Asbestos Exposure Limit, 43950-43989 [05-14510]

Agencies

• DEPARTMENT OF LABOR
• Mine Safety and Health Administration

[Federal Register Volume 70, Number 145 (Friday, July 29, 2005)]
[Proposed Rules]
[Pages 43950-43989]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-14510]



[[Page 43949]]

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Part II





Department of Labor





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Mine Safety and Health Administration



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30 CFR Parts 56, 57, and 71



Asbestos Exposure Limit; Proposed Rule

Federal Register / Vol. 70, No. 145 / Friday, July 29, 2005 / 
Proposed Rules

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DEPARTMENT OF LABOR

Mine Safety and Health Administration

30 CFR Parts 56, 57, and 71

RIN: 1219-AB24


Asbestos Exposure Limit

AGENCY: Mine Safety and Health Administration (MSHA), Labor.

ACTION: Proposed rule; notice of public hearings.

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SUMMARY: We (MSHA) are proposing to revise our existing health 
standards for asbestos exposure at metal and nonmetal mines, surface 
coal mines, and surface areas of underground coal mines. The proposed 
rule would reduce the full-shift permissible exposure limit and the 
excursion limit for airborne asbestos fibers, and make several 
nonsubstantive changes to add clarity to the standard. Exposure to 
asbestos has been associated with lung and other cancers, 
mesotheliomas, and asbestosis. This proposed rule would help assure 
that fewer miners who work in an environment where asbestos is present 
would suffer material impairment of health or functional capacity over 
their working lifetime.

DATES: We must receive your comments on or before September 20, 2005. 
We will hold public hearings on October 18 and 20. Details about the 
public hearings are in the SUPPLEMENTARY INFORMATION section of this 
preamble.

ADDRESSES: (1) To submit comments, please include ``RIN: 1219-AB24'' in 
the subject line of the message and send them to us at either of the 
following addresses.
     Federal e-Rulemaking portal: Go to https://
www.regulations.gov and follow the online instructions for submitting 
comments.
     E-mail: zzMSHA-comments@dol.gov. If you are unable to 
submit comments electronically, please identify them by ``RIN: 1219-
AB24'' and send them to us by any of the following methods.
     Fax: 202-693-9441.
     Mail, hand delivery, or courier: MSHA, Office of 
Standards, Regulations, and Variances, 1100 Wilson Blvd., Rm. 2350, 
Arlington, VA 22209-3939.
    (2) We will post all comments on the Internet without change, 
including any personal information they may contain. You may access the 
rulemaking docket via the Internet at https://www.msha.gov/regsinfo.htm 
or in person at MSHA's public reading room at 1100 Wilson Blvd., Rm. 
2349, Arlington, VA.
    (3) To receive an e-mail notification when we publish rulemaking 
documents in the Federal Register, subscribe to our list serve at 
https://www.msha.gov/subscriptions/subscribe.aspx.

FOR FURTHER INFORMATION CONTACT: Rebecca J. Smith at 202-693-9440 
(Voice), 202-693-9441 (Fax), or mailto:smith.rebecca@dol.gov (E-mail).

SUPPLEMENTARY INFORMATION:

I. Introduction

A. Outline of Preamble

    We are including the following outline to help you find information 
in this preamble more quickly.

I. Introduction
    A. Outline of Preamble
    B. Dates and Locations for Public Hearings
    C. Executive Summary
    D. Abbreviations and Acronyms
II. Background
    A. Scope of Proposed Rule
    B. Where Asbestos Is Found at Mining Operations
    C. Asbestos Minerals
III. History of Asbestos Regulation
    A. MSHA's Asbestos Standards for Mining
    B. OSHA's Asbestos Standards for General Industry and 
Construction
    C. Other Federal Agencies Regulating Asbestos
    D. Other Asbestos-Related Activities
    E. U.S. Department of Labor, Office of the Inspector General 
(OIG)
IV. Health Effects of Asbestos Exposure
    A. Summary of Asbestos Health Hazards
    B. Factors Affecting the Occurrence and Severity of Disease
    C. Specific Human Health Effects
    D. Support from Toxicological Studies of Human Health Effects of 
Asbestos Exposure
V. Characterization and Assessment of Exposures in Mining
    A. Determining Asbestos Exposures in Mining
    B. Exposures from Naturally Occurring Asbestos
    C. Exposures from Introduced (Commercial) Asbestos
    D. Sampling Data and Exposure Calculations
VI. The Application of OSHA's Risk Assessment to Mining
    A. Summary of Studies Used by OSHA in Its Risk Assessment
    B. Models Selected by OSHA (1986) for Specified Endpoints and 
for the Determination of Its PEL and STEL
    C. OSHA's Selection of Its PEL (0.1 f/cc)
    D. Applicability of OSHA's Risk Assessment to the Mining 
Industry
    E. Significance of Risk
VII. Section-by-Section Discussion of Proposed Rule
    A. Sections 56/57.5001(b)(1) and 71.702(a): Definitions
    B. Sections 56/57.5001(b)(2) and 71.702(b): Permissible Exposure 
Limits (PELs)
    C. Sections 56/57.5001(b)(3) and 71.702(c): Measurement of 
Airborne Fiber Concentration
    D. Discussion of Asbestos Take-Home Contamination
    E. Section 71.701(c) and (d): Sampling; General Requirements
VIII. Regulatory Analyses
    A. Executive Order (E.O.) 12866
    B. Feasibility
    C. Alternatives Considered
    D. Regulatory Flexibility Analysis (RFA) and Small Business 
Regulatory Enforcement Fairness Act (SBREFA)
    E. Other Regulatory Considerations
IX. Copy of the OSHA Reference Method (ORM)
X. References Cited in the Preamble

B. Dates and Locations for Public Hearings

    We will hold two public hearings. If you wish to make a statement 
for the record, please submit your request to us at least 5 days prior 
to the hearing dates by one of the methods listed in the ADDRESSES 
section above. The hearings will begin at 9 a.m. with an opening 
statement from MSHA, followed by statements or presentations from the 
public, and end after the last speaker (in any event not later than 5 
p.m.) on the following dates at the locations indicated:

October 18, 2005, Denver Federal Center, Sixth and Kipling, Second 
Street, Building 25, Denver, Colorado 80225, Phone: 303-231-5412.
October 20, 2005, Mine Safety and Health Administration, 1100 Wilson 
Boulevard, Room 2539, Arlington, Virginia 22209, Phone: 202-693-9457.
    We will hear scheduled speakers first, in the order that they sign 
in; however, you do not have to make a written request to speak. To the 
extent time is available, we will hear from persons making same-day 
requests. The presiding official may exercise discretion to ensure the 
orderly progress of the hearing by limiting the time allocated to each 
speaker for their presentation.
    The hearings will be conducted in an informal manner. Although 
formal rules of evidence or cross examination will not apply, the 
hearing panel may ask questions of speakers and a verbatim transcript 
of the proceedings will be prepared and made a part of the rulemaking 
record. We also will post the transcript on MSHA's Home Page at https://
www.msha.gov, on the Asbestos Single Source Page.
    Speakers and other attendees may present information to the MSHA 
panel for inclusion in the rulemaking record. We will accept written 
comments and data for the record from any interested party, including 
those not presenting oral statements. The post-hearing comment period 
will close on November 21, 2005, 30 days after the last public hearing.

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C. Executive Summary

    In March of 2001, the U.S. Department of Labor, Office of the 
Inspector General (OIG) published a report evaluating MSHA's 
enforcement actions at the vermiculite mine in Libby, Montana. The 
widespread asbestos contamination at this mine and surrounding 
community, together with the prevalence of asbestos-related illnesses 
and fatalities among persons living in this community, attracted press 
and public attention, which prompted the OIG investigation and report. 
The OIG found that MSHA had conducted regular inspections and personal 
exposure sampling at the mine, as required by the Federal Mine Safety 
and Health Act of 1977 (Mine Act). The OIG report stated, ``We do not 
believe that more inspections or sampling would have prevented the 
current situation in Libby.'' The OIG made five recommendations to 
MSHA; two of which we implemented immediately. The remaining 
recommendations are listed below:
     Lower the existing permissible exposure limit (PEL) for 
asbestos to a more protective level.
     Use transmission electron microscopy (TEM) instead of 
phase contrast microscopy (PCM) in the initial analysis of fiber 
samples that may contain asbestos.
     Implement special safety requirements to address take-home 
contamination.
    In response to the OIG's recommendations, MSHA published an advance 
notice of proposed rulemaking (ANPRM) on March 29, 2002 (67 FR 15134). 
MSHA also held seven public meetings around the country to seek input 
and obtain public comment on how best to protect miners from exposure 
to asbestos.
    Following review of all public comments and testimony taken at the 
public meetings, and relying on OSHA's 1986 asbestos risk assessment, 
we determined that it is appropriate to propose reducing the PELs for 
asbestos and clarify criteria for asbestos sample analysis. To enhance 
the health and safety of miners, we are proposing to lower the existing 
8-hour, time-weighted average (TWA) PEL of 2.0 f/cc to 0.1 f/cc, and to 
lower the short-term limit from 10.0 f/cc over a minimum sampling time 
of 15 minutes to an excursion limit PEL of 1.0 f/cc over a minimum 
sampling time of 30 minutes. To clarify the criteria for the analytical 
method in our existing standards, we are proposing to incorporate a 
reference to Appendix A of OSHA's asbestos standard (29 CFR 1910.1001). 
Appendix A specifies basic elements of a PCM method for analyzing 
airborne asbestos samples. It includes the same analytical elements 
specified in our existing standards and allows MSHA's use of other 
methods that meet the statistical equivalency criteria in OSHA's 
asbestos standard.
    The scope of this proposed rule, therefore, is limited to lowering 
the permissible exposure limits, an issue raised by the OIG; 
incorporating Appendix A of OSHA's asbestos standard for the analysis 
of our asbestos samples; and making several nonsubstantive conforming 
amendments to our existing rule language. After considering several 
regulatory approaches to prevent take-home contamination, we determined 
that non-regulatory measures could adequately address this potential 
hazard.

D. Abbreviations and Acronyms

    As a quick reference, we list below some of the abbreviations used 
in the preamble.

29 CFR Title 29, Code of Federal Regulations
30 CFR Title 30, Code of Federal Regulations
AFL-CIO American Federation of Labor and Congress of Industrial 
Organizations
ATSDR Agency for Toxic Substances and Disease Registry, Centers for 
Disease Control and Prevention, U.S. Department of Health and Human 
Services
Bureau former Bureau of Mines, U.S. Department of the Interior
cc cubic centimeter (cm3) = milliliter (mL)
EPA U.S. Environmental Protection Agency
f fiber(s)
FR Federal Register
Lpm liter(s) per minute
MESA former Mining Enforcement and Safety Administration, U.S. 
Department of the Interior (predecessor to MSHA)
MSHA Mine Safety and Health Administration, U.S. Department of Labor
mm millimeter = 1 thousandth of a meter (0.001 m)
mL milliliter = 1 thousandth of a liter (0.001 L) = cubic centimeter
NIOSH National Institute for Occupational Safety and Health, Centers 
for Disease Control and Prevention, U.S. Department of Health and 
Human Services
OIG Office of the Inspector General, U.S. Department of Labor
OSHA Occupational Safety and Health Administration, U.S. Department 
of Labor
PCM phase contrast microscopy
PEL permissible exposure limit
PLM polarized light microscopy
STEL short-term exposure limit
SWA shift-weighted average concentration
TEM transmission electron microscopy
TWA time-weighted average concentration
[mu]m micron = micrometer = 1 millionth of a meter (0.000001 m)
USGS U.S. Geological Survey, U.S. Department of the Interior

II. Background

A. Scope of Proposed Rule

    This proposed rule would apply to metal and nonmetal mines, surface 
coal mines, and the surface areas of underground coal mines. Because 
asbestos from any source poses a health hazard to miners if they inhale 
it, the proposed rule would cover all miners exposed to asbestos 
whether naturally occurring or contained in building materials, in 
other manufactured products at the mine, or in mine waste or tailings.
    The National Institute for Occupational Safety and Health (NIOSH) 
and other research organizations and scientists (see Table VI-5) have 
observed the occurrence of cancers and asbestosis among metal and 
nonmetal miners involved in the mining and milling of commodities that 
contain asbestos. For this reason, our primary focus at metal and 
nonmetal mines is on asbestos in pockets or veins of mined commodities. 
Historically, there has been no evidence of coal miners encountering 
naturally occurring asbestos.\1\ The more likely exposure to asbestos 
in coal mining would occur from introduced asbestos-containing 
products, such as asbestos-containing building materials (ACBM) in 
surface structures.
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    \1\ Personal communication with Professor Kot Unrug, Department 
of Mining Engineering, University of Kentucky, on November 14, 2003; 
and with Syd S. Peng, Chairman, Department of Mining Engineering, 
College of Engineering and Mineral Resources, West Virginia 
University, the week of October 24, 2003.
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    In 2000, the OIG investigated MSHA's activities at the vermiculite 
mine in Libby, Montana. The OIG's conclusions and recommendations, 
discussed later, are consistent with MSHA's observations and concerns 
that--
     Miners are exposed to asbestos at mining operations where 
the ore body or surrounding rock contains asbestos;
     Miners are potentially exposed to airborne asbestos at 
mine facilities with installed asbestos-containing material when it is 
disturbed during maintenance, construction, renovation, or demolition 
activities; and
     Family and community are potentially exposed if miners 
take asbestos home on their person, clothes, or equipment, or in their 
vehicle.
    We developed this proposed rule based on our experience with 
asbestos, our assessment of the health risks, the OIG's 
recommendations, and public comments on MSHA's ANPRM addressing the 
OIG's recommendations. We received numerous comments in response to the 
ANPRM and at the

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public meetings, some of which suggested or supported additional 
requirements beyond those addressed by the OIG. We believe that the 
comments to the ANPRM do not justify an expansion of the scope, at this 
time, beyond the recommendations specifically raised in the OIG report.
    On the contrary, we believe that our data support a narrowed scope 
in that we specifically are not proposing two of the OIG's 
recommendations, i.e., routine use of TEM for the initial analysis of 
exposure samples and promulgation of standards to prevent take-home 
contamination. We are proposing, however, to lower our permissible 
exposure limits.
    We have decided not to propose to change our existing definition of 
asbestos in this rulemaking. There are several reasons for this.
    First, this rulemaking is limited in scope. We believe that a 20-
fold lowering of the exposure limits, as we have proposed, together 
with our enhanced measures to educate the mining community about the 
asbestos hazard in mining, would increase protection for miners and 
help avoid the future development of situations such as that in Libby, 
Montana.
    Second, interest in the definition of asbestos extends to numerous 
agencies in Federal, state, and local governments. Our existing 
definition is consistent with several Federal agencies' regulatory 
provisions, including OSHA's. Changing the definition would require 
considerable interagency consultation and coordination; additional 
scientific evaluation; and an unnecessary delay in providing miners 
access to the benefits of this proposed rule.
    Third, we believe another Libby-like mining operation would not 
exist today because such a business arguably would not be economically 
viable. If a mine's ore contained significant amounts of asbestos-like 
minerals, there is a strong likelihood of potential liability risks, 
both from customers and workers, and the possibility that the mine's 
product would be commercially unmarketable. Such market forces are 
likely to compel mining companies of all sizes to sample the ore for 
the presence of hazardous fibrous minerals before purchasing or 
developing a mine site. In our view, these commercial reasons make it 
unlikely that a new Libby-like mining condition would arise in the 
future.

B. Where Asbestos Is Found at Mining Operations

    Asbestos is no longer mined as a commodity in the United States. 
Even so, veins, pockets, or intrusions of asbestos have been found in 
other ores in specific geographic regions, primarily in metamorphic or 
igneous rock.\2\ Although less common, it is not impossible to find 
asbestos in sedimentary rock, soil, and air from the weathering or 
abrasion of other asbestos-bearing rock.\3\ The areas where asbestos 
may be located can be determined from an understanding of the 
mineralogy of asbestos and the geology required for its formation. In 
some cases, visual inspection can detect the presence of asbestos. MSHA 
experience indicates that miners may encounter asbestos during the 
mining of a number of mineral commodities,\4\ such as talc, limestone 
and dolomite, vermiculite, wollastonite, banded ironstone and taconite, 
lizardite, and antigorite. Not all mines of a specific commodity 
contain asbestos in the ore, however, and the mines that do have 
asbestos in the ore may encounter it rarely.
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    \2\ MSHA (Bank), 1980.
    \3\ USGS, 1995.
    \4\ Roggli et al., 2002; Selden et al., 2001; Amandus et al., 
Part I, 1987; Amandus et al., Part III, 1987; Amandus and Wheeler, 
Part II, 1987.
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    Asbestos also is contained in building materials and other 
manufactured products found at mines. Contrary to the common public 
perception, asbestos is not banned in the United States.\5\ The U.S. 
Geological Survey (USGS) estimates that about 13,000 metric tons (29 
million pounds) of asbestos were used in product manufacturing in the 
United States during 2001.\6\ In addition to domestic manufacturing, 
the United States continues to import products that contain asbestos. 
Asbestos may be used for a number of purposes at a mine including 
insulation; reinforcement of cements; reinforcement of floor, wall, and 
building tile; and automotive clutch and brake linings.\7\ If asbestos 
is present at the mine, miners in the vicinity are potentially at 
increased risk from asbestos exposure, regardless of whether or not 
they are actually working with asbestos.
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    \5\ GETF Report, pp. 12-13, 2003.
    \6\ USGS (Virta), p. 28, 2003.
    \7\ Lemen, 2003; Paustenbach et al., 2003.
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C. Asbestos Minerals

    To understand the scientific literature, information about 
asbestos, and the issues raised in the public comments, it is important 
to understand the terminology used to describe minerals, asbestos, and 
fibers. This section briefly reviews a number of key terms and concepts 
associated with asbestos that we use in discussing this proposed rule.
1. Mineralogical Classification and Mineral Names
    The terminology used to refer to how minerals form and how they are 
named is complex. A mineral's physical properties, composition, 
crystalline structure, and morphology determine its classification. 
Asbestos minerals belong to either the serpentine (sheet silicate) or 
the amphibole (double-chain silicate) family of minerals. Most of the 
difficulties in classifying minerals as asbestos have involved the 
amphiboles. The formation of a particular mineral (chemical 
composition) or habit (morphology, crystalline structure) occurs 
gradually and may be incomplete, producing intermediate minerals that 
are difficult to classify. In the past, there have been several 
different systems used to classify and name minerals that, in some 
instances, led to inconsistent terminology and classification. 
Currently, there is no single, universally accepted system for naming 
minerals.
    Asbestos is a commercial term used to describe certain naturally 
occurring, hydrated silicate minerals. Several Federal agencies have 
regulations that focus on these minerals. The properties of asbestos 
that give it commercial value include low electrical and thermal 
conductivity, chemical and crystalline stability and durability, high 
tensile strength, flexibility, and friability. Much of the existing 
health risk data for asbestos uses commercial mineral terminology. 
Meeker et al. (2003) recognized the confusion associated with asbestos 
nomenclature, stating--

    Within much of the existing asbestos literature, mineral names 
are not applied in a uniform manner and are not all consistent with 
presently accepted mineralogical nomenclature and definitions.

    a. Variations in Mineral Morphology.
    There are many types of crystal habits, such as fibrous, acicular 
(slender and needle-like), massive (irregular form), and columnar 
(stout and column-like). The morphology of a mineral may not fit a 
precise definition. For example, Meeker et al. (2003) state that the 
Libby amphiboles contain ``a complete range of morphologies from 
prismatic crystals to asbestiform fibers.'' Some minerals crystallize 
in more than one habit. Some minerals, which can form in different 
habits, have a different name for each habit; others do not.\8\ For 
example, crocidolite is the name for the asbestiform habit and 
riebeckite is the name for the same mineral in its nonasbestiform 
habit. Tremolite and actinolite do not have different names

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depending on habit; therefore, to distinguish between the different 
habits, the descriptive term ``asbestiform'' or ``asbestos'' is added 
to the mineral's name. If the identifying, descriptive term is not used 
with the mineral name, misunderstandings or mistakes may occur.
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    \8\ Reger and Morgan, 1990; ATSDR, p. 138, 2001.
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    b. Variations in Mineral Composition.
    Atoms similar in size and valence state can replace each other 
within a mineral's crystal lattice, resulting in the formation of a 
different mineral in the same mineral series. This process is gradual 
and can occur to a different extent in the same mineral depending on 
the geological conditions during its formation. For example, tremolite 
contains magnesium, but no (or little) iron, and holds an end member 
position in its mineral series. Iron atoms can replace the magnesium 
atoms in tremolite and the resulting mineral may then be called 
actinolite. The quantity of iron needed before the mineral is called 
actinolite varies depending on the mineral classification scheme used. 
Another example is winchite, which is an intermediate member of the 
tremolite-glaucophane series, as well as an end member in its own 
sodic-calcic series.\9\ Given the chemical similarity within the 
series, winchite 
[(NaCa)Mg4(Al,Fe3+)Si8O 
22(OH)2] often has been reported as tremolite 
[Ca2Mg5Si8O22(OH)2
].
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    \9\ Leake et al., p. 222, 1997.
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    A specific rock formation may contain a continuum of minerals from 
one end member of a series to the other end member, creating a solid 
solution of intermediate minerals. These intermediate minerals are 
sometimes given names, while at other times they are not. Often, when 
the exact chemical composition is not determined or determined to be a 
number of different intermediate minerals, the mineral is named by one 
or more of its end members, such as tremolite-actinolite or 
cummingtonite-grunerite. The fibrous amphiboles in the Libby ore body, 
for example, contain both end members and several intermediate 
minerals. Meeker et al. (2003) state that--

    The variability of compositions on the micrometer scale can 
produce single fibrous particles that can have different amphibole 
names at different points of the particle.

    A mineral may also undergo transition to a different mineral 
series. Kelse and Thompson (1989), Ross (1978), and USGS (Virta, 2002) 
have commented on the chemical transition of anthophyllite to talc. 
Stewart and Lee (1992) stated that fibrous talc might contain 
intermediate particles not easily differentiated from asbestos. In the 
context of systems for naming and classifying fibrous amphiboles, 
Meeker et al. (2003) state that the regulatory literature often gives 
nominal compositions for a mineral without specifying chemical 
boundaries.
2. Differentiating Asbestiform and Nonasbestiform Habit
    In the asbestiform habit, mineral crystals grow forming long, 
thread-like fibers. When pressure is applied to an asbestos fiber, it 
bends much like a wire, rather than breaks. Fibers can separate into 
``fibrils'' of a smaller diameter (often less than 0.5 [mu]m). This 
effect is referred to as ``polyfilamentous,'' and should be viewed as 
one of the most important characteristics of asbestos. Appendix A of 
the Environmental Protection Agency's (EPA's) Method for the 
Determination of Asbestos in Bulk Building Materials \10\ defines 
asbestiform as follows:
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    \10\ EPA, 1993.

    * * * a mineral that is like asbestos, i.e., crystallized with 
the habit [morphology] of asbestos. Some asbestiform minerals may 
lack the properties which make asbestos commercially valuable, such 
as long fiber length and high tensile strength. With the light 
microscope, the asbestiform habit is generally recognized by the 
following characteristics:
    Mean aspect [length to width] ratios ranging from 20:1 to 100:1 
or higher for fibers longer than 5 micrometers. Aspect ratios should 
be determined for fibers, not bundles.
    Very thin fibrils, usually less than 0.5 micrometers in width, 
and two or more of the following:

--Parallel fibers occurring in bundles,
--Fiber bundles displaying splayed ends,
--Matted masses of individual fibers, and/or
--Fibers showing curvature.

    In the nonasbestiform habit, mineral crystals do not grow in long 
thin fibers. They grow in a more massive habit. For example, a long 
thin crystal may not be polyfilamentous nor possess high tensile 
strength and flexibility, but may break rather than bend. When pressure 
is applied, the nonasbestiform crystals fracture easily into prismatic 
particles, which are called cleavage fragments because they result from 
the particle's breaking or cleavage, rather than the crystal's 
formation or growth. Some particles are acicular (needle shaped), and 
stair-step cleavage along the edges of some particles is common.
    Cleavage fragments may be formed when nonfibrous amphibole minerals 
are crushed, as may occur in mining and milling operations. Cleavage 
fragments are not asbestiform and do not fall within our definition of 
asbestos. For some minerals, distinguishing between asbestiform fibers 
and cleavage fragments in certain size ranges is difficult or 
impossible when only a small number of structures are available for 
review, as opposed to a representative population. Meeker et al. (2003) 
states that it is often difficult or impossible to determine 
differences between acicular cleavage fragments and asbestiform mineral 
fibers on an individual fiber basis. A determination as to whether a 
mineral is asbestiform or not must be made, where possible, by applying 
existing analytical methods. Although we have received comments 
regarding the hazards associated with cleavage fragments, we do not 
intend to modify our existing definition of asbestos with this 
rulemaking.

III. History of Asbestos Regulation

    When Federal agencies responsible for occupational safety and 
health began to regulate occupational exposure to asbestos, studies had 
already established that the inhalation of asbestos fibers was a major 
cause of disability and death among exposed workers. The intent of 
these first asbestos rules was to protect workers from developing 
asbestosis.\11\
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    \11\ GETF Report, p. 33, 2003.
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A. MSHA's Asbestos Standards for Mining

    1967-1969. In 1967, under the former Bureau of Mines, predecessor 
to the Mining Enforcement and Safety Administration (MESA) and then 
MSHA, the standard for asbestos exposure in mining was an 8-hour, time-
weighted average (TWA) PEL of 5 mppcf (million particles per cubic foot 
of air). In 1969, the Bureau promulgated a 2 mppcf and 12 f/mL (fibers 
per milliliter) standard.
    1974-1976. In 1974, MESA promulgated a 5 f/mL standard for asbestos 
exposure in metal and nonmetal mines (39 FR 24316). In 1976, MESA 
promulgated a 2 f/cc standard (41 FR 10223) for asbestos exposure in 
surface areas of coal mines. We retained these standards under the 
authority of the Federal Mine Safety and Health Act of 1977.
    1978. In November 1978, we promulgated a 2 f/mL standard for 
asbestos exposure in metal and nonmetal mines (43 FR 54064). Since 
then, we have made only nonsubstantive changes to our asbestos 
standards, e.g., renumbering the section of the standard in 30 CFR.
    MSHA's existing standards for asbestos at metal and nonmetal mines 
at 30 CFR 56/57.5001 state,


[[Page 43954]]


    (b) The 8-hour time-weighted average airborne concentration of 
asbestos dust to which employees are exposed shall not exceed 2 
fibers per milliliter greater than 5 microns in length, as 
determined by the membrane filter method at 400-450 magnification (4 
millimeter objective) phase contrast illumination. No employees 
shall be exposed at any time to airborne concentrations of asbestos 
fibers in excess of 10 fibers longer than 5 micrometers, per 
milliliter of air, as determined by the membrane filter method over 
a minimum sampling time of 15 minutes. ``Asbestos'' is a generic 
term for a number of hydrated silicates that, when crushed or 
processed, separate into flexible fibers made up of fibrils. 
Although there are many asbestos minerals, the term ``asbestos'' as 
used herein is limited to the following minerals: chrysotile, 
Amosite, crocidolite, anthophylite asbestos, tremolite asbestos, and 
actinolite asbestos.

    The existing standard for asbestos at surface coal mines and 
surface work areas of underground coal mines at 30 CFR 71.702 states,

    (a) The 8-hour average airborne concentration of asbestos dust 
to which miners are exposed shall not exceed two fibers per cubic 
centimeter of air. Exposure to a concentration greater than two 
fibers per cubic centimeter of air, but not to exceed 10 fibers per 
cubic centimeter of air, may be permitted for a total of 1 hour each 
8-hour day. As used in this subpart, the term asbestos means 
chrysotile, amosite, crocidolite, anthophylite asbestos, tremolite 
asbestos, and actinolite asbestos but does not include nonfibrous or 
nonasbestiform minerals.
    (b) The determination of fiber concentration shall be made by 
counting all fibers longer than 5 micrometers in length and with a 
length-to-width ratio of at least 3 to 1 in at least 20 randomly 
selected fields using phase contrast microscopy at 400-450 
magnification.

    1989. In 1989, as part of our Air Quality rulemaking, we proposed 
to lower the full-shift exposure limit for asbestos from 2 f/cc to 0.2 
f/cc to address the excessive risk quantified in the Occupational 
Safety and Health Administration's (OSHA's) 1986 asbestos rule (54 FR 
35760). The Air Quality rulemaking, however, was withdrawn on September 
26, 2002 (67 FR 60611). MSHA has not reinstated the Air Quality 
rulemaking at this time.

B. OSHA's Asbestos Standards for General Industry and Construction

    1971-1972. The initial promulgation of OSHA standards on May 29, 
1971 (36 FR 10466) included a 12 f/cc PEL for asbestos. Then, on 
December 7, 1971, in response to a petition by the Industrial Union 
Department of the AFL-CIO, OSHA issued an emergency temporary standard 
(ETS) on asbestos that established an 8-hour, TWA PEL of 5 f/cc and a 
peak exposure level (ceiling limit) of 10 f/cc. In June 1972, OSHA 
promulgated these limits in a final rule.
    1975. In October 1975, OSHA proposed to revise its asbestos 
standard by reducing the 8-hour, TWA PEL to 0.5 f/cc with a ceiling 
limit of 5 f/cc for 15 minutes (40 FR 47652). OSHA stated that 
sufficient medical and scientific evidence had accumulated to warrant 
the designation of asbestos as a human carcinogen and that advances in 
monitoring and protective technology made re-examination of the 
standard appropriate. The final rule, however, reduced OSHA's 8-hour, 
TWA asbestos PEL to 2 f/cc due to feasibility concerns. This limit 
remained in effect until OSHA revised it in 1986.
    1983-1986. On November 4, 1983, OSHA published another emergency 
temporary standard (ETS) for asbestos (48 FR 51086), which would have 
lowered the 8-hour, TWA PEL from 2 f/cc to 0.5 f/cc. The Asbestos 
Information Association challenged the ETS in the U.S. Court of Appeals 
for the 5th Circuit. On March 7, 1984, ruling on Asbestos Information 
Association/North America v. OSHA (727 F.2d 415, 1984), the Court 
invalidated the ETS. Subsequent to this decision, OSHA published a 
proposed rule (49 FR 14116) that, together with the ETS, proposed two 
alternatives for lowering the 8-hour, TWA PEL: 0.2 f/cc and 0.5 f/cc.
    On June 17, 1986, OSHA issued comprehensive asbestos standards (51 
FR 22612) governing occupational exposure to asbestos in general 
industry workplaces (29 CFR 1910.1001), construction workplaces (29 CFR 
1926.1101), and shipyards (29 CFR 1915.1001). The separate standards 
shared the same asbestos PEL and most ancillary requirements. These 
standards reduced OSHA's 8-hour, TWA PEL to 0.2 f/cc from the previous 
2 f/cc limit. OSHA added specific provisions in the construction 
standard to cover unique hazards relating to asbestos abatement and 
demolition jobs.
    Although tremolite, actinolite, and anthophyllite exist in 
different forms, OSHA determined that all forms of these minerals would 
continue to be regulated. Following promulgation of the rule, several 
parties requested an administrative stay of the standard claiming that 
OSHA improperly included nonasbestiform minerals. A temporary stay was 
granted and OSHA initiated rulemaking to remove the nonasbestiform 
types of these minerals from the scope of the asbestos standards.
    1988. Several major participants in OSHA's rulemaking challenged 
various provisions of the 1986 revised standards. In Building 
Construction Trades Division (BCTD), AFL-CIO v. Brock (838 F.2d 1258, 
1988), the U.S. Court of Appeals for the District of Columbia upheld 
most of the challenged provisions, but remanded certain issues to OSHA 
for reconsideration. In partial response, on September 14, 1988, OSHA 
promulgated an excursion limit of 1 f/cc for asbestos as measured over 
a 30-minute sampling period (53 FR 35610).
    1992. OSHA's 1986 standards had applied to occupational exposure to 
nonasbestiform actinolite, tremolite, and anthophylite. On June 8, 
1992, OSHA deleted the nonasbestiform types of these minerals from the 
scope of its asbestos standards. In evaluating the record, OSHA found 
(57 FR 24310-24311) insufficient evidence that nonasbestiform 
actinolite, tremolite, and anthophyllite present ``a risk similar in 
kind and extent'' to their asbestiform counterparts. Additionally, the 
evidence did not show that OSHA's removal of the nonasbestiform types 
of these three minerals from its asbestos standard ``will pose a 
significant risk to exposed employees.''
    1994. On August 10, 1994, OSHA published a final rule (59 FR 40964) 
that lowered its 8-hour, TWA PEL for asbestos to 0.1 f/cc and retained 
the 1 f/cc excursion limit as measured over 30 minutes.

C. Other Federal Agencies Regulating Asbestos

    Because the health hazards of exposure to asbestos are well 
recognized, it is highly regulated. OSHA and MSHA have the primary 
authority to regulate occupational exposures to asbestos. EPA regulates 
asbestos exposure of state and local government workers in those states 
that do not have an OSHA State Plan covering them. A number of other 
Federal agencies, primarily EPA and the Consumer Product Safety 
Commission (CPSC), regulate non-occupational asbestos exposures. For 
example, CPSC regulates asbestos in consumer products, such as patching 
compounds, under the Federal Hazardous Substances Act.
    EPA regulates asbestos in air and materials. EPA's activities have 
focused on environmental issues and the public health by reducing 
emissions of hazardous gases and dusts from large industrial sources, 
such as taconite ore processing,\12\ and the cleanup of contaminated 
waste sites. EPA also regulates asbestos in schools. The mining and 
processing of vermiculite in Libby, Montana, resulted in the spread

[[Page 43955]]

of asbestos to numerous homes, schools, and businesses throughout the 
town. In November 1999, EPA responded to a request to study the 
environmental contamination in the town of Libby and widespread 
illnesses and death among its residents. In October 2002, EPA 
designated the area as a Superfund site.
---------------------------------------------------------------------------

    \12\ EPA (68 FR 61868), 2003.
---------------------------------------------------------------------------

D. Other Asbestos-Related Activities

    There have been increasing numbers of studies on asbestos and its 
hazards over the past 40 years. These efforts encompass government, 
industry, and academia on a local, national, and international scale. 
Government agencies and scientific groups in the United States, such as 
the National Institute for Occupational Safety and Health (NIOSH), the 
Agency for Toxic Substances and Disease Registry (ATSDR), the American 
Conference of Governmental Industrial Hygienists (ACGIH), and the 
National Toxicology Program (NTP), have addressed issues involving 
carcinogens, such as asbestos. Organizations from other countries, such 
as the United Kingdom (Health and Safety Executive) and Germany 
(Deutche Forschungsgemeinschaft), also have addressed occupational 
exposure to asbestos and other carcinogens. Similarly, the 
International Agency for Research on Cancer (IARC) has published a 
monograph on asbestos that summarizes evidence of its 
carcinogenicity.\13\
---------------------------------------------------------------------------

    \13\ IARC, 1987.
---------------------------------------------------------------------------

1. Interagency Asbestos Work Group (IAWG)
    OSHA's and EPA's overlapping responsibilities and common interest 
in addressing asbestos hazards led to the formation of the IAWG. 
Participating Federal agencies include EPA, OSHA, CPSC, MSHA, NIOSH, 
ATSDR, USGS, and the National Institute of Standards and Technology 
(NIST). This work group of government agencies facilitates the sharing 
of information and coordination of activities, including regulatory 
activities, environmental assessment, technical assistance, consumer 
protection, and developments in environmental analysis of contaminants. 
The IAWG also seeks to harmonize the policies, procedures, and 
enforcement activities of the participating agencies, thus minimizing 
or eliminating potential conflicts for the regulated community. For 
example, the IAWG is currently discussing the Federal definition of 
asbestos.
2. National Institute for Occupational Safety and Health (NIOSH)
    The Workers' Family Protection Act of 1992 (29 U.S.C. 671A) 
directed NIOSH to study contamination of workers' homes by hazardous 
substances, including asbestos, transported from the workplace. ATSDR, 
EPA, OSHA, MSHA, the U.S. Department of Energy (DOE), and the Centers 
for Disease Control and Prevention (CDC) assisted NIOSH in conducting 
the study. For this proposed rule we focused on the asbestos-related 
results of these studies.
    NIOSH (1995) published its study results in a Report to Congress on 
Workers' Home Contamination Study Conducted under the Workers' Family 
Protection Act. This report summarizes incidents of home contamination, 
including the health consequences, sources, and levels of 
contamination. The study documents cases of asbestos reaching workers' 
homes in 36 states in the United States and in 28 other countries. 
These cases covered a wide variety of materials, industries, and 
occupations. The means by which hazardous substances reached workers' 
homes and families included taking the substance home on the worker's 
body, clothing, tools, and equipment; cottage industries (i.e., work 
performed on home property); and family visits to the workplace. In an 
effort to reach employers and workers, NIOSH (1997) published its 
recommendations in Protect Your Family: Reduce Contamination at Home. 
This pamphlet summarizes the NIOSH study and provides recommendations 
to prevent this contamination.
3. Agency for Toxic Substances and Disease Registry (ATSDR)
    The Superfund Amendments and Reauthorization Act of 1986 (SARA) 
directed ATSDR to prepare toxicological profiles for hazardous 
substances most commonly found at specific waste sites. ATSDR and EPA 
determined which hazardous substances pose the most significant 
potential threat to human health and targeted them for study. Asbestos 
is one of these targeted substances. ATSDR published one of the most 
current toxicological profiles for asbestos in September 2001, which 
was an update of an earlier asbestos profile.
    In October 2002, ATSDR sponsored a meeting of expert panelists who 
presented their evaluation of state-of-the-art research concerning the 
relationship between fiber length and the toxicity of asbestos and 
synthetic vitreous fibers. We have reviewed the evidence and arguments 
presented in the updated asbestos toxicological profile and the meeting 
proceedings and have discussed this information in this preamble, where 
appropriate.

E. U.S. Department of Labor, Office of the Inspector General (OIG)

    In November 1999, a Seattle newspaper published a series of 
articles on the unusually high incidence of asbestos-related illnesses 
and fatalities among individuals who had lived in Libby, Montana. There 
was extensive national media attention surrounding the widespread 
environmental contamination and asbestos-related deaths in Libby. Dust 
and construction materials from the nearby vermiculite mine were the 
alleged cause. This mine had produced about 90 percent of the world's 
supply of vermiculite from 1924 until 1992.
    Because MSHA had jurisdiction over the mine for two decades before 
it closed, the OIG investigated MSHA's enforcement actions at the mine. 
The OIG confirmed that the processing of vermiculite at the mine 
exposed miners to asbestos. The miners then, inadvertently, had carried 
the asbestos home on their clothes and in their personal vehicles.\14\ 
In doing this, the miners continued to expose themselves and family 
members.
---------------------------------------------------------------------------

    \14\ Weis et al., 2001.
---------------------------------------------------------------------------

1. OIG Report on MSHA's Handling of Inspections at the W.R. Grace & 
Company Mine in Libby, Montana
    The OIG published its findings and recommendations in a report 
dated March 22, 2001. The OIG found that MSHA had appropriately 
conducted regular inspections and personal exposure sampling at the 
Libby mine and that there were no samples exceeding the 2.0 f/cc PEL 
for the 10 years prior to the mine closing in 1992. The OIG concluded, 
``We do not believe that more inspections or sampling would have 
prevented the current situation in Libby.'' The OIG stated its belief 
that there is a need for MSHA to lower its asbestos PEL.
    In its report, the OIG supported the development and implementation 
of control measures for asbestos and vermiculite mining and milling. 
They also made recommendations for improving our effectiveness in 
controlling this hazard. This proposed rule addresses our responses to 
several of the OIG's recommendations.
2. MSHA's Libby, Montana Experience
    W.R. Grace acquired the vermiculite mine in Libby, Montana, in 
1963. At that time, the amphibole in the

[[Page 43956]]

vermiculite was called tremolite, soda tremolite, soda-rich tremolite, 
or richterite, and researchers had already linked the mine dust to 
respiratory disease.\15\ The suggested exposure limit for asbestos in 
mining was much higher than current limits. The federal standard for 
asbestos in mining dropped from 5 mppcf (about 30 f/mL) in 1967 to 2 f/
mL in 1978. When MESA (predecessor agency to MSHA) began inspecting the 
operation, the exposure limit for asbestos was 5 f/mL.
---------------------------------------------------------------------------

    \15\ McDonald et al., 1986; Meeker et al., 2003; Peipins et al., 
2003.
---------------------------------------------------------------------------

    The mine operator, Federal mine inspectors, and representatives of 
the U.S. Public Health Service [part of the Centers for Disease Control 
and Prevention (CDC)] routinely sampled for asbestos at the Libby mine, 
starting before the mine switched to wet processing in 1974, and 
continued sampling periodically until the mine closed in 1992. MSHA 
sampling at the Libby mine found no exposures exceeding the 5.0 f/cc 
asbestos PEL from 1975 through 1978, and only a few over the 2.0 f/cc 
asbestos PEL from 1979 through 1986. Almost all the samples would have 
exceeded the 0.1 f/cc proposed limit. Miners' exposures continued to 
decrease and more recent sampling since 1986 found few exposures 
exceeding the OSHA PEL of 0.1 f/cc.
    The results from our personal exposure sampling at the Libby mine 
included many of the fibrous amphiboles present. In addition, the 
results from TEM analysis of the air samples characterized the 
mineralogy of the airborne fibers as tremolite and did not distinguish 
between the species of amphiboles. Further characterization of the 
amphibole minerals using Scanning Electron Microscopy/Energy Dispersive 
X-ray Spectroscopy technology shows proportions of about 84 percent 
winchite, 11 percent richterite, and 6 percent tremolite.\16\
---------------------------------------------------------------------------

    \16\ Meeker et al., 2003
---------------------------------------------------------------------------

    As early as 1980, MSHA had requested that NIOSH investigate health 
problems at all vermiculite operations, including the mine and mill in 
Libby, Montana. NIOSH published its study results in a series of three 
papers (Amandus et al., Part I, 1987; Amandus and Wheeler, Part II, 
1987; Amandus et al., Part III, 1987). The study of Amandus et al. 
(Part I, 1987) along with that of McDonald et al. (1986) found that, 
historically, the highest exposures to fibers at the Libby operation 
had occurred in the mill and that exposures had decreased between the 
1960's and 1970's. McDonald et al. (1986) reported--

    In 1974, the old dry and wet mills were closed and the ore was 
processed in a new mill built nearby which operated on an entirely 
wet basis in which separation was made by vibrating screens, 
Humphrey separators, and flotation.

McDonald et al. (1986) and Amandus and Wheeler (Part II, 1987) also 
showed that, even at reduced exposure levels, there was still increased 
risk of lung cancer among the Libby miners and millers.
3. MSHA's Efforts To Minimize Asbestos Take-Home Contamination
    ``Take-home'' contamination is contamination of workers' homes or 
vehicles by hazardous substances transported from the workplace. As 
discussed previously in this preamble, the widespread asbestos-related 
disease among the residents of Libby, Montana, was attributed, in part, 
to take-home contamination from the vermiculite mining and milling 
operation in that town. The OIG report on MSHA's activities recommended 
that we promulgate special safety standards similar to those in our 
1989 proposed Air Quality rule (54 FR 35760) to address take-home 
contamination.
    In our 1989 Air Quality proposed rule, we had proposed that miners 
wear protective clothing and other personal protective equipment before 
entering areas containing asbestos. Our Air Quality proposed rule also 
would have required miners to remove their protective clothing and 
store them in adequate containers to be disposed of or decontaminated 
by the mine operator. These proposed requirements were similar to those 
in OSHA's asbestos standard and to NIOSH's recommendations.
    In March 2000, shortly after the series of articles on asbestos-
related illnesses and deaths in Libby, Montana, we issued a Program 
Information Bulletin (PIB No. P00-3) about asbestos. The PIB served to 
remind the mining industry of the potential health hazards from 
exposure to airborne asbestos fibers and to raise awareness about 
potential asbestos exposure for miners, their families, and their 
communities. At that time, we also issued a Health Hazard Information 
Card (No. 21) about asbestos for distribution to miners to raise their 
awareness about the health hazards related to asbestos exposure.
    The PIB included information about asbestos, its carcinogenic and 
other significant health effects, how miners could be exposed, where 
asbestos occurs naturally on mining property, and what types of 
commercial products may contain asbestos. It included recommendations 
to help mine operators reduce miners' exposures, to prevent or minimize 
take-home contamination, and for the selection and use of respiratory 
protection. The PIB also urged mine operators to minimize exposures, to 
improve controls, and to train miners, listing specific training topics 
as essential for miners potentially exposed to asbestos.
    During this same period, 2000 to 2003, we conducted an asbestos 
awareness campaign and increased asbestos sampling. Section VII.D of 
this preamble contains an additional discussion of measures to prevent 
asbestos ``take-home'' contamination.
    We have decided not to pursue a regulatory approach to minimizing 
asbestos ``take-home'' contamination. Based on the existing levels of 
asbestos exposures in the mining industry, comments on our 2002 ANPRM, 
and testimony at the subsequent public meetings, we have determined 
that a non-regulatory approach would be effective in minimizing 
asbestos take-home contamination from mining operations.
4. Training Inspectors to Recognize and Sample for Asbestos
    The OIG recommended that we increase MSHA inspectors' skills for 
providing asbestos compliance assistance to mine operators. In 
response, we developed a half-day multimedia training program that 
includes the following:
     A PowerPoint-based training presentation that examines 
MSHA's procedures for air and bulk asbestos sampling.
     An updated ``Chapter 8--Asbestos Fibers'' from the Metal 
and Nonmetal Health Inspection and Procedures Handbook that serves as a 
text for the training sessions.
     A ``hands-on'' segment that allows the inspectors to 
examine asbestos and asbestiform rock samples and the equipment used 
for bulk sampling, and that provides the inspectors instruction and 
practice in assembling and calibrating asbestos fiber air sampling 
apparatus.
    We gave this asbestos training to journeymen inspectors from March 
2002 through April 2003, and added it to the training program for 
entry-level inspectors.

IV. Health Effects of Asbestos Exposure

    The health hazards from exposure to asbestos were discussed 
extensively in the preamble to OSHA's 1983 final rule (51 FR 22615). 
Subsequently, researchers have confirmed and

[[Page 43957]]

increased our knowledge of these hazards. Exposures in occupational and 
environmental settings are generally due to inhalation, although some 
asbestos may be absorbed through ingestion. While the part of the body 
most likely affected (target organ) is the lung, adverse health effects 
may extend to the linings of the chest, abdominal, and pelvic cavities, 
and the gastrointestinal tract. The damage following chronic exposure 
to asbestos is cumulative and irreversible. Workplace exposures to 
asbestos may be chronic, continuing for many years. The symptoms of 
asbestos-related adverse health effects may not become evident for 20 
or more years after first exposure (latency period).

A. Summary of Asbestos Health Hazards

    This section presents an overview of human health effects from 
exposure to asbestos. We are proposing to use OSHA's 1986 risk 
assessment to estimate the risk from asbestos exposures in mining. 
OSHA's risk assessment has withstood legal scrutiny and the more recent 
studies discussed later in this preamble support it. MSHA has placed 
OSHA's risk assessment in the asbestos rulemaking record. It can also 
be found at https://www.osha.gov.
    Studies first identified health problems associated with 
occupational exposure to asbestos in the early 20th century among 
workers involved in the manufacturing or use of asbestos-containing 
products.\17\ Early studies identified the inhalation of asbestos as 
the cause of asbestosis, a slowly progressive disease that produces 
lung scarring and loss of lung elasticity. Studies also found that 
asbestos caused lung and several other types of cancer. For example, 
mesotheliomas, rare cancers of the lining of the chest or abdominal 
cavities, are almost exclusively attributable to asbestos exposure. 
Once diagnosed, they are rapidly fatal. Asbestos-related diseases have 
long latency periods, commonly not producing symptoms for 20 to 30 
years following initial exposure.
---------------------------------------------------------------------------

    \17\ GETF Report, p. 38, 2003; OSHA (40 FR 47654), 1975.
---------------------------------------------------------------------------

    In the late 1960's, scientists correlated phase contrast microscopy 
fiber counting methods with the earlier types of dust measurements. 
This procedure provided a means to estimate earlier workers' asbestos 
exposures and enabled researchers to develop a dose-response 
relationship with the occurrence of disease. The British Occupational 
Hygiene Society reported \18\ that a worker exposed to 100 fiber-years 
per cubic centimeter (e.g., 50 years at 2 f/cc, 25 years at 4 f/cc, 10 
years at 10 f/cc) would have a 1 percent risk of developing early signs 
of asbestosis. The correlation of exposure levels with the disease 
experience of populations of exposed workers provided a basis for 
setting an occupational exposure limit for asbestos measured by the 
concentration of the fibers in air.
---------------------------------------------------------------------------

    \18\ Lane et al., 1968; OSHA (40 FR 47654), 1975.
---------------------------------------------------------------------------

    As mentioned previously, the hazardous effects from exposure to 
asbestos are now well known. For this reason, our discussion in this 
section will focus on the results of the more recent studies and 
literature reviews, those published since the publication of OSHA's 
risk assessment, and those involving miners. One such review by 
Tweedale (2002) stated,

    Asbestos has become the leading cause of occupational related 
cancer death, and the second most fatal manufactured carcinogen 
(after tobacco). In the public's mind, asbestos has been a hazard 
since the 1960s and 1970s. However, the knowledge that the material 
was a mortal health hazard dates back at least a century, and its 
carcinogenic properties have been appreciated for more than 50 
years.

    Greenberg (2003) also published a recent review of the biological 
effects of asbestos and provided a historical perspective similar to 
that of Tweedale.
    The three most commonly described adverse health effects associated 
with asbestos exposure are lung cancer, mesotheliomas, and pulmonary 
fibrosis (i.e., asbestosis). OSHA, in its 1986 asbestos rule, reviewed 
each of these diseases and provided details on the studies 
demonstrating the relationship between asbestos exposure and the 
clinical evidence of disease. In 2001, the ATSDR published an updated 
Toxicological Profile for Asbestos that also included an extensive 
discussion of these three diseases. A search of peer-reviewed 
scientific literature using databases, such as Gateway, PubMed, and 
ToxLine, accessed through the National Library of Medicine (NLM), 
yielded nearly 900 new references on asbestos from January 2000 to 
October 2003. Many of these recent articles \19\ continue to 
demonstrate and support findings of asbestos-induced lung cancer, 
mesotheliomas, and asbestosis, consistent with the conclusions of OSHA 
and ATSDR. Thus, in the scientific community, there is compelling 
evidence of the adverse health effects of asbestos exposure. This has 
led some researchers and stakeholders to recommend a worldwide ban of 
asbestos.\20\
---------------------------------------------------------------------------

    \19\ Baron, 2001; Bolton et al., 2002; Manning et al., 2002; 
Nicholson, 2001; Osinubi et al., 2000; Roach et al., 2002.
    \20\ Maltoni, 1999.
---------------------------------------------------------------------------

B. Factors Affecting the Occurrence and Severity of Disease

    The toxicity of asbestos, and the subsequent occurrence of disease, 
is related to its concentration (C) in the mine air and to the duration 
(T) of the miner's exposure. Other variables, such as the fiber's 
characteristics or the effectiveness of the miner's lung clearance 
mechanisms, also affect disease severity.
1. Concentration (C)
    Currently, the concentration (C) of asbestos is expressed as the 
number of fibers per cubic centimeter (f/cc). Some studies have also 
reported asbestos concentrations in the number of fibers per milliliter 
(f/mL), which is an equivalent concentration to f/cc. MSHA's existing 
PELs for asbestos are expressed in f/mL for metal and nonmetal mines 
and as f/cc for coal mines. To improve consistency and avoid confusion, 
we express the concentration of airborne fibers as f/cc in this 
proposed rule, for both coal and metal and nonmetal mines.
    Older scientific literature (i.e., 1960's and 1970's) reported 
exposure concentrations as million particles per cubic foot (mppcf) and 
applied a conversion factor to convert mppcf to f/cc. OSHA (51 FR 
22617) used a factor of 1.4 when performing these conversions. More 
recently, Hodgson and Darnton (2000) recommended the use of a factor of 
3. In our evaluation of the scientific literature, we did not 
critically evaluate the impact of these and other conversion factors. 
We note this difference here for completeness. Because we are relying 
on OSHA's risk assessment, we are using OSHA's conversion factor
2. Time (T)
    Epidemiological and toxicological studies generally report time (T) 
in years (yr). The product of exposure concentration and exposure 
duration (i.e., C x T) is referred to as ``fiber-years''.\21\ When 
developing exposure-response relationships for asbestos-induced health 
effects, researchers typically use ``fiber-years'' to indicate the 
level of workplace exposure. Finkelstein \22\ noted, however, that this 
product of exposure concentration times duration of exposure (C x T) 
assumes an equal weighting of each variable (C, T).
---------------------------------------------------------------------------

    \21\ ATSDR, 2001; Fischer et al., 2002; Liddell, 2001; Pohlabeln 
et al., 2002.
    \22\ Finkelstein, 1995; ATSDR, p. 42, 2001.

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[[Page 43958]]

3. Fiber Characteristics
    Baron (2001) reviewed techniques for the measurement of fibers and 
stated, ``* * * fiber dose, fiber dimension, and fiber durability are 
the three primary factors in determining fiber [asbestos] toxicity * * 
*''. Manning et al. (2002) also noted the important roles of bio-
persistence (i.e., durability), physical properties, and chemical 
properties in defining the ``toxicity, pathogenicity, and 
carcinogenicity'' of asbestos. Roach et al. (2002) stated that--

    Physical properties, such as length, diameter, length-to-width 
(aspect ratio), and texture, and chemical properties are believed to 
be determinants of fiber distribution [in the body] and disease 
severity.

    Many other investigators \23\ also have concluded that the 
dimensions of asbestos fibers are biologically important.
---------------------------------------------------------------------------

    \23\ ATSDR, 2001; Osinubi et al., 2000; Peacock et al., 2000; 
Langer et al., 1979.
---------------------------------------------------------------------------

    OSHA and MSHA currently specify that analysts count those fibers 
that are over 5.0 micrometers ([mu]m) in length with a length to 
diameter aspect ratio of at least 3:1. Several recent publications \24\ 
support this aspect ratio, although larger aspect ratios such as 5:1 or 
20:1 have been proposed.\25\ There is some evidence that longer, 
thinner asbestos fibers (e.g., greater than 20 [mu]m long and less than 
1 [mu]m in diameter) are more potent carcinogens than shorter fibers. 
Suzuki and Yuen (2002), however, concluded that ``Short, thin asbestos 
fibers should be included in the list of fiber types contributing to 
the induction of human malignant mesotheliomas * * * ''. More recently, 
Dodson et al. (2003) concluded that all lengths of asbestos fibers 
induce pathological responses and that researchers should exercise 
caution when excluding a population of inhaled fibers based on their 
length.
---------------------------------------------------------------------------

    \24\ ATSDR, 2001; Osinubi et al., 2000.
    \25\ Wylie et al., 1985.
---------------------------------------------------------------------------

    We have determined that researchers have found neither a reliable 
method for predicting the contribution of fiber length to the 
development of disease, nor evidence establishing the exact 
relationship between them. There is suggestive evidence that the 
dimensions of asbestos fibers may vary with different diseases. A 
continuum may exist in which shorter, wider fibers produce one disease, 
such as asbestosis, and longer, thinner fibers produce another, such as 
mesotheliomas.\26\ The scientific community continues to publish new 
data that will enable regulatory agencies, such as MSHA, to better 
understand the relationship between fiber dimensions, durability, 
inhaled dose, and other important factors that determine the health 
risks of exposure not only to asbestos, but also to other fibers.
---------------------------------------------------------------------------

    \26\ ATSDR, pp. 39-41, 2001; Mossman, pp. 47-50, 2003.
---------------------------------------------------------------------------

4. Differences in Fiber Potency
    The theory that the differences among fibers have an effect on 
their ability to produce adverse effects on human hea