[Federal Register Volume 61, Number 243 (Tuesday, December 17, 1996)]
[Proposed Rules]
[Pages 66348-66469]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-30733]
[[Page 66347]]
_______________________________________________________________________
Part II
Department of Labor
_______________________________________________________________________
Mine Safety and Health Administration
_______________________________________________________________________
30 CFR Parts 56, 57, 62, 70 and 71
Health Standards for Occupational Noise Exposure in Coal, Metal, and
Nonmetal Mines; Proposed Rule
Federal Register / Vol. 61, No. 243 / Tuesday, December 17, 1996 /
Proposed Rules
[[Page 66348]]
DEPARTMENT OF LABOR
Mine Safety and Health Administration
30 CFR Parts 56, 57, 62, 70 and 71
RIN 1219-AA53
Health Standards for Occupational Noise Exposure
AGENCY: Mine Safety and Health Administration (MSHA), Labor.
ACTION: Proposed rule.
-----------------------------------------------------------------------
SUMMARY: This proposed rule would replace MSHA's existing standards for
occupational noise exposure in coal mines and in metal and nonmetal
mines with a single new standard applicable to all mines.
This action is part of the Agency's ongoing review of its safety
and health standards. The review found that the Agency's existing noise
standards, which had been promulgated more than 20 years ago, are
inadequate to prevent the occurrence of occupational noise-induced
hearing loss (NIHL) among miners. There remains a significant risk to
miners of material impairment of health from workplace exposure to
noise over a working lifetime. The risk becomes significant when
exposure exceeds an 8-hour time-weighted average of 85 dBA.
DATES: Comments must be received on or before February 18, 1997. Submit
written comments on the information collection requirements by February
18, 1997.
ADDRESSES: Comments on the proposed rule may be transmitted by
electronic mail, fax, or mail. Comments by electronic mail must be
clearly identified as such and sent to this e-mail address:
[email protected]. Comments by fax must be clearly identified as such and
sent to: Mine Safety and Health Administration, Office of Standards,
Regulations, and Variances, 703-235-5551. Send mail comments to: Mine
Safety and Health Administration, Office of Standards, Regulations, and
Variances, Room 631, 4015 Wilson Boulevard, Arlington, VA 22203-1984.
Interested persons are encouraged to supplement written comments with
computer files or disks; please contact the Agency with any questions
about format. Written comments on the information collection
requirements may be submitted directly to the Office of Information and
Regulatory Affairs, OMB New Executive Office Building, 725 17th Street,
NW., Rm. 10235, Washington, D.C. 20503, Attn: Desk Officer for MSHA.
FOR FURTHER INFORMATION CONTACT: Patricia W. Silvey, Director; MSHA;
Office of Standards, Regulations, and Variances; 703-235-1910.
SUPPLEMENTARY INFORMATION:
Comprehensive Summary
The proposal would retain the existing permissible exposure level
(PEL) but establish a new ``action level''. The action level would be
an 8-hour time-weighted average of 85 dBA; the PEL would remain an 8-
hour time-weighted average of 90 dBA.
Whenever a miner's noise exposure exceeds the action level, the
miner would receive special training in noise protection.
When the miner's noise exposure exceeds the action level, but is
below the PEL, the operator would be required to make annual
audiometric (hearing) examinations available to the miner through
enrollment in a hearing conservation program, and to provide properly
fitted hearing protection in three circumstances--before the initial
hearing examination, if a significant threshold shift in hearing acuity
is detected, and at any other time upon miner request. If it will take
more than 6 months for the initial examination because of the need to
wait for a mobile test van, or a significant threshold shift in hearing
acuity is detected, the operator would also be required to ensure the
miner uses the provided hearing protection.
If a miner's exposure exceeds the PEL, the proposal would require
that the mine operator use all engineering and administrative controls
which it is feasible for that mine operator to utilize to reduce noise
to the PEL. The proper combination of engineering and administrative
controls would be left to the discretion of the mine operator.
Should the use of all feasible engineering and administrative
controls not reduce a miner's noise exposure to the PEL, the operator
would have to use those controls to lower exposure to as close to the
PEL as is feasible. In addition, the operator would have to provide any
such miner properly fitted hearing protection, ensure the miner uses
such protection, and ensure the miner takes the annual audiometric
examinations. Should a miner's exposure exceed an 8-hour time-weighted
average of 105 dBA, the operator must ensure the miner is provided and
uses both a plug and a muff type protector.
MSHA recognizes that successful implementation of these new uniform
health rules will require training of MSHA personnel and guidance to
miners and mine operators, particularly small mine operators.
Accordingly, the Agency proposes that the final rule take effect one
year after the date of publication of the final rule, and solicits
comments on whether a phased-in approach would permit some elements of
the new rule to be implemented more quickly.
The Supplementary Information accompanying this notice is detailed.
Accordingly, to facilitate review and comment by the mining community,
this material begins with questions and answers summarizing key points
about the proposal. Included are two charts comparing the main features
of the proposal to existing standards in the mining industry and those
applicable to other industries under the Occupational Safety and Health
Act. Also included are MSHA's estimates of the impacts of the proposal
from the Agency's preliminary Regulatory Impact Analysis (RIA), copies
of which are available from the Agency.
I. Questions and Answers, Required Notices, and History
(A) Questions and Answers About Key Features of this Proposal
(1) What Are the Key Features of This Proposal?
MSHA has developed a proposal that it estimates can reduce by two-
thirds the number of miners currently projected to suffer a material
impairment of their hearing--but which it estimates can be implemented
at a cost of less than $9 million to the mining industry as a whole.
The focus of the proposal is on the use of the most effective means
to control noise--engineering controls to eliminate the noise, or
administrative controls (e.g. rotating miner duties) to minimize noise
exposure--whenever feasible.
Specifically, the proposal requires that an operator use all
feasible engineering or administrative controls to reduce noise to the
PEL--a TWA8 of 90 dBA. While MSHA has determined there is a
significant risk of harm at a TWA8 of 85 dBA, the Agency believes
that it may not be feasible at this time for the mining industry to
control noise to this level using engineering and administrative
controls.
The proposal would require that steps be taken when noise exceeds a
TWA8 of 85 dBA, the ``action level'', to prevent hearing loss.
Operators would have to provide special instruction in noise, make
annual hearing examinations available, and provide properly fitted
hearing protection--before the initial examination, if a significant
threshold shift in hearing acuity is detected, and at any other time
upon a miner's
[[Page 66349]]
request. If it will take more than 6 months to take the initial
examination because of the need to wait for a mobile test van, or if a
significant threshold shift is detected, an operator would also be
required to ensure that the miner uses the hearing protection.
The proposal also provides for supplemental protection in those
cases in which individual operators are unable to reduce noise to the
PEL through the use of all feasible engineering or administrative
controls. The operator must ensure any miner so exposed takes the
annual hearing examinations, must provide properly fitted hearing
protection to all miners so exposed, and must ensure the hearing
protection is used by all miners so exposed.
The focus on engineering and administrative controls would
significantly change the way noise is addressed in the coal mining
industry. Currently, hearing protectors generally are allowed when a
coal miner's noise exposure exceeds the PEL. The proposal would require
a coal mine operator to use all feasible engineering and administrative
controls to reduce exposure to the PEL--the practice currently required
in the rest of the mining industry. MSHA estimates that this change
alone can prevent 3 out of every 5 impairments projected to occur due
to occupational noise exposure in the coal mining industry.
While this change would cost the coal mining industry more money
for implementation of engineering controls, MSHA estimates these costs
would be significantly offset by the paperwork savings the coal mining
industry will accrue under the proposal. In particular, MSHA is
proposing to replace the costly, paperwork-intensive requirements for
biannual coal miner noise exposure surveys, supplemental noise surveys,
calibration reports, survey reports, and survey certifications with a
performance-oriented requirement that mine operators establish a
monitoring program that effectively evaluates miner exposures. MSHA
believes the existing requirements have not been effective.
Other parts of the proposal would change current practices
throughout the mining industry. No actions are currently required if
noise exposures are below the PEL. Moreover, the proposal requires, for
the first time, certain explicit protections if an operator cannot
feasibly reduce noise exposures to the PEL through the use of all
feasible engineering and administrative controls.
MSHA's proposal also incorporates revisions warranted by our
increased understanding of the effects of noise, to the extent that the
Agency determined such changes would be feasible for the mining
industry to implement. For example, to reflect that exposure to sound
levels above 80 dBA is now generally recognized as harmful, the
proposal would include exposure to such sound levels in determining a
miner's noise dose. Such adjustment will result in more miners than at
present being determined to have noise exposures over the PEL, but the
Agency has determined that the industry can feasibly accommodate this
change.
(2) Do I Need To Read This Entire Notice To Understand the Proposal?
The Agency hopes these questions and answers will provide the
information most of the mining community will want. Nevertheless, MSHA
is accompanying publication of this proposed rule with a detailed
discussion of the information it has considered in developing the
proposal. That way, those interested in a particular topic can have the
benefit of the Agency's thinking in developing their comments.
The information is divided into five parts. Part I includes a
review of the projected impacts of the proposal, including benefits,
costs and paperwork, taken from the Agency's preliminary RIA. Part II
is the Agency's analysis of the current risks to miners from
occupational noise exposure. Part III is a section-by-section
discussion of the elements of the proposal. Part IV is an analysis of
the technological and economic feasibility of the proposal and of key
alternatives considered by the Agency. Part V is a complete list of
publications referenced by the Agency.
(3) What Are the Projected Impacts of the Proposed Rule?
The estimated benefits and costs and paperwork requirements of the
proposed rule are summarized in the following table, ``Summary of Key
Impacts of MSHA's Noise Proposal,'' followed by a brief explanation.
The Agency's estimates, and a complete description of the methodology
used to obtain them, are contained in the Agency's preliminary RIA, a
copy of which can be obtained from the Agency.
Summary of Key Impacts of MSHA's Noise Proposal *
----------------------------------------------------------------------------------------------------------------
Coal Metal/nonmetal All mining
----------------------------------------------------------------------------------------------------------------
Benefits:
% hearing impairments avoided...................... 81 57 67
# miners saved from hearing impairment............. 15,300 15,300 30,600
Annual costs (in millions of dollars).................. $0.3 $8 $8.3
Paperwork burden hours added/saved..................... (88,740) 73,755 (14,985)
----------------------------------------------------------------------------------------------------------------
* Rounded.
The analysis of benefits compares the number of miners who are
projected to incur a material impairment of their hearing under the
current rule with the number of miners who are projected to incur such
an impairment under the proposed rule. Overall for the mining
community, the proposal would reduce the risk of material impairment by
67%. More than 30,000 miners otherwise expected to develop a material
impairment would be spared.
As displayed in the chart entitled ``Benefits of MSHA Noise
Proposal in Saving Miners From Hearing Impairment,'' the most
significant benefits are expected in the coal sector. Engineering and
administrative controls are expected to significantly reduce noise
exposures above the PEL. A significant benefit also accrues from the
establishment of an action level: based on the assumption that most
employees exposed to noise between the action level and the PEL will
elect to use hearing protection for the first time at such levels.
While the metal and nonmetal mining industry already uses engineering
controls above the PEL, additional benefits are anticipated in this
regard; primarily because the change in the way noise dose would be
measured under the proposal would require the use of engineering and
administrative controls in more cases than at present. Like coal, a
benefit in
[[Page 66350]]
this sector is anticipated from the establishment of an action level.
As indicated by this chart, MSHA projects that even after
implementation of the proposal some miners will continue to develop a
material impairment of hearing. This is of serious concern to the
Agency. The Agency believes, however, that the mining industry may not
be able at this time to feasibly take actions which would eliminate the
remaining risk (see response to Questions 9 and 13 on this point). MSHA
is seeking comments on this issue.
Benefits of MSHA Noise Proposal in Saving Miners From Hearing Impairment
------------------------------------------------------------------------
Miners
------------------------------------------------------------------------
Coal:
Current expected impairment.. 15% of miners........... 18,947
Saved by eng/admin controls.. 58% of projected 11,072
impairment.
Saved by hearing protectors.. 22% of projected 4,232
impairment.
Saved by proposal............ 81% of projected 15,304
impairment.
Remaining expected impairment 3% of miners............ 3,643
Metal and Nonmetal:
Current expected impairment.. 13% of miners........... 26,977
Saved by eng/admin controls.. 11% of projected 2,693
impairment.
Saved by hearing protectors.. 46% of projected 12,320
impairment.
Saved by proposal............ 57% of projected 15,283
impairment.
Remaining expected impairment 6% of miners............ 11,694
Mining Industry as a Whole:
Current expected impairment.. 14% of miners........... 45,924
Saved by eng/admin controls.. 31% of projected 14,035
impairment.
Saved by hearing protectors.. 36% of projected 16,552
impairment.
Saved by proposal............ 67% of projected 30,587
impairment.
Remaining expected impairment 5% of miners............ 15,377
------------------------------------------------------------------------
MSHA's estimates of cost follow a standard approach in which
initial costs of compliance (like equipment purchase costs) are
amortized over ten years at seven percent and added to costs that recur
each year. The assumptions on what controls would be needed, how many
hours have to be spent on particular tasks, and the costs of the
personnel performing various tasks are set forth in detail in the
Agency's preliminary RIA.
MSHA estimates that the proposed rule would increase the mining
industry's costs by approximately $8.3 million annually for the first
10 years. MSHA estimates the proposed rule will cost the coal mining
industry about $300,000 a year; because while there will be additional
costs under the proposal, they will be significantly offset by the
elimination of the requirements for biannual noise surveys of coal
miners. Costs to the metal and nonmetal industry would rise by about $8
million annually.
The most costly aspect of the proposed rule would be the provision
of audiometric examinations--about $3.6 million, with about $2 million
of that borne by the metal and nonmetal mining industry. The provision
of engineering controls is estimated to cost about $3.5 million, with
about $2.2 million of this borne by the coal mining industry--which
would no longer be permitted, as at present, to substitute hearing
protectors for engineering or administrative controls. MSHA's costing
assumptions are described in its preliminary RIA; comments on this
methodology are being solicited.
The table entitled ``Cost Impacts of MSHA Noise Proposal''
summarizes the net annual costs of the proposal's requirements. An
explanation of the requirements is included in the questions and
answers that follow.
Cost Impacts of MSHA Noise Proposal
----------------------------------------------------------------------------------------------------------------
Task Total cost M/NM cost Coal cost
----------------------------------------------------------------------------------------------------------------
Engineering Controls............................................ $3,475,700 $1,289,000 $2,186,700
Dose Determination.............................................. (1,928,550) 1,734,895 (3,663,445)
Notification.................................................... 45,910 28,085 17,825
Record of Noise Surveys, et al.................................. (1,653,565) .............. (1,653,565)
Administrative Controls......................................... 16,595 6,580 10,015
HPDs (provide, selection, fit).................................. 926,710 792,560 134,150
Training........................................................ 1,834,560 1,071,140 763,420
Audiograms (base, annual); notice to miners..................... 3,574,030 1,964,970 1,609,060
Audiometric Test Procedures..................................... 195,835 113,835 82,000
Evaluation of Audiogram......................................... 892,215 492,215 400,000
Follow-up Evaluation............................................ 145,780 78,865 66,915
Follow-up Corrective Measures................................... 99,440 52,455 46,985
Notification of Results......................................... 138,710 74,340 54,370
Access to Records............................................... 23,710 18,865 4,845
Transfer of Records............................................. 5,040 2,950 2,090
Contractors..................................................... 541,640 316,320 225,320
-----------------------------------------------
Total..................................................... 8,323,760 8,037,075 286,685
----------------------------------------------------------------------------------------------------------------
MSHA's estimates of paperwork burden hours reflect the requirements
and definitions in the Paperwork Reduction Act. Overall, the proposal
would decrease paperwork requirements in the mining industry by about
14,985 burden hours. This reflects a savings to the coal mining
industry of 88,740 burden hours, as a result of a proposal to eliminate
[[Page 66351]]
existing requirements for biannual surveys of coal miners and other
various reports. The metal and nonmetal mining sector would have a net
increase of about 73,755 burden hours. The chart entitled ``Paperwork
Impacts of MSHA Noise Proposal'' summarizes the projected paperwork
burdens.
Paperwork Impacts of MSHA Noise Proposal
----------------------------------------------------------------------------------------------------------------
Paperwork requirement and associated
Section tasks Coal M/NM Total
----------------------------------------------------------------------------------------------------------------
62.120............................ Evaluate miners' noise exposure; (140,545) 5,295 (135,250)
notify miner of overexposure,
prepare and post administrative
controls; give miners copy of
administrative controls.
62.130............................ Prepare and file a training 4,000 6,270 10,270
certification.
62.140............................ Perform audiograms, notify miners to 30,655 39,275 69,930
appear for testing and need to avoid
high noise.
62.150............................ Compile an audiometric test record, 3,930 5,245 9,175
obtain a certification.
62.160............................ Provide information and audiometric 9,340 12,015 21,455
test record, perform audiometric
retests.
62.170............................ Perform audiometric evaluations and 475 570 1,045
follow-up evaluations.
62.180............................ Prepare a training certification for 335 365 700
retrained miners, review
effectiveness of engineering and
administrative controls.
62.190............................ Inform miner of test results, inform 2,715 3,585 6,300
miner of STS.
62.200............................ Provide access to records............ 255 1,000 1,255
62.210............................ Transfer records..................... 100 135 235
All............................... (any discrepancies due to rounding).. (88,740) 73,755 (14,985)
----------------------------------------------------------------------------------------------------------------
(4) What Special Consideration Did MSHA Give to Alternatives for the
Smallest Mines?
MSHA estimates that as a result of this proposal, metal and
nonmetal mines with less than 20 miners would incur an average cost
increase of about $500 per year in annual costs and annualized first
year costs. Coal mines with less than 20 miners would have an average
savings per mine of about $30, reflecting the elimination of the
numerous survey and paperwork requirements in the current noise rules
for the coal sector.
MSHA compared the proposed costs for small mines in each sector to
the estimated revenues and profits for small mines in each sector. MSHA
did this at various size levels. In each case, the costs as a
percentage of revenue are less than 1%, and the costs do not appear to
have any appreciable impact on profits. Accordingly, for the purposes
of the Regulatory Flexibility Act, MSHA has certified that the proposed
rule does not have a significant economic impact on a substantial
number of small entities.
The limited impacts on small mines reflect decisions by MSHA not to
propose more costly regulatory alternatives. In considering regulatory
alternatives for small mines, MSHA must observe the requirements of its
authorizing statute. Section 101(a)(6)(A) of the Mine Act requires the
Secretary to set standards which most adequately assure, on the basis
of the best available evidence, that no miner will suffer material
impairment of health over his/her working lifetime. In addition, the
Mine Act requires that the Secretary, when promulgating mandatory
standards pertaining to toxic materials or harmful physical agents,
consider other factors, such as the latest scientific data in the
field, the feasibility of the standard and experience gained under the
Act and other health and safety laws. Thus, the Mine Act requires that
the Secretary, in promulgating a standard, attain the highest degree of
health and safety protection for the miner, based on the ``best
available evidence,'' with feasibility a consideration.
As a result of this requirement, MSHA seriously considered two
alternatives that would have significantly increased costs for small
mine operators--lowering the PEL to a TWA8 of 85 dBA, and lowering
the exchange rate to 3 dB. In both cases, the evidence in favor of
these approaches was strong. But in both cases, MSHA has tentatively
concluded that it may not be feasible for the mining industry to
accomplish these more protective approaches. The impact of these
approaches on small mine operators was an important consideration in
this regard.
Part IV of this preamble contains a full discussion of MSHA's
preliminary conclusions about these alternatives. The graph labeled
``Effect of Alternative Exchange Rates and PELs on Allowable Exposure
Times at Various Decibel Levels'' provides an indication of what the
Agency's decisions in this regard mean in practice.
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In accordance with the Small Business Regulatory Enforcement and
Fairness Act (SBREFA), MSHA is taking actions to minimize the
compliance burden on small mines. The proposed effective date of the
rule would be a year after final promulgation, to provide adequate time
for small mines to achieve compliance. MSHA will also mail a copy of
the proposed rule to every mine operator which primarily benefits small
mine operators. MSHA is committed to writing the final rule in plain
English so it can be readily understood by miners and mine operators.
The Agency has committed itself to issuance of a compliance guide, and
is inviting comment on whether compliance workshops or other such
approaches would be valuable. (These proposed actions are discussed in
more detail in other Questions and Answers.)
The approximately 350 small sand and gravel or crushed stone
operations run by State, local and tribal governments may also be
interested in MSHA's analysis on the impacts of the proposed rule on
such entities. Such an analysis is required by the Unfunded Mandates
Reform Act of 1995. Like other small metal and nonmetal mines, their
costs for prevention of hearing loss are expected to average about $500
per year. Benefits to these governmental entities include fewer hearing
impairments and reduced workers' compensation costs.
(5) Why Is the Proposed Rule Needed?
MSHA has concluded that the existing rules to protect miners from
workplace noise exposure must be revised because current noise
exposures continue to create a significant risk of material impairment
of health to miners. MSHA estimates that 14% of U.S. miners--about
46,000 of them--can be expected under current exposure conditions to
develop a material impairment of hearing during a working lifetime. The
figures are 15% (19,000) of U.S. coal miners and 13% (27,000) of U.S.
metal and nonmetal miners.
Generally, prolonged exposure to noise over a period of several
years causes permanent damage to the auditory nerve and/or its sensory
components: the higher the noise exposure the more rapid the loss. The
loss may be so gradual, however, that a person may not realize that he
or she is becoming impaired until a substantial amount of hearing is
lost. This damage, known as noise-induced hearing loss or NIHL, is
irreversible, and makes it difficult to hear as well as understand
speech. In addition to the personal and social costs of hearing loss,
the loss of the ability to understand speech can have a significant
impact on miner safety which is highly dependent upon good
communication.
The Agency has carefully analyzed the risk miners currently face of
incurring such harm. What follows is a short summary of MSHA's risk
analysis (the complete analysis is presented as part II of the
Supplemental Information accompanying this notice).
First, the Agency considered the various definitions of impairment
used in the risk analyses in the literature. Three definitions of
impairment have been widely recognized within the scientific community
as useful for the purposes of assessing risk. All three focus on the
risks of acquiring a 25 dB hearing ``level''--the deviation from
audiometric zero. The three accepted approaches differ in that they
examine hearing acuity at a different set of frequencies. For the
purpose of its analysis, MSHA chose the approach that measures hearing
acuity at those frequencies most relevant to the ability to understand
human speech. This is the approach developed in 1972 by the National
Institute for Occupational Safety and Health (NIOSH) and subsequently
used by the Occupational Safety and Health Administration
[[Page 66353]]
(OSHA): a 25 dB hearing level at 1000, 2000 and 3000 Hz. The Agency is
aware that NIOSH is now considering a revised approach that would
include hearing acuity at 4000 Hz, but believes it is inappropriate to
utilize that approach until peer review has validated its utility.
Next, the Agency reviewed the major studies on the level of risk at
different noise exposures. The data consistently indicate that the risk
of developing a material impairment of hearing, as a result of a
working lifetime of occupational exposure, becomes significant when
workplace noise exposures exceed an eight-hour time-weighted average
(TWA8) of 85 dBA. The table entitled ``Excess Risk Estimates''
presents estimates by NIOSH of how the excess risk of developing a
material impairment (using its 1972 definition) varies with exposure
over a working lifetime.
Excess Risk Estimates
----------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------------------
Exposure (TWA8)............. <80 80-84.9 85-89.9 90-94.9 95-99.9 1
00
Excess Risk................. 0 3% 15% 29% 43% 54%
----------------------------------------------------------------------------------------------------------------
MSHA also reviewed a large body of data on the effects of varying
industrial noise exposures on worker hearing. These studies are
supportive of the same conclusion. MSHA refined its picture of what
occurs at lower sound levels by reviewing a number of other studies,
particularly those of workers in other countries.
To confirm the magnitude of the risks of NIHL among miners, MSHA
asked NIOSH to examine a body of audiometric data collected over the
years tracking hearing acuity among coal miners. The analysis (Franks,
1996) supports the data from the risk studies. It indicates that 90% of
these miners have a hearing impairment by age 50 as compared with only
10% of the general population. Further, Franks stated that miners,
after working 20 to 30 years, could find themselves in life-threatening
situations because safety signals and ``roof talk'' could go unheard.
(For the purposes of the analysis, NIOSH used a definition of hearing
impairment including losses at 4000 Hz; MSHA conducted its own analysis
of the data without the 4000 Hz, and the results are generally
consistent with those of NIOSH).
MSHA also examined other sources of data that might provide direct
confirmation of the risks of hearing loss to miners--comments received
in response to the Agency's Advance Notice of Proposed Rulemaking
(ANPRM), (December 4, 1989, 54 FR 50209), the reports of hearing loss
provided to the Agency by mine operators pursuant to 30 CFR part 50,
and workers' compensation data. In each case, the available data are
too limited to draw any conclusions. The Agency is requesting the
public to provide further information along these lines.
To develop a profile of the mining population at risk, MSHA began
by gathering information on noise exposures in the U.S. mining
industry.
Current exposures appear to be gradually declining in the metal and
nonmetal industry, where engineering or administrative controls are the
primary means of miner protection against NIHL. But the data indicate
that all sectors of the mining industry continue to have a significant
number of overexposures.
Charts II-9 and II-10 display exposure trends based on inspector
samples. Only those samples that exceed the PEL are displayed. For
1995, 14.4% of samples from the metal and nonmetal mining industry, and
22.5% of samples from the coal industry, exceeded the PEL. (Because
they are 3-D graphs, the data points sometimes look lower than they
are; the actual data points can be found in part II, Tables II-9 and
II-10.)
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These figures actually understate truly harmful exposures because
the samples were taken in a way that did not count any exposures to
sound levels below 90 dBA. As discussed herein (see Question 9), MSHA
has concluded that exposures to sound levels above 80 dBA are harmful.
Accordingly, to get a better picture of present harmful miner
exposures, MSHA examined the results of a special survey taking
thousands of
[[Page 66354]]
samples that included sound levels as low as 80 dBA. The results
indicate that 36.8% of coal samples, and 26.9% of the metal and
nonmetal samples would exceed the PEL if the lower, but still harmful,
sound levels are counted in the dose measurement.
To derive a risk profile of miners, the Agency utilized the
exposure data from the survey and the excess risk estimates. (The
methodology for developing the miner risk profile is explained in
detail in the Agency's preliminary RIA. Among other adjustments to the
sample data, MSHA assumed coal miners were currently receiving some
protection from hearing protectors; as a result, the estimates of
miners at excess risk are lower than might be suggested by the
foregoing figures.) Based on its analysis, MSHA estimates that 14% of
U.S. miners--about 46,000 miners--can be expected under current
exposure conditions to develop a material impairment of hearing of
handicapping or disabling proportions during a working lifetime. The
figures are 15% (19,000) of U.S. coal miners as a group and 13%
(27,000) of U.S. metal and nonmetal miners.
The Agency is interested in receiving additional data with respect
to the risks of noise exposure to workers and to the mining population
in particular, as well as comments on its risk methodology and
analysis.
(6) Why Proceed Without Waiting for NIOSH To Issue a New Criteria
Document on Noise Exposure?
As MSHA was preparing this notice for publication, the National
Institute for Occupational Safety and Health (NIOSH) released for peer
review a draft criteria document for occupational noise exposure to
update the one issued in 1972.
A summary of that draft, prepared and released by NIOSH, is
included in the discussion of the rulemaking history in the
Supplementary Information accompanying this notice. NIOSH is
considering whether the evidence on noise since 1972 warrants a change
in its recommendations. In some cases NIOSH is considering reiterating
its prior recommendations, and in other cases it is considering
changing its recommendations.
MSHA has determined that it would not be appropriate to delay
publication of this proposed rule to await the possible issuance of a
new NIOSH criteria document. The NIOSH draft is still being peer
reviewed, and MSHA does not believe it would be appropriate to delay
acting based upon the uncertain timing of the document's redrafting and
release. Moreover, many of the issues covered in the NIOSH draft have
been considered by MSHA, as part of the Agency's review of all the
latest scientific information on noise.
Should a new criteria document be issued before MSHA promulgates a
final rule, it will of course consider the NIOSH recommendations. The
summary of the NIOSH draft included in this notice should provide ample
notice to the mining community of the position NIOSH may take in a new
criteria document.
(7) What Mines Are Covered by the Proposal?
The proposal would apply one set of rules uniformly to all mines.
Those who responded to MSHA's ANPRM generally agreed that consolidation
and simplification of multiple standards into one rule may help to
facilitate understanding of, and thus compliance with, the regulatory
requirements for controlling noise exposures.
(8) Are There Special Definitions Applicable?
To help mine operators and miners, the proposed rule would include
definitions of some technical terms universally used in noise
measurement. But the proposed rule also includes some terms used in a
way that differs from usage in certain other contexts--e.g., under the
OSHA standard.
In particular, MSHA is proposing a non-standard use of the term
``hearing conservation program'' or ``HCP.'' Most hearing conservation
programs include provision for hearing examinations, training and the
use of hearing protectors. Since audiograms would be new for the mining
industry, unlike the other components, the Agency thought it might be
less confusing to treat the components separately. Accordingly, under
the MSHA proposal, hearing protector and training requirements are
established independently, and a ``hearing conservation program'' is
defined as a generic reference to those sections of the proposal that
set forth the requirements for an audiometric testing program.
(9) How Is a Miner's Noise Dose To Be Determined Under the Proposal?
The proposal sets forth a formula for dose computation, which is to
be measured over a full shift, which corresponds to the readouts of
most currently used personal noise dosimeters.
The proposal would continue the use of a 5-dB exchange rate. The
exchange rate is a measure of how quickly the dose of noise doubles.
Accordingly, the measure is the rate determining how much a miner's
exposure must be limited to compensate for increasing dose. Using the
5-dB exchange rate, the exposure time permitted at a sound level of 90
dBA is half that permitted at a sound level of 85 dBA--a miner gets the
same noise dose in 4 hours at 90 dBA as at 8 hours at 85 dBA.
The Agency gave serious consideration to changing the exchange rate
from 5 dB to 3 dB, and is specifically seeking comment on this
important matter. There is a consensus in the recent literature that
noise dose actually doubles more quickly than measured by the 5-dB
rate; the consensus is for an exchange rate of 3 dB. Moreover, the
current 5-dB exchange rate incorporates an assumption that there is
significant time for hearing to recover from high sound levels. MSHA
has concluded that noise exposure under mining conditions does not
warrant such an assumption. A 3-dB exchange rate does not incorporate
this assumption.
Nevertheless, the Agency is proposing to retain the existing 5-dB
exchange rate because of feasibility considerations. Changing to a 3-dB
rate from a 5-dB rate would significantly reduce the amount of time
that miners could be exposed to higher sound levels without exceeding
the PEL. For example, MSHA estimates that the percentage of miners
whose exposure would be in violation of the PEL would just about double
if a 3-dB exchange rate is used. This means mine operators would have
to utilize controls to reduce exposures to the PEL much more
frequently. Moreover, more expensive controls would often be required;
if doses are doubling more quickly, the controls needed to reduce
overexposures to the PEL would have to be more effective. Furthermore,
if a 3-dB exchange rate is used, it is extremely difficult to reduce
the noise exposures to the PEL with currently available engineering or
administrative noise controls or a combination thereof. Accordingly,
moving the industry to a 3-dB exchange rate may not be feasible at this
time.
The sound levels to be included in a miner's dose are being
expanded. At present, only exposures to sounds of 90 dBA and above are
included in determining a miner's dose under MSHA's standards. (Thus,
90 dBA is considered the ``threshold.'') The proposed rule would
include exposure to sound levels as low as 80 dBA. The Agency has
concluded that capturing such sound levels is necessary if it
establishes an action level based on an eight-hour time-weighted
average of 85 dBA. Among other reasons, exposure of a miner to an
extended shift (e.g.,16
[[Page 66355]]
hours) at just over 80 dBA can result in an exposure that exceeds the
action level. OSHA uses this threshold for its action level, but a
higher threshold for the PEL; based on the comments received in
response to its Advance Notice of Proposed Rulemaking, MSHA concluded
it would be easier for the mining industry to use a single threshold
for both purposes.
While necessary, this change will generally result in higher dose
readings in both the coal and metal and nonmetal sectors than at
present. (See the discussion of exposure data in response to Question
5). In this case, however, MSHA has concluded that this change would
clearly be feasible for the industry.
The proposed regulation would not allow dose measurements to be
adjusted to reflect the effect of hearing protectors. This provision
would reinforce MSHA's intent to preclude the current practice in the
coal mining industry of not issuing a citation based upon a noise
exposure that exceeds the PEL when the miners are wearing hearing
protection. (See Question 11 for additional information on this topic.)
(10) What Controls Are Required Whenever a Miner's Exposure Exceeds the
Action Level?
The proposal would require that all miners exposed above the action
level be provided special instruction in the hazards of noise and
protective methods. The training is to be provided annually for as long
as exposure exceeds the action level. (The nature of this instruction,
how it is to be provided, and how it can be coordinated with other
required miner training are discussed in response to other questions.)
(11) What Additional Controls Are Required If a Miner's Exposure
Exceeds the Action Level but Is Below the PEL?
An operator will be required to enroll a miner whose exposure
exceeds the action level in a hearing conservation program (HCP). While
enrollment in the HCP would require the operator to make annual
audiometric testing available to the miner, miners exposed to noise
below the PEL would have the right to decline taking any annual
audiometric testing. The requirements for such testing are discussed in
more detail in response to other questions.
MSHA is seeking comments on how to minimize the burden on mine
operators of providing audiometric examinations for those miners with
only a temporary attachment to the mining work force (e.g., summer
employees), while recognizing the importance of detecting and tracking
hearing loss among those who switch jobs.
In addition, the operator must provide properly fitted hearing
protection in 3 cases: before the initial hearing examination, if a
significant threshold shift in hearing acuity is detected, and at any
other time upon miner request.
Both MSHA and OSHA normally require an employer or operator to
ensure that personal protective equipment is in fact used; an operator
can be cited for failure to enforce rules to this effect. In the case
of this proposal, however, MSHA is making two exceptions in that
regard. First, should the initial hearing examination take less than 6
months to provide, the operator will not be required to ensure the
provided hearing protection be worn. The operator is obligated to
ensure protector use if more time is needed for the baseline
examination (e.g., to wait for a mobile test van). Second, hearing
protection provided because of miner request does not generate an
operator obligation to enforce the use of the requested protection. At
exposure levels above the action level but below the PEL, the
proposal's goal is to encourage the use of hearing protection by
training, providing choice, and encouraging proper fit--but the
proposal would not require hearing protector use unless the miner has a
significant threshold shift or unless the miner has to wait more than 6
months for a baseline examination.
(12) What Controls Are Required If a Miner's Exposure Exceeds the PEL?
If a miner's noise dose exceeds the PEL, the proposal would require
the mine operator to use all feasible engineering and administrative
controls to reduce the miner's noise exposure to that level. The mine
operator has a choice of whether to use engineering controls,
administrative controls, or both; but if administrative controls are
utilized, a copy of the procedures involved must be posted, and copies
given to the affected miners.
Under the proposal, a consistent hierarchy of controls is
established for all mines. Mine operators must first utilize all
feasible engineering and administrative controls to reduce sound levels
to the PEL before (as explained in response to question 15) relying on
other controls to protect against hearing loss. This approach is
consistent with that currently in place for metal and nonmetal mines,
but would be a change for coal mines. In the coal mining industry, MSHA
inspectors do not cite for noise overexposures without first deducting
from the measured dose the attenuating value of hearing protectors
being worn by the miners exposed to excessive levels of noise. In
practice, this means that personal protective equipment is in most
cases accepted as a substitute for engineering and administrative
controls.
MSHA has conducted research on the attenuating value of hearing
protectors under actual mining conditions and has reviewed the
literature on this issue. MSHA is aware that NIOSH is considering new
approaches on how to establish a system that will accurately derate
hearing protector attenuation values for actual workplace conditions;
but the Agency's own research suggests that the attenuation of a
hearing protector is highly variable in practice, and that the amount
of attenuation cannot be predicted accurately. This is discussed in
part III of the Supplementary Information accompanying this notice.
MSHA has also considered the data showing declining noise exposures
in the metal and nonmetal industry, and contrasted this with the data
on the coal mining industry.
The Agency has concluded that, in practice, reliance upon hearing
protectors to reduce noise exposures simply does not provide effective
protection against hearing loss to miners. The Agency does not contend
that properly fitted and maintained hearing protectors are worthless;
on the contrary, the Agency is proposing to rely upon them as a
supplemental control, and has taken their value into account in
conducting its risk and benefit analyses. MSHA has concluded, however,
that hearing protectors should no longer be relied upon as a primary
means of control, and that this change can bring about dramatic
reductions in the rate at which coal miners would otherwise be expected
to incur hearing impairments.
(13) For an Individual Mine Operator, What Are ``Feasible'' Engineering
and Administrative Controls?
The proposal would require a mine operator to use only such
engineering controls as are technologically feasible, and to use only
such engineering and administrative controls as are economically
feasible for that mine operator. Those in the metal and nonmetal mining
industry are already familiar with the Agency's policies and practices
in this regard, but those in the coal mining industry may wish to take
note of the following few paragraphs.
The Federal Mine Safety and Health Review Commission (Commission)
has addressed the issue of what MSHA must consider, with regard to
MSHA's existing noise standard for metal and
[[Page 66356]]
nonmetal mines, when determining what is a feasible noise control for
enforcement purposes at a particular mine. According to the Commission,
a control is considered feasible when: (1) The control reduces
exposure, (2) the control is economically achievable, and (3) the
control is technologically achievable. See Secretary of Labor v.
Callanan Industries, Inc., 5 FMSHRC 1900 (1983), and Secretary of Labor
v. A. H. Smith, 6 FMSHRC 199 (1984).
In determining technological feasibility of a proposed control, the
Commission has ruled that a control is deemed achievable 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 noise source. The control does not have to be ``off-the-
shelf;'' but, it must have a realistic basis in present technical
capabilities.
In determining economic feasibility, 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 its use to achieve those results. The
Commission has expressly stated that cost-benefit analysis is
unnecessary in order to determine whether a noise control is required.
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
exposure. Todilto Exploration and Development Corporation v. Secretary
of Labor, 5 FMSHRC 1894 (1983). No guidance has been provided by the
Commission as to what level of reduction is considered significant.
However, the Commission has accepted the Agency's determination that a
3 dBA reduction is significant.
In the metal and nonmetal mining industry, MSHA has interpreted the
``expected benefits'' to be the amount of noise reduction achievable by
the control. MSHA generally considers a reduction of 3 dBA or more to
be a significant reduction of the sound level. Consequently, a control
that achieves relatively little noise reduction at a high cost could be
viewed as not meeting the Commission's test of economic feasibility.
Accordingly, consistent with the case law, MSHA has considered
three factors in determining whether engineering controls are feasible
at a particular metal and nonmetal mine: first, the nature and extent
of the overexposure; second, the demonstrated effectiveness of
available technology; and third, whether the committed resources are
wholly out of proportion to the expected results. Before a violation of
these requirements of the standard could be found, MSHA would have to
determine that a worker has been overexposed; that administrative or
engineering controls are feasible; and that the mine operator failed to
install or maintain such controls.
Part III of the Supplemental Information accompanying this notice
provides many examples of engineering controls that are feasible for
mine operators to utilize, and the Agency and the former Bureau of
Mines (USBOM) have available many other materials in this regard.
Nevertheless, the Agency welcomes information about particular
operations for which it may be particularly difficult to control noise.
(14) Is It feasible for the Coal Mining Industry, and for the Metal and
Nonmetal Mining Industry, To Provide the Controls Proposed To Be
Required When Noise Exposures Exceed the PEL?
Part IV of the Supplementary Information in this notice provides a
detailed discussion of the statute's requirements and the Agency's
analysis in this regard. The Agency has concluded that the coal mining
industry as a whole, and the metal and nonmetal mining industry as a
whole, can meet these requirements at a PEL set at a TWA8 of 90
dBA.
In fact, the Agency seriously considered lowering the PEL. As noted
in response to Question 5, MSHA has concluded that there is a
significant risk of material impairment from noise exposures at or
above a TWA8 of 85 dBA. MSHA believes, however, that such a change
may not be feasible at this time for the mining industry. Based on an
analysis of exposure survey data, MSHA has concluded that if the PEL
were a TWA8 of 85 dBA, about two-thirds of the mine operators in
the metal and nonmetal mining industry, and about three-quarters of the
mine operators in the coal mining industry, would need to use
engineering and administrative controls to reduce current exposures.
Moreover, the engineering controls needed to reduce those exposures
would be more expensive, because they would have to be capable of
reducing the exposures further than with a PEL set at a TWA8 of 90
dBA.
(15) What Supplemental Controls Are Required If a Miner's Exposure
Cannot Be Feasibly Reduced to the PEL?
If reducing the dose to this level with such controls is not
feasible, the proposal requires the mine operator to use such controls
to lower the noise exposure as much as is feasible.
In addition, in such cases, the proposal requires that the operator
take extra steps to protect miner hearing. The operator must ensure any
miner so exposed takes the annual hearing examinations, must provide
properly fitted hearing protection to all miners so exposed, and must
ensure the hearing protection is used by all miners so exposed.
MSHA believes that when a miner is exposed to such high levels of
noise because engineering and administrative controls are not feasible
for an operator, these supplemental obligations are necessary to
protect miner hearing. Hearing protectors are not without their
discomforts, but the risk of hearing loss at such exposure levels ought
to be a controlling factor. While audiometric testing is not an
invasive procedure, the Agency is concerned that there may be economic
pressures and personal reasons that may lead miners to decline to take
hearing examinations. The information generated by these tests is
necessary, however, to trigger investigation of potentially serious
flaws in the layers of noise controls required at these high exposure
levels. In addition, the Agency believes that miners operating under
such high noise conditions should be aware of the severity of any
hearing loss; in a mining environment, this knowledge could have
implications for the safety of the miner and the safety of others.
Comments on this provision are specifically solicited.
(16) Is There an Absolute Maximum Noise Dose?
Under the proposal, a miner, as at present, is never to be exposed
to sound levels exceeding 115 dBA. This is because sound at that level
provides the full dose permitted in a matter of minutes.
There is, however, no dose which the Agency would require to be
abated without regard to whether it is feasible for an individual mine
operator. The proposal does provide that should a miner's noise
exposure exceed a TWA8 of 105 dBA during any workshift, the mine
operator shall, in addition to taking all actions required to protect
miners exposed above the PEL, also require the miner to use dual
hearing protection, i.e., both a plug type and a muff type hearing
protector. A TWA8 of 105 dBA is a dose of 800% of the PEL, using a
5-dB exchange rate. In the notice accompanying this proposal, the
Agency presents information about the mining jobs at which the
exposures of this level are occurring, and requests comment on
[[Page 66357]]
whether there should be an absolute dose ceiling regardless of the
feasibility of control by an individual mine operator.
(17) What Are an Operator's Obligations Under the Proposal To Monitor
Noise Exposures?
The proposal would require mine operators to establish a system of
monitoring which effectively evaluates each miner's noise exposure.
This will ensure that mine operators have the means to determine
whether a miner's exposure exceeds any of the limitations established
by this section, as well as to assess the effectiveness of noise
controls. The proposed rule is performance oriented in that the
regularity and methodology used to make this evaluation are not
specified; MSHA's own measurements will enable it to check on the
effectiveness of an operator's monitoring program. Specific
requirements for biannual noise surveys, monitoring records,
supplemental noise surveys, calibration reports, survey reports, and
survey certifications now applicable to the coal sector would be
revoked, significantly reducing cost and paperwork burdens.
(18) When Must Miners Be Notified of Monitoring Results?
The proposal would require that miners be notified in writing
should their exposure exceed any of the levels specified by this
section--whether based on operator or MSHA evaluations of noise. Notice
would be required within 15 calendar days.
The proposal has been designed to ensure that miners are made aware
of the hazards they currently face. Miners exposed above the action
level should be notified of that fact so, for example, they can
consider the importance of using provided, properly fitted and
maintained hearing protectors. On the other hand, the proposal does not
require notification of a particular miner if an exposure measurement
indicates that the miner's exposure has not changed and the miner has
within the last year been apprised of the same information. No
notification is required if a miner's measurement is below the action
level--although operators might wish to provide such notification if
this indicates a reduction in noise exposure.
(19) What Rules Are There To Ensure That Required Hearing Protectors
Provide Effective Protection?
Whenever hearing protectors are to be provided, they must be
provided in accordance with specific requirements. The miner is to have
a choice from at least one earplug type and muff type protector; and,
in the event dual hearing protection is required, a choice of one of
each. Whenever the mine operator is required to ensure that hearing
protection is worn (the circumstances are noted in response to prior
questions), it is worn by the miner when exposed to sound levels
required to be integrated into a miner's dose measurement, i.e., any
sound levels above 80 dBA. The hearing protector is to be fitted and
maintained in accordance with the manufacturer's instructions. Hearing
protectors and necessary replacements are to be provided at no cost to
the miner. Finally, should the miner suffer a medical pathology of the
ear, the miner is to be allowed to select a different hearing protector
from among those offered by the mine operator.
MSHA has concluded that existing rating systems for hearing
protectors do not provide a reliable measure of effectiveness under
normal mining working conditions. The Agency believes that the best way
to ensure such devices can provide effective protection is to focus on
the conditions affecting hearing protector use.
(20) How Frequently Must Required Training Be Provided?
If a miner's noise exposure exceeds the action level, training is
to be provided annually. The training is to be provided when the miner
is first determined to have exceeded the action level and every 12
months thereafter that the miner continues to exceed that level.
Annual refresher training is necessary to reinforce the proper
procedures for the use and care of hearing protectors, and the
importance of administrative and engineering controls. Additionally, it
serves to re-emphasize the hazards of noise and the purpose for
audiometric testing for those miners exposed above the PEL. MSHA
received comments in response to its Advance Notice of Proposed
Rulemaking (ANPRM) that supported an annual training requirement.
Studies have shown that the effectiveness of an HCP is highly dependent
on the proper use of hearing protectors and the commitment of both
management and the employees, both of which can be enhanced by
training.
(21) What Specifications Are There With Respect to the Instruction To
Be Provided During Required Training?
Miners would receive instruction in hearing protection: (1) the
need for such protection, (2) selection and fitting, and (3) proper use
of such protectors. Miners would also receive instruction about hearing
conservation programs: as to the operation of that program and the mine
operator's noise control efforts. There are no special qualifications
for instructors, nor any specifications on the hours of instruction.
Training is required to be provided without cost to the miner. The mine
operator would be required to certify the completion of any training
required by this part, and maintain the most recent certification for a
miner at the mine site for as long as the miner is required to use
hearing protectors or be enrolled in an HCP, and at least 6 months
thereafter.
(22) Can the Required Training Be Covered During Part 48 Training?
Yes, but it may not always be feasible to do so.
MSHA considered whether the requirements of part 48, ``Training and
Retraining of Miners,'' were adequate to ensure the training required
under this part. The requirements of part 48 specify the initial and
annual retraining of all miners in a list of subjects, many specified
in the law itself (section 115 of the Mine Safety and Health Act). The
importance of this training is emphasized by statutory requirements for
the submittal of training plans, on the specification of the hours to
be devoted to the training, and on the qualifications of instructors.
Training is required on noise, but it is in general terms, covering the
purpose of taking exposure measurements and on any health control plan
in effect at the mine. Mine operators may provide additional training,
but the topics that need to be covered may make this impracticable
within the prescribed time limits.
After considering the available information about the importance of
training requirements, and based upon its experience in implementing
the requirements of part 48, MSHA has determined that the requirements
of part 48 do not provide adequate noise training for those miners for
whom exposure is clearly a problem. Most current part 48 training is
neither comprehensive enough to provide such miners with the level of
education needed for the proper use of hearing protection devices, nor,
in the case of noisy mines, detailed enough on methods to reduce sound
levels.
Nevertheless, MSHA believes compliance with this proposal can in
many cases be fulfilled at the same time as scheduled part 48 training.
The Agency does not believe special language in proposed part 62 is
required to permit this action under part 48, but welcomes comment in
this regard. Mine operators who can do so are free to fulfill their
noise training requirements by covering the topics in initial and
[[Page 66358]]
annual part 48 training, and may so certify on the separate form
required by this part. If incorporated into part 48, mine operators
would, however, be required to submit a revised training plan to the
appropriate district office for approval. Some mine operators, however,
may not be able to incorporate these topics in their part 48 plans.
Moreover, it is important to note that there are some circumstances in
which training required under the proposal will likely not fit within a
regular schedule, e.g., the training required when a miner's exposure
is determined to require selection of a hearing protector or a new
protector.
MSHA has endeavored to make the training requirements as simple as
possible. If conducted separately from part 48 training, there are no
specifications on trainer qualifications, no minimal training time, nor
any training plans. If, however, the training is incorporated into part
48, then all applicable part 48 requirements will have to be met.
(23) If a Mine Operator Is Required To Offer Audiometric Testing, When
Must a Baseline Audiogram Be Taken?
It is critical to obtain a baseline audiogram before exposure to
hazardous noise. If this is not possible, then the baseline is to be
obtained as soon as is reasonably possible.
Due to remote locations and intermittent operations of many mines,
MSHA determined that allowing six months (or 12 months if a mobile test
van is used) for offering the baseline audiogram was reasonable. The 12
month period would allow mine operators to schedule many baseline and
annual audiograms simultaneously, and thus, substantially reduce the
cost when mobile test vans are used. Miners enrolled in a hearing
conservation program would be provided hearing protection until such
time as the baseline audiogram is conducted. In the case of a miner who
has to wait more than 6 months for a baseline examination because of
the need for a mobile test van, and in the case of a miner whose
exposures cannot be reduced to the PEL through the use of all feasible
engineering and administrative controls, the operator would be required
to ensure the hearing protection is worn.
MSHA has also determined that a 14-hour quiet period should precede
the baseline audiogram to ensure a valid result. Moreover, unlike the
OSHA rule, MSHA's proposal would not permit the use of hearing
protectors as a substitute for a quiet period. The Agency has
determined this is necessary to ensure that a temporary threshold shift
in hearing acuity does not occur during the quiet period, rendering the
baseline audiogram inaccurate. Moreover, MSHA's research has not shown
a reliable method for predicting hearing protector attenuation under
actual working conditions. Under the proposal, miners are to be
notified of the importance of compliance with the quiet period. MSHA is
not proposing to require this quiet period for annual audiograms,
although it may be in the mine operator's interest to do so.
(24) What Qualification Requirements Are Proposed for Those Who Will
Take Audiograms?
MSHA would require that an ``audiologist'' be certified by the
American Speech-Language-Hearing Association or licensed by a state
board of examiners. ``Qualified technicians'' would be required to have
been certified by the Council for Accreditation in Occupational Hearing
Conservation (CAOHC) or another recognized organization offering
equivalent certification. CAOHC or equivalent certification would
assure that the technicians are qualified. MSHA is not proposing to
require qualifications for physicians.
(25) Does the Proposal Specify Audiometric Test Procedures?
MSHA proposes not to include specific procedural requirements for
conducting audiometric tests, calibrating audiometers, and qualifying
audiometric test rooms. Instead, MSHA proposes a performance-oriented
requirement that audiometric testing be conducted in accordance with
scientifically validated procedures. MSHA would specify the test
frequencies, but would allow the physician or the audiologist to use
professional judgement in choosing the appropriate testing procedure(s)
and require certification of the scientific validity of the procedures.
While this approach may require somewhat more in the way of
paperwork requirements, MSHA believes this is far preferable to the
alternative of a detailed specification standard, which could stifle
technology and impede improvements in methodology.
(26) What Test Records Must Be Maintained?
The proposal would also specify what records must be maintained at
the mine site and the retention duration. The proposed items included
in the audiometric test record--name, job classification, audiograms
and certifications as to the procedures used to take them, any exposure
determinations, and the results of any follow-up examinations--would
provide information essential for evaluating a miner's audiogram, among
other purposes.
The proposal would require that the audiometric records be retained
for at least six months beyond the duration of the miner's employment.
The six-month retention period at the mine site would assure that test
records are not destroyed during what might be normal breaks in
employment and remain available for use by the mine operator to conduct
further evaluations upon the miner's return. In practice, MSHA believes
that many mine operators will keep a miner's audiograms long after the
miner's employment ceases, for use if the miner should file a
subsequent workers' compensation claim for hearing loss.
(27) How Are Audiograms To Be Evaluated?
MSHA's proposal would require that the mine operator inform the
person evaluating the audiogram of the requirements of this part and
provide such person with copies of the miner's audiometric test
records. The mine operator would be responsible for having a physician,
audiologist, or qualified technician determine if an audiogram is
valid, and to determine if a standard threshold shift in hearing acuity
(STS) or reportable hearing loss has occurred. Time frames within which
these actions must occur are part of the proposal.
The proposal would permit, but not require, mine operators to
adjust audiometric test results by applying a correction for
presbycusis, the progressive loss of hearing acuity associated with the
aging process, before determining whether an STS or reportable hearing
loss has occurred, and it includes tables for this purpose. The
proposed adjustment for presbycusis is optional, however, if a mine
operator uses this approach, it must be applied uniformly to both the
baseline and annual audiograms in accordance with the procedures and
values listed in the proposed standard. Although this is the position
taken in the proposal, MSHA notes that NIOSH recently has advised
against the use of presbycusis correction factors. Moreover, the Agency
is concerned about locking-in particular presbycusis adjustment tables.
MSHA, therefore, requests additional comments on whether to use
presbycusis corrections for audiograms and, if so, how to
[[Page 66359]]
provide for such adjustment in a regulatory context.
(28) What Happens If an Audiogram Is Not Valid?
A prompt retest is required.
When a valid audiogram cannot be obtained due to a suspected
medical pathology of the ear, and the physician or audiologist
evaluating the audiogram believes that the problem was caused or
aggravated by the miner's exposure to noise or the wearing of hearing
protectors, a miner must be referred for a clinical audiological or
otological evaluation as appropriate at mine operator expense.
If the physician or audiologist concludes that the suspected
medical pathology of the ear which prevents obtaining a valid audiogram
is unrelated to the miner's exposure to noise or the wearing of hearing
protectors, the miner is to be advised of the need for an otological
evaluation; but in such cases, no financial obligation would be imposed
on the mine operator.
A mine operator would be required to instruct the physician or
audiologist not to reveal to the mine operator any specific findings or
diagnoses unrelated to the miner's exposure to noise or the wearing of
hearing protectors without the written consent of the miner.
(29) What Corrective Measures Are Required When a Standard Threshold
Shift in Hearing Acuity (STS) Is Detected?
STS is defined in this proposal, as in OSHA's standard, as a change
in a worker's hearing acuity for the worse, relative to that worker's
baseline audiogram, of an average of 10 dB or more at 2000, 3000, and
4000 Hz in either ear.
If the STS is determined to be permanent, a supplemental baseline
is established and this becomes the baseline for determining any future
STS. This definition is sufficiently restrictive to locate meaningful
shifts in hearing, yet not so stringent as to create unnecessary
follow-up procedures. The frequencies were chosen for this purpose to
ensure hearing losses are detected as soon as feasible. While NIOSH is
currently considering an approach that would not require averaging at
several frequencies, this remains under peer review; moreover, the
averaging of hearing levels at adjacent frequencies will reduce the
effect of testing errors at single frequencies.
MSHA's proposal would require that, unless a physician or
audiologist determines that an STS is neither work-related nor
aggravated by occupational noise exposure, mine operators would have 30
days after the finding of an STS to--
(1) Retrain the miner;
(2) Provide the miner with the opportunity to select a hearing
protector, or a different hearing protector if the miner has previously
selected one; and
(3) Review the effectiveness of any engineering and administrative
controls to identify and correct any deficiencies. The proposal also
requires that an operator ensure that a miner with an STS wear the
provided hearing protector.
A hearing loss of 10 dB from a miner's prior hearing level is of
enough significance to warrant intervention by a mine operator, unless
it is determined the loss is not work-related. If the controls in place
are effective, including the training, this loss should not be
occurring. It should be noted that the retraining required is to take
place within 30 days after the finding of the STS, and thus it is
unlikely mine operators can satisfy this requirement through their part
48 training programs.
MSHA's proposal does not include a provision for transferring a
miner who incurs repeated STS's. A miner transfer program would be
complex to administer, and would probably not be feasible in the metal
and nonmetal sector. This sector consists largely of smaller mines
which may be unable to feasibly rotate workers to other assignments on
a long-term basis.
(30) When Must MSHA Be Notified About Hearing Loss?
Pursuant to 30 CFR part 50, MSHA must be notified of any
``reportable'' hearing loss. There is currently no uniform definition
of this term. The proposed rule would establish a uniform definition
for reporting a miner's hearing loss--a change in hearing acuity for
the worse relative to the miner's baseline audiogram of an average of
25 dB or more at 2000, 3000, and 4000 Hz in either ear. MSHA intends
that a loss for any miner need not be reported again until there is an
additional 25 dB loss. Having a uniform definition will ease reporting
burdens on mine operators while promoting the development of an
improved data base on hearing loss in the mining community.
MSHA has two specific questions in this regard on which it is
seeking comment. First, MSHA would like comment on how to define
``reportable'' hearing loss for those operators who do not have
audiometric test data. Not all mine operators will be required to
obtain audiometric test data under the proposed rule; thus, such
operators may not be able to use a definition of reportable hearing
loss defined in this manner.
Second, MSHA is concerned that reporting only losses of 25 dB may
not provide MSHA a full picture of hearing loss in the mining industry.
A loss of 25 dB is used by many states as a basis for making disability
awards. Some have recommended that any STS (10 dB loss) should be
captured in a hearing loss data base. OSHA, which currently requires
any 25 dB loss to be captured in an employer's log, has proposed to
capture any 15 dB loss. MSHA accordingly solicits comment on this
point.
(31) When Must a Miner Be Notified of Audiometric Testing Results?
The proposal would require the mine operator, within 10 working
days of receiving the results of an audiogram, or receiving the results
of a follow-up evaluation, to notify the miner in writing of the
results and interpretations, including any finding that an STS or
reportable hearing loss has occurred. The notification would include an
explanation of the need and reasons for any further testing or
evaluation that may be required.
MSHA believes that informing miners of the results of their
audiometric tests in a timely manner is critical to the success of an
HCP. Immediate feedback upon completion of the testing provides the
greatest benefit.
(32) Who Has Access to Exposure and Test Records Maintained by Mine
Operators?
Authorized representatives of the Secretaries of Labor and Health
and Human Services would have access to all records required under this
part.
Moreover under the proposal, a miner or former miner, or his/her
designated representative with written consent, would have access to
all the records that the mine operator is required to maintain under
this part for that individual miner or former miner. Also, the miners'
representative is in all cases to have access, for miners they
represent, to noise training records and to notices required to be made
to miners exposed to noise above various levels.
The mine operator would have 15 days from receipt of a written
request to provide such access. The proposal would define ``access'' as
the right to examine and copy records. The first copy of any record
requested by a person is to be provided without cost to that person,
and any additional copies requested by that person are to be provided
at reasonable cost.
[[Page 66360]]
Upon termination of employment, mine operators would be required to
provide a miner, without cost, an actual copy of all his or her own
records (those required under this part).
The proposed standard would require mine operators to transfer all
records (or a copy thereof) required by this part to any successor mine
operator. The successor mine operator would be required to receive
these records and maintain them for the period required. Additionally,
the successor mine operator would be required to use the baseline
audiogram obtained from the original mine operator (or supplemental
baseline audiogram as appropriate) for determining an STS and
reportable hearing loss.
MSHA has no uniform records access provision. The provisions
proposed here are similar to those in other health standards proposed
in recent years by the Agency. The Agency welcomes comment on whether
it needs to make changes to facilitate the use of electronic
recordkeeping systems.
(33) How Does the Proposal Compare With the Existing Standards?
MSHA has prepared two charts comparing some of the key features of
the proposed standard to MSHA's existing standards. A comparison to
OSHA's noise standard is also provided since many mine operators and
others are familiar with that standard.
It is important the reviewers exercise some caution in using these
charts. The entries were ``shorthanded'' to fit into the chart.
Accordingly, other parts of this preamble should be consulted for
details. In comparing the proposed rule with OSHA's standard, for
example, reviewers interested in differences on the definition of a
hearing conservation program should consult the answer to Question 8;
those interested in differences on the threshold should consult the
answer to Question 9; those interested in differences on employer
obligations to ensure the wearing of provided hearing protections
should consult the answer to Question 11; and those interested in
differences about the use of hearing protection in lieu of a quiet
period before a baseline audiogram should consult the answer to
Question 23.
Care should also be taken in consulting the existing standards
themselves. The entries in the charts and the discussions in the
preamble reflect legal and/or policy interpretations of the various
standards that now determine their meaning, something that would not be
apparent from an examination of the text of the standards.
To conserve space, the following abbreviations are used in the
charts: HP (hearing protection), HCP (hearing conservation program),
STS (standard threshold shift), TWA8 (time-weighted eight-hour
average), dBA (decibel, A-weighted), PEL (permissible exposure limit);
``admin'' (administrative), kHz (kilohertz), and N/A (none or not
applicable).
Comparison Chart 1: Exposure/Dose Triggers
----------------------------------------------------------------------------------------------------------------
Existing metal/
TWA8 noise above Proposal nonmetal Existing coal OSHA
----------------------------------------------------------------------------------------------------------------
85 dBA................ Provide training on No action required... No action required.. Enroll employee in
noise; enroll miner HCP (must offer
in HCP (must offer annual hearing
annual hearing test); if more than
test); provide HP 6 months before
before baseline baseline audiogram
audiogram taken, if taken (mobile van),
STS detected or upon employee must be
request of miner; provided and wear
must ensure miner HP; employee must
uses HP if more than also be provided
6 months for and use HP if STS
baseline (mobile detected.
van) or STS detected.
90 dBA................ Use all feasible Use all feasible Use all feasible Use all feasible
engineering and engineering or engineering or engineering or
admin. controls to admin. controls to admin. controls to admin. controls to
reach; if can't reach; if can't reach * * * but can reach * * * but if
reach 90 using such reach 90 using such first reduce exposure less than
controls, use controls, then must exposure reading by 100 dBA, can first
controls to get as also provide HP. rated value of HP reduce reading by
low as possible, minus 7 unless value of HP
provide HP to all cited for failure attenuation =.50 x
miners, ensure HP to require HP use; (rated value of HP
used and ensure must enroll miners minus 7).
hearing tests taken. in HCP if cited.
105 dBA............... Dual HP must be Limited requirement n/a................. n/a.
provided and used. for dual HP.
----------------------------------------------------------------------------------------------------------------
Comparison Chart 2: Issues
----------------------------------------------------------------------------------------------------------------
Existing metal/
Issue Proposal nonmetal Existing coal OSHA
----------------------------------------------------------------------------------------------------------------
Monitoring...................... Operator must No requirement on Mine operator Employer must
establish system mine operator. required to conduct
of monitoring conduct periodic represent.
exposures. monitoring. personal sampling
if info suggests
noise exceeds
action level.
Notification of exposure level.. Notify miner of Not required...... Not required...... Notify employee if
measured exposure exposure exceeds
level if: (a) action level.
exposure changed,
or (b) even if
shows no change
if miner not
notified within
last year.
[[Page 66361]]
Threshold: lowest sound levels 80 dBA............ 90 dBA............ 90 dBA............ 80 dBA for
counted. monitoring & HCP
enrollment but 90
dBA for PEL.
Exchange rate................... 5 dB.............. 5 dB.............. 5 dB.............. 5 dB.
Ceiling......................... 115 dBA........... 115 dBA........... 115 dBA........... 115 dBA.
Training on hearing protector Annual if above Part 48 general Part 48 general Annual if exposure
selection & use. action level. discussion. discussion. exceeds TWA8 of
85 dBA.
Training on audiology & employer Annual if above No................ No................ Audiology only;
program. action level. annual if
enrolled in HCP.
Quiet period before aud. exam... 14 hours for n/a............... n/a............... 14 hours for
baseline baseline
audiogram; can audiogram; can
not use hearing use hearing
protectors. protectors.
Standard threshold shift........ 10 dB av. shift @ n/a............... n/a............... 10 dB av. shift @
2, 3, & 4 KHz. 2, 3, & 4 KHz.
Reportable hearing loss......... Must report 25 dB Reporting required Reporting required No reporting; must
av. shift @ 2, 3, but level not but level not record 25 dB av.
& 4 kHz, either defined. defined. shift @ 2, 3, & 4
ear. kHz, either ear;
1/96 proposal
would drop to 15
dB.
Employee access to records...... Yes............... No................ No................ Yes.
----------------------------------------------------------------------------------------------------------------
(34) Is MSHA Going To Write the Final Rule in Plain English so Miners
and Mine Operators Can Understand Their Obligations?
The text of the proposed rule can be found at the very end of this
notice. While the Agency endeavored to write clearly, it is interested
in suggestions to make the final rule as comprehensible as possible to
mine operators and miners.
MSHA has developed two examples, based on the proposed rule, to
illustrate some alternative approaches it could take.
The first example illustrates one way in which a rule's
organization can be reformulated so as to serve as a more useful
reference tool. This proposal's table of contents begins as follows:
62.100 Purpose and scope; effective date.
62.110 Definitions
62.120 Limitations on noise exposure
The alternative version presents the table of contents as a series
of practical questions that are likely to be asked by the mining
community. The sections have been subdivided so as to address questions
one at a time. In the mining industry, the Department of the Interior
has also experimented with this approach, e.g., proposed coalbed
methane regulations (60 FR 47920).
62.100 What is the purpose of requiring mine operators to limit
miner noise exposure?
62.101 What kinds of mining operations are covered by this
regulation?
62.102 When does this regulation take effect?
62.110 What is meant by various technical terms used in this
regulation?
62.120 How is a miner's noise dose calculated?
62.121 How is dose converted to 8-hour time-weighted averages?
62.122 Can a miner's dose measurement be adjusted to reflect the
type of hearing protection being worn by the miner?
62.123 What are a mine operator's obligations to evaluate miner
noise exposure?
62.124 When must miners and/or their representatives be notified of
measured exposures?
62.130 What must a mine operator do whenever a miner's noise dose
exceeds the action level?
62.131 What else must a mine operator do if a miner's noise dose
exceeds the action level but remains below the PEL?
62.132 What else must a mine operator do if a miner's noise dose
exceeds the PEL?
62.133 What is the highest sound level to which a miner may be
lawfully exposed?
The contents of several of these sections might be more clear if
presented in a tabular format. This would be particularly useful where
the mine operator may have choices or has to do more than one thing. An
example involves the controls required at the action level. The current
proposal, as it would appear in the Code of Federal Regulations, as
paragraph (b) of proposed Sec. 62.120, is:
(b) Action level. When a miner's noise exposure exceeds a
TWA8 of 85 dBA during any workshift, or equivalently a dose of
50%, the operator shall take the actions specified in paragraphs (b)
(1) and (2) of this section and, at the request of the miner, also
take the actions specified in paragraph (b)(3) of this section.
(1) An operator shall provide the miner training that includes
the instruction required by Sec. 62.130, at the time exposure
exceeds the action level and every 12 months thereafter that
exposure continues to exceed the action level.
(2) An operator shall enroll the miner in a hearing conservation
program which shall meet the requirements of Secs. 62.140 through
62.190. Moreover, the operator shall, with respect to any miner
enrolled in such program, provide hearing protection in accordance
with the requirements of Sec. 62.125 until such time as a baseline
audiogram has been obtained. If it takes more than 6 months to
conduct the baseline audiogram, or if the miner is determined to
have incurred an STS, the operator shall ensure that the hearing
protection is provided to the miner and worn by the miner.
(3) At the request of any miner, the operator shall provide
hearing protection to the miner in accordance with the requirements
of Sec. 62.125.
The alternative format would appear, using the revised numbering
and naming conventions from example 1, somewhat like the following:
62.131 What specifically must a mine operator do if a miner's noise
dose exceeds the action level?
If a miner's noise exposure exceeds a dose of 50% (a TWA8 of
85 dBA):
------------------------------------------------------------------------
You must Which means you
------------------------------------------------------------------------
(a) Provide training................... Provide a miner with the
training required by MSHA's
rules--
(1) When his or her exposure
exceeds the action level; and
(2) Every 12 months thereafter
that his or her exposure
continues to exceed the action
level.
[[Page 66362]]
(b) Enroll the miner in a hearing (1) Offer the miner annual
conservation program. audiometric examinations that
comply with MSHA's rules for
hearing conservation programs;
and
(2) Provide a miner with
hearing protection until a
baseline audiogram has been
taken; and in the event that
will take more than 6 months
due to the needs to wait for a
mobile test van, require the
miner to use the hearing
protector; and
(3) Provide a miner with
hearing protection, and
require its use, whenever an
STS is detected.
(c) At the request of a miner, provide Provide hearing protection in
the miner with hearing protection. accordance with MSHA's rules.
------------------------------------------------------------------------
MSHA's rules for training are discussed in Sec. 62.137. MSHA's rules
for hearing conservation programs are discussed in Secs. 62.140
through 62.190. MSHA's rules for hearing protection are discussed in
Sec. 62.135.
MSHA has not yet consulted with the Office of the Federal Register
on the specifics of such approaches; moreover, the examples noted above
should not be considered as necessarily accurately representing the
content of MSHA's proposed rule. These caveats notwithstanding, the
Agency is interested in the potential of these approaches, and would
welcome comment on these specific examples.
(35) Is MSHA Going To Provide Adequate Guidance Before Implementing the
Rule?
The Agency plans to take several steps toward this end.
First, the Agency is proposing that the new standard not take
effect until one year after the date of publication of the final rule.
This should provide time to train MSHA personnel and provide mine
operators with technical assistance and guidance. An alternative would
be to phase in the new requirements. The Agency believes some could be
phased in quickly, but wants to avoid confusion. The Agency requests
comment on whether a phased-in approach is appropriate and how it might
most effectively be designed.
In addition, the Agency is committed to issuing a compliance guide
for mine operators before a final rule takes effect. MSHA would welcome
suggestions on matters that should be discussed in such a guide.
MSHA would also welcome comments on other actions it could take to
facilitate implementation, and in particular whether a series of
workshops would be useful.
(36) Are There Special Enforcement Issues of Which the Mining Community
Should Take Note?
Question 13 addresses the question of what constitutes ``feasible''
engineering and administrative controls.
Operators in the mining industry are aware that the Agency has
traditionally not cited an operator for exceeding the PEL unless the
Agency's measurement of noise shows that it exceeds a TWA8 of 92
dBA. This provides adequate room to accommodate, in an enforcement
context, any technical questions about MSHA's measurements. MSHA's
citation policy does not, however, alter operator obligations of the
rule, including those based on operator exposure readings.
The Agency is interested in comment on whether the new final rule
should include a provision requiring operators to develop a written
plan in certain cases. At the present time, coal operators in violation
of the PEL must submit for approval a plan for the administration of a
continuing, effective program to assure compliance including provision
for reducing environmental noise levels, hearing protectors, and
audiograms. No such plans are provided in the metal and nonmetal
sector. The proposed rule, which would establish a uniform approach to
noise for both sectors, would eliminate the current coal requirement,
because MSHA does not believe such plans need to be created every time
an operator violates the PEL. The Agency recognizes, however, that
achieving effective compliance in some cases would be furthered by the
existence of a written plan. In particular, such plans may be
appropriate when there is a history of multiple noise violations, or a
failure to effectively abate. Such plans would include specific details
on how operators will comply with the final rule; a failure to comply
with the plan's specifications would be enforceable through MSHA's
normal citation/order process. Making explicit provision in the
standard for such plans would ensure clarity about the Agency's
enforcement policy on noise.
The Agency notes that in some cases the proposal would require
operators to ensure certain miners wear hearing protection that is
provided, and ensure certain miners take tests that are offered.
Comment is welcome on how Agency personnel could distinguish these
miners from others.
(B) Executive Order 12866
In accordance with Executive Order 12866, MSHA has prepared a
preliminary analysis of the estimated costs and benefits associated
with the proposed revisions of the noise standards for coal and metal
and nonmetal mines.
The preliminary RIA containing this analysis is available from
MSHA. MSHA welcomes comments on its analysis and methodology. The
proposal would cost approximately $8.3 million and would save 765
hearing impairment cases annually. The benefits are expressed in terms
of cases of hearing impairment that can be avoided and have not been
monetized. Although the Agency has attempted to quantify the benefits,
it believes that monetization of these benefits would be difficult and
inappropriate.
Based upon the economic analysis, MSHA has determined that this
rule is not an economically significant regulatory action pursuant to
section 3(f)(1) of Executive Order 12866. The Agency does consider this
rulemaking significant under section 3(f)(4) of the Executive Order for
other reasons, and has so designated the rule in its annual agenda.
This means that while the Office of Management and Budget was provided
an opportunity to review this proposal and the preliminary RIA (as
discussed in the History section of this preamble), specific
determinations of the costs and benefits are not required pursuant to
section 6(a)(3)(C) of the Executive Order.
(C) Paperwork Reduction Act
This proposed rule contains information collections which are
subject to review by the Office of Management and Budget (OMB) under
the Paperwork Reduction Act of 1995 (PRA95). The title, description,
and respondent description of the information collection are shown
below with an estimate of the annual reporting burden. Included in the
estimate is the time for reviewing instructions, gathering and
maintaining the data needed, and completing and reviewing the
collection of information. With respect to the following collection of
information, MSHA invites comments on: (1) Whether the proposed
collection of information is necessary for proper performance of MSHA's
functions, including whether the information will have practical
utility; (2) the accuracy of MSHA's estimate of the burden of the
proposed collection of information, including the validity of the
methodology and assumptions used; (3) ways to enhance the quality,
utility, and
[[Page 66363]]
clarity of information to be collected; and (4) ways to minimize the
burden of the collection of information on respondents, including
through the use of automated collection techniques, when appropriate,
and other forms of information technology.
These estimates are an approximation of the average time expected
to be necessary for a collection of information. They are based on such
information as is available to MSHA.
Submission
The Agency has submitted a copy of this proposed rule to OMB for
its review and approval of these information collections. Interested
persons are requested to send comments regarding this information
collection, including suggestions for reducing this burden, to the
Office of Information and Regulatory Affairs, OMB New Executive Office
Bldg., 725 17th St. NW., Rm. 10235, Washington, DC 20503, Attn: Desk
Officer for MSHA. Submit written comments on the information collection
not later than February 18, 1997.
Description of Respondents
Those required to provide the information are mine operators and
individuals who are paid to perform tasks for the mine operator (e.g.,
physicians reporting the results of audiograms to the mine operator).
Description
The proposal contains information collection requirements in
Secs. 62.120, 62.130, 62.140, 62.150, 62.160, 62.170, 62.180, 62.190,
62.200, and 62.210. The following chart presents the paperwork
requirements by section.
Net Information Collection Burden Hours by Proposed Section
------------------------------------------------------------------------
Paperwork requirement and
Section associated tasks Hours
------------------------------------------------------------------------
62.120..................... Evaluate miners' noise (135,250)
exposure; notify miner of
overexposure; prepare and
post administrative controls;
give miners copy of
administrative controls.
62.130..................... Prepare and file a training 10,270
certification.
62.140..................... Perform audiograms; notify 69,930
miners to appear for testing
and need to avoid high noise.
62.150..................... Compile an audiometric test 9,175
record; obtain a
certification.
62.160..................... Provide information and 21,350
audiometric test record;
perform audiometric retests.
62.170..................... Perform otological evaluations 1,045
and provide information and
notice.
62.180..................... Prepare a training 700
certification for retrained
miners; review effectiveness
of engineering and
administrative controls.
62.190..................... Inform miner of test results; 6,300
inform miner of STS.
62.200..................... Provide access to records..... 1,255
62.210..................... Transfer records.............. 235
------------
Total................ .............................. (14,985)
------------------------------------------------------------------------
These paperwork requirements have been submitted to the Office of
Management and Budget (OMB) for review under section 3504(h) of the
Paperwork Reduction Act of 1995 (PRA 95). Respondents are not required
to respond to any collection of information unless it displays a
currently valid OMB control number.
The following chart summaries MSHA's estimates by section in
tabular form. Data is distributed by commodity. All numbers have been
rounded.
Net Information Collection Burden Hours by Commodity
------------------------------------------------------------------------
Metal/
Task Coal nonmetal
------------------------------------------------------------------------
62.120 Limitations on Noise Exposure......... (140,545) 5,295
62.130 Training.............................. 4,000 6,270
62.140 Audiometric Testing Program........... 30,655 39,275
62.150 Audiometric Test Procedures........... 3,930 5,245
62.160 Evaluation of Audiograms.............. 9,340 12,015
62.170 Followup Evaluation................... 475 570
62.180 Followup Corrective Measures.......... 335 365
62.190 Notification of Results............... 2,715 3,585
62.200 Access to Records..................... 255 1,000
62.210 Transfer of Records................... 100 135
-------------------------
Total (discrepancies due to rounding)... (88,740) 73,755
------------------------------------------------------------------------
Alternatively, the paperwork hours may be distributed between small
and large mines. The following table provides this analysis. Small
mines are those with less than 20 employees.
Net Information Collection Burden Hours by Mine Size
------------------------------------------------------------------------
Task Small Large
------------------------------------------------------------------------
62.120 Limitations on Noise Exposure......... (15,510) (119,740)
62.130 Training.............................. 2,965 7,305
62.140 Audiometric Testing Program........... 19,270 50,660
62.150 Audiometric Test Procedures........... 2,885 6,290
62.160 Evaluation of Audiograms.............. 6,185 15,170
62.170 Followup Evaluation................... 250 800
62.180 Followup Corrective Measures.......... 160 540
[[Page 66364]]
62.190 Notification of Results............... 1,935 4,365
62.200 Access to Records..................... 500 755
62.210 Transfer of Records................... 185 50
-------------------------
Total (discrepancies due to rounding)... 18,825 (33,805)
------------------------------------------------------------------------
Metal/nonmetal mines would incur 75,080 burden hours under the
proposal and coal mines would incur 55,675 hours. For metal/nonmetal
mines, the existing burden is 1,325 hours as defined and calculated
under PRA 95; this makes the net burden for metal/nonmetal mines 73,755
hours. For coal mines, the net burden is 88,740 fewer hours than the
existing burden as calculated under PRA 95. The proposal would result
in a net decrease of 14,985 burden hours associated with information
collection from that associated with the current requirements. It
should be noted that the existing burden hours are currently approved
in three separate paperwork packages and reflect burden hours
calculated under the provisions of the 1980 Paperwork Reduction Act
(PRA 80). MSHA is in the process of updating and combining these three
packages. The Agency's official paperwork submission accompanying this
proposal includes a chart comparing the existing burden hours under PRA
80, the existing burden hours under PRA 95, and the proposed burden
hours under PRA 95.
Additional detail is presented in the charts that follow. These
charts provide annual and annualized paperwork burden hours as measured
by PRA 95. Burden hours for tasks which predominantly would occur in
the first year only, dose determination and notification, are presented
in annualized form. Proposed Secs. 62.140(b)(3), 62.250 (b) and (c),
62.160 (a)(1) and (a)(3), 62.170 (b) and (c), 62.180(a), 62.190 (a)(1)
and (a)(2), 62.200(b) and 62.210(a) are anticipated to require the
paperwork burden of the mine operator providing instructions to the
clerical worker. This burden is included in the total hours per
regulation column.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Number of Maintenance
Regulation Number of Hours per Number of responses per Total hours and operating Annualized
respondents response responses respondent per regulation costs capital costs
--------------------------------------------------------------------------------------------------------------------------------------------------------
Small Metal and Nonmetal Mines
--------------------------------------------------------------------------------------------------------------------------------------------------------
62.120(f)(1)........................ 6,218 2.00 n/a n/a 3,530 $597,922 $1,315,604
62.120(f)(2)........................ 6,218 0.08 35,300 6 490 1,253 0
62.120(c)(1)........................ 18 1.75 18 1 25 0 0
62.120(c)(1)........................ 18 0.05 103 5 5 26 0
62.130(b)........................... 6,218 0.05 35,300 6 2,385 8,825 0
62.140(b)(1)........................ 2,430 1.00 13,779 6 13,780 413,370 0
62.140(b)(3)........................ 2,430 0.08 13,779 6 1,345 3,445 0
62.150(b)........................... 2,430 0.08 13,779 6 1,345 3,445 0
62.150(c)........................... 2,430 0.05 13,779 6 930 3,445 0
62.160(b)(1)........................ 300 1.50 1,720 6 2,585 86,000 0
62.160(a)(1)........................ 2,430 0.08 13,779 6 1,345 3,445 0
62.160(a)(3)........................ 2,430 0.05 13,779 6 930 3,445 0
62.170(a)........................... 15 2.00 90 6 180 22,500 0
62.170(b)........................... 15 0.08 90 6 9 23 0
62.170(c)........................... 15 0.08 90 6 9 23 0
62.180(a)........................... 320 0.05 1,808 6 90 452 0
62.180(c)........................... 15 2.00 15 1 20 0 0
62.190(a)(1)........................ 2,430 0.08 13,779 6 1,345 3,445 0
62.190(a)(2)........................ 320 0.08 1,812 6 180 1,461 0
62.200(b)........................... 60 0.10 4,374 12 440 1,094 0
62.210(a)........................... 361 0.25 361 1 125 0 0
Monitoring (existing)............... 1,705 2.00 n/a n/a 970 163,953 360,744
--------------------------------------------------------------------------------------------------------------------------------------------------------
Large Metal and Nonmetal Mines
--------------------------------------------------------------------------------------------------------------------------------------------------------
62.120(f)(1)........................ 1,023 5.00 n/a n/a 1,455 $98,372 $216,446
62.120(f)(2)........................ 1,023 0.08 75,700 75 875 2,687 0
62.120(c)(1)........................ 40 2.25 40 1 90 0 0
62.120(c)(1)........................ 40 0.05 2,972 70 150 726 0
62.130(b)........................... 1,023 0.05 75,700 75 3,885 18,925 0
62.140(b)(1)........................ 301 1.00 22,328 75 22,330 669,840 0
62.140(b)(3)........................ 301 0.08 22,328 75 1,820 5,582 0
62.150(b)........................... 301 0.08 22,328 75 1,820 5,582 0
62.150(c)........................... 301 0.05 22,328 75 1,150 5,582 0
62.160(b)(1)........................ 40 1.50 2,790 70 4,185 139,500 0
62.160(a)(1)........................ 301 0.08 22,328 70 1,820 5,582 0
62.160(a)(3)........................ 301 0.05 22,328 70 1,150 5,582 0
62.170(a)........................... 2 2.00 174 85 344 43,500 0
62.170(b)........................... 2 0.08 174 85 15 44 0
[[Page 66365]]
62.170(c)........................... 2 0.08 174 85 15 44 0
62.180(a)........................... 50 0.05 3,490 70 175 873 0
62.180(c)........................... 35 2.25 35 1 80 0 0
62.190(a)(1)........................ 301 0.08 22,328 75 1,820 5,582 0
62.190(a)(2)........................ 40 0.08 2,965 70 240 742 0
62.200(b)........................... 10 0.10 5,601 560 560 1,400 0
62.210(a)........................... 10 1.00 10 1 10 0 0
Monitoring (existing)............... 250 5.00 n/a n/a 355 24,040 52,895
--------------------------------------------------------------------------------------------------------------------------------------------------------
Small Coal Mines
--------------------------------------------------------------------------------------------------------------------------------------------------------
62.120(f)(1)........................ 1,255 2.00 n/a n/a 715 $120,681 $265,533
62.120(f)(2)........................ 1,255 0.08 9,020 7 120 320 0
62.120(c)(1)........................ 20 1.75 20 1 30 0 0
62.120(c)(1)........................ 20 0.05 173 7 10 43 0
62.130(b)........................... 1,255 0.05 9,020 7 580 2,255 0
62.140(b)(1)........................ 536 1.00 3,851 7 3,851 115,530 0
62.140(b)(3)........................ 536 0.08 3,851 7 360 963 0
62.150(b)........................... 536 0.08 3,851 7 360 963 0
62.150(c)........................... 536 0.05 3,851 7 250 963 0
62.160(b)(1)........................ 70 1.50 480 7 720 24,050 0
62.160(a)(1)........................ 536 0.08 3,851 7 360 1,926 0
62.160(a)(3)........................ 536 0.05 3,851 7 250 0 0
62.170(a)........................... 4 2.00 24 6 48 6,000 0
62.170(b)........................... 4 0.08 24 6 2 6 0
62.170(c)........................... 4 0.08 24 6 2 6 0
62.180(a)........................... 60 0.05 507 8 25 127 0
62.180(c)........................... 20 1.25 20 1 25 0 0
62.190(a)(1)........................ 536 0.05 3,851 7 360 963 0
62.190(a)(2)........................ 73 0.05 505 7 50 126 0
62.200(b)........................... 15 0.10 610 40 60 131 0
62.210(a)........................... 160 0.25 160 1 60 0 0
Monitoring (existing)............... 1,762 0.50 25,334 14 12,670 357,492 169,434
Audiograms (existing)............... 35 1.00 74 2 70 2,220 0
Supplemental Noise Survey........... 420 0.05 840 2 (120) 0 0
Supplemental Noise Survey........... 420 0.25 5,980 14 (2,990) 0 0
Written HCP......................... 90 6.00 90 1 (535) 0 0
Calibration Reports................. 1,762 0.25 1,762 1 (440) 0 0
Survey Reports...................... 1,762 0.05 1,762 1 (90) 0 0
Monitoring Records.................. 1,762 0.10 25,334 14 (2,530) 0 0
Survey Certificates................. 1,762 0.05 1,762 1 (90) 0 0
--------------------------------------------------------------------------------------------------------------------------------------------------------
Large Coal Mines
--------------------------------------------------------------------------------------------------------------------------------------------------------
62.120(f)(1)........................ 890 5.00 n/a n/a 1,265 $85,582 $188,306
62.120(f)(2)........................ 890 0.08 66,667 75 770 2,367 0
62.120(c)(1)........................ 45 2.25 45 1 75 1,309 0
62.120(c)(1)........................ 45 0.05 5,237 75 290 0 0
62.130(b)........................... 890 0.05 66,667 75 3,420 16,667 0
62.140(b)(1)........................ 334 1.00 25,007 75 25,007 750,210 0
62.140(b)(3)........................ 334 0.08 25,007 75 2,035 6,252 0
62.150(b)........................... 334 0.08 25,007 75 2,035 6,252 0
62.150(c)........................... 334 0.05 25,007 75 1,285 6,252 0
62.160(b)(1)........................ 40 1.50 3,126 80 4,690 156,300 0
62.160(a)(1)........................ 334 0.08 25,007 80 2,035 6,252 0
62.160(a)(3)........................ 334 0.05 25,007 80 1,285 6,252 0
62.170(a)........................... 3 2.00 196 65 392 49,000 0
62.170(b)........................... 3 0.08 196 65 16 49 0
62.170(c)........................... 3 0.08 196 65 16 49 0
62.180(a)........................... 400 0.05 3,908 35 195 977 0
62.180(c)........................... 40 2.25 40 1 90 0 0
62.190(a)(1)........................ 334 0.05 25,007 75 2,035 6,252 0
62.190(a)(2)........................ 40 0.05 3,322 80 270 831 0
62.200(b)........................... 10 0.10 1,934 194 195 484 0
62.210(c)........................... 40 1.00 40 1 40 0 0
Monitoring existing................. 1,134 0.50 169,424 150 84,710 230,077 239,932
Audiograms (existing)............... 6 1.00 542 90 540 0 0
[[Page 66366]]
Supplemental Noise Survey........... 293 0.05 43,712 150 (21,860) 0 0
Supplemental Noise Survey........... 293 0.25 293 1 (40) 0 0
Written HCP......................... 67 6.00 67 1 (405) 0 0
Calibration Reports................. 1,134 0.25 1,134 1 (280) 0 0
Survey Reports...................... 1,134 0.05 1,134 1 (60) 0 0
Monitoring Records.................. 1,134 0.10 169,424 150 (16,940) 0 0
Survey Certificates................. 1,134 0.05 1,134 1 (60) 0 0
--------------------------------------------------------------------------------------------------------------------------------------------------------
(D) Regulatory Flexibility Act
In accordance with Sec. 605 of the Regulatory Flexibility Act
(RFA), the Mine Safety and Health Administration certifies that the
noise proposal does not have a significant economic impact on a
substantial number of small entities. MSHA considers small mines to be
mines with fewer than 20 employees. However, for the purposes of the
RFA and this certification, MSHA has also evaluated the impact of the
proposal on mines up to and including those with fewer than 500
employees. No small governmental jurisdictions or nonprofit
organizations are affected. Under the Small Business Regulatory
Enforcement Fairness Act (SBREFA) amendments to the RFA, MSHA must
include in the proposal a factual basis for this certification. The
Agency also must publish the regulatory flexibility certification
statement in the Federal Register, along with the factual basis,
followed by an opportunity for comment by the public. The Agency has
consulted with the Small Business Administration (SBA) Office of
Advocacy and believes that this analysis provides a reasonable basis
for the certification in this case.
MSHA specifically solicits comment on the Agency's determination in
this regulatory flexibility certification statement, including cost
data and data sources. To facilitate the public participation in the
rulemaking process, MSHA will mail a copy of the proposed rule,
including the preamble and regulatory flexibility certification
statement, to every mine operator.
Factual Basis for Certification
The Agency has used a quantitative approach in concluding that the
proposed rule does not have a significant impact on a substantial
number of small entities. The Agency performed its analysis separately
for two groups of mines: the coal mining sector as a whole, and the
metal and nonmetal mining sector as a whole. Based on a review of
available sources of public data on the mining industry, the Agency
believes that a quantitative analysis of the impacts on various mining
subsectors (i.e., beyond the 4-digit SIC level) may not be feasible.
The Agency requests comments, however, on whether there are special
circumstances that warrant separate quantification of the impact of
this proposal on any mining subsector, and information on how it might
readily obtain the data necessary to conduct such a quantitative
analysis. The Agency is fully cognizant of the diversity of mining
operations in each sector, and has applied that knowledge as it
developed the proposal.
Under the RFA, MSHA must use the SBA definition for a small mine of
500 employees or fewer or, after consultation with the SBA Office of
Advocacy, establish an alternative definition for the mining industry
by publishing that definition in the Federal Register for notice and
comment. The alternative definition could be the Agency's traditional
definition of ``fewer than 20 miners,'' or some other definition. As
reflected in the certification, MSHA analyzed the costs of this
proposal for small and large mines using both the traditional Agency
definition, and SBA's definition, as required by RFA, of a small mine.
The Agency compared the costs of the proposal for small mines in each
sector to the revenues and profits for each sector for every size
category analyzed. In each case, the results indicated that the costs
as a percent of revenue are less than 1%. Further, the costs do not
appear to have any appreciable impact on profits.
The following table summarizes the results of this analysis for
mines which employ fewer than 500 miners, at various sizes.
Small Mines: Costs Compared to Revenues and Profits
--------------------------------------------------------------------------------------------------------------------------------------------------------
Total
Estimated Estimated Average estimated Estimated Cost as % Cost as %
costs revenue profit as % profits cost per of revenue of profit
(thous.) (millions) of revenue (millions) small mine
--------------------------------------------------------------------------------------------------------------------------------------------------------
Coal Mines:
Small <20................................................ ($45) $855 3.82 $33 ($26) -0.01 -0.14
Large >=20............................................... 332 19,094 3.82 729 293 0.00 0.05
Small <50............................................... 586 3,542 3.82 135 237 0.02 0.43
Large >=50............................................... (300) 16,408 3.82 627 (709) 0.00 -0.05
Small <100............................................... 832 6,061 3.82 232 309 0.01 0.36
Large >=100.............................................. (545) 13,888 3.82 531 (2,684) 0.00 -0.10
Small <250............................................... 677 12,624 3.82 482 240 0.01 0.14
Large >=250.............................................. (391) 7,326 3.82 280 (5,140) -0.01 -0.14
Small <500............................................... 382 19,117 3.82 730 132 0.00 0.05
Large >=500.............................................. (95) 831 3.82 32 (8,660) -0.01 -0.30
M/NM Mines:
Small <20................................................ 4,437 11,929 4.55 543 479 0.04 0.82
Large >=20............................................... 3,600 26,071 4.55 1,186 2,324 0.01 0.30
Small <50................................................ 5,731 18,814 4.55 856 557 0.03 0.67
Large >=50............................................... 2,306 19,186 4.55 873 4,359 0.01 0.26
[[Page 66367]]
Small <100............................................... 6,323 23,047 4.55 1,049 599 0.03 0.60
Large >=100.............................................. 1,714 14,953 4.55 680 6,418 0.01 0.25
Small <250............................................... 7,037 29,558 4.55 1,345 655 0.02 0.52
Large >=250.............................................. 1,000 8,442 4.55 384 14,492 0.01 0.26
Small <500............................................... 7,571 32,134 4.55 1,462 702 0.02 0.52
Large >=500.............................................. 466 5,866 4.55 267 17,249 0.01 0.17
--------------------------------------------------------------------------------------------------------------------------------------------------------
In determining revenues for coal mines, MSHA multiplied coal
production data (in tons) for mines in specific size categories
(reported to MSHA quarterly) by the average price per ton (from the
Department of Energy, Energy Information Administration, Annual Energy
Review 1995). For metal and nonmetal mines, the Agency estimated
revenues for specific mine size categories as the proportionate share
of these mines' contribution to the Gross National Product (from the
Department of the Interior, former Bureau of Mines, Mineral Commodity
Summaries 1996). Average profit as a percent of revenue for both coal
mines and metal and nonmetal mines comes from Dun & Bradstreet
Information Services, Industry Norms & Key Business Ratios, 1993-94.
Based on the information in the Agency's preliminary Regulatory
Impact Analysis (summarized in the ``costs'' table in the Question and
Answer section of this preamble), the costs of the proposal for all
metal and nonmetal mines with fewer than 20 employees would be $4.6
million; the average cost of the proposal for a small metal and
nonmetal mine with fewer than 20 employees is about $500. The average
cost of the proposal for a small metal and nonmetal mine with fewer
than 500 employees is about $700. For small coal mines with fewer than
20 employees, the proposal is estimated to result in a small net
savings of about $30. This savings results from the proposed
elimination of a substantial paperwork burden that now exists in the
coal mine sector for monitoring miners' noise exposures. For small coal
mines with fewer than 500 employees, the proposal is estimated to
result in a small net cost of about $130.
Regulatory Alternatives Rejected
The limited impacts on small mines, regardless of size definition,
reflect decisions by MSHA not to propose more costly regulatory
alternatives. In considering regulatory alternatives for small mines,
MSHA must observe the requirements of its authorizing statute. Section
101(a)(6)(A) of the Mine Act requires the Secretary to set standards
which most adequately assure, on the basis of the best available
evidence, that no miner will suffer material impairment of health over
his/her working lifetime. In addition, the Mine Act requires that the
Secretary, when promulgating mandatory standards pertaining to toxic
materials or harmful physical agents, consider other factors, such as
the latest scientific data in the field, the feasibility of the
standard and experience gained under the Act and other health and
safety laws. Thus, the Mine Act requires that the Secretary, in
promulgating a standard, attain the highest degree of health and safety
protection for the miner, based on the ``best available evidence,''
with feasibility as a consideration.
As a result of this statutory requirement, MSHA seriously
considered two alternatives that would have significantly increased
costs for small mine operators--lowering the PEL to a TWA8 of 85
dBA, and lowering the exchange rate to 3 dB. In both cases, the
scientific evidence in favor of these approaches was strong. But in
both cases, for the purpose of this proposal, MSHA has concluded that
it may not be feasible for the mining industry to accomplish these more
protective approaches. The impact of these approaches on small mine
operators was an important consideration in this regard. Part IV of
this preamble contains a full discussion of MSHA's preliminary
conclusions about these alternatives. The public is invited to propose
other alternatives for consideration.
Paperwork Impact
In accordance with the Regulatory Flexibility Act and the Paperwork
Reduction Act of 1995 (PRA 95), MSHA has analyzed the paperwork burden
for small mines. While the proposal results in a net paperwork burden
decrease for all mines, it results in an increase in paperwork hours.
For mines with fewer than 20 miners the proposal would result in an
increase of about 18,800 hours, and with fewer than 500 miners it would
result in a decrease of about 14,985 hours. The bulk of the new hours
(greater than 80%) is derived from the audiometric testing program and
procedures. While mines with fewer than 20 employees in the coal and
metal and nonmetal sectors will have extra burden hours associated with
new requirements, the net burden hours for small coal mines are
actually reduced, because the proposal would eliminate current
requirements for biannual noise surveys and other miscellaneous reports
and surveys in that sector. However, at this size level, there are more
metal and nonmetal mines than there are coal mines. Thus, at this size
level, the proposal would result in a net gain in paperwork burdens.
As required by PRA 95, MSHA has included in its paperwork burden
estimates the time needed to perform tasks associated with information
collection. For example, the proposed rule requires a mine operator to
notify a miner if the miner's noise exposure exceeds the action level.
In order to determine if notification is necessary, the mine operator
must perform dose determination monitoring. Although completion of the
notification would take 0.05 hour on average, the time for dose
determination must be included in the burden estimate according to the
new paperwork law. The proposal's average paperwork burden per small
metal and nonmetal mine is 4.8 hours and per small coal mine is 6 hours
per year.
Other Relevant Matters
In accordance with the Small Business Regulatory Enforcement
Fairness Act (SBREFA), MSHA is taking actions to minimize the
compliance burden on small mines. As discussed in the ``Questions and
Answers'' section of this preamble, MSHA is committed to writing the
final rule in plain English, so that it can be easily understood by
small mine operators. The proposed effective date of the rule would be
a year after final promulgation, to provide adequate time for small
mines to achieve compliance. Also, as stated
[[Page 66368]]
previously, MSHA will mail a copy of the proposed rule to every mine
operator which primarily benefits small mine operators. The Agency has
committed itself to issuance of a compliance guide for all mines, and
has invited comment on whether compliance workshops or other such
approaches would be valuable.
MSHA is considering whether to continue to use ``fewer than 20
miners'' as the definition of a small mine for purposes of the
Regulatory Flexibility Act (RFA). For this rulemaking's Regulatory
Flexibility Analysis, the Agency is using fewer than 20 employees, in
addition to the SBA's definition of fewer than 500, as required by the
RFA. MSHA presently is consulting with the SBA Office of the Chief
Counsel for Advocacy in order to determine an appropriate definition to
propose to the public for comment in the future. For purposes of this
proposed rule on noise, MSHA has continued its past practice of using
``under 20 miners'' as the appropriate point of reference, in addition
to SBA's definition. Reviewers will note that the paperwork and cost
discussions continue to refer to the impacts on ``small'' mines with
fewer than 20 employees. The Agency has not established a definition of
``small entity'' for purposes of the final rule. Based on this
analysis, MSHA concludes that whatever definition of ``small entity''
is eventually selected, the proposed noise rule does not have a
significant economic impact on a substantial number of small entities.
(E) Unfunded Mandates Act
MSHA has determined that, for purposes of Sec. 202 of the Unfunded
Mandates Reform Act of 1995, this proposal does not include any Federal
mandate that may result in increased expenditures by State, local, or
tribal governments in the aggregate of more than $100 million, or
increased expenditures by the private sector of more than $100 million.
Moreover, the Agency has determined that for purposes of Sec. 203 of
that Act, this proposed rule does not significantly or uniquely affect
small governments.
Background
The Unfunded Mandates Reform Act was enacted in 1995. While much of
the Act is designed to assist the Congress in determining whether its
actions will impose costly new mandates on State, local, and tribal
governments, the Act also includes requirements to assist Federal
agencies to make this same determination with respect to regulatory
actions.
Analysis
Based on the analysis in the Agency's preliminary Regulatory Impact
Statement (summarized in the ``cost'' table in the Questions and
Answers section of this preamble), the cost of this proposed rule for
the entire mining industry is less than $10 million. Accordingly, there
is no need for further analysis under Sec. 202 of the Unfunded Mandates
Reform Act.
MSHA has concluded that small governmental entities are not
significantly or uniquely impacted by the proposed regulation. The
proposed rule will impact approximately 14,000 coal and metal and
nonmetal mining operations; however, increased costs would be incurred
only by those operations where noise exposures exceed the allowable
limits. MSHA estimates that approximately 350 sand and gravel or
crushed stone operations are run by state, local, or tribal governments
and would be impacted by this rule. MSHA anticipates that these
entities would be able to reduce noise exposure below the PEL via
engineering and administrative controls and would not need to use a
Hearing Conservation Program, thereby minimizing their costs. MSHA
estimates that increased costs for these entities would be about $500
per year which would be partially offset by reduced worker compensation
costs. Other tangible benefits include reduction in the number of cases
of hearing impairment in these entities.
When MSHA issues the proposed rule, the Agency will affirmatively
seek input of any state, local, and tribal government which may be
affected by the noise rulemaking. This would include state and local
governmental entities who operate sand and gravel mines in the
construction and repair of highways and roads. MSHA will mail a copy of
the proposed rule to approximately 350 such entities.
Following is MSHA's state-by-state listing of sand and gravel mines
owned or operated by state or local governments.
The Agency welcomes any corrections.
State/County Owned/Operated Sand and Gravel Operations
[As of 12/08/95]
------------------------------------------------------------------------
State County City
State owned owned owned
------------------------------------------------------------------------
ARIZONA...................................... 2 2 .......
ARKANSAS..................................... ....... 5 .......
CALIFORNIA................................... ....... 4 .......
COLORADO..................................... 4 27 .......
IDAHO........................................ ....... 13 .......
ILLINOIS..................................... ....... 2 .......
INDIANA...................................... ....... 5 .......
IOWA......................................... ....... 2 .......
KANSAS....................................... ....... 2 .......
MAINE........................................ 5 ....... .......
MARYLAND..................................... ....... ....... 6
MICHIGAN..................................... ....... 8 .......
MISSISSIPPI.................................. ....... 5 .......
MISSOURI..................................... ....... 8 .......
MONTANA...................................... 8 34 .......
NEBRASKA..................................... ....... 2 .......
NEVADA....................................... ....... 1 .......
NEW MEXICO................................... ....... 4 .......
NEW YORK..................................... ....... 15 95
OKLAHOMA..................................... ....... 2 .......
OREGON....................................... ....... 11 .......
PENNSYLVANIA................................. ....... ....... 1
SOUTH CAROLINA............................... ....... 1 .......
SOUTH DAKOTA................................. ....... 15 .......
TENNESSEE.................................... ....... 3 .......
TEXAS........................................ ....... 6 .......
UTAH......................................... 1 5 .......
VERMONT...................................... ....... ....... 11
WASHINGTON................................... ....... 9 .......
WISCONSIN.................................... ....... 20 1
WYOMING...................................... ....... 1 .......
--------------------------
Total 346.............................. 20 212 114
------------------------------------------------------------------------
(F) Rulemaking History
MSHA's noise standards in metal and nonmetal mines (30 CFR 56/
57.5050) and in coal mines (Secs. 70.500 through 70.511, and
Secs. 71.800 through 71.805) were first published in the early 1970's.
These standards, derived from the Walsh-Healey Public Contracts Act
occupational noise standard, adopted a TWA8 PEL of 90 dBA and a 5-
dB exchange rate.
Because of the differences between the standards for coal mines and
those for metal and nonmetal mines, members of the mining community
with operations in coal and metal and nonmetal requested that MSHA
revise its standards to provide one set of noise standards covering all
mines. Other mine operators with facilities regulated by both MSHA and
OSHA suggested that MSHA promulgate noise standards which are generally
consistent with OSHA standards. The United Mine Workers also requested
that the Agency reconsider the existing standards to address several
asserted deficiencies.
Based on these comments and the incidence of noise-induced hearing
loss (NIHL) among miners, the Agency published an Advanced Notice of
Proposed Rulemaking (ANPRM) on December 4, 1989 (54 FR 50209). In this
[[Page 66369]]
ANPRM, the Agency solicited information for revision of the noise
standards for coal and metal and nonmetal mines. The Agency received
numerous comments which are reflected in this proposal from mine
operators, trade associations, labor groups, equipment manufacturers,
and other interested parties.
A draft of the proposed rule and accompanying analyses was sent to
the Office of Management and Budget and to the Chief Counsel for
Advocacy of the Small Business Administration, in accordance with law
and Executive Order. Consultations with these two agencies were
completed within 90 days. No substantive changes to the proposal were
recommended during these consultations, nor were any made by MSHA. The
Agency did receive valuable advice on the presentation of its initial
Regulatory Flexibility Analysis and on displaying the results of its
paperwork analysis, so as to better highlight the Agency's compliance
with PRA 95 and SBREFA.
In the Spring of 1996, the National Institute for Occupational
Safety and Health (NIOSH) released for peer review a draft criteria
document for occupational noise exposure to update the one issued in
1972. As indicated previously (see response to Question 6 in
``Questions and Answers''), MSHA has determined that it would not be
appropriate to delay publication of this proposed rule to await the
issuance of the final NIOSH criteria document.
A summary of the draft criteria document, prepared by NIOSH, is
reprinted here verbatim for those in the mining community who have not
otherwise received copies. This summary should provide ample notice of
the position NIOSH may be taking in a new criteria document.
April 16, 1996--(NIOSH) Summary of Recommendations, Criteria for a
Recommended Standard: Occupational Noise Exposure
1. Hearing Impairment and Risk Assessment
The protection goal incorporated in most definitions of hearing
impairment has been to preserve hearing at critical audiometric
frequencies for speech discrimination. Hearing impairment as defined
by NIOSH in 1972 was an average of the hearing threshold levels
(HTLs) at the audiometric frequencies of 1000, 2000 and 3000 Hertz
(Hz) that exceeded 25 decibels (dB). The 4000-Hz audiometric
frequency has been recognized as being not only sensitive to noise
but also extremely important for hearing and understanding speech in
unfavorable or noisy listening conditions. Because listening
conditions are not always ideal in everyday life, and on the basis
of the American Speech Language-Hearing Association Task Force's
proposal made in 1981, NIOSH has modified its definition of hearing
impairment to include the 4000-Hz audiometric frequency for use in
assessing the risk of occupational NIHL. Hence, with this
modification, NIOSH defines material hearing impairment as an
average of the HTLs at 1000, 2000, 3000 and 4000 Hz that exceeds 25
dB.
Because of the prolific occupational use of hearing protectors
since the early 1980's, new data that can be used to determine dose-
response relationships for NIHL in U.S. workers are not known to
exist. NIOSH recently conducted a risk assessment on occupational
noise-induced hearing loss (NIHL) using the original definition of
hearing impairment and the hearing data from the 1972 criteria
document. Although the risk model used in the new assessment is
different from the risk model used in 1972, the excess risk
estimates derived in the new assessment are comparable to those
published in 1972. The excess risk at age 60 from a 40-year
occupational exposure to an average daily noise level of 85
decibels, a weighted network (dBA) is approximately 14%, versus the
16% published in 1972. With the new NIOSH definition of hearing
impairment, and based on the new risk assessment, the excess risk at
the 85-dBA REL is 8%. Thus, the new risk assessment did not revise
the excess risk at the 85-dBA REL upward, and although there is
still evidence of excess risk at exposure levels below 85 dBA, NIOSH
is recommending that the current REL be retained.
2. Exchange Rate
Health effect outcomes are dependent on exposure level and
duration. This relationship is called the ``exchange rate,'' which
is the increment in decibels that requires the halving of exposure
time. The most commonly used exchange rates are 3 dB and 5 dB. A 3-
dB exchange rate requires that noise exposure time be halved for
each 3-dB increase in noise level; likewise, a 5-dB exchange rate
requires that exposure time be halved for each 5-dB increase. NIOSH
now recommends the 3-dB exchange rate. The 1972 criteria document
recommended the 5-dB exchange rate, which is what OSHA and MSHA
currently enforce. There is more scientific, although not
unequivocal, support for the 3-dB exchange rate than for the 5-dB
exchange rate, which is not based on scientific data and is derived
from a series of over-simplifications of the original criteria. The
3-dB exchange rate is recommended by the International Organization
for Standardization (ISO), and it is now enforced by most European
countries and some provinces of Canada. In the U.S., there have been
recent ``converts'' to the 3-dB exchange rate: the U.S. Air Force in
1993; and the American Conference of Governmental Industrial
Hygienists and the U.S. Army in 1994.
3. Ceiling Limit
In the 1972 criteria document, NIOSH recommended a ceiling limit
of 115 dBA, which is retained in this draft criteria document.
Exposures to noise levels greater than 115 dBA would not be
permitted regardless of the duration of the exposure. This ceiling
limit is based on the assumption that above a critical intensity
level the ear's response to energy no longer has a relation to the
duration of the exposure, but is only related to the intensity of
the exposure. Recent research with animals indicates that the
critical level is between 115 and 120 dBA. Below this critical
level, the amount of hearing loss is related to the intensity and
duration of exposure; but above this critical level, the
relationship does not hold. For a noise standard to be protective,
there should be a noise ceiling level above which no unprotected
exposure is permitted. Given the recent data, 115 dBA is a
reasonable ceiling limit beyond which no unprotected exposure should
be permitted.
4. Hearing Protectors
One consideration for selecting a hearing protector would be its
noise reduction capabilities, which are expressed in terms of a
noise reduction rating (NRR). The NRR is a single-number,
laboratory-derived rating required by the Environmental Protection
Agency (EPA) to be shown on the label of each hearing protector sold
in the U.S. In the late 1970's and early 1980's, two NIOSH field
studies found that insert-type hearing protectors in the field
provided less than one-half the attenuation measured in the
laboratory, and since the 1970's, 22 additional studies of ``real-
world'' attenuation with a variety of hearing protectors have shown
similar results.
In calculating the noise exposure to the wearer of a hearing
protector, OSHA has implemented the practice of derating the NRR by
one-half for all types of hearing protectors. In the 1972 criteria
document, NIOSH recommended the use of the equivalent full NRR
value, but now it recommends derating the NRR by 25%, 50% and 70%
for earmuffs, formable earplugs and all other earplugs,
respectively. This derating scheme is not perfect and is intended
only as an interim recommendation. If the testing and labeling
requirements for hearing protectors are to be changed, EPA must
initiate the rulemaking procedures because it has the statutory
authority. Given that the funding for EPA's Office of Noise
Abatement and Control was eliminated in the early 1980's, this
change is unlikely to occur in the near future.
The draft also recommends that hearing protectors be worn for
any noise exposure over 85 dBA, regardless of exposure duration.
This measure is simplistic but extremely protective because its
implementation does not require the calculation of time-weighted-
average (TWA) exposures. This ``hard-hat'' approach, as opposed to
predicating the requirement on TWA exposures, is a departure from
what was recommended in 1972. It appears to be a prudent policy,
which the U.S. Army has been using for years, but there are no data
in the document to support this recommendation.
5. Exposure Level Requiring a Hearing Loss Prevention Program
In this draft document, the requirement for a hearing loss
prevention program (HLPP), which includes audiometry, worker
education, etc., is triggered by the exposure level of 82 dBA, 8-
hour TWA (i.e., \1/2\ of the REL). This level is essentially an
``action level''--a concept developed in the mid-
[[Page 66370]]
1970's to address interday exposure variability and later adopted
in the Standards Completion Program as \1/2\ of an exposure limit.
In the 1972 criteria document, which preceded the Standards
Completion Program, the requirement for a HLPP began at the REL of
85 dBA, 8-hour TWA.
6. Types and Frequency of Audiometric Examinations
In this draft document, the recommended types (i.e., baseline,
monitoring, confirmation and exit audiograms) and frequency of
audiometric examinations are different from those in the 1972
criteria document. The new recommendations are in line with current
practices in HLPPs.
7. Significant Threshold Shift
Significant threshold shift is a shift in hearing threshold
levels, outside the range of audiometric testing variability
(5 dB), that warrants follow-up action to prevent
further hearing loss. NIOSH recommends an improved significant
threshold shift criterion, which is an increase of 15 dB in hearing
threshold at 500, 1000, 2000, 3000, 4000, or 6000 Hz that is
repeated for the same ear and frequency in back-to-back tests. This
criterion is different from that in the 1972 criteria document, and
has been selected from among several criteria on the bases of their
relative sensitivity and specificity. The new criterion has the
advantages of a high identification rate (identifying those workers
whose hearing thresholds have shifted toward higher levels) and a
low false-positive rate.
8. Age Correction on Audiogram
NIOSH recommends that age correction not be applied to an
individual's audiogram for the calculation of a significant
threshold shift. Although many people experience some decrease in
hearing sensitivity with age, age correction cannot be accurately
applied to audiograms in determining an individual's significant
threshold shift because the data on age-related hearing losses
describe only the statistical distributions in populations. Thus,
the median hearing loss attributable to presbycusis for a given age
group will not be generalizable to the presbycusis experienced by an
individual in that age group. The argument for age correction has
been that the employer should not be penalized for hearing losses
due to ageing. In the 1972 criteria document, NIOSH recommended age
correction but did not provide a rationale for it.
9. Evaluation of Program Effectiveness
To assess the effectiveness of a HLPP, it is necessary to have
an evaluation method that can monitor trends in the population of
workers enrolled in the program and thus indicate program
effectiveness before many individual shifts occur. In general, NIOSH
suggests that the success of a smaller HLPP should be judged by the
audiometric results of individual workers. An overall program
evaluation becomes critical when the number of workers grows so
large that one cannot simply look at each worker's audiometric
results and get an adequate picture of the program's efficacy. At
the present time, there is not one generally accepted method for the
overall evaluation of HLPPs. NIOSH recommends a significant
threshold shift incidence rate of 5% or less as evidence of an
effective HLPP. This method is currently the simplest procedure
available, and has no more disadvantages than other potential
evaluation methods.
10. American National Standards Institute (ANSI)
In the 1972 criteria document, NIOSH recommended several ANSI
standards for quality assurance in audiometry and in noise
measurements. Since then, these standards have been updated several
times. In the draft document, NIOSH recommends that these standards
be superseded with the latest versions as they become available. The
major advantage for this ``blanket'' endorsement is that the revised
criteria document will stay current with changing technology.
II. The Risks to Miners
This part of the preamble sets out the evidence collected by MSHA
to date with respect to whether there is a continuing risk to miners of
exposure to harmful levels of noise, despite existing standards, and
evidence on the level of that risk. Based upon this information, MSHA
has concluded that workplace noise exposure does continue to pose a
significant risk of material impairment of health and functional
capacity to miners.
The data presented in this part provide a profile of the mining
population at risk at different levels of workplace noise exposure. The
noise exposure limitations being proposed by the Agency, described in
part III, would not eliminate the risk of material impairment--although
they would cut the present risk by two-thirds. (The feasibility of
further reducing risk is discussed in part IV. The data in this part II
were utilized by the Agency to assist it in determining the cost to
industry of reducing risk to various levels, and thus in reaching the
Agency's conclusions about economic feasibility.)
There are a number of technical terms used throughout this section.
Reviewers not familiar with noise terminology should refer to the
discussion in part III of this preamble concerning proposed
Sec. 62.110, Definitions.
All the studies discussed and cited in this part are included in
the references listed in part V, along with similar studies reviewed by
the Agency. All constitute part of the Agency's rulemaking record.
The Agency is interested in receiving additional data with respect
to the risks of noise exposure.
Defining the Problem
Noise is one of the most pervasive health hazards in mining.
Exposure to hazardous sound levels results in the development of
occupational noise-induced hearing loss (NIHL), a serious physical,
psychological, and social problem. NIHL can be distinguished from aging
and medical factors, diagnosed, and prevented.
The National Institute for Occupational Safety and Health (NIOSH)
has identified the ten leading work-related diseases and injuries in
the publication, ``Proposed National Strategies for the Prevention of
Leading Work-Related Diseases and Injuries, Part 2.'' According to
NIOSH, NIHL is among these ``top ten'' diseases and injuries.
For many years, the risk of acquiring an NIHL was accepted as an
inevitable consequence associated with mining occupations. Miners use
mechanized equipment and work under conditions that often expose them
to hazardous sound levels. But MSHA standards, OSHA standards, military
standards, and others around the world have been established in
recognition of the controllability of this risk. Quieter equipment,
isolation of workers from noise sources, and limiting worker exposure
times are among the many well accepted methods now used to reduce the
costly incidence of NIHL.
NIHL can be temporary or permanent depending on the intensity and
duration of the noise exposure. Temporary hearing loss results from
short term exposures to noise, with normal hearing returning after a
period of rest. Generally, prolonged exposure to noise over a period of
several years causes permanent damage to the auditory nerve: the higher
the sound level the more rapid the loss. The loss may be so gradual,
however, that a person may not realize that he or she is becoming
impaired until a substantial amount of hearing acuity is lost.
Damage to the inner ear hair cells and auditory nerve makes it
difficult to hear as well as understand speech. This damage is
irreversible. Although people with NIHL sometimes can benefit from the
use of a hearing aid, the aid can never ``correct'' a hearing loss the
way eyeglasses usually can correct impaired vision. That is because
hearing aids primarily amplify sound without making it clearer or less
distorted. Also, they amplify the unwanted noise as well as the wanted
speech signals.
People with significant NIHL have difficulty with the perception of
speech. They are often frustrated by missing information that is vital
for social or vocational functioning, and can produce workplace safety
hazards. Also, people around them need to speak louder, and more
clearly to be understood. In addition, background noise has a much more
disruptive effect on hearing-
[[Page 66371]]
impaired individuals because they are less able to differentiate
between the wanted signal and the unwanted background noise.
There is a wealth of information on the relationship between noise
exposure and its auditory (hearing loss) and non-auditory
(physiological and psychosocial) effects.
Numerous studies are available which describe the effects of noise
on hearing as a function of sound level and duration. Dose-response
relationships have been well established for noise equal to or greater
than average sound levels of 85 dBA (see, e.g., Lempert and Henderson,
1973).
Although the non-auditory effects of noise are more difficult to
identify, document, and quantify than is hearing loss, recent
laboratory and field studies have implicated noise as a causative
factor in cardiovascular problems (Tomei et al., 1992 and Lercher et
al., 1993) and other illnesses such as hypertension (Talbott, 1990, and
Jansen, 1991). Decreasing the noise exposure from greater than 85 dBA
to less than 85 dBA significantly improved both the psychological and
physiological stress reactions (Melamed and Bruhis, 1996). However,
these studies of health effects have not been conclusive.
In Earlog 6, Berger (1981) discussed the adverse non-auditory
effects of noise exposure. He suggests that effective hearing
conservation programs may not only prevent NIHL, but also improve
general employee health and productivity.
Schmidt, et al. (1980) studied injury rates among workers in a
North Carolina cotton manufacturer exposed to noise ranging from 92 to
96 dBA. During the ten year time period studied, a significant
reduction in injury rates was observed for those workers who were in an
HCP, compared to those who were not.
Safety risks can specifically be created because workers harmed by
NIHL can no longer hear safety signals. Most people with an NIHL have
reduced hearing acuity at the higher frequencies and lose their ability
to distinguish consonants on which the intelligibility of speech
depends. For example, they would have difficulty in distinguishing
between ``fish'' and ``fist.''
Although MSHA recognizes that non-auditory effects of noise can be
significant, they are difficult to quantify; by contrast, the auditory
risks have a well-established dose-response relationship, and thus
provide a solid foundation on which to base regulatory action. The
Agency believes that reducing sound levels and protecting miners from
hazardous noise exposures will also reduce the non-auditory effects of
noise.
Definition of Material Impairment
Section 101(a)(6) of the Mine Safety and Health Act provides that
in setting standards to protect workers from the risks of harmful
physical agents, the Secretary ``shall set standards which most
adequately assure on the basis of the best available evidence that no
miner will suffer material impairment of health or functional capacity
even if such miner has regular exposure to the hazards dealt with by
such standard for the period of his working life.''
While the material impairment to which the law refers is material
impairment of ``health or functional capacity'', the term material
impairment in the literature on noise risk generally refers to a level
of harm which is considered handicapping or even disabling--a 25 dB
hearing level (deviation from audiometric zero)--so this had to be the
basis of MSHA's estimates of the risk of material impairment. The
scientific community has actually utilized over time at least three
different definitions of what constitutes ``material impairment'' in
the case of NIHL. All use a 25 dB hearing level, but each definition
has used a different set of frequencies. Of these, the Agency believes
the one developed in 1972 by NIOSH and subsequently used by OSHA is
most appropriate of the three for evaluating the risks faced by miners
of developing disabling NIHL. The OSHA/NIOSH definition of material
impairment of hearing is a 25 dB hearing level averaged over 1000,
2000, and 3000 Hertz (Hz) in either ear. As noted in the History
section of this preamble, the Agency is aware that NIOSH is currently
considering a new definition that also includes hearing loss at 4000
Hz; but until such an approach is peer reviewed and approved, MSHA
believes it is not an appropriate basis for evaluating risk.
Background
Ideally, a definition of material impairment based solely upon
audiometric tests that measure individual ability to understand speech
would best characterize the debilitating effects of an NIHL.
Unfortunately, these tests are complicated, not well standardized, and
therefore seldom used to determine hearing impairment. For these
reasons, most definitions of impairment are based solely on pure tone
audiometry.
Pure tone audiometric tests utilize an audiometer to measure the
hearing level threshold of an individual by determining the lowest
level of discrete frequency tones that the individual can hear. The
test procedures for conducting pure tone audiometry are relatively
simple, widely used, and have been standardized. Although there is
little debate among the scientific community about the usefulness of
pure tone audiometry in assessing hearing loss, some disagreement
exists as to the hearing level where hearing impairment begins and the
range of audiometric frequencies to use in making the assessment.
In issuing its Hearing Conservation Amendment (46 FR 4078), OSHA
defined hearing impairment as exceeding a 25 dB ``hearing level''
averaged over 1000, 2000, and 3000 Hertz (Hz) in either ear. Hearing
level is the deviation in hearing acuity from audiometric zero, the
lowest sound pressure level audible to the average normal-hearing young
adult. Positive values indicate poorer hearing acuity than audiometric
zero, while negative values indicate better hearing. Because OSHA based
its definition on a 1972 recommendation by NIOSH (1972), MSHA refers to
this definition as the OSHA/NIOSH criteria for hearing impairment.
NIOSH specifically developed its definition of hearing impairment
for understanding speech under everyday (noisy) conditions. NIOSH
concluded that ``the basis of hearing impairment should be not only the
ability to hear speech, but also to understand speech,'' and this is
best predicted by the hearing levels at 1000, 2000, and 3000 Hz.
When OSHA initially published its Hearing Conservation Amendment,
most medical professionals used the 1959 criteria developed by the
American Academy of Ophthalmology and Otolaryngology (AAOO), a subgroup
of the American Medical Association (AMA). This criteria (AAOO 1959)
defined hearing impairment as exceeding a 25 dB hearing level,
referenced to audiometric zero, averaged over 500, 1000, and 2000 Hz in
either ear (1959).
The American Academy of Otolaryngology Committee on Hearing and
Equilibrium and the American Council of Otolaryngology Committee on the
Medical Aspects of Noise (AAO-HNS) has since modified the 1959 criteria
by adding the hearing level at 3000 Hz to the hearing levels at 500,
1000, and 2000 Hz (1979).
Unlike the OSHA/NIOSH criteria, the AAOO 1959 and AAO-HNS 1979
criteria are for all types of hearing loss, including noise-induced
hearing loss (NIHL), and were mainly designed for hearing speech under
relatively quiet conditions.
[[Page 66372]]
In its ANPRM, MSHA asked for comments on a definition of hearing
impairment. Many commenters either directly or indirectly endorsed the
OSHA/NIOSH definition of hearing impairment. One commenter suggested
defining a significant material impairment as an average permanent
threshold shift of 25 dB or more at 1000, 2000, 3000, and 4000 Hz in
either ear. Other commenters supported the AAO-HNS 1979 criteria as the
level where impairment begins. (Several commenters suggested that MSHA
separately address a definition of hearing loss for reporting purposes;
this has been done, as discussed in part III of this preamble in
connection with proposed Sec. 62.190(b).)
Discussion
MSHA has determined that with respect to mine safety and health,
any definition of material impairment of hearing should relate to a
permanent, measurable loss of hearing which, unchecked, will limit the
ability to understand speech, as it is spoken in everyday social
(noisy) conditions. This is because speech comprehension is essential
for mine safety.
Measures of hearing impairment depend upon the frequencies used in
calculating the hearing impairment. At relatively low sound levels
(between 80 dBA and 90 dBA) the hearing loss is confined to the higher
audiometric frequencies. In order to show the effect of noise below 90
dBA on hearing, inclusion of test frequencies above 2000 Hz is
necessary. MSHA agrees with the many comments and studies cited to show
that high frequency hearing is critically important for the
understanding of speech and that every day speech is sometimes
distorted and often takes place in noisy conditions.
Therefore, MSHA has determined that for purposes of mine safety and
health, 3000 Hz should be included in any definition of material
impairment. In addition, 500 Hz should be excluded from any definition,
since it is not as critical for understanding speech and least affected
by noise. Of the three generally utilized definitions of noise--the
AAOO 1959, the AAO-HNS 1979, and the OSHA/NIOSH criteria--only the
latter meets this test.
All three of the aforementioned definitions of noise use a 25 dB
hearing level. As noted previously, this level of hearing loss relative
to audiometric zero is actually well beyond that at which there is harm
to health and also well beyond that at which workers suffer a loss of
functional capacity. Nevertheless, this is the measure used in almost
all of the studies of risk of noise exposure that have been done. This
constrains the definition of material impairment the Agency utilizes to
evaluate the available risk data.
Accordingly, solely for the purposes of evaluating the significance
of the available risk studies for miners, MSHA is adopting the OSHA/
NIOSH criteria, a 25 dB hearing level averaged over 1000, 2000, and
3000 Hertz (Hz) in either ear, as its definition of material
impairment.
With respect to risk evaluations, the number of persons meeting the
definition of impairment in any noise-exposed population will be higher
under the OSHA/NIOSH criteria than under the other criteria (AAOO 1959
and AAO-HNS 1979). This is because noise does not affect hearing acuity
equally across all frequencies. Typically, NIHL occurs first at 4000
Hz, then progresses into the lower and higher frequencies. The AAOO
1959 criteria is weighted toward the lower frequencies and was
developed to determine an individual's ability to communicate under
quiet conditions. Recognizing that an individual's ability to hear
speech in a noisy environment depends upon that person's ability to
hear sounds in the higher frequency range, the AAO-HNS added 3000 Hz to
the frequencies used in the AAOO 1959 criteria. The impact of this
modification is that the number of persons meeting the impairment
criteria in any noise-exposed population will be higher under the AAO-
HNS 1979 criteria than under the AAOO 1959 criteria. With the
elimination of the hearing level at 500 Hz from the frequency range
used, the OSHA/NIOSH definition is weighted even more toward the higher
frequencies than the AAO-HNS 1979 criteria, and thus even more are
determined to be impaired.
Moreover, selection of a criterion places some limitations on
direct comparisons of data sources available for risk assessment. Data
compiled using one definition of impairment are not readily
translatable to the others. Since there is no reliable mathematical
relationship among the three criteria for hearing impairment, it is not
possible to accurately predict the impact on a population using the
other two criteria when only the impact of one criterion is known. The
ideal way to convert from one hearing impairment criterion to another
would be to use the hearing level data for individual frequencies (raw
data), if still available from the individual audiograms. It is also
possible to crudely estimate the impact of one criterion to another
provided that summary data on individual frequencies are available.
Unfortunately, most of the data necessary to complete such conversions
are no longer available.
In the discussion of risk that follows in the next section of this
preamble, sources of data based on all three definitions of impairment
are presented, so this caveat about translation needs to be kept in
mind. As it turns out, however, data using all three definitions tend
to demonstrate the same result.
Risk of Impairment
The studies of risk reviewed in this section consistently indicate
that the risk of developing a material impairment (as defined in the
prior section for purposes of this discussion) becomes significant over
a working lifetime when workplace exposure exceeds average sound levels
of 85 dBA. The data indicate that while lowering exposure from an
average sound level of 90 dBA to one of 85 dBA does not eliminate the
risk, it does reduce the risk by approximately half.
Measuring Risk
It is not possible to determine the risk to individual miners of
particular levels of noise. Some miners will suffer harm long before
other miners from the same level of noise, and it is not possible to
measure susceptibility in advance. Risks can, however, be determined
for entire populations. According to Melnick (1982), professor emeritus
of audiology at Ohio State University:
Experts agree that information is available for deriving the
relationship of noise exposure to hearing loss. This information
serves as the basis for development of damage risk criteria. * * *
The relationship of noise to hearing is in the scientific domain.
The decisions inherent in development of damage risk criteria are
social, political, and economic. Damage risk criteria are
statistical concepts. Use of these criteria should be limited to
considerations of populations. Damage risk criteria are not
appropriate for use with individuals no matter how tempting such an
application might be.
The probability of acquiring a ``material impairment'' of hearing
in a given population can be determined by extrapolating from data
obtained from a test population exposed to the same sound levels. Three
methods are generally used to express this population risk:
(1) the hearing level of the exposed population;
(2) the percent of an exposed population meeting the selected
criteria; and
(3) the percent of an exposed population meeting the selected
criteria minus the percent of a non-noise exposed population meeting
the same criteria, provided both populations are
[[Page 66373]]
similar except for the occupational noise exposure.
The latter of these expressions is more commonly known as ``excess
risk''. The excess risk method separates that percentage of the
population expected to develop a hearing impairment from occupational
noise exposure from that percentage expected to develop an impairment
from non-occupational causes--for example, the normal aging process or
medical problems. Hearing impairment risk data will be presented here
using the excess risk method, because MSHA has concluded that this
method provides the most accurate picture of the risk of hearing loss
resulting from occupational noise exposure. OSHA also used this method
in quantifying the degree of risk in the preamble to its Hearing
Conservation Amendment.
Although studies of hearing loss consistently indicate that
increased noise exposure (either level or duration) results in
increased hearing loss, the reported risk estimates of occupational
NIHL can vary considerably from one study to another. As noted in the
prior section, the definition of ``material impairment'' used plays a
role. But two additional factors can be involved: the screening of the
control group (non-noise exposed group), and the threshold used to
define that group.
Some researchers do not screen their study and control populations,
while others use a variety of different screening criteria.
Theoretically, screening would not have a significant impact on the
magnitude of occupational NIHL experienced by given populations as long
as the same criteria are used to screen both the noise and the non-
noise populations being compared. However, when considering whether the
subjects have exceeded an established definition of material
impairment, failure to take into account any non-occupational noise
exposure and/or presbycusis (loss of hearing acuity due to aging) can
have a profound effect on the estimates of hearing acuity of an exposed
population. For example, if both the exposed and control populations
are screened to eliminate persons with a history of military exposure,
use of ototoxic medicines, noisy hobbies, conductive hearing loss from
acoustic trauma or illness, etc., the excess risk would be
significantly different from that determined using unscreened
populations.
The data presented here all use the same threshold. The threshold
refers to that average sound level below which no adverse effects from
noise exposure are expected to occur. Although researchers Kryter
(1970) and Ambasankaran et al. (1981) have reported hearing loss from
exposure to average sound levels below 80 dBA, most believe that the
risk of developing a material impairment of hearing from exposure to
such levels over a working lifetime is negligible. Accordingly, almost
all noise risk studies consider the population exposed only to average
levels of noise below 80 dBA as a ``non-noise exposed'' control group.
In turn, this becomes the baseline from which the excess risk of being
exposed to noise at higher levels is measured. When OSHA evaluated the
risk of hearing loss for its hearing conservation amendment, it took
the position that it was appropriate to consider the non-noise exposed
control group to those exposed to sound levels below 80 dBA. MSHA, for
the purpose of this proposal, agrees with OSHA's assessment.
As a result of these variations, the data available present a range
of risk estimates. As discussed later in the ``Conclusions'' section of
this part, for purposes of estimating the risks to miners, the Agency
has determined it should properly utilize the range of risk in those
studies based upon the OSHA/NIOSH definition of material impairment. As
noted in that discussion, however, even using the full range of the
data presented here would lead to a similar conclusion.
Review of Study Data
Table 1 is taken from the preamble to OSHA's Hearing Conservation
Amendment (46 FR 4084). It displays the percentage of the industrial
population expected to develop a hearing impairment meeting the AAOO
1959 criteria if exposed to the specified sound levels over a working
lifetime (40 years). This is a compilation of data developed by the
U.S. Environmental Protection Agency (EPA) in 1973, the International
Standards Organization (ISO) in 1975, and NIOSH in 1972. EPA, ISO, and
NIOSH developed their risk assessments using the AAOO 1959 criteria
because this was the format used by the original researchers in
presenting their data. OSHA's risk table was developed primarily from
studies of noise exposed populations in many sectors of general
industry.
Table II-1.--OSHA Risk Table
------------------------------------------------------------------------
Excess risk (%)
------------------------------
Sound level (dBA) ISO
(1975) EPA NIOSH Range
------------------------------------------------------------------------
80....................................... 0 5 3 0-5
85....................................... 10 12 15 10-15
90....................................... 21 22 29 21-29
------------------------------------------------------------------------
As seen in Table II-1, the excess risk of material impairment after
a working lifetime at an average noise exposure of 80 dBA is low, at an
average noise exposure of 85 dBA ranges from 10-15%, and at an average
noise exposure of 90 dBA it ranges from 21-29%. Table II-2 presents
further information on the risk assessments developed by NIOSH in their
criteria document (1972), one portion of which was included in Table
II-1. In Table II-2, data are based on both the AAOO 1959 criteria and
the OSHA/NIOSH criteria.
Table II-2.--NIOSH Risk Table
------------------------------------------------------------------------
Excess risk (%)
Sound level (dBA) -------------------------
OSHA/NIOSH AAOO 1959
------------------------------------------------------------------------
80............................................ 3 3
85............................................ 16 15
90............................................ 29 29
------------------------------------------------------------------------
As shown in Table II-2, NIOSH's risk assessment (1972) found little
difference using OSHA/NIOSH criteria when compared to AAOO 1959
criteria. However, as previously noted, NIOSH recommends using the
OSHA/NIOSH criteria for making risk assessments.
Several researchers have commented on how adjustments to the
criteria used would affect such excess risk figures. Suter (1988)
estimates that the excess risk would be somewhat higher if 500 Hz was
excluded and 3000 Hz was included in the definition of material
impairment. Sataloff (1984) also reported on the effect of adding 3000
Hz into the impairment criteria. He recalculated the effect of
including hearing loss at 3000 Hz to the AAOO 1959 definition of
hearing impairment and found that the prevalence of hearing impairment
increased considerably. After 20 years of exposure to intermittent
noise that peaked at 118 dBA, 3% of the workers experienced hearing
impairment according to the AAOO 1959 definition of hearing impairment.
If the AAO-HNS 1979 definition is used, the percentage increases to 9%.
Royster et al. (1978) confirmed that the exclusion of 500 Hz and the
inclusion of 3000 Hz increased the number of hearing impaired
individuals during a study of potential
[[Page 66374]]
workers' compensation costs for hearing impairment. Using an average
hearing loss of 25 dB as the criteria, Royster found that 3.5% of the
industrial workers developed a hearing impairment according to AAOO
1959, 6.2% according to AAO-HNS 1979, and 8.6% according to OSHA/NIOSH.
Table II-3, II-4 and II-5 display another set of data on the
working lifetime risk of material impairment, based upon the three
different criteria commonly used for defining material impairment.
Table II-3 is based on the AAO 1959 criteria, Table II-4 is based on
the AAO-HNS 1979 criteria, and Table II-5 is based on the OSHA/NIOSH
criteria. MSHA constructed these tables based on data presented in
Volume 1 of the Ohio State Research Foundation report (Melnick et al.,
1980) commissioned by OSHA. The hearing level data, used to construct
the tables, were taken from summary graphs in the report. The noise
exposed population is 65 years old with 40 years of noise exposure. The
control group was not screened as to the cause of any hearing loss;
therefore, the high level of non-occupational hearing loss may
underestimate the excess risk from occupational noise exposure. The
researchers added the noise-induced permanent threshold shift component
to the control data. Noise-induced permanent threshold shift (NIPTS) is
the actual shift in hearing level only due to noise exposure after
corrections.
As expected, the three tables produce different results, reflecting
that, for any given population, the excess risk for material impairment
will be greater using the AAO-HNS 1979 criteria than using the AAOO
1959. Likewise, the excess risk for material impairment will be greater
using the OSHA/NIOSH criteria than using the AAO-HNS 1979. All three
tables produce a smaller excess risk than did the data presented in
Table II-1.
Table II-3.--Risk of Impairment Using AAOO 1959 Definition of Impairment
Using Melnick, et al., 1980 Data
------------------------------------------------------------------------
Excess risk
Percent (%) with
Exposure with noise
impairment exposure
------------------------------------------------------------------------
Non-noise..................................... 26.8 0.0
80 dBA........................................ 26.8 0.0
85 dBA........................................ 27.8 1.0
90 dBA........................................ 31.4 4.6
------------------------------------------------------------------------
Table II-4.--Risk of Impairment Using AAO-HNS 1979 Definition of
Impairment Using Melnick, et al., 1980 Data
------------------------------------------------------------------------
Excess risk
Percent (%) with
Exposure with noise
impairment exposure
------------------------------------------------------------------------
Non-noise..................................... 41.6 0.0
80 dBA........................................ 41.8 0.2
85 dBA........................................ 44.4 2.8
90 dBA........................................ 50.0 8.4
------------------------------------------------------------------------
Table II-5.--Risk of Impairment Using OSHA/NIOSH Definition of
Impairment Using Melnick, et al., 1980 Data
------------------------------------------------------------------------
Excess risk
Percent (%) with
Exposure with noise
impairment exposure
------------------------------------------------------------------------
Non-noise..................................... 48.5 0.0
80 dBA........................................ 48.7 0.2
85 dBA........................................ 51.5 3.0
90 dBA........................................ 57.9 9.4
------------------------------------------------------------------------
Tables II-6 and II-7 present data derived by Melnick in Forensic
Audiology (1982) for damage risk due to noise exposure. These tables
use the AAO-HNS 1979 criteria. In these tables, the population is 60
years old with 40 years of exposure to the specified sound levels. In
both tables, the data represent NIPTS (noise induced permanent
threshold shift) calculated by Johnson, but the screening used in the
two tables is different. Melnick's data in Table II-6 is based upon the
screened presbycusis data (i.e. screened for non-occupational hearing
loss) of Robinson and Passchier-Vermeer, whereas Table II-7 is based on
unscreened non-occupational hearing loss data from the 1960-62 U.S.
Public Health Survey.
Overall, the excess risk information presented in these tables is
closer to that in Table II-1 than to that in Tables II-3, II-4, and II-
5, but still different. Tables II-6 and II-7 directly illustrate the
effect of screening populations in determining excess risk due to
occupational noise exposure. As seen in these tables, the percent with
impairment is greater in the table constructed with an unscreened
population as the base.
Table II-6.--Risk of Impairment Using Presbycusis Data of Passchier-
Vermeer and Robinson
------------------------------------------------------------------------
Excess risk
Percent (%) with
Exposure with noise
impairment exposure
------------------------------------------------------------------------
75 dBA........................................ 3 0
80 dBA........................................ 5 2
85 dBA........................................ 9 6
90 dBA........................................ 21 18
------------------------------------------------------------------------
Table II-7.--Risk of Impairment Using Non-occupational Hearing Loss Data
of Public Health Survey
------------------------------------------------------------------------
Excess risk
Percent (%) with
Exposure with noise
Impairment exposure
------------------------------------------------------------------------
75 dBA........................................ 27 0
80 dBA........................................ 29 2
85 dBA........................................ 33 6
90 dBA........................................ 40 13
------------------------------------------------------------------------
Chart ER1 displays the results of the various models. It should be
noted that both the P/V/Robinson (data from Table II-6) and the PHS
model (data from Table II-7) used the AAO-HNS 1979 criteria.
As noted in the History section of this preamble, the Agency is
aware that NIOSH is currently working on revising its estimates using a
different model and taking hearing loss at an additional frequency into
account; but until such an approach is peer reviewed and finalized,
MSHA has concluded it should not be considered here.
As illustrated by Chart ER1, the exact numbers of those at risk
varies with the study--because of the definition of material impairment
used, and because of the selection and threshold of the control group.
Notwithstanding these differences, the data consistently demonstrate
three points: (1) the excess risk increases as noise exposure
increases; (2) there is a significant risk of material impairment of
hearing loss for workers exposed over their working lifetimes to
average sound levels of 85 dBA; and (3) lowering the exposure from
average sound levels of 90 dBA to average sound levels of 85 dBA
reduces the excess risk of developing a material impairment by
approximately half.
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Related Studies of Worker Hearing Loss
There is a large body of data on the effects of varying industrial
sound levels on worker hearing. Some of these studies specifically
address the mining industry; moreover, MSHA has determined that
regardless of the industry in which the data were collected, exposures
to similar sound levels will result in similar degrees of material
impairment in the workers. These studies are supportive of the
conclusions reached in the previous section about noise risks at
different sound levels.
OSHA's 1981 preamble to its Hearing Conservation Amendment referred
to studies conducted by Baughn, Burns and Robinson, Martin, et al., and
Berger et al.
Baughn (1973) studied the effects of average noise exposures of 78
dBA, 86 dBA, and 90 dBA on 6,835 industrial workers employed in
Midwestern plants producing automobile parts. Noise exposures for these
workers were measured for 14 years and, through interviews, exposure
histories were estimated as far back as 40 years. The control and the
noise-exposed groups were not screened for anatomical abnormalities of
the ear.
Baughn used his data to provide estimates of the hearing levels of
workers exposed to 80 dBA, 85 dBA, and 92 dBA and extrapolated the
exposures up to 115 dBA. Based upon the analysis, the researcher
constructed an idealized graph which illustrated that 43% of 58-year
old workers exposed for 40 years to noise at 85 dBA would meet the AAOO
1959 criteria for hearing impairment. However, 33% of an identical non-
noise exposed population would be expected to meet the same impairment
criteria. The excess risk from exposure to noise at 85 dBA, therefore,
would be 10%. Using the same procedure, the excess risk for 80 dBA is
0% and for 90 dBA it is 19%.
Burns and Robinson (1970) studied the effects of noise on 759
British factory workers exposed to average sound levels between 75 dB
and 120 dB with durations ranging between one month and 50 years. The
control group consisted of 97 non-noise exposed workers. Thorough
screening removed the workers with exposure histories which were not
readily quantifiable, exposure to gunfire, ear disease or abnormality,
and language difficulty.
For this study, Burns and Robinson analyzed 4,000 audiograms and
found that the hearing levels of workers exposed to low sound levels
for long periods of time were equivalent to other workers exposed to
higher sound levels for shorter durations. From the data, the
researchers developed a mathematical model that predicts hearing loss
between 500 Hz and 6000 Hz in certain segments of the exposed
population. Using Burns and Robinson's mathematical model, MSHA
constructed Chart ER2. The chart shows that a noise exposure of 85 dBA
over a 40-year career is clearly hazardous to the hearing acuity of 60-
year-old workers.
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Martin et al. (1975) studied the prevalence of hearing loss in a
group of 228 Canadian steel workers, ranging in age from 18 to 65 years
of age, by comparing them to a control group of 143 office workers. The
researchers reported that the risk of hearing impairment (average of 25
dB at 500, 1000, and 2000 Hz) increases significantly between 85 dBA
and 90 dBA. Up to 22% of the population would be at risk of incurring a
hearing impairment with a 90 dBA PEL compared to 4% with an 85 dBA PEL.
Both the noise exposed and the control groups were screened to exclude
those workers with non-occupational hearing loss.
Berger, Royster, and Thomas (1978) studied 42 male and 58 female
workers employed at an industrial facility. The study included a
control group of 222 persons that was not exposed to occupational
noise. Of the 322 individuals included in the study, no one was
screened for exposures to non-occupational noise from past military
service, farming, hunting, or shop work, since these exposures were
common to all. The researchers found that exposure to a daily steady-
state Leq of 89 dBA for 10 years caused a measurable hearing loss
at 4000 Hz. According to the researchers, the measurable loss was in
close agreement with the predictions of Burns and Robinson, Baughn,
NIOSH, and Passchier-Vermeer.
Passchier-Vermeer (1974) reviewed the results of eight field
investigations on hearing loss among 20 groups of workers. About 4,600
people were included in the analysis. The researcher concluded that the
limit of permissible noise exposure (defined as the maximum level which
did not cause measurable noise-induced hearing loss, regardless of
years of exposure) was shown to be 80 dBA. Furthermore, the researcher
found that noise exposures above 90 dBA caused considerable hearing
loss in a large percentage of employees and therefore, recommended that
noise control measures be instituted at this level. The researcher also
recommended that audiometric testing be implemented when the noise
exposure exceeds 80 dBA.
NIOSH (Lempert and Henderson, 1973) published a report in which the
dose-response relationship for noise-induced hearing loss was
described. NIOSH studied 792 industrial workers whose average daily
noise exposures were 85 dBA, 90 dBA, and 95 dBA. The noise-exposed
workers were compared to a group of controls whose noise exposures were
lower than 80 dBA. The subjects ranged in age from 17 to 65 years old.
The exposures were primarily to steady-state noise but the exposure
levels fluctuated slightly in each category. Both the noise-exposed and
control groups were screened to exclude those exposed to gunfire as
well as those who showed some sign of ear disease or audiometric
abnormality. The report clearly shows that workers whose noise
exposures were 85 dBA experienced more hearing loss than the controls.
As the noise exposures increased to 90 dBA and 95 dBA, the magnitude of
the hearing loss increased.
NIOSH (1976) published the results from a study on the effects of
prolonged exposure to noise on the hearing acuity of 1,349 coal miners.
From this study, NIOSH concluded that coal miners were losing their
hearing acuity at a faster rate than would be expected from the
measured environmental sound levels. While the majority of noise
exposures were less than a TWA8 of 90 dBA, the measured hearing
loss of the older coal miners was indicative of noise exposures between
90 dBA and 95 dBA. Only 12% of the noise exposures exceeded a TWA8
of 90 dBA. NIOSH, however, offered as a possible explanation that some
miners are exposed to ``very intense noise'' for a sufficient number of
months to cause the hearing loss.
Coal miners in the NIOSH (1976) study had a greater percent of
impairment than the non-occupational exposed group (control group) at
each age level. Using OSHA/NIOSH definition of impairment, 70% of 60-
year-old coal miners were impaired while only a third of the control
group were impaired. This would correspond to an excess risk of 37%.
NIOSH also sponsored a study, conducted by Hopkinson (1981), on the
prevalence of middle ear disorders in coal miners. As part of this
study, the hearing acuity of 350 underground coal miners was measured.
The results of this study corroborated the results of the earlier NIOSH
study on the hearing acuity of underground coal miners. In both studies
the measured median hearing levels of the miners were the same.
However, the study did not present statistics on the percent of miners
incurring a hearing impairment nor the job classification of the
miners.
Studies of Harm at Lower Sound Levels
As our knowledge about the effects of noise increases, there is
increased need
[[Page 66377]]
to examine data that focuses on the harm that can occur at lower sound
levels. This section reviews some of the studies, particularly those of
workers from other countries, available in this regard.
The most recent data are derived using the International Standards
Organization's publication ISO 1999 (1990). The information in that
publication can be used to calculate the mean and various percentages
of a population's hearing levels. The noise exposures for the
population can range between 75 dBA and 100 dBA. Table II-8 presents
the hearing level of a 60-year-old male exposed to noise for 40 years.
The noise induced hearing permanent threshold shift was combined with
presbycusis values to determine the total hearing loss. The presbycusis
values were those from an unscreened population. The unscreened
population is believed to more accurately represent the mining
population since people with nonoccupational hearing loss would not be
excluded from becoming miners.
Table II-8.--Hearing Level for Selected Noise Exposures
------------------------------------------------------------------------
Hearing level in dB
-------------------------------
Sound Level in dBA 500 1000 2000 3000
Hz Hz Hz Hz
------------------------------------------------------------------------
80...................................... 12 6 10 30
85...................................... 12 6 11 33
90...................................... 12 6 16 42
------------------------------------------------------------------------
Information about the effects on hearing of lower noise exposures
can be particularly valuable in directing attention to the possibility
of identifying subpopulations particularly sensitive to noise. The
Committee on Hearing, Bioacoustics, and Biomechanics of the National
Research Council (CHABA) (1993) reviewed the scientific literature on
hazardous exposure to noise. The report, reaffirming many of the
earlier findings of the Committee, suggests that exposures below 76 dBA
to 78 dBA are needed to prevent a NIHL based upon temporary threshold
shift (TTS) studies; moreover, the report suggests that the sound level
be less than 85 dBA, and possibly less than 80 dBA, to guard against
any permanent hearing loss at 4000 Hz based upon field studies. But of
particular interest is the suggestion that therapeutic drugs, such as
aminoglycoside antibiotics and salicylates, can interact
synergistically with noise to yield more hearing loss than would be
expected by either stressor. Given the increasing use of salicylates
(aspirin) in heart maintenance regimens, the potential synergistic
effect may warrant further study.
Few current studies of unprotected U.S. workers exposed to a
TWA8 between 85 and 90 dBA are available because the OSHA hearing
conservation standard requires some protection at those levels for most
industries. The difficulty in constructing new retrospective studies of
U.S. workers has been noted by Kryter (1984) in his chapter on Noise-
Induced Hearing Loss and Its Prediction. He believes that the
retrospective studies of Baughn, Burns and Robinson, and the U.S.
Public Health Service are the best available on the subject of NIPTS.
Regarding current retrospective studies he states:
Furthermore, imposition of noise control and hearing
conservation programs in many industries in many countries over the
past 10 years or so make somewhat remote the possibility of
performing a meaningful retrospective study of the effects in
industry of noise on the unprotected ear.
Kryter included a formula for deriving the effective noise exposure
level for damage to hearing. This was used to determine, from a
population of workers, NIPTS at different percentiles of sensitivity at
various audiometric test frequencies.
Studies of workers from other countries can provide information of
particular value in assessing the consequences of workplace noise
exposure between 85 dBA and 90 dBA. MSHA has determined that while
differences in socioeconomic factors (e.g., recreational noise
exposure, use of ototoxic medicines, otitis media) make it difficult to
directly apply the results of studies of workers from other countries
to quantify the risk for U.S. workers, they can be used to establish
the existence of a risk in the 80 to 90 dBA range.
Rop, Raber, and Fischer (1979) studied the hearing loss of 35,212
male and female workers in several Austrian industries, including
mining and quarrying. The researchers measured the hearing levels of
workers exposed to sound levels ranging from less than 80 dBA up to 115
dBA, and arranged them into eight study groups based upon average
exposures. They assumed that exposure to sound levels less than 80 dBA
did not cause any hearing loss and workers exposed to these levels were
assigned to the control group.
Rop et al. reported that workers with 6 to 15 years of exposure at
85 dBA had significantly worse hearing than the control group. For the
five groups exposed between 80 dBA and 103.5 dBA, hearing loss tended
to increase steadily during their careers, but leveled off after 15
years. However, for workers exposed to sound levels above 103.5 dBA,
hearing loss continued to increase beyond 15 years.
Using the data collected during the study, Rop et al. developed a
statistical method for predicting hearing loss. The researchers
predicted that 20.1% of the 55-year old males in the control group with
15 years of work experience would incur hearing loss. For a comparable
group of males with exposures at 85 dBA the risk increased to 41.6%; at
92 dBA the risk increased to 43.6%; and at 106.5 dBA the risk increased
to 72.3%. Rop et al. concluded that exposure to sound levels at or
above 85 dBA damaged workers' hearing.
Schwetz et al. (1980) reported on a study of 25,000 Austrian
workers. The study concluded that the workers exposed to sound levels
between 85 dBA and 88 dBA experienced greater hearing loss than workers
exposed to sound levels less than 85 dBA. Because of this, Schwetz
recommended 85 dBA as the critical intensity (i.e., PEL). Furthermore,
the study concluded that a lack of hearing recovery occurs at 85 dBA
which is the ultimate cause of noise-induced hearing loss (NIHL).
Stekelenburg (1982) calculated the hearing loss due to presbycusis
according to Spoor and due to noise according to Passchier-Vermeer.
Based upon these calculations, Stekelenburg suggested that 80 dBA be
the acceptable level for noise exposure over a 40 year work history. At
this exposure, Stekelenburg calculates that impaired social hearing due
to noise would be expected in 10% of the population.
Bartsch et al. (1989) studied 537 textile workers. These
researchers defined hearing loss of social importance as a 40 dB
hearing level at 3000 Hz. The researchers found that hearing loss
resulting from exposures below 90 dBA mainly occurs at frequencies
above 8000 Hz (these frequencies are not normally tested during
conventional audiometry), and so concluded that this hearing loss was
not of ``social importance.'' Nevertheless, they recommended a hearing
loss risk criterion of 85 dBA be used to protect the workers' hearing.
These results are generally consistent with those of U.S. workers.
MSHA would, however, note its disagreement with the characterization of
the amount of hearing loss not being of ``social importance'' as
expressed in the Bartsch et. al (1989) study. The Agency has concluded
that a person will encounter hearing difficulty before their hearing
level reaches 40 dB at 3000 Hz. Studies, discussed earlier in
Definition of Material Impairment, address the importance of having
good hearing
[[Page 66378]]
acuity at 3000 Hz in order to adequately understand speech in everyday
noisy environments.
Reported Hearing Loss Among Miners
To confirm the magnitude of the risks of NIHL among miners, MSHA
examined evidence of reported hearing loss among miners--audiometric
data collected over the years tracking hearing acuity among miners, the
comments received in response to the Agency's ANPRM, reports of hearing
loss by mine operators pursuant to 30 CFR part 50, and workers'
compensation data. Such data could provide a quantitative determination
of material impairment.
With respect to audiometric data, MSHA asked NIOSH to examine a set
of data on coal miners. The analysis (Franks, 1996) supports the data
from scientific studies. It indicates that 90% of these coal miners
have a hearing impairment by age 50 as compared with only 10% of the
general population. Further, Franks stated that miners, after working
20 to 30 years, could find themselves in life threatening situations
since safety signals and ``roof talk'' could go unheard. (For the
purposes of the analysis, NIOSH used the definition of hearing
impairment it is now considering, an average 25 dB hearing level at
1000, 2000, 3000, and 4000 Hz; MSHA conducted its own analysis of the
data without the 4000 Hz, and the results are generally consistent with
those of NIOSH).
This section also reviews several other sources of data that might
provide direct information about the risks of hearing loss to miners:
the comments received in response to the Agency's ANPRM, the reports of
hearing loss provided to the Agency by mine operators pursuant to 30
CFR part 50, and workers' compensation data. In each case, the
available data are too limited to draw any conclusions. The Agency is
requesting the public to provide further information along these lines.
Audiometric Data Bases
Audiometric testing is not currently required in metal and nonmetal
mining and is only required when an overexposure to noise is determined
in coal mining. Certain mining companies conduct routine audiometric
testing on their employees, but the results of these tests are
confidential and are not published for public use. In addition, summary
reports of these audiometric tests are generally not available.
MSHA, however, has obtained an audiometric data base consisting of
20,021 audiograms conducted on 3,433 individual coal miners, in
connection with its ongoing efforts to assess the effectiveness of the
current standards in protecting miner health. The audiometric
evaluations were conducted between 1971 and 1994 with the bulk of the
audiograms conducted during the latter years.
NIOSH (Franks, 1996) has analyzed this data base. Each audiogram
was reviewed for validity and NIOSH audiologists directly reviewed more
than 2,500 audiograms. The review reduced the number of audiograms by
8.8% and the number of miners by 8.3%.
After deleting those audiograms judged to be invalid, NIOSH's
analysis indicates that 90% of these miners have a hearing impairment
by age 50 as compared with only 10% of the general population. Even at
age 69, only 50% of the non-noise exposed population acquire a hearing
impairment. Franks defined material impairment as an average 25 dB
hearing level at 1000, 2000, 3000, and 4000 Hz. This definition differs
from the MSHA definition of hearing impairment by the inclusion of 4000
Hz in the average.
By age 35 the average miner has a mild hearing loss and 20% have a
moderate loss. By contrast, fewer than 20% of the miners having
marginally normal hearing by age 64 while the upper 80% have moderate
to profound hearing loss. The lower 80% of the non-noise exposed
population will not acquire a hearing loss as severe as the one
obtained by the average miner regardless of how long they live.
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Further, Franks stated that miners, after working 20 to 30 years,
could find themselves in life threatening situations since safety
signal and roof talk could go unheard.
MSHA separately conducted an elementary analysis of the data, using
the definition of material impairment of hearing used throughout the
analyses in this preamble: an average 25 dB hearing level at 1000, 2000
and 3000 Hz. For MSHA's analysis, all audiograms were considered to be
valid (e.g., no contamination from temporary threshold shifts, sinus
conditions, etc.). Information on years of mining experience, noise
exposure, use of hearing protectors, and job function was not provided.
In order to reflect current trends, the percentage of current coal
miners with a material impairment of hearing was compared to historical
data (NIOSH's study on coal miners published in 1976). The audiometric
data were placed into a compatible format, e.g., age and hearing loss
criteria. Only those coal miners (2,861) whose latest audiogram was
taken between 1990 and 1994 were included in the analysis. The results
are shown in Chart R1 along with NIOSH's 1976 results for both the
noise exposed miners and the non-noise exposed controls.
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The data points for chart R1 are the mean of both ears at 1000, 2000
and 3000 Hz. The top line connects data points from the 1976 group, and
the middle line connects points from the 1990-1994 group; the bottom
line represents the non-noise exposed group.
As shown in Chart R1, it is obvious that many coal miners who had
audiograms taken from 1990 through 1994 have a material impairment of
hearing. These miners were still losing more of their hearing acuity
than non-noise exposed workers. This remains true even if the analysis
is limited to miners less than 40 years of age (i.e., those who have
worked only under the current coal noise regulations). The fact that
the loss is at a slower rate than shown in the 1976 data may indicate
some progress under the existing regulations compared with no
regulation.
Furthermore, MSHA analyzed the data for the number of standard
threshold shifts (STS's) and reportable hearing loss cases in order to
estimate the number of such events that may occur if the proposal is
adopted. In the proposal, MSHA defines an ``STS'' as a change in
hearing threshold level relative to the miner's original or
supplemental baseline audiogram of an average of 10 dB or more at 2000,
3000, and 4000 Hz in either ear. The importance of an STS is that it
reveals that a permanent loss in hearing acuity has occurred relative
to that miner's baseline. This is the type of loss that is deserving of
mine operator intervention. When the change from the baseline averages
25 dB or more at the same frequencies, the hearing loss must be
reported to MSHA so that the Agency can intervene if necessary. (MSHA
discusses the definition of STS and reportable hearing loss in detail
in the sections of this preamble dealing with proposed Secs. 62.160 and
62.190.) In both cases, the data differ from that in Chart R1, which is
looking at the hearing loss relative to audiometric zero--not the
individual miner's baseline.
For a second analysis, the first audiogram was assumed to be the
baseline. The last audiogram was compared to the baseline. Neither
audiogram was corrected for presbycusis. Also, because of the lack of
supporting data, no provision for excluding an STS as being non-
occupational was possible. A total of 3,102 coal miners had a baseline
and at least a second audiogram. However, only those miners whose
latest audiogram was conducted between 1990 and 1994 were considered.
The results are presented in Chart R2.
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Chart R2 clearly shows that many of the coal miners from 1990
through 1994 were found to have an STS. The likelihood of acquiring an
STS generally increases with advancing age. The MSHA analysis was
conducted in a conservative fashion. Because the intervening audiograms
were excluded from this analysis, the number of STSs is probably low
since only a single STS was recorded. There could be several
explanations for the drop in the percentage of STS's for the 65 year
old age group in chart R2, including, for example, changed work
assignments.
In addition to this privately maintained audiological data, there
have been two special NIOSH studies of the hearing acuity of coal
miners. These studies were reviewed in detail in the Risk of Impairment
section, above. The first study was published in 1976. Even though the
majority of noise exposures were found to be less than 90 dBA,
approximately 70% of the 60-year-old coal miners had a material
impairment of hearing using the OSHA/NIOSH definition. Another NIOSH
study, conducted by Hopkinson (1981), corroborated the results of the
earlier NIOSH study on the hearing acuity of coal miners.
Commenter Data
In its ANPRM, MSHA solicited comments on the number of current
miners with a hearing loss based on suggested criteria. Two commenters
provided information on the hearing acuity of miners. The first
commenter estimated that 45 to 50% of the employed miners have an STS
and at least 25% have an STS if corrected for presbycusis. Further,
this commenter estimated that about 25% of the miners have an average
hearing loss of 25 dB or more at 1000, 2000, and 3000 Hz. However, when
corrected for presbycusis, the percentage of miners with this level of
hearing loss decreased to about 15%.
The second commenter referenced a paper presented by Smith et al.
at the 1989 Alabama Governor's Safety and Health Conference. This
commenter stated that Smith et al. reported on the evaluation of serial
audiograms from 100 workers exposed to sound levels less than 85 dBA.
Smith et al. had found that 15% of these workers would have some degree
of hearing impairment using AAO-HNS 1979 impairment criteria. Smith et
al. also reported that at least 26% of the mining population would have
some degree of hearing impairment using the same criteria. Smith (1994)
confirmed the prevalence of material impairment among miners in a
letter to MSHA.
MSHA also requested information on hearing loss to individual
miners in its ANPRM. Specific information was requested on each miner
who had incurred a hearing loss, including the related noise exposure,
state workers' compensation award, cost of the award, miner's age,
occupation and degree of hearing loss. The Agency received few comments
pertaining to the information requested. The Agency requests additional
comment on these issues.
Reported Hearing Loss Data
Another potential body of information about hearing loss among
miners comes from reports mine operators are required to submit to MSHA
of such losses. At present, however, there is not a definition of
``reportable hearing loss'' linking what is reported to some particular
measurement. Rather, under 30 CFR part 50, mine operators are only
required to report cases of NIHL to MSHA when it is diagnosed by a
physician or when the miner receives an award of compensation.
Nevertheless, between 1985 and 1995 mine operators reported a total
of 2,402 cases of NIHL--and among these cases were a substantial number
of miners who began working at a mine after the implementation of the
current noise regulations.
Coal mine operators reported 608 cases among surface miners, 1,077
cases among underground miners, and 14 cases among miners whose work
positions were not identified. According to coal mine operators, 662 of
the 1,699 cases began working at a mine after the implementation of
noise regulations for coal mines (1972 for underground and 1973 for
surface). Workers with no reported mining experience were excluded from
this analysis, because their noise exposure history in mining was
unknown.
For the same period, metal and nonmetal mine operators reported 555
cases among surface miners and 148 cases among underground miners.
According to mine operators, 142 of the 703 cases began working at a
mine after the implementation of noise regulations for metal and
nonmetal mines (1975). As with the coal data, workers with no reported
mining experience were excluded.
[[Page 66381]]
Comparing the two types of mining, there were significantly more
reported hearing loss cases at coal mines than at metal and nonmetal
mines, and a higher proportion of those cases were to workers who began
working after the implementation of the current standards. This is
despite the fact that, at the present time, there are more metal and
nonmetal miners than coal miners employed in the U.S. A possible
explanation of the differences between reported cases of NIHL among
coal, metal and nonmetal miners may be the more frequent use of
engineering noise controls in metal and nonmetal mining.
MSHA reviewed the narrative associated with each NIHL case to
determine the degree of hearing loss. Although many narratives
contained information as to the reason for reporting the NIHL case,
others only listed the illness as ``hearing loss.'' Approximately half
the cases had no information on the severity of the hearing loss. Some
narratives contained information on the severity of the hearing loss,
such as an STS, OSHA reportable case, or percent disability. Based upon
the information in the narratives it is not possible to determine an
average severity for the NIHL cases.
However, at least 40% of the cases in coal mining were reported to
MSHA as the result of the miner being compensated for NIHL. Another 7%
of the cases filed a workers' compensation claim for NIHL. In metal and
nonmetal, at least 19% of the cases were the result of the miner being
compensated for NIHL. Nearly another 3% of the cases filed a workers'
compensation claim for NIHL.
MSHA contends that the number of cases reported to the Agency are
low because of the following factors: the lack of a specific definition
of a NIHL in MSHA's part 50 regulations which may result in confusion
on the part of mine operators about which cases to report; the lack of
consistency among the states' requirements for awarding compensation
for an NIHL and among physicians in diagnosing what constitutes a
hearing loss caused by noise; and the lack of periodic audiometric
testing in the mining industry.
In summary, current hearing loss reported to MSHA under part 50
cannot be used to accurately characterize the incidence, prevalence or
the severity of hearing loss in the mining industry. However, the part
50 data clearly show that miners are incurring NIHL.
Workers' Compensation Data
Another source of information about hearing loss among miners is
state workers' compensation agencies and insurance carriers. Many
states do not keep detailed workers' compensation data themselves;
categorization of data are inconsistent across the states; and there
are privacy concerns in obtaining the detailed information needed for
studies. MSHA would welcome information about studies of hearing loss
that have been performed by the insurance industry or others based on
this data.
Valoski (1994) studied the number of miners receiving workers'
compensation and the associated indemnity costs of those awards.
Despite contacting each state workers' compensation Agency and using
two national data bases, he was unable to obtain data for all states.
In fact, data were not available from a number of key mining states.
From the data that were available for study, Valoski reported that
between 1981 and 1985 at least 2,102 coal miners and 312 metal and
nonmetal miners were awarded compensation for occupational hearing
loss. The identified total indemnity costs of those awards exceeded
12.5 million dollars excluding rehabilitation or medical costs.
In Niemeier's letter to MSHA, Chan et al. of NIOSH (1995)
investigated the incidence of NIHL among miners using information from
the Bureau of Labor Statistics' (BLS) Supplementary Data System. Like
Valoski, he found the national data to be incomplete. Only 15 states
participated in the BLS program between 1984 and 1988. In these 15
states, a total of 217 miners (93 coal miners and 124 metal and
nonmetal miners) were awarded workers' compensation for NIHL. Chan et
al. stated that because of differing state workers' compensation
requirements, it is not possible to directly compare NIHL among the
states. These factors limit the usefulness of the obtained data.
MSHA also reviewed reports on workers' compensation in Canada and
Australia. The noise regulations and mining equipment used in these
countries are similar to those in the U.S. A recent report on workers'
compensation awards to miners in Ontario, Canada (1991) revealed that
between 1985 and 1989, NIHL was the second leading compensable
occupational disease. Approximately 250 claims for NIHL involving
miners were awarded annually during that time.
Lescouflair et al. (1980) studied 278 metal and asbestos miners in
Quebec, Canada, who claimed compensation for hearing loss. Of the 278
cases, 28.7% (80) were excluded as cases of non-mining NIHL.
Approximately 50% (99) of those remaining cases diagnosed as having
NIHL were shown to have a hearing impairment based upon the AAOO 1959
criteria and an estimated 63% (125) showed an impairment based upon
AAO-HNS 1979 criteria. The miners were exposed to noise for 15 to 49
years and showed a similar occurrence of hearing loss in both surface
and underground occupations. The researchers also reported that there
was no significant difference in NIHL among the miners for those
subjects exposed to a mixture of intermittent-continuous noise versus
intermittent noise except at 2000 Hz.
Eden (1993) reported on the Australian mining industry's experience
with hearing conservation. Eden quoted statistics from the Joint Coal
Board which revealed that NIHL comprised 59% to 80% of the reported
occupational diseases from 1982 to 1992. Eden also reported that in New
South Wales 474 of 16,789 coal miners were awarded compensation for
NIHL. The incidence rate for the total mining industry in New South
Wales was about 23 cases per 1,000 workers during 1990-1991. This was
the highest rate for any industry in New South Wales.
In conclusion, like reported cases of NIHL, the compensation data
are too incomplete to be used for quantitative estimates of the
prevalence of NIHL in the mining industry. But like the reported case
data, the compensation data that are available do show that numerous
cases are still being filed each year at considerable cost. Further,
according to the data reported by mine operators, many miners who
developed NIHL only worked in mining after the implementation of the
current noise regulations. While limited, this evidence of continued
risk supplements and supports the data previously presented from
scientific studies.
The Agency would welcome the submission of additional data to
supplement that which it has been able to gather to date.
Exposures in the U.S. Mining Industry
In this section MSHA presents information on noise exposure in the
U.S. mining industry, so as to develop a picture of the mining
population at a significant risk of incurring material impairment as a
result of that exposure. The exposure levels are particularly high in
the coal industry, where hearing protectors, rather than engineering or
administrative controls, remain the primary means of miner protection
against NIHL. But the data indicate that exposure levels remain high in
all sectors of the mining industry even
[[Page 66382]]
though noise regulations have been implemented for some time.
Inspection Data
The first presentation, Tables II-9 and II-10, reviews noise
exposure data collected by MSHA inspectors from thousands of samples
gathered over many years to check compliance with the current permitted
levels. Because the proposed rule would alter the way a miner's noise
dose is calculated in one respect, MSHA conducted a special survey to
obtain data that would reflect this change. The data are presented in
Tables II-11 and II-12. The survey data are also presented by
occupation in Tables II-13 and II-14. All the readings are in time-
weighted 8-hour averages.
Tables II-9 and II-10 display samples which present readings
exceeding the permissible exposure limit, a TWA8 of 90 dBA.
Table II-9 shows noise dose trends in metal and nonmetal mines
based on over 232,500 full-shift samples collected by MSHA from 1974
through 1995 using personal noise dosimeters.
Table II-9.--Metal and Nonmetal Noise Dose Trends 1974 to 1995 a
------------------------------------------------------------------------
Percent
Number of Number of of
Year samples samples > samples >
90 dBA 90 dBA
------------------------------------------------------------------------
1974................................... 363 139 38.3
1975................................... 3,826 1,661 43.4
1976................................... 9,164 3,725 40.6
1977................................... 13,485 5,047 37.4
1978................................... 17,326 6,415 37.0
1979................................... 21,176 7,638 36.1
1980................................... 15,185 5,203 34.3
1981................................... 11,278 3,651 32.4
1982................................... 3,208 876 27.3
1983................................... 7,628 2,188 28.7
1984................................... 8,525 2,311 27.1
1985................................... 8,040 2,094 26.0
1986................................... 9,213 2,402 26.1
1987................................... 10,145 2,818 27.8
1988................................... 10,514 2,417 23.0
1989................................... 10,279 2,208 21.5
1990................................... 13,067 2,721 20.8
1991................................... 14,936 2,947 19.7
1992................................... 14,622 2,809 19.2
1993................................... 14,566 2,529 17.4
1994................................... 15,979 2,627 16.4
1995................................... 13,865 1,989 14.4
------------------------------------------------------------------------
a Data from USBOM' MIDAS data base.
Table II-10 below presents noise dose trends in coal mines based on
75,691 full-shift samples collected by MSHA from 1986 through 1995
using personal noise dosimeters. MSHA actually began routine sampling
in coal mines in 1978; however, its data base did not begin until 1986.
Table II-10.--Coal Mine Noise Dose Trends, Fiscal Years 1986 to 1995
------------------------------------------------------------------------
Percent
Number of Number of of
Fiscal year samples samples samples
>90 dBA >90 dBA
------------------------------------------------------------------------
1986................................... 2,037 593 29.1
1987................................... 12,774 3,314 25.9
1988................................... 11,888 2,702 22.7
1989................................... 11,035 2,313 21.0
1990................................... 10,861 2,388 22.0
1991................................... 6,898 1,635 23.7
1992................................... 6,636 1,660 25.0
1993................................... 7,223 1,908 26.4
1994................................... 6,339 1,656 26.1
1995................................... 5,407 1,219 22.5
------------------------------------------------------------------------
The inspection data for the two sectors have also been graphed in
charts II-9 and II-10 for years in which MSHA collected data for both
sectors.
As illustrated by the charts, the metal and nonmetal sector shows a
gradual, but consistent, downward trend in the percent of samples
exceeding the current PEL. However, there was no such clear trend for
coal mines during the same time period. (It should be noted that while
the data points on these 3-D graphs come from the last column of the
tables, the shading may make them seem somewhat lower than they are in
fact.)
BILLING CODE 4510-43-P
[[Page 66383]]
[GRAPHIC] [TIFF OMITTED] TP17DE96.007
BILLING CODE 4510-43-C
[[Page 66384]]
There are several factors which must be considered when drawing any
conclusions from the data. MSHA sampling may be biased towards noisier
mines and occupations. Additionally, when an overexposure is found
during an initial survey, the data base includes both the initial
overexposure and the results of any resampling to determine compliance
after the mine operator has utilized engineering and/or administrative
controls. While these biases may tend to offset each other, their
specific impact cannot be quantified. These factors should, however,
impact both sectors roughly equally.
Dual Survey Data
MSHA has concluded that the information contained in Tables II-9
and II-10 understates the actual noise exposures in the industry
because the information was collected using a 90 dBA threshold level,
i.e. sound levels of less than 90 dBA are not integrated into the
results. As discussed later in part III of the preamble, in connection
with proposed Sec. 62.120(a), MSHA is proposing to change the threshold
level to integrate sound levels of between 80 dBA and 130 dBA because
MSHA has concluded that this is warranted by the weight of scientific
evidence. Integrating the sound levels between 80 dBA and 90 dBA into
the noise exposure will generally increase the measured noise dose. The
greater the amount of noise between 80 dBA and 90 dBA the greater the
impact on the measured noise dose.
Accordingly, MSHA conducted a special survey to compare noise
exposures at different threshold levels. The survey, referred to
hereinafter as the ``dual-threshold'' survey, involved the collection
of personal noise dosimeter data by MSHA inspectors in coal mines and
metal and nonmetal mines. Each sample was collected using a personal
noise dosimeter with the capability of simultaneously collecting data
at both a 90 dBA threshold and an 80 dBA threshold. All other dosimeter
settings were the same as those used during normal compliance
inspections (the 90 dB criterion level, 5-dB exchange rate, and A-
weighting system which are not now being proposed by MSHA for change).
The noise doses were mathematically converted to the appropriate
TWA8 using different criterion levels and threshold values.
Tables II-11 and II-12 display the dual-threshold data:
respectively in metal and nonmetal mines, and in coal mines. Table II-
11 specifically shows the dual-threshold data collected for metal and
nonmetal mines from March 1991 through December 1994 using personal
noise dosimeters. This data consisted of more than 42,000 full-shift
samples.
Table II-11.--M/NM Dual Threshold Samples at or Exceeding Specified TWA8 Sound Levels from March 1991 Through
December 1994
----------------------------------------------------------------------------------------------------------------
90 dBA thresholds 80 dBA threshold
---------------------------------------------------
TWA8 Sound Level (in dBA) Number of Percent of Number of Percent of
samples samples samples samples
----------------------------------------------------------------------------------------------------------------
90.......................................................... 7,360 17.4 11,150 26.5
85.......................................................... ........... ........... 28,250 66.9
----------------------------------------------------------------------------------------------------------------
Note: Two of the boxes in the table do not contain entries. This
is to avoid the potential for making an inappropriate comparison of
values. Direct comparison of TWA8 values determined with
different thresholds is not appropriate if the TWA8 is less
than one of the thresholds. An example may help to illustrate the
point. A miner exposed to a constant sound field of 85 dBA for 8
hours would be determined to have a noise dose of 0%, or a TWA8
of 0 dBA, if a 90 dBA threshold is used: none of the sound would be
counted in the computation. If the exposure was measured using an 80
dBA threshold, the dose would be 50%, or a TWA8 of 85 dBA.
Contrasting the measures taken with the two thresholds would be
inappropriate in such a case.
As indicated in Table II-11, 17.4% of all samples collected by MSHA
in metal and nonmetal mines during the specified time period equaled or
exceeded a TWA8 of 90 dBA using a 90 dBA threshold--slightly less
than the results of inspector sampling in Table II-9. In these
instances, engineering and/or administrative controls were required to
be implemented in the metal or nonmetal mines to reduce sound levels to
the PEL: a requirement that would be retained under the proposed rule.
When sound levels between 80 dBA and 90 dBA are taken into account,
however, 26.4% of the readings indicated non-compliance. Thus, changing
the threshold to properly reflect harmful sound levels indicates
harmful noise exposures in this industry are more significant than
revealed by the inspection data in Table II-9. Furthermore, 67% of the
samples in metal and nonmetal mines exceeded a TWA8 of 85 dBA
using an 80 dBA threshold.
MSHA dual-threshold sampling data for coal mines is presented in
Table II-12. This data consists of over 4,200 full-shift samples
collected from March 1991 through December 1995 using personal noise
dosimeters.
Table II-12.--MSHA Coal Dual Threshold Samples at or Exceeding Specified TWA8 Sound Levels from March 1991
Through December 1995
----------------------------------------------------------------------------------------------------------------
90 dBA threshold 80 dBA threshold
---------------------------------------------------
TWA8 Sound Level (in dBA) Number of Percent of Number of Percent of
samples samples samples samples
----------------------------------------------------------------------------------------------------------------
90.......................................................... 1,075 25.3 1,510 35.6
85.......................................................... ........... ........... 3,268 76.9
----------------------------------------------------------------------------------------------------------------
As indicated in Table II-12, 25.3% of all samples collected by MSHA
in coal mines during the specified time period equaled or exceeded a
TWA8 of 90 dBA using a 90 dBA threshold. This percentage increases
to 35.6% when an 80 dBA threshold is used. Furthermore, using an 80 dBA
threshold, almost 77% of the survey samples from the coal
[[Page 66385]]
industry showed noise exposures equaling or exceeding 85 dBA.
Tables II-13 and II-14 present some of the MSHA dual-threshold
sampling data by occupation for the most frequently sampled occupations
in metal and nonmetal mines and coal mines, respectively. A note of
caution: the only data presented in these tables is 90 threshold data
at a TWA8 of 90, and 80 threshold data at a TWA8 of 85.
Accordingly, the columns should not be compared. Perhaps the best way
to think of this presentation is as two independent analyses at how the
exposure levels of various job categories compare with each other.
Table II-13.--Percentage of MSHA M/NM Samples a by Selected Occupation,
Exceeding Specified TWA8 Sound Levels
------------------------------------------------------------------------
90 dBA 80 dBA
threshold Threshold
Number of -------------------------
Occupation samples Percent of Percent of
samples > samples >
90 dBA 85 dba
------------------------------------------------------------------------
Front-end-loader operator........ 12,812 12.9 67.7
Truck driver..................... 6,216 13.1 73.7
Crusher operator................. 5,357 19.9 65.1
Bulldozer operator............... 1,440 50.7 86.2
Bagger........................... 1,308 10.2 65.0
Sizing/washing plant operator.... 1,246 13.2 59.7
Dredge/barge attendant........... 1,124 27.2 78.7
Clean-up person.................. 927 19.3 71.3
Dry screen operator.............. 871 11.7 57.6
Utility worker................... 846 12.4 60.6
Mechanic......................... 761 3.8 43.9
Supervisors/administrators....... 730 9.0 32.2
Laborer.......................... 642 17.1 65.7
Dragline operator................ 583 34.0 82.5
Backhoe operator................. 546 8.4 52.6
Dryer/kiln operator.............. 517 10.5 55.5
Rotary drill operator (electric/
hydraulic)...................... 543 39.6 83.1
Rotary drill operator (pneumatic) 489 64.4 89.0
------------------------------------------------------------------------
a These occupations comprise about 87 percent of the 42,206 MSHA dual-
threshold samples collected in metal and nonmetal mines from March
1991 through December 1994. All samples were collected using a
personal noise dosimeter over a miner's full-shift.
Table II-14.--Percentage of MSHA Coal Samples by Occupation, Exceeding
Specified TWA8 Sound Levelsa
------------------------------------------------------------------------
90 dBA 80 dBA
threshold threshold
Number of -------------------------
Occupation samples Percent of Percent of
samples > samples >
90 dBA 85 dBA
------------------------------------------------------------------------
Continuous miner helper.......... 68 33.8 88.2
Continuous miner operator........ 262 49.6 96.2
Roof bolter operator (single).... 234 21.8 85.5
Roof bolter operator (twin)...... 92 31.5 98.9
shuttle car operator............. 260 13.5 78.5
Scoop car operator............... 94 18.1 74.5
Cutting machine operator......... 22 36.4 63.6
Headgate operator................ 20 40.0 100.0
Longwall operator................ 34 70.6 100.0
Jack setter (longwall)........... 25 32.0 68.0
Cleaning plant operator.......... 107 36.4 77.6
Bulldozer operator............... 225 48.9 94.2
Front-end-loader operator........ 244 16.0 76.6
Highwall drill operator.......... 83 21.7 77.1
Refuse/backfill truck driver..... 162 13.6 78.4
Coal truck driver................ 28 17.9 64.3
------------------------------------------------------------------------
a Above sampled occupations comprise about 71.0% of the 4,247 MSHA dual
threshold samples collected in coal mines from March 1991 to December
1995. All samples were collected using a personal noise dosimeter over
a miner's fullshift.
As shown in these tables, the percentage of miners exceeding the
specified sound levels varied greatly according to occupation. For
example, Table II-13 shows that only 8.4% of the backhoe operators in
metal and nonmetal mines had noise exposures exceeding a TWA8 of
90 dBA using a 90 dBA threshold, while 64.4% of the pneumatic rotary
drill operators had similar exposures. When reviewing the same two
occupations, 52.6% of the backhoe operators and 89.0% of the pneumatic
rotary drill operators would have noise exposures exceeding a TWA8
of 85 dBA using an 80 dBA threshold.
[[Page 66386]]
Conclusion; Miners at Significant Risk of Material Impairment
MSHA has prepared an exposure profile of miners based on the data
presented in this part; the methodology is summarized in the following
paragraphs and described in detail in the Agency's preliminary RIA.
Based on this profile, MSHA has concluded that despite many years under
existing standards, noise exposures in all sectors of mining continue
to pose a significant risk of material impairment to miners over a
working lifetime.
Specifically, MSHA estimates that 15% of coal miners will incur a
material impairment of hearing under present exposure conditions, or
18,947 coal miners. The figures are 13% of metal and non-metal miners
(26,977 metal and nonmetal miners) and 14% of miners as a group (45,924
miners). (The figures include contract miners but exclude certain
office workers.)
To derive this information, MSHA began with the 80 dBA exposure
data discussed in the prior section. The sampling data were sorted by
exposure range: e.g., samples with a TWA8 of between 80-84.9 dBA,
those between 85-89.9 dBA, those between 90-94.9 dBA, and so on.
The sampling data were then adjusted by subtracting 5 dBA from the
exposure readings for all samples that had a TWA8 of 90 dBA at the
90 threshold. These are the samples that would be above the current
PEL. MSHA assumed that mine operators currently issue personal HPDs to
miners exposed at or above the PEL, that miners are using the HPDs, and
that such protection reduces the miner's equivalent TWA8 noise
exposure by about 5 dBA. (There is an extended discussion in part III
of this preamble about hearing protector effectiveness, and appropriate
references, that shed further light on these assumptions.)
Then the percentage of adjusted samples within each range was
multiplied by MSHA's estimates of the total number of mine employees.
Those estimates are based on information gathered by the former USBOM
(and are presented in part IV of this preamble as part of the Agency's
industry profile).
Finally, to establish the number of miners expected to incur a
material impairment of hearing, the Agency multiplied the number of
miners in each exposure range by the risk of impairment of exposure at
that range for a lifetime. For this purpose, the Agency used the 1972
NIOSH risk estimates discussed earlier in this part. (The Agency is
aware that NIOSH is currently working on revising its estimates using a
different model and taking hearing loss at an additional frequency into
account; but until such an approach is peer reviewed, MSHA has
concluded it should rely upon the 1972 estimates.)
Based on these assumptions, Table II-15 presents MSHA's profile of
the projected number of miners currently at significant risk of
developing a material impairment of NIHL under existing exposure
conditions.
Table II-15.--Projected Number of Miners Likely To Incur NIHL Impairment under Existing Standards and Exposure Conditions
--------------------------------------------------------------------------------------------------------------------------------------------------------
<80 80-84.9 85-89.9 90-94.9 95-99.9 100-104.99 105 Total*
--------------------------------------------------------------------------------------------------------------------------------------------------------
Coal......................................... 0 599 11,956 5,622 643 111 16 18,947
M/NM......................................... 0 1,225 16,910 7,580 1,190 62 10 26,977
----------------------------------------------------------------------------------------------------------
Total *.................................. 0 1,825 28,866 13,201 1,833 173 26 45,924
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Includes contractor employees. Does not include office workers. Discrepancies are due to rounding.
When MSHA promulgated noise standards in 1971 for underground coal
mines, in 1972 for surface coal mines, and in 1974 for metal and
nonmetal mines, compliance with the requirements was thought to be
adequate to prevent the occurrence of NIHL in the mining industry.
Since that time, however, there have been numerous awards of
compensation for hearing loss among miners.
Moreover, MSHA's requirements are dated in light of the Agency's
experience, that of other domestic and foreign regulatory agencies, and
the recommendations of experts on what it takes to have an effective
prevention program. NIOSH, for example, currently recommends a
comprehensive program which includes the institution of an HCP to
prevent NIHL; MSHA's current standards do not include such protection.
In light of current scientific evidence demonstrating that NIHL
constitutes a serious hazard, the evidence of continuing harm to
miners, and the fact that MSHA standards no longer reflect experience
and expert advice, MSHA has concluded that there is a need to replace
its existing noise standards with new standards that would provide
additional protection to miners. Section 101(a)(6)(A) of the Federal
Mine Safety and Health Act of 1977 (Mine Act), states that MSHA's
promulgation of health standards must:
* * * [A]dequately assure on the basis of the best available
evidence that no miner will suffer material impairment of health or
functional capacity even if such miner has regular exposure to the
hazards dealt with by such standard for the period of his working
life.
Significant NIHL clearly is the type of material impairment of health,
which Congress has directed the Secretary of Labor (Secretary) to
prevent. MSHA has concluded that the new requirements in this proposal
are necessary to prevent large numbers of miners from suffering
material impairment of health resulting from exposure to noise.
Compliance will reduce NIHL among miners and the costs associated
therewith.
Based on these studies and MSHA's own calculations and analysis
presented above, the Agency has concluded that regulatory action is
necessary to address the continued excess risk of NIHL resulting from
mining employment.
III. Discussion of Proposed Rule
Summary
This part of the Supplementary Information reviews the provisions
of the proposed rule, along with the information, comments and
alternatives considered by MSHA in developing each feature of the
proposal.
While the Agency is seeking to present a complete picture of the
basis for its preliminary decisions, so as to facilitate comment, space
considerations preclude a full presentation of all of the sources
reviewed by the Agency. Part V is a complete reference list of those
sources. Among other things, part V contains a list of publications by
the former USBOM that were reviewed by the Agency. Many of these
describe methods for controlling noise for particular types of mining
equipment or facilities, and thus supplement the discussion in this
part about feasible engineering controls. All constitute part of the
Agency's rulemaking record.
[[Page 66387]]
In addition to the materials cited in part V, the Agency researched
the noise regulatory codes of a number of other jurisdictions--
including those of the military and of other countries. While these
codes are noted in this part in a few summary tables, and discussed in
connection with certain key requirements being proposed by the Agency,
the Agency has determined there is no need to elucidate their
requirements in each and every section of this part. Nevertheless,
these codes also constitute part of the Agency's rulemaking record.
Section 62.100 Purpose and Scope; Effective Date
Purpose
The purpose of the standards in proposed part 62 is the prevention
of occupational noise-induced hearing loss among miners. It is
important to clearly state the purpose of the regulations: to clarify
it to the regulated public and Agency personnel, and so that the
effectiveness of the regulations over time can be measured consistent
with principles under the Government Performance Results Act.
Scope
Part 62 would set forth health standards for all coal, metal and
nonmetal mines, both surface and underground, subject to the Federal
Mine Safety and Health Act of 1977. MSHA currently has four sets of
noise standards: for surface metal and nonmetal mines (30 CFR 56.5050),
for underground metal and nonmetal mines (30 CFR 57.5050), for
underground coal mines (30 CFR part 70, subpart F), and for surface
coal mines and surface work areas of underground coal mines (30 CFR
part 71, subpart I). In fact, however, there are really two groups of
standards: those applicable to coal mines and those applicable to metal
and nonmetal mines. This is because the surface and underground
standards for noise in metal and nonmetal mines are identical; the same
is true of the surface and underground standards for noise in coal
mines. The differences between the standards applicable in the coal
industry and in other mining industries are discussed in detail in the
following pages.
Part 62 would establish a single, uniform noise standard applicable
to all mines. This approach is favored by many. Those who responded to
MSHA's ANPRM generally agreed that consolidation and simplification of
multiple standards into one may help to facilitate understanding of,
and thus compliance with, regulatory requirements. Such an approach is
also traditional with noise: OSHA's standards apply uniformly to
hundreds of industries.
The proposed standard is not identical to the existing coal
standard nor to the existing metal and nonmetal standard. Nor is the
proposal identical to the noise standard which has been applicable to
most other industries since 1983 pursuant to the Occupational Safety
and Health Act (29 CFR 1910.95). Conditions in the mining industry,
experience with the current standards, MSHA's review of the latest
scientific information, the comments submitted in response to the
ANPRM, and the requirements of the Mine Safety and Health Act have led
the Agency to propose a standard that is unique in some respects.
Nevertheless, many key features in the proposal are identical to
features in one or more of the existing noise standards.
Several charts comparing the features of the proposed standard to
the features of existing MSHA and OSHA noise standards are included in
the ``Question and Answers'' in part I of the Supplementary Information
accompanying this notice.
Effective Date
MSHA recognizes that successful implementation of these new and
uniform health rules will require new training of MSHA personnel and
guidance to employees and mine operators, particularly small mine
operators. Accordingly the Agency is proposing that the new standards
take effect one year after the date of publication of the final rule.
An alternative would be to phase in the new requirements. The Agency
believes some could be phased in quickly, but wants to avoid confusion.
The Agency requests comment on whether a phased-in approach is
appropriate and how it might most effectively be designed.
Section 62.110 Definitions
The proposal would include some definitions to facilitate
understanding.
The definitions include some technical terms universally used in
noise measurement, e.g., criterion level.
The definitions also include some terms used in the mining industry
in a way that differs from usage in other contexts, e.g., usage under
the OSHA standard. One example is the term ``hearing conservation
program'' or ``HCP.'' Under the proposal, requirements for hearing
protectors and training are not always linked to audiometric testing
results as they are under the OSHA standard. To avoid confusion, the
proposal defines a hearing conservation program as a generic reference
to those sections of the proposal that set forth the requirements for
an audiometric testing program. Another example is the definition of
``qualified technician''.
The definitions also include some terms which are non-standard. In
particular, the Agency is proposing to use the term ``supplemental
baseline audiogram'' instead of the more commonly used ``revised
audiogram''; MSHA believes its terminology will make it easier for the
mining industry to understand the requirements of the proposal.
The discussion which immediately follows summarizes the salient
features of the definitions. A more detailed discussion of the
definitions is contained in those sections of the preamble which review
the context in which each definition is to be used.
Access
Access is the right to examine and copy records. This is consistent
with the use of this term in several of MSHA's and OSHA's existing
health standards.
Audiologist
A professional, specializing in the study and rehabilitation of
hearing, who is certified by the American Speech-Language-Hearing
Association or licensed by a state board of examiners. MSHA has
included this definition primarily to indicate which organizations
certify or license audiologists. MSHA has decided that all practicing
audiologists should be either licensed or certified by one or both of
the above organizations. This term is considered in the section of this
preamble that discusses proposed Sec. 62.140 Audiometric testing
program.
Baseline Audiogram
The audiogram against which future audiograms are usually compared.
By comparing an annual audiogram to the baseline audiogram the
progression of noise-induced hearing loss can be determined. This term
is considered in the section of this preamble that discusses proposed
Sec. 62.140, Audiometric testing program.
Criterion Level
This refers to the sound level which if applied for 8 hours results
in a dose of 100% of that permitted by the standard. Under proposed
Sec. 62.120(a), the criterion level would be a sound level of 90 dBA.
If applied for 8 hours, this sound level would result in a dose of 100%
of the permissible exposure limit (PEL), established by proposed
Sec. 62.120(c) as an 8-hour-time-weighted average of 90 dBA. The PEL
and the
[[Page 66388]]
criterion level are not the same thing. While the PEL is a sound level
of 90 dBA for 8 hours, it is also a sound level of 95 dBA for 4 hours;
the criterion level is always a constant, derived from what the PEL is
at 8 hours of exposure.
Decibel (dB)
Unit of measurement of sound. Decibel is used to describe
environmental/occupational sounds and hearing acuity.
Decibel, A-weighted (dBA)
Sound levels measured using the A-weighting network. There are
several frequency response networks which have been developed, as noted
in the section of the preamble discussing proposed Sec. 62.120(a). A-
weighting refers to the frequency response network closely
corresponding to the frequency response of the human ear. This network
attenuates sound energy in the upper and lower frequencies (<1000 and
>5000 Hz) and slightly amplifies those frequencies between 1000 and
5000 Hz. The characteristics of the A-weighting network are found in
ANSI S1.25-1991, ``Specification for Personal Noise Dosimeters''.
Designated Representative
A designated representative is an individual or organization to
whom a miner gives written authorization to exercise a right of access
to records, pursuant to proposed Sec. 62.200.
Exchange Rate
The amount of increase or decrease in sound level which would
require halving or doubling the allowable exposure time to maintain the
same noise dose. In this proposal, a 5-dBA increase in the sound level
would correspond to a halving of the allowable exposure time. Exchange
rate is discussed in detail in the section of this preamble discussing
proposed Sec. 62.120 Noise exposure levels.
Hearing Conservation Program (HCP)
An HCP is designed to detect early changes in a miner's hearing
acuity so that corrective action can be instituted to minimize future
hearing loss. In general parlance, an HCP is a system of audiological
examinations that provide guidance for the use of hearing protectors,
other controls, and training. In the proposed rule, however, hearing
protector use and training linked to audiological examinations are only
a limited subset of the hearing protector and training requirements.
Accordingly, to avoid confusion, the term ``hearing conservation
program'' in the proposed rule is defined as a generic reference to the
requirements of Secs. 62.140 through 62.190 of part 62, the
requirements dealing with audiological examinations and the corrective
actions linked thereto.
Hearing Protector
The purpose of this definition is to clarify that not all devices
or materials inserted in or that cover the ear to reduce the noise
exposure can qualify as a hearing protector. For example, MSHA does not
consider a hearing aid as a hearing protector.
A hearing protector must meet two requirements. First, to be a
hearing protector a device must be sold wholly or in part on the basis
of its ability to reduce the level of sound entering the ear. Thus,
cotton would not be an acceptable hearing protector. Second, the device
must have a scientifically accepted indicator of noise reduction value.
MSHA's definition encompasses that used in the Environmental
Protection Agency's (EPA) labeling standards for hearing protectors (40
CFR Sec. 211.203(m)). The EPA defines a hearing protector as:
* * * any device or material, capable of being worn on the head or
in the ear canal, that is sold wholly or in part on the basis of its
ability to reduce the level of sound entering the ear. This includes
devices of which hearing protection may not be the primary function,
but which are nonetheless sold partially as providing hearing
protection to the user.
EPA requires that all hearing protector manufacturers include
labeling information with their products that indicate their Noise
Reduction Rating (NRR). Thus, if a hearing protector has such a label,
the mine operator can be confident that it meets MSHA's definition of a
hearing protector. As noted in the discussions of proposed
Sec. 62.120(a), MSHA does not believe the NRR ratings are meaningful in
workplace situations; moreover, other organizations have recommended
that the EPA reconsider the rating system it uses. MSHA is therefore
not proposing to delimit the range of hearing protectors that may be
offered to only those with an NRR as such; rather, any scientifically
accepted indicator of noise reduction value will be acceptable evidence
of the product's purpose.
The Agency is interested in comments on this definition.
Hertz (Hz)
A unit of measurement of frequency, numerically equal to cycles per
second. The range of audible frequencies is 20 to 20,000 Hz.
Medical Pathology
A condition or disease affecting the ear. The term is used in the
proposed rule in contexts which do not require actual diagnosis and
treatment; see specifically the discussion of proposed Secs. 62.125 and
62.170. Medical conditions of this type should ultimately be diagnosed
and treated by a physician specialist, e.g., an otolaryngologist.
Qualified Technician
A technician who has been certified by the Council for
Accreditation in Occupational Hearing Conservation (CAOHC) or by
another recognized organization offering similar certification. MSHA
has decided that requiring a technician to be certified would ensure
that audiometric tests are administered by a competent person. The
definition of ``qualified technician'' is discussed in connection with
proposed Sec. 62.140 Audiometric testing program.
Reportable Hearing Loss
This defines the extent of hearing loss which must be reported to
MSHA so the Agency can intervene to prevent further hearing loss. Such
reporting is already required pursuant to 30 CFR part 50. This
definition clarifies how the requirements of 30 CFR part 50 apply in
the case of noise.
The definition in the proposed rule would require that hearing loss
be calculated by subtracting the current hearing levels from those on
the baseline audiogram at 2000, 3000, and 4000 Hz; when the permanent
hearing losses at each frequency are averaged (added up and divided by
three), the hearing loss must be reported if the average loss in either
ear has increased by 25 dB. In making this calculation, a supplemental
baseline audiogram would be used in lieu of the baseline audiogram in
those cases in which the supplemental audiogram was created because of
a significant improvement in hearing acuity, in accordance with the
provisions of proposed Sec. 62.140(d)(2).
The definition of reportable hearing loss is discussed in
connection with proposed Sec. 62.190, Notification of results;
reporting requirements. As discussed therein, the Agency is
specifically seeking comment on two points: (a) an appropriate
definition of reportable hearing loss in those cases in which operators
lack an audiometric test record; and (b) the nature of the hearing loss
that MSHA should capture through its part 50 reporting system.
[[Page 66389]]
Sound Level (in dBA)
The sound pressure level measured in decibels using the A-weighting
network and exponential time averaging. Pursuant to proposed
Sec. 62.120(a)(3)(iv), sound pressure levels would be measured using
the A-weighting network and the slow-response time constant. Sound
consists of pressure changes in air caused by vibrations. These
pressure changes produce waves that move out from the vibrating source.
The sound level is a measure of the magnitude of these pressure changes
and is generally perceived as loudness.
Standard Threshold Shift (STS)
This defines the extent of hearing loss which requires intervention
by a mine operator pursuant to proposed Sec. 62.180.
An STS is a measure of permanent change for the worse--relative to
a miner's baseline audiogram, or relative to the most recent
supplemental audiogram where one has been established pursuant to
proposed Sec. 62.140(d). The definition in the proposed rule would
require that hearing loss be calculated by subtracting the current
hearing levels from those measured by the baseline (or supplemental)
audiogram at 2000, 3000, and 4000 Hz; when the hearing losses at each
frequency are averaged (added up and divided by three), the hearing
loss would be considered an STS if the average loss in either ear has
reached 10 dB.
MSHA discusses this definition in detail in connection with
proposed Sec. 62.160, Evaluation of audiogram.
By contrast with an STS, a temporary threshold shift (TTS) is a
temporary change in hearing acuity, which corrects itself after sound
levels are decreased and does not permanently impair hearing. The
latter term is used frequently in the preamble, but is not needed in
the proposed rule.
Supplemental Baseline Audiogram
This is an annual audiogram used in certain specific cases in lieu
of the baseline audiogram to measure reportable hearing loss or
standard threshold shift. Some professionals prefer the term
``revised'' baseline audiogram; in this proposal, ``supplemental'' is
used to ensure mine operators are clear that the integrity of the
original ``baseline'' audiogram must be preserved.
A supplemental baseline audiogram is established under the
circumstances set forth in proposed Sec. 62.140(d)(1) or 62.140(d)(2).
See the discussion of those sections in this preamble, as well as the
related discussions of ``reportable hearing loss'' and ``standard
threshold shift.''
Time-Weighted Average-8 Hour (TWA8).
That sound level, which if constant over an 8-hour time period,
would result in the same noise dose as is measured. This yardstick
measurement is used in the rule in connection with various limitations;
for example, the proposed PEL would be a TWA8 of 90 dBA.
Not all noise measurement instruments give readouts in terms of
time-weighted 8-hour averages. Many personal noise dosimeters, for
example, measure noise as a percentage of permitted dosage, with the
PEL equated to 100%. Mine operators therefore need to convert noise
dose to an equivalent TWA8 to determine if the action level or the
PEL has been exceeded, and to evaluate the impact of engineering
controls. Accordingly, MSHA has provided a list of TWA8 conversion
values in Table 62-2, included in proposed Sec. 62.120. The table has
been compiled by equating a dose of 100% to the proposed PEL. For
example, a dose of 50% equals a TWA8 of 85 dBA--the level at which
some protective action must be taken under the proposal.
The TWA8 and the dose are to be used interchangeably. Since
the noise exposure will be measured for the entire shift, compliance
with the noise standard will be based upon the measured dose. If the
measured dose exceeds 100%, regardless of the length of the workshift,
the miner will be considered to be overexposed to noise. It would thus
be improper to adjust a TWA8 reading for an extended work shift.
Care should be taken not to assume that those models of personal
noise dosimeters which give readouts in both the noise dose and the
``average sound level'' in dBA are giving a TWA8 readout. The
``Lavg'', or average sound level, is the constant sound level
which equals the dose over the measurement period. The value of the
TWA8 is the same as the Lavg if the measurement period is 8
hours.
It should be noted that the TWA8 is a term used in the context
of a 5-dB exchange rate. In the context of a 3-dB exchange rate, the
equivalent term is the ``Leq,8''. The latter term is used
occasionally in the preamble--in discussing the possible use of a 3-dB
exchange rate, and in those studies performed with data from countries
using a 3-dB exchange rate.
Section 62.120 Limitations on Noise Exposure
Introduction
The provisions of this section of the proposed regulation deal with
some critical subjects: how to compute a miner's noise dose; the
hierarchy of controls at different noise exposure doses; and the
monitoring of noise exposure.
Specifically, paragraph (a) of proposed Sec. 62.120 provides the
parameters for computing the amount of noise to which a miner is
exposed--a miner's noise dose. Paragraphs (b) through (d) establish a
series of noise exposure limitations, and the specific mine operator
actions required if noise exceeds that level. Paragraph (e) establishes
a ceiling on sound levels to which a miner may be exposed. Paragraph
(f) establishes a mine operator's obligation to evaluate each miner's
noise exposure to determine if it exceeds any of the limitations
established by this section, and to notify miners at risk.
A short summary of each subsection follows. Thereafter, a more
detailed presentation is provided.
Sec. 62.120(a)
Proposed paragraph (a) sets forth a formula for dose computation
which corresponds to the measurements made by most current personal
noise dosimeters. It further specifies that: all sound levels from 80
dBA to at least 130 dBA be integrated into the dose measurement,
including impact/impulse noise in that range; noise be measured over a
full shift; a 5-dB exchange rate be used; and that measurements be made
using the A-weighting network and slow response instrument settings.
This paragraph also clarifies that measurement of noise dosage is to be
made without regard for the effect of a hearing protector.
The exchange rate is the measure that reflects how much of a
decrease in exposure time is required when the sound level increases.
The proposed 5-dB exchange rate is the same as under current standards.
Using that rate, the exposure permitted at a sound level of 90 dBA is
half that permitted at a sound level of 85 dBA--a miner gets the same
noise dose in 4 hours at 90 dBA as at 8 hours at 85 dBA.
The Agency currently uses a 5-dB exchange rate. There appears to be
a consensus in the recent literature for an exchange rate of 3-dB.
Moreover, the current 5-dB exhange rates incorporates an assumption
that there is significant time for hearing to recover from high sound
levels. MSHA has concluded that
[[Page 66390]]
noise exposure under mining conditions does not warrant such an
assumption. A 3-dB exchange rate does not incorporate this assumption.
Nevertheless, the Agency is proposing to retain the existing 5-dB
exchange rate because of feasibility considerations. Changing to a 3-dB
rate from a 5-dB rate would significantly reduce the amount of time
that miners could be exposed to higher sound levels without exceeding
the permissible exposure limit. For example, MSHA estimates that the
percentage of miners whose exposure would be in violation of a PEL set
at a Leq,8 of 90 dBA would be just about double that of a PEL set
at a TWA8 of 90 dBA. This means mine operators would have to
utilize controls to reduce exposures to the PEL more frequently--and
the controls required to reduce exposures that much would be more
expensive. Furthermore, it is extremely difficult to reduce the noise
exposures to below a Leq,8 of 90 dBA using currently available
engineering or administrative noise controls or a combination thereof.
Accordingly, moving the industry to a 3-dB exchange rate may be
infeasible at this time. (Part IV contains a further discussion of
feasibility issues.)
Two features proposed with respect to noise measurement of
particular significance are: lowering the threshold at which sound
levels are integrated into a miner's noise dose, and prohibiting the
adjustment of noise measurements to provide credit for hearing
protector attenuation.
MSHA is proposed that the threshold for integrating noise into dose
measurements be expanded to cover sounds as low as 80 dBA. This
decision is based on strong evidence that such exposures do contribute
to hearing impairment. While more protective than the present threshold
of 90 dBA, this change will generally result in higher dose readings in
both the coal and metal and nonmetal sectors than at present. For
example, MSHA's dual-threshold survey indicated that in the metal and
nonmetal industry, the percentage of samples above the PEL increased
from 17.4% at a 90 dBA threshold to 26.4% at an 80 dBA threshold; in
coal the figures increased from 25.3% to 35.6%.
Moreover, the proposed regulation would not allow dose measurements
to be adjusted in those cases in which miners are wearing hearing
protectors. This is consistent with the thrust of the proposal to
establish for all mining sectors a hierarchy of controls for noise in
which primary reliance will be upon engineering and administrative
controls.
Sec. 62.120(b)
Proposed paragraph (b) establishes an ``action level'' at a
TWA8 of 85 dBA.
The need for an action level reflects two facts: (1) There is a
significant risk of material impairment to miners from a lifetime of
exposure to noise at this level; and (2) the Agency believes it may not
be feasible at this time to lower the PEL to this level, since that
would require that mine operators use all feasible engineering and
administrative controls to reduce noise exposures to this level.
The proposal would require that all miners exposed above the action
level be provided special instruction in the hazards of noise and
protective methods. The training is to be provided annually for as long
as exposure exceeds the action level. (The nature of this instruction,
how it is to be provided, and how it can be coordinated with other
required miner training are subjects discussed in connection with
proposed Sec. 62.130.)
If a miner's exposure exceeds the action level but is below the
PEL, an operator will also be required to enroll a miner whose exposure
exceeds the action level in a hearing conservation program (HCP). While
enrollment in the HCP would require the operator to make annual
audiometric testing available to the miner, miners exposed to noise
below the PEL would have the right to decline taking any annual
audiometric testing. The requirements for such testing are discussed in
connection with proposed Sec. 62.140, audiometric test procedures. MSHA
is seeking comments on how to minimize the burden on mine operators of
providing audiometric examinations for those miners with only a
temporary attachment to the mining work force (e.g., summer employees),
while recognizing the importance of detecting and tracking hearing loss
among those who switch jobs.
In addition, the operator must provide properly fitted hearing
protection--before the initial hearing examination, if a significant
threshold shift in hearing acuity is detected, and at any other time
upon miner request. Should it take more than 6 months to provide the
initial hearing examination because of the need to wait for a mobile
test van, or should a significant threshold shift in hearing acuity be
detected, the operator would also be required to ensure that the miner
wear the hearing protection--even if the miner's noise exposure remains
under the PEL. (A discussion of the timeframes for audiometric tests,
and the use of mobile test vans, is included in the discussion of
proposed Sec. 62.140, audiometric test program. The definition of a
significant threshold shift is discussed in connection with proposed
Sec. 62.160, evaluation of audiogram).
An action level currently exists under OSHA but would be new to the
mining industry. As discussed herein, MSHA proposes to build upon the
requirements which have been used by OSHA while giving due regard to
implementation approaches appropriate to the circumstances of the
mining community.
Sec. 62.120(c)
Proposed paragraph (c) would establish the permissible exposure
limit (PEL) to noise for a miner as a TWA8 of 90 dBA during any
workshift. (This is also referred to as a dose measurement of 100%; the
action level TWA8 of 85 dBA is half this dose of noise.) The
proposal further provides that if the PEL is exceeded, in addition to
the controls required at the action level, the mine operator shall use
all feasible engineering and administrative controls to reduce the
miner's noise exposure to the PEL. The mine operator has a choice of
whether to use engineering controls, administrative controls, or both;
but if administrative controls are utilized, a copy of the procedures
involved must be posted, and copies given to the affected miners.
If reducing the dose to this level with such controls is not
feasible, the proposal requires the mine operator to use such controls
to lower the noise exposure as much as is feasible.
In addition, in such cases, the proposal requires that the operator
take extra steps to protect miner hearing. The operator must ensure all
miners so exposed take the annual hearing examinations, must provide
properly fitted hearing protection to all miners so exposed, and must
ensure the hearing protection is used by all miners so exposed.
Under the proposal, a consistent hierarchy of controls is
established for all mines. Mine operators must first utilize all
feasible engineering and administrative controls to reduce sound levels
to the PEL before relying on other controls to protect against hearing
loss. This approach is consistent with that currently in place for
metal and nonmetal mines, but would be a change for coal mines. As
discussed herein (in connection with proposed Sec. 62.125, hearing
protectors), MSHA has considerable evidence that primary reliance upon
hearing protectors, as is the current case in the coal industry, is
misplaced.
As under the present standards, the proposal would require a mine
operator
[[Page 66391]]
to use only such engineering controls as are technologically feasible,
and to use only such engineering and administrative controls as are
economically feasible for that mine operator.
As noted, the proposed rule provides for supplemental controls in
those cases in which the Agency concurs with a mine operator that the
use of all feasible engineering and administrative controls cannot
reduce noise to the PEL. MSHA believes that when a miner is exposed to
such high levels of noise, these supplemental obligations are necessary
to protect miner hearing. Hearing protectors are not without their
discomforts; but the risk of hearing loss at such exposure levels ought
to be the controlling factor. While audiometric testing is not an
invasive procedure, the Agency is concerned that there may be economic
pressures and personal reasons that may lead miners to decline to take
hearing examinations. The information generated by these tests is
necessary, however, to trigger investigation of potentially serious
flaws in the layers of noise controls required at these high exposure
levels. In addition, the Agency believes that miners operating under
such high noise conditions should be aware of the severity of any
hearing loss; in a mining environment, this knowledge could have
implications for the safety of the miner and the safety of others.
Comments on this provision are specifically solicited.
Sec. 62.120(d)
Proposed paragraph (d) provides that should a miner's noise
exposure exceed a TWA8 of 105 dBA during any workshift, a dose of
800% of the PEL, the mine operator shall, in addition to taking all of
the actions required when exceeding the PEL, require the miner to use
dual hearing protection--i.e. both a plug type and a muff type hearing
protector. In this context, the Agency presents information about the
mining jobs at which the exposures of this level are occurring; and
requests comment on whether there should be an absolute dose ceiling,
regardless of the feasibility of control by an individual mine
operator.
Sec. 62.120(e)
Proposed paragraph (e) would provide that at no time shall a miner
be exposed to sound levels exceeding 115 dBA.
Sec. 62.120(f)
Proposed paragraph (f) consists of two parts. First, it would
require mine operators to establish a system of monitoring which
effectively evaluates each miner's noise exposure. This will ensure
that mine operators have the means to determine whether a miner's
exposure exceeds any of the limitations established by this section, as
well as to assess the effectiveness of noise controls. The proposed
rule is performance oriented in that the regularity and methodology
used to make this evaluation are not specified. Specific requirements
for periodic monitoring now applicable to the coal sector would be
revoked.
Proposed paragraph (f) would also require that miners be notified
in writing should their exposure exceed any of the levels specified by
this section--whether based on operator or MSHA evaluations of noise.
Notice would be required within 15 calendar days.
The proposal has been designed to ensure that miners are made aware
of the hazards they currently face. Miners exposed above the action
level should be notified of that fact so, for example, they can
consider the importance of using provided, properly fitted and
maintained hearing protectors. On the other hand, the proposal does not
require notification of a particular miner if an exposure measurement
indicates that the miner's exposure has not changed and the miner has
within the last year been apprised of the same information.
The proposal has no provision for requiring the posting of warning
signs.
Dose Computation
Proposed Sec. 62.120(a) sets forth important technical
specifications on computing noise dose. These specifications were
utilized in the establishment of the limitations set forth in this
section; they therefore must be utilized in dose measurements taken to
determine compliance.
Using a Personal Dosimeter
The dose itself is usually read directly from a personal noise
dosimeter. The dosimeter is set to the specifications required by the
proposed standard (e.g. 80 dB threshold), attached to the miner, and
the total dose read out at the end of the full work shift.
Using a Sound Level Meter
Some operators may prefer to take a series of individual readings
with sound level meters, and derive the dose from these readings.
Accordingly, the proposal also sets forth the formula for determining
the dose in this fashion.
Proposed Sec. 62.120(a)(1) would specify that noise dose is to be
computed by combining the sound levels during various periods of time
during the miner's measurement period, in accordance with the formula:
D=100(C1/T1 + C2/T2+ * * * +Cn/Tn),
where:
D=the percent of permissible exposure,
Cn=the total time of exposure at a specified sound level, and
Tn=the reference duration of exposure at that level, as listed in
Table 62-1.
Table 62-1 contains reference durations for sound levels from 85 to
115 dBA. The sound levels to be integrated into the dose measurement
pursuant to this proposal actually range from 80 to 130 dBA. Reference
durations for sound levels not in the table can be calculated pursuant
to the formula in the table note. (For a detailed discussion of this
topic see the section of this preamble entitled Threshold and range of
integration.)
As noted, current personal noise dosimeters automatically compute a
miner's noise exposure essentially using the above formula. In fact,
noise dose is relatively simple to compute when the sound level is
constant throughout the work shift. For example, a miner is exposed to
95 dBA for 2 hours and has no additional noise exposure. The reference
duration, from Table 62-1, for 95 dBA is 4 hours. Substituting the
values into the above formula yields:
D=100 (\2/4\) or equivalently 50%.
When a miner is exposed to fluctuating sound levels, the total
noise dose can be computed using the same formula. For example, a miner
is exposed to 90 dBA for 1 hour, 95 dBA for 2 hours and 100 dBA for 1
hour. The reference durations from Table 62-1 are 8 hours, 4 hours, and
2 hours, respectively. Substituting the values into the above formula
yields:
D=100 (\1/8\+\2/4\+\1/2\ ) or 100 (0.125+0.50+0.50) or equivalently
112.5%.
Conversion of Dose to TWA8
Table 62-2, included in proposed Sec. 62.120(a)(2), has been
constructed to permit dosage measurements to be converted readily into
time-weighted average 8-hour (TWA8) measurements.
The TWA8 is the sound level which if constant over an 8-hour
time period, would result in the same noise dose as is measured. This
yardstick measurement is the one used to establish the action level,
PEL, and double-hearing protection supplemental control level in the
proposed regulation. Since personal noise dosimeters measure noise as a
percentage of permitted dosage, with the permissible exposure limit
(PEL) equated to 100%, this table allows for ready conversion of
[[Page 66392]]
those measurements into a form that measures compliance.
As stated previously, the TWA8 and the dose are to be used
interchangeably. It is intended that the TWA8 not be adjusted for
extended work shifts. Since the noise exposure will be measured for the
entire shift, compliance with the noise standard will be based upon the
measured dose. If the measured dose exceeds 100%, regardless of the
length of the workshift, the miner will be considered to be overexposed
to noise. MSHA requests commenters to review the proposed rule and
offer suggestions to help the Agency ensure that this intention is
clearly conveyed in the rulemaking language.
The table has been constructed by equating the proposed PEL to a
dose of 100%. More specifically, the TWA8 conversion values in
Table 62-2 are based on the use of a 90 dBA PEL, 80 dBA threshold, and
a 5-dB exchange rate. Interpolation for values not found in this table
can be determined from the following formula: TWA8=16.61
log10(D/100)+90, where D is the percent dose.
It is important to understand that the exposure is interpreted as
if averaged over 8 hours. Thus, if a miner only works for 5 or 6 hours,
the sound levels can be higher during those hours than if the miner
works for 8 hours. Conversely, if a miner works an extended shift
(greater than eight hours), the sound levels would need to be lower.
Some current models of personal noise dosimeters will provide readings
in both dose and the average sound level (Lavg) over the sampling
period. Although the Lavg is useful in some circumstances, it is
only equal to the TWA8 when the period sampled is 8 hours.
Consideration of Hearing Protector Attenuation
Proposed Sec. 62.120(a)(3)(i) would require that when determining a
miner's noise dose, the attenuation of hearing protectors not be
considered. This provision would supplement the intent of proposed
Sec. 62.120(c) to preclude the current practice in the coal industry of
not issuing a citation based upon a noise exposure that exceeds the PEL
when the miners are wearing hearing protection.
Several commenters recommended that no credit be given for hearing
protector attenuation in determining the miner's noise dose. These
commenters believed that engineering or administrative controls should
be given primacy over hearing protectors.
Other commenters, however, supported an allowance for hearing
protector attenuation. Their recommendations varied from allowing the
full NRR value, to allowing only a 5 decibel attenuation for all makes
and models of hearing protectors.
Field studies in mining by Giardino and Durkt (1996), Kogut and
Goff (1994), Giardino and Durkt (1994), Durkt (1993), Goff, et. al.
(1986), Durkt and Marraccini (1986), and Goff and Blank (1984) have
shown that the measured hearing protector attenuation at mines is far
less than the attenuation measured in the laboratory and is in some
cases minimal. Furthermore, the measured attenuations were highly
variable. These two factors make it virtually impossible to accurately
predict the in-mine effectiveness of hearing protectors in reducing
noise exposures. A more detailed discussion of hearing protector
performance and attenuation rating methods is presented in the Hearing
protector effectiveness section of this preamble.
Table III-1 presents three types of information from various
jurisdictions. These items are--
(1) the consideration of hearing protector attenuation when
determining the occupational noise exposure;
(2) the weighting network used for measuring occupational noise
exposure; and
(3) the instrument response time for measuring non-impulse/impact
occupational noise.
Table III-1.--Features of Selected Legislation or Guidelines for Evaluating Non-Impulse/Impact Noise Tabulated for Various Entities
--------------------------------------------------------------------------------------------------------------------------------------------------------
Credit for hearing protector
Entity attenuation Weighting network Response times
--------------------------------------------------------------------------------------------------------------------------------------------------------
U.S. Army........................ No............................. A-weighting.............. Slow.
U.S. Navy........................ Implied........................ A-weighting.............. Slow.
U.S. Air Force................... No............................. A-weighting.............. Slow.
Canada (consensus)............... Not addressed.................. A-weighting.............. Slow (SLM only).
EEC.............................. No............................. A-weighting.............. Slow or fast.
Australia (consensus)............ No............................. A-weighting.............. Fast (integrating SLM) or slow (SLM)
Australia (national)............. No............................. A-weighting.............. Fast (integrating SLM) or slow (SLM).
Western Australia................ No............................. A-weighting.............. Fast (integrating SLM) or slow (SLM).
South Africa..................... Implied no..................... A-weighting.............. Slow.
ISO (consensus).................. Implied no..................... A-weighting.............. Fast (SLM).
ACGIH (consensus)................ Implied no..................... A-weighting.............. Slow.
--------------------------------------------------------------------------------------------------------------------------------------------------------
In reviewing the procedures for exposure measurement in regulations
and codes of practice (mandatory or recommended) from the selected
branches of the U.S. armed services, international communities, the
ISO, and the ACGIH, MSHA found that some diversity exists among the
methods used (See Table III-1). Nearly all of the entities either
specify or imply that attenuation provided by hearing protectors should
not be considered in determining a worker's noise exposure.
Based on this information, MSHA has concluded that it would be
inappropriate to consider the attenuation of hearing protectors in
determining a miner's noise dose. As computed, the noise dose provides
a measurable foundation upon which can be built a noise control
program: including, as discussed herein, the use of hearing protectors
to attenuate that noise dose.
This provision would supplement the intent of proposed
Sec. 62.120(c) to preclude MSHA's current practice in the coal industry
of not issuing a citation based upon a noise exposure that exceeds the
PEL when the miners are wearing hearing protection. This is consistent
with the thrust of the proposal to establish for all mining sectors a
hierarchy of controls for noise in which primary reliance will be upon
engineering and administrative controls. These issues are discussed at
length in connection with proposed Sec. 62.120(c) under Hierarchy of
controls and Hearing protector effectiveness.
Threshold and Range of Integration
Proposed Sec. 62.120(a)(3)(ii) would require that all sound levels
from 80 dBA to 130 dBA be integrated into the
[[Page 66393]]
miner's noise dose for determining compliance with the PEL. Sound
levels less than 80 dBA would not be included in the noise exposure
computation. By not excluding any particular types of sound from the
requirement, MSHA intends that the term ``all sound levels'' include,
but is not limited to, continuous, intermittent, fluctuating, impulse,
and impact noise.
MSHA currently uses a threshold of 90 dBA for all purposes. OSHA,
however, uses a dual threshold: a 90 dBA threshold for measuring
whether a dose exceeds its PEL (TWA8 of 90 dBA), and an 80 dBA
threshold for determining whether a dose exceeds its action level
(TWA8 of 85 dBA).
Many of the commenters to MSHA's ANPRM supported a threshold of 80
dBA. Some specifically supported a single threshold. One of these
commenters stated the following:
It was an undue burden on employers when OSHA adopted a dual
threshold level (90 dBA when sampling for PEL and 80 dBA when
sampling for a Hearing Conservation Program). Few employers in our
practice understand the difference, and in fact, very few service
providers in our area understand the dramatic differences these two
threshold levels can create. MSHA has the opportunity to correct
this [oversight] by OSHA, and would be wise to adopt the 80-dBA
threshold.
Another commenter stated:
MSHA should use an 80-dBA threshold for integrating noise on
dosimeters for both compliance with the PEL and the action level.
The exposure characterization of levels between 80 dBA and 130 dBA
would be more accurate using an 80-dBA threshold dosimeter versus a
90-dBA integrating dosimeter.
A third commenter recommended the following:
One threshold level should be used for all measurements--80 dBA.
A single threshold level of 80 dBA, as compared to separate
thresholds of say, 90 dBA and 80 dBA, would greatly simplify and
reduce the costs of measuring noise exposure levels and would
provide an additional margin of safety.
Several commenters recommended that the current threshold of 90 dBA
be retained. One of these commenters stated the following:
* * * multiple thresholds would be extremely burdensome and
costly and would require companies to purchase and use meters that
integrate at different levels. * * * the requirement that more than
one threshold be used is unsupported by reliable and widely accepted
scientific data and is unnecessary for protection of the health of
miners.
Two commenters supported the use of a dual threshold consistent
with OSHA's current standard, while another commenter recommended a
threshold of 75 dBA, because EPA had said that 75 dBA equates to no
risk.
One mining association commented that a member company had
collected about 4,500 samples between 1985 and 1988 using personal
noise dosimeters set at an 80 dBA threshold and found that about 20% of
the measurements equalled or exceeded the PEL. MSHA notes these results
are comparable to the results of the dual-threshold survey conducted by
the Agency and reviewed in part II.
According to ACGIH (1994) all sound levels exceeding 80 dBA should
be integrated into the daily noise exposure. Because permissible
durations are presented for sound levels up to 139 dBA, the range of
integration can be inferred to be 80 to 139 dBA.
ANSI S1.25-1991, ``Specification for Personal Noise Dosimeters'',
recommends that the threshold level be set at least 5 dB below the
criterion level. Although ANSI S1.25-1991 specifies personal noise
dosimeters to have an operating range of at least 50 dB, most currently
manufactured personal noise dosimeters have an operating range greater
than 50 dB. In addition, these personal noise dosimeters will integrate
sound levels up to 140 dBA to include impulse/impact noise at pre-
selected thresholds of 80 dBA, 85 dBA, and 90 dBA.
There is general agreement among the EEC, the ISO, the
international community, and selected branches of the U.S. armed
services that all types of noise be integrated in the worker's noise
dose; however, a threshold is not always specified.
Moreover, based on its review of the available evidence, MSHA has
determined that the use of a single 80 dBA threshold for determining a
miner's noise exposure is necessary for miner protection. Its many
advantages include:
(1) it would address the risk of hearing impairment from prolonged
exposure (greater than 8 hours) above 80 dBA;
(2) it would improve the accuracy of exposure measurements,
ensuring that at-risk miners would be accurately identified;
(3) it is consistent with OSHA's 80 dBA threshold for HCP
requirements, allowing for comparison data;
(4) it would be less burdensome than using dual thresholds,
allowing the use of a single, less complex personal noise dosimeter to
collect the required information rather than a more expensive
instrument or two separate instruments; and
(5) a single threshold is appropriate in as much as MSHA's proposed
approach to hearing conservation is linked closely to other parts of
its proposal.
Several consequences should be noted of switching to a threshold of
80 dBA from the present threshold of 90 dBA. As noted in part II of
this preamble, MSHA inspectors conducted comparative sampling for
several years, simultaneously collecting readings at both the 90 dBA
and 80 dBA thresholds. Tables II-11 and II-12, located in part II of
the Preamble, show the effect of using an 80 dBA threshold versus a 90
dBA threshold with a criterion level of 90 dBA. Of the more than 42,000
samples collected in metal/non-metal mines, for example, 7,360 (17.4%)
exceeded a criterion of 90 dBA using a 90 dBA threshold; whereas,
11,150 (26.4%) exceeded the 90 dBA criterion using an 80 dBA threshold.
Hence, the use of an 80 dBA threshold will result in a higher
proportion of samples exceeding the PEL. Also, an 80 dBA threshold
means that in the case of an extended workshift of more than 8 hours,
sound levels that average below 90 dBA can result in a dose that
exceeds the PEL. For example, the PEL for a 16-hour workshift is 85
dBA, which equates to a TWA8 of 90 dBA.
Further, based upon research conducted by MSHA, the Agency has
determined that the effect of switching to a lower threshold is not
linear. Sound levels just under 90 dBA will have a much greater impact
on the dose computation than those nearer 80 dBA.
Full-Shift Sample
Proposed Sec. 62.120(a)(3)(ii) would also require that compliance
with the PEL or action level be based on the determination of a miner's
full-shift noise exposure. Typically, a full-shift measurement would be
taken with a personal noise dosimeter. This procedure would be
consistent with MSHA's existing noise standards and sampling
procedures.
OSHA's noise standard does not specify a sampling duration, other
than to require personal monitoring where circumstances such as high
worker mobility, significant variation in sound level, or a significant
component of impulse noise make area monitoring generally
inappropriate. OSHA does require that the sample be representative of
the worker's exposure.
In response to MSHA's ANPRM, numerous commenters addressed sampling
duration, including the question of novel work shifts (work shifts
differing from 8 hours). Many commenters stated that the noise
measurement should encompass the entire work shift regardless of
duration. For those shifts which exceed 8 hours,
[[Page 66394]]
a number of commenters suggested that the PEL be adjusted to account
for the longer work shift. Others suggested that the noise exposure be
adjusted.
Several commenters advocated the use of a 40-hour noise exposure
instead of a daily 8-hour noise exposure because of the widely varying
noise exposure of miners. These commenters believed that the 40-hour
exposure would present a better representation of the noise exposure.
A few commenters addressed partial shift sampling. At many small
mines, miners may be involved with several different jobs with
different noise exposures. Because of this, one commenter believed that
partial-shift sampling was more representative of a miner's noise
exposure. The commenter did not want the highest partial-shift noise
exposure projected to a full-shift and reported as the typical exposure
for that shift. Another commenter suggested that the survey duration
encompass at least two-thirds of the shift in order to represent a
full-shift sample.
Lancaster (1986), in a study of noise exposure of British coal
miners, reported that the variation in the day-to-day occupational
noise exposure of compressed air drillers and electricians had a range
that exceeded 30 dBA. The smallest range for any of the fifteen
occupations was 8 dBA. Lancaster reported that five-shift samples
greatly reduced the chance of getting an unrepresentative high or low
result. Further, Lancaster concluded that a five-shift sample was not a
reliable routine method for determining the long-term noise exposure.
In order to determine the long-term average noise exposure to within an
accuracy of 2 dBA, Lancaster stated that 4 to 57 samples are needed
depending upon the occupation.
MSHA concurs with the majority of commenters that full-shift
sampling is more representative of the noise exposure than partial-
shift sampling. Therefore, MSHA has determined that a full-shift
measurement is necessary because partial-shift noise surveys do not
account for such factors as: variable work tasks, worker mobility, and
no set production pattern for many mining situations. These occurrences
are commonplace in the mining industry.
The Agency did not include a long-term sampling requirement in the
proposal. Such a requirement would be burdensome to the mining industry
and is not relevant to compliance with the proposed standard, which
will be based upon a single full-shift sample by the Agency. (For
further consideration of MSHA compliance policy in this regard, see the
last of the Questions and Answers in part I.)
Impulse/Impact Noise
MSHA's proposal does not include a specific limit on impulse or
impact noise. Rather, it provides that all noise in the range from 80
dBA to 130 dBA be integrated into a miner's noise dose, including any
impulse/impact noises measured in those ranges. Most personal noise
dosimeters cover this range of sound levels. MSHA has concluded that,
currently, there is not a sufficient scientific consensus to support a
separate impulse/impact noise standard. Further, existing procedures,
for identifying and measuring such sound, lack the practicality to
enable its effective enforcement: for example, many personal noise
dosimeters do not permit use of the fast response settings needed to
isolate sounds of this type. Since industrial impulses are almost
always superimposed on a background of moderate-to-high levels of
continuous noise, and since both may be harmful, MSHA has determined
that it is only reasonable to consider their effect together, rather
than to treat each separately. As indicated below, there is ample
justification for this approach in the studies reviewed by MSHA and
comments submitted to the record.
MSHA's existing noise standards for coal mines do not include a
limit for impulse/impact noise. Both OSHA's and MSHA's Metal and
Nonmetal existing noise standards limit impulse/impact noise to a peak
level of 140 dB. Neither standard, however, specifically defines
impulse/impact noise nor procedures to measure it.
OSHA, in its Hearing Conservation Amendment, determined that
impulse noise should be combined with continuous noise to calculate
employee noise exposure for purposes of the HCP. OSHA's standard,
however, retains the 140 dB peak limit on impulse and impact noise. The
OSHA preamble to its Hearing Conservation Amendment (46 FR 4099)
stated:
Since industrial impulses are almost always superimposed on a
background of moderate to high levels of continuous noise * * * and
since both may be harmful, it is only reasonable to consider their
effects together rather than to treat each separately * * *. The
decision to measure all noise exposures for purposes of the hearing
conservation program is a pragmatic approach to the whole problem of
impulse noise. For, while there is some dispute as to the precise
definition and effect of impulse noise, there is general agreement
that impulse noise is damaging.
Impulse/impact noise is typically characterized by a rapid rise
time, high peak value of short duration, and rapid decay.
In 1974, OSHA proposed the following definition for impulse noise
(39 FR 37775):
* * * a sound with a rise time of not more than 35 milliseconds to
peak intensity and a duration of not more than 500 milliseconds to
the time when the level is 20 dB below the peak. If the impulses
recur at intervals of less than one-half second, they shall be
considered as continuous sound.
At that time, OSHA proposed to limit exposure to impulses at 140 dB
to 100 per day, and to permit a tenfold increase in the number of
impulses for each 10-dB decrease in the peak pressure of the impulse.
OSHA stated that this proposal was in accordance with the criterion
proposed by McRobert and Ward (1973). OSHA's proposal on impulse noise
exposure limits was identical to that recommended by the ACGIH (1986).
Currently, there is no uniformly accepted definition of impulse or
impact noise. ANSI S12.7-1986, ``Methods for Measurement of Impulse
Noise'', defines impulse noise as ``a single short burst or a series of
short bursts of sound pressure. The pressure-time history of a single
burst includes a rise to a peak pressure, followed by a decay of the
pressure envelope.''
The ACGIH (1986) states that:
Impulsive or impact noise is considered to be those variations
in noise levels [sound levels] that involve maxima at [time]
intervals of greater than one per second. Where the intervals are
less than one second, it should be considered continuous.
Integrating impulse/impact noise into the miner's noise dose is
broadly supported by many of the commenters. One commenter stated that
currently there is not enough scientific information to promulgate a
separate standard on impulse/impact noise. Several commenters advocated
retaining the current MSHA Metal and Nonmetal 140 dB peak limit.
However, two commenters indicated that exposure to this peak be limited
to 100 occurrences per work shift. One commenter on this issue
recommended that MSHA adopt the measurement methods described in ANSI
S12.7-1986, ``Methods for Measurement of Impulse Noise''. This ANSI
document, however, does not specify a criterion level for such noise.
Another commenter stated that 156 dB is most likely the critical point
at which the sensory components of the human ear disintegrate.
Defining impulse/impact noise, and setting an appropriate limit,
has proven to be an arduous task mainly because of the difficulty in
measuring such sound and differentiating it from non-impulse/impact
noise that may occur simultaneously. Impulse/impact noise
[[Page 66395]]
seldom occurs alone in the mining environment. Several commenters on
this issue indicated that current instrumentation, including in
particular the personal noise dosimeter, cannot distinguish between
impulse/impact and continuous noise occurring simultaneously. Some
commenters stated that although personal noise dosimeters cannot
distinguish between impulse/impact noise and continuous noise, newer
models of personal noise dosimeters are capable of accurately
integrating the two types of noise into a single combined dose.
The studies reviewed by MSHA and discussed below indicate that even
though there is no consensus as to a definition of impulse/impact
noise, all researchers and regulators agree that this type of noise is
damaging to hearing.
Ward (1990) stated that both impulse and impact noises involve high
sound pressure levels and short durations, so in a sense, they jointly
represent an extreme type of intermittent noise. He believed, however,
that there is considerable evidence that a distinction should be made
between impulse noise and impact noise, and that they should be treated
separately. Ward characterized impulse noise as ``A-duration,'' such as
that from gunfire. Whereas he characterized impact noise as ``B-
duration,'' having multiple, nearly equal peaks and a sustained
reverberation that may endure for a second or even longer.
Ward believed that recent research tends to support the conclusion
that impact noise can reasonably be expected to behave in a manner
similar to that of intermittent exposure to short bursts of otherwise
continuous but high-intensity noise. He stated that any predictive
scheme that accurately estimates the hazard of intermittent noise in
the range of time-weighted averages (TWA8) or Leq,8 of 110
dBA to 130 dBA also would be successful in predicting the hazard from
impact noise, and no ``correction for impulsiveness'' should be
necessary. He further stated, the same is true of impulse noise as long
as the level of the pulse does not exceed some ``critical'' value. If
the impulse exceeds this critical level, however, Ward believed that
the hazard increases rapidly with further increases in level or in the
number of impulses.
Ward stated that the most hazardous impulse would be one that has
its maximum energy in the most sensitive region of the human auditory
system: namely 2000 to 3000 Hz. This occurs when the A-duration is
around 0.2 milliseconds (ms). For pulses whose A-duration is in this
vicinity, he believed the critical level to be around 150 dB for the
average individual and around 140 dB for the most susceptible ears. He
believes, however, that his limit results in overprotection against
pulses whose A-duration is short (as in the case of cap guns) or long
(as with cannons or sonic booms).
Ward concluded that impulse noise may be the most important cause
of NIHL in the general population, not by a gradual erosion of auditory
sensitivity through repeated daily exposure, but rather by a single
event causing acoustic trauma. He emphasized, however, that the
determination of valid exposure limits for specific impulses is still a
major problem.
In the American Industrial Hygiene Association (AIHA) Noise &
Hearing Conservation Manual, Ward (1986) also expressed concern
regarding an impulse/impact noise limit. He stated:
Just where, if anywhere, this type of limit should be placed is
still undecided. Although the present OSHA regulations state:
``Exposure to impulsive or impact noise should not exceed 140 dB
peak sound pressure'' (Anon., 1971), this number was little more
than a guess when it was first proposed in the CHABA document
(Kryter et. al., 1966), and no convincing supportive evidence has
since appeared. While 140 dB may be a realistic ceiling for impact
noises, it is inappropriate for impulses, so exposure limits in
which the permitted peak level increases as the duration of the
pulses becomes shorter should continue to be used (Anon., 1968).
Volume II of the Ohio State University Research Foundation report
(Melnick et al., 1980) discussed the effects of single, high-level
impulses and stated:
There are insufficient data to develop distributions of hearing
loss as the function of the parameters of single, high-intensity
impulses. The very nature of the stimulus makes these effects on man
difficult to quantify.
This report, however, stated the following regarding single impulse
levels that could cause damage:
* * * In experiments with laboratory animals, impulses having peak
levels in the range of 150 to 160 dB were capable not only of
producing damage to the inner ear but also showed evidence of trauma
to the structures of the middle ear, including perforation of the
tympanic membrane (Eames et al., 1973). Pfander (1975) reports that,
in humans, perforations of the tympanic membrane were observed when
the peak level for an explosive impulse was in the range of 180 dB.
In his experiments with the effects of sonic booms on mice using
peak levels that range from 126 to 146 dB, with durations in excess
of 100 msec, Reinis (1976) reported that five such booms delivered
at the rate of 1 every 10 seconds are capable of producing bleeding
in the cochlea of the experimental animals.
The Committee on Hygiene Standards of the British Occupational
Hygiene Society (1976) developed standards for impulse noise. Their
recommendation referenced a study by Kryter and Garinther which
``showed that temporary hearing loss after exposure to 100 impulses
increased rapidly at sound pressure levels exceeding 170 dB.'' Kryter
and Garinther, however, recommended limiting instantaneous sound
pressure levels to 150 dBA, because special measurement techniques and
instruments would be needed to measure levels in excess of 150 dBA.
Shaw (1985) recommended, in the interest of simplicity and in
keeping with ISO/DIS 1999-1984, that the use of hearing protectors be
mandatory where there is exposure to noise at the work place with
instantaneous peak sound pressures exceeding 200 pascals (140 dB
relative to 20 micropascal). Shaw stated, however, that exposure to
many simple non-reverberant impulses (``clicks'') at that level would
be required to produce significant temporary threshold shift even in
the most sensitive ears. Shaw further discussed the concept of
``critical level'' and stresses that ``the relationship between peak
sound pressure level and mechanical or physiological stress * * * is
exceedingly complex.'' Shaw quoted McRobert and Ward (1973) who urged
that ``* * * damage risk criteria incorporate a more complicated
criterion for impulse and impact noise than a simple ceiling or peak
level * * *.''
ISO/DIS 1999-1990 (1990) also supported combining continuous noise
with impulse/impact noise in conjunction with the use of a 3-dB
exchange rate.
In discussing the combined effects of continuous and impulse/impact
noise, the ACGIH (1986) stated that:
Some studies have shown that the effects of combined impulse and
continuous noise are additive [Okada et al., Int. z Angew. Physiol.,
30:105-111 (1972)]. Other studies have shown that rapidly repeated
impulses [Coles and Rice, Occupational Hearing Loss, pp. 71-77
(1971)] and simultaneously continuous noise [Cohen et al., J.
Acoust. Soc. Am., 40:1371-1379 (1966)] in some cases provide up to
10 dB of protection.
Evans and Ming (1982) and Sulkowski and Lipowczan (1982), however,
supported the theory that impulse noise superimposed on steady-state
noise is more hazardous than the same levels of either separately.
Cluff (1982), professor of audiology at Arizona State University,
believed that the combined
[[Page 66396]]
continuous/impulse noise dose procedure should be approached with a
degree of caution. He stated that:
The procedure involves some knotty issues; not the least of
which is the issue of equal energy (3-dB doubling rule) vs
equinocivity (the principle embodied in the 5-dB doubling rule). One
other issue deserves mention also. What is impact/impulse noise? It
is a simple matter to describe impact/impulse noise in terms of its
source when the source is obvious and individual events are spaced
far apart temporally. It is quite another matter to describe it
differentially from continuous noise when the source is not obvious
and when individual events are repeated rapidly (as with the case of
gear trains, pneumatic chisels, conveyor belts, grinders, internal
combustion engines, etc.). Indeed, this difficulty may be central to
the heretofore tendency to class it as continuous noise when the
repetition rate exceeds one or two events per second. Were it not
that the weight of evidence appears to argue against this approach,
the simple thing would be to call it continuous noise and treat it
as such.
As shown in Tables III-4 and III-5 (in the section entitled
Permissible exposure level (PEL), discussing proposed Sec. 62.120(c)),
the majority of international communities and selected branches of the
U.S. armed services have adopted 140 dB peak as the upper limit for
sound levels in their respective regulations. However, there is no
consensus among these regulators as to a definition of impulse/impact
noise.
In reviewing the literature on impulse/impact noise, MSHA found
that such noise frequently is divided into two general categories: ``A-
duration'' impulses are short duration (measured in microseconds) and
non-reverberant in that they usually occur outside or in a sound
deadening environment; and ``B-duration'' impacts are of longer
duration (measured in milliseconds) and are reverberant mainly because
they occur inside where the sound is augmented by reflections from hard
surfaces. MSHA's experience indicates that there is seldom impulse
noise of A-duration in mills and underground mines, because of the
reverberant field. Scheduled blasting at surface mines would not be
impulse noise of A-duration because of the multiple detonations several
milliseconds apart in a semi-reverberant field when considering the
rock walls and floor.
MSHA is concerned about the practicality of enforcing an impulse/
impact noise limit in mining. Distinguishing impact/impulse noise from
continuous noise, according to most of the definitions discussed above,
would require sophisticated, delicate laboratory instrumentation. This
equipment is: cumbersome, not intrinsically safe, not readily
available, and not capable of withstanding the harsh mining
environment.
As pointed out by some commenters, there have been many
technological advances in the capabilities of noise measuring
instruments, and equipment now exists that can integrate impulse/impact
noise into the dose. The ability of personal noise dosimeters to
accurately integrate sound levels above 130 dBA into the noise dose,
however, may be questionable. ANSI S1.25-1991, ``Specification for
Personal Noise Dosimeters'', specifies that personal noise dosimeters
must have an operating range of 50 dB. ``Operating range'' is defined
by ANSI as the range between threshold and an upper sound level within
which a personal noise dosimeter operates within stated tolerances.
Accordingly, if an 80 dBA threshold is used, current personal noise
dosimeters would be required to meet ANSI tolerances up to 130 dBA.
As stated previously, MSHA has determined that there is little
noise in mining that could be characterized as impact or impulse given
their prevailing definitions. One source of impact noise that may
exceed the existing 140 dB criteria is that caused by blasting in
underground mines. MSHA has determined that noise from blasting in
underground mines would be considered impact noise rather than impulse
noise because of the highly reverberant environment.
In Volume II of the Ohio State University Research Foundation
report (Melnick et al., 1980), Melnick et al. states the following with
regard to measuring impulse/impact noise, such as that produced by
blasting:
Under conditions sufficient to produce measurable hearing loss,
it would be extremely fortuitous if measuring instruments were in
place to permit the assessment of the actual exposure of the single
impulsive event. Generally, these exposures are accidental in
nature.
Because blasting occurs at irregular intervals, with most miners
removed from the blast site prior to its initiation, it would be
difficult for MSHA to measure such exposures and to enforce a limit
designed to protect against such exposures.
MSHA considered many factors in determining the merit of proposing
an impulse/impact noise limit for the mining industry. Although there
is much evidence in the literature on the harmful effects of impulse/
impact noise, MSHA concluded that, currently, there is not a sufficient
scientific consensus to support a separate impulse/impact noise
standard. Further, existing procedures for identifying and measuring
such sound lack the practicality to enable its effective enforcement.
This is due, in part, to the complexity of the phenomena, where
consideration must be given to such factors as: the peak sound pressure
level; the wave form and crest factor; the rise and decay time; whether
it is A-duration or B-duration; the number of impulses per day; the
presence or absence of steady-state sound; the frequency spectrum of
the sound; and the protective effect of the middle ear acoustic reflex.
In conclusion, studies discussed above indicate that when impulse/
impact noise is combined with continuous noise, hearing loss is
exacerbated. Therefore, MSHA has determined that, for purposes of this
proposal, impulse/impact noise should be combined with continuous noise
for purposes of calculating a miner's noise exposure. Since industrial
impulses are almost always superimposed on a background of moderate-to-
high levels of continuous noise, and since both may be harmful, it is
only reasonable to consider their effect together, rather than to treat
each separately. There is ample justification for this approach in the
studies reviewed by MSHA and comments submitted to the record.
MSHA, however, requests further comment on this issue, particularly
on impulse/impact noise sources in mining which may not be integrated
adequately into the miner's noise dose. Additionally, MSHA requests
data addressing a critical level to prevent traumatic hearing loss;
what this critical level should be; whether it should be based on a
single event; and a practical scientifically validated method for its
discrete measurement.
Exchange Rate
The exchange rate is another factor which is involved in the
determination of noise dose. The exchange rate is the change in sound
level which corresponds to a doubling or a halving of the exposure
duration. For example, using a 5-dB exchange rate, a miner who receives
the maximum permitted noise dose over an 8-hour exposure to 90 dBA
would be determined to have accumulated the same dose as a result of
only a 4-hour exposure at 95 dBA. If the exchange rate were reduced to
3-dB, the same dose would be received with a 4-hour exposure at only 93
dBA. Other terms for exchange rate include ``doubling rate,'' ``trading
ratio,'' and ``time-intensity tradeoff.''
The Agency currently uses a 5-dB exchange rate. There appears to be
a concensus in the recent literature for an exchange rate of 3-dB,
although the Agency is seeking additional
[[Page 66397]]
information on this point. Moreover, the current 5-dB exchange rates
incorporates an assumption that there is significant time for hearing
to recover from high sound levels. MSHA has concluded that noise
exposure under mining conditions does not warrant such an assumption. A
3-dB exchange rate does not incorporate this assumption.
Nevertheless, the Agency is proposing to retain the existing 5-dB
exchange rate because of feasibility considerations. Changing to a 3-dB
rate from a 5-dB rate would significantly reduce the amount of time
that miners could be exposed to higher sound levels without exceeding
the permissible exposure limit. For example, MSHA estimates that the
percentage of miners whose exposure would be in violation of a PEL set
at a Leq,8 of 90 dBA would be just about double that of a PEL set
at a TWA8 of 90 dBA. This means mine operators would have to
utilize controls to reduce exposures to the PEL more frequently--and
the controls required to reduce exposures that much would be more
expensive. Furthermore, it is extremely difficult to reduce the noise
exposures to below a Leq,8 of 90 dBA using currently available
engineering or administrative noise controls or a combination thereof.
Accordingly, moving the industry to a 3-dB exchange rate may be
infeasible at this time. (Part IV contains a further discussion of
feasibility issues.)
OSHA, in its 1974 proposed noise standard (39 FR 37774), stated the
following regarding its decision to use a 5-dB exchange rate:
EPA recommended [in response to OSHA's proposal] a doubling rate
[exchange rate] of 3 dB. While the 3-dB doubling rate is
hypothetically correct for uninterrupted noise exposure, noise
exposure in industry is normally interrupted since there are several
breaks in the day's work. OSHA agrees with the Advisory Committee
[Standards Advisory Committee on Noise, appointed by the Assistant
Secretary for OSHA] that the doubling rate should be adjusted to
take into account the various breaks which occur in a workday.
Therefore, OSHA believes that a doubling rate of 5 dB is more
appropriate than the 3 dB.
MSHA received numerous comments regarding this particular issue.
Many refer to scientific studies showing the ability of the ear to
recover from temporary shifts (temporary threshold shifts, or TTS)
incurred during noise exposure. TTS should not be confused with PTS,
which refers to permanent theshold shifts--i.e., loss of hearing
acuity. Whether TTS and PTS are inexorably linked is a subject of
debate, as noted below.
Many commenters advocated retaining the existing 5-dB exchange
rate. Two of these commenters believed that there is sufficient support
in the scientific literature for a 3-dB exchange rate, but recommended
that MSHA retain using the 5-dB exchange rate so as to maintain
consistency between MSHA and OSHA.
A number of commenters, however, recommended a 3-dB exchange rate.
Several stated that it has greater scientific and technical validity.
Others supported the 3-dB exchange rate because it would be in
agreement with regulations in many countries outside the United States
and with the recently issued international standards [International
Standards Organization, ISO 1999.2] which the U.S. endorsed. One
commenter asserted that the ``use of the 3-dB, rather than a 5-dB,
exchange rate facilitates the calibration/characterization and the
interpretation of the performance of such [noise measuring]
instruments.'' Another commenter criticized the theory that the 3-dB
exchange rate only applies to steady state noise, stating the
following:
First, steady and intermittent noise merely identifies the
extremes of episodes of noise and quiet that most workers experience
in the course of a day. It is the rare exception to find workers who
experience either continuous or steady state noise. Recovery from
noise-induced damage, therefore, is unpredictable in the real world.
Second, the hypothesis of recovery during intermittent noise
exposure has not been empirically verified.
Other commenters stated that the use of the 3-dB exchange rate is
not appropriate in mining because exposures in the mining industry are
intermittent and, therefore, miner recovery from temporary threshold
shifts occurs during the working day. Finally, two commenters stated
that if the exchange rate were lowered, many of the personal noise
dosimeters currently in use would become obsolete and would have to be
replaced.
MSHA reviewed several recent studies relating to the selection of
an exchange rate. Kryter (1984) in his discussion of interruptions in
and durations of daily noise exposures, asserts that even short periods
of reduced noise exposure during the workday facilitate recovery, and
that a 5-dB exchange rate is thus appropriate to take this into
account. He states:
* * * it does not matter whether the off time is continuous or
interrupted during the 8-hour day. In either case, the recovery
process continues and is equally effective. For example, the level
of a noise of 8 hours duration per workday could be increased by 6
dB and cause no additional PTS provided its duration is decreased to
4 hours, either by reducing the total work period by 4 hours or by
introducing ``off'' periods (longer than 10 sec each) which total 4
hours. This, of course, is in reasonably close agreement with the
``5 dB exchange'' that would be allowed in some noise assessment
procedures, such as the U.S. Department of Labor Occupational Safety
and Health Administration (OSHA) regulations.
Dear (1987) supported retaining the 5-dB exchange rate based upon
the studies of Sulkowski (1980), Gosztonyi (1975), Scheiblechner
(1974), Schneider (1970) and Pell (1973). Further, Dear believed that
the studies of Passchier-Vermeer (1973) and Burns and Robinson (1970),
which formed the basis for Shaw's recommendation to adopt a 3-dB
exchange rate (discussed below), were critically flawed and furthermore
the findings of Passchier-Vermeer did not agree with those of Burns and
Robinson. Dear asserted that Shaw discounted other studies which showed
that the 5-dB exchange rate correlated well with hearing loss. Dear
claimed that for every study which supports the 3-dB exchange rate,
another supports the 5-dB exchange rate. Dear further contended that a
3-dB exchange rate was valid only for workplaces with no intermittent
noise exposure, which is a condition that rarely exists in American
workplaces.
Sataloff et al. (1984) studied the effect of intermittent noise
exposure on the hearing acuity of workers. This study corroborates an
earlier report, done by Sataloff et al. (1969) on the hearing acuity of
rock-drilling miners, that intermittent noise is not as hazardous as
continuous noise of the same intensity. In the more recent study, 295
industrial workers who did not use hearing protectors were exposed to
non-impact sound levels from 99 dBA to 118 dBA with quiet periods less
than 90 dBA. Most of the workers were exposed to the higher sound
levels. The researchers concluded that intermittent noise exposure
produced little hearing loss at frequencies below 3000 Hz; however, it
produced substantial damage at the higher frequencies. The pattern of
damage, exhibited by workers exposed to continuous noise, was also
realized at the lower audiometric frequencies. The researchers
attributed the difference in patterns of damage to the recovery of the
hair cells in the cochlea during quiet periods in the workers exposure
to intermittent noise.
Sataloff et al. (1984) also compared the hearing loss of a
population of 295 workers exposed to intermittent noise to other
studies on workers exposed to continuous noise conducted by Royster et
al., Botsford, and Johnson and Harris'
[[Page 66398]]
review of Baughn's findings. Sataloff et al. asserted that the
comparison indicated that workers exhibited more hearing loss when
exposed to continuous noise than from exposures to intermittent noise.
Although research showed that the loss caused by intermittent noise
differs substantially from the effects of continuous noise of the same
intensity, Sataloff et al. did not state an opinion as to which
exchange rate is most appropriate.
Hodge and Price (1978), in their review of damage risk criteria,
summarized that the 3-dB exchange rate was proposed to account for
variations in exposure time to both intermittent and continuous noise
and that the 5-dB exchange rate was proposed to account for the
``beneficial effect of recovery'' during quiet periods between such
exposures. They stated, however, that the sound level would need to
fall below 60 dBA to effect recovery. They concluded that neither the
3-dB nor 5-dB exchange rate fits the hearing loss at all frequencies or
under all conditions and there will be controversy in this area for
many years to come.
Cluff (1982), professor of audiology at Arizona State University,
states that:
* * * while equinocivity (the principle embodied in the 5-dB
doubling rate) may be an applicable basis for determining noise dose
for lower levels of noise, its credibility suffers as the level of
the noise increases above 90 dBA. * * * The only justification for
equinocivity, in lieu of equal energy [3-dB exchange rate], is that
on-the-job exposure to noise will probably be intermittent. * * *
Applying the above logic to very high noise levels [sound levels],
intermittent exposure may be claimed for noise levels of 115 dBA,
for instance, only if the duration of each individual exposure is
substantially shorter than the approximately two minute maximum that
would be allowed under equal energy.
Bies and Hansen (1990) developed an equation fitting a 6-dB
exchange rate to the ISO 1999: 1990(E) data, instead of the 3-dB
exchange rate as presented by ISO. Essentially, they showed that the
mathematical solution fitting an equation to the hearing loss data
contained in ISO 1999: 1990(E) is not unique.
Macrae (1991) published an article which refutes Bies and Hansen's
findings. Macrae studied people with a sensorineural hearing loss at
4000 Hz to determine the progression of the loss in relation to
presbycusis. Macrae's data supported ISO 1999 which uses a 3-dB
exchange rate. Macrae believed that Bies and Hansen erred by assuming
that hearing loss, due to presbycusis and noise exposure, was additive
on an antilogarithmic basis at 4000 Hz. Because the progression of
hearing loss at other frequencies was not studied, Macrae could not
reach any definite conclusions as to the progression of hearing loss at
frequencies other than 4000 Hz.
According to the Committee on Hearing, Bioacoustics, and
Biomechanics of the National Research Council (CHABA) (1993), the data
for specifying an exchange rate were not conclusive.
Compared to steady-state noise data, little data exist on the
effect of intermittent or time varying noise exposure. Depending upon
the length of time of the exposure, an exchange rate of between 0-dB
and 8-dB is appropriate. Each of these single number exchange rates is
valid for a limited set of exposure conditions. Therefore, CHABA did
not recommend an exchange rate. Additionally, CHABA concluded that the
maximum sound level for effective quiet is approximately 80 dBA at most
frequencies.
NIOSH (1995) recommends a 3-dB exchange rate based upon the latest
scientific data. This recommendation represents a change in NIOSH's
position on exchange rate from that included in the 1972 Criteria for
Recommended Standard * * * Occupational Exposure to Noise.
NIOSH presents many reasons for this change in position. In their
1972 criteria document, NIOSH based the recommendation for a 5-dB
exchange rate on earlier recommendations of CHABA (Kryter et al.,
1966). CHABA's 1966 recommendations were predicated on three
postulates, which included--
(1) TTS2 (temporary threshold shift measured two minutes after
cessation of the noise exposure) is a valid predictor of permanent
threshold shift (PTS);
(2) equivalent TTS2's obtained from exposures were equally
hazardous; and
(3) TTS2 is a consistent measure of the effects of a single
day's exposure to noise.
Since that time, NIOSH believes that more recent scientific studies
have proven these postulates to be erroneous. Another assumption that
NIOSH found for justifying the 5-dB exchange rate was that
interruptions will be of ``equal length and spacing so that a number of
identical exposure cycles are distributed uniformly throughout the
day.''
Although NIOSH found that intermittent noise exposure is less
harmful than continuous noise exposure, NIOSH has determined that the
beneficial effects of intermittency which allow for recovery from TTS
are not found in industry today. The quiet periods are too loud and too
short to permit recovery of TTS before the next exposure to harmful
noise.
NIOSH cites field studies by Sataloff et al. (1969), Holmgren et
al. (1971), Johansson et al. (1973), and Institut National de Recherche
et de Securite (1978), to show the beneficial effect of intermittency
of noise exposure in mining and forestry. Studies by NIOSH (1976),
NIOSH (1982), Passchier-Vermeer (1973) and Shaw (1985), not supporting
this finding were also cited. NIOSH, however, concludes that ``the
ameliorative effect of intermittency does not support the use of the 5-
dB exchange rate.''
The Shaw study (1985) supports the 3-dB exchange rate based on the
premise that a 3-dB exchange rate better fits the epidemiological data
on the relationship between noise exposure and hearing loss. Shaw also
criticizes the use of the 5-dB exchange rate because it was based upon
the assumption that a permanent threshold shift (PTS) is related
directly to temporary threshold shift (TTS). Shaw believes that no
researcher has adequately demonstrated a relationship between PTS and
TTS. Furthermore, he states that the 5-dB exchange rate does not take
into account variations in the temporal pattern of exposure.
Suter (1983) conducted a comprehensive review of the literature on
exchange rate. She concluded that the 5-dB exchange rate is under-
protective in many situations and that the 3-dB exchange rate is more
firmly supported by the scientific evidence for assessing hearing
impairment as a function of sound level and duration. Suter, however,
stated that:
The situation becomes more complex when noise becomes truly
intermittent, in other words, when there are large differences
between high and low levels, and levels in between occur rarely. The
studies of forestry workers and miners [Sataloff et al. 1969;
Holmgren 1971; Johansson 1973; and Institute National de Recherche
et de Securite 1978] indicate that the frequent periods of quiet
between noise bursts can in some circumstances, ameliorate the
effects of noise exposure.
Regarding the literature review, Suter explained that the
researchers' findings have been refuted by two NIOSH studies of
intermittently exposed coal miners (NIOSH, 1976) and firefighters
(NIOSH, 1982). In addition, the researchers' studies suffer from
various methodological problems such as inadequate characterization of
exposure, sporadic wearing of hearing protectors, small sample size,
etc. Nevertheless, Suter believed that these studies show a valid
trend, in that the intermittency of exposure can offset the effects of
noise exposure, especially in view of
[[Page 66399]]
some of the animal studies (Ward and Turner, 1982). Suter further
stated that:
The logical consequence of such a trend [intermittent noise
exposure being less hazardous than continuous noise exposure] would
be to allow an adjustment to the maximum permissible exposure limit
for outdoor, intermittent noise exposure. This is by contrast to a
5-dB exchange rate, for which there is virtually no scientific
justification * * *.
Suter suggested using a 3-dB exchange rate along with an adjustment
of 2 dB to the PEL for outdoor noise. She stated that ``The exact
amount of such an adjustment should await clarification by further
scientific evidence.''
According to Sliney (1993), chair of the ACGIH Physical Agents TLV
Committee, (ACGIH) revised its exchange rate from 5-dB to 3-dB, on the
basis that the use of a 5-dB exchange rate is not wise for short
exposure periods. The ACGIH stated that allowable durations for high
sound levels which are permitted with a 5-dB exchange rate are
excessive. In addition, ACGIH believed that, with a 3-dB exchange rate,
an upper limit for the TLV was capped by a 140 dBC impulse peak sound
pressure level. Both the 1971 and 1990 versions of the ISO 1999
standard employ the 3-dB exchange rate.
Evans and Ming (1982) studied five groups of employees in noisy
occupations using personal noise dosimeters which integrated sound
levels based on a 3-dB exchange rate. The noise exposures ranged from
80 dBA to 102 dBA. They used a mathematical model developed by Robinson
and Shipton based upon a 3-dB exchange rate for predicting hearing loss
among exposed workers. Evans and Ming stated that the observed noise-
induced hearing loss (NIHL) of workers in the spinning, weaving, and
bottling industries agreed with those predicted by Robinson and
Shipton's model. The hearing loss of workers in the metal-work
industry, however, tended to be greater than those predicted. The
authors believed that the significant amount of impulse noise
contributing to the noise exposures in this industry explained the
difference. Evans and Ming concluded that the use of Robinson and
Shipton's prediction method is valid for predicting the hearing loss
risk for various noise exposures.
As will be displayed later in Tables III-4 and III-5, the 3-dB
exchange rate is also used by many international communities and
selected branches of the U.S. armed services.
Although occupations in the mining industry are typically exposed
to varying sound levels, most miners are continuously exposed to noise
above 80 dBA. Because the majority of exposures are continuously above
80 dBA, little or no time is available to permit ``recovery time'' from
TTS. Thus, miners experience little recovery from the effects of these
noise exposures. ``Recovery time'' is a basic tenet of the current 5-dB
exchange rate; thus, the Agency has concluded the continuous nature of
noise exposure in the mining industry is more realistically
characterized by the 3-dB exchange rate.
Although the Agency has reached this conclusion, and although there
appears to be a growing consensus supporting the use of a 3-dB exchange
rate among the scientific community, international regulators, and the
U.S. armed services, MSHA has chosen to retain a 5-dB exchange rate for
its proposal because there are significant feasibility implications of
adopting a 3-dB rate--both economic and technological.
With respect to economic feasibility, MSHA conducted a study of the
effect of a 3-dB exchange rate on the measured noise exposure of U.S.
metal and nonmetal miners. The mine inspectors collected measurements
during the course of their regular inspections using personal noise
dosimeters which collected data using 5-dB and 3-dB exchange rates
simultaneously. These data are presented in Table III-2.
Table III-2.--M/NM Samples a Exceeding Specified Sound Levels Collected by MSHA From May 1995 to October 1995
----------------------------------------------------------------------------------------------------------------
5-dB exchange rate 3-dB exchange rate
---------------------------------------------------
Sound level (in dBA) Number of Percent of Number of Percent of
samples samples samples samples
----------------------------------------------------------------------------------------------------------------
90.......................................................... 491 16.5 1483 49.9
85.......................................................... ........... ........... 2543 85.5
----------------------------------------------------------------------------------------------------------------
a Total of 2974 samples. Two of the boxes in the table do not contain entries. This is to avoid the potential
for making an inappropriate comparison of values. Direct comparison of TWA8 values determined with different
thresholds is not appropriate if the TWA8 is less than one of the thresholds. An example may help to
illustrate the point. A miner exposed to a constant sound field of 85 dBA for 8 hours would be determined to
have a noise dose of 0%, or a TWA8 of 0 dBA, if a 90 dBA threshold is used: none of the sound would be counted
in the computation. If the exposure was measured using an 80 dBA threshold, the dose would be 50%, or a TWA8
of 85 dBA. Contrasting the measures taken with the two thresholds would be inappropriate in such a case.
The measurements in Table III-2 for a 5-dB exchange rate were made
using a 90-dBA threshold while the 3-dB exchange rate data were
obtained without a threshold. To get a better picture of the impact of
moving from a 5-dB exchange rate to a 3-dB exchange rate if, as
proposed, the Agency adopts an 80-dBA threshold, Table III-3 has been
constructed. The data for the 5-dB exchange rate comes from the
Agency's dual-threshold survey for metal and nonmetal mines, presented
in Table II-11. This also allows for the analysis of data at values
below a TWA8 of 90 dBA, something which is not possible with a 90
dBA threshold. The data for the 3-dB exchange rate come from Table III-
2--switching to an 80 dB threshold does not significantly change the 3-
dB readings in Table III-2.
Table III-3.--Metal/Nonmetal Samples Exceeding Specified Sound Levels at
Different Exchange Rates
------------------------------------------------------------------------
5-dB
------------------------------------------------- 3-dB percent
Sound level (in dBA) Percent
------------------------------------------------------------------------
90..................... 26.9 49.9
85..................... 67.6 85.5
------------------------------------------------------------------------
As indicated in Table III-3 the selection of an exchange rate
substantially affects the measured noise
[[Page 66400]]
exposure. The percentage of miners whose noise exposure would exceed a
PEL set at a TWA8 of 90 dBA (or an LEq,8 of 90 dBA in the
case of a 3-dB exchange rate) increases from 26.9% to 49.9% when the
exchange rate changes from 5-dB to 3-dB. Looking at the numbers another
way, as compared with using a 5-dB exchange rate, using a 3-dB exchange
rate would result in the need to utilize engineering or administrative
controls to limit the exposure of twice as many miners. Moreover, the
engineering controls required would be more expensive since it would
take a more stringent control to bring down, to the PEL, exposures that
double every 3-dB. The table also reveals that to switch to a 3-dB
exchange rate and setting the PEL at an Leq,8 of 85 dBA would
increase the percentage of miners whose exposure is out of compliance
with the PEL from 67.6% to 85.5%.
MSHA has not compiled similar data for coal mining, although the
consequences would be similar. Accordingly, MSHA believes that using a
3-dB exchange rate would have significant implications for the U.S.
mining industry.
With respect to technological feasibility, it is extremely
difficult to reduce the noise exposures to a Leq,8 of 90 dBA using
currently available engineering or administrative noise controls or a
combination thereof. For many pieces of existing equipment it is not
practical to apply engineering controls without seriously compromising
the equipment's operational capacity.
Accordingly, as discussed in part IV of this preamble, moving the
industry to a 3-dB exchange rate may be infeasible at this time.
MSHA believes that the determination of an appropriate exchange
rate is one of the more noteworthy issues in the proposed rule.
Accordingly, MSHA requests further comment and data on this issue. In
particular, MSHA notes that the studies supportive of a 5-dB rate are
generally dated, and requests information about any more current study
supporting that exchange rate.
A-weighting, slow-response
Proposed Sec. 62.120(a)(3)(iv) requires that the instruments used
for measuring noise exposures be set for the A-weighting network and
slow-response (exponential time averaging). This is identical to the
existing MSHA regulations for exposures to non-impulse/impact noise.
OSHA also uses the A-weighting network and the slow-response time for
evaluating exposure to noise.
Weighting networks were designed to approximate the response of the
human ear to tones of equal loudness. The human ear does not respond to
all levels of tones in the same way. At low sound pressure levels
(e.g., 50 dB) the ear discriminates against low-frequency and high-
frequency tones. At higher sound pressure levels (e.g., 90 dB), the ear
no longer discriminates against low- and high-frequency tones. Although
the human ear does not discriminate against low-frequency tones at high
sound levels, the low-frequency tones are less damaging to hearing than
mid-frequency tones.
Several weighting networks have been developed to take these
differences into account: known as A, B, and C. Early researchers
suggested using them all in combination: the A-weighting network when
the sound pressure level was less than 55 dB, the B-weighting network
between 55 and 85 dB, and the C-weighting network for sound pressure
levels exceeding 85 dB (Scott, 1957). Since that time, however,
concensus has developed on the use of the A-weighting network.
Response time, also known as a time constant, refers to the speed
at which the instrument responds to a fluctuating noise.
There are five responses defined in ANSI S1.4-1983, ``Specification
for Sound Level Meters''. They are fast, slow, impulse, exponential,
and peak. The quickest response is the peak response and the slowest is
the slow. Originally the slow response (1000 milliseconds) was used to
characterize occupational noise exposure. This response was used since
it was easier to read the needle deflections on a meter in rapidly
fluctuating noise. For this type of noise the needle deflections using
the fast response (125 milliseconds) were too difficult for the human
eye to follow. ANSI S1.25-1991, ``Specification for Personal Noise
Dosimeters'', prescribes only the slow and the fast responses for
personal noise dosimeters. Many of the older, but not obsolete,
personal noise dosimeters only have the slow response. Furthermore, the
slow response was used for characterizing the noise exposure when most
damage risk criteria were developed.
Many commenters suggested that MSHA adopt OSHA's instrumentation
requirements. This would imply that noise is to be measured on the A-
weighting network and the slow response. However, one commenter
suggested that MSHA use the fast response for evaluating noise
exposure, because ``Use of fast response will result in a more accurate
assessment of employee exposure.''
Prior to the adoption of the A-weighting network to evaluate noise
exposure, the scientific community used more complex methods (e.g.,
octave bands and speech interference levels).
ACGIH (1986) reports that:
* * * Botsford demonstrated that A-weighted levels are as
reliable as octave band levels in the prediction of effects on
hearing in 80% of the occupational noises considered, and slightly
more conservative in 16% of the cases. Passchier-Vermeer and Cohen
et al. similarly demonstrated that A-weighted levels provide a
reasonable estimate of the hazard to hearing in most industrial
environments.
The National Safety Council's Book, Fundamentals of Industrial
Hygiene, Fourth Edition (Plog et al., 1995) states that:
The A-weighted sound level measurement has become popular in the
assessment of overall noise hazard because it is thought to provide
a rating of industrial broadband noises that indicates the injurious
effects such noise has on the human ear.
NIOSH (1972) recommended the continued use of the A-weighted sound
level measurement in its criteria document for a recommended standard
on occupational noise exposure. In this criteria document they state:
As a result of its simplicity and accuracy in rating hazard to
hearing, the A-weighted sound level was adopted as the measure for
assessing noise exposure by the American Conference of Governmental
Industrial Hygienist (ACGIH) and by Intersociety Committee
consisting of representatives from the American Academy of
Occupational Medicine, American Academy of Ophthalmology and
Otolaryngology, ACGIH, Industrial Hygiene Association, and the
Industrial Medical Association. A-weighted sound level measurement
was adopted by the U.S. Department of Labor as part of the
Occupational Safety and Health Standards and by the British
Occupational Hygiene Society in its Hygiene Standards for Wide-Band
Noise.
In reviewing the procedures for exposure measurement in regulations
and codes of practice (mandatory or recommended) from the EEC, the ISO,
the international community, and selected branches of the U.S. armed
services (see Tables III-4 and III-5), MSHA found that there is general
agreement among these groups that measurements be taken using the A-
weighting network and most agree to use the slow-response instrument
settings. ISO 1999 (1990) recommends that if sound level meters are
used to measure noise exposure, then the instrument should be set on A-
weighted, fast-response. In Australia, integrating sound level meters
should be
[[Page 66401]]
set to fast-response while other sound level meters should be set to
slow-response.
The scientific community and most regulatory entities around the
world accept the A-weighting network and slow-response time as
appropriate measurement parameters for characterizing noise exposures.
These parameters have been used by the U.S. Department of Labor, since
the adoption of the Walsh-Healey Public Contracts Act noise regulations
of 1969.
Based upon comments and the good correlation between hearing loss
and A-weighted noise exposures, MSHA proposes to continue using A-
weighting and slow-response when determining a miner's noise exposure.
Action Level
Proposed Sec. 62.120(b) establishes an ``action level'' at a
TWA8 of 85 dBA.
The need for an action level reflects two facts: 1) there is a
significant risk of material impairment to miners from a lifetime of
exposure to noise at this level; and 2) the Agency believes it may not
be feasible at this time to lower the PEL to this level, since that
would require that mine operators use all feasible engineering and
administrative controls to reduce noise exposures to this level.
The proposal would require that all miners exposed above the action
level be provided special instruction in the hazards of noise and
protective methods. The training is to be provided annually for as long
as exposure exceeds the action level. (The nature of this instruction,
how it is to be provided, and how it can be coordinated with other
required miner training are subjects discussed in connection with
proposed Sec. 62.130.)
If a miner's exposure exceeds the action level but is below the
PEL, an operator will also be required to enroll a miner whose exposure
exceeds the action level in a hearing conservation program (HCP). While
enrollment in the HCP would require the operator to make annual
audiometric testing available to the miner, miners exposed to noise
below the PEL would have the right to decline taking any annual
audiometric testing. MSHA's proposed testing requirements related to
the action level are consistent with those of the OSHA HCP. The
requirements for such testing are discussed in connection with proposed
Sec. 62.140, audiometric testing program.
MSHA is seeking comments on how to minimize the burden on mine
operators of providing audiometric examinations for those miners with
only a temporary attachment to the mining work force (e.g. summer
employees), while recognizing the importance of detecting and tracking
hearing loss among those who switch jobs.
In addition, the operator must provide properly fitted hearing
protection--before the initial hearing examination, if a significant
threshold shift in hearing acuity is detected, and at any other time
upon miner request. Should it take more than 6 months to provide the
initial hearing examination because of the need to wait for a mobile
test van, or should a significant threshold shift in hearing acuity be
detected, the operator would also be required to ensure that the miner
wears the hearing protection--even if the miner's noise exposure
remains under the PEL. (A discussion of the time frames for audiometric
tests, and the use of mobile test vans, is included in the discussion
of proposed Sec. 62.140, audiometric testing program. The definition of
a significant threshold shift is discussed in connection with proposed
Sec. 62.160, evaluation of audiogram.)
An action level currently exists under OSHA but would be new to the
mining industry. As discussed herein, MSHA proposes to build upon the
requirements which have been used by OSHA while giving due regard to
implementation approaches appropriate to the circumstances of the
mining community.
Comments on Action Level
Several commenters recommended an action level of 85 dBA for
triggering the requirements of an HCP.
Many of those who commented in response to MSHA's ANPRM discussed
hearing protection and audiometric testing. Some of these comments shed
light on the relationship and comparative benefits of these approaches.
Some commenters supported the use of hearing protectors as an
integral part of an HCP, while other commenters recommended that
hearing protectors be supplied even when not required so as to afford
greater protection. Other commenters expressed three common concerns
over the use of hearing protectors--
(1) difficulty with speech communication and the masking of warning
signals (roof talk, backup alarms, etc.), especially for those miners
with a pre-existing hearing loss;
(2) miner acceptance, including comfort; and
(3) personal hygiene.
The latter two issues of miner acceptance and personal hygiene are
discussed in detail in the sections of the preamble entitled Selection
of hearing protectors and Maintenance of hearing protectors,
respectively (in connection with proposed Sec. 62.125).
Several commenters suggested alternatives for dealing with
communication problems associated with the use of hearing protectors by
those with a hearing loss or in the presence of background noise. These
alternatives included use of a ``buddy'' system, visual warnings,
communication headsets, vitro-tactile warning systems, flat-frequency
response hearing protectors, and notch-amplification earmuffs.
Many commenters specifically mentioned the problem of miner
acceptance of hearing protectors. One of these commenters stated: ``* *
* there is anecdotal reporting to suggest that miners resist wearing
hearing protective devices.''
One commenter stated: ``Another [usage] problem may be the use of
muffs with additional safety equipment, e.g. hard hats and safety
glasses, that may be required for use by the miners.'' Other commenters
either had no problems with hearing protectors or felt that any
problems could be overcome with the proper training.
In addition to the comments received in response to MSHA's ANPRM on
this issue, several researchers and organizations have taken a position
in regard to the use of hearing protectors.
Shaw (1985) reviewed much of the same literature as OSHA when the
1983 Hearing Conservation Amendment was prepared. Shaw's study supports
requiring both hearing protectors and an HCP for exposures exceeding 85
dBA.
In Communication in Noisy Environments (Coleman et al., 1984), the
authors state that:
* * * excessive attenuation needs to be minimized and the
frequency response of the protector is of particular importance in
this respect. * * * (S)everal authors * * * suggest that a protector
which passed relatively more low frequencies could increase remote
masking and produce potential communication difficulties for some
members of the population. This effect has been demonstrated to be
of practical significance for coal mining conditions * * * A flat
frequency response for a protector is necessary to counter the
effect.
Michael (1991) recommends that the hearing protector attenuate the
noise with an adequate margin of safety; however, the hearing protector
should not unnecessarily reduce important aural communications. To
accomplish this goal, the hearing protector's attenuation
characteristics should be matched to the noise exposure spectra as
close as possible. This way the hearing protector will minimally change
[[Page 66402]]
the worker's perception of the noise. Michael also points out that
overall noise reduction achieved by a hearing protector can be
substantially influenced by the spectra of the noise.
Chiusano et al. (1995) reported that a communication headset,
without gain limiters, can expose communication workers to hazardous
sound levels. The noise exposures ranged from 79.9 dBA to 103.8 dBA,
with the average exposure being 87.0 dBA. Furthermore, the peak sound
pressure levels ranged from 119.2 dB to 148.8 dB, with the average
being 140.8 dB. Some recommendations presented by the authors to
control the noise exposure were to include peak clipping, bandwidth
limitations, signal compression, computerized gain control, and
improving the signal to noise ratio.
In the CAOHC Manual, Miller (1985) states that many authorities
consider OSHA's requirement on who must wear hearing protectors to be
``unwieldy.'' This manual states further that ``A more practical and
workable approach is to require all workers exposed to levels of 85-dBA
or higher to use PHPD's [personal hearing protection devices]
regardless of whether the audiograms show an STS.''
According to Suter (1986): ``Because hearing loss may occur in
people chronically exposed to levels of 85-dBA and above, it is wise to
use protectors that attenuate to 85-dBA in all cases.''
The U.S. Armed Services, as well as the European Economic Community
and other foreign countries, require the use of hearing protection when
sound levels exceed 85 dBA.
General Discussion of Action Level and Requirements
The Agency has concluded that there is a significant risk of
material impairment to miners from a lifetime of exposure to noise at a
TWA8 of 85 dBA. In mining, the first line of defense against risks
has always been training. Accordingly, the proposal provides for annual
instruction--to enhance awareness of noise risks, operator
requirements, and available controls. This training would be required
for any miner whose exposure is above the action level.
MSHA's requirements for this training, and a discussion of how it
can be coordinated with existing training requirements, are in proposed
Sec. 62.130. As discussed below in connection with that section, MSHA
received many comments in response to its Advance Notice of Proposed
Rulemaking that supported the value of an annual training requirement.
Studies have shown that the effectiveness of a hearing protection
program is highly dependent on the proper use of hearing protectors and
the commitment of both management and employees, and annual training is
critical to reinforce both the knowledge and commitment.
The Agency believes it may not be feasible at this time to require
mine operators to reduce noise exposures to a TWA8 of 85 dBA. A
detailed discussion on this point can be found in Part IV of this
preamble. Thus, for exposures between a TWA8 of 85 dBA (the action
level), and a TWA8 of 90 dBA (the PEL), the available tools to
supplement training are limited to hearing protectors and annual
audiometric examinations.
Hearing protectors offer only limited noise protection. As
discussed in detail in connection with proposed Sec. 62.125, studies
indicate that hearing protectors may provide significantly less than
their rated protection under actual mining conditions. Nevertheless,
MSHA believes that if hearing protection is properly utilized--that is,
if the requirements under proposed Sec. 62.125 are implemented--they
generally can be relied on to provide at least 5 dBA attenuation, and
thus could realistically protect the majority of miners whose noise
exposure falls between the action level and the PEL.
The comments that MSHA received in response to its ANPRM, however,
suggest that ensuring the protectors are properly fitted, maintained
and utilized may continue to prove difficult--even once the proposed
new standards in this regard (see the discussion of proposed
Sec. 62.125) are taken into account. For example:
(1) The mining environment presents hazards which require a miner
to be aware of his/her surroundings. Many underground miners claim that
the use of hearing protectors interferes with their ability to hear
warning signals or roof talk. This interference may be particularly
pronounced among miners who already have a significant degree of
hearing loss, and such miners may justifiably be reluctant to use
hearing protectors;
(2) Hearing protectors (earmuffs and earplugs) are difficult to
keep clean in the mining environment which can lead to irritation or
infection of the ear(s);
(3) Earmuffs are often uncomfortable when worn in hot environments
(e.g., surface mines during periods of extreme heat or some deep
underground mines);
(4) Hearing protectors experience a degradation of attenuation when
moved from their original position. This condition can occur often when
hearing protectors are worn by a miner operating vibrating equipment
(e.g., pneumatic drills, continuous mining machines, mobile equipment),
wearing certain types of personal protective gear (e.g., safety
glasses, hardhats, respirators, welder's hood, etc.), or sweating;
(5) The effectiveness of hearing protectors is highly dependent
upon proper fit and use by the miner. While the amount of protection
afforded by engineering controls can be easily measured, the
attenuation of hearing protectors under actual working conditions can
only be estimated; and
(6) Generally, hearing protectors are not effective in reducing low
frequency noise. As most mining machinery emits predominantly low
frequency noise, the use of hearing protectors may have a negligible
effect in reducing the overall sound level.
To alleviate these problems, both operators and miners must be
committed to working through individual concerns about hearing
protection. MSHA believes that the best way to facilitate this
process--at exposure levels between the action level and the PEL, and
with a few exceptions--is to have operators provide instruction and
make suitable hearing protectors available to miners upon request. If
protectors are requested, they would have to be provided in accordance
with the requirements of Sec. 62.125--i.e. a choice of plug or muff
type, properly fitted, maintained, and replaced under certain
conditions. An operator would generally not, at such exposure levels,
have an obligation to enforce the use of hearing protection. MSHA
believes that the combination of knowledge, availability, and properly
selected, fit and maintained equipment may be the best way to encourage
hearing protector use.
MSHA would require an operator to provide a miner with a hearing
protector while awaiting a baseline audiometric examination; but with
the exception noted below, the operator would not have to enforce the
use of the protector as long as the miner's exposure does not exceed
the PEL.
In two cases, however, MSHA proposes to require operators to
enforce hearing protector use at exposures below the PEL. The first
case would be in the event a miner exposed above the action level has
to wait more than 6 months for a baseline audiometric examination. As
noted in proposed Sec. 62.140, the baseline examination is normally to
take place within 6 months of a determination that a miner is at risk
because his or her exposure exceeds the action level; however, the time
frame can be extended for an additional 6 months if the operator has to
wait for a
[[Page 66403]]
mobile test van. In such cases, the miner is exposed to harm for an
extended period of time without the benefit of audiometric test data,
and MSHA believes it would be appropriate to require protection to be
worn. This is the approach taken under OSHA's noise requirements.
In addition, an operator would be obligated to ensure the miner
uses provided hearing protection when audiometric examinations indicate
a significant threshold shift (STS) in hearing acuity has occurred and
the miner's exposure exceeds the action level. (The evaluation of
audiograms, and the determination of whether or not there is an STS, is
the subject of proposed Sec. 62.160.) MSHA believes that once there is
evidence from the tests that the miner is incurring hearing loss, it is
appropriate to require that hearing protectors be worn as long as
exposure exceeds the action level.
Annual audiometric examinations cost more than providing hearing
protection--but as already recognized by many in the mining industry,
and all the industries which operate under OSHA's requirements, such
examinations provide important information, especially in an
environment in which hearing protector use has the problems noted
previously. The act of enrolling miners in a ``hearing conservation
program'' (HCP) can help emphasize to those individuals that they
should pay more attention to the training and available controls. It
also helps miner representatives, operators, and MSHA focus available
resources on those miners who have actually suffered an STS at lower
noise exposures. While MSHA is not proposing to require operators to
compel miners to take the annual examinations at exposure levels below
the PEL, and expects that many miners may be reluctant to take
examinations out of concern about how the information would be used,
MSHA anticipates that over time the required training would lead to
growing use of such examinations within the mining industry. (MSHA's
preliminary RIA assumes only limited participation at such exposure
levels during the initial years of the rule's implementation.)
Participation in an HCP
MSHA has no standards addressing hearing conservation plans or
programs in its existing metal and nonmetal regulations. However, an
indeterminate number of mines have voluntarily established HCP's. MSHA
estimates that 5% of small mines, and 20% of large mines, have such
programs.
Existing MSHA coal noise standards require mine operators to submit
``* * * a plan for the administration of a continuing, effective
hearing conservation program,'' within 60 days following the issuance
of a notice of violation [citation] for subjecting a miner to a noise
exposure exceeding the PEL. This plan must include provisions for pre-
employment and periodic audiograms. The regulation, however, does not
specify the procedures nor the time frame for obtaining these
audiograms. Additionally, due to coal's policy of considering hearing
protector attenuation in determining compliance with the PEL, few
miners are found overexposed.
OSHA's noise standard requires that all employees exposed above the
action level (TWA8 of 85 dBA) be enrolled in an HCP. OSHA's HCP
requirements include provisions addressing exposure assessment,
training, audiometric testing, hearing protectors, notification, and
recordkeeping.
Several commenters recommended requiring an HCP whenever a miner's
exposure exceeds a TWA8 of 85 dBA, or equivalently a noise dose of
50%.
Under MSHA's proposal, participation in an HCP would be provided by
the mine operator at no cost to the miner. OSHA also specifies that
audiometric testing and hearing protectors be provided at no cost to
the employees. MSHA intends that the audiometric testing be given
during normal working hours (on-site or off-site) and that miners
participating in these activities receive wages for the time spent in
their involvement. If the audiometric testing is provided off-site,
MSHA intends the mine operator to compensate the miners for the
additional costs, such as mileage, meals, and lodging, that they may
incur.
Elements of an HCP
Some of the elements often considered to be part of an HCP are
handled through separate, free-standing requirements under MSHA's
proposal. These include hearing protection and training, and an
employer's obligation to evaluate the noise to which miners are exposed
to determine if specified levels are exceeded. Accordingly, the
proposal uses the term HCP to refer essentially to annual audiometric
testing and required follow up examinations and actions.
Under OSHA's noise standard, the elements of an HCP include:
(1) monitoring employee noise exposure;
(2) wearing hearing protectors;
(3) education and training; and
(4) audiometric testing and medical evaluation.
In its ANPRM, MSHA requested information concerning the elements
which would be appropriate for inclusion in an HCP for mining. MSHA
received numerous comments concerning this issue. Of these, many
supported MSHA's adoption of HCP requirements similar to OSHA's,
including:
* * * Assessment, monitoring, engineering and/or administrative
controls, hearing protective devices, employee education,
audiometric testing, interpretation of audiometric tests and follow-
up, and appropriate record keeping.
Although there was a consensus among commenters on the elements of
an HCP, there was considerable variation in the substantive aspects of
these elements. Commenters ranged from wanting more performance
oriented requirements to wanting more specific requirements with fewer
exceptions than in the existing OSHA rule.
One commenter wanted ``* * * a more stringent program than the
present OSHA HCP * * *''. Another felt that no program should be
implemented until ``* * * sufficient evidence and testing demonstrates
a need for the program to protect the hearing of miners.'' Another
commenter believed that audiograms were a needless expense, but that
hearing protectors should be required for all miners exposed to
hazardous sound levels. Several commenters believed that HCP's were of
no value, stating ``Our experience with HCP's indicates they are wasted
bureaucratic red tape and present no benefit to the employees.''
``Guidelines for the Conduct of an Occupational Hearing
Conservation Program'' (1987) developed by the American Occupational
Medical Association's Noise and Hearing Conservation Committee of the
Council on Scientific Affairs presents the basic elements of an HCP.
They recommend that each program include: (1) measurement of exposure;
(2) engineering controls; (3) use of hearing protectors; (4)
audiometric testing and medical evaluation; (5) education and training;
(6) assessment of program effectiveness; and (7) management support.
MSHA agrees with the majority of the commenters to the ANPRM.
However, as noted, MSHA proposes to require some of these elements
through free-standing requirements. Accordingly, the proposal uses the
term HCP to refer essentially to annual audiometric testing and
required follow up examinations and actions. Overall, the requirements
of MSHA's proposal are generally
[[Page 66404]]
consistent with OSHA's current HCP requirements and with the
requirements of the U.S. armed services and the international
community.
MSHA reviewed HCPs in effect at a variety of organizations. The
HCPs consist mainly of monitoring employee noise exposure, controlling
the noise, training employees, and conducting audiometric testing. The
Agency believes that when engineering and administrative controls are
not able to reduce a miner's exposure to within the PEL, annual
audiometric testing and medical evaluation would enable mine operators
and miners to take proper precautions to identify early hearing loss
and thereby prevent further deterioration of hearing. This is discussed
in more detail in those sections of the preamble reviewing the proposed
HCP requirements (proposed Sec. 62.140 et. seq.).
Effectiveness of HCP's
Although many commenters to MSHA's ANPRM stated that an HCP is
needed, only a few commenters specifically addressed the effectiveness
of an HCP.
One commenter referenced a study (ANSI, 1990; Royster and Royster,
1988) which indicated that the HCP at five out of 17 companies, or less
than 30%, could be considered effective/adequate. This inadequacy,
however, could be attributed to a lack of commitment by the companies
in carrying out all of the necessary components of the HCP. This study
found that, for the HCP to be successful, it is critical that a single
individual have control over the program and its implementation.
Furthermore, management must make a commitment to ensure that the
program is fully implemented.
Another commenter, representing nonmetal mining companies,
indicated that its members have not experienced large numbers of claims
for hearing loss and this may be a reflection of program effectiveness.
In addition to the above comments, MSHA reviewed several studies
regarding the effectiveness of HCP's. Villeneuve and Caza (1986)
reported on the HCP for a Canadian mining company. Under this HCP,
miners undergo audiometric evaluations, receive training, and wear
hearing protectors. After ten years, the incidence of workers'
compensation claims for hearing loss has diminished.
After obtaining audiometric data from three Ontario employers who
had HCP's, Abel and Haythornthwaite (1984) investigated the progression
of NIHL. Workers for the first employer (public utility) had their
maximum hearing loss between 2000 and 6000 Hz. Further, 78% of the
workers who reported never wearing their hearing protectors experienced
25 dB of hearing loss at 4000 Hz. For those workers who wore their
hearing protectors at least half of the time, 38% had the same degree
of hearing loss.
At the second employer (mining company) about half the drillers
incurred a hearing loss of 1 dB per year or more at 4000 Hz. Motorman
chute blasters incurred an average change of hearing of a little over 1
dB per year. This compares to a hearing loss of 0.5 dB per year for the
control group. Further, in subjects who were over 50 years of age,
100%, 88% and 38% of the drillers, the motorman chute blasters, and the
controls respectively had a hearing loss that exceeded 25 dB at 4000
Hz.
Finally, workers at a foundry and steel mill showed a 0.13 dB per
year hearing loss at 1000 Hz and 1.3 dB per year at 4000 Hz. Their
hearing loss was similar to the miners.
Abel (1986) reported on the progression of NIHL among three groups
of workers, including miners. All noise-exposed workers had exposures
exceeding 85 dBA and were enrolled in an HCP. One requirement of the
HCP was mandatory use of hearing protectors. At 4000 Hz, the noise-
exposed workers lost their hearing acuity at 1.5 dB per year compared
to 0.5 dB per year for the control group, who were office workers.
Despite mandatory use of hearing protectors, most workers in the
Abel study admitted to wearing their hearing protectors less than 50%
of the time. Further, many modified their hearing protectors to provide
greater comfort. Many of the modifications had a deleterious effect on
the attenuation.
Gosztonyi (1975) reported on his evaluation of an HCP at a large
manufacturing plant. The study covered a 5-year period (1969-1974)
shortly after the passage of the Walsh-Healey Public Contracts Act
noise regulations. The study covered 213 employees with a median age of
43 years. The workers were divided into three groups based on their
noise exposure. These were: (1) 71 office workers exposed to sound
levels of 50 to 70 dBA; (2) 71 workers in the machine shop exposed to
sound levels of 80 to 85 dBA; and (3) 71 workers (wearing hearing
protectors) in the chipping and grinding areas of the iron and steel
foundry exposed to sound levels of 100 to 110 dBA. Gosztonyi found
that, over a 5-year period, the hearing loss incurred by workers in
group (3) were no greater than the losses exhibited by the other groups
at each frequency, regardless of the baseline hearing thresholds. He
concluded that an HCP (consisting of periodic noise exposure
assessments, annual audiometric testing, and the mandatory use of
hearing protectors) instituted when noise exposures exceed a hearing
conservation criterion of approximately 90 dBA adequately protects the
hearing of noise-exposed workers.
Pell and Dear (1989) reported the following:
Two longitudinal studies of changes in hearing threshold levels
and one study of the prevalence of hearing impairment in noise
exposed and non-exposed workers have clearly indicated that DuPont's
hearing conservation program has been effective in preventing
occupationally noise-induced hearing loss [NIHL].
Several reports on the effectiveness of DuPont's HCP have been
published. DuPont's HCP requires the wearing of hearing protectors in
high noise areas, audiometric testing, and monitoring of noise
exposure. In the first study Pell (1972) showed, via a retrospective
study, that the hearing of workers was being protected. The hearing
levels of workers in high noise areas were compared to the hearing
levels of workers in quieter areas (below approximately 90 dBA). Both
groups of workers had comparable hearing levels at frequencies between
500 and 2000 Hz. At higher frequencies the median hearing level of
quieter area workers was slightly better than the median hearing level
of high noise area workers. Although the differences were statistically
significant, the author believed that the small differences lacked
practical importance. Moreover, the difference was much less than the
hearing loss which occurred due to presbycusis and other non-
occupational factors. Comparing the results to a study published by
Nixon and Glorig (1961) on unprotected workers, Pell concluded that the
DuPont workers experienced much less hearing loss.
Later, Pell (1973) published the initial results of a 5-year
longitudinal study on the same workers. The sound level to which
workers were exposed in the quiet areas could approach 90 dBA, but most
exposures were between 50 and 70 dBA. The workers in the highest noise
areas were required to wear hearing protectors and most of the workers
in the moderate noise areas chose to wear hearing protectors. A
comparison of workers' hearing levels at 3000, 4000, and 6000 Hz
revealed that there was no increased hearing loss among workers who
wore hearing protectors in high noise areas versus the workers in the
quiet areas. The researcher concluded that:
[[Page 66405]]
The analysis of changes in hearing threshold levels over a 5-
year period has clearly indicated that persons who work in areas
where noise levels (sound levels) exceeded 90 dBA showed hearing
losses that were no greater than those experienced by persons who
worked in areas where the noise levels (sound levels) were less than
90 dBA. It is evident, therefore, that a hearing conservation
program in which the hearing conservation criterion is approximately
90 dBA can successfully protect the hearing of noise-exposed
workers.
Pell believed that his study confirmed the earlier conclusion that
DuPont's HCP was effective in preventing occupational hearing loss.
Pell emphasized, however, that this study cannot reveal the effects of
these sound levels on hearing acuity but is intended only to evaluate
the effectiveness of the HCP. The third study is a continuation of the
second study. In this study, Pell and Dear (1988) evaluated the
effectiveness of DuPont's HCP over 20 years. However, the study did not
involve the same workers over the entire time frame for many reasons.
Furthermore, the researchers divided the workers into three categories:
workers exposed to noise under 85 dBA; between 85 to 94 dBA; and 95 dBA
or higher. The mean differences, over a 3-year period between workers
in noisy (over 85 dBA and wearing hearing protectors) and quiet areas,
were small. Evaluating the prevalence of hearing impairment using the
AAO-HNS 1979 definition showed that the high noise areas had slightly
higher prevalence rates of hearing impairment. After adjusting for
presbycusis, only 7.1% of the workers in the high noise areas developed
a hearing impairment. Pell and Dear concluded that presbycusis was by
far the major factor in developing a hearing impairment. Furthermore,
independent clinical evaluations of the non-presbycusis cases revealed
that socioeconomic factors, (e.g., differences in off-the-job noise
exposures and otological disease), may account for much of the excess
hearing impairment of the noise-exposed workers. Pell and Dear
attributed the effectiveness of DuPont's HCP to educating the workers
to the hazards of noise, hearing protector fitting, and supervision.
Because of these components, DuPont workers received greater noise
reduction from foam earplugs than did workers in other industries. Pell
and Dear believe that effective use of hearing protectors is the
overwhelming factor in approaching avoidance of problem hearing loss.
In addition, Pell and Dear believe that employees exposed above 90 dBA
are better protected by using appropriate hearing protectors rather
than implementing engineering controls to reduce the noise to 89 dBA or
even 84 dBA.
Savell and Toothman (1987) studied the HCP at a factory. The
workers whose time-weighted average noise exposures ranged from 86 to
103 dBA were required to wear hearing protectors as a condition of
employment which was strictly enforced. These workers were employed
between 8 and 12 years. Only the employees with more than 25 months off
the job during the course of the study were excluded in order to obtain
a large sample (265 workers). The group mean hearing levels from the
latest audiograms were compared to the initial audiograms. Savell and
Toothman did not find any significant change in hearing acuity over the
course of the study. Therefore, they concluded that mandatory use of
hearing protectors in an HCP can protect the hearing acuity of workers.
Bruhl and Ivarsson (1994) conducted a longitudinal study of the HCP
at an automobile stamping plant over a 15-year period. The researchers
evaluated workers' hearing levels over the frequency range of 2000 to
8000 Hz. Workers' hearing levels were compared to the hearing levels of
a ``highly screened'' non-noise exposed male population. For sheet
metal workers, the HCP reduced the noise-induced permanent threshold
shift. Bruhl and Ivarsson concluded that the HCP, which included
effective use of hearing protectors and reduction of sound levels, can
eliminate occupational NIHL.
Franks et al. (1989) examined the hearing conservation records of a
large printing company with multiple facilities. They examined the
records for factors associated with the development of an STS. Franks
et al. indicated that ``* * * statistically significant factors
associated with Standard Threshold Shift [STS] were from medical and
non-occupational noise exposure histories, and not occupational noise
exposure.'' In other words, the HCP was effective since the hearing
loss developed by the workers was from non-occupational exposures.
Moretz (1990), reporting on the work of the ANSI S12.12 working
group, stated that ``A pilot analysis of industry's audiometric data
found that fewer than 20 percent of the programs [HCP's] are
effective.'' Moretz further reported that Alice Suter, a member of this
ANSI working group, had stated that ``the actual percentage of
companies with effective programs is probably even lower * * *,''
because the ANSI working group had looked at data from relatively large
companies. Suter thought that smaller companies are less likely to have
the resources necessary to operate an effective HCP.
The National Institutes of Health (NIH), in its Consensus Statement
on Noise and Hearing Loss (1990), states that ``many existing hearing
conservation programs remain ineffective due to poor organization and
inadequately trained program staff.''
Although evidence indicates that a properly supervised and operated
HCP can provide effective protection, in many instances, HCP's have
failed due to the lack of necessary supervision and adherence to proper
procedures and principles. Furthermore, the studies which showed HCP's
to be effective were mainly of short term durations (five years or
less). There is a lack of evidence that long term HCP's protect the
hearing acuity of workers. Pell and Dear's 20 year study (1988) was in
actuality two shorter longitudinal studies covering a five-year period
at the beginning of the study and a three-year period at the end. In
both of these shorter studies the hearing level of the participants did
not change at a rate different from the non-noise exposed controls.
The two other long-term studies, Bruhl and Ivarsson (1994) and
Bruhl et al. (1994) demonstrated that HCP's were effective in reducing
noise-induced permanent threshold shift. At the plant both engineering
noise control and hearing protectors were utilized to reduce worker's
exposure to noise. Therefore, these studies indicate engineering noise
control is a necessary component of an effective long-term HCP.
Rink (1996) studied the hearing loss of workers enrolled in HCPs.
Between 1991 and 1995 nearly 590,000 audiograms were given. During the
years the percentage of STSs decreased each year--from 4.69% to 1.22%.
Further, Rink reported that about 50% of the STS consistent with noise
exposure were persistent (confirmed STSs). The remainder were not
permanent. Rink concluded that aggressively adhering to and enforcing
the hearing conservation policies proposed by OSHA in 1983 can reduce
and effectively control NIHL.
Many of the above studies indicate that an HCP can be effective in
preventing hearing loss, but only if management and workers strictly
adhere to its requirements. Several of these studies also concluded
that engineering controls were a necessary part of an effective HCP.
This is not inconsistent with MSHA's conclusions about the
[[Page 66406]]
importance of commitment by both operators and miners.
Evaluation of HCP Effectiveness
MSHA has not included a methodology or a requirement for mine
operators to test the effectiveness of their HCP's. Currently, both
MSHA's Coal and OSHA's noise standards require an effective HCP, but do
not specify a procedure for evaluating the effectiveness of the
program. Further, Metal and Nonmetal's noise standard has no
requirement for an HCP.
In its ANPRM, MSHA also requested information concerning
appropriate methods or requirements for evaluating the effectiveness of
HCP's. One commenter felt that evaluation criteria are unnecessary and
that the HCP is effective if exposures are reduced. Another commenter
stated that uniform evaluation criteria have not been adopted. Another
suggested that NIOSH be given the task of evaluating the effectiveness
of HCP's for the mining industry.
A number of commenters believed that it was essential for MSHA to
address procedures for evaluating the effectiveness of HCP's. Several
of these commenters suggested that MSHA monitor the activities of the
ANSI S12.12 Working Group for Evaluation of HCP's and consider using
the guidelines established by this group, once they were finalized.
ANSI has published a draft standard, ANSI S12.13-1991 Audiometric
Database Analysis (ADBA), which describes techniques for evaluating the
effectiveness of the HCP's.
Adera et al. (1993) studied the effect of using ADBA to determine
the effectiveness of a utility company's HCP which had 2,317
participants. The hearing acuity of the utility workers was compared to
the hearing acuity of tobacco company employees (control population).
The tobacco company employees were one of the control populations used
in developing the draft ANSI standard S12.13-1991. The control
population's noise exposure was approximately 87 dBA and they wore
hearing protectors consistently. While the ADBA method deemed the HCP
acceptable, epidemiological techniques showed the workers to be at risk
of developing a hearing loss. The age-adjusted risk of developing a
hearing loss was 2.3 times that of the control population.
Simpson, Stewart, and Hecksel (1992) studied HCP's at 28 small
companies representing 2,183 employees of which 865 qualified for ANSI
analysis. The researchers concluded that companies with less than 100
employees may have difficulty in meeting ANSI S12.13-1991 data
requirements for more than two consecutive years of data analyses due
to employee turnover and absenteeism. Sample sizes smaller than 30
employees are likely to be more sensitive to outlier scores. Smaller
sample sizes were also more likely to be rated marginal or unacceptable
due to biasing effects of sample size. For 1990, the percent of STS's
ranged from 0% to 3.8% at the individual plants. The rate of STS's
across all 28 plants was 1.5%.
Simpson, Stewart and Kaltenbach (1994) investigated early
indicators of HCP performance. A total of 27,047 employees (3,245
controls and 23,802 subjects) in 21 HCP's were included in the study.
The rate of STS in the control groups ranged from 2.5 to 5.7% while the
exposed groups had a rate between 4.6 and 28%. Comparing the incidence
of STS's with ANSI S12.13-1991 indicators, the researchers concluded
that the incidence of STS's was as good as the ANSI test criteria as an
early indicator of the effectiveness of an HCP from the first two
audiograms.
NIOSH (1995) recommended a simple method of determining the
effectiveness of an HCP. According to NIOSH, if less than 5% (1 out of
20) of the noise-exposed workers enrolled in an HCP incur an
occupationally-induced STS, the HCP is deemed effective. According to
NIOSH, this method should be used to continually monitor the results of
audiometric testing to indicate the effectiveness of the HCP before
many individuals incur permanent shifts in hearing acuity.
While MSHA recognizes that the ADBA technique may be promising, the
Agency is concerned that it may not be practical for the majority of
mine operators. The ADBA technique may not be applied reliably to
populations of fewer than 30 individuals and about 90% of the 15,000
mines under MSHA's jurisdiction employ less than 30 miners. Even if
every miner was placed in an HCP, regardless of noise exposure, less
than 10% of the mines could consider using the ANSI draft ADBA
procedures to evaluate their HCP. ADBA analysis also may not be
appropriate if the workforce being analyzed is not stable, exhibiting a
high turnover rate. MSHA has determined that this may be the case for
many small mines which operate seasonally, are portable, or change
geographic locations. Currently, the annual turnover rate in mining
ranges from 2% in large coal mines to 11% in small metal and nonmetal
mines.
In addition, ADBA requires several years of data before the
analysis can be conducted. Consequently, ADBA cannot be used to
immediately determine the effectiveness of an HCP unless audiograms
were collected prior to the effective date of the rule.
Finally, existing procedures for conducting ADBA call for the use
of audiograms taken without observing a quiet period. Both OSHA's
existing standard and this proposal require a 14-hour quiet period
before conducting a baseline audiogram. These standards, however, do
not address a quiet period for annual audiograms, leaving the choice to
the employer or the mine operator. Consequently, where a quiet period
is used, those audiograms could not be used in conducting ADBA.
MSHA also is concerned that the statistical methods employed by
ADBA require the use of a computer, which many small mine operators may
not have. Consequently, many mine operators may need to employ outside
consultants to conduct this analysis. Because the ADBA techniques are
relatively new, a sufficient number of consultants, who fully
understand and can utilize this analytical technique, may not be
available. Despite the problems with ADBA analysis for the mining
industry, MSHA recognizes that it may be a valuable tool for
identifying and correcting problems in an HCP before an STS occurs.
MSHA does not wish to discourage mine operators from using this
technique.
The analysis of an HCP's effectiveness can be as simple as
comparing a current audiogram with prior audiograms. This simple
approach, however, can be extremely time consuming and may not identify
trends among miners.
Further, international communities and selected branches of the
U.S. armed services require the effectiveness of the HCP's to be
evaluated even though they do not include specific methods for the
evaluation.
MSHA, however, is not specifying a methodology to determine the
effectiveness of an HCP for several reasons. First, there is not a
consensus among researchers and commenters as to a method even though a
draft ANSI standard (ADBA) has been published on this issue. Secondly,
the techniques for evaluating the effectiveness of an HCP that have
been developed are not appropriate to an HCP with few participants.
MSHA estimates that most HCP's in the mining industry would not have a
sufficient number of participants to be tested. Further, MSHA contends
that there are few consultants and fewer mine operators with the
expertise to evaluate the effectiveness of an HCP.
MSHA requests specific suggestions on practical methods which could
be used in the mining industry, particularly among small mine
[[Page 66407]]
operators, to evaluate the effectiveness of HCP's. MSHA also requests
comments on NIOSH's above stated recommendations.
Temporary or Seasonal Miners
The proposal would not provide any exemption from the requirements
to provide audiometric examinations for temporary or seasonal miners.
OSHA has no such explicit requirement. Moreover to create such an
exemption would mean that workers who change jobs--within a single
industry, or between industries--might end up never having a check on
hearing loss even if working in very noisy conditions.
The proposal does include certain provisions that might in practice
exclude some miners from examinations otherwise required. A mine
operator has up to 6 months to conduct a baseline audiogram--up to 12
months if a mobile van is used. Thus in practice, the operator's
obligation to provide examinations does not extend to those miners who
leave employment before this time and who do not subsequently return to
work for the same operator. Many summer employees might fall into this
category.
MSHA solicits further comment on this issue.
Permissible Exposure Level (PEL)
Proposed Sec. 62.120(c) provides as follows:
No miner shall be exposed to noise in excess of a TWA8 of
90 dBA (PEL) during any workshift, or equivalently a dose of 100%.
(1) If a miner's noise exposure exceeds the PEL, the operator
shall, in addition to taking the actions required under paragraph
(b) of this section, use all feasible engineering and administrative
controls to reduce the miner's noise exposure to the PEL. When
administrative controls are used to reduce a miner's exposure, the
operator shall post these procedures on the mine bulletin board and
provide a copy to affected miners.
(2) If a miner's noise exposure exceeds the PEL despite the use
of the controls required by paragraph (c)(1) of this section, the
operator shall take the actions required by this paragraph for that
miner.
(i) The operator shall use the controls required by paragraph
(c)(1) of this section to reduce the miner's noise exposure to as
low a level as is feasible.
(ii) The operator shall ensure that a miner whose exposure
exceeds the PEL takes the hearing examinations offered through
enrollment in the hearing conservation program.
(iii) The operator shall provide hearing protection to a miner
whose exposure exceeds the PEL and shall ensure the use thereof. The
hearing protection shall be provided and used in accordance with the
requirements of Sec. 62.125.
This paragraph would establish the permissible exposure limit (PEL)
to noise for a miner as a TWA8 of 90 dBA during any workshift.
(This is also referred to as a dose measurement of 100%; the action
level TWA8 of 85 dBA is half this dose of noise.)
The PEL is a time-weighted average sound level to which a miner may
be exposed that establishes the maximum dose of noise permitted. Under
the proposal, this is established as a TWA8 of 90 dBA--the same as
at present. TWA8 refers to a time-weighted-8-hour average, a term
defined in proposed Sec. 62.110. The exposure needed to reach the PEL
varies by sound level and time. For example, the PEL would be reached
as a result of exposure to a sound level of 90 dBA for 8 hours, but
also reached by exposure to a sound level of 95 dBA for only 4 hours or
92 dBA for 6.1 hours.
The Agency considered proposing a different PEL. As noted in part
II of the preamble, MSHA has concluded that there is a significant risk
of material impairment from noise exposures at or above a TWA8 of
85 dBA. MSHA considered setting the PEL at this level, but as discussed
in part IV of this preamble believes that this may not be feasible at
this time for the mining industry. Accordingly, the Agency is proposing
to keep the PEL at a TWA8 of 90 dBA--the level in effect for the
mining industry and under OSHA. The PEL is a dose twice that which
would be received at the level at which there is a significant risk of
material impairment.
While the PEL would not change, the actions required if noise
exposure exceeds the PEL would in many cases be different from those
currently required.
Under the proposal, a hierarchy of controls is established for all
mines. Mine operators must first utilize all feasible engineering and
administrative controls to reduce sound levels to the PEL. This
approach is more consistent with MSHA's existing noise standards for
metal and nonmetal mines than for coal mines. Under the current metal
and nonmetal regulations, mine operators have to utilize either
engineering or administrative controls to reduce noise to the PEL or as
close thereto as feasible. In the coal industry, MSHA inspectors do not
cite for noise without first deducting the attenuating value of hearing
protectors being worn by the miners subjected to excessive exposures of
noise. In practice, this means personal protective equipment is in most
cases accepted as a substitute for engineering and administrative
controls.
As under the present standards, the proposal would require a mine
operator to use only such engineering controls as are technologically
feasible, and to use only such engineering and administrative controls
as are economically feasible for that mine operator.
Moreover, the proposed rule spells out explicit requirements that
will supplement these controls in those cases in which the Agency
concurs with a mine operator that the use of all feasible engineering
and administrative controls cannot reduce noise to the PEL. All sectors
of the mining industry will, in such cases, have to provide all miners
exposed above the PEL with a properly fitting hearing protector, ensure
the miners use those protectors, and ensure that miners take their
annual hearing examinations.
Existing Standards
MSHA's existing metal and nonmetal noise standards require the use
of feasible engineering and administrative controls when a miner's
noise exposure exceeds the PEL. Hearing protectors are also required if
the exposure cannot be reduced to within the PEL. The existing metal
and nonmetal standards do not, however, require the mine operator to
post the procedures for any administrative controls used, to conduct
specific training, or to enroll miners in hearing conservation
programs.
MSHA's existing noise practices for coal mines are significantly
different from those for metal and nonmetal mines. The difference stems
from the circumstances under which the Agency is authorized to issue
citations. In metal and nonmetal mines, a citation is issued based
exclusively on the exposure measurement--when MSHA measures an exposure
at a TWA8 of 90 dBA. But in coal mines, a citation is not issued
in such a case if the miners are wearing hearing protection judged to
be appropriate. The appropriateness is based on the EPA noise reduction
rating minus 7 dB; in practice, most hearing protectors have ratings
which meet this official test for many coal mine exposures.
Accordingly, citations are seldom issued.
When coal mine operators do receive a citation for a miner's noise
exposure exceeding the PEL, they are required to promptly institute
administrative and/or engineering controls to assure compliance.
Additionally, within 60 days of receiving a citation, coal mine
operators are required to submit to MSHA a plan for the administration
of a continuing, effective hearing conservation program, including
provisions for--
(1) Reducing environmental noise levels;
[[Page 66408]]
(2) Making personal ear protective devices available to miners;
(3) Conducting pre-placement and periodic audiograms; and,
(4) Instituting engineering and administrative controls to ensure
compliance with the standard (underground only).
With regard to MSHA's existing noise standard, the Federal Mine
Safety and Health Review Commission (Commission) has addressed the
issue of what MSHA must consider, when determining what is a feasible
noise control for enforcement purposes, at a particular mine. According
to the Commission, a control is considered feasible when: (1) the
control reduces exposure, (2) the control is economically achievable,
and (3) the control is technologically achievable. See Secretary of
Labor v. Callanan Industries, Inc., 5 FMSHRC 1900 (1983), and Secretary
of Labor v. A. H. Smith, 6 FMSHRC 199 (1984).
In determining technological feasibility of a regulation, the
Commission has ruled that a control is deemed achievable 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 noise source. The control does not have to be ``off-the-
shelf''; but, it must have a realistic basis in present technical
capabilities.
In determining economic feasibility, 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 its use to achieve those results. The
Commission has expressly stated that cost-benefit analysis is
unnecessary in order to determine whether a noise control is required.
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
exposure. Todilto Exploration and Development Corporation v. Secretary
of Labor, 5 FMSHRC 1894 (1983). No guidance has been provided by the
Commission as to what level of reduction is considered significant.
However, the Commission has accepted the Agency's determination that a
3 dBA reduction is significant.
MSHA has interpreted the ``expected benefits'' to be the amount of
noise reduction achievable by the control. MSHA generally considers a
reduction of 3 dBA or more to be a significant reduction of the sound
level because it represents at least a 50% reduction in sound energy.
Consequently, a control that achieves relatively little noise reduction
at a high cost could be viewed as not meeting the Commission's test of
economic feasibility.
Consistent with the case law, MSHA considers three factors in
determining whether engineering controls are feasible at a particular
mine: first, the nature and extent of the overexposure; second, the
demonstrated effectiveness of available technology; and third, whether
the committed resources are wholly out of proportion to the expected
results. Before a violation of these requirements of the standard could
be found, MSHA would have to determine that a worker has been
overexposed; that administrative or engineering controls are feasible;
and that the mine operator failed to install or maintain such controls.
(See also the discussion of enforcement policy in the last of the
Questions and Answers in part I.)
OSHA's PEL is a TWA8 of 90 dBA, computed using a 90 dBA
threshold. The standard requires the use of feasible engineering or
administrative controls when a citation for exceeding the PEL is
issued. Under OSHA policy (CPL 2.45A CH-12), however, if an effective
HCP is in place, no STS has been detected, and adequate hearing
protectors are utilized, no citation will be issued for noise exposures
up to a TWA8 of 100 dBA if the costs to implement the HCP are less
than those of engineering or administrative controls. In determining
the appropriateness of hearing protection for this purpose, OSHA
reduces the EPA rating by 7; but it then further reduces effectiveness
by halving the result of that calculation. (A more detailed discussion
of hearing protector derating approaches can be found in the section on
Hearing Protector Effectiveness, part of the discussion of proposed
Sec. 62.125.)
Comments and Studies on PEL
Several commenters to MSHA's ANPRM recommended a PEL of 85 dBA. One
of these stated the following:
The current PEL provides inadequate protection for miner's
hearing. The 90 dB(A) PEL is excessive and permits noise exposure
that will result in significant hearing loss among exposed miners.
Specifically, 21 to 29% of workers exposed to 90 dBA for 40 years
will suffer material impairment of hearing. Material impairment of
hearing, defined by OSHA in this case, is 25 dBA or more loss for
the frequencies 1, 2, and 3 kHz. Based on this risk of damage, OSHA
adopted a hearing conservation program that is required when noise
exposure reaches 85 dBA TWA.
Another of these commenters recommended a PEL of 85 dBA with an 80
dBA action level. This commenter stated that:
Both OSHA and the National Institute for Occupational Safety and
Health (NIOSH) have recommended a PEL of 85 dBA. This level seems to
be an appropriate PEL for mining as well, since the numbers of
miners with hearing loss continues to be a problem. Obviously a more
conservative approach would be to utilize 80 dBA as the action level
to trigger the implementation provisions of an HCP. Although more
costly, the benefits for prevention of NIHL would certainly be
substantial.
Many commenters on this issue, however, believe that MSHA's current
PEL of 90 dBA should be retained and that it is adequate to protect
miners. One commenter referenced Bartsch (see Related Studies in the
III. Nature of the Hazard section of this preamble) as supporting
evidence for retaining the PEL of 90 dBA. Three commenters cited lack
of compensable noise-induced hearing loss (NIHL) cases among miners in
their geographical area as a positive indication that the current PEL
is adequate and they questioned the benefit of reducing the PEL to 85
dBA. These commenters also stated that about 20% of the miners in their
area were exposed to average sound levels above 85 dBA, but under 90
dBA.
In addition to the comments received in response to its ANPRM, MSHA
also reviewed numerous studies and standards relating to the
establishment of a PEL.
The Physical Agents Threshold Limit Value Committee of American
Conference of Governmental Industrial Hygienists (ACGIH) (1993) has
adopted a Threshold Limit Value (TLV) of 85 dBA Leq,8. The
committee believed that there was a clear consensus that an 85 dBA TLV
was valid and needed to protect the hearing acuity of workers at the
higher audiometric frequencies of 3000 and 4000 Hz.
Stekelenburg (1982) suggests that 80 dBA be the acceptable level
for noise exposure over a 40 year work history. Moreover, the
researcher suggests that extra precautions are necessary for sensitive
individuals and that these people need to be identified during the
first five years of exposure to noise.
Embleton (1994) summarized the occupational noise regulations
(pertaining to: PEL, exchange rate, and the upper limit for noise
exposure) from 17 countries and selected branches of the U.S. armed
services. His summary table (absent the recommendations in his report)
is reproduced below as Table III-4.
[[Page 66409]]
Table III-4.--Some Features of Legislation Tabulated for Various Countries*
--------------------------------------------------------------------------------------------------------------------------------------------------------
Limit for
LAeq 8-hour exposure engineering or Limit for monitoring
Country (jurisdiction) rate Exchange rate administrative hearing Upper limit for sound level
controls
--------------------------------------------------------------------------------------------------------------------------------------------------------
Australia (varies by state).. 85 dB................ 3 dB.......... 85 dBA.......... 85 dBA............... 140 dB lin, peak.
Brazil....................... 85 dB................ 5 dB.......... 90 dBA, no 85 dBA............... 130 dB peak.
exposure >115
dBA if no
protection.
Canada:
(Federal)................ 87 dB................ 3 dB.......... 87 dB........... 84 dBA............... 140 dB peak.
(ON, QU, NB)............. 90 dB................ 5 dB.......... 90 dBA.......... 85 dBA (a)...........
(AB, NS, NF)............. 85 dB................ 5 dB.......... 85 dBA..........
(BC)..................... 90 dB................ 3 dB.......... 90 dBA..........
China........................ 70-90................ 3 dB.......... ................ ..................... 115 dBA.
Finland...................... 85 dB................ 3 dB.......... 85 dB...........
France (b)................... 85 dB................ 3 dB.......... 90 dBA or 140 dB 85 dBA............... 135 dB peak.
peak.
Germany (b), (c)............. 85 dB................ 3 dB.......... 90 dBA.......... 85 dBA............... 140 dB peak.
Hungary...................... 85 dB................ 3 dB.......... 90 dBA.......... ..................... 125 dBA or 140 dB peak.
Israel....................... 85 dB 5 dB........... .............. ................ 115 dBA or 140 dB
peak..
Italy........................ 85 dB................ 3 dB.......... 90 dB........... 85 dB................ 140 dB peak.
Netherlands.................. 80 dB................ 3 dB.......... 85 dB........... 140 dB peak..........
New Zealand.................. 85 dB................ 3 dB.......... 85 dBA +3 dB 115 dBA slow or 140
exchange rate. dB peak..
Norway....................... 85 dB................ 3 dB.......... ................ 80 dBA............... 110 dBA.
Spain........................ 85 dB................ 3 dB.......... 90 dBA.......... 80 dBA............... 140 dB peak.
Sweden....................... 85 dB................ 3 dB.......... 90 dBA.......... 80 dBA............... 115 dBA or 140 dBC.
United Kingdom............... 85 dB................ 3 dB.......... 90 dBA.......... 85 dBA............... 140 dB peak.
USA (d)...................... 90 dB (TWA8)......... 5 dB.......... 90 dBA but no 85 dBA............... 115 dBA or 140 dB peak.
exposure >115
dBA.
USA Army and Air Force)...... 84 dB................ 3 dB.......... ................ 85 dBA............... 140 dB peak.
--------------------------------------------------------------------------------------------------------------------------------------------------------
*Embleton (1994).
Information for countries not represented by Member Societies participating in the Working Party is taken from Ref. 15.
(a) A more complex situation is simplified to fit this tabulation.
(b) These countries require the noise declaration of machinery, the use of the quietest machinery where reasonably possible, and reduced reflection of
noise in the building, regardless of sound or exposure levels.
(c) The noise exposure consists of LAeq and adjustments for tonal character and impulsiveness.
(d) TWA is Time Weighted Average. The regulations in the U.S. are unusually complex because different thresholds are used to compute levels to initiate
hearing programs (85 dBA), noise exposure monitoring (80 dBA), and noise reduction measures (90 dBA), each using a 5-dB exchange rate.
Embleton included recommendations based upon current practice taken
from the various jurisdictions:
----------------------------------------------------------------------------------------------------------------
Limit for engineering
LAeq 8-hour ex- Exchange rate or administrative Limit for monitoring Upper limit for
posure rate controls hearing sound level
----------------------------------------------------------------------------------------------------------------
85 dBA............... 3 dBA................ Use quietest machines On hiring and at 140 dB peak.
and room absorption intervals thereafter.
in workplaces.
----------------------------------------------------------------------------------------------------------------
He stated that:
The primary goal of this report and its recommendations is to
reduce the risk of long term hearing damage and expose people to a
practical minimum. . . . Each feature recommended had been
considered to be practicable by at least one national jurisdiction
and there may be some experience of its usefulness. Much current
legislation was enacted several years ago, before the more recent
scientific evidence was available and before it was integrated into
current understanding of this complex scientific topic.
The U.S. armed services and possibly some international communities
do not go through a public rulemaking process in establishing their
respective noise regulations. Nevertheless, MSHA has included these
sources to show that a consensus exists on noise legislation. Table
III-5 lists information similar to that included in Table III-4 for
several additional entities. Furthermore, there was a discrepancy found
in Table III-4 as per the information provided for the U.S. armed
services. The corrected information is included in Table III-5
(compiled by MSHA).
Table III-5.--Features of Noise Exposure Criteria for Additional Entities
--------------------------------------------------------------------------------------------------------------------------------------------------------
Limit for
LAeq 8- hour exgineering or Limit for
Country or jurisdiction exposure rate Exchange rate administrative monitoring hearing Upper limit for sound level
controls
--------------------------------------------------------------------------------------------------------------------------------------------------------
American Conference of 85 dBA............. 3-dB.............. .................... 85 dBA............. 140 dBC peak.
Governmental Industrial
Hygienists (ACGIH).
[[Page 66410]]
European Economic Community (EEC). 85 dBA............. 3-dB.............. 90 dBA.............. 85 dBA............. 140 dB peak.
South Africa...................... 85 dBA............. 3-dB.............. 85 dBA.............. 85 dBA............. 115 dBA or 150 dB.
U.S. Air Force.................... 85 dBA............. 3-dB.............. 85 dBA.............. 85 dBA............. 115 dBA or 140 dB.
U.S. Army......................... 85 dBA............. 3-dB.............. 85 dBA.............. 85 dBA............. 140 dB.
U.S. Navy......................... 84 dBA............. 4-dB.............. 84 dBA.............. 84 dBA............. 140 dB.
State of Western Australia........ 90 dBA............. 3-dB.............. 90 dBA.............. ................... 140 dB.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Because the information contained in Tables III-4 and III-5 does
not include every jurisdiction, MSHA solicits additional information on
features of noise legislation for comparison purposes.
Hierarchy of Controls
The proposal would require mine operators to use all feasible
engineering or administrative controls or a combination of these
controls to reduce a miner's daily noise exposure to the PEL. If these
controls do not reduce the exposure to the PEL, then they shall be used
to reduce the exposure as low as feasible. The proposal does not place
preference on the use of engineering controls over administrative
controls; but all feasible controls of both types must be implemented
to reduce noise exposure to the PEL or as close thereto as is possible
when all feasible controls are utilized.
MSHA's proposed requirements for either feasible engineering or
administrative controls or a combination of these controls are closer
to MSHA's existing noise standards for metal and nonmetal mines than to
the standards for coal mines.
In metal and nonmetal mines, engineering or administrative controls
are required to the extent feasible when exposures exceed a TWA8
of 90 dBA. Current metal and nonmetal enforcement requirements equate
engineering and administrative controls and do not accept hearing
protectors in lieu of such controls. Mine operators in these
industries, which have a significant percentage of small employers,
generally opt to use engineering controls over administrative controls,
citing practical difficulties with the implementation of the latter.
Administrative controls reduce exposure by limiting the amount of time
that a miner is exposed to noise, through such actions as rotation of
miners to areas having lower sound levels, rescheduling of tasks, and
modifying work activities.
The hierarchy of noise control for coal mines is significantly
different. In determining whether the mine operator is in violation of
the PEL, MSHA deducts from noise exposure measurements the corrected
attenuation of hearing protectors being worn by the miners. Given
normal conditions in these mines, when hearing protectors are being
worn, no citation is issued.
OSHA's standard requires the use of feasible engineering or
administrative controls. As discussed above, however, current OSHA
policy allows employers to rely on a combination of other controls--
enrollment in an HCP, no STS, and adequate hearing protectors (measured
in accordance with specifications adjusted for the purpose of the
policy)--up to a noise exposure of 100 dBA, provided that the cost is
less than that of the engineering and/or administrative controls.
A number of commenters responding to MSHA's ANPRM, specifically
supported the primacy of engineering controls. One commenter supported
the primacy of engineering controls citing anecdotal evidence that
miners resist wearing hearing protectors. Another commenter stated that
engineering controls for mining are far more available than commonly
thought.
Several commenters stated that administrative controls can be
effective but are often impractical. One commenter stated that
administrative controls are effective but are of limited use at small
operations because there are not enough people to rotate through the
various jobs. Another commenter stated that although the use of
administrative controls may lower the exposure of an individual miner
such controls have the disadvantage of increasing overall exposure to a
larger population. A third commenter stated that administrative
controls should be the least preferred control method.
A significant number of commenters specifically requested that MSHA
allow the use of hearing protectors in lieu of engineering or
administrative controls, as long as the hearing protector provided
adequate attenuation. These commenters believed that hearing protectors
were equally as effective as engineering and administrative controls.
Many commenters recommended that MSHA allow the mine operator a
choice or combination of controls, including the use of an HCP. Several
commenters stated the following:
There is no logical reason to handcuff operators by limiting
flexibility and freedom of choice in selecting the most appropriate
method of noise protection for the particular application;
providing, of course, the method is effective.
For some reason HPD's (hearing protection devices) have been
regulated to be a third class behind administrative, and engineering
controls. It is our experience the HPD's provide more effective,
less costly, and more reliable protection than engineering or
administrative controls in many circumstances. The employee
acceptance is also good to excellent. Therefore the discrimination
against HPD's should be removed in any future regulations.
Dear (1987) contends that employers can manage the risk of hearing
impairment by encouraging all employees to participate in the HCP and
that an HCP can be as effective, in many cases, as the use of other,
more costly controls. He believes that some workers are better served
by wearing hearing protectors than reducing the noise via engineering
controls to the PEL. He contends that removing the hearing protectors
when the sound levels are reduced to 90 dBA [by engineering controls]
would expose workers to at least 90 dBA; whereas, use of hearing
protectors would reduce exposures much lower. Dear cites studies
conducted by DuPont on their employees to show the effectiveness of
hearing protectors. Employees in the DuPont HCP, which includes hearing
protectors and begins at approximately 90 dBA, had not developed
hearing impairment during the study period.
Pell and Dear (1988) believe that employees exposed above 90 dBA
are better protected by using appropriate hearing protectors, rather
than implementing engineering controls to
[[Page 66411]]
reduce the noise to 89 dBA or even 84 dBA.
Berger (1983) states the following regarding engineering controls
versus hearing protectors:
When one compares engineering noise controls to HPDs [hearing
protectors], it must be remembered that the same types of problems
which afflict HPD performance in the RW [real world], will tend to
reduce the effectiveness of noise control measures as well. For
example, one of the most commonly used treatments is an enclosure.
If it is not well fitted, or left partially ajar, or circumvented by
an inconvenienced employee, or its gaskets and seals age,
deteriorate, or break in any way, then its performance will be
degraded in a manner similar to that which has been observed for
poorly fitted and misused HPDs. When noise control is achieved by
improved adjustments and lubrication, there must be a trained and
dedicated employee to monitor the maintenance schedule, just as
employees must care for and maintain their HPDs. In fact most
engineering noise control procedures, except for some source noise
control accomplished through equipment redesign, require maintenance
and periodic adjustment or replacement to continue functioning
properly. And except for enclosures, noise reductions of 10 dB or
more are often difficult to achieve and maintain. Thus HPDs remain
one of the most important protective methods for a hearing
conservationist to consider, and can provide an effective adjunct to
engineering noise controls in the majority of industrial noise
environments.
Nilsson et al. (1977) studied hearing loss in shipbuilding workers.
The workers were divided into two groups. In the first group, the
workers were exposed to 94 dBA with 95% of the workers using hearing
protectors. In the second group, the workers were exposed to 88 dBA and
90% of them wore hearing protectors. Both groups were subjected to
impulse noise up to 135 dB. Despite the fact that the vast majority of
the workers in both groups wore hearing protectors, cases of noise-
induced hearing loss (NIHL) were common. The mean pure tone audiograms
showed the typical noise dip at 4000 Hz. For increased exposure
durations, the amount of NIHL increased. Workers exposed to 94 dBA
exhibited more hearing loss than those exposed to 88 dBA. Nilsson
concluded that 58.1% of all of the workers had some degree of hearing
impairment, and only 1.8% was caused by factors other than noise after
excluding hearing loss due to heredity, skull injury, or ear disease.
According to Nilsson et al., the hearing protectors should have
attenuated the noise by at least 13 dBA. This study concluded that
reliance on hearing protectors alone is not sufficient to protect the
hearing acuity of the workers.
NIOSH's position regarding the hierarchy of controls is stated in
their December 16, 1994 comments to MSHA (NIOSH 1994). According to
NIOSH there are three elements of an effective hierarchy of controls.
They are--
1. Prevent or contain hazardous workplace emissions at their
source;
2. Remove the emissions from the pathway between the source and the
worker; and
3. Control the exposure of the worker with barriers between the
worker and the hazardous work environment.
NIOSH further states that the essential characteristics of specific
control solutions are--
1. The levels of protection afforded workers must be reliable,
consistent, and adequate;
2. The efficacy of the protection for each individual worker must
be determinable during use throughout the lifespan of the system;
3. The solution must minimize dependence on human intervention for
its efficacy so as to increase its reliability; and
4. The solution must consider all routes of entry into worker's
bodies and should not exacerbate existing health or safety problems or
create additional problems of its own.
NIOSH (1988), in its publication entitled ``Proposed National
Strategy for the Prevention of Noise-Induced Hearing Loss''
(Publication No. 89-135), encouraged OSHA to rescind its policy of
accepting HCP's in lieu of either feasible engineering and/or
administrative controls and states:
It is extremely foolhardy to regard hearing protection as a
preferred way to limit noise exposures because most employees obtain
only half the sound attenuation possible from hearing protectors.
Even with training, some workers fail to obtain maximum benefit from
these protectors because they have difficulty adjusting them
properly, or they refuse to wear them because they fear such devices
will impair their ability to perform their jobs properly or hear
warning signals. If, however, noise is reduced by engineering and/or
administrative controls, the limitations of hearing protectors are
of less concern.
In the report, ``Preventing Illness and Injury in the Workplace,''
the Office of Technology Assessment (1985) found that health
professionals rank engineering controls as the priority means of
controlling exposure, followed by administrative controls, with
personal protective equipment as a last resort.
The National Hearing Conservation Association (NHCA) in a letter
from their President, Susan Cooper Megerson (1994), to Joseph Dear,
Assistant Secretary of Labor for Occupational Safety and Health, urged
OSHA to rescind its policy of accepting an HCP in lieu of engineering
noise controls for exposures up to 100 dBA. NHCA contends that feasible
engineering controls should be the preferred method of controlling the
noise. Further, NHCA states that ``Most hearing protectors, as they are
worn in the field, do not provide sufficient attenuation to bring
workers' exposures from 100 dB(A) to safe noise levels.''
Suter (1994) in a letter to Sue Andrei of OSHA's Policy Directorate
urged OSHA to rescind its policy of accepting an HCP in lieu of
engineering and/or administrative controls for exposures up to 100 dBA.
Suter contends that most HCPs are ineffective due to hearing protectors
providing only a fraction of their laboratory attenuation. Further,
Suter urges OSHA to re-emphasize engineering noise controls.
MSHA understands that the two letters to OSHA were sent in response
to an OSHA request for comment on how to design a priority scheme for
OSHA standards. No responses were issued, and the priority scheme is
still pending. MSHA has also reviewed a recent letter to the EPA from
the American Industrial Hygiene Association questioning the rating
system used to label hearing protectors with attenuation values; this
is discussed above in the section on Hearing protector effectiveness
(in connection with proposed 62.125).
In summary, commenters and researchers on this issue were divided
as to whether engineering/administrative controls should have primacy
over the use of hearing protectors or an HCP. Most of the international
community, U.S. armed services, and NIOSH, however, discourage the use
of hearing protectors and an HCP as the primary means of control and
accept their use only when engineering and administrative controls
failed to achieve a significant reduction in the worker's exposure.
Administrative controls reduce exposure by limiting the amount of
time that a miner is exposed to noise, through such actions as rotation
of miners to areas having lower sound levels, rescheduling of tasks,
and modifying work activities. Many mine operators have demonstrated
that administrative controls can be as effective and less costly than
the installation of engineering controls. However, the use of
administrative controls may be limited by labor/management agreements,
limitations on the number of qualified miners capable of handling a
specific task, or difficulty in ensuring that miners adhere to the
[[Page 66412]]
administrative controls. Additionally, administrative controls have the
potential draw back of exposing multiple workers to high sound levels
for designated time periods. Because the effectiveness of
administrative controls is based on adherence to these strict time
periods, mine operators may find it difficult to verify compliance with
the administrative procedures.
Although there are some disadvantages to using administrative
controls, the Agency has determined that in certain circumstances they
can be as effective as engineering controls. MSHA, therefore, believes
that the mine operator should have the option to choose which method of
control to use--provided that all feasible controls must be utilized if
needed to reduce sound levels to or below the PEL. This would give mine
operators maximum flexibility when considering the intricacies of their
operation in complying with the regulation. Administrative controls,
utilized properly, spread the risk over a larger population although at
a lower risk to each individual.
A related type of control would be the transfer of miners to other
assignments. The Mine Safety and Health Act provides for the Agency to
prescribe such an approach in certain cases. MSHA considered proposals
to do so in cases in which an STS is detected. Discussion of this topic
is covered by the section of the preamble that reviews proposed
Sec. 62.180.
Based upon its review of the available evidence, MSHA concludes
that a reduction of a miner's risk of material impairment due to
occupational NIHL noise can best be achieved through the use of all
feasible engineering or administrative controls or a combination
thereof. The use of engineering controls inherently provides the most
consistent and reliable protection because such controls do not depend
upon individual human performance or intervention to function. MSHA's
proposal would, however, allow mine operators to use either engineering
or administrative controls. This would provide the mine operator with
the flexibility to select the most appropriate control for the
situation. These methods would be given clear primacy over personal
protective controls. While MSHA is aware that NIOSH is seeking to
develop an approach that would more accurately derate hearing
protectors in actual workplace use, the prospects for this remain
uncertain; moreover, the issues associated with the consistency and
reliability of personal protective equipment use would remain.
Engineering Noise Controls for Mining Equipment
Engineering noise controls reduce exposure by modifying the noise
source, noise path or the receiver's environment thereby decreasing the
miner's exposure to harmful sound levels. Examples of these three types
of engineering controls are exhaust mufflers, barriers, and
environmental cabs, respectively. Exposures may also be controlled by
substituting quieter mining equipment. For example, a diamond wire saw
can be substituted for a conventional hand-held channel burner in the
dimension stone industry.
MSHA has listed feasible engineering controls for the major
classifications of equipment used in metal and nonmetal mines in its
Program Policy Manual, Volume IV. The engineering controls referenced
in this manual have been evaluated by MSHA Technical Support and proven
feasible and effective in the mining industry. This document is
currently used by MSHA inspectors and others to assist in determining
if engineering controls are feasible. Following are some examples of
the feasible controls covered in that manual.
1. Acoustically treated cabs. For mining equipment such as haul
trucks, front-end-loaders, bulldozers, track drills, and underground
jumbo drills, acoustically treated cabs are among the most effective
noise controls. Such cabs are widely available, from the original
equipment manufacturer and the manufacturers of retrofit cabs, for
machines manufactured within the past 20 years. The noise reduction of
factory installed acoustically treated cabs is generally more effective
than that of retrofit cabs. According to some manufacturers, sound
levels at the mine operator's position inside factory cabs are often
below 90 dBA and in some cases below 85 dBA.
Occasionally, underground mining conditions are such that full-
sized surface haulage equipment can be used. Where this is possible,
such equipment can be equipped with a cab as described above.
Additionally, some manufacturers offer cabs for lower profile
underground mining equipment such as scoop-trams, shuttle cars, and
haul trucks. The use of cabs on such underground mobile haulage
equipment generally is feasible provided it does not create a safety
hazard due to impaired visibility.
The former USBOM has published two how-to manuals entitled
``Bulldozer Noise Controls'' (1980), and ``Front-End Loader Noise
Controls'' (1981) that describe in great detail how to install a
retrofit cab and install acoustical materials.
2. Barrier shields. For some equipment, generally over 20 years
old, an environmental cab may not be available from the original
equipment manufacturer or from manufacturers of retrofit cabs. In such
cases, a partial barrier with selective placement of acoustical
material can generally be installed at nominal cost to block the noise
reaching the equipment operator. These techniques are also demonstrated
in ``Bulldozer Noise Controls'' (1980).
Barrier shields and partial enclosures can also be used on track
drills where full cabs are not feasible. Such shields and enclosures
can be either free standing or attached to the drill. Typically,
however, they are not as effective as cabs and usually do not reduce
the miner's noise exposure to within MSHA's current 90 dBA PEL. This
barrier can be constructed at minimal cost from used conveyor belting.
3. Exhaust mufflers. In addition to an environmental cab or barrier
shield, diesel powered equipment can be equipped with an effective
exhaust muffler. The end of the muffler's exhaust pipe should be
located as far away from the equipment operator as possible, and the
exhaust directed away from the operator. For underground mining
equipment, exhaust mufflers are generally not needed where water
scrubbers are used. A water scrubber offers some noise reduction and
the addition of an exhaust muffler may create excessive back pressure
or interfere with the proper functioning of the scrubber. However,
exhaust mufflers can be installed on underground equipment where
catalytic converters are used.
Exhaust mufflers can also be installed on pneumatically powered
equipment. For example, exhaust mufflers are offered by the
manufacturers of almost every jackleg drill, chipping hammer, and jack
hammer. In the few cases where such exhaust mufflers are not available
from the factory, they can be easily constructed by the mine operator.
MSHA has a videotape available showing the construction of such an
exhaust muffler for a jackleg drill. This muffler can be constructed at
minimal cost from a section of rubber motorcycle tire.
4. Acoustical materials. Various types of acoustical materials can
be strategically used to block, absorb, and/or dampen sound. Generally
such materials are installed on the inside walls of equipment cabs or
operator compartments and in control rooms and booths. For example:
barrier and
[[Page 66413]]
absorptive materials can be used to reduce noise emanating from the
engine and transmission compartments; and acoustic material can be
applied to the firewall between the employee and transmission
compartment. Noise reduction varies depending upon the specific
application. Care must be taken to use acoustical materials that will
not create a fire hazard.
5. Control rooms and booths. Acoustically treated control rooms and
booths are frequently used in mills, processing plants, or at portable
operations, to protect miners from noise created by crushing,
screening, or processing equipment. Such control rooms and booths
typically are successful in reducing exposures of employees working in
them to below 85 dBA.
6. Substitution of equipment. In a few cases, where sound levels
are particularly severe, and neither retrofit nor factory controls are
available, the equipment may need to be replaced with a quieter type.
For example, hand-held channel burners had been used for many years to
cut granite in dimension stone quarries. These were basically small jet
engines on a pole, fueled by diesel fuel and compressed air. The pole
was held by the channel burner operator and the flame was directed
against the granite. The intense heat caused the granite to spall and
by moving the flame back and forth a channel could be created. Sound
levels typically exceeded 120 dBA at the operator's ear.
Several years ago, alternative and quieter methods of cutting the
granite were developed. These included replacing the channel burner
with either a diamond wire saw, hydraulic or pneumatic slot drill, or
water jet. Dimension stone operators were notified by MSHA of the
availability of these alternatives and given time to phase out the use
of diesel-fueled, hand-held burners and replace them with one of the
quieter alternatives. MSHA also has a videotape describing these
various alternatives.
7. New equipment design. Using the channel burners as an example, a
new design of channel burner was engineered which automated the
process. The hand-held channel burners can be replaced with automated
channel burners using liquid oxygen. The automated design does not
require the operator to be near the channel burner, thereby using
distance to attenuate the noise.
In addition to the noise controls described in MSHA's Program
Policy Manual, Volume IV, a number of other documents are available
describing effective noise controls for coal, metal and nonmetal
mines--controls for underground equipment and controls for surface
equipment.
The MSHA document entitled, ``Summary of Noise Controls for Mining
Machinery,'' (Maraccini et al., 1986) provides case histories of
effective noise controls installed on specific makes and models of
mining equipment. The case histories describe the controls used, their
cost, and the amount of noise reduction achieved. MSHA believes that
the controls utilized in these specific cases can be extended to other
pieces of mining equipment.
Furthermore, the former USBOM, which has been responsible for
conducting research leading to improved equipment and methods for
controlling safety and health hazards in mining, published a handbook
entitled, ``Mining Machinery Noise Control Guidelines, 1983.''
(Bartholomae and Parker, 1983) This handbook describes engineering
noise controls for coal, metal and nonmetal mining equipment. The
former USBOM also published numerous documents describing noise
controls for mining machinery. Many of these research reports are
listed in the USBOM publication IC9004, ``The Bureau of Mines Noise-
Control Research Program--A 10-Year Review.'' (Aljoe et al., 1985) Part
V of this preamble contains a list of USBOM publications dealing with
particular types of equipment.
In particular, these include noise control methods for coal cutting
equipment, longwall equipment, conveyors, and diesel equipment.
Underground coal mining equipment may require some unique noise
controls. However, for coal cutting machines such as continuous miners
and longwall shears, the use of remote control is the single most
significant noise control. The installation of noise dampening
materials and enclosure of motors and gear cases can be used to aid in
controlling noise of coal transporting equipment such as conveyors and
belt systems. Diesel equipment used underground can use controls
similar to those used on surface equipment. Mufflers, sound controlled
cabs, and barriers will provide much of the needed noise control for
this type of equipment.
Finally, while MSHA is not making any assumptions about the
development of new technologies, it would be interested to learn of any
processes under development that could further assist mine operators in
controlling noise. For example, the former USBOM (Burks and
Bartholomae, 1992) has developed a variable speed chain conveyor which
can be used to reduce the noise exposure of continuous miner operators
and loading machine operators in particular. An empty conveyor is
noisier than a full one because the coal covering the conveyor inhibits
the radiation of noise. The variable speed chain conveyor only operates
when necessary to convey coal. To date the manufacturers of mining
machines have apparently not adopted this technology, despite the fact
that it has the added benefits of reduced dust emissions, reduced power
consumption, and reduced maintenance costs.
Although most of the USBOM noise control documents are not
specifically discussed in this section, MSHA has reviewed them. The
reviewed documents are listed in the references and are available to
the mining community. For additional information on USBOM noise control
projects contact: Mr. Edward D. Thimons, U.S. Department of Energy,
Pittsburgh Research Center, P.O. 18070, Pittsburgh, PA 15236, (412)
892-6683, Fax (412) 892-4259.
Posting of Administrative Control Procedures
The proposal would require that the mine operator post a copy of
any administrative controls in effect on the mine bulletin board, and
provide affected miners with a copy. As required by Section 109 of the
Mine Act, a mine operator must have a bulletin board. Documents
containing pertinent mine information are required to be posted by
various mandatory standards (e.g., training plan, emergency
communication numbers, MSHA citations, etc.). This is an ideal place to
require the administrative procedures to be posted, since most miners
are familiar with its location and the importance of documents placed
on it.
The existing MSHA coal noise regulations do not require written
administrative controls, unless these controls are part of a hearing
conservation plan. Further, if written, the administrative controls are
not required to be posted. However, the affected miner would be
informed of the administrative procedures as part of his/her required
part 48 training. Neither MSHA's current metal and nonmetal nor OSHA's
noise regulations require that administrative controls, if used, be in
writing and posted.
MSHA did not receive any comments on this issue.
MSHA has concluded that it is important that administrative
controls be posted, since miners must actively comply for the controls
to be effective. Posting would facilitate informing miners of work
practices necessary for
[[Page 66414]]
reducing their noise exposures, especially when temporarily assigned to
a different job. Since the administrative controls must be in writing
to be posted on the mine bulletin board, MSHA believes that providing
the affected miners with copies would not be a significant burden as
compared to other possible methods of notification and is likely to be
more much more effective in ensuring miners are on notice of their
obligation to comply.
Supplementary Controls
Under proposed Sec. 62.120(b), any miner exposed above the action
level will receive special training in noise protection, and be
enrolled in a hearing conservation program in which annual audiometric
tests are offered. Any miner exposed above that level is to receive
hearing protection upon request, as is any miner who incurs an STS or
who is waiting for a baseline audiogram. The operator must ensure
hearing protection is worn, however, in only two cases: if there is an
STS, and if it will take more than 6 months to get the baseline
audiogram because of the need to wait for a mobile test van.
Under proposed Sec. 62.120(c), if exposures exceed the PEL, and
cannot be feasibly reduced to the PEL through the use of all feasible
engineering and administrative controls, a few additional requirements
would be applicable. All miners so exposed must be provided hearing
protection, and required to use the hearing protection. In addition,
the operator would be required to ensure that miners take the scheduled
audiometric examinations.
The circumstances under which hearing protection must be worn are
discussed more fully in connection with proposed Sec. 62.125.
MSHA is proposing that mine operators require miners enrolled in an
HCP to participate in audiometric testing once exposures exceed the
PEL. This is not the case under OSHA; however, MSHA believes this
approach is warranted in the mining industry.
The information generated by these tests can serve as triggers for
both the mine operator and the Agency to investigate more thoroughly
the implementation of noise controls. If an employee incurs a standard
threshold shift, at the very least a hearing protector needs to be
provided or changed. The audiological information can provide useful
clues to the noise causing the problem, and point to an undetected
failure of various controls: engineering controls, administrative
controls, or the failure to properly fit, maintain or utilize hearing
protectors. If an employee incurs a reportable hearing loss, it is an
indication that despite regular MSHA inspections, some serious problem
has not been detected or resolved and a more thorough analysis is
probably required. If the required audiological examinations are not
taken, standard threshold shifts and cases of reportable hearing loss
will go unreported.
In addition, the Agency wants to ensure that miners are aware of
the severity of any hearing loss; in a mining environment, this
knowledge could have implications for the safety of the miner and the
safety of others. Miners who do not recognize that they have a hearing
problem--and hearing loss occurs gradually and is often hard for
individuals to accept--may be less willing than those who have been
advised they have a problem to pay attention to the problem. The
proposed regulation provides for annual training, but a notification of
a detectable change in hearing acuity would certainly help to focus
attention.
The Agency is concerned that unless such participation is
mandatory, the cost of the examinations, however limited, might create
an incentive for mine operators to encourage miners to waive the
examinations. Concern about the implications of health examinations on
their job security may likewise discourage miners from taking
examinations. The voluntary X-ray surveillance program currently
offered to coal miners has a poor record of participation. This is not
an unusual situation in the mining industry, where retention of good,
well-paying jobs is a priority for most workers.
Finally, it should be noted that audiometric testing is not an
invasive procedure. No damaging radiation is involved, nor is there any
penetration with a needle or other device.
Comments on this provision are specifically solicited. In
particular, experience from companies in which such examinations are
mandated would be welcome. The Agency recognizes there may be concern
on the part of some miners that if mine operators are provided with
audiometric information, it could lead to the discharge of miners who
are developing hearing loss problems so as to minimize potential
workers' compensation claims.
Dual Hearing Protection
Proposed Sec. 62.120(d) would require that, in addition to the
controls required for noise exposure that exceed the PEL, a mine
operator provide dual hearing protectors to a miner whose noise
exposure exceeds a TWA8 of 105 dBA during any workshift, a dose of
800% of the PEL. The mine operator must also ensure that they are worn.
An earplug type protector would be worn under an earmuff type
protector.
Currently, neither MSHA nor OSHA specifically mandate the use of
dual hearing protection. In practice, however, existing rules require
dual hearing protection under some circumstances.
Under current Coal and Metal and Nonmetal noise policy, dual
hearing protection would be required whenever the attenuation of a
single hearing protector does not reduce the miner's noise exposure to
within the PEL.
Also, due to MSHA's current procedures for determining the
attenuation of hearing protectors (discussed under Hearing protector
effectiveness of this preamble), dual hearing protection would almost
always be required when miners are exposed to sound levels above 112
dBA. As discussed below, the attenuation provided by dual hearing
protectors is less than the sum of their individual attenuations. MSHA
policy currently specifies that 6 dB be added to the attenuation of the
hearing protector having the higher attenuation.
OSHA requires that ``adequate'' hearing protection be provided to
and worn by workers. Employers would thus have to utilize dual hearing
protection in some cases to get the needed attenuation. However, no
specific dose level triggering dual hearing protection level has been
established by OSHA.
No commenter addressed the exposure above which dual hearing
protection would be required. One commenter suggested that MSHA
consider dual hearing protection to provide 5 dB more attenuation than
the hearing protector with the higher attenuation. Another commenter,
disagreed with current MSHA Metal and Nonmetal policy and believed that
more than 6 dBA credit should be given above the attenuation of the
higher component (earplug or earmuff) when dual hearing protectors are
worn. This commenter did not, however, specify how much credit should
be given.
Research has demonstrated that dual hearing protection affords the
wearer greater attenuation than either earplugs or earmuffs alone.
Berger in EARLOG 13 (1984) has shown that the use of dual hearing
protectors provides greater attenuation. The attenuation of the dual
hearing protection is at least 5 dB greater than the attenuation of
either hearing protector alone. This attenuation, however, is much less
than the sum of the individual Noise Reduction Rating (NRR) values and
is dependent on the frequency. Dual hearing protectors are especially
important for noise which is dominated
[[Page 66415]]
by low to middle frequency sounds. The performance of dual hearing
protectors is not influenced greatly by the selection of the earmuff;
however, the selection of the earplug has a strong influence on the
attenuation below 2000 Hz. For noises which are dominated by sounds
above 2000 Hz, the attenuation of dual hearing protectors is limited by
flanking bone conduction paths to the inner ear. Berger recommends dual
hearing protectors whenever the TWA8 exceeds 105 dBA.
Michael (1991) believes that, because of complex coupling factors,
the attenuation from wearing both earplugs and earmuffs cannot be
predicted accurately. If the attenuation of the earplug and earmuff is
about the same at a given frequency, then the resultant attenuation
should be 3 to 6 dB greater than the higher of the two individual
attenuations. However, if one attenuation is much greater than the
other, then the resultant attenuation will be slightly more than the
higher attenuation.
Nixon and Berger (1991) report that earplugs, worn in combination
with earmuffs or helmets, typically provided more attenuation than
either hearing protector alone. The gain, in attenuation at individual
frequencies, varies between 0 to 15 dB. At or above 2000 Hz, the
attenuation of the combination is limited by bone conduction to
approximately 40 to 50 dB. Below 2000 Hz, the selection of the earplug
is critical for increasing the attenuation. There is little change in
the attenuation of different types of earmuffs at frequencies below
2000 Hz.
Bertrand and Zeiden (1993) determined that miners exposed to sound
levels of 118 dBA were afforded protection consistent with a sound
level of 98 dBA by the use of earmuffs. The earmuff had an NRR of 24
dB. Consequently, the earmuff alone could not provide attenuation
sufficient to protect the miner's hearing acuity.
Research has clearly demonstrated that dual hearing protection
provides greater attenuation than either hearing protector alone.
Further, the U.S. armed services require dual hearing protection for
workers exposed to high sound levels. MSHA concurs that the additional
attenuation afforded by the use of dual hearing protection is necessary
to protect miners who are exposed to high sound levels. Furthermore,
MSHA has concluded that a TWA8 of 105 dBA (800%) is a prudent
level above which dual hearing protection should be required. This
level of noise exposure can quickly damage the hearing acuity of the
exposed miner.
Dose Ceiling
Although the statement of the PEL in Sec. 62.120(c) is absolute
that no miner shall be exposed to noise above a TWA8 of 90 dBA,
the remainder of that paragraph and paragraph (d) deal with situations
where in fact miners are going to be exposed to noise in excess of the
PEL for some period of time--due to the economic feasibility of
administrative and engineering controls for a particular mine operator,
or due to the technological feasibility of engineering controls as to a
particular operation. The seriousness of this situation for miners is
indicated by the fact that MSHA is proposing that dual hearing
protectors be required at a TWA8 of 105 dBA: a noise dose of 800%.
The Agency is interested in comments on whether there is some noise
dose which should be established as an absolute dose ceiling by the
regulation, regardless of the implications for a particular mine
operator or operation. The circumstances in which this might pose a
problem for the mining industry appear to be very limited. While coal
inspection data over the years have indicated some exposures over 800%,
MSHA believes these are anomolies for which well-known controls are
available. If there are problems, they are likely to be in the metal
and nonmetal sector.
On the one hand, the dual-survey data indicate that using the 80
dBA threshold level, only about one-quarter of one percent (0.28%) of
metal and non-metal exposures exceed a noise dose of 800%. The data
indicate, however, that there remain a few specific job categories in
the metal and nonmetal sector which experience a significant problem
with noise exposures of this dimension, as indicated in Table III-6.
The sample size is provided to illustrate that in some cases, the
percentages are based on limited data.
Table III-6: Metal/Nonmetal Job Categories in Which More Than 1% of
Recorded Exposures Are Over a TWA8 of 105 dBA (800% of PEL)
------------------------------------------------------------------------
No. > No. of Percent
Code Job category 105 sample > 105
------------------------------------------------------------------------
134............ Jet-piercing channel 5 9 56
operator.
234............ Jet-piercing drill 1 3 33
operator.
058............ Drift miner.............. 15 55 27
057............ Stope miner.............. 9 39 23
534............ Jackleg or stopper drill 7 31 23
operator.
434............ Churn drill operator..... 1 7 14
334............ Wagon drill operator..... 3 30 10
034............ Diamond drill operator... 3 46 7
046............ Rock or roof bolter...... 2 38 5
734............ Rotary (pneumatic) drill 20 478 4
operator.
634............ Rotary (electric or 11 544 2
hydraulic) drill
operator.
934............ Jumbo percussion drill 2 111 2
operator.
399............ Dimension stone cutter 3 301 1
and polisher; rock sawer.
------------------------------------------------------------------------
Notes: Miscellaneous job categories where less than 1% of recorded
exposures exceeded TWA8 of 105 dBA are not displayed. Numbers are for
four year period, 1991-1994.
The job descriptions do not necessarily indicate the equipment in
use; for example, the stope miners and drift miners may well have been
using the same equipment as the jackleg drill operators. Based on the
Agency's experience, there are only a few pieces of equipment used in
mining for which no control other than multiple hearing protectors is
currently available.
The data illustrate that many exposures at this level are
preventable. Even with the jackleg drills more than 75% of the
exposures were controlled to less than a TWA8 of 105 dBA. The data
base from which the above information was drawn found nine bulldozer
operators and three truck drivers
[[Page 66416]]
exposed to noise above 800% of the PEL; and while these constituted
only a small fraction of the samples of those job categories, 0.7% and
0.05% respectively, the Agency is disturbed to find any such samples at
all given that the metal and nonmetal industry has for some years been
operating under a requirement to use engineering and administrative
controls to bring sound levels down to the PEL or as close thereto as
is feasible.
Accordingly, MSHA requests comment on whether there should be an
absolute dose ceiling, regardless of the economic feasibility of
control by an individual mine operator, and what that should be. MSHA
also requests comment on whether such a dose ceiling should be
technology forcing--i.e. apply regardless of the technological
feasibility of currently available controls.
Ceiling Level
Proposed Sec. 62.120(e) would retain MSHA's current 115 dBA ceiling
level for continuous and intermittent noise. The 115 dBA ceiling level
is intended to protect individuals from high sound levels which last
longer than those typically characterized by impulse/impact noise.
The 115 dBA ceiling level originated out of the Walsh-Healey Public
Contracts Act which formed the basis of current Department of Labor
noise regulations. OSHA, in its 1974 proposed noise standard (39 FR
37775), specified that the 115 dBA limit was a maximum steady state
sound level which was not to be exceeded regardless of the time-
weighted average dose computation.
In its ANPRM, MSHA did not specifically request comments on the 115
dBA ceiling limit. One commenter, however, presented a view on the 115
dBA level. This commenter stated that ``Few professionals would allow a
worker to remain unprotected while exposed to 115 dBA for 15 minutes.''
MSHA's review of available literature found a diversity of opinions
on the choice of a ceiling level for exposures to continuous and
intermittent noise.
At the 93rd Meeting of the Acoustical Society of America, Johnson
and Schori (1977) reported that 115 dBA for 15 minutes may be grossly
under protective, while an upper limit of 115 dBA, regardless of the
time of the exposure, is unduly restrictive. For example, they found
significant temporary threshold shift from exposure to 115 dBA for only
2.7 minutes. On the other hand, they found virtually no such shift from
exposure to 130 dBA for 10 seconds and minimal shift (median of 2 dB)
when exposed to 120 dBA for 40 seconds--although MSHA would point out
it knows of no mining tasks taking such a limited time. In any event,
this shows that the ceiling limit is dependent upon both time and
intensity.
Cluff (1984) stated that ``The selection of 115 dBA for 15 minutes
is arbitrary and represents several contradictions.'' He agreed with
Johnson, however, that exposures to 115 dBA for 15 minutes is
dangerous. Cluff stated that ``this danger is magnified by extending
the 5 dB rule to 130 dBA'' and suggested that a 3-dB or 4-dB exchange
rate may have merit as a solution.
Others discussed different ceiling limits to prevent temporary
threshold shift which may lead to a permanent NIHL. The U.S. Army's
Technical Memorandum 13-67, ``Criteria for Assessing Hearing Damage
Risk from Impulse-Noise Exposure'' (Coles, 1967) stated that:
It has been customary in steady-state noise DRC [damage risk
criteria] * * * to include an upper limit of about 135 dB for
unprotected noise exposure for any duration, however short. In most
cases it is understood by implication only, rather than by direct
statement, that this restriction is not intended to apply to impulse
noise * * *
The technical memorandum, however, stated further that:
The relationship between TTS [temporary threshold shift]
resulting from a single noise exposure and permanent threshold shift
(PTS) to be expected from habitual exposure is not known with
certainty even for steady-state noise.
In Acoustic Parameters of Hazardous Noise Exposures, however,
Henderson (1990) discussed a critical level above which damage by
acoustic trauma begins. He stated that:
At levels above 120 dB SPL [sound pressure level] the cochlea
begins to be damaged by direct mechanical destruction, i.e., the
organ of Corti can be lifted off the basilar membrane, tight-cell
junctions can be ripped apart, and the tympanic membrane can be
ruptured. The level at which mechanical damage occurs has been
called the ``critical level,'' but it is important to recognize that
there is not a critical level but rather a transition point that is
related to the spectrum and temporal pattern of the exposure.
CHABA (1993) believed that single exposure to sound levels above
140 dBA can permanently damage hearing. Furthermore, the threshold for
pain is dependent upon the frequency of the noise. This threshold lies
between 135 and 140 dB.
Ward (1990) stated that:
* * * a ``critical exposure'' for production of immediate severe
loss, presumably associated with structural failure in the cochlea
rather than with metabolic fatigue, is dependent not on the energy
in the exposure (p2t) but on a different quantity given by
integrating the fourth power of the pressure over time. * * * The
best estimate for the critical exposure in man is around 1011
Pa4-sec for a median value, although individual differences in
susceptibility and vulnerability mean that the range will be very
great.
NIOSH (1995) recommends that the 115 dBA ceiling limit be retained.
Citing recent medical research, NIOSH believes that the critical level
is between 115 and 120 dBA. Above the critical level, immediate
structural damage to the ear occurs. This structural damage causes a
loss of hearing acuity.
ACGIH (1994) recommended that exposures to occupational noise
should not be permitted above 139 dBA. Further, for sound levels equal
to or exceeding 103 dBA, ACGIH believes that the exposure be ``limited
by the noise source--not by administrative control.''
As illustrated by the above discussed studies, there is no
consensus among the scientific community as to a sound level above
which permanent damage occurs (regardless of the duration of exposure).
However, many researchers believe the critical level is slightly above
115 dBA and is time dependent with an allowable duration of less than
15 minutes.
International communities and selected branches of the U.S. armed
services specify a ceiling level; however, there is no agreement among
these groups either.
There are relatively few noise sources in the mining industry that
produce sound levels exceeding 115 dBA (e.g., unmuffled pneumatic rock
drills and hand-held channel burners). However, these sources often
operate during most of the work shift with resulting full-shift noise
exposure considerably over the PEL. Currently, MSHA surveys these noise
sources by taking spot readings with Type 2 sound level meters rather
than conducting full-shift sampling with a personal noise dosimeter.
The requirements for Type 2 sound level meters are in ANSI S1.4-1983,
``Specification for Sound Level Meters.'' MSHA intends to continue
sampling these sources using a sound level meter.
Even though this proposal has retained the 115 dBA ceiling level
for noise exposure, sound levels above 115 dBA are to be included in
the determination of the noise dose. The Agency has determined that it
is important to include sound levels above 115 dBA in the noise dose so
that the miner's noise exposure is accurately assessed. By having an
accurate assessment, the mine operator will be
[[Page 66417]]
able to provide hearing protectors with maximum attenuation and take
steps to ensure that the hearing protectors are effectively fitted and
properly worn.
MSHA believes that exposure to sound levels exceeding 115 dBA,
regardless of duration, may potentially result in acute hearing loss
among susceptible individuals. Although there is a lack of scientific
consensus on the exact time of safe exposure, the majority believe that
15 minutes is hazardous. Accordingly, MSHA believes retention of the
current ceiling is warranted. The Agency, however, welcomes additional
comment on this issue.
Exposure Determination by Operators
Proposed Sec. 62.120(f)(1) would require mine operators to
establish a system of monitoring which effectively evaluates each
miner's noise exposure. This will ensure that mine operators have the
means to determine whether a miner's exposure exceeds any of the
limitations established by this section, as well as to assess the
effectiveness of noise controls. The proposed rule is performance
oriented in that the regularity and methodology used to make this
evaluation are not specified. Specific requirements for periodic
monitoring by qualified persons now applicable to the coal sector would
be revoked.
Under the approach proposed, mine operators may design a monitoring
program suitable for each specific mine site. Mine operators would be
expected to utilize survey methods and instrumentation which are
scientifically valid and based on sound industrial hygiene practice.
Although calibration requirements are not specifically mandated in
the proposal, good industrial hygiene practice dictates that any
instrumentation used for determining a worker's occupational exposure
to a contaminant, in this case noise, be calibrated. The calibration
program should be composed of three phases--type testing of
instruments, laboratory calibration of the instruments, and field
calibration. Seiler and Giardino (1996) discussed the importance of
each of these classes of calibrations.
Briefly, type testing is an exhaustive testing of a model of
instrument to ascertain that it complies with a standard, such as the
ANSI standard for personal noise dosimeters. Laboratory calibration is
an extensive calibration that ascertains that an individual instrument
meets factory specifications. Finally, field calibration is a brief
procedure conducted before and after a survey to ascertain that an
instrument is operating properly.
The mine operator has the responsibility of accurately determining
a miner's noise exposure. In order to do this properly the type of
instrumentation needs to be considered. In the cramped quarters of an
underground mine and on mobile mining equipment, it may not be possible
to accurately evaluate a miner's noise exposure without endangering the
technician if a sound level meter is used. Other occupations cannot be
sampled with a sound level meter because the most exposed ear is not
accessible to the technician. For the above occupations, a personal
noise dosimeter would need to be used. An analysis of noise exposures
collected from 1986 through 1992 by the MSHA coal inspectorate revealed
that 21.8% of the occupations could only be sampled using personal
noise dosimeters. These occupations comprised nearly 60% of the surveys
conducted by the inspectors.
A program would be expected to evaluate noise exposure in adequate
detail to enable the mine operator to reasonably determine which miners
work in areas requiring the institution of the controls that may be
required. Sufficient evidence of a noise monitoring program must be
available during mine inspections to permit the evaluation by MSHA of
the program's effectiveness. The Agency will also take its own surveys
of noise exposure during inspections to ascertain miner exposure and to
evaluate the effectiveness of the mine operator's monitoring program.
MSHA believes that this proposal affirms a mine operator's
obligation to take the action needed to determine whether or not a
miner is in compliance with the exposure limitation requirements of the
proposed regulation. At the same time, it allows mine operators maximum
flexibility for determining a miner's noise exposure.
MSHA believes that mine operators have a number of incentives to
monitor sound levels on a regular basis to ensure they can:
(1) Avoid the costs associated with needlessly including or
retaining a miner in an HCP or providing special noise training;
(2) Assess the effectiveness or need for either engineering or
administrative controls or a combination of these controls to meet the
TWA8 of 90 dBA;
(3) Document the miner's exposure for workers' compensation
purposes;
(4) Provide information to health professionals evaluating miners'
health and audiograms; and
(5) Avoid citations and penalties during the regular Agency
inspections in the mining industry for failure to comply with the
standard's requirements.
The results of operator monitoring will not be sent to MSHA, nor
will monitoring results be used to determine compliance with the
applicable noise standard. Mine operators are, however, under an
obligation to take certain actions based upon any noise measurements
they conduct. Proposed Sec. 62.120 requires mine operators to take
specific corrective action when a miner's noise exposure exceeds the
various limitations set forth in the section. It also requires that
miners be notified whenever a mine operator determines that their noise
exposure exceeds the action level.
The requirements of proposed Sec. 62.120(a), as to how noise is to
be measured for the purposes of this proposal, would need to be
followed by mine operators in their monitoring. These requirements
include: disregarding the attenuation of any hearing protector worn by
the miner, integrating all sound levels from 80 dBA to at least 130 dBA
during a miner's full workshift, using a 90 dBA criterion level and a
5-dB exchange rate, and using an A-weighting and slow-response
instrument setting. Mine operators would, of course, be free to take
any additional measurements that they deem appropriate: for example,
taking peak-response readings to measure any impact/impulse noise.
MSHA current coal noise standards (30 CFR Secs. 70.500/71.800)
require mine operators to monitor each miner's noise exposure twice a
year and certify the results to MSHA. These standards also specify when
and how to sample, who is qualified to sample, and reporting
requirements.
MSHA's noise standards (30 CFR Secs. 56/57.5050) for metal and
nonmetal mines do not contain any operator sampling requirements,
although they do require that mine operators maintain exposures in
compliance with the PEL. In order to do this effectively, many metal
and nonmetal mine operators conduct their own monitoring.
OSHA's noise standard requires employers to implement a monitoring
program when information indicates that any employee's noise exposure
may equal or exceed the action level (TWA8 of 85 dBA). OSHA allows
employers to use representative personal or area sampling; however, in
areas with significant variations in sound level or high worker
mobility, the employer would have to show that area sampling produces
results equivalent to personal sampling. OSHA also requires the
[[Page 66418]]
employer to repeat the monitoring in specific situations.
MSHA's ANPRM solicited comments on the frequency of monitoring, the
sampling strategy, and the use of the information obtained. The ANPRM
also asked whether specification-oriented or performance-oriented
requirements would be more appropriate. At that time, the Agency
solicited comments based on the premise that the proposed rule would
include a detailed monitoring requirement and the commenters responded
accordingly. However, since MSHA has decided not to propose detailed
monitoring requirements, the Agency has not addressed specific issues
regarding area versus personal monitoring, instrumentation
specifications, calibration requirements, or other related monitoring
issues.
Many commenters preferred performance-oriented standards, similar
to OSHA's, that would allow mine operator discretion in when and how to
sample. One of these commenters stated:
The goal of the monitoring effort should not be simply to
collect noise exposure data, but rather to accomplish the goal of
eliminating job-related noise induced hearing loss. With this goal
in mind, the operator would need to have collected noise exposure
information on the jobs that he had reason to believe were above the
85 dBA action level. This information would be necessary to identify
those workers that should be included in the HCP as well as areas
and equipment where noise controls are needed.
If the operator does not choose to monitor for noise, he should
have an alternate plan that accomplished the same goal: i.e.,
includes all non-office workers in the HCP regardless of noise
exposure, perform a sound level survey to identify mandatory hearing
protection areas and equipment, etc. It is recommended that MSHA
adopt the logic outlined in the OSHA noise standard, 29 CFR
1910.95(d) (1), (2) and (3).
Conversely, two commenters recommended a specification-oriented
rule. One of these recommended personal monitoring on an annual basis
and the other simply recommended personal or area monitoring.
Finally, two commenters had a different view on monitoring. They
recommended that MSHA, rather than the mine operator, conduct all
monitoring for the purpose of this proposed standard. In response to
these commenters, the Agency would point out that it is the
responsibility of mine operators to ensure the safety and health of
their miners. MSHA sampling programs are to audit the mine operators to
ensure the protection of miners. Moreover, MSHA does not have the
resources to sample every miner annually. Metal and Nonmetal has
specific health sampling guidelines which require periodic sampling of
selected mining occupations. MSHA currently conducts over 20,000 full-
shift noise exposure surveys in the mining industry annually. Although
MSHA intends to continue measuring the noise exposure of miners in
order to determine compliance, it can only sample a small percentage of
the exposed mining population annually. Mine operators are responsible
for knowing at all times when their employees exceed applicable limits
so that appropriate action can be taken.
The Agency, however, is willing to share its sampling results and
analyses of these results with the mining industry. Mine operators who
do not conduct their own monitoring could use the MSHA data along with
information from equipment manufacturers to estimate a miner's noise
exposure. This could be beneficial to all mine operators, particularly
small mine operators with limited resources. If, however, as a result
of this proposal, MSHA changes the threshold, prior sampling conducted
by the Agency may not provide an accurate indication of whether a
miner's noise exposure exceeds the new standard.
Although a mine operator could use prior MSHA sampling results, and
information from equipment manufacturers, such use would not relieve
the mine operator of responsibility to appropriately determine a
miner's noise exposure. Therefore, it would behoove mine operators to
determine a miner's noise exposure by methods comparable to those which
would be used by MSHA, as outlined in Sec. 62.120(a).
Although numerous commenters and organizations supported the need
for monitoring, most favored a performance-oriented approach and did
not specify a procedure to be followed. MSHA agrees. The Agency
believes that the focus of the noise standard should be on preventing
NIHL and reducing miners' noise exposures and that it would be
counterproductive to specify detailed monitoring requirements or
procedures. Also, the Agency does not want to stifle improvements in
monitoring technology or methodology.
Moreover, the Agency believes that the current specification-
oriented coal operator monitoring produces results that in fact are not
representative of miners' noise exposure. For example, in FY 1994, coal
mine operators conducted approximately 180,000 noise surveys (two per
miner) and found 36 miners to be overexposed (their exposures exceeded
132%). However, MSHA does not know the extent to which mine operators
may be including credit for the wearing of hearing protection in the
determination of the miner's exposure. Conversely, MSHA conducted 6,339
surveys in coal mines and found 857 exposures exceeding the 132%.
However, only 62 of these surveys resulted in a violation due to credit
being given for use of hearing protection. This indicates that despite
having specification-oriented monitoring requirements, current operator
sampling in coal mines may not be providing results consistent with
those found by MSHA.
For monitoring compliance with this proposal, the Agency intends to
use validated scientific methodology. Current MSHA sampling procedures
and policies are listed in MSHA's Program Policy Manual and its Coal,
and Metal and Nonmetal, Health Inspection Procedures Handbooks. Copies
of these documents are available for review and copying in MSHA
offices. MSHA's sampling procedures, however, would be modified to be
consistent with Sec. 62.120(a) of this proposal once the rule is
finalized.
Currently, MSHA bases its noise exposure compliance determinations
on personal full-shift sampling with a personal noise dosimeter. The
calibration of the personal noise dosimeters is checked before and
after each survey. Additionally, annual laboratory calibration is
conducted to assure measurement accuracy. The personal noise
dosimeter's microphone is positioned on the top of the miner's
shoulder, midway between the neck and the end of the shoulder, with the
microphone diaphragm pointing in a vertical upward direction. The
microphone is placed on the shoulder that is normally between the
principal noise source and the miner's ear. Sampling is conducted while
the miner performs his/her normal duties.
In the development of this proposal, MSHA also reviewed the noise
monitoring programs of the U.S. Armed Services and other jurisdictions.
Although MSHA has described its current noise sampling procedures,
the Agency may decide to modify or change these procedures based upon
new or improved sampling methods, instrumentation, or technology.
Employee Notification
Proposed Sec. 62.120(f)(2) would require that within 15 calendar
days of determining that a miner's exposure exceeds the action level,
the permissible exposure level, the dual hearing protection level, or
the ceiling level established by this section, the mine
[[Page 66419]]
operator notify the miner in writing of the overexposure and the
corrective action being taken. If the miner's exposure has not changed
from one of these levels to another, and the miner has been notified of
his exposure at that level within the past year, no notification needs
to be provided; if the level has changed, or there has been no
notification in the past year, notification is to be provided. The
proposal specifically states that these notifications are triggered by
exposure evaluations conducted either by the operator or by an MSHA
inspector.
At the present time, MSHA does not require notification, though it
is implied in those cases in which a coal miner is enrolled in an HCP
for having exceeded the PEL. OSHA's standard requires that employees be
notified in writing of monitoring results that exceed the action level
within 21 days of the monitoring.
The proposed requirement is consistent with Section 103(c) of the
Mine Act. Section 103(c) of the Mine Act states in pertinent part that:
Each operator shall promptly notify any miner who has been or is
being exposed to * * * harmful physical agents * * * at levels which
exceed those prescribed by an applicable mandatory health or safety
standard promulgated under section 101 * * * and shall inform the
miner who is being thus exposed of the corrective action being
taken.
Many commenters supported miner notification of all sampling
results and stated that such is current company policy. Several of
these commenters recommended that the specific method of notification
be left to the discretion of the mine operator. One commenter
specifically stated that through notification, ``the employee could
help facilitate a solution to the problem and be more committed to
following safety procedures.'' This commenter also stated that
``requiring written notification is not effective when dealing with
persons who cannot read or do not have the background to understand the
meaning of the notification's contents.''
A mining association commented ``* * * that miners should be made
aware when their exposure exceeds allowable limits * * *'' and that ``*
* * employees should have knowledge of their exposure and any
subsequent hearing loss. * * *'' This association suggested, however,
that notification ``* * * be in the form of entry into the HCP. * * *''
Several other commenters recommended that MSHA's requirements be the
same as OSHA's.
After reviewing the comments and the regulations from the U.S.
Armed Forces and international organizations, MSHA concludes that
notification should be provided for exposure at any level defined in
the proposed regulation. At the action level, there is a significant
risk of material impairment (as discussed in part II of this preamble).
Notification will be needed at this level because under the proposal,
if the noise exceeds that level, the mine operator would be required to
take protective action (hearing protectors and enrollment in an HCP).
Notification at this level would explain to the miners the reason why
it is necessary for them to wear their hearing protectors. Moreover,
since the harm occurs at this level, notification is required under
Sec. 103(c) of the 1977 Mine Act. Notification at the permissible
exposure level and dual hearing protection level--exposures
respectively 2 and 16 times the dose at the action level--is necessary
to ensure the miner understands the rationale for added protection and
the actions being taken by the mine operator to lower noise exposures.
The same is true for any exposures exceeding the ceiling level.
MSHA believes there is no need to notify a miner of every exposure
determination, as long as the miner is cognizant of the general level
of his or her exposure--so that the miner pays attention to noise
exposure and noise abatement efforts (including the use of properly
fitted and maintained hearing protectors). If an exposure measurement
for a miner demonstrates a change in that miner's situation--e.g., from
below the PEL to over the PEL, or from over the PEL to above the dual-
hearing protector level--the miners should be made aware of this fact.
Moreover, even if the miner's situation has not changed, the miner
should be reminded of his or her overexposure when it is measured if
notification has not been made recently. MSHA welcomes comment on the
proper balance to strike between the need for notification and
nonproductive paperwork.
MSHA has concluded that the notification should be in writing. This
would ensure that the miner does not misconstrue the measured level nor
the actions being taken.
Warning Signs
The proposed rule has no provision for requiring the posting of
warning signs. While MSHA acknowledges the value of posting warning
signs, the process is inherently complicated in the ever changing
mining environment, and MSHA believes the training requirements it is
proposing should ensure miners are apprised of noise hazards to which
they may be exposed.
Section 101(a)(7) of the Mine Act requires that health or safety
standards promulgated by MSHA:
* * * prescribe the use of labels or other appropriate forms of
warning as are necessary to insure that miners are apprised of all
hazards to which they are exposed, * * *
Existing MSHA noise standards do not exercise this authority with
respect to noise, and do not require the posting of warning signs.
When OSHA promulgated its Hearing Conservation Amendment, it did
not include a requirement for warning signs. OSHA stated in the
preamble to the final rule, that the use of warning signs to warn
employees about noise hazards in high noise areas should be left to the
discretion of the employer. In so doing, OSHA stated that noise is more
readily discernible than other harmful physical agents and therefore a
specific warning sign requirement may not be necessary to protect
employees, and that in certain circumstances such signs might confuse
rather than serve a useful educational purpose. OSHA also recognized
that the employer is more familiar with the workplace environment and
will be in a better position to determine if the posting of signs in a
given situation will aid in the success of the company's HCP. Further,
OSHA stated that other methods, such as training, may be more
appropriate for apprising employees of the hazards of noise.
In its ANPRM, MSHA asked whether it should require warning signs in
areas exceeding a specified sound level, and what this sound level
should be. Numerous commenters specifically addressed the issue of
warning signs and were about equally divided over whether such a
requirement is necessary. Those commenters supporting the use of
warning signs varied considerably on criteria for their use. For
example, one commenter indicated that warning signs should only be
posted in areas where an immediate threat of injury exists, such as
areas with impact noise above 140 dB or constant noise above 115 dBA.
Other commenters said that warning signs should only be required on
non-mobile equipment, or in areas where the use of hearing protectors
is mandatory.
Among those commenters that did not support the use of warning
signs, several stated that MSHA's standard should be performance-
oriented and allow the mine operator to decide how to warn its
employees, such as through training, safety meetings, notification of
exposure results, etc. One commenter
[[Page 66420]]
stated that in the mining environment it would be difficult to
illuminate signs to the point they could be read and understood, and
that they would be difficult to maintain in most mining situations.
This commenter also believed that the nature of certain mining
operations does not lend itself to the use of signs because the work
area is constantly changing. Another commenter agreed, stating that
warning signs would be difficult to keep current in mobile operations.
Warning signs could provide an indication to miners that they are
entering an area where the wearing of hearing protectors is required.
Some mine operators have voluntarily placed warning signs in high noise
areas such as preparation facilities and on surface mobile equipment.
MSHA believes, due to the dynamic nature of mining (advancing
underground faces, changing quarry perimeters, a mobile workforce,
etc.), that a requirement for the installation of fixed warning signs
may be difficult to implement. Warning signs may also be inappropriate
where miners do not work a fixed period of time in the area covered by
the sign. For example, a miner in an area with a 90 dBA sound level for
less than four hours, with no significant noise exposure for the rest
of the day, would not be required to wear hearing protectors under
MSHA's proposal, whereas a miner who spends more than four hours in
that area would.
After careful analysis of the literature and review of regulatory
requirements from international communities and the U.S. Armed
Services, MSHA believes that training may be a more appropriate vehicle
to inform workers of the hazards of noise to their hearing. Further,
the Agency believes that the posting of warning signs for noise should
be optional and left to the discretion of the mine operator. The
proposed rule would require initial and annual training for all miners
exposed above the action level as discussed under Sec. 62.130 Training
of this preamble.
Though MSHA is not proposing to require warning signs for noise, it
expects that many mine operators will voluntarily post such signs to
indicate to miners locations where hearing protectors must be worn. If,
however, mine operators choose to use administrative controls to reduce
a miner's noise exposure, the proposal would require that the affected
miner be informed of the administrative procedures and that such
controls be posted on the mine bulletin board. Such procedures may
provide notification of sound levels in specific work locations.
Section 62.125 Hearing Protectors.
Whenever hearing protectors are required to be provided by the
proposed regulations, they must be provided in accordance with the
requirements of this section.
The miner is to have a choice from at least one earplug type and
muff type protector; and, in the event dual hearing protection is
required, a choice of one of each. The mine operator is to ensure that
in those cases when hearing protection is required to be worn, it is
worn by miners exposed to sound levels required to be integrated into
the miner's dose measurement: i.e., sound levels above 80 dBA. The
hearing protector is to be fitted and maintained in accordance with the
manufacturer's instructions. Hearing protectors and necessary
replacements are to be provided by the mine operator at no cost to the
miner. Finally, should the hearing protector cause or aggravate a
medical pathology of the ear, the miner is to be allowed to select a
different hearing protector from among those offered by the mine
operator.
Selection of Hearing Protector
The proposal requires that if hearing protectors are required to be
provided to miners for any reasons, the mine operator shall provide a
choice of one earplug type and one muff type, and ensure proper fit.
Earmuffs include both active and passive; earplugs include disposable
earplugs, pre-molded earplugs, custom-molded earplugs, and canal caps.
The proposal also requires that the training in hearing protection
specified in proposed Sec. 62.130(a) be received at least once before
the miner has to make a choice: to ensure the miner understands the
choices available.
While these requirements are limited, they will help to
significantly encourage hearing protector use and effectiveness. The
proposal does not seek to constrain mine operator selection of
protectors. As noted herein, hearing protectors come in a wide variety,
for different purposes, and with different attenuation values. MSHA
believes that mine operators have an incentive to provide a wide
variety of types to encourage safe and effective use.
MSHA's existing noise standards require mine operators to provide
adequate hearing protectors, but do not specify that a variety of
hearing protectors be offered. OSHA's noise standard requires that
employees be given the opportunity to select from a variety of suitable
hearing protectors provided by the employer; however, the variety is
not defined. OSHA states in the 1981 preamble to its Hearing
Conservation Amendment (46 FR 4152) that ``The company must make a
concerted effort to find the right protector for each worker-one that
offers the appropriate amount of attenuation, is accepted in terms of
comfort, and is used by the employee.''
In its ANPRM, MSHA asked whether mine operators should be required
to make available a selection of hearing protectors. Almost all of the
commenters on this issue were in favor of this provision. Some
specifically recommended that the mine operator provide a choice of at
least three different models, including at least one earmuff and one
earplug. One commenter suggested that the selection should include at
least six models. Most commenters indicated that the need to provide a
variety of hearing protectors is more related to fitting and comfort
than on the labeled attenuation per se.
One commenter recommended against providing a variety of hearing
protectors, stating that ``It is the responsibility of the mine
operator to evaluate the various noise exposures, and to select the
appropriate HPDs [hearing protectors].'' The commenter maintained that
the mine operator should only have to provide an alternative hearing
protector when the individual has a specific condition which precludes
the use of the selected hearing protector.
Several commenters addressed the need to allow the miner to choose
a hearing protector that is comfortable. One commenter stated that:
The most effective hearing protector is one that is worn and
worn properly. If the hearing protector is not comfortable or the
employee cannot wear a certain type of plug or muff, then the
hearing protector will not be worn and the HCP will not be
effective.
Another commenter maintained that ``* * * the principal usage problem
with HPD's is that because of discomfort, interference with necessary
communication, and interference with normal work routines, many HPD's
are not worn.'' While another commenter stated:
The performance of hearing protectors in the field (including
the manners in which they are used, not used, or misused by workers
in situations in which HPDs are needed, but are uncomfortable,
unsafe, or otherwise inconvenient) is frequently inferior to their
performance when tested in idealized laboratory conditions and there
are substantial variations among individual susceptibilities to
noise-induced hearing loss [NIHL].
The National Hearing Conservation Association's Task Force on
Hearing Protector Effectiveness (Royster, 1995)
[[Page 66421]]
recommends that the employer consider many criteria when selecting the
variety of hearing protectors from which workers are to choose. The
most important criterion for choosing a hearing protector is ``the
ability of a wearer to achieve a comfortable noise-blocking seal which
can be maintained during all noise exposures.'' Other criteria include
hearing protector's noise reduction, wearer's daily noise exposure,
variations in sound level during a work shift, user preference,
communication needs, hearing acuity of the wearer, compatibility with
other safety equipment, wearer's physical limitations, and climate and
working conditions. Physical limitations (missing fingers, arthritis,
limited hand strength) may restrict users from properly inserting
compressible foam earplugs in their ears.
Berger (1986) stated that comfort must be considered when selecting
hearing protectors. If the laboratory attenuation of a hearing
protector is very high, but it is uncomfortable to wear, the actual in-
use attenuation may be reduced or even nonexistent. Conversely, a
comfortable hearing protector with less attenuation may be worn
consistently, thereby providing greater effective protection.
In EARLOG 8, Berger (1981) asserted that an employee should have
two weeks to try out an adequate hearing protector and select another
one if the original selection does not perform satisfactorily.
In the report, Communication in Noisy Environments (Coleman et al.,
1984), the authors stated that:
Although acceptability is in part governed by the comfort of the
devices, there are other factors such as concern with hygiene,
belief in (real or presumed) communication difficulties, and social
constraints which can influence the extent to which workers will use
the protection provided. * * * Sweetland (1981) found concern about
communication difficulties to be a major factor in mine workers
acceptance of protectors.
The authors further stated that:
In general, ear inserts [earplugs] appear less attractive than
circumaural protectors [earmuffs] for mining conditions. A helmet
mounted circumaural protector is to be preferred on grounds of
comfort, ease of fitting and removal, reliability of attenuation,
and acceptability in terms of hygiene; whereas ear inserts of the
compressible foam type may produce marginally less interference with
communication and they will impair localization less, they are
likely to be more comfortable in hot and humid conditions.
Pfeiffer (1992) suggested that greater care be exercised when
selecting hearing protectors for workers experiencing hearing loss.
Pfeiffer stated that it is important not to overprotect the worker
which can cause difficulty in communicating. If this happens, the
worker will be reluctant to wear the hearing protector.
MSHA recognizes that local mine conditions such as dust,
temperature, and humidity can cause one type of hearing protector to be
more suitable than another. For example, under normal mining
conditions, some miners may experience problems with earmuffs because
of a buildup of perspiration under the seals.
Based on such factors and on comments received in response to the
ANPRM, MSHA concluded that the minimum selection appropriate to offer
miners with normal hearing consists of at least one type of earmuff and
one type of earplug. MSHA expects that each hearing protector in the
selection would provide adequate attenuation. Further, a consensus of
the U.S. armed services and international communities agrees that
workers should choose from a selection of several hearing protectors.
If miners are allowed to choose from a selection of hearing
protectors, particularly if given appropriate training as is required
under this proposal, they will be more apt to wear and care for them in
such a manner as to obtain the maximum amount of protection. Providing
miners with a choice from a selection of hearing protectors will foster
greater acceptance and use. Further, MSHA recognizes that a trial
period may be necessary for the miner to determine if using the
selected hearing protector for a prolonged period causes significant
discomfort. If significant discomfort occurs, MSHA encourages the mine
operator to allow the miner an opportunity to select an alternate
hearing protector. Selection of an alternative hearing protector is
mandatory under the proposal if required by a medical condition.
There are several factors which the affected miner needs to
consider before choosing a hearing protector from the selection
offered, and which miners will learn about through the training
specified under proposed Sec. 62.130(a). These factors include--
(1) Hearing protectors must fit properly to provide the estimated
amount of protection;
(2) People have all shapes and sizes of ear canals, and fitting
commonly used earplugs to an unusually shaped ear canal may be
uncomfortable or harmful to the individual. For those earplugs which
need to be fitted to the size of the ear canal, all available sizes of
that earplug should be available for fitting and use. Some employees
may need a different size for each ear when their ear canals are of a
different size or configuration; and
(3) Hearing impaired miners may need special hearing protectors
which provide adequate attenuation, yet permit auditory reception.
With regard to the latter, MSHA is not at this time proposing that
any special type of hearing protector be provided, nor any type of
protector be excluded, for those miners who are already hearing
impaired. However, MSHA will endeavor to ensure operators understand
that special care should be taken in providing a hearing protector for
the safety of a miner with a significant hearing loss. Most earplugs
and earmuffs attenuate sound unequally across all frequencies and are
most effective at attenuating high frequency sounds. Hearing loss due
to noise and aging reaches its peak at the higher audiometric
frequencies. Because of these factors, a miner wearing a hearing
protector, without specific accommodation for any significant hearing
loss, would hear distorted auditory signals which would significantly
hamper communication. A miner, with a significant hearing loss and
wearing hearing protectors, could be placed in a hazardous situation
because he/she could not hear or comprehend an audible warning.
Although some commenters have recommended the use of communication
type hearing protectors for hearing impaired miners, MSHA will caution
mine operators against their use in very high noise areas because the
sound level produced under the cup may be hazardous. Some manufacturers
of communication type hearing protectors, however, have placed limiters
in the electronics to protect against the speaker in the cup producing
hazardous sound levels.
Even though some researchers have indicated that using a hearing
protector may cause communication problems for an impaired miner,
commenters have presented many practical ways of resolving this
problem. Consequently, MSHA chose not to propose specific requirements
regarding hearing protectors for impaired miners to allow the mine
operators maximum flexibility.
MSHA solicits comments on whether mine operators should be required
to provide an additional type of hearing protector, such as flat
response, level dependent or active noise control earmuff, for miners
with a hearing impairment, or whether any type of protector should be
explicitly excluded for such miners.
[[Page 66422]]
Hearing Protector Effectiveness
MSHA received many comments on the attenuation, or effectiveness,
of hearing protectors. The issue arises in a number of contexts,
including what role a hearing protector's attenuating characteristics
should play in the selection of the most appropriate hearing protector
in those cases requiring hearing protection.
While MSHA recognizes the importance of proper selection, MSHA has
decided not to incorporate specific procedures into its proposal on
rating the effectiveness of hearing protectors. Based on the
information presented herein, MSHA has concluded there is not presently
a generally acceptable method of predicting hearing protector
attenuation in the field. Moreover, MSHA has determined that there are
other factors which are equally or more important than a hearing
protector's attenuation for ensuring that a miner is protected from
NIHL. These factors include: (1) comfort, (2) training, (3) fit, (4)
maintenance, and (5) consistent use.
Nevertheless, MSHA realizes the merits of having a valid
methodology for determining the attenuation of hearing protectors--for
a variety of reasons, including facilitation of the selection of the
most appropriate hearing protector when selection and use is required.
The Agency, therefore, solicits comments on a scientifically based, yet
practical, method for determining the effectiveness of hearing
protectors as used under mining conditions. In addition, comments on
field estimates of hearing protector attenuation, especially the NIOSH
(1995) derating scheme, are encouraged.
Current MSHA regulations do not explicitly address this issue. MSHA
policy, however, specifies a procedure for calculating a hearing
protector's effective attenuation based upon the Noise Reduction Rating
(NRR) provided by the manufacturer. Manufacturers currently determine
an NRR for each hearing protector from laboratory testing in accordance
with EPA regulations (40 CFR Sec. 211.206 and Sec. 211.207). The NRR is
intended to provide an estimate of the noise reduction achievable under
optimal conditions and was designed to be used with C-weighted sound
levels. Because MSHA measures noise exposure with A-weighting instead
of C-weighting, it adjusts the NRR by subtracting 7 dB. As reported by
Maraccini (1987), this 7-dB adjustment accounts for the average
difference between the C-weighted and A-weighted sound levels in
mining.
OSHA's standard does specify the hearing protector attenuation
required. Under OSHA's standard, attenuation must be sufficient to
reduce an employee's noise exposure to a TWA8 of 90 dBA; except
that if the worker is experiencing an STS, then the hearing protector
must reduce the noise exposure to a TWA8 of 85 dBA. Employers are
required to use one of four methods to determine the noise exposure
beneath the hearing protector. These methods are NRR and NIOSH methods
1, 2, or 3 as described in the ``List of Personal Hearing Protectors
and Attenuation Data,'' HEW Publication No. 76-120, NIOSH 1975, pp. 21-
37. The NRR is the most convenient method to use and is a
simplification of NIOSH method 2. In addition, when the NRR is to be
used with A-weighted sound levels, OSHA requires that 7 dB be
subtracted from the NRR.
As noted in connection with the discussion of proposed
Sec. 62.120(c), where an employer wishes to take advantage of OSHA's
policy of not citing overexposures when, among other factors, adequate
hearing protection is being used, a more stringent method of
determining the effectiveness of hearing protectors is used by OSHA. In
evaluating hearing protector effectiveness in this context, OSHA also
subtracts 7 dB from the hearing protector's stated NRR to adjust for
the difference in weighting systems, but further derates the NRR by
50%. All types of hearing protectors are treated the same way. The
derating is done to account for the significant reductions, which
various researchers have found, in hearing protector attenuation under
industrial conditions when compared to laboratory conditions.
One commenter to MSHA's ANPRM indicated that laboratory protocols
have been developed and are being tested which may be more
representative of the actual field performance of hearing protectors,
but noted that validated and agreed upon standardized procedures are
still some years away. This commenter stated:
The real-world attenuation data which form the basis for our
criteria are taken from Berger's summary (1983) of 10 field studies,
utilizing 1551 employees, wearing seven different types of earplugs
and greater than nine different types of earmuffs, in over 50
different industries, and his more recent paper (Berger, 1988) which
discusses additional current studies. Although the data can be
separated by plugs and muffs, the variability within the plug
category is such that some of the better attenuating earplugs
overlap with the earmuffs. Therefore, for a general regulatory
guideline, the data averaged across all HPDs and employee subjects
is taken from the two papers. This results in an NRR84 of
approximately 10 dB (i.e., the NRR computed with a one-standard
deviation correction which estimates the protection at the 84th
percentile).
Since the NRR is meant to be subtracted from the C-weighted
sound level, and the regulation is formulated in terms of A-weighted
levels, an indicator of representative C-A values for the mining
industry is then required. The 100 NIOSH noises (NIOSH, 1975) which
have often been taken to be representative of general industry have
median C-A of about 2 dB, and 90% have C-As of <6.5 dB. However,
mining noises may exhibit greater low-frequency energy. For example
the data in Kogut (1990) which represent 17 different types of
equipment in the metal/nonmetal mining industry (coal excluded),
show a mean C-A of 6.7 dB, but the Kogut values are not a
statistically representative sample of the mining industry. For our
purposes we will average the two estimates and presume a median C-A
for mining of 5 dB.
With an NRR for 84% of the users of 10 dB, and C-A value for
typical mining noises of 5 dB, the credit for HPD attenuation for
most of the users in the typical mining noises is 10-5=5 dB. Adding
this value of 5 dB to the PEL of 90 dBA sets the second cutoff level
of 95 dBA.
This commenter also stated that NRR's do not provide a good indication
of either relative or absolute field performance; thus, ``there is no
good way to accurately derate existing lab data to predict field
performance.''
In The NIOSH Compendium of Hearing Protection Devices (1994)
several sets of laboratory measured attenuations, besides the NRR, are
listed. These data were obtained using different standardized methods.
NIOSH presents examples of using each method to estimate the sound
level beneath the hearing protector. In addition, NIOSH presents
physical features (i.e., number of flanges, composition, compatibility
with other personal safety equipment, etc.) of the hearing protectors.
NIOSH (1995) recommends a derating scheme based upon the type of
hearing protector. NIOSH acknowledges that hearing protector wearers do
not attain the laboratory attenuation in industrial situations.
Accordingly, they recommend that to ascertain the effectiveness of a
hearing protector in workplace use, the NRR for an earmuff, formable
earplugs, and all other earplugs would be derated by 25%, 50%, and 70%,
respectively.
The National Hearing Conservation Association's Task Force on
Hearing Protector Effectiveness (Royster, 1995) recommends that the
EPA's NRR for hearing protector attenuation be replaced with a new
NRR(SF), which the researchers felt more realistically reflects the
field performance of hearing protectors. The NRR(SF)'s are determined
by laboratory testing for hearing protector attenuation after the
[[Page 66423]]
subject fits the hearing protector to his/her head. This differs from
the EPA's NRR value which is determined after the researcher fits the
hearing protector to the subject. Regardless of the method used, the
amount of attenuation provided by a hearing protector will vary among
the individual subjects resulting in a range of attenuation values. The
Task Force stresses that it is not possible to predict the field
attenuation of a given hearing protector for an individual; it
concluded, however, that the NRR(SF) would be a more realistic
estimate. In addition, small differences (less than 3 dB) in the NRR or
NRR(SF) are not believed to be of practical consequence. The Task Force
recommends continued audiometric testing whenever hearing protectors
are used.
MSHA notes that the American Industrial Hygiene Association (AIHA,
1995) recently sent the EPA a letter requesting that the EPA revise its
rule on noise labeling requirements for hearing protectors. The reasons
cited for requesting a revision of EPA's NRR rating system included--
(1) the current method of rating hearing protectors overestimates the
actual workplace protection from 140 to almost 2000 percent; (2) the
inability to predict absolute levels of protection from labeled values;
(3) the labeled values are a poor predictor of relative performance of
one hearing protector versus another; (4) there are no provisions for
retesting the hearing protectors on a recurring basis; and (5) there is
no requirement for quality assessment or accreditation of the test
laboratory.
Michael (1991) believed that the simplification needed to obtain a
single number rating (NRR) caused it to be inaccurate. Instead of the
NRR, the researcher recommended using the spectra of the noise in
conjunction with the attenuation characteristics to select the most
appropriate hearing protector. This is even more important when the
wearer has sensorineural hearing loss.
Many field studies on the attenuation of hearing protectors have
been conducted in the mining industry by Giardino and Durkt (1996),
Kogut and Goff (1994), Giardino and Durkt (1994), Bertrand and Zeiden
(1993), Durkt (1993), Goff et. al. (1986), Durkt and Marraccini (1986),
Goff and Blank (1984), and Savich (1979). With the exception of
Bertrand and Zeiden (1993), these researchers reported that hearing
protectors provided much less attenuation than that measured in the
laboratory. Some researchers tested new earmuffs while others tested
old earmuffs. In many instances attenuation was minimal and highly
variable. These studies indicate that hearing protector attenuation
cannot be reliably predicted under actual use conditions and is
substantially less than that indicated by the NRR from the
manufacturer.
Bertrand and Zeiden (1993) determined the effectiveness of hearing
protectors by measuring the hearing level of miners exposed to sound
levels exceeding 115 dBA. These researchers found that although the
hearing protectors provided less attenuation, the difference was not
significant. For example, miners exposed to 118 dBA had hearing levels
consistent with exposure to 98 dBA. Therefore, the hearing protector
whose NRR was 24 provided 20 dBA of attenuation.
Durkt (1993) studied the effectiveness of 11 models of new earmuffs
using miniature microphones inside and outside the cups. At surface
mines, 107 tests were conducted on operators of equipment, including
bulldozers, front-end-loaders, and overburden drills. Durkt concluded
that the effectiveness of the earmuff was related to the noise
spectrum. Moreover, the measured noise reduction was much less than the
NRR when the noise spectrum contained significant amounts of low
frequency noise. Most diesel-powered equipment generate noise which is
primarily in the low frequency range.
Kogut and Goff (1994) studied the effectiveness of earmuffs being
used in both surface and underground mines. A total of 540 tests were
conducted on miners wearing their normal earmuffs. The procedure was
similar, but not identical, to the procedure used by Durkt (1993). Like
Durkt, the researchers concluded the noise reduction afforded by
earmuffs was related to the spectrum of the noise. According to the
researchers, ``The earmuffs' effectiveness in reducing noise exhibited
great variability and frequently fell far short of the NRR.''
Furthermore, a simple method of reliably predicting the effectiveness
of earmuffs eluded the researchers. A complex method was developed for
predicting the effectiveness of earmuffs; however, it lacks
practicality.
Giardino and Durkt (1996) and Giardino and Durkt (1994) expanded on
the previous two discussed studies. A total of 1,265 tests were
performed on 545 different machines (20 different machine types).
According to the researchers, earmuffs provided minimal noise reduction
for the operators of equipment powered by internal combustion engines.
The researchers concluded that the NRR was a poor predictor of earmuff
performance under actual mining conditions. Furthermore, they reported
that the NRR is not a good indicator for comparing different models of
earmuffs.
Numerous research studies performed in other industries by Pfeiffer
(1992), Hempstock and Hill (1990), Green et al. (1989), Behar (1985),
Lempert and Edwards (1983), Crawford and Nozza (1981), and Regan (1975)
indicate that hearing protector effectiveness is substantially less
than the NRR value indicated by the manufacturer.
Furthermore, Regan (1975) found that earmuff type protectors yield
the most attenuation and custom molded earplugs the least. Behar (1985)
found that the measured NRR, in industrial situations, averaged 14.9 dB
lower and reached 25 dB lower than the manufacturer's nominal value.
Green et al. (1989) reported workers, who were using earplugs, were
receiving one-third to one-half of the laboratory based NRR value and
workers enrolled in an effective HCP obtain greater attenuation from
their hearing protectors. Crawford and Nozza (1981) reported that the
average attenuations of the earplugs were typically 50% of the
manufacturer's values, except for user-molded earplugs whose field
attenuation was near the laboratory values.
Lempert and Edwards (1983) reported, ``In the majority of cases,
workers received less than one-half of the potential attenuation of the
earplugs'' and concluded, ``Regardless of the type of earplug used by a
particular plant, a large portion of the workers received little or no
attenuation.''
Hempstock and Hill (1990) reported that the workplace performance
of earmuffs more closely approximated the laboratory performance than
earplugs. For both earmuffs and earplugs, the measured workplace
attenuations were lower and the standard deviations higher than those
measured in the laboratory. The researchers attributed these results to
the ease of fitting an earmuff compared to fitting an earplug. Their
study revealed that the degradation was dependent upon the model of
hearing protector and even differed between sites. Another result was
that safety glasses substantially degraded the performance of earmuffs.
Workers wearing safety glasses received approximately one-half of the
laboratory attenuation. However, the researchers did not find that
headband tension was a factor in the attenuation of earmuffs.
Royster et al. (1996) found that the wearing of safety glasses
reduced the attenuation of earmuffs by about 5 dB at all frequencies.
Pfeiffer (1992) reported on studies of hearing protector
effectiveness in
[[Page 66424]]
German industry. According to Pfeiffer earplugs provided between 10 and
15 dB less attenuation and earmuffs about 6 dB less in industry than in
the laboratory. As part of the study, used muffs, which were not
obviously defective (e.g., missing liners, headbands stretched out of
shape, cushions missing or broken), were tested against new ones. The
older earmuffs provided significantly less attenuation than new ones.
The degradation of attenuation was dependent upon the model and
frequency tested and exceeded 7 dB for some frequencies.
Abel and Rokas (1986) reported that the attenuation of earplugs
decreases as a function of wearing time and that head and jaw movement
hastened the decrease. At Noise-Con 81, Berger (1981) also concluded
that the performance of hearing protectors decreased as a function of
wearing time. Kasden and D'Aniello (1976, 1978) found that the custom
molded earplugs retained their attenuation after three hours of use
during normal activity; however, typical earplug performance degraded
over the three hours of use. Krutt and Mazor (1980) reported that the
attenuation of mineral down earplugs decreased over a three-hour
wearing period. These researchers did not observe any degradation of
the attenuation of expandable foam earplugs. Cluff (1989) investigated
the effect of jaw movement on the attenuation provided by earplugs and,
determined the change in attenuation was dependent on type of earplug.
The self-expanding viscose foam earplugs retained more of their
attenuation than multi-flanged or glass-fiber earplugs. Casali and
Grenell (1989) tested the effect of activity on the attenuation
provided by an earmuff and found that only at 125 Hz was there a
significant degradation in attenuation. Furthermore, the attenuation of
an earmuff was highly dependent upon the fit.
Royster and Royster (1990) report that the noise reduction rating
(NRR) cannot be used to determine, or rank order, the real world
attenuation of hearing protectors. Two individuals, using the same
model of hearing protector, can obtain vastly different levels of
attenuation. Royster and Royster stated that ``Products that are more
goof-proof (earmuffs and foam earplugs) provided higher real-world
attenuation than other HPDs.''
Casali and Park (1992) reported that the noise attenuation at 500
or 1000 Hz showed a high correlation with the total noise attenuation
of hearing protectors. Therefore, the researchers believe that models
can be developed to predict the total attenuation of hearing protectors
based upon the measured attenuation at a single frequency. This would
eliminate the need to derate the NRR so that it accurately reflects the
field attenuation. The prediction method, they believe, will provide
information on the adequacy of the worn hearing protector and can be
used in objectively fitting the hearing protector.
Berger (1992) reported on the progress of the ANSI Working Group
S12/WG11, ``Field Effectiveness and Physical Characteristics of Hearing
Protectors'', on developing or identifying laboratory and/or field
procedure(s) which yield useful estimates of field performance of
hearing protectors. The Working Group was established to address the
clearly demonstrable divergence between laboratory and field
attenuations of hearing protectors.
Berger also summarized the results of 16 studies involving over
2,600 subjects on the field attenuation of hearing protectors. Earplug
attenuation averaged about 25% of the published U.S. laboratory
attenuations (range 6 to 52%) and earmuff attenuations averaged about
60% of the laboratory attenuations (range 33 to 74%).
Royster et al (1996) reported on the progress of the American
National Standards Institute Working Group (S12/WG11) charged with
developing a laboratory methodology of rating hearing protectors which
reflects the attenuation obtained by workers. Hearing protector
attenuation measured using this methodology reflects the attenuation
achieved by workers in a well managed hearing conservation program. The
Working Group has developed a methodology and is in the process of
drafting an ANSI standard around it. However, it will be some time
before the standard is adopted. Even if the standard is adopted, there
will be some legal ramifications, as the EPA would have to append their
regulations to adopt this standard as the method for rating hearing
protectors. As part of the testing of the methodology, the researchers
found that the instructions which manufacturers include with their
hearing protectors may be inadequate. Some of the test subjects could
not properly don the earplug, from simply reading the manufacturer's
instructions.
As demonstrated above, many researchers have developed standardized
methods of measuring the attenuation of hearing protectors in a
laboratory setting. In addition, many researchers have compared the
results of laboratory attenuations to estimated or measured field
attenuations. However, based on a review of the major studies, MSHA
notes that researchers have yet to develop standardized tests for
measuring the field attenuation of hearing protectors.
MSHA is cognizant of the potential for increased use of diesel
equipment in mines in coming years. Diesel engine noise, a common
mining noise control problem, is predominantly low frequency noise. In
this regard, the Agency notes that hearing protectors are generally
more effective in reducing high frequency noise than low frequency
noise. Thus, noise from diesel engines contains the frequencies where
hearing protectors are least able to attenuate the noise. The
consequence is that hearing protectors poorly protect workers from
excessive noise exposure when the source of the noise is a diesel
engine.
Some special hearing protectors, notably flat response hearing
protectors, attenuate the sound across all frequencies the same. In
developing a flat response hearing protector, the manufacturer degraded
the attenuation at the high frequency instead of enhancing the low
frequency attenuation.
MSHA has concluded that at this time there is not a consensus among
the scientific community as to a reliable method of predicting the
actual attenuation received from hearing protectors in the mining
environment. Additionally, experience indicates that miners do not
receive the full attenuation measured in the laboratory (NRR). Research
data indicate that many workers receive only a small fraction of the
NRR. Therefore, the Agency has determined that one cannot rely solely
on the EPA's NRR value.
Because of the lack of an acceptable method of predicting hearing
protector attenuation in the field, MSHA chose not to include a method
for determining the adequacy of hearing protectors in the proposed
noise regulations.
It should be noted that in order to ensure hearing protection
devices have undergone testing to ensure quality, MSHA is proposing
that the definition of ``hearing protector'' permit only devices having
a ``scientifically accepted indicator of noise reduction value.'' The
Agency solicits comments as to alternatives to the NRR that could be
used in this regard.
Wearing of Hearing Protectors
Proposed Sec. 62.120 would require that hearing protectors must be
worn in certain cases: if noise exceeds the action level and a baseline
audiogram has not taken place within 6 months after the exposure is
determined; if an STS has been detected; and whenever a miner is
[[Page 66425]]
exposed to noise levels above the PEL. In such cases, proposed
Sec. 62.125 would provide that the hearing protectors must be worn when
the miner is ``exposed to sound levels which are required to be
integrated into a miner's noise exposure measurement.'' This means that
if a miner is required to wear hearing protectors, those protectors
must be worn when that miner is exposed to sound levels above 80 dBA;
sounds above that level have been demonstrated to be harmful, while
such a demonstration has not been made for sound levels less than 80
dBA.
MSHA recognizes that mine operators may want to develop particular
policies on exactly when hearing protectors can be removed, and sees no
need to delimit how this might be done. This practical approach, when
taken together with the proposed requirements for employee training
about hearing protectors and ensuring selection and proper fit of
hearing protectors should facilitate the appropriate use of hearing
protectors.
Both MSHA's and OSHA's existing standards require that hearing
protectors be worn when the employee's noise dose exceeds permissible
levels. Neither standard, however, specifies a sound level below which
workers could remove their hearing protectors. Although MSHA received
general comments on levels above which hearing protectors should be
worn, MSHA did not receive any specific comments addressing wearing
practices or under what conditions it would be safe to remove a hearing
protector.
As has been emphasized, hearing protectors are only effective if
they are worn. Chart NR1 illustrates that the amount of attenuation
provided is highly dependent upon the duration a hearing protector is
worn.
BILLING CODE 4510-43-P
[GRAPHIC] [TIFF OMITTED] TP17DE96.008
Chart NR1 demonstrates that if a hearing protector with an NRR of
29 dB is worn only half the time, the wearer will effectively obtain
only about 5 dB of attenuation. Thus, it is critical for mine operators
to ensure that the hearing protectors provided are worn. An NRR of 29
dB is among the highest NRR values reported by hearing protector
manufacturers.
Although MSHA did not ask a specific question in its ANPRM on
monitoring effective usage of hearing protectors, several commenters
recommended that MSHA require mine operators to supervise the proper
wearing of hearing protectors.
Despite mandatory use of hearing protectors, most workers in the
Abel (1986) study admitted to wearing their hearing protectors less
than 50% of the time. Further, many modified their hearing protectors
to provide greater comfort. Many of the modifications had a deleterious
effect on the attenuation.
In EARLOG 8, Berger (1981) contends that persons, who are more
prone to otitis externa (infections), would need to be monitored more
closely for failure to wear their hearing protectors. Persons with a
medical pathology of the ear are more likely to resist wearing a
hearing protector because of pain or extreme discomfort associated with
its use.
Based on the comments received and MSHA's experience, one critical
factor impacting on miner use is their concern that wearing hearing
protectors can, under some circumstances, create serious safety risks.
Apart from the information previously noted in connection with the
discussion of the proper selection of a hearing protector by miners
already suffering hearing loss, there is the issue whether hearing
protectors diminish the ability of even miners with good hearing to
hear ``roof talk.'' Prout et al. (1973) stated that:
Personal ear protectors do not generally prevent a miner from
hearing and analyzing roof talk when the noise level [sound level]
is sufficiently high as to require the use of ear protectors.
However, the ability to interpret roof warning signals is degraded
by the use of ear protectors in quiet. Consequently, ear protectors
should be removed when the noisy machines are shut down.
MSHA is reviewing its own records for further information on the
effect of hearing protectors on safety, and welcomes further
information from commenters. Of course, MSHA recognizes that failure to
wear hearing protectors may accomplish nothing in some cases. For
example, if some surface haulage fatal accidents result because high
sound levels from mining machinery mask the backup alarms, taking off
hearing protectors is not going to make the working environment any
safer. Indeed it is more likely that the miner would suffer a temporary
threshold shift which would make it
[[Page 66426]]
even more likely the backup alarm was missed.
MSHA's review of the literature and codes revealed that the U.S.
armed services and many international communities have specified sound
levels above which hearing protectors must be worn.
MSHA believes proposing specific trigger levels for hearing
protectors in specific circumstances would be burdensome and require
mine operators to conduct a comprehensive survey on each piece of
equipment. A more practical approach would be for mine operators to
ensure through their policies that hearing protectors are worn whenever
noise producing equipment is operating in the miner's work area, and
permit miners to remove their hearing protectors in areas with low
sound levels (below 80 dBA). This would minimize the miner's feeling of
isolation and communication difficulties caused by the wearing of
hearing protectors in such areas. As previously presented, most
researchers have indicated that sound levels below 80 dBA are not
hazardous.
The Agency, however, requests additional comment on this issue,
and, as noted above, on the specific issue of whether hearing
protection can be a safety hazard.
Fitting of Hearing Protectors
The proposal would require that mine operators ensure that hearing
protectors be fitted in accordance with manufacturer's instructions.
MSHA's existing noise standards do not address requirements for
fitting hearing protectors. OSHA's existing standards require that
employers ensure proper initial fitting and supervise the correct use
of all hearing protectors.
Many commenters on this issue recommended fitting.
Most of these specified use of the manufacturer's instructions for
fitting. A few of these specifically recommended that miners be fitted
by individuals trained in the fitting of hearing protectors. Other
commenters did not recommend fitting per se, but recommended that mine
operators provide a variety of types and sizes of hearing protectors to
ensure proper fit.
Several commenters indicated that some types of hearing protectors
do not require fitting. One commenter recommended use of Audiometric
Data Base Analysis (ADBA) to determine hearing protector effectiveness.
Other than ADBA, this commenter believed that there was insufficient
data at this time to recommend a criterion for proper fitting.
In EARLOG 17, Berger (1985) recommends that ``Prior to issuing HPDs
the fitter should visually examine the external ear to identify any
medical or anatomical conditions which might interfere with or be
aggravated by the use of the protector in question.''
In Communication in Noisy Environments, Coleman et al. (1984)
stated:
If a protector cannot be removed or fitted easily and quickly,
it may be either left on when not needed, possibly impairing
communication * * * or not fitted when needed, reducing the
protection from noise exposure. Ease of fitting is therefore a
desirable attribute for coal mining conditions.
Sweetland (1981) found that circumaural protectors were removed
and replaced more often than earplugs in mining conditions, which
could be taken as an indication that the former devices were easier
to fit and use. * * * Factors, such as the time required to hold a
compressible foam plug in position for it to achieve its design
performance, and the procedure required to fit inserts correctly,
which involves reaching around the back of the head to grasp the
earlobe, can reduce their acceptability for mining conditions.
At Noise-Con 81, Berger (1981) reported that the attenuation was
greater when noise was used to help in the fitting of hearing
protectors although the variability was not significantly greater.
Carter and Upfold (1993) investigated methods of determining the
attenuation provided by foam earplugs. Both an earmuff with an earphone
and a cushion with an earphone gave results comparable to the standard
laboratory method and could be used to estimate the group attenuation
of foam earplugs. However, the results of the measured attenuation for
individuals were not as good as that for the group. The researchers,
therefore, concluded that neither method with earmuffs or cushions
could be used to determine the attenuation provided by a foam earplug
to an individual, although the methods could be used to check the
effectiveness of fitting and training of a group.
Merry et al. (1992) reported that subjects obtained greater
attenuation from earplugs if an experimenter directs the fitting using
the subject's response to noise when compared to subjects simply
reading the manufacturer's instructions and inserting their own
earplugs.
Chung et al. (1983) reported that the major factor affecting the
earmuff performance was the fit which is dependent upon headband
tension. Adequate tension is necessary for good attenuation. However,
high headband tension generally caused discomfort. The same occurred
when the earmuff seal was cracked. However, no effect of the age of the
earmuffs was observed. Chung et al. concluded that training and proper
fitting can increase the effectiveness of earmuffs, thus protecting
workers from incurring noise-induced hearing loss (NIHL).
Phoon and Lee (1993) studied workers who developed NIHL in
Singapore. For 103 of 156 earplug users (66%) who developed NIHL, there
was a mismatch between the earplug and the size of both ear canals. In
13.5% of these workers, the mismatch occurred in one ear.
Royster et al. (1996) reported the manufacturer's instructions were
not always adequate in describing the procedures for donning a hearing
protector. Several subjects improperly inserted earplugs during a
laboratory experiment of hearing protector attenuation. The
inappropriately inserted earplugs would be considered improperly fitted
hearing protectors.
ANSI S3.19-1974, ``Method for the Measurement of Real-Ear
Protection of Hearing Protectors and Physical Attenuation of
Earmuffs'', recommends that 60 to 70 dB white noise be used when the
subject fits a hearing protector. White noise has essentially a random
spectrum with equal energy per unit frequency bandwidth over a
specified bandwidth.
As described above, researchers have identified several techniques
for both subjectively and objectively evaluating the fit of hearing
protectors. While many of the techniques show promise, there is no
consensus as to which method is best. Most techniques are applicable to
a specific type of hearing protector and are not practical for use by
many mine operators. These techniques are discussed further under the
Hearing Protector Effectiveness section of this preamble.
MSHA also considered the use of ADBA (Audiometric Data Base
Analysis) to determine the effectiveness of hearing protectors in lieu
of subjective fitting requirements. Since ADBA does not provide
immediate feedback as to the fit of a hearing protector, MSHA has
concluded that ADBA is inappropriate for determining the fit of a
hearing protector. ADBA analysis requires multiple subjects, not an
individual, before a conclusion of adequacy is determined. Besides ADBA
determines the adequacy of the HCP (protecting the hearing acuity of a
group of workers), not the adequacy of protecting an individual.
Moreover, MSHA believes that ADBA is not practical for most mining
operations as discussed under the Evaluation of HCP effectiveness
section of this preamble. Furthermore, ADBA requires several audiograms
which are conducted on an
[[Page 66427]]
annual basis. In the interim, the hearing acuity of a miner could be
irreversibly damaged.
As supported by the researchers and many commenters, MSHA agrees
that proper fitting is necessary to ensure optimal effectiveness of
hearing protectors and that it should not be left solely up to the
individual miner to determine if the hearing protector fits properly.
Further, MSHA is concerned that some manufacturer's instructions are
not adequate to ensure the proper fitting of a hearing protector.
Although comfortable hearing protectors should be provided, MSHA is
also concerned that some miners may choose hearing protectors that are
too loose or otherwise improperly fit, and consequently not achieve
adequate noise reduction.
In light of the wide variety of hearing protectors available, the
broad range of subjective fitting procedures, and the lack of consensus
on an objective fitting method, MSHA concluded that the manufacturer's
instructions are the best criteria for fitting. MSHA encourages
commenters to provide information on any standardized methods of
testing the fit of hearing protectors.
Maintenance of Hearing Protectors
MSHA's proposal would also require mine operators to ensure that
hearing protectors are maintained in accordance with manufacturer's
instructions. Neither MSHA's nor OSHA's existing noise standards
address requirements for maintaining hearing protectors.
MSHA recognizes that it is difficult to keep hearing protectors
clean in the mining environment. Using contaminated hearing protectors,
however, may contribute to a medical pathology of the ear. Once the
skin has been abraded or inflamed, it is easier for microorganisms
normally found in the ear to invade the skin. When hearing protectors
are implicated as the cause of inflammation of the external ear canal
(otitis externa), often the hearing protector is contaminated with an
irritating or abrasive substance. This situation can be corrected with
proper cleaning of the hearing protector before use.
MSHA's proposal is designed to ensure that miners not develop
medical problems while they are attempting to protect themselves from
the hazard of noise. If an earplug cannot be adequately cleaned, then
the mine operator would have to replace it.
In addition to providing guidance on the fitting of hearing
protectors, manufacturers also provide instructions on the proper care
and cleaning of their hearing protectors. Many recommend soap, warm
water, and careful rinsing. Solvents and disinfectants generally are
discouraged as cleaning agents because they can cause skin irritation
and some can damage the hearing protector. In most cases, the proper
insertion technique for earplugs would just be a matter of applying
common sense, i.e., cleaning the hands before rolling and/or inserting
earplugs.
Several commenters addressed hygiene problems when the hearing
protectors become dirty. One of these commenters stated that miners
would need to clean their permanent hearing protector daily and that
irritation due to sweating and skin contact with the hearing protector
can be a problem associated with its use.
In EARLOG 5, Berger (1980) states that permanent [non-disposable]
hearing protectors should be replaced between two and 12 times per
year. The constant wearing of hearing protectors causes them to lose
their effectiveness. For example, headbands on earmuffs can lose their
compression ability; the soft seals surrounding the ear cup on earmuffs
can become inflexible; and plastic earplugs can develop cracks, can
shrink, or can lose their elasticity.
As referenced in EARLOG 17 (Berger, 1985), Forshaw and Cruchley
studied the effects of washing the hearing protectors worn by long-
range patrol aircraft crews. The crews were divided into three groups:
one group wore pre-molded earplugs; the second group wore foam earplugs
washed after each use; and the third group wore foam earplugs which
were washed weekly. Examinations by medical officers revealed no fungal
or clinically significant bacterial infections among the three groups.
MSHA also reviewed standards from the U.S. Armed Forces and the
international community on the topic of hearing protector maintenance.
The consensus of the standards was that damaged or deteriorated hearing
protectors must be replaced.
Miners have also been known to alter the hearing protection
provided to make them more comfortable. Such alterations have included
cutting off the end of earplugs or stretching out the head-band on
earmuffs. These alterations can significantly decrease the hearing
protector's attenuation.
Hearing protectors can also be damaged from exposure to heat, cold,
ozone, chemicals, or dirt. Such conditions are common in the mining
industry, and mine operators must periodically check the hearing
protectors provided and replace them when damage is found.
Hearing Protectors Provided at No Cost to Miner
The proposal would also require the mine operator to provide
necessary replacements at no cost. This is intended to ensure that the
mine operator repairs or replaces a miner's hearing protector when it
becomes damaged or deteriorated to the point that the required
protection is compromised.
MSHA believes that it is essential for mine operators to replace
worn-out or damaged hearing protectors in order to maintain their
effectiveness. This is in agreement with the international community
and the U.S. armed services. Damaged or deteriorated hearing protectors
do not provide their designed optimum amount of protection. Further,
MSHA believes that the manufacturer's instructions are the best source
of information as to the proper procedures for maintaining a particular
protector.
MSHA's existing noise standards do not specifically address the
replacement of hearing protectors. OSHA's noise standards simply
require that hearing protectors be replaced as necessary.
MSHA received no direct comments to its ANPRM on the issue of mine
operators supplying commercially available hearing protectors at no
cost to the miner. However, several commenters supported adopting
requirements similar to OSHA's which includes provisions for providing
hearing protectors at no cost to the worker.
Replacement of hearing protectors would be based on the
manufacturer's instructions, upon finding any deterioration that could
adversely affect the hearing protectors attenuation, or upon a need for
the miner to choose a different hearing protector due to a medical
pathology caused or aggravated by the initial hearing protector
provided (see following section which discusses medical pathology). For
example, manufacturers of disposable earplugs may state in their
instructions that they should be replaced after each use.
Replacement of Hearing Protector Due to Medical Pathology
MSHA's proposal would also require the mine operator to provide an
individual miner with a different, more acceptable, type of hearing
protector when presented with evidence of a medical pathology (e.g.,
otitis externa or contact dermatitis). The definition of ``medical
pathology'' is intended to be broad enough to cover injuries. If, for
example, a miner would suffer a burn in the ear canal which would
preclude the wearing of earplugs, an employee who
[[Page 66428]]
elected earplugs should have the opportunity to now select a muff.
MSHA does not intend to require that the evidence of a medical
pathology be a diagnosis by a physician specialist--nor to require mine
operator action without any evidence whatsoever. The goal here is a
practical one: exchange the hearing protector if there appears to be a
medical problem. A preliminary diagnosis of medical pathology by a
family physician or nurse should be accepted by an employer for the
purposes of this requirement.
In EARLOG 17, Berger (1985) discusses some predisposing factors for
otitis externa. These include allergy to chemicals or hair dyes and
sprays; dermatitis; chronic draining middle ear infections; excessive
cerumen (ear wax); and systemic conditions which lower the body
resistance, such as anemia, vitamin deficiencies, diabetes, and
endocrine disorders. Disposable hearing protectors may be warranted for
those individuals prone to infections. The researcher reported that the
prevalence of otitis externa is approximately 2% in both users and
nonusers of hearing protectors. He stated that:
Although hearing protection devices should not be worn in the
presence of some preexisting ear canal pathologies, and care must be
exercised regarding selection and use under certain environmental
conditions, regular wearing of HPDs does not normally increase the
likelihood of contracting otitis externa.
Furthermore, Royster and Royster in EARLOG 17 (Berger, 1985)
reported on a situation in which underground miners in a warm and humid
environment were experiencing otitis externa. Switching from a pre-
molded vinyl earplug to a foam earplug decreased the incidence of this
condition.
Although documented cases of hearing protectors causing infections
in the ear canal or on the skin surrounding the ear are not prevalent,
MSHA is aware of at least one reported case of an ear infection in the
mining industry specifically attributed to the use of hearing
protectors.
MSHA's existing noise standards do not specifically address the
replacement of hearing protectors. OSHA's noise standards simply
require that hearing protectors be replaced as necessary.
Based upon the research and several international standards, MSHA
believes that hearing protectors need to be replaced whenever a medical
pathology is present. Such replacements would also be at no cost to the
miner.
Section 62.130 Training
Summary
Proposed Sec. 62.130 would provide the specifications for
instruction and certification of training required by the proposed
rule. Proposed Sec. 62.120 requires such training for all miners
exposed above the action level, and annually thereafter if still
exposed above that level. Proposed Sec. 62.180 requires retraining for
every miner who incurs an STS.
Miners would receive instruction in the value of hearing
protectors, selection and fitting of protectors, and proper use of such
protectors. Miners would also receive instruction as to the operation
of an operator's hearing program and in the mine operator's noise
control efforts. There are no special qualifications for instructors,
nor any specifications on the hours of instruction. Training is
required to be provided without cost to the miner. The mine operator
would be required to certify the completion of any training required by
this part, and maintain the most recent certification for a miner at
the mine site for as long as the miner is required to use hearing
protectors or be enrolled in an HCP, and at least 6 months thereafter.
MSHA considered whether the requirements of part 48, ``Training and
Retraining of Miners,'' were adequate to ensure the training required
under this part. The requirements of part 48 specify the initial and
annual retraining of all miners in a list of subjects, many specified
in the law itself (section 115 of the Mine Safety and Health Act). The
importance of this training is emphasized by statutory requirements for
the submittal of training plans, on the specification of the hours to
be devoted to the training, and on the qualifications of instructors.
Training is required on noise, but it is in general terms, covering the
purpose of taking exposure measurements and on any health control plan
in effect at the mine. Mine operators may provide additional training,
but the topics that need to be covered often make this impracticable
within the prescribed time limits.
After considering the available information about the importance
and prevalence of training requirements, and based upon its experience
in implementing the requirements of part 48, MSHA has determined that
the requirements of part 48 do not provide adequate noise training for
those miners for whom exposure is clearly a problem. Part 48 training
is neither comprehensive enough to provide such miners with the level
of education needed for the proper use of hearing protection devices,
nor, in the case of noisy mines, detailed enough on methods to reduce
sound levels.
Nevertheless, MSHA believes compliance with this proposal can in
many cases be fulfilled at the same time as scheduled part 48 training.
The Agency does not believe special language in proposed part 62 is
required to permit this action under part 48, but welcomes comment in
this regard. Mine operators who can do so are free to fulfill their
training requirements under Sec. 62.120 by covering the topics in
initial and annual part 48 training, and so certify on the separate
form required by this part. If incorporated into part 48, mine
operators would, however, be required to submit a revised training plan
to the local district office for approval. Some mine operators may not
have room in their part 48 plans, however, to be able to incorporate
these topics. Moreover, some training required under the proposal will
clearly not fit within a regular schedule: e.g., the training required
by Sec. 62.180 whenever a standard threshold shift in hearing acuity is
detected.
MSHA has endeavored to make the training requirements as simple as
possible. If conducted separate from part 48, there are no
specifications on trainer qualifications, no minimal training time, nor
any training plans. If however the training is incorporated into part
48, then all applicable part 48 requirements will have to be met.
Background
Training requirements are a mainstay of mine safety and health.
Although MSHA has no training requirements in its existing noise
regulations, the general training requirements set forth in part 48
require basic training as to the purpose of taking noise measurements,
and in any health (noise) control plans that are in effect at the mine.
Numerous commenters responding to MSHA's ANPRM, expressed
considerable support for miner training on noise and its effects and
believed that it is an essential element of any effective HCP. Many of
these commenters specifically supported annual refresher training.
Commenters differed, however, in their opinions as to how training
could best be accomplished. Several commenters recommended that MSHA
incorporate any training requirements related to this standard into
MSHA's existing training requirements under 30 CFR part 48--Training
and Retraining of Miners. A few commenters believed that the training
requirements in MSHA's part 48 were adequate and that no additional
instruction was needed.
[[Page 66429]]
One commenter suggests that the initial training class be limited
to less than 10 individuals (Berger, 1988; Royster and Royster, 1985).
Although training may best be accomplished in small groups, MSHA's
proposal would not limit the size of any training classes.
There is considerable precedent for requiring training as part of
noise control programs.
OSHA's noise standard has training requirements which are similar
to those in MSHA's proposed noise standard with a few exceptions. These
exceptions are discussed later in this section.
In OSHA's 1981 preamble (46 FR 4157), Morrill stresses the
importance of worker education in overcoming workers objections to
wearing hearing protectors. This document quotes a Dr. Maas as saying
that, ``Supervisors must sell employees on the need and value of
hearing protection devices. When employees understand what the
protective measure is for, it will be accepted because the employee
realizes it is for his own good.'' A number of comments to OSHA's
Hearing Conservation Amendment (46 FR 4157) indicated that workers are
reluctant to appear weak or ridiculous as a result of wearing hearing
protectors. Suter (1986) states, ``Workers who understand the mechanism
of hearing and how it is lost will be more motivated to protect
themselves.'' Other researchers concur with this opinion (Wright,
(1980) and Royster et al., (1982)).
CAOHC (Miller, 1985) states the following regarding the need for
training as part of an effective program (HCP):
A critical component of the OHC [Occupational Hearing
Conservation] program is the employee education program (EEP). In
many respects, the EEP is the most important aspect of the OHC
program since it is designed to increase the auditory consciousness
of the employee regarding the hazardous effects of noise exposure
and by so doing to get him to use effective forms of PHPD's
[personal hearing protective devices] conscientiously and
consistently. Such use of PHPD's will actually protect the worker's
hearing, while the other aspects of the program, important as they
are, will not do so. No amount of noise monitoring or audiometric
testing, for example, will protect hearing.
MSHA also reviewed the training requirements set forth in
international standards and those of the U.S. Armed Services. The
consensus was that training was necessary; however, the training
interval was not always specified.
Training About Hearing Protector Selection and Use
Section 62.130(a) specifically provides that the training is to
include instruction in--
(1) the effects of noise on hearing;
(2) the purpose and value of wearing hearing protectors;
(3) the advantages and disadvantages of the hearing protectors to
be offered;
(4) the care, fitting, and use of the hearing protector worn by the
miner;
(5) the general requirements of the regulation;
(6) the operator's and miner's respective tasks in maintaining mine
noise controls; and
(7) the purpose and value of audiometric testing and a summary of
the procedures.
OSHA requires annual training on the same elements except it does
not require training on the requirements of its noise standard. It is
MSHA's view, however, that some training on the requirements of the
standard is necessary in order for employees to understand the role
hearing protection plays in a broader protection scheme.
Purpose, Advantages, and Disadvantages of Hearing Protectors Offered
Instruction on this topic would help the miner make an informed
choice as to which hearing protector to use. This basic instruction
would be initially required when the mine operator first determines the
miner's noise exposure exceeds the action level. Moreover, pursuant to
proposed Sec. 62.125, this instruction must be provided at least once
before the miner must make a selection of a hearing protector.
Furthermore, it would need to be repeated annually thereafter, because
hearing protectors should be replaced periodically.
MSHA anticipates the training would address specific advantages and
disadvantages of earmuffs, earplugs, and canal caps as they relate to
the needs of the miner and the specific conditions at the mine. For
example, an electrician who opts to use an earmuff must understand the
need to use one with dielectric properties to minimize the chance of
incurring an electrical shock when working around energized equipment.
An over-the-head earmuff is unsuited for those miners required to wear
hardhats: the earmuff would interfere with the wearing of the hardhat
as the hardhat could not be placed over the headband. In addition, the
mine operator should discuss the specific advantages and disadvantages
of any special hearing protectors offered such as active noise
reduction, level-dependent, flat-response, and notch-amplification
hearing protectors, or a communication headset. For example, a miner
with a sensorineural hearing loss in the higher frequencies may require
a different type of hearing protector than a miner with a conductive
hearing loss across all frequencies. Accommodating the hearing loss may
require a level-dependent, active noise reduction, or notch-
amplification hearing protector to improve the miner's ability to
communicate and hear warning signals in a noisy environment. All miners
need to understand the relative advantages and disadvantages of
earmuffs and earplugs as they are not at all obvious: hence, the
necessity for training.
Some advantages of earmuffs (circumaural hearing protectors)
include: they are easily donned and removed by the miner when working
in intermittent noise; they offer protection against dust in the ear
canal; they are not easily misplaced or lost; they fit people with
unusually shaped ear canals; and they can be worn over earplugs. Berger
in EARLOG 3 (1980), and Coleman et al. (1984) reported that one major
disadvantage of earmuffs is that they hinder a miner's ability to
localize the direction of sounds. If the miner's safety depends on the
ability to localize sounds, then this disadvantage would preclude the
use of earmuffs. Other potential disadvantages of earmuffs include:
discomfort; headache; a feeling of claustrophobia; excessive warmth and
perspiration under the muff seal; and skin irritation. Earmuffs may
present problems if the miner wears safety glasses or earrings.
Eyeglass temples reduce the attenuation afforded by earmuffs.
In EARLOG 19, Berger (1988) states that the use of eyeglasses with
an earmuff can break the seal of the earmuff and cause a loss of
attenuation of up to 6 dB depending on the frequency of the noise.
Royster et al. (1996) tested the effect of wearing two different
safety glasses on the attenuation of an earmuff. The researchers found
that the attenuation was reduced by about 5 dB across all frequencies.
Barham et al. (1989) investigated the effects of safety glasses and
hair on the effectiveness of earmuffs. The wearing of safety glasses
decreased the noise reduction up to 4 dB depending upon the frequency.
The glasses had slender and flexible wire-reinforced side frames so
that the side frames would fit close to the head. Not only did the
safety glasses decrease the average noise reduction, they also reduced
the variability (standard deviation) of the
[[Page 66430]]
noise reduction realized among the individuals. The type of hair and
its length influenced the noise reduction provided by earmuffs.
Individuals with short hair realized up to 5 dB more protection,
depending upon the frequency, than individuals with long or curly hair
and beards.
Michael (1991) asserts that glasses with plastic temples may cause
a loss of attenuation from 1 to 8 dB, due to breaking the seal of the
earmuff. In some cases, this loss can be substantially reduced if
small, close fitting wire temples are employed.
Nixon and Berger (1991) report that temples of eyeglasses reduce
the efficacy of earmuffs normally by 3 to 7 dB provided the cushions of
the earmuffs are in good shape. This effect varies among earmuffs and
it also depends upon the style and fit of the eyeglasses. To minimize
the effect of wearing eyeglasses, the temples should be as thin as
possible and fit close to the side of the head.
Savich (1979) measured the noise attenuation of earmuffs. Because
of long hair and safety glasses, the earmuffs provided less attenuation
than expected based upon laboratory tests. Furthermore, head size has a
significant influence on the attenuation because of different clamping
forces. Increased clamping force increases the attenuation.
Some advantages of earplugs include: they are cooler, if the miner
has to work in a hot, humid environment; they are more easily worn with
safety glasses, hardhats, and other personal safety equipment (e.g.,
air-purifying or welding helmets); and they fit miners who have
extremely large external ears. One disadvantage of an earplug is that
inserting it into the ear canal could present a personal hygiene
problem if the miner removes and reinserts it several times during the
day. A miner who is susceptible to ear infections or secretes
significant amounts of ear wax may be better suited for using earmuffs.
As noted earlier in this section, training is critical to miner
cooperation. MSHA has concluded, after reviewing the scientific
literature, U.S. Armed Forces regulations, and standards from the
international community, that requiring the mine operator to instruct
each miner required to wear hearing protectors on the purpose,
advantages, and disadvantages of the choices available will facilitate
hearing protector use and effectiveness.
Care, Fitting, and Use of the Hearing Protector Selected
In response to MSHA's ANPRM, many commenters supported the need to
train employees on the proper fitting, care, and use of hearing
protectors.
Merry et al. (1992) studied the effect of fitting instructions on
the resulting attenuations of earplugs. Novice subjects were given
earplugs. The difference in their hearing thresholds between the
unoccluded and occluded conditions was the attenuation of the earplug.
The subjects obtained greater attenuation whenever the experimenter
assisted the subject in fitting the earplug than when the subject
merely read the manufacturer's instructions before donning the earplug.
Furthermore, the researchers noted that the attenuations obtained by
the subject when just the manufacturer's instructions were read is
comparable to the attenuations measured under industrial conditions.
Casali and Lam (1986) reported that the proper design and
presentation of user insertion/donning instructions are critical to the
amount of attenuation afforded by hearing protectors. They found that
in some cases, the magnitude of protection afforded by the use of
earplugs exhibited greater than a twofold increase when training ranged
from no instruction to detailed and model instruction. Their study also
showed that the attenuations afforded by earmuffs and earcaps were not
as influenced by the level of instruction as were earplugs. Casali and
Lam concluded that any instruction technique provided an improvement in
attenuation over no instruction at all. However, they found no
statistically significant differences among the type of instruction
used. They also stated that regardless of the insertion/application
instruction type selected, it is imperative that workers be retrained
periodically in hearing protector insertion practices, hearing
protector sizing, and hearing protector care to maintain optimal
hearing conservation.
Royster et al. (1996) had novice users of hearing protectors don
the protectors after reading the manufacturer's instructions. Since
some users failed to properly don the hearing protectors, the
researchers concluded that the instructions provided by the
manufacturer were not always adequate. Consequently, additional
instruction should be provided to assure the proper donning of hearing
protectors.
Barham et al. (1989) reported that the noise reduction achieved by
an earmuff improved by approximately 4 dB for a group and up to 6 dB
for an individual following instruction on its use. Not only did the
attenuation increase but also the standard deviation (a measure of
variability) decreased. Therefore, instruction significantly improved
the noise reduction achieved by the wearer of an earmuff.
Park and Casali (1991) studied the effects of two levels (minimal
and detailed) of instruction on the measured attenuation obtained by
regular hearing protector users. The users were tested using different
hearing protectors from the ones they normally wore. The amount of
noise attenuation increased and the standard deviations decreased when
the investigators presented the instructions and demonstrated the
proper manner to don and doff hearing protectors as compared to the
employees simply reading the instructions. The efficiency of earplugs
was found to be highly sensitive to the degree of instruction while
earmuffs and canal caps were not.
MSHA believes that training is critical to the effective use of
hearing protectors, and that miners must be shown how to use, fit, and
care for their hearing protectors if they are to be effective. Further,
the instructions should be repeated at yearly intervals to maintain
effectiveness. Simply instructing the miner to read manufacturer's
directions on the hearing protector container would not be adequate.
MSHA is concerned that some manufacturer's instructions are inadequate
for the proper fitting of hearing protectors. The effectiveness of
hearing protectors can be highly dependent on how they fit the
individual wearer. Not all people will achieve the same degree of fit
or effectiveness from the same hearing protector.
Training About Hearing Conservation Program and Operator Noise Controls
OSHA's noise standard has similar training requirements with the
exception that they do not require training on the respective
responsibilities of the employer and employee in maintaining controls.
MSHA has determined that training miners enrolled in an HCP on the
respective responsibilities of mine operator and miner is necessary to
obtain maximum effectiveness from an HCP. Miner cooperation and support
is required, for example, to ensure:
(1) The hearing protector provided fits properly each time it is
donned;
(2) The hearing protector is worn whenever the miner is exposed to
hazardous sound levels;
(3) Exposure to high sound levels is avoided for at least 14 hours
before taking the baseline audiogram;
(4) Participation in the audiometric testing;
(5) Cooperation with any administrative control(s) instituted by
the mine operator; and
[[Page 66431]]
(6) Use and maintenance of the engineering noise controls provided
by the mine operator.
MSHA believes that a miner's understanding and motivation would be
enhanced by conducting initial and annual training in these areas. The
rationale for retraining miners who suffer an STS is discussed in
connection with Sec. 62.180, Follow-up corrective measures when STS
detected.
MSHA believes that a miner must also be trained to understand the
audiometric tests. This will enable miners to understand their own
results and determine the effect of wearing hearing protectors.
Effectiveness. MSHA has endeavored to make the training
requirements as simple as possible. If conducted separate from part 48,
there are no specifications on trainer qualifications, no minimal
training time, nor any training plans. If however the training is
incorporated into part 48, then all applicable part 48 requirements
will have to be met.
While this approach reduces the burden on those mine operators who
cannot incorporate part or all of the noise training into part 48
training, it also means that certain safeguards in effect for part 48
training will not be directly applicable to that noise training not
provided during part 48 training. There would be no review of a noise
training plan, for example, to ensure that the instruction is adequate
or that the training is to be given in the language spoken by most of
the miners. Comments on this point are solicited.
The Agency believes it can ensure the noise requirements have been
fulfilled by checking with exposed miners to ensure that the required
training elements have been covered and that the certifications are
valid.
Certification. Section 62.130(b) of the proposal would require
that, upon completion of any training required under this part, the
mine operator certify the date and type of training (initial or annual)
given each miner. The certification would be signed by the person
conducting the training.
It is standard practice in the mining industry to require
certification of training, as a way of facilitating compliance.
Training received under part 48 must be certified. The certification
form used for part 48 does not have a separate line on which to
indicate that the training required under the proposed noise standard
has been completed; moreover, this would not be suitable in any event
for noise training given independently of part 48 training as may often
be the case.
MSHA believes that it is important to record the type and date of
any training conducted under its proposed noise regulations. A written
record, together with miner interviews, provide the Agency necessary
checks to ensure the training is provided as required with only a
minimal burden.
An optional approach on which MSHA would welcome comment is to
simply require that a mine operator must, upon request, give an MSHA
inspector copies of all materials related to the employer's noise
training program. This is the approach taken by OSHA.
Retention. Section 62.130(b) of MSHA's proposal would require the
mine operator to retain the most recent certification at the mine site
for as long as the miner is exposed to noise above the level which
initiated the training and for at least six months thereafter.
MSHA has a retention requirement for part 48 training. Part 48
training records are to be retained for two years for currently
employed miners or for 60 days after the termination of employment.
OSHA has no retention requirement for training records.
The Agency believes it is important to retain training records in
order to verify that the required training has been provided, as with
the certification requirements. The retention requirement is short and
not burdensome: only the most recent record must be retained, and then
only until the miner's exposure drops beneath the level which initiated
the training (or 6 months after cessation if employment should that
come before the exposure level has dropped).
Section 62.140 Audiometric Testing Program
This section of the proposal would establish basic procedures for
the audiometric testing program in which those miners enrolled in a
hearing conservation program (HCP) will participate. It includes
provisions for: qualifications of personnel performing the audiograms,
baseline audiograms, annual audiograms, and supplemental baseline
audiograms.
MSHA is seeking explicit comment on a number of points. What
follows is a brief summary of some key features of this section of the
proposal.
With respect to qualifications of personnel, MSHA would require
that an ``audiologist'' be certified by the American Speech-Language-
Hearing Association or licensed by a state board of examiners.
``Qualified technicians'' would be required to have been certified by
the Council for Accreditation in Occupational Hearing Conservation
(CAOHC) or another recognized organization offering equivalent
certification. CAOHC or equivalent certification would assure that the
technicians are qualified. MSHA is not proposing to require
qualifications for physicians.
It is critical to obtain a baseline audiogram before exposure to
hazardous noise. If this is not possible, then the baseline is to be
obtained as soon as is reasonably possible. Due to remote locations and
intermittent operations of many mines, MSHA determined that allowing
six months (or 12 months if a mobile test van is used) for obtaining
the baseline audiogram was reasonable. The 12 month period would allow
mine operators to schedule many baseline and annual audiograms
simultaneously, and thus, substantially reduce the cost when mobile
test vans are used. Pursuant to proposed Sec. 62.120(b), miners would
be provided hearing protection until such time as the baseline
audiogram is conducted; and in the event the miner has to wait for more
than 6 months to get a baseline audiogram because a mobile test van is
used, the operator would be required to ensure the use of hearing
protection.
MSHA has also determined that a 14-hour quiet period should precede
the baseline audiogram to ensure a valid result: hearing protectors
will not be considered a substitute for a quiet period under the
proposal, and miners are to be notified of the importance of compliance
with the quiet period.
MSHA has concluded that audiograms need to be provided annually for
miners enrolled in an HCP. MSHA is not proposing to require this quiet
period for annual audiograms, though it may be in the mine operator's
interest to do so.
Background
Under existing standards for coal mines, MSHA requires pre-
employment and periodic audiograms at those mines under a hearing
conservation plan, but includes no specific procedures or time frames
for obtaining these audiograms. Moreover, at present, less than 1% of
the coal miners are covered by a hearing conservation plan. MSHA
currently does not have any requirements addressing audiometric testing
for metal and nonmetal mines.
OSHA's noise standard also contains requirements for qualifications
of personnel and for baseline, annual, and supplemental baseline
audiograms. The limited number of differences between the OSHA standard
and the MSHA proposal are noted in the discussion that follows.
[[Page 66432]]
Qualifications of Personnel
Section 62.140(a) of MSHA's proposal would require that audiometric
tests be conducted by a physician, an audiologist, or a qualified
technician who is under the direction or supervision of a physician or
an audiologist.
MSHA would require that an ``audiologist'' be certified by the
American Speech-Language-Hearing Association or licensed by a state
board of examiners. ``Qualified technicians'' would be required to have
been certified by the Council for Accreditation and Occupational
Hearing Conservation (CAOHC) or another recognized organization
offering equivalent certification.
OSHA's noise standard requires that--
Audiometric tests shall be performed by a licensed or certified
audiologist, otolaryngologist, or other physician, or by a
technician who is certified by the Council of Accreditation for
Occupational Hearing Conservation, or who has satisfactorily
demonstrated competence in administering audiometric examinations,
obtaining valid audiograms, and properly using, maintaining and
checking calibration and proper functioning of the audiometers being
used. A technician who operated microprocessor audiometers does not
need to be certified. A technician who performs audiometric tests
must be responsible to an audiologist, otolaryngologist or
physician.
MSHA received comments that specifically addressed the
qualifications of persons conducting audiometric tests. Some commenters
were concerned that physicians may not have the specific knowledge
necessary to conduct audiometric testing. One of these commenters
stated that:
* * * many physicians are not well versed in problems of
audition, especially occupational noise induced hearing loss [NIHL].
If physicians are to be included in the list of acceptable
supervisors, they should be limited to ``qualified occupational
physicians,'' or perhaps ``qualified occupational physicians with
audiological experience.''
Other commenters recognized that technicians need specific
training, but disagreed as to whether formal certification was
necessary. Many commenters specifically stated that MSHA should require
CAOHC certification as the minimum acceptable criteria for training of
audiometric technicians.
Many commenters specifically recommended or implied that MSHA treat
technicians who operate microprocessor audiometers the same as
technicians who operate other types of audiometers. One stated that:
The use of a microprocessor audiometer does not guarantee a
valid, reliable audiogram, nor does it obviate the need for the
technician to be familiar with the important interpersonal and
procedural details of administering an audiogram and providing
feedback to the employees.
Other commenters, however, stated that persons who operate
microprocessors do not need to be certified, but it was unclear whether
they thought that training and demonstration of competency would be
necessary for such technicians. Finally one commenter wanted ``maximum
flexibility in audiometric testing.''
One commenter on this issue stated that:
* * * We do not believe that there are other qualified medical
personnel [other than an audiologist or physician] who understand
the principles of interpreting an audiogram appropriately.
The U.S. Army (1991), Air Force (1991), and Navy (1994) regulations
require that a physician, audiologist or technician conduct the
audiometric tests. The audiometric technician must be CAOHC certified
or certified through military medical training and be under the
supervision of a physician or audiologist.
MSHA believes that it is unnecessary to specify that physicians be
``licensed'' or ``qualified.'' All states require physicians to be
licensed. MSHA is concerned, however, that licensing does not imply
qualification to conduct audiometric testing, evaluate audiograms, and
supervise technicians in these areas. The Agency expects physicians to
exercise professional judgement when evaluating their own
qualifications to conduct audiometric testing. In addition, the medical
profession enforces a high degree of accountability and ethical
standards. Nevertheless, further comment is requested on this issue.
MSHA believes that certification or licensing of audiologists is
essential to an effective HCP. Properly trained and certified
audiologists would be qualified to conduct audiometric testing,
evaluate audiograms, and supervise technicians. Unlike physicians, MSHA
believes that certification or licensing presupposes that the
audiologist would be qualified to conduct audiometric testing.
With respect to qualified technicians, MSHA considered the comments
on this topic filed in response to the ANPRM and concluded that
qualified technicians need to be certified by CAOHC or by an
organization offering equivalent training. CAOHC or equivalent
certification would assure that the technicians are qualified. While
MSHA recognizes that the OSHA standard allows physicians discretion to
judge the qualifications of technicians, MSHA believes requiring
certification is not restrictive and best ensures quality control. MSHA
would also require CAOHC or equivalent certification for technicians
who operate microprocessor audiometers. The Agency concludes that
requiring CAOHC or equivalent certification would not be overly
burdensome on the mining industry.
NIOSH commented on OSHA's proposed rule, and again on MSHA's ANPRM,
that there may not be enough CAOHC courses offered in a given year, or
in a wide enough geographical area, to require that all technicians be
CAOHC certified. OSHA's preamble (46 FR 4128) in 1981 indicated that,
at that time, there were about 6,700 CAOHC certified technicians and
700 course directors. Since 1981, however, the number of CAOHC course
directors has decreased to about 400, but the number of certified
technicians has increased to about 14,000. Although this number of
certified technicians may be sufficient to conduct the required
audiograms in the mining industry, MSHA believes that promulgation of
this rule will result in even more individuals seeking certification.
In addition to CAOHC certification for audiometric technicians, MSHA
would also accept training by any other recognized organization
offering equivalent certification. MSHA requests information on any
other nationally recognized program for the certification of persons to
conduct audiometric tests.
MSHA also considered the ``qualifications of personnel''
requirements from U.S. Armed Forces codes and international standards.
The consensus was that the technician needed to be trained in
conducting audiometric testing.
Although the proposal would not require that the audiologist or
physician be present when the technician conducts the audiometric test,
MSHA would require that they directly supervise the technician to
ensure strict adherence to testing procedures and measurement
parameters.
Baseline Audiogram
Section 62.140(b) of MSHA's proposal would require that, within six
months of a miner's enrollment in an HCP, the miner shall be offered a
valid baseline audiogram of the miner's hearing acuity against which
subsequent annual audiograms can be compared. This would include miners
with temporary layoffs, such as those miners employed at seasonal
operations. However, the proposal would allow up to 12 months
[[Page 66433]]
to obtain a baseline audiogram when a mobile test van is used.
Under existing standards for coal mines, MSHA does not specifically
address a time frame for offering a baseline audiogram for those miners
under a hearing conservation plan. MSHA has no requirements for
baseline audiograms in its current metal and nonmetal noise regulation.
This proposal is consistent with OSHA's noise regulation.
The proposal would allow mine operators to use existing audiograms
as the baseline, provided that they meet the testing requirements of
this part. OSHA also accepts existing audiograms as a baseline because,
in most cases, accepting old baseline audiograms is more protective for
the employee. OSHA reasoned that:
* * * old baselines will allow the true extent of the hearing
loss over the years to be evaluated. Obtaining a new baseline
audiogram after many years of noise exposure might be less
protective since the new audiogram might show higher thresholds and
the true extent of future losses would appear smaller than when
compared with the original baseline.
All commenters, addressing the issue of audiograms recognized the
need to establish a baseline. The commenters varied, however, on the
time needed to establish this baseline, i.e., from 30 days up to one
year from the first exposure to noise. One stated that ``* * * the
first annual or periodic audiogram should be allowed to be considered
as the baseline or pre-employment audiogram.'' Most of the commenters,
who specified a time frame for completing the baseline audiogram,
agreed with OSHA's position of allowing up to six months. Only one
comment was received, on the 1-year time allowed, for audiometric
testing with mobile test vans. This commenter was concerned that miners
might be exposed to noise, in the interim period, until the test van
was available and recommended ``that the employees utilize hearing
protection from the time they are enrolled in an HCP.''
NIOSH (1995) recommended that the baseline audiogram be conducted
within 30 days of enrollment in an HCP, even if a mobile test van is
used. NIOSH believes it is unacceptable to wait up to six months for a
baseline audiogram, because exposure to high sound levels for a
relatively short period of time can adversely affect the hearing acuity
of susceptible individuals.
MSHA has also taken into consideration requirements of the U.S.
Armed Forces and the international community with respect to baseline
audiograms. Many in the international community and the U.S. armed
services agree that the baseline audiogram is of primary importance.
MSHA has determined that the baseline audiogram is essential,
because it is the reference against which subsequent audiograms are to
be compared. The comparison will be used to determine the extent of
hearing loss. If the baseline audiometric test is not conducted
properly, it will not reflect the miner's true hearing thresholds and
any changes between baseline and subsequent tests may be masked.
Further, existing audiograms may be used as the baseline, if they meet
the testing requirements of this part. The use of pre-existing
audiograms would be more protective for the affected miner and less
burdensome on the mine operator.
Because of the baseline audiogram's importance, it is critical to
obtain one before exposure to hazardous noise. If this is not possible,
then the baseline is to be obtained as soon as is reasonably possible.
Due to remote locations and intermittent operations of many mines, MSHA
determined that allowing six months (or 12 months if a mobile test van
is used) for obtaining the baseline audiogram was reasonable. The 12
month period would allow mine operators to schedule many baseline and
annual audiograms simultaneously, and thus, substantially reduce the
cost when mobile test vans are used.
It should be noted that the provisions of Sec. 62.120 of MSHA's
proposal would require mine operators to ensure that all miners
enrolled in a hearing conservation program be provided hearing
protectors until they receive a baseline audiogram; and require the
operator to ensure the protection is used if the need to wait for a
mobile test van delays the initial audiogram past 6 months.
MSHA solicits additional comments on the appropriate time frame for
obtaining audiograms, especially in remote mining areas.
14-hour Quiet Period
Section 62.140(b)(2) of the proposal would require that the mine
operator ensure that the affected miner is not exposed to workplace
noise for at least a 14-hour period immediately prior to receiving the
baseline audiogram.
MSHA has no existing requirement in this area. The proposal is
similar to OSHA's noise standard except that, as discussed below, OSHA
permits the use of hearing protectors in lieu of removal from workplace
noise.
The 14-hour quiet period is intended to provide a miner's hearing
with sufficient rest to allow recovery from any temporary threshold
shift (TTS) caused by pre-test noise exposure. If the baseline
audiogram is skewed by TTS, subsequent comparisons to annual audiograms
would not provide accurate indications of the extent of damage incurred
during the time span between the baseline and subsequent tests.
There were numerous comments concerning the time frame for a quiet
period. Of these, most suggested that the 14 hours mandated in OSHA's
noise standard was sufficient to minimize any TTS. Others recommended
different time frames for the quiet period. One stated that ``* * *
there are sufficient human data in the literature to establish that a
14-hour quiet period is too short.'' Several commented that:
A suitable quiet period of 24 hours prior to the performance of
audiometric testing would be preferred. However, a 16-hour quiet
period would often meet the needs of most operations, being the
amount of time normally between the end of one days work and
starting time for the next.
One thought that eight hours was enough. Another commented that a quiet
period should be allowed but not required for the initial test.
Further, this commenter stated that 24 hours should be required for
confirmation testing.
Fodor and Oleinick (1986) in their paper on workers' compensation
reported that one researcher found full recovery from ``physiological
fatigue'' in 16 hours, with recovery from ``pathological fatigue''
taking longer. This researcher reported that the initial recovery seems
to be a logarithmic function of time and the longer recovery period is
a linear function. Most researchers, however, report complete recovery
from TTS taking no longer than 16 hours provided the TTS did not exceed
40 dB. On the other hand, some states require that a worker be away
from noise exposure for six months before evaluating hearing loss for
workers' compensation purposes.
MSHA concludes, after reviewing the scientific literature and the
standards of various jurisdictions, that the length of time required to
obtain full recovery from TTS depends upon the magnitude of the sound
pressure level, the length of exposure, the frequencies affected, the
person's age, and the person's susceptibility to hearing damage.
Because the mine operator has no control over the non-occupational
noise exposure of a miner, MSHA decided against limiting non-
occupational noise to a specified sound level during the quiet period;
however, as noted below, MSHA is requiring that the mine operator
notify employees of the need to avoid high levels of noise during the
14-hour period preceding the test, which it
[[Page 66434]]
hopes will limit non-occupational noise exposure. With the exception of
the EEC (15 minute quiet period), the consensus of the international
community and the U.S. armed services is that there should be a quiet
period of at least 14 hours. MSHA decided that a 14-hour quiet period
would be the most appropriate alternative and is consistent with OSHA's
requirements, comments to the ANPRM, and its review of available
literature. A quiet period longer than 14 hours could place an undue
burden on mine operators as the miner may have to stay away from work
to comply with the quiet period if the miner works a slightly extended
shift; many work shifts exceed 8 hours especially when a lunch period
is taken into account.
Use of Hearing Protectors for 14-hour Quiet Periods
Section 62.140(b)(2) of the proposed standard would also prohibit
the use of hearing protectors as a substitute for the 14-hour quiet
period. As noted previously, OSHA currently does allow hearing
protectors to be used during the required 14-hour quiet period.
When it first promulgated its Hearing Conservation Amendment in
1981, OSHA did not permit the substitution of hearing protectors for
the 14-hour quiet period. This decision generated much discussion among
commenters believing that it was unnecessarily restrictive. Even
professional audiologists strongly disagreed on this issue. One
commenter suggested that if the hearing protector reduced the level of
sound energy reaching the ear to 80 dBA or less, this would effectively
reduce the amount of baseline contamination to less than the usual
amount of audiometric measurement error. Commenters also cited problems
such as additional overtime wages, disruptions of work schedules, and
non-occupational noise exposure.
In 1983, OSHA revised its Hearing Conservation Amendment to allow
the use of hearing protectors as an alternative for the 14-hour quiet
period prior to the baseline audiogram. OSHA concurred with the large
number of commenters who testified that the use of hearing protectors
may provide sufficient attenuation to prevent noise-induced TTS from
contaminating baseline audiograms.
MSHA received many comments addressing this issue. Several of these
stated that hearing protectors should not be substituted for the quiet
period. Their general consensus can be summarized by one commenter who
stated that:
* * * the use of HPDs cannot be relied upon to reduce the noise
in all cases to a level suitable to be considered quiet for the
purpose of establishing baseline audiograms, especially if
individual variations in susceptibility to noise induced hearing
loss are considered.
Other commenters believed that the use of hearing protectors should be
allowed because they prevent TTS. One such commenter wanted a
qualification stating that:
* * * in many instances it may simply not be practical or
possible to test everyone for their baselines as they come to the
workshift, and thus reliance on HPDs for the 14-hr. noise-free
period is required. Thus MSHA should allow use of HPDs in lieu of
the 14 hrs., but with the following stipulation:
* * * no more than five days prior to the test, 1) the employees
whose hearing is to be evaluated receive refresher training in the
use of their protectors, and 2) the condition of the hearing
protector(s) the employee is to wear is checked and found
satisfactory. Any employee whose TWA exceeds 100 dBA shall be
required to wear an earplug together with an earmuff * * *
Some researchers, Shaw (1985) and Suter (1983), contend that sound
levels must be below 72 dBA to be considered ``effective quiet.''
Schwetz et al. (1980) found that a sound level below 85 dBA is needed
for recovery of TTS. Individuals with TTS recovered their normal
hearing quicker when exposed to 75 dBA sound level rather than 85 dBA.
The NIOSH Criteria Document (1972) recommends a sound pressure level of
65 dB as ``effective quiet'' based on work by Schmidek et al (1972).
Hodge and Price (1978) concluded that the level would have to fall
below 60 dBA to be effective quiet and not contribute to the
development of a TTS.
MSHA's proposal differs from OSHA's standard, in that it would not
allow hearing protectors to be substituted for the 14-hour quiet period
prior to the baseline audiogram. Although MSHA recognizes that its
decision may pose some scheduling problems for mine operators, it
should be emphasized that the quiet period is required only for the
baseline audiogram. Mine operators, however, may choose to employ it
for the annual audiograms.
MSHA has determined that the problems associated with the use of
individual hearing protectors are too great to guarantee an accurate
baseline measurement. Data indicate that in order to provide effective
quiet, the sound levels encountered during the quiet period would need
to be below 80 dBA. MSHA is particularly concerned with the ability of
hearing protectors to attenuate noise to such low levels in order to
prevent contamination of the baseline. Even at 80 dBA, some researchers
concluded that this level may be inadequate for the most susceptible
individuals. Moreover, the typical sound levels in mining are higher
than those experienced in general industry; therefore, hearing
protectors would need to attenuate the noise to a greater degree.
Although MSHA contends that hearing protectors can provide some
protection to miners whose exposures do not exceed the PEL, MSHA has
concluded that engineering and administrative controls provide much
more effective protection. MSHA's concerns with the ability of hearing
protectors to provide adequate attenuation are addressed in connection
with the requirements of proposed Sec. 62.120(b), under the heading of
Hearing protector effectiveness.
Notification to Avoid High Sound Levels
Section 62.140(b)(3) of the proposal would require mine operators
to notify miners to avoid high levels of non-occupational noise during
the 14-hour period before taking the baseline audiogram. This
requirement is the same as OSHA's noise standard.
In the 1983 preamble to its Hearing Conservation Amendment (48 FR
9757), OSHA emphasizes that, even if workers received this information
in training classes, such notification would aid memory and, thus,
provide additional support to the goal of obtaining a valid baseline
audiogram. OSHA concludes its discussion of this issue as follows:
Although employers are not responsible for employee noise
exposures sustained away from the workplace, the likelihood of non-
occupational noise exposure contaminating the baseline audiogram can
be substantially reduced by counseling workers of the need to avoid
such exposures in the period before their baseline test. Therefore,
this requirement is necessary and appropriate for the implementation
of a successful hearing conservation program.
Only a few commenters offered an opinion on this specific issue in
response to MSHA's ANPRM. These commenters agreed that workers need to
be advised to avoid non-occupational noise exposure prior to taking the
baseline audiogram.
MSHA believes that it is appropriate for operators to notify miners
of the importance of avoiding high noise areas in order to obtain valid
baseline audiograms. The proposed requirement is consistent with OSHA's
noise standard and the limited commenter responses.
Annual Audiogram
Section 62.140(c) of MSHA's proposal requires that, after
establishing a baseline, the miner to be offered a new
[[Page 66435]]
audiogram once every 12 months as long as the miner remains in the HCP.
Existing MSHA standards require coal mine operators to submit a
hearing conservation plan, which includes conducting periodic
audiograms, for each miner exposed to noise in excess of the PEL.
Because the use of hearing protectors is considered to provide
compliance with the PEL in this industry, few receive audiograms.
Moreover, there are no standards requiring audiograms for metal and
nonmetal workers.
OSHA requires, after the baseline audiogram has been obtained, an
annual audiogram for each employee exposed at or above its action level
to identify changes in hearing acuity, so that the use of hearing
protectors can be prescribed or other follow-up measures initiated
before hearing loss progresses. The preamble to OSHA's hearing
conservation amendment (46 FR 4143) states:
OSHA has chosen to retain the annual audiometric test
requirement because of the potential seriousness of the hearing
damage that can occur within a 2-year period. For employees exposed
to high levels of noise, a 2-year period between audiograms might
allow too much hearing loss to occur before identifying the loss and
taking remedial steps.
In response to its ANPRM, MSHA received numerous comments that
specifically addressed periodic audiograms. Many of these supported
annual testing and a few recommended a different time period. These
latter commenters suggested the following alternative time periods:
once or twice a year, depending on the intensity of the exposure; every
other year; and based upon need.
MSHA concludes that the determination of an STS in the one-year
period between required audiograms is meaningful for detecting the type
of problems for which HCP enrollment is the purpose. Detection of an
STS triggers several important actions under the proposal. Retraining
of the miner would be required. If the miner is enrolled in the HCP as
a result of noise exposure above the action level, but the miner's
noise exposure is below the PEL, detection of an STS would require the
provision of a hearing protector--which a miner at that exposure level
would otherwise not be required to utilize. If the miner was already
using a hearing protector, it would have to be replaced. Detection of
an STS would also require reevaluation of the engineering and
administrative controls being used. Waiting two years or more between
periodic audiograms could allow excessive hearing damage to miners.
MSHA also recognizes that some miners may be more susceptible to
hearing damage from noise exposure, and a few may be exposed to high
sound levels, such that annual audiometric testing may not be frequent
enough to prevent an STS.
In light of the comments to MSHA's ANPRM, the Agency's review of
the literature and pertinent governmental regulations, and OSHA's
existing requirements, MSHA has tentatively concluded that annual
audiometric testing is both necessary and appropriate. Annual
audiometric testing is an integral part of a comprehensive HCP.
Supplemental Baseline
Section 62.140(d) of MSHA's proposal would require the mine
operator to establish a ``supplemental audiogram'' when: (1) the STS
revealed by the annual audiogram is persistent, or (2) the hearing
threshold shown in the annual audiogram indicates significant
improvement over the baseline audiogram.
These proposed requirements are similar to those in OSHA's noise
standard except for the terminology.
In response to its ANPRM, MSHA received numerous comments on
circumstances in which it was not appropriate to use the original
baseline audiogram. Many commenters were in favor of revising the
baseline if an STS was persistent. One stressed the need for clear
guidelines for baseline revision to avoid the use of a variety of
creative methods which could result in different STS totals. Other
commenters were in favor of revising the baseline if the annual
audiogram showed an improvement in hearing. Another recommended
revising the baseline only if the improvement was consistent for at
least two or three consecutive tests. A final commenter wanted the
baseline revised only if there was a testing error.
MSHA believes, after reviewing these comments and standards of the
U.S. Armed Forces, that revising the baseline after an STS has been
identified would prevent this same STS from being identified
repeatedly. The annual audiogram on which the STS is identified would
then become the ``supplemental baseline audiogram.'' This supplemental
baseline would be used for comparison with future annual audiograms to
identify a second STS. The ``baseline audiogram'' would continue to be
used to quantify the total hearing loss in determining whether the loss
constitutes a ``reportable hearing loss''. To avoid confusion in the
mining industry, MSHA is proposing the term ``supplemental baseline''
rather than the term ``revised baseline'' used under OSHA. Since all
audiograms are to be retained as part of the audiometric test record
(see Sec. 62.150(c)), supplementation of the baseline audiogram would
not permit the destruction of the original baseline audiogram.
MSHA would also require supplementation of the baseline if the
annual audiogram shows significant improvement in hearing level because
this would more closely resemble the miner's actual hearing acuity
prior to being exposed to occupational noise. In this case,
supplementation of the baseline would be more protective because it
would allow more accurate evaluation of the true extent of future
hearing loss. Therefore, when a baseline is revised due to an
improvement of hearing acuity, this supplemental baseline would be
considered as the original baseline for determining when an STS occurs
and for quantifying the total hearing loss for reportablility under
part 50. The latter is reflected in the definition of reportable
hearing loss.
Section 62.150 Audiometric Test Procedures
MSHA proposes not to include specific procedural requirements for
conducting audiometric tests, calibrating audiometers, and qualifying
audiometric test rooms. Instead, MSHA proposes a performance-oriented
requirement that audiometric testing be conducted in accordance with
scientifically validated procedures. MSHA would specify the test
frequencies, but would allow the physician or the audiologist to use
professional judgment in choosing the appropriate testing procedure(s)
and require certification of the scientific validity of the procedures.
While this approach may require somewhat more in the way of
paperwork requirements, MSHA believes this is far preferable to the
alternative of a detailed specification standard, which could stifle
technology and impede improvements in methodology.
The proposal would also specify what records must be maintained,
and for how long, at the mine site. The proposed items included in the
audiometric test record--name, job classification, audiograms and
certifications as to the procedures used to take them, any exposure
determinations, and the results of any follow-up examinations--would
provide information essential for evaluating a miner's audiogram, among
other purposes.
[[Page 66436]]
The records are to be retained for at least six months beyond the
duration of the miner's employment. The six month retention period at
the mine site would assure that the audiometric test records of miners
who have short periods of unemployment are not destroyed and are
available for use by the mine operator to conduct further evaluations
upon the miner's return. In practice, MSHA believes that many mine
operators will keep miner's audiograms long after the miner's
employment ceases, for use if the miner should file a subsequent
workers' compensation claim for hearing loss.
Currently MSHA's metal and nonmetal noise standards do not contain
audiometric testing provisions. While Coal's noise standard requires
audiometric testing, it does not specify how it is to be conducted.
MSHA's proposal differs from OSHA's noise standard which contains
detailed procedures in 29 CFR Sec. 1910.95(h) and the associated
Appendices C, D, and E.
Several commenters generally supported MSHA's adoption of
audiometric testing requirements that are the same as OSHA's. A number
of commenters made specific recommendations regarding various aspects
of conducting audiograms including audiometric test instruments,
calibration procedures, and audiometric test rooms. Since MSHA has
decided not to specify audiometric test requirements in the proposed
rule, a discussion of the comments on specific procedures is not
included (except in the section which follows, Test procedures).
ANSI has several standards which impact the audiometric test
procedure. ANSI S3.21-1978 ``Methods for Manual Pure-Tone Threshold
Audiometry'' provides detailed procedures for conducting audiometric
tests. ANSI S3.1-1991 ``Criteria for Maximum Ambient Noise Levels for
Audiometric Test Rooms'' provides a criteria for the maximum background
sound pressure levels neccessary in order to obtain a valid audiogram.
ANSI S3.6-1996 ``Specifications for Audiommeters'' provides design
criteria for various classes of audiometers.
After reviewing comments, the scientific literature and several
governmental standards, MSHA chose not to include detailed, highly
technical procedures and criteria for conducting audiometric testing in
the proposal. Instead MSHA chose a performance-oriented approach by
proposing to require that audiometric testing procedures be governed by
scientifically validated methods. Because the person responsible for
conducting the tests is a physician, audiologist, or qualified
technician, he/she should be familiar with scientifically validated
procedures. MSHA would allow the physician or the audiologist to use
professional judgement in choosing the appropriate testing
procedure(s).
Moreover, audiometer manufacturers provide recommendations on
audiometer use and calibration (both laboratory and field). Because the
manufacturers are aware of the intricacies of their instruments, they
would be the most qualified to issue recommendations on the use and
calibration of their audiometers. By following manufacturer's
recommendations accurate audiometric testing is assured without MSHA
mandating detailed calibration specifications.
By not specifying a single test procedure, MSHA would permit the
use of any scientifically validated procedure. If a new, possibly more
accurate procedure would be validated, the medical professional could
readily adopt its use. If, however, current procedures were adopted in
the rule, an amendment would be needed to permit the use of any new
procedure.
Even though MSHA found no single comprehensive criteria for
audiometric testing, save OSHA's, there are criteria which deal with
various aspects of testing. For example, ANSI has standards on
background sound pressure levels for audiometric testing, methods for
pure tone audiometry, and for specifications for audiometers. MSHA
expects that most audiograms would be conducted using OSHA's
requirements, since many physicians and audiologists are familiar with
those regulations. Further, many texts and CAOHC training courses
discuss OSHA's audiometric testing procedures and criteria. Although
MSHA has not proposed detailed specifications in its standard, the
Agency contemplates publication of nonmandatory guidelines describing
what it believes to be the latest scientific procedures for conducting
audiometric tests.
MSHA, realizing that performance-oriented standards for audiometric
testing may be controversial, solicits comments on this approach, and
continues to solicit comments on the audiometric test procedures,
permissible background sound pressure levels, and calibration
requirements for audiometers.
Test Frequencies
The proposal would require that audiometric tests be pure tone, air
conduction, hearing threshold examinations, with test frequencies at
500, 1000, 2000, 3000, 4000, and 6000 Hz. The proposal also specifies
that these examinations be taken separately for each ear at the given
test frequencies. In response to MSHA's ANPRM, no commenters
specifically addressed audiometric test frequencies. Several, however,
generally supported MSHA's adoption of audiometric testing requirements
that are the same as OSHA's. MSHA's proposal would be consistent with
OSHA's requirements with respect to testing frequencies, as well as
consistent with the NIOSH criteria document (1972).
Although none of the commenters directly addressed audiometric test
procedures, several stated that MSHA should adopt or follow the OSHA
Hearing Conservation Amendment.
As noted in part II of this preamble, noise-induced hearing loss is
a permanent sensorineural condition that cannot be improved medically.
It is characterized by a declining sensitivity to high frequency
sounds. This loss usually appears first and is most severe at the 4000
Hz frequency. The ``4000 Hz notch'' in the audiogram is typical of
NIHL. Continued exposure causes the loss to include other audiometric
test frequencies, with 500 Hz being the least affected. While 500,
1000, and 6000 Hz are not included in the definition of STS, MSHA, like
OSHA, believes that these test frequencies contribute to a more
complete audiometric profile and are helpful in assessing the validity
of the audiogram as a whole. Furthermore, the inclusion of 500 and 1000
Hz makes it easier for an audiologist or physician to differentiate
conductive hearing loss from NIHL, and the inclusion of 6000 Hz would
better differentiate between presbycusis and NIHL.
Certification
Section 62.150(b) of MSHA's proposal would require that mine
operators obtain a certification, from whomever conducts audiometric
tests under this part, that such tests were conducted according to a
scientifically validated procedure.
OSHA's current noise standard does not require such certification.
OSHA has specific audiological test procedures, allowable background
sound pressure levels in audiometric test rooms, and audiometer
calibration requirements. MSHA's metal and nonmetal noise standards do
not contain audiometric testing provisions. While Coal's noise standard
requires audiometric testing, it does not specify how it is to be
conducted.
MSHA did not address this issue of certification in its ANPRM and,
therefore, no comments were received.
[[Page 66437]]
MSHA's proposal would relieve the mine operator from specifying the
audiological test procedure and criteria. The mine operator would rely
on the professional judgement of the physician or audiologist to select
the appropriate tests and criteria. Certification would not be accepted
from a qualified technician; pursuant to the proposed provisions in
Sec. 62.140, qualified technicians are to perform their work under the
supervision of a physician or audiologist. MSHA believes that it is
necessary for the physician or audiologist to certify that the
audiological tests were conducted in accordance with a scientifically
validated procedure. In most cases, the mine operator does not have
sufficient medical knowledge to determine if the tests were properly
conducted and must rely on the judgement of a physician or audiologist.
The certification will stand as evidence that the audiological tests
were conducted in accordance with the requirements for a scientifically
validated procedure.
Audiometric Test Recordkeeping and Retention
Section 62.150(c) of MSHA's proposal would require that mine
operators maintain a record of each required audiometric test. This
record would contain--
(1) the name and job classification of the miner tested
(2) a copy of the miner's audiogram(s) (original baseline, annual,
and supplemental baseline);
(3) certification(s) that the tests were conducted using
scientifically validated procedures;
(4) any exposure determination for the miner; and
(5) the results of any follow-up examination(s).
This information would not have to be written on the actual
audiogram as long as it was kept with the audiogram. The audiometric
test records would be required to be maintained at the mine site for
the duration of the affected miner's employment plus at least six
months.
Although not defined in this proposal, by the term ``duration of
employment'' MSHA means the period of time between the date of a
miner's initial hiring and the date on which the miner is released,
quits, retires, or dies. There must be a lapse of at least six months
beyond formal termination of employment before a mine operator could
destroy the audiometric test records. Moreover, it is MSHA's intent
that a layoff, strike, lockout, furlough, period of leave (both paid
and unpaid), or other temporary break in service would not be
considered as a formal termination of employment, even if it exceeds
six months.
MSHA's existing standards have no requirements in this area. OSHA's
noise standard requires that employers maintain a record of the
audiometric test results and maintain these records for the duration of
employment.
Since the publication of the noise standard, OSHA promulgated 29
CFR 1910.20 Access to employee medical records. This standard applies
to all medical records required to be kept pursuant to OSHA standards--
noise records are treated in the same way as carcinogen records. Under
1910.20, OSHA requires that medical records for each employee be
maintained for at least the duration of employment plus (30) years,
with the exception of employees who have worked for less than (1) year
for the employer. The medical records for these employees need not be
retained beyond the term of employment if they are provided to the
employee upon termination. Further this standard requires that exposure
records be maintained for at least 30 years.
Additionally, OSHA's noise standard requires that the audiometric
test record include--
(1) name and job classification of the employees;
(2) date of the audiogram;
(3) examiner's name;
(4) date of the last acoustic or exhaustive calibration of the
audiometer; and
(5) employee's most recent noise exposure assessment.
Additionally, employers are required to maintain an accurate record
of background sound pressure levels in audiometric test rooms. OSHA's
noise standard has no requirement to maintain these records at the
employer's work site.
MSHA received a number of comments specifically addressing time
frames for maintaining audiometric test records. One commenter
recommended that they be maintained for 30 years. Two commenters
recommended that such records be retained for the duration of the
miner's employment plus 30 years. Most of the commenters on this issue
recommended that MSHA require that audiometric test results be kept for
the duration of employment.
MSHA also reviewed the audiometric test recordkeeping and retention
requirements from the U.S. Armed Forces and various other countries.
Generally, the audiometric test record is to be maintained for at least
the duration of employment.
MSHA considered allowing mine operators to keep the audiometric
test record at a location other than the mine site. The Agency
concluded, however, that this alternative was impractical because it
could delay MSHA's access to such records. Furthermore, it would be
burdensome for mine operators to copy and mail the records or send a
fax of these records to the Agency.
MSHA believes that this record should be retained for at least six
months beyond the duration of the miner's employment. The risk of harm
stops with the cessation of employment; keeping the records an
additional 6 months would assure that a miner's audiometric test
records are not destroyed and are available for use by the mine
operator to conduct further evaluations should a miner return within
that time period. In practice, MSHA believes that many mine operators
will keep miner's audiograms long after the miner's employment ceases,
for use if the miner should file a subsequent workers' compensation
claim for hearing loss. In some states, the worker has many years
following employment to file such a claim.
The proposed items included in the audiometric test record would
provide essential information to MSHA and to the health professional
for evaluating a miner's audiogram. The information is also necessary
for identifying the audiograms, evaluating whether the audiometric
tests have been conducted properly, and for determining whether the
results are valid. Further, the information is critical for the
evaluator in determining whether an identified hearing loss was not
work related or aggravated by occupational noise exposure.
Section 62.160 Evaluation of Audiograms
MSHA's proposal would require that the mine operator inform the
person evaluating the audiogram of the requirements of this part and
provide them with copies of the miner's audiometric test records. The
mine operator would be responsible for having a physician, audiologist,
or qualified technician determine if an audiogram is valid and if a
standard threshold shift (STS) or reportable hearing loss has
occurred--in which case certain actions are required pursuant to
Sec. 62.180 and Sec. 62.190. Time frames and privacy protection are
part of the proposal, as is a requirement for a prompt retest if an
audiogram is invalid.
STS is defined in this proposal, as in OSHA's standard, as a change
in a worker's hearing acuity for the worse,
[[Page 66438]]
relative to that worker's baseline audiogram, of an average of 10 dB or
more at 2000, 3000, and 4000 Hz in either ear. If the STS is determined
to be permanent, a supplemental baseline is established pursuant to
Sec. 62.140 and this becomes the baseline for determining any future
STS. This definition is sufficiently restrictive to locate meaningful
shifts in hearing, yet not so stringent as to create unnecessary
follow-up procedures; the averaging of hearing levels at adjacent
frequencies will reduce the effect of testing errors at single
frequencies.
The proposal would permit but not require mine operators to adjust
audiometric test results by applying a correction for presbycusis
before determining whether an STS or reportable hearing loss has
occurred, and it includes tables for this purpose. Presbycusis is the
progressive loss of hearing acuity associated with the aging process.
The proposed adjustment for presbycusis is optional; however, if a mine
operator uses this approach, it must be applied uniformly to both the
baseline and annual audiograms in accordance with the procedures and
values listed in the proposed standard. Although this is the position
taken in the proposal, MSHA notes that the latest NIOSH advice on this
topic has advised against the use of presbycusis correction factors.
Moreover, the Agency is concerned about locking-in specific presbycusis
adjustment tables. MSHA, therefore, requests additional comments on
whether to use presbycusis corrections for audiograms and, if so, how
to provide for such adjustment in a regulatory context.
MSHA's existing noise standards do not address the evaluation of
audiograms. MSHA's proposed requirements would be similar to those in
OSHA's noise standard; the few differences are noted below.
Information Provided to Reviewer
Section 62.160(a)(1) of MSHA's proposal would require that the mine
operator inform the person evaluating the audiogram of the requirements
of this part and provide the evaluator with copies of the miner's
audiometric test records. OSHA requires employers to provide the
persons evaluating audiograms with a copy of the requirements of its
standard, copies of the employee's baseline and most recent audiometric
test records, background sound pressure levels in the audiometric test
room, and a record of audiometer calibration.
In its ANPRM, MSHA did not address what information the mine
operator should provide to the person evaluating audiograms. The
commenters, therefore, did not address this issue specifically. In
discussing related topics, some commenters recommended that MSHA adopt
OSHA's requirements on this issue.
Recently, research has implicated exposure to chemicals as
aggravating hearing loss, Fetcher (1995), Morata (1989, 1993, 1995).
MSHA requests comments as to how to address various aspects of this
possible relationship. For example, could exposure to chemicals cause
an invalid audiogram? What information should reviewers have about
chemical exposure? Any research results on this topic would be welcome.
MSHA believes that providing certain information is necessary for
physicians and audiologists to evaluate the accuracy and validity of
miners' audiograms. For example, the evaluator would need to know the
procedure for determining an STS, the criteria for retest or medical
follow-up, presbycusis correction procedures, and recordkeeping
requirements.
Review of audiogram. Under Sec. 62.160(a)(2) of this proposal, the
mine operator would be responsible for having a physician, audiologist,
or qualified technician determine if an audiogram is valid and if an
STS or reportable hearing loss has occurred. MSHA's proposal is
consistent with the present OSHA noise standard.
Of the many commenters on this specific issue, most believed that
professional review was necessary. One of these said that ``MSHA should
require an audiologist or physician to evaluate audiograms that show
standard threshold shifts [STS] or other unusual changes''.
A few commenters felt that professional review was unnecessary.
These commenters indicated that the person conducting the audiogram
could inform the employee of the results, and explain the significance
of these results, so that the employee could make any decisions
regarding further testing or evaluation.
The U.S. Armed Services and the international community vary on the
medical expertise required to review audiograms.
MSHA believes that audiograms need to be reviewed for validity; as
noted below, if audiograms are not valid, the proposal would require a
retest. Examples of questionable audiograms are audiograms that show:
large unilateral differences in hearing thresholds between the two
ears; unusual frequency patterns that are not typical of NIHL;
thresholds that are not repeatable; or an unusually large hearing loss
over a yearly period. MSHA maintains that the review of audiograms is
an integral part of an audiometric testing program.
Qualifications for Audiogram Reviewers
Under Sec. 62.160(a)(2) of this proposal, a mine operator would be
required to have a physician, audiologist or a qualified technician who
would be under the supervision of a physician or audiologist evaluate
audiograms to determine their validity and whether an STS or reportable
hearing loss has occurred. The qualifications of these individuals to
conduct this evaluation are discussed under Sec. 62.140 Qualifications
of personnel along with the comments received on this issue.
Standard Threshold Shift (STS)
This proposal would require the evaluator to determine whether a
miner has incurred an STS in his/her hearing. STS is defined in this
proposal as a change in a worker's hearing threshold relative to that
worker's baseline audiogram of an average of 10 dB or more at 2000,
3000, and 4000 Hz in either ear. This requires that hearing loss be
calculated by subtracting the current hearing levels from those on the
baseline audiogram at 2000, 3000, and 4000 Hz; when the hearing losses
at each frequency are averaged (added up and divided by three); if the
average loss in either ear has reached 10 dB, it constitutes an STS. If
the STS is determined to be permanent, a supplemental baseline is
established pursuant to Sec. 62.140 and this becomes the baseline for
determining any future STS. The definitions of ``baseline audiogram'',
``supplemental baseline audiogram'', and ``standard threshold shift''
are discussed in detail in connection with proposed Sec. 62.110.
OSHA defines an STS in essentially the same way, requiring that
employees' annual audiograms be compared to their baseline audiogram to
determine if the annual audiogram is valid and if an STS has developed.
Of the numerous comments addressing the issue of STS in response to
MSHA's ANPRM, many endorsed OSHA's definition of STS. One commenter
stated that:
The Standard Threshold Shift (STS) concept is the basic
foundation of a hearing conservation program and is the best
indicator of early noise-induced hearing loss [NIHL]. It enables
those conducting the audiometric examinations to have the needed
``red flag'' to indicate when additional testing or evaluation is
needed. It also enables the effectiveness of the employer's hearing
conservation program to be evaluated and monitored. The criteria
must be sensitive enough to identify meaningful changes in hearing
but must not be so sensitive as to
[[Page 66439]]
pick up spurious shifts or ``false-positives.'' * * * Identifying a
standard threshold shift therefore means that the shift value must
be outside the range of audiometric error ( 5 dB) and
serious enough to warrant prompt attention.* * * The averaging of
shifts over adjacent frequencies minimizes normal test error, and
random errors will tend to cancel each other out. * * *
In considering the frequencies to be used, it is noted that 4000
Hz is generally considered to be affected by noise the earliest and
most severely. The 2000 and 3000 Hz frequencies are very important
in understanding speech and should also be included in the
definition of STS.
For the above-mentioned reasons, as well as simplifying the
process in facilities which have operations under both MSHA and OSHA
jurisdiction, we recommend MSHA adopt an average shift of 10 dB or
more at 2000, 3000, and 4000 Hz, relative to the baseline audiogram.
* * *
Of those commenters who did not endorse OSHA's STS criteria, one
stated that OSHA's STS definition was ``* * * not stringent enough and
the worker hearing loss has progressed too far with this shift to be a
reliable preventive measure.'' Another stated--
* * * the suggested criteria [OSHA's STS definition] provides no
benefit but additional testing, specialist costs, reporting,
administrative costs, and potential MSHA punitive fines. * * *
The STS concept is misguided. A significant percentage * * * of
people will have changes take place in their hearing which would
qualify as an STS without any exposure to occupational noise.
Royster (1992) proposes a definition of STS that is different from
OSHA's. In her definition, 15 dB of hearing loss (relative to the
baseline) must occur at any audiometric test frequency from 500 to 6000
Hz on two sequential audiograms, before the STS is established. The 15
dB of hearing loss which occurs on two sequential audiograms identifies
the largest number of true positives (permanent threshold shifts) and
the least number of false positives (temporary threshold shifts
mistakenly identified as permanent threshold shifts).
NIOSH (1995) recommends that the criteria for an STS be a 15 dB
decrease in hearing acuity at any one of the audiometric test
frequencies from 500 to 6000 Hz on two sequential audiograms. The shift
in hearing acuity must be in the same ear. The second audiogram would
be administered as soon as reasonable. NIOSH believes this criteria is
sufficiently stringent to detect beginning hearing loss, yet won't
include workers whose hearing acuity is simply showing normal
variability. If the 15 dB change is found, an immediate retest should
be conducted and followed by a confirmation test within 30 days. The
confirmation test should be preceded by 14 hours of quiet.
This draft criteria for STS differs from the criteria recommended
by NIOSH in their 1972 criteria document. NIOSH's previous criteria
defined STS as a change of 10 dB or more at 500, 1000, 2000 or 3000 Hz;
or 15 dB or more at 4000 or 6000 Hz.
There are some instances where large shifts in hearing level occur
at higher test frequencies (4000 and 6000 Hz) with little or no change
in hearing level at the middle frequencies. While large shifts are
uncommon, they may occur in noise-sensitive individuals, especially in
the early stages of NIHL. Correctly identifying significant threshold
shifts is particularly important for workers who have already begun to
lose their hearing. The proposed definition of STS would identify
individuals suffering shifts as large as 30 dB at 4000 Hz with no
shifts at the lower frequencies (30 plus 0 plus 0 divided by 3 equals
10, an STS). This permits the early identification of individuals at
risk, so that corrective measures could be taken.
MSHA's proposed definition of STS is sufficiently restrictive to
locate meaningful shifts in hearing, yet not so stringent as to create
unnecessary follow-up procedures. The averaging of hearing levels at
adjacent frequencies will reduce the effect of testing errors at single
frequencies. The occurrence of an STS is serious enough to warrant
prompt attention because it may be a precursor to material impairment
of hearing. It is important to note that MSHA does not equate STS with
material impairment caused by NIHL.
MSHA believes, after considering the relevant factors and reviewing
current U.S. military and international standards, that the proposed
definition of STS is the most appropriate and consistent with the
purposes of its hearing conservation standard. The proposed definition
of STS--
(1) is adequately supported in OSHA's record for its Hearing
Conservation Amendment;
(2) is the criteria recommended or accepted by most commenters to
MSHA's ANPRM;
(3) results in a high degree of accuracy in identifying workers for
follow-up;
(4) concentrates on those frequencies that are the earliest or the
most severely affected by noise; and
(5) is a recognized and relatively simple approach.
Because NIOSH revised its recommendation for the criteria of an
STS, MSHA requests comments on NIOSH's new criteria. Furthermore, any
data on the advisability of using either the MSHA proposed criteria of
STS or NIOSH's criteria of STS would be welcomed.
Reportable Hearing Loss
The proposal would require the evaluator to determine if there has
been a ``reportable hearing loss''. See the discussion of ``Reporting
noise-induced hearing loss (NIHL)'' under Sec. 62.190 Notification of
results.
Instruction to Medical Professional
Section 62.160(a)(3) of the proposal would require the mine
operator to instruct the physician or audiologist not to reveal to the
mine operator any specific findings or diagnoses unrelated to the
miner's exposure to noise or the wearing of hearing protectors without
the written consent of the miner. Currently, neither MSHA nor OSHA have
such a provision in their noise standards; OSHA does have such
provisions in air quality standards like benzene and lead.
The topic of instructions to medical professionals was not raised
in the ANPRM. Therefore, no comments on this issue were received.
MSHA believes that this requirement is necessary to safeguard the
privacy of individuals. The mine operator does not need to be informed
of medical conditions unrelated to occupational noise exposure. MSHA's
rationale is that if the mine operator had confidential medical
information, the mine operator could use it to justify an adverse
action against the miner.
30-Day Requirement
According to Sec. 62.160(a)(4) of MSHA's proposal, the mine
operator would have 30 days to obtain the audiometric results and the
interpretation of the results from the person evaluating the audiogram.
OSHA does not specify a time period for evaluating audiograms.
MSHA's ANPRM did not address the issue of time frame for evaluating
audiograms. A few commenters, however, expressed concern with the
length of time that some service providers take to report results to
the employer. One stated that:
Service providers have taken undue advantage of a perceived
`grace period' in the OSHA Hearing Conservation Amendment to inform
employees of a shift in hearing. * * * the lag time may total six to
eight weeks. This is a disservice to the employee, and is certainly
preventable.
Notification of STS, including the optional retest of STS-
affected employees, should be completed within a 30-day period
following testing. OSHA's time limit of 21 days following
notification to the employer creates a loophole which makes the
employee wait all too long for feedback regarding STS.
[[Page 66440]]
The other commenter stated that:
In reality, from the time the hearing test is sent to an
audiologist or physician to review, it is reviewed, recommendations
made, it is returned to the plant personnel and the plant has 21
days to notify the employee, the total process often stretches into
a 45-60 day time frame.
MSHA believes that a 30-day limit to evaluate audiograms is
reasonable and necessary to prevent undue delays in the evaluation of
the audiogram and notification to the miner of the results. Under
proposed Sec. 62.190, a miner would have to be notified within 10
working days of audiogram results obtained by the mine operator, as
discussed in connection with that section; accordingly, the net result
of these provisions is a maximum delay of approximately 44 days from
the date of audiometric testing to the notification of the miner. If a
retest was conducted, which, as discussed below must be done within 30
days of receiving a determination that the original test was invalid,
this delay in notification could be as long as 104 days. If the miner's
employment ceases during this delay period, the mine operator would be
required to provide the miner with a copy of the audiometric test
records as required by Sec. 62.200(c), including the results of all
testing, as soon as the record is complete. MSHA welcomes comments on
this issue.
Audiometric Retest
Section 62.160(b)(1) of the proposal would require a mine operator
to conduct a retest, if the audiogram was judged to be invalid, within
30 calendar days of receiving this information--provided, however, that
the 30-day time frame is stayed until any medical pathology resulting
in the invalid audiogram has improved to the point that a valid
audiogram may be obtained. In addition, Sec. 62.160(b)(2) of the
proposal would allow a mine operator to obtain one retest within 30
days after an STS or reportable hearing loss is found, and to
substitute the retest audiogram for the annual audiogram. The latter
retest is not mandatory.
OSHA also permits a retest within 30 days to confirm an STS, but
does not specifically require a retest if the audiogram is judged to be
invalid.
Many commenters supported OSHA's retest provision as written, while
others supported it with qualifications. One commenter believed that a
60-day period was appropriate. Another believed that a 30-day
limitation to both retest and notify was appropriate because:
Service providers have taken undue advantage of a perceived
grace period in the OSHA Hearing Conservation Amendment to inform
employees of a shift in hearing. By the time audiometric tests are
administered, entered into a computer, returned to an employer, and
then finally returned to the employee, the lag time may total six to
eight weeks. This is a disservice to the employee, and is certainly
preventable.
Other commenters stated different views. One commenter stated that:
* * * most programs involve the use of testing vans that cannot
easily make a return trip in 30 days because of scheduling limits.
It would also be extremely expensive to make a return trip to
confirm a single STS. If an employee is found to have a significant
hearing loss, he should be required to wear hearing protectors in
all noise environments of 85 dBA or greater. If the next scheduled
audiogram also shows the hearing loss, then the loss should be
considered confirmed.
Another commenter stated that:
* * * an employee with a change in hearing could be immediately
counseled, refitted [i.e., hearing protectors], educated, notified
and return to his job. This would be more cost-effective than
bringing him back prior to the shift to get a hearing test showing
there is no STS.
MSHA believes, after considering comments and reviewing U.S. armed
forces and international standards, that the retest provisions are
necessary to assure that valid audiograms are provided in a timely
fashion. The retest should be conducted within a reasonable time, and
30 days is believed to be adequate, with the caveat that this time
frame does not begin to run until any medical pathology causing a
validity problem has improved to the point that a valid audiogram can
be obtained. MSHA recognizes that in such cases it will not be possible
to wait for a mobile van; but MSHA believes that in the limited number
of cases where a retest is required, it is appropriate and necessary to
send the miner to the nearest available facility for such a test.
The provision to obtain an optional retest if an STS is detected is
desirable. This would permit the mine operator to substantiate that an
STS had occurred, thus confirming permanent hearing loss. By detecting
only permanent hearing loss, the mine operator would have better
information on which to base administrative, technical, and financial
decisions relative to retraining the miner, permitting the miner to
select a different or additional hearing protector, and reviewing the
effectiveness of the noise controls.
Use of Age Correction (Presbycusis Factors)
Section 62.160(c) of the proposal would permit mine operators to
adjust audiometric test results by applying a correction for
presbycusis before determining whether an STS or reportable hearing
loss has occurred. Presbycusis is the progressive loss of hearing
acuity associated with the aging process. This adjustment for
presbycusis is optional; however, if it is used, it must be applied
uniformly to both the baseline and annual audiograms in accordance with
the procedures and values listed in Sec. 62.160(c) (1) through (4).
OSHA's noise standard also permits the use of presbycusis
correction factors. MSHA's proposal would be essentially the same as
OSHA's Appendix F: Calculations and Application of Age Corrections to
Audiograms. Both MSHA's proposal and OSHA's Appendix F adopt the
procedures and age correction tables used by NIOSH in its criteria
document (1972).
Commenters to OSHA's Hearing Conservation Amendment (48 FR 9763)
suggested that the use of such presbycusis factors also would account
for those cases of NIHL that arise from causes other than occupational
noise exposure. In the preamble to its Hearing Conservation Amendment
(48 FR 9763), OSHA states that:
* * * these correction factors will aid in distinguishing between
occupationally induced and age-induced hearing loss. This is
particularly important because the pattern of hearing loss due to
aging closely resembles that of noise-induced hearing loss [NIHL]. *
* * Therefore, although * * * the use of a correction factor may
complicate calculation procedures and cause some errors, * * *
professional supervision of the hearing conservation program will
ensure that audiometric technicians understand how to use the age
correction chart * * *
Most commenters who addressed this issue in MSHA's ANPRM, contend
that the use of presbycusis correction factors is appropriate. Many of
these commenters supported MSHA's use of the same criteria as in OSHA's
Appendix F. Other commenters recommended age corrections different than
those used by OSHA. One commenter suggested that MSHA use the ISO
1999.2 (1989) standard. Another one suggested that, because the NIOSH
criteria is almost 20 years old, ``The criteria used should be the most
recent and [accepted] data.''
Several commenters believed that applying presbycusis factors would
reduce unnecessary recordkeeping and follow-up procedures. One stated
that:
Many audiometric computer programs used for processing data have
this correction calculation built in the software. To change to some
other criteria or to remove this factor will result in the
modification of numerous systems and a need to switch back and
forth,
[[Page 66441]]
depending on whether the operator is OSHA or MSHA regulated.
Another of these suggested that MSHA require the use of such correction
factors, rather than allow their use to be optional, because such
optional use could result in discrepancies in results among audiometric
testing services.
A few commenters suggested that it would be better not to adjust
audiometric test results for presbycusis. They maintained that the
place to claim credit for presbycusis is in determining workers'
compensation and not in the institution of an HCP. These commenters
believed that not everyone who ages loses their hearing to the same
degree, and that the use of presbycusis corrections might mask changes
for older adults who have previously had good hearing.
Finally, one commenter recommended that MSHA seek medical advice
from national sources to determine what the medical community
recognizes as changes occurring from aging.
In contrast to NIOSH's presentation of one set of presbycusis data,
the ISO Document ISO 1999:1990(E) (1990) gives a dual set of values for
the non-industrial noise exposed population. These data are offered in
two tables. One table represents a highly screened, otologically normal
population, i.e., persons in a normal state of health, free from all
signs and symptoms of ear disease and obstructing wax in the ear
canals, and having no history of undue exposure to noise. The second
table represents an unscreened population from an industrialized
country. The ISO states that the choice of using the screened or
unscreened data base depends on what question is to be answered. It
states:
For example, if the amount of compensation that could be due to
a population of noise-exposed workers is to be estimated, and
otological irregularities and non-occupational noise exposure are
not considered in compensation cases, unscreened populations will
form the more appropriate data bases.
The ISO further states, however, that its standard ``* * * is based on
statistical data and therefore shall not be used to predict or assess
the hearing impairment or hearing handicap of individual persons.'' The
ISO data would be more difficult to use than NIOSH data because its
interpretation would require a higher level of statistical and
mathematical expertise.
NIOSH (1995) now recommends that audiograms not be corrected for
presbycusis. NIOSH believes that it is inappropriate to apply
presbycusis correction factors from a population to an individual.
Furthermore, there are no data to confirm that a 50 year old in 1995
will incur the same hearing loss due to aging that a 50 year old did in
1970. If the worker's audiogram is to be corrected for presbycusis,
then the hearing loss of a non-occupational noise exposed group with
the same demographic characteristics as the worker should be used.
However, these kinds of data are not complete nor are they readily
available.
The following is an example of the use of presbycusis correction
factors as proposed in MSHA's noise standard--
(a) Determine from Tables 62-3 or 62-4 the age correction values
for the miner by--
(1) Finding the age at which the baseline audiogram (or
supplementary baseline audiogram if appropriate) was taken and
recording the corresponding values of age correction at 2000 Hz through
4000 Hz; and
(2) Finding the age at which the most recent audiogram was taken
and recording the corresponding values of age correction at 2000 Hz
through 4000 Hz.
(b) Subtract the value found in step (1) from the value found in
step (2). The differences calculated represent that portion of the
change in hearing that may be due to aging.
(c) Subtract the value found in step (b) from the hearing threshold
level found in the annual audiogram to obtain the adjusted annual
audiogram hearing threshold level.
(d) Subtract the hearing threshold in the baseline audiogram (or
supplemental baseline audiogram as appropriate) from the adjusted
annual audiogram hearing threshold level to obtain the age-corrected
threshold shift.
Example: A miner is a 32-year-old male. The audiometric history in
decibels is shown below for his right ear. A threshold shift of 10 dB
at 2000 and 3000 Hz and 20 dB at 4000 Hz exists between the audiograms
taken at ages 27 and 32. A retest audiogram has confirmed this shift.
------------------------------------------------------------------------
Audiometric test
frequency (Hz)
Miner's age -----------------------
2000 3000 4000
------------------------------------------------------------------------
26............................................. 5 5 10
*27............................................. 0 0 5
28............................................. 0 0 10
29............................................. 0 5 15
30............................................. 5 10 20
31............................................. 10 20 15
+32............................................. 10 10 25
------------------------------------------------------------------------
An asterisk (*) has been used to identify the supplemental baseline
audiogram and a plus (+) the most recent audiogram. The annual
audiogram taken at age 27 becomes a supplemental baseline audiogram
(and is used in calculating hearing loss) because it shows a
significant improvement over the baseline audiogram taken at age 26.
Steps (a) and (b). Find the age correction values (in dB) at age 27
and age 32 in Table 62-3. The difference, shown below, represents the
amount of hearing loss that may be attributed to aging in the time
period between the baseline audiogram and the most recent audiogram.
------------------------------------------------------------------------
Frequency (Hz)
-----------------------
2000 3000 4000
------------------------------------------------------------------------
Age 32.......................................... 5 7 10
Age 27.......................................... 4 6 7
Difference...................................... 1 1 3
------------------------------------------------------------------------
Step (c). Subtract the difference determined in step (b) from the
hearing levels in the most recent audiogram. In this example, the
adjusted hearing threshold levels are as follows:
------------------------------------------------------------------------
Frequency (Hz)
-----------------------
2000 3000 4000
------------------------------------------------------------------------
Age 32.......................................... 10 10 25
Correction...................................... 1 1 3
Adjusted........................................ 9 9 22
------------------------------------------------------------------------
Step (d). Subtract the hearing threshold level in the baseline
audiogram from the adjusted annual audiogram hearing threshold to
obtain the age-corrected threshold shift.
------------------------------------------------------------------------
Frequency (Hz)
-----------------------
2000 3000 4000
------------------------------------------------------------------------
Adjusted........................................ 9 9 22
Baseline........................................ 0 0 5
Shift........................................... 9 9 17
------------------------------------------------------------------------
The average threshold shift at 2000, 3000, and 4000 Hz without age
correction is (10+10+20)/3=13.3 dB. The average age-corrected threshold
shift at 2000, 3000, and 4000 Hz is (9+9+17)/3=11.7 dB. This shift is
an STS because it exceeds 10 dB, but it is not, as yet, a reportable
hearing loss (25 dB). Intervention at this point should prevent further
loss and subsequent impairment.
MSHA agrees that not all individuals are affected by presbycusis to
the same degree. Additionally, studies have
[[Page 66442]]
shown that individuals in environments free from noise exposure display
little evidence of presbycusis. MSHA is concerned that the use of
presbycusis corrections may allow some miners to incur excess work-
related hearing loss. For example, some miners may not have off-the-job
noise exposure and may not have a decrement in their hearing due to
aging at the levels specified in the presbycusis correction table.
Nevertheless, MSHA maintains that at this time, allowing the adjustment
of audiometric test results for presbycusis is both reasonable and
appropriate. In industrial audiometry, this correction is often used to
determine occupational NIHL by adjusting the measured hearing level to
compensate for the normal loss of hearing due to aging. This is
particularly important because the pattern of hearing loss due to aging
resembles that of NIHL. The use of age corrections will help the mine
operator judge how well the HCP is working. Such adjustments are
consistent with current scientific practice, OSHA's standard, and the
recommendations of the majority of the commenters to MSHA's ANPRM.
MSHA selected the NIOSH presbycusis data so that all mine operators
who correct audiograms for aging will be using the same data. Though
there may be slight variations at individual frequencies, the NIOSH
presbycusis values are similar to those of other well known presbycusis
data bases, such as the U.S. Public Health Service data, those used by
Robinson and Burns, and those of Passchier-Vermeer. The NIOSH data are
for a highly screened population which excluded individuals with any
significant noise exposure on-the-job, off-the-job, or during military
service. Using a single set of presbycusis values will standardize the
process of determining STS nationwide. If MSHA allowed mine operators
to select their own presbycusis values, there could be major
nonuniformity in determining STS's and reportable hearing losses.
Nevertheless, the Agency is concerned about locking-in particular
presbycusis adjustment tables, and requests additional comments on how
to provide for a presbycusis adjustment in a regulatory context.
In conclusion, MSHA believes that, at this time, scientific data
and the consensus of commenters support allowing the use of the
presbycusis correction factors presented in Tables 62-3 and 62-4.
Although this is the position taken in the proposal, MSHA notes that
the latest NIOSH advice on this topic has advised against the use of
presbycusis correction factors. MSHA, therefore, requests additional
comments on whether to use presbycusis corrections for audiograms.
Section 62.170 Follow-up Evaluation When Audiogram Invalid
This section of the proposal provides that when a valid audiogram
cannot be obtained due to a suspected medical pathology of the ear, and
the physician or audiologist evaluating the audiogram believes that the
problem was caused or aggravated by the miner's exposure to noise or
the wearing of hearing protectors, a miner must be referred for a
clinical audiological or otological evaluation as appropriate at mine
operator expense.
This section also provides that if the physician or audiologist
concludes that the suspected medical pathology of the ear which
prevents obtaining a valid audiogram is unrelated to the miner's
exposure to noise or the wearing of hearing protectors, the miner be
advised of the need for an otological evaluation; but in such cases, no
financial obligation would be imposed on mine operators.
Finally, this section would require the mine operator to instruct
the physician or audiologist not to reveal to the mine operator any
specific findings or diagnoses unrelated to the miner's exposure to
noise or the wearing of hearing protectors without the written consent
of the miner.
OSHA's noise standard has similar follow-up requirements, except
for the nondisclosure provision. MSHA's current noise standards have no
follow-up evaluation provisions.
In response to MSHA's ANPRM, many commenters supported OSHA's or
similar requirements for referring employees to a physician for a
medical follow-up. A few commenters, however, stated that ``MSHA need
not include criteria for directing miners for further medical follow-up
nor require a physician, audiologist, or other qualified medical
personnel to evaluate the audiograms.''
Another commenter stated the following regarding who should pay for
these follow-up evaluations:
* * * I have a standard recommendation when working with
companies that they pay for all initial medical evaluations in order
to determine disposition. I think it is as important to them to have
documentation that an employee has a medical problem just as [when]
he has an occupational one.
The decision as to which type of evaluation, clinical audiological
evaluation or otological, is appropriate will depend upon the
circumstances. Standards from the international community and the U.S.
Armed Forces vary to some degree regarding certain elements, such as
the extent of follow-up examinations. A clinical audiological
evaluation is generally more comprehensive, intensive, and accurate
than the routine audiometric testing conducted for HCP purposes. For
example, such testing may be warranted if an unusually large threshold
shift occurs in one year given relatively low noise exposures. An
otological evaluation, on the other hand, is a medical procedure
conducted by a physician specialist (e.g., otolaryngologist) to
identify a medical pathology of the ear. Audiometric testing can imply
the existence of such a medical pathology. For example, a hearing loss
in only one ear can indicate the existence of an acoustic neuroma (type
of tumor) at an early stage. Such discovery could be potentially life
saving. Another more common reason for an otological examination would
be for the removal of impacted ear wax (cerumen) which reduces hearing
acuity and can be aggravated by the use of insert-type hearing
protectors.
Making the determinations under this section would not require a
diagnosis by a physician specialist confirming a medical pathology. The
proposal is intended to allow the audiologist or physician authorized
to review the audiograms to make a determination as to whether a
follow-up examination is appropriate--and who pays for it. Accordingly,
the word ``suspected'' precedes the words ``medical pathology'' in this
section.
If the person evaluating the audiogram believes that the suspected
medical pathology is related to occupational noise exposure or to the
wearing of hearing protectors, the proposal would require the mine
operator to pay for the miner's follow-up medical evaluations. MSHA
believes that the mine operator has the primary responsibility for
work-related medical problems. On the other hand, if the person
evaluating the audiogram determines that the suspected medical
pathology is not related to the wearing of hearing protectors, then the
proposal would require the mine operator to instruct the medical
professional to inform the miner of the need for medical follow-up, but
would not require the mine operator to pay for it or to be informed of
the findings. In such cases, therefore, the follow-up otological
examination would be at the miner's expense. Although MSHA agrees that
taking action to keep miners healthy would be beneficial to the mine
operator, the Agency contends that it would be inappropriate to require
mine
[[Page 66443]]
operators to pay for non-work-related medical problems.
MSHA also does not believe that it would be appropriate for mine
operators to be informed of medical findings that are unrelated to the
miner's occupational noise exposure or to the wearing of hearing
protectors. If a mine operator would want this information, the
proposal would permit the release of this information only upon the
written consent of the miner. MSHA has included this provision out of
concern for the privacy rights of the miner. A related provision is
considered in somewhat more detail in the discussion of proposed
Sec. 62.160.
Section 62.180 Follow-Up Corrective Measures When STS Detected
MSHA's proposal would require that, unless a physician or
audiologist determines that an STS is neither work-related nor
aggravated by occupational noise exposure, mine operators would have 30
calendar days after the finding of an STS to--
(1) Retrain the miner in accordance with Sec. 62.130;
(2) Provide the miner with the opportunity to select a hearing
protector, or a different hearing protector if the miner has previously
selected one, from the selection offered under Sec. 62.125; and
(3) Review the effectiveness of any engineering and administrative
controls to identify and correct any deficiencies. In addition,
pursuant to proposed Sec. 62.120(b), an operator would be required to
ensure that a miner who has incurred an STS wears provided hearing
protection.
A hearing loss of 10 dB from a miner's prior hearing level is of
enough significance to warrant intervention by a mine operator, unless
it is determined the loss is not work-related. If the controls in place
are effective--including the training--this loss should not be
occurring. It should be noted that the retraining required is to take
place within 30 days after the finding of the STS, and thus it is
unlikely mine operators can satisfy this requirement through their part
48 training programs.
MSHA's proposal does not include a provision for transferring a
miner who incurs repeated STS's or a reportable hearing loss. A miner
transfer program would be complex to administer, and would probably not
be feasible in the metal and nonmetal sector. This sector consists
largely of smaller mines which may be unable to rotate workers to other
assignments on a long-term basis.
Most commenters on this issue suggested that MSHA adopt OSHA's
requirements. One of these commenters, however, disagreed with OSHA's
allowance for discontinued use of hearing protectors when an STS was
found to be temporary. The remaining two commenters recommended that
the mine operator only be required to retrain the miner in the use and
fit of the hearing protector.
OSHA's noise standard requires that the work-relatedness of an STS
be determined only by a physician. Employees, who have a work-related
STS and are not using hearing protectors, must be fitted with hearing
protectors, be trained in their use and care, and be required to use
them. Employees who have an STS and are using hearing protectors must
be refitted, be retrained, and be provided with hearing protectors
offering greater attenuation when necessary. OSHA does not stipulate a
time frame for conducting follow-up procedures.
MSHA believes that audiologists have sufficient training and
medical expertise to determine the work-relatedness of an STS, and that
it would be needlessly restrictive to limit this determination to a
physician as in OSHA's standard.
MSHA, however, like OSHA would not permit technicians to make this
determination. MSHA believes that while qualified to conduct and
evaluate audiograms under the supervision of a physician or
audiologist, technicians do not have the necessary training nor medical
expertise to determine if an STS is work related. MSHA has determined
that it is necessary to have a physician or audiologist determine the
possible work relatedness of any STS. For example, the physician may
determine that a miner's STS resulted from: a bad cold or sinus
condition; taking certain medication, such as heavy doses of aspirin;
or an acoustic neuroma (type of tumor). Careful diagnosis may, on the
other hand, reveal that the STS is work related and caused by improper
fit of the hearing protector.
MSHA, after reviewing comments and related regulations, believes
that the proposed corrective measures are adequate and necessary to
prevent further deterioration of the miner's hearing acuity after an
STS has been determined. MSHA believes that the 30 day requirement for
retraining, selection of a hearing protector or different hearing
protector, and evaluation of noise controls is reasonable.
Retraining
If a miner has an STS, Sec. 62.180(a) of this proposal would
require that the miner be retrained in accordance with Sec. 62.130, and
a record kept of such training.
The specific training elements contained in Sec. 62.130 are
discussed in the provisions of this preamble describing those
respective sections, including the required certification thereof. Such
retraining could be conducted in conjunction with the annual refresher
training, under 30 CFR part 48, but only if the latter is so approved
and scheduled to be completed within 30 days of the finding of an STS.
If the annual refresher training is not conducted within 30 days, the
retraining for miners with an STS would have to be conducted
separately. It would not be permissible to wait until the next annual
refresher training.
Provide Opportunity To Select a Hearing Protector or Different Hearing
Protector
In the mining industry, miners are typically exposed to high sound
levels and some of the miners may be more susceptible to hearing loss
from the noise exposures than others. Consequently, if a miner is
diagnosed with an STS, then he or she must be given the opportunity to
select a hearing protector or different hearing protector.
Section 62.180(b) of this proposal directs the mine operator to
afford the miner the opportunity to select adequate hearing protection
from those offered by the mine operator under Sec. 62.125. While that
section of the proposal only requires the mine operator to offer one
type of ear plug and one type of ear muff, MSHA presumes that most mine
operators will offer a range of each. Pursuant to Sec. 62.120(b), the
operator is required to ensure that a miner with an STS wears the
hearing protector.
The choice of hearing protectors from this selection will be based
on the miner's personal preference. The benefits of allowing the miner
to select his/her hearing protector are discussed under Sec. 62.125
Selection of hearing protector. MSHA believes that even though a miner
may select a protector with a noise reduction rating lower than that
which might be selected by a mine operator in such cases, factors such
as comfort are more critical in ensuring that the miner will fully
utilize this critical piece of personal protective equipment. Moreover,
as discussed in the section on Hearing protector effectiveness, MSHA
has concluded that there is no standardized objective method to
determine whether an additional or different hearing protector would
provide the miner with greater protection. MSHA requests further
comment on this issue.
[[Page 66444]]
Review Effectiveness of Controls
Upon the finding of an STS, MSHA would require, under
Sec. 62.180(c) of the proposal, the mine operator to review the
effectiveness of any engineering and administrative controls. The mine
operator would need to correct any deficiencies. The implementation and
maintenance of either engineering or administrative controls or a
combination of such controls above the PEL is the primary method for
reducing a miner's noise exposure and, thus, reducing the risk of
hearing loss. OSHA's current noise regulation does not require a review
of the effectiveness of engineering and administrative controls when an
STS is found.
The inadequacy of engineering or administrative controls or a
combination of such controls may well be the contributing factor in the
development of a miner's STS. Thus, the proposal would require the mine
operator to review the effectiveness of controls and update or modify
them, as necessary and feasible, to reduce the miner's noise exposure.
Miner Transfer
The Federal Mine Safety and Health Act of 1977 (30 U.S.C. 811)
requires health standards to include, as appropriate, provisions for
removing a miner from hazardous exposure where that miner may suffer
material impairment of health or functional capacity. MSHA has decided
not to include such a provision in its proposal.
MSHA's current noise standards do not contain such a transfer
provision. Nor does the OSHA noise standard have such a requirement.
In its ANPRM, MSHA requested comments regarding the need for a
transfer provision in the proposed rule for a miner with a diagnosed
occupational hearing loss. In response, many commenters stated that a
miner transfer provision is not appropriate. Some of the concerns
expressed by the commenters included: the negotiation of disability
accommodation sections in labor contracts; problems with rate retention
and seniority provisions in existing contracts; the contribution of
non-occupational noise exposure to the hearing loss; uncertainty as to
the etiology of the hearing loss; and the impracticality in small
operations. However, several commenters disagreed, indicating that the
transfer of a miner is appropriate when other efforts to halt the
progression of the hearing loss have failed. They added that the safety
of a miner with a hearing loss would be jeopardized, due to the
inability to hear warning signals and/or understand verbal instructions
in the noisy environment (a hazard to other miners as well).
Several of the U.S. Armed Forces, and some other countries, allow
for removal or transfer of employees from noisy areas.
Although MSHA would encourage mine operators to transfer miners who
have incurred a hearing impairment, MSHA believes that a miner transfer
provision would not be feasible, at the vast majority of small mining
operations, because of limited personnel and non-noise exposed
occupations. At larger mines transfer may be feasible; however, MSHA
believes that the obligation to utilize all feasible administrative (as
well as engineering controls) would reduce miner exposure time to
harmful noise in much the same way as a transfer provision but without
unwarranted complexity.
Section 62.190 Notification of Results; Reporting Requirements
This section of the proposal would require that miners be notified
of audiometric test findings, and that the Agency be notified of any
instances of ``reportable hearing loss.''
The proposal would require the mine operator, within 10 working
days of receiving the results of an audiogram, or the results of a
follow-up evaluation pursuant to Sec. 62.170(a)--those follow-ups on
which the mine operator would receive results--to notify the miner in
writing of the results and interpretations, including any finding that
an STS or reportable hearing loss has occured. The notification would
include an explanation of the need and reasons for any further testing
or evaluation that may be required.
MSHA believes that informing miners of the results of their
audiometric tests in a timely manner is critical to the success of an
HCP. Immediate feedback upon completion of the testing provides the
greatest benefit.
The proposal would require mine operators to inform MSHA of any
reportable hearing loss, unless the physician or audiologist has
determined the loss is neither work-related nor aggravated by
occupational noise exposure. This essentially restates for noise the
requirements of 30 CFR part 50, but with an explicit definition of
reportable hearing loss for the first time. Having a uniform definition
will ease reporting burdens on mine operators while promoting the
development of an improved data base on hearing loss in the mining
community.
The proposal would define a reportable hearing loss as a change in
hearing acuity for the worse relative to the miner's baseline audiogram
of an average of 25 dB or more at 2000, 3000, and 4000 Hz in either
ear. Should an annual audiogram actually indicate an improvement in
hearing at any time, this audiogram would, pursuant to Sec. 62.140,
become the baseline for purposes of determining whether a reportable
hearing loss has occurred. As noted herein, MSHA is seeking comment on
whether part 50 should collect information on harm on less dramatic
shifts in hearing acuity, and how reporting should be accomplished in
cases in which an operator lacks audiometric data.
Notification of the Miner
Section 62.190(a) of MSHA's proposal would require that within 10
working days of receiving the results of an audiogram or follow-up
evaluation, the mine operator shall notify the miner in writing of--
(1) the results and interpretation of an audiometric test,
including any finding of an STS or a reportable hearing loss; and
(2) if applicable, the need and reasons for any further testing or
evaluation.
MSHA has no current requirements in this area. The proposed time
frame is consistent with the time frame for notification to the Agency,
under part 50, of cases of reportable hearing loss. MSHA's proposal
would differ from OSHA's standard in this regard and in several other
respects: the miner would be informed of the need and reason for
further medical evaluations, and the miner would be informed of the
finding of a reportable hearing loss. Moreover, OSHA's requirement does
not specify how long, following the annual audiogram, an employer can
take to make this determination.
All commenters on this issue favored notifying the employee of the
results of audiometric testing and follow-up examinations. They
differed, however, as to the time to be allotted for such notification
and the requirements of such notification.
Many commenters endorsed OSHA's requirements. One commenter agreed
that written notification be provided within 21 days, the same as OSHA,
but recommended that such notice be provided for all audiometric test
results. This commenter stated:
It is our policy to notify all employees of the results of their
audiometric tests in writing. An appropriate time frame would be 21
days from the time the employee's facility is made aware of the
results. If the time frame for notification is 21 days from the time
of the actual test, many problems may arise. If a mobile testing
service is utilized, the results may not be sent in for analysis for
at least
[[Page 66445]]
a week. Our audiological staff reviews all of our audiograms in-
house rather than relying on outside services for analysis. Some of
our testing services microfilm the tests or analyze them separately
which means that a delay of a few weeks may occur. The purpose
should be that the employee receive results in a timely enough
fashion so that they are meaningful.
One commenter recommended that written notification be provided to
the miner within 30 days of determining a confirmed STS. Another
commenter recommended that miners be notified of an STS, including any
optional retest, within 30 days of the testing. This commenter stated
that:
Service providers have taken undue advantage of a perceived
grace period in the OSHA Hearing Conservation Amendment to inform
employees of a shift in hearing. By the time audiometric tests are
administered, entered into a computer, returned to an employer, and
then finally returned to the employee, the lag time may total six to
eight weeks. This is a disservice to the employee, and is certainly
preventable.
Notification of STS, including the optional retest of STS-
affected employees, should be completed within a 30-day period
following testing. OSHA's time limit of 21 days following
notification to the employer creates a loophole which makes the
employee wait all too long for feedback regarding STS.
Other commenters recommended notifying miners of the results of their
audiometric tests, but did not specify a time frame.
The U.S. Armed Forces regulations, and standards of some members of
the international community, vary on the time frame for notification.
The time frame in MSHA's proposal is shorter than the time frame
for notification in OSHA's standard, but is consistent with MSHA's
requirement that the Agency be notified of reportable hearing losses
within 10 working days. MSHA's proposal would also differ from OSHA's
standard in that the miner would be informed of the need and reason for
further medical evaluations; and the miner would be informed of the
finding of a reportable hearing loss. In addition, pursuant to
Sec. 62.170(b), MSHA's proposal would require the mine operator to
instruct the physician to notify the miner of the need for an
otological examination based upon a medical pathology of the ear that
is unrelated to the affected miner's noise exposure or the wearing of
hearing protectors. MSHA believes that miners have a right to know the
results of any medical tests conducted on them.
MSHA believes that it is appropriate to require written
notification. Under proposed Sec. 62.200, the miner would in any event
have access to all required records under this part upon written
request. Providing the notices in writing would ensure there are no
misunderstandings on the part of miners as to the severity of the
problem.
MSHA believes that informing miners of the results of their
audiometric tests in a timely manner is critical to the success of an
HCP. Immediate feedback upon completion of the testing provides the
greatest benefit. Generally, the employee shows the most interest and
concern regarding the effects of noise on his/her hearing immediately
following testing. Providing the results several weeks or months later
may have less of an impact. In many cases, however, it may not be
feasible or practical to inform miners immediately of the results of
their audiometric tests. The proposal, consequently, would allow mine
operators up to 10 working days to inform the miner (the same time
period as provided under part 50 for notification of MSHA of cases of
reportable hearing loss). Because the proposal would allow up to 30
calendar days to evaluate audiograms, it could be as long as 44 days
following testing before the miner is informed of the results. In the
case of an audiometric retest, it could be as long as 104 days before
the miner is informed of the results of the retest. MSHA believes that
it is necessary to specify a maximum time frame for informing miners of
the audiometric test results in order to prevent undue delays.
Reporting Noise-Induced Hearing Loss (NIHL)
Section 62.190(b) of this proposal would require the mine operator
to report hearing loss under 30 CFR part 50, if the results of an
audiogram or follow-up evaluation indicate that a miner has incurred a
``reportable hearing loss.'' This section is designed to refine, in
light of this proposal, MSHA's existing reporting requirements for
injuries and illnesses in 30 CFR part 50, so as to ease reporting
burdens on employers while promoting the development of an improved
data base on hearing loss in the mining community.
The current reporting requirements provide that mine operators
report a hearing loss whenever a physician determines that it is work
related, or whenever an award of compensation is made. NIHL is
specifically listed among the examples of occupational illnesses to be
reported when it is work related. The proposal would establish the
reporting definition for this purpose: but the report would only be
required under part 50 if the hearing loss is suspected to be work
related.
OSHA does not have reporting requirements: i.e., a level which
triggers notification to the agency so that it can intervene. It does,
however, have recording requirements for noise, so that information is
gathered about NIHL and is available to employers, employees, and
agency personnel. In June 1991, OSHA issued its current policy (1991)
for reporting NIHL (on the OSHA Form 200). This policy requires
employers to record a work-related shift in hearing of 25 dB or more in
either ear from the original baseline audiogram averaged over 2000,
3000, and 4000 Hz. The recording criteria use identical evaluation
frequencies as required for determining an STS. The policy allows a
correction for presbycusis when determining reportability. In January
1996, OSHA published a proposal to revise agency recordkeeping
standards. Under the proposal's mandatory Appendix B, the recording
requirement would drop to a work-related shift in hearing of 15 dB or
more in either ear. OSHA notes it is proposing this change to ensure
the recording of any STS (a 10 dB shift under OSHA's standard), with
some allowance made for instrumentation variance.
In its ANPRM, MSHA discussed the problems that the Agency is
experiencing with its existing reporting requirements. Of the
commenters addressing this issue, many recommended that MSHA require
reporting of a 10-dB average loss in either ear at 2000, 3000, and 4000
Hz (the OSHA STS criteria). One commenter favored reporting any job-
related loss and another stated that the criteria of reporting an STS
was too high because ``* * * the worker['s] hearing loss has progressed
too far with this shift to be a reliable preventative measure.'' Other
commenters stated that the STS criteria represent a slight change in
hearing and is not meaningful for reporting purposes. Two commenters
recommended that the criteria for reporting be that used for defining
impairment (the AAO-HNS 1979 criteria).
Some hearing conservation associations have opposed OSHA's current
policy, arguing that employers should record the NIHL when the employee
incurs an STS. Driscoll and Morrill (1987) presented the position of
the American Industrial Hygiene Association (AIHA) in a paper entitled
``A Position Paper on a Recommended Criterion for Recording
Occupational Hearing Loss on OSHA Form 200''. AIHA concluded that ``a
confirmed STS which results from workplace noise exposure is considered
an appropriate
[[Page 66446]]
measure for surveillance or recordkeeping purposes.''
The National Hearing Conservation Association (NHCA) in a letter
from their President, Susan Cooper Megerson (1994), to Joseph Dear,
Assistant Secretary of Labor for Occupational Safety and Health, urged
OSHA to require the recording of an occupational hearing loss when an
STS was confirmed. NHCA contends that recording hearing loss after it
reaches an average of 25 dB or more at 2000, 3000, and 4000 Hz is
``dangerously underprotective and not technically well founded.''
Suter (1994) in a letter to Sue Andrei of OSHA's Policy Directorate
urged OSHA to adopt a policy of recording persistent occupational
hearing loss at an STS instead of at an average of 25 dB or more at
2000, 3000, and 4000 Hz.
MSHA's proposal would define a ``reportable hearing loss'' as a
change in hearing threshold relative to the miner's original baseline
audiogram of an average of 25 dB or more in either ear at 2000, 3000,
and 4000 Hz. If a physician determines that the hearing loss is neither
work-related nor aggravated by occupational noise exposure, then it
would not be considered a reportable illness under part 50. As
discussed in connection with proposed Sec. 62.140, if an audiological
exam showed a significant improvement in hearing acuity, the original
baseline would be supplemented to reflect this: a correction which
would then affect the reportability of hearing loss. Furthermore, as
noted in the discussion of proposed Sec. 62.160, the proposal would
allow the correction of audiograms for presbycusis when determining the
reportability of shifts in hearing threshold levels.
In selecting its reporting criteria, MSHA took into account that a
loss of this magnitude is one that diminishes quality of life and the
ability to understand speech in noisy environments. MSHA's reporting
criteria, although not impairment per se, represent a substantial loss
which would provide a reliable indication of the effectiveness of
MSHA's rule and enforcement programs. Moreover, the calculation would
be the same as that used to determine an STS and, thus, not an extra
burden. The use of other criteria, such as the AAO-HNS 1979 criteria
for impairment, would require an additional set of calculations at
different frequencies.
MSHA is concerned, however, that reporting only losses of 25 dB may
not provide MSHA a full picture of hearing loss in the mining industry.
A loss of 25 dB is used by many states as a basis for making disability
awards. Some have recommended that any STS (10 dB loss) should be
captured in a hearing loss data base. OSHA, which currently requires
any 25 dB loss to be captured in an employer's log, has proposed to
capture any 15 dB loss. MSHA accordingly solicits comment on this
point.
An important goal of the proposal is to clarify the level of
hearing loss which is reportable. MSHA believes that its current
reporting requirements are vague; consequently, cases of NIHL are
inconsistently reported or not reported. Some mine operators have
reported even a small loss, while others only reported when a miner
received an award of compensation. In other cases, mine operators have
not reported when an award of compensation was granted because the
miners had retired. Inconsistent reporting also results because worker
compensation regulations vary from state to state, i.e., the same
hearing loss would be compensable and thus reportable in some states
and not in others. For these reasons, current hearing loss data
reported to MSHA under part 50 cannot be used to accurately
characterize either the prevalence or the degree of hearing loss in the
mining industry.
Reporting at a specified level, as required by the proposal, would
eliminate reliance on workers' compensation awards as a criteria for
defining NIHL to be reported. Nevertheless, part 50 would still require
that awards of compensation be reported in those cases when the loss
had not been previously reported. Two general examples of such cases
are (1) if the miner had incurred the loss before the current mine
operator conducted the baseline or pre-employment audiogram and
subsequent testing did not measure a reportable loss, and (2) if the
miner had not been in an HCP or had not received an audiometric test
while employed by the operator.
In this regard, MSHA would like comment on how to define
``reportable'' hearing loss for those operators who do not have
audiometric test data. Not all mine operators will be required to
obtain audiometric test data under the proposed rule; thus, such
operators may not be able to use a definition of reportable hearing
loss defined in this manner. MSHA also requests specific suggestions on
how to capture data on work-related NIHL: (1) that is not discovered
until after the miner's employment is terminated; and (2) that the
miner had accumulated from work with several employers.
MSHA does not expect mine operators to report the same reportable
hearing loss each year that a miner works at the mine. The next
reportable hearing loss would not be reported until the miner incurs
another 25 dB shift (50 dB shift from the original baseline). MSHA does
intend for each ear to be treated independently in terms of a
reportable event, unless the reportable loss occurs in both ears during
a particular year. (For example, 28.7 dB, left ear, 25.9 dB, right ear,
not corrected for presbycusis.) Although not specifically required in
its proposal, MSHA anticipates that mine operators would indicate when
reporting to MSHA--
(1) the actual average hearing loss;
(2) in which ear(s) the loss occurred; and
(3) whether the audiograms were corrected for presbycusis. (For
example, 28.7 dB, left ear, corrected for presbycusis.)
Section 62.200 Access to Records
Authorized representatives of the Secretaries of Labor and Health
and Human Services would have immediate access to all records required
under this part.
Moreover under the proposal, a miner or former miner, or his/her
designated representative with written consent, would have access to
all the records that the mine operator is required to maintain under
this part for that individual miner or former miner. Also, the miners'
representative is in all cases to have access, for miners they
represent, to noise training records and notices required under
Sec. 62.120(f) to be given to miners exposed to noise above various
levels.
The mine operator would have 15 days from receipt of a written
request to provide such access. The proposal would define ``access'' as
the right to examine and copy records. The first copy of any record
requested by a person is to be provided without cost to that person,
and any additional copies requested by that person are to be provided
at reasonable cost.
Upon termination of employment, mine operators would be required to
provide a miner without cost an actual copy of all his/her own records
(those required under this part).
MSHA has no uniform records access provision that address these
issues--though the Agency and NIOSH do have statutory rights to access.
The provisions proposed here are similar to those in other health
standards proposed in recent years by the Agency.
Section 103(c) of the Mine Act states that:
[[Page 66447]]
The Secretary, in cooperation with the Secretary of Health,
Education, and Welfare, [now Health and Human Services] shall issue
regulations requiring operators to maintain accurate records of
employee exposures to potentially toxic materials or harmful
physical agents which are required to be monitored or measured under
any applicable mandatory health or safety standard promulgated under
this Act. Such regulations shall provide miners or their
representatives with an opportunity to observe such monitoring or
measuring, and to have access to the records thereof. Such
regulations shall also make appropriate provisions for each miner or
former miner to have access to such records as will indicate his own
exposure to toxic materials or harmful physical agents.
OSHA's requirements for access to records incorporate its standards
for ``Access to Employee Exposure and Medical Records'' [29 CFR
Sec. 1910.20(a)-(e) and (g)-(i)]. OSHA's requirements and MSHA's
proposal are essentially the same.
All of the commenters addressing this issue favored providing
affected miners with reasonable access to required records. Most of
these commenters also recommended that the request for access to
records be in writing.
The Agency agrees, after reviewing comments and related
regulations, that access to noise records by both employees and the
government is essential, and does not believe the costs of providing
such access will be significant. As noted by OSHA, in its preamble to
its proposed Hearing Conservation Amendment (46 FR 4161)--
Such access will serve to educate employees as to the state of
their hearing and the effectiveness of the program, and will
encourage their conscientious participation in it. The information
in the records will be invaluable to the Assistant Secretary in the
enforcement of the amendment and will be useful in research into the
effects of occupational noise exposure. The Director of NIOSH will
also be primarily interested in the records for research purposes.
MSHA also agrees that requests from miners, miner's designated
representatives, and miner's representatives be in writing. This
requirement would benefit both the miners and mine operators by
protecting them in matters of dispute regarding the date on which the
request was submitted. MSHA's access to records requirements would not
preclude the mine operators from requiring the requester to sign a
receipt after receiving the records. In addition, the definition of
miner's ``designated representative'' specifies that such person have
written authorization to request records for each miner or former miner
represented. Because requested records may contain personal, private
information, MSHA intends that the miner's designated representative
would present such authorization to the mine operator when requesting
records on behalf of a miner or former miner.
According to the proposal the mine operator would have 15 days to
provide the miner, former miner, or miner's designated representative
access to the requested records. MSHA believes that it is reasonable to
require the mine operator to provide access because the proposal would
require the records to be maintained at the mine site.
The mine operator has some choice as to how to provide records
requested by an employee or representative. The mine operator could
provide a copy, make available mechanical copying facilities, or loan
the record to the requester for a reasonable time to enable a copy to
be made. The proposal provides that if a copy is requested, however, it
shall be provided, and the first copy shall be at no cost. If a copy of
the record had been provided previously without cost, the proposal
would allow the mine operator to charge reasonable, non-discriminatory
administrative costs for providing an additional copy of the record.
The mine operator, however, could not charge for the first copy of new
information which subsequently had been added to the record.
MSHA believes that its proposed requirements for access to records
are both reasonable and necessary to meet its mandate under the Mine
Act. MSHA would welcome comments on what actions are required, if any,
to facilitate the maintenance of records in electronic form by those
mine operators who desire to do so, while ensuring access in accordance
with these proposed requirements.
Section 62.210 Transfer of Records
The proposed standard would require mine operators to transfer all
records (or a copy thereof) required by this part to any successor mine
operator. The successor mine operator would be required to receive
these records and maintain them for the period required. Additionally,
the successor mine operator would be required to use the baseline
audiogram obtained from the original mine operator (or supplemental
baseline audiogram as appropriate) for determining an STS and
reportable hearing loss.
MSHA's existing noise standards do not address the transfer of
records, nor does MSHA have general standards on this point. The
provisions proposed here are similar to those in other health standards
proposed in recent years by the Agency. OSHA's standard requires
transfer of records and, in addition, incorporates by reference
transfer provisions found in its ``Access to Employee Exposure and
Medical Records'' standards (29 CFR 1910.20 (h)). MSHA's proposal
regarding the transfer of records is essentially the same as in OSHA's
regulations.
MSHA's ANPRM did not address the transfer of records and no
comments were received on this subject. MSHA considered OSHA's
requirements and believes that they are both reasonable and necessary
to ensure that records are maintained for the required periods of time
when a mine operator ceases to do business.
Requiring successor mine operators to use the prior baseline
audiogram will provide the miners with a greater degree of protection
by assuring that an STS or reportable hearing loss is based on the
original or supplemental baseline taken under the original mine
operator, instead of based on a new baseline. Generally if a new
baseline would be established by a successor mine operator, the miner
would need to lose additional hearing acuity before the corrective
action triggered by the occurrence of an STS is implemented or a
hearing loss is required to be reported.
IV. Feasibility
MSHA has tentatively concluded that it is feasible for the mining
industry to take the actions specified in the proposed rule. MSHA has
also tentatively concluded that at this time, it may not be feasible
for the mining industry to comply with two changes that would otherwise
be warranted to further reduce the risk of impairment from occupational
NIHL--reducing the PEL to a TWA8 of 85 dBA, and reducing the
exchange rate from 5-dB to 3-dB.
As background, this part begins with a review of the pertinent
legal requirements for setting health standards under the Mine Act and
an economic profile of the mining industry.
Pertinent Legal Requirements
Section 101(a)(6)(A) of the Mine Act requires the Secretary to set
standards which most adequately assure, on the basis of the best
available evidence, that no miner will suffer material impairment of
health over his/ her working lifetime. In addition, the Mine Act
requires that the Secretary, when promulgating mandatory standards
pertaining to toxic materials or harmful physical agents, consider
other factors, such as the latest scientific data in the field, the
feasibility of the standard and experience gained under the Act and
other health and safety laws. Thus, the
[[Page 66448]]
Mine Act requires that the Secretary, in promulgating a standard,
attain the highest degree of health and safety protection for the
miner, based on the ``best available evidence,'' with feasibility a
consideration.
Feasibility in this context refers to both economic and
technological feasibility. It also refers to what is feasible for an
entire industry, not an individual mine operator; although for this
purpose, MSHA has considered independently the situations of the coal
mining sector and the metal and nonmetal mining sector.
In relation to feasibility, the legislative history of the Mine Act
states that:
* * * 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 court of appeals have recognized, occupational safety
and health statutes should be viewed as ``technology-forcing''
legislation, and a proposed health standard should not be rejected
as infeasible when the necessary technology looms in today's
horizon. (AFL-CIO v. Brennan, 530 F.2d 109); (CA 3 1975) Society of
Plastics Industry v. OSHA, 509 F.2d 1301 (CA 2), 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 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. S. Rep. No. 95-181,
95th Cong., 1st Sess. 21 (1977).
Thus, standards may be economically feasible even though industry
considers them economically burdensome.
Though the Mine Act and its legislative history are not specific in
defining feasibility, the courts have clarified the meaning of
feasibility. The Supreme Court, in American Textile Manufacturers'
Institute v. Donovan (OSHA Cotton Dust), 452 U.S. 490, 508-509 (1981),
defined the word ``feasible'' as ``capable of being done, executed, or
effected.'' The Court stated that a standard would not be considered
economically feasible if an entire industry's competitive structure was
threatened. According to the Court, the appropriate inquiry into a
standard's economic feasibility is whether the standard is capable of
being achieved.
Courts do not expect hard and precise predictions from agencies
regarding feasibility. Under the ``arbitrary and capricious standard,''
used in judicial review of agency rulemaking under the Administrative
Procedures Act, an agency need only base its predictions on reasonable
inferences drawn from the existing facts. An agency is required to
produce a reasonable assessment of the likely range of costs that a new
standard will have on an industry. The 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 v. Marshall, 647 F.2d 1189 (D.C. Cir.
1980).
In developing a new health standard, an agency must also show that
modern technology has at least conceived some industrial strategies or
devices that are likely to be capable of meeting the standard, and
which industry is generally capable of adopting. United Steelworkers of
America v. Marshall, supra at 1272. If only the most technologically
advanced companies in an industry are capable of meeting the standard,
then that would be sufficient demonstration of feasibility (this would
be true even if only some of the operations met the standard for some
of the time). American Iron and Steel Institute v. OSHA, 577 F. 2d 825
(3d Cir. 1978) at 832-835, see also Industrial Union Dep't., AFL-CIO v.
Hodgson, 499 F. 2d 467 (D.C. Cir. 1974).
In evaluating the feasibility of particular requirements under
these legal tests, MSHA took into account how it anticipates
interpreting those requirements. For example, in the case of the
requirement that mine operators use all feasible engineering and
administrative controls, the Agency considered legal guidance from the
Federal Mine Safety and Health Review Commission as to what MSHA must
consider, for enforcement purposes, as a feasible noise control at a
particular mine. This guidance is discussed in the ``Questions and
Answers'' in part I (see Question 12). MSHA also used its expert
knowledge of particular equipment or methods of noise control available
in the industry, and considered exposure data indicating the extent to
which the industry would be out of compliance should a particular
proposal be adopted.
Industry Profile
Determining the feasibility of controls for the mining sector
requires consideration of the composition and economics of that sector.
The following information is reprinted from MSHA's preliminary
Regulatory Impact Analysis (RIA), and was considered by the Agency in
reaching preliminary conclusions.
Overall Structure of the Mining Industry
MSHA divides the mining industry into two major segments based on
commodity, the coal mining industry and the metal and nonmetal mining
industry. These major industry segments are further divided based on
type of operation (underground mines, surface mines, and independent
mills, plants, shops, and yards). MSHA maintains its own data on mine
type, size, and employment. MSHA also collects data on the number of
contractors and contractor employees by major industry segment.
MSHA categorizes mines as to size based on employment. For the
purpose of analyzing this proposed rule, MSHA defines small mines to be
those having fewer than 20 employees and large mines to be those having
at least 20 employees. Table IV-1 presents the number of small and
large mines and the corresponding number of miners, excluding
contractors, by major industry segment and mine type. Although MSHA
does not maintain a data base of the numbers of miners by job title,
Table IV-2 presents an estimate of the numbers of miners by job title
groups based in part on research conducted by the U.S. Department of
the Interior, Bureau of Mines. The Agency does not maintain a data base
which would allow determination of the types of services provided by
independent contractors or the job titles of contractor employees.
Table IV-3, however, presents MSHA data on the numbers of independent
contractors and the corresponding numbers of employees by major
industry segment and the size of the operation based on employment.
[[Page 66449]]
Table IV-1.--Distribution of Operations and Employment (Excluding Contractors) by Mine Type, Commodity, and Size
----------------------------------------------------------------------------------------------------------------
Small (<20 EES) Large (>20 EES) Total
-----------------------------------------------------------------------------
Mine type Number of Number of Number of Number of Number of Number of
mines miners Mines Miners Mines Miners
----------------------------------------------------------------------------------------------------------------
Coal:
Underground................... 466 4,630 606 49,370 1,072 54,000
Surface....................... 875 5,337 396 30,173 1,271 35,510
Shp/Yrd/Mll/Plnt.............. 421 2,701 132 5,169 553 7,870
Office workers................ ........... 752 ........... 5,030 ........... 5,782
-----------------------------------------------------------------------------
Coal Subtotal................. 1,762 13,420 1,134 89,742 2,896 103,162
=============================================================================
Metal/nonmetal (M/NM):
Underground................... 141 1,191 134 16,736 275 17,927
Surface....................... 8,838 49,214 1,192 79,230 10,030 128,444
Shp/Yrd/Mll/Plnt.............. 288 2,146 223 18,889 511 21,035
Office workers................ ........... 8,530 ........... 18,644 ........... 27,174
-----------------------------------------------------------------------------
M/NM Subtotal................. 9,267 61,081 1,549 133,499 10,816 194,580
=============================================================================
Total all mines....... 11,029 74,501 2,683 223,241 13,712 297,742
----------------------------------------------------------------------------------------------------------------
Source: U.S. Department of Labor, Mine Safety and Health Administration, Office of Standards, Regulations, and
Variances, based on preliminary 1995 MIS data (quarter 1-quarter 4, 1995). MSHA estimates assume that operator
office workers are distributed the same as non-office workers.
Table IV-2.--Mining Workforce Estimates by Job Title Groups (Including Office Workers and Excluding Contractor
Employees)
----------------------------------------------------------------------------------------------------------------
Coal mining M/NM mining Total
Job title groups -----------------------------------------------------------------------------
Percent Miners Percent Miners Percent Miners
----------------------------------------------------------------------------------------------------------------
Backhoe-crane-dragline-shovel
operator......................... 1.9 2,004 2.5 4,938 2.3 6,942
Beltman-belt cleaner (coal)-belt
repairman........................ 3.4 3,473 0.4 800 1.4 4,273
Blaster........................... 0.8 810 0.3 605 0.5 1,415
Continuous miner & related machine
operator......................... 4.2 4,282 (\1\) (\1\) 1.4 4,282
Deckhand-barge & dredge operator.. 0.2 156 0.6 1,103 0.4 1,259
Dozer-heavy & mobile equipment
operator......................... 6.8 7,038 2.7 5,289 4.1 12,326
Driller-auger operator (coal)-rock
bolter (m/nm).................... 1.9 1,910 1.9 3,700 1.9 5,611
Electrician-wireman (coal)-lampman 4.0 4,127 1.9 3,780 2.7 7,908
Front-end loader-forklift (m/nm)
operator......................... 2.8 2,876 7.2 13,943 5.7 16,820
Grader-scraper operator........... 1.6 1,636 0.7 1,323 1.0 2,959
Laborer-miner-utility man......... 15.0 15,477 10.3 20,021 11.9 35,498
Longwall operator................. 0.7 689 (\1\) (\1\) 0.2 689
Manager-foreman-supervisor........ 11.1 11,423 10.1 19,685 10.5 31,108
Mechanic-welder-oiler-machinist... 15.0 15,457 14.7 28,546 14.8 44,003
Mine technical support............ 4.4 4,521 6.7 13,039 5.9 17,561
Office workers.................... 5.6 5,782 14.0 27,174 11.1 32,956
Plant operator-warehouseman....... 3.8 3,921 14.0 27,315 10.5 31,236
Roof bolter-rock driller (coal)... 5.3 5,459 0 0 1.8 5,459
Scoop tractor operator-motorman
(coal)........................... 3.4 3,510 0 0 1.2 3,510
Shuttle car-tram (m/nm) operator.. 3.6 3,756 0.8 1,607 1.8 5,363
Stone cutter-finisher............. 0 0 0.5 879 0.3 879
Truck driver...................... 4.7 4,854 10.7 20,832 8.6 25,686
-----------------------------------------------------------------------------
Total....................... 100 103,162 100 194,580 100 297,742
----------------------------------------------------------------------------------------------------------------
\1\ Continuous miner and longwall operators at metal/nonmetal mines are included in the job group ``laborer-
miner-utility man.''
Extrapolated from U.S. Bureau of Mines, Characterization of the 1986 Coal Mining Workforce (IC 9192) and
Characterization of the 1986 Metal and Nonmetal Mining Workforce (IC 9193), 1988.
Table IV-3.-- Distribution of Contractors (Contr) and Contractor Employees (Miners) by Major Industry Segment
and Size of Operation
----------------------------------------------------------------------------------------------------------------
Small (<20) Large (20) Total
-----------------------------------------------------------------------------
Contractors Number of Number of Number of Number of Number of Number of
contr. miners contr. miners contr. miners
----------------------------------------------------------------------------------------------------------------
Coal:
Other than office............. 3,580 14,310 291 12,863 3,871 27,173
[[Page 66450]]
Office workers................ ........... 1,291 ........... 1,160 ........... 2,451
-----------------------------------------------------------------------------
Coal Subtotal............... 3,580 15,601 291 14,023 3,871 29,624
=============================================================================
Metal/nonmetal (M/NM):
Other than office............. 2,656 12,921 352 20,975 3,008 33,896
Office workers................ ........... 734 ........... 1,191 ........... 1,925
M/NM Subtotal................. 2,656 13,655 352 22,166 3,008 35,821
-----------------------------------------------------------------------------
Total....................... 6,236 29,256 643 36,189 6,879 65,445
----------------------------------------------------------------------------------------------------------------
Source: U.S. Department of Labor, Mine Safety and Health Administration, Office of Standards, Regulations, and
Variances, based on preliminary 1995 MIS data (quarter 1-quarter 4, 1995). MSHA estimates assume that
contractor office workers are distributed the same as non-office workers.
Economic Characteristics
The U.S. mining industry's 1995 production is worth in excess of
$58 billion in raw mineral resources. Coal mining contributed about $20
billion to the Gross Domestic Product in 1995 and metal and nonmetal
mining contributed about $38 billion. Another $17 billion is reclaimed
annually from recycled metal and mineral materials such as scrap iron,
aluminum, and glass.
The Agency obtained financial information on the various mineral
commodities primarily from the U.S. Department of the Interior, Bureau
of Mines, and the U.S. Department of Energy, Energy Information
Administration.
Structure of the Coal Mining Industry
MSHA separates the U.S. coal mining industry into two major
commodity groups, bituminous and anthracite. The bituminous group
includes the mining of subbituminous coal and lignite. Bituminous
operations represent over 93% of the coal mining operations, employ
over 98% of the coal miners, and account for over 99% of the coal
production. About 60% of the bituminous operations are large; whereas
about 90% of the anthracite operations are small.
Underground bituminous mines are more mechanized than anthracite
mines in that most, if not all, underground anthracite mines still
hand-load. Over 70% of the underground bituminous mines use continuous
mining and longwall mining methods. The remaining use drills, cutters,
and scoops. Although underground coal mines generally use electrical
equipment, a growing number of underground coal mines use diesel
haulage equipment.
Surface mining methods include drilling, blasting, and hauling and
are similar for all commodity types. Most surface mines use front-end
loaders, bulldozers, shovels, or trucks for coal haulage. A few still
use rail haulage. Although some coal may be crushed to facilitate
cleaning or mixing, coal processing usually involves cleaning, sizing,
and grading.
Preliminary data for 1995 indicate that there are about 2900 active
coal mines of which 1760 are small mines (about 61% of the total) and
1130 are large mines (about 39% of the total).
These data indicate employment at coal mines to be about 103,200 of
which about 13,400 (13% of the total) worked at small mines and 89,700
(87% of the total) worked at large mines. MSHA estimates that the
average employment is 8 miners at small coal mines and 79 miners at
large coal mines.
Structure of the Metal/Nonmetal Mining Industry
The metal and nonmetal mining industry consists of about 70
different commodities including metals, industrial minerals, stone, and
sand and gravel. Preliminary data for 1995 indicate that there are
about 10,820 active metal and nonmetal mines of which 9270 are small
mines (about 86% of the total) and 1550 are large mines (about 14% of
the total).
These data indicate employment at metal and nonmetal mines to be
about 194,600 of which about 61,100 (31% of the total) worked at small
mines and 133,500 (69% of the total) worked at large mines. MSHA
estimates that the average employment is 7 miners at small metal and
nonmetal mines and 86 miners at large metal and nonmetal mines. Table
II-4 presents the number of metal and nonmetal mines and miners by
major commodity category, mine size, and employment. In addition, MSHA
estimates that about 350 mines are owned by state, county, or city
governments.
Table IV-4.--Estimated Distribution of Metal/Nonmetal Mines and Miners 1
----------------------------------------------------------------------------------------------------------------
Small (<20 EES) Large (>20 EES) Total
-----------------------------------------------------------------------------
Commodity Number of Number of Number of Number of Number of Number of
Mines Miners Mines Miners Mines Miners
----------------------------------------------------------------------------------------------------------------
Metal............................. 176 1,199 193 46,296 369 47,495
Nonmetal.......................... 546 3,496 231 25,436 777 28,932
Stone............................. 2,640 23,003 894 53,157 3,534 76,160
Sand and Gravel................... 5,905 33,383 231 8,610 6,136 41,993
-----------------------------------------------------------------------------
Total....................... 9,267 61,081 1,549 133,499 10,816 194,580
----------------------------------------------------------------------------------------------------------------
1 Includes office workers. Excludes contractors.
[[Page 66451]]
Metal Mining
Metal mining in the U.S. consists of about 25 different
commodities. Most metal commodities include only one or two mining
operations. Metal mining operations represent about 3% of the metal and
nonmetal mines, employ about 24% of the metal and nonmetal miners, and
account for about 35% of the value of metal and nonmetal minerals
produced in the U.S. About 48% of the metal mining operations are
small.
Underground metal mining uses a few basic mining methods, such as
stope, room and pillar, and block caving with primary noise sources
being diesel haulage equipment, pneumatic drills, and mills. Larger
underground metal mines use more hydraulic drills and track-mounted
haulage; whereas, smaller underground metal mines use more hand-held
pneumatic drills. Stope mining uses more hand-held equipment. Surface
metal mines include some of the largest mines in the world. Surface
mining methods (drill, blast, haul) use the largest equipment and are
similar for all commodity types.
Nonmetal Mining
For enforcement and statistical purposes, MSHA separates stone and
sand and gravel mining from other nonmetal mining. There are about 35
different nonmetal commodities, not including stone or sand and gravel.
About half of the nonmetal commodities include less than 10 mining
operations; some include only one or two mining operations. Nonmetal
mining operations represent about 7% of the metal and nonmetal mines,
employ about 15% of the metal and nonmetal miners, and account for
about 34% of the value of metal and nonmetal minerals produced in the
U.S. About 70% of the nonmetal mining operations are small.
Nonmetal mining uses a wide variety of underground mining methods.
For example, potash mines use continuous miners similar to coal mining;
oil shale uses in-situ retorting; and gilsonite uses hand-held
pneumatic chippers. Some nonmetal commodities use kilns and dryers in
ore processing. Others use crushers and mills similar to metal mining.
Underground nonmetal mining operations generally use more block caving,
room and pillar, and retreat mining methods; less hand-held equipment;
and more electrical equipment than metal mining operations. As with
underground mining, surface mining methods vary more than for other
commodity groups. In addition to drilling, blasting, and hauling,
surface nonmetal mining methods include other types of mining methods,
such as evaporation beds and dredging.
Stone Mining
There are basically only eight different stone commodities of which
seven are further classified as either dimension stone or crushed and
broken stone. Stone mining operations represent about 33% of the metal
and nonmetal mines, employ about 39% of the metal and nonmetal miners,
and account for about 19% of the value of metal and nonmetal minerals
produced in the U.S. About 75% of the stone mining operations are
small.
Stone generally is mined from quarries using only a few different
methods and diesel haulage to transfer the ore from the quarry to the
mill. Crushed stone mines typically drill and blast; whereas, dimension
stone mines typically use channel burners, drills, or wire saws.
Milling typically includes jaw crushers, vibratory crushers, and
vibratory sizing screens.
Sand and Gravel Mining
Based on the number of mines, sand and gravel mining represents the
single largest commodity group in the U.S. mining industry. About 57%
of the metal and nonmetal mines are sand and gravel operations. They
employ about 22% of the metal and nonmetal miners and account for about
11% of the value of metal and nonmetal minerals produced in the U.S.
Over 95% of the sand and gravel operations are small.
Construction sand and gravel is generally gathered from surface
deposits using dredges or draglines and only washing and screening
milling methods. As in other surface mining operations, sand and gravel
uses diesel haulage equipment, such as front-end loaders, trucks, and
bulldozers. In addition, industrial sand and silica flour operations
mill the ore using crushers, ball mills, screens, and classifiers.
Economic Characteristics of the Coal Mining Industry
The U.S. Department of Energy, Energy Information Administration,
reported that the U.S. coal industry produced a record 1.03 billion
tons of coal in 1994 with a value of about $20 billion. Of the several
different types of coal commodities, bituminous and subbituminous coal
account for 91% of all coal production (940 million tons). The
remainder of U.S. coal production is lignite (86 million tons) and
anthracite (4 million tons). Although anthracite offers superior
burning qualities, it contributes only a small and diminishing share of
total coal production. Less than 0.4% of U.S. coal production in 1994
was anthracite.
Mines east of the Mississippi account for about 53% of the current
U.S. coal production. For the period 1949 through 1995, coal production
east of the Mississippi River fluctuated relatively little from a low
of 395 million tons in 1954 to 630 million tons in 1990. (It was 568
million tons in 1994.) During this same period, however, coal
production west of the Mississippi increased each year from a low of 20
million tons in 1959 to a record 490 million tons in 1995. The growth
in western coal is due in part to environmental concerns that led to
increased demand for low-sulfur coal, which is concentrated in the
West. In addition, surface mining, with its higher average
productivity, is much more prevalent in the West.
Preliminary MSHA data for 1995 indicate that small mines produced
about 4% of the total coal mine production (about 44 million tons) and
large mines produced about 96% of the total (983 million tons). MSHA
calculations indicate that the average total production per miner for
1995 was about 3,500 tons at small mines and 11,400 tons at large
mines. The average total coal production for 1995 was about 25,000 tons
per small mine and 867,000 tons per large mine.
The 1994 estimate of the average value of coal at the point of
production is about $19 per ton for bituminous coal and lignite, and
$36 per ton for anthracite. MSHA chose to use $19 per ton as the value
for all coal production because anthracite contributes such a small
amount to total production that the higher value per ton of anthracite
does not greatly impact the total value. The total value of coal
production in 1995 was about $20 billion of which about $0.9 billion
was produced by small mines and $19.1 billion was produced by large
mines. On a per mine basis, the average coal production was valued at
$0.5 million per small mine and $17 million per large mine.
Coal is used for several purposes including the production of
electricity. The predominant consumer of coal is the U.S. electric
utility industry which used 829 million tons of coal in 1995 or 80% of
the coal produced. Other coal consumers include coke plants (33 million
tons), residential and commercial consumption (6 million tons), and
miscellaneous other industrial uses (73 million tons). This last
category includes the use of coal products in the manufacturing of
other products, such as plastics, dyes, drugs, explosives, solvents,
refrigerants, and fertilizers.
[[Page 66452]]
The current rate of U.S. coal production exceeds U.S. consumption
by roughly 90 million tons annually. In 1995, 89 million tons of this
excess production was exported and the remainder was stockpiled. Japan
(11.8 million tons), Canada (9.4 million tons), and Italy (9.1 million
tons) were the top three importers of U.S. coal. Year-to-year
fluctuations in exports of U.S. coal vary more than domestic
consumption. During the 1990's, changes in exports from the previous
year varied from a 24% increase to a 27% decrease; whereas, changes in
domestic consumption only varied from a 4% increase to a 1% decrease.
The U.S. coal industry enjoys a fairly constant domestic demand.
Its demand by electric utilities continues to increase annually. MSHA
does not expect a substantial change in coal demand by utilities in the
near future because of the high conversion costs of changing a fuel
source in the electric utility industry. Energy experts predict that
coal will continue to be the dominant fuel source of choice for power
plants built in the future. Nuclear and hydropower currently comprise,
and are anticipated in the future to comprise, a small fraction of fuel
sources for utilities.
The international market for coal was marked by several notable
events in the 1990's. The breakup of the Soviet Union (USSR), a new
political regime in South Africa, and economic policy changes in the
United Kingdom and Germany contributed to price and demand changes in
coal's global marketplace; newly independent, former USSR republics
provided competition to U.S. companies for a share of the European coal
market; and the deep European recession of 1993-1994 caused exports of
coal to decrease. Similarly, the cessation of the economic boycott of
South Africa, and its new political leadership, has led to new interest
in South African exports. South Africa ranks third after Australia and
the U.S. in coal exports. Its coal exploration and mining have the
nation poised to maintain its global position. The privatization of
British power companies and the elimination of coal subsidies in
Germany have led to an increased interest in U.S. coal. These
international economic policy changes are predicted to create a
substantial export opportunity for U.S. coal over the long term.
The net effect of these aforementioned international activities
appears to be a continued demand for U.S. coal at or near current
level. The U.S. can expect additional competition, however, from other
current coal producing countries (e.g., Australia, South Africa, former
USSR republics, Poland), as well as from new suppliers in Colombia,
Venezuela, China, and Indonesia. The U.S. coal industry has vast
reserves of unmined coal which is predicted to sustain coal's demand
for another half millennium if mined at the current rate.
The economic health of the coal industry may be summarized as a
fairly stable market which may be subject to periodic price and demand
fluctuations. These fluctuations are largely functions of domestic
supply disruptions and increased international competition. The 1993
average profit as a percent of revenue for the coal mining industry was
about 3-4% after taxes.
Economic Characteristics of the Metal and Nonmetal Mining Industry:
Summary
The 1995 value of all metal and nonmetal mining output is about $38
billion. Metal mining contributes $13.2 billion to this total and
includes metals such as aluminum, copper, gold, and iron. Nonmetal
mining is valued at $12.9 billion and includes commodities such as
cement, clay, and salt. Stone mining contributes about $7.2 billion and
sand and gravel contributes about $4.3 billion to this total.
The entire metal and nonmetal mining industry is markedly diverse
not only in terms of the breadth of minerals, but also in terms of each
commodity's usage. For example, metals such as iron and aluminum are
used to produce vehicles and other heavy duty equipment, as well as
consumer goods such as household equipment and soda pop cans. Other
metals, such as uranium and titanium, have limited uses. Nonmetals like
cement are used in construction while salt is used as a food additive
and on roads in the winter. Soda ash, phosphate rock, and potash also
have a wide variety of commercial uses. Stone and sand and gravel are
used in numerous industries including the construction of roads and
buildings.
A detailed economic picture of the metal and nonmetal mining
industry is difficult to develop because most mines are either
privately held corporations or sole proprietorships, or subsidiaries of
publicly owned companies. Privately held corporations and sole
proprietorships do not make their financial data available to the
public. Further, parent companies are not required to separate
financial data for subsidiaries in their reports to the Securities and
Exchange Commission. As a result, financial data are available for only
a few metal and nonmetal companies and these data are not
representative of the entire industry. Each commodity has a unique
market demand structure. The following discussion focuses on market
forces on a few specific commodities of the metal and nonmetal
industry.
Metal Mining
Historically, the value of metals production has exhibited
considerable instability. In the early 1980's, excess capacity, large
inventories, and weak demand depressed the international market for
metals while the strong dollar placed U.S. producers at a competitive
disadvantage with foreign producers. Reacting to this, many metal
mining companies reduced work forces, eliminated marginal facilities,
sold non-core businesses, and restructured. At the same time, new
mining technologies were developed and wage increases were restrained.
As a result, the metal mining firms now operating are more efficient
and have lower break-even prices than those that operated in the
1970's.
For the purposes of this analysis, MSHA uses the Standard and
Poor's methodology of dividing metal mining into two categories: iron
ore and alloying metals, and copper and precious metals. Metal mine
production is valued in excess of $13 billion. Copper, aluminum, gold,
and iron are the highest revenue producers of the metal industry.
Variations in the prices for iron and alloying metals, such as
nickel, aluminum, molybdenum, vanadium, platinum, and lead, coincide
closely with fluctuations in the market for durable goods, such as
vehicles and heavy duty equipment. As a result, the market for these
metals is cyclical in nature and is impacted directly by changes in
aggregate demand and the economy in general.
Both nickel and aluminum have experienced strong price fluctuations
over the past few years; however, with the U.S. and world economies
improving, demand for such alloys is improving and prices have begun to
recover. It must be noted that primary production of aluminum will
continue to be impacted by the push to recycle. Recycling of aluminum
now accounts for 30% of the aluminum used and this percent is expected
to rise in the coming years. Due to the increase in aluminum recycling,
prices have been falling and inventories rising since the mid to late
1980's.
The market for copper and precious metals, such as gold and silver,
is marked by great uncertainty and price volatility. Prices for gold
and silver fluctuated by as much as 17 to 25%, respectively, during
1993. The copper market recovered substantially during
[[Page 66453]]
1994, posting a 3.7% growth in demand by 1995. The gold and silver
markets, however, continue to be marred with speculative demand spurs;
consistent recovery and growth have been difficult to achieve due to
uncertainty of U.S. buyers and shifts in production in South Africa and
Russia. In 1993, Russia began to cut back its gold production which had
generated low prices in the global market since 1990.
Overall, the production from metal mining increased by about 5.5%
from 1987 to 1995; 1995 estimates put capacity utilization at 84%. MSHA
expects that the net result for the metal mining industry may be
reduced demand but sustained prices. The 1993 average profit as a
percent of revenue for the metal mining industry was about a 1.3% loss
after taxes.
Nonmetal Mining, Including Stone and Sand and Gravel
Nonmetal mine production is valued at more than $24 billion.
Included in this figure is the production of granite, limestone,
marble, slate, and other forms of crushed and broken or dimension
stone. Other prosperous commodities in the nonmetal category include
salt, clay, phosphate rock, and soda ash. Market demand for these
products tends not to vary greatly with fluctuations in aggregate
demand. Stone is the leading revenue generator with 1994 production
valued at $7.2 billion. Construction sand and gravel and industrial
sand 1995 production is valued at about $4.3 billion.
Evaluating financial information for nonmetal mining operations is
particularly difficult. Financial data are available only for
relatively large mining operations and these often engage in a wide
variety of activities of which mining is typically only a small part.
Many large mining firms have financial interests in mines or mills of
different commodities, thereby making it difficult to evaluate the
financial aspects of any specific commodity. Publicly held firms are
not required to separate financial data for their subsidiaries in their
reports to the Securities and Exchange Commission and financial data
are not available for most of the small mines because they are not
publicly owned. (About 98% of the small metal and nonmetal mining
operations are stone, sand and gravel, or other nonmetal operations.)
This discussion of the economic characteristics of the nonmetal mining
industry does not separately address sand and gravel, stone, and
miscellaneous other nonmetal mining operations as was done in the
discussion of the nonmetal mining industry's structure.
Sand and gravel and stone products, including cement, have a
cyclical demand structure. As a recession intensifies, demand for these
products sharply decreases. Some stability in the market was achieved
during 1993 and early 1994. Demand for stone, particularly cement, is
expected to grow by as much as 4.8% and demand for sand and gravel is
expected to grow by as much as 2.3%.
The U.S. is the largest soda ash producer in the world with its
1994 production valued at about $650 million. Soda ash is used in the
production of glass, soap and detergents, paper, and food. Both salt
and soda ash have a fairly constant demand structure due to the
products' uses and the lack of suitable substitutes. A 1994 industry
analysis indicates shifts in the world demand for salt. European
demand, impelled by the economic breakdown of Central and Eastern
Europe, has declined; however, growth in demand has increased in Asia
and the Far East.
Phosphate rock, which is used primarily to manufacture fertilizer,
has an unusual market structure. U.S. production and exports of
phosphate rock have declined in recent years and imports from Morocco
increased by 180% from 1991 to 1992.
The remaining nonmetal commodities which include boron fluorspar,
oil shale, and other minerals are produced typically by a small number
of mining operations. Despite this fact, annual production of pumice,
perlite, vermiculite, and some others is valued at the tens of millions
of dollars for each product.
Overall, the production from nonmetal mining remained relatively
stable from 1987 to 1995; 1995 estimates put capacity utilization for
stone and earth minerals at about 97%. The net result for the nonmetal
mining industry may be higher demand for stone and various other
commodities and increased prices. The 1993 average profit as a percent
of revenue was about 3-4% for nonmetal mine production, excluding stone
and sand and gravel; about 8% for stone mining; and about 5% for sand
and gravel.
Feasibility of Requiring the Use of Engineering and Administrative
Controls at a TWA8 of 90 dBA
In this proposal, MSHA has determined that the Mine Act's objective
to protect miners from material impairment of health can be met by
requiring mine operators to use all feasible engineering and
administrative controls. This approach is close to that already
required in the metal and nonmetal sector of the industry. In the coal
sector, attenuation of hearing protectors have been considered in
determining compliance with the PEL, and in practice this has meant
that few mine operators have had to institute engineering or
administrative controls.
The approach gives mine operators flexibility to choose those
controls or combinations of controls which would be the most effective
in reducing exposure to noise. If the institution of administrative
controls does not adequately protect the miners in a given work
situation, MSHA will require the implementation of feasible engineering
controls. Under this approach, the Agency has to determine in the
particular situation that the proposed engineering controls are
feasible prior to requiring their implementation. Likewise, if the
engineering controls prove inadequate, the Agency will require the
implementation of feasible administrative controls.
In the metal and nonmetal industry where this approach is currently
implemented, smaller operations predominate. As a result,
administrative controls are seldom feasible, and engineering controls
may not be economically feasible for some operations. Moreover, given
the technology available in this sector, in a few cases complete
engineering solutions may not be technologically feasible. However
based on the information on available controls reviewed in part III,
including methods developed by the former Bureau of Mines, MSHA
believes there are few cases in which noise cannot be significantly
reduced through some sort of engineering control (including miner
isolation). The Agency has specifically solicited comments on the
feasibility of controls for metal and nonmetal equipment and operations
identified as generating sound levels above a TWA8 of 105 dBA; as
noted in part III, exposures exceeding this level constitute less than
one-quarter of one percent of all exposures, and many mine operators do
manage to control the exposures from such equipment. And the Agency
welcomes comments on other specific feasibility concerns. Based on its
review, MSHA believes most metal and nonmetal mine operators will find
feasible engineering controls that meet their requirements.
In the coal industry, many mine operators are larger and the
technology is different. Many coal mine operators are large enough to
be able to use administrative controls where engineering controls are
not economically feasible. Moreover, based
[[Page 66454]]
on the information reviewed in part III, MSHA is confident that
engineering solutions are available that can significantly reduce noise
in almost all situations in which coal mining noise exceeds the PEL.
Moreover, the Agency notes that the available engineering solutions are
constantly changing--for example, it may be easier today than it used
to be to find retrofit cabs for older equipment. Even in problem areas
like coal preparation plants and highwall areas there are available
solutions. In coal preparation plants, motor enclosures, operator
control booths, material dampening of chutes and transfer points, and
process area enclosures can bring about significant reductions in
exposure; for highwall areas, exhaust mufflers and compressor barriers
can do the same. The Agency would be interested in comments on problems
encountered in controlling noise in coal operations and on solutions
that have proved effective.
In concluding that such requirements are feasible in the mining
industry, MSHA takes into account that the proposed rule would require
a mine operator to use all feasible engineering and administrative
controls. On the one hand this means that MSHA will require mine
operators to consider all possible controls so as to find a combination
that will in fact reduce noise as much as possible. MSHA's enforcement
policy in this regard has been noted earlier in this section (and in
the Question and Answer section in part I). On the other hand, there
may be situations where no combination of engineering and
administrative controls to reduce exposures to the PEL is economically
or technologically feasible. In such cases, the proposed standard
specifies the other actions a mine operator must take to protect
workers to the maximum extent possible--including the use of
engineering and administrative controls to reduce exposures to the
maximum extent that is feasible.
Following is further discussion of the feasibility of
administrative controls and engineering controls, respectively.
Feasibility of Administrative Controls
Administrative controls refers to the practice of limiting the
exposure of individual miners to a noise source. Administrative
controls reduce exposure through such actions as rotation of miners to
areas having lower sound levels, rescheduling of tasks, modifying work
activities, or limiting the amount of time that a miner is exposed to
noise.
The feasibility of administrative controls to solve particular
noise problems in any mine may be limited by a number of factors:
limitations on the number of qualified miners capable of handling a
specific task, labor/management agreements affecting duty assignments,
or difficulty in ensuring that miners adhere to the administrative
controls. Further, because the effectiveness of administrative controls
is based on adherence to these strict time periods, mine operators may
find it difficult to verify compliance with the administrative
procedures.
As explained in the discussion of proposed Sec. 62.120(c), it is
MSHA's experience that administrative controls are relatively more
feasible for mines with many employees and relatively less feasible for
mines with fewer employees. As demonstrated by the industry profile,
the mines in the coal industry are generally larger mines. It is MSHA's
experience that many coal mine operators may prefer administrative
controls as the primary noise control. This is, in fact, the reasons
proposed Sec. 62.120(c) was designed to preserve mine operator choice.
The use of such controls is much less feasible in the smaller mines
that characterize the metal and nonmetal industry.
Feasibility of Engineering Controls
If administrative controls are not feasible, or cannot by
themselves reduce noise to the PEL, mine operators are to use all
feasible engineering controls. This discussion is divided into two
parts: the technological feasibility of such controls, and the economic
feasibility of such controls.
Technological Feasibility of Engineering Controls
MSHA is an active and knowledgeable partner in continually refining
and improving existing noise control technology. At the request of
MSHA's Coal Mine Safety and Health or Metal and Nonmetal Mine Safety
and Health, MSHA's Technical Support actively assists mine operators in
developing noise controls. Based upon this knowledge, and MSHA's
experience, the Agency has determined that feasible engineering
controls exist for the majority of equipment used in mining.
MSHA has evaluated under actual mining conditions newly developed
noise controls for surface self-propelled equipment, underground diesel
powered haulage equipment, jumbo drills, track drills, hand-held
percussive drills, draglines/shovels, portable crushers, channel
burners, and mills, and has found them to be effective in reducing
miners' noise exposure. Some of these feasible engineering controls are
already designed into new equipment. In many cases, effective and
feasible controls are available through retrofitting or the proper use
of noise barriers. A more detailed discussion regarding the
availability of these controls is contained in part III of this
preamble (see Engineering Noise Controls for Mining Equipment, in the
discussion of proposed Sec. 62.120(c) in part III). Part V of this
preamble contains a list of publications of the former USBOM evaluating
noise controls for various types of mining equipment.
As noted previously, there are some instances where current noise
control technology still cannot reduce sound levels to within a
TWA8 of 90 dBA and where quieter replacement equipment may not be
feasible. An example of this is a pneumatic jackleg drill used in
hardrock mining. MSHA's data on equipment producing high levels of
noise are discussed in part III (see the discussion of a possible dose
ceiling in proposed Sec. 62.120(e)).
Economic Feasibility of Engineering Controls
The data from MSHA's dual-threshold survey, presented in Tables II-
11 and II-12 in part II of this preamble, indicate that even with the
proposed new threshold level (80 dBA), almost three-quarters of the
metal and nonmetal samples, and almost two-thirds of the coal samples,
already are below the PEL. No additional controls would be required in
these cases.
The Agency has determined that the incremental costs of the
requirements for engineering controls would be $3.5 million a year for
ten years, of which $2.2 million is allocable to the coal sector and
$1.3 million to the metal and nonmetal sector. (The additional costs to
the metal and nonmetal sector reflect in part the proposed lowering of
the threshold, which will result in the measurement of more
overexposures than at present.)
As described in more detail in the Agency's preliminary RIA, to
calculate the costs for engineering controls, MSHA evaluated various
engineering controls and their related costs.
In determining which engineering controls the metal and nonmetal
industry will have to use under the proposed rule, MSHA considered the
engineering controls that are used under the current rule. MSHA
believes that metal and nonmetal mine operators may generally have
exhausted the least costly engineering controls to comply with the
current rule for some job groups. Compliance with the proposed rule for
these job groups would require
[[Page 66455]]
that the mine operator use more expensive controls--specifically,
retrofitting equipment--or purchase new equipment. For other job
groups, however, mine operators may have used only those controls
necessary to comply with the PEL and the less costly controls may still
be available. To determine the cost of engineering controls, MSHA
looked at the average cost of such engineering controls.
For the coal industry, HPDs have generally been substituted for
engineering and administrative controls, so the industry has not
exhausted the use of relatively inexpensive controls which have been
demonstrated to be capable of bringing about significant reductions of
sound levels. Even though the average cost of such controls would be
less than for the metal and nonmetal industry, the change in approach
would require controls be used much more often than at present. This is
why the industry would experience a relatively higher expense for
engineering controls.
MSHA believes the requirements for engineering and administrative
controls clearly meet the feasibility requirements of the law. Based on
the comments received in response to its ANPRM and discussed below,
MSHA believes some in the industry may misunderstand the nature of the
engineering controls required. In many cases, inexpensive controls may
effectively eliminate overexposures.
Comments on Feasibility of Engineering and Administrative Controls
MSHA received numerous comments indicating that engineering
controls were not feasible to reduce a miner's noise exposure to within
the PEL for many types of mining equipment. Several commenters stated
that engineering controls are most effective when they are designed
into equipment versus applied by retrofitting. Other commenters stated
that retrofit noise controls are often not as durable or effective as
controls installed by the equipment manufacturer. One commenter
suggested that MSHA establish approval and certification procedures for
equipment noise emissions, similar to those established in part 18 for
permissible equipment used in gassy mines.
In response to the commenters who indicated that engineering
controls were not feasible for many types of mining equipment, MSHA
would point out that significant progress has been made in developing
quieter mining equipment since the mid-1970's when MSHA's existing
noise standards were promulgated. Currently, almost all pneumatic drill
manufacturers offer exhaust mufflers where few were available in the
early 1970's. Similarly, almost all manufacturers of mobile surface
equipment offer environmental and/or acoustically treated cabs. Some
manufacturers also offer acoustically treated cabs for underground
mining equipment, such as jumbo drills and scoop trams. As noted, the
availability of feasible engineering noise controls is discussed in
greater detail in the section of the preamble on Engineering Noise
Controls for Mining Equipment.
MSHA does not agree with the commenter who suggested that MSHA
establish approval and certification for equipment noise emissions
similar to part 18. Such a process could be more costly and limit a
mine operator's flexibility in implementing noise control procedures.
The most cited disadvantage of engineering controls is cost. In
particular, some commenters are concerned that they would be required
to install controls that would not, by themselves, be adequate to
attain compliance. If this occurs, the proposal would also require that
administrative controls be used to reduce exposure to the PEL;
moreover, if a combination of controls does not reduce exposures to the
PEL, hearing protectors must be worn and the affected miners enrolled
in an HCP. These commenters believe that in such cases, costs to
install engineering controls are wasted since they still may have to
resort to these additional controls. More significantly, mine operators
are concerned that requiring engineering controls will usually require
the purchase of new equipment.
The first concern is misplaced. Controlling noise requires the
hierarchy of requirements proposed by Sec. 62.120(c). A mine operator
has a choice as to what mix of engineering and administrative controls
to use as long as together they reduce noise exposures to the PEL or as
close thereto as feasible. Hearing protectors and enrollment in a
hearing conservation program are helpful when nothing more can feasibly
be done to reduce noise exposure, but they are not a substitute.
MSHA generally agrees with the commenters who stated that
engineering controls are most effective when factory installed. The
Agency would encourage mine operators to purchase mining machinery
equipped with appropriate noise controls offered by the original
equipment manufacturer rather than retrofitting noise controls. Almost
every piece of mining equipment currently manufactured has optional
noise control packages. Based on comments and MSHA's experience in
noise control, the Agency has concluded that engineering controls
designed and installed by the manufacturer for a particular unit will
generally be more effective and durable than a retrofit control of
similar design. Additionally, the cost of such controls may in some
cases be substantially higher if it is purchased from the equipment
manufacturer on a retrofit basis, rather than at the time the unit was
originally built.
At the same time, as discussed in part III, MSHA has determined
that some retrofit controls may be as effective as controls offered by
equipment manufacturers. Examples of engineering controls which are
routinely retrofitted onto existing mining equipment include:
environmental cabs; control booths; sound barriers and baffles; exhaust
mufflers; and the application of acoustical materials to equipment
firewalls and the inside walls of cabs and control booths. Moreover,
many successful retrofit noise controls (e.g., cabs, barrier shields,
and drill exhaust mufflers) were developed by operators using materials
readily available. Often the miners who use the equipment offer
valuable suggestions on improving the design and effectiveness of these
controls. Some of the controls developed by the mine operators have
been adopted by manufacturers for use on both existing and new
equipment. MSHA has determined that allowing the mine operator to
develop controls provides the mine operator with maximum flexibility in
complying with the standard thereby eliminating the need in those cases
to purchase manufacturer installed controls.
Infeasibility of PEL at TWA8 of 85 dBA
MSHA seriously considered lowering the PEL to a TWA8 of 85 dBA
because of its conclusion that there is a significant risk of material
impairment from noise exposures at or above this level. The Agency has
tentatively concluded, however, that it may not be feasible at this
time for the mining industry to reduce noise to that level.
Exposure data collected by MSHA indicate that with a PEL at a
TWA8 of 85 dBA and an 80 dBA threshold, over two-thirds of the
mine operators in the metal and nonmetal industry, and over three-
quarters of the mine operators in the coal industry, would need to use
engineering and administrative controls to reduce current exposures.
(See Tables II-11 and II-12 in part II.)
Moreover, the engineering controls needed to reduce those exposures
would be more expensive, because they would have to reduce the
exposures further than with a PEL set at a TWA8 of 90 dBA.
Accordingly, the Agency
[[Page 66456]]
does not believe it can demonstrate that a reasonable probability
exists that the typical mine operator will currently be able to develop
and install controls that will meet such a standard.
It is true that the proposed standard only requires that individual
mine operators use those controls which are feasible for that mine
operator. The feasibility requirement under the statute, however, is
that the Agency make a reasonable prediction, based on the ``best
available evidence,'' as to whether an industry can generally comply
with a standard within an allotted period of time. The Agency must show
that a reasonable probability exists that the typical mine operator
will be able to develop and install controls that will meet the
standard. Accordingly, MSHA believes that if most mine operators are
unlikely to be able to use engineering and administrative controls to
bring noise levels to a TWA8 of 85 dBA, the standard is not
feasible for the industry as a whole.
Infeasibility of Exchange Rate of 3-dB
The exchange rate is a measure of how quickly the dose of noise
doubles. Accordingly, the measure is the rate determining how much a
miner's exposure must be limited to compensate for increasing dose. For
example, at a 5-dB exchange rate, the exposure permitted at a sound
level of 90 dBA is half that permitted at a sound level of 85 dBA; a
miner gets the same noise dose in 4 hours at 90 dBA as at 8 hours at 85
dBA.
The Agency gave serious consideration to changing the exchange rate
from 5-dB to 3-dB, and is specifically seeking comment on this
important matter. There is a consensus in the recent literature that
noise dose actually doubles more quickly than measured by the 5-dB
rate, and in particular consensus for an exchange rate of 3-dB.
Moreover, MSHA has concluded that the type of noise exposure in the
mining environment tends to warrant an exchange rate that does not
assume significant time for hearing to recover from high sound levels--
the current exchange rate incorporates such an assumption. A full
discussion of the scientific merits of various exchange rates, and of
the rates used by various regulatory authorities, can be found in part
III of the Preamble (as part of the discussion of proposed
Sec. 62.120(a), dose determination).
Nevertheless, the Agency is proposing to retain the existing 5-dB
exchange rate because of feasibility considerations. Changing to a 3-dB
rate from a 5-dB rate would significantly reduce the amount of time
that miners could be exposed to higher sound levels without exceeding
the permissible exposure limit. For example, MSHA estimates that the
percentage of miners whose exposure would be in violation of a PEL set
at a TWA8 of 90 dBA would about double if a 3-dB exchange rate is
used. (See Table III-3 in the exchange rate discussion in part III. The
table also indicates what would happen if the PEL were set at a
TWA8 of 85 dBA). This means mine operators would have to utilize
controls to reduce exposures to the PEL more frequently. Moreover, more
expensive controls would often be required, since the need to reduce
exposures more to get them down to the PEL.
The feasibility requirement under the statute is that the Agency
make a reasonable prediction, based on the ``best available evidence,''
as to whether an industry can generally comply with a standard within
an allotted period of time. The Agency must show that a reasonable
probability exists that the typical mine operator will be able to
develop and install controls that will meet the standard. The exposure
data noted indicate it may be difficult for MSHA to make such a
showing.
Furthermore, if a 3-dB exchange rate is used, it is extremely
difficult to reduce the noise exposures to below the PEL with currently
available engineering or administrative noise controls or a combination
thereof.
Accordingly, MSHA has tentatively concluded that moving the
industry to a 3-dB exchange rate may not be feasible at this time.
Conclusion
Based on the information before it, the Agency has tentatively
concluded that the proposed rule meets the statutory requirements for
feasibility, and that it may not be feasible for the mining industry,
as a whole, at this time, to require a more protective regimen.
The Agency is particularly interested in receiving additional data
that would be relevant in making final determinations on the points
discussed above.
V. References
``A Code of Practice for Noise Control in the Workplace,'' Occupational
Health, Safety and Welfare Commission on Western Australia, August
1991.
Abel, Sharon M. and Caroline A. Haythornthwaite, ``The Progression of
Noise-Induced Hearing Loss,'' Journal of Otolaryngology, 13:1-36, 1984.
Abel, Sharon M., ``Noise-Induced Hearing Loss and Hearing Protective
Devices,'' Canadian Journal of Public Health, 77(1):104-107, May-June
1986.
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[[Page 66464]]
Florida, May 1-4, 1994, pp. 1017-1022.
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in Mine Noise Regulations on Longwall Mining,'' Paper presented at
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1992, pp. 43-50.
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Annual Meeting, Phoenix, Arizona, February 24-27, 1992, pp. 279-285.
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List of Subjects
30 CFR Parts 56 and 57
Metal and nonmetal, Mine safety and health, Noise.
30 CFR Part 62
Mine safety and health, Noise.
30 CFR Parts 70 and 71
Coal, Mine safety and health, Noise.
[[Page 66465]]
Dated: November 26, 1996.
J. Davitt McAteer,
Assistant Secretary for Mine Safety and Health.
It is proposed to amend Chapter I of Title 30 of the Code of
Federal Regulations as follows:
PART 56--[AMENDED]
1. The authority citation for part 56 continues to read as follows:
Authority: 30 U.S.C. 811, 957, 961.
2. Section 56.5050 and the undesignated center heading preceding it
are removed.
PART 57--[AMENDED]
3. The authority citation for part 57 continues to read as follows:
Authority: 30 U.S.C. 811, 957, 961.
4. Section 57.5050 and the undesignated center heading preceding it
are removed.
PART 70--[AMENDED]
5. The authority citation for part 70 continues to read as follows:
Authority: 30 U.S.C. 811 and 961.
6. Subpart F (Secs. 70.500-70.511) is removed.
PART 71--[AMENDED]
7. The authority citation for part 71 continues to read as follows:
Authority: 30 U.S.C. 811, 951, 957, 961.
8. Subpart I (Secs. 71.800-71.805) is removed.
9. Subchapter M is redesignated as subchapter I, subchapter N is
redesignated as subchapter K, and Subchapter N is reserved.
10. A new Subchapter M is added, ``Uniform Mine Health
Regulations.''
11. A new part 62 is added to new Subchapter M to read as follows:
PART 62--OCCUPATIONAL NOISE EXPOSURE
Sec.
62.100 Purpose and scope; effective date.
62.110 Definitions.
62.120 Limitations on noise exposure.
62.125 Hearing protectors.
62.130 Training.
62.140 Audiometric testing program.
62.150 Audiometric test procedures.
62.160 Evaluation of audiogram.
62.170 Follow-up evaluation when audiogram invalid.
62.180 Follow-up corrective measures when STS detected.
62.190 Notification of results; reporting requirements.
62.200 Access to records.
62.210 Transfer of records.
Authority: 30 U.S.C. 811, 857, 861.
Sec. 62.100 Purpose and scope; effective date.
The purpose of these standards is the prevention of occupational
noise-induced hearing loss among miners. This part sets forth mandatory
health standards for each surface and underground metal, nonmetal, and
coal mine subject to the Federal Mine Safety and Health Act of 1977.
The provisions of this part shall take effect (one year from the date
of publication of the final rule).
Sec. 62.110 Definitions.
The following definitions apply in this part:
Access. The right to examine and copy records.
Audiologist. A professional, specializing in the study and
rehabilitation of hearing, who is certified by the American Speech-
Language-Hearing Association (ASHA) or licensed by a state board of
examiners.
Baseline audiogram. The audiogram recorded pursuant to Sec. 62.140
against which subsequent audiograms are compared to determine the
extent of hearing loss, except in those specific situations in which
this part requires the use of a supplemental baseline audiogram for
such a purpose.
Criterion level. The sound level which if constantly applied for 8
hours results in a dose of 100% of that permitted by the standard.
Decibel (dB). A unit of measure of sound levels. MSHA defines
decibel in two different ways depending upon the use.
(1) For measuring sound pressure levels, the decibel is 20 times
the common logarithm of the ratio of the measured sound pressure to the
standard reference pressure of 20 micropascals (Pa), which is
the threshold of normal hearing acuity at 1000 Hz.
(2) For measuring hearing threshold levels, the decibel is the
difference between audiometric zero (reference pressure equal to 0
hearing threshold level) and the threshold of hearing of the individual
being tested at each test frequency.
Decibel, A-weighted (dBA). Sound levels measured using the A-
weighting network. A-weighting refers to the frequency response network
closely corresponding to the frequency response of the human ear. This
network attenuates sound energy in the lower and upper frequencies
(<1000 and >5000 Hz) and slightly amplifies those frequencies between
1000 and 5000 Hz to which the ear is more sensitive.
Designated representative. Any individual or organization to whom a
miner gives written authorization to exercise a right of access to
records.
Exchange rate. The amount of increase in sound level, in decibels,
which would require halving of the allowable exposure time to maintain
the same noise dose.
Hearing conservation program (HCP). The term is used in this part
as a generic reference to the requirements of Secs. 62.140 through
62.190, such as audiometric testing, evaluation and follow-up
examinations.
Hearing protector. Any device or material, capable of being worn on
the head or in the ear canal, sold wholly or in part on the basis of
its ability to reduce the level of sound entering the ear, and that has
a scientifically accepted indicator of noise reduction value.
Hertz (Hz). Unit of measurement of frequency numerically equal to
cycles per second. The audible range of frequencies for humans with
normal hearing is 20 to 20000 Hz.
Medical pathology. A condition or disease affecting the ear.
Qualified technician. A technician who has been certified by the
Council for Accreditation in Occupational Hearing Conservation (CAOHC)
or by another recognized organization offering equivalent
certification.
Reportable hearing loss. A change in hearing acuity for the worse,
relative to the miner's baseline audiogram or, in the case of a
supplemental baseline audiogram established pursuant to
Sec. 62.140(d)(2), relative to such supplemental baseline audiogram, of
an average of 25 dB or more at 2000, 3000, and 4000 Hz in either ear.
Sound level. The sound pressure level measured in decibels using a
weighting network (e.g., A-weighted) and exponential time averaging
(e.g., slow response). The A-weighting network and the slow response
time are defined in ANSI S1.4-1983, ``American National Standard
Specification for Sound Level Meters.''
Standard threshold shift (STS). A change in hearing acuity for the
worse relative to the miner's baseline audiogram, or relative to the
most recent supplemental baseline audiogram where one has been
established, of an average of 10 dB or more at 2000, 3000, and 4000 Hz
in either ear.
Supplemental baseline audiogram. An annual audiogram designated, as
a result of the circumstances set forth in Sec. 62.140(d)(1) or those
set forth in Sec. 62.140(d)(2), to be utilized in lieu of a miner's
original baseline audiogram in measuring changes in hearing acuity.
[[Page 66466]]
Time-weighted average-8 hour (TWA8). That sound level, which
if constant over 8 hours, would result in the same noise dose as is
measured.
Sec. 62.120 Limitations on noise exposure.
(a) Dose determination.
(1) A miner's noise dose (D) is computed by the formula: D =
100(C1/T1 + C2/T2 + * * * + Cn/Tn), where
Cn is the total time of exposure at a specified sound level, and
Tn is the reference duration of exposure at that sound level set
forth in Table 62-1.
(2) Table 62-2 is to be utilized when converting noise measurements
from dosage readings to equivalent TWA8 readings.
Table 62-1.--Reference Duration
------------------------------------------------------------------------
Reference
L (dBA, slow-response sound level) Duration, T
(hour)
------------------------------------------------------------------------
85......................................................... 16.0
86......................................................... 13.9
87......................................................... 12.1
88......................................................... 10.6
89......................................................... 9.2
90......................................................... 8.0
91......................................................... 7.0
92......................................................... 6.1
93......................................................... 5.3
94......................................................... 4.6
95......................................................... 4.0
96......................................................... 3.5
97......................................................... 3.0
98......................................................... 2.6
99......................................................... 2.3
100........................................................ 2.0
101........................................................ 1.7
102........................................................ 1.5
103........................................................ 1.3
104........................................................ 1.1
105........................................................ 1.0
106........................................................ 0.87
107........................................................ 0.76
108........................................................ 0.66
109........................................................ 0.57
110........................................................ 0.50
111........................................................ 0.44
112........................................................ 0.38
113........................................................ 0.33
114........................................................ 0.29
115........................................................ 0.25
------------------------------------------------------------------------
Note: For any value, the reference duration (T) in hours is computed by:
T = 8/2(L-90)/5, where L is the measured A-weighted, slow-response
sound level.
Table 62-2.--Conversion From ``Dose'' to Equivalent TWA8
------------------------------------------------------------------------
Dose (percent noise exposure) TWA8
------------------------------------------------------------------------
25......................................................... 80.0
29......................................................... 81.0
33......................................................... 82.0
38......................................................... 83.0
44......................................................... 84.0
50......................................................... 85.0
57......................................................... 86.0
66......................................................... 87.0
76......................................................... 88.0
87......................................................... 89.0
100........................................................ 90.0
115........................................................ 91.0
132........................................................ 92.0
152........................................................ 93.0
174........................................................ 94.0
200........................................................ 95.0
230........................................................ 96.0
264........................................................ 97.0
303........................................................ 98.0
350........................................................ 99.0
400........................................................ 100.0
460........................................................ 101.0
530........................................................ 102.0
610........................................................ 103.0
700........................................................ 104.0
800........................................................ 105.0
920........................................................ 106.0
1056....................................................... 107.0
1213....................................................... 108.0
1393....................................................... 109.0
1600....................................................... 110.0
1838....................................................... 111.0
2111....................................................... 112.0
2425....................................................... 113.0
2786....................................................... 114.0
3200....................................................... 115.0
3676....................................................... 116.0
4222....................................................... 117.0
4850....................................................... 118.0
5572....................................................... 119.0
6400....................................................... 120.0
------------------------------------------------------------------------
Interpolate between the values found in this Table, or extend the table,
by using the formula: TWA8 = 16.61 log10 (D/100) + 90.
(3) A miner's noise exposure measurement shall:
(i) Not be adjusted on account of the use of any hearing protector;
(ii) Integrate all sound levels from 80 dBA to at least 130 dBA
during the miner's full workshift;
(iii) Use a 90 dBA criterion level and a 5-dB exchange rate; and
(iv) Use an A-weighting and a slow-response instrument setting.
(b) Action level. When a miner's noise exposure exceeds a TWA8
of 85 dBA during any workshift, or equivalently a dose of 50%, the
operator shall take the actions specified in paragraphs (b)(1) and (2)
of this section and, at the request of the miner, also take the actions
specified in paragraph (b)(3) of this section.
(1) An operator shall provide the miner training that includes the
instruction required by Sec. 62.130, at the time exposure exceeds the
action level and every 12 months thereafter that exposure continues to
exceed the action level.
(2) An operator shall enroll the miner in a hearing conservation
program which shall meet the requirements of Secs. 62.140 through
62.190. Moreover, the operator shall, with respect to any miner
enrolled in such program, provide hearing protection in accordance with
the requirements of Sec. 62.125 until such time as a baseline audiogram
has been obtained. If it takes more than 6 months to conduct the
baseline audiogram, or if the miner is determined to have incurred an
STS, the operator shall ensure that the hearing protection is provided
to the miner and worn by the miner.
(3) At the request of any miner, the operator shall provide hearing
protection to the miner in accordance with the requirements of
Sec. 62.125.
(c) Permissible exposure level (PEL). No miner shall be exposed to
noise exceeding a TWA8 of 90 dBA (PEL) during any workshift, or
equivalently a dose of 100%.
(1) If a miner's noise exposure exceeds the PEL, the operator
shall, in addition to taking the actions required under paragraph (b)
of this section, use all feasible engineering and administrative
controls to reduce the miner's noise exposure to the PEL. When
administrative controls are used to reduce a miner's exposure, the
operator shall post these procedures on the mine bulletin board and
provide a copy to affected miners.
(2) If a miner's noise exposure exceeds the PEL despite the use of
the controls required by paragraph (c)(1) of this section, the operator
shall take the actions required by this paragraph for that miner.
(i) The operator shall use the controls required by paragraph
(c)(1) of this section to reduce the miner's noise exposure to as low a
level as is feasible.
(ii) The operator shall ensure that a miner whose exposure exceeds
the PEL takes the hearing examinations offered through enrollment in
the hearing conservation program.
(iii) The operator shall provide hearing protection to a miner
whose exposure exceeds the PEL and shall ensure the use thereof. The
hearing protection shall be provided and used in accordance with the
requirements of Sec. 62.125.
(d) Dual hearing protection level. Whenever a miner's noise
exposure exceeds a TWA8 of 105 dBA during any workshift, or
equivalently a dose of 800%, the operator shall ensure that the miner
is provided and uses both ear plug and ear muff type protectors
pursuant to Sec. 62.125.
(e) Ceiling level. At no time shall a miner be exposed to sound
levels exceeding 115 dBA.
[[Page 66467]]
(f) Operator exposure evaluation; employee notification.
(1) Operators shall establish a system of monitoring which
effectively evaluates each miner's noise exposure.
(2) Whenever a miner's exposure is determined to exceed the action
level, the permissible exposure level, the dual hearing protection
level, or the ceiling level established by this section, according to
exposure evaluations conducted either by the operator or by
representatives of the Secretary of Labor, and the miner has not
received notification of exposure at such level within the prior 12
months, the operator shall, within 15 calendar days, notify the miner
in writing of the exposure determination and the corrective action
being taken. The operator shall maintain at the mine site a copy of any
such miner notification, or a list on which the relevant information
about that miner's notice is recorded, for the duration of the affected
miner's exposure above the action level and for at least 6 months
thereafter.
Sec. 62.125 Hearing protectors.
When hearing protection is required pursuant to this part, an
operator shall:
(a) Allow the miner, after such miner has received the training
specified by Sec. 62.130 at least once, to choose a hearing protector
from at least one muff type and one plug type, and in the event dual-
hearing protection is required, to choose one of each type;
(b) In those cases in which the operator is required to ensure the
use by a miner of hearing protection, ensure that the protector is worn
by the miner when exposed to sound levels which are required to be
integrated into a miner's noise exposure measurement;
(c) Ensure that the hearing protection is fitted and maintained in
accordance with the manufacturer's instructions;
(d) Provide the hearing protectors and necessary replacements at no
cost to the miner; and
(e) Allow the miner to choose a different hearing protector if
wearing the selected protector is subsequently precluded due to medical
pathology of the ear.
Sec. 62.130 Training.
(a) Miner training required by this part shall include the
following instruction:
(1) The effects of noise on hearing;
(2) The purpose and value of wearing hearing protectors;
(3) The advantages and disadvantages of the hearing protectors to
be offered;
(4) The care, fitting, and use of the hearing protector worn by the
miner and the various types of hearing protectors offered by the
operator;
(5) The general requirements of this part;
(6) The operator's and miner's respective tasks in maintaining mine
noise controls; and
(7) The purpose and value of audiometric testing and a summary of
the procedures.
(b) The training requirement under this part shall only be met if
the operator certifies the date and type of training given each miner.
The type of training may be initial noise training of a miner, annual
retraining of a miner, or special retraining required for a miner as a
result of the detection of an STS. The certification shall be signed by
the person conducting the training. The operator shall maintain the
miner's most recent certification at the mine site for as long as the
miner is exposed to noise above the level which required the training
and for at least 6 months thereafter.
Sec. 62.140 Audiometric testing program.
(a) Audiometric tests performed pursuant to this part shall be
conducted by a physician, an audiologist, or a qualified technician
under the direction or supervision of a physician or an audiologist,
and pursuant to the procedures set forth in Sec. 62.150.
(b) Baseline audiogram. A miner enrolled in a hearing conservation
program shall be offered a valid baseline audiogram of the miner's
hearing acuity against which subsequent annual audiograms can be
compared.
(1) The valid baseline audiogram shall be offered within 6 months
of enrolling the miner in an HCP, except that where mobile test vans
are used to meet the audiometric test requirements of this section, the
valid baseline audiogram shall be offered within 12 months of enrolling
the miner in an HCP. An existing audiogram of the miner's hearing
acuity may be used as the baseline audiogram if it meets the
audiometric testing requirements of this part.
(2) The operator shall not expose the miner to workplace noise for
at least 14 hours before conducting the baseline audiogram. Hearing
protectors shall not be used as a substitute for this quiet period.
(3) The operator shall notify miners of the need to avoid high
levels of noise during the 14-hour quiet period before taking the
baseline audiogram.
(4) The operator shall not revise either a miner's baseline
audiogram, or supplemental baseline audiogram where one has been
established, due to changes in enrollment status in the HCP except for
periods of unemployment exceeding 6 consecutive months.
(c) Annual audiogram. After establishing the baseline audiogram,
the operator shall offer a subsequent valid audiogram at intervals not
exceeding 12 months for as long as the miner remains in the HCP.
(d) Supplemental baseline audiogram. An annual audiogram shall be
deemed to be a supplemental baseline audiogram when, in the judgment of
the audiologist or physician:
(1) The standard threshold shift (STS) revealed by the audiogram is
permanent; or
(2) The hearing threshold shown in the annual audiogram indicates
significant improvement over the baseline audiogram.
Sec. 62.150 Audiometric test procedures.
(a) The operator shall assure that all audiometric testing required
under this part is conducted in accordance with scientifically
validated procedures. Audiometric tests shall be pure tone, air
conduction, hearing threshold examinations, with test frequencies
including as a minimum 500, 1000, 2000, 3000, 4000, and 6000 Hz. Each
ear shall be tested separately.
(b) The operator shall obtain from the physician, audiologist, or
qualified technician who conducts an audiometric test required under
this part, a certification that the testing was conducted in accordance
with paragraph (a) of this section.
(c) The operator shall compile an audiometric test record for each
miner tested. Such record shall include the following:
(1) Name and job classification of the miner who has undergone the
audiometric test(s);
(2) A copy of all of the miner's audiograms required under this
part;
(3) Certification(s) as required under paragraph (b) of this
section;
(4) Any exposure determination for the miner; and
(5) The results of any follow-up examination(s).
(d) Audiometric test records shall be maintained at the mine site
for the duration of the affected miner's employment plus at least 6
months.
Sec. 62.160 Evaluation of audiogram.
(a) The operator shall:
(1) Inform persons evaluating audiograms of the requirements of
this part and provide them with a copy of the miner's audiometric test
records;
(2) Have a physician, an audiologist, or a qualified technician who
is under the direction or supervision of a physician or audiologist:
(i) Determine if the audiogram is valid; and
[[Page 66468]]
(ii) Determine if an STS or a reportable hearing loss, as defined
in this part, has occurred;
(3) Instruct the physician or audiologist not to reveal to the
operator any specific findings or diagnoses unrelated to the miner's
exposure to noise or wearing of hearing protectors without the written
consent of the miner; and
(4) Obtain the results, and the interpretation of the results of
any audiogram conducted under this part within 30 calendar days of
conducting the audiogram.
(b)(1) The operator shall conduct an audiometric retest within 30
calendar days of receiving a determination that a required audiogram is
invalid and that any medical pathology has improved to the point that a
valid audiogram may be obtained.
(2) If the results of an annual audiogram demonstrate that the
miner has incurred an STS or reportable hearing loss, the operator may
conduct one retest within 30 calendar days of receiving the results of
the audiogram and consider the results of the retest as the annual
audiogram.
(c) In determining whether an STS or reportable hearing loss has
occurred, allowance may be made for the contribution of aging
(presbycusis) to the change in hearing level by adjusting the
audiograms used in making those determinations according to the
following procedures:
(1) Determine from Tables 62-3 or 62-4 the age correction values
for the miner by:
(i) Finding the age at which the baseline audiogram, or
supplemental baseline audiogram as appropriate, was taken, and
recording the corresponding values of age corrections at 2000, 3000,
and 4000 Hz; and
(ii) Finding the age at which the most recent audiogram was taken
and recording the corresponding values of age corrections at 2000,
3000, and 4000 Hz.
(2) Subtract the value determined in paragraph (c)(1)(i) of this
section from the value determined in paragraph (c)(1)(ii) of this
section. The differences calculated represent that portion of the
change in hearing that may be due to aging.
(3) Subtract the value determined in paragraph (c)(2) of this
section from the hearing threshold level found in the annual audiogram
to obtain the adjusted annual audiogram hearing threshold level.
(4) Subtract the hearing threshold in the baseline audiogram or
supplemental baseline audiogram from the adjusted annual audiogram
hearing threshold level determined in paragraph (c)(3) of this section
to obtain the age-corrected threshold shift.
Table 62-3.--Age Correction Value in Decibels for Males
------------------------------------------------------------------------
Audiometric test
frequencies (Hz)
Years --------------------------
2000 3000 4000
------------------------------------------------------------------------
20 or younger................................ 3 4 5
21........................................... 3 4 5
22........................................... 3 4 5
23........................................... 3 4 6
24........................................... 3 5 6
25........................................... 3 5 7
26........................................... 4 5 7
27........................................... 4 6 7
28........................................... 4 6 8
29........................................... 4 6 8
30........................................... 4 6 9
31........................................... 4 7 9
32........................................... 5 7 10
33........................................... 5 7 10
34........................................... 5 8 11
35........................................... 5 8 11
36........................................... 5 9 12
37........................................... 6 9 12
38........................................... 6 9 13
39........................................... 6 10 14
40........................................... 6 10 14
41........................................... 6 10 14
42........................................... 7 11 16
43........................................... 7 12 16
44........................................... 7 12 17
45........................................... 7 13 18
46........................................... 8 13 19
47........................................... 8 14 19
48........................................... 8 14 20
49........................................... 9 15 21
50........................................... 9 16 22
51........................................... 9 16 23
52........................................... 10 17 24
53........................................... 10 18 25
54........................................... 10 18 26
55........................................... 11 19 27
56........................................... 11 20 28
57........................................... 11 21 29
58........................................... 12 22 31
59........................................... 12 22 32
60 or older.................................. 13 23 33
------------------------------------------------------------------------
Table 62-4.--Age Correction Value in Decibels for Females
------------------------------------------------------------------------
Audiometric test
frequencies (Hz)
Years --------------------------
2000 3000 4000
------------------------------------------------------------------------
20 or younger................................ 4 3 3
21........................................... 4 4 3
22........................................... 4 4 4
23........................................... 5 4 4
24........................................... 5 4 4
25........................................... 5 4 4
26........................................... 5 5 4
27........................................... 5 5 5
28........................................... 5 5 5
29........................................... 5 5 5
30........................................... 6 5 5
31........................................... 6 6 5
32........................................... 6 6 6
33........................................... 6 6 6
34........................................... 6 6 6
35........................................... 6 7 7
36........................................... 7 7 7
37........................................... 7 7 7
38........................................... 7 7 7
39........................................... 7 8 8
40........................................... 7 8 8
41........................................... 8 8 8
42........................................... 8 9 9
43........................................... 8 9 9
44........................................... 8 9 9
45........................................... 8 10 10
46........................................... 9 10 10
47........................................... 9 10 11
48........................................... 9 11 11
49........................................... 9 11 11
50........................................... 10 11 12
51........................................... 10 12 12
52........................................... 10 12 13
53........................................... 10 13 13
54........................................... 11 13 14
55........................................... 11 14 14
56........................................... 11 14 15
57........................................... 11 15 15
58........................................... 12 15 16
59........................................... 12 16 16
60 or older.................................. 12 16 17
------------------------------------------------------------------------
Sec. 62.170 Follow-up evaluation when audiogram invalid.
(a) If a valid audiogram cannot be obtained due to a suspected
medical pathology of the ear which the physician or audiologist
believes was caused or aggravated by the miner's exposure to noise or
the wearing of hearing protectors, the operator shall refer the miner
for a clinical audiological evaluation or an otological examination, as
appropriate, at no cost to the miner.
(b) The operator shall instruct the physician or audiologist that
if a valid audiogram cannot be obtained due to a suspected medical
pathology of the ear which the physician or audiologist concludes is
unrelated to the miner's exposure to noise or the wearing of hearing
protectors, the physician or audiologist shall inform the miner of the
need for an otological examination.
(c) The operator shall instruct the physician or audiologist not to
reveal to the operator any specific findings or diagnoses unrelated to
the miner's exposure to noise or the wearing of hearing protectors
without the written consent of the miner.
[[Page 66469]]
Sec. 62.180 Follow-up corrective measures when STS detected.
Unless a physician or audiologist determines that an STS is neither
work-related nor aggravated by occupational noise exposure, the
operator shall within 30 calendar days of receiving evidence of an STS
or receiving the results of a retest confirming an STS:
(a) Retrain the miner, including the instruction required by
Sec. 62.130;
(b) Provide the miner with the opportunity to select a hearing
protector, or a different hearing protector if the miner has previously
selected a hearing protector, from among those offered by the operator
pursuant to Sec. 62.125; and
(c) Review the effectiveness of any engineering and administrative
controls to identify and correct any deficiencies.
Sec. 62.190 Notification of results; reporting requirements.
(a) Within 10 working days of receiving the results of an
audiogram, or receiving the results of a follow-up evaluation required
under Sec. 62.170(a), the operator shall notify the miner in writing
of:
(1) The results and interpretation of the audiometric test,
including any finding of an STS or reportable hearing loss; and
(2) If applicable, the need and reasons for any further testing or
evaluation.
(b) If evaluation of the audiogram shows that a miner has incurred
a reportable hearing loss as defined in this part, the operator shall
report such loss to MSHA as a noise-induced hearing loss in accordance
with part 50 of this title unless a physician or audiologist has
determined that the loss is neither work-related nor aggravated by
occupational noise exposure.
Sec. 62.200 Access to records.
(a) The authorized representatives of the Secretaries of Labor and
Health and Human Services shall have access to all records required
under this part. Upon written request, the operator shall provide,
within 15 calendar days of the request, access to records as indicated
below:
(1) The miner, former miner, or, with the miner's written consent,
the miner's designated representative shall have access to all records
that the operator is required to maintain for that individual miner
under this part; and
(2) The miners' representative shall in all cases have access to
training records compiled pursuant to section Sec. 62.130, and to
copies of notices made pursuant to Sec. 62.120(f)(2), for the miners
whom they represent.
(b) Upon termination of a miner's employment, the operator shall
provide the miner without cost with a copy of all records that the
operator is required to maintain for that individual miner under this
part.
(c) If a person who has access to certain records under this
section requests a copy of a record, the operator shall provide the
first copy of such record requested by a person at no cost to that
person, and any additional copies requested by that person at
reasonable cost.
Sec. 62.210 Transfer of records.
(a) Whenever an operator ceases to do business, that operator shall
transfer all records required to be maintained by this part, or a copy
thereof, to any successor operator who shall receive these records and
maintain them for the required period.
(b) The successor operator shall use the baseline audiogram, or
supplemental baseline audiogram as appropriate, obtained by the
original operator for determining the existence of an STS or reportable
hearing loss.
[FR Doc. 96-30733 Filed 12-16-96; 8:45 am]
BILLING CODE 4510-43-P