(g). The
Mine Act requires the Secretary of Labor (Secretary) to develop and
promulgate improved mandatory health or safety standards to prevent
hazardous and unhealthy conditions and protect the health and safety of
the nation's miners. 30 U.S.C. 811(a). The Secretary must set standards
to assure, based on the best available evidence, that no miners will
suffer material impairment of health or functional capacity from
exposure to toxic materials or harmful physical agents over their
working lives. 30 U.S.C. 811(a)(6)(A). Section 103(h) of the Mine Act
gives the Secretary the authority to promulgate standards involving
recordkeeping and reporting. 30 U.S.C. 813(h). Additionally, section
508 of the Mine Act gives the Secretary the authority to issue
regulations to carry out any provision of the Mine Act. 30 U.S.C. 957.
[[Page 44948]]
Description and Estimate of the Number of Small Entities to Which the
Proposed Rule Would Apply
The proposed rule would affect MNM and coal mining operations. To
determine the number of small entities subject to the proposed rule,
MSHA reviewed the North American Industrial Classification System
(NAICS), the standard used by Federal statistical agencies in
classifying business establishments, as well as information from the
Office of Advocacy of the Small Business Administration (SBA). MSHA
used its data from the MSHA Standardized Information System (MSIS) to
identify the responsible party for each mine. MSHA then combined that
information with the size classification information.
First, MSHA determined that mining operations that fall into 25
NAICS-based industry classifications may be subject to the proposed
rule. These industry categories and their accompanying six-digit NAICS
codes are shown in Table X-1.\67\
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\67\ The NAICS classifications used in this analysis are drawn
from a recent version of the NAICS (though, for reasons described
below, not the latest version, which was published in January 2022).
SBA established definitions of small entities for each of the
categories in the earlier version, which were effective in August
2019. This version of NAICS categories was needed for this analysis,
in order for MSHA to cross-tabulate (or crosswalk) its data on mines
and controllers with Bureau of Census data on revenues by NAICS
codes, where these Census data were organized by the same NAICS
codes that were in the earlier version. No comparable revenue data,
at this writing, had yet been revised to the most recent NAICS
categories, which prevented MSHA from using those categories. MSHA
identified 25 NAICS categories (in the previous system) that
accounted for all mining activities.
---------------------------------------------------------------------------
Second, MSHA matched the NAICS classifications with SBA small-
entity size standards (based on number of employees) to determine the
number of small entities within each of the respective NAICS codes. See
Table X-1.
Third, MSHA counted the number of small-entity controllers in each
NAICS code, after determining that a ``controller'' who owns and
controls a mine as the appropriate unit of this IRFA analysis (based on
SBA guidance) (Small Business Administration 2017). A controller is a
parent company owning or controlling one or more mines. A controller
can also be a firm, whereas a mine can be an establishment. Table X-1
shows the count of all controllers and a count of small-entity
controllers in each NAICS code. Some ``unique controllers'' are
included in more than one NAICS code because they own or control
multiple mines, each producing a different commodity. For this
analysis, however, MSHA single-counted these unique controllers; for
example, a controller who owns three mines in three different NAICS
codes was only counted once.
Based on this methodology, MSHA estimated that in 2021, there were
a total of 5,879 controllers, 5,007 of which were small-entity
controllers. Many controllers owned one or two mines, while some
controllers owned hundreds of mines nationwide (or worldwide). The
5,007 small-entity controllers owned a total of 8,240 mines out of
11,791 mines in operation in 2021.\68\
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\68\ The number of controllers and mines examined in this
regulatory flexibility analysis are those specifically known to
operate in 2021. The year 2021 is the most current year for which
complete information were available. Such information about
controllers as parent companies might include, for example,
knowledge of whether the parent company is a large, multinational
corporation, which has bearing on this regulatory flexibility
analysis. Because the benefit-cost analysis performed on the
proposed rule did not need this kind of detailed information about
controllers, it was able to have a broader scope to include data
from other years besides 2021, which it did. As a result, the
benefit cost analysis included a larger number of mines (and
affected mines) and controllers. The key factor for this regulatory
flexibility analysis is the estimated ratio of the regulatory cost
per revenue for controllers, as reflected by the most current data.
The estimation of this ratio is robustly addressed in MSHA's
analysis of the 5,879 controllers in 2021 (which is not impacted by
the exclusion of other years in this analyis).
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[[Page 44950]]
Description of the Projected Reporting, Recordkeeping, and Other
Compliance Requirements for Small Entities
As explained earlier, the proposed rule would establish a PEL of 50
[micro]g/m\3\ and an action level of 25 [micro]g/m\3\ for a full-shift
exposure, calculated as 8-hour TWA. The proposed rule would also
include other requirements. Examples include baseline, periodic, and
corrective action sampling, semi-annual evaluations, medical
surveillance, respiratory protection, and recordkeeping.
With regard to the paperwork burden on small entities, MSHA's
proposed rule would create new information collection requests for the
mining industry. As described in greater detail in Section XI below,
these requirements include the collection of information involving: (1)
exposure monitoring--samplings and semi-annual evaluations, (2)
corrective actions taken, (3) miners unable to wear respirators, and
(4) medical surveillance for MNM miners. Table XI-2 displays an annual
estimate of information collection burden for the whole mining
industry. Compliance costs on small entities that include recordkeeping
costs are discussed below.
Estimation of the Compliance Costs and Relative Burden to Small
Entities
MSHA estimated the average annual regulatory cost per small-entity
controller (based on a 3 percent discount rate), as well as the average
annual revenue per small-entity controller. MSHA estimated, for each
controller, the additional annual cost of the proposed regulation as a
proportion of that controller's annual revenue. The average of these
proportions (weighting controllers equally) was 0.122 percent, below a
3 percent threshold used for significant impact. That is, for every $1
million in revenue earned by a controller, the average regulatory cost
was estimated to be $1,220.
Total Compliance Cost. MSHA estimated that the proposed rule would
have an average cost of $60.23 million per year in 2021 dollars at a
real discount rate of 3 percent. The estimated costs for the proposed
rule would represent the additional costs necessary for mine operators
to achieve full compliance with the proposed rule.
Compliance Costs by Small-Entity Controllers. Because mines (as
well as controllers) vary in the scale of their operations, MSHA first
estimated additional regulatory costs on a per-miner basis. MSHA
anticipated that the additional regulatory costs per miner would vary
across the six major commodity categories: coal, metal, nonmetal,
stone, crushed limestone, and sand and gravel. MSHA analyzed employment
data linked with controller data. By combining this information with
compliance cost information, MSHA derived estimates of the regulatory
costs for small-entity controllers. MSHA then estimated the regulatory
cost for each of the 5,007 small-entity controllers identified in 2021.
See the average annual regulatory cost per controller in Table X-2.
Revenues by Small-Entity Controllers. MSHA estimated revenues for
each small-entity controller. The Agency estimated revenues per
employee, by mine, and by controller, using data published by the U.S.
Bureau of Census in their report, ``Statistics of U.S. Businesses''
(SUSB).\69\ The SUSB data provided revenue estimates for enterprises in
each NAICS code and for each ``size category'' (based on number of
employees) within each NAICS code. The enterprise data considered
controllers that had operations in more than one NAICS code. MSHA
summed the estimated revenue for the establishments within the same
NAICS code to create multiple enterprises with different NAICS codes
and compare constructed enterprises with the SUSB data to estimate the
revenue for each of these size-category-specific enterprises. This
methodology was relevant for the ``largest'' of small-entity
controllers, which controlled more than one mine, sometimes operating
in different NAICS categories. Most small-entity controllers operated
only one mine, meaning that no summation was required because only the
number of employees in a single mine needed to be counted.
---------------------------------------------------------------------------
\69\ U.S. Census Bureau, ``Statistics of U.S. Businesses,''
released May 2021. https://www.census.gov/data/tables/2017/econ/susb/2017-susb-annual.html. Data in the report were in reference to
the year 2017, which MSHA adjusted to 2021 dollars. Data on revenues
are presented in the report under the equivalent term ``receipts.''
MSHA converted the 2017 revenues to 2021 dollars using the GDP
Implicit Price Deflator published by the Bureau of Economic Analysis
October 26, 2022, Table 1.1.9 Implicit Price Deflators for Gross
Domestic Product, Series A191RD. https://apps.bea.gov/histdata/fileStructDisplay.cfm?HMI=7&DY=2022&DQ=Q3&DV=Advance&dNRD=October-28-2022. The index was 107.749 for 2017 and 118.895 for 2021,
creating an adjustment factor (from 2017 to 2021 dollars) of
118.895/107.749 or 1.103.
---------------------------------------------------------------------------
MSHA estimated revenues for each small-entity controller. Some
small-entity controllers had mines belonging to different NAICS codes.
This factor precluded MSHA from being able to precisely categorize
small-entity controllers by NAICS code. MSHA estimated each small-
entity controller's revenues.\70\
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\70\ In a small number of cases (in terms of NAICS codes and
size categories) the SUSB data were incomplete. In these cases, MSHA
imputed revenue/employee ratios based on closely related data for
comparable NAICS-size categories. MSHA then used these imputed
revenue/employee ratios to estimate the revenues of some small-
entity controllers, by the methodology just described.
---------------------------------------------------------------------------
Some of the small-entity controllers may also have operations in
non-mining industries. If so, total revenues, including those from non-
mining operations, would be higher than estimated here, and the ratios
of regulatory costs to revenues shown in the summary table may be
overestimated.
MSHA developed estimates of the number of miners for each small-
entity controller, and for each NAICS category within each controller's
activities. MSHA then combined these data with SUSB data on revenues by
NAICS category and size category to generate estimated revenues for
each small-entity controller. See the estimated average annual revenue
per controller in Table X-2.
Ratio of Compliance Cost to Revenue. From the two sets of estimates
described above--costs and revenues--for each small-entity controller,
MSHA generated estimates of the ratios of regulatory cost to revenue,
for each controller. Table X-2 shows the number of controllers, average
annual regulatory costs, average annual revenue, and average cost as a
percent of revenue.
[[Page 44951]]
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Relevant Federal Rules Which May Duplicate, Overlap, or Conflict With
the Proposed Rule
There are no Federal rules that may duplicate, overlap, or conflict
with the proposed rule.
Significant Alternatives and Their Impact on Small Entities
MSHA considered two alternatives in the proposed rule. Under
Alternative 1, the proposed PEL would remain unchanged at 50 [mu]g/m\3\
and the proposed action level would remain unchanged at 25 [mu]g/m\3\.
Further, mine operators would conduct: (1) baseline sampling for miners
who may be exposed to respirable crystalline silica at or above the
proposed action level of 25 [mu]g/m\3\, (2) periodic sampling twice per
year, and (3) annual evaluation of changing mining processes or
conditions that would reasonably be expected to result in new or
increased exposures. Under Alternative 2, the proposed PEL would be set
at 25 [mu]g/m\3\; mine operators would install whatever controls are
necessary to meet this PEL; and no action level would be proposed.
Further, mine operators would: (1) not be required to conduct baseline
sampling or periodic sampling, (2) conduct semi-annual evaluations of
changing conditions, and (3) sample as frequently as necessary to
determine the adequacy of controls. Additional detail on the two
regulatory alternatives MSHA considered can be found in IX. Summary of
Preliminary Regulatory Impact Analysis and Regulatory Alternatives and
in the standalone PRIA document.
MSHA believes the proposed rule would provide improved health
protections for miners and would be achievable for all mines. In
developing the proposed rule, MSHA has included flexibilities for
operators in the implementation of updated respiratory protection
standard, which would reduce the burden on small entities. MSHA has
made the following determinations regarding the two alternatives
considered:
Alternative 1, ``Changes in Sampling and Evaluation
Requirements,'' would reduce overall costs to the mining industry by
26.2 percent, for costs calculated at both a 3 percent and 7 percent
discount rate. These reduced costs would be proportionally experienced
by small entities. The average costs as a percent of revenues for small
entities would then be reduced (relative to the proposed rule) from
0.12 percent to 0.09 percent.
Alternative 2, ``Changes in Sampling and Evaluation
Requirements and the Proposed PEL,'' would increase overall costs to
the mining industry by 701.9 percent, for costs calculated at a 3
percent discount rate, and by 930.2 percent for costs calculated at a 7
percent discount rate. The average costs as a percent of revenues for
small entities would then rise (relative to the proposed rule) from
0.12 percent to 0.98 percent, based on a 3 percent discount rate, and
from 0.12 percent to 1.259 percent based on a 7 percent discount rate.
MSHA is seeking comments or additional information from
stakeholders on whether there are alternatives the Agency should
consider that would accomplish the objectives of this rulemaking while
reducing the impact on small entities.
Conclusion
MSHA estimated that small-entity controllers would be expected to
incur, on average, additional regulatory costs equaling approximately
0.122 percent of their revenues (or $1,220 for every $1 million in
revenues).
As required under the RFA, MSHA is complying with its obligation to
consult with the SBA's Chief Counsel for Advocacy on this proposed rule
and on this initial regulatory flexibility analysis. Consistent with
Agency's practice, notes of any meetings with the Chief Counsel for
Advocacy's office on this proposed rule, or any written communications,
will be placed in the rulemaking record.
XI. Paperwork Reduction Act
The Paperwork Reduction Act of 1995 (44 U.S.C. 3501-3521) provides
for the Federal Government's collection, use,
[[Page 44952]]
and dissemination of information. The goals of the Paperwork Reduction
Act include minimizing paperwork and reporting burdens and ensuring the
maximum possible utility from the information that is collected under 5
CFR part 1320. The Paperwork Reduction Act requires Federal agencies to
obtain approval from the Office of Management and Budget (OMB) before
requesting or requiring ``a collection of information'' from the
public.
As part of the Paperwork Reduction Act process, agencies are
generally required to provide a notice in the Federal Register
concerning each proposed collection of information to solicit, among
other things, comment on the necessity of the information collection
and its estimated burden, as required in 44 U.S.C. 3506(c)(2)(A). To
comply with this requirement, MSHA is publishing a notice of proposed
collection of information in the proposed rule titled, Lowering Miners'
Exposure to Respirable Crystalline Silica and Improving Respiratory
Protection.
This rulemaking would require the creation of a new information
collection as well as modification to the burdens for existing
collections. As required by the Paperwork Reduction Act, the Department
has submitted information collections, including a new information
collection and revisions of two existing collections, to OMB for review
to reflect new burdens and changes to existing burdens.
I. New Information Collection Under Proposed Part 60, Respirable
Crystalline Silica
Under proposed part 60 entitled ``Respirable Crystalline Silica,''
some new burdens would apply to all mine operators, and other burdens
would apply to only some mine operators. Below, the new information
collection burden that would be created by proposed part 60 is
discussed.
Proposed Sec. 60.16 lists all the recordkeeping requirements
related to proposed part 60. Each of the requirements are discussed
below:
Proposed Sec. 60.12 would require mine operators to make a record
for each sampling and each evaluation conducted pursuant to this
section. The sampling record would consist of the sample date, the
occupations sampled, and the concentrations of respirable crystalline
silica and respirable dust. The mine operator would also retain
laboratory reports on sampling results. The semi-annual evaluation
record would include the date of the evaluation and a record of the
mine operator's evaluation of any changes in mining operations that may
reasonably be expected to result in new or increased respirable
crystalline silica exposures. In addition, the mine operator would be
required to post the sampling and evaluation records and the laboratory
report on the mine bulletin board and, if applicable, by electronic
means, for the next 31 days, upon receipt. All records would be
retained for at least 2 years from the date of each sampling or
evaluation.
Proposed Sec. 60.13 would require mine operators to make a record
of corrective actions and the dates of the corrective actions. The
corrective action records would be retained for at least 2 years from
the date of each corrective action.
Proposed Sec. 60.14 would require mine operators to retain a
record of the written determination by a PLHCP that a miner who may be
required to use a respirator is unable to wear a respirator. The
written determination record would be retained for the duration of a
miner's employment plus 6 months.
Proposed Sec. 60.15 would require MNM mine operators to obtain a
written medical opinion from the PLHCP or specialist within 30 days of
a miner's medical examination. The written medical opinion would
contain the date of the medical examination, a statement that the
examination has met the requirements of this proposed section, and any
recommended limitations on the miner's use of respirators. The written
medical opinion record would be retained for the duration of a miner's
employment plus 6 months.
II. Changes to Existing Information Collections
This proposed rulemaking would result in non-substantive changes to
existing information collection packages. One change under OMB Control
Number 1219-0011 is to occur after 1219-0NEW, Respirable Crystalline
Silica Standard, is approved by OMB. The other change is the
discontinuance of the existing information collection package under OMB
Control Number 1219-0048 which is also to occur after OMB approval of
1219-0NEW, Respirable Crystalline Silica Standard.
OMB Control Number 1219-0011, Respirable Coal Mine Dust Sampling,
involves records for quarterly sampling of respirable dust in coal
mines. The supporting statement references quartz and a reduced
standard for respirable dust when quartz is present; however, there is
no specific recordkeeping requirement that is associated with those
references. Due to changes in the proposed rule, MSHA would make a non-
substantive change to the supporting statement by removing such
references. However, there would be no changes in paperwork burden and
costs in this information collection.
OMB Control Number 1219-0048, Respirator Program Records, involves
recordkeeping requirements under 30 CFR parts 56 and 57 for MNM mines
when respiratory protection is used. MSHA is proposing to update the
existing respiratory protection standard and permit mine operators to
select the requirements of the standard that are applicable to their
mines. This proposed change would eliminate the paperwork burden
associated with respiratory protection resulting in the request to
discontinue the existing information collection.
A. Solicitation of Comments
Pursuant to the Paperwork Reduction Act, MSHA has prepared and
submitted an information collection request (ICR) to OMB for the
collection of information requirements identified in this proposed rule
for OMB's review in accordance with 44 U.S.C. 3507(d). MSHA is
soliciting comments concerning the proposed information collection
related to respirable crystalline silica. MSHA is particularly
interested in comments that:
Evaluate whether the proposed collection of information is
necessary for the proper performance of the functions of the agency,
including whether the information will have practical utility;
Evaluate the accuracy of the agency's estimate of the
burden of the proposed collection of information, including the
validity of the methodology and assumptions used;
Suggest methods to enhance the quality, utility, and
clarity of the information to be collected; and
Minimize the burden of the collection of information on
those who are to respond, including through the use of appropriate
automated, electronic, mechanical, or other technological collection
techniques or other forms of information technology (e.g., permitting
electronic submission of responses).
B. Proposed Information Collection Requirements
I. Type of Review: New Collection.
OMB Control Number: 1219-0NEW.
1. Title: Respirable Crystalline Silica Standard.
2. Description of the ICR: The proposed rule on respirable
crystalline silica contains collection of information requirements that
would assist miners and mine operators in identifying exposures to
respirable crystalline silica
[[Page 44953]]
in order to track actual and potential occupational exposure and action
taken to control such exposure.
There are provisions of this proposed rule that would take effect
at different times after the implementation of this proposed rule, and
there are provisions that would have different burden hours, burden
costs, and responses each year. Therefore, MSHA shows the estimates of
burden hours, burden costs, and responses in three separate years.
3. Summary of the Collection of Information: Highlighted below are
the key assumptions, by provision, used in the burden estimates in
Table XI-1:
Proposed Sec. 60.12--Exposure Monitoring
ICR. Proposed Sec. 60.12 would require mine operators to make a
record for each baseline sampling, corrective action sampling, periodic
sampling, semi-annual evaluation, and post-evaluation sampling, as
previously described.
Number of respondents. For proposed Sec. 60.12, the respondents
would consist of all active mines because operators of active mines are
assumed to perform baseline sampling and conduct semi-annual
evaluations.
MSHA counts the number of active mines in 2019, defining an active
mine as one that had at least 520 employment hours (equivalent to 1
person working full time for a quarter) in at least one quarter of
2019. Using this definition, MSHA estimates that a total of 12,631
mines (11,525 MNM mines and 1,106 coal mines) would generate sampling
and evaluation records.
Annual number of responses. The estimated average annual number of
responses would be 142,408, including 24,439 for baseline sampling,
9,237 for sampling after corrective actions, 64,116 for periodic
sampling, 42,103 for semi-annual evaluation recording and posting, and
2,513 for post-evaluation sampling.
MSHA assumes that all the active mines (12,631 mines) would conduct
baseline sampling once in the first year. In succeeding years, about
253 new mines would conduct baseline sampling with an average of 5.6
samples per mine. The estimated number of periodic samplings is
calculated based on the following factors: the number of miners with
sampling results at or above the proposed action level (25 [mu]g/m\3\)
but at or below the PEL (50 [mu]g/m\3\), the percent of miners needed
for representative samples, and the number of quarters mines would be
in operation. In year 1, MSHA expects the sampling to begin in the
second half of the year, thereby decreasing the number of samples by
half. As a result, MSHA estimates that an annual average of 64,116
periodic samples would be conducted in the first three years.
Furthermore, MSHA assumes that all 12,631 mines would record semi-
annual evaluation results twice a year--except in year 1, when it would
be done once--and then post those results on a mine bulletin board, or
if applicable, by electronic means. MSHA estimates mines would conduct
sampling as a result of their semi-annual evaluations and an average of
four miners would be sampled, resulting in an annual average of 2,513
samples.
MSHA estimates that about 22 percent of active mines (2,771 mines
in total) would have at least one miner overexposed to respirable
crystalline silica. MSHA further estimates that the 2,771 mines that
would then conduct corrective action sampling for about four areas per
mine. In year 1, they would sample in half as many areas.
Estimated annual burden. The estimated average annual burden would
be 31,392 hours, including 6,110 hours for baseline sampling, 2,309 for
corrective action sampling, 16,029 hours for periodic sampling, 6,316
hours for semi-annual evaluation recording and posting, and 628 hours
for post-evaluation sampling. MSHA estimates that it would take 15
minutes to record the sampling results, 15 minutes to record the
results of a semi-annual evaluation, and 3 minutes to post each of the
evaluation results on the mine bulletin board, and, if applicable, by
electronic means.
Proposed Sec. 60.13--Corrective Actions
ICR. Proposed Sec. 60.13 would require mine operators to make a
record of corrective actions, as previously described.
Number of respondents. For proposed Sec. 60.13, only those mines
with at least one miner exposure above the proposed PEL are assumed to
carry out the proposed requirement. MSHA estimates that about 22
percent of active mines (2,771 mines in total) would have at least one
miner overexposed to respirable crystalline silica.
Annual number of responses. The estimated average annual number of
responses would be 14,922, including 9,237 for corrective action
records, and 5,685 for miner respirator records. MSHA estimates that
the 2,771 mines that will be required to conduct and record corrective
actions will do so for about four mine areas, except in year 1, when it
would be done in half as many mine areas. MSHA further estimates this
will affect 6,822 miners per year--except in year 1, when half as many
miners would be affected--with each miner requiring a record of the
miner being given access to a respirator until the corrective action is
taken.
Estimated annual burden. The estimated average annual burden would
be 1,054 hours, including 769.7 for corrective action records and 284.3
for miner respirator records. MSHA estimates that it takes five minutes
to record a corrective action and the date. On average, it takes three
minutes to note a miner's access to a respirator.
Proposed Sec. 60.14--Respiratory Protection
ICR. Proposed Sec. 60.14 would require mine operators to retain a
record of the determination by a PLHCP that a miner who may be required
to use a respirator is unable to wear a respirator, as previously
described.
Number of respondents. For proposed Sec. 60.14, MSHA assumes that
33 percent of mine operators would have their miners use respiratory
protection as a temporary measure and keep records of their miners'
ability to wear respirators. The number of respondents would be, on
average, 603 mines per year, with each mine assumed to have at least
some miners wearing respirators.
Annual number of responses. The estimated annual number of
responses would be 1,205, with an average of two miners for each of the
603 mines.
Estimated annual burden. The estimated annual burden would be 603
hours. MSHA assumes it takes 30 minutes to record this information for
about two miners for each of the 603 mines.
Proposed Sec. 60.15--Medical Surveillance for Mental and Nonmetal
Miners
ICR. Proposed Sec. 60.15 would require MNM mine operators to
obtain a written medical opinion from a PLHCP or specialist regarding
any recommended limitations on a miner's use of respirators, as
previously described.
Number of respondents. MSHA assumes that 75 percent of eligible MNM
miners (current MNM miners), including contract workers, would make use
of the opportunity to receive a voluntary medical exam that is paid by
their mine operator. As a result, an average of 25,175 current miners
are estimated to receive voluntary medical exams per year. This
estimate represents the upper range of the participation rate of
voluntary medical exams by miners. MSHA is using the upper end of the
range to avoid underestimating compliance costs.
MSHA further estimates that 8,392 miners in a given year, including
contract workers, would be new miners and contractors who would undergo
mandatory medical examinations.
[[Page 44954]]
MSHA estimated that the turnover of MNM miners would be 8,392 miners
per year (1/22 of the estimated total of 184,615 MNM workers with an
average number of 22 years on the job before leaving the mining
industry). The estimated total respondents per year therefore would be
33,567 (= 8,392 + 25,175).
Annual number of responses. The estimated annual number of
responses would be 33,567, including 8,392 new miners and 25,175
current miners.
Estimated annual burden. The estimated annual burden would be 8,392
hours, including 2,098 hours for new MNM miners and 6,294 hours for
current miners. MSHA estimates it takes 15 minutes to record the
medical examination results for each of the 33,567 miners.
Total Recordkeeping and Documentation Burden for Proposed Part 60
[GRAPHIC] [TIFF OMITTED] TP13JY23.048
As shown in Table XI-1, the total number of respondents is 46,198:
12,631 mines plus 33,567 miners; the estimated annual number of
responses would be 192,102; and the estimated annual burden would be
41,440 hours. These estimates are based on the conservative assumption
that 75 percent of eligible current miners would take part in medical
surveillance, which could overestimate the recordkeeping cost and
burden. The following estimates of information collection burden are
summarized in Table XI-2.
1. Affected Public: Businesses or For-Profit.
2. Estimated Number of Respondents: 47,456 respondents in the first
year; 46,198 respondents in the second year; and 44,939 respondents in
the third year.
3. Frequency: On Occasion.
4. Estimated Number of Responses: 192,990 responses in the first
year; 197,021 responses in the second year; and 186,294 responses in
the third year.
5. Estimated Number of Burden Hours: 44,678 hours in the first
year; 41,162 hours in the second year; and 38,480 hours in the third
year.
6. Estimated Hour Burden Costs: $2,843,901 in the first year;
$2,558,724 in the second year; and $2,377,996 in the third year.
7. Estimated Capital Costs to Respondents: $25,262 in each of the
three years.
[GRAPHIC] [TIFF OMITTED] TP13JY23.049
Most of the reduction in the number of responses and burden hours
from the first year to the second year is a result of baseline sampling
being carried out in all current mines in the first year
[[Page 44955]]
while only being carried out in new mines starting from the second
year.
For a detailed summary of the burden hours and related costs by
provision, see the Preliminary Regulatory Impact Analysis (PRIA)
accompanying the proposed rule. The PRIA includes the estimated costs
and assumptions for the paperwork requirements related to this proposed
rule.
C. Changes to Existing Information Collection Requirements
I. Type of review: Non-substantive change to currently approved
information collection.
OMB Control Number: 1219-0011.
1. Title: Respirable Coal Mine Dust Sampling.
2. Description of the ICR:
Background
In October 2022, MSHA received OMB approval for the reauthorization
of the Respirable Coal Mine Dust Sampling under OMB Control Number
1219-0011. This information collection request outlines the legal
authority, procedures, burden, and costs associated with recordkeeping
and reporting requirements for coal mine operators. MSHA's standards
require that coal mine operators sample respirable coal mine dust
quarterly and make records of such samples.
Summary of Changes
This non-substantive change request is to revise the supporting
statement for this information collection request due to the proposed
PEL for respirable crystalline silica for all miners in this proposed
rule. These proposed revisions would remove any reference in the
information collection request to quartz or the reduction of the
respirable dust standard due to the presence of quartz. This change
does not modify the authority, affected mine operators, or paperwork
burden.
3. Summary of the Collection of Information:
Changes in Burden
The calculated burden including respondents and responses remain
the same.
Affected Public: Businesses or For-Profit.
Estimated Number of Respondents: 676 (0 from this rulemaking).
Frequency: On occasion.
Estimated Number of Responses: 995,102 (0 from this rulemaking).
Estimated Number of Burden Hours: 58,259 (0 from this rulemaking).
Estimated Hour Burden Costs: $3,271,611 ($0 from this rulemaking).
Estimated Capital Costs to Respondents: $29,835 ($0 from this
rulemaking).
II. Type of Review: Discontinued information collection request.
OMB Control Number: 1219-0048.
1. Title: Respirator Program Records.
2. Description of the ICR:
Background
Title 30 CFR parts 56 and 57 incorporate by reference requirements
of ANSI Z88.2-1969, ``Practices for Respiratory Protection.'' Under
this standard, certain records are required to be kept in connection
with respirators. The proposed rule would incorporate by reference ASTM
F3387-19, ``Standard Practice for Respiratory Protection,'' in 30 CFR
parts 56 and 57 to replace the Agency's existing respiratory protection
standard. The proposal would require mine operators' respiratory
protection plans to include certain minimally acceptable program
elements, but beyond that, would permit mine operators to select the
requirements of ASTM F3387-19 that are applicable to their mines.
Summary of Changes
The proposed rule would remove the paperwork burden associated with
respiratory protection in the information collection request.
3. Summary of the Collection of Information:
Changes in Burden
MSHA has submitted a request to discontinue OMB Control Number
1219-0048, eliminating all paperwork burden associated with the
information collection request. It would discontinue upon the effective
date of the final rule.
Affected Public: Businesses or For-Profit.
Estimated Number of Respondents: 0 (-350 from this rulemaking).
Frequency: On occasion.
Estimated Number of Responses: 0 (-630 from this rulemaking).
Estimated Number of Burden Hours: 0 (-3,588 from this rulemaking).
Estimated Hour Burden Costs: $0 (-$284,084 from this rulemaking).
Estimated Capital Costs to Respondents: $0 (-$140,000 from this
rulemaking).
D. Submitting Comments
The information collection package for this proposal has been
submitted to OMB for review under 44 U.S.C. 3506(c) of the Paperwork
Reduction Act of 1995, as amended. Comments on the information
collection requirements should be sent to MSHA by one of the methods
previously explained in the DATES section of this preamble.
The information collection request will be available on https://www.regulations.gov. MSHA cautions the commenter against providing any
information in the submission that should not be publicly disclosed.
Full comments, including personal information provided, will be made
available on www.regulations.gov and www.reginfo.gov.
The public may also examine publicly available documents at the
Mine Safety and Health Administration, 201 12th South, Suite 4E401,
Arlington, VA 22202-5450. Sign in at the receptionist's desk on the 4th
floor via the East elevator. Before visiting MSHA in person, call 202-
693-9440 to make an appointment and determine if any special health
precautions are required in keeping with the Department of Labor's
COVID-19 policy.
Questions about the information collection requirements may be
directed to the contact person listed in the FOR FURTHER INFORMATION
CONTACT section of this preamble.
E. Docket and Inquiries
Those wishing to download comments and other materials relating to
paperwork determinations should use the procedures described in this
preamble. One may also obtain a copy of this ICR by going to https://www.reginfo.gov/public/do/PRAMain, clicking on ``Currently under
Review--Open for Public Comments'' and scrolling down to ``Department
of Labor.''
A Federal agency cannot conduct or sponsor a collection of
information unless it is approved by OMB under the Paperwork Reduction
Act and displays a currently valid OMB control number. The public is
not required to respond to a collection of information unless the
collection of information displays a currently valid OMB control
number.
XII. Other Regulatory Considerations
A. National Environmental Policy Act
The National Environmental Policy Act (NEPA) of 1969 (42 U.S.C.
4321 et seq.), requires each Federal agency to consider the
environmental effects of final actions and to prepare an Environmental
Impact Statement on major actions significantly affecting the quality
of the environment. MSHA has reviewed the proposed standard in
accordance with NEPA requirements, the regulations of the Council on
Environmental Quality (40 CFR part 1500), and the Department of Labor's
NEPA procedures (29 CFR part 11). As a result of this review, MSHA has
determined that this proposed rule will
[[Page 44956]]
not have a significant environmental impact. Accordingly, MSHA has not
conducted an environmental assessment nor provided an environmental
impact statement.
B. The Unfunded Mandates Reform Act of 1995
MSHA has reviewed the proposed rule under the Unfunded Mandates
Reform Act of 1995 (2 U.S.C. 1501 et seq.). The Unfunded Mandates
Reform Act requires Federal agencies to assess the effects of their
discretionary regulatory actions. In particular, the Act addresses
actions that may result in the expenditure by State, local, and Tribal
governments, in the aggregate, or by the private sector, of $100
million or more (adjusted annually for inflation) in any 1 year (5
U.S.C. 1532(a)). MSHA has determined that this proposed rule does not
result in such an expenditure. Accordingly, the Unfunded Mandates
Reform Act requires no further Agency action or analysis.
C. The Treasury and General Government Appropriations Act of 1999:
Assessment of Federal Regulations and Policies on Families
Section 654 of the Treasury and General Government Appropriations
Act of 1999 (5 U.S.C. 601 note) requires agencies to assess the impact
of Agency action on family well-being. MSHA has determined that the
proposed rule will have no effect on family stability or safety,
marital commitment, parental rights and authority, or income or poverty
of families and children, as defined in the Act. The proposed rule
impacts the mine industry and does not impose requirements on states or
families. Accordingly, MSHA certifies that this proposed rule will not
impact family well-being, as defined in the Act.
D. Executive Order 12630: Government Actions and Interference With
Constitutionally Protected Property Rights
Section 5 of E.O. 12630 requires Federal agencies to ``identify the
takings implications of proposed regulatory actions . . .'' MSHA has
determined that the proposed rule does not implement a taking of
private property or otherwise have takings implications. Accordingly,
E.O. 12630 requires no further Agency action or analysis.
E. Executive Order 12988: Civil Justice Reform
The proposed rule was written to provide a clear legal standard for
affected conduct and was carefully reviewed to eliminate drafting
errors and ambiguities so as to minimize litigation and avoid undue
burden on the Federal court system. Accordingly, the proposed rule
meets the applicable standards provided in section 3 of E.O. 12988,
Civil Justice Reform.
F. Executive Order 13045: Protection of Children From Environmental
Health Risks and Safety Risks
E.O. 13045 requires Federal agencies submitting covered regulatory
actions to OMB's Office of Information and Regulatory Affairs (OIRA)
for review, pursuant to E.O. 12866, to provide OIRA with (1) an
evaluation of the environmental health or safety effects that the
planned regulation may have on children, and (2) an explanation of why
the planned regulation is preferable to other potentially effective and
reasonably feasible alternatives considered by the agency. In E.O.
13045, ``covered regulatory action'' is defined as rules that may (1)
be significant under Executive Order 12866 Section 3(f)(1) (i.e., a
rulemaking that has an annual effect on the economy of $200 million or
more or would adversely affect in a material way the economy, a sector
of the economy, productivity, competition, jobs, the environment,
public health or safety, or State, local or Tribal governments or
communities), and (2) concern an environmental health risk or safety
risk that an agency has reason to believe may disproportionately affect
children. Environmental health risks and safety risks refer to risks to
health or to safety that are attributable to products or substances
that the child is likely to come in to contact with or ingest through
air, food, water, soil, or product use or exposure.
MSHA has determined that, in accordance with E.O. 13045, while the
proposed rule is considered significant under E.O. 12866 Section
3(f)(1), it does not concern an environmental health or safety risk
that may have a disproportionate impact on children. MSHA's proposed
rule would lower the occupational exposure limit to respirable
crystalline silica for all miners, take other actions to protect miners
from adverse health risks associated with exposure to respirable
crystalline silica, and require updated respiratory standards to better
protect miners from all airborne hazards.
MSHA is aware of studies which have characterized and assessed the
risks posed by ``take-home'' exposure pathways for hazardous dust
particles. However, the proposed rule's primary reliance on engineering
and administrative controls to protect miners from respirable
crystalline silica exposures helps minimize risks associated with
``take-home'' exposures by reducing or eliminating silica that is in
the mine atmosphere or the miner's personal breathing zone. The risks
of take-home exposures are further minimized by MSHA's existing
standards, operators' policies and procedures, and operators' use of
clothing cleaning systems.
MSHA's existing standards limit miners' exposures to respirable
crystalline silica. MSHA also requires coal mine operators to provide
miners bathing facilities and change rooms. Miners have access to these
facilities to shower and change their work clothes at the end of each
shift. In addition, some mine operators provide miners with clean
company clothing for each shift, have policies and procedures for
cleaning or disposing of contaminated clothing, and provide a boot wash
for miners to clean work boots during and after each shift. Moreover,
some operators use clothing cleaning systems that can remove dust from
a miner's clothing. Many of these systems include NIOSH-designed dust
removal booths that use compressed air to remove dust, which is then
vacuumed through a filter to remove airborne contaminants. Overall, the
Agency's standards, mine operators' policies and procedures, and other
safety practices including the use of clothing cleaning systems help to
reduce or eliminate the amount of take-home exposure, therefore
protecting other persons in a miner's household or persons who come in
to contact with the miner outside of the mine site.
MSHA identified one epidemiological study (Onyije et al., 2022)
that suggests a possible association between paternal exposure to
respirable crystalline silica and childhood leukemia. However, this
study does not provide dose-response data which would be needed to
establish the dose of respirable crystalline silica which results in a
no-adverse-effect-level (NOAEL) for childhood leukemia. This potential
association has not been independently confirmed by another study. MSHA
invites comment on the identification of any other scientific or
academic study or information that evaluates the potential association
between paternal exposure to respirable crystalline silica and
childhood leukemia during the NPRM's public comment period.
MSHA also invites comment on the identification of any scientific
or academic study or information that evaluates the potential risks to
female workers who are exposed to respirable crystalline silica during
pregnancy.
MSHA has no evidence that the environmental health or safety risks
posed by respirable crystalline silica,
[[Page 44957]]
including ``take-home'' exposure to respirable crystalline silica,
disproportionately affect children. Therefore, MSHA preliminarily
concludes no further analysis or action is needed, in accordance with
E.O. 13045.
G. Executive Order 13132: Federalism
MSHA has determined that the proposed rule does not have
``federalism implications'' because it will not ``have substantial
direct effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government.'' Accordingly,
under E.O. 13132, no further Agency action or analysis is required.
H. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments
MSHA has determined the proposed rule does not have ``tribal
implications'' because it will not ``have substantial direct effects on
one or more Indian tribes, on the relationship between the Federal
Government and Indian tribes, or on the distribution of power and
responsibilities between the Federal Government and Indian tribes.''
Accordingly, under E.O. 13175, no further Agency action or analysis is
required.
I. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
E.O. 13211 requires agencies to publish a Statement of Energy
Effects for ``significant energy actions,'' which are agency actions
that are ``likely to have a significant adverse effect on the supply,
distribution, or use of energy'' including a ``shortfall in supply,
price increases, and increased use of foreign supplies.'' MSHA has
reviewed the proposal for its impact on the supply, distribution, and
use of energy because it applies to the mining industry. The proposed
rule would result in annualized compliance costs of $4.85 million using
a 3 percent real discount rate and $4.97 million using a 7 percent real
discount rate for the coal mine industry relative to annual revenue of
$27.03 billion. The proposal would also result in annualized compliance
costs of $54.23 million using a 3 percent real discount rate and $55.72
million using a 7 percent real discount rate for the metal/nonmetal
mine industry relative to annual revenue of $88.32 billion. Because it
is not ``likely to have a significant adverse effect on the supply,
distribution, or use of energy'' including a ``shortfall in supply,
price increases, and increased use of foreign supplies,'' it is not a
``significant energy action.'' Accordingly, E.O. 13211 requires no
further agency action or analysis.
J. Executive Order 13272: Proper Consideration of Small Entities in
Agency Rulemaking
MSHA has thoroughly reviewed the proposed rule to assess and take
appropriate account of its potential impact on small businesses, small
governmental jurisdictions, and small organizations. MSHA's analysis is
presented in Section X. Initial Regulatory Flexibility Analysis.
K. Executive Order 13985: Advancing Racial Equity and Support for
Underserved Communities Through the Federal Government
E.O. 13985 provides ``that the Federal Government should pursue a
comprehensive approach to advancing equity for all, including people of
color and others who have been historically underserved, marginalized,
and adversely affected by persistent poverty and inequality.'' E.O.
13985 defines ``equity'' as ``consistent and systematic fair, just, and
impartial treatment of all individuals, including individuals who
belong to underserved communities that have been denied such treatment,
such as Black, Latino, and Indigenous and Native American persons,
Asian Americans and Pacific Islanders and other persons of color;
members of religious minorities; lesbian, gay, bisexual, transgender,
and queer (LGBTQ+) persons; persons with disabilities; persons who live
in rural areas; and persons otherwise adversely affected by persistent
poverty or inequality.'' To assess the impact of the proposed rule on
equity, MSHA considered two factors: (1) the racial/ethnic distribution
in mining in NAICS 212 (which does not include oil and gas extraction)
compared to the racial/ethnic distribution of the U.S. workforce (Table
XII-1), and (2) the extent to which mining may be concentrated within
general mining communities (Table XII-2).
In 2008, NIOSH conducted a survey of mines, which entailed sending
a survey packet to 2,321 mining operations to collect a wide range of
information, including demographic information on miners. NIOSH's 2012
report, entitled ``National Survey of the Mining Population: Part I:
Employees'' reported the findings of this survey (NIOSH 2012a). Race
and ethnicity information about U.S. mine workers is presented in Table
XII-1. Of all mine workers, including miners as well as administrative
employees at mines, 93.4 percent of mine workers were white, compared
to 80.6 percent of all U.S workers.\71\ There were larger percentages
of American Indian or Alaska Native and Native Hawaiian or Other
Pacific Islander people in the mining industry compared to all U.S.
workers, while there were smaller percentages of Asian, Black or
African American, and Hispanic/Latino people in the mining industry
compared to all U.S. workers.
---------------------------------------------------------------------------
\71\ National data on workers by race were not available for the
year 2008; comparable data for 2012 are provided for comparison
under the assumption that there would not be major differences in
distributions between these two years.
---------------------------------------------------------------------------
Table XII-2 shows that there are 22 mining communities, defined as
counties where at least 2 percent of the population is working in the
mining industry.\72\ Although the total population in this table
represents only 0.15 percent of the U.S. population, it represents 12.0
percent of all mine workers. The average per capita income in these
communities in 2020, $47,977,\73\ was lower than the U.S. average,
$59,510, representing 80.6 percent of the U.S. average. However, each
county's average per capita income varies substantially, ranging from
56.4 percent of the U.S. average to 146.8 percent.
---------------------------------------------------------------------------
\72\ Although 2 percent may appear to be a small number for
identifying a mining community, one might consider that if the
average household with one parent working as a miner has five
members in total, then approximately 10 percent of households in the
area would be directly associated with mining. While 10 percent may
also appear small, this refers to the county. There are likely
particular areas that have a heavier concentration of mining
households.
\73\ This is a simple average rather than a weighted average by
population.
---------------------------------------------------------------------------
The proposed rule would lower exposure to respirable crystalline
silica and improve respiratory protection for all mine workers. MSHA
determined that the proposed rule is consistent with the goals of E.O.
13985 and would support the advancement of equity for all workers at
mines, including those who are historically underserved and
marginalized.
BILLING CODE 4520-43-P
[[Page 44958]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.050
[[Page 44959]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.051
[[Page 44960]]
BILLING CODE 4520-43-C
L. Availability of Materials To Be Incorporated by Reference
The Office of the Federal Register (OFR) has regulations concerning
incorporation by reference. 5 U.S.C. 552(a); 1 CFR part 51. These
regulations require that information that is incorporated by reference
in a rule be ``reasonably available'' to the public. They also require
discussion in the preamble to the rule of the ways in which materials
it proposes to incorporate by reference are reasonably available to
interested parties or how it worked to make those materials reasonably
available to interested parties. Additionally, the preamble to the rule
must summarize the material. 1 CFR 51.5(b).
In accordance with the OFR's requirements, MSHA provides in the
following: (a) summaries of the materials to be incorporated by
reference and (b) information on the public availability of the
materials and on how interested parties can access the materials during
the comment period and upon finalization of the rule.
ASTM F3387-19, ``Standard Practice for Respiratory Protection''
(ASTM F3387-19) ASTM F3387-19 is a voluntary consensus standard that
represents up-to-date advancements in respiratory protection
technologies, practices, and techniques. The standard includes
provisions for selection, fitting, use, and care of respirators
designed to remove airborne contaminants from the air using filters,
cartridges, or canisters, as well as respirators that protect miners in
oxygen-deficient or immediately dangerous to life or health
atmospheres. These provisions are based on NIOSH's long-standing
experience of testing and approving respirators for occupational use
and OSHA's research and rulemaking on respiratory protection. The
proposed rule would incorporate by reference ASTM F3387-19 in existing
Sec. Sec. 56.5005, 57.5005, and 72.710 and in proposed Sec.
60.14(c)(2) to better protect all miners from airborne hazards. MSHA
believes that incorporating by reference ASTM F3387-19 would provide
mine operators with up-to-date requirements for respirator technology,
reflecting an improved understanding of effective respiratory
protection and therefore better protecting the health and safety of
miners. For further details on MSHA's proposed update to the Agency's
existing respiratory protection standard, please see section VII.C of
this preamble, Updating MSHA Respiratory Protection Standards by
Incorporating by Reference ASTM F3387-19.
A paper copy or printable version of ASTM F3387-19 may be purchased
by mine operators or any member of the public at any time from ASTM
International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
PA 19428-2959; https://www.astm.org/. ASTM International makes read-
only versions of its standards that have been referenced or
incorporated into Federal regulation or laws available free of charge
at its online Reading Room, https://www.astm.org/products-services/reading-room.html. During the comment period, a read-only version of
ASTM F3387-19 will be made available free of charge.\74\
---------------------------------------------------------------------------
\74\ The read-only version of ASTM F3387-19 available for public
review during the comment period can be accessed using the following
link--https://tinyurl.com/mwk97hjn.
---------------------------------------------------------------------------
In addition, during the comment period and upon finalization of
this rule, ASTM F3387-19 will be available for review free of charge at
MSHA headquarters at 201 12th Street South, Arlington, VA 22202-5450
(202-693-9440).
ISO 7708:1995: Air Quality--Particle Size Fraction Definitions for
Health-Related Sampling.
ISO 7708:1995 is an international consensus standard that defines
sampling conventions for particle size fractions used in assessing
possible health effects of airborne particles in the workplace and
ambient environment. It defines conventions for the inhalable,
thoracic, and respirable fractions. The proposed rule would incorporate
by reference ISO 7708:1995 in proposed Sec. 60.12(f)(4) to ensure
consistent sampling collection by mine operators through the
utilization of samplers conforming to ISO 7708:1995.
A paper copy or printable version of ISO 7708:1995 may be purchased
by mine operators or any member of the public at any time from ISO, CP
56, CH-1211 Geneva 20, Switzerland; phone: + 41 22 749 01 11; fax: + 41
22 733 34 30; website: www.iso.org/. ISO makes read-only versions of
its standards that have been incorporated by reference in the CFR
available free of charge at its online Incorporation by Reference
Portal, https://ibr.ansi.org/Default.aspx.
In addition, during the comment period and upon finalization of
this rule, ISO 7708:1995 will be available for review free of charge at
MSHA headquarters at 201 12th Street South, Arlington, VA 22202-5450,
(202-693-9440).
TLV's Threshold Limit Values for Chemical Substances in Workroom
Air Adopted by ACGIH for 1973.
This material is referenced in the amendatory text of this document
but has already been approved for appendix A. No changes are proposed.
XIII. References Cited in the Preamble
Abraham, J.L. and Wiesenfeld, S.L. 1997. Two cases of fatal PMF in
an ongoing epidemic of accelerated silicosis in oilfield
sandblasters: Lung pathology and mineralogy. Annals of Occupational.
Hygiene, Vol. 41, Supplement 1, pp. 440-447, 1997.
Agency for Toxic Substances and Disease Registry (ATSDR). 2019.
Toxicological profile for silica. U.S. Department of Health and
Human Services, Centers for Disease Control and Prevention, Division
of Toxicology and Human Health Sciences, Atlanta, GA.
Almberg, K.S., Friedman, L.S., Rose, C.S., Go, L.H.T., Cohen, R.A.
2020. Progression of coal workers' pneumoconiosis absent further
exposure. Occupational and Environmental Medicine. 77:748-751.
Almberg, K.S., Halldin, C.N., Blackley, D.J., Laney, A.S., Storey,
E., Rose, C.S., Go, L.H.T. and Cohen, R.A. 2018a. Progressive
massive fibrosis resurgence identified in U.S. coal miners filing
for black lung benefits, 1970-2016. Annals of American Thoracic
Society. 15(12): 1420-1426.
Am. Fuel & Petrochemical Manufacturers v. Env't Prot. Agency, 3
F.4th 373, 384 (D.C. Cir. 2021).
American Conference of Governmental Industrial Hygienists (ACGIH)
2022. TLV chemical substances introduction. https://www.acgih.org/science/tlv-bei-guidelines/tlv-chemical-substances-introduction/.
American Conference of Governmental Industrial Hygienists (ACGIH).
2010: Silica, crystalline: [alpha]-Quartz and cristobalite.
Documentation of TLV Recommendation. Cincinnati, Ohio.
American Conference of Governmental Industrial Hygienists (ACGIH).
TLVs[supreg] Threshold limit values for chemical substances in
workroom air adopted by the American Conference of Government
Industrial Hygienists for 1973. Journal of Occupational Medicine.
1974; 16(1):39-49 PMID: 4814108.
American Iron and Steel Institute et al., v. Occupational Safety and
Health Administration, 577 F.2d 825 (3d Cir. 1978).
American Society of Testing and Materials (ASTM). 2019. Standard
practice for respiratory protection. F3387-19. West Conshohocken,
PA.
American Thoracic Society (ATS). 2010a. Breathing in America:
Diseases, progress, and hope. Ed: D.E. Schraufnagel. American
Thoracic Society. 282 pages.
American Thoracic Society (ATS). 2010b. An official American
Thoracic Society public policy statement: Novel risk factors and the
global burden of chronic obstructive pulmonary disease. By: Eisner
M.D., Anthonisen, N., Coultas, D., Kuenzli, N., Perez-Padilla, R.,
Postma, D., Romieu, I., Silverman, E.K., and Balmes, J.R. American
Journal of Respiratory and Critical Care Medicine. 182:693-718.
[[Page 44961]]
American Thoracic Society (ATS). 1997. Adverse effects of
crystalline silica exposure. Committee members Beckett W., Abraham,
J., Becklake M., et al. American Journal of Respiratory Critical
Care Medicine. 155:761-768.
Ant[atilde]o, V.C., Petsonk, E.L., Sokolow, L.Z., Wolfe, A.L.,
Pinheiro, G.A., Attfield, M.D., 2005. Rapidly progressive coal
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XIV. Appendix
Appendix A
Description of MSHA Respirable Crystalline Silica Samples
This document describes the respirable crystalline silica
samples used in this rulemaking. The Mine Safety and Health
Administration (MSHA) collected these samples from metal/nonmetal
(MNM) and coal mines and analyzed the data to support this
rulemaking. Technical details are discussed in the following
attachments.
MNM Respirable Dust Sample Dataset, 2005-2019
From January 1, 2005, to December 31, 2019, 104,354 valid MNM
respirable dust samples were entered into the MSHA Technical Support
Laboratory Information Management System (LIMS) database.\75\ The
dataset includes MNM mine respirable dust personal exposure samples
collected by MSHA inspectors. A total of 57,824 samples contained a
respirable dust mass of 0.100 mg or greater (referred as
``sufficient-mass dust samples''), while a total of 46,530 samples
contained a respirable dust mass of less than 0.100 mg (referred as
``insufficient-mass dust samples'').
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\75\ Only valid (non-void) MNM respirable dust samples were
included in the LIMS dataset. Voided samples include any samples
with a documented reason which occurred during the sampling and/or
the MSHA's laboratory analysis for invalidating the results.
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Respirable dust samples collected by MSHA inspectors are
assigned a three-digit ``contaminant code'' based on the contaminant
in the sample. MSHA's contaminant codes group contaminants based on
their health effects \76\ and are assigned by the MSHA Laboratory
based on sample type and analysis results. The codes link
information, such as contaminant description, permissible exposure
limit (PEL), and the units of measure for each contaminant sampled.
---------------------------------------------------------------------------
\76\ For example, contaminant code 523 indicates that dust from
that sample contained 1 percent or more respirable crystalline
silica (quartz). Exposure to respirable crystalline silica has been
linked to the following health outcomes: silicosis, non-malignant
respiratory disease, lung cancer, and renal disease.
---------------------------------------------------------------------------
The MNM respirable crystalline silica dataset includes five
contaminant codes.
MNM Respirable Dust Sample Contaminant Codes
Contaminant code 521--MNM respirable dust samples that
were not analyzed for respirable crystalline silica.
Contaminant code 523--MNM respirable dust samples
containing 1 percent or more quartz.
Contaminant code 525--MNM respirable dust samples
containing cristobalite.
Contaminant code 121--MNM respirable dust samples
containing less than 1 percent quartz where the commodity is listed
as a ``nuisance particulate'' in Appendix E of the TLVs[supreg]
Threshold Limit Values for Chemical Substances in Workroom Air
Adopted by ACGIH for 1973 (reproduced in Table A-1).
Contaminant code 131--MNM respirable dust samples
containing less than 1 percent quartz where the commodity is not
listed as a ``nuisance particulate'' in Appendix E of the 1973 ACGIH
TLV[supreg] Handbook.
BILLING CODE 4520-43-P
[GRAPHIC] [TIFF OMITTED] TP13JY23.052
MNM Respirable Dust Samples With a Mass of at Least 0.100 milligram
(mg) (Sufficient-Mass Dust Samples)
The 57,824 samples that contained at least 0.100 mg of
respirable dust were analyzed to quantify their respirable
crystalline silica content--mostly respirable quartz but also
respirable cristobalite. The respirable crystalline silica
concentrations were entered into the MSHA Standardized Information
System (MSIS) database (internal facing) and Mine Data Retrieval
System (MDRS) database (public facing). Those MNM respirable dust
samples with a mass of at least 0.100 mg are analyzed and contained
in MSIS. MSIS and MDRS differ from LIMS in that some of the fields
associated with a sample can be modified or corrected by the
inspector. These correctable fields include Mine ID, Location Code,
and Job Code. Inspectors cannot access or modify the fields in the
LIMS database.
[[Page 44971]]
From the database, 55 samples \77\ were removed because they
were erroneous, had an incorrect flow rate, had insufficient
sampling time, or were duplicated. This resulted in a final dataset
of 57,769 MNM samples that contained a mass of at least 0.100 mg of
respirable dust. Datasets containing the analyzed samples that MSHA
removed and retained can be found in the rulemaking docket MSHA-
2023-0001.
---------------------------------------------------------------------------
\77\ There were 55 samples removed: 7 samples had no detected
mass gain (denoted as ``0 mg''); 1 sample was a partial shift that
was not originally marked correctly; 1 sample was removed at the
request of the district; 44 samples had flow rates outside the
acceptable range of 1.616-1.785 L/min; and 2 samples were duplicates
of samples that were already in the dataset. This resulted in the
final sample size of 57,769 = 57,824-(7 + 1 + 1 + 44 + 2).
---------------------------------------------------------------------------
MNM Respirable Dust Samples With a Mass of Less Than 0.100 mg
(Insufficient-Mass Samples)
The LIMS database also included 46,530 MNM respirable dust
samples that contained less than 0.100 mg of respirable dust. These
samples did not meet the minimum dust mass criterion of 0.100 mg and
were not analyzed for respirable crystalline silica by MSHA's
Laboratory.
From these 46,530 samples, 167 samples \78\ were removed because
they were erroneous, had an incorrect flow rate, or had insufficient
sampling time. This resulted in 46,363 remaining MNM samples
containing less than 0.100 mg of respirable dust. These samples were
assigned to contaminant code 521, indicating that the samples were
not analyzed for quartz. Datasets containing the unanalyzed samples
that MSHA removed and retained can be found in the rulemaking docket
MSHA-2023-0001.
---------------------------------------------------------------------------
\78\ There were 167 samples removed: 75 samples had a cassette
mass less than -0.03 mg (based on instrument tolerances, samples
that report a cassette mass between -0.03 mg and 0 mg were treated
as having a mass of 0 mg, samples with masses below that threshold
of -0.03 mg were excluded); 52 samples had Mine IDs that did not
report employment for any year from 2005-2019; 31 samples had flow
rates outside the acceptable range of 1.615-1.785 L/min; six samples
had sampling times of less than 30 minutes; and three samples had
invalid Job Codes. This resulted in the final sample size of 46,363
= 46,530-(75 + 52 + 31 + 6 + 3).
---------------------------------------------------------------------------
All MNM Respirable Dust Samples
After removing the 222 samples mentioned above (55 sufficient-
mass and 167 insufficient-mass), the dataset consisted of 104,132
MNM respirable dust samples: 57,769 sufficient-mass samples and
46,363 insufficient-mass samples. A breakdown of the MNM respirable
dust samples is included in Table A-2.
[GRAPHIC] [TIFF OMITTED] TP13JY23.053
BILLING CODE 4520-43-C
Coal Respirable Dust Sample Dataset, 2016-2021
From August 1, 2016, to July 31, 2021, 113,607 valid respirable
dust samples from coal mines were collected by MSHA inspectors and
entered in the LIMS database.\79\ For coal mines, the analysis is
based on samples collected by inspectors beginning on August 1,
2016, when Phase III of MSHA's 2014 respirable coal mine dust (RCMD)
standard went into effect. Samples taken prior to implementation of
the RCMD standard would not be representative of current respirable
crystalline silica exposure levels in coal mines.
---------------------------------------------------------------------------
\79\ Only valid (non-void) coal respirable dust samples were
included in the LIMS dataset. Voided samples include any samples
with a documented reason which occurred during the sampling and/or
the MSHA's Laboratory analysis for invalidating the results.
---------------------------------------------------------------------------
Of these samples collected by MSHA inspectors, 67,963 samples
were analyzed for respirable crystalline silica; 45,644 samples
[[Page 44972]]
were not. Respirable dust samples from coal mines contain the
records of the sample type, and the occupation of the miner sampled.
A coal sample's type is based on the location within the mine as
well as the occupation of the miner sampled. Below is a list of coal
sample types and descriptions, as well as the mass of respirable
dust required for that type of sample to be analyzed for respirable
crystalline silica.
Type 1--Designated occupation (DO). The occupation on a
mechanized mining unit (MMU) that has been determined by results of
respirable dust samples to have the greatest respirable dust
concentration. Designated occupation samples must contain at least
0.100 mg of respirable dust to be analyzed for respirable
crystalline silica.
Type 2--Other designated occupation (ODO). Occupations
other than the DO on an MMU that are also designated for sampling,
required by 30 CFR part 70. These samples must contain at least
0.100 mg of respirable dust to be analyzed for respirable
crystalline silica.
Type 3--Designated area (DA). Designated area samples
are from specific locations in the mine identified by the operator
in the mine ventilation plan under 30 CFR 75.371(t), where samples
will be collected to measure respirable dust generation sources in
the active workings. These samples must contain at least 0.100 mg of
respirable dust to be analyzed for respirable crystalline silica.
Type 4--Designated work position (DWP). A designated
work position in a surface coal mine or surface work area of an
underground coal mine designated for sampling to measure respirable
dust generation sources in the active workings. Designated work
position samples must contain at least 0.200 mg of respirable dust
to be analyzed for respirable crystalline silica. There are
exceptions for certain occupations: bulldozer operator (MSIS general
occupation code 368), high wall drill operator (code 384), high wall
drill helper (code 383), blaster/shotfirer (code 307), refuse/
backfill truck driver (code 386), or high lift operator/front end
loader (code 382). Samples from these occupations must have at least
0.100 mg of respirable dust to be analyzed for respirable
crystalline silica.
Type 5--Part 90 miner. A Part 90 miner is employed at a
coal mine and has exercised the option under the old section 203(b)
program (36 FR 20601, Oct. 27, 1971) or under 30 CFR 90.3 to work in
an area of a mine where the average concentration of respirable dust
in the mine atmosphere during each shift to which a miner is exposed
is continuously maintained at or below the applicable standard and
has not waived these rights. A sample from a Part 90 miner must
contain at least 0.100 mg of respirable dust to be analyzed for
respirable crystalline silica.
Type 6--Non-designated area (NDA). Non-designated area
samples are taken from locations in the mine that are not identified
by the operator in the mine ventilation plan under 30 CFR 75.371(t)
as areas where samples will be collected to measure respirable dust
generation sources in the active workings. These samples are not
analyzed for respirable crystalline silica.
Type 7--Intake air samples are taken from air that has
not yet ventilated the last working place on any split of any
working section or any worked-out area, whether pillared or non-
pillared, as per 30 CFR 75.301. These samples are not analyzed for
respirable crystalline silica.
Type 8--Non-designated work position (NDWP). A work
position in a surface coal mine or a surface work area of an
underground coal mine that is sampled during a regular health
inspection to measure respirable dust generation sources in the
active workings but has not been designated for mandatory sampling.
For the analysis of respirable crystalline silica, these samples
must have at least 0.200 mg of respirable dust. There are exceptions
for certain occupations: bulldozer operator (MSIS general occupation
code 368), high wall drill operator (code 384), high wall drill
helper (code 383), blaster/shotfirer (code 307), refuse/backfill
truck driver (code 386), or high lift operator/front end loader
(code 382). Samples taken from these occupations must contain at
least 0.100 mg respirable dust to be analyzed for respirable
crystalline silica.
Coal Respirable Dust Samples Analyzed for Respirable Crystalline Silica
There were 67,963 samples from coal mines collected by MSHA
inspectors from underground and surface coal mining operations that
were analyzed for respirable crystalline silica. These results were
entered first into LIMS, and then into MSIS and MDRS. Results from
MSIS were used as they may be updated by the inspectors at later
dates.\80\ From those 67,963 samples, 4,836 samples were removed as
they were environmental samples, voided in MSIS, or had other
errors.\81\ This resulted in a dataset of 63,127 samples from coal
mines that were analyzed for respirable crystalline silica. Datasets
containing the analyzed samples that MSHA removed and retained can
be found in the rulemaking docket MSHA-2023-0001.
---------------------------------------------------------------------------
\80\ As mentioned in the section concerning samples for MNM
mines, MSIS and MDRS differ from LIMS in that some data fields can
be modified or corrected by the inspector. These correctable fields
include Mine ID, Location Code, and Job Code.
\81\ There were 4,836 samples removed: 4,199 samples were
environmental and not personal samples (see Sample Type explanation
for more detail); 631 samples had been voided after they had been
entered into MSIS; and 6 had invalid Job Codes. This resulted in the
final sample size of 63,127 = 67,963-(4,199 + 631 + 6).
---------------------------------------------------------------------------
Coal Respirable Dust Samples Not Analyzed for Respirable Crystalline
Silica
Similar to MNM respirable dust samples, the LIMS database
includes 45,644 coal samples that did not meet the criteria for
analysis and were thus not analyzed for respirable crystalline
silica content.\82\ After removing 13,243 \83\ samples that were
environmental samples, erroneous, or had voided controls, there were
32,401 samples that were not analyzed for respirable crystalline
silica. Datasets containing the unanalyzed samples that MSHA removed
and retained can be found in the rulemaking docket MSHA-2023-0001.
---------------------------------------------------------------------------
\82\ In addition to the criteria listed above, samples from Shop
Welders (code 319) are not analyzed for respirable crystalline
silica as they are instead analyzed for welding fumes.
\83\ There were 13,243 samples removed: 6 samples had
typographical errors; 14 samples had a cassette mass less than -0.03
mg (based on instrument tolerances, samples that report a cassette
mass between -0.03 mg and 0 mg were treated as having a mass of 0
mg); 92 samples had invalid Job Codes; 12,724 were environmental
samples; 44 samples had an occupation code of 000 despite having a
personal sample `Sample Type'; 271 samples had controls that were
voided; and 92 came from Job Code 319--Welder (see Footnote 82).
This resulted in the final sample size of 32,401 = 50,545-(6 + 14 +
92 + 12,724 + 44 + 271 + 92).
---------------------------------------------------------------------------
All Coal Respirable Dust Samples
In total, 18,079 respirable dust samples from coal mines were
removed from the original datasets: 4,836 samples that were analyzed
for respirable crystalline silica and 13,243 samples that were not.
This created a final dataset of 95,528 samples: 63,127 analyzed
samples and 32,401 samples that were not analyzed.\84\ A breakdown
of respirable dust samples from coal mines is included in Table A-3.
---------------------------------------------------------------------------
\84\ This dataset did not include any other coal mine respirable
dust sample types collected by MSHA inspectors--i.e., sample types 3
(designated area samples), types 6 (Non-face occupations) and 7
(Intake air), samples taken on the surface mine shop welder (n=319),
and all voided samples. Voided samples are any samples that have a
documented reason which occurred during the sampling and/or
laboratory analysis for invalidating the results.
---------------------------------------------------------------------------
BILLING CODE 4520-43-P
[[Page 44973]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.054
Attachment 1. MNM Samples Analyzed for Cristobalite
Cristobalite is one of the three polymorphs of respirable
crystalline silica analyzed by MSHA's Laboratory upon request that
is included in this proposed rule. At the request of the inspector,
MNM \85\ respirable dust samples that contain at least 0.050 mg of
respirable dust are analyzed for cristobalite. Of the 57,769
retained MNM samples that contained at least 0.050 mg of respirable
dust, 0.6 percent (or 359 samples) were analyzed for cristobalite.
Coal respirable dust samples are not analyzed for cristobalite.\86\
---------------------------------------------------------------------------
\85\ See Attachment 2. Technical Background about Measuring
Respirable Crystalline Silica, for more information.
\86\ See Attachment 2. Technical Background about Measuring
Respirable Crystalline Silica, for more information.
[GRAPHIC] [TIFF OMITTED] TP13JY23.055
While the samples that were analyzed for cristobalite were
assigned to all four contaminant codes seen in this dataset, the
majority were assigned contaminant code 523.
[[Page 44974]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.056
The distribution of the 359 samples by cristobalite mass can be
seen in Table A1-3.\87\
---------------------------------------------------------------------------
\87\ Of the 369 samples that were analyzed for cristobalite, 334
had a value for cristobalite mass that was less than the limit of
detection (LOD) for cristobalite, 10 [micro]g. As such these samples
were assigned a value of 5 [micro]g of cristobalite, one half the
LOD. See Attachment 2. Technical Background about Measuring
Respirable Crystalline Silica, for more information.
[GRAPHIC] [TIFF OMITTED] TP13JY23.057
The mass of each sample was then used to calculate a
cristobalite concentration by dividing the mass of cristobalite by
the volume of air sampled (0.816 m\3\). The calculated
concentrations ranged from 6 [micro]g/m\3\ to 53 [micro]g/m\3\.\88\
---------------------------------------------------------------------------
\88\ One sample had a cristobalite concentration of 53 [micro]g/
m\3\. It was sampled in July of 2011 at Mine ID 4405407 and cassette
number 610892. The commodity being mined was Stone: Crushed, Broken
Quartzite. The occupation of the miner being sampled was Miners in
Other Occupations: Job Code 513--Building and Maintenance.
[GRAPHIC] [TIFF OMITTED] TP13JY23.058
[[Page 44975]]
BILLING CODE 4520-43-C
Attachment 2. Technical Background About Measuring Respirable
Crystalline Silica
In the proposed rule, respirable crystalline silica refers to
three polymorphs: quartz, cristobalite, and tridymite. MSHA's
Laboratory uses two methods to analyze respirable crystalline silica
content in mine respirable dust samples. The first method, X-ray
diffraction (XRD), separately analyzes quartz, cristobalite, and
tridymite contents in respirable dust samples that mine inspectors
obtain at MNM mine sites (MSHA Method P-2, 2018a). The second
method, Fourier transform infrared spectroscopy (FTIR), is used to
analyze quartz in respirable dust samples obtained at coal mines
(MSHA Method P-7, 2018b and 2020). Although the XRD method can be
expanded from MNM to coal dust samples, MSHA chooses to use the FTIR
method for coal dust samples because it is a faster and less
expensive method. However, the current MSHA P-7 FTIR method cannot
quantify quartz if cristobalite and/or tridymite are present in the
sample. The method also corrects the quartz result for the presence
of kaolinite, an interfering mineral for quartz analysis in coal
dust.
Limits of Detection and Limits of Quantification for Silica Sample Data
The Limits of Detection (LOD) and Limits of Quantification (LOQ)
are the two terms used to describe the method capability. The LOD
refers to the smallest amount of the target analyte (respirable
crystalline silica) that can be detected in the sample and
distinguished from zero with an acceptable confidence level that the
analyte is actually present. It can also be described as the
instrument signal that is needed to report with a specified
confidence that the analyte is present. The LOQ refers to the
smallest amount of the target analyte that can be repeatedly and
accurately quantified in the sample with a specified precision. The
LOQ is higher than the LOD. The values of the LOD and LOQ are
specific to MSHA's Laboratory as well as the instrumentation and
analytical method used to perform the analysis. These values do not
change from one batch to another when samples are analyzed on the
same equipment using the same method. However, their levels may
change over time due to updated analytical methods and technological
advances. The values of the LOD and LOQ for the methods (XRD and
FTIR) used in analyzing respirable crystalline silica samples are
explained in MSHA documents for MNM samples and coal samples (MSHA
Method P-2, 2018a; MSHA Method P-7, 2018b and 2020). MSHA
periodically updates these values to reflect progress in its
analytical methods. The values of LOD and LOQ were last updated in
2022 for MNM samples and in 2020 for coal samples.
The values of LODs and LOQs for respirable crystalline silica in
samples from MSHA inspectors depend on several factors, including
the analytical method used (XRD or FTIR) and the silica polymorph
analyzed (quartz, cristobalite, or tridymite), as presented in Table
A2-1.
For a sample with respirable crystalline silica content less
than the method LOD, the maximum concentration is calculated as the
respirable crystalline silica mass equivalent to LOD divided by the
volume of air sampled. For example, if no quartz is detected by XRD
analysis for an MNM sample, the method LOD is 5 [micro]g. If that
sample is collected at 1.7 L/min air flow rate for 480 minutes
(i.e., 8 hours), the air sample volume would be 816 L (= 1.7 L/min *
480 minutes), or 0.816 m\3\. The calculated maximum concentration
associated with a sample having respirable crystalline silica mass
below the method LOD would be 6 [micro]g/m\3\ (= 5 [micro]g/0.816
m\3\). The ``half maximum concentration'' is the midpoint between 0
and the calculated maximum respirable crystalline silica
concentration, which is 3 [micro]g/m\3\ (= \1/2\ * 6 [micro]g/m\3\)
in this example.
BILLING CODE 4520-43-P
[[Page 44976]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.059
The air volume is treated differently for MNM and coal samples
under the existing standards. In the case of MNM samples, 8-hour
equivalent time weighted averages (TWAs) are calculated using 480
minutes (8 hours) and a flow rate of 1.7 L/min, even if samples are
collected for a longer duration. In contrast, coal TWAs are
calculated using the full duration of the shift and a flow rate of
2.0 L/min and converted to an MRE equivalent concentration under
existing standards.
Assumptions for Analyzed Samples
Samples from MNM mines that contain at least 0.100 mg of dust
mass are analyzed for the presence of quartz and/or cristobalite.
For samples from coal mines, the minimum amount of respirable dust
in a sample to be analyzed for respirable crystalline silica is
determined by sample type and the occupation of the miner sampled.
For Sample Types 1, 2, and 5, the sample must contain at least 0.100
mg of respirable dust. For Sample Types 4 and 8, the sample must
contain at least 0.200 mg of respirable dust unless it comes from
one of the following occupations: bulldozer operator (MSIS general
occupation code 368), high wall drill operator (code 384), high wall
drill helper (code 383), blaster/shotfirer (code 307), refuse/
backfill truck driver (code 386), and high lift operator/front end
loader (code 382). Samples taken from these occupations must contain
at least 0.100 mg respirable dust to be analyzed for respirable
crystalline silica. Samples from Shop Welders (code 319) are never
analyzed for quartz, as they instead are sent for welding fume
analysis.
MSHA makes separate assumptions based on the mass of respirable
crystalline silica for a sample, whether it is above or below the
method LOD. For all samples reporting a mass of respirable
crystalline silica greater or equal to the method LOD, MSHA used the
reported values to calculate the respirable crystalline silica
concentration for the sample. For samples with values below the
method LOD, including samples reported as containing 0 [micro]g of
silica, MSHA used \1/2\ of the LOD to calculate the respirable
crystalline silica concentration of the sample. MSHA understands
that its assumptions regarding samples with respirable crystalline
silica mass below the method LOD will have a minimal impact on the
assessment.\89\
---------------------------------------------------------------------------
\89\ In its Final Regulatory Economic Analysis (FREA) for its
2016 silica rule, OSHA observed: ``. . . that XRD analysis of quartz
from samples prepared from reference materials can achieve LODs and
LOQs between 5 and 10 [micro]g was not disputed in the [rulemaking]
record.'' (OSHA, 2016).
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[[Page 44977]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.060
The reported value of respirable crystalline silica mass from an
MNM or coal sample can fall under one of the four groups: (1) at or
above the method LOQ, (2) at or above the method LOD but below the
LOQ, (3) greater than 0 [mu]g but less than the method LOD, or (4)
equal to 0 [mu]g. MSHA treats these samples differently based on
their respirable crystalline silica mass.
Quartz Mass at or Above the Method LOQ
For MNM and coal samples reporting quartz mass at or above the
method LOQs, MSHA uses the values reported by the MSHA's Laboratory.
Quartz Mass Between Method LOD and LOQ
For MNM and coal samples reporting quartz mass at or above the
method LOD but below the LOQ, MSHA uses the values reported by the
MSHA's Laboratory.
Quartz Mass Between the Method LOD and 0 mg
A review of respirable crystalline silica samples in LIMS
reveals that some samples had a respirable crystalline silica mass
below the LOD of the analytical methods but greater than 0 [mu]g.
Values in this range (i.e., below the method LOD but greater than 0
[mu]g) cannot reliably indicate the presence of respirable
crystalline silica. The mass of silica in these is too small to
reliably detect, but the concentration of silica could be up to the
calculated maximum concentration based on the method LOD. For
example, consider a sample from an MNM mine that was analyzed for
quartz and had a reported quartz mass of 4 [mu]g. This falls below
the LOD of 5 [mu]g but above 0 [mu]g, and as such the sample could
actually contain anywhere from 0 [mu]g of quartz up to the LOD value
of 5 [mu]g of quartz.
In these cases, MSHA used \1/2\ the LOD value to calculate
respirable crystalline silica concentration. MSHA explored other
options to treat these samples such as treating the reported silica
mass as 0 [mu]g/m\3\ (lower bound) as well as assuming the sample
silica mass is just below the LOD and assigning each sample a value
of the method LOD (upper bound). The use of the \1/2\ LOD value is
considered a reasonable assumption since using either the lower
bound of 0 [mu]g/m\3\ or the upper bound of the associated method's
LOD could under or overestimate exposures, respectively. The
assumption is not expected to impact the assessment of silica
concentration because any sample results with respirable crystalline
silica mass below the method LODs (between 3-10 [mu]g/m\3\) would
also have been well below the lowest exposure profile range (<25
[mu]g/m\3\).
Quartz Mass of 0 mg
A portion of the MNM and coal samples below the LOD are listed
as having respirable crystalline silica (specifically quartz) mass
levels of 0 [mu]g. For these samples, instead of treating the mass
of silica in the sample as a true zero, MSHA replaced the value with
\1/2\ the LOD of the associated method. Although the respirable
crystalline silica mass of these samples is less than the LOD, it is
likely that the sample still contains a small amount of respirable
crystalline silica. Hence, MSHA assumes a value of \1/2\ LOD in its
calculation of respirable crystalline silica concentration for these
samples. This assumption is considered to be reasonable because
using the lower bound of 0 [mu]g/m\3\ for these samples could
underestimate the respirable crystalline silica concentration while
using the upper bound of method LODs could overestimate the
respirable crystalline silica concentration.
Table A2-3 presents an example for quartz, one of the respirable
crystalline silica polymorphs. This table shows the LOD of quartz
mass and the possible range of quartz concentrations for samples
reporting a quartz mass of 0 [mu]g. These adjusted concentrations
are expected to have a limited impact of the assessment of
respirable crystalline silica concentration, as supported by MSHA's
sensitivity analyses.
[[Page 44978]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.061
Cristobalite Measurement
Respirable dust samples from MNM mines are rarely analyzed for
cristobalite by MSHA, and respirable coal dust samples are not
analyzed for the presence of cristobalite. MNM samples are analyzed
for the presence of cristobalite only when requested by MSHA
inspectors because the geological or work conditions indicate this
specific polymorph may be present. The LIMS database includes
samples for which cristobalite was analyzed, either with or without
quartz analysis. MSHA uses similar assumptions for cristobalite and
quartz.
The cristobalite LOD for these samples is 10 [mu]g. The MSHA
Laboratory-reported values are used for analyzed dust samples with
cristobalite mass values equal to or above the method LODs. Samples
that were analyzed for cristobalite and had a cristobalite mass
value below the method LOD were assigned values of \1/2\ LOD, or 5
[mu]g. For example, 267 samples, or 74.4 percent of the 359 samples
that were analyzed for cristobalite, reported a value of 0 [mu]g of
cristobalite; these were assigned a value of 5 [mu]g.
When a sample is analyzed for two polymorphs (i.e., both quartz
and cristobalite), detectable quartz and cristobalite are summed to
generate the total respirable crystalline silica. If only one of
these polymorphs is detected, the sample concentration is based on
the detected polymorph. If the concentrations of both polymorphs
(quartz and cristobalite) are reported as 0 [mu]g/m\3\, \1/2\ mass
LOD is assumed in calculating the concentrations and the resulting
concentrations are summed.
Unanalyzed Samples
There are also samples whose dust mass fell below their
associated mass threshold, and as such, they were not analyzed for
the presence of quartz and/or cristobalite. The respirable dust mass
for a sample was considered to be 0 [mu]g when the net mass gain of
dust was 0 [mu]g or less.
References
MSHA. 2018. P-2: X-Ray Diffraction Determination of Quartz and
Cristobalite in Respirable Metal/Nonmetal Mine Dust.
MSHA. 2018a. P-7: Infrared Determination of Quartz in Respirable
Coal Mine Dust.
MSHA. 2020. P-7: Determination of Quartz in Respirable Coal Mine
Dust by Fourier Transform Infrared Spectroscopy.
OSHA, 2016. Final Regulatory Economic Analysis (FEA) for OSHA's
Final Rule on Respirable Crystalline Silica, Chapter IV.3.2.3--
Sensitivity of Sampling and Analytical Methods.
Appendix B
Mining Commodity Groups
For this rulemaking analysis, the mining industries are grouped
into six commodities--Coal, Metal, Nonmetal, Stone, Crushed
Limestone, and Sand and Gravel. The table below shows the six
commodity groupings based on the Standard Industrial Classification
(SIC) codes and the North American Industry Classification System
(NAICS) codes. The SIC system is a predecessor of NAICS using
industry titles to standardize industry classification. The NAICS is
widely used by Federal statistical agencies, including the Small
Business Administration (SBA), for classifying business
establishments for the purpose of collecting, analyzing, and
publishing statistical data related to the U.S. business economy.
[[Page 44979]]
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[GRAPHIC] [TIFF OMITTED] TP13JY23.063
Appendix C
Occupational Categories for Respirable Crystalline Silica Sample
Collection
This Appendix explains how MSHA categorized MNM and coal samples
in constructing respirable crystalline silica exposure profile
tables for the current rulemaking. MSHA has developed respirable
crystalline silica exposure profile tables using its inspectors'
sampling data and results. One set of exposure profile tables
displays the analysis of 15 years of respirable crystalline silica
sampling data from MNM mines (Attachment 1), and the other set
displays the analysis of 5 years of respirable crystalline silica
samples collected at coal mines (Attachment 2).\90\ In the MNM
tables, the respirable crystalline silica concentration information
is broken out by 5 commodities (e.g., ``Metal,'' ``Crushed
Limestone,'' etc.) and then by 11 occupational categories (e.g.,
``Drillers,'' ``Stone Cutting Operators,'' etc.). The data for coal
mining is disaggregated by 2 locations (``Underground'' and
``Surface'') and then by 9 occupational categories (e.g., ``Crusher
Operators,'' ``Continuous Mining Machine Operators,'' etc.).
---------------------------------------------------------------------------
\90\ For coal mines, the analysis is based on samples collected
by inspectors beginning on August 1, 2016, when Phase III of MSHA's
2014 RCMD standard went into effect. Samples taken prior to
implementation of the RCMD standard would not be representative of
current respirable crystalline silica exposure levels in coal mines.
---------------------------------------------------------------------------
Job Codes and Respirable Dust Sampling
MSHA inspectors use job codes to label samples of respirable
dust when they conduct health inspections.\91\ Following the
sampling strategy outlined in the most recent
[[Page 44980]]
MSHA Health Inspection Procedures Handbook (December 2020; PH20-V-
4), the inspectors determine potential airborne hazards to which
miners may be exposed, including respirable dust, and then take
samples from the appropriate miners or working areas at a mine.
Using gravimetric samplers, the inspectors collect respirable dust
samples at MNM and coal mines. When submitting the collected samples
to MSHA's Laboratory for analysis, the inspectors label their
samples with the three-digit job code that best describes the duties
that each miner was performing during the sampling period.
---------------------------------------------------------------------------
\91\ The job codes have been referred to as both job codes and
occupation codes by MSHA. For example, in the Mine Data Retrieval
System, they are called job codes; in other materials, including
MSHA's Inspection Application System (IAS), they are called
occupational codes. For the purposes of this document, the term job
code has been used to clearly differentiate the job codes from the
occupational categories.
---------------------------------------------------------------------------
The three-digit job codes are taken from MSHA's Inspection
Application System (IAS), which includes 220 job codes for coal
mines and 121 job codes for MNM mines. Attachments 3 and 4 include
the IAS job codes for coal and MNM operations, respectively.
Coal Job Codes: The coal job codes have generally been
consistent over time, with new codes added when needed. For example,
IAS has the same job code for the duties of a coal ``supervisor/
foreman'' as two predecessor documents--the ``Job Code Pocket
Cards'' for coal mining, used by MSHA's predecessor, the Mining
Enforcement and Safety Administration (MESA) (see Attachment 5), and
a Fall 1983 Mine Safety and Health publication. An example is
presented below in Table C-1. In the three-digit coal job code, the
first digit generally identifies where the work is taking place in
the mine: 0 (Underground Section Workers--Face); 1 (General
Underground--Non-Face); 2 (Underground Transportation--Non-Face); 3
(Surface); 4 (Supervisory and Staff); 5 (MSHA--State); and 6 (Shaft
and Slope Sinking). The coal codes starting with 6 were added in
2020 to better delineate the samples for miners conducting shaft and
slope sinking activities.
[GRAPHIC] [TIFF OMITTED] TP13JY23.064
MNM Job Codes: Many of the 121 MNM job codes are similar to the
coal job codes, as noted in Attachment 4. One major difference is
that unlike the coal job codes, MNM job codes are not based on the
location of the work/job. The first digit of the three-digit MNM job
code does not indicate whether a job is located at an underground or
surface area of the mine. For example, a ``MNM Diamond Drill
Operator'' (Job Code 034) could be working on the surface or
underground, whereas a ``Coal Drill Operator'' would have a
different job code based on the miner's location within a mine (Job
Code 034--underground at the face; Job Code 334--at the surface).
Occupational Categories for the Respirable Crystalline Silica
Rulemaking
Some of the original work to group the MNM job codes into
occupational categories was completed in 2010 in support of earlier
rulemaking efforts. The MNM occupational categories were developed
first and were later updated with additional sampling data as it
became available. The coal occupational categories were developed
several years later and were generally modeled after the MNM tables;
however, coal occupational categories are first divided based on
surface and underground locations because occupational activities at
different locations of a mine can have differing impacts on coal
miners' exposures to respirable crystalline silica. In 2020, MSHA's
Laboratory used 9 coal and 14 MNM occupational categories for its
respirable crystalline silica data analyses.
For the respirable crystalline silica exposure profile tables in
the proposed respirable crystalline silica rule, MSHA made no change
to the 9 coal occupational categories, but condensed the 14 MNM
occupational categories to 11. These occupational categories are
meant to reasonably group multiple job codes with similar
occupational activities/tasks and engineering controls. The grouping
of job codes into occupational categories purposely focused on the
occupational activities/tasks and exposure risk of the miner
performing a particular job rather than the type of mining equipment
utilized by the miner. The creation of occupational categories based
on the types of equipment utilized by miners would have failed to
accurately characterize the risk of individual miners.
Coal Occupational Categories
There are 220 job codes for coal miners in IAS.\92\ Overall, 209
job codes are included in the 9 occupational categories. Some job
codes were excluded, primarily because sampling data were not
available for those job codes. The codes that have been excluded
are:
---------------------------------------------------------------------------
\92\ IAS also contains 272 coal job codes that are used to fill
out a Mine Accident, Injury and Illness Report (MSHA Form 7000-1).
These codes were not included in the respirable crystalline silica
exposure profile tables and are not discussed further in this
document.
---------------------------------------------------------------------------
Job code 0 ``Area,'' because area samples are not
specific to any one occupation.
Job code 398 ``Groundman,'' because there were no
sample data for this code in the respirable crystalline silica
sampling dataset.
Job codes 590 ``Education Specialist,'' 591 ``Mineral
Industrial Safety Officer,'' 592 ``Mine Safety Instructor,'' and 594
``Training Specialist,'' because there were no coal respirable
crystalline silica (quartz) data for these codes for the timeframe
selected.
Job codes 602 ``Electrician,'' 604 ``Mechanic,'' 609
``Supply Person,'' 632 ``Ventilation Worker,'' and 635 ``Continuous
Miner Operator Helper,'' because there were no sample data for these
codes in the respirable crystalline silica sampling dataset.
The remaining 209 coal job codes are first divided by the job
location--underground or surface--because potential respirable
crystalline silica exposures at coal mines can vary depending on
where a miner works at a given mine. (Three job codes are used in
[[Page 44981]]
both underground and surface locations: job codes 402 ``Master
Electrician,'' 404 ``Master Mechanic,'' and 497 ``Clerk/
Timekeeper.'') The underground and surface job codes are further
grouped on the basis of the types of tasks and typical engineering
controls. For example, as shown in Figure 1, the underground
``Continuous Mining Machine Operators'' occupational category
includes 14 different occupations that involve drilling activities--
occupations such as ``Coal Drill Helper,'' ``Coal Drill Operator,''
and ``Rock Driller.'' The underground ``Operators of Large Powered
Haulage Equipment'' occupational category has 12 similar occupations
including ``Loading Machine Operator,'' ``Shuttle Car Operator,''
and ``Motorman.''
[GRAPHIC] [TIFF OMITTED] TP13JY23.065
There are five categories of underground occupations and four
categories of surface occupations.
The five underground occupational categories include:
(1) Continuous Mining Machine Operators (e.g., Coal Drill Helper
and Coal Drill Operator);
(2) Operators of Large Powered Haulage Equipment (e.g., Shuttle
Car, Tractor, Scoop Car);
(3) Longwall Workers (e.g., Headgate Operator and Jack Setter
(Longwall));
(4) Roof Bolters (e.g., Roof Bolter and Roof Bolter Helper); and
(5) Underground Miners (e.g., Electrician, Mechanic, Belt Man/
Conveyor Man, and Laborer, etc.).
The four surface occupational categories include:
(1) Drillers (e.g., Coal Drill Operator, Coal Drill Helper, and
Auger Operator);
(2) Operators of Large Powered Haulage Equipment (e.g., Backhoe,
Forklift, and Shuttle Car);
(3) Crusher Operators (e.g., Crusher Attendant, Washer Operator,
and Scalper-Screen Operator); and
(4) Mobile Workers (e.g., Electrician, Mechanic, Blaster,
Cleanup Man, Mine Foreman, etc.).
Attachments 1 and 3 provide the full lists of occupational
categories and coal job codes.
MNM Occupational Categories
From the 121 MNM job codes in IAS, 120 job codes are included in
the occupational categories and 1 job code is excluded. The code
that has been excluded is:
Job code 413 ``Janitor,'' because there were no sample
data for this code in the respirable crystalline silica sampling
dataset.
Of the 120 job codes included, 1 job code was listed in both the
``Crushing Equipment and Plant Operators'' occupational category and
the ``Kiln, Mill and Concentrator Workers'' category. The code that
was used twice is:
Job Code 388 ``Screen/Scalper Operators,'' because MNM
job codes do not indicate the location where the work is taking
place and this work can be conducted either in a plant or on the
surface of the mine.
The final 121 MNM job codes (with job code 388 included twice)
were first grouped into 14 occupational categories based on the
types of tasks and typical engineering controls used. For example,
as seen in Figure 2, the ``Drillers'' occupational category includes
the 20 different occupations that involve drilling activities, such
as ``Diamond Drill Operator,'' ``Drill Operator Churn,'' and
``Continuous Miner Operator.'' ``Belt Cleaner,'' ``Belt Crew,'' and
``Belt Vulcanizer'' are included in the occupational category,
``Conveyor Operators.'' Similar tasks were grouped together because
the work activities and respirable crystalline silica exposures were
anticipated to be comparable.
[[Page 44982]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.066
The 14 occupational categories were:
(1) Bagging Machines;
(2) Stone Saws;
(3) Stone Trimmers, Splitters;
(4) Truck Loading Stations;
(5) Mobile Workers (e.g., Laborers, Electricians, Mechanics, and
Supervisors);
(6) Conveyors;
(7) Crushers;
(8) Dry Screening Plants;
(9) Kilns/Dryers, Rotary Mills, Ball Mills, and Flotation/
Concentrators;
(10) Large Powered Haulage Equipment (e.g., Trucks, FELs,
Bulldozers, and Scalers);
(11) Small Powered Haulage Equipment (e.g., Bobcats and
Forklifts);
(12) Jackhammers;
(13) Drills; and
(14) Other Occupations.
After additional consideration, it was determined that the
original 14 categories could be further condensed into the final 11
categories since some of the occupational categories contained job
codes where the types of tasks and engineering and administrative
controls were similar enough to be combined.
The final 11 occupational categories include:
(1) Drillers (e.g., Diamond Drill Operator, Wagon Drill
Operator, and Drill Helper);
(2) Stone Cutting Operators (e.g., Jackhammer Operator, Cutting
Machine Operator, and Cutting Machine Helper);
(3) Operators of Large Powered Haulage Equipment (e.g., Trucks,
Bulldozers, and Scalers);
(4) Conveyor Operators (e.g., Belt Cleaner, Belt Crew, and Belt
Vulcanizer);
(5) Crushing Equipment and Plant Operators (Crusher Operator/
Worker, Scalper Screen Operator, and Dry Screen Plant Operator);
(6) Kiln, Mill, and Concentrator Workers (e.g., Ball Mill
Operator, Leaching Operator, and Pelletizer Operator);
(7) Operators of Small Powered Haulage Equipment (e.g., Bobcats,
Shuttle Car, and Forklifts);
(8) Packaging Equipment Operators (e.g., Bagging Operator and
Packaging Operations Worker);
(9) Truck Loading Station Tenders (e.g., Dump Operator and Truck
Loader);
(10) Mobile Workers (Laborers, Electricians, Mechanics, and
Supervisors, etc.); and
(11) Miners in Other Occupations (Welder, Dragline Operator,
Shotcrete/Gunite Man, and Dredge/Barge Operator, etc.).
The sampling data for each of the 11 occupational categories
were then summarized by commodity group (``Metal,'' ``Nonmetal,''
``Stone,'' ``Crushed Limestone,'' and ``Sand and Gravel'') based on
the material being extracted.\93\ The available sampling data were
then collated for each occupation and commodity and summarized by
concentration ranges in the exposure profile tables for MNM mines.
---------------------------------------------------------------------------
\93\ Crushed Limestone and Sand and Gravel were considered
separately because these commodities make up a large percentage of
inspection samples. Watts et al. (2012). Respirable crystalline
silica [Quartz] Concentration Trends in Metal and Nonmetal Mining, J
Occ Environ Hyg 9:12, 720-732.
---------------------------------------------------------------------------
Attachment 1: Tables for MNM
[[Page 44983]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.067
[[Page 44984]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.068
[[Page 44985]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.069
[[Page 44986]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.070
[[Page 44987]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.071
[[Page 44988]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.072
[[Page 44989]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.073
[[Page 44990]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.074
[[Page 44991]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.075
[[Page 44992]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.076
[[Page 44993]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.077
Attachment 2: Tables for Coal
[[Page 44994]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.078
[[Page 44995]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.079
[[Page 44996]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.080
[[Page 44997]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.081
[[Page 44998]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.082
[[Page 44999]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.083
[[Page 45000]]
Attachment 3: Coal Job Codes
The complete list of job codes that are found in IAS, as of
March 11, 2022, are included below, with Table C3-1 listing job
codes for coal miners. For coal, the first digit of the job code
identifies where the work is taking place. For example, codes
starting with 0 represent jobs that occur at the underground face of
the mine. Job codes that start with 6 were added in 2020.
0--Underground Section Workers (Face)
1--General Underground (Non-Face)
2--Underground Transportation (Non-Face)
3--Surface
4--Supervisory and Staff
5--MSHA--State
6--Shaft and Slope Sinking
[GRAPHIC] [TIFF OMITTED] TP13JY23.084
[[Page 45001]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.085
[[Page 45002]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.086
[[Page 45003]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.087
Attachment 4: MNM Job Codes
The complete list of job codes that are found in IAS, as of
March 11, 2022, are included below with Table C4-1 outlining job
codes for MNM miners.
[[Page 45004]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.088
[[Page 45005]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.089
[[Page 45006]]
Attachment 5. Examples of Job Code Pocket Cards
Inspectors previously received pocket-sized job code cards for
use in filling out forms with the correct job code. Now, a drop-down
menu in IAS is used to select the codes. Table C5-1 contains
Underground Coal Mining Occupation Codes from Coal Job Code Cards
used by MESA between 1973 and 1977. Table C5-2 contains Surface
Occupation Codes from Coal Job Codes used by MESA between 1973 and
1977.
[GRAPHIC] [TIFF OMITTED] TP13JY23.090
[[Page 45007]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.091
[GRAPHIC] [TIFF OMITTED] TP13JY23.092
[[Page 45008]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.093
MNM Job Code Cards (1997)
Table C5-3 includes MNM Job Codes from a MNM Job Code Card
printed in 1997 by the GPO and which referenced a 1981 MSHA form
(MSHA Form 4000-50, Sept. 1981).
[[Page 45009]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.094
[[Page 45010]]
[GRAPHIC] [TIFF OMITTED] TP13JY23.095
BILLING CODE 4520-43-C
List of Subjects
30 CFR Part 56
Chemicals, Electric power, Explosives, Fire prevention, Hazardous
substances, Incorporation by reference, Metal and nonmetal mining, Mine
safety and health, Noise control, Reporting and recordkeeping
requirements, Surface mining.
30 CFR Part 57
Chemicals, Electric power, Explosives, Fire prevention, Gases,
Hazardous substances, Incorporation by reference, Metal and nonmetal
mining, Mine safety and health, Noise control, Radiation protection,
Reporting and recordkeeping requirements, Underground mining.
30 CFR Part 60
Coal, Incorporation by reference, Metal and nonmetal mining,
Medical surveillance, Mine safety and health, Respirable crystalline
silica, Reporting and recordkeeping requirements, Surface mining,
Underground mining.
30 CFR Part 70
Coal, Mine safety and health, Reporting and recordkeeping
requirements, Respirable dust, Underground coal mines.
30 CFR Part 71
Coal, Mine safety and health, Reporting and recordkeeping
requirements, Surface coal mines, Underground coal mines.
30 CFR Part 72
Coal, Health standards, Incorporation by reference, Mine safety and
health, Training, Underground mining.
30 CFR Part 75
Coal, Mine safety and health, Reporting and recordkeeping
requirements, Underground coal mines, Ventilation.
[[Page 45011]]
30 CFR Part 90
Coal, Mine safety and health, Reporting and recordkeeping
requirements, Respirable dust.
Christopher J. Williamson,
Assistant Secretary of Labor for Mine Safety and Health.
For the reasons discussed in the preamble, the Mine Safety and
Health Administration is proposing to amend 30 CFR subchapters K, M,
and O as follows:
Subchapter K-Metal and Nonmetal Mine Safety and Health
PART 56--SAFETY AND HEALTH STANDARDS--SURFACE METAL AND NONMETAL
MINES
0
1. The authority citation for part 56 continues to read as follows:
Authority: 30 U.S.C. 811.
Subpart D--Air Quality and Physical Agents
0
2. Amend Sec. 56.5001 by revising paragraph (a) to read as follows:
Sec. 56.5001 Exposure limits for airborne contaminants.
* * * * *
(a) Except as provided in paragraph (b) of this section and in part
60 of this chapter, the exposure to airborne contaminants shall not
exceed, on the basis of a time weighted average, the threshold limit
values adopted by the American Conference of Governmental Industrial
Hygienists, as set forth and explained in the 1973 edition of the
Conference's publication, entitled ``TLV's Threshold Limit Values for
Chemical Substances in Workroom Air Adopted by ACGIH for 1973,'' pages
1 through 54. This publication is incorporated by reference into this
section with the approval of the Director of the Federal Register under
5 U.S.C. 552(a) and 1 CFR part 51. This material is available for
inspection at the Mine Safety and Health Administration (MSHA) and at
the National Archives and Records Administration (NARA). Contact MSHA
at: MSHA's Office of Standards, Regulations, and Variances, 201 12th
Street South, Arlington, VA 22202-5450; 202-693-9440; or at any MSHA
Metal and Nonmetal Mine Safety and Health District Office. For
information on the availability of this material at NARA, visit
www.archives.gov/federal-register/cfr/ibr-locations.html or email
[email protected]. The material may be obtained from American
Conference of Governmental Industrial Hygienists, 1330 Kemper Meadow
Drive, Attn: Customer Service, Cincinnati, OH 45240; www.acgih.org.
* * * * *
0
3. Amend Sec. 56.5005 by revising the introductory text and paragraphs
(b) and (c) to read as follows:
Sec. 56.5005 Control of exposure to airborne contaminants.
Control of employee exposure to harmful airborne contaminants shall
be, insofar as feasible, by prevention of contamination, removal by
exhaust ventilation, or by dilution with uncontaminated air. However,
where accepted engineering control measures have not been developed or
when necessary by the nature of work involved (for example, while
establishing controls or occasional entry into hazardous atmospheres to
perform maintenance or investigation), employees may work for
reasonable periods of time in concentrations of airborne contaminants
exceeding permissible levels if they are protected by appropriate
respiratory protective equipment. Whenever respiratory protective
equipment is used, its selection, fitting, maintenance, cleaning,
training, supervision, and use shall meet the following minimum
requirements:
* * * * *
(b) Approved respirators shall be selected, fitted, cleaned, used,
and maintained in accordance with the requirements, as applicable, of
ASTM F3387-19. ASTM F3387-19, Standard Practice for Respiratory
Protection approved August 1, 2019, is incorporated by reference into
this section with the approval of the Director of the Federal Register
under 5 U.S.C. 552(a) and 1 CFR part 51. This material is available for
inspection at the Mine Safety and Health Administration (MSHA) and at
the National Archives and Records Administration (NARA). Contact MSHA
at: MSHA's Office of Standards, Regulations, and Variances, 201 12th
Street South, Arlington, VA 22202-5450; 202-693-9440; or any Mine
Safety and Health Enforcement District Office. For information on the
availability of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The
material may be obtained from ASTM International, 100 Barr Harbor
Drive, P.O. Box C700, West Conshohocken, PA 19428-2959; www.astm.org/.
(c) When respiratory protection is used in atmospheres immediately
dangerous to life or health (IDLH), the presence of at least one other
person with backup equipment and rescue capability shall be required in
the event of failure of the respiratory equipment.
PART 57--SAFETY AND HEALTH STANDARDS--UNDERGROUND METAL AND
NONMETAL MINES
0
4. The authority citation for part 57 continues to read as follows:
Authority: 30 U.S.C. 811.
Subpart D--Air Quality, Radiation, Physical Agents, and Diesel
Particulate Matter
0
5. Amend Sec. 57.5001 by revising paragraph (a) to read as follows:
Sec. 57.5001 Exposure limits for airborne contaminants.
* * * * *
(a) Except as provided in paragraph (b) of this section and in part
60 of this chapter, the exposure to airborne contaminants shall not
exceed, on the basis of a time weighted average, the threshold limit
values adopted by the American Conference of Governmental Industrial
Hygienists, as set forth and explained in the 1973 edition of the
Conference's publication, entitled ``TLV's Threshold Limit Values for
Chemical Substances in Workroom Air Adopted by ACGIH for 1973,'' pages
1 through 54. Excursions above the listed thresholds shall not be of a
greater magnitude than is characterized as permissible by the
Conference. This publication is incorporated by reference into this
section with the approval of the Director of the Federal Register under
5 U.S.C. 552(a) and 1 CFR part 51. This material is available for
inspection at the Mine Safety and Health Administration (MSHA) and at
the National Archives and Records Administration (NARA). Contact MSHA
at: MSHA's Office of Standards, Regulations, and Variances, 201 12th
Street South, Arlington, VA 22202-5450; 202-693-9440; or any MSHA Metal
and Nonmetal Mine Safety and Health District Office. For information on
the availability of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email
[email protected]. The material may be obtained from American
Conference of Governmental Industrial Hygienists by writing to 1330
Kemper Meadow Drive, Attn: Customer Service, Cincinnati, OH 45240;
www.acgih.org.
* * * * *
0
6. Amend Sec. 57.5005 by revising the introductory text and paragraphs
(b) and (c) to read as follows:
Sec. 57.5005 Control of exposure to airborne contaminants.
Control of employee exposure to harmful airborne contaminants shall
be, insofar as feasible, by prevention of contamination, removal by
exhaust
[[Page 45012]]
ventilation, or by dilution with uncontaminated air. However, where
accepted engineering control measures have not been developed or when
necessary by the nature of work involved (for example, while
establishing controls or occasional entry into hazardous atmospheres to
perform maintenance or investigation), employees may work for
reasonable periods of time in concentrations of airborne contaminants
exceeding permissible levels if they are protected by appropriate
respiratory protective equipment. Whenever respiratory protective
equipment is used, its selection, fitting, maintenance, cleaning,
training, supervision, and use shall meet the following minimum
requirements:
* * * * *
(b) Approved respirators shall be selected, fitted, cleaned, used,
and maintained in accordance with the requirements, as applicable, of
ASTM F3387-19. ASTM F3387-19, Standard Practice for Respiratory
Protection approved August 1, 2019, is incorporated by reference into
this section with the approval of the Director of the Federal Register
under 5 U.S.C. 552(a) and 1 CFR part 51. This material is available for
inspection at the Mine Safety and Health Administration (MSHA) and at
the National Archives and Records Administration (NARA). Contact MSHA
at: MSHA's Office of Standards, Regulations, and Variances, 201 12th
Street South, Arlington, VA 22202-5450; 202-693-9440; or any Mine
Safety and Health Enforcement District Office. For information on the
availability of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The
material may be obtained from ASTM International, 100 Barr Harbor
Drive, P.O. Box C700, West Conshohocken, PA 19428-2959; www.astm.org/.
(c) When respiratory protection is used in atmospheres immediately
dangerous to life or health (IDLH), the presence of at least one other
person with backup equipment and rescue capability shall be required in
the event of failure of the respiratory equipment.
Subchapter M-Uniform Mine Health Regulations
0
7. Add part 60 to subchapter M to read as follows:
PART 60-RESPIRABLE CRYSTALLINE SILICA
Sec.
60.1 Scope; effective date.
60.2 Definitions.
60.10 Permissible exposure limit (PEL).
60.11 Methods of compliance.
60.12 Exposure monitoring.
60.13 Corrective actions.
60.14 Respiratory protection.
60.15 Medical surveillance for metal and nonmetal miners.
60.16 Recordkeeping requirements.
60.17 Severability.
Authority: 30 U.S.C. 811, 813(h) and 957.
Sec. 60.1 Scope; effective date.
This part sets forth mandatory health standards for each surface
and underground metal, nonmetal, and coal mine subject to the Federal
Mine Safety and Health Act of 1977, as amended. Requirements regarding
medical surveillance for metal and nonmetal miners are also included.
The provisions of this part are effective [date 120 days after
publication of the final rule].
Sec. 60.2 Definitions.
The following definitions apply in this part:
Action level means an airborne concentration of respirable
crystalline silica of 25 micrograms per cubic meter of air ([mu]g/m\3\)
for a full-shift exposure, calculated as an 8-hour time-weighted
average (TWA).
Objective data means information, such as air monitoring data from
industry-wide surveys or calculations based on the composition of a
substance, demonstrating miner exposure to respirable crystalline
silica associated with a particular product or material or a specific
process, task, or activity. The data must reflect mining conditions
closely resembling or with a higher exposure potential than the
processes, types of material, control methods, work practices, and
environmental conditions in the operator's current operations.
Respirable crystalline silica means quartz, cristobalite, and/or
tridymite contained in airborne particles that are determined to be
respirable by a sampling device designed to meet the characteristics
for respirable-particle-size-selective samplers that conform to the
International Organization for Standardization (ISO) 7708:1995: Air
Quality--Particle Size Fraction Definitions for Health-Related
Sampling.
Specialist means an American Board-Certified Specialist in
Pulmonary Disease or an American Board-Certified Specialist in
Occupational Medicine.
Sec. 60.10 Permissible exposure limit (PEL).
The mine operator shall ensure that no miner is exposed to an
airborne concentration of respirable crystalline silica in excess of 50
[mu]g/m\3\ for a full-shift exposure, calculated as an 8-hour TWA.
Sec. 60.11 Methods of compliance.
(a) The mine operator shall install, use, and maintain feasible
engineering controls, supplemented by administrative controls when
necessary, to keep each miner's exposure at or below the PEL, except as
specified in Sec. 60.14.
(b) Rotation of miners shall not be considered an acceptable
administrative control used for compliance with this part.
Sec. 60.12 Exposure monitoring.
(a) Baseline sampling. (1) The mine operator shall perform baseline
sampling within the first 180 days after [date 120 days after
publication of the final rule] to assess the full shift, 8-hour TWA
exposure of respirable crystalline silica for each miner who is or may
reasonably be expected to be exposed to respirable crystalline silica.
(2) The mine operator is not required to conduct periodic sampling
under paragraph (b) of this section if the baseline sampling indicates
that miner exposures are below the action level and if the conditions
in either paragraph (a)(2)(i) or (ii) of this section are met:
(i) One of the following sources from within the preceding 12
months of baseline sampling indicates that miner exposures are below
the action level:
(A) Sampling conducted by the Secretary; or
(B) Mine operator sampling conducted in accordance with paragraphs
(f) and (g) of this section; or
(C) Objective data.
(ii) Subsequent sampling that is conducted within 3 months after
the baseline sampling indicates that miner exposures are below the
action level.
(b) Periodic sampling. Where the most recent sampling indicates
that miner exposures are at or above the action level but at or below
the PEL, the mine operator shall sample within 3 months of that
sampling and continue to sample within 3 months of the previous
sampling until two consecutive samplings indicate that miner exposures
are below the action level.
(c) Corrective actions sampling. Where the most recent sampling
indicates that miner exposures are above the PEL, the mine operator
shall sample after corrective actions taken pursuant to Sec. 60.13
until the sampling indicates that miner exposures are at or below the
PEL.
(d) Semi-annual evaluation. At least every 6 months after [date one
year after the effective date of the final rule], mine operators shall
evaluate any changes in
[[Page 45013]]
production, processes, engineering or administrative controls, or other
factors that may reasonably be expected to result in new or increased
respirable crystalline silica exposures. Once the evaluation is
completed, the mine operator shall:
(1) Make a record of the evaluation and the date of the evaluation;
and
(2) Post the record on the mine bulletin board and, if applicable,
by electronic means, for the next 31 days.
(e) Post-evaluation sampling. If the mine operator determines as a
result of the semi-annual evaluation under paragraph (d) of this
section that miners may be exposed to respirable crystalline silica at
or above the action level, the mine operator shall perform sampling to
assess the full shift, 8-hour TWA exposure of respirable crystalline
silica for each miner who is or may reasonably be expected to be at or
above the action level.
(f) Sampling requirements. (1) Sampling shall be performed for the
duration of a miner's regular full shift and during typical mining
activities.
(2) The full-shift, 8-hour TWA exposure for such miners shall be
measured based on:
(i) Personal breathing-zone air samples for metal and nonmetal
operations; or
(ii) Occupational environmental samples collected in accordance
with Sec. 70.201(c) or (b) or Sec. 90.201(b) of this chapter for coal
operations.
(3) Where several miners perform the same tasks on the same shift
and in the same work area, the mine operator may sample a
representative fraction (at least two) of these miners to meet the
requirements in paragraphs (a) through (e) of this section. In sampling
a representative fraction of miners, the mine operator shall select the
miners who are expected to have the highest exposure to respirable
crystalline silica.
(4) The mine operator shall use respirable-particle-size-selective
samplers that conform to ISO 7708:1995 to determine compliance with the
PEL. ISO 7708:1995, Air Quality--Particle Size Fraction Definitions for
Health-Related Sampling, Edition 1, 1995-04, is incorporated by
reference into this section with the approval of the Director of the
Federal Register under 5 U.S.C. 552(a) and 1 CFR part 51. This material
is available for inspection at the Mine Safety and Health
Administration (MSHA) and at the National Archives and Records
Administration (NARA). Contact MSHA at: MSHA's Office of Standards,
Regulations, and Variances, 201 12th Street South, Arlington, VA 22202-
5450; 202-693-9440; or any Mine Safety and Health Enforcement District
Office. For information on the availability of this material at NARA,
visit www.archives.gov/federal-register/cfr/ibr-locations.html or email
[email protected]. The material may be obtained from the
International Organization for Standardization (ISO), CP 56, CH-1211
Geneva 20, Switzerland; phone: + 41 22 749 01 11; fax: + 41 22 733 34
30; website: www.iso.org.
(g) Methods of sample analysis. (1) The mine operator shall use a
laboratory that is accredited to ISO/IEC 17025 ``General requirements
for the competence of testing and calibration laboratories'' with
respect to respirable crystalline silica analyses, where the
accreditation has been issued by a body that is compliant with ISO/IEC
17011 ``Conformity assessment--Requirements for accreditation bodies
accrediting conformity assessment bodies.''
(2) The mine operator shall ensure that the laboratory evaluates
all samples using respirable crystalline silica analytical methods
specified by MSHA, the National Institute for Occupational Safety and
Health (NIOSH), or the Occupational Safety and Health Administration
(OSHA).
(h) Sampling records. For each sample taken pursuant to paragraphs
(a) through (e) of this section, the mine operator shall make a record
of the sample date, the occupations sampled, and the concentrations of
respirable crystalline silica and respirable dust, and post the record
and the laboratory report on the mine bulletin board and, if
applicable, by electronic means, for the next 31 days, upon receipt.
Sec. 60.13 Corrective actions.
(a) If any sampling indicates that a miner's exposure exceeds the
PEL, the mine operator shall:
(1) Make approved respirators available to affected miners before
the start of the next work shift in accordance with Sec. 60.14;
(2) Ensure that affected miners wear respirators properly for the
full shift or during the period of overexposure until miner exposures
are at or below the PEL; and
(3) Immediately take corrective actions to lower the concentration
of respirable crystalline silica to at or below the PEL.
(4) Once corrective actions have been taken, the mine operator
shall:
(i) Conduct sampling pursuant to Sec. 60.12(c); and
(ii) Take additional or new corrective actions until sampling
indicates miner exposures are at or below the PEL.
(b) The mine operator shall make a record of corrective actions and
the dates of the corrective actions under paragraph (a) of this
section.
Sec. 60.14 Respiratory protection.
(a) Temporary non-routine use of respirators. The mine operator
shall use respiratory protection as a temporary measure in accordance
with paragraph (c) of this section. Miners must use respirators when
working in concentrations of respirable crystalline silica above the
PEL while:
(1) Engineering control measures are being developed and
implemented; or
(2) It is necessary by the nature of work involved.
(b) Miners unable to wear respirators. Upon written determination
by a physician or other licensed health care professional (PLHCP) that
an affected miner is unable to wear a respirator, the miner shall be
temporarily transferred either to work in a separate area of the same
mine or to an occupation at the same mine where respiratory protection
is not required.
(1) The affected miner shall continue to receive compensation at no
less than the regular rate of pay in the occupation held by that miner
immediately prior to the transfer.
(2) The affected miner may be transferred back to the miner's
initial work area or occupation when temporary non-routine use of
respirators under paragraph (a) of this section is no longer required.
(c) Respiratory protection requirements. (1) Affected miners shall
be provided with a NIOSH-approved atmosphere-supplying respirator or
NIOSH-approved air-purifying respirator equipped with the following:
(i) Particulate protection classified as 100 series under 42 CFR
part 84; or
(ii) Particulate protection classified as High Efficiency ``HE''
under 42 CFR part 84.
(2) Approved respirators shall be selected, fitted, used, and
maintained in accordance with the requirements, as applicable, of ASTM
F3387-19. ASTM F3387-19, Standard Practice for Respiratory Protection
approved August 1, 2019, is incorporated by reference into this section
with the approval of the Director of the Federal Register under 5
U.S.C. 552(a) and 1 CFR part 51. This material is available for
inspection at the Mine Safety and Health Administration (MSHA) and at
the National Archives and Records Administration (NARA). Contact MSHA
at: MSHA's Office of Standards, Regulations, and Variances, 201 12th
Street South, Arlington, VA 22202-5450; 202-693-9440; or any Mine
Safety and Health Enforcement District Office. For information on the
availability of
[[Page 45014]]
this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The material may be
obtained from ASTM International, 100 Barr Harbor Drive, PO Box C700,
West Conshohocken, PA 19428-2959; www.astm.org/.
Sec. 60.15 Medical surveillance for metal and nonmetal miners.
(a) Medical surveillance. Each operator of a metal and nonmetal
mine shall provide to each miner periodic medical examinations
performed by a physician or other licensed health care professional
(PLHCP) or specialist, as defined in Sec. 60.2, at no cost to the
miner.
(1) Medical examinations shall be provided at frequencies specified
in this section.
(2) Medical examinations shall include:
(i) A medical and work history, with emphasis on: past and present
exposure to respirable crystalline silica, dust, and other agents
affecting the respiratory system; any history of respiratory system
dysfunction, including diagnoses and symptoms of respiratory disease
(e.g., shortness of breath, cough, wheezing); history of tuberculosis;
and smoking status and history;
(ii) A physical examination with special emphasis on the
respiratory system;
(iii) A chest X-ray (a single posteroanterior radiographic
projection or radiograph of the chest at full inspiration recorded on
either film (no less than 14 x 17 inches and no more than 16 x 17
inches) or digital radiography systems), classified according to the
International Labour Office (ILO) International Classification of
Radiographs of Pneumoconioses by a NIOSH-certified B Reader; and
(iv) A pulmonary function test to include forced vital capacity
(FVC) and forced expiratory volume in one second (FEV1) and
FEV1/FVC ratio, administered by a spirometry technician with
a current certificate from a NIOSH-approved Spirometry Program Sponsor.
(b) Voluntary medical examinations. Each mine operator shall
provide the opportunity to have the medical examinations specified in
paragraph (a) of this section at least every 5 years to all miners
employed at the mine. The medical examinations shall be available
during a 6-month period that begins no less than 3.5 years and not more
than 4.5 years from the end of the last 6-month period.
(c) Mandatory medical examinations. For each miner who begins work
in the mining industry for the first time, the mine operator shall
provide medical examinations specified in paragraph (a) of this section
as follows:
(1) An initial medical examination no later than 30 days after
beginning employment;
(2) A follow-up medical examination no later than 3 years after the
initial examination in paragraph (c)(1) of this section; and
(3) A follow-up medical examination conducted by a specialist no
later than 2 years after the examinations in paragraph (c)(2) of this
section if the chest X-ray shows evidence of pneumoconiosis or the
spirometry examination indicates evidence of decreased lung function.
(d) Medical examinations results. The results of medical
examinations or tests made pursuant to this section shall be provided
only to the miner, and at the request of the miner, to the miner's
designated physician.
(e) Written medical opinion. The mine operator shall obtain a
written medical opinion from the PLHCP or specialist within 30 days of
the medical examination. The written opinion shall contain only the
following:
(1) The date of the medical examination;
(2) A statement that the examination has met the requirements of
this section; and
(3) Any recommended limitations on the miner's use of respirators.
(f) Written medical opinion records. The mine operator shall
maintain a record of the written medical opinions received from the
PLHCP or specialist under paragraph (e) of this section.
Sec. 60.16 Recordkeeping requirements.
(a) Table 1 to this paragraph (a) lists the records the mine
operator shall retain and their retention period.
(1) Evaluation records made under Sec. 60.12(d) shall be retained
for at least 2 years from the date of each evaluation.
(2) Sampling records made under Sec. 60.12(h) shall be retained
for at least 2 years from the sample date.
(3) Corrective action records made under Sec. 60.13(b) shall be
retained for at least 2 years from the date of each corrective action.
These records must be stored with the records of related sampling under
Sec. 60.12(h).
(4) Written determination records received from a PLHCP under Sec.
60.14(b) shall be retained for the duration of the miner's employment
plus 6 months.
(5) Written medical opinion records received from a PLHCP or
specialist under Sec. 60.15(f) shall be retained for the duration of
the miner's employment plus 6 months.
Table 1 to Paragraph (a)--Recordkeeping Requirements
------------------------------------------------------------------------
Record Section references Retention period
------------------------------------------------------------------------
1. Evaluation records........... Sec. 60.12(d)... At least 2 years
from date of each
evaluation.
2. Sampling records............. Sec. 60.12(h)... At least 2 years
from sample date.
3. Corrective action records.... Sec. 60.13(b)... At least 2 years
from date of each
corrective
action.
4. Written determination records Sec. 60.14(b)... Duration of
received from a PLHCP. miner's
employment plus 6
months.
5. Written medical opinion Sec. 60.15(f)... Duration of
records received from a PLHCP miner's
or specialist. employment plus 6
months.
------------------------------------------------------------------------
(b) Upon request from an authorized representative of the
Secretary, from an authorized representative of miners, or from miners,
mine operators shall promptly provide access to any record listed in
this section.
Sec. 60.17 Severability.
Each section of this part, as well as sections in 30 CFR parts 56,
57, 70, 71, 72, 75, and 90 that address respirable crystalline silica
or respiratory protection, is separate and severable from the other
sections and provisions. If any provision of this subpart is held to be
invalid or unenforceable by its terms, or as applied to any person,
entity, or circumstance, or is stayed or enjoined, that provision shall
be construed so as to continue to give the maximum effect to the
provision permitted by law, unless such holding shall be one of utter
invalidity or unenforceability, in which event the provision shall be
severable from these
[[Page 45015]]
sections and shall not affect the remainder thereof.
Subchapter O--Coal Mine Safety and Health
PART 70--MANDATORY HEALTH STANDARDS--UNDERGROUND COAL MINES
0
8. The authority citation for part 70 continues to read as follows:
Authority: 30 U.S.C. 811, 813(h), 957.
Subpart A--General
Sec. 70.2 [Amended]
0
9. Amend Sec. 70.2 by removing the definition of ``Quartz''.
Subpart B--Dust Standards
Sec. 70.101 [Removed and Reserved]
0
10. Remove and reserve Sec. 70.101.
Subpart C--Sampling Procedures
0
11. Amend Sec. 70.205 by revising paragraph (c) to read as follows:
Sec. 70.205 Approved sampling devices; operation; air flowrate.
* * * * *
(c) If using a CPDM, the person certified in sampling shall monitor
the dust concentrations and the sampling status conditions being
reported by the sampling device at mid-shift or more frequently as
specified in the approved mine ventilation plan to assure: The sampling
device is in the proper location and operating properly; and the work
environment of the occupation or DA being sampled remains in compliance
with the standard at the end of the shift. This monitoring is not
required if the sampling device is being operated in an anthracite coal
mine using the full box, open breast, or slant breast mining method.
Sec. 70.206 [Removed and Reserved]
0
12. Remove and reserve Sec. 70.206.
Sec. 70.207 [Removed and Reserved]
0
13. Remove and reserve Sec. 70.207.
0
14. Amend Sec. 70.208 by:
0
a. Removing and reserving paragraph (c);
0
b. Revising paragraphs (d), (e) introductory text, (e)(2), (f), (g),
(h) introductory text, (h)(2), (i) introductory text, and (i)(1); and
0
c. Adding table 1.
The revisions and addition read as follows:
Sec. 70.208 Quarterly sampling; mechanized mining units.
* * * * *
(d) If a normal production shift is not achieved, the DO or ODO
sample for that shift may be voided by MSHA. However, any sample,
regardless of production, that exceeds the standard by at least 0.1 mg/
m\3\ shall be used in the determination of the equivalent concentration
for that occupation.
(e) When a valid representative sample taken in accordance with
this section meets or exceeds the ECV in table 1 to this section that
corresponds to the particular sampling device used, the operator shall:
* * * * *
(2) Immediately take corrective action to lower the concentration
of respirable dust to at or below the respirable dust standard; and
* * * * *
(f) Noncompliance with the standard is demonstrated during the
sampling period when:
(1) Three or more valid representative samples meet or exceed the
ECV in table 1 to this section that corresponds to the particular
sampling device used; or
(2) The average for all valid representative samples meets or
exceeds the ECV in table 1 to this section that corresponds to the
particular sampling device used.
(g)(1) Unless otherwise directed by the District Manager, upon
issuance of a citation for a violation of the standard involving a DO
in an MMU, paragraph (a)(1) of this section shall not apply to the DO
in that MMU until the violation is abated and the citation is
terminated in accordance with paragraphs (h) and (i) of this section.
(2) Unless otherwise directed by the District Manager, upon
issuance of a citation for a violation of the standard involving a type
of ODO in an MMU, paragraph (a)(2) of this section shall not apply to
that ODO type in that MMU until the violation is abated and the
citation is terminated in accordance with paragraphs (h) and (i) of
this section.
(h) Upon issuance of a citation for violation of the standard, the
operator shall take the following actions sequentially:
* * * * *
(2) Immediately take corrective action to lower the concentration
of respirable coal mine dust to at or below the standard; and
* * * * *
(i) A citation for a violation of the standard shall be terminated
by MSHA when:
(1) Each of the five valid representative samples is at or below
the standard; and
* * * * *
Table 1 to Sec. 70.208--Excessive Concentration Values (ECV) Based on a Single Sample, Three Samples, or the
Average of Five or Fifteen Full-Shift CMDPSU/CPDM Concentration Measurements
----------------------------------------------------------------------------------------------------------------
ECV (mg/m\3\)
Section Samples -------------------------------
CMDPSU CPDM
----------------------------------------------------------------------------------------------------------------
70.208 (e)................................. 70.100(a)--Single sample........... 1.79 1.70
70.100(b)--Single sample........... 0.74 0.57
70.208(f)(1)............................... 70.100(a)--3 or more samples....... 1.79 1.70
70.100(b)--3 or more samples....... 0.74 0.57
70.208(f)(2)............................... 70.100(a)--5 sample average........ 1.63 1.59
70.100(b)--5 sample average........ 0.61 0.53
70.208(f)(2)............................... 70.100(a)--15 sample average....... 1.58 1.56
70.100(b)--15 sample average....... 0.57 0.52
70.208(i)(1)............................... 70.100(a)--Each of 5 samples....... 1.79 1.70
70.100(b)--Each of 5 samples....... 0.74 0.57
----------------------------------------------------------------------------------------------------------------
0
15. Amend Sec. 70.209 by:
0
a. Removing and reserving paragraph (b);
0
b. Revising paragraphs (c) introductory text, (c)(2), (d), (e), (f)
introductory text, (f)(2), (g) introductory text, and (g)(1); and
0
c. Adding table 1.
The revisions and addition read as follows:
[[Page 45016]]
Sec. 70.209 Quarterly sampling; designated areas.
* * * * *
(c) When a valid representative sample taken in accordance with
this section meets or exceeds the ECV in table 1 to this section that
corresponds to the particular sampling device used, the operator shall:
* * * * *
(2) Immediately take corrective action to lower the concentration
of respirable dust to at or below the respirable dust standard; and
* * * * *
(d) Noncompliance with the standard is demonstrated during the
sampling period when:
(1) Two or more valid representative samples meet or exceed the ECV
in table 1 to this section that corresponds to the particular sampling
device used; or
(2) The average for all valid representative samples meets or
exceeds the ECV in table 1 to this section that corresponds to the
particular sampling device used.
(e) Unless otherwise directed by the District Manager, upon
issuance of a citation for a violation of the standard, paragraph (a)
of this section shall not apply to that DA until the violation is
abated and the citation is terminated in accordance with paragraphs (f)
and (g) of this section.
(f) Upon issuance of a citation for a violation of the standard,
the operator shall take the following actions sequentially:
* * * * *
(2) Immediately take corrective action to lower the concentration
of respirable coal mine dust to at or below the standard; and
* * * * *
(g) A citation for a violation of the standard shall be terminated
by MSHA when:
(1) Each of the five valid representative samples is at or below
the standard; and
* * * * *
Table 1 to Sec. 70.209--Excessive Concentration Values (ECV) Based on a Single Sample, Two Samples, or the
Average of Five or Fifteen Full-Shift CMDPSU/CPDM Concentration Measurements
----------------------------------------------------------------------------------------------------------------
ECV (mg/m\3\)
Section Samples -------------------------------
CMDPSU CPDM
----------------------------------------------------------------------------------------------------------------
70.209 (c)................................. 70.100(a)--Single sample........... 1.79 1.70
70.100(b)--Single sample........... 0.74 0.57
70.209(d)(1)............................... 70.100(a)--2 or more samples....... 1.79 1.70
70.100(b)--2 or more samples....... 0.74 0.57
70.209(d)(2)............................... 70.100(a)--5 sample average........ 1.63 1.59
70.100(b)--5 sample average........ 0.61 0.53
70.209(d)(2)............................... 70.100(a)--15 sample average....... 1.58 1.56
70.100(b)--15 sample average....... 0.57 0.52
70.209(g)(1)............................... 70.100(a)--Each of 5 samples....... 1.79 1.70
70.100(b)--Each of 5 samples....... 0.74 0.57
----------------------------------------------------------------------------------------------------------------
Table 70--1 to Subpart C of Part 70 [Removed]
0
16. Remove table 70-1 to subpart C of part 70.
Table 70--2 to Subpart C of Part 70 [Removed]
0
17. Remove table 70-2 to subpart C of part 70.
PART 71--MANDATORY HEALTH STANDARDS--SURFACE COAL MINES AND SURFACE
WORK AREAS OF UNDERGROUND COAL MINES
0
18. The authority citation for part 71 continues to read as follows:
Authority: 30 U.S.C. 811, 813(h), 957.
Subpart A--General
Sec. 71.2 [Amended]
0
19. Amend Sec. 71.2 by removing the definition of ``Quartz''.
Subpart B--Dust Standards
Sec. 71.101 [Removed and Reserved]
0
20. Remove and reserve Sec. 71.101.
Subpart C--Sampling Procedures
0
21. Amend Sec. 71.205 by revising paragraph (c) to read as follows:
Sec. 71.205 Approved sampling devices; operation; air flowrate.
* * * * *
(c) If using a CPDM, the person certified in sampling shall monitor
the dust concentrations and the sampling status conditions being
reported by the sampling device at mid-shift or more frequently as
specified in the approved respirable dust control plan, if applicable,
to assure: The sampling device is in the proper location and operating
properly; and the work environment of the occupation being sampled
remains in compliance with the standard at the end of the shift.
0
22. Amend Sec. 71.206 by:
0
a. Removing and reserving paragraph (b);
0
b. Revising paragraphs (e), (g), (h) introductory text, (h)(2), (i),
(j), (k) introductory text, (k)(2), and (l);
0
c. Removing tables 71-1 and 71-2;
0
d. Revising paragraphs (m) and (n); and
0
e. Adding table 1.
The revisions and addition read as follows:
Sec. 71.206 Quarterly sampling; designated work positions.
* * * * *
(e) Each DWP sample shall be taken on a normal work shift. If a
normal work shift is not achieved, the respirable dust sample shall be
transmitted to MSHA with a notation by the person certified in sampling
on the back of the dust data card stating that the sample was not taken
on a normal work shift. When a normal work shift is not achieved, the
sample for that shift may be voided by MSHA. However, any sample,
regardless of whether a normal work shift was achieved, that exceeds
the standard by at least 0.1 mg/m\3\ shall be used in the determination
of the equivalent concentration for that occupation.
* * * * *
(g) Upon notification from MSHA that any valid representative
sample taken from a DWP to meet the requirements of paragraph (a) of
this section exceeds the standard, the operator shall, within 15
calendar days of notification, sample that DWP each normal work shift
until five valid representative samples are
[[Page 45017]]
taken. The operator shall begin sampling on the first normal work shift
following receipt of notification.
(h) When a valid representative sample taken in accordance with
this section meets or exceeds the excessive concentration value (ECV)
in table 1 to this section that corresponds to the particular sampling
device used, the mine operator shall:
* * * * *
(2) Immediately take corrective action to lower the concentration
of respirable coal mine dust to at or below the standard; and
* * * * *
(i) Noncompliance with the standard is demonstrated during the
sampling period when:
(1) Two or more valid representative samples meet or exceed the ECV
in table 1 to this section that corresponds to the particular sampling
device used; or
(2) The average for all valid representative samples meets or
exceeds the ECV in table 1 to this section that corresponds to the
particular sampling device used.
(j) Unless otherwise directed by the District Manager, upon
issuance of a citation for a violation of the standard, paragraph (a)
of this section shall not apply to that DWP until the violation is
abated and the citation is terminated in accordance with paragraphs (k)
and (l) of this section.
(k) Upon issuance of a citation for violation of the standard, the
operator shall take the following actions sequentially:
* * * * *
(2) Immediately take corrective action to lower the concentration
of respirable coal mine dust to at or below the standard; and
* * * * *
(l) A citation for violation of the standard shall be terminated by
MSHA when the equivalent concentration of each of the five valid
representative samples is at or below the standard.
(m) The District Manager may designate for sampling under this
section additional work positions at a surface coal mine and at a
surface work area of an underground coal mine where a concentration of
respirable dust exceeding 50 percent of the standard has been measured
by one or more MSHA valid representative samples.
(n) The District Manager may withdraw from sampling any DWP
designated for sampling under paragraph (m) of this section upon
finding that the operator is able to maintain continuing compliance
with the standard. This finding shall be based on the results of MSHA
and operator valid representative samples taken during at least a 12-
month period.
Table 1 to Sec. 71.206--Excessive Concentration Values (ECV) Based on a Single Sample, Two Samples, or the
Average of Five Full-Shift CMDPSU/CPDM Concentration Measurements
----------------------------------------------------------------------------------------------------------------
ECV (mg/m\3\)
Section Samples -------------------------------
CMDPSU CPDM
----------------------------------------------------------------------------------------------------------------
71.206(h)..................................... Single sample................... 1.79 1.70
71.206(i)(1).................................. 2 or more samples............... 1.79 1.70
71.206(i)(2).................................. 5 sample average................ 1.63 1.59
71.206(l)..................................... Each of 5 samples............... 1.79 1.70
----------------------------------------------------------------------------------------------------------------
Subpart D--Respirable Dust Control Plans
0
23. Amend Sec. 71.300 by revising paragraph (a) introductory text to
read as follows:
Sec. 71.300 Respirable dust control plan; filing requirements.
(a) Within 15 calendar days after the termination date of a
citation for violation of the standard, the operator shall submit to
the District Manager for approval a written respirable dust control
plan applicable to the DWP identified in the citation. The respirable
dust control plan and revisions thereof shall be suitable to the
conditions and the mining system of the coal mine and shall be adequate
to continuously maintain respirable dust to at or below the standard at
the DWP identified in the citation.
* * * * *
0
24. Amend Sec. 71.301 by revising paragraph (a)(1) to read as follows:
Sec. 71.301 Respirable dust control plan; approval by District
Manager and posting.
(a) * * *
(1) The respirable dust control measures would be likely to
maintain concentrations of respirable coal mine dust at or below the
standard; and
* * * * *
PART 72--HEALTH STANDARDS FOR COAL MINES
0
25. The authority citation for part 72 continues to read as follows:
Authority: 30 U.S.C. 811, 813(h), 957.
Subpart E--Miscellaneous
0
26. Revise Sec. 72.710 to read as follows:
Sec. 72.710 Selection, fit, use, and maintenance of approved
respirators.
Approved respirators shall be selected, fitted, used, and
maintained in accordance with the provisions of a respiratory
protection program consistent with the requirements, as applicable, of
ASTM F3387-19. ASTM F3387-19, Standard Practice for Respiratory
Protection approved August 1, 2019, is incorporated by reference into
this section with the approval of the Director of the Federal Register
under 5 U.S.C. 552(a) and 1 CFR part 51. This material is available for
inspection at the Mine Safety and Health Administration (MSHA) and at
the National Archives and Records Administration (NARA). Contact MSHA
at: MSHA's Office of Standards, Regulations, and Variances, 201 12th
Street South, Arlington, VA 22202-5450; 202-693-9440; or any Mine
Safety and Health Enforcement District Office. For information on the
availability of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The
material may be obtained from ASTM International, 100 Barr Harbor
Drive, P.O. Box C700, West Conshohocken, PA 19428-2959; www.astm.org/.
0
27. Revise Sec. 72.800 to read as follows:
Sec. 72.800 Single, full-shift measurement of respirable coal mine
dust.
The Secretary will use a single, full-shift measurement of
respirable coal mine dust to determine the average concentration on a
shift since that measurement accurately represents atmospheric
conditions to which a miner is exposed during such shift. Noncompliance
with the respirable dust standard, in accordance with this subchapter,
is demonstrated when a single, full-shift measurement taken by
[[Page 45018]]
MSHA meets or exceeds the applicable ECV in table 1 to Sec. 70.208,
table 1 to Sec. 70.209, table 1 to Sec. 71.206, or table 1 to Sec.
90.207 of this chapter that corresponds to the particular sampling
device used. Upon issuance of a citation for a violation of the
standard, and for MSHA to terminate the citation, the mine operator
shall take the specified actions in this subchapter.
PART 75--MANDATORY SAFETY STANDARDS--UNDERGROUND COAL MINES
0
28. The authority citation for part 75 continues to read as follows:
Authority: 30 U.S.C. 811, 813(h), 957.
Subpart D--Ventilation
0
29. Amend Sec. 75.350 by:
0
a. Revising paragraph (b)(3)(i);
0
b. Removing paragraph (b)(3)(ii); and
0
c. Redesignating (b)(3)(iii) as (b)(3)(ii).
The revision reads as follows:
Sec. 75.350 Belt air course ventilation.
* * * * *
(b) * * *
(3) * * *
(i) The average concentration of respirable dust in the belt air
course, when used as a section intake air course, shall be maintained
at or below 0.5 milligrams per cubic meter of air (mg/m\3\).
* * * * *
PART 90--MANDATORY HEALTH STANDARDS--COAL MINERS WHO HAVE EVIDENCE
OF THE DEVELOPMENT OF PNEUMOCONIOSIS
0
30. The authority citation for part 90 continues to read as follows:
Authority: 30 U.S.C. 811, 813(h), 957.
Subpart A--General
0
31. Amend Sec. 90.2 by revising the definition of ``Part 90 miner''
and removing the definition of ``Quartz''.
The revision reads as follows:
Sec. 90.2 Definitions.
* * * * *
Part 90 miner. A miner employed at a coal mine who has exercised
the option under the old section 203(b) program (36 FR 20601 preview
citation details, October 27, 1971), or under Sec. 90.3 to work in an
area of a mine where the average concentration of respirable dust in
the mine atmosphere during each shift to which that miner is exposed is
continuously maintained at or below the standard, and who has not
waived these rights.
* * * * *
0
32. Amend Sec. 90.3 by revising paragraph (a) to read as follows:
Sec. 90.3 Part 90 option; notice of eligibility; exercise of option.
(a) Any miner employed at a coal mine who, in the judgment of the
Secretary of HHS, has evidence of the development of pneumoconiosis
based on a chest X-ray, read and classified in the manner prescribed by
the Secretary of HHS, or based on other medical examinations shall be
afforded the option to work in an area of a mine where the average
concentration of respirable dust in the mine atmosphere during each
shift to which that miner is exposed is continuously maintained at or
below the standard. Each of these miners shall be notified in writing
of eligibility to exercise the option.
* * * * *
Subpart B--Dust Standards, Rights of Part 90 Miners
Sec. 90.101 [Removed and Reserved]
0
33. Remove and reserve Sec. 90.101.
0
34. Amend Sec. 90.102 by revising paragraph (a) to read as follows:
Sec. 90.102 Transfer; notice.
(a) Whenever a Part 90 miner is transferred in order to meet the
standard, the operator shall transfer the miner to an existing position
at the same coal mine on the same shift or shift rotation on which the
miner was employed immediately before the transfer. The operator may
transfer a Part 90 miner to a different coal mine, a newly created
position or a position on a different shift or shift rotation if the
miner agrees in writing to the transfer. The requirements of this
paragraph do not apply when the respirable dust concentration in a Part
90 miner's work position complies with the standard but circumstances,
such as reductions in workforce or changes in operational status,
require a change in the miner's job or shift assignment.
* * * * *
0
35. Amend Sec. 90.104 by revising paragraph (a)(2) to read as follows:
Sec. 90.104 Waiver of rights; re-exercise of option.
(a) * * *
(2) Applying for and accepting a position in an area of a mine
which the miner knows has an average respirable dust concentration
exceeding the standard; or
* * * * *
Subpart C--Sampling Procedures
0
36. Amend Sec. 90.205 by revising paragraph (c) to read as follows:
Sec. 90.205 Approved sampling devices; operation; air flowrate.
* * * * *
(c) If using a CPDM, the person certified in sampling shall monitor
the dust concentrations and the sampling status conditions being
reported by the sampling device at mid-shift or more frequently as
specified in the approved respirable dust control plan, if applicable,
to assure: The sampling device is in the proper location and operating
properly; and the work environment of the Part 90 miner being sampled
remains in compliance with the standard at the end of the shift. This
monitoring is not required if the sampling device is being operated in
an anthracite coal mine using the full box, open breast, or slant
breast mining method.
0
37. Amend Sec. 90.206 by revising paragraphs (b) and (c) to read as
follows:
Sec. 90.206 Exercise of option or transfer sampling.
* * * * *
(b) Noncompliance with the standard shall be determined in
accordance with Sec. 90.207(d).
(c) Upon issuance of a citation for a violation of the standard,
the operator shall comply with Sec. 90.207(f).
0
38. Amend Sec. 90.207 by:
0
a. Removing and reserving paragraph (b);
0
b. Revising paragraphs (c) introductory text, (c)(2), (d), (e), (f)
introductory text, (f)(2) introductory text, (f)(2)(ii), and (g);
0
c. Removing tables 90-1 and 90-2; and
0
d. Adding table 1.
The revisions and addition read as follows:
Sec. 90.207 Quarterly sampling.
* * * * *
(c) When a valid representative sample taken in accordance with
this section meets or exceeds the ECV in table 1 to this section
corresponding to the particular sampling device used, the mine operator
shall:
* * * * *
(2) Immediately take corrective action to lower the concentration
of respirable coal mine dust to below the standard; and
* * * * *
(d) Noncompliance with the standard is demonstrated during the
sampling period when:
(1) Two or more valid representative samples meet or exceed the ECV
in table 1 to this section that corresponds to the particular sampling
device used; or
(2) The average for all valid representative samples meets or
exceeds
[[Page 45019]]
the ECV in table 1 to this section that corresponds to the particular
sampling device used.
(e) Unless otherwise directed by the District Manager, upon
issuance of a citation for a violation of the standard, paragraph (a)
of this section shall not apply to that Part 90 miner until the
violation is abated and the citation is terminated in accordance with
paragraphs (f) and (g) of this section.
(f) Upon issuance of a citation for a violation of the standard,
the operator shall take the following actions sequentially:
* * * * *
(2) Immediately take corrective action to lower the concentration
of respirable dust to below the standard. If the corrective action
involves:
* * * * *
(ii) Transferring the Part 90 miner to another work position at the
mine to meet the standard, the operator shall comply with Sec. 90.102
and then sample the affected miner in accordance with Sec. 90.206(a).
* * * * *
(g) A citation for a violation of the standard shall be terminated
by MSHA when the equivalent concentration of each of the five valid
representative samples is below the standard.
Table 1 to Sec. 90.207--Excessive Concentration Values (ECV) Based on a Single Sample, Two Samples, or the
Average of Five Full-Shift CMDPSU/CPDM Concentration Measurements
----------------------------------------------------------------------------------------------------------------
ECV (mg/m\3\)
Section Samples -------------------------------
CMDPSU CPDM
----------------------------------------------------------------------------------------------------------------
90.207(c)..................................... Single sample................... 0.74 0.57
90.207(d)(1).................................. 2 or more samples............... 0.74 0.57
90.207(d)(2).................................. 5 sample average................ 0.61 0.53
90.207(g)..................................... Each of 5 samples............... 0.74 0.57
----------------------------------------------------------------------------------------------------------------
Subpart D--Respirable Dust Control Plans
0
39. Amend Sec. 90.300 by revising paragraphs (a) and (b)(3) to read as
follows:
Sec. 90.300 Respirable dust control plan; filing requirements.
(a) If an operator abates a violation of the standard by reducing
the respirable dust level in the position of the Part 90 miner, the
operator shall submit to the District Manager for approval a written
respirable dust control plan for the Part 90 miner in the position
identified in the citation within 15 calendar days after the citation
is terminated. The respirable dust control plan and revisions thereof
shall be suitable to the conditions and the mining system of the coal
mine and shall be adequate to continuously maintain respirable dust
below the standard for that Part 90 miner.
(b) * * *
(3) A detailed description of how each of the respirable dust
control measures used to continuously maintain concentrations of
respirable coal mine dust below the standard; and
* * * * *
0
40. Amend Sec. 90.301 by revising paragraphs (a)(1) and (b) to read as
follows:
Sec. 90.301 Respirable dust control plan; approval by District
Manager; copy to part 90 miner.
(a) * * *
(1) The respirable dust control measures would be likely to
maintain concentrations of respirable coal mine dust below the
standard; and
* * * * *
(b) MSHA may take respirable dust samples to determine whether the
respirable dust control measures in the operator's plan effectively
maintain concentrations of respirable coal mine dust below the
standard.
* * * * *
[FR Doc. 2023-14199 Filed 7-6-23; 11:15 am]
BILLING CODE 4520-43-P
