Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners, 32868-32968 [05-10681]
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Federal Register / Vol. 70, No. 107 / Monday, June 6, 2005 / Rules and Regulations
AGENCY:
compliance. Furthermore, this final
rule: Requires MSHA to consider
economic as well as technological
feasibility in determining if operators
qualify for an extension of time in
which to meet the final DPM limit;
deletes the requirement for a control
plan; and makes conforming changes to
existing provisions concerning
compliance determinations,
environmental monitoring and
recordkeeping.
SUMMARY: This final rule revises
MSHA’s existing standards addressing
diesel particulate matter (DPM)
exposure in underground metal and
nonmetal (M/NM) mines. In this final
rule, MSHA changes the interim
concentration limit measured by total
carbon (TC) to a comparable permissible
exposure limit (PEL) measured by
elemental carbon (EC), which renders a
more accurate DPM exposure
measurement. Also, this final rule
increases flexibility of compliance for
mine operators by requiring MSHA’s
longstanding hierarchy of controls for
its other exposure-based health
standards at M/NM mines, but retains
the prohibition on rotation of miners for
Effective Date: The final rule is
effective on July 6, 2005.
FOR FURTHER INFORMATION CONTACT:
Office of Standards, Regulations, and
Variances, MSHA, 1100 Wilson Blvd.,
Room 2350, Arlington, Virginia 22209–
3939; 202–693–9440 (telephone); or
202–693–9441 (facsimile).
You may obtain copies of this final
rule and the Regulatory Economic
Analysis (REA) in alternative formats by
calling 202–693–9440. The alternative
formats available are either a large print
version of these documents or electronic
files that can be sent to you either on a
computer disk or as an attachment to an
e-mail. The documents also are
available on the Internet at https://
www.msha.gov/REGSINFO.HTM.
SUPPLEMENTARY INFORMATION:
DEPARTMENT OF LABOR
Mine Safety and Health Administration
30 CFR Part 57
RIN 1219–AB29
Diesel Particulate Matter Exposure of
Underground Metal and Nonmetal
Miners
Mine Safety and Health
Administration (MSHA), Labor.
ACTION: Final rule.
DATES:
Commission .......................................................................
CV ......................................................................................
DE .......................................................................................
DOCs ..................................................................................
DPF .....................................................................................
DPM ...................................................................................
EC .......................................................................................
ETS .....................................................................................
Filter Selection Guide .......................................................
First Partial Settlement Agreement ..................................
HEI .....................................................................................
HWE ...................................................................................
MARG .................................................................................
M/NM .................................................................................
MSHA .................................................................................
NIOSH ................................................................................
NTP ....................................................................................
OC ......................................................................................
PAPR ..................................................................................
PEL .....................................................................................
PPM ....................................................................................
QRA ....................................................................................
REA ....................................................................................
Second Partial Settlement Agreement .............................
SD .......................................................................................
SKC ....................................................................................
TC .......................................................................................
USWA ................................................................................
µg/cm 2 ...............................................................................
µg/m 3 .................................................................................
2001 final rule ...................................................................
Amended 2001 final rule ..................................................
2002 final rule ...................................................................
2002 ANPRM .....................................................................
2003 NPRM ........................................................................
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Outline of Preamble
This outline will assist the mining
community in finding information in
this preamble.
I. List of Common Terms
II. Rulemaking Background
A. First Partial Settlement Agreement
B. Second Partial Settlement Agreement
III. The Final PEL
IV. The 31-Mine Study
A. Summary
B. Subsequent Activities
V. Compliance Assistance
A. Baseline Sampling
B. DPM Control Technology
VI. DPM Exposures and Risk Assessment
A. Introduction
B. DPM Exposures in Underground M/NM
Mines
C. Health Effects
D. Significance of Risk
VII. Feasibility
A. Background
B. Technological Feasibility
C. Economic Feasibility
VIII. Summary of Costs and Benefits
IX. Section-by-Section Analysis
X. Distribution Table
XI. Regulatory Impact Analysis
XII. References Cited
I. List of Common Terms
Listed below are the common terms
used in the preamble.
Federal Mine Safety and Health Review Commission.
coefficient of variation.
diesel exhaust.
diesel oxidation catalysts.
diesel particulate filter.
diesel particulate matter.
elemental carbon.
environmental tobacco smoke.
Diesel Particulate Filter. Selection Guide for Diesel-powered Equipment in Metal
and Nonmetal Mines.
66 FR 35518 (2001) & 66 FR 35521 (2001): basis for July 5, 2001 NPRM.
Health Effects Institute.
healthy worker effect.
Methane Awareness Resource Group.
metal/non-metal.
Mine Safety and Health Administration.
National Institute for Occupational Safety and Health.
National Toxicology Program.
organic carbon.
powered air-purifying respirator.
permissible exposure limit.
parts per million.
quantitative risk assessment.
Regulatory Economic Analysis.
67 FR 47296 (2002): basis for August 14, 2003 NPRM.
standard deviation.
SKC, Inc.
total carbon.
United Steelworkers of America.
micrograms per square centimeter.
micrograms per cubic meter.
January 19, 2001 DPM final rule.
2001 final rule amended on February 27, 2002.
February 27, 2002 final rule.
Advance Notice of Proposed Rulemaking published on September 25, 2002.
Notice of Proposed Rulemaking published on August 14, 2003.
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II. Rulemaking Background
On January 19, 2001, MSHA
published a final rule (2001 final rule)
addressing DPM exposure in
underground M/NM mines (66 FR
5706), amended on February 27, 2002 at
67 FR 9180 (2002 final rule). The 2001
final rule established new health
standards for underground M/NM mines
that use equipment powered by diesel
engines. The effective date of the 2001
final rule was listed as March 20, 2001.
On January 29, 2001, AngloGold (Jerritt
Canyon) Corp. and Kennecott Greens
Creek Mining Company filed a petition
for review of the 2001 final rule in the
District of Columbia Circuit Court of
Appeals. On February 7, 2001, the
Georgia Mining Association, the
National Mining Association (NMA), the
Salt Institute, and the Methane
Awareness Resource Group (MARG)
Diesel Coalition filed a similar petition
in the Eleventh Circuit. On March 14,
2001, Getchell Gold Corporation
petitioned for review of the rule in the
District of Columbia Circuit. The three
petitions were consolidated, and are
pending in the District of Columbia
Circuit. The United Steelworkers of
America (USWA) intervened in the
litigation.
While these challenges were pending,
the AngloGold petitioners filed with
MSHA an application for
reconsideration and amendment of the
2001 final rule and for postponement of
the effective date of the 2001 final rule
pending judicial review. The Georgia
Mining Association petitioners similarly
filed with MSHA a request for an
administrative stay or postponement of
the effective date of the 2001 final rule.
On March 15, 2001, MSHA delayed the
effective date of the 2001 final rule until
May 21, 2001, in accordance with a
January 20, 2001 memorandum from the
President’s Chief of Staff (66 FR 15032).
The delay was necessary to give
Department of Labor officials the
opportunity for further review and
consideration of new regulations. On
May 21, 2001 (66 FR 27863), MSHA
published a document in the Federal
Register delaying the effective date of
the 2001 final rule until July 5, 2001.
The purpose of this delay was to allow
the Department of Labor the opportunity
to engage in further negotiations to
settle the legal challenges to the 2001
final rule.
A. First Partial DPM Settlement
Agreement
As a result of a partial settlement
agreement with the litigants, MSHA
published two documents in the
Federal Register on July 5, 2001
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The document also stayed the
effectiveness of the following provisions
pending completion of this final rule:
• § 57.5060(d), Permitting miners to
work in areas where the level of DPM
exceeds the applicable concentration
limit with advance approval from the
Secretary;
• § 57.5060(e), Prohibiting the use of
personal protective equipment (PPE) to
comply with the concentration limits;
• § 57.5060(f) Prohibiting the use of
administrative controls to comply with
the concentration limits; and
• § 57.5062, DPM control plan.
Finally, the July 18, 2002, document
outlined the terms of the DPM
settlement agreement and announced
MSHA’s intent to propose specific
changes to the rule, as discussed below.
On September 25, 2002, MSHA
published an Advance Notice of
Proposed Rulemaking (2002 ANPRM)
(67 FR 60199) to amend certain
provisions of the 2001 DPM rule.
The comment period closed on
November 25, 2002. MSHA received
comments from underground M/NM
mine operators, trade associations,
organized labor, public interest groups
and individuals. On August 14, 2003,
MSHA published the 2003 NPRM in the
Federal Register (68 FR 48668)
recommending certain revisions to the
DPM rule as part of a settlement
B. Second Partial Settlement Agreement agreement reached in response to a legal
challenge to the DPM standard. Public
Settlement negotiations continued on hearings were held in Salt Lake City,
the remaining unresolved issues in the
Utah; St. Louis, Missouri; Pittsburgh,
litigation. On July 15, 2002, the parties
Pennsylvania; and Arlington, Virginia in
signed an agreement (second partial
September and October 2003. The
settlement agreement) that formed the
comment period closed on October 14,
basis for MSHA’s August 14, 2003
2003. On February 20, 2004, MSHA
proposed rule (68 FR 48668) (2003
published a document in the Federal
NPRM). On July 18, 2002, MSHA
Register announcing a limited
published a document in the Federal
reopening of the comment period on the
Register (67 FR 47296) announcing,
2003 NPRM. This document reopened
among other things, that the following
the comment period to obtain public
provisions of the 2001 final rule would
input on three new documents related
become effective on July 20, 2002:
to the August 14, 2003 rulemaking (69
• § 57.5060(a), Addressing the interim FR 7881). The three documents were as
concentration limit of 400 micrograms
follows:
of TC per cubic meter of air;
(1) United States (U.S.) Department of
• § 57.5061, Compliance
Health and Human Services, Center for
determinations; and
Disease Control, National Institute of
• § 57.5071, Environmental
Occupational Safety and Health, ‘‘The
monitoring.
Effectiveness of Selected Technologies
The document also announced that
in Controlling Diesel Emissions in an
the following provisions of the rule
Underground Mine—Isolated Zone
would continue in effect:
Study at Stillwater Mining Company’s
• § 57.5065, Fueling practices;
Nye Mine,’’ January 5, 2004.
• § 57.5066, Maintenance standards;
(2) U.S. Department of Labor, Bureau
• § 57.5067, Engines;
of Labor Statistics, and U.S. Department
• § 57.5070, Miner training; and
of Health and Human Services, Center
for Disease Control, National Institute of
• § 57.5075, Diesel particulate
Occupational Safety and Health,
records, as they relate to the
‘‘Respirator Usage in Private Sector
requirements of the rule that went into
Firms, 2001,’’ September, 2003.
effect on July 20, 2002.
addressing the 2001 final rule. One
document (66 FR 35518) delayed the
effective date of § 57.5066(b) regarding
the tagging provision of the
maintenance standard; clarified the
effective dates of certain provisions of
the 2001 final rule; and included
correcting amendments.
The second document (66 FR 35521)
proposed a rule to clarify § 57.5066(b)(1)
and (b)(2) regarding maintenance and to
add a new paragraph (b)(3) to § 57.5067
regarding the transfer of existing
equipment between underground mines.
MSHA published these changes as a
final rule on February 27, 2002 (67 FR
9180) (2002 final rule), with an effective
date of March 29, 2002.
Under the first partial settlement
agreement, MSHA also conducted joint
sampling with industry and labor at 31
underground M/NM mines to determine
existing concentration levels of DPM; to
assess the performance of the SKC, Inc.,
Eighty Four, PA (SKC) submicron dust
sampler with the NIOSH Method 5040;
to assess the feasibility of achieving
compliance with the standard’s
concentration limits at the 31 mines;
and to assess the impact of interferences
on samples collected in the M/NM
underground mining environment
before the limits established in the final
rule became effective. The final report
was issued on January 6, 2003.
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(3) Chase, Gerald, ‘‘Characterizations
of Lung Cancer in Cohort Studies and a
NIOSH Study on Health Effects of Diesel
Exhaust in Miners,’’ undated, received
January 5, 2004.
The subsequent comment period
closed on April 5, 2004. MSHA received
and reviewed written and oral
statements on the 2003 NPRM from all
segments of the mining community.
MSHA informed the mining
community in both its 2002 ANPRM
and its 2003 NPRM of its intentions to
incorporate into the record of the
current rulemaking the existing
rulemaking record, including the risk
assessment to the 2001 final rule.
Commenters were encouraged to submit
additional evidence of new scientific
data related to health risks to
underground M/NM miners from
exposure to DPM.
This final rule for DPM exposure at
M/NM mines is based on consideration
of the entire rulemaking record,
including all written comments and
exhibits received related to the 2001
final rule as well as all related data
received to the close of this rulemaking
record. To serve the interest of the
mining community, MSHA is revising
§§ 57.5060, 57.5061, 57.5071, and
57.5075 and republishing §§ 57.5065,
57.5066, 57.5067, and 57.5070 of the
DPM standards at 30 CFR part 57 in
order to present all sections in their
entirety in this document. What follows
is a discussion of the specific revisions
to the 2001 DPM standard:
• § 57.5060(a) addressing the interim
limit on concentration of DPM. MSHA
has changed the 2001 final rule’s
interim concentration limit of 400
micrograms of TC per cubic meter of air
(400TC µg/m3) to a comparable
permissible exposure limit of 308
micrograms of EC per cubic meter of air
(308EC µ/m3);
• § 57.5060(c) addressing application
and approval requirements for an
extension of time in which to reduce the
final DPM limit. MSHA has changed the
2001 final rule by requiring MSHA to
consider economic feasibility along with
technological feasibility factors in
weighing whether to grant special
extensions; has deleted the limit on the
number of special extensions that may
be granted to each mine; has limited
each extension to a period of one year;
has allowed for annual renewals of
special extensions; and has allowed the
MSHA District Manager, rather than the
Secretary, to grant extensions. This final
rule retains the scope of the 2001
provision for operators to apply for
extensions to the final DPM limit;
• § 57.5060(d) addressing certain
exceptions to the concentration limits;
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• § 57.5060(e) prohibiting use of PPE
to comply with the concentration limits;
• § 57.5060(f) prohibiting use of
administrative controls to comply with
the concentration limits. MSHA has
changed the 2001 final rule by
implementing the current hierarchy of
controls as adopted in MSHA’s other
exposure-based health standards for M/
NM mines. MSHA’s hierarchy includes
primacy of engineering and
administrative controls to the extent
feasible to reduce a miner’s exposure to
the PEL, but MSHA continues to
prohibit rotation of miners for
compliance purposes. If a miner’s
exposure cannot be reduced to the PEL
with use of feasible controls, controls
are infeasible, or do not produce
significant reductions in DPM
exposures, the new final rule requires
mine operators to supplement a miner’s
protection with respirators and
implement a respiratory protection
program. This respiratory protection
program must meet the requirements in
existing 30 CFR 57.5005, but miners
may only use the respirator filters
specified by MSHA for DPM in this
section. Therefore, MSHA removes the
2001 prohibition against use of
respiratory protection without approval
by the Secretary and clarifies that use of
administrative controls other than
rotation of miners is allowed;
• § 57.5062, addressing the diesel
particulate control plan. This final rule
removes the existing requirement for a
DPM control plan; and
• conforming changes to the
following existing standards that were
proposed on August 14, 2003:
Æ § 57.5061, addressing compliance
determinations;
Æ § 57.5071, addressing exposure
monitoring; and,
Æ § 57.5075, addressing
recordkeeping requirements.
This final rule does not include
provisions for written procedures for
administrative controls, a written
respiratory protection program, medical
examination of miners before they are
required to wear respiratory protection,
and medical transfer of miners who are
unable to wear respiratory protection for
medical and psychological reasons.
III. The Final Concentration Limit
In the 2002 ANPRM, MSHA notified
the mining community that this
rulemaking would revise both the
interim concentration limit of 400
micrograms per cubic meter of air and
the final concentration limit of 160
micrograms per cubic meter of air under
§ 57.5060(a) and (b) of the 2001 final
rule. Some commenters to the ANPRM
recommended that MSHA propose
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separate rulemakings for revising the
interim and final DPM limits to give
MSHA an opportunity to gather further
information to establish a final DPM
limit. In the 2003 NPRM, MSHA agreed
with these commenters and solicited
other information from the mining
community that would lead to an
appropriate final DPM standard.
Moreover, MSHA announced its
intentions to publish a separate
rulemaking to amend the existing final
concentration limit in § 57.5060(b). To
assist MSHA in achieving this purpose,
MSHA requested comments on an
appropriate final permissible exposure
limit rather than a concentration limit;
and asked for information on an
appropriate surrogate for measuring
miners’ DPM exposures. MSHA
concluded its request for information by
clarifying that revisions to the final
DPM concentration limit would not be
a part of this rulemaking.
In their comments to the 2003 NPRM,
organized labor requested that MSHA
lower the final DPM limit below 160
micrograms based on feasibility data
and the significance of the health risks
from exposure to DPM. Industry trade
associations and individual mine
operators recommended that MSHA
repeal the final limit based on issues
related to health effects, inability of the
mining industry to meet a lower limit
than 400 micrograms per cubic meter of
air, and the need for MSHA to have the
results from the National Institute for
Occupational Safety and Health/
National Cancer Institute (NIOSH/NCI)
study and exposure-response data.
MSHA believes that evidence in the
current DPM rulemaking record is
inadequate for MSHA to make
determinations regarding revision to the
final DPM limit.
IV. The 31-Mine Study
A. Summary
On January 19, 2001, MSHA
published a final standard addressing
exposure of underground metal and
nonmetal miners to diesel particulate
matter (DPM). The standard contained
staggered effective dates for interim and
final concentration limits. The standard
was challenged by industry trade
associations and several mining
companies, and the United Steelworkers
of America (USWA) intervened in the
litigation. The parties agreed to resolve
their differences through settlement
negotiations with MSHA. Thereafter,
MSHA delayed the effective date of
certain provisions of the standard. As
part of the settlement negotiations,
MSHA agreed to conduct joint sampling
with the litigants at 31 metal and
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nonmetal underground mines covered
by the standard to determine existing
concentration levels of DPM in
operating mines and to measure DPM
levels in the presence of known or
suspected interferences.
on Data Collected During a Joint MSHA/
Industry Study of DPM Levels in
Underground Metal And Nonmetal
Mines’’ (Report on the 31-Mine Study).
MSHA’s major conclusions drawn from
the study are as follows:
The goals of the study were to use the
sampling results and related information to
assess:
—The validity, precision and feasibility of
the sampling and analysis method
specified by the diesel standard (NIOSH
Method 5040);
—The magnitude of interferences that occur
when conducting enforcement sampling
for total carbon as a surrogate for diesel
particulate matter (DPM) in mining
environments; and,
—The technological and economic feasibility
of the underground metal and nonmetal
(MNM) mine operators to achieve
compliance with the interim and final
DPM concentration limits.
—The parties developed a joint MSHA/
Industry study protocol to guide sampling
and analysis of DPM levels in 31 mines.
The parties also developed four
subprotocols to guide investigations of the
known or suspected interferences, which
included mineral dust, drill oil mist, oil
mist generated during ammonium nitrate/
fuel oil (ANFO) loading operations, and
environmental tobacco smoke (ETS). The
parties also agreed to study other potential
sampling problems, including any
manufacturing defects of the DPM
sampling cassette. (Executive Summary,
Report on the 31-Mine Study)
—The analytical method specified by the
diesel standard gives an accurate measure
of the TC content of a filter sample and the
analytical method is appropriate for
making compliance determinations of DPM
exposures of underground metal and
nonmetal miners.
—SKC satisfactorily addressed concerns over
defects in the DPM sampling cassettes and
availability of cassettes to both MSHA and
mine operators.
—Compliance with both the interim and final
concentration limits may be both
technologically and economically feasible
for metal and nonmetal underground
mines in the study. MSHA, however, has
limited in-mine documentation on DPM
control technology. As a result, MSHA’s
position on feasibility does not reflect
consideration of current complications
with respect to implementation of controls,
such as retrofitting and regeneration of
filters. MSHA acknowledges that these
issues may influence the extent to which
controls are feasible. The Agency is
continuing to consult with the National
Institute of Occupational Safety and
Health, industry and labor representatives
on the availability of practical mine worthy
filter technology.
—The submicron impactor was effective in
removing the mineral dust, and therefore
its potential interference, from DPM
samples. Remaining interference from
carbonate interference is removed by
subtracting the 4th organic peak from the
analysis. No reasonable method of
sampling was found to eliminate
interferences from oil mist or that would
effectively measure DPM levels in the
presence of ETS with TC as the surrogate
* * * (Executive Summary, Report on the
31-Mine Study)
MSHA requested that NIOSH peer
review the draft Report on the 31-Mine
Study, and NIOSH’s conclusions were
as follows:
1. Most mines have DPM concentrations
higher than 400TC µg/m3.
2. The impactor was effective in
eliminating mineral dust from collecting onto
the filter analyzed for carbon by NIOSH
Method 5040.
3. The ANFO data was inconclusive.
4. Oil mist from the stoper drill is a submicron aerosol and a potential interference.
Oil mist contamination from the driller can
be avoided by sampling upstream of stope or
far enough downstream that the oil mist has
been diluted enough to give minimal TC
concentrations (if this type of sampling is
possible).
5. No information about the interference of
environmental tobacco smoke is present in
this report.
6. The inter-laboratory comparison of the
NIOSH method 5040 of paired punches from
the same filter showed reasonable agreement
between MSHA results and commercial
laboratory results and excellent agreement
between MSHA and NIOSH laboratory
results. (Summary of Findings of this Report
in ‘‘NIOSH Comments and recommendations
on the MSHA DRAFT report: Report on the
Joint MSHA/Industry Study: Determination
of DPM Levels in Underground Metal and
Nonmetal Mines,’’ dated June 3, 2002)
On January 6, 2003, MSHA issued its
final report entitled, ‘‘MSHA’s Report
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MSHA’s complete report on the 31Mine Study is contained in the
rulemaking record.
MSHA and NIOSH have reviewed the
performance characteristics of the SKC
sampler, and are satisfied that it
accurately measures exposures to DPM.
NIOSH found in laboratory and field
data that the SKC DPM cassette
collected DPM efficiently. In a side
protocol of the 31-Mine Study, MSHA
tested the efficiency of the SKC DPM
cassette to avoid mineral dust in four
different mines and did not measure any
mineral dust on the filter when the SKC
DPM cassette was used. This was
confirmed by laboratory results at
NIOSH. (Noll, J. D., Timko, R. J.,
McWilliams, L., Hall, P., Haney, R.,
‘‘Sampling Results of the Improved SKC
Diesel Particulate Matter Cassette,’’
JOEH, 2005 Jan; 2(1):29–37.)
Results of the 31-Mine Study and the
MSHA baseline compliance assistance
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sampling demonstrated that the SKC
submicron impactor removed potential
interferences from mineral dust from the
collected sample.
Interference from drill oil mist was
found on personal samples collected on
the stoper and jackleg drillers and on
area samples collected in the stope
where drilling was being performed.
Use of a dynamic blank did not
eliminate drill oil mist interference.
Tests to confirm whether oil mist from
ANFO loading operations could be an
interference were not conclusive.
Blasting did not interfere with diesel
particulate measurements. MSHA found
no reasonable method of sampling to
eliminate interferences from oil mist
when TC is used as the surrogate.
No reliable marker was identified for
confirming the presence of ETS in an
atmosphere containing DPM. Use of the
impactor does not remove the ETS as an
interferent. No reasonable method of
sampling was found that would
effectively measure DPM levels in the
presence of ETS with TC as the
surrogate.
MSHA has found that the use of EC
eliminates potential sampling
interference from drill oil mist, tobacco
smoke, and organic solvents, and that
EC consistently represents DPM. In
comparison to using TC as the DPM
surrogate, using EC would impose fewer
restrictions or caveats on sampling
strategy (locations and durations),
would produce a measurement much
less subject to questions, and inherently
would be more precise. Furthermore,
NIOSH, the scientific literature, and the
MSHA laboratory tests indicate that
DPM, on average, is approximately 60 to
80% elemental carbon, firmly
establishing EC as a valid surrogate for
DPM.
As part of the 31-Mine Study,
representatives from MSHA, NIOSH,
and SKC met to address the following
issues:
• The quality of manufactured SKC
DPM cassettes;
• The feasibility of adding a dynamic
blank filter to the SKC DPM cassette;
and
• The possibility of putting a number
on each SKC DPM cassette.
Also, in its October 16, 2001 letter,
MSHA informed SKC about the
problems that MSHA and the industry
encountered using the SKC DPM
sampling cassette with the submicron
impactor. These problems included:
dark flecks, alleged leaks, loose fitting
nozzles and connectors, and difficulty
in shipping the sampler. As discussed
in the report on the 31-Mine Study, SKC
was responsive in addressing those
concerns.
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B. Subsequent Activities
Some industry commenters continued
to state that the sampling and analytical
processes for DPM are too new for
regulatory use. Other commenters
questioned the availability and
reliability of the SKC impactor.
MSHA moved expeditiously to help
resolve the back-order and
manufacturing delays for samplers
reported in the 31-Mine Study.
However, operators who sample
alongside MSHA continued to request
ample notice to have enough samplers
available. MSHA purchased many of the
initial production runs of these
samplers to conduct its compliance
assistance baseline sampling. Once the
initial orders were filled, the sampler
became more widely available.
Some commenters stated that SKC
changed the impactor, and that NIOSH
should test the new SKC sampler and
evaluate its comparability to the model
used in the 31-Mine Study. One of these
commenters stated that the shelf life of
the prior sampler affected TC
measurements by adsorbing organic
carbon (OC) from the polystyrene
assembly onto the filter media and
increasing TC measurement. These
commenters questioned MSHA’s
changes to the SKC sampler following
completion of the 31-Mine Study, and
suggested that a defect to the sampler
could have affected the results of the
study. During the 31-Mine Study,
MSHA observed that the deposit area of
the SKC submicron impactor filter was
not as consistent as those obtained for
preliminary evaluation. This was
attributed to inconsistent crimping of
the aluminum foil cone on the filter
capsule.
Prior to the 31-Mine Study, MSHA
had determined the deposit area of the
sample filter to be 9.12 square
centimeters (cm2) with a standard
deviation of 3.1 percent (%). During the
initial phases of the sampling analysis
of the 31-Mine Study, it became
apparent that the variability of the
deposit area was greater than originally
determined. The filter area is critical to
the concentration calculation. The filter
area (measured in cm2) is multiplied by
the results of the analysis (micrograms
per cm2) to get the total filter loading
(micrograms). While individual filter
areas could be measured, it is more
practical to have a uniform deposit area
for the calculations. As a result, NIOSH
and MSHA consulted with SKC to
develop an improved filter cassette
design. With the cooperation of MSHA
and the technical recommendations and
extensive experimental verification by
NIOSH, SKC was able to modify their
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23:23 Jun 03, 2005
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cassette design to produce a consistent
and regular DPM deposit area,
satisfactorily resolving the problem.
SKC, in cooperation with MSHA and
NIOSH, then modified the DPM cassette
following the 31-Mine Study.
The modification was limited to
replacing the foil filter capsule with a 32
millimeter (32-mm) ring. This was done
to give a more uniform deposit area
(8.04 cm2) with negligible variability,
and to accommodate two 38-mm quartz
fiber filters in tandem (double filters).
These double filters are assembled into
a single cassette along with the
impactor. The 38-mm filters also
eliminate cassette leakage around the
filters. These modifications were
completed and incorporated into units
manufactured after November 1, 2002.
The results of this project were
prepared into a scientific publication,
‘‘Sampling Results of the Improved SKC
Diesel Particulate Matter Cassette,’’
referenced above. This paper has been
peer reviewed and was published in
January 2005. The following abstract
was prepared for the study results:
Diesel particulate matter (DPM) samples
from underground metal/non-metal mines
are collected on quartz fiber filters and
measured for carbon content using National
Institute for Occupational Safety and Health
Method 5040. If size selective samplers are
not used to collect DPM in the presence of
carbonaceous ore dust, both the ore dust and
DPM will collect on the quartz filters,
causing the carbon attributed to DPM to be
artificially high. Because the DPM particle
size is much smaller than that of
mechanically generated mine dust aerosols, it
can be separated from the larger mine dust
aerosol by a single stage impactor. The SKC
DPM cassette is a single stage impactor
designed to collect only DPM aerosols in the
presence of carbonaceous mine ore aerosols,
which are commonly found in underground
nonmetal mines. However, there is limited
data on how efficiently the SKC DPM cassette
can collect DPM in the presence of ore dust.
In this study, we investigated the ability of
the SKC DPM cassette to collect DPM while
segregating ore dust from the sample. We
found that the SKC DPM cassette accurately
collected DPM. In the presence of carbonbased ore aerosols having an average
concentration of 8 mg/m3, no ore dust was
detected on SKC DPM cassette filters. We did
discover a problem: the surface areas of the
DPM deposits on SKC DPM cassettes,
manufactured prior to August 2002, were
inconsistent. To correct this problem, SKC
modified the cassette. The new cassette
produced, with 99% confidence, a range of
DPM deposit areas between 8.05 and 8.28
cm2, a difference of less than 3%.
Because the design of the inlet
cyclone, impaction nozzles, and the
impaction plate and the flow rate did
not change, the modifications to the
filter assembly did not alter the
collection or separation performance of
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the impactor. Throughout the
compliance baseline sampling, the
impactor has been a consistent and
reliable sampling cassette.
Tandem filters were used in the oil
mist and ANFO interference evaluations
during the 31-Mine Study. The top filter
collects the sample and the bottom filter
is a dynamic blank. The dynamic blank
provides a unique field blank for each
DPM cassette. The use of EC as a
surrogate would resolve the
commenter’s concern about shelf life
and OC out-gassing on the filter. Shelf
life and OC out-gassing are issues
relative to OC measurements. These two
issues do not apply to an EC
measurement. Once the cassettes have
been preheated during manufacturing,
there is no source, other than sampling,
to add EC to the sealed cassette filters.
MSHA discussed in the preamble to
the 2003 NPRM issues related to
interferences, field blanks and the error
factor. Some comments on the 2003
NPRM still expressed concerns on
interferences and further stated that the
MSHA industrial hygiene studies,
conducted to verify the magnitude of
the interference problem, were not
published or peer reviewed and should
be removed from the rulemaking record.
However, MSHA, organized labor, and
the mining industry, through the
negotiations process, jointly developed
the protocol for conducting the 31-Mine
Study. All of the parties agreed on the
protocol following numerous
discussions among industry, labor, and
government experts, and had an
opportunity to comment and make
changes to the document. Thereafter,
MSHA conducted the study, following
the agreed upon protocol, and published
its results. Before publication, the report
was peer reviewed by NIOSH. Industry
was given an opportunity to publish
their separate results simultaneously
with the government. During this
rulemaking, industry submitted to
MSHA through the notice and comment
process their conclusions on the 31Mine Study in a report titled,
‘‘Technical and Economic Feasibility of
DPM Regulations.’’ The industry report
is contained in the rulemaking record,
and was considered by MSHA in
reaching determinations for this final
rule.
(1) Interferences
In response to the question on
whether there are interferences when EC
is used as the surrogate, some
commenters stated that interferences
were thoroughly discussed in the
preamble to the 2001 final rule, and that
reasonable practices to avoid them were
stipulated in the rule itself. According
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to these commenters, this problem
should not be revisited in this
rulemaking.
Other commenters maintained that
the 31-Mine Study did not contain the
necessary protocols to address all
potential interferences. Thus, in their
view, MSHA does not have all the data
required to answer this question. More
specifically, some commenters stated
that carbonaceous particulate in host
rock has a smaller diameter than the
impactor cut point and so, may
contaminate EC samples. These
commenters then concluded that MSHA
should propose additional research and
seek comments on the research before
concluding that sampling EC with an
impactor will eliminate all interference
problems. However, no data were
presented to support this claim or
conclusion. Commenters submitted no
new information relative to
interferences in response to the 2003
NPRM.
(2) Field Blanks
A field blank is an unexposed control
filter meant to account for background
interferences and systematic
contamination in the field, spurious
effects due to manufacturing and storage
of the filter, and systematic analytical
errors. The tandem filter arrangement in
the sample cassette provides a primary
filter for collecting an air sample and a
second filter, behind (after) the primary
filter, which provides a separate control
filter for each sample. This is a much
more flexible method of sampling for
the mining industry, since it eliminates
the need to send a separate control filter
to the analytical lab. MSHA informed
the public of its intentions to adjust the
EC result obtained for each sample by
the result obtained for the
corresponding media blank when
MSHA measures for compliance
purposes. When MSHA conducts
compliance measurements, MSHA will
adjust the result obtained for each
corresponding sample by the field blank
(tandem filter) result. No comments or
information related to field blanks were
submitted to MSHA in response to the
2003 NPRM.
In its comments on the 2002 ANPRM,
NIOSH noted that two types of blanks,
media and field, are normally used for
quality assurance purposes. A media
blank accounts for systematic
contamination that may occur during
manufacturing or storage. A field blank
accounts for possible systematic
contamination in the field. NIOSH does
not recommend use of field blanks
when EC is the surrogate. This is
because EC measurements are not
subject to sources of contamination in
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23:23 Jun 03, 2005
Jkt 205001
the field that would affect OC and TC
results. Quartz-fiber filters are prone to
OC vapor contamination in the field and
to contamination by less volatile OC
(such as oils) during handling. However,
such contamination is irrelevant when
EC is the surrogate.
(3) Error Factor
MSHA intends to cite a violation of
the DPMEC exposure limit only when
MSHA has valid evidence that a
violation actually occurred. As with all
other measurement-based M/NM
compliance determinations, MSHA will
issue a citation only if a measurement
demonstrates noncompliance with at
least 95% confidence. MSHA will
achieve this 95% confidence level by
comparing each EC measurement to the
EC exposure limit multiplied by an
appropriate error factor. Generally, an
error factor is used to compensate for
certain known inaccuracies in the
sampling and analytical process,
including such things as the reliability
of sampling equipment and precision of
analytical instrumentation. MSHA will
continue to determine that an
overexposure has occurred when a
sample exceeds the interim limit times
the error factor.
In this rulemaking, MSHA is
discussing the procedure used to obtain
the error factor. This procedure is
further discussed on the MSHA web site
at www.msha.gov under, ‘‘Single Source
Page for Metal and Nonmetal Diesel
Particulate Matter Regulations.’’ Error
factors are based on sampling and
analytic errors. The manufacturers of
sampling devices thoroughly investigate
and quantify the error factors for their
devices. While MSHA does not
frequently change an error factor, it
retains that latitude should significant
changes to either analytical or sampling
technology occur.
The formula for the error factor was
based on three factors involved in
making an eight-hour equivalent fullshift measurement of EC concentration
using NIOSH Method 5040: (1)
Variability in air volume (i.e., pump
performance relative to the nominal
airflow of 1.7 L/min); (2) variability of
the deposit area of particles on the filter
(cm2); and (3) accuracy of the laboratory
analysis of EC density within the
deposit (µg/cm2). Modifications made to
the sampler since the time of the 31Mine Study have no bearing on the first
and third of these factors. Variability of
the filter deposit area was represented
by a 3.1% coefficient of variation, based
on an experiment carried out before the
foil filter capsule in the sampling
cassette was replaced by a 32-mm ring.
Measurements subsequent to
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32873
introduction of the ring show that
variability of the filter deposit area is
now less than 3.1% (Noll, J. D., et al,
‘‘Sampling Results of the Improved SKC
Diesel Particulate Matter Cassette’’).
This change slightly reduces the error
factor stipulated for EC measurements,
but not by enough to be of any practical
significance.
MSHA’s error factor model accounts
for the joint and related variability in
laboratory analysis, and combines that
variability with pump flow rate, sample
collection size, and other sampling and
analytic variables. MSHA was then able
to determine the appropriate error factor
for EC samples based on a statistically
strong database.
The analytical method (NIOSH 5040)
relies on a punch taken from inside the
deposit area on the sample filter. In
effect, the punch is a sample of the dust
sample. To account for uniformity in the
distribution of DPM deposited on the
filter, as reflected by different possible
locations at which a punch might be
extracted, MSHA compared two
punches taken from different locations
on the same filter to evaluate the
accuracy of the analytical method.
Therefore, variability between punch
results due to their location on the filter
is also included in the error factor as
calculated by MSHA.
Commenters to the 2003 NPRM
further questioned whether the NIOSH
Method 5040 has been commercially
tested. As in the preamble to the 2003
NPRM, MSHA has discussed in detail
its findings regarding the NIOSH
Method 5040 in this section. NIOSH’s
peer review of the 31-Mine Study also
concludes that the analytical method
specified by the diesel standard gives an
accurate measure of the TC content of a
filter sample. NIOSH confirmed this
position by letter of February 8, 2002, in
which NIOSH stated that,
MSHA is following the procedures of NIOSH
Method 5040, based on our review of MSHA
P13 (MSHA’s protocol for sample analysis by
NIOSH Method 5040) and a visit to the
MSHA laboratory.
V. Compliance Assistance
A. Baseline Sampling Summary
Under the second partial DPM
settlement agreement, MSHA agreed to
provide compliance assistance to the
M/NM underground mining industry for
a one-year period from July 20, 2002
through July 19, 2003. As part of its
compliance assistance activities, MSHA
agreed to conduct baseline sampling of
miners’ personal exposures at every
underground mine covered by the 2001
final rule.
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Our baseline sampling began in
October 2002 and continued through
October 2003. During this period a total
of 1,194 valid baseline samples were
collected. A total of 183 underground
M/NM mines are represented by this
analysis. The number of samples per
mine range from one to twenty. All 874
valid baseline sampling results in the
analysis published in the preamble of
the 2003 NPRM are included in this
updated analysis. MSHA is including
320 additional valid samples because
MSHA decided to continue to conduct
baseline sampling after July 19, 2003 in
response to mine operators’ concerns.
MSHA has analyzed all baseline
samples, and updated its analysis. Some
of these mines were either not in
operation or were implementing major
changes to ventilation systems during
the original baseline period. MSHA is
including supplementary samples from
seasonal and intermittent mines, mines
that were under-represented, and mines
that were not represented in the analysis
published in the preamble to the 2003
NPRM. Sixty mines included in the
former analysis had additional samples
taken during the extended assistance
period. There are 12 mines in this
updated analysis that were not
represented in the 2003 analysis. The
results of this sampling were used by
MSHA in this preamble to estimate
current DPM exposure levels in
underground M/NM mines using diesel
equipment. These sampling results also
assist mine operators in developing
compliance strategies based on actual
exposure levels.
This section summarizes analytical
results of personal sampling for DPM
collected during compliance assistance.
There are a total of 1,206 samples.
However, 12 samples are invalid due to
abnormal sample deposits, broken
cassettes or filters, contaminated backup
pads, instrument failure or pump
failure. Table V–1 lists the frequencies
[EC
(
Jkt 205001
(
)
Flow Rate ( Lpm ) × 480 ( minutes)
EC = The corrected elemental carbon
concentration measured in the
thermal/optical carbon analyzer,
µg/cm2,
OC = The corrected organic carbon
concentration measured in the
thermal/optical carbon analyzer,
µg/cm2,
23:23 Jun 03, 2005
)
regardless of the number of hours
worked. For the 1,194 valid personal
samples, 85% were collected for at least
eight hours. TC and EC levels, as well
as DPM levels, are reported in units of
micrograms per cubic meter for an 8hour full shift equivalent.
MSHA collected DPM samples with
SKC submicron dust samplers that use
Dorr-Oliver cyclones and submicron
impactors. The samples were analyzed
either at MSHA’s Pittsburgh Safety and
Health Technology Center, Dust
Division Laboratory or at the Clayton
Laboratory using MSHA Method P–13
(NIOSH Analytical Method 5040,
NIOSH Manual of Analytical Methods
(NMAM), Fourth Edition, September 30,
1999) for determining the TC content.
Each sample was analyzed for organic,
elemental, and carbonaceous carbon and
calculated TC. Raw analytical results
from both laboratories as well as
administrative information about the
sample were stored electronically in
MSHA’s Laboratory Information
Management System.
If a raw carbon result was greater than
or equal to 30 µg/cm2 of EC or 40 µg/
cm2 of TC from the exposed filter
loading, then the analysis was repeated
using a separate punch of the same
filter. The results of these two analyses
were then averaged. The companion
tandem blank was also tested for the
same analyses. Otherwise, an
unexposed filter from the same
manufacturer’s lot was used to correct
for background levels. In the event the
initial TC result was greater than 100TC
µg/cm2, a smaller punch of the same
exposed filter (in duplicate and with the
corresponding blank) was taken and
used in the analysis. Blank-corrected
averaged results were used in the
analysis when the sample was tested in
duplicate.
The equation used to calculate a 480minute (8-hour) full shift equivalent
(FSE) exposure of TC is Total Carbon
Concentration =
(
× 1.3] or [OC + EC] µg/cm 2 × A cm 2 × 1,000 L/ m 3
Where:
VerDate jul<14>2003
of invalid samples within each
commodity.
The mines that were sampled produce
clay, sand, gypsum, copper, gold,
platinum, silver, gem stones, dimension
marble, granite, lead-zinc, limestone,
lime, potash, molybdenum, salt, trona,
and other miscellaneous metal or
nonmetal ores. These commodities were
grouped into four general categories for
calculating summary statistics: Metal,
stone, trona, and other nonmetal (N/M)
mines. These categories were selected to
be consistent with the categories used
for analysis of data for the 31-Mine
Study. Most commodities are well
represented in this analysis with the
average number of valid samples per
mine ranging from 6.0 to 8.2 (average
across all mines is 6.5 samples per
mine). The average number of samples
per mine classified as ‘‘Gold Ore
Mining, N.E.C.’’ increased from an
average of 2.0 samples per mine
published in the 2003 NPRM preamble
to an average of 4.6 samples in this data
set. Approximately 79% of all mines
sampled during the assistance period
have four or more results from DPM
sampling in this analysis. Table V–3
lists the number of samples for each
category of specific commodity. Average
number of samples for more general
commodity groups is listed in Table
V–2.
MSHA used the same sampling
strategies for collecting baseline samples
as it intends to use for collecting
samples for enforcement purposes.
These sampling procedures are
described in the Metal and Nonmetal
Health Inspection Procedures Handbook
(PH90–IV–4), Chapter A, ‘‘Compliance
Sampling Procedures’’ and Draft
Chapter T, ‘‘Diesel Particulate Matter
Sampling.’’ Chapter A includes detailed
guidelines for selecting and obtaining
personal samples for various
contaminants. All personal samples
were collected in the miner’s breathing
zone and for the miner’s full shift
A = The surface area of the deposit on
the filter media used to collect the
sample, cm2,
Flow Rate = Flow rate of the air pump
used to collect the sample measured
in Liters per minute, and
480 minutes = Standardized eight-hour
work shift.
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)
All levels of carbon or DPM are
reported in 8-hour full shift equivalent
TC concentrations measured in µg/m3.
Because personal sampling was
conducted and no attempt was made to
avoid interference from cigarette smoke
or other OC sources, TC was also
calculated using the formula prescribed
in the second partial DPM settlement
agreement:
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06JNR2
ER06jn05.014</MATH>
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Federal Register / Vol. 70, No. 107 / Monday, June 6, 2005 / Rules and Regulations
Total Carbon Concentration = EC ×
1.3.
MSHA agreed to use the lower of the
two values (EC × 1.3 or EC + OC) for
enforcement until a final rule is
published reflecting EC as the surrogate.
The electronic records of the 1,194
samples available for analysis were
reviewed for inconsistencies. Internally
inconsistent or extreme values were
questioned, researched, and verified.
Although no samples were invalidated
as a result of the administrative
verification, 12 samples (1.0%) were
removed from the data set for reasons
unrelated to the values obtained. The
reasons for invalidating these samples
are listed in Table V–1. These samples
were subjected to the same laboratory
quality assessments as samples
collected for compliance purposes.
Accordingly, MSHA has included 1,194
samples from miners in the analyses.
Table V–2 is a list of the number of
valid samples by commodity group.
TABLE V–1.—REASONS FOR EXCLUDING SAMPLES.
Reason for excluding from analysis
Metal
Stone
Trona
Other N/M
Total
Abnormal Sample Deposit .......................................................................
Cassette/Filter Broken .............................................................................
Contaminated Backup Pad ......................................................................
Instrument Failure ....................................................................................
Pump Failed .............................................................................................
0
0
1
1
1
1
2
0
1
4
0
0
0
0
0
0
1
0
0
0
1
3
1
2
5
Total ..................................................................................................
3
8
0
1
12
TABLE V–2.—NUMBER OF MINES AND VALID SAMPLES, BY COMMODITY GROUP.
Commodity group
Number of mines
Average number
of valid samples
by mine
Number of valid
samples
Metal ..........................................................................................................................
Stone ..........................................................................................................................
Trona ..........................................................................................................................
Other N/M ..................................................................................................................
40
115
4
24
284
689
25
196
7.1
6.0
6.3
8.2
Total ....................................................................................................................
183
1,194
6.5
Table V–3 lists the number of samples
collected by specific commodities and
sorted by average number of samples
per mine. Although MSHA made efforts
to sample all underground M/NM mines
covered by this rulemaking within the
specified time frame, several mines have
few or no samples for DPM in this
analysis. Some M/NM mining
operations are seasonal in that they are
operated intermittently or operate at less
than full production during certain
times. These types of variable
production schedules limited efforts to
collect compliance assistance samples.
MSHA extended its period of baseline
sampling especially to incorporate into
its analysis those mines with a low
sampling frequency or where no
samples were collected as of March 26,
2003.
TABLE V–3.—NUMBER OF VALID SAMPLES PER MINE FOR SPECIFIC COMMODITIES
Specific commodity
No. of mines
Gemstones Mining, N.E.C ...........................................................................................................
Dimension Marble Mining ............................................................................................................
Limestone ....................................................................................................................................
Talc Mining ..................................................................................................................................
Uranium-Vanadium Ore Mining, N.E.C .......................................................................................
Gold Ore Mining, N.E.C ...............................................................................................................
Construction Sand & Gravel Mining, N.E.C ................................................................................
Crushed & Broken Sandstone Mining .........................................................................................
Hydraulic Cement ........................................................................................................................
Lime, N.E.C .................................................................................................................................
Copper Ore Mining, N.E.C ..........................................................................................................
Dimension Limestone Mining ......................................................................................................
Crushed & Broken Limestone Mining, N.E.C ..............................................................................
Crushed & Broken Marble Mining ...............................................................................................
Trona Mining ................................................................................................................................
Crushed & Broken Stone Mining, N.E.C .....................................................................................
Gypsum Mining ............................................................................................................................
Salt Mining ...................................................................................................................................
Clay, Ceramic & Refractory Minerals, N.E.C ..............................................................................
Miscellaneous Metal Ore Mining, N.E.C .....................................................................................
Lead-Zinc Ore Mining, N.E.C ......................................................................................................
Platinum Group Ore Mining .........................................................................................................
Potash Mining ..............................................................................................................................
Molybdenum Ore Mining .............................................................................................................
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23:23 Jun 03, 2005
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E:\FR\FM\06JNR2.SGM
2
3
2
1
1
19
1
1
1
4
2
3
90
4
4
4
4
14
1
1
10
2
3
2
06JNR2
No. of
samples
5
9
6
3
3
87
5
5
5
20
11
18
550
25
25
28
29
122
9
9
96
20
30
22
Average samples per mine
2.5
3.0
3.0
3.0
3.0
4.6
5.0
5.0
5.0
5.0
5.5
6.0
6.1
6.3
6.3
7.0
7.3
8.7
9.0
9.0
9.6
10.0
10.0
11.0
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Federal Register / Vol. 70, No. 107 / Monday, June 6, 2005 / Rules and Regulations
TABLE V–3.—NUMBER OF VALID SAMPLES PER MINE FOR SPECIFIC COMMODITIES—Continued
Specific commodity
No. of
samples
No. of mines
Average samples per mine
Silver Ore Mining, N.E.C .............................................................................................................
Miscellaneous Nonmetallic Minerals, N.E.C ................................................................................
3
1
36
16
12.0
16.0
Average of all samples .........................................................................................................
183
1,194
6.5
There are 63 different occupations in
underground M/NM mines represented
in this analysis. The most frequently
sampled occupations are Blaster, Drill
Operator, Front-end Loader Operator,
Truck Driver, Scaling (Mechanical), and
Mechanic. Table V–4 lists the number of
valid samples by occupation and
commodity group. Only occupations
with 14 or more total samples are listed
individually. Occupations with fewer
samples were aggregated into a
combined group for this table.
TABLE V–4.—VALID SAMPLES, BY OCCUPATION AND MINE CATEGORY.
Occupation
Metal
Stone
Trona
Other N/M
Total
Truck Driver .............................................................................................
Front-end Loader Operator ......................................................................
Blaster, Powder Gang ..............................................................................
Scaling (mechanical) ................................................................................
Drill Operator, Rotary ...............................................................................
Drill Operator, Jumbo Perc. .....................................................................
Mechanic ..................................................................................................
Complete Load-Haul-Dump .....................................................................
Utility Man ................................................................................................
Scaling (hand) ..........................................................................................
Mucking Mach. Operator .........................................................................
Roof Bolter, Rock .....................................................................................
Drill Operator, Rotary Air .........................................................................
Miner, Drift ...............................................................................................
Crusher Oper/Worker ...............................................................................
Miner, Stope ............................................................................................
All Others Combined ................................................................................
87
40
12
1
3
10
7
7
6
4
19
5
1
16
0
14
52
152
149
98
66
63
19
15
2
4
20
1
9
19
1
13
0
58
0
6
0
0
0
0
0
0
15
0
0
0
0
0
0
0
4
13
19
24
13
9
9
12
23
4
2
3
7
1
0
2
0
55
252
214
134
80
75
38
34
32
29
26
23
21
21
17
15
14
169
Totals ................................................................................................
284
689
25
196
1,194
TC levels calculated by EC × 1.3 were
lower than TC levels calculated by OC
+ EC in 858 (72%) of the 1,194 baseline
samples. Of the 336 samples where TC
= OC + EC was the lower value, 68% of
the TC = EC × 1.3 values were within
12% of the TC = OC + EC value. Table
V–5 summarizes the results of the
baseline samples when determining the
TC level using either EC × 1.3 or OC +
EC. Approximately 6.4% of the paired
results did not concur with respect to
the 400TC µg/m3 standard when
measuring TC by the two calculations
(OC + EC vs. EC × 1.3). Approximately
19.3% of the samples were above the
400TC µg/m3 interim concentration
limit when using TC = EC × 1.3 and
approximately 22.7% were above the
concentration limit when using TC = OC
+ EC. There is 93.6% concurrence
between the two methods of calculating
TC and comparing the calculations to
the 400TC µg/m3 interim concentration
limit.
TABLE V–5.—COMPARISON OF RESULTS WITH 400TC µG/M3 CALCULATING TC BY OC + EC OR EC × 1.3
EC × 1.3
All valid samples
Total
< 400TC µg/m3
> 400TC µg/m3
> 400TC µg/m3 ......................................................................................................................
905
(75.8%)
59
(4.9%)
18
(1.5%)
212
(17.8%)
923
(77.3%)
271
(22.7%)
Total ......................................................................................................................................
964
(80.7%)
230
(19.3%)
1,194
(100.0%)
OC+EC.
< 400TC µg/m3 ......................................................................................................................
Table V–6 lists the 26 occupations
found to have at least one sample in
which the level of TC was over the
400TC µg/m3 interim concentration
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limit (TC = EC × 1.3). Table V–6 is
sorted by the median (middle) TC result.
The median is reported because it is a
more robust measure of the middle
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value. Changing a single value won’t
change the median very much. In
contrast, the value of the mean can be
strongly affected by a single value that
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is very low or very high. The table also
lists the minimum value, maximum
value, and the total number of valid
samples for these occupations. TC
values varied widely among all miners’
occupations.
TABLE V–6.—OCCUPATIONS WITH AT LEAST ONE SAMPLE GREATER THAN OR EQUAL TO 400TC µG/M3 (TC = EC× 1.3)
Total samples
Occupation
Diamond Drill Operator ............................................................................................................
Ground Control/Timberman .....................................................................................................
Washer Operator .....................................................................................................................
Engineer ...................................................................................................................................
Roof Bolter, Mounted ...............................................................................................................
Mucking Mach. Operator .........................................................................................................
Miner, Stope ............................................................................................................................
Cleanup Man ...........................................................................................................................
Scoop-Tram Operator ..............................................................................................................
Drill Operator, Rotary Air .........................................................................................................
Miner, Drift ...............................................................................................................................
Blaster, Powder Gang .............................................................................................................
Belt Crew .................................................................................................................................
Roof Bolter, Rock ....................................................................................................................
Truck Driver .............................................................................................................................
Shuttle Car Operator (diesel) ..................................................................................................
Complete Load-Haul-Dump .....................................................................................................
Drill Operator, Jumbo Perc ......................................................................................................
Drill Operator, Rotary ...............................................................................................................
Motorman .................................................................................................................................
Front-end Loader Operator ......................................................................................................
Scaling (mechanical) ...............................................................................................................
Supervisor, Co. Official ............................................................................................................
Utility Man ................................................................................................................................
Scaling (hand) ..........................................................................................................................
Mechanic ..................................................................................................................................
Table V–7 and Chart V–1 provide the
percent of overexposures among the
four commodity groups. Chart V–2
provides the number of overexposures
among the four commodity groups. The
metal mines have the highest percent of
overexposures followed by stone, then
other non-metal mines. For all samples
TC, µg/m3
Minimum
1
2
4
1
12
23
14
2
7
21
17
134
8
21
252
3
32
38
75
8
214
80
13
29
26
34
2,030
368
353
438
98
15
100
66
14
0
16
6
26
63
0
95
19
5
3
59
0
0
1
29
18
0
Median
Maximum
2,030
545
438
438
335
334
283
283
272
240
228
227
225
223
211
201
189
179
171
168
158
139
130
94
87
84
2,030
722
808
438
1,063
872
622
499
583
1,353
1,459
1,340
502
1,310
1,581
419
824
1,098
1,109
419
2,979
1,246
856
991
2,013
420
combined, 19.3% were above 400TC µg/
m3.
TABLE V–7.—BASELINE SAMPLES BY COMMODITY (TC = EC × 1.3)
Number <
400TC µg/m3
Commodity
Metal ................................................................................................................
Stone ................................................................................................................
Other N/M ........................................................................................................
Trona ................................................................................................................
All Mines ..........................................................................................................
Number >
400TC µg/m3
195
571
174
24
964
89
118
22
1
230
BILLING CODE 4510–43–U
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Total Samples
284
689
196
25
1,194
Percent >
400TC µg/m3
31.3
17.1
11.2
4.0
19.3
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32879
Chart V–3 shows the number of mines
with a specific number of
overexposures. Examination of the
frequency of mines with one or more
overexposures shows that 68 mines
(37%) are in this category. There were
no mines with more than 12 samples
> 400TC µg/m3 for that mine.
At four of the mines, all samples
taken during the assistance period were
above 400TC µg/m3. Between one and
ten samples were taken at each of these
four mines. No overexposures were
found in 115 (63%) of the mines
sampled. (See Chart V–4.)
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BILLING CODE 4510–43–C
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Federal Register / Vol. 70, No. 107 / Monday, June 6, 2005 / Rules and Regulations
Tables V–8 and V–9 summarize
sample statistics by commodity for TC
calculated by TC = EC × 1.3 and TC =
EC + OC respectively. Overall, the mean
TC as calculated by EC × 1.3 is 255 µg/
m3. The median level is 174 µg/m3. The
mean TC level by OC + EC is 293 µg/
m3 and the median level is 226 µg/m3.
Individual exposure levels of TC vary
widely within all commodities and most
mines. The commodity groupings
reported in Tables V–8 and V–9 were
chosen to be consistent with those
reported in the 31-Mine Study and the
Quantitative Risk Assessment (QRA) for
this rule.
The mean and median TC values for
each group, using EC × 1.3, are lower
than the interim compliance limit of 400
µg/m3. The mean (median) TC value for
metal mines is 356(271) µg/m3. The
mean (median) for stone mines is
236(149), other non-metal mines is
194(148), and trona mines is 105(82) µg/
m3. Table V–8 lists additional statistics
for TC values compiled by commodity.
TABLE V–8.—AVERAGE LEVELS OF TC BY COMMODITY MEASURED IN µG/M3 (EC × 1.3)
[Estimated 8-hour Full Shift Equivalent TC Concentration (µg/m3)]
Metal
No. of Samples ........................................................................................
Maximum .................................................................................................
Median .....................................................................................................
Mean ........................................................................................................
Std. Error ..........................................................................................
95% CI Upper ...................................................................................
95% CI Lower ...................................................................................
The mean and median TC values for
each group of mines as calculated by OC
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Stone
284
2,026
271
356
19
392
319
+ EC are also lower than the interim
compliance limit of 400 µg/m3. The
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Other N/M
689
2,979
149
236
10
256
216
196
960
148
194
12
217
172
Trona
25
407
82
105
16
138
73
All Mines
1,194
2,979
174
255
8
270
239
mean (median) TC value for metal
mines is 370(313) µg/m3. The mean for
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TC = EC × 1.3
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Federal Register / Vol. 70, No. 107 / Monday, June 6, 2005 / Rules and Regulations
stone mines is 282(209), other nonmetal mines is 238(191) and for trona
mines is 140(126) µg/m3. Table V–9 lists
additional statistics for TC values
compiled by commodity group.
TABLE V–9.—AVERAGE LEVELS OF TC BY COMMODITY GROUP MEASURED IN µG/M3 (OC + EC)
[Estimated 8-hour Full Shift Equivalent TC Concentration (µg/m3)]
TC = OC + EC
Metal
No. of Samples ........................................................................................
Maximum .................................................................................................
Median .....................................................................................................
Mean ........................................................................................................
Std. Error ..........................................................................................
95% CI Upper ...................................................................................
95% CI Lower ...................................................................................
Tables V–10, V–11, and V–12 show
summary statistics for whole DPM
exposures for the baseline sampling and
the 31-Mine Study. For baseline
sampling whole DPM was calculated by
EC × 1.3 × 1.25 and by (OC + EC) × 1.25.
The 1.25 factor represents the
assumption that TC comprises 80% of
Stone
284
2,045
313
370
17
404
336
Other N/M
689
2,796
209
282
11
303
261
196
1,230
191
238
12
263
214
Trona
All Mines
25
344
126
140
12
165
115
1,194
2,796
226
293
8
308
278
whole DPM concentrations, the mean
(median) value is 444(339) µg/m3 for
metal mines, 295(186) for stone mines,
243(185) for other non-metal mines, and
132(102) µg/m3 for trona mines. The
whole DPM exposures for Table V–11
were calculated as (OC + EC) × 1.25.
whole DPM. The other 20% includes
the solid aerosols such as ash
particulates, metallic abrasion particles,
sulfates and silicates. The vast majority
of these particulates are in the submicron range.
Section VI–B discusses the
relationship between EC and TC. For
TABLE V–10.—BASELINE WHOLE DPM CONCENTRATIONS (EC × 1.3 × 1.25, µG/M3), BY MINE CATEGORY
[Estimated 8-hour Full Shift Equivalent Whole DPM Concentration (µg/m3)]
DPM = EC × 1.3 × 1.25
Metal
Number of Samples .................................................................................
Maximum .................................................................................................
Median .....................................................................................................
Mean ........................................................................................................
Std. Error ..........................................................................................
95% CI Upper ...................................................................................
95% CI Lower ...................................................................................
Stone
284
2,532
339
444
23
490
399
Other N/M
689
3,724
186
295
13
320
270
196
1,200
185
243
15
272
214
Trona
All Mines
25
509
102
132
20
173
91
1,194
3,724
218
318
10
338
299
TABLE V–11.—BASELINE WHOLE DPM CONCENTRATIONS ((EC + OC) × 1.25, µG/M 3), BY MINE CATEGORY
[Estimated 8-hour Full Shift Equivalent Whole DPM Concentration (µg/m3)]
DPM = (EC + OC) × 1.25
Metal
Number of Samples .................................................................................
Maximum .................................................................................................
Median .....................................................................................................
Mean ........................................................................................................
Std. Error ..........................................................................................
95% CI Upper ...................................................................................
95% CI Lower ...................................................................................
The mean whole DPM concentration
for metal and stone mines (as measured
Stone
284
2,556
392
463
21
505
421
Other N/M
689
3,495
262
353
13
379
327
by (EC + OC) × 1.25) was significantly
lower during baseline compliance
196
1,538
238
298
16
329
267
Trona
25
430
158
175
15
206
144
All Mines
1,194
3,495
283
366
10
385
347
assistance sampling than the levels
measured during the 31-Mine Study.
TABLE V–12.—31-MINE STUDY WHOLE DPM CONCENTRATIONS (µG/M3) BY MINE CATEGORY
[Estimated 8-hour Full Shift Equivalent Whole DPM Concentration (µg/m3)]
DPM = (EC + OC) × 1.25
Metal
Number of Samples .........................................................................................................
Maximum .........................................................................................................................
Median .............................................................................................................................
Mean ................................................................................................................................
Std. Error ..................................................................................................................
95% CI Upper ...........................................................................................................
95% CI Lower ...........................................................................................................
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116
2,581
491
610
45
699
522
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Stone
105
1,845
331
466
36
537
394
06JNR2
Other N/M
83
1,210
341
359
27
412
306
Trona
54
331
82
94
9
113
75
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Federal Register / Vol. 70, No. 107 / Monday, June 6, 2005 / Rules and Regulations
NM mining industry. Additionally, the
industry has continued to change the
diesel-powered fleet to low emission
engines that reduce DPM exposure.
Workers inside equipment cabs were
not sampled during the 31-Mine Study
BILLING CODE 4510–43–U
MSHA received several comments on
the baseline sampling. Some
commenters stated that many mines
were sampled in a manner that rendered
results exceedingly low and not
representative of operating conditions.
Commenters also stated that the results
of independent DPM sampling
conducted by operators indicate
MSHA’s results underestimate DPM
exposure. These commenters did not
provide data or analyses from mine
operators’ sampling programs to
substantiate their claim.
MSHA compliance specialists
collected baseline samples in the same
manner they have been instructed to use
for collecting samples for enforcement
purposes. It is expected that personal
exposure to DPM will fluctuate due to
variations in day to day operations in a
mine. Reported levels of DPM are
representative of the exposures of the
highest risk miners identified during
compliance assistance. In an ideal
situation, and with unlimited resources,
every potentially exposed miner would
be individually sampled. It is not
necessary or practical, however, to
sample all miners on a mine property in
order to evaluate personal exposures.
Suspected and potential health hazards
may be reasonably and adequately
evaluated by sampling the maximum
risk miner in a work area. The
maximum risk miner is the one
expected to have the greatest exposure
of all of the miners in the area. Other
miners in the same work area or area of
common exposure sources may
reasonably be expected to experience
lesser concentrations of occupational
hazards than the maximum risk miner.
There may be more than one maximum
risk miner when activities, operations,
and exposure sources vary throughout
the day. MSHA acknowledges that some
samples were not taken on the highest
possible risk occupation at some mines.
As previously stated, we continued
baseline sampling past the date of July
19, 2003 in response to this concern.
A miner experiences high risk
because of the location and type of tasks
performed relative to the source of the
suspected hazard. The miner’s predicted
environment or duties may change
during the course of the work shift. If
the working conditions present during
the exposure assessment are not typical
of the regular mining operation, the
sample results may not represent the
typical exposure for that occupation.
Compliance specialists strive to
characterize the higher exposure levels
during typical work shifts. The baseline
samples are representative of the
conditions experienced on work shifts
during the defined compliance
assistance period. MSHA has obtained
the best available information for
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due to possible interference from
cigarette smoke. During baseline
compliance assistance sampling,
however, personal samples were taken
on miners inside cabs.
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Chart V–5 compares the means from
Tables V–10, V–11 and V–12. The mines
selected in the 31-Mine Study (Table V–
12) were not randomly selected, and the
study is, therefore, not considered
representative of the underground M/
Federal Register / Vol. 70, No. 107 / Monday, June 6, 2005 / Rules and Regulations
characterizing recent activities at the
relevant M/NM mines.
B. DPM Control Technology
MSHA participated in a number of
compliance assistance activities
directed at improving sampling and
assisting mine operators with selecting
and implementing appropriate DPM
control technology. Some of these
activities were directed to either a
segment of the mining industry, or to
the entire industry, while others were
conducted on a mine specific basis. In
general, activities directed toward a
large number of mines included
outreach programs, workshops, website
postings and publications, while
activities directed at an individual mine
included evaluation of a specific control
technology, and review of the
technology in use by or available to a
specific mine.
Regional DPM Seminars. During
September and October, 2002, MSHA
conducted regional DPM seminars at the
following locations: Ebensburg, PA;
Knoxville, TN; Lexington, KY; Des
Moines, IA; Kansas City, MO;
Albuquerque, NM; Coeur d’Alene, ID;
Green River, WY; and Elko, NV. MSHA
offered these full-day seminars free of
charge in the major underground M/NM
mining regions of the country to
facilitate attendance by key mining
industry personnel. The seminars
covered the health effects of DPM
exposure, the history and specific
provisions of the regulation, DPM
controls, DPM sampling, and the DPM
Estimator, a computerized program that
calculates DPM concentration
reduction.
NIOSH Diesel Emission and Control
Technologies in Underground M/NM
Mines Workshops. MSHA participated
in these two workshops in February,
2003 in Cincinnati, OH and March,
2003, in Salt Lake City, UT. The
workshops served several purposes.
They provided technical presentations
and a forum for discussing control
technology for reducing exposure to
particulate matter and gaseous
emissions from the exhaust of dieselpowered vehicles in underground
mines. Additionally, they intended to
help mine managers, maintenance
personnel, safety and health
professionals, and ventilation engineers
select and apply control technologies in
their mines. Speakers, representing
MSHA, NIOSH, and several mining
companies, provided ample time for
questions and in-depth technical
discussion of issues raised by
participants.
National Stone, Sand & Gravel
Association (NSSGA)/MSHA DPM
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Sampling Workshop. This three day
seminar, hosted by the Rogers Group,
Inc.’s Jefferson County Stone and
Underground in Louisville, Kentucky,
was held on December 11 through 13,
2002. On the first day, MSHA reviewed
DPM sampling procedures, and
presented training on pump calibration,
sample train assembly and note taking.
On the second day, participants traveled
to the Rogers Group Jefferson County
Mine to conduct full shift sampling on
underground miners. Our technical
support staff took ventilation
measurements and collected area
samples to assess DPM emissions in the
mine. On the third day, MSHA reviewed
engine emission and ventilation
measurements. Additionally, MSHA
reviewed and discussed DPM outreach
material. Approximately 10 industry
participants attended the seminar.
Nevada Mining Association Safety
Committee. In April, 2003, MSHA
discussed DPM control technologies at a
meeting of the Nevada Mining
Association Safety Committee in Elko,
NV. Discussion topics included biodiesel fuel blends, various fuel additives
and fuel pre-treatment devices, mine
ventilation, environmental cabs, clean
engines, and diesel particulate filter
(DPF) systems. Mining company
representatives discussed their
experiences with and perspectives on
these technologies. MSHA discussed
experiences and observations that it
made at various mines, and results of its
laboratory and field testing.
MSHA South Central Joint Mine
Safety and Health Conference. MSHA
presented a DPM workshop at this
conference in April 2003, in New
Orleans, LA. The workshop included a
detailed history and explanation of the
provisions of the DPM regulation, and a
technical presentation on feasible DPM
engineering controls. At the April 2004
conference in Albuquerque, NM, MSHA
presented a review of DPM control
strategies that have generally been
adopted in the underground M/NM
mining industry.
National Meeting of the Joseph A.
Holmes Safety Association, National
Association of State Mine Inspection
and Training Agencies, Mine Safety
Institute of America, and Western
TRAM (Training Resources Applied to
Mining). MSHA presented a DPM
workshop at this conference in June
2003, in Reno, NV. The workshop
included a detailed history and
explanation of the provisions of the
regulation, and a technical presentation
on DPM sampling, analytical tools for
identifying and evaluating DPM sources
in mines, and feasible DPM engineering
controls.
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32883
DPM Sampling and Control
Workshops. In March 2004, MSHA
presented full one day workshops in
Bloomington, IN and Des Moines, IA. In
these workshops, MSHA reviewed the
sampling procedures that MSHA
inspectors would use for DPM, and
MSHA provided hands on instruction to
the participants in these procedures.
MSHA also presented a review of DPM
control strategies that have generally
been adopted in the underground M/
NM mining industry.
Equipment Manufacturers
Association (EMA) DPM Workshop. In
August 2003, MSHA conducted a DPM
workshop for the EMA in Chicago, IL.
At this workshop, MSHA reviewed the
M/NM DPM regulations, discussed the
need for clean engine technology,
explained engine emission testing for
mines, reviewed the importance of
environmental cabs and discussed
ventilation issues.
Web site. Our Web site,
www.msha.gov, contains a single source
page for DPM rules for M/NM mines.
The page has links to specific topics,
including:
• Draft Metal and Nonmetal Health
Inspection Procedures Handbook,
Chapter T—Diesel Particulate Matter
Sampling.
• DRAFT Diesel Particulate Matter
Sampling Field Notes.
• Metal and Nonmetal Diesel
Particulate Matter Standard Error Factor
for TC Analysis.
• MSHA Metal and Nonmetal DPM
Standard Compliance Guide of August
5, 2003, addressing the interim DPM
limit.
• NIOSH Listserver.
• MSHA-NIOSH Diesel Particulate
Filter Selection Guide for Dieselpowered Equipment in Metal and
Nonmetal Mines (Filter Selection
Guide), last updated February 20, 2003.
• Baseline DPM Sample Results,
updated October 2003.
• Presentation from Compliance
Assistance Workshop, October 16, 2002.
• Summary of Requirements: MSHA
Standard on Diesel Particulate Matter
Exposure of Underground Metal and
Nonmetal Miners that are in effect as of
July 20, 2002.
• Link to SKC Web site: SKC Diesel
Particulate Matter Cassette with
Precision-jeweled Impactor.
• Diesel Particulate Matter Control
Technologies, last updated January 14,
2004.
—Table I: Paper/Synthetic Filters.
—Table II: Non-Catalyzed Particulate
Filters, Base Metal Particulate Filters,
Specially Catalyzed Particulate
Filters, and High Temperature
Disposable Filters.
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Federal Register / Vol. 70, No. 107 / Monday, June 6, 2005 / Rules and Regulations
—Table III: Catalyzed (Platinum Based)
Diesel Particulate Filters.
• Work Place Emissions Control
Estimator.
• Federal Register documents
concerning this and prior DPM
rulemakings.
• Public comments on this
rulemaking.
• Economic analyses for this rule and
prior DPM rules.
• MSHA News Release: MSHA Rules
Will Control Miners’ Exposure to Diesel
Particulate, January 18, 2001.
• Program Information Bulletins:
—PIB01–10 Diesel Particulate Matter
Exposure of Underground Metal and
Nonmetal Miners, August 28, 2001.
—PIB02–04 Potential Health Hazard
Caused by Platinum-Based Catalyzed
Diesel Particulate Matter Exhaust
Filters, May 31, 2002.
—PIB02–08 Diesel Particulate Matter
Exposure of Underground Metal and
Nonmetal Miners-—Summary of
Settlement Agreement, August 12,
2002.
Additionally, our diesel single source
page for the coal industry contains
topics that may also be of interest to the
M/NM mining industry, particularly for
those operations at gassy mines where
permissible equipment is required.
Specific control technology studies.
Following the settlement agreement,
MSHA was invited by various mining
companies to evaluate the effectiveness
of different control technologies for
DPM, including ceramic filters,
alternative fuels and a fuel oxygenator.
Company participation was essential to
the success of each test. MSHA
evaluated ceramic filters in two mines,
one where MSHA was the only
investigator and one where NIOSH was
the primary investigator. In our test,
MSHA evaluated DPM on a production
unit with and without ceramic filters
installed on the loader and trucks. In the
NIOSH study a variety of ceramic filters
were tested in an isolated zone.
MSHA evaluated bio-diesel fuel in
two mines. In one, MSHA evaluated a
20% and a 50% recycled bio-diesel fuel
and a 50% new bio-diesel. In the other,
MSHA evaluated a 35% recycled biodiesel fuel and a 35% new bio-diesel.
MSHA evaluated the fuel catalyst
system in one mine. MSHA sampled the
mine exhaust with fuel catalyst systems
installed on all production equipment,
and also without the units installed.
MSHA evaluated water emulsion
diesel fuel in four mines.
Following is a summary of the
individual mine technology evaluation
studies:
Kennecott Greens Creek Mining
Company: MSHA participated with
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Kennecott Greens Creek Mining
Company in a collaborative test to verify
the efficiency of catalyzed ceramic DPFs
for reducing diesel particulate
emissions. The goal of the testing was to
identify site-specific practical mineworthy filter technology.
This series of tests was designed to
determine the reduction in emissions
and personal exposure that can be
achieved when ceramic filters are
installed on a loader and associated
haulage trucks operating in a production
stope. MSHA also determined relative
engine gaseous and DPM emissions for
the equipment under specific load
conditions.
MSHA conducted the tests over a twoweek period. MSHA sampled three
shifts with ceramic after-filters installed;
and three shifts without the after-filters.
MSHA also collected personal samples
to assess worker exposures, and area
samples to assess engine emissions.
MSHA took both gaseous and diesel
particulate measurements.
Sampling results indicate significant
reductions in both personal exposures
and engine emissions. These results also
indicated that factors such as diesel
particulate contamination of intake air,
stope ventilation parameters, and
isolated atmospheres in vehicle cabs as
well as the ceramic DPFs may have a
significant impact on personal
exposures. The following findings and
conclusions were obtained from the test:
1. The results of the raw exhaust gas
measurements conducted during the test
indicate that the engines were operating
properly.
2. The ceramic filters installed on the
machines used in this test do not
adversely affect machine operation.
Even with some apparent visual
cracking from the rotation of the filter
media, the ceramic filters removed more
than 90% of the DPM. The filters
passively regenerated during machine
operation.
3. The Bosch smoke test provides an
indication of filter deterioration;
however, the colorization method does
not quantify the results.
4. Personal DPM exposures were
reduced by 60% to 68% when afterfilters were used.
5. CO levels decreased by up to onehalf while the catalyzed filters were
used. There appeared to be an increase
in NO2 (Nitrous Dioxide) while
catalyzed filters were being used;
however, it is unclear whether this
increase was due to data variability,
changes in ventilation rate, or the use of
the catalyzed filters.
6. The use of cabs reduced DPM
exposure by 75% when DPFs were in
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use and by 80% when DPFs were not in
use.
7. Ventilation airflow was provided to
the stopes through fans with rigid and
bag tubing. Airflow was the same or
greater than the Particulate Index, but
typically lower than the gaseous
ventilation rate.
8. The use of ceramic DPFs reduced
average engine DPM emissions by 96%.
9. The reduction in personal exposure
was not attributed solely to DPF
performance because other factors such
as ventilation, upwind equipment use,
and cabs also influence personal
exposure.
Carmeuse North America, Inc.,
Maysville Mine: MSHA entered into a
collaborative effort with NIOSH,
industry, and the Kentucky Department
of Energy to test DPM emissions and
exposures when using various blends of
bio-diesel fuels in an underground stone
mine. As part of our compliance
assistance program, MSHA provided
support to mining operations to evaluate
diesel particulate control technologies.
The test was initiated by the industry
partner, and, along with NIOSH, MSHA
provided support for test design, data
collection, and sample and data
analysis. The project was funded by
Carmeuse and Kentucky Department of
Energy, through the Kentucky Clean
Fuels Coalition.
The initial test was conducted in two
phases, using a 20% and a 50% biodiesel blend of recycled vegetable oil
(RVO), each mixed with low sulfur No.
2 standard diesel fuel. Baseline
conditions were established using low
sulfur No. 2 standard diesel fuel. In a
third phase of the test, a 50% blend of
new soy bio-diesel fuel was tested.
Area samples were collected at shafts
to assess equipment emissions. Personal
samples were collected to assess worker
exposure. These samples were analyzed
by NIOSH using the NIOSH 5040
method to determine TC and EC
concentrations. Results indicate that
significant reductions in emissions and
worker exposure were obtained for all
bio-diesel mixtures. These reductions
were in terms of both elemental and TC.
Results for the 20% and 50% RVO
indicated 33% and 69% reductions in
DPM emissions, respectively. Results for
the tests on the 50% blend of new soy
bio-diesel fuel, showed about a 37%
reduction in DPM emissions.
Carmeuse North America, Inc., Black
River Mine: Following the success of the
bio-diesel tests at Maysville Mine,
Carmeuse requested our assistance in
continuing the bio-diesel optimization
testing at their Black River Mine. Two
bio-diesel blends were tested, and a
baseline test was made. In each test
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personal exposures and the mine
exhaust were tested for two shifts. The
two bio-diesel blends included a 35%
RVO and a 35% blend of new soy oil.
Results for the 35% RVO showed a 32%
reduction in DPM emissions. Results of
the 35% blend of new soy bio-diesel
fuel showed an approximate 16%
reduction in DPM emissions.
Stone Creek Brick Company, Water
Emulsion Fuel Tests: During the Stone
Creek Brick Company compliance
assistance visit, MSHA identified
several control strategies that would
reduce DPM emissions and exposures.
These strategies included: The
installation of clean engines, the use of
alternative fuels, and an increase in
mine ventilation. The mine chose to
implement alternative fuel use followed
by an engine replacement program.
MSHA provided in-mine testing to
evaluate the impact of using an
alternative fuel. The company chose to
use a water emulsion fuel. This fuel is
an EPA approved fuel, consisting of a
20% blend of water with No. 2 diesel
fuel. A surfactant is added to keep the
water and diesel fuel from separating.
MSHA sampled at the mine before
(using No. 2 diesel fuel) and after the
implementation of the fuel. MSHA
collected personal samples to evaluate
the worker exposure and area samples
to evaluate emissions.
Results of the testing showed that the
highest exposure was reduced from
823TC µg/m3 to 321TC µg/m3 (61%
reduction). EC emissions were reduced
by 49% and TC emissions were reduced
by 3%. The lack of a reduction in TC
emissions was attributed to the lower
combustion temperature resulting from
the water emulsion fuel and the older
engine technology in use. The older
engines have larger injector nozzles
which do not provide efficient fuel
burning. The mine has been using the
fuel for approximately one year, and
continues to be satisfied with the
results.
Carmeuse North American, Inc.,
Maysville Mine, Water Emulsion Fuel
Tests: MSHA provided assistance to
Carmeuse North American, Inc., to
evaluate summer and winter blends of
a water emulsion fuel at their Maysville
Mine. For the first test, emission
reductions for a 10% blend (winter
blend) of water with No. 2 diesel fuel
was compared to a 35% blend of RVO.
Emission reductions were compared to
both a 35% blend of RVO and standard
No. 2 diesel fuel. MSHA collected
personal samples to evaluate the worker
exposure and area samples to evaluate
emissions.
Results of the testing showed that the
highest average exposure (high scaler
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working outside a cab) was reduced
from 254TC µg/m3 to 145TC µg/m3 (43%
reduction) when changing from RVO to
the water emulsion. EC emissions were
reduced by 52% and TC emissions were
reduced by 49% for the water emulsion
to 35% RVO fuel comparison. EC
emissions were reduced by 77% and TC
emissions were reduced by 74% for the
water emulsion to standard diesel fuel
comparison.
For the second test, emission
reductions for a 20% blend (summer
blend) of water with No. 2 diesel fuel
was compared to a 35% blend of RVO.
Emission reductions were compared to
both a 35% blend of RVO and standard
No. 2 diesel fuel. The comparison to No.
2 diesel fuel was obtained by combining
the water emulsion to the 35% RVO
results and previously obtained 35%
RVO to No. 2 diesel fuel results. MSHA
collected personal samples to evaluate
the worker exposure and area samples
to evaluate emissions. For the summer
blend, EC emissions were reduced by
60% and TC emissions were reduced by
59% for the water emulsion to 35%
RVO fuel comparison. EC emissions
were reduced by 81% and TC emissions
were reduced by 79% for the water
emulsion to standard diesel fuel
comparison.
Carmeuse North American, Inc.,
Black River Mine, Water Emulsion Fuel
Tests: MSHA provided assistance to
Carmeuse North American, Inc. to
evaluate summer and winter blends of
a water emulsion fuel at their Black
River Mine. For these tests, emission
reductions for 10% and 20% blends
(winter blend) of water with No. 2 diesel
fuel was compared to a 35% blend of
RVO. Emission reductions were
compared to both a 35% blend of RVO
and standard No. 2 diesel fuel. MSHA
collected personal samples to evaluate
the worker exposure and area samples
to evaluate emissions.
For the winter blend (10%), EC
emissions were reduced by 46% and TC
emissions were reduced by 45% for the
water emulsion to 35% RVO fuel
comparison. EC emissions were reduced
by 63% and TC emissions were reduced
by 62%, for the water emulsion to
standard No. 2 diesel fuel comparison.
For the summer blend (20%), EC
emissions were reduced by 61% and TC
emissions were reduced by 54% for the
water emulsion to 35% RVO fuel
comparison. EC emissions were reduced
by 73% and TC emissions were reduced
by 68% for the water emulsion to
standard diesel fuel comparison.
Martin Marietta, Durham Mine, Water
Emulsion Fuel Tests: MSHA provided
assistance to Martin Marietta to evaluate
a summer blend of water emulsion fuel
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32885
at their Durham Mine. This was a multilevel mine, with a 15% ramp between
levels. For this test, emissions for a 20%
blend of water with No. 2 diesel fuel
was compared to standard No. 2 diesel
fuel. MSHA collected personal samples
to evaluate the worker exposure and
area samples to evaluate emissions.
Even with the 15% ramps, the loss in
horsepower due to the fuel did not
adversely effect the mine operations.
Results of the testing showed that the
highest average exposure (powder crew
working outside a cab) was reduced
from 372TC µg/m3 to 54TC µg/m3 (85%
reduction) when changing from No. 2
diesel fuel to the water emulsion. EC
emissions were reduced by
approximately 80% for the water
emulsion compared to standard diesel.
Rogers Group, Jefferson County Mine:
MSHA was invited to this mine to
evaluate a fuel catalyst system that was
installed in the fuel line of the diesel
equipment. The company had installed
the units to increase fuel economy, and
sought to determine the effects of the
units on DPM. Prior to the units having
been installed, MSHA had conducted
baseline sampling and had collected
personal samples on production
workers and area samples in the mine
exhaust airflow. After the units were
installed on loaders and trucks and the
units had accumulated 100 hours of
operation, sampling was repeated.
Results indicated that the use of the fuel
catalyst had no measurable effect on
either DPM exposure or emissions.
Summary of DPM control technology:
In addition to conducting baseline
sampling and providing assistance in
developing DPM control strategies at
specific mines, MSHA assessed the
effectiveness of various DPM controls
during and following the compliance
assistance period. These controls
included alternative fuels, fuel
oxygenators, environmental cabs and
ceramic DPFs. Alternative fuels
evaluated included various blends of
bio-diesel fuels (including both Virgin
Soy Oil (VSO) and RVO), No. 1 diesel
fuel, and water emulsion fuels.
The resulting reduction in DPM
emissions for each of these controls is
given in Chart V–6. All reductions are
compared to diesel emissions with low
sulfur No. 2 diesel fuel. All bio-diesel
tests were conducted at mines with
relatively clean engines. The first water
emulsion test was conducted at a mine
utilizing older engines. Subsequent
water emulsion tests were conducted at
mines utilizing clean engines with
oxidation catalytic converters.
BILLING CODE 4510–43–U
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Assistance for Developing Control
Strategies
Martin Marietta Aggregates: MSHA
provided compliance assistance during
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full-day visits at the North Indianapolis
Mine and the Parkville Mine in March,
2003, and at the Kaskaskia Mine and the
Manheim Mine in May, 2003. MSHA
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reviewed each mine’s DPM sampling
history, current operating and
equipment maintenance practices,
ventilation, diesel equipment inventory,
and steps taken to date and future plans
to reduce DPM exposures. MSHA
discussed the full range of engineering
controls, demonstrated an exhaust
temperature measurement and data
logging system, and presented a
spreadsheet for using such data to select
appropriate filter systems. MSHA
presented a simple approach for
measuring the effectiveness of cab air
filtering and pressurization systems,
identified the highest DPM-emitting
equipment (so future equipmentspecific DPM control efforts could be
appropriately focused), and discussed
the likely effect of various ventilation
system upgrades.
Rogers Group, Oldham County Mine:
MSHA provided compliance assistance
at this mine during a full-day visit in
November 2002. MSHA conducted
extensive DPM sampling at the mine,
collecting both personal exposure
samples and area samples. Further,
MSHA collected DPM samples from
both inside and outside of equipment
cabs. No personal samples exceeded
160TC µg/m3. MSHA reviewed current
operating and equipment maintenance
practices, ventilation, diesel equipment
inventory, and steps taken to date and
future plans to reduce DPM exposures.
MSHA discussed the full range of
engineering controls. Results from this
survey indicate the environmental cabs
significantly reduced the DPM exposure
of equipment operators.
Rogers Group, Jefferson County Mine:
MSHA provided compliance assistance
at this mine during a full-day visit in
December 2002. MSHA collected both
personal exposure samples and area
samples. The highest personal sample,
collected on the loader, was 468TC µg/
m 3. This loader was operated with the
window open. MSHA reviewed current
operating and equipment maintenance
practices, ventilation, diesel equipment
inventory, and steps taken to date and
future plans to reduce DPM exposures.
Mechanical ventilation was provided for
the mine. MSHA discussed the full
range of engineering controls,
demonstrated an exhaust temperature
measurement and data logging system,
and presented a spreadsheet for using
such data to select appropriate filter
systems. MSHA presented a simple
approach for measuring the
effectiveness of cab air filtering and
pressurization systems, identified the
highest DPM-emitting equipment (so
future equipment-specific control efforts
could be appropriately focused), and
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discussed the likely effect of various
ventilation system upgrades.
Nalley and Gibson, Georgetown Mine:
MSHA provided compliance assistance
at this mine during a full-day visit in
May 2003. MSHA reviewed current
operating and equipment maintenance
practices, ventilation, diesel equipment
inventory, and steps taken to date and
future plans to reduce DPM exposures.
MSHA collected DPM samples to assess
improvements since the baseline
sampling. At that time, mechanical
ventilation provided airflow to the
mine. MSHA discussed the full range of
engineering controls, demonstrated an
exhaust temperature measurement and
data logging system, and presented a
spreadsheet for using such data to select
appropriate filter systems. MSHA
presented a simple approach for
measuring the effectiveness of cab air
filtering and pressurization systems,
identified the highest DPM-emitting
equipment (so future equipmentspecific DPM control efforts could be
appropriately focused), and discussed
the likely effect of various ventilation
system upgrades.
Stone Creek Brick Company: MSHA
provided compliance assistance at this
mine during a full-day visit in May
2003. MSHA reviewed current operating
and equipment maintenance practices,
ventilation, diesel equipment inventory,
and steps taken to date and future plans
to reduce DPM exposures. MSHA
collected DPM samples from
underground miners. The mine was
using mechanical ventilation. None of
the equipment had environmental cabs.
MSHA discussed the full range of
engineering controls, presented a
spreadsheet for using such data to select
appropriate filter systems, identified the
highest DPM-emitting equipment (so
future equipment-specific DPM control
efforts could be appropriately focused),
and discussed the likely effect of
various ventilation system upgrades.
Wisconsin Industrial Sand Co.,
Maiden Rock Mine: MSHA provided
compliance assistance at this mine
during a full-day visit in May 2003.
MSHA reviewed the mine’s current
operating and equipment maintenance
practices, ventilation, diesel equipment
inventory, and steps taken to date and
future plans to reduce DPM exposures.
MSHA discussed the full range of
engineering controls, presented a
spreadsheet for using such data to select
appropriate filter systems, and
identified the highest DPM-emitting
equipment so future equipment-specific
DPM control efforts could be
appropriately focused.
Gouverneur Talc Company, Inc., No.
4 Mine: MSHA provided compliance
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32887
assistance at this mine during a full-day
visit in May 2003. DPM samples were
collected on underground workers.
MSHA reviewed then current operating
and equipment maintenance practices,
ventilation, diesel equipment inventory,
and steps taken to date and future plans
to reduce DPM exposures. MSHA
discussed the full range of engineering
controls, demonstrated an exhaust
temperature measurement and data
logging system, and presented a
spreadsheet for using such data to select
appropriate filter systems. MSHA
presented a simple approach for
measuring the effectiveness of cab air
filtering and pressurization systems,
identified the highest DPM-emitting
equipment (so future equipmentspecific control efforts could be
appropriately focused), and discussed
the likely effect of various ventilation
system upgrades.
Additional specific mine compliance
assistance: Following the initial
baseline sampling period, MSHA
compiled a list of mines having at least
one DPM sample which exceeded the
400TC µg/m3 limit. Of the 183 mines
sampled, approximately 69 mines had at
least one sample over the 400TC µg/m3
interim TC limit. Of the 69 mines with
one or more overexposures, 44 used
room and pillar mining methods. These
include stone mines, salt mines and a
potash mine. Of the 44 room and pillar
mines, MSHA provided specific
compliance assistance to 36 of these
mines (two mines were closed and two
mines declined assistance). Although
trona mines use room and pillar mining
methods, they were not visited because
they were in compliance with the 400TC
µg/m3 limit. The remaining 15 mines
with overexposures were multilevel
metal mines using a variety of stoping
mining methods. Industry seminars
were provided to assist these mines.
Typically, the high risk workers in the
mines visited were the face workers that
worked outside an environmental cab.
Production loader and truck operators
had elevated exposures when they
either did not have an environmental
cab or when the cab was not being
properly maintained. Additional high
risk workers include the blasting crew,
drillers, and roof bolters.
During each mine visit, DPM samples
were collected unless the mine had been
recently sampled or the mine reported
no additional DPM controls had been
implemented since MSHA’s previous
sampling was conducted. The DPM
controls, including engines, ventilation,
cabs, fuels and work practices, were
reviewed with mine management.
Specific engine emission rates, mine
ventilation rates, cab pressures and
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work practices were determined. At
some mines, a temperature trace of an
engine exhaust was made. The
information was entered into a
computer spreadsheet model to assess
the effect of control changes on DPM
levels and to assist the mine in
developing a DPM control strategy.
Laboratory Compliance Assistance: In
addition to the compliance assistance
field tests, our diesel testing laboratory
has been working with manufacturers to
evaluate various types of DPM control
technologies. Certain of these
technologies can be applied in either
underground M/NM or coal mines.
Evaluating paper/synthetic media as
exhaust filters: MSHA has evaluated
paper/synthetic media as exhaust filters.
These filters have shown DPM removal
efficiencies in excess of 90% in the
laboratory when tested on our test
engine using the test specified in
subpart E of part 7. The laboratory has
tested approximately 20 different paper/
synthetic media from 10 different filter
manufacturers. Although much of this
work is directed to underground coal
mine applications for use on
permissible equipment, this technology
is available for use on permissible
equipment that is used in underground
gassy M/NM mines. In addition, some
underground coal mine operators have
considered adding exhaust heat
exchanger systems to nonpermissible
equipment in order to use the paper/
synthetic filters in place of ceramic
filters. The heat exchanger is needed to
reduce the exhaust gas temperature to
below 302° F for these types of filters.
This could also be an option for
equipment in M/NM mines, particularly
gassy mines where permissible
equipment is required.
Evaluating Ceramic Filter Systems:
MSHA worked with six ceramic filter
manufacturers to evaluate the effects of
their catalytic wash-coats on NO2
production. As discussed under the
‘‘Effectiveness of the DPM Estimator’’
portion of this preamble, catalytic washcoats on the ceramic filters may cause
increases in NO2 levels. MSHA used our
test engine (Caterpillar 3306 PCNA) and
followed the test procedures in subpart
E of 30 CFR part 7. The DPM single
source webpage lists the ceramic filters
that have significantly increased NO2
levels, as well as the ceramic filters that
are not known to increase NO2 levels.
MSHA tested the DPM removal
efficiencies of these filters during the
laboratory tests. The efficiency results
agree with the efficiencies posted on our
web site DPM Control Technologies
with Percent Removal Efficiency page
(85% for cordierite and 87% for silicon
carbide). Finally, MSHA worked with
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NIOSH during these tests to collect DPM
samples for EC analysis using the
NIOSH 5040 method. The laboratory
results showed that the filters removed
EC at up to 99% efficiency.
Evaluation of Fuel Oxygenator
System: MSHA’S laboratory completed
tests on the Rentar TM in-line fuel
catalyst. The Rentar TM unit was
installed on a CaterpillarTM 3306
ATAAC, which was coupled to a
generator. MSHA used an electrical load
bank to load the engine under various
operating conditions. To establish a
baseline, MSHA tested the engine for
gaseous and DPM emissions without the
Rentar TM unit. The unit was then
installed, and MSHA operated the
engine for a 100 hour break-in period.
MSHA then repeated the gaseous and
DPM emission measurements. The test
results of the one laboratory evaluation
for this control device to date showed
no significant reductions in whole
diesel particulate, however, the data did
not show any adverse effects on the raw
whole DPM exhaust emission. NIOSH’s
results were consistent with MSHA’s
results, and showed no significant EC
reductions and no adverse effects on the
engine’s emissions. MSHA has
discussed with Rentar TM further
laboratory tests.
Evaluation of a Magnet System:
MSHA performed laboratory tests for
Ecomax, a manufacturer of a magnet
system installed on the fuel line, oil
filter, air intake and radiator. MSHA
performed a preliminary field test of
this product at a surface aggregate
operation. The magnetic device
demonstrated a 30% reduction in CO
levels. The laboratory tests were
performed with the Ecomax system
installed and compared to our baseline
engine data. The test results of the one
laboratory evaluation for this control
device to date showed no significant
reductions in whole diesel particulate,
however, the data did not show any
adverse effects on the raw DPM exhaust
emissions.
Evaluation of the Fuel Preporator
System: MSHA’s laboratory tested a fuel
preparator system. The system is
designed to remove collected air from
the fuel system for better fuel
combustion. The results of the system
installed were compared to the baseline
engine. The test results of the one
laboratory evaluation for this control
device to date showed no significant
reductions in whole diesel particulate,
however, the data did not show any
adverse effects on the raw DPM exhaust
emissions. NIOSH also conducted tests
in our lab on the Fuel Preporator and
the results were consistent with
MSHA’s results. There were no
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significant EC reductions and no
adverse effects on the engine’s
emissions.
VI. DPM Exposures and Risk
Assessment
A. Introduction
In support of the 2001 final rule,
MSHA published a comprehensive risk
assessment (66 FR at 5752–5855, with
corrections at 35518–35520). In the
following discussion, we will refer to
the risk assessment published in
conjunction with the 2001 final rule as
the ‘‘2001 risk assessment.’’
The 2001 risk assessment presented
MSHA’s evaluation of health risks
associated with DPM exposure levels
encountered in the mining industry.
This was based on a review of the
scientific literature available through
March 31, 2000, along with
consideration of all material submitted
during the applicable public comment
periods.
The 2001 risk assessment was divided
into three main sections. Section 1 (66
FR at 5753–5764) contained a
discussion of U.S. miner exposures
based on field data collected through
mid-1998. An important conclusion of
this section was that, prior to the 2001
final rule,
* * * median dpm concentrations observed
in some underground mines are up to 200
times as high as mean environmental
exposures in the most heavily polluted urban
areas [footnote deleted] and up to 10 times
as high as median exposures estimated for
the most heavily exposed workers in other
occupational groups. [66 FR at 5764]
Section 2 of the 2001 risk assessment
(66 FR at 5764–5822) reviewed the
available scientific literature on health
effects associated with DPM exposures.
This review covered effects of both
acute and chronic exposures and also
contained a discussion of potential
mechanisms of toxicity. The review of
acute effects included anecdotal reports
of symptoms experienced by exposed
miners, studies based on exposures to
diesel emissions, and studies based on
exposures to particulate matter in the
ambient air. The review of chronic
effects included studies based
specifically on exposures to diesel
emissions and studies based more
generally on exposures to fine
particulate matter in the ambient air. As
part of this discussion, MSHA evaluated
47 epidemiologic studies examining the
prevalence of lung cancer within groups
of workers occupationally exposed to
DPM and discussed the criteria used to
evaluate and rank these studies (66 FR
at 5774–5810). For both acute and
chronic health effects, information from
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genotoxicity studies and studies on
laboratory animals was discussed in the
separate subsection on mechanisms of
toxicity. Section 2 of the 2001 risk
assessment also explained MSHA’s
rationale for utilizing certain types of
information whose relevance had been
questioned during the public comment
periods: health effects observed in
animals, health effects that are
reversible, and health effects associated
with fine particulate matter in the
ambient air (66 FR at 5765–55767).
In section 3 of the 2001 risk
assessment (66 FR at 5822–5855),
MSHA evaluated the best available
evidence to ascertain whether exposure
levels currently existing in mines
warranted regulatory action pursuant to
the Mine Act. To do this, MSHA
addressed three questions: (a) Whether
health effects associated with
occupational DPM exposures constitute
a ‘‘material impairment’’ to miner health
or functional capacity; (b) whether
exposed miners were at significant
excess risk of incurring any of these
material impairments; and (c) whether
the 2001 final rule would substantially
reduce such risks. After careful
consideration of all the submitted
public comments, the 2001 risk
assessment established three main
conclusions:
1. Exposure to dpm can materially impair
miner health or functional capacity. These
material impairments include acute sensory
irritations and respiratory symptoms
(including allergenic responses); premature
death from cardiovascular, cardiopulmonary,
or respiratory causes; and lung cancer.
2. At dpm levels currently observed in
underground mines, many miners are
presently at significant risk of incurring these
material impairments due to their
occupational exposures to dpm over a
working lifetime.
3. By reducing dpm concentrations in
underground mines, the rule will
substantially reduce the risks of material
impairment faced by underground miners
exposed to dpm at current levels.
The third of these conclusions was
supported primarily by a quantitative
risk assessment for lung cancer (66 FR
at 5848–5854).
Throughout the current rulemaking,
MSHA advised the mining community
of its intent to include the 2001 risk
assessment in the current rulemaking
record to support this final rule. In this
preamble, MSHA supplements the 2001
risk assessment with new exposure data
and health effects literature published
after March 31, 2000. MSHA asked that
public comment be focused on this
supplemental information.
Nevertheless, some commenters
presented critiques challenging the 2001
risk assessment and disputing scientific
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support for any DPM exposure limit,
especially by means of an EC surrogate.
Other commenters endorsed the 2001
risk assessment and stated that recent
scientific publications support MSHA’s
conclusions.
MSHA also received a number of
comments from the mining industry
suggesting that the risk assessment lacks
an adequate scientific foundation and
does not comply with present
requirements under OMB and
information quality guidelines to use
the best available, peer reviewed
science. The risk assessment sustaining
this final rule uses the best available,
peer-reviewed scientific studies. It
supplements the risk assessment
sustaining the 2001 final rule and the
existing coal DPM final rule also
promulgated on January 19, 2001 (66 FR
5526) (coal rule). The coal rule was
unchallenged by the mining
community.
Before promulgating the 2001 final
rule, MSHA provided a copy of its draft
risk assessment supporting the 2001
rule for peer review to two experts in
the field of epidemiology and risk
assessment. These experts evaluated the
overall methodology used by MSHA in
the draft risk assessment, the
appropriateness of the studies selected
by MSHA, and MSHA’s conclusions.
MSHA had the draft independently
peer-reviewed, published the evidence
and tentative conclusions for public
comment, and incorporated the
reviewers’ recommendations in the final
version. In the 2001 risk assessment,
MSHA carefully laid out the best
available evidence, including
shortcomings inherent in that evidence.
Of particular note is that the two
quantitative meta-analyses of lung
cancer studies supporting the 2001 risk
assessment were peer reviewed and
published in scientific journals. (Bhatia,
Rajiv, et al., ‘‘Diesel Exhaust Exposure
and Lung Cancer,’’ Journal of
Epidemiology, 9:84–91, January 1998,
and Lipsett M., and Campleman, Susan,
‘‘Occupational Exposure to Diesel
Exhaust and Lung Cancer: A MetaAnalysis,’’ American Journal of Public
Health, (89) 1009–1017, July 1999).
MSHA informed the public as early as
September 25, 2002, in the 2002
ANPRM for this final rule, and again in
the 2003 NPRM, that MSHA would
incorporate the existing rulemaking
record, including the 2001 risk
assessment, into the record of this
rulemaking. MSHA was open to
considering any new scientific evidence
relating to its risk assessment.
Commenters were encouraged in the
instant rulemaking to submit additional
evidence of new scientific information
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related to health risks associated with
exposure to DPM. After considering
both the more recent scientific literature
and all of the submitted comments,
MSHA has concluded that no change is
warranted in the 2001 risk assessment’s
conclusions with respect to health risks
associated with DPM exposures.
Section VI.B updates Section 1 of the
2001 risk assessment by summarizing
the new exposure data that became
available after publication of the 2001
final rule. This summary includes a
description of the relationship between
EC and TC observed in these exposure
measurements, and addresses public
comments on possible health
implications of substituting EC for TC as
a surrogate measure of DPM. In Section
VI.C, MSHA reviews some of the more
recent scientific literature (April 2000–
March 2003) pertaining to adverse
health effects of DPM and fine
particulates in general. In addition, this
section updates the 2001 risk
assessment’s discussion of scientific
evidence on mechanisms of DPM
toxicity. Thus, Section VI.C
supplements Section 2 of the 2001 risk
assessment. Section VI.C also discusses
a document by Dr. Gerald Chase that
purports to analyze preliminary data
extracted from an ongoing NIOSH/NCI
study. Finally, in Section VI.D, MSHA
assesses current risk to underground M/
NM miners in light of the most recent
exposure and health effects information.
Section VI.D also responds to a critique
of the 2001 risk assessment submitted
by Dr. Jonathan Borak on behalf of the
MARG Diesel Coalition (MARG) and the
NMA.
B. DPM Exposures in Underground M/
NM Mines
In Section 1 of the 2001 risk
assessment, MSHA evaluated exposures
based on 355 samples collected at 27
underground U.S. M/NM mines prior to
promulgating the 2001 rule. Mean DPM
concentrations found in the production
areas and haulageways at those mines
ranged from about 285 µg/m3 to about
2000 µg/m3, with some individual
measurements exceeding 3500 µg/m3.
The overall mean DPM concentration
was 808 µg/m3. All of the samples
considered in the 2001 risk assessment
were collected prior to 1999, and some
were collected as long ago as 1989.
Two new bodies of DPM exposure
data, collected after promulgation of the
2001 final rule, have now been
compiled for underground M/NM
mines: (1) Data collected in 2001 and
2002 from 31 mines for purposes of the
31-Mine Study and (2) data collected
between 10/30/2002 and 10/29/2003
from 183 mines to establish a baseline
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for future samples. Key results from
these two datasets are summarized in
the next two subsections below.
Following these summaries, the
relationship between EC and TC,
including the ratio of EC to TC (EC:TC)
is discussed. This discussion is based
exclusively on samples taken for the 31Mine Study, since those samples were
controlled for potential TC interferences
from tobacco smoking and oil mist,
whereas the baseline samples were not.
The subsection concludes with a
response to comments on the potential
health effects of substituting EC for TC
as a surrogate measure of DPM.
It should be noted that the new
exposure data reflect conditions at least
two years, and up to five years, later
than the most recent miners’ exposure
data considered in the 2001 risk
assessment. Furthermore, all of the new
exposure data were obtained after
promulgation of the 2001 rule. It is,
therefore, reasonable to expect that the
data discussed below would show
generally different exposure levels than
those presented in the 2001 risk
assessment—both on account of normal
technological changes over time and
because of DPM controls that may have
been implemented in response to the
2001 rule.
(1) Data from 31-Mine Study
MSHA collected 464 DPM samples in
2001 and 2002 at 31 underground M/
NM mines. (For a more detailed
description, see MSHA’s final report on
the 31-Mine Study.) Of these 464
samples, 106 were voided—mostly
because of potential interference by
sources of OC other than DPM. Table
VI–1 shows how the remaining 358
valid DPM samples were distributed
across four broad mine categories. All
samples at one of the metal mines were
voided, leaving 30 mines with valid
samples indicating DPM concentrations.
TABLE VI–1.—NUMBER OF DPM SAMPLES, BY MINE CATEGORY
Number of mines
with valid samples
Metal
Stone
Trona
Other
Number of valid
samples
Avg. number of
valid samples per
mine
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
11
9
3
7
116
105
54
83
10.5
11.7
18.0
11.9
Total ....................................................................................................................
30
358
12.5
Table VI–2 summarizes the valid DPM
concentrations observed in each mine
category, assuming that submicrometer
TC, as measured by the SKC sampler,
comprises 80% of all DPM. The mean
concentration across all 358 valid
samples was 432 µg/m3 (Std. error =
21.0 µg/m3). The mean concentration
was greatest at metal mines, followed by
stone and ‘‘other.’’ At the three trona
mines sampled, both the mean and
median DPM concentration were
substantially lower than what was
observed for the other categories. This
was due to the increased ventilation
used at these mines to control methane
emissions.
TABLE VI–2.—DPM CONCENTRATIONS (µ/M3), BY MINE CATEGORY
[DPM Is Estimated by TC ÷ 0.8]
Metal
No. of samples .........................................................................................
Minimum ..................................................................................................
Maximum .................................................................................................
Median .....................................................................................................
Mean ........................................................................................................
Std. Error ..........................................................................................
95% UCL ..........................................................................................
95% LCL ...........................................................................................
After adjusting for differences in
sample types and in occupations
sampled, DPM concentrations at the
non-trona mines were estimated to be
about four to five times the
concentrations found at the trona mines.
Although there were significant
differences between individual mines,
the adjusted differences between the
general categories of metal, stone, and
other mines were not statistically
significant.1 For the 304 valid samples
1 These conclusions derive from an analysis of
variance, based on TC measurements, described in
the Report on the 31-Mine Study. They depend on
an assumption that the ratio of DPM to TC is
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116
46.
2581.
491.
610.
44.7
699.
522.
taken at mines other than trona, the
mean DPM concentration was 492 µg/
m3 (Std. error = 23.0 µg/m3).
Again assuming that submicrometer
TC as measured by the SKC sampler
comprises 80% of DPM, the mean DPM
concentration observed was 1019 µg/m3
at the single mine exhibiting greatest
DPM levels. Four of the nine valid
samples at this mine exceeded 1487 µg/
m3. In contrast, DPM concentrations
never exceeded 500 µg/m3 at 8 of the 30
mines with valid samples (2 of the 11
uncorrelated with mine category, sample type (i.e.,
personal or area), and occupation.
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Stone
Trona
105
16.
1845.
331.
465.
36.0
537.
394.
54
20.
331.
82.
94.
9.4
113.
75.
Other
83
27.
1210.
341.
359.
26.6
412.
306.
metal mines, 1 of the 3 stone, all 3 trona,
and 2 of the 7 others). (Note that 500 µg/
m3 is the whole particulate equivalent
of the 400TC µg/m3 interim limit.) Some
individual measurements exceeded
200DPM µg/m3 at all but one of the
mines sampled.
(2) Baseline Data
MSHA s baseline sampling results are
presented in Section III, Compliance
Assistance. These results provide the
basis for the present discussion. The
baseline samples discussed here, in
connection with the risk assessment,
were collected and analyzed between
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October 30, 2002 and October 29, 2003.
They comprise a total of 1,194 valid
samples collected from 183 mines.
MSHA is including 320 additional valid
samples because MSHA decided to
continue to conduct baseline sampling
after July 19, 2003 in response to mine
operator’s concerns. Some of these
mines were either not in operation or
were implementing major changes to
ventilation systems during the original
baseline period. MSHA is including
supplementary samples from seasonal
and intermittent mines, mines that were
under-represented, and mines that were
not represented in the analysis
published in the proposed preamble in
2003.
Table VI–3 summarizes, by general
commodity, the EC levels measured
during MSHA’s baseline sampling
through October 29, 2003. The overall
mean eight-hour full shift equivalent EC
concentration was 196 µg/m3, and the
overall median was 134 µg/m3. Table
VI–4 provides a similar summary for
estimated DPM levels, using DPM ≈ TC/
0.8 and TC ≈ 1.3 × EC.2 Under these
assumptions, the estimated mean DPM
level was 318 µg/m3, and the median
was 218 µg/m3. Since the baseline data
and the 31-Mine Study both showed
significantly lower levels at trona mines
than at other underground M/NM
mines, Tables VI–3 and VI–4 present
overall results both including and
excluding the three underground trona
mines sampled.3
TABLE VI–3.—BASELINE EC CONCENTRATIONS
8-hour Full Shift Equivalent EC Concentration (µg/m3 )
Metal
No. of Samples ........................................................................................
Maximum ..................................................................................................
Median .....................................................................................................
Mean ........................................................................................................
Std. Error ..........................................................................................
95% UCL ..........................................................................................
95% LCL ...........................................................................................
Other
N/M
Stone
284
1,558
208
273
14
302
245
689
2,291
115
181
8
197
166
Trona
196
738
114
150
9
167
132
Total
25
313
63
81
12
106
56
1,194
2,291
134
196
6
208
184
Total excluding
Trona
1,169
2,291
137
198
6
210
186
TABLE VI–4.—BASELINE DPM CONCENTRATIONS
[DPM is estimated by (1.3 × EC) ÷ 0.8]
Estimated 8-hour Full Shift Equivalent DPM Concentration (µg/m3 )
Metal
No. of Samples ........................................................................................
Maximum ..................................................................................................
Median .....................................................................................................
Mean ........................................................................................................
Std. Error ..........................................................................................
95% UCL ..........................................................................................
95% LCL ...........................................................................................
Baseline EC sample results varied
widely between mines within
commodities and also within most
mines. Table VI–5 summarizes baseline
Stone
284
2,532
339
444
23
490
399
Other N/
M
689
3,724
186
295
13
320
270
EC results for the 26 occupations found
to have at least one sample where the
EC level exceeded the 308 µg/m3 8-hour
full shift equivalent interim EC limit. As
Trona
196
1,200
185
243
15
272
214
Total
25
509
102
132
20
173
91
1,194
3,724
218
318
10
338
299
Total excluding
Trona
1,169
3,724
223
322
10
342
303
indicated by the table, EC levels varied
widely within each occupation.
TABLE VI–5.—BASELINE EC CONCENTRATIONS FOR OCCUPATIONS WITH AT LEAST ONE VALUE EXCEEDING INTERIM EC
LIMIT
Number of
valid samples
Occupation
8-hour full shift equivalent EC Concentration (µg/m3 )
Minimum
1
2
4
1
12
23
14
2 The relationship DPM ≈ TC/0.8 is the same as
that assumed in the 2001 risk assessment. The
relationship TC 1.3 × EC was formulated under the
settlement agreement, based on TC:EC ratios
intervals reported in Tables VI–3 and VI–4 should
be interpreted with caution.
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1,561
419
337
337
258
257
218
Maximum
Diamond Drill Operator ....................................................................................................
Ground Control/Timberman .............................................................................................
Washer Operator .............................................................................................................
Engineer ...........................................................................................................................
Roof Bolter, Mounted .......................................................................................................
Mucking Mach. Operator .................................................................................................
Miner, Stope ....................................................................................................................
observed in the joint 31-Mine Study, as described
in the subsection VI.3 of this preamble.
3 The distributions of EC values are skewed.
Therefore, the standard errors and confidence
1,561
283
272
337
76
12
77
Median
1,561
555
621
337
818
671
479
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TABLE VI–5.—BASELINE EC CONCENTRATIONS FOR OCCUPATIONS WITH AT LEAST ONE VALUE EXCEEDING INTERIM EC
LIMIT—Continued
Number of
valid samples
Occupation
Cleanup Man ...................................................................................................................
Scoop-Tram Operator ......................................................................................................
Drill Operator, Rotary Air .................................................................................................
Miner, Drift .......................................................................................................................
Blaster, Powder Gang .....................................................................................................
Belt Crew .........................................................................................................................
Roof Bolter, Rock ............................................................................................................
Truck Driver .....................................................................................................................
Shuttle Car Operator (diesel) ..........................................................................................
Complete Load-Haul-Dump .............................................................................................
Drill Operator, Jumbo Perc ..............................................................................................
Drill Operator, Rotary .......................................................................................................
Motorman .........................................................................................................................
Front-end Loader Operator ..............................................................................................
Scaling (mechanical) .......................................................................................................
Supervisor, Co. Official ....................................................................................................
Utility Man ........................................................................................................................
Scaling (hand) ..................................................................................................................
Mechanic ..........................................................................................................................
Figure VI–1 depicts, by mine category,
the percentage of baseline samples that
exceeded the interim EC limit of 308 µg/
m3. Underground metal mines exhibited
the highest proportion of samples
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exceeding this limit, followed by stone
and then other nonmetal mines. In the
three trona mines sampled, 24 of the 25
samples were lower than the proposed
limit. Across all commodities, 19.3% of
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8-hour full shift equivalent EC Concentration (µg/m3 )
Minimum
2
7
21
17
134
8
21
252
3
32
38
75
8
214
80
13
29
26
34
51
10
0
12
5
20
48
0
73
14
4
2
46
0
0
1
22
14
0
Median
Maximum
217
210
185
175
175
173
172
162
154
145
137
132
129
121
107
100
73
67
64
the 1,194 valid baseline samples
exceeded the interim EC limit.
BILLING CODE 4510–43–U
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384
449
1,041
1,122
1,031
386
1,007
1,216
323
634
845
853
322
2,291
958
658
762
1,548
323
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each mine. In 115 of the 183 mines
sampled (63%), none of the baseline EC
measurements exceeded 308 µg/m3. The
remaining 68 mines (37%) had at least
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one sample for which EC exceeded 308
µg/m3. All samples taken at 4 of the
mines exceeded the interim limit.
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Figure VI–2 shows how samples
exceeding the interim EC limit were
distributed over individual mines. One
to 20 baseline samples were taken at
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BILLING CODE 4510–43–C
(3) Relationship Between EC and TC
The 2001 final rule stipulated that TC
(i.e., EC + OC) measurements would be
used to monitor and limit DPM
concentration levels. Although it was
recognized that TC measurements were
subject to various interferences from
non-DPM sources, MSHA believed that,
in underground metal and nonmetal
mines, it could effectively eliminate
such interferences by a combination of
selective sampling procedures and
careful analytical techniques. During the
31-Mine Study, however, MSHA found
no reasonable sampling method that
would adequately protect TC
measurements from interference by such
sources of organic carbon as oil mist and
ammonium nitrate fuel oil (ANFO).
Furthermore, MSHA found that it was
cumbersome and impractical to restrict
its TC sampling so as to avoid potential
interference from environmental
tobacco smoke (ETS). Indeed, as
indicated earlier, nearly one fourth of
the TC samples collected during the 31Mine Study (106 out of 464) had to be
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voided on account of potential
interferences from extraneous sources of
OC. Therefore, in concert with the
Second Partial Settlement Agreement,
the 2003 NPRM proposed to ‘‘[r]evise
the existing diesel particulate matter
(DPM) interim concentration limit
measured by total carbon (TC) to a
comparable permissible exposure limit
(PEL) measured by elemental carbon
(EC) which renders a more accurate
DPM exposure measurement.’’ (68 FR
48668) Using EC as the surrogate
permits direct sampling of miners (such
as those who smoke, operate jackleg
drills, or load ANFO) for whom accurate
DPM monitoring would be difficult or
impossible using TC measurements.
Also in accordance with the Second
Partial Settlement Agreement, the
NPRM proposed to convert the existing
interim exposure limit, expressed in
terms of TC measurements, to a
‘‘comparable’’ EC limit by applying a
specific conversion factor obtained from
data gathered during the 31-Mine Study,
as explained below. MSHA is adopting
this proposal with the intention of
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providing at least the same degree of
protection to miners as the existing
interim limit. However, since it is
unlikely that EC and OC have identical
health effects, it is important to consider
the extent to which the ratio of EC to OC
(and hence of EC to TC) may vary in
different underground mining
environments.
Unlike the 31-Mine Study, no special
precautions were taken during MSHA’s
baseline sampling to avoid ETS or other
substances that could potentially
interfere with using TC as a surrogate
measure of DPM. Therefore, the baseline
data should not be used to evaluate the
OC content of DPM or the ratio of EC to
TC within DPM. In the 31-Mine Study,
on the other hand, great care was taken
to void all samples that may have been
exposed to ETS or other extraneous
sources of OC.
Consequently, the analysis of the
EC:TC ratio presented here relies
entirely on data from the 31-Mine
Study. It is important to note that nearly
all of the samples in this study were
taken in the absence of exhaust filters to
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32895
control DPM emissions. Since exhaust
filters may have different effects on EC
and OC emissions, the results described
here apply only to mine areas where
exhaust filters are not employed.
Figure VI–3 plots the EC:TC ratios
observed in the 31-Mine Study against
the corresponding TC concentrations.
The various symbols shown in the plot
identify samples taken at the same
mine. The EC:TC ratio ranged from 23%
to 100%, with a mean of 75.7% and a
median of 78.2%. Note that the
reciprocal of 0.78, which is 1.3, equals
the median of the TC:EC ratio observed
in these samples.4 The 1.3 TC:EC ratio
was the value accepted, under terms of
the settlement agreement, for the
purpose of temporarily converting EC
measurements to TC measurements.
BILLING CODE 4510–43–C
based on the EC and TC data obtained
from the 31-Mine Study. Both the
original 400 µg/m3 TC limit and the new
308 µg/m3 EC limit were exceeded by
about 31% to 32% of the samples. The
difference (one sample out of 358) is not
statistically significant in the aggregate.
Seven samples, however, exceeded the
TC limit but not the EC limit, and six
samples exceeded the EC limit but not
the TC limit.
4 The median of reciprocal values is always equal
to the reciprocal of the median. This relationship
does not hold for the mean.
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The 2001 rule set a TC interim
concentration limit of 400 µg/m3. Under
the new rule, this TC interim limit is
replaced with an EC interim limit of
400/1.3 = 308 µg/m3. Table VI–6
indicates the impact of this change,
BILLING CODE 4510–43–U
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TABLE VI–6.—COMPLIANCE WITH ORIGINAL 400 µG/M3 TC LIMIT AND/OR NEW 308 µG/M3 EC LIMIT. NUMBERS IN
PARENTHESES ARE PERCENTAGES
TC > 400 µg/m3
EC > 308 µg/m3
Total
No
Yes
No ..............................................................................................................................
Yes .............................................................................................................................
239 (66.8)
6 (1.7)
7 (2.0)
106 (29.6)
246 (68.7)
112 (31.3)
Total ....................................................................................................................
245 (68.4)
113 (31.6)
358 (100.0)
Several commenters noted that the
ratio of EC to TC in DPM can vary
widely. One commenter pointed out
that EC appeared to make up nearly all
of the TC at the mine with which he was
affiliated. This commenter stated that
replacing a 400 µg/m3 TC limit with a
308 µg/m3 EC limit would impose a
much more stringent standard at that
mine. Another commenter noted that a
308 µg/m3 EC limit would be less
protective of miners than the 400 µg/m3
TC limit in cases where the ratio of EC
comprised less than 78% of the TC.
MARG submitted comments by a
consultant, Dr. Jonathan Borak, who
emphasized that the highly variable
nature of the EC to OC ratio introduces
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‘‘large and important uncertainties in
the exposure assessments needed to
sustain QRA [i.e., quantitative risk
assessment].’’
As indicated by Figure VI–3, the
percentage of EC tended to increase
with increasing TC concentration—
except for cases showing a TC
concentration of less than about 60 µg/
m3. In many of the samples for which
TC < 60 µg/m3, the recorded ratio of EC
to TC was at or near 100%. Since TC
concentrations less than 60 µg/m3
appear to deviate from the general
pattern and are far below the interim
limit, our response to commenters
concerns about variability in the ratio of
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EC to TC will focus on those samples for
which TC exceeds 60 µg/m3.
There were 319 samples with TC > 60
µg/m3. For these samples, the mean and
median EC:TC ratio were 76.3% and
78.4%, respectively. In accordance with
standard statistical practice, an arcsine
transformation was applied to these 319
EC:TC ratios in order to normalize them
for further statistical analysis (Snedecor
and Cochran, Statistical Methods, 7th
Ed., pp 290–291). The transformed
EC:TC ratios are plotted against
corresponding TC concentrations in
Figure VI–4. Various symbols are used
to identify the mineral commodity
corresponding to each sample.
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BILLING CODE 4510–43–C
It is clear from Figures VI–3 and VI–
4 that individual samples in the 31Mine Study exhibited considerable
variation in their EC:TC ratios. What is
not so clear from these plots, however,
is whether different mines and/or
working environments tended to
experience different EC:TC ratios. To
answer this question, an analysis of
variance (ANOVA) was performed to
determine whether there were
statistically significant differences in the
EC:TC ratios exhibited at different
mines and on different days at the same
mine. Table VI–7 contains the results of
this ANOVA. At a confidence level
exceeding 99.9%, the data show
statistically significant differences in the
mean EC:TC ratios between mines and
between different sampling days within
mines.
TABLE VI–7.—ANALYSIS OF VARIANCE FOR ARCSIN OF EC:TC RATIOS, RESTRICTED TO SAMPLES WITH TC > 60 µG/M3
MINE ............................................................................................................................
DAY within MINE .........................................................................................................
Error .............................................................................................................................
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3.360
1.643
4.295
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30
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square
0.116
0.055
0.017
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3.290
P
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0.000
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Figure VI–5 illustrates the magnitude
and extent of differences in the mean
EC:TC ratio between mines. Note that
values on the arcsin scale of 0.7, 0.9,
and 1.1 correspond to EC:TC ratios of
64%, 78%, and 89%, respectively.
Since TC = EC + OC, variability in the
EC:TC ratio corresponds to variability in
the ratio of either EC or TC to OC. Dr.
Borak stated that if DPM is carcinogenic,
then the carcinogenic agents (for
humans) are probably in the organic
fraction (i.e., OC). Consequently,
according to Dr. Borak, neither EC nor
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TC provides an appropriate surrogate for
assessing or limiting health risks.
MSHA believes that Dr. Borak’s
assumption that any carcinogenic effect
of DPM is due entirely to the organic
fraction is speculative. This assumption
contradicts findings reported by
Ichinose et al. (1997b) and does not take
into account the contribution that
inflammation and active oxygen radicals
induced by the inorganic carbon core of
DPM may have in promoting lung
cancers. Indeed, identifying the toxic
components of DPM, and particulate
matter in general, is an important
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research focus of a variety of
government agencies and scientific
organizations (see, for example: Health
Effects Institute, 2003; Environmental
Protection Agency, 2004b). The 2001
risk assessment discusses possible
mechanisms of carcinogenesis for which
both EC and OC would be relevant
factors (66 FR at 5811–5822). Multiple
routes of carcinogenesis may operate in
human lungs—some requiring only the
various organic mutagens in DPM and
others involving induction of free
radicals by the EC core, either alone or
in combination with the organics.
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In focusing on the carcinogenic agents
in OC, Dr. Borak has also ignored noncancer health effects documented in the
2001 risk assessment—e.g.,
immunological, inflammatory, and
allergenic responses in healthy human
volunteers exposed to 300DPM µg/m3
(i.e., ∼ 240TC µg/m3) for as little as one
hour (66 FR at 5769–70, 5816–17, 5820,
5823, 5837, 5841, 5847).
The 308 µg/m3 interim EC PEL
established by this rule is intended to be
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commensurate with the interim TC limit
of 400 µg/m3 established under the 2001
rule—i.e., to be equally protective and
equally feasible. Although, as shown by
Table VI–7 and Figure VI–5, the EC:TC
ratio can exhibit considerable variability
in specific cases, MSHA has concluded
that application of the 1.3 average
conversion factor, as suggested in the
second partial settlement agreement,
generally achieves the goal of equal
protection and feasibility.
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C. Health Effects
A key conclusion of the 2001 risk
assessment was:
Exposure to DPM can materially impair
miner health or functional capacity. These
material impairments include acute sensory
irritations and respiratory symptoms
(including allergenic responses); premature
death from cardiovascular, cardiopulmonary,
or respiratory causes; and lung cancer. [66 FR
at 5854–5855]
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MSHA has reviewed the scientific
literature pertaining to health effects of
fine particulates in general and DPM in
particular published later than what was
considered in the 2001 risk assessment.
As will be shown below, the more
recent scientific evidence generally
supports the conclusion above, and
nothing in our review suggests that it
should be altered. In fact, the U.S.
Environmental Protection Agency (EPA)
recently reached very similar
conclusions after reviewing all of the
evidence to date (EPA; 2002, 2004b).
Some commenters endorsed the 2001
risk assessment, and suggested that the
latest evidence strengthens its
conclusions. For example, one group of
commenters jointly stated:
The evidence presented in MSHA’s 2001 risk
assessment is overwhelming * * * The
evidence linking exposure to particulate air
pollution and/or diesel particulate matter
with lung cancer, cardiovascular and
cardiopulmonary and other adverse health
effects continues to mount.
Similarly, another pair of commenters
jointly stated that ‘‘[t]he scientific
evidence for the [adverse] health effects
of DPM is overwhelming’’ and that
‘‘evidence for the carcinogenicity and
non-cancer health effects of DPM has
grown since 1998.’’
Other commenters contended that all
of the evidence to date is insufficient to
support limitation of occupational DPM
exposures. Several of these commenters
ignored evidence presented in the 2001
risk assessment and/or mischaracterized
its conclusions. For example, the NMA,
MARG, and the Nevada Mining
Association (NVMA) all erroneously
stated that promulgation of the 2001
rule was based on only ‘‘two principal
health concerns: (1) The transitory,
reversible health effects of exposure to
DPM; and, (2) the long-term impacts
that may result in an excess risk of lung
cancer for exposed workers.’’ Actually,
as shown in the conclusion cited above,
the 2001 risk assessment identified
three different kinds of material health
impairment associated with DPM
exposure: (1) Acute sensory irritations
and respiratory symptoms (including
allergenic responses); (2) premature
death from cardiovascular,
cardiopulmonary, or respiratory causes;
and (3) lung cancer. Although the
cardiovascular, cardiopulmonary, and
respiratory effects leading to an
increased risk of premature death were
associated with acute DPM exposures,
commenters presented no evidence that
any such effects were ‘‘transitory’’ or
‘‘reversible.’’ Nor did commenters
present evidence that immunological
responses associated with either short-
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term or long-term DPM exposure were
‘‘transitory’’ or ‘‘reversible.’’
In addition, some commenters
erroneously stated that ‘‘no
[quantitative] dose/response
relationship related to the PELs could be
demonstrated by MSHA.’’ These
commenters apparently ignored the
discussion of exposure-response
relationships in the 2001 risk
assessment (66 FR at 5847–54) and
failed, specifically, to note the
quantitative exposure-response
relationships shown for lung cancer in
the two tables provided (66 FR at 5852–
53). Relevant exposure-response
relationships were also demonstrated in
articles by Pope et al. cited in the 2003
NPRM, which will be discussed further
below.
Some commenters objected that the
exposure-response relationships
presented in the 2001 risk assessment
did not justify adoption of the specific
DPM exposure limits promulgated.
These commenters mistakenly assumed
the limits set forth in the 2001 final rule
were derived from an exposure-response
relationship. As explained in 66 FR at
5710–14, the choice of exposure limits,
while justified by quantifiable adverse
health effects, was actually driven by
feasibility concerns. The exposureresponse relationships provided clear
evidence of adverse human health
effects (both cancer and non-cancer) at
levels far below those determined to be
feasible for mining.
In the 2003 NPRM, MSHA identified
scientific literature pertaining to health
effects of fine particulates in general and
DPM in particular published subsequent
to the 2001 final rule. The 2003 NPRM
stated MSHA’s intentions to continue its
reliance on the 2001 risk assessment
and cited the newer literature in a
neutral manner, soliciting public
comment on its implications for the
2001 risk assessment.
Two commenters complained that
MSHA had not described the recent
scientific literature in sufficient detail to
determine whether it supports the 2001
risk assessment. Most of the
commenters who evaluated the recent
literature found that it supported and/or
strengthened the conclusions of the
2001 risk assessment. Some other
commenters, however, disagreed.
Accordingly MSHA will present the
supplemental literature in more detail
than in the 2003 NPRM and explain
why MSHA believes that it continues to
support the 2001 risk assessment. This
discussion will include our review of an
analysis by Dr. Gerald Chase of some
preliminary data from an ongoing
NIOSH/NCI study.
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The scientific literature cited in the
2003 NPRM was meant only to update
and supplement the evidence of health
effects cited in the 2001 risk assessment.
Although MSHA believes the 2001 risk
assessment presented ample evidence to
justify its conclusions, MSHA is adding
this supplemental literature because it
represents more recent scientific
investigations related to DPM health
effects. The following discussion of
literature cited in the 2003 NPRM is
organized into four categories, roughly
corresponding to the three types of
material health impairments identified
in the 2001 risk assessment, followed by
a category covering toxicology studies:
(1) Respiratory and immunological
effects, including asthma, (2)
cardiovascular and cardiopulmonary
effects, (3) cancer, and (4) mechanisms
of toxicity. Although the discussion of
cancer will focus on lung cancer, it will
also take note of two recent metaanalyses of epidemiological studies
investigating DPM in connection with
bladder and pancreatic cancers.
(1) Respiratory and Immunological
Effects, Including Allergenic Responses
In the 2001 risk assessment, acute
sensory irritations with respiratory
symptoms, including immunological or
allergenic effects such as asthmatic
responses were grouped together, and
all such effects as material health
impairments likely to be caused or
exacerbated by excessive DPM
exposures were identified. This finding
was based on human experimental and
epidemiological studies and was
supported by experimental toxicology.
(For an explanation of why MSHA
considers such effects to be material
impairments, regardless of whether they
are ‘‘reversible,’’ See, 66 FR at 5766.)
Table VI–8 summarizes six additional
studies dealing with possible respiratory
and immunological effects of DPM and/
or fine particulates in general. Three of
these studies (Frew et al., 2001; Holgate
et al., 2002; Salvi et al., 2000) involved
experiments in which human subjects
inhaled specified doses of DPM. These
three studies all support the view that
occupational DPM exposures are likely
to promote or exacerbate adverse
respiratory symptoms and
immunological responses. A fourth
study (Svartengren et al., 2000) exposed
human subjects to high and low doses
of an unspecified mix of diesel and
gasoline engine exhausts. Although 30minute PM2.5 exposures greater than 100
µg/m3 were found to increase asthmatic
response, the authors of this study
attributed the effects they observed
primarily to NO2 exposure. The fifth
study (Oliver et al., 2001) attempted to
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relate pulmonary function test results
and asthmatic conditions to estimated
lifetime diesel exposure in a cohort of
359 ‘‘heavy and highway’’ (HH)
construction workers. After adjustment
for smoking and other potential
confounders, the results indicated an
elevated risk of asthma for exposed
workers in enclosed spaces (tunnel
workers), relative to other HH workers.
The lack of additional statistically
significant results may be attributable to
the small cohort size. The sixth study
(Fusco et al., 2001) examined the
relationship between various markers of
engine exhaust pollution levels and
daily hospital admissions for acute
respiratory infections, COPD, asthma,
and total respiratory conditions in
Rome, Italy. No direct measurements of
32901
fine particulate concentrations were
available. However, having found a
significant correlation between
respiratory-related admissions and CO
and NO2 levels, the authors noted that
since CO and NO2 are good indicators
of combustion products in vehicular
exhaust, the detected effects may be due
to unmeasured fine and ultrafine
particles.
TABLE VI–8.—STUDIES OF HUMAN RESPIRATORY AND IMMUNOLOGICAL EFFECTS, 2000–2002
Authors, year
Description
Key results
Frew et al., 2001 ..................
25 healthy subjects and 15 subjects with mild asthma
were exposed to diesel exhaust (108 µg/m3) or filtered air for 2 hr, with intermittent exercise. Lung
function was assessed using a computerized whole
body plethysmograph. Airway responses were sampled by bronchial wash (BW), bronchoalveolar lavage
(BAL), and mucosal biopsies 6 hr after ceasing exposures.
Fusco et al., 2001 ................
Analysis of daily hospital admissions for acute respiratory infections, COPD, asthma, and total respiratory conditions in Rome, Italy.
Holgate et al. 2002 ..............
25 healthy and 15 asthmatic subjects were exposed for
2 hours to 100 µg/m3 of DPM and to filtered air on
separate days. Another 30 healthy subjects were exposed for 2 hours to DPM concentrations ranging
from 25 to 311 µg/m3 and compared to 12 different
healthy subjects exposed to filtered air. Exposure effects were assessed using lung function tests and
biochemical tests of bronchial tissue samples.
Pulmonary function tests and questionnaire data were
obtained for 350 ‘‘heavy and highway’’ (HH) construction workers. Intensity of DPM exposure was estimated according to job classification. Duration of exposure was estimated based on length of union
membership.
Both the asthmatic and healthy subjects developed increased airway resistance after exposure to diesel
emissions, but airway inflammatory responses were
different for the 2 groups. The healthy subjects
showed statistically significant BW neutrophilia and
BAL lymphocytosis 6 hr after exposure. The
neutrophilic response of the healthy subjects was
less intense than that seen in a previous study using
a DPM concentration of 300 µg/m3.
Respiratory admissions among adults were significantly
correlated with CO and NO2 levels, but not with suspended particles. The authors noted that since CO
and NO2 are good indicators of combustion products
in vehicular exhaust, the detected effects may be due
to unmeasured fine and ultrafine particles.
Healthy and asthmatic subjects exhibited evidence of
bronchioconstriction immediately after exposure
Biochemical tests of inflammation yielded mixed results
but showed small inflammatory changes in healthy
subjects after DPM inhalation.
Oliver et al., 2001 ................
Salvi et al., 2000 ..................
15 healthy nonsmoking volunteers were exposed to
300 µg/m3 DPM and clean air for one hour at least
three weeks apart. Biochemical analyses were performed on bronchial tissue and bronchial wash cells
obtained six hours after each exposure.
Svartengren et al;. 2000 ......
Twenty nonsmoking subjects with mild allergic asthma
were exposed for 30 minutes to high and low levels
of engine exhaust air pollution on two separate occasions at least four weeks apart. Respiratory symptoms and pulmonary function were measured immediately before, during and after both exposure periods. Four hours after each exposure, the test subjects were challenged with a low dose of inhaled allergen. Lung function and asthmatic reactions were
monitored for several hours after exposure.
The 2003 NPRM also cited five new
review articles that summarize the
scientific literature pertaining to the
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After adjusting for smoking and some other potential
confounders, HH workers showed elevated risk of
asthma. One subgroup (tunnel workers) also showed
elevated risk of both undiagnosed asthma and chronic bronchitis, compared to other HH workers.
Respiratory symptoms appeared to declined with exposure duration as measured length of union membership. The authors interpreted this as suggesting that
HH workers tend to leave their trade when they experience adverse respiratory symptoms.
Diesel exhaust exposure enhanced gene transcription
of IL–8 in the bronchial tissue and airway cells and
increased IL–8 and GRO-a protein expression in the
bronchial epithelium. This was accompanied by a
trend toward increased IL–5 mRNA gene transcripts
in the bronchial tissue. Study showed effects on
chemokine and cytokine production in the lower airways of healthy adults. These substances attract and
activate leukocytes. They are associated with the
pathophysiology of asthma and allergic rhintisi.
Subjects with PM2.5 exposure ≥ 100 µg/m3 exhibited
slightly increased asthmatic responses.
Association with adverse outcome variables were
weaker for particulates than for NO2.
respiratory and immunological effects of
DPM and fine particulate matter in
general. These review articles,
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published after the 2001 risk
assessment, are identified and briefly
described in Table VI–9. The three
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articles most specifically dealing with
DPM effects are Pandya et al. (2002),
Peden at al. (2002), and Sydbom et al.
(2001). In general, these reviews
indicate that while DPM is likely to
contribute to asthmatic and/or other
immunological responses, the role of
DPM in producing these health effects is
complex. As noted by Pandya et al. (op
cit.), DPM may have a far greater impact
as an adjuvant with allergens than
alone. Nevertheless, all three of these
review articles support the view that
there is significant evidence of adverse
respiratory and immunological effects to
warrant regulating DPM exposures. The
remaining review articles (Gavett and
Koren, 2001; Patton and Lopez, 2002)
offer little new support for the 2001 risk
assessment, but MSHA found no studies
that either refute or challenge the 2001
risk assessment.
TABLE VI–9.—REVIEW ARTICLES ON RESPIRATORY AND IMMUNOLOGICAL EFFECTS, 1999–2002
Authors, year
Description
Key results
Gavett and Koren, 2001 ......
Summarizes results of EPA studies done to determine
whether PM can enhance allergic sensitization or exacerbate existing asthma or asthma-like responses in
humans and animal models.
Reviews human and animal research relevant to question of whether DPM is associated with asthma.
Studies indicate that PM enhances allergic sensitization
in animal models of allergy exacerbate inflammation
and airway hyper-responsiveness in asthmatics and
animal models of asthma.
Evidence indicates that DPM is associated with the inflammatory and immune responses involved in asthma, but DPM appears to have far greater impact as
an adjuvant with allergens than alone.
DPM appears to augment IgE, trigger eosinophil
degranulation, and stimulate release of numerous
cytokines and chemokines. DPM may also promote
the cytotoxic effects of free radicals in the airways.
Evidence suggests that air pollutants (including DPM)
‘‘affect allergic response by different mechanisms.
Pollutants may increase total IgE levels and
potentiate the initial sensitization to allergens and the
IgE response to a subsequent allergen exposure.
Pollutants also may act by increasing allergic airway
inflammation and by directly stimulating airway inflammation. In addition, it is well known that pollutants can be direct irritants of the airways, increasing
symptoms in patients with allergic syndromes.’’
DPM ‘‘may play a significant role not only in asthma exacerbation but also in TH2 inflammation via the actions
of
polyaromatic
hydrocarbons
on
B
lymphocytes.’’
‘‘* * * PM in which the active agents are biologically
active metal ions and organic residues * * * may
have significant effects on asthma, especially modulating immune function, as demonstrated by the role
of polyaromatic hydrocarbons from diesel exhaust in
IgE production.’’
The epidemiological support for particle effects on asthma and respiratory health is very evident; and respiratory, immunological, and systemic effects of DPM
have been documented in a wide variety of experimental studies.
Acute effects of DPM exposure include irritation of the
nose and eyes, lung function changes, and airway inflammation.
Exposure studies in healthy humans have documented
a number of profound inflammatory changes in the
airways, notably, before changes in pulmonary function can be detected. Such effects may be even
more detrimental in subjects with compromised pulmonary function.
Ultrafine particles are currently suspected of being the
most aggressive particulate component of diesel exhaust.
Pandya et al. 2002 ...............
Patton and Lopez, 2002 ......
Review of evidence and mechanisms for the role of air
pollutants in allergic airways disease.
Peden, 2002 .........................
Review of ‘‘studies that exemplify the impact of ozone,
particulates, and toxic components of particulates on
asthma.’’.
Sydbom et al. 2001 ..............
Review of scientific literature on health effects of disease exhaust, especially the DPM components.
In its 2002 ‘‘Health Assessment
Document for Diesel Engine Exhaust,’’
the Environmental Protection Agency
(EPA) reached the following conclusion
with respect to immunological effects of
diesel exhaust:
Recent human and animal studies show that
acute DE [diesel exhaust] exposure episodes
can exacerbate immunological reactions to
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other allergens or initiate a DE-specific
allergenic reaction. The effects seem to be
associated with both the organic and carbon
core fraction of DPM. In human subjects,
intranasal administration of DPM has
resulted in measurable increases of IgE
antibody production and increased nasal
mRNA for some proinflammatory cytokines.
These types of responses also are markers
typical of asthma, though for DE, evidence
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has not been produced in humans that DE
exposure results in asthma. The ability of
DPM to act as an adjuvant to other allergens
also has been demonstrated in human
subjects. (EPA, 2002)
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(2) Cardiovascular and
Cardiopulmonary Effects
In the 2001 risk assessment, the
evidence presented for DPM’s adverse
cardiovascular and cardiopulmonary
effects relied on data from air pollution
studies in the ambient air. This
evidence identifies premature death
from cardiovascular, cardiopulmonary,
or respiratory causes as an endpoint
significantly associated with exposures
to fine particulates. The 2001 risk
assessment found that ‘‘[t]he mortality
effects of acute exposures appear to be
primarily attributable to combustionrelated particles in PM2.5 [i.e., fine
Particulate Matter] (such as DPM)
* * *.’’
There are difficulties involved in
utilizing the evidence from such studies
in assessing risks to miners from
occupational DPM exposures. As noted
in the 2001 risk assessment,
First, although dpm is a fine particulate,
ambient air also contains fine particulates
other than dpm. Therefore, health effects
associated with exposures to fine particulate
matter in air pollution studies are not
associated specifically with exposures to
dpm or any other one kind of fine particulate
matter. Second, observations of adverse
health effects in segments of the general
population do not necessarily apply to the
population of miners. Since, due to age and
selection factors, the health of miners differs
from that of the public as a whole, it is
possible that fine particles might not affect
miners, as a group, to the same degree as the
general population.
However,
Since dpm is a type of respirable particle,
information about health effects associated
with exposures to respirable particles, and
especially to fine particulate matter, is
certainly relevant, even if difficult to apply
directly to dpm exposures. [66 FR 5767]
Pope (2000) reviewed the
epidemiological evidence for adverse
health effects of PM2.5 and characterized
populations at increased risk due to
PM2.5 exposure. He found that ‘‘[t]he
overall epidemiologic evidence
indicates a probable link between fine
particulate air pollution and adverse
effects on cardiopulmonary health.’’ The
observed endpoints include ‘‘death from
cardiac and pulmonary disease,
emergency and physician office visits
for asthma and other cardiorespiratory
disorders, hospital admissions for
cardiopulmonary disease, increased
32903
reported respiratory symptoms, and
decreased measured lung function.’’
Moreover, according to Pope, recent
research suggests that ‘‘those who are
susceptible to increased risk of mortality
from acutely elevated PM may include
more than just the most old and frail
who are already very near death.’’ Pope
went on to state that, with respect to
chronic exposure, ‘‘[t]here is no
evidence that increased mortality risk is
confined to any well-defined
susceptible subgroup.’’
Table VI–10 identifies five studies on
cardiovascular and cardiopulmonary
effects published since the 2001 risk
assessment (Lippmann et al., 2000;
Magari et al., 2001; Pope et al., 2002;
Samet et al., 2000a, 2000b; Wichmann
et al., 2000). Three of these studies
(Pope et al., 2002; Samet et al., 2000a,
2000b; Wichmann et al., 2000)
significantly strengthen MSHA’s
existing evidence implicating
particulate exposures with premature
mortality from cardiovascular and
cardiopulmonary causes.5 The Samet
and Pope (2002) articles both establish
statistically significant exposureresponse relationships.
TABLE VI–10.—STUDIES RELATING TO CARDIOVASCULAR AND CARDIOPULMONARY EFFECTS, 2000–2002
Authors, years
Description
Key results
Lippmann et al. 2000 ...........
Day-to-day fluctuations in particulate air pollution in the
Detroit area were compared with corresponding fluctuations in daily deaths and hospital admissions for
1985–1990 and 1992–1994.
Magari et al., 2001 ...............
Longitudinal study of a male occupational cohort examined the relationship between PM2.5 exposure and
cardiac autonomic function.
Pope et al., 2002 .................
Prospective cohort mortality study, based on data collected for Cancer Prevention II Study, which began in
1982. Questionnaires were used to obtain individual
risk factor data (age, sex, race, weight, height, smoking history, education, marital status, diet, alcohol
consumption, and occupational exposures). For
about 500,000 adults, these were combined with air
pollution data for metropolitan areas throughout the
U.S. and with vital status and cause of death data
through 1998.
Time series analyses were conducted on data from the
20 and 90 largest U.S. cities to investigate relationships between PM10 and other pollutants and daily
mortality.
After adjustment for the presence of other pollutants,
significant associations were found between particulate levels and an increased risk of death due to circulatory causes. However, relative risks were about
the same for PM2.5 and larger particles.
After adjusting for potential confounding factors such as
age, time of day, and urinary nicotine level, PM2.5 exposure was significantly associated with disturbances
in cardiac autonomic function.
After adjustment for other risk factors and potential confounders, using a variety of statistical methods, fine
particulate (PM2.5) exposures were significantly associated with cardiopulmonary mortality (and also with
lung cancer).
Each 10-µg/m3 increase in mean level of ambient fine
particulate air pollution was associated with an increase of approximately 6% in the risk of
cardiopulmonary mortality.
Samet et al., 2000a, 2000b
Wichmann et al., 2000 .........
Time series analyses were conducted on data from Erfurt, Germany to investigate relationships between
the number and mass concentrations of ultrafine and
fine particles and daily mortality.
Results of both the 20-city and 90-city mortality analyses are consistent with an average increase in cardiovascular and cardiopulmonary deaths of more
than 0.5% for every 10 µg/m3 increase in PM10
measured the day before death. (Estimated effects
are, in general, slightly lower using a more stringent
statistical analysis. See Dominici et al., 2002.)
Higher levels of both fine and ultrafine particle concentrations were significantly associated with increased mortality rate.
5 As discussed below, Pope et al. (2002) also
provides strong evidence linking chronic PM2.5
exposure with an elevated risk of lung cancer.
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Pope et al. (2002) warrants special
attention because this study addresses
chronic effects of long-term PM2.5
exposures. (Other studies on PM2.5,
described in the 2001 risk assessment,
have almost all dealt with acute
exposure effects.) The authors
concluded that ‘‘* * * the findings of
this study provide the strongest
evidence to date that long-term
exposure to fine particulate air pollution
* * * is an important risk factor for
cardiopulmonary mortality.’’ In the
2001 risk assessment, the conclusion
related to cardiopulmonary effects was
motivated mostly by evidence on shortterm exposures from daily time series
analyses. Therefore, in finding a
significant increase in cardiopulmonary
mortality attributable to chronic fine
particulate exposures, this study
provides important supplement
evidence supporting this conclusion.
The portion of the study related to lung
cancer effects is summarized in the next
section.
The EPA’s 2004 Air Quality Criteria
Document for particulate matter (EPA,
2004b) describes a number of additional
studies related to the cardiopulmonary
and cardiovascular effects of PM2.5,
including work published later than that
cited in the 2003 NPRM. One of the
summary conclusions presented in that
document is:
Overall, there is strong epidemiological
evidence linking (a) short-term (hours, days)
exposures to PM2.5 with cardiovascular and
respiratory mortality and morbidity, and (b)
long-term (years, decades) PM2.5 exposure
with cardiovascular and lung cancer
mortality and respiratory morbidity. The
associations between PM2.5 and these various
health endpoints are positive and often
statistically significant. [EPA, 2004b, Sec. 9
p. 46]
1. Cancer Effects
The 2001 risk assessment concluded
that DPM exposure, at occupational
levels encountered in mining, was likely
to increase the risk of lung cancer. The
assessment also found that there was
insufficient evidence to establish a
causal relationship between DPM and
other forms of cancer. Both of these
conclusions are supported by the most
recent scientific literature. The first part
of this update contains a description of
three new human research studies and
a literature review relating DPM and/or
other fine particulate exposures to lung
cancer. Since it relates specifically to
lung cancer, this subsection also
discusses Dr. Chase’s analysis. New
research on the relationship between
DPM exposures and other forms of
cancer are described immediately after
the lung cancer discussion.
Lung Cancer
Table VI–11 presents three human
studies pertaining to the association
between lung cancer and exposures to
DPM or fine particulates in general
completed after the 2001 risk
assessment was done.
TABLE VI–11.—STUDIES ON LUNG CANCER EFFECTS, 2000–2002.
Authors, year
Description
Key results
Boffetta et al., 2001 .............
Cohort consisting of entire Swedish working population
other than farmers. Exposure assessment based on
job title and industry, classified according to probability and intensity of diesel exhaust exposure.
Gustavsson et al., 2000 .......
Case-control study involving all 1,042 male cases of
lung cancer and 2,364 randomly selected controls
(matched by age and inclusion year) in Stockholm
County, Sweden from 1985 through 1990. Semiquantitative assessment of exposure to diesel exhaust. Relative Risk (RR) estimates adjusted for age,
selection year, tobacco smoking, residential radon,
occupational exposures to asbestos and combustion
products, and environmental exposure to NO2.
Prospective cohort mortality study using data collected
for the American Cancer Society Cancer Prevention
II Study (began 1982). Questionnaires used to obtain
individual risk factor data including age, sex, race,
weight, height, smoking history, education, marital
status, diet, alcohol consumption, and occupational
exposures. This risk factor data combined with air
pollution data for metropolitan areas throughout U.S.
and vital status and cause of death data through
1998 for about 500,000 adults.
Statistically significant elevations in relative risk (RR) of
lung cancer among men for job categories with medium, and high exposure to diesel exhaust, compared to workers in jobs classified as having no occupational exposure
Adjusted RR for the highest quartile of estimated lifetime exposure was 1.63, compared to the group with
no exposure.
Pope et al., 2002 .................
Boffetta et al. (2001) investigated a
Swedish cohort comprised of the whole
Swedish working population not
employed as farmers. Job title and
industry were classified according to
probability and intensity of diesel
exhaust exposure in 1960 and 1970 and
also according to the authors’
confidence in the assessment. Cohort
members were followed up for mortality
for the 19-year period from 1971
through 1989. Cause of death and
specific cancer type, when applicable,
were obtained from national registries.
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After adjusting for other risk factors and potential cofounders, chronic PM2.5 exposures found to be significantly associated with elevated lung cancer mortality. Each 10-µg/m3 increase in mean level of ambient fine particulate air pollution (PM2.5) associated
with statistically significant increase of approximately
8% in risk of lung cancer mortality.
Compared to workers in jobs
classified as having no occupational
exposure to diesel emissions, relative
risks (RR) of lung cancer among men
were 0.95, 1.1, and 1.3 for job categories
with low, medium, and high exposure
intensity, respectively. The elevated
risks for the medium and high exposure
groups were statistically significant, and
no similar pattern was observed for
other cancer types. The authors
concluded that these results ‘‘provide
evidence of a positive exposureresponse relationship between exposure
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to diesel emissions and lung cancer
among men.’’
Although this study adds to the
cumulative weight of evidence
establishing a causal link between DPM
exposure and lung cancer, it does not
provide very strong evidence when
viewed in isolation. One weakness of
the study is that the exposure
assessment was based on self-reported
occupation and industry, with no
information on duration of employment
in various jobs. (This sort of uncertainty
in the exposure assessment, however,
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would not normally be expected to
induce a false exposure-response
relationship.) Another weakness is that
there was no information on potential
confounders, such as tobacco smoking
and lifestyle factors that may be
associated with certain jobs. While
recognizing this limitation, the authors
considered it unlikely that confounders
could account for the increasing trend
in relative risk observed according to
intensity of diesel exposure.
Gustavsson et al. (2000) performed a
case-control study involving all 1,042
male cases of lung cancer and 2364
randomly selected controls (matched by
age and inclusion year) in Stockholm
County, Sweden from 1985 through
1990. Occupational exposure, smoking
habits, and other potential risk factors
were assessed based on written
questionnaires mailed to the subject or
next of kin. Relative Risk (RR) estimates
were adjusted for age, selection year,
tobacco smoking, residential radon,
occupational exposures to asbestos and
combustion products, and
environmental exposure to NO2.
Compared to the group with no
exposure, adjusted RR for the highest
quartile of estimated lifetime exposure
was 1.63 (95% CI = 1.14 to 2.33). The
authors concluded that ‘‘[t]he present
findings add further evidence for an
association between diesel exhaust and
lung cancer * * * ’’
Strengths of this study include a semiquantitative exposure assessment and
adjustment of the relative risk for
several important potential
confounders. The statistically
significant result corroborates the
finding of a link between DPM exposure
and lung cancer in MSHA’s 2001 risk
assessment.
Pope et al. (2002) used the cohort
established by the American Cancer
Society Cancer Prevention II Study to
examine the relationship between lung
cancer and PM2.5 air pollution. This
prospective cohort mortality study,
which began in 1982, used
questionnaires to obtain individual risk
factor data (age, sex, race, weight,
height, smoking history, education,
marital status, diet, alcohol
consumption, and occupational
exposures). For about 500,000 adults,
these risk factors were combined with
air pollution data for metropolitan areas
throughout the U.S. and with vital
status and cause of death data through
1998.
After adjusting for other risk factors
and potential confounders, using a
variety of statistical methods, chronic
PM2.5 exposures were found to be
significantly associated with elevated
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lung cancer mortality.6 Each 10 µg/m3
increase in the mean level of ambient
fine particulate air pollution was
associated with a statistically significant
increase of approximately 8% in the risk
of lung cancer mortality. Within the
range of exposures found in the study,
the exposure-response relationship
between PM2.5 and lung cancer was
monotonically increasing. The authors
concluded that ‘‘[e]levated fine
particulate exposures were associated
with significant increases in lung cancer
mortality * * * even after controlling
for cigarette smoking, diet, occupational
exposure, other individual risk factors,
and after controlling for regional and
other spatial differences.’’
Szadkowska-Stanczyk and
Ruszkowska (2000) performed a
literature review of studies relating to
the carcinogenic effects of diesel
emissions. The authors concluded that
long-term exposure (> 20 years) was
associated with a 30% to 40% increase
in lung cancer risk in workers in the
transport industry. This article was
written in Polish, and MSHA was
unable to obtain a translation of it for
this update. However, based on the
English abstract, it appears to add no
new information to the 2001 risk
assessment.
Several commenters expressed
opinions on the unpublished document
by Dr. Gerald Chase (2004) entitled
Characterizations of Lung Cancer in
Cohort Studies and a NIOSH Study on
Health Effects of Diesel Exhaust in
Miners, which was placed into the
public record at MARG’s request. This
document presents an analysis of some
preliminary data provided by NIOSH
and NCI at a public stakeholder meeting
held on Nov. 5, 2003. These data were
taken from unpublished charts that
NIOSH and NCI used to inform the
public on the status and progress of
their ongoing project, A Cohort
Mortality Study with a Nested CaseControl Study of Lung Cancer and
Diesel Exhaust Among Nonmetal Miners
[NIOSH/NCI 1997]. Researchers
involved in that project have thus far
published no analyses or conclusions
based on these data. Dr. Chase, however,
concluded that ‘‘based on the limited
data available to date, the number and
pattern of lung cancer deaths reported
* * * are in agreement with lung cancer
deaths from the general population for
the age groups involved * * *’’ and
‘‘* * * are possible without attributing
any excess cancers to the study subject
6 As discussed earlier, Pope et al. (2002) also
provides strong evidence that chronic PM2.5
exposure increases the risk of premature
cardiopulmonary mortality.
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32905
matter: diesel exhaust’’ [emphasis
added]. He offered no opinion as to
whether the preliminary data actually
demonstrate that there were no excess
lung cancers attributable to DPM
exposures.
Although Dr. Chase noted that his
analyses and conclusions were limited
and based on incomplete information,
some commenters interpreted his report
as casting serious doubt on any
increased risk of lung cancer associated
with occupational DPM exposures. For
example, one commenter said the report
‘‘suggests lung cancer is not a problem
in this worker population.’’ Another
commenter interpreted Dr. Chase’s
findings as providing ‘‘startling
evidence rebutting MSHA’s PELs and
risk analysis.’’ Other industry
commenters asserted that Dr. Chase’s
analysis ‘‘eliminates the rationale upon
which the final 160 microgram standard
was premised.’’ Another commenter
claimed that Dr. Chase’s analysis shows
MSHA’s justification for limiting DPM
exposures is ‘‘contradicted by the
NIOSH/NCI data.’’
Commenters representing organized
labor, on the other hand, focused on the
preliminary and incomplete nature of
the data Dr. Chase analyzed. One such
commenter pointed out that these data
had not been made directly available on
MSHA’s website and that the status of
the NIOSH/NCI study was not discussed
in the re-opening announcement.
Another commenter argued that the
Chase analysis does not meet minimal
standards of ‘‘real epidemiological
research’’ and that it ‘‘is worthless for
the purpose of [MSHA’s DPM]
rulemaking.’’ This commenter also
stated that ‘‘the record already contains
ample evidence of the carcinogenicity of
DPM’’ and that ‘‘the NIOSH/NCI study
will not shake those findings, even if it
should prove to be inconclusive.’’
The Chase analysis ignores at least
three factors that can reasonably be
expected to heavily influence the
findings of the NIOSH/NCI study: (a)
Differentiation between exposed and
unexposed miners within the study, (b)
quantification of exposure, and (c)
possible ‘‘healthy worker effect.’’
According to the 1997 NIOSH/NCI
study protocol, these three factors will
be taken fully into account before any
conclusions are published. The
remainder of this subsection will
explain how ignoring them, as in the
Chase report, can mask adverse health
effects potentially associated with DPM
exposures.
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(a) Differentiation Between Exposed and
Unexposed Miners
Approximately 50% of the miners in
the NIOSH/NCI study cohort are
expected to be surface workers (NIOSH/
NCI, 1997, Tables A.1 and B.2). These
miners are likely to have experienced
far lower levels of DPM exposure than
underground miners in the cohort. The
NIOSH/NCI study protocol specifies
that such members of the cohort—i.e.,
those who have had little or no
occupational DPM exposure ‘‘will be
used as the ‘‘unexposed’’ control group
for the study. In other words, the
protocol calls for statistically comparing
the health of these surface workers to
the health of the much more highly
exposed underground workers.
Dr. Chase did not distinguish between
surface and underground workers in the
cohort. Consequently, his analysis may
dilute the lung cancer rate for exposed
miners by combining it with the rate for
miners with relatively little exposure.
As noted by Dr. Chase, the preliminary
data presented indicate that 9.8% of the
deaths in the overall cohort were from
lung cancer. He also suggests that the
normal or ‘‘background’’ percentage is
8.0%, based on the national lung cancer
mortality rate and that the excess of
9.8% over 8.0% is not statistically
significant. Suppose, however, that the
overall excess of lung cancer deaths
arose entirely from that half of the
cohort comprising exposed,
underground workers. Then, for miners
in the ‘‘exposed’’ group, the percentage
of deaths from lung cancer would
actually be 11.6%. Since 8.0/2 + 11.6/
2 = 9.8, the 8.0% rate for surface
workers would have diluted the 11.6%
rate for exposed underground workers
to yield an average rate of 9.8%. In this
case, the lung cancer rate for
underground miners would be about
45% greater than the national
background rate (i.e., 11.6/8.0).
Dr. Chase also claims that the 8%
‘‘background’’ rate is too low, since it
combines all ages and includes
relatively low lung cancer death rates
for ages below 55 years. Although it is
true that age-specific lung cancer
mortality rates increase after age 55, this
should be considered only in
conjunction with the age at death for
members of the specific study cohort.
Approximately two-thirds of the cohort
members were born after 1940, with a
maximum age at death of 56 years. For
this age group, less than 5% of all
deaths are attributed to lung cancer.
Therefore, for purposes of comparison
with this particular study cohort, an 8%
background rate may be too high rather
than too low, and the excess for
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underground workers may be even
greater than the 45% indicated above.
(b) Quantification of Exposure
As explained in the 2001 risk
assessment, quantification of exposure
was an important element in MSHA’s
evaluation of epidemiologic studies on
DPM and lung cancer (FR 66 at 5784–
5785, 5795ff). Relatively little weight
was placed on studies that took no
account of duration and intensity of
exposure. At the time of the NIOSH/NCI
Joint Study Meeting to discuss
information with stakeholders on the
progress of the study, exposure data for
individual miners still were being
processed. Since such exposure data
were not presented at the meeting, they
could not be used in Dr. Chase’s
analysis.
The lack of detailed exposure data in
Dr. Chase’s analysis could potentially
cause major distortions in interpretation
of the results. The study cohort includes
a number of workers with relatively
short exposure duration. This is
demonstrated by a 1981 NIOSH study
showing that the mean tenure of
underground trona miners working in
1976 was only about 3 years for ages
greater than 25 years. (Attfield et al.
1981). The two largest trona mines
included in that study were also
included in the NIOSH/NCI study
(identified as Numbers 6 and 8 in Table
A.1 of the 1997 NIOSH/NCI study
protocol). Therefore, a substantial
portion of the NIOSH/NCI study cohort
may have been occupationally exposed
to DPM for three years or less. If such
short exposures produce little or no
excess in lung cancers, then this portion
of the cohort could mask a significant
excess among workers with longer
exposures. Since Dr. Chase’s analysis
lumps miners together without regard to
exposure duration, it provides no
effective way to evaluate effects
associated with long-term exposure.
(c) Internal Versus External Analysis
Another important element in
MSHA’s evaluation of epidemiologic
studies on DPM and lung cancer was
equitable composition of the groups
being compared (FR 66 at 5783–5784,
5795ff). As explained in the Federal
Register, comparison of an exposed
cohort to an external control group can
give rise to various forms of selection
bias. For example, the ‘‘healthy worker
effect,’’ which is widely recognized in
the occupational health literature, tends
to reduce estimates of excess risk in a
group of workers when that group is
compared to a general population.
Several of the lung cancer cohort studies
reviewed in the 2001 risk assessment
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cohorts showed no excess lung cancers
among exposed workers compared to an
external population. Nevertheless, those
studies showed excess lung cancers
among exposed workers compared to
otherwise similar but unexposed
workers.
To avoid selection biases, the 2001
risk assessment favored comparisons
against internal control groups or
studies that compensated for the healthy
worker effect by means of an
appropriate adjustment. Dr. Chase’s
analysis, however, focuses entirely on
external comparisons with no
compensating adjustment—an approach
that the 2001 risk assessment generally
discounted. Although the NIOSH/NCI
study protocol explicitly calls for
internal comparisons, the detailed
exposure data necessary for such
comparisons were not available to Dr.
Chase since they were not presented
during the November 5, 2003 public
meeting.
(d) Conclusions Regarding Dr. Chase’s
Analysis
Dr. Chase has argued that some
preliminary and incomplete data made
available from the NIOSH/NCI study do
not demonstrate any excess lung cancer
associated with DPM exposure. Even if
Dr. Chase is correct, however, this may
merely reflect limitations of the
preliminary and incomplete data upon
which his analysis relies. Because
necessary data were not yet available,
the Chase analysis was unable to
consider a possible healthy worker
effect, occupationally unexposed
workers within the cohort, or
potentially important variations in
exposure intensity and duration. When
the NIOSH/NCI study is completed, we
are confident that it will take all these
factors into account in accordance with
the protocol.
MSHA concludes that the data on
which Dr. Chase’s analysis is based are
inadequate for identifying or assessing
the relationship between occupational
DPM exposure and excess lung cancer
mortality. These incomplete data
provide little insight into what a
comprehensive analysis of the NIOSH/
NCI study results will ultimately show,
when carried out in accordance with the
study protocol.
Bladder Cancer
Boffetta and Silverman (2001)
performed a meta-analysis of 44
independent results from 29 distinct
studies of bladder cancer in
occupational groups with varying
exposure to diesel exhaust. Studies were
included only if there were at least five
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years between time of first exposure and
development of bladder cancer.
Separate quantitative meta-analyses
were performed for heavy equipment
operators, truck drivers, bus drivers, and
studies with semi-quantitative exposure
assessments based on a job exposure
matrix (JEM). The overall relative risk
(RR) for heavy equipment operators was
RR = 1.37 (95% CI: 1.05–1.81); for truck
drivers, RR = 1.17 (1.06–1.29); for bus
drivers, RR = 1.33 (1.22–1.45); and for
JEM, RR = 1.13 (1.0–1.27).
A quantitative meta-analysis was also
performed on 8 independent studies
showing results for ‘‘high’’ diesel
exposure. The combined results were
RR = 1.23 (1.12–1.36) for ‘‘any
exposure’’ and RR = 1.44 (1.18–1.76) for
‘‘high exposure.’’
The authors discovered a strong
indication of publication bias for truck
and bus driver studies, a tendency for
studies to be published only when they
showed a positive result. However, the
summary RR for the seven largest truck
or bus driver studies was 1.26 (1.18–
1.34), which is very close to the RR
based on all 27 truck or bus driver
results. There was no indication of
publication bias for studies with semiquantitative exposure assessments.
The results of this meta-analysis
suggest a statistically significant
association between diesel exposure and
an elevated risk of bladder cancer not
fully explained by publication bias.
Nevertheless, potential confounding by
vibration, dietary factors, and
infrequency of urination among drivers
preclude a causal interpretation of this
association.
Not included in this meta-analysis
was a study by Zeegers et al. (2001).
This was a prospective case-cohort
study involving 98 cases of bladder
cancer among men occupationally
exposed to diesel exhaust. A cohort of
58,279 men who were 55 to 69 years old
in 1986 was followed up through
December 1992. Exposure was assessed
by job history given on a selfadministered questionnaire, combined
with experts’ assessment of the
exposure probability for each job. A
‘‘cumulative probability of exposure’’
was determined by multiplying job
duration by the corresponding exposure
probability. Four categories of relative
cumulative exposure probability were
defined: none, lowest third, middle
third, and highest third. Relative risks
were adjusted for age, cigarette smoking,
and exposure to other occupational risk
factors.
The relative risk for the category with
highest cumulative probability of
exposure was RR = 1.17 (95% CI: 0.74–
1.84). In light of the meta-analysis
results described above, the lack of
statistical significance found in this
study may be due to low statistical
power for detecting diesel exhaust
effects, combined with nondifferential
errors in the exposure assessment.
As with the epidemiological studies
on diesel exposure and bladder cancer
considered in the meta-analysis, no
adjustment was made in this study for
infrequency of urination or for dietary
patterns possibly associated with
occupations having diesel exposures.
Therefore, this study, like the metaanalysis performed by Boffetta and
Silverman, has no impact on the 2001
risk assessment.
Pancreatic Cancer
¨
Ojajarvi et al. (2000) performed a
meta-analysis of 161 independent
results from 92 studies on the
relationship between diesel exhaust
exposure and pancreatic cancer. No
elevated risk was associated with diesel
exposure. The combined relative risk
was RR = 1.0 (95% CI: 0.9–1.3). This
result is consistent with the 2001 risk
assessment, which identified lung
cancer and bladder cancer as the only
forms of cancer for which there was
evidence of an association with DPM
exposure.
4. Mechanisms of Toxicity
Table VI–12 describes 15 DPM
toxicity studies published after the 2001
risk assessment and cited in the 2003
NPRM. Table VI–12 also describes a
16th toxicity study (Arlt et al., 2002),
which was cited by Dr. Jonathan Borak
in comments submitted by MARG. All
of these studies lend some degree of
support to the conclusions of the 2001
risk assessment. In addition to briefly
describing each study and its key
results, the table identifies the agent(s)
of toxicity investigated and indicates
how the results support the risk
assessment by categorizing the toxic
effects and/or markers of toxicity found.
The categories used to classify toxic
effects are: (A) Immunological and/or
allergic reactions, (B) inflammation, (C)
mutagenicity and/or DNA adduct
formation, (D) induction of free oxygen
radicals, (E) airflow obstruction; (F)
impaired clearance; (G) reduced defense
mechanisms; and (H) adverse
cardiovascular effects.
TABLE VI–12.—STUDIES ON TOXICOLOGICAL EFFECTS OF DPM EXPOSURE, 2000–2002
Authors, year
Al-Humadi et al., 2002
Arlt et al., 2002 ...........
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Description
Key results
IT instillation in rats of 5 mg/kg Exposure to DPM or
saline, DPM, or carbon black.
carbon black augments OVA sensitization; particle
composition (of
DPM) may not be
critical for adjuvant
effect.
In Vitro and in Vivo: investiga- Increased DNA adduct
tion of metabolic activation of
formation due to in
3-nitrobenzanthrone (3-NBA)
the presence of
by human enzymes.
human N,O
acetyltransferases
and
sulfotransferases.
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Agent(s) of toxicity
Toxic
effect(s)
*
DPM and carbon
black particles.
A
3-NBA, a constituent
of the organic fraction of DPM.
C
Limitations
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TABLE VI–12.—STUDIES ON TOXICOLOGICAL EFFECTS OF DPM EXPOSURE, 2000–2002—Continued
Toxic
effect(s)
*
Authors, year
Description
Key results
Agent(s) of toxicity
¨
Bunger et al., 2000 .....
In Vitro: assessment of content
of polynuclear aromatic compounds and mutagenicity of
DPM generated from four
fuels, Ames assay used.
DE generated from
diesel engine.
DPM collected on filters and soluble organic extracts prepared.
C
Carero et al., 2001 .....
In Vitro: assessment of DPM,
carbon black, and urban particulate matter genotoxicity,
human alveolar epithelial
cells used.
Production of black
carbon and
polynuclear aromatic compounds
that are mutagenic;
correlation with sulfur content of fuel
and engine speed.
DNA Damage produced, but no
cytotoxicity produced.
C
Castranova et al.,
2001.
In Vitro: assessment of DPM DPM depresses antion
alveolar
macrophage
microbial potential
functions and role of adof macrophages,
sorbed chemicals; rat alvethereby increasing
olar macrophages used.
susceptibility of lung
In Vivo: assessment of DPM on
to infections, this inalveolar macrophage funchibitory effect due to
tions and role of adsorbed
adsorbed chemicals
chemicals, use of IT instillarather than carbon
tion in rats.
core of DPM.
In
Vitro:
assessment
of Adverse effects of DE
cytokine production, spleen
on cytokine and
cells used.
antibody production
In Vivo: assessment of cytokine
by creating an improduction profile following IP
balance of helper Tsensitization to OA and subcell functions.
sequent exposure to 1.0 mg/
mg 3 DE for 12 hr/day, 7
days/week over 4 weeks,
mouse inhalation model used.
In Vivo: assessment of infec- Exposure to
tivity and allergenicity folwoodsmoke inlowing
exposure
to
creased susceptiwoodsmoke,
oil
furnace
bility to and severity
emissions, or residual oil fly
of streptococcal inash, mouse inhalation model
fection, exposure to
used, IT instillation used in
residual oil fly ash
rats.
increased pulmonary hypersensitivity reactions.
In
Vitro:
assessment
of Seasonal variations in
cytotoxic effects (cell proPM, in their soluliferation, DNA damage) of
bility, and in their
PM2.5 (fine PM and PM2.5¥10
ability to produce
(coarse PM), rat embryo
cytotoxicity.
fibroblast cells used.
Long-term exposure to
non-killing doses of
PM may lead to accumulation of DNA
lesions.
In Vitro: assessment of adduct Temporal and doseformation following exposure
dependent DNA
to DPM, DPM extracts,
adduct formation by
benzo[a]pyrene, or 5-methylPAHs.
chrysene, mammary car- Carcinogenci PAHs
cinoma cells used.
from diesel extracts
lead to stable DNA
adduct formation.
DPM, urban particulate matter (UPM),
and carbon black
(CB).
DPM, UPM purchased
from NIST, CB purchased from Cabot.
No information on
generation of DPM.
(details may be found
in previous publications from this lab).
Fujimaki et al., 2001 ...
Gilmour et al., 2001 ....
Hsiao et al., 2000 .......
Kuljukka-Rabb et al.,
2001.
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DE generated from
diesel engine.
DPM, CO2, SO2, and
NO/NO2/NOx measured.
Limitations
D, F, G
A
Sensitization to OA
via IP injection.
Changes in pulmonary
function not assessed.
Woodsmoke, oil furnace emissions,
and residual oil fly
ash (ROFA) used.
A, B
No DPM used.
PM collected Hong
Kong area and solvent-extractable organic compounds
used.
C
No DPM used.
Some DPM purchased
from NIST, some
DPM collected on
filters from diesel
vehicle, and solvent-extractable organic compounds
used.
C
Use of only soluble organic fraction of
DPM.
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TABLE VI–12.—STUDIES ON TOXICOLOGICAL EFFECTS OF DPM EXPOSURE, 2000–2002—Continued
Toxic
effect(s)
*
Authors, year
Description
Key results
Agent(s) of toxicity
Moyer et al., 2002 ......
In Vivo: 2-phase retrospective
study, review of NTP data
from 90-day and 2-yr exposures to particulates, use of
mouse inhalation model.
Induction and/or exacerbation of arteritis
following chronic exposure (beyond 90day) to particulates.
B, H
Saito et al., 2002 ........
In Vivo: assessment of cytokine
expression following exposure to DE (100 µg/m3 or 3
mg/m3 DPM) for 7-hrs/day ×
5 days/wk × 4 wks, mouse
inhalation model used.
Sato et al., 2000 .........
In Vivo: assessment of mutant
frequency
and
mutation
spectra in lung following 4wk exposure to 1 or 6 mg/m3
DE, transgenic rat ihalation
model used.
DE alters
immunological responses in the lung
and may increase
susceptibility to
pathogens, lowdose DE may induce allergic/asthmatic reactions.
DE produced lesions
in DNA and was
mutagenic in rat
lung.
Indium phosphide, cobalt sulfate
heptahydrate, vanadium pentoxide,
gallium arsenide,
nickel oxide, nickel
subsulfide, nickel
sulfate hexahydrate,
talc, molybdenum
trioxide used.
DE generated from
diesel engine.
DPM, CO, SO2 and
NO2 measured.
C
Van Zijverden et al.,
2000.
In
Vivo:
assessment
of
immuno-modulating capacity
of DPM, carbon black, and
silica particles, mouse model
used (sc injection into hind
footpad).
DPM skew immune
response toward T
helper 2 (Th2) side,
and may facilitate
initiation of allergy.
Vincent et al., 2001 ....
In Vivo: assessment of cardiovascular effects following 4hr exposure to 4.2 mg/m3
diesel soot, 4.6 mg/m3 carbon black, or 48 mg/m3 ambient urban particulates, rat
inhalation model used.
Walters et al., 2001 ....
In Vivo: assessment of airway
reactivity/responsiveness,
and BAL cells and BAL
cytokines following exposure
to 0.5 mg/mouse aspirated
DPM, ambient PM, or coal fly
ash.
Increases in
endothelin¥1 and
¥3 (two
vasoregulators) following ambient
urban particulates
and diesel soot exposure.
Small increases in
blood pressure following exposure to
ambient urban
particualtes.
Dose and time-dependent changes in
airway responsiveness and inflammation following exposure to PM.
Increase in BAL cellularity following exposure to DPM, but
airway reactivity/responsiveness unchanged.
DE generated from
light-duty diesel engine.
Concentration of suspended particulate
matter (SPM) measured, 11 PAHs and
nitrated PAHs identified and
quantitated in SPM.
DPM, carbon black
particles (CBP) and
silica particles (SIP)
used.
DPM donated by
Nijmegen University, CBP and SIP
purchased from
BrunschwichChemie
and Sigma.
Diesel soot, carbon
black and urban air
particulates used.
Diesel soot purchased
from NIST, carbon
black donated by
University of California, urban air
particulates collected in Ottawa.
DPM, PM, and coal fly
ash used.
DPM purchased from
NIST, PM collected
in Baltimore, and
coal fly ash obtained from Baltimore power plant.
A, B
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Limitations
Nine particulate compounds selected to
represent al PM.
A
A
H
Questionable relevance of exposure
route (sc injection).
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TABLE VI–12.—STUDIES ON TOXICOLOGICAL EFFECTS OF DPM EXPOSURE, 2000–2002—Continued
Authors, year
Description
Key results
Whitekus et al., 2002 ..
In Vitro: assessment of ability
of six antioxidants to interfere
in DPM-mediated oxidative
stress, cell cultures used.
In Vivo: assessment of sensitization to OA and/or DPM
and possible modulation by
thiol antioxidants, mouse inhalation model used.
Thiol antioxidants
(given as a
pretreatment) inhibit
adjuvant effects of
DPM in the induction of OA sensitization.
Toxic
effect(s)
*
Agent(s) of toxicity
DE generated from
light-duty diesel engine, DPM collected, dissolved in
saline, and aerosolized.
A, D
Limitations
Changes in pulmonary
function associated
with sensitization
not assessed.
* KEY:
(A) Immunological and/or allergic reactions.
(B) Inflammation.
(C) Mutagenicity/DNA adduct formation.
(D) Induction of free oxygen radicals cardiovascular effects.
(E) Airflow obstruction.
(F) Impaired clearance.
(G) Reduced defense mechanisms.
(H) Adverse.
In addition to the new toxicity
studies, four new reviews on various
aspects of the scientific literature related
to mechanisms of DPM toxicity were
cited in the 2003 NPRM. These are
listed in Table VI–13. Two of these
reviews (ILSI, 2000 and Oberdoerster,
2002) focus on the applicability of the
DPM rat toxicity studies to low-dose
extrapolation for humans and conclude
that such extrapolation is not
appropriate. Since the 2001 risk
assessment does not attempt to make
any such extrapolation, these reviews
do not affect MSHA’s conclusions. As
noted in the 2001 risk assessment,
evidence that the carcinogenic effects of
DPM in rats are due to overload of the
rats’ lung clearance mechanism does not
rule out a mutagenic mechanism of
carcinogenesis at lower exposure levels
in other species. The other two review
articles generally support the discussion
in the 2001 risk assessment of
inflammation responses due to DPM
exposures.
TABLE VI–13.—REVIEW ARTICLES ON TOXICOLOGICAL EFFECTS OF DPM EXPOSURE, 2000–2002
Authors, year
Description
ILSI Risk Science Institute
Workshop Participants, 2000.
Review of rat inhalation studies on chronic exposures to
DPM and to other poorly
soluble nonfibrous particles
of low acute toxicity that are
not directly genotoxic.
Review of animal inhalation
studies on chronic exposures to DE, carbon black,
titanium dioxide, talc and
coal dust.
In Vivo: review of
toxicokinetics and effects of
fibrous and nonfibrous particles.
Nikula, 2000 .............................
Oberdoerster, 2002 ..................
Veronesi and Oortigiesen,
2001.
Conclusions
In Vitro: review of nasal and
pulmonary innervation (receptors) and pulmonary responses to PM, mainly
BEAS cells sensory neurons
used.
Agent(s) of toxicity
No overload of rat lungs at
lower lung doses of DPM
and no lung cancer hazard
anticipated at lower doses.
Poorly soluble particles nonfibrous particles of low acute
toxicity and not directly
genotoxic (PSPs).
Species differences in pulmonary retention patterns
and lung tissue responses
following chronic exposure
to DE.
High-dose rat lung tumors produced by poorly soluble particles of low cytotoxicity
(e.g., DPM) not appropriate
for low-dose extrapolation
(to humans); lung overload
occurs in rodents at high
doses.
Pulmonary receptors stimulated/activated by PM, leading to inflammatory responses.
DE, carbon black, titanium dioxide, talc and coal dust.
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B, F
Fibrous particles, and nonfibrous particles that are
poorly soluble and have low
cytotoxicity (PSP).
PM: residual oil fly ash,
woodstove emissions, volcanic dust, urban ambient
particulates, coal fly ash,
and and oil fly ash.
* KEY:
(A) Immunological and/or allergic reactions
(B) Inflammation
(C) Mutagenicity/DNA adduct formation
(D) Induction of free oxygen radicals
(E) Airflow obstruction
(F) Impaired clearance
(G) Reduced defense mechanisms
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Toxic
effects
*
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Federal Register / Vol. 70, No. 107 / Monday, June 6, 2005 / Rules and Regulations
32911
(H) Adverse cardiovascular effects.
D. Significance of Risk
The first principal conclusion of the
2001 risk assessment was:
Exposure to DPM can materially impair
miner health or functional capacity. These
material impairments include acute sensory
irritations and respiratory symptoms
(including allergenic responses); premature
death from cardiovascular, cardiopulmonary,
or respiratory causes; and lung cancer.
MSHA agrees with those commenters
who characterized the weight of
evidence from the most recent scientific
literature as supporting or even
strengthening this conclusion.
Furthermore, this conclusion has also
been corroborated by comprehensive
scientific literature reviews carried out
by other institutions and government
agencies.
In 2002, for example, the U.S. EPA,
with the concurrence of its Clean Air
Scientific Advisory Committee
(CASAC), published its Health
Assessment Document for Diesel Engine
Exhaust (EPA, 2002). With respect to
sensory irritations, respiratory
symptoms, and immunological effects,
this document concluded that:
At relatively high acute exposures, DE [diesel
exhaust] can cause acute irritation to the eye
and upper respiratory airways and symptoms
of respiratory irritation which may be
temporarily debilitating. Evidence also shows
that DE has immunological toxicity that can
induce allergic responses (some of which are
also typical of asthma) and/or exacerbate
existing respiratory allergies. [EPA, 2002]
In 2003, the World Health
Organization (WHO) issued a review
report on particulate matter air
pollution and health. WHO concluded
that ‘‘fine particles (commonly
measured as PM2.5) are strongly
associated with mortality and other
endpoints such as hospitalization for
cardiopulmonary disease, so that it is
recommended that air quality guidelines
for PM2.5 be further developed.’’ (WHO,
2003)
In the 10th edition of its Report on
Carcinogens, the National Toxicology
Program (NTP) of the National Institutes
of Health formally retained its
designation of diesel exhaust
particulates as ‘‘reasonably anticipated
to be a human carcinogen.’’ (U.S. Dept.
of Health and Human Services, 2002)
The report noted that:
Diesel exhaust contains identified mutagens
and carcinogens both in the vapor phase and
associated with respirable particles. Diesel
exhaust particles are considered likely to
account for the human lung cancer findings
because they are almost all of a size small
enough to penetrate to the alveolar region.
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* * * Because of their high surface area,
diesel exhaust particulates are capable of
adsorbing relatively large amounts of organic
material * * * A variety of mutagens and
carcinogens such as PAH and nitro-PAH
* * * are adsorbed by the particulates. There
is sufficient evidence for the carcinogenicity
for 15 PAHs (a number of these PAHs are
found in diesel exhaust particulate
emissions) in experimental animals. The
nitroarenes (five listed) meet the established
criteria for listing as ‘‘reasonably anticipated
to be a human carcinogen’’ based on
carcinogenicity experiments with laboratory
animals. [U.S. Dept. of Health and Human
Services, 2002]
Similarly, EPA’s 2002 Health
Assessment Document for Diesel Engine
Exhaust concluded that diesel exhaust
(as measured by DPM) is ‘‘likely to be
a human carcinogen.’’ Furthermore, the
assessment concluded that ‘‘[s]trong
evidence exists for a causal relationship
between risk for lung cancer and
occupational exposure to
D[iesel]E[xhaust] in certain
occupational workers.’’ (EPA, 2002, Sec.
9, p. 20)
Although most commenters agreed
that the adverse health effects associated
with miners’ DPM exposures warranted
an exposure limit, some commenters
continued to challenge the scientific
basis for linking DPM exposures with an
increased risk of lung cancer. An
industry trade group submitted a
critique of the 2001 risk assessment by
Dr. Jonathan Borak, and this critique
was endorsed by several other
commenters representing the mining
industry. The following discussion
addresses Dr. Borak’s comments in the
same order that he presented them.
1. Dr. Borak suggested that MSHA
should have classified studies into 3
categories: positive, negative, and
inconclusive. He indicated that MSHA’s
classification was asymmetric in the
way that it classified studies as
‘‘positive’’ or ‘‘negative,’’ thereby
distorting the results of MSHA’s
tabulation and nonparametric sign test,
as presented in the 2001 risk
assessment.
This comment was apparently based
on a misunderstanding of how MSHA
classified a study as ‘‘negative’’ for
purposes of the sign test. In describing
MSHA’s criterion for classifying a study
as negative, Dr. Borak quoted a passage
from the 2001 risk assessment that
actually pertained to a statistically
significant negative study. The
tabulations to which Dr. Borak referred
symmetrically counted epidemiologic
results as positive or negative based on
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whether the reported relative risk or
odds ratio fell above or below 1.0.
2. Dr. Borak stated that ‘‘MSHA
approached the analysis as though any
study failing to document a protective
effect of diesel must perforce be
evidence of a harmful effect.’’
This statement is false and stems from
Dr. Borak’s misunderstanding of the
symmetric criteria for MSHA’s
tabulations, as explained above.
Furthermore, Dr. Borak’s discussion of
statistical significance and hypothesis
testing in connection with this comment
is applicable to evaluating the results of
a single study—not to risk assessment
based on combining multiple results.
To evaluate the statistical significance
of the aggregated epidemiologic
evidence, the 2001 risk assessment
relied largely on two meta-analyses
(Bhatia et al., 1998; Lipsett and
Campleman, 1999). MSHA applied the
nonparametric sign test to its tabulation
of all 47 studies in order to roughly
summarize the combined evidence.
3. Dr. Borak quoted the 2001 risk
assessment as stating that ‘‘MSHA
regards a real 10% increase in the risk
of lung cancer (i.e., a relative risk of 1.1)
as constituting a clearly significant
health hazard.’’ He then stated that the
concept of a ‘‘real 10-percent increase’’
is ‘‘actually undefined and subjective.’’
Dr. Borak paraphrased language in the
2001 risk assessment, substituting a
‘‘reported’’ 10% increase for a ‘‘real’’
10% increase (top of his p. 5). The risk
assessment’s distinction between
‘‘reported’’ and ‘‘real’’ relative risks is
important and corresponds to the
fundamental distinction between a
statistical estimate and the quantity
being estimated.
Contrary to Dr. Borak’s
characterization, the risk assessment
recognized that epidemiological results
are often subject to a great deal of
statistical uncertainty. Such uncertainty
can be expressed by means of a
confidence interval for the ‘‘real’’ value
being estimated by a ‘‘reported’’ result.
For example, a reported relative risk
(RR) of 1.5 estimates the real relative
risk underlying a particular study, for
which a 95% confidence interval might
be 1.3 to 1.7. This interval is designed
to circumscribe the real relative risk
with 95% probability.
A 95% confidence interval for the real
relative risk may be so broad (e.g., 0.8
to 1.4) as to overlap 1.0 and thereby
render the reported result statistically
non-significant. Because of the
statistical uncertainty associated with a
reported RR, extremely large study
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Federal Register / Vol. 70, No. 107 / Monday, June 6, 2005 / Rules and Regulations
populations are required in order to
obtain statistically significant results
when the real relative risk is near 1.0.
The point being made in the passage
that Dr. Borak quoted and then
incorrectly paraphrased is that
notwithstanding this statistical
uncertainty, a real (as opposed to merely
reported) 10% increase in the risk of
lung cancer would constitute a clearly
significant health effect. Therefore,
reported results whose associated
confidence intervals overlap 1.1 are
consistent with potential health effects
that are sufficiently large to be of
practical significance.
4. Dr. Borak asserted that ‘‘* * *
Federal Courts have held that relative
risks of less than 2.0 are not sufficient
for showing causation * * * but MSHA
has rejected that view.’’
MSHA has not rejected the view
expressed in the court decisions to
which Dr. Borak alluded. Daubert v.
Merrell Dow Pharmaceuticals, 509 U.S.
579 (1993); and Hall v. Baxter
Healthcare Corp., 947 F Supp. 1387
(1996). As explained in the 2001 risk
assessment, these decisions pertain to
establishing the specific cause of disease
for a particular person and not to
establishing the increased risk
attributable to an exposure. (FR 66 at
5787–5789) This distinction was
illustrated by two analogies in the 2001
risk assessment: (1) There is low
probability that a particular death was
caused by lighting, but exposure to
lighting is nevertheless hazardous; and
(2) a specific smoker may not be able to
prove that his or her lung cancer was
‘‘more likely than not’’ caused by radon
exposure, yet radon exposure
significantly increases the risk—
especially for smokers. (FR 66 at 5787)
As stated in the 2001 risk assessment,
the court decisions are inapplicable
because ‘‘[t]he excess risk of an
outcome, given an excessive exposure,
is not the same thing as the likelihood
that an excessive exposure caused the
outcome in a given case.’’ (FR 66 5787)
Dr. Borak ignored MSHA’s
explanation of why the federal court
rulings do not apply to the 2001 risk
assessment. Instead, he attempted to
differentiate the available epidemiologic
studies on diesel exposure and lung
cancer from examples, presented in the
risk assessment, of studies reporting RR
less than 2.0 that were nevertheless
instrumental in previous clinical and
public health policy decisions. For
example, Dr. Borak pointed out that all
ten of the results cited on the
relationship between smoking and
cardiovascular-related deaths achieved
statistical significance. The risk
assessment presented these examples,
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however, only to support the position
that there is ‘‘ample precedent’’ for
utilizing studies with RR less than 2.0
in a risk assessment. This was in
response to comments urging MSHA to
ignore all such results, even the many
results with RR less than 2.0 that were
also statistically significant. Thus, the
ten results linking smoking to
cardiovascular deaths, eight of which
involved RR less than 2.0, adequately
serve their intended illustrative
purpose. Similarly, Dr. Borak’s
discussion of radon studies is not
germane to their use as examples of
studies with RR less than 2.0 that have
not been generally discounted.
Although the residential radon studies
cited may, as Dr. Borak suggests, have
been more powerful and had better
exposure assessments than those
available for DPM, they nevertheless
demonstrate that there has been no
blanket rejection of epidemiologic
results whenever RR is less than 2.0.
5. Dr. Borak objected to what he
termed MSHA’s ‘‘reliance on the
‘healthy worker effect’ [HWE] to explain
the finding of small or no differences in
various studies.’’ He argued that ‘‘[a]s a
result, MSHA has biased its own
evaluation of this literature in a manner
that exaggerates the alleged human
cancer risks of DPM, while diminishing
studies that are not directly supportive
of the MSHA perspective.’’
The 2001 risk assessment expresses a
clear preference for studies using
internal comparisons or well-matched
cases and controls—studies in which
the question of whether an HWE
adjustment is desirable does not even
arise. In fact, internal comparisons or
matched cases and controls were
utilized in all eight of the
epidemiological studies identified in the
risk assessment as presenting ‘‘the best
currently available epidemiological
evidence.’’ In contrast, the risk
assessment identified six negative (i.e.,
RR or OR < 1.0) studies (out of 47) and
noted that all six relied on unmatched
cases and controls or on external
comparisons to general populations,
with no allowance for any potential
HWE. However, potential bias due to
HWE was not the only weakness
identified in these six studies. The
assessment also noted that five of the six
studies had low statistical power due to
a small study population, insufficient
allowance for latency, or both.
Furthermore, the assessment noted that
all six of these negative studies
contained weak DPM exposure
assessments and failed to adjust for
potentially different patterns of tobacco
smoking in the disparate groups being
compared. Dr. Borak did not dispute
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MSHA’s exclusion of these six studies
from the rank of best available
epidemiologic evidence.
More specifically, Dr. Borak objected
to a relatively simple method of
adjusting for the HWE used in one part
of a meta-analysis by Bhatia et al. (1998)
and also in some of the individual
studies cited in the risk assessment. Dr.
Borak noted that ‘‘most epidemiologists
agree that the effects of selection bias
are generally more important early in a
person’s work life and do not apply
equally to all diseases and disease
processes.’’ Citing the adjustment
formula from Bhatia et al. (1998), Dr.
Borak claimed that it is ‘‘implicit
throughout the MSHA discussion’’ that
‘‘the effects of HWE on observed lung
cancer mortality are essentially
equivalent (i.e., proportional) to its
effects on mortality from all causes.’’
Although most epidemiologists may
agree selection biases do not apply
equally to all diseases, this does not
render consideration of HWE irrelevant
to epidemiologic studies of lung cancer.
Health Effects Institute (HEI) (1999)
states that ‘‘[w]orker mortality tends to
be below average for all major causes of
death.’’ The 2001 risk assessment
accepted a proportional adjustment only
insofar as it was utilized in some of the
published epidemiological studies.
Although Dr. Borak may be correct that
compensating for HWE is not really so
simple, a proportional adjustment may
nevertheless be better than no
adjustment at all. MSHA did not itself
make any such adjustments or otherwise
attempt to quantify the impact of HWE
in any of the studies. MSHA did,
however, accept HWE adjustments as
they appeared in published studies.
Although he did not explicitly say so,
Dr. Borak presumably shares what he
says is ‘‘the general view that studies of
cancer, particularly lung cancers, are
not much affected by HWE.’’ This view,
however, is not universal. It is not, for
example, shared by HEI (1999) or U.S.
EPA (2002). Dr. Borak dwelled on preemployment interviews and health
exams as a source of HWE that would
probably not apply to lung cancer
studies, but pre-employment health
screenings are not, after all, the only
potential source of bias leading to HWE.
Dr. Borak did not dispute the
proposition that HWE reflects a
potential bias when a working
population is compared to a more
general control population, or that this
may be one of several factors
contributing to a lack of positive results
or statistical significance in some
studies. As he has suggested, the
potential impact of HWE in lung cancer
studies may be greatest among those
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involving the shortest latency
allowances and/or follow-up times.
¨
6. In the study published by Saverin
et al. (1999), exposure measurements
were obtained in 1992, whereas ‘‘the
mines ceased production in 1991’’ when
‘‘most of the miners were dismissed and
abandoned underground work and
exposure.’’ Based on this apparent
discrepancy, Dr. Borak questioned the
¨
argument used by Saverin et al., and
accepted in the risk assessment, to
justify their assumption that their
exposure measurements were
representative of exposures from 1970 to
1991. Dr. Borak speculated that the
1992 exposure measurements were
likely to have been made during a
‘‘staged simulation’’ and that these
measurements may have
underestimated DPM levels under
conditions of routine production.
To resolve this issue, MSHA
¨
contacted Dr. Saverin directly and asked
him to explain the sequence of events
relating to mine closures and exposure
measurements. Dr. Saverin replied as
follows:
* * * [t]he full potash production of
millions of tons per year in the seventies and
eighties declined in the years after 1989, the
official closing date being in 1991. But until
1994, there was a lot of mining activity
underground because a mine cannot be
abandoned immediately. So, in 1992, we had
no problems to find exposure conditions not
merely similar to but exactly like the routineproduction situation before. Thus, we did not
have to rely on any staged simulation but
made our measurements as state of the art
¨
requires. [Saverin, R. 2005]
Thus, despite any ambiguity in the
¨
published article, Dr. Saverin maintains
that the 1992 measurements were
obtained under normal production
conditions and were fully representative
of exposures from 1970 through 1991.
¨
MSHA accepts Dr. Saverin’s assessment.
As stated in the 2001 risk assessment,
NIOSH commented that ‘‘[d]espite the
limitations discussed * * * the findings
¨
from the Saverin et al. (1999) study
should be used as an alternative source
of data for quantifying the possible lung
cancer risks associated with Dpm
exposures.’’ MSHA is not relying on any
single study but, instead, is basing its
evaluation on the weight of evidence
from all available data.
7. Dr. Borak identified a number of
weaknesses and limitations in the
¨
epidemiologic studies by Saverin et al.
(1999) and Johnston et al. (1997).
Despite their shortcomings, the 2001
risk assessment ranked these two
studies among the eight ‘‘that provide
the best currently available
epidemiologic evidence.’’
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As Dr. Borak indicated, all of the
weaknesses and limitations he
identified were recognized and
discussed in the 2001 risk assessment.
The risk assessment consistently and
repeatedly emphasized that the strength
of evidence relating DPM exposure to an
increased risk of lung cancer lies not in
any individual study but in the
cumulative weight of the research
literature taken as a whole. As stated in
the risk assessment,
* * * MSHA recognizes that no single one
of the existing epidemiologic studies, viewed
in isolation, provides conclusive evidence of
a causal connection between DPM exposure
and an elevated risk of lung cancer in
humans. Consistency and coherency of
results, however, do provide such evidence.
An appropriate analogy for the collective
epidemiologic evidence is a braided steel
cable, which is far stronger than any of the
individual strands of wire making it up. (66
FR at 5825)
Both of the additional
epidemiological studies cited in the
2003 NPRM specifically relating DPM
exposures to lung cancer (Gustavsson et
al., 2000 and Boffetta et al., 2001) found
statistically significant positive results.
The 2002 EPA document, which was
compiled too early to consider these two
newest studies, concluded that even at
the far lower levels typically
encountered in ambient air, ‘‘[t]he
available evidence [from toxicity studies
and occupational epidemiology]
indicates that chronic inhalation of DE
is likely to pose a lung cancer hazard to
humans.’’
This conclusion has now received
important additional confirmation from
a large scale mortality study involving
exposure to combustion-related fine
particulate air pollution (Pope et al.,
2002). This study, which included
estimates of lung cancer effects, was
cited in the NPRM but not considered
in either the 2001 risk assessment or the
2002 EPA document. As described
earlier, a statistically significant
exposure-response relationship was
discovered between chronic PM2.5
exposure in the ambient air and an
increased risk of lung cancer. This
finding is especially significant for
confirming causality because it
represents an entirely new source of
evidence not subject to unknown biases
that might tend to distort occupational
epidemiology results in the same
direction.
Dr. Borak also stated that presently
available data are insufficient to
establish an exposure-response
relationship for lung cancer that would
justify setting the PEL at any specific
level. The 2001 risk assessment
recognizes uncertainty in lung cancer
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32913
exposure-response and presents a broad
range of estimated exposure-response
relationships (66 FR at 5852–53). Even
the lowest estimate shows unacceptable
risk at levels commonly encountered in
underground mines. Lack of a definitive
exposure-response relationship means
MSHA cannot precisely distinguish
differences in health effects—e.g.,
between 50DPM µg/m3 and 100DPM µg/
m3. Nevertheless, as explained below,
MSHA can confidently say that
exposures above the interim PEL are
significantly more hazardous than
exposures below the interim PEL.
The second principal conclusion of
the 2001 risk assessment was:
At DPM levels currently observed in
underground mines, many miners are
presently at significant risk of incurring these
material impairments due to their
occupational exposures to DPM over a
working lifetime.
As described in Section VI.B, two new
bodies of exposure data have been
compiled since promulgation of the
2001 rule. Comparison of these data is
not straightforward, since they
employed different methods for
measuring DPM. Nevertheless, the data
suggest that exposure levels in many
underground M/NM mines have
dropped significantly, as compared to
the 1989–1999 period covered by the
2001 risk assessment.
The 2001 risk assessment quantified
excess lung cancer risk based on a mean
DPM concentration of 808 µg/m3. This
was based on 355 MSHA area and
personal samples collected in
production areas and haulageways at 27
underground M/NM mines between
1989 and 1999. Nearly all of these
samples were collected without an
impactor and analyzed for DPM content
using the RCD method. The new
samples, on the other hand, were
collected with an impactor and
analyzed for TC or EC using NIOSH
Method 5040. To see how more recent
exposure levels tie into the quantitative
exposure-response models used in the
2001 risk assessment, it is necessary to
convert sample results from both new
sources of exposure data to approximate
DPM concentrations.
Samples from the 31-Mine Study were
collected in 2001 using an impactor and
were analyzed by NIOSH Method 5040.
These samples showed a mean DPM
concentration of 432 µg/m3—assuming,
as in the 2001 risk assessment, that TC
comprises 80 percent of total DPM.
Excluding the samples from trona
mines, which were found to have
significantly lower DPM levels than the
other 27 underground M/NM mines
with valid samples, the mean DPM
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concentration was approximately 492
µg/m3.7
The other, more recent and more
extensive, body of DPM exposure data
considered here consists of 1,194
baseline samples obtained at 183 mines
in 2002–2003. These samples were all
collected using a submicrometer
impactor and analyzed by NIOSH
Method 5040. Assuming that TC ≈1.3 ×
EC and, as before, that TC comprises
about 80 percent of the DPM, the mean
DPM concentration observed was
approximately 320 µg/m3.8 MSHA
considers the baseline sampling results
to be more broadly representative of
DPM concentrations currently
experienced by underground M/NM
miners than the generally higher DPM
concentrations reported in the 31-Mine
Study. Since the baseline samples were
collected later, part of the apparent
reduction in mean concentration levels
may be due to improved DPM controls
implemented in response to the 2001
rule.
The 2001 risk assessment used the
best available data on DPM exposures at
underground M/NM mines to quantify
excess lung cancer risk. ‘‘Excess risk’’
refers to the lifetime probability of dying
from lung cancer during or after a 45year occupational DPM exposure. This
probability is expressed as the expected
excess number of lung cancer deaths per
thousand miners occupationally
exposed to DPM at a specified mean
DPM concentration. The excess is
calculated relative to baseline, agespecific lung cancer mortality rates
taken from standard mortality tables. In
order to properly estimate this excess, it
is necessary to calculate, at each year of
life after occupational exposure begins,
the expected number of persons
surviving to that age with and without
DPM exposure at the specified level. At
each age, standard actuarial adjustments
must be made in the number of
survivors to account for the risk of dying
from causes other than lung cancer.
Occupational exposure is assumed to
begin at age 20 and to continue, for
surviving miners, until retirement at age
65. The accumulation of lifetime excess
risk continues after retirement through
the age of 85 years.
Table VI–14, taken from the 2001 risk
assessment, shows a range of excess
lung cancer estimates at mean exposures
equal to the interim and final DPM
limits. The eight exposure-response
models employed were based on studies
by Saverin et al. (1999), Johnston et al.
(1997), and Steenland et al. (1998).
Assuming that TC is 80 percent of
whole DPM, and that the mean ratio of
TC to EC is 1.3, the interim DPM limit
of 500 µg/m3 shown in Table VI–14
corresponds to the 308 µg/m3 EC
surrogate limit adopted under the
present rulemaking.
TABLE VI–14.—EXCESS LUNG CANCER RISK EXPECTED AT SPECIFIED DPM EXPOSURE LEVELS OVER AN OCCUPATIONAL
LIFETIME
[Extracted from Table III–7 of the 2001 risk assessment]
Excess lung cancer deaths per
1,000 occupationally exposed
workers †
Study and statistical model
Final DPM
limit
200 µg/m3
¨
Saverin et al. (1999):
Poisson, full cohort ...........................................................................................................................................
Cox, full cohort .................................................................................................................................................
Poisson, subcohort ...........................................................................................................................................
Cox, subcohort .................................................................................................................................................
Steenland et al. (1998):
5-year lag, log of cumulative exposure ............................................................................................................
5-year lag, simple cumulative exposure ...........................................................................................................
Johnston et al. (1997):
15-year lag, mine-adjusted ...............................................................................................................................
15-year lag, mine-unadjusted ...........................................................................................................................
Interim DPM
limit
500 µg/m3
15
70
93
182
44
280
391
677
67
159
89
620
313
513
724
783
† Assumes 45-year occupational exposure at 1,920 hours per year from age 20 to retirement at age 65. Lifetime risk of lung cancer adjusted
for competing risk of death from other causes and calculated through age 85. Baseline lung cancer and overall mortality rates from NCHS
(1996).
The mean DPM concentration levels
estimated from both the 31-Mine Study
(432–492 µg/m3, depending on whether
trona mines are included) and the
baseline samples (≈320 µg/m3) fall
between the interim and final DPM
limits shown in Table VI–14. All of the
exposure-response models shown are
monotonic (i.e., increased exposure
yields increased excess risk, though not
proportionately so). Therefore, using the
most current available estimates of
mean exposure levels, they all predict
excess lung cancer risks somewhere
between those shown for the interim
and final limits. Thus, despite
substantial improvements apparently
attained since the 1989–1999 sampling
period addressed by the 2001 risk
assessment, underground M/NM miners
are still faced with an unacceptable risk
of lung cancer due to their occupational
DPM exposures.
The third principal conclusion of the
2001 risk assessment was:
7 These values may be somewhat inflated due to
the old ‘‘crimped foil’’ SKC sampler design used for
many of the samples collected during the 31-Mine
Study. As explained elsewhere in this preamble,
this design resulted in lower-than-expected filter
deposit areas in many cases, leading to
overestimates of the corresponding TC
concentrations. (The SKC sampler design was
eventually modified by substituting a retainer ring
for the crimped foil. However, the systematic errors
in deposit area observed during the 31-Mine Study
have no bearing on the ‘‘paired punch comparison’’
used in that study to evaluate analytical
measurement precision.)
8 The laboratory analysis of the baseline samples
yielded two measures of TC: TC = EC + OC and TC
= 1.3 × EC. However, since the intention under
baseline sampling was to rely always on the lesser
of these two values from each sample, no
precautions were taken to avoid sampling near
tobacco smoke and other substances that potentially
interfere with the use of TC = EC + OC as a
surrogate measure of DPM. Therefore, in the present
discussion, MSHA is using only the TC = 1.3 × EC
value to estimate baseline DPM levels.
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By reducing DPM concentrations in
underground mines, the rule will
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substantially reduce the risks of material
impairment faced by underground miners
exposed to DPM at current levels.
Although DPM levels have apparently
declined since 1989–1999, MSHA
expects that further improvements will
continue to significantly and
substantially reduce the health risks
identified for miners. There is clear
evidence of DPM’s adverse health
effects, not only at pre-2001 levels but
also at the generally lower levels
currently observed at many
underground mines. These effects are
material health impairments as
specified under section 101(a)(6)(A) of
the Mine Act. From the baseline
sampling results, 68 out of the 183
mines (37%) had at least one sample
exceeding the interim exposure limit.
Because the exposure-response
relationships shown in Table VI–14 are
monotonic, MSHA expects that
industry-wide implementation of the
interim limit will significantly reduce
the risk of lung cancer among miners.
VII. Feasibility
A. Background
Section 101(a)(6)(A) of the Mine Act
requires the Secretary of Labor in
establishing health standards, to most
adequately assure, on the basis of the
best available evidence, that no miner
will suffer material impairment of
health or functional capacity over his or
her working life. Standards promulgated
under this section must be based upon
research, demonstrations, experiments,
and such other information as may be
appropriate. MSHA, in setting health
standards, is required to achieve the
highest degree of health and safety
protection for the miner, and must
consider the latest available scientific
data in the field, the feasibility of the
standards, and experience gained under
this or other health and safety laws.
The legislative history of the Mine Act
states:
This section further provides that ‘‘other
considerations’’ in the setting of health
standards are ‘‘the latest available scientific
data in the field, the feasibility of the
standards, and experience gained under this
and other health and safety laws.’’ While
feasibility of the standard may be taken into
consideration with respect to engineering
controls, this factor should have a
substantially less significant role. Thus, the
Secretary may appropriately consider the
state of the engineering art in industry at the
time the standard is promulgated. However,
as the circuit courts of appeals have
recognized, occupational safety and health
statutes should be viewed as ‘‘technologyforcing’’ legislation, and a proposed health
standard should not be rejected as infeasible
‘‘when the necessary technology looms on
today’s horizon’’. AFL–CIO v. Brennan, 530
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F.2d 109 (3d Cir. 1975); Society of Plastics
Industry v. OSHA, 509 F.2d 1301 (2d Cir.
1975), cert. denied 427 U.S. 992 (1975).
Similarly, information on the economic
impact of a health standard, which is
provided to the Secretary of Labor at a
[public] hearing or during the public
comment period, may be given weight by the
Secretary. In adopting the language of [this
section], the Committee wishes to emphasize
that it rejects the view that cost benefit ratios
alone may be the basis for depriving miners
of the health protection which the law was
intended to insure. Rep. No. 95–181, 95th
Cong. 1st Sess. 21 (1977).
In promulgating standards, hard and
precise predictions from agencies
regarding feasibility are not required.
The ‘‘arbitrary and capricious test’’ is
usually applied to judicial review of
rules issued in accordance with the
Administrative Procedure Act. The
legislative history of the Mine Act
further indicates that Congress
explicitly intended the ‘‘arbitrary and
capricious test’’ be applied to judicial
review of mandatory MSHA standards.
‘‘This test would require the reviewing
court to scrutinize the Secretary’s action
to determine whether it was rational in
light of the evidence before him and
reasonably related to the law’s
purposes.’’ S. Rep. No. 95–181, 95th
Cong., 1st Sess. 21 (1977). In achieving
the Congressional intent of feasibility
under the Mine Act, MSHA may also
consider reasonable time periods of
implementation. Ibid. at 21.
Though the Mine Act and its
legislative history are not specific in
defining feasibility, the Supreme Court
has clarified the meaning of feasibility
in the context of OSHA health standards
in American Textile Manufacturers’
Institute v. Donovan (OSHA Cotton
Dust), 452 U.S. 490, 508–09 (1981), as
‘‘capable of being done, executed, or
effected,’’ both technologically and
economically.
MSHA need only base its predictions
on reasonable inferences drawn from
existing facts. In order to establish the
economic and technological feasibility
of a new rule, an agency is required to
produce a reasonable assessment of the
likely range of costs that a new standard
will have on an industry, and an agency
must show that a reasonable probability
exists that the typical firm in an
industry will be able to develop and
install controls that will meet the
standard. United Steelworkers of
America, AFL–CIO–CLC v. Marshall,
(OSHA Lead) 647 F.2d 1189, 1273.
B. Technological Feasibility
Courts have ruled that in order for a
standard to be technologically feasible
an agency must show that modern
technology has at least conceived some
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32915
industrial strategies or devices that are
likely to be capable of meeting the
standard, and which industry is
generally capable of adopting. Ibid.
(citing American Iron and Steel Institute
v. OSHA, (AISI–I) 577 F.2d 825 (3d Cir.
1978) at 832–35; and, Industrial Union
Dep’t., AFL–CIO v. Hodgson, 499 F.2d
467 (DC Cir.1974)); American Iron and
Steel Institute v. OSHA, (AISI–II) 939
F.2d 975, 980 (DC Cir. 1991). The
existence of general technical
knowledge relating to materials and
methods which may be available and
adaptable to a specific situation
establishes technical feasibility. A
control may be technologically feasible
when ‘‘if through reasonable application
of existing products, devices or work
methods with human skills and
abilities, a workable engineering control
can be applied’’ to the source of the
hazard. It need not be an ‘‘off-the-shelf’’
product, but ‘‘it must have a realistic
basis in present technical capabilities.’’
(Secretary of Labor v. Callanan
Industries, Inc. (Noise), 5 FMSHRC
1900, 1908 (1983)).
The Secretary may also impose a
standard that requires protective
equipment, such as respirators, if
technology does not exist to lower
exposures to safe levels. See United
Steelworkers of America, AFL–CIO–CLC
v. Marshall, (OSHA Lead) 647 F.2d
1189, 1269 (DC Cir. 1981).
MSHA has established that it is
technologically feasible to reduce
underground miners’ exposures to the
DPM interim permissible exposure limit
(PEL) of 308 micrograms of EC per cubic
meter of air (308EC µg/m3) by using
available engineering control technology
and various administrative control
methods. However, MSHA
acknowledges that compliance
difficulties may be encountered at some
mines due to implementation issues and
the cost of purchasing and installing
certain types of controls. Therefore, this
final rule incorporates the industrial
hygiene concept of a hierarchy of
controls for implementing DPM
controls. To attain the interim DPM
limit, mine operators are required to
install, use, and maintain engineering
and administrative controls to the extent
feasible. When such controls do not
reduce a miner’s exposure to the DPM
limit, controls are infeasible, or controls
do not produce significant reductions in
DPM exposures, operators must
continue to use all feasible engineering
and administrative controls and
supplement them with respiratory
protection. When respiratory protection
is required under the final standard,
mine operators must establish a
respiratory protection program that
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meets the specified requirements. Thus,
MSHA has provided a regulatory
scheme that adequately accomplishes
control of exposure under
circumstances where a mine operator
cannot reduce a miner’s exposure to the
interim PEL solely by use of engineering
and administrative controls, including
work practices.
DPM control technology is not new to
the mining industry. MSHA has
afforded the mining industry a
significant period of time to implement
DPM controls. The existing DPM
standard was first promulgated on
January 19, 2001 (66 FR 5706) with an
effective date of July 19, 2002 for
meeting the interim concentration limit
of 400 micrograms of TC per cubic
meter of air. The instant rulemaking
provides for a comparable EC PEL of
308 EC µg/m3. Under the settlement
agreement, MSHA allowed mine
operators an additional year in which to
begin to install appropriate engineering
and administrative controls to reduce
DPM levels due to feasibility constraints
at that time. Altogether, the mining
industry has had over four years to
institute controls required under this
rulemaking. Any controls currently used
to meet the existing concentration limit
can be used to reduce miners’ exposures
to the interim PEL.
MSHA acknowledges that the current
DPM rulemaking record lacks sufficient
feasibility documentation to justify
lowering the DPM limit below 308 EC
µg/m3 at this time. Therefore, MSHA is
not lowering the limit in this
rulemaking. MSHA believes that this
interim limit is reasonable, and that
MSHA can document feasibility across
the affected sector of underground M/
NM mines. MSHA is continuing to
gather information on the feasibility of
the mining industry to comply with a
final DPM PEL of less than 308 EC µg/m3
MSHA emphasizes that a DPM control
may be deemed feasible, and therefore
be required by MSHA even if a miner’s
exposure is not reduced to the DPM
limit. Mine operators cited for DPM
overexposures will continue to be
required to implement feasible
engineering and administrative controls
even if these controls are not fully
successful in attaining the DPM
exposure limit. In the context of this
rule, feasible DPM controls must be
capable of achieving a significant
reduction in DPM. MSHA considers a
significant reduction in DPM to be at
least a 25% reduction in the affected
miners’ exposures. Thus, for mines that
are out of compliance with the DPM
interim limit, controls would be
required that attain compliance, or that
achieve at least a 25% reduction in DPM
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exposure if it is not possible to attain
compliance by implementing feasible
controls. If feasible engineering and
administrative controls are not capable
of attaining compliance, or at least of
achieving a DPM exposure reduction of
25%, MSHA would not require the
implementation of those controls. In
such cases, which MSHA believes will
be very limited, MSHA would require
miners to be protected using appropriate
respiratory protective equipment.
Some commenters criticized the 25%
threshold for a significant reduction
because it lacks a scientific basis, and
that controls should be evaluated
individually in reference to site-specific
conditions and DPM levels for
significance or effectiveness. MSHA
notes that the 25% threshold for DPM
is lower than the 50% threshold
adopted in MSHA’s noise rule.
However, DPM’s classification as a
carcinogen justifies the more protective
25% level for determining whether
controls achieve a significant reduction
for purposes of assessing feasibility.
MSHA also notes that most of the
practical and effective controls that are
currently available, such as DPM filters,
enclosed cabs with filtered breathing
air, and low-emission engines will
achieve at least a 25% reduction. Other
controls such as ventilation upgrades or
alternative fuel blends may achieve a
25% reduction, depending on exposure
circumstances and the specific nature of
the subject control. It should also be
noted that reductions of less than 25%
could be due to normal day-to-day
variations in mining operations as
opposed to reductions due to
implementing a control technology.
MSHA’s Compliance Guide includes the
25% significant reduction for
determining feasibility.
If a particular DPM control were
capable of achieving at least a 25%
reduction all by itself, MSHA would
evaluate the costs of that individual
control to determine its economic
feasibility. If a number of controls could
together achieve at least a 25%
reduction, but no individual control, if
implemented by itself, could achieve a
25% reduction, MSHA would evaluate
the total costs of all controls added
together to determine their economic
feasibility as a group. In determining
whether a combination of controls is
economically feasible, MSHA would
consider whether the total cost of the
combination of controls is wholly out of
proportion to the expected results.
MSHA will not cost the controls
individually, but will combine their
expected results to determine if the 25%
significant reduction criteria can be
satisfied.
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MSHA’s rulemaking record
addressing feasibility includes: MSHA’s
final report on the 31-Mine Study;
NIOSH’s peer review of the 31-Mine
Study; results from MSHA’s baseline
sampling at mines covered under the
DPM standard; results of MSHA’s
comprehensive compliance assistance
work at mining operations with
implementation issues affecting
feasibility; NIOSH’s conclusions on the
performance of the SKC sampler and the
availability of technology for control of
DPM; NIOSH’s Diesel Emissions
Workshops in 2003 in Cincinnati and
Salt Lake City; the Filter Selection
Guide posted on the MSHA and NIOSH
Web sites; MSHA’s final report on DPM
filter efficiency; NIOSH’s report titled,
‘‘Review of Technology Available to the
Underground Mining Industry for
Control of Diesel Emissions’’; and, the
NIOSH Phase I Isozone study titled,
‘‘The Effectiveness of Selected
Technologies in Controlling Diesel
Emissions in an Underground Mine—
Isolated Zone Study at Stillwater
Mining Company’s Nye Mine’’ all of
which were developed following
promulgation of the 2001 DPM final
rule.
One other NIOSH document resulting
from the DPM M/NM Partnership
became available to MSHA in April
2004. That document is titled, ‘‘An
Evaluation of the Effects of Diesel
Particulate Filter Systems on Air
Quality and Personal Exposure of
Miners at Stillwater Mining Case Study:
Production Zone (Phase II Study).’’ As
stated in the final report:
The objective of Phase II of this study was
to determine the effects of those DPF systems
being used on production vehicles at
Stillwater Mine on workplace concentrations
of EC and regulated gases in an actual mining
application where multiple diesel-powered
vehicles operated simultaneously during fullshift mining activities.
MSHA evaluated this evidence as it
relates to feasibility and found that
unlike the Phase I Isozone Study, the
Phase II study does not contain any new
significant information affecting the
ability of the mining industry to comply
with the requirements of this final rule.
MSHA, therefore, finds this data to be
cumulative in nature and has included
it in the rulemaking record as
supplemental information. MSHA
discusses the Phase II study results in
more detail in this section of the
preamble. MSHA emphasizes that mine
operators obtained access to this study
on the date of publication since the
study was generated by the DPM M/NM
Partnership.
MSHA committed to implementing
several initiatives related to
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enforcement and enhancing the mining
industry’s ability to comply with the
2001 final rule. Among other things,
MSHA agreed that it would not issue
citations for potential violations of the
interim concentration limit promulgated
in the 2001 standard until after MSHA
and NIOSH were satisfied with the
performance characteristics of the SKC
sampler and the availability of practical
mine worthy DPM filter technology.
MSHA also agreed to provide DPM
sampling training for its inspectors, and
to provide comprehensive compliance
assistance to the industry through July
19, 2003. MSHA’s compliance
assistance activities included:
• Conducting compliance assistance
meetings throughout the country to
discuss how to comply with the DPM
standard;
• Providing a compliance guide
answering key questions;
• Conducting an inventory of existing
underground diesel-powered
equipment;
• Providing information to mine
operators on feasible DPM controls; and,
• Obtaining baseline sampling results
at each underground mine covered
under the standard solely for the
purpose of compliance assistance rather
than for enforcement purposes.
Additional compliance assistance
activities also were conducted, and are
discussed later in this section of the
preamble.
During the compliance assistance
period, MSHA agreed that mine
operators would not be cited for
potential violations of the interim limit
provided they took good-faith steps to
develop and implement a written
compliance strategy and cooperated
with MSHA. Also, MSHA would issue
a noncompliance citation for exceeding
the interim concentration limit only if
MSHA believed that an operator was not
acting in good faith, or if an operator
failed to cooperate in the compliance
assistance. Per the agreement, after July
19, 2003, MSHA began to issue citations
for violations associated with the
interim limit. During the compliance
assistance period (through July 19,
2003), MSHA did not identify any
mines that failed to take good faith steps
toward achieving compliance or
cooperate with MSHA. Consequently,
no citations for violations associated
with the interim limit were issued prior
to July 20, 2003.
MSHA provided DPM training to its
inspectors and to the extent possible,
completed its compliance assistance
activities in accordance with the
settlement agreement. During September
and October 2002, seminars covering
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the rule, MSHA’s enforcement policy,
DPM sampling, and DPM engineering
control technologies were held in
Ebensburg, PA, Knoxville, TN,
Lexington, KY, Des Moines, IA, Kansas
City, MO, Albuquerque, NM, Coeur
d’Alene, ID, Elko, NV, and Green River,
WY. The DPM Compliance Guide was
posted on the MSHA DPM Single
Source Page and also issued as an
MSHA Program Policy Letter (PPL
#P03–IV–1, effective August 19, 2003).
Extensive information on feasible
controls for DPM was included in the
Compliance Guide/Program Policy
Letter and listed on MSHA’s DPM
Single Source Page for DPM. The
inventory of diesel engines was
completed September 30, 2002. Baseline
DPM samples were not obtained at a
remaining few mines until after July 20,
2003 primarily to allow time to cover
sampling at intermittent operations.
However, enforcement sampling at these
mines was delayed until after
completion of baseline sampling to
provide these mine operators with
further opportunity to implement
controls, if necessary.
As discussed below in this section of
the preamble, both MSHA and NIOSH
are satisfied with the performance of the
SKC sampler and on the availability of
practical DPM filter technology.
DPM Sampling Method. Though not
under substantive review in this
rulemaking, existing § 57.5061(b)
establishes that MSHA will continue to
sample miners’ personal exposures by
using a respirable dust sampler
equipped with a submicrometer
impactor and analyze samples for the
amount of EC using the NIOSH
Analytical Method 5040, or any other
method that NIOSH determines gives
equal or improved accuracy in DPM
sampling. The DPM sampling method is
discussed in the section-by-section
portion of this preamble under
§ 57.5060(a) addressing the permissible
exposure limit. MSHA includes a more
detailed discussion of its sampling
method on its DPM Single Source Web
page. Based on current information in
the rulemaking record, MSHA
concludes that it has a technologically
feasible measurement method that
operators and MSHA can use to
accurately determine if miners’
exposures exceed the interim PEL.
Performance of the SKC Sampler.
MSHA and NIOSH are satisfied with the
performance of the SKC sampler. The
31-Mine Study includes a
comprehensive discussion of MSHA’s
and NIOSH’s work with SKC that
improved the performance of the
sampler. In MSHA’s final report on the
31-Mine Study, it concluded that SKC
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32917
satisfactorily addressed concerns over
earlier known defects in the DPM
sampling cassettes and availability of
cassettes to both MSHA and mine
operators. Just prior to and during the
31-Mine Study, NIOSH and MSHA
observed that the perimeter of the DPM
deposit on the filter was not
consistently circular and varied among
the SKC samplers. This resulted in a
variable and unpredictable deposit area.
The cause of this was found and quite
successfully remedied allowing NIOSH
to express its satisfaction with the
performance of the SKC sampler by
letter of June 25, 2003, to MSHA that
states, in part:
Concurrent with the work of the partnership
were research tasks to ensure that diesel
particulate matter can be accurately
measured in these mines. The SKC DPM
cassette is a size selective sampler designed
to collect DPM samples that are characterized
by an aerodynamic diameter less than 0.8µm,
while avoiding contamination with mineral
dust. The use of the SKC sampler could not
be recommended initially because of a
problem relating to irregular deposition of
DPM on the cassette sample. However, this
problem has been solved, and we are now
satisfied with the performance of the SKC
sampler. The research regarding the
performance of the SKC sampler has been
documented, peer-reviewed, and is currently
accepted for publication by Applied
Occupational and Environmental Hygiene
Journal.
Baseline Sampling. For the 2001
standard, MSHA based its feasibility
projections on an average DPM
concentration level of over 800TC µg/m3.
MSHA found in the 31-Mine Study that
miners’ average TC exposure was 345
µg/m3. MSHA’s baseline sampling
revealed that miners average EC
exposure was 196 µg/m3. The average
TC exposure measured as EC + OC was
293 µg/m3, and as calculated by EC × 1.3
was 255 µg/m3. MSHA believes that
these lower averages probably result
from the introduction of DPFs, clean
engines, better maintenance, and the
elimination of interferences as
confirmed by MSHA’s compliance
assistance baseline sampling. The
baseline sampling results are discussed
in detail in Section V.
DPM Enforcement. MSHA believes
that final §57.5060(d) adequately
addresses feasibility issues related to
meeting the interim limit of 308EC µg/
m3 under § 57.5060(a). Under these
sections, MSHA has amended the type
of exposure that will be regulated along
with the methods of compliance with
the interim PEL to provide mine
operators with greater flexibility in
reducing DPM exposures. This final
DPM rule adopts MSHA’s long-standing
enforcement practice established for
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other exposure-based standards
applicable to M/NM mines. Also, MSHA
underscores the fact that the
enforcement scheme established in this
final rule also is based on the DPM
settlement agreement.
In spite of the changes in this final
rule that increase flexibility, MSHA
realizes that some mine operators will
continue to need on-site technical
assistance. MSHA is committed to
assisting these operators in special
mining situations that could affect the
successful use of DPFs or other
engineering control systems. Mine
operators can request this assistance
from their respective MSHA District
Manager.
Additionally, MSHA concludes that
the established hierarchy of controls for
complying with the DPM interim limit
adequately protects miners from
exposure to DPM in those circumstances
where MSHA found control methods to
be infeasible under existing
§ 57.5060(d)(2) for certain activities
including inspection, maintenance and
repair activities. MSHA has removed
from this final rule the requirement for
mine operators to apply to the Secretary
of Labor for relief from applying control
technology to comply with the final
DPM limit. Instead, MSHA’s hierarchy
of controls strategy will result in quicker
responses to supplementing protection
for miners exposed to the health risks
associated with DPM.
MSHA believes that it has sufficiently
accommodated the mining industry’s
needs with respect to complying with
the DPM standard and has developed an
appropriate and reasonable enforcement
scheme under this rule. MSHA
estimates that approximately 183 mines
are covered under the standard. These
mines produce commodities such as
gold, limestone, trona, platinum, lead,
silver, zinc, marble, gypsum, salt, and
potash. Based on MSHA’s baseline
sampling results, over 70% of these
underground mines were in compliance
with the interim DPM limit.
MSHA is confident that engineering
and administrative controls (including
work practice controls) exist that are
capable of reducing DPM exposures to
the interim PEL of 308EC µg/m3 in all
types of underground M/NM mines.
MSHA believes that virtually all mine
operators will successfully attain
compliance with the interim limit by
choosing from among various currently
available feasible engineering and
administrative DPM control options,
including but not limited to DPF
systems, ventilation upgrades, oxidation
catalytic converters, alternative fuels,
fuel additives, enclosures such as cabs
and booths with filtered breathing air,
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improved diesel engine maintenance
procedures and instrumentation, diesel
engines with lower DPM emissions,
various work practices and
administrative controls. MSHA has
given the mining industry flexibility
under the final standard in selecting the
individual or combination of DPM
controls that best suit a mine operator’s
specific needs, conditions, and
operating practices.
MSHA received numerous comments
concerning the technological feasibility
of the 2003 NPRM. Some commenters
opposed any changes in the 2001 DPM
standard. A few of these commenters
suggested that MSHA’s current
rulemaking record does not support
revising the 2001 final rule. They
believe that in order to justify a change
that in their view reduces health
protection, MSHA must first make a
determination that the DPM limits
established in the 2001 final rule are
infeasible for the mining industry as a
whole to attain. These commenters note
that, to the contrary, MSHA fully
substantiated its conclusions regarding
feasibility in the 2001 final rule.
According to these commenters,
during the period from August 2001
through January 2002, MSHA stated in
the final report to the 31-Mine Study
that the mean concentration of DPM was
345TC µg/m3, substantially below the
required concentration limit of 400TC
µg/m3. These commenters pointed out
that these results were obtained at a
time when MSHA believes few mining
operations had begun to implement
DPM controls, or where the
implementation of such controls was in
its early stages and had not yet achieved
significant reductions in DPM exposure.
Other supportive evidence noted by
these commenters included the results
of the baseline sampling indicating that
only 30% of the mines tested were out
of compliance.
MSHA agrees that it should utilize
data from its final report on the 31-Mine
Study and the baseline sampling in
assessing technological feasibility, but
MSHA does not consider the mean
concentration obtained in the 31-Mine
Study or the number of mines with
baseline samples exceeding the interim
limit to be the definitive data sources in
this assessment. For example, although
the mean concentration of DPM
reported in the final report to the 31Mine Study was only 345TC µg/m3, the
mean DPM concentration value does not
reflect the wide range of sample results
obtained between mines or within
individual mines, some of which
exceeded 1000TC µg/m3. Likewise,
although only 30% of the mines had
baseline sampling results exceeding the
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interim limit, MSHA expects some of
these mines may have encountered
compliance difficulties due to
implementation issues relating to such
factors as DPF regeneration and
retrofitting DPFs to existing pieces of
equipment, and due to the costs of
purchasing and installing DPM controls.
Therefore, in assessing technological
feasibility, MSHA believes it should
also consider data obtained
subsequently from other sources,
including MSHA’s comprehensive
compliance assistance work at mining
operations, current agency enforcement
experience, the NIOSH Diesel Emissions
Workshops in Cincinnati and Salt Lake
City, and the NIOSH Phase I Isozone
Study. MSHA agrees with commenters
who take the position that the interim
DPM limit can be attained by the
industry as a whole through
implementation of feasible engineering
and/or administrative (including work
practice) controls. However, MSHA
does not agree with commenters who
oppose any changes to the 2001 final
rule.
Some commenters suggested that the
proposed modification to the 2001
standard would reduce health
protection for miners, a consequence
that § 101(a)(9) of the Mine Act
prohibits. MSHA disagrees. Section
101(a)(9) of the Mine Act provides that:
‘‘No mandatory health or safety
standard promulgated under this title
shall reduce the protection afforded
miners by an existing mandatory health
or safety standard.’’ MSHA interprets
this provision of the Mine Act to require
that all of the health or safety benefits
resulting from a new standard be at least
equivalent to all of the health or safety
benefits resulting from the existing
standard when the two sets of benefits
are evaluated as a whole. Int’l Union v.
Federal Mine Safety and Health Admin.,
920 F.2d 960, 962–64 (DC Cir. 1990);
Int’l Union v. Federal Mine Safety and
Health Admin., 931 F.2d 908, 911 (DC
Cir 1991).
In fact, MSHA believes that the
interim EC limit established in this
rulemaking is comparable to the existing
TC limit. Correcting the surrogate for
identifying miners’ exposures to DPM is
critical for protection of miners and will
result in a valid DPM sample that
MSHA can adequately substantiate.
MSHA’s hierarchy of controls strategy
in the final rule is based on longstanding industrial hygiene practice in
both the mining industry and general
industry. As implemented in this final
rule, the hierarchy of controls ensures
that the most protective means of
compliance (engineering and
administrative controls) are used first,
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and that respiratory protection is
permitted only where MSHA
determines that: Engineering and
administrative controls are infeasible;
controls do not produce significant
reductions in DPM exposures; or
controls do not reduce exposures to the
interim DPM limit.
The DPM litigants raised their
concerns to MSHA with implementation
issues related to regeneration and
retrofitting exhaust after-treatment
controls on existing mining equipment.
These, along with various other
compliance concerns, eventually led to
the 31-Mine Study. At that time, only a
few mine operators in the U.S. had
begun to implement after-treatment
control technology on their
underground diesel-powered
equipment. As is often the case when
unfamiliar technologies are integrated
into an industry sector, the process was
slow, and at least initially, the results
were less-than-fully satisfactory. As
noted elsewhere in this section, many
mine operators, for example,
experimented with DPF installations on
a few pieces of equipment on a trial
basis, with mixed results at best. MSHA
does not dispute these findings, but
believes that DPF failures were the
result of inappropriate DPF selection for
a given application. However at the
time, these operators were convinced
that DPF technology was fundamentally
deficient for application in underground
mining. In an effort to resolve a variety
of issues raised by the industry that
were believed to present potential
compliance problems, MSHA agreed to
conduct the 31-Mine Study.
Many commenters also claimed that
MSHA’s determination that the rule is
technologically feasible assumed the
widespread utilization of DPFs, which
these commenters do not believe have
proven mine worthy and which may be
affected by the aforementioned
implementation issues. In response,
MSHA notes that while it continues to
highly recommend use of DPFs, its
technological feasibility determination
was based on the application of a
variety of engineering and
administrative control approaches for
obtaining compliance, and was not
limited to DPFs. MSHA has determined
that DPF systems are available and mine
worthy for controlling miners’
exposures to DPM. As discussed later in
this section of the preamble, both
MSHA and NIOSH are satisfied that
DPF systems are currently available for
most mining equipment, and that these
systems can be successfully applied if
mine operators make informed
decisions regarding filter selection,
retrofitting, engine and equipment
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deployment, operation, and
maintenance, and specifically work
through issues such as in-use
efficiencies, secondary emissions,
engine backpressure, DPF regeneration,
DPF reliability and durability.
Implementation issues, such as DPF
regeneration and retrofitting DPFs to
existing pieces of equipment, primarily
affect a small number of mines. Mines
affected are those that will need to
utilize DPFs to attain compliance
because other control options, such as
ventilation upgrades, low-emission
engines, alternative diesel fuels, and
cabs with filtered breathing air are
either infeasible at these particular
mines, or because these mine operators
have already utilized these other control
options to the maximum extent feasible
but have not yet attained compliance.
Since a variety of feasible control
options are available, and
implementation issues relating to DPFs
affect a relatively small number of
mines, the industry as a whole will not
be impeded from attaining compliance
with the interim PEL.
MSHA does not dispute this early
experience with DPF installations in
U.S. underground mines, and in fact,
acknowledged these concerns in the
final report of the 31-Mine Study. One
of the major conclusions of the study
states:
Compliance with both the interim and final
concentration limits may be both
technologically and economically feasible for
metal and nonmetal underground mines in
the study. MSHA, however, has limited inmine documentation on DPM control
technology. As a result, MSHA’s position on
feasibility does not reflect consideration of
current complications with respect to
implementation of controls, such as
retrofitting and regeneration of filters. MSHA
acknowledges that these issues may
influence the extent to which controls are
feasible. The Agency is continuing to consult
with the National Institute of Occupational
Safety and Health, industry and labor
representatives on the availability of practical
mine worthy filter technology.
After completing the 31-Mine Study,
however, MSHA obtained additional
documentation on DPM control
technology that it had previously
lacked. This information includes data
on both implementation issues and
costs, and was obtained from such
sources as MSHA’s comprehensive
compliance assistance activities,
MSHA’s enforcement experience, and
NIOSH’s Diesel Emission Workshops in
Cincinnati and Salt Lake City. Also,
MSHA now has in-mine data on the
filter efficiency of DPFs in U.S. mines as
a result of the NIOSH Phase I Isozone
study (discussed in detail in this
preamble).
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Effectiveness of the DPM Estimator.
MSHA’s DPM Estimator is a Microsoft
Excel spreadsheet computer program
that calculates the reduction in DPM
concentration that can be obtained by
implementing individual, or
combinations of engineering controls in
a given production area of a mine.
MSHA has repeatedly advised the
mining community throughout the DPM
rulemakings that the Estimator is one of
many tools that can be used to assist
mine operators with assessing feasibility
of compliance with the DPM limits.
MSHA used the estimator to support its
feasibility assessment for the 2001 final
rule, as well as the feasibility section of
the 31-Mine Study which is used to
support this final rule.
The analyses in the 31-Mine Study
were based on the highest DPM sample
result obtained at each mine. Using the
Estimator, new DPM levels were
computed for this ‘‘worst case’’ sample
result based on the application of one,
or a combination of the following
control technologies: DPFs, low
emission engines, and upgraded
ventilation. To adequately protect all
miners even if the mine operator
changes equipment deployment
schemes in the future, the methodology
for the technological feasibility analysis
required all major emission sources at a
given mine, plus similar spare
equipment, to be provided with the
same DPM controls that were specified
for the equipment associated with the
‘‘worst case’’ sample result.
Likewise, the economic feasibility
analysis for each mine was based on
costing the same controls for all major
DPM emission sources, and similar
spare equipment, as were required to
reduce the ‘‘worst case’’ sample result to
the compliance level. The rationale for
this approach is that if the same controls
are applied to all major DPM sources
and spare equipment as are required to
attain compliance for the ‘‘worst case’’
exposures, all exposures in the mine
will be reduced at least to the
compliance level, if not lower,
regardless of future equipment usage,
equipment deployment, mine
production levels, etc.
In the 31-Mine Study, DPFs were
assumed to be capable of achieving an
80% reduction in DPM emissions. This
80% filtration efficiency value was
based on laboratory tests. Since the 2001
final rule was promulgated, MSHA has
obtained the results of the NIOSH Phase
I Isozone Study conducted under actual
in-mine testing, and which concludes
that filter efficiency is about 75% for
total DPM and ranged over 88% to 90%
for EC for ceramic monolith wall-flow
type DPFs of either silicon carbide or
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cordierite composition. DPM reductions
obtained by replacing older existing
engines with new, low-emission engines
are based on the DPM emissions of the
new engine relative to the DPM
emissions of the existing engine. For
instance, if a new engine emits 0.10
grams per brake horsepower-hour (g/
bhp-hr) of DPM and the existing engine
emits 0.50 g/bhp-hr of DPM, the
Estimator would compute a DPM
reduction of 80% when the new engine
replaces the existing engine. DPM
reductions obtained through ventilation
upgrades are based on the new
ventilation airflow rate compared to the
existing ventilation airflow rate. For
example, if the new ventilation airflow
rate is 80,000 cfm and the existing
airflow rate is 40,000 cfm, the Estimator
would compute a reduction in the DPM
concentration of 50%.
The Estimator was peer-reviewed
during the 2001 final rulemaking and
was published both as an SME Preprint
for the 1998 SME Annual Meeting
(Preprint 98–146, March 1998) and in
the April 2000 SME Journal. Its
predictions have been compared to
actual in-mine DPM measurements
(before and after DPM controls were
implemented) with good agreement.
Indeed, one commenter who was critical
of the Estimator, nonetheless, noted
that, ‘‘The math which forms the basis
for the Estimator’s calculations cannot
be challenged ‘‘total exhaust emissions
from diesel equipment (in grams/hr)
when diluted with mine ventilation air
flows (in cubic feet per minute) yield an
estimated DPM concentration (in microgram per cubic meter) if the emissions
are perfectly mixed with the air flow.’’
Despite its sound mathematical basis,
this and other commenters stated that
the Estimator was flawed, and hence,
the technological and economic
feasibility assessments were likewise
flawed. These commenters specifically
stated that the Estimator was flawed
because two inputs utilized by the
Estimator, DPM emissions (both raw
and reduced via DPFs) and air flows, are
subject to interpretation and
assumptions. Furthermore, they believe
that the Estimator’s computations of
DPM concentrations are valid only if
engine emissions are perfectly mixed
with the air flow, which they suggest
does not occur in an actual mine.
MSHA disagrees with this conclusion.
These commenters make an erroneous
assumption with respect to MSHA’s
utilization of the Estimator. The
Estimator actually incorporates two
independent means of calculating DPM
levels: one based on DPM sampling data
for the subject mine, and one based on
the absence of such sampling data.
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Where no sampling data exist, the
Estimator calculates DPM levels based
on a straightforward mathematical ratio
of DPM emitted from the tailpipe (or
DPF, in the case of filtered exhaust) per
volume of ventilation air flow over that
piece of equipment. This is referred to
in the Estimator as the ‘‘Column B’’
option for calculating DPM
concentrations. The commenters’
observation that the Estimator fails to
account for imperfect mixing between
DPM emissions and ventilating air flows
is a valid criticism of the ‘‘Column B’’
option. For this and other reasons, the
Estimator’s instructions urge users to
utilize the ‘‘Column A’’ option
whenever sampling data are available.
In the ‘‘Column A’’ option, the
Estimator’s calculations are ‘‘calibrated’’
to actual sampling data. Whatever
complex mixing between DPM
emissions and ventilating air flows
existed when DPM samples were
obtained, are assumed to prevail after
implementation of a DPM control. This
is an entirely reasonable assumption,
and in fact, there is no engineering basis
to assume otherwise. Indeed,
comparisons of ‘‘Column A’’ Estimator
calculations and actual DPM
measurements taken in mines before
and after implementation of DPM
controls have shown good agreement,
indicating that Estimator calculations do
adequately incorporate consideration for
complex mixing of DPM and air flows
when the ‘‘Column A’’ option is used.
The Estimator was originally
developed with both the Column A and
Column B options because at that time,
the specialized equipment required for
DPM sampling, such as the submicron
impactor, was not widely available.
Consequently, few mine operators were
able to obtain the in-mine DPM sample
data required for utilizing the Column A
option. Now that the required sampling
equipment is readily available, MSHA
strongly recommends that the Column A
option be used exclusively, as MSHA
did in the 31-Mine Study. Since all
Estimator analyses conducted during
the 31-Mine Study utilized the
Estimator’s ‘‘Column A’’ option, the
comment regarding imperfect mixing is
not relevant.
The Estimator utilizes raw (an
unfiltered emission) tailpipe DPM
emissions per se as an input data value
only when a low-emission engine is
specified as a DPM control. For most of
the mines in the 31-Mine Study,
unfiltered tailpipe DPM emissions were
not factored into Estimator analysis
because a change in engines was not
specified. Where new engines were
specified, MSHA based its estimate of
unfiltered tailpipe emissions on
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laboratory dynamometer testing
conducted according to the EPA 8-mode
test duty cycle. This test is a common
standard used by government and
industry for diesel engine emissions
analysis. Where actual test data were
not available for a given engine,
emissions were estimated based on the
type of engine (make and model, model
year, direct injection, pre-chamber,
naturally aspirated, turbocharged,
electronic controlled, etc.) and
horsepower. Filtered emissions were
assumed to be 20% of unfiltered
tailpipe emissions, corresponding to
80% filter efficiency. As noted above,
the 80% filter efficiency was a
conservative assumption based on
MSHA and other laboratory and NIOSH
in-mine test data indicating DPM
efficiencies of 80% to 87% for both
cordierite and silicon carbide filters.
Note that these efficiencies relate to
DPM filtration. Higher filtration
efficiencies are obtained for TC and EC.
Air flows, where relevant for estimator
analysis, were based on the sampler’s
comments, and/or the accompanying
mine ventilation plans or maps.
A number of commenters suggested
that MSHA’s DPM sampling results in
isolated sections of mines are assumed
by MSHA to be representative of ongoing exposure levels in those mines,
despite the fact that results varied
widely. In the 31-Mine Study, MSHA
did not, in fact, assume a sample result
from an isolated section of a mine was
necessarily representative of on-going
DPM exposure levels throughout that
mine. The study methodology stipulated
that the highest observed DPM level for
a given mine would be the basis for
specifying DPM controls for the entire
mine. A key underlying assumption of
this methodology is that DPM levels do
vary, often significantly, from one part
of a mine to another. However, to insure
that study findings would be
conservative, the study methodology
required that the highest DPM level, not
the average or lowest DPM level, was
the basis for specifying controls.
Some commenters asserted that when
analyzing sampling data for the 31-Mine
Study, MSHA assumed that ventilation
flows measured at the sampling location
applied throughout the subject section
of the mine. They also asserted that
MSHA assumed effective ventilation for
dilution existed throughout the mine,
and that neither of these assumptions
was necessarily valid. For most of the
mines in the 31-Mine Study for which
a DPM reduction was necessary,
ventilation was not an issue, and
consequently, MSHA did not specify
any changes in ventilation. For these
mines, DPM reductions were obtained
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by utilizing DPFs and/or low-emission
engines, and the only assumption
regarding ventilation was that it would
not be changed.
In the few cases where ventilation
upgrades were specified, the upgrades
were limited to auxiliary systems that
supplied air to the sampled area only.
Initial air flows utilized by the Estimator
for those areas prior to implementing
the upgrades were based on the
comments and/or any accompanying
ventilation plans or maps accompanying
the sample. Where upgraded auxiliary
ventilation was specified, MSHA
frequently noted deficiencies in existing
auxiliary ventilation system
components such as inappropriately
placed fans and blast-damaged or
otherwise deteriorated and
compromised vent bags. In these cases,
the specified ventilation changes
involved simply correcting the obvious
deficiencies in the existing systems and
increasing fan capacity.
MSHA recognizes that there has to be
a sufficient air quantity present in the
main ventilation system in order for an
auxiliary system to function properly
(i.e. without recirculation), and that
DPM levels in the main ventilation
system from which the auxiliary system
draws its air must be sufficiently below
the DPM limit to prevent miners’
overexposures in the stopes.
Some commenters stated that in the
31-Mine Study, MSHA assumed that the
only equipment needing DPM controls
was the equipment operating while
sampling took place. As noted above,
the study methodology insured a
conservative result by applying the
same controls required to attain
compliance for the equipment
associated with the ‘‘worst case’’ sample
to all similar DPM sources (and spares)
in the entire mine, even if the subject
‘‘worst case’’ sample concentration was
substantially higher than the remaining
samples for that mine, and regardless of
whether a particular piece of equipment
was operating during sampling or not.
For most mines in the study requiring
DPM reductions, controls were specified
for all or most of the normal production
contingent of equipment, along with an
allowance for spare equipment,
particularly loaders and trucks, which
are typically the largest source of DPM.
Some commenters stated that in the
31-Mine Study, MSHA assumed 80%
DPF filtration efficiency, and gave no
consideration to potential NO2 problems
related to DPFs. As noted above, the
assumption of 80% filtration efficiency
is conservative, and is based on actual
laboratory and in-mine test data.
Regarding NO2 generation from DPFs
and the associated health concerns,
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MSHA acknowledges that NO2 can be
produced by passive DPFs that are
wash-coated with platinum-based
catalysts. However, when such filters
are utilized under reasonable ventilation
conditions, the NO2 increases should be
manageable and should not constitute a
serious health hazard or compliance
problem for the mine operator. An
example of successfully using highly
platinum-catalyzed DPFs without
creating hazardous NO2 concentrations
is Greens Creek mine which has
installed such filter systems on its large
trucks and loaders. During MSHA
compliance assistance sampling at this
mine in January 2002, NO2 increases of
around 1 ppm were observed
downstream of stopes where 1 loader
and 2 or 3 trucks were operating for 2
to 3 hours.
MSHA also notes that in situations
where passive DPF regeneration is
desired, but where ventilation may be
insufficient to adequately dilute and
carry away harmful NO2 concentrations,
alternatives to highly platinumcatalyzed DPFs exist. Examples include
base metal catalyzed DPFs and lightly
platinum-catalyzed filters used in
conjunction with a fuel-borne catalyst,
which have a regeneration temperature
somewhat higher than highly platinumcatalyzed filters. These passively
regenerating DPFs do not increase NO2
concentrations compared to unfiltered
exhaust emissions.
Even more importantly, however, in
the 31-Mine Study, all DPFs were
specified as active type regeneration
systems, not passive type systems.
Likewise, in the corresponding
economic feasibility assessment, all
costs for DPFs included an assumption
that mine operators would opt for active
regeneration. Without detailed on-site
analysis and evaluation of the subject
equipment and duty cycles, MSHA
could not assume a DPF system would
passively regenerate. Also, active filter
systems are typically more costly than
an equivalent passive system, so
specifying an active system would be
more conservative from a costing
perspective. Since actively regenerated
DPFs have no platinum wash-coatings
applied to the filters (and in fact, have
no wash-coatings at all), they do not
produce any increased NO2 emissions
compared to unfiltered engines. NO2
emissions and associated health
concerns were not addressed in the 31Mine Study because the DPM controls
specified in the study did not affect NO2
emissions.
Some commenters also stated that
MSHA failed to specify any major
ventilation upgrades (new main fans,
new ventilation shafts, etc.) in the 31-
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Mine Study, and that by avoiding major
ventilation upgrades, the resulting
compliance cost estimates were
unrealistically low. In responding,
MSHA notes that it did not specify any
major ventilation upgrades in the 31Mine Study because, based on the study
methodology, the analysis did not
indicate the need for major ventilation
upgrades in order to attain compliance
with either the interim or final DPM
limits at any of the 31 mines.
This does not mean that major
ventilation upgrades would have been
ill-advised, ineffective, or unbeneficial
for any of the mines in the study. MSHA
did note in the final report that
strategies other than those specified in
the study could also be successful, and
there may be valid reasons why a mine
operator might choose a different mix of
controls (such as a major ventilation
upgrade) for a given mine based on
mine-specific factors to which MSHA’s
analysts were not privy at the time of
the study. It was explicitly stated in the
final report that the DPM controls
specified for a particular mine did not
necessarily represent the only feasible
control strategy, nor the optimal control
strategy for that mine. The purpose of
specifying controls for each mine was
simply to demonstrate that feasible
controls capable of attaining compliance
existed, and to provide a framework for
costing such controls on a mine-by-mine
basis.
Indeed, since the completion of the
31-Mine Study, MSHA has observed
that mine operators in the stone
industry, for example, have chosen to
attain compliance without utilizing
DPFs. These operators instead have
opted to upgrade ventilation (usually by
adding or re-positioning booster fans
and installing or repairing ventilation
control structures such as air curtains
and brattices), install low-emission
engines, utilize equipment cabs with
filtered breathing air, initiate a variety of
work practices that contribute to
reducing personal exposures to DPM,
and in a few cases, use alternative diesel
fuels such as bio-diesel fuel blends and
diesel/water emulsions.
Some of these mine operators may
have had reasons other than DPM
compliance alone that helped justify
their decisions. For example, ventilation
upgrades can also improve gaseous
emission levels, dust levels, visibility,
clearance of blasting smoke and gases,
and inefficient or even
counterproductive deployment of
booster fans. Mine operators that have
opted to replace older, dirty engines
with newer, low emission engines
benefit from greater fuel economy and
better maintenance diagnostics. Cabs
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with filtered breathing air improve
operator comfort and productivity, as
well as reducing dust and noise
exposures.
DPF Systems.
DPFs suitable for any duty cycle are
currently commercially available for
most engine sizes and types used in
underground M/NM mining. DPF
options include silicon carbide and
cordierite ceramic monolith type wall
flow filters designed for passive
regeneration, active on-board or active
off-board regeneration, or passive/active
regeneration. For most filters requiring
active regeneration, the time required
for filter regeneration varies from less
than 1 hour to 8 hours, depending on
system type. Another option that is
suitable for smaller, light duty
equipment is a high-temperature
disposable pleated element filter.
Although every mine is unique, and
virtually every DPF application has
unique features, the variety of DPF
systems available make it feasible to
apply a DPF to most types of equipment
or engines, and application or duty
cycle. The only exception known to
MSHA would be applying a DPF to a
very old (pre-1970s vintage technology)
engine having very high DPM emissions
and a medium or light duty cycle. In
theory, such an application would
collect DPM, but due to rapid soot
build-up on the filter media and
corresponding rapid increase in engine
back-pressure, such a DPF application
would probably be impractical. MSHA
has observed very few such engines in
the underground M/NM mining
industry, but in the few instances where
emissions from such engines need to be
controlled, mine operators are advised
to choose a control option other than a
DPF.
MSHA is aware of reports by mining
companies and others that some DPFs
have not performed satisfactorily in the
field. These reports refer to problems
such as short filter life (a matter of
weeks in some cases), equipment that
bogs down when filters are installed,
and uncontrolled regenerations and
similar problems resulting in damaged
or destroyed filters. MSHA has
determined that most DPF failures result
from inappropriate filter selection due
to the failure by mine operators to fully
consider all filter selection criteria prior
to ordering DPF systems. In a few cases,
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filter failures were traced to
manufacturing defects that were later
resolved, while in a few others, an
unrelated component failure on the host
equipment (such as a turbocharger
failure) caused a failure in the
downstream DPF.
Most problems with filter selection
relate to the installation of a passively
regenerating type filter on a machine
that does not produce sufficient exhaust
temperature for a sufficient portion of
the duty cycle to initiate passive
regeneration. A passive type filter that
doesn’t regenerate continues to trap soot
until the backpressure on the engine
causes the engine to ‘‘bog down,’’ or an
uncontrolled regeneration occurs. The
system may function satisfactorily for a
while, either regenerating as expected,
or at least partially regenerating. But if
the machine’s duty cycle lessens in
severity, even for a single shift (for
example, a production loader that is
normally worked very hard might be
used for a shift to perform road
maintenance or clean-up duty), the filter
may become overloaded.
MSHA’s determination that DPFs are
a technologically feasible DPM control
option is based on two factors:
Laboratory and in-mine testing which
has documented their high filtration
efficiency, and numerous successful
applications in routine production
mining situations where DPFs have
been appropriately matched to
machines and duty cycles. When DPFs
are properly selected and maintained for
an application, the result is optimal
performance and maximum filter life.
In order to achieve satisfactory filter
performance, filter life, and filtration
efficiency, it is critical that a DPF be
appropriately matched both to the diesel
engine, and to the duty cycle and
intended application of the subject
equipment. For example, two identical
machines may need different types of
filter systems based on the machines’
respective duty cycles. One machine
that works hard due to the road grades
that the machine must transverse during
a shift may generate sufficient exhaust
gas temperatures to support a passive
regeneration DPF system. However, the
second machine may run continuously
on flat roads in the mine and, therefore,
may not be capable of generating
sufficient exhaust gas temperatures to
support passive regeneration.
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Consequently, the second machine must
use an active regenerating DPF system,
or change out a disposable filter on a
regular basis. Importantly, if the first
machine, due for example to a
breakdown of the second machine,
assumes the second machine’s duties,
even on a temporary basis, it would be
very possible if not likely, that its
passive DPF system would fail to
regenerate. Hence, when specifying a
DPF system for a particular piece of
equipment, mine operators should
consider not only the intended
application and duty cycle of the
machine, but also other applications
and duty cycles to which that machine
may be occasionally assigned on a
nonroutine basis.
In order to assist the mining industry
in selecting an appropriate filter, the
MSHA and NIOSH internet web sites
include a comprehensive compliance
assistance tool, the Filter Selection
Guide. One of many MSHA DPM
compliance assistance tools, the Filter
Selection Guide provides mine
operators with detailed step-by-step
assistance in selecting appropriate DPF
systems that are compatible with their
specific equipment and duty cycles.
Also, the Filter Selection Guide
provides information on modifications
and adjustments to diesel-powered
equipment that mine operators may
have to make to successfully apply DPF
systems.
Prior to initiating the DPF selection
process, mine operators should make
certain that they are properly
maintaining their engines, and that the
engines are not consuming excessive
amounts of crankcase oil. Operators
should then obtain exhaust temperature
logs or traces for several shifts, and use
these traces to help select the
appropriate DPF system for that
machine and application. Exhaust
temperature traces can be analyzed by
mine personnel or DPF suppliers to
assist in selecting a workable DPF
system. Exhaust gas temperatures are an
important factor in selecting a DPF
because passive filter regeneration is
possible only if sufficient exhaust gas
temperatures are attained for specified
minimum time periods throughout the
engine’s duty cycle. The exhaust
temperatures that must be attained, and
the corresponding DPFs, are listed in
Table VII–1.
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32923
TABLE VII–1.—CERAMIC WALL-FLOW MONOLITH DPF REGENERATION OPTIONS
DPF regeneration type
Temperature that
exhaust must exceed
at least 30% of the
time for passive regeneration to occur
DPF media
Comments
Passive ........................
>550°C .......................
Uncatalyzed media; can be either cordierite
or silicon carbide.
>390°C .......................
>340°C .......................
Base metal catalyzed cordierite ......................
Lightly platinum-catalyzed cordierite or silicon
carbide with fuel additive.
>325°C .......................
Platinum-catalyzed cordierite or silicon carbide.
Not applicable ............
Uncatalyzed cordierite or silicon carbide ........
Not applicable ............
Uncatalyzed silicon carbide or cordierite ........
Exhaust temperatures >550°C rarely if ever
occur; thus, passive regeneration of
uncatalyzed DPFs is not a practical option.
No increase in NO2.
Special provisions must be made to ensure
additive is always present in fuel and that
equipment w/o DPFs cannot be fueled with
additive-containing fuel. No increase in
NO2.
Lab results indicate significant NO to NO2
conversion; field results are mixed; successful application depends on consistently
achieving required exhaust temperatures
and adequate ventilation to dilute and carry
away NO2.
DPFs manually regenerated on-board or offboard depending on system design.
Active/passive1 type system uses fuel burner
to assist regeneration at any exhaust gas
temperature and duty cycle; regeneration
initiated automatically based on exhaust
backpressure.
Active ...........................
1 MSHA is aware of another type of active/passive system utilizing an on-board electrical heating source to assist regeneration of sintered
metal filter media, but is not aware of any underground mining applications of this system at this time.
As Table VII–1 indicates, passive DPF
systems will regenerate successfully at
or above the exhaust gas temperature
specified by the manufacturer. However,
these exhaust gas temperatures must be
maintained for at least 30% of the shift
to be sufficient for passive regeneration.
An active regenerating system will work
at any exhaust temperatures.
The tune of the engine will also be a
factor for proper regeneration. If an
engine goes out of tune and begins to
emit higher DPM concentrations in the
exhaust, the exhaust backpressure may
increase too quickly. Therefore, MSHA
and DPF manufacturers recommend that
mine operators install backpressure
monitoring devices on machines
equipped with DPFs in order to
properly monitor the condition and
regeneration state of the filter.
In the DPM settlement agreement,
MSHA agreed to a compliance
assistance period of one year beginning
July 20, 2002 and ending July 19, 2003.
Among its many compliance assistance
activities during this period, MSHA
examined the mine worthiness of
available DPF systems. In the preamble
discussion to the 2003 NPRM, MSHA
stated:
MSHA has found that most mine operators
can successfully resolve their
implementation issues if they make informed
decisions regarding filter selection,
retrofitting, engine and equipment
deployment, operations, and maintenance.
The Agency recognizes that practical mine-
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worthy DPF systems for retrofitting most
existing diesel powered equipment in
underground metal and nonmetal mines are
commercially available and are mine worthy
to effectively reduce miners’ exposures to
DPM. MSHA also recognizes that installation
of DPF systems will require mine operators
to work through technical and operational
situations unique to their specific mining
circumstances. In view of that, MSHA has
provided comprehensive compliance
assistance to the underground metal and
nonmetal mining industry.
NIOSH also stated its position on the
DPF systems currently available for
most mining equipment during this
period. By letter of June 25, 2003, to
MSHA, NIOSH stated:
With regard to the availability of filters and
the interim standard, the experience to date
has shown that while diesel particulate filter
(DPF) systems for retrofitting most existing
diesel-powered equipment in underground
metal and nonmetal mines are commercially
available, the successful application of these
systems is predicated on solving technical
and operational issues associated with the
circumstances unique to each mine.
Operators will need to make informed
decisions regarding filter selection,
retrofitting, engine and equipment
deployment, operation, and maintenance,
and specifically work through issues such as
in-use efficiencies, secondary emissions,
engine backpressure, DPF regeneration, DPF
reliability and durability. NIOSH is of the
opinion that these issues can be solved if the
informed decisions mentioned above are
made. This view is supported by comments
made by mine operators at the NIOSH-
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sponsored workshops entitled ‘‘Diesel
Emissions and Control Technologies in
Underground Metal and Nonmetal Mines.’’
Analysis of the recently completed Stillwater
Mine experiments and related in-mine tests
will also provide information regarding inmine filter efficiency performance of these
systems as compared to their performance in
the laboratory.
Assuming that the results show comparable
filter efficiency performance, metal/nonmetal
mine operators in similar circumstances will
be able to use the information with
confidence to predict performance results in
reducing DPM levels in particular
applications.
MSHA believes that this document
confirms that DPF systems are available
and mine-worthy to reduce miners’
exposures to DPM.
Some commenters stated that the
intermittent duty cycles (bursts of heavy
work, followed by idle time) common
for large front-end loaders used in the
stone mining industry are unlikely to
produce sufficiently high exhaust
temperatures for passive regenerating
DPFs to be a feasible DPM control
option. MSHA notes that during its 2003
compliance assistance visits, exhaust
temperature monitoring conducted on a
production loader indicated sufficient
temperatures for a sufficient portion of
the duty cycle to permit that loader to
utilize a passively regenerating DPF
system. Clearly, such limited testing
was not definitive, and the mine
operator would need to conduct
additional temperature monitoring to
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verify these results over the complete
range of work activities performed by
this loader. However, there was nothing
particularly unusual about this loader or
its duty cycle, so the commenter’s
suggestion that loaders in the stone
industry, in general, cannot utilize
passive regenerating DPFs, is inaccurate.
Also, MSHA notes that there are
feasible alternatives to passive
regeneration for filtering the exhaust of
any size engine used in the stone
mining industry. Mine operators could
choose on-board or off-board active
regeneration, including an on-board fuel
burner type system that actively
regenerates the filter during normal
production operations without any
intervention by the equipment operator,
without shutting down the equipment,
and without any increase in NO2
generation.
Industry commenters related the
experiences of four mining companies
to support the position that DPF systems
are not a technologically feasible DPM
control option for attaining compliance
with the interim DPM limit in
underground mining applications. The
four companies were the Stillwater
Mining Company (Stillwater mine in
Montana), Newmont Gold (Carlin East
and Deep Post mines in Nevada),
Kennecott Minerals (Greens Creek mine
in Alaska), and Cargill Salt (Avery
Island mine in Louisiana).
Commenters reported that platinum
wash-coated passive DPFs have proven
successful at the Stillwater mine. They
indicated that the equipment best suited
to utilizing passive systems includes 19
primary haulage trucks, eight
locomotives, and two large LHDs which
together, are estimated to account for
about 35% of the mine’s DPM
emissions. This equipment tends to
work in haulageways where there is
frequently a good ventilation air flow.
However, as noted elsewhere in this
section of this preamble, the
commenters noted problems with high
NO2 emissions from equipment fitted
with platinum wash-coated passive
DPFs. MSHA has determined that the
NO2 problems at this mine result from
inadequate ventilation, and that high
NO2 levels at this mine pre-dated the
use of platinum wash-coated passive
DPFs.
These commenters indicated that the
remaining 321 machines at this mine do
not have high enough duty cycles and
exhaust temperatures to utilize passive
DPFs, and that active DPF systems are
not considered feasible by the mine
operator. As discussed in detail below
in this section, MSHA believes that the
mine operator’s determination of
infeasibility of active filters is based on
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a proposed active filtration concept that
is not optimal for this mine.
These same commenters also
discussed the technological and
economic feasibility analyses for the
Stillwater mine included in the 31-Mine
Study. MSHA has acknowledged that
the cost estimates contained in the 31Mine Study final report significantly
underestimate the probable DPM
compliance costs for this mine. At the
time the 31-Mine Study was conducted,
MSHA’s analysts had been supplied
with inaccurate information regarding
this mine’s diesel equipment inventory.
MSHA subsequently revised its analysis
based on updated equipment inventory
data. The revised estimate of
compliance cost for the Stillwater mine
is considerably higher than the estimate
included in the 31-Mine Study.
However, as discussed later in this
section, it is nonetheless consistent with
the estimated compliance cost for a
precious metals mine of this size as
detailed in MSHA’s REA for the 2001
final rule.
The commenters indicated that
Newmont has experimented with both
passive and active DPFs in the Carlin
East and Deep Post mines, and that a
problem exists. The commenters state
that engine backpressures range from 37
to 43 inches of mercury when DPFs are
in use, and one of their engine
suppliers, Caterpillar, will not warrant
engines when backpressure exceeds 27
inches of mercury. In response, MSHA
references the NIOSH/MSHA Filter
Selection Guide, which states that DPF
systems must be sized so that
backpressure is within the engine
manufacturer’s specifications.
The commenters go on to relate
Newmont’s successes with DPFs,
including both platinum wash-coated
passive filters on haulage trucks and
base metal wash-coated passive/active
filters on smaller LHDs and jammers.
Although elevated NO2 emissions can
be associated with platinum washcoated DPFs, the trucks equipped with
these filters are used to haul ore up well
ventilated ramps to the surface, so the
potential for NO2 overexposure is
minimized. The smaller LHDs and
jammers are typically used in
production areas with lower ventilation
rates, so base metal wash-coated filters
are used which do not generate NO2.
Because of the limited duty cycle of
these smaller machines, total filter
regeneration may not occur. However,
the wash-coat promotes enough
regeneration that the filters are able to
function properly between set service
intervals that coincide with the
equipment’s preventive maintenance
schedule, at which time the filters are
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changed-out, and the ‘‘dirty’’ filters
actively regenerated off-board.
The commenters also related
Newmont’s experience with ‘‘failed’’
DPFs, including a filter that was
destroyed due to excess vibration and
another that was destroyed when an
upstream turbocharger failed and blew
oil into the DPF. However, the
commenter went on to describe the
steps taken by Newmont to successfully
correct the vibration problem (shock
absorbing filter mounts), and the other
destroyed DPF was clearly caused by
the failed turbocharger, not an integral
failure of the DPF. MSHA has
repeatedly advised the mining
community that a certain amount of
applications engineering will be
required to insure the successful
deployment of DPFs on underground
mining equipment. The vibration failure
example illustrates that as mine
operators obtain experience with DPFs,
problems will inevitably be
encountered, but they can be readily
solved by applying reasonably simple
hardware solutions.
These commenters also questioned
MSHA’s assumptions regarding the
feasibility of auxiliary ventilation
system upgrades discussed in the 31Mine Study, however, the upgrades
specified for Carlin East in the 31-Mine
Study related to achieving the final
DPM limit. Compliance with the interim
limit was projected without ventilation
upgrades.
These commenters concluded that
overall DPM compliance costs are too
high for Newmont Gold. Newmont
estimates that the, ‘‘purchase and
installation of DPFs, including
downtime on production vehicles, will
be $1.9 million for its two mines—Deep
Post and Carlin East.’’ No further cost
breakdown is provided, so MSHA could
not assess the reasonableness of this
estimate. However, accepting this
estimate as submitted, and assuming a
two-year DPF service life, Newmont’s
estimate of its DPF costs implies a
yearly cost of $1.05 million for the two
mines ($1.9 million annualized over two
years at a 7% discount rate). MSHA
notes in the REA for the 2001 final DPM
rule that its estimated compliance cost
for a medium-sized gold mine
employing 20 to 500 miners is $171,900
per year based on a diesel equipment
fleet size of 24 pieces of diesel
equipment. This estimate was based on
analysis indicating about 78% of overall
compliance costs would relate to DPFs.
Adjusting MSHA’s estimated annual
cost to correspond to the combined 166
pieces of equipment at Newmont’s two
mines yields an estimated annual DPFrelated compliance cost of about
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$927,000, which is only 12% less than
Newmont’s estimate of its annual DPFrelated compliance cost.
The same commenters described DPF
installations on haulage trucks and
loaders equipped with Detroit Diesel
Series 60 engines rated at 450
horsepower and 350 horsepower,
respectively, at the Kennecott Greens
Creek mine in Alaska. Regarding the
trucks, the same commenters reported
that, ‘‘After initial problems, mainly
caused by incorrect installation and
sizing of filters, the mine has
successfully equipped its fleet of six
Toro trucks with DPFs.’’ This
experience confirms two important
aspects of DPF utilization that MSHA
has emphasized repeatedly in its
compliance assistance communications
with the industry, including (1) the
likely need for a certain amount of
applications engineering to resolve
implementation and installation issues,
and (2) the need to appropriately match
the DPF to the machine and duty cycle.
With respect to installations on two
identical Toro 1250 loaders, it was
noted that the platinum wash-coated
DPF on one unit consistently passively
regenerated, while the DPF on the other
unit, which had a lesser duty cycle and
exhaust temperatures that were 40 to
50°C lower, did not. This experience
does not illustrate the failure of DPF
technology. Rather, it confirms MSHA’s
consistent advice that the successful
deployment of passively regenerating
DPFs requires careful determination of
exhaust temperatures to assess whether
passive regeneration is feasible for that
particular machine and in that
application. Indeed, in this example, the
filter functioned precisely as designed.
The failure of the filter to passively
regenerate on the second machine could
have been reliably predicted based on
the exhaust temperature data.
In their comments, industry also
relates Greens Creek’s successful
application of an active DPF system on
an Elphinstone R1300 31⁄2-yd LHD with
a Cat engine. This loader is used for
relatively light duty clean up work, and
is therefore not a suitable candidate for
application of a passively regenerating
DPF.
It should be noted that industry also
commented that, ‘‘Those engines in the
250–350 horsepower, and greater-than
350 horsepower ranges are considered
unsuitable for DPFs with present
technology. This general conclusion of
unsuitability for DPF usage for these
large engines comes from use of DPFs in
real mine situations.’’ These statements
are directly contradicted by Greens
Creek’s successful experience filtering
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the exhaust from 350 horsepower and
475 horsepower engines.
Industry also presented the
experience of Cargill Salt’s Avery Island
mine in Louisiana which installed two
DCL Mine X DPF filters on a Cat 992G
loader equipped with a Cat 3412 engine
rated at 650 horsepower. One 15 inch
diameter by 15 inch long filter was
connected to each bank of the V–12
engine. This model DPF is wash-coated
with a platinum catalyst to facilitate
passive regeneration. The mine reported
that there are no problems with elevated
NO2 levels, and visible emissions have
been reduced. However, the mine also
reported that the loader has lost almost
all of its power, to such an extent that
the loader is only used for clean-up
duty.
These symptoms—no elevated NO2
levels, visible emissions reduced, and
loss of power—are all typical of a
mismatch between the duty cycle of the
application and the performance
specifications of the DPF. In order to
passively regenerate, this DPF requires
exhaust temperatures of about 325°C or
higher for at least 30% of its duty cycle.
An insufficiently demanding duty cycle
produces lower exhaust temperatures
which are not sufficient to ignite and
burn off accumulated DPM. Such a filter
continues to collect DPM, resulting in
lower visible emissions, but as the filter
loads, even for a single work shift,
backpressure on the engine increases,
resulting in loss of power. Although
these commenters report that mine
mechanics worked closely with the
local Caterpillar dealer in installing the
system, it is very likely that this
experience illustrates an inappropriate
DPF application rather than a failed
filter system.
Normally, the local Caterpillar dealers
and any other engine manufacturer’s
dealers work more with issues
concerning the engine installation and
repairs than with DPM filter
applications. Since engine
manufacturers at this time do not install
a DPF to the engine at the time of engine
production, the local engine dealers are
not usually familiar with DPF systems
that are installed as retrofits on the
engine.
However, even in the case of the
Greens Creek experience, where the
mine operator worked with the engine
manufacturer, the vehicle manufacturer,
and the filter manufacturer at the onset
to incorporate a DPF on a new machine,
the mine still initially had a failure of
the DPF because of regeneration issues.
As Greens Creek reported,
the unit (DPF) was used on a waste rock
backhaul route, with loads being carried
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32925
down the ramp or on relatively flat hauls.
Had the unit been used for ore haulage uphill
routes, it would have achieved the high
exhaust temperatures for the designed
passive regeneration.
This mine’s experience continues to
emphasize that the mine must
understand the duty cycle of the
machine to which the DPF is being
equipped to see if the duty cycle can
support the regeneration needed for the
DPF. In the case of Greens Creek, the
waste rock backhaul vehicle did not
have a sufficiently demanding duty
cycle to generate the exhaust gas
temperature needed for regeneration for
a passive regeneration system. In such
instances, the mine operator needs to go
to another method of regeneration for
the vehicle’s DPF as discussed
elsewhere in this preamble. Mine
operators should also refer to the M/NM
Filter Selection Guide on MSHA’s Web
site for assistance in choosing the
appropriate DPF system for its
particular circumstances.
Industry also discussed various issues
relating to compliance problems for
stone mines, such as feasibility of filters
for large engines, biodiesel fuel, and
ventilation. These issues are addressed
elsewhere in this preamble in sections
that deal specifically with these topics.
Some commenters stated that MSHA
presumed that operators would retrofit
DPFs on existing diesel-powered
equipment as the primary method of
compliance. These commenters
questioned whether implementation
issues with retrofitting and regeneration
would make DPFs infeasible. In
response, MSHA has determined on the
basis of in-mine tests conducted by
NIOSH, MSHA, individual mining
companies and others, and on the
experiences of mining companies that
have implemented DPM filtration on a
routine production basis, that DPFs are
a practical, mine-worthy, and effective
means for reducing exposure to DPM in
underground M/NM mines. Further,
MSHA has determined that use of DPFs
independently or in conjunction with
other feasible and effective DPM
engineering and administrative controls
will enable most mine operators to
attain compliance with the DPM interim
limit. However, MSHA agrees with the
commenters that implementation issues
with retrofitting and regeneration may
present compliance difficulties for some
mines, and additional time may be
required at some mines due to the cost
of purchasing and installing controls.
Many commenters have cited
problems with DPFs which they believe
support the contention that DPFs are
neither technologically nor
economically feasible. As noted above,
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some commenters provided examples
from several underground mines that
experienced failed DPFs. Commenters
indicated that a ceramic filter, using
passive type regeneration would be the
only type filter that would be acceptable
to them. Commenters also stated that
ceramic DPFs that require active
regeneration, a fuel borne catalyst, a
catalyst that could have the potential to
increase NO2 emissions, and any kind of
filter for engines less than 50
horsepower or greater than 250
horsepower were infeasible for use in
underground M/NM mines. Some
commenters described installations that
produced high exhaust backpressure on
engines that could lead to voiding
engine warranties or render a vehicle
unusable. A commenter also stated that
the number of regeneration stations that
would be required to be built and
maintained would make active
regeneration infeasible.
Other commenters stated that when
DPFs are appropriately sized and fitted
to equipment, and there is a good match
between the equipment application/
duty cycle and the DPF regeneration
method, long filter life and significant
DPM reductions will result. Several
commenters indicated that, after an
initial trial-and-error ‘‘learning period,’’
they had experienced success with
passive type DPFs and were using them
on a routine production basis.
Some commenters stated that DPFs
continue to be a feasible technology for
significantly reducing DPM exposures.
One commenter reported the successful
application of an on-board active
regeneration DPF. This system includes
an exhaust backpressure monitor that
warns the equipment operator when
DPF regeneration is required. This is a
feature MSHA recommends for all DPF
installations.
As noted above, MSHA acknowledges
the numerous documented examples of
failed DPF applications in the
underground M/NM mining industry.
However, MSHA believes such failures
are the result of inappropriate filter
selection, manufacturing defects, and
unrelated failures of equipment
components (such as turbochargers) that
have caused damage to DPFs. MSHA is
confident that proper filter selection
will result in satisfactory long term DPF
performance, and NIOSH agrees with
MSHA that DPFs are technologically
feasible for most mining equipment after
some technical and operational
problems are solved, and that these
problems can be solved in most cases.
To help mine operators avoid having
to rely on costly and time consuming
trial-and-error methods for DPF
selection, the Filter Selection Guide was
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developed. It is the result of a joint
effort of MSHA and the Diesel Team
from the NIOSH Pittsburgh Research
Laboratory. The Filter Guide provides
mine operators with information on
feasible and available DPFs. NIOSH will
work with MSHA to maintain the Filter
Guide on the internet.
MSHA continues to urge mine
operators to thoroughly evaluate each
application to insure that the
appropriate DPF and regeneration
system is chosen. Such an evaluation is
well within the technical capabilities of
most mine operators to perform. For the
few operators that would be unable to
independently perform this evaluation,
technical assistance can be obtained
from mining equipment manufacturers,
engine manufacturers, DPF
manufacturers, and MSHA.
As noted earlier, selection of an
appropriate DPF for a given application
requires consideration of such factors as
engine type, model, and horsepower, as
well as the intended usage of the
equipment and related equipment duty
cycles. Mine operators are fully capable
of obtaining this information for every
piece of equipment that is a candidate
for DPF installation. In addition, the
engine’s DPM emission rate and exhaust
temperatures must be obtained. For
MSHA-approved engines, DPM
emission rates are determined by MSHA
and included with the engine approval.
For non-approved engines, DPM
emission information can be obtained
from the engine manufacturer or
estimated based on the characteristics of
the engine (direct injection, prechamber, make and model, model year,
naturally aspirated, turbocharged,
electronically controlled, etc.). To
obtain exhaust temperatures, various
inexpensive (approximately $200) data
logging thermocouple systems are
commercially available that can be
attached to the exhaust system to
provide detailed exhaust temperature
profiles over time periods ranging from
several hours to several shifts. During its
compliance assistance mine visits in the
spring and summer of 2003, MSHA
noted that several mine operators had
acquired exhaust temperature data
logging systems and were using them to
systematically measure exhaust
temperatures on equipment that might
need to be equipped with a DPF in the
future.
DPFs collect significant amounts of
DPM from the engine’s exhaust, thus
lowering DPM exposures. This fact was
not disputed by the commenters. The
results from MSHA’s compliance
assistance work with Kennecott at their
Greens Creek Mine, NIOSH’s isolated
zone tests conducted at the Stillwater
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Mine, NIOSH’s production zone tests at
the Stillwater mine, MSHA’s laboratory
data, laboratory and in-mine test results
from Canadian and European studies,
and various other industry applications
prove that DPFs provide high efficiency
reductions in both DPM and EC. For EC,
the data indicate filtration efficiencies
as high as 90% to 99+%.
MSHA disputes commenters’ views
that if passive regeneration cannot be
successfully employed (due, for
example, to an insufficient duty cycle
and correspondingly low engine exhaust
temperatures), then DPM filter
technology is infeasible. Passive
regeneration is only one of many
regeneration schemes available to the
mine operator. Clearly, not all machines
or all applications are suitable for
passive regeneration. One commenter
stated that one of his firm’s two loaders
was able to use a passive regeneration
DPF due to the exhaust gas temperatures
reached during its duty cycle, while the
other could not or was marginal. This
experience demonstrates precisely what
MSHA’s consistent message to the
industry has been—that successful
application of passive regeneration
DPFs depends on matching the filter to
the application, and mine-worthy
systems are commercially available for
most any machine and any duty cycle.
It is important to note that a
sufficiently heavy duty cycle does not,
by itself, guarantee that a passive
regeneration DPF will function properly
and provide satisfactory long-term
performance. It is an essential
prerequisite, but the other steps in the
DPF selection process must also be
followed rigorously. Without the
necessary exhaust temperatures for the
specified amount of time, passive
regeneration is impossible, regardless of
how carefully the other steps in the
selection process are followed.
However, once the necessary exhaust
temperature profile has been verified
through sufficient in-mine temperature
monitoring, users are urged to carefully
complete the remaining steps in the
selection process.
For whatever reason, if a particular
machine requires a DPF, but is an
unsuitable candidate for application of
a passive regeneration system, the mine
operator has the option of using a
combination passive/active regeneration
scheme or to use a purely active
regeneration system. Because the option
exists for utilizing either passive, active/
passive, or active regeneration systems,
MSHA maintains that a suitable DPF
system is available for any size diesel
engine and any application in the
underground M/NM mining industry.
The mine operator may need to address
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various implementation issues regarding
retrofitting and regeneration, but MSHA
is confident these issues can be
resolved.
NIOSH’s Phase I Isozone and Phase II
Production Zone Studies Related to
DPFs at the Stillwater Mine. NIOSH
conducted a series of in-mine tests on
DPF systems at the Stillwater Mining
Company’s underground platinum mine
at Nye, MT. The tests were conducted
in two phases. The Phase I tests were
conducted from May 19–30, 2003, and
the Phase II tests were conducted from
September 8–12, 2003. The purpose of
Phase I was to assess the effectiveness
of DPM control technologies in an
isolated zone. The purpose of Phase II
was to assess the capability of DPFs to
effectively control the exposure of
underground miners to DPM in actual
in-mine production mining scenarios.
NIOSH issued two final reports on
these studies. The final report for Phase
I was entitled ‘‘Effectiveness of Selected
Technologies in Controlling Diesel
Emissions in an Underground Mine—
Isolated Zone Study At Stillwater
Mining Company’s Nye Mine,’’ and the
report was released on January 5, 2004.
NIOSH included the following in its
discussion of the objective of the study:
The objective of this study was to
determine the in-situ effectiveness of the
selected technologies available to the
underground mining industry for reducing
particulate matter and gaseous emissions
from diesel-powered equipment. The
protocol was established to determine the
effectiveness of those technologies in an
underground environment under operating
conditions that closely resemble actual
production scenarios.
The study was designed to provide
Stillwater, and the general mining
community, with better insights into the
performance of control technologies and
enable them to identify the appropriate
devices for reducing diesel emissions. The
focus of the Stillwater research was on
technologies that offer solutions for reducing
DPM emissions. This report provides the
results and assessment of the following
control technologies: diesel particulate DPFs,
disposable paper DPFs, diesel oxidation
catalytic converter, and reformulated fuels.
The Phase II final report was entitled,
‘‘An Evaluation of the Effects of Diesel
Particulate Filter Systems on Air
Quality and Personal Exposures of
Miners at Stillwater Mine Case Study:
Production Zone,’’ and the report was
released April 1, 2004. The objective of
Phase II was to determine the effects of
DPF systems installed on production
equipment at the Stillwater Mine on
workplace concentrations of EC and
regulated gases in an actual production
mining application where multiple
diesel-powered vehicles operated
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simultaneously during full shift mining
activities. The effects of DPF systems
were examined by comparing ambient
concentrations of EC, CO, CO2, NO, and
NO2 in a production area for two
different test conditions. For the
baseline condition, all vehicles that
operated within the ventilation split
were equipped with standard exhaust
systems—a diesel oxidation catalyst
(DOC) and muffler—but without DPFs.
For the second condition, three of the
vehicles, an LHD and two haulage
trucks had their DOC and muffler
systems replaced with DPF systems.
The NIOSH Phase II study conducted
at the Stillwater Mine is similar to the
in-mine tests conducted by MSHA in
January 2003 as a part of its compliance
assistance program at the Kennecott
Greens Creek Mine near Juneau, AK,
which is discussed elsewhere in this
preamble.
NIOSH Phase I study. The majority of
the control devices tested were DPFs.
Phase I also tested biodiesel fuel and the
differences between #1 diesel fuel (D1)
and #2 diesel fuel (D2). DPFs included
both ceramic and high temperature
disposable (synthetic media) filters.
NIOSH reported that some problems did
occur during the tests, mainly dealing
with ventilation issues in the isolated
zone and an occasional vehicle passing
nearby the intake to the isolated zone.
However, these problems were minor
and did not compromise most tests.
As reported, NIOSH chose to
normalize the data based on MSHA’s
nameplate gaseous ventilation rates.
One commenter stated that he
understood why NIOSH normalized the
Phase I data to the MSHA nameplate,
however, the commenter felt this was a
disservice to the miners since M/NM
mines do not have to comply with the
ventilation rates on the approval plates.
Indeed, engines in M/NM mines are not
required to be MSHA approved and
ventilation rates are not available for
non-MSHA approved engines. MSHA
agrees with the commenter that the
Phase I report had the correct intent to
normalize the data for reporting
purposes. MSHA also agrees that the
results may not be typical for operations
in the M/NM sector because the
ventilation schemes used by many M/
NM mines do not comply with approval
plate quantities for MSHA approved
engines.
The Phase I report shows that the EC
reduction in the isolated zone with one
system was 88%, and that two other
systems gave greater than 96% EC
reductions when the measured
concentrations were normalized by
ventilation rate. NIOSH reported that
several tests were discarded and not
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reported due to unexplainably low CO2
concentrations found at low ventilation
rates.
The filter media used in all the DPF
systems during the Phase I test was
either Cordierite, Silicon Carbide, or the
disposable high temperature synthetic
material. (An analysis conducted by an
MSHA contracted laboratory indicated
the synthetic material is fiberglass.) All
the DPF media have very similar
efficiencies for EC reductions. Even
though NIOSH did not report the EC
reduction efficiencies of all the DPF
systems tested in Phase I, MSHA
believes, based on its own evaluations,
that the efficiencies for EC reductions of
those DPFs not reported would have
been approximately equal to the results
obtained for DPF systems that were
reported.
Many commenters agreed that the
Phase I study accomplished its objective
by showing that DPM filters are viable
for reducing DPM from diesel engines
and that the filter systems performed as
designed. However, some of these
commenters stated that the elaborate
test setup in the Phase I study was only
a replication of a laboratory type
environment that did not represent
actual mine conditions. Commenters
pointed out that some of the control
technologies did not perform as well as
expected during the study.
MSHA agrees that the Phase I study
demonstrated that DPM filters are an
effective tool for reducing DPM emitted
from diesel engines. The Phase I study
did involve an elaborate test setup, but
this test setup was primarily aimed at
controlling the ventilation conditions so
that extraneous DPM from upstream
diesel traffic would be eliminated,
thereby enabling a meaningful and
accurate determination of the DPM
reductions obtained by the various DPFs
tested. In other respects, however, the
test setup was quite realistic, in that the
testing occurred underground and
involved a realistic simulation of a
production mining operation. For
example, in testing of LHDs, the test
protocol required a production LHD to
repeatedly follow a proscribed duty
cycle involving loading at a muckpile,
tramming up a 9% grade along the main
haulageway a distance of approximately
1,000 feet with a loaded bucket, various
forward and reverse maneuvers over
short travel distances at each end of the
haulageway, and raising and lowering a
loaded bucket to simulate loading a
haulage truck. Other than the removal of
existing exhaust system components
(DOC and muffler) to accommodate
installing the subject DPFs, and the
installation of certain monitoring
instrumentation, the equipment used in
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the study was unmodified and in ‘‘as is’’
condition from the mine’s equipment
inventory. Although this testing was
based on simulated mining operations,
the suggestion that it replicates a
laboratory environment is an inaccurate
characterization.
MSHA believes that the Phase I
Isozone data is sound science,
establishing with certainty that DPFs
can be implemented on a broad scale in
mines in the U.S. and that DPFs are
capable of achieving significant
reductions in miner’s DPM exposures.
MSHA notes that these data are
consistent with the results of other
similar tests, including both laboratory
tests conducted by MSHA, NIOSH and
others, and a Canadian in-mine isolated
zone test in which NIOSH also
participated. MSHA discussed the
results of this Canadian test in the
preamble to the 2001 final rule.
One commenter stated that the Phase
I isolated zone test should have been
completed long before the DPM rule was
rushed to publication. MSHA does not
agree with the commenter. In fact,
MSHA used the results of the above
mentioned Canadian isolated zone
study in its original 2001 DPM rule to
show the effectiveness of DPFs. The
recent NIOSH isolated zone testing
confirmed the results obtained by the
Canadians. As noted above, the
pertinent data that were derived from
the Canadian study on the efficiencies
of DPFs were referenced in the preamble
to the 2001 final rule.
At the end of the Phase I report,
NIOSH indicated that the Stillwater
mine had at that time over one dozen
DPFs in use for a combined total of over
22,000 operating hours. NIOSH reported
that only one of these DPFs had failed
(runaway regeneration), and that the
other systems have been virtually
maintenance free. Again, even though
Stillwater’s experiences with DPFs on a
routine production mining basis have
been with heavily platinum-catalyzed
passive systems, the commercially
available DPF media are the same for
passive systems using other catalyst
wash coats as well as for active
regeneration systems that utilize
uncatalyzed filter media. Moreover, all
DPF media basically provide equivalent
filtration efficiencies for DPM, TC, and
EC.
NIOSH Phase II study. The Phase II
study confirmed and expanded on the
results obtained in the Phase I study. In
the final report, NIOSH indicated that
greater EC reductions were observed in
the field than were obtained in the
laboratory for whole diesel particulate:
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* * * laboratory determination of DPF
efficiencies, based on reductions in total
DPM mass (fairly equivalent to TPM [Total
Particulate Matter]), substantially
underestimates the ability of DPF systems to
reduce EC emissions, the metric used by
MSHA for compliance,* * *
which highlights the high EC filtration
efficiency for DPFs.
MSHA believes that the Phase II study
helped to confirm existing agency data
that shows that it is technologically
feasible to reduce miners’ exposures to
DPM to the 308EC µg/m3 interim PEL.
The Phase II study utilized three
machines (1 LHD and 2 Haul Trucks)
equipped for the first three days with
highly platinum-catalyzed Englehard
DPX DPFs, and the last day without
the DPFs, but with DOCs. The
equipment engaged in normal
production activities in a typical
production mining area of the Stillwater
mine, as opposed to the simulated
mining tasks that were conducted in an
isolated zone in the Phase I study.
Personal sampling on equipment
operators was conducted, as well as area
sampling upstream and downstream
from the working area where the
equipment was operating. Tests were
conducted with and without DPFs
installed so that the capability of the
DPFs to reduce personal DPM exposures
and DPM levels in the ambient mine air
could be quantified.
The results of the personal EC
samples from the three machine
operators equipped with filters were
provided in the final report. NIOSH did
not report Day 1 results due to
inadequate sampling locations. The EC
results for personal samples for Day 3
showed that the DPM exposures of all
three miners were well below 308EC µg/
m3, and in fact, well below 160EC µg/
m3. Day 2 showed exposures also below
308EC µg/m3, but almost double the
results of Day 3. However, it appears
that the ventilation air flow through the
working area on Day 2 was about half
the ventilation air flow for Day 3. Thus,
the differences in measured DPM levels
are not contradictory, but rather,
demonstrate the effectiveness of
increased ventilation flow as an
engineering control to reduce DPM
levels in the ambient air. The EC
reduction efficiencies of the DPFs based
on personal exposures comparing test
days with and without the filters in
place were approximately 71% for the
LHD operator and 78% for the haul
truck drivers. These reductions are very
similar to the results obtained for
personal exposures in the Greens Creek
study conducted by MSHA in January
2003.
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NIOSH reported that some of the
filters used during the Phase II testing
at Stillwater may have been
compromised. However, NIOSH
indicated in the Phase II final report
that, ‘‘* * * even when the DPF
systems are performing below
expectations, they can significantly
reduce the EC concentrations when
compared to conditions when DPF
systems were not used.’’ Significantly,
MSHA made a very similar observation
in its report on Greens Creek. During
testing at Greens Creek, there were
obvious visible cracks in some of the
ceramic media. But analysis of DPM
concentrations in the equipment
exhaust indicated that EC filtration
efficiency was still quite high (>90%)
despite the cracks. Clearly, even
compromised DPM filters can reduce
personal DPM exposures to levels below
the interim PEL.
NIOSH reported increased NO2
concentrations during the study when
using DPFs, and suggested that the
source of the increase was the platinum
catalyst used as a wash coat for the
Cordierite filter media. The platinum
wash coat on the filter is used for
regeneration purposes and does not
affect filter efficiency for EC
measurements. Therefore, the reduction
observed in EC concentrations from the
Phase II study should be expected when
any filter is installed that has a
Cordierite filter media. As discussed
elsewhere in this preamble, a Silicon
Carbide filter media is also used in
many DPF systems and EC filtering
efficiency for Silicon Carbide is very
similar to Cordierite.
As noted above, NIOSH reported
increases in NO2 concentrations when
highly platinum-catalyzed DPFs were
used. NIOSH stated in the Phase I final
report that ‘‘* * * if the required MSHA
ventilation rates were maintained
during the tests, the average
concentration of NO2 over the test
periods would have not exceeded 3
ppm, the long term exposure limit for
NO2.’’ The greatest increase in NO2
during the Phase I study came from the
highly platinum-catalyzed DPF. When
this filter was used, the ceiling limit of
5 ppm was briefly exceeded each time
the equipment repeated the duty cycle.
These NO2 peaks were noted at the
downstream sampling location and at
about the same levels at a sampling
location on the equipment near the
operator’s position.
NIOSH stated in the Phase II report
that tests 2 and 3 (with DPF installed)
were terminated when the multi-gas
monitor carried by the equipment
operator indicated that the 5 ppm NO2
ceiling limit had been exceeded. NIOSH
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reported that they also believe the NO2
level may have been above 5 ppm for
personal exposure on test 4 when the
DPFs were not installed on the
machines (DOCs were installed on test
4).
Although tests 2 and 3 were
terminated earlier than planned, these
tests lasted between approximately 23⁄4
hours and 43⁄4 hours, respectively.
MSHA believes that these tests were
sufficient in duration to demonstrate the
differences in EC exposures with and
without DPFs. At most mines, mucking
operations in an individual stope or
development end are usually completed
within 2–4 hours. In fact, the Greens
Creek report results were based on
approximately 2–3 hours of sample
time, which was the total time required
to muck out the subject stopes.
From the intake side to the return side
of the Phase II test zone, average NO2
increase as reported were 1.2 ppm for
Day 2, and 1.1 ppm for Day 3 with
DPFs. The average NO2 increase was
1.1ppm for Day 4 with DOCs. It is
significant to note that these increases
are consistent with the NO2 increases
observed during the Greens Creek tests,
and would not be expected to result in
hazardous NO2 exposures in mines with
adequate ventilation. It should also be
noted that there was no significant
difference between average NO2
increases with and without DPFs in the
test area (the DPFs were replaced by
DOCs on Day 4).
As stated above, NIOSH noted that
Phase II tests 2 and 3 were terminated
early due to excessive NO2 levels
measured in the cabs of the test
equipment. Due to the layout of the area
where Phase II tests were conducted, it
is likely that the vehicles experiencing
the highest NO2 levels were operated for
part of the duty cycle in a lower
quantity of ventilation air than was
available in the main haulageway. The
observed personal overexposures to NO2
occurred when the haul trucks were in
this poorly ventilated area where the
intake air split at an orepass and a
development section. MSHA believes
that if the air flows to these locations
had been maintained at levels near the
nameplate value, the overexposure to
NO2 would very likely not have
occurred.
It should be noted that MSHA has
documented very low ventilation air
flows in several stopes at the mine
where NIOSH’s Phase II study was
conducted. Ventilation measurements
obtained by MSHA during a compliance
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assistance visit to the mine in June 2004
identified significant leakages from most
of the auxiliary stope ventilation
systems that were evaluated. In the six
stopes for which ventilation air flow
measurements could be obtained at both
the auxiliary fan location and at the end
of the vent bag, the average air flow at
the fan location was 24,400 cfm and the
average flow at the end of the vent bag
was 5,100 cfm. In one stope, auxiliary
ventilation system leakage was 89% and
in another, leakage was 85%. Even in
stopes where auxiliary system leakage
was relatively low, significant
recirculation was observed. With stope
ventilation flow rates compromised to
this extent due to auxiliary system
leakage and recirculation, it is not
surprising that both high gaseous
emission levels and high DPM
emissions have been measured at this
mine.
The NIOSH Phase II data show that
gaseous contaminant levels and
ventilation flows had stabilized in the
test area a short time after the testing
was initiated (within approximately the
first 30 minutes), indicating that roughly
steady-state conditions had been
achieved. If tests 2 and 3 had not been
terminated prematurely (i.e., if the
poorly ventilated area had been
sufficiently ventilated), it is therefore
likely that the reported DPM and
gaseous emission levels could have been
maintained indefinitely, or at least until
mining operations were completed in
the test area.
As stated earlier, MSHA advised mine
operators through the issuance of a PIB
that the use of highly platinumcatalyzed DPFs has the potential to
increase concentrations of NO2. The
increases in NO2 observed during the
Stillwater Phase I and Phase II tests
demonstrate that mine operators who
choose to use highly platinum-catalyzed
DPFs must maintain sufficient
ventilation in areas where the machines
operate, and must monitor for any
increases in NO2. This advice is
particularly important for mines that
had experienced NO2 problems prior to
the introduction of platinum washcoated DPFs, as was the case at the
Stillwater mine. Where NO2 levels
cannot be adequately controlled by
ventilation, alternatives to highly
platinum-catalyzed passive filter
systems are commercially available
which do not increase ambient NO2
levels. An example that is particularly
well suited to heavy duty applications
is the fuel burner type active
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regenerating DPF. A system of this type
is currently installed and under
evaluation at the Stillwater mine.
The results of these studies support
MSHA’s position that feasible control
technology exists that is commercially
available to effectively reduce miner
exposures to DPM. As with any new
mining machinery, mine operators will
need to thoroughly evaluate their needs
prior to ordering DPF systems to insure
that each system is appropriate to the
piece of equipment, engine, application,
and duty cycle. Failure to appropriately
consider these factors will likely result
in poor filter performance, poor engine
performance, possible engine and filter
damage, or all of the above. Alluding to
this issue, NIOSH states in the Phase II
study final report that, ‘‘Due to the
nature of the study, Phase II did not
address other and no less important
matters relating to the application of
control technologies in underground
mines. These matters include selection
of DPF regeneration strategies,
economic, logistical, and technical
feasibility of implementation of various
DPF systems on mining vehicles, and
the reliability and durability of the
systems in mine settings.’’
MSHA has consistently stated that the
application of commercially available
DPF systems is a task that requires
mines to evaluate machine installations
on a case by case and application by
application basis. NIOSH agrees.
Consequently, NIOSH and MSHA
jointly developed an on-line Internetbased Filter Selection Guide which is
discussed elsewhere in this preamble.
NIOSH’s written response to MSHA in
this rulemaking supports the use of
DPFs as a control device that can
significantly reduce DPM exposures, but
also states that the mine operator must
evaluate each machine prior to selection
and installation of DPM filter systems to
insure a successful match between filter
and application. When properly
selected and installed for an
application, DPFs are both durable and
mine worthy. Almost without
exception, failed DPFs that have been
reported to MSHA were the result of
inappropriate filter selection,
manufacturer defect, or the failure of an
unrelated component (usually the
turbocharger) that affected the DPF.
Active Regeneration DPFs. The active
regeneration systems discussed below
are normally not catalyzed so they do
not produce an increase in NO2.
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TABLE VII–2.—SCENARIOS FOR ACTIVE REGENERATION.
System name
Regenerating location
Regenerating controller
location
Comments
On-board ..............................
On-board ..............................
On Equipment ...................
On Equipment ...................
Off-board ..............................
Off equipment ....................
On Equipment ...................
Designated and fixed-location.
Fixed-location ....................
On-board ..............................
On-equipment ....................
Requires on-board source of electric power.
Requires equipment to come to a specific regeneration site.
DPFs are exchanged and must be small enough to be
handled by one person. Increases number of DPFs
needed.
System is complex yet fuel burner provides advantage
of regeneration during equipment use.
Scenarios for active regeneration
systems are listed in Table VII–2. The
second system listed in Table VII–2 is
an on-board active system that requires
about one to two hours of machine
down time for regeneration, which
might be available between shifts at
some mines. To regenerate these filters,
the piece of equipment must be parked
at a designated location during the
regeneration period so that the filter can
be connected to electrical power and
compressed air. MSHA recognizes that
presently in some mines, production
equipment is not necessarily brought to
a central location at the end of each
shift. At such mines, operators may
need to make operational changes to
accommodate such DPF regeneration
designs.
Alternatively, mine operators may
choose off-board active regeneration
type filters, wherein, for example, the
equipment operator removes the DPF at
the end of the shift and brings it to a
central station for regeneration. The
next operator of that piece of equipment
takes a regenerated DPF to the
equipment at the start of the next shift.
This system enables uninterrupted
equipment operation, and does not
require the equipment to travel to a
central location for filter regeneration at
the end of the shift. Where active offboard filters are used, the size and
weight of the filter element is a
significant factor in filter selection and
overall system feasibility, as mine
personnel need to be capable of
removing the filter at the end of the shift
and transporting it to a central
regeneration station. Multiple DPFs may
be installed on a machine in place of a
single large filter in order to decrease
the size and weight of individual DPFs.
Engine malfunctions and effects on
DPF. Normally in mining, engine
malfunctions are indicated by
excessively smoky exhaust. That
indicator will not occur when a DPF
system is installed. Malfunctions such
as excessive soot emissions, intake air
restriction, fouled injector, and overfueling, may result in an abnormal rise
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On-equipment during operation.
in back pressure in systems that do not
spontaneously regenerate. Also, these
conditions could lead to abnormal
changes in back pressure in passive
systems because the malfunction may
raise exhaust temperatures causing the
excess soot to be burned off. These
malfunctions may be detected during
the usual 250-hour maintenance and
emissions checks conducted upstream
of the DPF using carbon monoxide (CO)
as an indicator. The other major filter
malfunction is excessive oil
consumption that is sometimes
associated with blue smoke that could
be masked by the performance of the
DPF. However, excessive oil
consumption leads to a rapid increase in
baseline backpressure due to ash
accumulation. Excessive oil
consumption can be detected if records
are kept on oil usage.
Detecting malfunctioning DPF. As
noted above, the DPF can be damaged
mainly by thermal events such as
thermal runaway. Shock, vibration, or
improper ‘‘canning’’ of the filter element
in the DPF can also lead to leaks around
the filter element. A Bacharach/Bosch
smoke spot test can be used to verify the
integrity of a DPF. Smoke spot numbers
below ‘‘1’’ indicate a good filter; smoke
numbers above ‘‘2’’ indicate that the
DPF may be cracked or leaking. Smoke
spot and CO tests during routine 250
hour preventative maintenance are good
diagnostic practices. Note that although
a smoke spot number above ‘‘2’’ may
indicate a cracked or leaking filter, such
a result does not necessarily mean the
filter has ‘‘failed’’ and is not functioning
adequately. In MSHA evaluations of
DPF performance at the Greens Creek
mine, filters that tested with smoke
numbers above ‘‘2’’ of 7 were still
shown to be over 90% effective in
capturing EC, based on subsequent
NIOSH 5040 analysis of the smoke spot
filters.
Low DPM-Emitting Engines. Through
its 2003 and 2004 compliance assistance
mine visits and a review of its nationwide inventory of diesel engines used in
underground M/NM mines, MSHA has
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determined that hundreds of low DPM
emission engines have been introduced
into underground M/NM mines in
recent years. MSHA notes that, for many
mines in the stone sector, use of low
emission engines has been one of the
primary means of achieving compliance
with the interim PEL.
EPA and European on-highway and
non-road engine emission standards
have forced engine manufacturers to
reduce both DPM and gaseous emissions
from their engines. Mine operators can
purchase newer design engines with
low DPM emissions in their new dieselpowered equipment as well as
retrofitting such engines in their older
equipment.
As noted earlier in this section of the
preamble, the amount of DPM reduction
that can be obtained by switching to low
DPM emitting engines depends on the
emission rate of the original engine
compared to the emission rate of the
replacement engine. For example, if the
original engine emits 1.0 gram of DPM
per horsepower per hour of operation,
and the replacement engine emits 0.2
grams of DPM per horsepower per hour
of operation, the engine replacement
would achieve an 80% reduction in
emitted DPM. Other benefits of newer
technology engines include better fuel
economy and more efficient
maintenance diagnostics. The improved
maintenance diagnostics associated
with electronic engine monitoring
systems enable lower overall equipment
operating costs as well as allowing mine
operators to better monitor their engines
and provide the appropriate
maintenance to keep exhaust emissions
as low as possible.
During the compliance assistance
visits to mines that had at least one
baseline DPM sample result exceeding
the interim DPM limit, MSHA observed
numerous new or nearly new pieces of
equipment powered by Original
Equipment Manufacturer (OEM)installed MSHA-Approved engines that
had very high DPM emissions. The
operators at these mines indicated that
they were unaware of the DPM
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emissions of the engines that were
supplied in the equipment they had just
purchased. They believed that by
specifying an MSHA-Approved engine,
they would be in full compliance with
the rule. While it is true that MSHAApproved engines satisfy the
requirements of § 57.5067, not all
MSHA-Approved engines are
necessarily low in DPM emissions. NonApproved EPA Tier 1 (for engines less
than 50 horsepower or 175 horsepower
and greater) and Tier 2 (for engines of
50 horsepower or greater, but less than
175 horsepower) engines are also
compliant with § 56.6067, but they have
lower DPM emissions. During the
compliance assistance visits, and in
subsequent discussions with the
Equipment Manufacturer’s Association
(EMA), MSHA emphasized the need for
modern low DPM emission engines to
be installed in new machines earmarked
for the underground mining industry.
Ventilation Upgrades. Several
commenters expressed the view that
ventilation system upgrades, though
potentially effective in principle, would
be infeasible to implement for many
mines. Specific problems that could
prevent mines from increasing
ventilation system capacity include
inherent mine design geometry and
configurations (drift size and shape),
space limitations, and other external
prohibitions, as well as economic
considerations.
MSHA acknowledges that ventilation
system upgrades may not be the most
cost effective DPM control for many
mines, and for others, ventilation
upgrades may be entirely impractical.
However, at many other mines, perhaps
the majority of mines affected by this
rule, ventilation improvements would
be an attractive DPM control option,
either implemented by itself or in
combination with other controls.
Indeed, MSHA observed during its
DPM compliance assistance visits that
ventilation upgrades have been
implemented at many mines in the
stone sector for DPM control, directly
contradicting the commenters’ assertion
that ventilation upgrades are infeasible.
Nearly every stone mine visited by
MSHA had completed, had begun, or
was planning to implement ventilation
system upgrades.
At many high-back room-and-pillar
stone mines, MSHA observed
ventilation systems that were
characterized by (1) inadequate main
fan capacity (or no main fan at all), (2)
ventilation control structures (air walls,
stoppings, curtains, regulators, air
doors, brattices, etc.) that are poorly
positioned, in poor condition, or
altogether absent, (3) free standing
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booster fans that are too few in number,
too small in capacity, and located
inappropriately, and (4) no auxiliary
ventilation for development ends
(working faces). At some mines, the
‘‘piston effect’’ of trucks traveling along
haul roads underground, along with
natural ventilation pressure, provide the
primary or only driving forces to move
air.
In naturally ventilated mines,
temperature-induced differences in air
density between the surface and
underground result in natural air flows
through mine openings at different
elevations. Warmer and lighter mine air
rises up out of a mine during the colder
winter months, which draws in cooler
and heavier air at lower elevation mine
openings. In the summer, cooler and
denser mine air flows out of lower
elevation openings, which draws
warmer less dense air into higher
elevation openings. Under the right
conditions, such air flows can be
significant, but they are usually
inadequate by themselves to dilute and
carry away DPM sufficiently to reduce
miners’ exposures to the interim limit.
The other principal shortcoming of
natural ventilation is the inherent lack
of a method of controlling air flow
quantity and direction. Ventilation air
flows can slow or stop when
temperature differences between the
surface and underground are small
(common in the spring and fall), and the
flow direction reverses between summer
and winter, and sometimes even
between morning and afternoon.
Mine operators normally supplement
natural ventilation with booster fans
underground. However, if overall air
flow is inadequate, as is usually the case
with naturally ventilated mines, and
when mine elevation differences or
surface and underground temperature
differences are small, booster fans are
largely ineffective.
The all too frequent result of these
deficiencies is a ventilation system that
is plagued by insufficient dilution of
airborne contaminants, short circuiting,
recirculation, and airflow direction and
volume that are not controllable by the
mine operator. These systems are barely
adequate (and sometimes inadequate)
for maintaining acceptable air quality
with respect to gaseous pollutants (CO,
CO2, NO, NO2, SO2, etc.), and are totally
inadequate for maintaining acceptable
concentrations of DPM. Mines
experiencing these problems could
benefit greatly from upgrading main,
booster, and/or auxiliary fans, along
with the construction and maintenance
of effective ventilation control
structures.
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MSHA believes that ventilation
upgrades alone, along with the normal
turnover of engines to newer, lowpolluting models, may be sufficient for
many stone mines to achieve
compliance with the interim DPM limit.
Consequently, MSHA has urged the
mining industry to utilize mechanical
ventilation to improve overall air flows
and to enable better control of
ventilating air.
Ventilation fan upgrades for the stone
mining sector are usually relatively
inexpensive due to the low mine
resistance associated with large
openings. In many of these mines, a
250,000 cfm air flow can be obtained at
less than 1 inch of water gage pressure.
This air flow can be provided by a 50
horsepower motor. The major cost in
these applications is usually
distribution of the air flow underground
to insure that adequate air quantities
reach the working faces rather than
short-circuiting to a return or
recirculating around free-standing
booster fans. Good air flow distribution
requires such practices as installing or
repairing ventilation control structures
(brattice line, air curtains, etc.) or
changes in mine design to incorporate
unmined pillars as air walls.
Deep multi-level metal mines have
entirely different geometries and
configurations from high-back roomand-pillar stone mines. They typically
require highly complex ventilation
systems to support mine development
and production. These systems are
professionally designed, they require
large capital investments in shafts,
raises, control structures, fans, and duct
work, and they are costly to maintain
and operate. At these mines, high
ventilation system costs provide a major
economic incentive to operators to
optimize system design and
performance, and therefore, there are
typically few if any feasible upgrades to
main ventilation system elements that
these mines haven’t already
implemented, or would have
implemented anyway, whether or not
the DPM rule existed. Accordingly, and
though it remains an option that might
be attractive in new development,
MSHA expects very few mines of this
type to implement major ventilation
system upgrades to achieve compliance
with this rule.
Despite the built-in incentives to
design and operate efficient ventilation
systems, however, MSHA has observed
aspects of ventilation system operation
at such mines that can be improved,
usually relating to auxiliary ventilation
in stopes. Auxiliary fans are sometimes
sized inappropriately for a given
application, being either too small (not
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enough air flow) or too large (causing
recirculation). Auxiliary fans are
sometimes poorly positioned, so that
they draw a mixture of fresh and
recirculated air into a stope. Auxiliary
fans are sometimes connected to
multiple branching ventilation ducts, so
that the air volume reaching a particular
stope face may be considerably less than
the fan is capable of delivering. Perhaps
most often, the ventilation duct is in
poor repair, was installed improperly, or
has been damaged by blasting or passing
equipment to the extent that the volume
of air reaching the face is only a tiny
fraction of that supplied by the fan.
MSHA believes that these and similar
problems exist at many mines, even if
the main ventilation system is well
designed and efficiently operated.
An example is the mine where NIOSH
conducted its Phase II Production Zone
study of DPFs. As noted earlier, several
auxiliary stope ventilation systems were
evaluated by MSHA during an extended
compliance assistance visit to this mine
in June 2004. In the six stopes for which
ventilation air flow measurements could
be obtained at both the auxiliary fan
location and at the end of the vent bag,
the average air flow at the fan location
was 24,400 cfm and the average flow at
the end of the vent bag was 5,100 cfm.
Auxiliary ventilation system leakage
was 89% in one stope and 85% in
another. Even in stopes where auxiliary
system leakage was relatively low,
significant recirculation was observed.
Optimized auxiliary ventilation
system performance alone, as one
commenter noted, will not necessarily
insure compliance with the DPM
interim limit. Auxiliary ventilation
systems simply direct air to a stope face
so that the DPM generated within the
stope can be diluted, transported back
to, and carried away by the main
ventilation air course. If this air is
already heavily contaminated with DPM
when it is directed into a stope, as could
happen at mines employing series or
cascading ventilation, its ability to
dilute newly-generated DPM is
diminished. In these situations, the
intake to the auxiliary system must be
sufficiently clean to achieve the desired
amount of dilution, requiring
implementation of effective DPM
controls upstream of the auxiliary
system intake. Such upstream controls
might include a variety of approaches,
such as DPM filters, low-polluting
engines, alternate fuels or fuel blends,
and various work practice controls, as
well as main ventilation system
upgrades at the few mines where they
might be feasible. Toward the return
end of a series or cascading ventilation
system, if the DPM concentration of the
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auxiliary system intake is still excessive,
other engineering control options would
include enclosed cabs with filtered
breathing air on the equipment that
operates within the stope, or remote
control operation of the equipment in
the stope to remove the operator from
the stope altogether.
Environmental Cabs With Filtered
Breathing Air. Cabs on mobile
equipment and control rooms or booths
for stationary installations, if provided
with filtered breathing air, can be highly
effective for reducing personal DPM
exposures. MSHA has determined that
environmental cabs can reduce operator
exposures to DPM by 50% to 80%. In
addition, such cabs and booths can
significantly reduce exposures to
harmful noise and dust, and they can
also improve equipment operator
comfort and productivity.
The majority of equipment used in
underground M/NM mining, especially
in stone mines, have suitable cabs
installed. However, MSHA has observed
that many cabs, due to poor
maintenance and operating practices,
fail to provide effective control of DPM
exposure. Typical problems are broken
windows, ineffective door seals,
inoperative AC systems and fans,
plugged or missing air filters, openings
into the cab where hoses or cables enter,
and lack of company policies requiring
doors and windows to be maintained in
the closed position during operations.
Some cab ventilation and filtration
systems are undersized for the volume
of air they should be moving. During
MSHA’s compliance assistance visits in
2003, MSHA observed numerous pieces
of equipment, especially face drills, that
were equipped with undersized cab air
filtration systems. Research has shown
that cab ventilation systems should be
sized to achieve approximately one-half
to one air change per minute in their
respective cabs. For example, a 100
cubic foot cab should be ventilated by
a system having the capacity to move 50
to 100 cubic feet per minute. Cabs
should also be sealed to obtain a
positive pressure greater than 0.2 inches
of water gage.
MSHA DPM-Related Compliance
Assistance. As noted earlier, MSHA has
engaged in extensive DPM-related
compliance assistance since the existing
rule was issued in 2001, and these
activities are continuing. Compliance
assistance has included seminars at
various locations throughout the
country, hands-on sampling training
workshops, the online Filter Selection
Guide, a compliance guide, a ‘‘single
source’’ internet Web site devoted to
underground M/NM DPM issues, DPM
baseline sampling at all mines affected
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by the rule, online listings of MSHAApproved diesel engines and DPF
efficiencies, the Estimator, and on-site
compliance assistance visits at dozens
of mines, among others.
MSHA continues to consult with the
M/NM Diesel Partnership (the
Partnership). The Partnership is
composed of NIOSH, industry trade
associations, and organized labor.
MSHA is not a member of the
Partnership due to its ongoing DPM
rulemaking activities. The primary
purpose of the Partnership is to identify
technically and economically feasible
controls to curtail particulate matter
emissions from existing and new dieselpowered vehicles in underground metal
and nonmetal mines.
MSHA’s diesel testing laboratory
located in Triadelphia, WV has been
active in evaluating many DPM control
technologies. An example is the
investigation to characterize NO2
emissions from catalyzed DPFs. As a
result of this work, MSHA provided
information to the mining community
on the effects of catalyzed DPF’s on NO2
production. MSHA’s laboratory
determined under steady state engine
operating conditions, that a heavily
platinum-catalyzed DPF would increase
the NO2 concentration measured in the
raw exhaust after the exhaust gas passed
through the DPF. The increase in NO2
was compared to the required gaseous
ventilation rate for the test engine
without the DPF installed. The
laboratory data showed that the gaseous
ventilation rate would increase with a
highly platinum-catalyzed DPF
installed. MSHA’s laboratory also tested
DPFs that were either specially
catalyzed with platinum (lower washcoat platinum content) or a base metal
wash-coat (no platinum used). The
results of the laboratory tests showed no
increase in the gaseous ventilation
quantity when compared to the quantity
without the DPFs installed. MSHA
provided the industry with a Program
Information Bulletin (PIB) P02–04,
‘‘Potential Health Hazard Caused By
Platinum-Based Catalyzed Diesel
Particulate Matter Exhaust Filters,’’
dated May 31, 2002. This PIB is located
on MSHA’s web page at the following
internet address: https://www.msha.gov/
regs/complian/PIB/2002/pib02–04.htm.
The PIB states that mine operators that
choose to use catalyzed DPFs that have
shown an increase in NO2 in the
laboratory need to ensure that the
machines installed with these filters
have adequate ventilation, and
recommends that personal monitoring
for NO2 should be performed.
MSHA also provides an updated list
on the internet of DPFs that have been
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evaluated by MSHA. The internet
address is: https://www.msha.gov/01–
995/Coal/DPM-FilterEfflist.pdf. This list
is divided into three tables. Table I
includes paper and synthetic filters,
mainly intended to be disposable. These
DPFs are only used when the exhaust
gas temperature is maintained to below
302°F, as is required in inby areas of
gassy mines. This is normally
accomplished by the use of an exhaust
gas heat exchanger. Temperature
sensors and backpressure sensors must
be used with these filters to protect the
DPF from exhaust gas temperatures that
would exceed 302 °F or backpressures
that would exceed the engine
manufactures allowable limit. Table II
lists ceramic and high temperature
disposable pleated element media DPFs
that do not increase the concentration of
NO2 in the exhaust. Table III lists the
DPFs that are platinum-catalyzed and
have been determined in the laboratory
to increase NO2 concentrations above
the test engine’s gaseous ventilation
rate.
MSHA’s laboratory has also
conducted limited tests on several
control technologies other than DPFs.
Evaluations have been conducted on an
Ecomax which consists of a series of
magnets installed on the fuel system
lines, Rentar, an in-line fuel catalyst
installed in the machine’s fuel line, and
the Fuel Preporator, a system for
removing collected air from the fuel
system design for better fuel
combustion. The test results of the
laboratory evaluations were
inconclusive in demonstrating
significant reductions in whole diesel
particulate, however the data did not
show any adverse effects on the raw
DPM exhaust emissions.
NIOSH also analyzed the Rentar and
Fuel Preporator for their EC reduction
potential. NIOSH’s results were
consistent with MSHA’s results, and
showed no significant EC reductions
and no adverse effects on the engine
emissions.
MSHA’s laboratory evaluated the
changes in engine exhaust emissions
when operating at high altitudes (greater
than 1000 feet in elevation). MSHA used
two electronic fuel injected engines for
the test, a Mercedes 904 and a Deutz
BF4M 1013FC. MSHA first conducted
field tests at engine laboratories located
at 4000 feet and 6700 feet. Next, MSHA
brought the two test engines to its
laboratory. Using an altitude simulator
setup, MSHA verified the accuracy of
the simulator and ran various tests to
evaluate the effects of altitude on the
gaseous emissions and DPM. This high
altitude work led to the development of
guidelines that MSHA is using for
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approving diesel engines under 30 CFR,
part 7, subpart E for engine operation
above 1000 feet.
MSHA received comments suggesting
that its compliance assistance visits at
various mine sites support the position
that the DPM rule, even at the 400TC µg/
m3 interim limit, is economically and
technologically infeasible. MSHA did
visit a number of mines that were not
in compliance with the interim DPM
limit to provide compliance assistance,
but at each such mine, the operator was
presented with recommendations for
utilizing feasible engineering and work
practice controls for attaining
compliance. MSHA determined that
these mines were out-of-compliance not
because it was infeasible for them to
attain compliance, but because the
respective mine operators had not yet
fully implemented all feasible controls
that were available to them.
MSHA’s compliance assistance work
at the Greens Creek mine included an
evaluation of DPM reductions obtained
using heavily platinum-catalyzed
ceramic DPFs that relied on passive
regeneration. The machines were
equipped with engines ranging from 300
to 475 horsepower. The results of this
testing showed that personal DPM
exposures for the subject equipment
operators (loaders and haulage trucks)
were reduced by 57% to 70% when the
DPFs were installed. The use of the
ceramic DPFs reduced the average
engine emissions by 96%.
The Greens Creek report also showed
that high DPM reductions (>90%)
occurred even when a ceramic filter was
compromised by cracking around the
edges. This cracking was determined to
be caused by a manufacturing defect
related to the ‘‘canning’’ process
(securing the ceramic filter in a stainless
steel ‘‘can’’ for installation on the
subject diesel equipment). Through
discussions with the manufacturer,
Greens Creek resolved the problem, and
DPFs delivered since then have
performed satisfactorily without any
cracking. In addition, the use of
environmental cabs reduced the DPM
concentrations (i.e., concentration
inside the cab versus outside the cab) by
75% when DPFs were used and 80%
when DPFs were not in use.
As expected, NO2 increases were
observed during these tests because the
mine operator was using heavily
platinum-catalyzed DPFs. However, the
increases were so small (about 1 ppm in
the downstream air flow compared to
the upstream air flow in the area where
a loader and two or three trucks were
operating) that it was unclear whether
the cause was data variability, slight
changes in ventilation rate, or the use of
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heavily platinum-catalyzed DPFs.
Greens Creek stated in its comments to
this rulemaking that a 1–2 ppm increase
in NO2 is experienced when highly
platinum-catalyzed DPFs are used, but
that this increase has been manageable
for the mine.
MSHA agrees that a highly platinumcatalyzed filter may increase NO2 levels
based on engine duty cycle and
ventilation. NO2 is formed from NO in
the engine’s exhaust in the presence of
the catalyst. This reaction occurs at
exhaust gas temperatures of
approximately 325°C. This temperature
is also the temperature at which the
platinum catalyst will allow for passive
regeneration. Manufacturers of
platinum-catalyzed DPFs have normally
wash-coated their filters with large
amounts of platinum to make sure that
the DPFs will regenerate. This large
concentration of platinum, in
combination with the relatively long
retention time of the exhaust gas in the
filter, results in the formation of NO2.
Manufacturers have been evaluating
wash-coat formulations containing less
platinum loading to lower the NO2
effects. Catalytic converters are also
wash-coated with platinum; however,
the loading used on catalytic converters
is lower than ceramic DPFs, and due to
faster movement of the exhaust gas
through the catalytic converter
compared to the ceramic filter, NO2
increases are minimal. One
manufacturer provides an exhaust gas
recirculation system (EGR) that reduces
both oxides of nitrogen (NOX) and DPM
when used in combination with a DPF.
Mine operators also have the option of
using DPFs that are not heavily washcoated with a platinum catalyst. One
manufacturer offers a lightly platinumcatalyzed DPF that is used in
conjunction with a platinum-cerium
fuel-borne catalyst (Fuel additive). This
system has a slightly higher passive
regeneration temperature requirement
than heavily platinum-catalyzed DPFs,
but it produces no excess NO2. Other
options which do not produce excess
NO2 include base metal catalyzed
passive regenerating DPFs, and various
on-board and off-board active
regenerating DPFs. As noted earlier, part
of the DPF selection process involves an
evaluation of potential NO2 problems
along with related ventilation issues.
Where NO2 exposures could be
problematic, MSHA recommends that
heavily platinum-catalyzed DPFs be
avoided.
Table VII–1 provides information in
the ‘‘Comments’’ column on the effects
of DPF catalysts on NO2 emissions.
MSHA has tested in their laboratory the
types of DPFs listed, and has posted on
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its website a list of the DPFs that can
cause NO2 increases from the engine
and those catalytic formulations that do
not significantly increase NO2.
MSHA is currently not aware of
problems with overexposure to NO2 at
mines using platinum-catalyzed DPFs
on a routine production basis, where the
overexposures are uniquely related to
the DPFs. One mine operator that had
been experiencing frequent
overexposures to NO2 noted that these
overexposures ceased after a major
ventilation upgrade, despite increased
use of heavily platinum-catalyzed DPFs.
PIB #02–04 alerted mine operators
that the platinum-catalyzed DPFs
identified on MSHA’s website could
increase NO2. MSHA continues to
advise mine operators to monitor for
any increases in ambient NO2
concentrations with the addition of
platinum-catalyzed DPFs to their
inventory.
When NIOSH’s Phase II study tests 2
and 3 were terminated prematurely due
to high NO2 levels, the overexposures
were determined to be due mainly to
insufficient ventilation. As discussed
previously, the average increase in NO2
from the use of platinum-catalyzed
DPFs in the test area was approximately
1 ppm, but brief 3–5 ppm spikes were
also observed. As stated above, mine
operators are advised to sample for NO2
when platinum wash-coated DPFs are
used to ensure miners are not
overexposed. Mine operators who use
platinum-catalyzed DPFs should
maintain ventilation systems that are
able to remove or dilute the NO2 to a
non-hazardous level, and they must be
aware of localized areas where NO2
could build up more quickly and create
a health hazard for exposed miners.
As discussed in the Greens Creek
report, the use of catalyzed DPFs at that
mine did not produce substantial
increases in NO2 levels. MSHA is
continuing to work with filter
manufacturers to evaluate catalytic
formulations on NO2 generation.
Stillwater mine DPM compliance. In
its comments addressing the 2003
NPRM, Stillwater Mining Company
(SMC) provided discussion and several
tables detailing its estimated DPMrelated compliance costs. In its April
2004 comments in response to the
February 20, 2004 limited reopening of
the public record on this rulemaking,
SMC provided further discussion and
another compliance cost summary table
which grouped cost elements into major
categories. These estimates totaled about
$114 to $117 million over a 10 year
period.
Using the Stillwater compliance cost
estimates and other information
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obtained by MSHA during visits to the
Stillwater mine, MSHA analyzed and
evaluated Stillwater’s estimated costs
and developed a compliance cost
estimate for this mine based on an
alternative DPM control strategy. This
analysis and evaluation is discussed
below, and a summary is provided in
Table VII–3. MSHA conducted this
analysis and evaluation to demonstrate
both to Stillwater and to other mines
having some of the same or similar
equipment, mine layouts, and operating
practices that their choice of control
strategy can significantly impact overall
compliance costs, and therefore, the
feasibility of compliance.
MSHA’s estimated yearly compliance
costs for this mine, which are based
largely on the itemized cost estimates
provided by Stillwater, are between
$1.24 million and $2.09 million per
year. The lower end of this range relates
to estimated compliance costs not
including a recent $9 million ventilation
upgrade. As discussed below, although
Stillwater included the cost of this
upgrade in its estimated DPM
compliance costs, MSHA believes this
cost item should not be considered
DPM-related, or is only partially
attributable to DPM compliance because
the ventilation system at this mine
required a major upgrade anyway,
independent of DPM issues. MSHA’s
$2.09 million yearly compliance cost
estimate includes the $9 million
ventilation upgrade.
Although Stillwater’s DPM-related
compliance costs will be significant,
they are not substantially different from
expectations based on MSHA’s 2001
REA. In the REA for the 2001 final DPM
rule, MSHA determined that annual
compliance costs would be about
$128,000 for an average underground
M/NM mine. However, Stillwater’s
mining operations are not representative
of an average mine. Its fleet of 350+
pieces of diesel equipment is many
times larger than the average mine’s.
MSHA’s estimated yearly DPM-related
compliance costs for large precious
metals mines included in the REA was
$659,987, based on a fleet size of 133
diesel vehicles. Stillwater’s fleet is
about 2.6 times larger than the 133
vehicle basis for this estimate. Thus,
yearly compliance costs of 2.6 ×
$659,987, or $1.72 million for Stillwater
would be consistent with the 2001
REA’s compliance cost estimate for a
precious metals mining operation of this
size.
If the cost of Stillwater’s recent
ventilation system upgrade is not
included as a DPM compliance cost,
which as noted below, is a reasonable
determination based on long-standing
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ventilation system deficiencies at this
mine, Stillwater’s estimated yearly
compliance cost would be $1.24
million. As noted in the preceding
paragraph, by way of comparison, an
estimated compliance cost of $1.72
million for a precious metals mine of
this size would be consistent with the
2001 REA. If, however, the entire
ventilation system upgrade is
considered DPM-related, MSHA’s
estimated yearly compliance cost of
$2.09 million for Stillwater would be
about 22% higher than expected, based
on the 2001 REA. If the entire
ventilation system upgrade is
considered DPM-related, but the annual
savings resulting from the associated
reduction in ventilation fan power
consumption is deducted from the
annualized cost of the upgrade, MSHA’s
estimated yearly compliance cost of
$1.57 million for Stillwater would be
about 9.5% less than expected, based on
the 2001 REA.
For MSHA’s analysis and evaluation,
Stillwater’s DPM compliance costs were
grouped into six major cost categories.
The analysis and evaluation of these six
major cost categories is discussed
below:
1. Ventilation. As noted above, a $9
million ventilation upgrade was
recently completed at the Stillwater
mine, and the cost of this upgrade was
included by Stillwater in its DPM
compliance cost estimate. However,
MSHA believes this upgrade would
have been necessary with or without a
DPM rule due to ongoing air quality
problems and plans for increased mine
development. Thus, this expenditure
should not be considered a DPM
compliance cost, or at most, only
partially a DPM compliance cost.
Total ventilation at the mine prior to
the upgrade was about 627,000 cfm,
corresponding to approximately 52 cfm/
actual utilized horsepower. After the
upgrade, total ventilation volume
increased to 840,000 cfm, which is
about 69 cfm/actual utilized
horsepower.
Most of Stillwater’s diesel equipment
has MSHA nameplate ventilation rates
between 50 and 70 cfm/horsepower.
These laboratory derived values indicate
the ventilation necessary to maintain
compliance with MSHA exposure limits
for CO, CO2, NO, and NO2. Taking into
account such practical in-mine factors
as varying equipment duty cycles,
imperfect mixing, use of DOCs, etc.,
acceptable air quality can sometimes be
attained at ventilation rates somewhat
less than the nameplate values.
However, other factors, including outof-tune engines, marginal auxiliary
ventilation system performance, on-shift
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blasting, and heavy concentrations of
diesel equipment in particular sections
of a mine can result in chronic localized
noncompliance with gaseous emission
limits.
For example, Stillwater has had a
persistent problem with NO2
overexposures for many years,
indicating inadequate ventilation. Per
company policy, whenever an NO2
monitor (carried by equipment
operators) exceeded 5 dpm at the
operator’s location, that operator was
removed to the surface. The mine
operator has frequently removed miners
to the surface for this reason over recent
years. Thus, the ventilation upgrade was
overdue, even without consideration for
DPM levels underground.
Other considerations also factored
into the decision to carry out the
ventilation upgrade, including planned
production tonnage increases, the need
to utilize trucks to haul ore up grade
from below the level of the shaft bottom,
an excessive number of booster fans
(sometimes competing with each other
for limited air), and the desire to
increase the number of ventilation
intakes into the mine (resulting in more
fresh air escape routes and lower intake
air velocities to improve miner comfort
and dust conditions). By any number of
measures, mine development had
overreached the old ventilation system.
The ventilation upgrade accomplished
all of the above objectives, and resulted
in a reduction of total fan power
consumption by 1,000 horsepower.
Even if this ventilation upgrade could
be entirely attributed to DPM
compliance, the cost must be
annualized over the expected 20+ year
life of the asset, so the yearly cost (using
a 7% discount rate) would be about
$850,000. This yearly cost is partially
offset by savings in electricity costs
resulting from the 1,000 horsepower
reduction in fan power consumption, so
the ventilation upgrade actually resulted
in a net annual cost to Stillwater of only
about $197,000 (1,000 hp × 24 hours/
day × 365 days/year × 0.745 kw-hr/hphr × 10¢/kw-hr = $652,620; $849,536 ¥
$652,620 = $196,916).
2. Diesel Engines and Engine
Upgrades. Only a portion of the expense
of new diesel engines and engine
upgrades should be considered a DPM
compliance cost. Diesel engines have a
finite life and need to be renewed and
replaced periodically. Some new
engines and engine upgrades would
have been necessary with or without a
DPM rule. Also, new, low-emission
engines enable improved operating
efficiencies due to lower fuel
consumption and better maintenance
diagnostics, resulting in significant
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operating cost savings that partially offset purchase costs.
Like the ventilation upgrade,
however, even if the total cost of
engines and engine upgrades was
attributable to DPM compliance, these
costs (estimated by Stillwater at $1.2
million) must be annualized over the
expected 10 year life of an engine,
resulting in a yearly cost of about
$171,000 (using a 7% discount rate).
3. Soot Traps, Filters, Passive DPFs.
The mine currently has fewer than 30
passive regeneration DPF systems and
only one passive/active regeneration
DPF system (fuel burner) in use, and
reports no operational problems at this
time, except one filter destroyed by a
failed turbo-charger.
In its comments to the 2003 NPRM,
Stillwater outlined a plan for utilizing a
combination of passive and active DPFs
to control DPM in its mine. Passive
filters would be used where equipment
duty cycles and corresponding exhaust
temperatures suggested the application
would be successful, and active filters
would be utilized on the remaining
equipment. Stillwater reports $160,000
in passive filter costs to date. Assuming
a filter life of two years, this results in
a yearly cost of about $88,500 (using a
7% discount rate).
4. Engine Test Equipment. The engine
test equipment has a 5-year life,
resulting in an annualized cost of about
$68,000 (using a 7% discount rate).
5. Emissions expenditure. The basis
for Stillwater’s ‘‘Emissions expenditure’’
line item cost of $43,000/month is
unclear. As noted above, the mine
currently has fewer than 30 passive
regeneration DPF systems and only one
active regeneration DPF system in use,
and reports no operational problems at
this time, except one filter destroyed by
a failed turbo-charger. Engine-related
emissions expenses are addressed in the
diesel engines, engine upgrades, and
engine test equipment line items above.
However, ‘‘emissions expenditures’’ of
$516,000 per year ($43,000 per month ×
12 months) are included as submitted
by Stillwater in MSHA’s estimated
compliance cost.
6. Active Regeneration Systems.
Based on Stillwater’s existing
knowledge base relating to equipment
duty cycles and exhaust temperatures,
their plan for controlling DPM
emissions included passive filters for
only a small percentage of the mines’
fleet: the large loaders and ore haulage
trucks. In contrast, about 200 vehicles
were expected to require active
regeneration DPF systems.
For costing the active systems,
Stillwater made the following
assumptions:
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32935
a. Regeneration of the DPFs would be
accomplished on-board the vehicles.
Vehicles equipped with DPFs would
travel from their normal work areas
(stopes, develop ends, haulageways,
etc.) to specially excavated regeneration
stations provided with the necessary
means of connecting the filters to power
and compressed air. Upon arrival at a
regeneration station, the filters would be
‘‘plugged in’’ to electrical power and
compressed air utilities to accomplish
regeneration.
b. In addition to including the costs
of filters and associated regeneration
equipment, Stillwater’s active DPF cost
estimates also included excavating the
regeneration stations and installing the
required electrical power and
compressed air.
c. To insure reasonable travel
distances to regeneration stations as
mine workings advance over time,
Stillwater’s cost estimate was developed
in the context of a 10-yr mine plan that
included the excavation of new
regeneration stations periodically over
the 10 years.
Stillwater’s total estimated costs for
active filter systems, regeneration
equipment, and regeneration stations
was about $104.4 million over the 10-yr
period of the mine plan. Of this total,
$100.8 million (96.6%) was for
excavation of the regeneration stations,
and $3.6 million was for active filter
systems and regeneration equipment.
Neither the number of active systems
required at Stillwater, nor the estimated
total cost of implementing active filters
as specified in Stillwater’s comments is
disputed by MSHA. However, MSHA
does not believe the particular plan
developed by Stillwater is the optimal
means of utilizing active DPM filters at
this mine. Various alternative
approaches for utilizing active filters
exist which would be far less costly.
Since excavating regeneration stations
accounted for over 96% of the total cost
of implementing Stillwater’s active filter
plan, alternatives that do not include
such excavation costs would have a
significant cost advantage over
Stillwater’s plan. It is somewhat curious
that Stillwater developed its active DPF
plan on the basis of this particular onboard active regeneration system,
despite the extraordinarily high cost of
excavating the regeneration stations,
and Stillwater’s prior experience with
premature failure of the on-board
heating elements built into the filters.
A lower cost alternative to Stillwater’s
approach utilizes an on-board fuel
burner system to regenerate filters. The
ArvinMeritor system has been on trial
at this mine since February 2004 with
excellent results. This system actively
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regenerates the filter media during
normal equipment operations, and does
not require the host vehicle to travel to
a regeneration station to regenerate its
filter.
Another less costly alternative would
be to utilize off-board regeneration
instead of on-board regeneration. In offboard regeneration, a dirty filter is
removed and replaced with a clean filter
at the beginning of each shift. During
shift change, the dirty filters are then
transported by the equipment operator
or a designated filter attendant to a
central regeneration station or stations.
Such stations could be a fraction of
the size of the regeneration stations
envisioned in Stillwater’s plan, because
they would only need to accommodate
the filters, not the host vehicles. Since
the host vehicles would not need to
travel to the regeneration stations, the
travel distance from normal work areas
to the regeneration stations would be
less important, greatly lessening the
need for frequent construction of new
regeneration stations as the workings
advance. It is very likely that such
stations could be co-located in existing
underground shops, unused muck bays,
unused parking areas, or other similar
areas.
Off-board regeneration might not be
practical on larger machines due to the
size of the filters. For larger machines
that are not suitable for passive
regenerating filters, the fuel burner
approach might be preferable. But many
of the machines targeted for active
filtration are quite small, having 40 to
80 horsepower engines. Active filters for
these engines are correspondingly small,
and could be easily and quickly
removed and replaced using quick
disconnect fittings.
Another lower cost option would be
to utilize disposable high-temperature
synthetic fabric filters, especially on
smaller, light duty equipment such as
pickups, boss buggies, and skid steers.
Depending on equipment utilization,
such filters might only need to be
replaced once or twice per week.
In Table VII–3, the line for active
filters shows the 10-year cost of
Stillwater’s plan for utilizing active
filters along with MSHA’s estimate of
the yearly cost of alternatives to
Stillwater’s plan. MSHA’s cost estimate
for this line item is based on Stillwater’s
estimated cost for active filter systems,
minus the cost of excavating
regenerations stations, or $3.6 million
over 10 years. Annualizing these active
filter costs over the two-year expected
life of these filters using a discount rate
of 7% results in a yearly cost of about
$398,000.
TABLE VII–3.—STILLWATER’S AND MSHA’S DPM COMPLIANCE COST ESTIMATES
Cost item
Stillwater’s cost estimate
MSHA cost estimate
MSHA comments
Mine Ventilation Upgrade ....
>$9 million .........................
$0 .......................................
This upgrade necessary with or without DPM rule to
address ongoing air quality problems and plans for
mine development.
Even if upgrade necessary for DPM compliance, this
capital cost annualized over expected 20+ year life
of the asset.
Annualized cost over expected 20+ year life of the
asset minus annual power cost savings.
Some engines/upgrades part of normal turnover of engines and not DPM compliance cost. Cost of engines/upgrades annualized over 10 year expected
engine life.
Cost of test equipment annualized over 5 year expected equipment life.
Cost of DPFs annualized over 2 year expected filter
life.
Cost element is unclear based on current filter use.
Less costly approaches for implementing active regeneration were overlooked. Approaches that do not require excavation of regeneration stations save
$100.8 million over 10 years. $3.6 million would still
be required for filters and regeneration equipment,
however, this expense would be incurred over 10
years.
$849,536/yr 1 .....................
$327,440/yr 1 .....................
Engine upgrades, other
misc. expenses.
>$1.2 million ......................
$170,853/yr 1 .....................
Test Equipment ...................
>$280,000 .........................
$68,289/yr 1 .......................
Soot traps, filters, passive
DPFs.
Emissions expenditure ........
Active DPF systems, regeneration equipment, and regeneration station excavation.
$160,000 ............................
$88,495/yr 1 .......................
$43,000/month ...................
$104.4 million over 10
years.
$516,000/yr 1 .....................
$398,226/yr 2 .....................
$104.4 million over 10
years for active DPFs,
plus $10–$13 million for
other costs over 10
years. Total cost $114–
$117 million over 10
years.
Annual cost of $1.24 to
$2.09 million.
$1.24 million if cost of ventilation upgrade is not included;.
$2.09 million if cost of ventilation upgrade is included;.
$1.57 million if cost of ventilation upgrade is included minus power cost
savings.
Grand Total ...............
Certain cost elements should not be considered DPM
compliance costs. However, even including ALL listed costs for ventilation, passive and active DPFs,
engines/engine upgrades, test equip, and emissions
expenditures, MSHA estimates total yearly cost for
DPM compliance will not exceed $2.09 million. Excluding ventilation, estimated total yearly cost is
$1.24 million. Including ventilation but considering
power cost savings, estimated total yearly cost is
$1.57 million. Estimated yearly compliance cost of
$1.72 million for a precious metals mine of this size
would be consistent with 2001 REA.
Notes:
1 Cost estimate based on commenter’s estimated cost, annualized over the expected life of the item using a 7% discount rate. The
annualization factor for a capital expenditure is 9.4% for 20 years, 14.2% for 10 years, 24.4% for 5 years, and 55.3% for 2 years.
2 Cost estimate based on commenter’s estimated cost for active systems minus the cost of excavating regeneration stations, annualized over
the expected life of the active systems.
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Federal Register / Vol. 70, No. 107 / Monday, June 6, 2005 / Rules and Regulations
Kerford Limestone DPM compliance.
Kerford Limestone reported the results
of a consultant’s study that indicated
compliance with the DPM limit for that
mine would cost $348,000 for engine
improvements, $1.15 million for
ventilation upgrades, and $25,500 to
$38,500 per year for DPFs. They
reported investing $975,000 to date
toward DPM compliance.
Kerford’s engine costs of $348,000,
when annualized over 10 years at a
discount rate of 7%, results in a yearly
cost of about $49,500. The $1.15 million
ventilation cost, when annualized at the
same discount over the expected 20+
year life of this asset, results in a yearly
cost of about $108,600. When these two
yearly costs are added to the maximum
estimated annual DPF cost of $38,500,
the total yearly cost for Kerford is about
$196,600.
Without commenting specifically on
the reasonableness of Kerford’s itemized
cost estimates or whether the overall
DPM control strategy proposed by its
consultant was optimized for this mine,
MSHA notes that Kerford’s self-reported
total yearly compliance cost of about
$196,000 is not excessive for an
underground stone mine in its size
category. By way of comparison, a
yearly compliance cost of over $300,000
for a stone mine of this size would be
consistent with MSHA’s REA for the
existing 2001 final rule.
MSHA’s REA for the existing 2001
final rule estimated compliance costs for
a medium sized (20 to 500 employees)
stone mine to be $150,738. However,
this estimate was based on a fleet size
of 9.5 pieces of production equipment
for this industry sector and mine size
category. Kerford operates 19 pieces of
production equipment. Adjusting the
REA estimate of $150,738 for the larger
fleet size at Kerford results in an
estimated yearly compliance cost of
$301,476. Thus, Kerford’s estimated
$196,600 yearly compliance cost is only
about 65% of the level that would be
expected for an underground stone mine
of this size, based on the 2001 REA. The
cost is virtually unchanged in the REA
supporting this final rule.
It was suggested by a commenter that
MSHA underestimated Kerford
Limestone’s compliance costs by over
$1 million, and it was further suggested
that this underestimate, if extrapolated
to the entire underground stone mining
industry, resulted in industry-wide
compliance costs exceeding $100
million. However, Kerford Limestone’s
yearly compliance costs, using its own
cost estimates, are substantially less
than expected, based on the 2001 REA
for a medium sized underground stone
mine.
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Bio-Diesel tests at Carmeuse Black
River and Maysville mines. Commenters
stated that in-mine tests with bio-diesel
fuel produced measurable reductions in
ambient DPM concentrations, but did
not bring the subject mine into
compliance. These comments refer to
MSHA’s compliance assistance work at
the Carmeuse Black River and Maysville
stone mines in Kentucky. At both
mines, the use of bio-diesel fuel
produced reductions in DPM. The
recycled vegetable oil (RVO) with a 50%
blend of bio-diesel to standard diesel
fuel showed a 69% reduction in DPM,
based on TC, for the area samples at the
Maysville mine. Personal samples
collected at the Black River Mine
showed a 44% reduction in DPM with
RVO at a 35% blend of bio-diesel to
standard diesel fuel. The Virgin Soy Oil
(VSO) mixtures showed reductions, but
they were not as effective as the RVO at
similar blends.
The Maysville mine was in
compliance with the interim limit based
on the baseline samples and the samples
taken with bio-diesel. In contrast, the
Black River Mine was not in compliance
with the interim limit based on the
samples taken, even with the reduction
in DPM using bio-diesel. One main
difference between the two mines was
that the Maysville mine had
significantly more ventilation than
Black River. This result indicates that
the Black River mine will have to
implement additional DPM controls to
come into compliance, such as
ventilation upgrades, cleaner engines, or
DPFs.
These commenters did not dispute the
DPM reductions obtained. However,
they indicated the following: That Deutz
Corporation’s Technical Circular does
not approve the use of bio-diesel blends
above 20%; that a 50% bio-diesel fuel
presented insurmountable equipment
problems; and that the cost of bio-diesel
has increased significantly, adversely
impacting the feasibility potential of the
20% mixture.
MSHA reviewed Deutz’s Technical
Circular (0199–3005en), and discussed
this issue with Deutz. The Technical
Circular provides a general statement
that bio-diesel fuel is approved for
Deutz brand engines. The Technical
Circular does not mention any
limitation on the use of bio-diesel above
a certain percentage blend. Deutz
requires that all fuels used in their
¨
engines meet Deutsches Institute fur
Normung e.V. (DIN) specifications
(German National Standards). The Deutz
Technical Circular provides the DIN
specifications for bio-diesel fuel.
Comments regarding equipment
problems relate to reports of bio-diesel
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32937
fuel causing clogging of fuel filters,
resulting in excessive equipment
downtime. One commenter expressed
concern that Tier 2 engines used fuel
filtering systems that would not be
compatible with bio-diesel. MSHA
understands that engine manufacturers
are working with the filter
manufacturers to provide the best
filtration for all engines. MSHA is not
aware of any unique changes for EPA
Tier 2 engines as related to fuel filtering
systems or for utilizing bio-diesel fuel.
As the engine technology continues to
improve, especially in the area of the
fuel system components, better fuel
filtration systems will be utilized by the
engine manufacturers.
There are frequent references in the
technical literature to bio-diesel fuels
initially cleaning old sediments out of
fuel lines, thereby causing fuel filters to
clog. It follows that fuel filters should be
changed more frequently when biodiesel is first used in a fuel system.
However, the commenter suggests an
entirely different type of incompatibility
that is not limited to the transition
period when bio-diesel is first used.
This may or may not be a unique
situation that may take additional work
to resolve. The mine may have to install
an additional by-pass filtering system on
the machine to allow the operator to
switch to another set of fuel filters
instead of shutting down production if
a fuel filter clogs.
MSHA is not aware of long term filter
clogging with the use of bio-diesel fuel.
However, through the NIOSH ListServer, mine operators have the
opportunity to share experiences like
the filter clogging problem with the
mining community, and possibly
receive a solution. A mine operator may
use the List-Server to ask others in the
mining community if their problem has
been observed in other situations.
Interested parties can respond, thus
sharing experiences and solutions in a
timely manner. The List-Server was
established by the diesel team at
NIOSH, Pittsburgh in response to the
expressed and obvious need for a means
to disseminate and share information
and experiences concerning the
application of available technologies for
the reduction of miner exposures to
DPM and gaseous emissions in
underground mines.
Regarding the cost of bio-diesel,
MSHA acknowledges that users pay a
premium for bio-diesel over standard
diesel fuel. The cost for bio-diesel can
vary based on such factors as market
price swings in the cost of feed-stocks,
state tax incentives, proximity to
production facilities, etc., but normally,
where bio-diesel is available, the
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premium is about one cent per gallon
per percent bio-diesel in the fuel blend.
At higher percentage bio-diesel blends,
this premium can result in significantly
higher overall fuel costs for the enduser. Depending on mine-specific
factors, however, use of bio-diesel may
be a cost-effective DPM control option,
either used by itself or in conjunction
with other controls. Since the rule is
performance oriented, the mine operator
is free to choose the means of
compliance.
Based on these results and other data,
MSHA’s believes that bio-diesel is a
feasible DPM control. In the case of the
Black River mine, bio-diesel would have
to be used in combination with other
controls for the mine to achieve
compliance, or the mine operator may
choose to abandon bio-diesel altogether
and rely entirely on other controls for
attaining compliance. MSHA disagrees
with the commenters’ assertion that a
50% bio-diesel blend presents
‘‘insurmountable equipment problems.’’
Bio-diesel is recognized by the EPA as
an alternative clean fuel, engine
manufacturers do not recommend
against its use, and clogging can be
prevented by the use of by-pass filtering
systems.
Water Emulsion Fuel: As discussed
under the MSHA compliance assistance
activities, we conducted tests at four
mines to evaluate water emulsion fuel.
These tests included a test at a small
clay mine that used older technology
engines, two single level limestone
mines that used clean burning engines,
and one multilevel limestone mine that
used clean burning engines. Summer
(20% water) and winter (10% water)
blends of fuel were tested at two mines.
Only summer blends of fuel were tested
at the other two mines. MSHA evaluated
the reduction in total mine DPM
emissions by taking measurements at
the mine exhaust openings, with and
without the water emulsion fuel in use,
and comparing these to similarly made
measurements when standard No. 2
diesel fuel was used. Table VII–4
summarizes the reductions in emissions
measured for the tests.
For clean burning engines the
reduction in DPM emissions (as EC)
ranged from 63 to 81 percent. For older
engines the reduction in DPM emissions
(as EC) was approximately 49 percent.
Personal exposures were also reduced,
however, this reduction was more
variable than the reduction in engine
emissions. This variability was
attributed to the use of cabs, location in
the mine and the specific ventilation
rates at the work area in the mine.
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an integrated DPM control strategy for
their mines. For example, in stone
mines where haulage trucks transport
Percent re- Percent re- broken stone out of the mine to a surface
duction in
duction in crusher, and where the truck drivers are
Mine
EC
EC
protected by effective environmental
(winter
(summer
cabs with filtered breathing air, MSHA
blend)
blend)
recommends that the main ramp used
Clay .......................
49 by the haulage trucks to travel out of the
Limestone .............
77
81 mine be maintained as an exhaust air
Limestone .............
63
73 course. Typically, the combined
Multilevel Limehorsepower of the production loader
stone .................
80 and haulage trucks at a stone mine
exceeds the horsepower of all other
For each mine test, equipment
equipment combined. When haulage
operators reported a noticeable loss of
trucks travel loaded upgrade out of the
horsepower. However, this horsepower
mine, they generate significant amounts
loss, even in the multilevel limestone
of DPM. If the ramp used by these trucks
mine, did not adversely effect
is maintained as an intake air course,
production. In fact, during several of the the fresh air supply for the entire mine
mine tests, production was significantly can become contaminated. Maintaining
above normal. The water emulsion fuel
this ramp as an exhaust air course and
was favorably received by the
requiring the loaded trucks to haul up
employees. Workers reported that
this ramp as an administrative control
visibility improved. The water emulsion enables the mine operator to provide
fuel has the same per gallon cost as No.
better ventilation air quality along the
2 diesel fuel. Several operators reported face line. Depending on mine layout and
as much as a 20 percent increase in fuel ventilation, it may be possible to
usage to compensate for the power loss. maintain all ramps traveled by the
During the water emulsion fuel tests,
haulage trucks as exhaust air courses. It
a potential operating problem was
is especially important, however, that
observed when the fuel was used in
the ramps used for upgrade loaded
Deutz engines. Simply put, some
haulage be maintained as exhaust air
engines would not run. The source of
courses. This combination of
this problem was traced by the engine
engineering (cabs and ventilation) and
and fuel manufacturers to a high
administrative controls (loaded trucks
efficiency water separator in the engine
haul up the ramps used as exhaust air
fuel line. The engine and fuel
course) particularly benefits powder
manufacturers have indicated that the
crew workers who are required to work
problem can be corrected by replacing
most of their shift outside of a protective
the standard high efficiency water
cab.
separator with a less efficient unit.
Some commenters stated that the
We believe that the use of water
industry has exhausted the ‘‘easy’’
emulsion fuels provides a significant
methods of DPM control, and reducing
reduction in diesel engine emissions
DPM to lower limits would be
over a broad range of applications.
prohibitively expensive. MSHA is not
Currently the biggest impediment to the entirely certain what is meant by ‘‘easy’’
use of the emulsified fuel is
methods, but suspects the commenter
distribution. The manufacturer is
was referring to DPM controls other
making efforts to make the fuel more
than major ventilation upgrades (new
widely available.
main fans, new ventilation shafts, etc.)
MSHA has not tested the fuel at high
and DPFs, which are either more costly
altitude mines (above 5000 feet). At
than other options, or are perceived as
these elevations there are potential
more costly. At some mines, ‘‘easy’’
problems due to additional horsepower
could also mean ‘‘familiar,’’ indicating
loss, steep grades and low winter
the methods and strategies with which
temperatures. MSHA is working with
these mine operators have had actual
the fuel manufacturer and mining
first-hand experience. Based on this
industry to evaluate these concerns.
meaning, easy upgrades appear to be:
Combining DPM Controls Into An
Ventilation fans (main or booster),
Overall Strategy. The DPM rule allows
airflow distribution systems,
mine operators flexibility in choosing
environmental cabs, modern engines
engineering and administrative controls and alternate fuels.
that are appropriate for site-specific
By either definition, MSHA believes
conditions and operating practices.
that only a small portion of the industry
During its compliance assistance visits,
has exhausted these control methods.
MSHA urged mine operators to combine For example, based on compliance
various engineering and administrative
assistance mine visits, baseline
controls, including work practices, into
sampling results, and other data, MSHA
TABLE VII–4.—EMISSION REDUCTIONS
FOR WATER EMULSION FUEL TESTS
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has observed that many mines have not
yet implemented relatively low cost
ventilation upgrades, and that at most
mines that have initiated such
programs, not all necessary upgrades
have been completed.
Another example involves
environmental cabs with filtered
breathing air. As noted above, even
though most major pieces of production
equipment in stone mines are provided
with cabs, the corresponding health
benefits are seldom fully realized due to
open or broken windows, company
policies that permit equipment to be
operated with its doors open,
inoperative or poorly maintained AC
systems and cab pressurizing fans,
damaged door seal gaskets, etc.
A final example relates to the failure
to employ effective work practices such
as utilizing return air courses as truck
haulage roads when the truck drivers
are protected by environmental cabs
with filtered breathing air.
MSHA determined that compliance
costs were economically feasible for the
M/NM mining industry. In the REA for
the 2001 final DPM rule, MSHA
determined that annual compliance
costs would be about $128,000 for an
average underground M/NM mine.
Some mines, in particular mine size and
commodity groups, because of mining
methods used, equipment deployments,
etc., would be expected to incur higher
than average compliance costs. For
example, the REA estimated yearly
compliance costs for large precious
metals mines to be $660,000. Based on
its compliance assistance mine visits,
baseline sampling results, and other
data, MSHA believes that most mines
have expended far less than the
expected $128,000 yearly for DPM
compliance. Though expenditures will
undoubtedly need to rise in the future
as the familiar and less costly DPM
control methods are exhausted, they are
not expected to exceed levels previously
determined by MSHA to be
economically feasible.
C. Economic Feasibility
MSHA has determined that a PEL of
308 micrograms per cubic meter of air
(308EC µg/m3) is economically feasible
for the M/NM mining industry.
Economic feasibility does not guarantee
the continued viability of individual
employers, but instead, considers the
industry in its entirety. It would not be
inconsistent with the Mine Act to have
a company which turned a profit by
lagging behind the rest of an industry in
providing for the health and safety of its
workers to consequently find itself
financially unable to comply with a new
standard; See United Steelworkers of
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America v. Marshall, 647 F.2d 1189,
1265 (1980). Although it was not
Congress’ intent to protect workers by
putting their employers out of business,
the increase in production costs or the
decrease in profits would not be
sufficient to strike down a standard. See
Industrial Union Dep’t., 499 F.2d at 477.
On the contrary, a standard would not
be considered economically feasible if
an entire industry’s competitive
structure were threatened. Id. at 478;
See also, AISI–II, 939 F.2d 975, 980 (DC
Cir. 1991); United Steelworkers, 647
F.2d at 1264–65; AISI–I, 577 F.2d 825,
835–36 (1978). This would be of
particular concern in the case of foreign
competition, if American companies
were unable to compete with imports or
substitute products. The cost to
government and the public, adequacy of
supply, questions of employment, and
utilization of energy may all be
considered when analyzing feasibility.
MSHA has also determined that there
will be a small cost savings in economic
impact on the mining industry under
this final rule, because the requirements
for meeting the PEL are similar to those
in the existing DPM enforcement policy
for the 2001 DPM standard. Specifically,
MSHA will continue to require mine
operators to establish, use and maintain
all feasible engineering and
administrative control methods to
reduce a miner’s exposure to the PEL.
The final rule affords mine operators the
flexibility to choose either engineering
or administrative controls, or a
combination of controls to reduce a
miner’s exposure. In the event that
controls do not reduce a miner’s
exposure to the PEL, are not feasible, or
do not produce significant reductions in
DPM exposures, the operator must use
and maintain controls to reduce the
miner’s exposure to as low as feasible
and supplement controls with
respiratory protection. Mine operators
must establish a respiratory protection
program when controls are infeasible. If
MSHA confirms that mine operators
have met all of the abovementioned
requirements for addressing a miner’s
overexposure, and the miner’s exposure
continues to exceed the PEL (not
counting respirators), MSHA will not
issue a citation for an overexposure.
Instead, MSHA will continue to monitor
the circumstances leading to the miner’s
overexposure, and as controls become
feasible, MSHA will require the mine
operator to install and maintain them to
reduce the miner’s exposure to the PEL.
MSHA believes that it has established
in this final rulemaking that the new
interim PEL is comparable to the TC
interim concentration limit. Therefore,
in determining the economic feasibility
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32939
of engineering and administrative
controls that the M/NM underground
industry will have to use under this
final rule, MSHA evaluated the cost of
controls that are used to comply with
the existing DPM TC interim
concentration limit to that of the newly
promulgated EC interim PEL. These
controls include DPFs, ventilation
upgrades, oxidation catalytic converters,
alternative fuels, fuel additives,
enclosures such as cabs and booths,
improved maintenance procedures,
newer engines, various work practices
and administrative controls. MSHA’s
evaluation includes costs of retrofitting
existing diesel-powered equipment and
regeneration of DPFs.
On the basis of evidence in the
rulemaking record, including MSHA’s
current enforcement experience, MSHA
has determined that this final rule
results in a cost savings of $3,634 per
year, primarily due to MSHA’s
determination to delete the DPM control
plan.
In highly unusual circumstances
where the use of further controls may
not be economically viable, the standard
provides for a hierarchy of control
strategy that allows specifically for the
cost impact to be considered on a caseby-case basis. MSHA’s DPM
enforcement policy, therefore, takes into
account the financial hardship on an
individualized basis which MSHA
believes effectively accommodates mine
operator’s economic concerns,
particularly those of small mine
operators.
Whether controls are feasible for
individual mine operators is based in
part upon legal guidance from decisions
of the independent Federal Mine Safety
and Health Review Commission
(Commission) involving enforcement of
MSHA’s noise standards for M/NM
mines, 30 CFR 56.5–50 (revised and
recodified at 30 CFR 62.130). According
to the Commission, a control is feasible
when it: (1) Reduces exposure; (2) is
economically achievable; and (3) is
technologically achievable. See
Secretary of Labor v. A. H. Smith, 6
FMSHRC 199, 201–02 (1984); Secretary
of Labor v. Callanan Industries, Inc., 5
FMSHRC 1900, 1907–09 (1983).
In determining the economic
feasibility of an engineering control, the
Commission has ruled that MSHA must
assess whether the costs of the control
are disproportionate to the ‘‘expected
benefits,’’ and whether the costs are so
great that it is irrational to require
implementation of the control to
achieve those results. The Commission
has expressly stated that cost-benefit
analysis is unnecessary to determine
whether a control is required.
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Consistent with Commission case law,
MSHA considers three factors in
determining whether engineering
controls are feasible at a particular
mine: (1) The nature and extent of the
overexposure; (2) the demonstrated
effectiveness of available technology;
and (3) whether the committed
resources are wholly out of proportion
to the expected results. A violation
under the final standard will entail an
agency determination that a miner was
overexposed, that controls are feasible,
and that the mine operator failed to
install or maintain such controls.
According to the Commission, an
engineering control may be feasible
even though it fails to reduce exposure
to permissible levels contained in the
standard, as long as there is a significant
reduction in a miner’s exposure. Todilto
Exploration and Development
Corporation v. Secretary of Labor, 5
FMSHRC 1894, 1897 (1983).
MSHA will consistently utilize its
longstanding enforcement procedures
under its other exposure-based
standards at M/NM mines. As a result,
MSHA will consider the total cost of the
control or combination of controls
relative to the expected benefits from
implementation of the control or
combination of controls when
determining whether the costs are
wholly out of proportion to results. If
controls are capable of achieving a 25%
reduction, MSHA will evaluate the cost
of controls and determine whether their
costs would be a rational expenditure to
achieve the expected results.
MSHA emphasizes that the concept of
‘‘a combination of controls’’ is not new
to the mining industry. It is MSHA’s
consistent practice not to cost controls
individually, but rather, combine their
expected results to determine if the 25%
significant reduction criteria, as
discussed earlier in this section, can be
satisfied.
MSHA heavily weighs the potential
benefits to miners’ health when
considering economic feasibility and
does not conclude economic
infeasibility merely because controls are
expensive. Mine operators have the
responsibility for demonstrating to
MSHA that technologically feasible
controls are so costly as to result in a
significant economic hardship.
In situations where MSHA finds that
the mine operator has not installed all
feasible controls, MSHA will issue a
citation and establish a reasonable
abatement date. Based on a mine’s
technological or economic
circumstances, the standard gives
MSHA the flexibility to extend the
period within which a violation must be
corrected. If a particular mine operator
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is cited for violating the DPM PEL, but
that operator believes that the standard
is technologically or economically
infeasible for that operation, the
operator ultimately can challenge the
citation in an enforcement proceeding
before the independent Commission.
MSHA found that most of the
practical and effective DPM controls
that are available, such as DPFs,
enclosed cabs with filtered breathing
air, alternative diesel fuels, and lowemission engines, will achieve at least a
25% reduction in DPM exposure.
Though this final rule affords each mine
operator the flexibility to select the DPM
control or combination of controls that
are appropriate to their site-specific
conditions, MSHA believes that the
most cost effective DPM controls are
DPF systems. MSHA believes that there
are a number of available DPFs that do
not increase production of NO2.
MSHA estimates that DPFs for the M/
NM underground mining industry range
in cost from $5,000 to $12,000 per filter.
This range of cost is consistent with the
reported DPF costs from the NIOSH
Phase I Study. A typical example is a
15″ x 15″ Engelhard DPX platinumcatalyzed DPF used on 475 horsepower
haulage trucks at a multilevel metal
mine in Alaska that costs $8,700.
The average life expectancy of a DPF
is approximately 8,000 hours. Some
commenters, however, have reported
life expectancies of between 2,000 and
4,000 hours, while some other
commenters have reported life
expectancies for longer than 8,000
hours. However, in most of these cases
the shortened DPF life was due to a
malfunction of another piece of
equipment, installation problems or a
manufacturer’s defect, depending on the
type of DPF selected by an operator.
MSHA’s 8,000 hour estimate is based on
an operation and maintenance guide
prepared by DCL Incorporated and two
technical papers given at the Mining
Diesel Emission Conference in Toronto,
Canada, November 1999. (See MSHA’s
REA for 2001 final rule.) Support for
this estimate is provided by NIOSH in
its publication titled ‘‘Review
Technology Available to the
Underground Mining Industry for
Control of Diesel Emissions’’ (George H.
Schnakenberg, PhD, Information
Circular 9462, 2002) which reports that
average ceramic DPF service life at
Agrium’s Canadian potash mines is 5
years. This publication also references
reports of a few Engelhard DPFs that
have been in service 10 years.
MSHA believes that the requirements
for engineering and administrative
controls clearly meet the feasibility
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requirements of the Mine Act, its
legislative history and related case law.
The trends in DPM control technology
development to date, especially DPFs,
indicate that manufacturers are creating
more innovative designs. MSHA
believes that more cost effective control
methods are on the horizon. This
reasoning is supported by a recently
published EPA final rule for the control
of emissions from nonroad diesel
engines. The ‘‘Clean Air Nonroad
Diesel—Final Rule’’ (Control of
Emissions of Air Pollution from
Nonroad Diesel Engines and Fuel, 69 FR
38958 (2004)) sets emission standards
for airborne contaminants, including
DPM, for all diesel engine horsepower
ranges. For engines up to 750
horsepower, the requirements will be
phased in from 2008 through 2014. For
engines above 750 horsepower, the final
compliance date is extended to 2015.
EPA’s Clean Air Nonroad Diesel Rule is
a comprehensive national program to
reduce emissions from future non-road
diesel engines used in industries such
as construction, agriculture and mining.
To meet these emission standards,
engine manufacturers will produce new
engines with advanced emission-control
technologies similar to catalytic
technologies used in passenger cars.
Exhaust emissions from these engines
will decrease by more than 90%.
Because the emission-control devices
can be damaged by sulfur, the EPA is
also adopting a limit to decrease the
allowable level of sulfur in nonroad
diesel fuel by more than 99% from
current levels (from approximately
3,000 parts per million [ppm] now to 15
ppm in 2010). This will be consistent
with the on-highway fuel sulfur
requirements. New engine standards
take effect, based on engine horsepower,
starting in 2008. Both the EPA and the
diesel engine manufacturers agree that
clean engine technology alone cannot
achieve EPA’s newly mandated
emission limits; manufacturers will also
have to use advanced technology
options such as DPFs.
MSHA believes DPFs are currently
commercially available for any engine,
application, or duty cycle used in
underground M/NM mining. These new
EPA rules, however, will undoubtedly
be technology forcing and result in an
increase in the variety, features, and
capabilities of DPFs from which mine
operators may choose, as well as lower
the cost of DPFs and promote other
technological innovation in this field.
In spite of these trends in new
technology, MSHA recognizes that, in a
few cases, individual mine operators,
particularly small operators, may have
economic difficulty in achieving full
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compliance with the interim limit
immediately because of a lack of
financial resources to purchase and
install engineering controls. MSHA’s
revised enforcement strategy is designed
to accommodate this problem. Under
this enforcement strategy, MSHA allows
mine operators with feasibility issues
the necessary time to reduce exposures
to the interim PEL.
MSHA also has demonstrated that the
effective date for this final rule does not
pose an economic burden for
underground M/NM mine operators. As
stated earlier, the EC surrogate standard
is comparable to the existing TC
surrogate standard which has been in
effect since July 2002, and has been
enforced by MSHA since July 20, 2003.
Consequently, MSHA cannot justify
affording mine operators additional time
to comply with an exposure limit
currently enforced. MSHA believes that
the startup date is justified by the
rulemaking record and the mining
industry’s present capability of
complying with the existing interim
limit.
Moreover, MSHA has afforded the
underground M/NM mining industry
additional consideration in relieving the
financial impact of this final rule by
delaying the period of time that was
allowed for compliance with the 2001
comparable TC concentration limit. In
response to concerns raised by the
mining industry and the terms of the
DPM settlement agreement, MSHA
allowed as much as 21⁄2 years for a DPM
compliance phase-in strategy.
Specifically, on March 15, 2001,
MSHA published a notice delaying the
effective date of the final DPM rule of
January 19, 2001, (66 FR 5706) until
May 21, 2001 (66 FR 15032). By notice
of May 21, 2001, (66 FR 27863), MSHA
delayed the final rule another 45 days,
until July 5, 2001. Furthermore, by
notice of July 5, 2001, (67 FR 9180),
MSHA delayed § 57.5066(b),
Maintenance standards, relating to
‘‘tagging’’ requirements. MSHA also
clarified that the interim concentration
limit at § 57.5060(a) and its related
provisions in the final rule would not
apply until after July 19, 2002, pursuant
to its original effective date. By notice
of July 18, 2002, MSHA stayed the
effectiveness of: § 57.5060(d), permitting
miners to work in areas where DPM
exceeds the applicable concentration
limit with advance approval from the
Secretary; § 57.5060(e), prohibiting the
use of PPE to comply with the
concentration limits; § 57.5060(f),
prohibiting the use of administrative
controls to comply with the
concentration limits; and, § 57.5062,
addressing the DPM control plan. These
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provisions were stayed pending
completion of this final rule.
Finally, in the DPM settlement
agreement, MSHA agreed to enforce:
§ 57.5060(a), addressing the interim
concentration of 400 micrograms of TC
per cubic meter of air; § 57.5061,
addressing compliance determinations;
§ 57.5070, addressing miner training;
and § 57.5071, addressing
environmental monitoring. However, to
further assist the mining industry in
instituting engineering controls, MSHA
gave the mining industry an additional
year, from July 20, 2002, until July 20,
2003, to begin to develop a written
strategy of how they intended to comply
with the interim DPM concentration
limit. Operators with DPM levels above
the concentration limit were to begin to
order and install controls to reduce
miners’ exposures by July 20, 2003.
Concurrently, MSHA provided
comprehensive compliance assistance to
M/NM underground operators. MSHA
retained the discretion to take
appropriate enforcement actions against
operators who refuse either to cooperate
in good faith with MSHA’s compliance
assistance, or to take good-faith steps to
develop and implement a written
compliance strategy for their mines.
Mine operators had the obligation to
develop a strategy to control DPM
emissions and order engineering
controls. MSHA began enforcing the
interim limit at M/NM underground
mines on July 20, 2003, under the terms
of the settlement agreement.
MSHA received a number of
comments in response to its proposed
economic feasibility discussion. Several
commenters wanted MSHA to define
‘‘economic feasibility.’’ They believe
that controls should be considered
economically feasible if implementation
would not bankrupt the company or
force the mine to close. They also
believe that MSHA’s 2003 NPRM did
not indicate how MSHA will enforce the
new language and wanted access to
records of feasibility determinations
made by MSHA. MSHA has chosen not
to define ‘‘economic feasibility’’ nor
‘‘technological feasibility’’ since the
Supreme Court has done so in the
OSHA Cotton Dust decision. As stated
earlier in this part, the Supreme Court
defined ‘‘feasibility’’ as ‘‘capable of
being done’’ (American Textile
Manufacturers’ Institute v. Donovan
(OSHA Cotton Dust), 452 U.S. 490, 508–
509 (1981)). This preamble also
discusses how the independent
Commission explains the Secretary’s
burden of proof in establishing
technological and economic feasibility
of controls.
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Commenters criticized the high costs
of DPM controls associated with
attempts to achieve a significant
reduction. These commenters stated that
mine ventilation systems cost more than
$100 million and provide a benefit only
of a 3% to 4% DPM reduction, whereas
a less-than $100 million administrative
control could achieve a 21% to 22%
reduction.
First, MSHA disputes the assertion
that a ventilation system costs $100
million. MSHA assumes mines already
have some form of ventilation, since
ventilation is needed whether or not
DPM is a consideration. The existing
system may be minimal, and rely partly
or largely on natural ventilation, but a
basic ventilation network must be
present per existing MSHA ventilation
regulations (§ 57.8518 through
§ 57.8535) and air quality standards
(§ 57.5001 through § 57.5039) to support
normal mining operations. Thus, in the
context of the final rule, the question is
not whether a ventilation system needs
to be provided for compliance, but
rather, whether an upgrade to an
existing ventilation system is needed. If
so, mine operators must examine
whether major additions (new shaft,
new main fan, etc.) are required, versus
relatively minor improvements such as
booster fans, auxiliary ventilation
system upgrades, or repair or extensions
to existing ventilation control
structures. Even in an extreme case
where a new ventilation shaft and main
fan installation could be justified solely
on the basis of DPM compliance, such
upgrades cost far less than $100 million.
Costs in the range of $5 million to as
much as $20 million would be more
accurate.
MSHA also notes that the level of
DPM reduction obtained through a
ventilation upgrade is proportional to
the ratio of new ventilation air flow to
the existing ventilation air flow. If
overall air flow is doubled, DPM levels
would be roughly cut in half. Of course
factors such as imperfect mixing and
effective distribution of air flow
underground would ultimately
determine the actual DPM reduction
achieved. Major ventilation upgrades
costing $5 to $20 million would
typically result in DPM reductions of at
least 20% to 30% or more, which is far
greater than the 3% to 4% reduction
that commenters estimated for a
ventilation upgrade costing $100
million.
It is also significant to note that some
DPM controls that may be easier fixes
for controlling DPM exposures may
actually be quite high in overall lifecycle costs compared to other
approaches that mine operators perceive
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to be higher cost options. For example,
if the operator of a stone mine
determined that compliance could be
achieved by installing a 150 horsepower
fan costing $25,000, this control option
might appear to be advantageous
compared to installing DPFs with an
expected filter life of two years on the
mine’s production loader and three
haulage trucks at a cost of $60,000 (4
filters × $15,000 per filter = $60,000).
However, if the total cost of the
ventilation upgrade is considered,
including power costs to operate the fan
12 hours per day 6 days per week, the
annual cost for ventilation surpasses the
cost for filters. The $60,000 cost for
DPFs, annualized over the two-year
filter life is $33,186 (using a 7%
discount rate). The fan power cost alone
would be over $40,000 annually at $0.10
per kilowatt-hour (150hp × 12 hours/
day × 6 days/week × 52 weeks/year ×
0.745 kw-hr/hp-hr × .10 $/kw-hr).
One commenter suggested that
MSHA’s failure to specify major
ventilation upgrades for any mine in its
31-Mine Study results in a serious
underestimate of compliance costs for
those mines and the industry as a
whole. This commenter states that the
trona mines have already attained
compliance with the final limit because
of their high ventilation air flow rates,
and that similarly high flows will be
required at many other mines to attain
compliance.
MSHA notes that the final rule is
performance oriented, and allows mine
operators great latitude to choose the
DPM control or controls that are most
efficient and cost effective for a given
mine. The trona mines are required to
ventilate at very high rates for reasons
other than DPM compliance to address
methane issues, for instance. For them,
ventilation is the logical DPM control
because the control is already in place.
Other type mines have more and varied
choices, and selecting the optimum
DPM control strategy involves
evaluation of a broad range of factors
such as current DPM levels, equipment
and engines used, equipment
deployments, mine layout, existing
ventilation system, availability of
alternate diesel fuels, and many more.
For reasons of financial self-interest,
mine operators would be unwise to
implement high cost controls that
achieve very little DPM reduction, such
as a $100 million ventilation system that
reduces DPM levels by only 3% to 4%.
Such a choice would preclude less
costly and more effective options
available, such as DPFs, low emission
engines, alternative diesel fuels, and
cabs with filtered breathing air.
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As stated earlier, the final rule
incorporates economic feasibility in its
hierarchy of controls enforcement
scheme. MSHA, likewise, could not
require a mine operator to implement a
control or combination of controls
where the costs are wholly out of
proportion to the expected results.
MSHA would judge a ventilation
upgrade costing $100 million, or even
$5 to $20 million that achieves a DPM
reduction of 3% to 4% as infeasible
because the cost is wholly out of
proportion to the expected results, and
it is likely a mine operator would
consider it a poor DPM compliance
strategy for the same reason. The
commenter suggests a lower cost
administrative control that achieves a
21% to 22% reduction would be a better
choice. MSHA agrees, if this control in
combination with other controls would
result in at least a 25% reduction.
As noted previously, with some DPFs,
filter efficiency is as high as 99+% for
EC. MSHA, however, believes that both
economic and technological feasibility
must be considered. Whereas filter
efficiency is a major component of
technological feasibility, MSHA must
consider all aspects of feasibility
including implementation issues and
cost of compliance to the mining
industry. As stated earlier in this
preamble, MSHA believes that some
mine operators would need more time
to meet a lower DPM limit presently
based on economic feasibility and
implementation issues with DPFs.
Establishing a lower interim limit in
this final rule would present
complications with respect to economic
feasibility, particularly where
ventilation upgrades would be needed
to meet a lower limit. Moreover, MSHA
envisions that mine operators would
have to filter larger numbers of dieselpowered equipment in order to meet a
lower limit. Such a requirement could
impose higher costs for the mining
industry before experience is gained at
the current level and the mining
industry is given adequate time to meet
a lower standard.
Some commenters objected to
MSHA’s assessment of the number of
mining operations that will need costly
ventilation upgrades. These operators
believe that a large number of mines
will have to make ventilation
improvements, provide cab
improvements, add other engineering
controls, implement other
administrative controls, replace engines,
and utilize DPFs. In response, the DPM
rulemaking record does not sustain this
position. MSHA found in its baseline
sampling that only 37% of the mining
operations covered by this DPM rule
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had miners overexposed to DPM.
Consequently, at 63% of the mines
sampled, MSHA found no
overexposures to DPM. MSHA
conducted this sampling in the same
manner as it does its enforcement of the
2001 interim limit DPM rule. MSHA
collected roughly 1,194 samples at 183
mines. Additionally, MSHA responded
to each mine operator’s request for
compliance assistance and technical
support for resolving engineering
control implementation issues. The
results of MSHA’s work are included in
the rulemaking record. Overall, the
mining industry has been successful in
reducing average DPM levels as
demonstrated in the comparison of
baseline sampling and 31-Mine Study
data shown in Chart V–5.
Also, in the 31-Mine Study, MSHA
established that most mining operations
would not need major ventilation
changes, but rather, could implement
less costly ventilation upgrades and
DPFs. In most instances, the ventilation
upgrades require no more than adding
booster fans or auxiliary ventilation, and
repairs or extensions to ventilation
control structures such as brattice lines
or air walls.
A commenter suggested that
ventilation costs for complying with the
DPM rule for the Kerford Limestone
mine were projected to be $1.15 million,
plus $348,450 for engine replacements,
plus an additional $25,500 to $38,500
for DPF maintenance. According to the
commenter, this mine has invested
$975,000 since October 2001, primarily
for ventilation improvements including
sinking a shaft, consultant costs, a new
blasting truck, and a new engine for a
bolter. The commenter points out that in
the 31-Mine Study, MSHA projected
that first-year compliance costs for this
same mine would be only $77,600, and
suggests the discrepancy is an example
of MSHA’s underestimate of DPM
compliance costs.
MSHA notes that 13 DPM samples
were taken during the 31-Mine Study at
the Kerford mine. Sample results ranged
from 143TC µg/m3 to 490TC µg/m3. Per
the 31-Mine Study methodology, DPM
controls were specified based on the
highest sample result. However, since
the highest sample result only exceeded
the interim DPM limit by about 23%
(490TC µg/m3 versus the interim DPM
limit of 400TC µg/m3), the controls
necessary to attain compliance at this
mine were not very extensive. Indeed,
MSHA’s analysis indicated that
controlling DPM emissions from the
mine’s three loaders (two loaders used
in normal operations plus one spare)
using active DPF systems with filter
efficiencies of 80% would enable the
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mine to attain compliance with the
interim limit. MSHA estimated the first
year cost of three filter systems for the
subject loaders plus an oven for
regenerating the filters (active off-board
regeneration) to be $77,600.
MSHA has not seen the consultant’s
report that indicates new engines, DPFs,
and a major ventilation upgrade would
be required for the Kerford mine to
comply with the interim DPM limit.
However, these recommendations
appear excessive based on MSHA’s
analysis in the 31-Mine Study and also
on the fact that compliance for this mine
requires only a relatively small
reduction in DPM levels from 490TC µg/
m3 to 400TC µg/m3.
As noted in the 31-Mine Study final
report, MSHA is not suggesting that its
findings represent the optimum
compliance strategy for this or any
mine. Rather, MSHA maintained merely
that the controls specified in the final
report are feasible and would be
expected to attain compliance. MSHA
suspects that the combination of
controls recommended by Kerford’s
consultant, though capable of attaining
compliance, is not the optimum and
most cost effective approach available.
As discussed in the Technological
Feasibility section of this preamble,
MSHA also notes that the total yearly
cost represented by the consultant’s
recommended engine, ventilation
system, and DPF expenditures is
roughly in line with MSHA’s 2001 REA
estimate for an average mine, even
though Kerford Limestone is
substantially larger than average. The
engine costs of $348,000, when
annualized over 10 years at a discount
rate of 7%, results in a yearly cost of
$49,500. The $1.15 million ventilation
cost, when annualized over the
expected 20+ year life of this asset,
results in a yearly cost of $108,600.
When these two yearly costs are added
to the maximum estimated annual DPF
cost of $38,500, the total yearly cost for
Kerford is about $196,600. When
compared to the MSHA REA’s estimated
compliance cost of over $300,000 for a
stone mine of this size, Kerford’s costs
are significantly less.
Some mines, in particular mine size
and commodity groups, because of their
mining methods used, equipment
deployments, etc., would be expected to
incur higher than average compliance
costs of $128,000 per year. For example,
the REA estimated yearly compliance
costs for large precious metals mines to
be $660,000. Based on its compliance
assistance mine visits, baseline
sampling results, and other data, MSHA
believes that most mines have expended
far less than the expected $128,000
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yearly for DPM compliance. Though
expenditures will undoubtedly need to
rise in the future as the easy DPM
control methods are exhausted, they are
not expected to exceed levels previously
determined by MSHA to be
economically feasible.
Another mine that disputed MSHA’s
estimated DPM compliance cost
estimates is the Stillwater Mine. MSHA
estimated in the 31-Mine Study that
DPM filters would be required on all
LHDs and haulage trucks at this mine in
order to attain compliance with the
interim limit. Accordingly, MSHA
estimated Stillwater’s first year costs to
be $470,100 and annual costs to be
$108,163 for three loaders and twelve
trucks used in normal mining
production operations plus three more
spare loaders and four more spare
trucks. In its comments on the 2003
NPRM, Stillwater indicated that its total
diesel equipment inventory consists of
over 350 pieces of diesel equipment,
including over 90 loaders and 40
haulage trucks, plus miscellaneous
production equipment and spares.
MSHA has since acknowledged that it
had an inaccurate inventory of diesel
equipment for the Stillwater mine when
the 31-Mine Study was conducted. On
the basis of the newly obtained
inventory data, MSHA raised its
compliance cost estimate for this mine
to $935,000 to cover DPFs for the total
production fleet.
In its comments on the 2003 NPRM,
Stillwater submitted its own compliance
cost estimates. This estimate included a
$9 million ventilation upgrade,
$160,000 for passive DPFs, $1.2 million
for engine upgrades, $280,000 for engine
test equipment, $43,000 per month in
emissions expenditures, over $100
million over ten years for active DPFs,
plus various miscellaneous costs.
Combining these items resulted in an
estimated annual compliance cost for
Stillwater of $11 to $12 million.
Clearly, the most significant cost item
listed by Stillwater is active DPF
systems. However, almost 97% of
Stillwater’s estimated active DPF
systems costs are for excavation of
parking areas. Stillwater’s active DPF
system implementation plan specified
on-board active filter regeneration,
wherein a vehicle would travel to a
regeneration station and its DPF would
be connected to electrical power and
compressed air for regeneration. To
insure reasonable travel distances
between normal working areas and
regeneration stations, Stillwater’s active
filter cost estimate was developed in the
context of a ten-year mine plan, wherein
new regeneration stations would be
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32943
excavated periodically with the advance
of the mine workings.
As discussed in detail in the
Technological Feasibility section of this
preamble, MSHA analyzed and
evaluated the Stillwater compliance cost
estimate, and determined that
compliance could be attained at a much
lower cost. Since the cost of excavating
regeneration stations was such a
significant component of Stillwater’s
overall cost estimate, MSHA focused on
eliminating this cost element. As
explained in the Technological
Feasibility section, MSHA described
three feasible alternative approaches for
utilizing active filtration that do not
require excavation of regeneration
station parking areas. Although MSHA
disputed several of the remaining cost
items, MSHA nonetheless accepted
these costs as submitted by Stillwater in
developing an alternate compliance cost
estimate for this mine. The inclusion of
these disputed items accounts for
MSHA’s estimated compliance cost of
$1.57 million for the Stillwater mine
being somewhat higher than the revised
31-Mine Study cost estimate of
$935,000.
As noted in the Technological
Feasibility section of this preamble,
MSHA’s estimate of $1.57 million in
annual DPM compliance cost is
significant. However, it is less than
MSHA estimated in the REA for the
2001 final DPM rule for a large precious
metals mine. The REA estimated annual
compliance costs of $660,000 based on
a fleet size of 133 vehicles. Adjustment
for Stillwater’s fleet size of 350+
vehicles results in an estimated
compliance cost of $1.7 million.
Several other commenters suggested
that MSHA’s compliance cost estimates,
in general, were unrealistically low.
However, without specific examples to
evaluate and analyze, such comments
are difficult to refute. MSHA has
supported its cost estimating
methodologies in general, and where
specific examples have been provided
by commenters, MSHA has fully
supported its compliance cost estimates,
such as the above discussions of the
Kerford and Stillwater mines.
Except for general comments
regarding the DPM Estimator, MSHA
did not receive information to dispute
the technological and economic
feasibility for mines using room and
pillar mining methods to meet the 308EC
µg/m3 limit. These mines include stone,
salt, trona and potash mines. When
additional controls were necessary to
attain DPM compliance, these mines
have typically elected to meet the
interim limit by upgrading ventilation,
using cabs with filtered breathing air,
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use of alternative fuels, and using
equipment with clean engines. The
comments received from mines in these
sectors of industry focused on the
difficulties of installing after-filters on
large, high horsepower equipment and
the increasing cost of bio-diesel fuel.
These issues, along with the DPM
Estimator, are discussed in detail in the
Technological Feasibility section of this
preamble.
VIII. Summary of Costs and Benefits
The provisions in this final rule will
increase compliance flexibility with the
existing final rule, and continue to
reduce significant health risks to
underground miners. These risks
include lung cancer and death from
cardiovascular, cardiopulmonary, or
respiratory causes, as well as sensory
irritations and respiratory symptoms. In
Chapter III of the REA in support of the
2001 final rule, MSHA demonstrated
that the rule will reduce a significant
health risk to underground miners. This
risk included the potential for illnesses
and premature death, as well as the
attendant costs to the miners’ families,
to the miners’ employers, and to society
at large. Benefits of the January 19, 2001
final rule include reductions in lung
cancers. MSHA estimated that in the
long run, as the mining population turns
over, a minimum of 8.5 lung cancer
deaths per year will be avoided. MSHA
noted that this estimate was a lower
bound figure that could significantly
underestimate the magnitude of the
health benefits. For example, the
estimate based on the mean value of all
the studies examined in the 2001 final
rule was 49 lung cancer deaths avoided
per year. MSHA uses the 2001 risk
assessment for support of this rule.
This final rule results in net cost
savings of approximately $3,634
annually, primarily due to reduced
recordkeeping requirements. All MSHA
cost estimates are presented in 2002
dollars. This represents an average
annual savings of $20 per mine for the
177 underground metal/non-metal
mines that would be affected by this
2003 NPRM. Of these 177 mines, 66
have fewer than 20 workers, 107 have
20 to 500 workers; and 4 have more than
500 workers. The cost savings per mine
for mines with fewer than 20 workers
will be $74. The cost increase per mine
for mines having 20 to 500 workers and
more than 500 workers will be $10 and
$10, respectively. In the 2001 REA,
MSHA estimated that the costs per
underground dieselized metal or
nonmetal mine for the existing rule to
be about $128,000 annually, and the
total cost to the mining sector to be
about $25.1 million a year, even with
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such as those who smoke, operate
jackleg drills or load ANFO, for whom
valid personal samples would be
difficult to obtain with TC as the
surrogate for DPM.
IX. Section-By-Section Discussion of the
MSHA has found that EC consistently
Final Rule
represents DPM. Compared to using TC
A. Section 57.5060(a) Interim DPM Limit as the DPM surrogate, using EC
accomplishes the following: Imposes
MSHA’s existing interim DPM limit at
fewer restrictions or caveats on
§ 57.5060(a), which became applicable
sampling strategy (locations and
July 20, 2002, restricts TC
durations); produces a more accurate
concentrations in underground mines to
measurement; and inherently will be
400TC µ/m3. The concentration limit
more precise than TC. Furthermore,
applies to areas where miners normally
NIOSH, the scientific literature, and the
work or travel. In the 2001 final rule,
MSHA laboratory tests (see NIOSH letter
MSHA chose TC as the surrogate for
dated April 3, 2002 and July 31, 2000
measuring DPM concentrations.
comment to the proposed rule for the
Consistent with the 2003 NPRM, final 2001 rule) indicate that DPM, on
§ 57.5060(a) changes the surrogate from
average, is approximately 60% to 80%
TC to EC, which renders a more
EC, firmly establishing EC as a valid
accurate measurement. In addition,
surrogate for DPM.
MSHA is basing the interim limit on a
Under the new standard, MSHA is not
miner’s personal exposure rather than
reducing the protection from that
on an environmental concentration,
afforded miners under the former
which results in a PEL. The new interim interim TC concentration limit, since
limit restricts a miner’s personal
the old TC and new EC limits are
exposure for a full shift to 308EC µg/m3.
comparable in exposure reduction.
MSHA believes that this new interim
Establishing a standard that focuses
limit is comparable to the existing TC
control efforts on diminishing the DPM
limit.
level in air breathed by a miner is
Because EC comprises only a fraction
supported by some commenters in
of TC, MSHA used a conversion factor
labor. Some commenters stated, ‘‘We
to adapt the former interim
agree that personal sampling gives a
concentration limit of TC to a new EC
better representation of real exposure,
PEL. MSHA proposed to use a factor of
and we support the change.’’
1.3, to be divided into 400TC µg/m3,
MSHA has determined that this new
which produces a reasonable estimate of interim limit is both technologically and
TC without interferences. The final EC
economically feasible for the M/NM
limit is based on the median TC to EC
mining industry to achieve. Although
(TC/EC) ratio of 1.3 that was observed
the risk assessment indicates that a
for valid samples in the 31-Mine Study
lower DPM limit would enhance miner
and the DPM settlement agreement. The protection, it would be infeasible at this
1.3 factor also is supported by
time for the underground M/NM mining
information provided by NIOSH
industry to reach a lower interim limit.
indicating that the ratio of TC to EC in
MSHA will continue to monitor the
the 31-Mine Study is 1.25 to 1.67. Most
feasibility of the affected mining
commenters to MSHA’s 2003 NPRM
industry to comply with a lower EC
supported an interim EC PEL of 400TC
exposure limit. MSHA believes that it is
µg/m3 divided by 1.3 = 308EC µg/m3.
critical to gain compliance experience,
Also in the 31-Mine Study, MSHA
both from the standpoint of DPF
concluded that the submicron impactor
efficiency and implementation issues
that MSHA used for DPM sampling was raised by the mining industry during
effective in removing carbonaceous
this rulemaking, in order to address a
mineral dust from the DPM sampler,
final DPM limit.
Most commenters supported the value
and therefore, its potential for
of 308EC µg/m3 for the interim PEL.
interfering with the MSHA sampling
analysis. The remaining carbonate
Some commenters suggested a limit of
interference is removed from the sample 320EC µg/m3 as the preferred PEL. Some
analysis by subtracting the 4th organic
of these commenters cited research by
peak. No reasonable method of sampling Cohen, Borak and Hall in support of
was found in the 31-Mine Study that
their position. The evidence in the
would eliminate interferences from
rulemaking record, however,
sources of oil mist and ammonium
overwhelmingly supports MSHA’s
nitrate fuel oil (ANFO). Moreover,
decisions on the appropriate interim
MSHA could not determine DPM levels DPM limit of 308EC µg/m3. MSHA’s
in the presence of ETS with TC as the
review of the cited publication by these
surrogate. Using EC as the surrogate will authors demonstrated no reference to a
enable MSHA to directly sample miners, value of 320EC µg/m3. A 320EC µg/m3
the extended phase-in time. Nearly all
of those anticipated costs would be
investments in equipment to meet the
interim and final concentration limits.
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limit value would have resulted from
using a conversion factor of 1.25, and
represents the high end of the range
reported by NIOSH. MSHA disagrees
with using a limit of 320EC µg/m3 and
believes that the limit of 308EC µg/m3 is
the appropriate limit based on the
evidence contained in the rulemaking
record.
Another commenter stated that mine
data gathered since the current final rule
was promulgated requires MSHA to
lower the 2001 interim limit. This
commenter believes that all of industry
could reach compliance with the
interim concentration limit without
significant economic investment and
that the control technology is available
to reduce DPM to below the 2001
interim limit for feasible costs.
MSHA agrees that most of the M/NM
mining industry has the capability of
reaching the new interim PEL. MSHA,
however, does not agree that
compliance with the new PEL can be
accomplished in every instance and
circumstance due to implementation
issues that vary from mine to mine.
During MSHA’s compliance
assistance visits, on many occasions it
was observed that mines had purchased
new equipment or installed modern
engines in existing equipment. Several
mines were using or testing alternative
fuels and many mines had made
upgrades to their ventilation systems by
improving airflow distribution systems.
MSHA mostly observed that mines had
not begun to install DPM filters to
reduce miners’ exposures, as
recommended by MSHA as the most
cost-effective method of compliance.
The DPM standard does not specify that
mine operators must use a specific type
of control, but MSHA recommended
DPFs as a very effective method for
controlling DPM. MSHA chose to leave
that decision to the individual mine
operator’s judgment.
Most commenters from industry and
labor continued to strongly support the
change in the surrogate from TC to EC.
These commenters stated that given the
interferences known to be present in
underground mining environments,
using EC as the surrogate would
improve the accuracy of MSHA
samples. Some commenters criticized
MSHA for not realizing earlier that EC
was a more appropriate surrogate than
TC and that use of EC would lower
sampling costs of the mining industry.
At the time that the 2001 final rule was
promulgated, MSHA’s rulemaking
record supported TC as the more
appropriate surrogate. Following
completion of the 31-Mine Study,
MSHA obtained sufficient data to
change the surrogate.
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Some other commenters opposed
changing the surrogate. One commenter
stated that the change is without
foundation because the record does not
support MSHA’s claim that the amount
of EC is an accurate surrogate for the
amounts of DPM that need to be
measured under actual mining
conditions. MSHA disagrees. MSHA
supports using EC as the most suitable
surrogate for measuring DPM. Moreover,
this commenter believes that the record
does not support MSHA’s claim that
there is no solution to interference
issues that arise when TC is used as the
surrogate for DPM. MSHA disagrees
with this comment, as well. Data in the
rulemaking record from the 31-Mine
Study demonstrates that there is no
‘‘reasonable’’ solution to interference
issues when using TC as the surrogate.
Another commenter stated that MSHA
should consider using a better surrogate
than EC, since most DPM studies were
conducted on whole DPM which would
measure exposure to the most relevant
substance. In addition, this commenter
believes that a substance other than EC
could be the ultimate carcinogenic agent
in DPM. Many organic compounds in
DPM are known carcinogens, and there
is no stable EC:TC ratio. This
commenter also believes that
interferences from ETS introduce less
variability than EC. Furthermore, the
commenter states that the interference
problem could be solved another way
since Harvard investigators have
successfully adjusted DPM
measurements for ETS. Since the
commenter did not provide a specific
reference cite for the Harvard
investigation, MSHA was unable to
verify this claim. MSHA based its
decisions in this final rule on the best
data available to MSHA. That data
demonstrates that measuring EC for
determining DPM exposures will allow
MSHA to sample miners’ exposures in
the presence of ETS without
interference issues. No adjustment has
to be made in the sample analysis
because ETS does not affect the
measurement of EC. During the 31-Mine
Study, NIOSH found that there was no
reliable marker for cigarette smoke in
the presence of DPM.
Some commenters suggested that
MSHA establish an ‘‘action level * * *
at which additional sampling and some
controls kick in.’’ These commenters
recognized that it would be difficult for
MSHA to enforce an action level below
the PEL. MSHA believes that the best
method of protecting miners from
exposure to DPM is through the primary
use of reliable controls. In Section VII of
its feasibility analysis, MSHA
determined that the rulemaking record
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32945
has little evidence at this time to lower
the PEL due to implementation and cost
issues for the mining industry. Also,
MSHA’s air quality standards for M/NM
mines do not include requirements for
regulating action levels for other
airborne contaminants. Furthermore,
pursuant to § 57.5071 of the DPM rule,
mine operators are required to monitor
as often as necessary to effectively
determine whether the concentration of
DPM in any area of the mine where
miners normally work or travel exceeds
the applicable limit. In MSHA’s
experience at M/NM mines, this
approach to worker protection is more
effective and practical than establishing
an ‘‘action level’’ that the commenters
recognize may be unenforceable.
Several comments were received on
the use and development of the error
factor for DPM sampling. One
commenter stated that error factors give
the benefit of doubt to mine operators
and exposes miners to DPM above an
already inadequate exposure limit. This
commenter also stated that miners’
health should be given precedence over
mine operators’ property rights. MSHA
believes that it has the burden of
proving that a sample is above the PEL
for enforcement purposes.
Establishment of an error factor assists
MSHA and reviewing courts in knowing
when that burden has been met. Mine
operators should review their sample
results and make decisions on the level
of controls required or when
improvements to controls might be
necessary. However, MSHA’s practice
has been to cite only when an exposure
sample exceeds the standard times the
error factor.
MARG submitted data and a
consultant’s comments on the sampling
and analytical variability of EC
measurements. These comments will be
referred to below as the ‘‘Borak/Sirianni
analysis.’’ The Borak/Sirianni analysis
examined three bodies of EC sampling
data. The first of these consisted of 25
groups of four or five simultaneous EC
concentration measurements collected
by MARG and summarized in Table 1 of
the appendix submitted with the Borak/
Sirianni analysis. This dataset,
identified below as the ‘‘MARG basket
data,’’ is a portion of the data obtained
in the MARG study which was
conducted in seven underground
nonmetal mines (Cohen HJ, Borak J, Hall
T, et al.: Exposure of miners to diesel
exhaust particulates in underground
nonmetal mines, Am Ind Hyg Assoc J
63:651–658, 2002). The second body of
data, identified below as the ‘‘baseline
paired punches,’’ consisted of two
analytical EC results on each of 223
samples from MSHA’s compliance
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assistance database. The third body of
data examined in the Borak/Sirianni
analysis was a relatively small subset
(63 samples out of over 800) of the
paired-punch EC data available from the
31-Mine Study. This dataset will be
identified below as the ‘‘31-Mine Study
Subset.’’
Based on the Borak/Siriani analysis,
MARG concluded that ‘‘* * * the
[measurement] system is not accurate
and not feasible.’’ MSHA disagrees. Our
analysis of the same data shows
variability of the EC measurements
presented to be well within acceptable
limits. As will be shown below, the
Borak/Sirianni analysis is
mathematically invalid.
Each of the datasets is discussed
below, first with respect to deficiencies
in the Borak/Sirianni analysis and then
with respect to what the submitted data
actually reveal about sampling and
analytical variability.
MARG Basket Data
The submitted MARG basket data
consisted of 25 groups of four or five
samples in which at least one EC
measurement fell within the range of 75
µg/m3 to 200 µg/m3. Neither MARG nor
the Borak/Sirianni analysis explained
whether MARG collected additional
basket data falling outside of this range.
Additionally, no explanation was
provided as to why the submitted data
were restricted in this way, if more data
were collected.
Unfortunately, the samples were
collected without the submicron
impactor. The sample results are,
therefore, not appropriate to use in this
rulemaking. The study reference does
not indicate the type of filter holder and
cyclone attachment configuration or if
the mineral-dust-related carbonate that
occurs in the organic portion of the
analysis was subtracted off the OC
determination.
When using a filter holder with an
internal cyclone connection, the cyclone
nozzle acts as an impactor jet and
mineral dust is deposited in the center
of the filter. This gives a high level of
mineral dust in the center of the filter,
and a non-uniform deposit of material
on the filter surface. A non-uniform
deposit precludes any analysis of
duplicate sample punch repeatability.
Additionally, three of the seven mines
produced either limestone or trona.
Both of these minerals contain
carbonates which are evolved in the
organic portion of the analysis. Failure
to remove this mineral dust by use of an
impactor may affect the split point
between OC and EC. The referenced
study indicates that up to 15 mg/m3 of
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total mineral dust was present at one of
the mines.
MARG did not provide individual
sample results for this dataset. Nor did
MARG provide any information on
sampling times or filter loadings (µg/
cm2), both of which affect expected
analytical variability. Only summary
data, consisting of the EC measurement
range, mean, standard deviation (SD),
and coefficient of variation (CV), were
provided for each group of ‘‘four or
five’’ samples. There was no indication
of which groups contained four and
which groups contained five samples.
Despite the statistical instability of
estimated SDs, CVs, and means based
on as few as four or five measurements,
no confidence intervals or other
measures of statistical uncertainty were
provided for the summary statistics.
The Borak/Sirianni analysis consisted
of tabulating ‘‘the number and
proportion of baskets corresponding to
CV ranges of 0–4.99, 5–9.99, >10 and
>12.5%. More specifically, Borak/
Sirianni observed that ‘‘32% of baskets
containing at least one sample in the
75–200 µg/m3 range had a CV ≥ 12.5%.’’
Although they presented no
mathematical evaluation of this finding
s statistical significance, Borak/Sirianni
concluded that it was ‘‘inconsistent
with the NIOSH criteria for
appropriateness of analytical methods
and does not meet guidelines presented
in the proposed Final Rule.’’ 9
The Borak/Sirianni analysis of these
data appears to be founded on an
elementary misconception: That a high
percentage of individual baskets with
CV > 12.5% (based on four or five
measurements per basket) provides
evidence of a high sampling and
analytical CV. Actually, as
demonstrated below, the Borak/Sirianni
finding reflects statistical instability
(i.e., lack of reliability) in CV estimates
calculated using only four or five
measurements. CV estimates based on a
limited number of measurements
display random variability around the
true CV value underlying the
measurement process. It should,
therefore, be expected that many of the
CV estimates based on individual
baskets will fall below, many will fall
above, and none or few will fall exactly
on the true CV. More specifically, the
Borak/Sirianni finding is entirely
consistent with a measurement process
satisfying the NIOSH accuracy criterion.
To illustrate this point, MSHA
generated a dataset of 10,000 simulated
measurements randomly drawn from a
log normal distribution having mean =
9 The proposed rule does not, in fact, present any
such guidelines.
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126 and CV = 12%.10 More than 96% of
these measurements fell within ±25% of
the 126 mean or ‘‘reference value,’’
thereby showing that the simulated
measurement process satisfied the
NIOSH Accuracy Criterion. The 10,000
‘‘measurements’’ were then grouped
into simulated ‘‘baskets’’ of four or five
measurements each,11 and a separate
unbiased estimate of the CV was
calculated from the data within each
basket. This resulted in 2,250 separate
CV estimates of the same underlying
CV, with each calculation based on four
or five measurements. Figure IX–1
displays the cumulative distribution of
the individual CV estimates. Despite the
fact that the underlying CV was 12% for
all these data, 808 (35.9%) of the CV
estimates based on individual baskets
exceeded 12%. This demonstrates that
the corresponding Borak/Sirianni
finding (32%) is consistent with
meeting the NIOSH Accuracy Criterion.
As mentioned earlier, MARG did not
provide filter loadings (µg/cm2) or
sampling times for the basket data.
Figure IX–2, which is derived from the
paired-punch comparison of EC results
from the 31-Mine Study,12 shows how
NIOSH Method 5040 analytical
uncertainty is expected to vary with
different filter loadings. In the range of
EC concentrations exhibited by MARG’s
basket data, sampling times
substantially less than 480 minutes
could substantially increase variability
in the analytical results due to relatively
low filter loadings. Even if we assume,
however, that MARG’s basket samples
were all taken for at least 480 minutes,
the submitted data do not show
excessive sampling and analytical
variability. A crude estimate of the
10 The simulated data were generated and
analyzed using SYSTAT Statistical Software,
Version 10. A computer file containing this dataset,
along with a number indicating the ‘‘basket’’ to
which each ‘‘measurement’’ was randomly
assigned, is being placed into the public record
under the name SYMBASKETS.txt. The mean value
of 126 was chosen to coincide with the overall
mean concentration for the MARG basket data, but
this choice has no substantive bearing on the
results. The CV value of 12% was chosen in order
to exemplify an unbiased measurement process that
satisfies the NIOSH accuracy criterion.
11 Since the Borak/Sirianni analysis did not reveal
how many of MARG’s baskets contained four and
how many contained five samples, the 10,000
simulated measurements were divided equally into
baskets of four and five. This resulted in 1250
simulated ‘‘baskets’’ of four measurements each and
1000 ‘‘baskets’’ of five measurements each.
12 Analytical imprecision of EC measurements is
quantified, based on paired-punch results from the
31-Mine Study, in the technical document on
MSHA’s Web site cited as Reference #4 in the
Borak/Sirianni Analysis. In the notation of that
document, the quantity plotted in Figure IX–2 is
CVm [X] calculated using st = 0.256. st incorporates
both intra- and inter-laboratory analytical
variability.
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approximately 10 times the filter
loading in µg/cm2 (8.04 × 1000/480/1.7
= 9.85). As a result, the 126 µg/m3
corresponds to a mean EC filter loading
of 12.8 µg/cm2. Figure IX–2 shows that,
at this loading, the CV expected for
analytical variability alone is
approximately 10%. Since variability
MARG provided no indication that
any of the analytical results for its
basket data were averaged over two
punches, as per MSHA’s procedure for
samples used to cite noncompliance
with the DPM standard (2003 NPRM, 68
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within baskets reflects not only
analytical variability but also variability
in the volume of air pumped and in
location within each basket, an overall
CV of 10.8% is neither surprising nor
excessive.
BILLING CODE 4510–43–U
FR 48672). It should, therefore, be noted
that the analytical component of
variability observed in these data would
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overall CV can be obtained by pooling
results from all 25 baskets. The average
of the 25 CV values given is 10.8% at
a mean EC concentration of 126 µg/m3.
For a dpm sample, collected with the
submicron impactor (filter area 8.04
cm2), for 480 minutes at a flow rate of
1.7 Lpm, the concentration in µg/m3 is
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portion of variability amounted to a CV
of 10%, then this would have been
reduced to 7.1% if two punches had
been averaged for every measurement.
BILLING CODE 4510–43–C
content.13 In accordance with MSHA’s
interim policy for DPM noncompliance
determinations, a second punch was
analyzed from each of these samples
because the first punch showed EC ≥ 30
Baseline Paired Punches
The baseline paired-punch data
examined in the Borak/Sirianni analysis
consisted of laboratory results from 223
samples, collected during MSHA’s
baseline compliance assistance program,
that were analyzed twice for EC
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13 The Borak/Sirianni analysis erroneously states
that all 223 of these samples were ‘‘collected using
an older version of the SKC impactor that differs
from the impactor proscribed [sic] in the proposed
final rule.’’ We assume that the intended word was
‘‘prescribed.’’ As explained in the 2003 NPRM at 68
FR 48679–80 and 48706, there has been no change
to the impactor in the SKC sampler. For reasons
explained elsewhere in this preamble, an
improvement was made in the SKC filter capsule,
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but this change has no bearing on the comparison
of paired punches taken from within the area of
deposit on the filter. The older design, employing
a crimped foil capsule, was used for 93 of the 223
samples. The remaining 130 samples utilized the
newer design, in which a retaining ring replaced the
crimped foil.
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have been reduced by a factor equal to
if such averaging had been performed
√2. For example, if the analytical
Federal Register / Vol. 70, No. 107 / Monday, June 6, 2005 / Rules and Regulations
µg/cm2 or TC ≥ 40 µg/cm2 (see 2003
NPRM, 68 FR 48672). Results from the
two punches were then averaged for
purposes of determining compliance or
noncompliance with the interim
exposure limit.
The Borak/Sirianni analysis of these
223 paired-punch results consisted of
calculating, for each pair, the
‘‘percentage difference’’ between the
two punch results and tabulating the
frequency of cases in which that
quantity fell into three categories: 0–
4.99%, 5–9.99%, and ≥10%. The
‘‘percentage difference’’ was apparently
calculated as 100X|X1¥X2|÷X1, where X1
is the first measurement recorded
within each pair. No explanation was
given of the statistical properties of this
quantity, and no discussion was
presented of its mathematical
relationship to a CV, which is defined
quite differently. In particular, Borak/
Sirianni made no attempt to relate the
‘‘percentage difference’’ mathematically
to CVA, which refers to the coefficient
of variation for the average (not
difference!) of two punch results.
Nevertheless, the authors concluded
(without explanation) that the frequency
of cases in which the ‘‘percentage
difference’’ exceeded MSHA’s estimate
of CVA indicates that MSHA’s estimate
is too low. They also asserted that ‘‘it is
almost certain’’ that these data
‘‘document failure to meet the NIOSH
and MSHA acceptability criteria.’’
The Borak/Sirianni analysis of these
data commits the following five errors.
The first three of these distort their
analysis sufficiently to render its
conclusions entirely without merit.
1. Our best estimate of the true carbon
loading on a filter is given by the
average of the two available punch
results from that filter. Therefore,
individual measurement errors are best
estimated as the distance of each result
from the midpoint between them. In
contrast, the ‘‘percentage difference,’’ as
defined by the Borak/Sirianni formula,
is twice the size of the percentage
deviation of either punch result from
the midpoint between them. This serves
to exaggerate the deviation of each
result from the true value.
Mathematically, the relative standard
deviation (RSD) of the difference
exceeds the RSD of an individual punch
result by a factor of √2 (prior to any
blank adjustment).
2. Borak/Sirianni fail to account for
the fact that MSHA’s estimate of CVA
applies to the average of two punch
results, rather than to an individual
analytical measurement. The RSD of an
individual punch result exceeds the
RSD of the two-punch average by
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another factor of √2 (again, prior to any
blank adjustment).
3. The combined effect of (1) and (2)
is that, when blank adjustments are
negligible, variability in the ‘‘percentage
difference,’’ as expressed by an
appropriate CV within pairs, would be
expected to exceed analytical
imprecision in a 2-punch average by a
factor of 2. However, Borak/Sirianni
made no attempt to calculate such a CV
or make any other meaningful
comparison. Instead, they simply
tabulated instances in which the
‘‘percentage difference’’ exceeded CVA.
CVA, like any coefficient of variation,
does not represent an upper bound on
individual deviations or differences.
Indeed, approximately one-third of
individual errors (without regard to
direction) would normally be expected
to exceed the corresponding CV. (This is
why MSHA multiplies the appropriate
CV by a ‘‘confidence coefficient’’ when
establishing a 1-tailed 95% confidence
error factor for noncompliance
determinations.) Combining the factor of
2 explained above with a 95% 2-tailed
confidence coefficient (1.96),
‘‘percentage differences,’’ as defined by
Borak/Sirianni, are expected to exceed
2×1.96×CV more than 5% of the time.
(The reason such excesses would be
expected more than 5% of the time is
given below, under point 4.)
4. The Borak/Sirianni method of
calculating ‘‘percentage difference’’
causes such differences to take on more
extreme values than they would if they
were calculated relative to the average
of the two punch results (i.e., if the
denominator of the calculation were the
average of X1 and X2 rather than just the
X1 result). For example, using the
Borak/Sirianni formula, a sample with
two punch results of 192 and 212 would
yield a ‘‘percentage difference’’ of either
10.4% or 9.4%, depending on which
one of the two measurements is
recorded as X1. If, instead, the average
of X1 and X2 were used as the
denominator, then the percentage
difference would be calculated as
9.9%.14 So long as the smaller result is
equally likely to be X1 as X2, the Borak/
Sirianni formula for ‘‘percentage
difference’’ increases some percentage
differences and decreases others.
Nevertheless, as shown in this example,
the Borak/Sirianni formula artificially
increases the count of differences
exceeding 10% (or any other specified
value). Furthermore, as will be
explained later, the Borak/Sirianni
14 Note that, in this example, the relative
deviation of either X1 or X2 from the midpoint
between them is actually 10/202 = 4.95%. This
would be the appropriate value for comparison to
a CV or RSD quantifying measurement imprecision.
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32949
formula for ‘‘percentage difference’’
induces an even greater systematic bias
in their analysis of the 31-Mine Study
subset.
5. The Borak/Sirianni analysis ignores
heterogeneity of the analytical CV
within the range of EC loadings
considered. As indicated by Figure IX–
2, the frequency of relatively large
percentage differences would be
expected to increase at low EC loadings.
The method shown in ‘‘Metal and
Nonmetal Diesel Particulate Matter
(Dpm) Standard Error Factor for TC
Analysis,’’ published on MSHA’s Web
site at https://www.msha.gov/01–995/
dieselerrorfactor.pdf, provides one way
of properly estimating analytical
variability from the baseline paired
punches while accounting for such
heterogeneity. This method was also
published as Appendix II of the 31-Mine
Study (BKG–54–2) and as Appendix 2 of
MSHA’s web document on the error
factor (AB29–BKG–61, cited as Ref. #4
by Borak/Sirianni).
To properly analyze the baseline
paired punch data by the method of
MSHA’s web document on the error
factor, the square root of each punch
result (µg/cm2) is first calculated. Next,
we calculate the difference between
square roots within each pair and
compute the standard deviation of these
differences. The result for these data is
an estimated SD of s = 0.175. Contrary
to the Borak/Sirianni conclusions, this
is substantially less than the
corresponding value, sτ=0.256, derived
from EC analyses on 621 pairs of
punches obtained during the 31-Mine
Study and published in MSHA’s web
document on the error factor (Borak/
Sirianni Ref. #4). Although Borak/
Sirianni stated that ‘‘MSHA has not
evaluated its proposed method by
means of systematic determinations of
the CV for samples obtained under real
mining settings,’’ their Ref. #4 contains
such an evaluation based on real mine
data (621 pairs of punches) obtained
during the 31-Mine Study. The lower
analytical variability exhibited in these
baseline paired punch data, as
compared to the 31-Mine Study, is not
surprising, since, for the baseline
samples, both punches within each pair
were analyzed by the same laboratory.
For the 31-Mine Study, this was not
generally the case, so both intra- and
inter-laboratory variability are included
in sτ.
As shown in MSHA’s web document
on the error factor, the analytical CV for
an individual punch result (X) at a
specified loading (µ) is given by
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CVµ [ X] = σ
2
.
µ
This quantity, which is plotted in Figure
IX–2 using s = 0.256, must be further
divided by √2 to specify analytical
imprecision for a 2-punch average, as in
the value of CVA cited by Borak/
Sirianni. Therefore, at an EC loading of
µ = 10 µg/cm2, the estimated analytical
error CV for a 2-punch average is 8.1%
using s = 0.256 (as in MSHA’s web
document on the error factor) or 5.5%
using s = 0.175 (based on the baseline
paired-punch data). For simplicity, the
effect of applying a blank adjustment
(by means of a control filter) has been
left out of these calculations. However,
the formula for CVA provided in
MSHA’s web document (AB29–BKG–
61) does account for the effect of a blank
adjustment on analytical variability.
31-Mine Study Subset
The third body of data examined in
the Borak/Sirianni analysis consisted of
63 pairs of EC results extracted from the
31-Mine Study. As in the baseline
paired punches, each pair consisted of
the results for two punches taken from
the same sample filter. Each analytical
EC punch result was converted to a
blank-adjusted EC concentration (µg/m3)
and multiplied by 1.3.
No explanation was provided as to
why these particular 63 pairs were
included in the Borak/Sirianni analysis
while about 750 other paired punch
results available from the 31-Mine
Study were excluded. However, by
examining the identification numbers of
the 63 samples included, MSHA
determined that they included 52
samples collected from the three trona
mines involved in the 31-Mine Study,
along with 11 samples collected from
one of the lead/zinc mines. All 63 of
these samples had one of the punches
acidified so that the effects of such
acidification could be evaluated. But
this was apparently not the only
inclusion criterion, since the Borak/
Sirianni analysis excluded
approximately 150 other paired-punch
samples in which one of the punches
was acidified. Acidification is the
process by which carbonates (CaCO3)
are chemically removed from a DPM
sample prior to the Method 5040
analysis. The collected DPM filter is
exposed to hydrochloric (HCl) acid
vapors. The chlorine combines with the
calcium; carbon dioxide and water are
evolved from the sample. Results from
the 31-Mine Study showed that the
submicron impactor successfully
removed the carbonate minerals from
the sample, and that acidification was
not required prior to the analysis.
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MSHA based its statistical analysis of
EC analytical precision (AB29–BKG–61)
on all 621 paired-punch samples from
the 31-Mine Study for which (1) valid
analytical results were available on both
punches and (2) both punches had
received identical treatment with
respect to acidification. Since all 63
samples included in the Borak/Sirianni
analysis had one punch acidified and
the other not acidified, they, along with
approximately 150 other such samples
were excluded from MSHA’s statistical
analysis of analytical precision.
The Borak/Sirianni method of
analyzing these data was, with one
notable exception, identical to the
method they used for the baseline
paired punches. As in their statistical
analysis of the baseline paired punches,
they tabulated, for these 63 samples, the
frequency of cases in which the
‘‘percentage difference’’ fell into three
categories: 0–4.99%, 5–9.99%, and
≥10%. The only methodological
difference was that, for these data, the
percentage difference was always
calculated relative to the lower of the
two punch results within each pair.
Borak/Sirianni provided no explanation
or justification for why they rearranged
the data within each pair so that the
lower value always appears as ‘‘Punch
A’’ and thus forms the denominator in
their calculation of percentage
difference.
The Borak/Sirianni analysis reached
the same conclusion with respect to this
dataset as with the baseline paired
punches: that ‘‘it is almost certain’’ that
these data ‘‘document failure to meet
the NIOSH and MSHA acceptability
criteria.’’ Likewise, since they used
essentially the same statistical method,
the authors reproduced the same five
fallacies described earlier in connection
with the baseline paired punches. There
are, however, at least three more reasons
why the Borak/Sirianni analysis of this
particular dataset is invalid, in addition
to points 1–5 above:
6. One of the punches in each pair
was acidified, and the other was not.
Therefore, differences in the analytical
results within pairs confound analytical
variability with the potential effects of
acidification and differential handling.
For this reason, these 63 samples (along
with all others that were similarly
treated) were excluded from MSHA’s
paired-punch analysis of analytical
variability (AB29–BKG–61).
7. Fifty of the 63 Punch A results
(79%) fell below 10 µg/cm2 and 33 of
them (52%) fell below 5 µg/cm2. As
shown in Figure 2, EC loadings below
5 µg/cm2 exhibit substantially greater
analytical variability than loadings
corresponding to EC concentration
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limits anticipated in the second partial
settlement agreement. Indeed, results for
the three samples showing the greatest
‘‘percentage difference’’ all fell below
the minimum value (2 µg/cm2) normally
reported by a laboratory EC analysis.
8. In addition to the bias explained
under point 4 above, the Borak/Sirianni
calculation of ‘‘percentage difference’’
was further biased by rearranging the
data within each pair so that the ‘‘Punch
A’’ result (X1) is always less than
‘‘Punch B’’ (X2). If the Punch A and B
designations (as provided in the original
31-Mine Study spreadsheet) had been
left unchanged, then the ‘‘percentage
difference’’ would sometimes have been
calculated relative to the lower value
and sometimes relative to the higher, as
in the Borak/Sirianni analysis of the
baseline paired punches. In their
analysis of the 31-Mine Study subset,
however, the lower of the two values
always forms the denominator for the
‘‘percentage difference.’’ This yields
systematically higher percentages than a
denominator equal to the average of the
two punches.
The sample identified as SKC–1D–166
illustrates the impact of points 7 and 8
on the Borak/Sirianni analysis and
conclusions. In the original spreadsheet,
the EC results for Punch A and B, prior
to any blank adjustment, were 0.92 µg/
cm2 and 0.76 µg/cm2. Under normal
procedures, EC values this low would
not even be reported by the laboratory.
However, the percentage difference,
relative to the average of these two
values, is 9.5%. A percentage difference
of this magnitude is inconsequential,
given that the mean EC loading is only
0.84 µg/cm2. In the Borak/Sirianni
analysis, however, a blank adjustment of
0.58 µg/cm2 was applied to both punch
results, yielding adjusted values of 0.34
and 0.18 µg/cm2. The punch A and B
designations were then switched, and
the percentage difference was calculated
relative to the lower value, yielding a
reported 89% difference. (If the punch
A and punch B designations had not
been switched, then Borak/Sirianni
would presumably have reported the
‘‘percentage difference’’ as 47%.) Thus,
the reported percentage difference is
mostly an artifact of applying the blank
adjustment to such small EC loadings
and of calculating the percentage
relative to the lower value.
Despite the additional potential
variability attributable to differential
handling of the punches, punch-topunch variability in this dataset appears
to be well within acceptable limits
when the EC loadings are taken into
account. The estimated value of s
calculated for these 63 data pairs by the
method of MSHA’s web document on
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the error factor is 0.090. This is
substantially lower than the
corresponding value (s∞ = 0.256) used
in the calculation of CVA for the average
of two blank-adjusted punches as
described in MSHA’s web document
(AB29–BKG–61). Therefore, contrary to
the Borak/Sirianni assessment, this
dataset exhibits less variability than
what MSHA has assumed in
determining an appropriate error factor.
MSHA believes that this data, when
analyzed correctly, verifies that the
sampling and analytical method meet
the NIOSH criteria.
B. Section 57.5060(c)
Section 57.5060(c) of the 2001 final
rule allows mine operators to apply to
the Secretary for additional time to meet
the final concentration limit of 160TC
µg/m3 of air. Operators are allowed only
one special extension per mine, which
cannot exceed a period of two years.
The rule also contains certification and
posting requirements and requires
operators to provide a copy of the
approved application to the authorized
representative of miners. The rule,
however, does not apply to the interim
concentration limit.
In the DPM settlement agreement,
MSHA agreed to adapt this provision to
apply it to the interim EC limit, include
consideration of economic feasibility,
and allow for annual renewals of special
extensions. MSHA proposed to revise
the standard pursuant to the terms of
the settlement agreement.
Unlike the 2003 NPRM, final
§ 57.5060(c)(1) does not expand the
scope of the provision to the interim
PEL. Instead, MSHA has decided to
retain the scope of the 2001 final rule so
that a special extension applies solely to
the final concentration limit. MSHA
believes that the feasibility data in the
rulemaking record does not justify
providing for an extension of time in
which to comply with the interim PEL.
MSHA found that the baseline sampling
results project that 63% of miners
sampled were not overexposed to the
interim DPM limit. In the 2001 final
rule, MSHA intended that this provision
apply to mine operators who needed
more time to implement technological
solutions to control DPM in their
individual mines. Also, MSHA wanted
to give mine operators some flexibility
where the regulatory scheme prohibited
administrative controls and respiratory
protection. Under this final rule, MSHA
has included its traditional hierarchy of
controls. The test for determining if an
individual operator has implemented all
feasible controls is very similar to that
for qualifying for a special extension
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absent burdensome paperwork
requirements.
MSHA believes that by incorporating
the hierarchy of controls approach, this
final rule addresses the primary concern
expressed by industry commenters who
supported special extensions: that
compliance with the interim DPM limit
using engineering and administrative
controls alone is not feasible for each
individual operator’s circumstances.
MSHA, however, has decided to retain
the 2001 requirement, as revised, for the
final concentration limit. At this time,
the DPM rulemaking record does not
contain sufficient information to delete
the requirement as it applies to the final
limit.
In final § 57.5060(c)(1), MSHA will
consider both economic and
technological feasibility when
determining whether operators qualify
for a special extension for the final
concentration limit. MSHA believes that
both technological and economic
feasibility must be assessed on a caseby-case basis. Therefore, mine operators
will have an opportunity to demonstrate
to MSHA that there is no cost-effective
solution to reducing a miner’s exposure
to DPM.
Section 57.5060(c)(1) also authorizes
the MSHA District Manager, rather than
the Secretary, to approve special
extensions to the final concentration
limit. MSHA believes that the district
managers have extensive knowledge of
the specific conditions and
circumstances that exist at mines within
their regions. Consequently, MSHA has
determined that they are the appropriate
entity to assess technical and economic
feasibility issues at mines. In unusual or
particularly complex circumstances,
district staff may be assisted by
personnel from MSHA’s Directorate of
Technical Support.
When determining whether to grant a
special extension for complying with
the final concentration limit, MSHA
will apply the criteria of the standard.
MSHA will conduct an analysis of the
circumstances at a mining operation to
determine whether the mine operator
has exhausted all feasible engineering
and administrative controls before using
respiratory protection to supplement
controls. A mine operator’s application
for an extension must include
information that explains why the
operator believes engineering and
administrative controls sufficient to
achieve compliance with the applicable
limit are economically and/or
technologically infeasible. The
application also must include the most
recent DPM monitoring results, and
specify the actions the operator intends
to take during the extension period to
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32951
minimize miners’ exposures to DPM,
such as monitoring, ordering controls,
adjusting ventilation, respiratory
protection, and other good faith actions
of the mine operator. The circumstances
under which MSHA requires respiratory
protection are in this final § 57.5060(d).
In order for MSHA to approve an
application for a special extension,
MSHA will evaluate whether the mine
operator has utilized all feasible
controls. Such an evaluation will
involve consideration of numerous
factors including the specific mining
conditions, type of mining equipment
used, nature of the overexposure,
controls used by the mine operator, and
MSHA policy and case law governing
the economic and technological
feasibility of controls. Comprehensive
discussion regarding economic and
technological feasibility, and
enforcement of feasible controls is
included elsewhere in this preamble.
Where an extension is granted,
overexposed miners will be required to
wear respiratory protection under a
respiratory protection program as
specified in § 57.5060(d). As MSHA
stated in the preamble to the 2003
NPRM, it does not intend for PPE to be
permitted during an extension period as
a substitute for feasible engineering and
administrative controls. Rather, MSHA
will require mine operators to
implement all feasible engineering and
administrative controls to reduce
exposures to the applicable limit, or if
that is not possible, to the lowest level
feasible. Once these controls are
implemented, MSHA will consider
whether to grant the extension. During
the period of the extension, the mine
operator will be required to maintain
these engineering and administrative
controls, along with implementation of
a respiratory protection program fully
compliant with ANSI Z88.2–1969 for all
miners whose exposure to DPM
continues to exceed the applicable DPM
limit.
Like the 2003 NPRM, § 57.5060(c)(2)
of the final rule retains the requirement
for the mine operator to certify that one
copy of the application was posted at
the mine site for at least 30 days prior
to the date of application, and another
copy was provided to the authorized
representative of miners. It is the
agency’s position that such advance
notification provides miners with the
opportunity to provide comments to the
District Manager regarding the
information provided by the mine
operator in the application. This record
also is subject to access to records
requirements under § 57.5075 of the
2001 final rule.
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One commenter questioned the need
for the requirement under
§ 57.5060(c)(2) to provide advance
notification to a miners’ representative
when a mine operator is going to submit
an application for a special extension.
This commenter suggested instead that
it is sufficient to give a copy to the
miner’s representative at the time the
application is submitted. MSHA
disagrees for the above reasons.
Final § 57.5060(c)(3) limits each
special extension to a period of one year
from the date of approval, and removes
the limit on the number of special
extensions that may be granted to each
mine. MSHA’s determination is based
on limited data in the rulemaking record
at this time to conclude that mine
operators feasibly can meet the final
DPM limit.
MSHA also considered longer
durations for special extensions. MSHA
acknowledges that durations longer than
one year would reduce the paperwork
burden on mine operators. However,
MSHA rejected the concept, since
MSHA has observed rapid progress in
the development of improved DPM
control technology since 2001.
Moreover, introduction of new mining
equipment models increasingly include
features aimed at better reducing DPM
exposures, such as cleaner engines and
better environmental cabs. It is not
MSHA’s intent to allow mine operators
to use respiratory protection for
extended periods of time where controls
are feasible.
Other commenters who supported the
proposed changes to § 57.5060(c)
wanted the criteria used for granting or
denying a special extension to be
communicated clearly and
unambiguously to the mining industry
in the body of the standard. Moreover,
these commenters wanted MSHA to give
a mine operator an extension if the
operator meets the criteria under this
standard.
Given that each mine has unique
circumstances affecting economic or
technological feasibility to comply with
the DPM standard, MSHA chose to
include generic criteria in the standard
for mine operators to develop and for
MSHA to consider in granting
extensions.
Final § 57.5060(c)(4) requires mine
operators to comply with the terms of an
approved application for a special
extension. This provision also requires
mine operators to post a copy of the
approved application at the mine site
for the duration of the extension, and
provide a copy to the authorized
representative of the miners.
One commenter stated that posting a
copy of the application on the mine
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bulletin board for the duration of the
extension is excessive. As an
alternative, this commenter suggested
posting the application for a sufficient
time for miners to view it. MSHA
believes that miners and their
representatives should have the right to
review the approved special extension
at the mine site for the duration of its
effectiveness. Consequently, MSHA has
retained the posting requirement in this
final rule.
MSHA requested comments on
whether proposed § 57.5060(c) would be
necessary in light of MSHA’s
recommendations to prescribe use of
feasible engineering and administrative
controls supplemented by respiratory
protection. MSHA also requested that
the public give examples of how this
requirement would benefit mine
operators if it were included in the final
regulatory framework. MSHA stated in
the preamble to the 2003 NPRM that it
was interested in avoiding duplication
and increased paperwork for the mining
industry to resolve feasibility issues at
individual mining operations.
Therefore, MSHA was seeking further
input from the public on the need for
proposed § 57.5060(c) and how this
provision fits within the comprehensive
structure of the current rulemaking.
With respect to the interim limit,
MSHA agrees with the commenter who
observed that MSHA routinely handles
compliance problems that are due to
circumstances beyond the control of the
mine operator without special
extensions, and that therefore, if these
same procedures are followed with
respect to DPM, special extensions of
the interim DPM limit are not justified.
The commenter’s other suggestion that
remaining issues regarding special
extensions be deferred until rulemaking
begins on the final DPM limit will be
considered by MSHA at that time. Until
then, provisions relating to special
extensions to the final DPM limit have
been retained in this final rule.
MSHA apprised the mining
community in the proposed preamble of
its concerns over whether a special
extension is necessary given the changes
to the methods of compliance in the
new final rule. MSHA believes that
these revisions accomplish the same
objective as a special extension, but
without the associated paperwork and
recordkeeping. MSHA explained that it
believed special extensions were
appropriate in the context of the original
2001 final rule, because it prohibited
respiratory protection and
administrative controls as means of
compliance. The 2001 final rule would
have required mine operators to comply
with the applicable DPM limit using
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only engineering and work practice
controls. Respiratory protection and
administrative controls (defined
uniquely as job rotation) were expressly
prohibited as means of compliance.
Numerous comments to the 2003
NPRM were received concerning this
provision. Several commenters
supported the proposed changes to
§ 57.5060(c). Some other commenters
supported the proposed changes, but
suggested that an appeals process
should be specified so a mine that is
denied a special extension by the
District Manager could appeal that
decision to a higher authority. Several
commenters who supported the
addition of an appeals process suggested
that a time limit of 30 days be imposed
on the District Manager to determine
whether to grant a special extension. In
addition, they suggested that an
additional 60 days be provided for an
appeal if the District Manager does not
grant the special extension. MSHA
believes that the Mine Act currently
affords mine operators adequate due
process rights to a hearing on the merits
before an administrative law judge (ALJ)
of the independent Commission. If an
operator disagrees with the ALJ’s
decision, the operator may request an
appeal before the Commission, which is
composed of five independent
commissioners. Any person adversely
affected by a determination of the
Commission may obtain review from a
U.S. court of appeals for the applicable
circuit. For the foregoing reasons,
MSHA sees no reasonable basis for
creating parallel procedures to
accomplish the same objective as
existing procedures.
One of the commenters suggested that
MSHA grant extensions prior to
issuance of a citation for an
overexposure to DPM, rather than using
the citation as the triggering event that
initiates the special extension process.
Under the final provision, a citation
does not need to be issued before MSHA
can grant an extension. MSHA,
however, must assess feasibility of
compliance before granting an extension
or denying an application for an
extension. If MSHA finds a miner
overexposed to DPM and the mine
operator does not comply with all
aspects of § 57.5060(d), MSHA will cite
the operator for noncompliance.
Several comments were received that
were opposed to any form of special
extension or any mechanism by which
mine operators could delay compliance
with the applicable DPM limits using
exclusively engineering or work practice
controls. Commenters who opposed
special extensions stated that MSHA
lacks evidence to substantiate the need
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for expanding the scope of the special
extension provision to include the
interim limit. These commenters believe
that the rulemaking record adequately
documents feasibility of the mining
industry, as a whole, to comply with the
DPM limits. Commenters noted that
MSHA requested examples that
substantiate this need, but none were
submitted by the mining industry. One
commenter suggested that just because
some operators require technical help
doesn’t mean the rule is infeasible for
the industry as a whole. This
commenter also noted that the proposed
changes to the special extension
provision address both the interim and
final DPM limits, despite the fact that
the preamble to the 2003 NPRM stated
that MSHA, ‘‘is only now seeking
information about whether the final
limit needs to be changed.’’
MSHA wishes to clarify that it
proposed making changes to
§ 57.5060(c) that would have applied
special extensions to both the interim
and final DPM limits. MSHA strongly
agrees that the mining industry, as a
whole, can comply with the interim
PEL. Also, the 31-Mine Study, baseline
sampling results, compliance assistance
visits, and MSHA’s current experience
with enforcing a comparable interim
limit all sustain MSHA’s determination
regarding the interim PEL. MSHA,
however, does not have adequate
evidence at this time to delete the
special extension requirement for the
final concentration limit.
Commenters opposed to special
extensions also expressed that the
proposed changes to the special
extension provision are less protective
than the existing provision because
respirators could be substituted for more
protective engineering and work
practice controls. These commenters
stated further that such action violates
the Mine Act requirement in Section
101(a)(6)(a) that such rules attain the
highest degree of protection for miners,
with feasibility as a consideration. Since
these commenters believe feasible
engineering and work practice controls
exist for the industry as a whole to
comply with the applicable DPM limits,
they reasoned that a provision
permitting compliance by respirators
would constitute a diminution of
protection to miners. MSHA disagrees.
Nowhere does this final rule allow
respiratory protection in lieu of feasible
engineering and administrative controls.
If anything, MSHA has provided greater
protection for miners by allowing
prompt usage of supplemental
protection for miners when feasible
controls have been exhausted.
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C. Sections 57.5060(d) and 57.5060(e)
Section 57.5060(d) of the 2001 final
rule permits miners engaged in specific
activities involving inspection,
maintenance, or repair activities to work
in concentrations of DPM that exceed
the interim and final limits, with
advance approval from the Secretary.
MSHA specifies in the standard that
advance approval is limited to activities
conducted as follows:
(i) For inspection, maintenance or repair
activities to be conducted:
(A) In areas where miners work or travel
infrequently or for brief periods of time;
(B) In areas where miners otherwise work
exclusively inside of enclosed and
environmentally controlled cabs, booths and
similar structures with filtered breathing air;
or
(C) In shafts, inclines, slopes, adits, tunnels
and similar workings that the operator
designates as return or exhaust air courses
and that miners use for access into the mine
or egress from the mine;
Operators must meet the conditions
set forth in the standard for protecting
miners when they engage in the
specified activities in order to qualify
for approval of the Secretary to use
respiratory protection and work
practices. MSHA considers work
practices a component of administrative
controls.
In tandem with this requirement is
§ 57.5060(e) of the 2001 final rule which
prohibits use of respiratory protection to
comply with the concentration limits,
except as specified in an approved
extension under § 57.5060(c), and then,
only for activities related to inspection,
repair, or maintenance activities.
Additionally, Section 57.5060(f) of the
2001 final rule prohibits use of
administrative controls to comply with
the concentration limits. On July 18,
2002, MSHA stayed §§ 57.5060(d), (e)
and (f) of the 2001 final rule (67 FR
47296) pending completion of their
revisions in this final rulemaking.
Pursuant to the DPM settlement
agreement, MSHA proposed to adopt
the same hierarchy of controls as
required in MSHA’s other exposurebased health standards for M/NM
mines, and considered requiring
application to the Secretary before
respirators could be used to comply
with the DPM standard. MSHA further
specified that employee rotation would
not be allowed as an administrative
control for compliance with this
standard.
As proposed, the new final rule on the
interim limit requires that when a
miner’s exposure exceeds the PEL,
operators must reduce the miner’s
exposure by installing, using and
maintaining feasible engineering and
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32953
administrative controls; except
operators are prohibited from rotating a
miner to meet the DPM limits. When
controls do not reduce a miner’s
exposure to the DPM limits, controls are
infeasible, or controls do not produce
significant reductions in DPM
exposures, operators must continue to
use all feasible controls and supplement
them with a respiratory protection
program, the details of which are
discussed below in this preamble. The
new final rule does not include
requirements for written administrative
control procedures, written respiratory
protection programs, medical
examinations of respirator wearers or
transfer of miners unable to wear
respirators. Additionally, the new final
rule deletes § 57.5060(e), prohibiting
respiratory protection as a method of
compliance with the DPM rule, and
§ 57.5060(f), prohibiting the use of
administrative controls for compliance
with the 2001 final rule.
The new final rule does not give
preference to engineering controls over
administrative controls. MSHA will
require all feasible controls, of both
types if necessary, to be implemented to
reduce a miner’s exposure to DPM.
Employee rotation, however, is not
permitted as an administrative control
under this standard. Under the new
final rule, mine operators have a choice
of which control method they will use
first. MSHA intended for mine operators
to have the flexibility to choose to start
with engineering or administrative
controls, or a combination of both, for
the control method that best suits their
circumstances.
MSHA, however, believes that
engineering controls should be included
in the first tier of any control method for
protecting miners against exposure to
airborne contaminants. Engineering
controls provide a permanent method of
modifying the exposure source, or they
modify the environment of the exposed
miner. As a result, they decrease the
miner’s exposure to hazardous levels of
DPM. Moreover, engineering controls
are more consistent and reliable
protection for miners. The effectiveness
of engineering controls can be readily
determined and assessed. Routine
maintenance of engineering controls
provides greater effectiveness.
In the 2001 final rule, MSHA
uniquely defined administrative
controls as ‘‘worker rotation.’’ MSHA
historically has considered other types
of controls, besides worker rotation, to
be administrative controls, including
work practice controls which MSHA
permits under this new final rule.
Work practice controls are changes in
the manner work tasks are performed in
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order to reduce or eliminate a hazard.
MSHA strongly believes that these types
of administrative controls do not
compromise miners’ health and safety
and do not reduce the level of
protection provided miners under the
existing final rule. Moreover, mine
operators should be given the flexibility
to choose to start with either
engineering or administrative controls,
or a combination of both, for the control
method best suited for their mines.
Some examples of work practice
controls include: Minimizing engine
idling; limiting number of dieselpowered equipment operating in an
area; reducing or limiting engine
horsepower; hauling upgrade in exhaust
drifts rather than in intake; and limiting
the number of persons working in high
exposure areas.
MSHA’s regulatory scheme for its
hierarchy of controls is based on its
current enforcement policy for its
airborne contaminants which are
included in MSHA’s M/NM air quality
standards (30 CFR 56/57.5001–.5006).
Under these standards, MSHA requires
mine operators to abate a citation for an
overexposure to airborne contaminants
by using feasible engineering and
administrative controls to reduce the
miner’s exposure to the contaminant’s
exposure limit. Respiratory protection is
required to supplement feasible controls
that do not reduce a miner’s exposure to
the permissible level. The air quality
standards do not contain a requirement
for mine operators to develop written
administrative control procedures, nor
does MSHA’s enforcement policy
require a written respiratory protection
program. (See MSHA Program Policy
Manual, Volume IV, Parts 56 and 57,
Subpart D, §§ .5001 and .5005, August
30, 1990).
Some commenters opposed changing
the control method from that of the 2001
final rule, while others supported
removing the prohibition on
administrative controls and respirators
in order to have greater compliance
flexibility. MSHA agrees that operators
should be afforded greater flexibility of
compliance where such modifications to
the DPM standard do not compromise or
lower miners’ health protection from
that provided under the 2001 final rule.
Additionally, miners should be afforded
the added protection of respirators
when engineering and administrative
controls are not feasible, cannot reduce
DPM exposures to within permissible
limits, or cannot achieve significant
reduction in DPM levels.
MSHA evaluated the potential
consequences of relying on the
hierarchy of controls in the final rule.
MSHA also examined different control
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methods but abandoned them since they
were less protective than those in the
2001 final rule. These approaches
included allowing rotation of miners,
and respiratory protection upon
application to the Secretary of Labor.
MSHA also examined giving preference
for engineering controls as a first resort
with a lesser role for administrative
controls, including work practices.
Though some of these approaches
would save money for the mining
industry, MSHA found that they either
could be less protective or, in some
cases, too restrictive for the mining
industry in complying with the DPM
rule. There is also insufficient scientific
evidence in the rulemaking record to
justify some of these changes for
controlling exposure to a potential
human carcinogen. For example,
allowing worker rotation would increase
the number of persons exposed to a
potential carcinogen and thereby
increase the number of individuals at
risk.
Commenters suggested that MSHA
lacks legal justification for its hierarchy
of controls and reliance on other MSHA
rules does not justify this approach.
Many commenters believe that MSHA
should allow mine operators to use
respiratory protection on an equal
footing with engineering and
administrative controls. In fact, some
commenters believe that respiratory
protection is an engineering control.
MSHA disagrees. MSHA believes that it
has adopted an approach that is
supported by the best available evidence
and sustains the standard industrial
hygiene practice to rely first upon
engineering and administrative controls
to reduce a person’s exposure to
hazardous airborne contaminants.
Throughout this rulemaking, MSHA
has asked the mining community for
their views on the appropriate role for
administrative controls, and whether it
would be necessary for MSHA to require
written administrative procedures. In
response to the 2003 NPRM, the mining
industry strongly objected to written
administrative procedures. Commenters
stated that such a requirement would
increase compliance costs and reduce
efficiency and personnel availability.
Organized labor recommended that
MSHA require operators to have written
administrative control strategies and
post them on the mine’s bulletin board.
MSHA’s M/NM air quality standards
do not require that administrative
controls be in writing. However, written
administrative controls are required
under MSHA’s more recently
promulgated noise standard at 30 CFR
part 62. Although the 2001 final rule
specifically prohibits the use of
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administrative controls, it does not
prohibit other types of work practices
which MSHA considers to be
administrative controls. The 2001 final
rule does not include a requirement that
mine operators develop a written work
practice control strategy when using
such controls to achieve compliance
with the PEL, however, MSHA
recommends it as a good industrial
hygiene practice. MSHA is relying upon
its current experience under the air
quality standards that do not include
written administrative control
procedures. Thus far, the lack of these
written procedures has not hindered
MSHA’s effective enforcement of its air
quality standards. Where possible,
MSHA is avoiding additional paperwork
burdens under the final DPM rule.
MSHA also proposed to prohibit
rotation of miners as an administrative
control to comply with the final DPM
rule. Most commenters requested that
job rotation be allowed because it is a
low cost control method and it increases
management flexibility to achieve
compliance. These commenters,
however, offered no scientific evidence
in support of their position. Organized
labor and some other commenters
opposed allowing worker rotation. They
stated that rotation may reduce the risk
to an individual miner, but it will not
necessarily reduce the overall risk to the
population of miners; also, depending
on the shape of the dose response curve,
it may actually increase the population
risk, resulting in more cancer overall.
As stated earlier, the 2001 risk
assessment upon which this rule is
based classifies DPM as a probable
human carcinogen. The majority of
scientific data for regulating exposures
to carcinogens supports that job rotation
is an unacceptable method for
controlling exposure to both known and
probable human carcinogens because it
increases the number of persons
exposed. Recent OSHA chemicalspecific regulations for both known
human carcinogens and probable
human carcinogens prohibit job rotation
as a means of compliance. Examples
include the OSHA standards for
asbestos, butadiene, and ethylene oxide,
which are known human carcinogens
(based on the CDC National Toxicology
Program (NTP) Report on Carcinogens
for 2002 (Report on Carcinogens, Tenth
Edition; U.S. Department of Health and
Human Services, Public Health Service,
National Toxicology Program, December
2002.)), and OSHA standards for
methylenedianiline at 29 CFR
§ 1910.1050 and methylene chloride, (29
CFR § 1910.1052), which are reasonably
anticipated to be human carcinogens
(based on the same NTP report). DPM
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also appears on the NTP listing of
chemicals that are reasonably
anticipated to be human carcinogens.
Therefore, based on the scientific data
in the DPM rulemaking record, final
§ 57.5060(e) retains the prohibition on
the rotation of miners as an
administrative control used for
compliance with this the DPM rule.
Engineering controls are intended to
refer to controls that remove the DPM
hazard by applying such methods as
modification, substitution, isolation,
enclosure, and ventilation. MSHA
would consider a control to be effective
in reducing DPM exposure if credible
scientific or engineering studies
conclude that a control will achieve a
significant reduction in exposure.
Additionally, MSHA will consider a
control to be effective if MSHA finds
that similar diesel equipment operating
under similar conditions has
demonstrated that the equipment is
capable of significantly reducing
exposures. These significant reductions
may be achieved either by a single
control, or in combination with other
controls, and in either laboratory or
field trials. MSHA believes that a 25%
or greater reduction in DPM exposure is
significant. MSHA discusses this issue
in more detail in the Feasibility section
of this preamble.
MSHA considers certain traditional
methods for control of exposure to
airborne contaminants to be
technologically feasible for controlling
exposures to DPM, such as improved
ventilation (main and/or auxiliary) and
enclosed cabs with filtered breathing
air. Improving ventilation may involve
upgrading main fans, use of booster
fans, and use of auxiliary fans that may
or may not be connected to flexible or
rigid ventilation duct, as well as
installation of ventilation control
structures such as air walls, stoppings,
brattices, doors, and regulators. At most
mines, cabs with filtered breathing air
are technologically feasible for many
newer model trucks, loaders, scalers,
drills, and other similar equipment.
However, use of enclosed cabs with
filtered breathing air may not be feasible
as a retrofit to certain older equipment
or where the function performed by
miners using a particular piece of
equipment is inconsistent with any type
of cab (e.g., loading blastholes from a
powder truck, installing utilities from a
scissors-lift truck) or where the height of
the mine roof is insufficient for cab
clearance. Other examples of effective
DPM engineering controls that MSHA
would consider to be technologically
feasible include: DPM exhaust filters;
certain alternative fuels; fuel blends;
fuel additives; fuel pre-treatment
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devices; and replacement of older, highemission engines with modern, lowemission engines.
MSHA asked for comments on the
appropriate role for respiratory
protection in controlling DPM exposure.
Although commenters disagree on the
types of restrictions that MSHA should
place on their use, most commenters
indicated that respirators with some
restriction on their use should be
permitted as a means of compliance
with the DPM limits. Some commenters
believe MSHA DPM regulations should
conform verbatim to the current
respirator requirements in MSHA’s air
quality standards at 30 CFR 57.5005.
Other commenters felt that the only
change MSHA should make to the
existing requirements for respirator use
in 30 CFR 57.5005, would be to add
requirements for filters. Comments were
received from those who believe that
PPE such as respiratory protection may
be far more effective in protecting
miners from suspected DPM health
effects than any available and feasible
engineering control technology.
Other commenters suggested MSHA
model its respirator program after
OSHA’s generic standard for respiratory
protection at 29 CFR 1910.134. One
commenter said that routine use of
respirators for any normal production
job or activity should be allowed only
under a special extension and only for
the final exposure limit, or where
controls are in the process of being
installed. They and other commenters
also said that respirators are hard to
tolerate under the best of conditions,
and that a 10-minute break should be
allowed every two hours, so the miner
can remove the respirator in clean air.
Another commenter requested that
respirators not be used for the purpose
of determining compliance. Some of the
objections to the use of respirators that
were given by commenters are:
Respirators leak, interfere with
communication, increase the work of
breathing, and are stressful; instead of
creating one system to protect all
workers, use of respirators creates one
system per worker, each of which needs
maintenance; some workers cannot wear
respirators for a variety of reasons; and
routine use of respirators breeds
carelessness.
MSHA agrees that respiratory
protection does not provide comparable
protection to that of engineering and
administrative controls. Therefore, the
new final rule only requires respiratory
protection as a supplement to feasible
engineering and administrative controls.
When controls do not reduce a miner’s
DPM exposure to the limit, controls are
infeasible, or controls do not produce
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32955
significant reductions in DPM
exposures, then controls must be used
to reduce the miner’s exposure to as low
a level as feasible and be supplemented
with respiratory protection in
accordance with 30 CFR 57.5005(a), (b),
and 30 CFR 57.5060(d)(1) and (d)(2).
Based on observations and experience
in underground M/NM mines, MSHA
continues to believe that feasible
engineering and administrative controls
exist to adequately address most
overexposures to the interim DPM limit.
However, MSHA is not persuaded that
all DPM overexposures can be
eliminated through implementation of
feasible engineering and administrative
controls alone. Extra protective
measures such as those afforded by
respiratory protection must be taken to
protect miners in such circumstances.
Therefore, MSHA’s final § 57.5060(d)
conforms to the current respirator
requirements in MSHA’s air quality
standards in § 57.5005, with the
addition that the types of filters
appropriate for protection from DPM are
specified.
Type of Respiratory Protection
In the 2003 NPRM, MSHA proposed
that filters for air purifying respirators,
used to comply with the DPM limits, be
certified in accordance with 30 CFR part
11 as a high efficiency particulate air
(HEPA) filter; certified per 42 CFR part
84 as 99.97% efficient; or, certified by
NIOSH for DPM. Additionally, the 2003
NPRM would have required that nonpowered, negative-pressure, air
purifying, particulate-filter respirators
use an R-or P-series filter or any filter
certified by NIOSH for DPM. It also
specified that R-series filters not be used
for longer than one work shift.
MSHA requested comments on the
type of respirators that would be
suitable for protection against DPM.
Some commenters suggested that
various commercially available
respirators, including those with
filtering facepieces, were suitable for
protection against particles smaller than
DPM, and would therefore be suitable
for DPM as well. NIOSH recommended
that respirators used for protection
against DPM have an R–100 or P–100
certification per 42 CFR part 84. NIOSH
also recommended against using N-rated
respirators since diesel exhaust contains
oil, and aerosols containing oil can
degrade the performance of N-rated
filters.
As some commenters suggested,
MSHA is adhering to the provisions for
respiratory protection afforded in
accordance with § 57.5005(a) and (b).
However, § 57.5005(a) requires that
respirators approved by NIOSH under
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42 CFR part 84 which are applicable
and suitable for the purpose intended be
furnished and miners use the protective
equipment in accordance with training
and instruction. Currently, there is no
non-powered, negative-pressure, air
purifying, particulate-filter respirator
certified by NIOSH as appropriate for
protection from DPM. In order to protect
miners from DPM exposure, MSHA is
adopting the NIOSH recommendation
that respirators be NIOSH certified per
42 CFR part 84 as a high-efficiency
particulate air (HEPA) filter, certified
per 30 CFR part 11 as 99.97% efficient,
or certified by NIOSH for DPM. MSHA
is technology-forcing in its rulemaking,
and therefore, addressed the likelihood
that a respirator may be approved in the
future by NIOSH for DPM. MSHA is also
adopting the NIOSH recommendation
that filters used in non-powered,
negative-pressure, air purifying
respirators be either R- or P-series.
In MSHA PPL No. P03–IV–1, effective
August 8, 2003, MSHA addressed the
question of whether a powered airpurifying respirator (PAPR) could
provide suitable respiratory protection
from DPM. MSHA stated, ‘‘Yes, if the
PAPR is equipped with filters that meet
one of the following criteria:
• Certified by NIOSH under 30 CFR
part 11 as high efficiency particulate air
(HEPA) filter;
• Certified by NIOSH under 42 CFR
part 84 as 99.97% efficient; or
• Certified by NIOSH for DPM.’’
This holds true for compliance with
final § 57.5060, and MSHA’s position
will be reiterated in MSHA’s
compliance guide for the new final rule.
MSHA believes that most workers who
are medically unable to use a negative
pressure respirator will be able to use a
PAPR, which offers considerably less
breathing resistance than a negative
pressure respirator. Employees who
cannot use a negative pressure
respirator could be provided with a less
physiologically burdensome respirator
that will enable them to continue in
their jobs protected against DPM
exposure.
NIOSH also recommended that
combination filters capable of removing
both particulates and organic vapor be
specified, since organic vapors and
gases can be adsorbed onto DPM.
MSHA, however, does not have data
substantiating that a DPM overexposure
would necessarily indicate an
associated overexposure to organic
vapors. Therefore, the final rule does
not require respirators to be certified for
organic vapor. If simultaneous sampling
for DPM and organic vapors indicate
overexposure to both contaminants, any
subsequent citation(s) relating to the
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overexposures would require that
respirators be used and equipped with
a filter or combination of filters rated for
both DPM and organic vapors.
Based on the above comments and
discussion, MSHA’s final rule on the
interim limit requires that when
respirators are used for compliance with
the DPM limits, that air purifying
respirators be equipped with either:
(i) Filters certified by NIOSH under 30
CFR part 11 as a high efficiency
particulate air (HEPA) filter;
(ii) Filters certified by NIOSH under
42 CFR part 84 as 99.97% efficient; or
(iii) Filters certified by NIOSH for
DPM.
Additionally, when non-powered,
negative-pressure, air purifying,
particulate-filter respirators are used for
compliance, the final rule requires the
use of an R- or P-series filter, or any
filter certified by NIOSH for DPM, and
that an R-series filter not be used for
longer than one work shift.
Written Respiratory Protection
Program. The 2003 NPRM
recommended that when respirators
were used for compliance with the DPM
limits, their use be in accordance with
MSHA Air Quality Standard,
§ 57.5005(a), (b), and § 57.5060(d)(1) and
(d)(2). Section 57.5005(b) incorporates
by reference, ANSI Z88.2–1969,
‘‘American National Standards Practices
for Respiratory Protection.’’ ANSI 1969
contains numerous recommended
practices for the appropriate selection,
use, and maintenance of respirators.
Included among these is a
recommendation that written standard
operating procedures governing the
selection and use of respirators be
established. MSHA’s enforcement
policy on its air quality standards has
focused on several of the key
recommendations in ANSI 1969,
including fit testing, maintenance, and
cleaning of respirators. MSHA’s policy,
however, is silent regarding the ANSI
recommendation on written standard
operating procedures. Accordingly,
under the 2003 NPRM, a written
respirator program would not have been
required.
In MSHA’s 2003 NPRM, it asked the
mining community to submit further
information for justifying a written
respiratory protection program,
including cost data, benefits to miners’
health, and projected paperwork
burden.
One commenter stated that it was
wrong to create a respiratory protection
requirement that treats exposure to DPM
differently than other gaseous
substances requiring the use of such
protective means. Another commenter
stated that proposing changes to
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MSHA’s respirator standard creates
multiple technical, scientific, medical,
and economic issues that must be
closely examined from the perspective
of MSHA’s statutory mandates. This
commenter suggested that given the vast
number of issues involved, it would be
inappropriate to consider respirator
standard changes in an ‘‘expedited’’
rulemaking limited to the DPM
standard. Other commenters also
suggested that MSHA address any
additional respiratory protection
requirements in a separate, generic
rulemaking applicable to all
contaminants. Some commenters
opposed a written program because they
believe the rule already carries too
heavy a paperwork burden.
Commenters supporting a
requirement for a written respirator
program suggested that it is an essential
element of a respiratory protection plan
and that MSHA’s requirements for
respiratory protection should be
modeled after OSHA’s requirements in
29 CFR 1910.134.
MSHA agrees with commenters who
believe that the final respiratory
protection provisions should be
consistent with the current air quality
requirements. Therefore, MSHA has
decided not to require that respiratory
protection programs be in writing in this
final rule.
Medical Evaluation and Miner
Transfer. The 2003 NPRM did not
include provisions addressing the
medical evaluation of respirator wearers
or the transfer of miners unable to wear
respirators due to medical and
psychological conditions. MSHA,
however, asked for further information
from the public as to whether the final
rule should include requirements for
medical examination and transfer.
Commenters were asked to submit cost
implications of such a program.
In MSHA’s 2003 NPRM, it discussed
this issue at length and asked
commenters to provide their views for
consideration in the final rule.
Moreover, MSHA included in this
discussion its statutory authority to
promulgate, where appropriate, medical
surveillance and transfer of miner
requirements to prevent miners from
being exposed to health hazards. The
Mine Act provision addressing this
issue is Section 101(a)(7) which states,
in pertinent part:
Where appropriate, such mandatory
standard shall also prescribe suitable
protective equipment and control or
technological procedures to be used in
connection with such hazards and shall
provide for monitoring or measuring miner
exposure at such locations and intervals, and
in such manner so as to assure the maximum
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protection of miners. In addition, where
appropriate, any such mandatory standard
shall prescribe the type and frequency of
medical examinations or other tests which
shall be made available, by the operator at his
cost, to miners exposed to such hazards in
order to most effectively determine whether
the health of such miners is adversely
affected by such exposure. Where
appropriate, the mandatory standard shall
provide that where a determination is made
that a miner may suffer material impairment
of health or functional capacity by reason of
exposure to the hazard covered by such
mandatory standard, that miner shall be
removed from such exposure and reassigned.
Any miner transferred as a result of such
exposure shall continue to receive
compensation for such work at no less than
the regular rate of pay for miners in the
classification such miner held immediately
prior to his transfer. In the event of the
transfer of a miner pursuant to the preceding
sentence, increases in wages of the
transferred miner shall be based upon the
new work classification.
Currently, MSHA standards do not
require medical transfer of M/NM
miners. Existing standards at 30 CFR 56/
57.5005(b) for control of miners’
exposures to airborne contaminants
require that mine operators establish a
respiratory protection program
consistent with the ANSI Z88.2–1969
‘‘American National Standard for
Respiratory Protection’’ which includes
medical determinations for potential
respirator wearers. However, MSHA’s
air quality enforcement policy for M/
NM mines is silent regarding this
recommendation. ANSI Z88.2–1969 also
does not include any recommendations
regarding the transfer of persons unable
to wear a respirator.
OSHA acknowledges within its
current standards addressing respiratory
protection at 29 CFR 1910.134(e) that
use of a respirator may place a
physiological burden on workers while
using them. OSHA requires employers
to provide medical evaluations before
an employee is fit tested or required to
use respiratory protection. Employers
are required to have a physician or other
licensed health care professional have
the worker complete a questionnaire, or
in the alternative, conduct an initial
medical examination in order to make
the determination. If the worker has a
positive response to certain specified
questions, the employer must provide a
follow-up medical examination. The
questionnaire is contained in the body
of the OSHA rule. The preamble to the
OSHA final rule states:
Specific medical conditions can
compromise an employee’s ability to tolerate
the physiological burdens imposed by
respirator use, thereby placing the employee
at increased risk of illness, injury, and even
death (Exs. 64–363, 64–427). These medical
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conditions include cardiovascular and
respiratory diseases (e.g., a history of high
blood pressure, angina, heart attack, cardiac
arrhythmias, stroke, asthma, chronic
bronchitis, emphysema), reduced pulmonary
function caused by other factors (e.g.,
smoking or prior exposure to respiratory
hazards), neurological or musculoskeletal
disorders (e.g., ringing in the ears, epilepsy,
lower back pain), and impaired sensory
function (e.g., a perforated ear drum, reduced
olfactory function). Psychological conditions,
such as claustrophobia, can also impair the
effective use of respirators by employees and
may also cause, independent of physiological
burdens, significant elevations in heart rate,
blood pressure, and respiratory rate that can
jeopardize the health of employees who are
at high risk for cardiopulmonary disease (Ex.
22–14). One commenter (Ex. 54–429)
emphasized the importance of evaluating
claustrophobia and severe anxiety, noting
that these conditions are often detected
during respirator training. (See 63 FR 1152,
at 330, 01/08/1998)
NIOSH, in its response to MSHA’s
proposed DPM rule, recommended that
‘‘mine operators be required to have a
written respiratory protection program,
analogous to that required by OSHA for
general industry in 29 CFR 1910.134
Respiratory Protection, that is work-site
specific and includes administration by
a trained program administrator,
respirator selection criteria, worker
training, a program to determine that the
workers are medically able to use
respiratory protective equipment, and
provisions for regular evaluation of the
program’s effectiveness.’’
Organized labor and industry were
divided on this issue. In general,
industry commenters oppose any
additions to the respiratory protection
requirements for compliance with the
current air quality standards. Some
commenters also suggested that MSHA
address any additional respiratory
protection requirements in a separate
rulemaking applicable to all airborne
contaminants. Organized labor strongly
emphasized in their comments that to
protect miners’ jobs, the final rule must
contain requirements for an effective
respiratory protection program,
including a written program, medical
evaluation of respirator wearers, and
transfer of miners unable to wear
respirators. Some commenters stated
that their respiratory protection
programs already provide for medical
examination of miners before they are
required to wear respiratory protection.
One commenter stated that in an
underground mine, transfer of
employees to areas free of diesel exhaust
would be extremely difficult.
MSHA believes that it is feasible for
mine operators to achieve compliance
with the interim limit by using effective
engineering and administrative controls
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32957
in most circumstances. As a result,
MSHA projects that there will be very
few instances where miners will be
required to wear respirators for longterm compliance. Further, mine
operators have several alternatives in
respirator selection. They can choose
either positive- or negative-pressure
respirators, or powered or non-powered
air purifying respirators. Those few
miners who have a medical condition
that would prevent them from wearing
a negative-pressure respirator could be
provided with and could normally wear
a powered air purifying respirator.
MSHA believes that it would be a rare
occurrence to encounter a miner who
could not wear any type of respirator
due to a medical condition.
Whereas MSHA agrees that there is
sound evidence establishing that some
persons may have difficulty wearing
respirators and should be prohibited
from wearing these devices, MSHA
finds that many mine operators have
voluntarily established programs to
medically evaluate miners’ ability to
wear respirators. One document in the
rulemaking record that supports this
position was developed by the Bureau
of Labor Statistics of the Department of
Labor and the National Institute for
Occupational Safety and Health. These
two agencies issued a recent joint
survey report entitled ‘‘Respirator Usage
in Private Sector Firms, 2001.’’ This
publication summarizes the results of a
questionnaire mailed to over 40,000
general industry and mining companies.
The survey found that 64% (2,246) of
the estimated 3,493 mining companies
that used respirators during the 12
months prior to the survey assess
employees’ medical fitness to wear
respirators. The survey also found that
61% (2,138) of these mining companies
have written procedures and schedules
for maintaining respirators. The 3,493
mining companies, however, included
establishments that extract oil and gas.
Although the Mine Act requires,
where appropriate, that MSHA
standards prescribe the type and
frequency of medical examinations to
determine whether the health of miners
is adversely affected by exposure to
hazards, it does not mandate medical
examinations to determine a miner’s
ability to wear PPE for protection from
those hazards.
Based on the above, MSHA believes a
requirement for medical evaluation of
respirator wearers, and transfer of
miners unable to wear respirators is
inappropriate for this rulemaking. Such
requirements would have minimal
application, particularly considering the
extent to which mine operators are
voluntarily implementing such
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provisions and the limited long term use
of respirators envisioned under the
interim rule.
Application To Use Respirators
Section 57.5060(d) of the 2001 final
rule permits miners engaged in specific
activities involving inspection,
maintenance, or repair activities to work
in concentrations of DPM that exceed
the interim and final limits, to use
respiratory protection with advance
approval from the Secretary. In MSHA’s
2003 NPRM, it proposed several
changes to its requirements on
respiratory protection, including
deleting the requirement that mine
operators apply in writing to the
Secretary for approval to use respiratory
protection.
Although some commenters
recommended requiring approval by the
Secretary before respiratory protection
should be permitted as a means of
compliance with the applicable DPM
limit, MSHA was not persuaded that
such a step would be necessary, and the
final § 57.5060(d) does not include this
recommendation. Respiratory protection
functions as a supplemental control.
Operators must have ready access to
respirators when they must be used to
supplement protection provided by
controls. When a mine operator is
issued a citation under § 57.5060(d) for
a miner’s exposure exceeding the
applicable DPM limit, and the mine
operator intends to use respiratory
protection as an interim control
measure, MSHA will make certain that
a respiratory protection program is
established and appropriate respirators
are used in accordance with
§ 57.5005(a), (b) and § 57.5060(d)(1) and
(d)(2) concerning filter selection for airpurifying respirators. Accordingly, the
requirement to apply in writing to the
Secretary for approval to use respiratory
protection can be deleted from the
existing rule without reducing
protection to the miners.
D. Section 57.5061
Determination
Compliance
(1) Section 57.5061(a)
Under existing 57.5061(a), the
Secretary determines compliance with
‘‘an applicable limit on the
concentration of [DPM] pursuant to
§ 57.5060.’’ MSHA only proposed
conforming changes to § 57.5061(a). As
proposed, final § 57.5061(a) deletes the
term ‘‘concentration limit’’ and replaces
it with the term ‘‘DPM limit’’ to reflect
a permissible exposure limit in
§ 57.5060(a) and a concentration limit in
existing § 57.5060(b). MSHA did not
receive comments specific to this
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conforming change. MSHA did not
propose changes to the single sample
compliance determination but received
comments from industry on this issue.
Those comments are beyond the scope
of this rulemaking and not included in
this preamble discussion.
(2) Section 57.5061(b)
Compliance determinations under
existing § 57.5061(b) are based on TC
measurements. As in the 2003 NPRM,
final § 57.5061(b) reflects that
compliance determinations will be
based on EC measurements instead of
TC. This change conforms to the
proposed change in the interim limit in
§ 57.5060(a). Copies of the NIOSH 5040
Analytical Method can be obtained at
www.cdc.gov/niosh or it can be obtained
by contacting MSHA’s Pittsburgh Safety
and the Health Technology Center, P.O.
Box 18233, Cochrans Mill Road,
Pittsburgh, PA 15236. As a result, the
address in the existing rule is removed
from the regulatory language.
MSHA did not receive comments on
this conforming change.
(3) Section 57.5061(c)
Under existing § 57.5061(c), the
Secretary determined the appropriate
sampling strategy for conducting
compliance sampling utilizing personal
sampling, occupational sampling, or
area sampling, based on the
circumstances of a particular exposure.
MSHA proposed that § 57.5061(c)
specify that only personal sampling
would be utilized for compliance
determinations. The final rule adopts
this change which does not alter
compliance requirements for mine
operators.
MSHA believes that, since it has
adopted EC as the surrogate for DPM,
personal sampling alone will result in
an accurate determination of miner
exposure to DPM. Section 57.5060(a)
establishes a DPM limit that specifically
relates to the exposure of miners to
DPM. Since the limit relates to the
exposure of miners, the appropriate
sampling method to determine
compliance is personal sampling. In this
respect, the sampling method for
compliance determination with this rule
is consistent with MSHA’s longstanding
practice of utilizing personal sampling
to determine compliance with exposure
limits for other airborne contaminants
in the M/NM sector.
MSHA anticipates several benefits of
standardizing personal sampling as the
compliance sampling method. MSHA
expects that mine operators and miners
are already familiar with personal
sampling, since MSHA utilizes it
routinely when compliance sampling
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for noise, dust, and other airborne
contaminants. Utilizing personal
sampling eliminates possible disputes
that could have arisen over whether an
area sample was obtained ‘‘where
miners normally work or travel.’’ Mine
operators who choose to conduct
environmental monitoring for DPM
under § 57.5071 using MSHA’s
compliance sampling method will not
need to anticipate which sampling
method MSHA would most likely have
selected (personal, area, or
occupational) based on the
circumstances of a particular exposure.
Personal sampling avoids situations
where area sampling is intended to
capture the exposure of a particular
miner for the full work shift even if that
miner moves to a new location during
the shift. Personal sampling for EC
avoids the problem of determining
compliance for an equipment operator
who is a smoker and who works inside
an enclosed cab. The measurement of
DPM using EC as the surrogate is not
affected by ETS. Under the existing rule,
this miner could not be sampled inside
the cab due to interference from tobacco
smoke, and area sampling outside the
cab would not indicate that miner’s
DPM exposure or the impact of the
environmental cab.
Most industry and labor commenters
supported personal sampling. A few
commenters, however, were opposed to
the elimination of area and occupational
sampling for compliance determination.
Two commenters suggested that relying
on personal sampling alone would
enable a mine operator to influence the
sampling result to the mine operator’s
advantage by re-assigning a miner being
sampled to an area with lower DPM
levels. MSHA believes that although a
mine operator may attempt to defeat
compliance sampling by re-assigning
the miner being sampled, MSHA’s
existing enforcement authority is
adequate to ensure a valid and
representative sample can nonetheless
be obtained. If the miner being sampled
for DPM is re-assigned to a different
workplace with lower DPM levels, or
the miner’s DPM exposure is
deliberately manipulated by some other
means, such as by withdrawing a
‘‘dirty’’ piece of equipment from the
area where the miner is working, the
inspector has the authority to
investigate the circumstances, and
invalidate the sample if the inspector
determines that the miner’s workday
was not representative.
Other commenters supported the
retention of area and occupational
sampling to give inspectors flexibility
and to avoid sample tampering. While
MSHA is sensitive to these issues, it
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believes it has the authority to address
them in existing enforcement
procedures.
One commenter suggested that
exposure be defined for this regulation
as ‘‘the exposure that would occur if the
employee were not using respiratory
protective equipment.’’ MSHA agrees
with this position but believes that it is
unnecessary to be this specific in the
regulation. MSHA’s longstanding
practice for assessing exposure to an
airborne contaminant is to not give
credit for respiratory protection in
determining a worker’s exposure.
MSHA, however, does encourage
workers to use respiratory protection.
MSHA believes that the use of EC as
the DPM surrogate allows the exclusive
use of personal sampling to establish
compliance with the DPM limit. MSHA
believes that this consistency in
sampling strategy outweighs concerns of
commenters.
E. Section 57.5062 DPM Control Plan
Existing § 57.5062 requires mine
operators to establish a DPM control
plan, or modify the plan, upon receiving
a citation for an overexposure to the
concentration limit in § 57.5060. A
single citation triggers the plan. A
violation of the plan is citable without
consideration of the current DPM
concentration level. The operator must
demonstrate that the new or modified
plan will be effective in controlling the
DPM concentration to the limit. The
existing rule also sets forth a number of
other specific details about the plan,
including a description of controls that
the operator will use to maintain the
DPM concentration; a list of dieselpowered units maintained by the mine
operator; information about each unit’s
emission control device; demonstration
of the plan’s effectiveness; verification
sampling; retention of a copy of the
control plan at the mine site for the
duration of the plan plus one year; and
a plan duration of three years from the
date of the violation requiring
establishment of the plan. By notice of
July 18, 2002, MSHA stayed the
effectiveness of this standard pending
completion of this rulemaking (67 FR
47296).
In accordance with the DPM
settlement agreement, MSHA agreed to
publish a notice of proposed rulemaking
to revise current § 57.5062. The
settlement agreement, however, did not
specify how MSHA should revise this
section. In its 2003 NPRM, MSHA
proposed provisions to modify and
simplify the plan requirements,
including deleting the requirement for
operators to demonstrate plan
effectiveness by monitoring.
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MSHA’s rationale for requiring a DPM
control plan was derived from the rule’s
initial approach to setting control
requirements. MSHA recognized that
every mine covered by this rule had
unique conditions and circumstances
that affect DPM exposures such as the
number and sizes of diesel-powered
engines, idling duration and frequency,
emission controls, diesel maintenance
practices, and ventilation. MSHA was
also interested in developing uniform
DPM control requirements that would
be effective in protecting miners’ health
and practical for the mining industry to
implement. MSHA acknowledges that
there are numerous approaches in
accomplishing this objective.
In the existing rule, the control plan
would only have to include a
description of the controls the operator
would use to maintain the concentration
of DPM to the applicable limit, a list of
diesel-powered units maintained by the
mine operator, information about any
units emission control device, and the
parameters of any other methods used to
control the concentration of DPM.
Operators could also consolidate the
DPM control plan with ventilation plan.
In proposed § 57.5062, MSHA would
require an operator to establish a written
control plan, or modify an existing
control plan, if it will take the mine
operator more than 90 calendar days
from the date of a citation to achieve
compliance. A single violation of the
PEL would continue to be the basis for
triggering the requirement for a control
plan. The control plan would remain in
effect for a one-year period following
termination of the citation. Mine
operators would also be required to
include in the plan a description of the
controls that will be used to reduce the
miners’ exposures to the PEL.
Although MSHA proposed to retain
the control plan, MSHA clearly alerted
the mining community of the possibility
that it would delete the control plan in
the final rule. MSHA raised concerns
with justifying the need for a control
plan requirement in light of the other
proposed revisions to the DPM rule,
including MSHA’s traditional hierarchy
of controls for exposure-based
standards. MSHA also currently
maintains an inventory of the dieselpowered equipment in each mine.
Consequently, MSHA asked the mining
community for its views on this
alternative approach in light of the other
proposed changes to the DPM standard.
MSHA received a number of comments
on this issue.
Some commenters were in favor of
retaining the control plan provisions
and stated that MSHA had provided no
evidence indicating that control plans
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32959
are infeasible. Several other commenters
who oppose deleting the control plan
requirement stated that planning is
essential for any complex activity, and
that mine operators have spent a great
deal of time and money in this
rulemaking, arguing that the control of
DPM is exceedingly complex. They felt
it was hard to understand how mine
operators could simultaneously argue
that control plans are unnecessary.
Other commenters favored deleting
existing § 57.5062 because the hierarchy
of controls would ensure that operators
employ all reasonable means to
maintain allowable levels of DPM. Some
of these commenters stated that if
compliance cannot be achieved through
engineering and administrative controls,
they were required to use respiratory
protection, and the end result would be
that miners are protected from
overexposure. They stated that a mine
operator would get a citation if miners
are not protected, and during the
abatement period the operator must
comply with DPM requirements
addressing maintenance, after-treatment
controls, low sulfur fuel, proper idling
practices and tagging requirements.
Commenters opposed to retention of
the control plan provisions felt that a
control plan would add nothing to
miner health, and create a paperwork
burden. They stated the enforcement
process provides all the documentation
necessary for compliance. They also
believe that the requirement for a
control plan is a disproportionate
response to a single overexposure.
MSHA initially intended to apply a
concentration limit that would result in
controlling DPM in the underground
mine environment. Since MSHA has
changed the compliance approach from
a concentration limit to a personal
exposure limit, the control plan would
have to address each miner’s
overexposure, rather than reducing
mine-wide concentrations.
MSHA agrees with commenters who
believe that the control plan is
unjustifiable in the final rule. Moreover,
the DPM rulemaking record contains
little, if any, rationalization in support
of retaining this provision. The
hierarchy of controls in the final rule
ensures that operators employ all means
to maintain allowable exposure levels of
DPM. MSHA is, therefore, deleting
existing § 57.5062, DPM control plan.
MSHA can monitor an operator’s good
faith efforts and obtain supporting
documentation during regular
inspections. Operators may choose to
control DPM emissions by filtering the
diesel-powered equipment; installing
cleaner-burning engines; increasing
ventilation; improving fleet
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management; utilizing administrative
controls; or using a variety of other
readily available controls, all without
consulting with, or seeking approval
from MSHA.
MSHA also agrees with those
commenters that expressed concerns
about the increase in paperwork
requirements. In promulgating
standards for the mining industry,
MSHA takes considerable initiative to
avoid placing an unreasonable burden
upon mine operators, especially small
mine operators. It was never MSHA’s
intent to have unnecessary duplication
of effort in obtaining compliance under
the DPM rule.
The existing rule also contained a
requirement in § 57.5062(c) that the
operator must demonstrate plan
effectiveness by monitoring. Although
MSHA has deleted the control plan
requirements in this final rule, MSHA
believes that monitoring to verify the
effectiveness of DPM controls is
adequately addressed under § 57.5071,
which requires mine operators to
monitor in order to determine, under
conditions that can be reasonably
anticipated in the mine, whether DPM
exposures exceed the applicable limits
specified in § 57.5060. These
requirements provide an effective
alternative to the existing requirement
in § 57.5062(c) for operators to
demonstrate plan effectiveness by
monitoring. Further, MSHA will
conduct additional compliance
sampling whenever MSHA suspects that
miners’ exposures to DPM are not being
maintained to the PEL.
Although a control plan might serve
to deter repeat overexposures, MSHA
can utilize existing enforcement tools to
accomplish this purpose. For example,
MSHA often asks operators to provide a
control strategy to justify extending
citations. MSHA also documents action
taken by the operator to comply when
terminating a citation. Further, repeat
overexposures can be cited with a
higher degree of negligence that
typically require a higher penalty
assessment. Failure to correct
overexposure conditions in a timely
manner could also be addressed through
existing mechanisms such as Section
104(b) of the Mine Act that includes
sanctions currently employed for failure
to abate violations.
F. Section 57.5075 Diesel Particulate
Records
Existing § 57.5075(a) summarizes the
recordkeeping requirements of the DPM
standards contained in §§ 57.5060
through 57.5071. As proposed, MSHA
has renumbered the Diesel Particulate
Recordkeeping Requirements table and
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added the recordkeeping requirement
established in existing § 57.5071(c) for
records of corrective actions taken. This
notation was inadvertently omitted from
the table in the 2001 final rule.
MSHA also proposed that the record
of corrective action be retained ‘‘until
the citation is terminated.’’ MSHA has
changed this retention period in the
final rule to ‘‘Until the corrective action
is completed.’’
As proposed, MSHA also has deleted
the table entry for existing § 57.5060(d),
‘‘approved plan for miners to perform
inspection, maintenance or repair
activities in areas exceeding the
concentration limit,’’ as the
corresponding provision of the rule was
deleted.
MSHA also deleted, as proposed,
records relating to § 57.5062(c),
‘‘compliance plan verification sample
results.’’
Finally, the final rule eliminates the
additional recordkeeping requirements
relating to control plans pursuant to
§ 57.5062 since this final rule deletes
the existing requirements for such
plans.
Of the comments received on the
general subject of recordkeeping, only
two were directed at the proposed
changes to the recordkeeping
requirements. Of the comments that
were relevant to the scope of this
rulemaking, most of the comments
expressed concern about the
recordkeeping burden required by
§ 57.5062(a) as related to control plans.
As noted above, the control plan
requirement has been removed from the
final rule.
One of the two comments that
addressed proposed changes to the
recordkeeping requirements identified
possible errors in the Diesel Particulate
Recordkeeping Requirements table in
§ 57.5075(a) (Recordkeeping
Requirements table). The commenter
noted that the existing rule requires that
a record of applications approved for
extensions of time to comply with the
exposure limits must be retained one
year beyond the duration of the
extension. The commenter stated that
this requirement did not reflect MSHA’s
intent as stated in the preamble to the
existing rule to retain this record for the
duration of the extension. MSHA agrees
that the recordkeeping requirement
listed in the existing rule was in error.
MSHA proposed to correct this error in
the 2003 NPRM and has adopted the
change in this rule. The final rule
clarifies that the required retention time
for this record is for the duration of the
extension.
This commenter also noted that the
retention time for evidence of corrective
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action taken as a result of a mine
operator’s environmental monitoring
per § 57.5071(c) was listed in Table
57.5075(a) in the 2003 NPRM as, ‘‘Until
the citation is terminated.’’ MSHA
agrees that this table entry is in error, as
a citation would not be issued on the
basis of an operator’s environmental
monitoring. MSHA has corrected the
table entry in the final rule to read
‘‘Until the corrective action is
completed.’’
The other comment relating to
proposed changes in recordkeeping
requirements expressed the general
concern that the information collection
provisions of the rule are not necessary
for MSHA to perform its functions. The
commenter suggested reducing the
paperwork burden by relying on current
testing for gaseous emissions and
deleting the final DPM limit from the
rule.
MSHA believes that each record
specified in § 57.5075 relates to
information that MSHA must have
access to in order to determine that the
mine operator is complying with the
corresponding provisions of the rule.
X. Distribution Table
Old section
57.5060(a) ................
57.5060(b) ................
57.5060(c) .................
57.5060(d) ................
57.5060(e) ................
57.5060(f) .................
57.5061 .....................
57.5062 .....................
57.5065 .....................
57.5066 .....................
57.5067 .....................
57.5070 .....................
57.5071 .....................
57.5075 .....................
New section
57.5060(a)
57.5060(b)
57.5060(c)
57.5060(d)
57.5060(d)
57.5060(d) and (e)
57.5061
Removed
57.5065
57.5066
57.5067
57.5070
57.5071
57.5075
XI. Regulatory Impact Analysis
This part of the preamble reviews
several impact analyses which MSHA is
required to provide in connection with
its final rulemakings. The full text of
these analyses can be found at MSHA’s
Regulatory Economic Analysis (REA)
Web page which is available from
MSHA at https://www.msha.gov/
REGSINFO.HTM.
A. Costs and Benefits: Executive Order
12866 Regulatory Planning and Review
and Regulatory Flexibility Act
Executive Order 12866, as amended
by Executive Order 13258, requires that
regulatory agencies assess both the costs
and benefits of regulations. The final
rule will result in estimated net cost
savings (negative costs) for underground
M/NM mine operators of $3,634 per
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year. This represents an average yearly
savings of $20 per mine for the 177
underground metal/non-metal mines
that will be affected by this final rule.
Of these 177 mines, 66 have fewer than
20 workers; 107 have 20 to 500 workers;
and 4 have more than 500 workers. For
a complete breakdown of the
compliance costs and savings of the
final rule, see Chapter IV of the REA
associated with this rulemaking.
The amended provisions in this final
rule will increase flexibility of
compliance with the existing final rule,
but continue to reduce significant health
risks to underground miners. Benefits of
the existing final rule are those
discussed by MSHA in the REA for the
January 19, 2001 final rule and include
reductions in lung cancers. In the long
run, as the mining population turns
over, MSHA estimates that a minimum
of 8.5 lung cancer deaths will be
avoided per year. Other benefits noted
in the 2001 REA were reductions in the
risk of death from cardiovascular,
cardiopulmonary, or respiratory causes
and reductions in the risk of sensory
irritation and respiratory symptoms.
B. Regulatory Flexibility Act (RFA) and
Small Business Regulatory Enforcement
Fairness Act (SBREFA)
The Regulatory Flexibility Act (RFA)
requires regulatory agencies to consider
a rule’s economic impact on small
entities. Under the RFA, MSHA must
use the Small Business Administration’s
(SBA’s) criterion for a small entity in
determining a rule’s economic impact
unless, after consultation with the SBA
Office of Advocacy, MSHA establishes
an alternative definition for a small
mine operator and publishes that
definition in the Federal Register for
notice and comment. For the mining
industry, SBA defines ‘‘small’’ as a mine
operator with 500 or fewer employees.
Traditionally, MSHA has also looked at
the impacts of its final rules on a subset
of mines with 500 or fewer employees—
those with fewer than 20 employees,
which the mining community refers to
as ‘‘small mines.’’ These small mines
differ from larger mines not only in the
number of employees, but also, among
other things, in economies of scale in
material produced, in the type and
amount of production equipment, and
in supply inventory. Therefore, their
costs of complying with MSHA rules
and the impact of MSHA rules on them
would also tend to be different. It is for
this reason that ‘‘small mines,’’ as
traditionally defined by the mining
community, are of special concern to
MSHA.
Therefore, MSHA’s analysis complies
with the legal requirements of the RFA
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for an analysis of the impacts on ‘‘small
entities’’ while continuing MSHA’s
traditional look at ‘‘small mines.’’ Using
SBA’s definition of a small mine
operator, the estimated yearly net
compliance cost savings of this final
rule on small underground M/NM mine
operators is approximately $3,675.
These estimated yearly net compliance
cost savings compare with estimated
annual revenues of approximately $2.35
billion for small underground M/NM
mine operators with 500 or fewer
employees. Using MSHA’s definition of
a small mine operator, the estimated
yearly net compliance cost savings of
this final rule on small underground M/
NM mine operators is approximately
$4,795. These estimated yearly net
compliance cost savings compare with
estimated annual revenues of
approximately $0.14 billion for small
underground M/NM mine operators
with 20 or fewer employees.
MSHA concludes that the final DPM
rule would not have a significant
economic impact on a substantial
number of small entities that are
covered by this rulemaking. MSHA has
determined that this is the case both for
mines affected by this rulemaking with
fewer than 20 employees and for mines
affected by this rulemaking with 500 or
fewer employees. MSHA has certified
these findings to the SBA. The factual
basis for this certification is discussed
in Chapter V of the REA associated with
this rulemaking.
C. Paperwork Reduction Act (PRA)
This final rule contains changes to
information collection requirements in
various provisions. Most of these
paperwork requirements were
previously approved by OMB as part of
OMB Control Number 1219–0135. The
information collection requirements are
summarized below and explained in
detail in the REA that accompanies the
rule. The REA includes the estimated
costs and assumptions for the
paperwork requirements related to this
final rule. A copy of the REA is
available on our Web site at https://
www.msha.gov/regsinfo.htm and can
also be obtained in hard copy from
MSHA. These information collection
requirements have been submitted to
OMB for review under 44 U.S.C. 3504(h)
of the Paperwork Reduction Act of 1995,
as amended. Respondents are not
required to respond to any collection of
information unless it displays a current
valid OMB control number.
As a result of this rule, mine operators
will obtain burden hour and cost
savings for the first two years that the
rule is in effect. In the third year that the
rule is in effect, mine operators will
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32961
incur a net increase in burden hours and
costs. For every year thereafter, burden
hours and costs will be the same as in
the third year.
In the first year of the rule, mine
operators will incur burden hour
savings of approximately 274 hours.
These savings will result from mine
operators (1) not having to apply for
approval from the Secretary to work in
concentrations of DPM exceeding the
applicable limit under § 57.5060(d) of
the 2001 final rule and maintaining the
conditions of the approval during the
period that the interim concentration
limit is in effect; and (2) not having to
write a DPM Control Plan under
§ 57.5062.
In the second year of the rule, mine
operators’ burden savings increase to
about 961 hours. These savings will
result from mine operators (1) not
having to apply for approval from the
Secretary to work in concentrations of
DPM exceeding the applicable limit
under § 57.5060(d) of the 2001 final rule
and maintaining the conditions of the
approval during the period that the final
concentration limit is in effect; and (2)
not having to write a DPM Control Plan
under § 57.5062.
In the third year of the rule, mine
operators will incur a net increase of
about 368 burden hours. This increased
burden occurs because mine operators
will no longer experience the savings
from not having to apply for approval
from the Secretary to work in
concentrations of DPM exceeding the
applicable limit under § 57.5060(d) of
the 2001 final rule and maintaining the
conditions of the approval during the
period that the final concentration limit
would be in effect; and will incur an
increase in burden associated with
requesting special extensions of the
final concentration limit under
§ 57.5060(c).
Mine operators incur a net increase in
paperwork burden costs of $12,250 per
year. This net increase is composed of
an annualized cost increase of $24,181
per year from changes to § 57.5060(c);
an annualized cost decrease of $6,394
per year from changes to § 57.5060(d);
and an annualized cost decrease of
$5,537 per year from changes to
§ 57.5062.
In comparison with the 2003 NPRM,
this final rule revises two provisions
(§§ 57.5060(c) and 57.5062) in a manner
that reduces the burden hours and
associated costs. These reductions in
burden hours and associated cost
savings relative to the 2003 NPRM are
incorporated into the calculations of the
previous paragraphs, which compare
the final rule with the existing rule.
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Sections 57.5071 and 57.5075 both
involve information collection
activities. Section 57.5071 triggers
notice requirements when
environmental monitoring indicates that
the DPM limit has been exceeded. The
paperwork burden for this provision has
not changed from the former
requirements. Section 57.5075
summarizes in chart form the
recordkeeping requirements of the rule.
The paperwork burden has only
changed for three of the provisions
listed, §§ 57.5060(c), 57.5060(d), and
57.5062. These provisions are discussed
more fully above and in the REA.
MSHA received several comments
regarding information collection. Some
commenters stated that the paperwork
requirements for developing a control
plan were too burdensome, and others
stated that they were justified. MSHA
has removed the requirement for control
plans due to the establishment of the
hierarchy of controls for meeting the
interim PEL. Removal of the control
plan requirement is discussed at length
under the section-by-section discussion
for § 57.5062.
Some commenters stated that all
information collection activities
associated with the rule including DPM
sampling and analysis mandates, the
plan provisions, the posting
requirements, and all of the required
records are unnecessary because MSHA
can perform its job without such
requirements as demonstrated by the
existence of standards that control other
diesel exhaust components. MSHA
disagrees. Although MSHA has deleted
certain information collection
requirements in this final rule, it
considers those included to be
necessary to determine whether mine
operators are in compliance with the
rule.
and the Department of Labor’s NEPA
procedures (29 CFR part 11).
This final rule has no significant
impact on air, water, or soil quality;
plant or animal life; the use of land; or
other aspects on the human
environment. MSHA solicited public
comment concerning the accuracy and
completeness of this environmental
assessment when this rule was first
proposed, and received no comments
relevant to this environmental
assessment. MSHA finds, therefore, that
the final rule has no significant impact
on the human environment.
Accordingly, MSHA has not provided
an environmental impact statement.
D. The Unfunded Mandates Reform Act
of 1995
This final rule does not include any
Federal mandate that may result in
increased expenditures by State, local,
or tribal governments; nor does it
increase private sector expenditures by
more than $100 million annually; nor
does it significantly or uniquely affect
small governments. Accordingly, the
Unfunded Mandates Reform Act of 1995
(2 U.S.C. 1501 et seq.) requires no
further agency action or analysis.
This final 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 undue burden on the Federal court
system. Accordingly, this final rule
meets the applicable standards provided
in Section 3 of Executive Order 12988,
Civil Justice Reform.
E. National Environmental Policy Act
MSHA has reviewed this final rule in
accordance with the requirements of the
National Environmental Policy Act
(NEPA) of 1969 (42 U.S.C. 4321 et seq.),
the regulations of the Council on
Environmental Quality (40 U.S.C. 1500),
This final rule has no adverse impact
on children. Accordingly, Executive
Order 13045, Protection of Children
from Environmental Health Risks and
Safety Risks, as amended by Executive
Orders 13229 and 13296, requires no
further agency action or analysis.
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F. The Treasury and General
Government Appropriations Act of
1999: Assessment of Federal
Regulations and Policies on Families
This final rule has no affect on family
well-being or stability, marital
commitment, parental rights or
authority, or income or poverty of
families and children. Accordingly,
Section 654 of the Treasury and General
Government Appropriations Act of 1999
(5 U.S.C. 601 note) requires no further
agency action, analysis, or assessment.
G. Executive Order 12630: Government
Actions and Interference With
Constitutionally Protected Property
Rights
This final rule does not implement a
policy with takings implications.
Accordingly, Executive Order 12630,
Governmental Actions and Interference
with Constitutionally Protected Property
Rights, requires no further agency action
or analysis.
H. Executive Order 12988: Civil Justice
Reform
I. Executive Order 13045: Protection of
Children From Environmental Health
Risks and Safety Risks
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J. Executive Order 13132: Federalism
This final rule does not have
‘‘federalism implications,’’ because it
does 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, Executive Order 13132,
Federalism, requires no further agency
action or analysis.
K. Executive Order 13175: Consultation
and Coordination With Indian Tribal
Governments
This final rule does not have ‘‘tribal
implications,’’ because it does 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, Executive Order 13175,
Consultation and Coordination with
Indian Tribal Governments, requires no
further agency action or analysis.
L. Executive Order 13211: Actions
Concerning Regulations That
Significantly Affect Energy Supply,
Distribution, or Use
Regulation of the M/NM sector of the
mining industry has no significant
impact on the supply, distribution, or
use of energy. This final rule is not a
‘‘significant energy action,’’ 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).’’
Accordingly, Executive Order 13211,
Actions Concerning Regulations That
Significantly Affect Energy Supply,
Distribution, or Use, requires no further
agency action or analysis.
M. Executive Order 13272: Proper
Consideration of Small Entities in
Agency Rulemaking
MSHA has thoroughly reviewed this
final rule to assess and take appropriate
account of its potential impact on small
businesses, small governmental
jurisdictions, and small organizations.
As discussed in Chapter V of the REA,
MSHA has determined and certified that
this final rule will not have a significant
economic impact on a substantial
number of small entities. MSHA
solicited public comment concerning
the accuracy and completeness of this
potential impact when the rule was first
proposed. The agency took appropriate
account of comments received relevant
to the rule’s potential impact on small
entities. Accordingly, Executive Order
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13272, Proper Consideration of Small
Entities in Agency Rulemaking, requires
no further agency action or analysis.
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Anderson, R. [2004] ‘‘An Evaluation of the
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Bugarski, A., Schnakenberg, G., Noll, J.,
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Castranova V., et al. ‘‘Effect of Exposure to
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NIOSH Carbon Measurements,’’ Aerosol
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Chase, Gerald. ‘‘Characterizations of Lung
Cancer in Cohort Studies and a NIOSH
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in Miners,’’ undated, received by MSHA on
January 5, 2004.
Cohen, H.J., Borak, J., Hall, T., et al: Exposure
of miners to diesel exhaust particulates in
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diesel exhaust induce a neutrophilic
response and upregulate IL–8 mRNA in
healthy subjects but not in asthmatic
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2001;124:324–325.
Fujimaki, H., et al. ‘‘Induction of the
imbalance of helper T-cell functions in
mice exposed to diesel exhaust,’’ Sci Total
Environ, 2001 Apr 10;270(1–3):113–21.
Fusco, D., et al. ‘‘Air Pollution and Hospital
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Rome, Italy,’’ Eur Respir J, 2001 Jun;17(6):
1143–50.
Gavett S. H., et al. ‘‘The Role of Particulate
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Int Arch Allergy Imm, 2001 Jan-Mar;124(l3): 109–12.
Gerbec, E. J. and Pomroy, W. ‘‘Diesel
Particulate Concentrations from DPM Tests
at the Columbus Junction Mine,’’ River
Products Company, Inc., Iowa City, Iowa,
2002 May.
Gilmour, M. I., et al. ‘‘Air Pollutant-enhanced
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32–40.
Haney, R. A., Fields, K. G, Pomroy, W.,
Saseen, G., Good, M. ‘‘Tests to Assess the
Performance of Ceramic Diesel Particulate
Filters for Reducing Diesel Emissions,’’
Proceedings of the 10th U. S. Mine
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Alaska, Anchorage, Alaska, 2004, May 6.
Head, H. John. ‘‘Technical and Economic
Feasibility of DPM Regulations,’’ MARG
Diesel Coalition Report (Attachment to
MSHA’s Comment No. 41), October 14,
2003.
Health Effects Institute, ‘‘Diesel Emissions
and Lung Cancer: Epidemiology and
Quantitative Risk Assessment,’’ A Special
Report of the Institute’s Diesel
Epidemiology Expert Panel, June 1999.
Health Effects Institute, ‘‘Improving
Estimates of Diesel and Other Emissions
for Epidemiological Studies,’’ April 2003.
Holgate, Stephen T., et al., ‘‘Health Effects of
Acute Exposure to Air Pollution, Part I:
Healthy and Asthmatic Subjects Exposed
to Diesel Exhaust,’’ Health Effects Institute
Research Report No. 112 (Partial Preprint
Version), December 2002.
Hsiao W. L., et al. ‘‘Cytotoxicity of PM(2.5)
and PM(2.5–10) Ambient Air Pollutants
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Assays,’’ Mutat Res, 2000 Nov 20;471(l-2):
45–55.
Ichinose, Takamichi, et. al., ‘‘Murine Strain
Differences in Allergic Airway
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122:183–0192, 1997a.
Ichinose, et. al., ‘‘Lung Carcinogenesis and
Formation of in Mice by Diesel Exhaust
Particles,’’ Carcinogenesis, 18:185–192,
1997b.
Indus. Union Dep’t, AFL-CIO v. Hodgson, 499
F.2d 467 (DC Cir. 1974).
International Union v. Federal Mine Safety
and Health Administration, 920 F.2d 960
(DC Cir. 1990).
International Union v. Federal Mine Safety
and Health Administration, 931 F.2d 908
(DC Cir. 1991).
International Life Sciences Institute (ILSI)
Risk Science Institute Workshop
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Lung Response To Particle Overload For
Human Risk Assessment: A Workshop
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Kuljukka-Rabb, T., et al. ‘‘Time- and DoseDependent DNA Binding of PAHs Derived
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Benzo[a]pyrene and 5-Methychrysene in a
Human Mammary Carcinoma Cell Line
(MCF–7),’’ Mutagenesis, 2001 Jul;16(4):
353–358.
Larsen, C., Levendis, Y., and Shimato, K.
‘‘Filtration Assessment and Thermal
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Mortality and Morbidity in Urban
Populations,’’ Health Effects Institute
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Lipsett M., and Campleman, Susan,
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and Lung Cancer: A Meta-Analysis,’’
American Journal of Public Health, (89)
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Magari, S. R., et al. ‘‘Association of heart rate
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28;104(9): 986–991.
Mayer, A., Matter, U., Czerwinski, J., Heeb,
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index.html], March.
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MSHA. Catalyzed diesel particulate matter
trap tests to determine DPM filtering
efficiency and gaseous emissions. Diesel
Test Laboratory Report. 2002 June 3. 8 pp.
MSHA. Diesel Particulate Matter Settlement
Agreement, 66 FR 35518 (2001) and 66 FR
35521 (2001).
MSHA. Diesel Particulate Matter Settlement
Agreement, 68 FR 48668 (2002).
MSHA. Evaluation of Rentar in-line fuel
catalyst. MSHA Docket No.: BKG–100.
MSHA. Executive Summary, Report on the
31-Mine Study.
MSHA. ‘‘Metal and Nonmetal Diesel
Particulate Filter Selection Guide’’ (Filter
Selection Guide). https://www.msha.gov/
nioshmnmfilterselectionguide/
dpmfilterguide.htm.
MSHA. Metal and Nonmetal Diesel
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REGS/COMPLIAN/PPM/PMVOL4C.HTM.
MSHA. Metal and Nonmetal Health
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MSHA, OSRV, Final Regulatory Economic
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Barrick Goldstrike Mines, Inc., Elko, Nevada,
Sampling for Diesel Particulate
Interferences, November 16, 1999; dated
March 15, 2000.
Black River Mine, Carmeuse Lime and Stone,
Inc., Butler, Kentucky, PS&HTC–DD–03–
316, Diesel Particulate Concentrations from
DPM Study, March 18 and 19, 2003, April
8 and 9, 2003, and April 29 and 30, 2003;
dated August 15, 2003.
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Black River Mine, Carmeuse Lime and Stone,
Inc., Butler, Pendleton County, Kentucky,
PS&HTC–DD–04–420, Diesel Particulate
Matter Compliance Assistance Studies,
March 16–18, 2004, April 13 and 14, 2004,
and May 25 and 26, 2004; dated July 14,
2004.
Blue Rapids Mine, Blue Rapids, Kansas,
Georgia-Pacific Gypsum Corporation,
Diesel Particulate Compliance Assistance
Visit, September 10, 2003; dated December
2, 2003.
Burning Springs Mine, Martin Marietta
Materials Inc., Wood County, West
Virginia, Dust Compliance Assistance Visit
to Evaluate Effects of Diesel Equipment
Modification, July 29 and 30, 2003 and
October 7 and 8, 2003; dated March 23,
2004.
Clover Bottom Mine, M.A. Walker, LLC,
Clover Bottom, Kentucky, July 8, 2003;
dated August 15, 2003.
Durham Mine, Martin Marietta Aggregates,
Inc., Marion County, Iowa, PS&HTC–DD–
04–423, Diesel Particulate Concentrations
from Diesel Particulate Matter Studies,
April 6 and 7, 2004 and May 25 and 26,
2004; dated August 19, 2004.
Fletcher Mine, The Doe Run Company,
Viburnum, Missouri, Compliance
Assistance Visit, July 8, 2003; dated
September 4, 2003.
Georgetown Mine, Nally and Gibson,
Georgetown, Kentucky, Compliance
Assistance Visit, May 7, 2003; dated
August 15, 2003.
Governeur Talc Company, Inc., No. 4 Mine,
Lewis County, New York, Diesel
Particulate Compliance Assistance Survey,
June 18, 2003; dated July 3, 2003.
Greens Creek Mine, Kennecott Minerals,
Juneau, Alaska, January 22–30, 2003; dated
June 17, 2003.
Greer Limestone Mine, Greer Limestone
Company, Monongalia County, WV, Diesel
Particulate Compliance Assistance Survey,
September 16, 2003; dated December 2,
2003.
Hampton Corners Mine, American Rock Salt
Company LLC, Livingston County, New
York, Diesel Particulate Compliance
Assistance Survey, March 23 and 24, 2004;
dated May 14, 2004.
Hampton Corners Mine, Martin Marietta
Materials, Inc., Livingston County, New
York, PS&HTC–DD–04–422,
Environmental Diesel Particulate Matter
Investigation, March 23 and 24, 2004.
Independence Mine, Rocca Processing, LLC,
Independence, Missouri, Diesel Particulate
Compliance Assistance Survey, June 25,
2003; dated July 3, 2003.
Inland Quarries, AmeriCold Logistics, LLC,
Kansas City, Kansas, Diesel Particulate
Compliance Assistance Survey, July 17,
2003; dated August 15, 2003.
Jefferson County Stone Mine, Rogers Group,
Inc., Jefferson County, Kentucky, DPM
Compliance Assistance Visit, December 12,
2002; dated March 10, 2003.
Jefferson County Stone Mine, Rogers Group,
Inc., Jefferson County, Kentucky, PS&HTC–
DD–03–312, Dust Compliance Assistance
Visit to evaluate effects of Diesel
Equipment Modification, January 28–30,
2003 and June 9 and 10, 2003; dated
September 4, 2003.
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Kaylor No. 3 Mine, Brady’s Bend
Corporation, Armstrong County,
Pennsylvania, Diesel Particulate
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25, 2003; dated October 20, 2003.
Kerford Limestone Mine, Kerford Limestone
Company, Weeping Water, Nebraska,
Diesel Particulate Compliance Assistance
Survey, September 10, 2003; dated October
20, 2003.
Lyons Salt Mine, Lyons Salt Company,
Lyons, Kansas, Diesel Particulate
Compliance Assistance Visit, September 9,
2003; dated November 3, 2003.
M&M Lime Company, Inc. Mine,
Worthington, Armstrong County,
Pennsylvania, Diesel Particulate
Compliance Assistance Survey, June 18,
2003; dated July 3, 2003.
Maysville Mine, Carmeuse North America,
Inc., Maysville, Kentucky, PS&HTC–DD–
03–308, Diesel Particulate Concentrations
from Diesel Particulate Matter Studies,
December 10–12, 2002, January 7–9, 2003,
and February 4–6, 2003; dated August 29,
2003.
Maysville Mine, Carmeuse North America,
Inc., Maysville, Kentucky, PS&HTC–DD–
03–311, Diesel Particulate Concentrations
from Diesel Particulate Matter Studies,
February 4–6, 2003 and April 1–3, 2003;
dated August 29, 2003.
Maysville Mine, Carmeuse North America,
Inc., Maysville, Kentucky, PS&HTC–DD–
04–416, Diesel Particulate Concentrations
from Diesel Particulate Matter Studies,
January 6 and 7, 2004, and February 2 and
3, 2004; dated April 2, 2004.
Oldham County Stone Mine, Rogers Group,
Inc., Oldham County, Kentucky, DPM
Compliance Assistance Visit, November 20
and 21, 2002; dated February 10, 2003.
Randolph Mine, Hunt Midwest Mining, Inc.,
Diesel Particulate Compliance Assistance
Survey, July 18, 2003; dated August 15,
2003.
Rock Springs Mine, Liter’s Quarry, Inc.,
Diesel Particulate Compliance Assistance
Survey, July 9, 2003; dated August 15,
2003.
Stamper Mine, Hunt Midwest Mining, Inc.,
Platte County, Missouri, Diesel Particulate
Compliance Assistance Survey, July 15,
2003; dated August 15, 2003.
Stillwater Mine, Stillwater Mining Company,
Nye, Montana, PS&HTC 33–04–428, Diesel
Particulate Matter Compliance Assistance,
June 7–17, 2004; dated August 6, 2004.
Stone Creek Brick Company Mine, Marsh A
C JR Company, Stone Creek, Ohio,
PS&HTC–DD–03–320, Diesel Particulate
Compliance Assistance Visit, May 21,
2003; dated August 15, 2003.
Stone Creek Brick Company Mine, Marsh A
C JR Company, Stone Creek, Ohio,
PS&HTC–DD–03–322, Diesel Particulate
Concentrations from Diesel Particulate
Matter Studies, June 10 and 11, 2003 and
July 29–30, 2003; dated August 29, 2003.
Sweetwater Mine, The Doe Run Company,
Viburnum, Missouri, Diesel Particulate
Compliance Assistance Visit, July 9, 2003;
dated September 4, 2003.
Table Rock #1 Mine, Table Rock Asphalt
Construction Company, Inc., Taney
County, Missouri, Diesel Particulate
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Compliance Assistance Visit, November
18, 2003; dated February 18, 2004.
Table Rock #3 Mine, Table Rock Asphalt
Construction Company, Inc., Stone County,
Missouri, Diesel Particulate Compliance
Assistance Visit, November 19, 2003; dated
February 18, 2004.
Weeping Water Mine, Martin Marietta
Aggregates, Diesel Compliance Assistance
Survey, September 9, 2003; dated October
14, 2003.
Winfield Lime and Stone Company, Inc.,
Cabot, Butler County, Pennsylvania, Diesel
Particulate Compliance Assistance Survey,
June 19, 2003; dated July 3, 2003.
MSHA. Program Information Bulletin No.
P02–04, ‘‘Potential Health Hazard Caused
by Platinum-Based Catalyzed Diesel
Particulate Matter Exhaust Filters,’’ May
31, 2002. Available from: (https://
www.msha.gov/regs/complian/PIB/2002/
pib02–04.htm.)
MSHA. Program Policy Letter (PPL #PO3–IV–
1, effective August 19, 2003.
MSHA. Program Policy Manual, Volume IV,
Parts 56 and 57, Subpart D, Section
.5001(a)/.5005, August 30, 1990.
MSHA. Results of ceramic trap testing at
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for minimizing NO2 (nitrogen dioxide)
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September 2002.
MSHA. Results of MSHA Baseline
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MSHA. Side Protocol of 31-Mine Study to
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Metal And Nonmetal Mines’’ (Report on
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Nikula K.J. ‘‘Rat Lung Tumors Induced by
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NIOSH, ‘‘Comments and recommendations
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Nonmetal Mines,’’ June 3, 2002.
NIOSH, ‘‘Diesel Emissions and Control
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Nonmetal Mines,’’ Edited notes prepared
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27, 2003 Cincinnati, Ohio and March 4,
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NIOSH, The Effectiveness of Selected
Technologies in Controlling Diesel
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NIOSH Analytical Method 5040, Elemental
Carbon, December 14, 1994. Copies of the
NIOSH 5040 Analytical Method can be
obtained at www.cdc.gov/niosh or they can
be obtained by contacting MSHA’s
Pittsburgh Safety and the Health
Technology Center, P.O. Box 18233,
Cochrans Mill Road, Pittsburgh, PA 15236.
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NIOSH Conference, Diesel Emissions and
Control Technologies in Underground
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March, 2003.
NIOSH Information Circular 8462, ‘‘Review
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List of Subjects in 30 CFR Part 57
Diesel particulate matter, Metal and
Nonmetal, Mine Safety and Health,
Underground mines.
Accordingly, chapter I of title 30 of the
Code of Federal Regulations is amended
as follows:
I
PART 57—SAFETY AND HEALTH
STANDARDS—UNDERGROUND
METAL AND NONMETAL MINES
1. The authority citation for part 57
continues to read as follows:
I
Authority: 30 U.S.C. 811 and 813.
§ 57.5062
[Removed]
2. Section 57.5062 is removed.
3. Also, in part 57:
I A. Sections 57.5060, 57.5061, 57.5071,
and 57.5075 are revised; and
I B. Sections 57.5065, 57.5066, 57.5067,
and 57.5070 are republished without
change.
The text reads as follows:
I
I
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§ 57.5060 Limit on exposure to diesel
particulate matter.
(a) A miner’s personal exposure to
diesel particulate matter (DPM) in an
underground mine must not exceed an
average eight-hour equivalent full shift
airborne concentration of 308
micrograms of elemental carbon per
cubic meter of air (308EC g/m3). [This
interim permissible exposure limit
(PEL) remains in effect until the final
DPM exposure limit becomes effective.
When the final DPM exposure limit
becomes effective, MSHA will publish a
document in the Federal Register.]
(b) After January 19, 2006, any mine
operator covered by this part must limit
the concentration of diesel particulate
matter to which miners are exposed in
underground areas of a mine by
restricting the average eight-hour
equivalent full shift airborne
concentration of total carbon, where
miners normally work or travel, to 160
micrograms per cubic meter of air
(160TC µg/m3). (c)(1) If a mine requires
additional time to come into compliance
with the final DPM limit established in
§ 57.5060 (b) due to technological or
economic constraints, the operator of
the mine may file an application with
the District Manager for a special
extension.
(2) The mine operator must certify on
the application that the operator has
posted one copy of the application at
the mine site for at least 30 days prior
to the date of application, and has
provided another copy to the authorized
representative of miners.
(3) No approval of a special extension
shall exceed a period of one year from
the date of approval. Mine operators
may file for additional special
extensions provided each extension
does not exceed a period of one year. An
application must include the following
information:
(i) A statement that diesel-powered
equipment was used in the mine prior
to October 29, 1998;
(ii) Documentation supporting that
controls are technologically or
economically infeasible at this time to
reduce the miner’s exposure to the final
DPM limit.
(iii) The most recent DPM monitoring
results.
(iv) The actions the operator will take
during the extension to minimize
exposure of miners to DPM.
(4) A mine operator must comply with
the terms of any approved application
for a special extension, post a copy of
the approved application for a special
extension at the mine site for the
duration of the special extension period,
and provide a copy of the approved
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application to the authorized
representative of miners.
(d) The mine operator must install,
use, and maintain feasible engineering
and administrative controls to reduce a
miner’s exposure to or below the DPM
limit established in this section. When
controls do not reduce a miner’s DPM
exposure to the limit, controls are
infeasible, or controls do not produce
significant reductions in DPM
exposures, controls must be used to
reduce the miner’s exposure to as low
a level as feasible and must be
supplemented with respiratory
protection in accordance with
§ 57.5005(a), (b), and paragraphs (d)(1)
and (d)(2) of this section.
(1) Air purifying respirators must be
equipped with the following:
(i) Filters certified by NIOSH under 30
CFR part 11 (appearing in the July 1,
1994 edition of 30 CFR, parts 1 to 199)
as a high efficiency particulate air
(HEPA) filter;
(ii) Filters certified by NIOSH under
42 CFR part 84 as 99.97% efficient; or
(iii) Filters certified by NIOSH for
DPM.
(2) Non-powered, negative-pressure,
air purifying, particulate-filter
respirators shall use an R- or P-series
filter or any filter certified by NIOSH for
DPM. An R-series filter shall not be used
for longer than one work shift.
(e) Rotation of miners shall not be
considered an acceptable administrative
control used for compliance with the
DPM standard.
§ 57.5061
Compliance determinations.
(a) MSHA will use a single sample
collected and analyzed by the Secretary
in accordance with the requirements of
this section as an adequate basis for a
determination of noncompliance with
the DPM limit.
(b) The Secretary will collect samples
of DPM by using a respirable dust
sampler equipped with a submicrometer
impactor and analyze the samples for
the amount of elemental carbon using
the method described in NIOSH
Analytical Method 5040, except that the
Secretary also may use any methods of
collection and analysis subsequently
determined by NIOSH to provide equal
or improved accuracy for the
measurement of DPM.
(c) The Secretary will use full-shift
personal sampling for compliance
determinations.
§ 57.5065
Fueling practices.
(a) Diesel fuel used to power
equipment in underground areas must
not have a sulfur content greater than
0.05 percent. The operator must retain
purchase records that demonstrate
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compliance with this requirement for
one year after the date of purchase.
(b) The operator must only use fuel
additives registered by the U.S.
Environmental Protection Agency in
diesel powered equipment operated in
underground areas.
§ 57.5066
Maintenance standards.
(a) Any diesel powered equipment
operated at any time in underground
areas must meet the following
maintenance standards:
(1) The operator must maintain any
approved engine in approved condition;
(2) The operator must maintain the
emission related components of any
non-approved engine to manufacturer
specifications; and
(3) The operator must maintain any
emission or particulate control device
installed on the equipment in effective
operating condition.
(b)(1) A mine operator must authorize
each miner operating diesel-powered
equipment underground to affix a
visible and dated tag to the equipment
when the miner notes evidence that the
equipment may require maintenance in
order to comply with the maintenance
standards of paragraph (a) of this
section. The term evidence means
visible smoke or odor that is unusual for
that piece of equipment under normal
operating procedures, or obvious or
visible defects in the exhaust emissions
control system or in the engine affecting
emissions.
(2) A mine operator must ensure that
any equipment tagged pursuant to this
section is promptly examined by a
person authorized to maintain diesel
equipment, and that the affixed tag not
be removed until the examination has
been completed. The term promptly
means before the end of the next shift
during which a qualified mechanic is
scheduled to work.
(3) A mine operator must retain a log
of any equipment tagged pursuant to
this section. The log must include the
date the equipment is tagged, the date
the equipment is examined, the name of
the person examining the equipment,
and any action taken as a result of the
examination. The operator must retain
the information in the log for one year
after the date the tagged equipment was
examined.
(c) Persons authorized by a mine
operator to maintain diesel equipment
covered by paragraph (a) of this section
32967
must be qualified, by virtue of training
or experience, to ensure that the
maintenance standards of paragraph (a)
of this section are observed. An operator
must retain appropriate evidence of the
competence of any person to perform
specific maintenance tasks in
compliance with those standards for one
year after the date of any maintenance,
and upon request must provide the
documentation to the authorized
representative of the Secretary.
§ 57.5067
Engines.
(a) Any diesel engine introduced into
an underground area of a mine covered
by this part after July 5, 2001, other than
an engine in an ambulance or fire
fighting equipment which is utilized in
accordance with mine fire fighting and
evacuation plans, must either:
(1) Have affixed a plate evidencing
approval of the engine pursuant to
subpart E of part 7 of this title or
pursuant to part 36 of this title; or
(2) Meet or exceed the applicable
particulate matter emission
requirements of the Environmental
Protection Administration listed in
Table 57.5067–1, as follows:
TABLE 57.5067–1
EPA requirement
40
40
40
40
CFR
CFR
CFR
CFR
EPA category
86.094–8(a)(1)(i)(A)(2) .........................
86.094–9(a)(1)(i)(A)(2) .........................
86.094–11(a)(1)(iv)(B) ..........................
89.112(a) ..............................................
PM limit
light duty vehicle ...............................................................
light duty truck ..................................................................
heavy duty highway engine ..............................................
nonroad (tier, power range) ..............................................
tier 1 kW<8 (hp<11) .........................................................
tier 1 8≤kW<19 (11≤hp<25) .............................................
tier 1 19≤kW<37(25≤hp<50) .............................................
tier 2 37≤kW<75(50≤hp<100) ...........................................
tier 2 75≤kW<130(100≤hp<175) .......................................
tier 1 130≤kW<225(175≤hp<300) .....................................
tier 1 225≤kW<450(300≤hp<600) .....................................
tier 1 450≤kW<560(600≤hp<750) .....................................
tier 1 kW≥560(hp≥750) .....................................................
0.1 g/mile.
0.1 g/mile.
0.1 g/bhp-hr.
varies by power range:
1.0 g/kW-hr (0.75 g/bhp-hr).
0.80 g/kW-hr (0.60 g/bhp-hr).
0.80 g/kW-hr (0.60 g/bhp-hr).
0.40 g/kW-hr (0.30 g/bhp-hr).
0.30 g/kW-hr (0.22 g/bhp-hr).
0.54 g/kW-hr (0.40 g/bhp-hr).
0.54 g/kW-hr (0.40 g/bhp-hr).
0.54 g/kW-hr (0.40 g/bhp-hr).
0.54 g/kW-hr (0.40 g/bhp-hr).
Notes:
‘‘g’’ means grams.
‘‘hp’’ means horsepower.
‘‘g/bhp-hr’’ means grams/brake horsepower-hour.
‘‘kW’’ means kilowatt.
‘‘g/kW-hr’’ means grams/kilowatt-hour.
(b) For purposes of paragraph (a):
(1) The term ‘‘introduced’’ means any
engine added to the underground
inventory of engines of the mine in
question, including:
(i) An engine in newly purchased
equipment;
(ii) An engine in used equipment
brought into the mine; and
(iii) A replacement engine that has a
different serial number than the engine
it is replacing; but
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(2) The term ‘‘introduced’’ does not
include engines that were previously
part of the mine inventory and rebuilt.
(3) The term ‘‘introduced’’ does not
include the transfer of engines or
equipment from the inventory of one
underground mine to another
underground mine operated by the same
mine operator.
§ 57.5070
Miner training.
(a) Mine operators must provide
annual training to all miners at a mine
covered by this part who can reasonably
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be expected to be exposed to diesel
emissions on that property. The training
must include—
(1) The health risks associated with
exposure to diesel particulate matter;
(2) The methods used in the mine to
control diesel particulate matter
concentrations;
(3) Identification of the personnel
responsible for maintaining those
controls; and
(4) Actions miners must take to
ensure the controls operate as intended.
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(b) An operator must retain a record
at the mine site of the training required
by this section for one year after
completion of the training.
§ 57.5071
Exposure monitoring.
(a) Mine operators must monitor as
often as necessary to effectively
determine, under conditions that can be
reasonably anticipated in the mine,
whether the average personal full-shift
airborne exposure to DPM exceeds the
DPM limit specified in § 57.5060.
(b) The mine operator must provide
affected miners and their
representatives with an opportunity to
observe exposure monitoring required
by this section. Mine operators must
give prior notice to affected miners and
their representatives of the date and
time of intended monitoring.
(c) If any monitoring performed under
this section indicates that a miner’s
exposure to diesel particulate matter
exceeds the DPM limit specified in
§ 57.5060, the operator must promptly
post notice of the corrective action being
taken on the mine bulletin board,
initiate corrective action by the next
work shift, and promptly complete such
corrective action.
(d)(1) The results of monitoring for
diesel particulate matter, including any
results received by a mine operator from
sampling performed by the Secretary,
must be posted on the mine bulletin
board within 15 days of receipt and
must remain posted for 30 days. The
operator must provide a copy of the
results to the authorized representative
of miners.
(2) The mine operator must retain for
five years (from the date of sampling),
the results of any samples the operator
collected as a result of monitoring under
this section, and information about the
sampling method used for obtaining the
samples.
§ 57.5075(a)
Diesel particulate records.
(a) Table 57.5075(a), ‘‘Diesel
Particulate Recordkeeping
Requirements,’’ lists the records the
operator must retain pursuant to
§§ 57.5060 through 57.5071, and the
duration for which particular records
must be retained.
TABLE 57.5075(A).—DIESEL PARTICULATE RECORDKEEPING REQUIREMENTS
Record
Section reference
1. Approved application for extension of time to comply with
exposure limits.
2. Purchase records noting sulfur content of diesel fuel ..........
3. Maintenance log ....................................................................
4. Evidence of competence to perform maintenance ...............
5. Annual training provided to potentially exposed miners .......
6. Record of corrective action ...................................................
7. Sampling method used to effectively evaluate a miner’s
personal exposure, and sample results.
§ 57.5060(c) ......
Duration of extension.
§ 57.5065(a)
§ 57.5066(b)
§ 57.5066(c)
§ 57.5070(b)
§ 57.5071(c)
§ 57.5071(d)
1 year beyond date of purchase.
1 year after date any equipment is tagged.
1 year after date maintenance performed.
1 year beyond date training completed.
Until the corrective action is completed.
5 years from sample date.
(b)(1) Any record listed in this section
which is required to be retained at the
mine site may, notwithstanding such
requirement, be retained elsewhere if
the mine operator can immediately
access the record from the mine site by
electronic transmission.
(2) Upon request from an authorized
representative of the Secretary of Labor,
the Secretary of Health and Human
Services, or from the authorized
representative of miners, mine operators
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.....
.....
......
.....
......
.....
Retention time
must promptly provide access to any
record listed in the table in this section.
(3) An operator must provide access
to a miner, former miner, or, with the
miner’s or former miner’s written
consent, a personal representative of a
miner, to any record required to be
maintained pursuant to § 57.5071 to the
extent the information pertains to the
miner or former miner. The operator
must provide the first copy of a
requested record at no cost, and any
additional copies at reasonable cost.
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(4) Whenever an operator ceases to do
business, that operator must transfer all
records required to be maintained by
this part, or a copy thereof, to any
successor operator who must maintain
them for the required period.
Dated: May 23, 2005.
David G. Dye,
Acting Assistant Secretary for Mine Safety
and Health.
[FR Doc. 05–10681 Filed 6–3–05; 8:45 am]
BILLING CODE 4510–43–U
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]]>Agencies
[Federal Register Volume 70, Number 107 (Monday, June 6, 2005)]
[Rules and Regulations]
[Pages 32868-32968]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-10681]
[[Page 32867]]
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Part II
Department of Labor
-----------------------------------------------------------------------
Mine Safety and Health Administration
-----------------------------------------------------------------------
30 CFR Part 57
Diesel Particulate Matter Exposure of Underground Metal and Nonmetal
Miners; Final Rule
Federal Register / Vol. 70, No. 107 / Monday, June 6, 2005 / Rules
and Regulations
[[Page 32868]]
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DEPARTMENT OF LABOR
Mine Safety and Health Administration
30 CFR Part 57
RIN 1219-AB29
Diesel Particulate Matter Exposure of Underground Metal and
Nonmetal Miners
AGENCY: Mine Safety and Health Administration (MSHA), Labor.
ACTION: Final rule.
-----------------------------------------------------------------------
SUMMARY: This final rule revises MSHA's existing standards addressing
diesel particulate matter (DPM) exposure in underground metal and
nonmetal (M/NM) mines. In this final rule, MSHA changes the interim
concentration limit measured by total carbon (TC) to a comparable
permissible exposure limit (PEL) measured by elemental carbon (EC),
which renders a more accurate DPM exposure measurement. Also, this
final rule increases flexibility of compliance for mine operators by
requiring MSHA's longstanding hierarchy of controls for its other
exposure-based health standards at M/NM mines, but retains the
prohibition on rotation of miners for compliance. Furthermore, this
final rule: Requires MSHA to consider economic as well as technological
feasibility in determining if operators qualify for an extension of
time in which to meet the final DPM limit; deletes the requirement for
a control plan; and makes conforming changes to existing provisions
concerning compliance determinations, environmental monitoring and
recordkeeping.
DATES: Effective Date: The final rule is effective on July 6, 2005.
FOR FURTHER INFORMATION CONTACT: Office of Standards, Regulations, and
Variances, MSHA, 1100 Wilson Blvd., Room 2350, Arlington, Virginia
22209-3939; 202-693-9440 (telephone); or 202-693-9441 (facsimile).
You may obtain copies of this final rule and the Regulatory
Economic Analysis (REA) in alternative formats by calling 202-693-9440.
The alternative formats available are either a large print version of
these documents or electronic files that can be sent to you either on a
computer disk or as an attachment to an e-mail. The documents also are
available on the Internet at https://www.msha.gov/REGSINFO.HTM.
SUPPLEMENTARY INFORMATION:
Outline of Preamble
This outline will assist the mining community in finding
information in this preamble.
I. List of Common Terms
II. Rulemaking Background
A. First Partial Settlement Agreement
B. Second Partial Settlement Agreement
III. The Final PEL
IV. The 31-Mine Study
A. Summary
B. Subsequent Activities
V. Compliance Assistance
A. Baseline Sampling
B. DPM Control Technology
VI. DPM Exposures and Risk Assessment
A. Introduction
B. DPM Exposures in Underground M/NM Mines
C. Health Effects
D. Significance of Risk
VII. Feasibility
A. Background
B. Technological Feasibility
C. Economic Feasibility
VIII. Summary of Costs and Benefits
IX. Section-by-Section Analysis
X. Distribution Table
XI. Regulatory Impact Analysis
XII. References Cited
I. List of Common Terms
Listed below are the common terms used in the preamble.
Commission........................ Federal Mine Safety and Health
Review Commission.
CV................................ coefficient of variation.
DE................................ diesel exhaust.
DOCs.............................. diesel oxidation catalysts.
DPF............................... diesel particulate filter.
DPM............................... diesel particulate matter.
EC................................ elemental carbon.
ETS............................... environmental tobacco smoke.
Filter Selection Guide............ Diesel Particulate Filter. Selection
Guide for Diesel-powered Equipment
in Metal and Nonmetal Mines.
First Partial Settlement Agreement 66 FR 35518 (2001) & 66 FR 35521
(2001): basis for July 5, 2001
NPRM.
HEI............................... Health Effects Institute.
HWE............................... healthy worker effect.
MARG.............................. Methane Awareness Resource Group.
M/NM.............................. metal/non-metal.
MSHA.............................. Mine Safety and Health
Administration.
NIOSH............................. National Institute for Occupational
Safety and Health.
NTP............................... National Toxicology Program.
OC................................ organic carbon.
PAPR.............................. powered air-purifying respirator.
PEL............................... permissible exposure limit.
PPM............................... parts per million.
QRA............................... quantitative risk assessment.
REA............................... Regulatory Economic Analysis.
Second Partial Settlement 67 FR 47296 (2002): basis for August
Agreement. 14, 2003 NPRM.
SD................................ standard deviation.
SKC............................... SKC, Inc.
TC................................ total carbon.
USWA.............................. United Steelworkers of America.
[mu]g/cm \2\...................... micrograms per square centimeter.
[mu]g/m \3\....................... micrograms per cubic meter.
2001 final rule................... January 19, 2001 DPM final rule.
Amended 2001 final rule........... 2001 final rule amended on February
27, 2002.
2002 final rule................... February 27, 2002 final rule.
2002 ANPRM........................ Advance Notice of Proposed
Rulemaking published on September
25, 2002.
2003 NPRM......................... Notice of Proposed Rulemaking
published on August 14, 2003.
[[Page 32869]]
II. Rulemaking Background
On January 19, 2001, MSHA published a final rule (2001 final rule)
addressing DPM exposure in underground M/NM mines (66 FR 5706), amended
on February 27, 2002 at 67 FR 9180 (2002 final rule). The 2001 final
rule established new health standards for underground M/NM mines that
use equipment powered by diesel engines. The effective date of the 2001
final rule was listed as March 20, 2001. On January 29, 2001, AngloGold
(Jerritt Canyon) Corp. and Kennecott Greens Creek Mining Company filed
a petition for review of the 2001 final rule in the District of
Columbia Circuit Court of Appeals. On February 7, 2001, the Georgia
Mining Association, the National Mining Association (NMA), the Salt
Institute, and the Methane Awareness Resource Group (MARG) Diesel
Coalition filed a similar petition in the Eleventh Circuit. On March
14, 2001, Getchell Gold Corporation petitioned for review of the rule
in the District of Columbia Circuit. The three petitions were
consolidated, and are pending in the District of Columbia Circuit. The
United Steelworkers of America (USWA) intervened in the litigation.
While these challenges were pending, the AngloGold petitioners
filed with MSHA an application for reconsideration and amendment of the
2001 final rule and for postponement of the effective date of the 2001
final rule pending judicial review. The Georgia Mining Association
petitioners similarly filed with MSHA a request for an administrative
stay or postponement of the effective date of the 2001 final rule. On
March 15, 2001, MSHA delayed the effective date of the 2001 final rule
until May 21, 2001, in accordance with a January 20, 2001 memorandum
from the President's Chief of Staff (66 FR 15032). The delay was
necessary to give Department of Labor officials the opportunity for
further review and consideration of new regulations. On May 21, 2001
(66 FR 27863), MSHA published a document in the Federal Register
delaying the effective date of the 2001 final rule until July 5, 2001.
The purpose of this delay was to allow the Department of Labor the
opportunity to engage in further negotiations to settle the legal
challenges to the 2001 final rule.
A. First Partial DPM Settlement Agreement
As a result of a partial settlement agreement with the litigants,
MSHA published two documents in the Federal Register on July 5, 2001
addressing the 2001 final rule. One document (66 FR 35518) delayed the
effective date of Sec. 57.5066(b) regarding the tagging provision of
the maintenance standard; clarified the effective dates of certain
provisions of the 2001 final rule; and included correcting amendments.
The second document (66 FR 35521) proposed a rule to clarify Sec.
57.5066(b)(1) and (b)(2) regarding maintenance and to add a new
paragraph (b)(3) to Sec. 57.5067 regarding the transfer of existing
equipment between underground mines. MSHA published these changes as a
final rule on February 27, 2002 (67 FR 9180) (2002 final rule), with an
effective date of March 29, 2002.
Under the first partial settlement agreement, MSHA also conducted
joint sampling with industry and labor at 31 underground M/NM mines to
determine existing concentration levels of DPM; to assess the
performance of the SKC, Inc., Eighty Four, PA (SKC) submicron dust
sampler with the NIOSH Method 5040; to assess the feasibility of
achieving compliance with the standard's concentration limits at the 31
mines; and to assess the impact of interferences on samples collected
in the M/NM underground mining environment before the limits
established in the final rule became effective. The final report was
issued on January 6, 2003.
B. Second Partial Settlement Agreement
Settlement negotiations continued on the remaining unresolved
issues in the litigation. On July 15, 2002, the parties signed an
agreement (second partial settlement agreement) that formed the basis
for MSHA's August 14, 2003 proposed rule (68 FR 48668) (2003 NPRM). On
July 18, 2002, MSHA published a document in the Federal Register (67 FR
47296) announcing, among other things, that the following provisions of
the 2001 final rule would become effective on July 20, 2002:
Sec. 57.5060(a), Addressing the interim concentration
limit of 400 micrograms of TC per cubic meter of air;
Sec. 57.5061, Compliance determinations; and
Sec. 57.5071, Environmental monitoring.
The document also announced that the following provisions of the
rule would continue in effect:
Sec. 57.5065, Fueling practices;
Sec. 57.5066, Maintenance standards;
Sec. 57.5067, Engines;
Sec. 57.5070, Miner training; and
Sec. 57.5075, Diesel particulate records, as they relate
to the requirements of the rule that went into effect on July 20, 2002.
The document also stayed the effectiveness of the following
provisions pending completion of this final rule:
Sec. 57.5060(d), Permitting miners to work in areas where
the level of DPM exceeds the applicable concentration limit with
advance approval from the Secretary;
Sec. 57.5060(e), Prohibiting the use of personal
protective equipment (PPE) to comply with the concentration limits;
Sec. 57.5060(f) Prohibiting the use of administrative
controls to comply with the concentration limits; and
Sec. 57.5062, DPM control plan.
Finally, the July 18, 2002, document outlined the terms of the DPM
settlement agreement and announced MSHA's intent to propose specific
changes to the rule, as discussed below.
On September 25, 2002, MSHA published an Advance Notice of Proposed
Rulemaking (2002 ANPRM) (67 FR 60199) to amend certain provisions of
the 2001 DPM rule.
The comment period closed on November 25, 2002. MSHA received
comments from underground M/NM mine operators, trade associations,
organized labor, public interest groups and individuals. On August 14,
2003, MSHA published the 2003 NPRM in the Federal Register (68 FR
48668) recommending certain revisions to the DPM rule as part of a
settlement agreement reached in response to a legal challenge to the
DPM standard. Public hearings were held in Salt Lake City, Utah; St.
Louis, Missouri; Pittsburgh, Pennsylvania; and Arlington, Virginia in
September and October 2003. The comment period closed on October 14,
2003. On February 20, 2004, MSHA published a document in the Federal
Register announcing a limited reopening of the comment period on the
2003 NPRM. This document reopened the comment period to obtain public
input on three new documents related to the August 14, 2003 rulemaking
(69 FR 7881). The three documents were as follows:
(1) United States (U.S.) Department of Health and Human Services,
Center for Disease Control, National Institute of Occupational Safety
and Health, ``The Effectiveness of Selected Technologies in Controlling
Diesel Emissions in an Underground Mine--Isolated Zone Study at
Stillwater Mining Company's Nye Mine,'' January 5, 2004.
(2) U.S. Department of Labor, Bureau of Labor Statistics, and U.S.
Department of Health and Human Services, Center for Disease Control,
National Institute of Occupational Safety and Health, ``Respirator
Usage in Private Sector Firms, 2001,'' September, 2003.
[[Page 32870]]
(3) Chase, Gerald, ``Characterizations of Lung Cancer in Cohort
Studies and a NIOSH Study on Health Effects of Diesel Exhaust in
Miners,'' undated, received January 5, 2004.
The subsequent comment period closed on April 5, 2004. MSHA
received and reviewed written and oral statements on the 2003 NPRM from
all segments of the mining community.
MSHA informed the mining community in both its 2002 ANPRM and its
2003 NPRM of its intentions to incorporate into the record of the
current rulemaking the existing rulemaking record, including the risk
assessment to the 2001 final rule. Commenters were encouraged to submit
additional evidence of new scientific data related to health risks to
underground M/NM miners from exposure to DPM.
This final rule for DPM exposure at M/NM mines is based on
consideration of the entire rulemaking record, including all written
comments and exhibits received related to the 2001 final rule as well
as all related data received to the close of this rulemaking record. To
serve the interest of the mining community, MSHA is revising Sec. Sec.
57.5060, 57.5061, 57.5071, and 57.5075 and republishing Sec. Sec.
57.5065, 57.5066, 57.5067, and 57.5070 of the DPM standards at 30 CFR
part 57 in order to present all sections in their entirety in this
document. What follows is a discussion of the specific revisions to the
2001 DPM standard:
Sec. 57.5060(a) addressing the interim limit on
concentration of DPM. MSHA has changed the 2001 final rule's interim
concentration limit of 400 micrograms of TC per cubic meter of air
(400TC [mu]g/m3) to a comparable permissible
exposure limit of 308 micrograms of EC per cubic meter of air
(308EC [mu]/m3);
Sec. 57.5060(c) addressing application and approval
requirements for an extension of time in which to reduce the final DPM
limit. MSHA has changed the 2001 final rule by requiring MSHA to
consider economic feasibility along with technological feasibility
factors in weighing whether to grant special extensions; has deleted
the limit on the number of special extensions that may be granted to
each mine; has limited each extension to a period of one year; has
allowed for annual renewals of special extensions; and has allowed the
MSHA District Manager, rather than the Secretary, to grant extensions.
This final rule retains the scope of the 2001 provision for operators
to apply for extensions to the final DPM limit;
Sec. 57.5060(d) addressing certain exceptions to the
concentration limits;
Sec. 57.5060(e) prohibiting use of PPE to comply with the
concentration limits;
Sec. 57.5060(f) prohibiting use of administrative
controls to comply with the concentration limits. MSHA has changed the
2001 final rule by implementing the current hierarchy of controls as
adopted in MSHA's other exposure-based health standards for M/NM mines.
MSHA's hierarchy includes primacy of engineering and administrative
controls to the extent feasible to reduce a miner's exposure to the
PEL, but MSHA continues to prohibit rotation of miners for compliance
purposes. If a miner's exposure cannot be reduced to the PEL with use
of feasible controls, controls are infeasible, or do not produce
significant reductions in DPM exposures, the new final rule requires
mine operators to supplement a miner's protection with respirators and
implement a respiratory protection program. This respiratory protection
program must meet the requirements in existing 30 CFR 57.5005, but
miners may only use the respirator filters specified by MSHA for DPM in
this section. Therefore, MSHA removes the 2001 prohibition against use
of respiratory protection without approval by the Secretary and
clarifies that use of administrative controls other than rotation of
miners is allowed;
Sec. 57.5062, addressing the diesel particulate control
plan. This final rule removes the existing requirement for a DPM
control plan; and
conforming changes to the following existing standards
that were proposed on August 14, 2003:
[cir] Sec. 57.5061, addressing compliance determinations;
[cir] Sec. 57.5071, addressing exposure monitoring; and,
[cir] Sec. 57.5075, addressing recordkeeping requirements.
This final rule does not include provisions for written procedures
for administrative controls, a written respiratory protection program,
medical examination of miners before they are required to wear
respiratory protection, and medical transfer of miners who are unable
to wear respiratory protection for medical and psychological reasons.
III. The Final Concentration Limit
In the 2002 ANPRM, MSHA notified the mining community that this
rulemaking would revise both the interim concentration limit of 400
micrograms per cubic meter of air and the final concentration limit of
160 micrograms per cubic meter of air under Sec. 57.5060(a) and (b) of
the 2001 final rule. Some commenters to the ANPRM recommended that MSHA
propose separate rulemakings for revising the interim and final DPM
limits to give MSHA an opportunity to gather further information to
establish a final DPM limit. In the 2003 NPRM, MSHA agreed with these
commenters and solicited other information from the mining community
that would lead to an appropriate final DPM standard. Moreover, MSHA
announced its intentions to publish a separate rulemaking to amend the
existing final concentration limit in Sec. 57.5060(b). To assist MSHA
in achieving this purpose, MSHA requested comments on an appropriate
final permissible exposure limit rather than a concentration limit; and
asked for information on an appropriate surrogate for measuring miners'
DPM exposures. MSHA concluded its request for information by clarifying
that revisions to the final DPM concentration limit would not be a part
of this rulemaking.
In their comments to the 2003 NPRM, organized labor requested that
MSHA lower the final DPM limit below 160 micrograms based on
feasibility data and the significance of the health risks from exposure
to DPM. Industry trade associations and individual mine operators
recommended that MSHA repeal the final limit based on issues related to
health effects, inability of the mining industry to meet a lower limit
than 400 micrograms per cubic meter of air, and the need for MSHA to
have the results from the National Institute for Occupational Safety
and Health/National Cancer Institute (NIOSH/NCI) study and exposure-
response data.
MSHA believes that evidence in the current DPM rulemaking record is
inadequate for MSHA to make determinations regarding revision to the
final DPM limit.
IV. The 31-Mine Study
A. Summary
On January 19, 2001, MSHA published a final standard addressing
exposure of underground metal and nonmetal miners to diesel particulate
matter (DPM). The standard contained staggered effective dates for
interim and final concentration limits. The standard was challenged by
industry trade associations and several mining companies, and the
United Steelworkers of America (USWA) intervened in the litigation. The
parties agreed to resolve their differences through settlement
negotiations with MSHA. Thereafter, MSHA delayed the effective date of
certain provisions of the standard. As part of the settlement
negotiations, MSHA agreed to conduct joint sampling with the litigants
at 31 metal and
[[Page 32871]]
nonmetal underground mines covered by the standard to determine
existing concentration levels of DPM in operating mines and to measure
DPM levels in the presence of known or suspected interferences.
The goals of the study were to use the sampling results and
related information to assess:
--The validity, precision and feasibility of the sampling and
analysis method specified by the diesel standard (NIOSH Method
5040);
--The magnitude of interferences that occur when conducting
enforcement sampling for total carbon as a surrogate for diesel
particulate matter (DPM) in mining environments; and,
--The technological and economic feasibility of the underground
metal and nonmetal (MNM) mine operators to achieve compliance with
the interim and final DPM concentration limits.
--The parties developed a joint MSHA/Industry study protocol to
guide sampling and analysis of DPM levels in 31 mines. The parties
also developed four subprotocols to guide investigations of the
known or suspected interferences, which included mineral dust, drill
oil mist, oil mist generated during ammonium nitrate/fuel oil (ANFO)
loading operations, and environmental tobacco smoke (ETS). The
parties also agreed to study other potential sampling problems,
including any manufacturing defects of the DPM sampling cassette.
(Executive Summary, Report on the 31-Mine Study)
MSHA requested that NIOSH peer review the draft Report on the 31-
Mine Study, and NIOSH's conclusions were as follows:
1. Most mines have DPM concentrations higher than
400TC [mu]g/m\3\.
2. The impactor was effective in eliminating mineral dust from
collecting onto the filter analyzed for carbon by NIOSH Method 5040.
3. The ANFO data was inconclusive.
4. Oil mist from the stoper drill is a sub-micron aerosol and a
potential interference. Oil mist contamination from the driller can
be avoided by sampling upstream of stope or far enough downstream
that the oil mist has been diluted enough to give minimal TC
concentrations (if this type of sampling is possible).
5. No information about the interference of environmental
tobacco smoke is present in this report.
6. The inter-laboratory comparison of the NIOSH method 5040 of
paired punches from the same filter showed reasonable agreement
between MSHA results and commercial laboratory results and excellent
agreement between MSHA and NIOSH laboratory results. (Summary of
Findings of this Report in ``NIOSH Comments and recommendations on
the MSHA DRAFT report: Report on the Joint MSHA/Industry Study:
Determination of DPM Levels in Underground Metal and Nonmetal
Mines,'' dated June 3, 2002)
On January 6, 2003, MSHA issued its final report entitled, ``MSHA's
Report on Data Collected During a Joint MSHA/Industry Study of DPM
Levels in Underground Metal And Nonmetal Mines'' (Report on the 31-Mine
Study). MSHA's major conclusions drawn from the study are as follows:
--The analytical method specified by the diesel standard gives an
accurate measure of the TC content of a filter sample and the
analytical method is appropriate for making compliance
determinations of DPM exposures of underground metal and nonmetal
miners.
--SKC satisfactorily addressed concerns over defects in the DPM
sampling cassettes and availability of cassettes to both MSHA and
mine operators.
--Compliance with both the interim and final concentration limits
may be both technologically and economically feasible for metal and
nonmetal underground mines in the study. MSHA, however, has limited
in-mine documentation on DPM control technology. As a result, MSHA's
position on feasibility does not reflect consideration of current
complications with respect to implementation of controls, such as
retrofitting and regeneration of filters. MSHA acknowledges that
these issues may influence the extent to which controls are
feasible. The Agency is continuing to consult with the National
Institute of Occupational Safety and Health, industry and labor
representatives on the availability of practical mine worthy filter
technology.
--The submicron impactor was effective in removing the mineral dust,
and therefore its potential interference, from DPM samples.
Remaining interference from carbonate interference is removed by
subtracting the 4th organic peak from the analysis. No reasonable
method of sampling was found to eliminate interferences from oil
mist or that would effectively measure DPM levels in the presence of
ETS with TC as the surrogate * * * (Executive Summary, Report on the
31-Mine Study)
MSHA's complete report on the 31-Mine Study is contained in the
rulemaking record.
MSHA and NIOSH have reviewed the performance characteristics of the
SKC sampler, and are satisfied that it accurately measures exposures to
DPM. NIOSH found in laboratory and field data that the SKC DPM cassette
collected DPM efficiently. In a side protocol of the 31-Mine Study,
MSHA tested the efficiency of the SKC DPM cassette to avoid mineral
dust in four different mines and did not measure any mineral dust on
the filter when the SKC DPM cassette was used. This was confirmed by
laboratory results at NIOSH. (Noll, J. D., Timko, R. J., McWilliams,
L., Hall, P., Haney, R., ``Sampling Results of the Improved SKC Diesel
Particulate Matter Cassette,'' JOEH, 2005 Jan; 2(1):29-37.)
Results of the 31-Mine Study and the MSHA baseline compliance
assistance sampling demonstrated that the SKC submicron impactor
removed potential interferences from mineral dust from the collected
sample.
Interference from drill oil mist was found on personal samples
collected on the stoper and jackleg drillers and on area samples
collected in the stope where drilling was being performed. Use of a
dynamic blank did not eliminate drill oil mist interference. Tests to
confirm whether oil mist from ANFO loading operations could be an
interference were not conclusive. Blasting did not interfere with
diesel particulate measurements. MSHA found no reasonable method of
sampling to eliminate interferences from oil mist when TC is used as
the surrogate.
No reliable marker was identified for confirming the presence of
ETS in an atmosphere containing DPM. Use of the impactor does not
remove the ETS as an interferent. No reasonable method of sampling was
found that would effectively measure DPM levels in the presence of ETS
with TC as the surrogate.
MSHA has found that the use of EC eliminates potential sampling
interference from drill oil mist, tobacco smoke, and organic solvents,
and that EC consistently represents DPM. In comparison to using TC as
the DPM surrogate, using EC would impose fewer restrictions or caveats
on sampling strategy (locations and durations), would produce a
measurement much less subject to questions, and inherently would be
more precise. Furthermore, NIOSH, the scientific literature, and the
MSHA laboratory tests indicate that DPM, on average, is approximately
60 to 80% elemental carbon, firmly establishing EC as a valid surrogate
for DPM.
As part of the 31-Mine Study, representatives from MSHA, NIOSH, and
SKC met to address the following issues:
The quality of manufactured SKC DPM cassettes;
The feasibility of adding a dynamic blank filter to the
SKC DPM cassette; and
The possibility of putting a number on each SKC DPM
cassette.
Also, in its October 16, 2001 letter, MSHA informed SKC about the
problems that MSHA and the industry encountered using the SKC DPM
sampling cassette with the submicron impactor. These problems included:
dark flecks, alleged leaks, loose fitting nozzles and connectors, and
difficulty in shipping the sampler. As discussed in the report on the
31-Mine Study, SKC was responsive in addressing those concerns.
[[Page 32872]]
B. Subsequent Activities
Some industry commenters continued to state that the sampling and
analytical processes for DPM are too new for regulatory use. Other
commenters questioned the availability and reliability of the SKC
impactor.
MSHA moved expeditiously to help resolve the back-order and
manufacturing delays for samplers reported in the 31-Mine Study.
However, operators who sample alongside MSHA continued to request ample
notice to have enough samplers available. MSHA purchased many of the
initial production runs of these samplers to conduct its compliance
assistance baseline sampling. Once the initial orders were filled, the
sampler became more widely available.
Some commenters stated that SKC changed the impactor, and that
NIOSH should test the new SKC sampler and evaluate its comparability to
the model used in the 31-Mine Study. One of these commenters stated
that the shelf life of the prior sampler affected TC measurements by
adsorbing organic carbon (OC) from the polystyrene assembly onto the
filter media and increasing TC measurement. These commenters questioned
MSHA's changes to the SKC sampler following completion of the 31-Mine
Study, and suggested that a defect to the sampler could have affected
the results of the study. During the 31-Mine Study, MSHA observed that
the deposit area of the SKC submicron impactor filter was not as
consistent as those obtained for preliminary evaluation. This was
attributed to inconsistent crimping of the aluminum foil cone on the
filter capsule.
Prior to the 31-Mine Study, MSHA had determined the deposit area of
the sample filter to be 9.12 square centimeters (cm\2\) with a standard
deviation of 3.1 percent (%). During the initial phases of the sampling
analysis of the 31-Mine Study, it became apparent that the variability
of the deposit area was greater than originally determined. The filter
area is critical to the concentration calculation. The filter area
(measured in cm\2\) is multiplied by the results of the analysis
(micrograms per cm\2\) to get the total filter loading (micrograms).
While individual filter areas could be measured, it is more practical
to have a uniform deposit area for the calculations. As a result, NIOSH
and MSHA consulted with SKC to develop an improved filter cassette
design. With the cooperation of MSHA and the technical recommendations
and extensive experimental verification by NIOSH, SKC was able to
modify their cassette design to produce a consistent and regular DPM
deposit area, satisfactorily resolving the problem. SKC, in cooperation
with MSHA and NIOSH, then modified the DPM cassette following the 31-
Mine Study.
The modification was limited to replacing the foil filter capsule
with a 32 millimeter (32-mm) ring. This was done to give a more uniform
deposit area (8.04 cm\2\) with negligible variability, and to
accommodate two 38-mm quartz fiber filters in tandem (double filters).
These double filters are assembled into a single cassette along with
the impactor. The 38-mm filters also eliminate cassette leakage around
the filters. These modifications were completed and incorporated into
units manufactured after November 1, 2002.
The results of this project were prepared into a scientific
publication, ``Sampling Results of the Improved SKC Diesel Particulate
Matter Cassette,'' referenced above. This paper has been peer reviewed
and was published in January 2005. The following abstract was prepared
for the study results:
Diesel particulate matter (DPM) samples from underground metal/
non-metal mines are collected on quartz fiber filters and measured
for carbon content using National Institute for Occupational Safety
and Health Method 5040. If size selective samplers are not used to
collect DPM in the presence of carbonaceous ore dust, both the ore
dust and DPM will collect on the quartz filters, causing the carbon
attributed to DPM to be artificially high. Because the DPM particle
size is much smaller than that of mechanically generated mine dust
aerosols, it can be separated from the larger mine dust aerosol by a
single stage impactor. The SKC DPM cassette is a single stage
impactor designed to collect only DPM aerosols in the presence of
carbonaceous mine ore aerosols, which are commonly found in
underground nonmetal mines. However, there is limited data on how
efficiently the SKC DPM cassette can collect DPM in the presence of
ore dust. In this study, we investigated the ability of the SKC DPM
cassette to collect DPM while segregating ore dust from the sample.
We found that the SKC DPM cassette accurately collected DPM. In the
presence of carbon-based ore aerosols having an average
concentration of 8 mg/m3, no ore dust was detected on SKC
DPM cassette filters. We did discover a problem: the surface areas
of the DPM deposits on SKC DPM cassettes, manufactured prior to
August 2002, were inconsistent. To correct this problem, SKC
modified the cassette. The new cassette produced, with 99%
confidence, a range of DPM deposit areas between 8.05 and 8.28
cm2, a difference of less than 3%.
Because the design of the inlet cyclone, impaction nozzles, and the
impaction plate and the flow rate did not change, the modifications to
the filter assembly did not alter the collection or separation
performance of the impactor. Throughout the compliance baseline
sampling, the impactor has been a consistent and reliable sampling
cassette.
Tandem filters were used in the oil mist and ANFO interference
evaluations during the 31-Mine Study. The top filter collects the
sample and the bottom filter is a dynamic blank. The dynamic blank
provides a unique field blank for each DPM cassette. The use of EC as a
surrogate would resolve the commenter's concern about shelf life and OC
out-gassing on the filter. Shelf life and OC out-gassing are issues
relative to OC measurements. These two issues do not apply to an EC
measurement. Once the cassettes have been preheated during
manufacturing, there is no source, other than sampling, to add EC to
the sealed cassette filters.
MSHA discussed in the preamble to the 2003 NPRM issues related to
interferences, field blanks and the error factor. Some comments on the
2003 NPRM still expressed concerns on interferences and further stated
that the MSHA industrial hygiene studies, conducted to verify the
magnitude of the interference problem, were not published or peer
reviewed and should be removed from the rulemaking record. However,
MSHA, organized labor, and the mining industry, through the
negotiations process, jointly developed the protocol for conducting the
31-Mine Study. All of the parties agreed on the protocol following
numerous discussions among industry, labor, and government experts, and
had an opportunity to comment and make changes to the document.
Thereafter, MSHA conducted the study, following the agreed upon
protocol, and published its results. Before publication, the report was
peer reviewed by NIOSH. Industry was given an opportunity to publish
their separate results simultaneously with the government. During this
rulemaking, industry submitted to MSHA through the notice and comment
process their conclusions on the 31-Mine Study in a report titled,
``Technical and Economic Feasibility of DPM Regulations.'' The industry
report is contained in the rulemaking record, and was considered by
MSHA in reaching determinations for this final rule.
(1) Interferences
In response to the question on whether there are interferences when
EC is used as the surrogate, some commenters stated that interferences
were thoroughly discussed in the preamble to the 2001 final rule, and
that reasonable practices to avoid them were stipulated in the rule
itself. According
[[Page 32873]]
to these commenters, this problem should not be revisited in this
rulemaking.
Other commenters maintained that the 31-Mine Study did not contain
the necessary protocols to address all potential interferences. Thus,
in their view, MSHA does not have all the data required to answer this
question. More specifically, some commenters stated that carbonaceous
particulate in host rock has a smaller diameter than the impactor cut
point and so, may contaminate EC samples. These commenters then
concluded that MSHA should propose additional research and seek
comments on the research before concluding that sampling EC with an
impactor will eliminate all interference problems. However, no data
were presented to support this claim or conclusion. Commenters
submitted no new information relative to interferences in response to
the 2003 NPRM.
(2) Field Blanks
A field blank is an unexposed control filter meant to account for
background interferences and systematic contamination in the field,
spurious effects due to manufacturing and storage of the filter, and
systematic analytical errors. The tandem filter arrangement in the
sample cassette provides a primary filter for collecting an air sample
and a second filter, behind (after) the primary filter, which provides
a separate control filter for each sample. This is a much more flexible
method of sampling for the mining industry, since it eliminates the
need to send a separate control filter to the analytical lab. MSHA
informed the public of its intentions to adjust the EC result obtained
for each sample by the result obtained for the corresponding media
blank when MSHA measures for compliance purposes. When MSHA conducts
compliance measurements, MSHA will adjust the result obtained for each
corresponding sample by the field blank (tandem filter) result. No
comments or information related to field blanks were submitted to MSHA
in response to the 2003 NPRM.
In its comments on the 2002 ANPRM, NIOSH noted that two types of
blanks, media and field, are normally used for quality assurance
purposes. A media blank accounts for systematic contamination that may
occur during manufacturing or storage. A field blank accounts for
possible systematic contamination in the field. NIOSH does not
recommend use of field blanks when EC is the surrogate. This is because
EC measurements are not subject to sources of contamination in the
field that would affect OC and TC results. Quartz-fiber filters are
prone to OC vapor contamination in the field and to contamination by
less volatile OC (such as oils) during handling. However, such
contamination is irrelevant when EC is the surrogate.
(3) Error Factor
MSHA intends to cite a violation of the DPMEC exposure
limit only when MSHA has valid evidence that a violation actually
occurred. As with all other measurement-based M/NM compliance
determinations, MSHA will issue a citation only if a measurement
demonstrates noncompliance with at least 95% confidence. MSHA will
achieve this 95% confidence level by comparing each EC measurement to
the EC exposure limit multiplied by an appropriate error factor.
Generally, an error factor is used to compensate for certain known
inaccuracies in the sampling and analytical process, including such
things as the reliability of sampling equipment and precision of
analytical instrumentation. MSHA will continue to determine that an
overexposure has occurred when a sample exceeds the interim limit times
the error factor.
In this rulemaking, MSHA is discussing the procedure used to obtain
the error factor. This procedure is further discussed on the MSHA web
site at www.msha.gov under, ``Single Source Page for Metal and Nonmetal
Diesel Particulate Matter Regulations.'' Error factors are based on
sampling and analytic errors. The manufacturers of sampling devices
thoroughly investigate and quantify the error factors for their
devices. While MSHA does not frequently change an error factor, it
retains that latitude should significant changes to either analytical
or sampling technology occur.
The formula for the error factor was based on three factors
involved in making an eight-hour equivalent full-shift measurement of
EC concentration using NIOSH Method 5040: (1) Variability in air volume
(i.e., pump performance relative to the nominal airflow of 1.7 L/min);
(2) variability of the deposit area of particles on the filter
(cm2); and (3) accuracy of the laboratory analysis of EC
density within the deposit ([mu]g/cm2). Modifications made
to the sampler since the time of the 31-Mine Study have no bearing on
the first and third of these factors. Variability of the filter deposit
area was represented by a 3.1% coefficient of variation, based on an
experiment carried out before the foil filter capsule in the sampling
cassette was replaced by a 32-mm ring. Measurements subsequent to
introduction of the ring show that variability of the filter deposit
area is now less than 3.1% (Noll, J. D., et al, ``Sampling Results of
the Improved SKC Diesel Particulate Matter Cassette''). This change
slightly reduces the error factor stipulated for EC measurements, but
not by enough to be of any practical significance.
MSHA's error factor model accounts for the joint and related
variability in laboratory analysis, and combines that variability with
pump flow rate, sample collection size, and other sampling and analytic
variables. MSHA was then able to determine the appropriate error factor
for EC samples based on a statistically strong database.
The analytical method (NIOSH 5040) relies on a punch taken from
inside the deposit area on the sample filter. In effect, the punch is a
sample of the dust sample. To account for uniformity in the
distribution of DPM deposited on the filter, as reflected by different
possible locations at which a punch might be extracted, MSHA compared
two punches taken from different locations on the same filter to
evaluate the accuracy of the analytical method. Therefore, variability
between punch results due to their location on the filter is also
included in the error factor as calculated by MSHA.
Commenters to the 2003 NPRM further questioned whether the NIOSH
Method 5040 has been commercially tested. As in the preamble to the
2003 NPRM, MSHA has discussed in detail its findings regarding the
NIOSH Method 5040 in this section. NIOSH's peer review of the 31-Mine
Study also concludes that the analytical method specified by the diesel
standard gives an accurate measure of the TC content of a filter
sample. NIOSH confirmed this position by letter of February 8, 2002, in
which NIOSH stated that,
MSHA is following the procedures of NIOSH Method 5040, based on our
review of MSHA P13 (MSHA's protocol for sample analysis by NIOSH
Method 5040) and a visit to the MSHA laboratory.
V. Compliance Assistance
A. Baseline Sampling Summary
Under the second partial DPM settlement agreement, MSHA agreed to
provide compliance assistance to the M/NM underground mining industry
for a one-year period from July 20, 2002 through July 19, 2003. As part
of its compliance assistance activities, MSHA agreed to conduct
baseline sampling of miners' personal exposures at every underground
mine covered by the 2001 final rule.
[[Page 32874]]
Our baseline sampling began in October 2002 and continued through
October 2003. During this period a total of 1,194 valid baseline
samples were collected. A total of 183 underground M/NM mines are
represented by this analysis. The number of samples per mine range from
one to twenty. All 874 valid baseline sampling results in the analysis
published in the preamble of the 2003 NPRM are included in this updated
analysis. MSHA is including 320 additional valid samples because MSHA
decided to continue to conduct baseline sampling after July 19, 2003 in
response to mine operators' concerns. MSHA has analyzed all baseline
samples, and updated its analysis. Some of these mines were either not
in operation or were implementing major changes to ventilation systems
during the original baseline period. MSHA is including supplementary
samples from seasonal and intermittent mines, mines that were under-
represented, and mines that were not represented in the analysis
published in the preamble to the 2003 NPRM. Sixty mines included in the
former analysis had additional samples taken during the extended
assistance period. There are 12 mines in this updated analysis that
were not represented in the 2003 analysis. The results of this sampling
were used by MSHA in this preamble to estimate current DPM exposure
levels in underground M/NM mines using diesel equipment. These sampling
results also assist mine operators in developing compliance strategies
based on actual exposure levels.
This section summarizes analytical results of personal sampling for
DPM collected during compliance assistance. There are a total of 1,206
samples. However, 12 samples are invalid due to abnormal sample
deposits, broken cassettes or filters, contaminated backup pads,
instrument failure or pump failure. Table V-1 lists the frequencies of
invalid samples within each commodity.
The mines that were sampled produce clay, sand, gypsum, copper,
gold, platinum, silver, gem stones, dimension marble, granite, lead-
zinc, limestone, lime, potash, molybdenum, salt, trona, and other
miscellaneous metal or nonmetal ores. These commodities were grouped
into four general categories for calculating summary statistics: Metal,
stone, trona, and other nonmetal (N/M) mines. These categories were
selected to be consistent with the categories used for analysis of data
for the 31-Mine Study. Most commodities are well represented in this
analysis with the average number of valid samples per mine ranging from
6.0 to 8.2 (average across all mines is 6.5 samples per mine). The
average number of samples per mine classified as ``Gold Ore Mining,
N.E.C.'' increased from an average of 2.0 samples per mine published in
the 2003 NPRM preamble to an average of 4.6 samples in this data set.
Approximately 79% of all mines sampled during the assistance period
have four or more results from DPM sampling in this analysis. Table V-3
lists the number of samples for each category of specific commodity.
Average number of samples for more general commodity groups is listed
in Table V-2.
MSHA used the same sampling strategies for collecting baseline
samples as it intends to use for collecting samples for enforcement
purposes. These sampling procedures are described in the Metal and
Nonmetal Health Inspection Procedures Handbook (PH90-IV-4), Chapter A,
``Compliance Sampling Procedures'' and Draft Chapter T, ``Diesel
Particulate Matter Sampling.'' Chapter A includes detailed guidelines
for selecting and obtaining personal samples for various contaminants.
All personal samples were collected in the miner's breathing zone and
for the miner's full shift regardless of the number of hours worked.
For the 1,194 valid personal samples, 85% were collected for at least
eight hours. TC and EC levels, as well as DPM levels, are reported in
units of micrograms per cubic meter for an 8-hour full shift
equivalent.
MSHA collected DPM samples with SKC submicron dust samplers that
use Dorr-Oliver cyclones and submicron impactors. The samples were
analyzed either at MSHA's Pittsburgh Safety and Health Technology
Center, Dust Division Laboratory or at the Clayton Laboratory using
MSHA Method P-13 (NIOSH Analytical Method 5040, NIOSH Manual of
Analytical Methods (NMAM), Fourth Edition, September 30, 1999) for
determining the TC content. Each sample was analyzed for organic,
elemental, and carbonaceous carbon and calculated TC. Raw analytical
results from both laboratories as well as administrative information
about the sample were stored electronically in MSHA's Laboratory
Information Management System.
If a raw carbon result was greater than or equal to 30 [mu]g/
cm2 of EC or 40 [mu]g/cm2 of TC from the exposed
filter loading, then the analysis was repeated using a separate punch
of the same filter. The results of these two analyses were then
averaged. The companion tandem blank was also tested for the same
analyses. Otherwise, an unexposed filter from the same manufacturer's
lot was used to correct for background levels. In the event the initial
TC result was greater than 100TC [mu]g/cm2, a
smaller punch of the same exposed filter (in duplicate and with the
corresponding blank) was taken and used in the analysis. Blank-
corrected averaged results were used in the analysis when the sample
was tested in duplicate.
The equation used to calculate a 480-minute (8-hour) full shift
equivalent (FSE) exposure of TC is Total Carbon Concentration =
[GRAPHIC] [TIFF OMITTED] TR06JN05.014
Where:
EC = The corrected elemental carbon concentration measured in the
thermal/optical carbon analyzer, [mu]g/cm\2\,
OC = The corrected organic carbon concentration measured in the
thermal/optical carbon analyzer, [mu]g/cm\2\,
A = The surface area of the deposit on the filter media used to collect
the sample, cm\2\,
Flow Rate = Flow rate of the air pump used to collect the sample
measured in Liters per minute, and
480 minutes = Standardized eight-hour work shift.
All levels of carbon or DPM are reported in 8-hour full shift
equivalent TC concentrations measured in [mu]g/m\3\.
Because personal sampling was conducted and no attempt was made to
avoid interference from cigarette smoke or other OC sources, TC was
also calculated using the formula prescribed in the second partial DPM
settlement agreement:
[[Page 32875]]
Total Carbon Concentration = EC x 1.3.
MSHA agreed to use the lower of the two values (EC x 1.3 or EC +
OC) for enforcement until a final rule is published reflecting EC as
the surrogate.
The electronic records of the 1,194 samples available for analysis
were reviewed for inconsistencies. Internally inconsistent or extreme
values were questioned, researched, and verified. Although no samples
were invalidated as a result of the administrative verification, 12
samples (1.0%) were removed from the data set for reasons unrelated to
the values obtained. The reasons for invalidating these samples are
listed in Table V-1. These samples were subjected to the same
laboratory quality assessments as samples collected for compliance
purposes. Accordingly, MSHA has included 1,194 samples from miners in
the analyses. Table V-2 is a list of the number of valid samples by
commodity group.
Table V-1.--Reasons for Excluding Samples.
----------------------------------------------------------------------------------------------------------------
Reason for excluding from analysis Metal Stone Trona Other N/M Total
----------------------------------------------------------------------------------------------------------------
Abnormal Sample Deposit........................ 0 1 0 0 1
Cassette/Filter Broken......................... 0 2 0 1 3
Contaminated Backup Pad........................ 1 0 0 0 1
Instrument Failure............................. 1 1 0 0 2
Pump Failed.................................... 1 4 0 0 5
------------------------------------------------
Total...................................... 3 8 0 1 12
----------------------------------------------------------------------------------------------------------------
Table V-2.--Number of Mines and Valid Samples, by Commodity Group.
----------------------------------------------------------------------------------------------------------------
Average number of
Commodity group Number of mines Number of valid valid samples by
samples mine
----------------------------------------------------------------------------------------------------------------
Metal.................................................. 40 284 7.1
Stone.................................................. 115 689 6.0
Trona.................................................. 4 25 6.3
Other N/M.............................................. 24 196 8.2
--------------------------------------------------------
Total.............................................. 183 1,194 6.5
----------------------------------------------------------------------------------------------------------------
Table V-3 lists the number of samples collected by specific
commodities and sorted by average number of samples per mine. Although
MSHA made efforts to sample all underground M/NM mines covered by this
rulemaking within the specified time frame, several mines have few or
no samples for DPM in this analysis. Some M/NM mining operations are
seasonal in that they are operated intermittently or operate at less
than full production during certain times. These types of variable
production schedules limited efforts to collect compliance assistance
samples. MSHA extended its period of baseline sampling especially to
incorporate into its analysis those mines with a low sampling frequency
or where no samples were collected as of March 26, 2003.
Table V-3.--Number of Valid Samples per Mine for Specific Commodities
----------------------------------------------------------------------------------------------------------------
Average
Specific commodity No. of mines No. of samples per
samples mine
----------------------------------------------------------------------------------------------------------------
Gemstones Mining, N.E.C......................................... 2 5 2.5
Dimension Marble Mining......................................... 3 9 3.0
Limestone....................................................... 2 6 3.0
Talc Mining..................................................... 1 3 3.0
Uranium-Vanadium Ore Mining, N.E.C.............................. 1 3 3.0
Gold Ore Mining, N.E.C.......................................... 19 87 4.6
Construction Sand & Gravel Mining, N.E.C........................ 1 5 5.0
Crushed & Broken Sandstone Mining............................... 1 5 5.0
Hydraulic Cement................................................ 1 5 5.0
Lime, N.E.C..................................................... 4 20 5.0
Copper Ore Mining, N.E.C........................................ 2 11 5.5
Dimension Limestone Mining...................................... 3 18 6.0
Crushed & Broken Limestone Mining, N.E.C........................ 90 550 6.1
Crushed & Broken Marble Mining.................................. 4 25 6.3
Trona Mining.................................................... 4 25 6.3
Crushed & Broken Stone Mining, N.E.C............................ 4 28 7.0
Gypsum Mining................................................... 4 29 7.3
Salt Mining..................................................... 14 122 8.7
Clay, Ceramic & Refractory Minerals, N.E.C...................... 1 9 9.0
Miscellaneous Metal Ore Mining, N.E.C........................... 1 9 9.0
Lead-Zinc Ore Mining, N.E.C..................................... 10 96 9.6
Platinum Group Ore Mining....................................... 2 20 10.0
Potash Mining................................................... 3 30 10.0
Molybdenum Ore Mining........................................... 2 22 11.0
[[Page 32876]]
Silver Ore Mining, N.E.C........................................ 3 36 12.0
Miscellaneous Nonmetallic Minerals, N.E.C....................... 1 16 16.0
-----------------
Average of all samples...................................... 183 1,194 6.5
----------------------------------------------------------------------------------------------------------------
There are 63 different occupations in underground M/NM mines
represented in this analysis. The most frequently sampled occupations
are Blaster, Drill Operator, Front-end Loader Operator, Truck Driver,
Scaling (Mechanical), and Mechanic. Table V-4 lists the number of valid
samples by occupation and commodity group. Only occupations with 14 or
more total samples are listed individually. Occupations with fewer
samples were aggregated into a combined group for this table.
Table V-4.--Valid Samples, by Occupation and Mine Category.
----------------------------------------------------------------------------------------------------------------
Occupation Metal Stone Trona Other N/M Total
----------------------------------------------------------------------------------------------------------------
Truck Driver................................... 87 152 0 13 252
Front-end Loader Operator...................... 40 149 6 19 214
Blaster, Powder Gang........................... 12 98 0 24 134
Scaling (mechanical)........................... 1 66 0 13 80
Drill Operator, Rotary......................... 3 63 0 9 75
Drill Operator, Jumbo Perc..................... 10 19 0 9 38
Mechanic....................................... 7 15 0 12 34
Complete Load-Haul-Dump........................ 7 2 0 23 32
Utility Man.................................... 6 4 15 4 29
Scaling (hand)................................. 4 20 0 2 26
Mucking Mach. Operator......................... 19 1 0 3 23
Roof Bolter, Rock.............................. 5 9 0 7 21
Drill Operator, Rotary Air..................... 1 19 0 1 21
Miner, Drift................................... 16 1 0 0 17
Crusher Oper/Worker............................ 0 13 0 2 15
Miner, Stope................................... 14 0 0 0 14
All Others Combined............................ 52 58 4 55 169
--------------
Totals..................................... 284 689 25 196 1,194
----------------------------------------------------------------------------------------------------------------
TC levels calculated by EC x 1.3 were lower than TC levels
calculated by OC + EC in 858 (72%) of the 1,194 baseline samples. Of
the 336 samples where TC = OC + EC was the lower value, 68% of the TC =
EC x 1.3 values were within 12% of the TC = OC + EC value. Table V-5
summarizes the results of the baseline samples when determining the TC
level using either EC x 1.3 or OC + EC. Approximately 6.4% of the
paired results did not concur with respect to the 400TC
[mu]g/m\3\ standard when measuring TC by the two calculations (OC + EC
vs. EC x 1.3). Approximately 19.3% of the samples were above the
400TC [mu]g/m\3\ interim concentration limit when using TC =
EC x 1.3 and approximately 22.7% were above the concentration limit
when using TC = OC + EC. There is 93.6% concurrence between the two
methods of calculating TC and comparing the calculations to the
400TC [mu]g/m\3\ interim concentration limit.
Table V-5.--Comparison of Results With 400TC [mu]g/m3 Calculating TC by OC + EC or EC x 1.3
----------------------------------------------------------------------------------------------------------------
EC x 1.3
--------------------------------
All valid samples < 400TC [mu]g/ > 400TC [mu]g/ Total
m\3\ m\3\
----------------------------------------------------------------------------------------------------------------
OC+EC...........................................................
< 400TC [mu]g/m\3\.......................................... 905 18 923
(75.8%) (1.5%) (77.3%)
> 400TC [mu]g/m\3\.......................................... 59 212 271
(4.9%) (17.8%) (22.7%)
-----------------
Total....................................................... 964 230 1,194
(80.7%) (19.3%) (100.0%)
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