Health Standards for Occupational Noise Exposure
Federal RegisterSep 13, 1999
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SUMMARY: This final comprehensive rule replaces MSHA's existing
standards for occupational noise exposure in coal mines and metal and
nonmetal mines. The final rule establishes uniform requirements to
protect the Nation's miners from occupational noise-induced hearing
loss. The rule is derived in part from existing MSHA noise standards,
and from the Department of Labor's existing occupational noise exposure
standard for general industry promulgated by the Occupational Safety
and Health Administration (OSHA).
As a result of the Agency's ongoing review of its safety and health
standards, MSHA determined that its existing noise standards, which are
more than twenty years old, do not adequately protect miners from
occupational noise-induced hearing loss. A significant risk to miners
of material impairment of health from workplace exposure to noise over
a working lifetime exists when miners' exposure exceeds an 8-hour time-
weighted average (TWA8) of 85 dBA.
MSHA expects that the final rule will significantly reduce the risk
of material impairment within the mining industry as a whole.
DATES: The final rule is effective September 13, 2000.
FOR FURTHER INFORMATION CONTACT: Carol J. Jones, Acting Director,
Office of Standards, Regulations, and Variances, MSHA, 4015 Wilson
Boulevard, Arlington, VA 22203-1984. Ms. Jones can be reached at
[email protected] (Internet E-mail), 703/235-1910 (voice), or 703/235-
5551 (fax).
SUPPLEMENTARY INFORMATION:
I. Background
a. Noise-Induced Hearing Loss
Noise is one of the most pervasive health hazards in mining. The
National Institute for Occupational Safety and Health (NIOSH) has
identified noise-induced hearing loss as one of the ten leading work-
related diseases and injuries. Exposure to hazardous sound levels
results in the development of occupational noise-induced hearing loss,
which is distinguishable from hearing loss associated with aging or
with medical conditions. For many years, the risk of acquiring noise-
induced hearing loss was accepted as an inevitable consequence of
mining occupations, in which the use of mechanized equipment often
subjects miners to hazardous noise exposures. But noise-induced hearing
loss can be diagnosed, prevented, and its progress delayed.
Prolonged exposure to noise over a period of years generally causes
permanent damage to the auditory nerve or its sensory components.
Hearing loss is rapid when exposures are over a prolonged period at
high sound levels. Hearing loss may also be gradual, so that the
impairment is not noticed until after a substantial amount of hearing
loss occurs. Noise-induced hearing loss is irreversible. Considerable
safety risks arise because workers with noise-induced hearing loss may
not hear audible warnings and safety signals. In addition, most people
with noise-induced hearing loss have reduced hearing sensitivity to
higher frequencies and lose the ability to discriminate consonants,
making them unable to distinguish among words differing only by one or
more consonants. This impairment jeopardizes the safety of affected
miners as well as the safety of those around them, and, as a result,
general employee health and productivity.
Revising the existing rules to protect miners from noise-induced
hearing loss is necessary because exposure to workplace noise continues
to present a significant risk of material impairment of health to
miners. MSHA estimates that 13.4% of the mining population of the
United States (approximately 13,000 coal miners and 24,000 metal and
nonmetal miners) will develop a material hearing impairment during a
working lifetime under current working conditions. MSHA anticipates
that miners will benefit substantially from the final rule's effect of
improving miner health and lessening the personal and social hardships
of occupational noise-induced hearing loss.
b. Rulemaking Process
MSHA's existing noise standards in metal and nonmetal mines (30 CFR
Secs. 56.5050 and 57.5050) and in coal mines (30 CFR Secs. 70.500-
70.511, and Secs. 71.800-71.805) were originally promulgated in the
early 1970's. They were derived from the Walsh-Healey Public Contracts
Act occupational noise standard, which adopted a permissible exposure
level of 90 dBA, a 5-dB exchange rate, and a 90-dBA threshold. After
considering the recurrent incidence of noise-induced hearing loss among
miners and repeated recommendations from the mining community that MSHA
adopt a single noise standard covering all mines, MSHA published an
Advance Notice of Proposed Rulemaking (ANPRM) (54 FR 50209) on December
4, 1989. In response, the Agency received numerous comments from mine
operators, trade associations, labor groups, equipment manufacturers,
and other interested parties.
After reviewing the comments to the ANPRM, MSHA published a
proposed rule (61 FR 66348) on December 17, 1996. The comment period,
originally scheduled to close on February 18, 1997, was extended to
April 21, 1997 (62 FR 5554), and 6 public hearings were conducted in
Beckley, West Virginia; St. Louis, Missouri; Denver, Colorado; Las
Vegas, Nevada; Atlanta, Georgia; and Washington, D.C. Transcripts of
the proceedings were made available to the public. Supplementary
statements and data were received from interested persons until the
record closed on August 1, 1997.
After the close of the record, NIOSH sent MSHA a report entitled,
``Prevalence of Hearing Loss For Noise-Exposed Metal/Nonmetal Miners.''
On December 16, 1997, MSHA published a notice (62 FR 65777) announcing
that the report was available and had been entered into the rulemaking
record. Then, on December 23, 1997, MSHA published a follow-up notice
(62 FR 67013) inviting interested persons to comment on the NIOSH
report, with the comment period closing on February 23, 1998.
Early commenters on the proposal expressed concern that the spirit
of section 103(c) of the Federal Mine Safety and Health Act of 1977
(Mine Act) was not being met. Section 103(c) requires that miners or
their representatives be allowed to observe any monitoring or measuring
of hazards in their workplaces and to have access to monitoring
records. Proposed Sec. 62.120(f) contained a provision requiring
operators to establish a system of monitoring for effectively
evaluating each miner's noise exposure, but did not require that miners
be allowed to observe.
In response, on December 31, 1997, MSHA published a notice (62 FR
68468) supplementing its proposed rule with proposed Sec. 62.120(g),
asked for comments, and scheduled a public hearing. The comment period
for the supplement closed on February 17, and a public hearing was held
in
[[Page 49549]]
Washington, DC on March 10. The post-hearing comment period and
rulemaking record closed on April 9, 1998.
On May 26, 1998, MSHA published a notice (63 FR 28496) announcing
its preliminary determination of no significant environmental impact;
requesting comments; and reopening the rulemaking record for the
limited purpose of receiving these comments.
The agency received many comments on the proposed noise rule,
including the supplemental proposed rule on observation of monitoring.
The agency received a total of 182 written and electronic comments. In
addition, 57 speakers provided verbal comments at the public hearings.
Comments were received from various entities including mine operators,
industry trade associations, such as the National Mining Association,
National Stone Association, American Iron and Steel Institute and
American Portland Cement Alliance; organized labor groups, such as the
United Mine Workers of America and the United Steelworkers of America;
noise equipment manufacturers; the American Industrial Hygiene
Association; the National Hearing Conservation Association; the
Acoustical Society of America; colleges and universities; and other
Federal agencies, such as NIOSH and the U.S. Small Business
Administration.
c. Current Standards
MSHA's existing maximum noise exposure levels for metal and
nonmetal mines (30 CFR 56/57.5050) and for coal mines (30 CFR 70.500
through 70.511 and 71.800 through 71.805), were derived from the Walsh-
Healey Public Contracts Act occupational noise standard. The standards
adopted a permissible exposure level of 90 dBA as an eight-hour time
weighted average and a 5-dB exchange rate.
MSHA's existing metal and nonmetal noise standards require the use
of feasible engineering or administrative controls when a miner's noise
exposure exceeds the permissible exposure level. Hearing protectors are
also required if the exposure cannot be reduced to within the
permissible exposure level. The existing metal and nonmetal standards
do not 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 practices for coal mines are different from those
for metal and nonmetal mines due to differences in 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. In coal mines, a citation is not issued if appropriate
hearing protectors are being worn. Moreover, when a coal mine operator
receives a citation for noise exposure exceeding the permissible
exposure level, the operator is required to promptly institute
administrative and/or engineering controls to assure compliance. In
addition, within 60 days of receiving the citation, a coal mine
operator is required to submit a plan to MSHA for the administration of
a continuing, effective hearing conservation program.
The Federal Mine Safety and Health Review Commission (Commission)
has addressed the ``feasibility'' of noise controls regarding the
existing standards. In determining technological feasibility, the
Commission has held 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
held 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. In Todilto Exploration and Development Corporation, 5
FMSHRC 1894 (1983), the Commission 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.
MSHA estimates that the costs attributable to the final rule
requirement to use engineering and administrative controls would be
significantly offset by the paperwork savings the coal mining industry
will accrue. The existing costly, paperwork-intensive requirements for
biannual coal miner noise exposure surveys, supplemental noise surveys,
calibration reports, survey reports, and survey certifications are
eliminated by the final rule. Rather, the final rule has a flexible
requirement for mine operators to establish a monitoring program that
effectively evaluates miner exposures.
II. Final Rule
a. General Requirements Applicable to All Mines
The following summarizes general requirements for all mines in the
final rule although, the rule and this preamble should be consulted for
details. A mine operator must establish a system of monitoring which
evaluates each miner's noise exposure. In addition, the mine operator
must give prior notice and provide affected miners and their
representatives with an opportunity to observe the monitoring. When an
exposure equals or exceeds the action level, exceeds the permissible
exposure level, or exceeds the dual hearing protection level, the mine
operator must notify a miner of his or her exposure. A copy of the
notification must be kept for the duration of the affected miner's
exposure at or above the action level and for at least 6 months
thereafter.
If a miner's noise exposure is less than the action level, no
action is required by the mine operator. If the miner's exposure equals
or exceeds the action level, but does not exceed the permissible
exposure level, the operator must enroll the miner in a hearing
conservation program which includes a system of monitoring, voluntary
use of operator-provided hearing protectors, voluntary audiometric
testing, training, and record keeping. If a miner's exposure exceeds
the permissible exposure level, the operator must use or continue to
use all feasible engineering and administrative controls to reduce
exposure to the permissible exposure level, enroll the miner in a
hearing conservation program including ensuring the use of operator-
provided hearing protectors, post administrative controls and provide a
copy to the affected miner; and must never permit a miner to be exposed
to sound levels exceeding 115 dBA. If a miner's exposure exceeds the
dual hearing protection level, the operator must enroll the miner in a
hearing conservation program, continue to meet all the requirements for
exposures above the permissible exposure level, and
[[Page 49550]]
ensure the concurrent use of an earplug and earmuff.
b. Major Features of the Final Rule
Consistent with OSHA's noise exposure standard, MSHA has adopted
the existing permissible exposure level of 90 dBA as an 8-hour time-
weighted average (TWA8). The final rule, however, requires
the use of all feasible engineering and administrative controls to
reduce a miner's noise exposure to the permissible exposure level. Such
controls may be used separately or in combination. When controls do not
reduce exposure to the permissible exposure level, miners must be
provided hearing protectors and mine operators are required to ensure
that the miners use them.
The final rule also addresses a currently recognized hazard that is
not covered by existing standards: noise exposures at or above a
TWA8 of 85 dBA but below the permissible exposure level.
Exposure at a TWA8 of 85 dBA is termed the ``action level,''
and, under the final rule, mine operators are required to enroll miners
exposed at or above the action level in a hearing conservation program
consisting of exposure monitoring, the use of hearing protectors,
audiometric testing, training, and recordkeeping.
The final rule has been revised from the proposal in several
respects, which makes it more consistent with existing OSHA
regulations:
MSHA had proposed that all sound levels between 80 dBA and 130 dBA
be included in determining exposure for both the action level and
permissible exposure level. Based on comments received, the final rule
requires inclusion of sound levels between 90 dBA and at least 140 dBA
for determining exposure with respect to the permissible exposure
level. The final rule adopts the proposed inclusion of sound levels
from 80 dBA to at least 130 dBA for determining exposure with respect
to the action level.
In response to the proposed definition of a hearing conservation
program, commenters suggested that, for the sake of consistency, the
final rule adopt the existing definition included in the OSHA noise
standard. MSHA agrees and has revised the final rule to incorporate all
relevant elements of a hearing conservation program under this
definition.
The proposed rule would have required mine operators to ensure that
miners participate in an audiometric testing program if their noise
exposures were above the permissible exposure level. In response to
commenters, the final rule requires only that mine operators offer
audiometric testing, leaving it to the miner to decide whether to
participate in the testing program.
The proposed rule would have required that mine operators ensure
that miners were not exposed to workplace noise during a 14-hour quiet
period required before a baseline audiogram is taken. In addition, the
use of hearing protectors would not have been permitted as a substitute
for the quiet period. Many commenters suggested that prohibiting the
use of hearing protectors to meet the quiet period requirement was not
practical, because many miners work 12-hour shifts and that OSHA's
noise standard allows hearing protection to be used during the quiet
period. The final rule permits the use of hearing protectors during the
quiet period.
The proposed rule would have required a mine operator, upon
termination of a miner's employment, to provide the miner with a copy
of the records required under part 62. Commenters overwhelmingly
supported giving copies of records only to those miners who request
them. In response to comments, the proposed provision was not adopted
in the final rule, and the final rule instead requires that mine
operators provide copies of records to miners upon request.
The final rule departs from the OSHA noise standard in several
respects:
The final rule adopts the proposed ``dual hearing protection
level'' at a TWA8 of 105 dBA. This requirement for dual
hearing protection is supported by research showing that greater noise
reduction results from the use of both earplugs and earmuffs than from
either type of hearing protector alone. Accordingly, mine operators
must provide and require the use of both an earplug and an earmuff at a
TWA8 of 105 dBA.
The final rule does not include detailed, technical procedures and
criteria for conducting audiometric testing. Rather, the rule is
performance-oriented, requiring only that audiometric testing be
conducted in accordance with scientifically validated procedures, such
as those in OSHA's noise standard.
Nor does the final rule require determining the adequacy of hearing
protectors. Although OSHA's noise standard includes such information in
its mandatory Appendix B, MSHA's research on mining applications
indicates that hearing protectors provide less reduction than their
ratings suggest and that the reduction achieved is highly variable.
These two factors prevent accurate prediction of the effectiveness of
hearing protectors for a given individual. However, MSHA recognizes
that in some environments it may not be feasible to reduce miners'
noise exposures to the permissible exposure level with the use of
engineering or administrative controls. In these circumstances, the
interim use of personal hearing protectors may offer the best
protection until controls become feasible and can be implemented.
The final rule is consistent with Executive Order 12866, the
Regulatory Flexibility Act, the Small Business Regulatory Enforcement
Fairness Act (SBREFA), the National Environmental Policy Act (NEPA),
the Paperwork Reduction Act, the Unfunded Mandates Reform Act, and the
Mine Act. MSHA estimates that metal and nonmetal mines with fewer than
20 miners would incur an average cost increase of about $460 annually.
Coal mines with fewer than 20 miners would have an average cost
increase of about $400, reflecting the elimination of the numerous
survey and paperwork requirements in the current noise rules for the
coal sector.
In accordance with the SBREFA Amendments to the Regulatory
Flexibility Act, MSHA has taken steps to minimize the compliance burden
on small mines. The effective date of the final rule, one year after
promulgation, provides time for small mines to achieve compliance. In
addition, MSHA is mailing a copy of the final rule to each mine
operator, which benefits small mine operators.
MSHA anticipates that the mining community will benefit
substantially from the final rule. The primary benefit will be a
sizable reduction, by as much as two-thirds, in the incidence of
occupational hearing impairment among miners. The final rule will also
serve to mitigate the progression of hearing loss in working miners and
preserve the health and quality of life of miners newly entering the
industry.
Two charts compare key features of the final standard to MSHA's
existing standards. Note that entries in the charts and the discussions
in the preamble reflect legal and/or policy interpretations that would
not be apparent from the text of the standards. Other parts of this
preamble should be consulted for details.
[[Page 49551]]
Chart 1: General Requirements
----------------------------------------------------------------------------------------------------------------
Existing metal and
Noise level Final rule nonmetal rules Existing coal rules
----------------------------------------------------------------------------------------------------------------
At or above a TWA8 of 85 dBA Enroll miner in HCP which No requirements....... No requirements.
(action level). includes requirements for
training, monitoring,
recordkeeping, voluntary
hearing tests, voluntary
use of operator-provided
HP in most cases, but use
of HP is mandatory in
particular instances.
Above a TWA8 of 90 dBA (PEL)....... Use or continue to use all Use all feasible Use all feasible
feasible engineering and engineering or engineering and/or
administrative controls to administrative administrative
reduce exposure to PEL; controls and provide controls, but can
enroll miner in an HCP HP if noise level first reduce exposure
including ensuring use of cannot be lowered to by rated value of HP
operator-provided HP, post PEL. minus 7 unless cited
administrative controls for failure to
and provide copy to require HP use; also
affected miner, never must enroll miners in
permit miner to be exposed HCP if cited.
to sound levels exceeding
115 dBA.
At or above 105 dBA (dual hearing Ensure concurrent use of Limited requirement N/A
protection level). earplug and earmuff type for dual HPs.
HPs in addition to above
requirements for the
action level and PEL.
----------------------------------------------------------------------------------------------------------------
Abbreviations: HP (hearing protector), HCP (hearing conservation program), TWA8 (eight-hour time-weighted
average), dBA (decibel, A-weighted), PEL (permissible exposure level); Hz (hertz), and n/a (not applicable).
Comparison Chart 2: General Features
----------------------------------------------------------------------------------------------------------------
Existing metal and
Feature Final rule nonmetal rules Existing coal rules
----------------------------------------------------------------------------------------------------------------
Monitoring......................... Operator must establish an No requirement on mine Mine operator required
effective system of operator. to conduct periodic
monitoring noise exposure. monitoring.
Notification of exposure........... Operator must notify miner Not required.......... Not required.
of certain exposures.
Dual Threshold (lowest sound level 85 dBA for action level and 90 dBA for PEL........ 90 dBA for PEL.
counted). 90 dBA for PEL.
Exchange rate...................... 5 dB....................... 5 dB.................. 5 dB.
Training........................... Specific training Part 48............... Part 48.
requirements.
Quiet period prior to audiometric 14 hours for baseline N/A................... N/A.
examination. audiogram and use of HP
permitted.
Standard Threshold shift........... Average of 10 dB at 2000, N/A................... N/A.
3000, and 4000 Hz in
either ear.
Reportable hearing loss............ Average of 25 dB at 2000, Reporting required but Reporting required but
3000, and 4000 Hz in level was undefined. level was undefined.
either ear.
Employee access to records......... Available upon request..... N/A................... N/A.
----------------------------------------------------------------------------------------------------------------
Abbreviations: HP (hearing protector), dBA (decibel, A-weighted), PEL (permissible exposure limit); Hz (hertz),
n/a (not applicable).
III. Paperwork Reduction Act of 1995
The information collection requirements contained in this final
rule have been submitted to the Office of Management and Budget (OMB)
for review under the Paperwork Reduction Act of 1995 (44 U.S.C. 3501-
3520), as implemented by OMB in regulations at 5 CFR part 1320. The
Paperwork Reduction Act of 1995 (PRA 95) defines collection of
information as ``the obtaining, causing to be obtained, soliciting, or
requiring the disclosure to third parties or the public of facts or
opinions by or for an agency regardless of form or format.'' (44 U.S.C.
3502(3)(A)). Under PRA 95, no person may be required to respond to, or
may be subjected to a penalty for failure to comply with, these
information collection requirements until they have been approved and
MSHA has announced the assigned OMB control number. The OMB control
number, when assigned, will be announced by separate notice in the
Federal Register. In accordance with Sec. 1320.11(h) of the
implementing regulations, OMB has 60 days from today's publication date
in which to approve, disapprove, or instruct MSHA to make a change to
the information collection requirements in this final rule.
Recordkeeping requirements in the final rule are found in
Secs. 62.110, 62.130, 62.170, 62.171, 62.172, 62.173, 62.174, 62.175,
62.180, and 62.190.
MSHA received comments both supporting and opposing the proposed
information collection requirements. MSHA has reviewed these comments.
Several commenters questioned MSHA's estimates of the paperwork burden
reduction of the noise rule. Two commenters noted that the February
1984 Program Information Bulletin 84-1C ``eliminated virtually all
paperwork requirements for operators'' and that the ``paperwork
involves one letter and two 32 cent stamps per year per coal
operator.'' The February 1984 Program Information Bulletin eliminated
the requirement for the completion and submission to MSHA of a Coal
Mine Noise Data Report Form when operator noise exposure surveys are
found to be within compliance. The Program Information Bulletin
retained the requirement that a written and signed statement
(certification) be submitted to MSHA that the required surveys were
made and that the surveys show compliance. The Program Information
Bulletin did not drop the requirement for noise surveys to be
conducted, exclude the requirement for supplemental noise surveys for
exposures at or above the permissible exposure level (and a submission
of them), or eliminate the requirement of
[[Page 49552]]
surveying all miners and retaining a record.
In addition, as MSHA stated in the proposal, there are labor and
equipment costs related to performing the surveys twice a year,
completing survey reports and certifications, doing calibration reports
annually, and collecting a noise monitoring record for all coal miners.
Under PRA 95, all activities related to the generation of a paperwork
item must be considered when calculating the costs and burden of
paperwork tasks. For these reasons, MSHA's estimates in the final rule
are consistent with the requirements of PRA 95.
Other commenters stated that they will still have to conduct
surveys, retain survey records, conduct training and audiometric
testing, and implement engineering and administrative controls to
demonstrate compliance. The existing standards require coal mine
operators to perform semiannual monitoring for each miner. Under the
final rule, mine operators must establish a system of monitoring that
evaluates each miner's noise exposure sufficiently to determine
continuing compliance with this part. However, under the final rule
mine operators may use their own monitoring records as well as the
Agency's data from inspector sampling to determine compliance.
Some commenters stated that the performance-based system of
monitoring may result in increased monitoring. MSHA anticipates that a
number of mine operators will use some form of representative sampling
within job classes or work areas to minimize costs related to dose
determination. In addition, large operators who use the same equipment
on more than one shift may conduct monitoring on a single shift to
determine miner exposures, provided that the circumstances are similar.
The Agency published a supplemental proposal that would give
affected miners and their representatives the right to observe operator
monitoring. MSHA estimated that the time required for observation of
monitoring would take about 2 hours annually at small mines and about 5
hours annually at large mines. Several commenters questioned the
Agency's estimates. One commenter questioned the Agency's estimate of 5
hours for a large mine. The commenter believed that for a mine which
employed 1,500 workers, 12,000 hours will be spent on noise monitoring
(1,500 workers * an 8 hour workday). Under the final rule, mine
operators will need to determine miners' exposure; this may be achieved
in a number of ways including the use of existing monitoring records
(particularly for coal mine operators), review of MSHA sampling
records, or by the use of representative sampling. Since mine operators
are not specifically required by the final rule to monitor each
employee but may use a more flexible approach, MSHA anticipates that
its estimates of an average of 2 hours and 5 hours annually at small
and large mines respectively (reflecting 30 minute monitoring for each
of four miners in a small mine and ten miners in a large mine) are
reasonable.
Another commenter questioned if there will be an observation time
limit and also believed that MSHA's estimate of 5 hours annually was
too low. Also, a commenter questioned MSHA's estimates of lost
production, the length of time needed for observation, and MSHA's
average time estimates per small mine and per large mine. A commenter
also believed that the total estimated annual information collection
burden was low. With the exception of the one commenter who provided
the estimate of 12,000 hours annually to observe monitoring, none
provided data to support their statements.
At the public hearing, several commenters testified that they
considered MSHA's time estimates and photocopy cost estimates high. In
particular, they believed that the time to give instructions to the
secretary were excessive. Further, they stated MSHA's estimates for the
length of time to perform typing and posting were too high. Other
commenters stated that the bulk of the paperwork would be completed by
safety professionals and industrial hygienists as opposed to clerical
workers. Based upon a review of all the comments and MSHA's experience,
the Agency believes the estimates in the final rule are reasonable.
The proposed rule would have required mine operators to obtain from
the physician, audiologist, or qualified technician who conducts an
audiometric test a certification that each test was conducted in
accordance with scientifically validated procedures. Commenters stated
that requiring mine operators to obtain a certification for each
individual audiogram was unduly burdensome. The Agency agrees and the
proposed certification requirement has not been adopted in the final
rule. Under the final rule, evidence is simply required that the
audiograms were conducted in accordance with scientifically validated
procedures. For example, the evidence may consist of a single statement
from the audiometric test provider or a single billing record that
indicates that required procedures were followed for a number of
audiograms.
The proposed rule would have required mine operators to provide
miners with a copy of all their records relating to this standard when
those miners terminate employment. Commenters stated that this was an
unnecessary requirement which generated too much paper and that miners
may not even want a copy of the records. In response, the final rule
requires mine operators to provide copies of records to a miner if the
miner requests such records.
Numerous commenters stated that records should not have to be
retained at the mine site. MSHA agrees and the final rule provides that
records are not required to be maintained at the mine site, and
therefore can be electronically filed in a central location, so long as
the records are made available to the authorized representative of the
Secretary upon request within a reasonable time, in most cases one day.
Although the final rule does not require backing up the data, some
means are necessary to ensure that electronically stored information is
not compromised or lost. MSHA encourages mine operators who store
records electronically to provide a mechanism that will allow the
continued storage and retrieval of records in the year 2000.
MSHA solicited comment on what actions would be 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 requirements. The Agency received several comments
supporting electronic storage of records, but no specifics regarding
actions required to facilitate the maintenance of the records in
electronic form. In revising the requirements from those that appeared
in the proposed rule, MSHA has evaluated the necessity and usefulness
of the collection of information; reevaluated MSHA's estimate of the
information collection burden, including the validity of the underlying
methodology and assumptions; and minimized the information collection
burden on respondents to the greatest extent possible. The following
charts provide, by section, the paperwork requirements for Year 1 and
for each succeeding year, respectively.
[[Page 49553]]
Table 1.--Summary of Net Information Collection Burden Hours in Year 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
Coal mines M/NM mines
Section Paperwork requirements and associated ---------------------------------------------------- Total
tasks Small Large Small Large
--------------------------------------------------------------------------------------------------------------------------------------------------------
62.110 to 62.130.............................. Evaluate noise exposure; notify miners, (7,988) (50,666) 14,605 12,579 (31,471)
prepare, post, and distribute
administrative controls; and permit
observation of monitoring.
62.170........................................ Perform audiograms; and notify miners 940 4,181 3,577 5,271 13,969
to appear for testing and of need to
avoid high noise levels.
62.171........................................ Compile an audiometric test record; and 1,021 4,616 3,882 5,820 15,339
obtain evidence.
62.172........................................ Provide information and audiometric 1,413 4,374 5,474 5,513 16,774
test record; and perform audiometric
retests.
62.173........................................ Perform otological evaluations; and 7 27 29 34 98
provide information and notice.
62.174........................................ Prepare a retraining certification; and 105 334 407 420 1,266
review effectiveness of engineering
and administrative controls.
62.175........................................ Inform miners of test results and tSTS. 1,038 4,623 3,950 5,829 15,440
62.180........................................ Prepare and file a training 1,280 4,165 4,957 5,180 15,581
certificate..
62.190........................................ Provide access to, and transfer, 244 303 1,027 915 2,489
records.
----------------------------------------------------------------
Total................................... ..................................... (1,941) (28,045) 37,909 41,561 49,484
--------------------------------------------------------------------------------------------------------------------------------------------------------
Table 2.--Summary of Net Information Collection Burden Hours for After Year 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
Coal mines M/NM mines
Section Paperwork requirements and associated ---------------------------------------------------- Total
tasks Small Large Small Large
--------------------------------------------------------------------------------------------------------------------------------------------------------
62.110 to 62.130.............................. Evaluate noise exposure; notify miners, (8,532) (48,006) 6,595 3,567 (46,376)
prepare, post, and distribute
administrative controls; and permit
observation of monitoring.
62.171........................................ Compile an audiometric test record; and 153 692 582 873 2,301
obtain evidence.
62.172........................................ Provide information and audiometric 212 656 821 827 2,516
test record; and perform audiometric
retests.
62.173........................................ Perform otological evaluations; and 1 4 4 5 15
provide information and notice.
62.174........................................ Prepare a retraining certification; and 16 53 62 67 198
review effectiveness of engineering
and administrative controls.
62.175........................................ Inform miners of test results and STS.. 156 694 593 874 2,316
----------------------------------------------------------------
Total................................... ....................................... (7,994) (45,907) 8,658 6,213 (39,029)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Executive Order 12866 and Regulatory Flexibility Analysis
In accordance with Executive Order 12866, MSHA has prepared a final
analysis of the estimated costs and benefits associated with the
revisions of the noise standards for coal and metal and nonmetal mines.
The final Regulatory Economic Analysis containing this analysis is
available from MSHA. The final rule will cost approximately $8.7
million annually and will prevent or contribute to the prevention of
approximately 595 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.
Regulatory Flexibility Certification
In accordance with section 605 of the Regulatory Flexibility Act,
the Mine Safety and Health Administration certifies that the final
noise rule does not have a significant economic impact on a substantial
number of small entities. Traditionally, MSHA considers small mines to
be mines with fewer than 20 employees. Under the Regulatory Flexibility
Act, 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 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 final rule for small and large mines using both the traditional
Agency definition and SBA's definition, as required by the Regulatory
Flexibility Act, of a small mine. No small governmental jurisdictions
or
[[Page 49554]]
nonprofit organizations are adversely affected.
Under the Small Business Regulatory Enforcement Fairness Act
(SBREFA) amendments to the Regulatory Flexibility Act, MSHA must
include in the final rule a factual basis for this certification. The
Agency must also publish the regulatory flexibility certification
statement in the Federal Register, along with the factual basis,
followed by an opportunity for the public to comment. 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.
In the proposal, MSHA specifically solicited comments on the
Agency's regulatory flexibility certification statement, including cost
estimates and data sources. To facilitate public participation in the
rulemaking process, MSHA mailed a copy of the proposal and will mail a
copy of the final rule, including the preamble and regulatory
flexibility certification statement, to every mine operator and miners'
representative.
Factual Basis for Certification
General Approach
The Agency's analysis of impacts on ``small entities'' and ``small
mines'' begins with a ``screening'' analysis. The screening compares
the estimated compliance costs of the final rule for small mine
operators in the affected sector to the estimated revenues for that
sector. When estimated compliance costs are less than 1 percent of
estimated revenues (for the size categories considered), the Agency
believes it is generally appropriate to conclude that there is no
significant impact on a substantial number of small entities. When
estimated compliance costs approach or exceed 1 percent of revenue, it
tends to indicate that further analysis may be warranted.
Derivation of Costs and Revenues
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 (that
is, beyond the 4-digit SIC level) is not feasible. The Agency requested
comments, however, on whether there are special circumstances that
warrant separate quantification of the impact of this final rule 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 final rule.
In determining revenues for coal mines, MSHA multiplied coal
production data (in tons) for mines in specific size categories
(reported to MSHA quarterly) by $18.14 per ton, Department of Energy
(1997). 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, Department of
Interior (1998).
Results of Screening Analysis
As shown in the following chart, for coal mine operators with fewer
than 20 employees, the estimated yearly cost of the final rule is $400
per mine operator, and estimated yearly costs as a percentage of
revenues are 0.08 percent. As shown in the next chart, for coal mine
operators with 500 or fewer employees, the estimated yearly savings
from the final rule are $634 per mine operator. The savings are due to
the elimination of existing coal industry requirements for performing
and recording semiannual surveys and other related surveys and reports.
Table 1.--The Impact of Final Rule on the Coal Mining Industry *
----------------------------------------------------------------------------------------------------------------
Estimated Cost as
Mine type Estimated Estimated revenue cost per percent of
costs mine revenue
----------------------------------------------------------------------------------------------------------------
Small (20)................................. 763,112 18,964,691,818 727 0.00
----------------------------------------------------------------------------------------------------------------
* Source: Preliminary Data 1997 from CM441 and Department of Energy/Energy Information Agency. Annual Energy
Review 1997. POE/EIA-038497. July 1998. P. 187.
Table 2.--The Impact of Final Rule on the Coal Mining Industry *
----------------------------------------------------------------------------------------------------------------
Estimated Cost as
Mine type Estimated Estimated revenue cost per percent of
costs mine revenue
----------------------------------------------------------------------------------------------------------------
Small (500)................................ $1,296,461 $19,038,974,646 $508 0.01
Large (20).............................. 3,056,036 27,348,977,991 1,945 0.01
----------------------------------------------------------------------------------------------------------------
* Source: Preliminary Data 1997 from CM441 and Department of Interior, Bureau of Mines, Mineral.
Table 4.--Distribution of Mine Operations and Employment by Mine Type and Size Including Independent Contractors
and Contractor Workers Potentially Affected by the Final Rule *
----------------------------------------------------------------------------------------------------------------
Coal Metal/nonmetal
-----------------------------------------------------------------------------
Mine Size (No. of employees) No. of No. of Miners per No. of No. of Miners per
mines miners mine mines miners mine
----------------------------------------------------------------------------------------------------------------
Small (20)............. 1,133 82,142 72.48 1,666 122,378 73.45
-----------------------------------------------------------------------------
Total....................... 3,535 96,489 27.30 11,764 179,238 15.24
----------------------------------------------------------------------------------------------------------------
* Source: Table 2 and Table 3. Office workers are not included in these employment figures.
In all cases, the cost of complying with the final rule is less
than one percent of revenues, well below the level suggesting that the
final rule might have a significant impact on a substantial number of
small entities. Accordingly, MSHA has certified that there is no such
impact on small coal mines or small metal/nonmetal mines.
Regulatory Alternatives Considered
The limited impacts on small mines, regardless of size definition,
reflect decisions by MSHA not to include 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 considered two
alternatives that would have significantly increased costs for small
mine operators lowering the permissible exposure level 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 commenters offered divergent views on the alternatives. In
both cases, for the purpose of this final rule, MSHA has concluded that
it would 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.
Further, MSHA proposed using an 80-dBA threshold for determining
the permissible exposure level. If the Agency had done this, the number
of mines with exposure levels at or above the permissible exposure
level would have increased substantially. Accordingly, with more mines
above this level, the total cost of compliance would have been higher,
including penalties. Many commenters opposed the change in the
threshold. They believed that the current 90-dBA threshold was
sufficient for achieving adequate health protection for miners and was
compatible with OSHA's noise standard. Additionally, as discussed in
more detail later in the preamble, MSHA did not intend to change the
permissible exposure level for noise. A change in the threshold would
have had this effect. For these reasons, the final rule includes the
existing threshold for the permissible exposure level.
Under the proposal, the mine operator would have had to make
certain that miners exposed above the permissible exposure level take
the audiometric examination. Several commenters expressed concerns
about the enforceability of this provision. MSHA considered these
concerns, and under the final rule, audiometric testing is voluntary.
In this regard, it is also compatible with OSHA's noise standard.
In addition, under the proposal, mine operators would not have been
allowed to use hearing protectors as a substitute for the 14-hour quiet
period prior to an audiogram. Mine operators had stated that they could
not, without substantial burden to production and management, meet this
requirement. Some noted that in cases in which the audiometric testing
cannot be scheduled on a day after a non-work day, the only way to
ensure a 14-hour quiet period was to pay the miner not to work. Under
the final rule, mine operators may use hearing protectors as a
substitute for the quiet period. Again, this is compatible with OSHA's
noise standard.
Paperwork Impact
In accordance with the Regulatory Flexibility Act and the Paperwork
Reduction Act of 1995, MSHA has analyzed the paperwork burden for both
metal and nonmetal and coal mines. While the final rule results in a
net paperwork burden decrease for large coal mines in year one and both
small and large coal mines after year one, there will be an increase in
paperwork burden hours for small coal mines in year one and in metal
and nonmetal mines' year one and every year thereafter.
For small coal mines with fewer than 20 miners the final rule will
result in an increase of about 485 paperwork burden hours in year one.
After year one there will be a savings of 4,438 paperwork burden hours
for small coal mines. For large coal mines with 20 or more miners, the
final rule will result in a decrease of about 10,405 paperwork
[[Page 49556]]
burden hours in year one, and a savings of 28,498 each year thereafter.
For metal and nonmetal mines, the final rule will result in an increase
of paperwork burden hours for both small and large mines. There will be
an increase of 33,955 paperwork burden hours for small metal and
nonmetal mines and increase of 38,183 paperwork burden hours for large
metal and nonmetal mines in year one. After year one, there will be an
increase of 15,526 paperwork burden hours per year for small metal and
nonmetal mines, and an increase of 14,331 per year for large.
Although the substantial increases in paperwork burden hours result
from Secs. 62.175 and 62.180 for coal mines, these will be offset by
the net savings of Secs. 62.110-62.130, which eliminate current
requirements for biannual noise surveys and other miscellaneous reports
and surveys in that sector. However, for metal and nonmetal mines there
will be an increase in paperwork burden hours associated with complying
with the final rule.
As required by the Paperwork Reduction Act of 1995, MSHA has
included in its paperwork burden estimates the time needed to perform
tasks associated with information collection. For example, the final
rule requires a mine operator to notify a miner if the miner's noise
exposure equals or exceeds the action level. In order to determine if
notification is necessary, the mine operator must perform a dose
determination. MSHA has included the time needed for dose determination
in its burden estimate, as required under PRA 95.
Small Business Regulatory Enforcement Fairness Act (SBREFA)
In accordance with the Small Business Regulatory Enforcement
Fairness Act (SBREFA) amendments to the Regulatory Flexibility Act,
MSHA carefully considered all of the proposed requirements, in addition
to alternatives to the proposal, to ensure that the final rule would
provide the least burdensome impact necessary to promote miner health.
MSHA believes that it has complied with the SBREFA amendments.
The preamble to the proposed rule included a full discussion of
MSHA's preliminary conclusions about regulatory alternatives. The
public was invited to suggest additional alternatives for compliance.
MSHA is taking several actions to minimize the compliance burden on
small mines. The effective date of the final rule will be a full year
after its publication, to provide adequate time for small mines to
achieve compliance and for MSHA to brief the mining community about the
rule's requirements. Also, as stated previously, MSHA will mail a copy
of the final rule to every mine operator, which benefits small mine
operators. The Agency has committed itself to issuance of a compliance
guide for all mines; MSHA believes that compliance workshops or other
approaches will be valuable and the Agency will hold such workshops if
requested.
For this rulemaking's Regulatory Flexibility Analysis, the Agency
is using its traditional definition of ``small mine'' as a mine with
fewer than 20 employees, in addition to the SBA's definition of
operations with fewer than 500 employees, as required by the Regulatory
Flexibility Act. For purposes of this final rule, 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 final noise rule does
not have a significant economic impact on a substantial number of small
entities.
Executive Order 13045: Protection of Children From Environmental Health
Risks and Safety Risks
In accordance with Executive Order 13045, MSHA has evaluated the
environmental health and safety effects of the final rule on children.
The Agency has determined that the final rule will have no adverse
effects on children.
Environmental Assessment
The final noise rule has been reviewed in accordance with the
requirements of the National Environmental Policy Act (NEPA) of 1969
(42 U.S.C. 4321 et seq.), the regulations of the Council of
Environmental Quality (CEQ) (40 CFR part 1500) and the Department of
Labor's NEPA compliance procedures (29 CFR part 11). In the Federal
Register of May 26, 1998 (63 FR 28496), MSHA made a preliminary
determination that the proposed noise rule was of a type that does not
have a significant impact on the human environment. In response, one
comment was received by the Agency. The commenter expressed a concern
that the Agency had not prepared an environmental assessment in
accordance with NEPA, the CEQ and the Department's procedural
regulations. MSHA's preliminary determination was based on its
Regulatory Impact Analysis which explained the costs and benefits of
the proposed rule. MSHA has complied with the requirements of the NEPA,
including the Department of Labor's compliance procedures and the
regulations of the Council on Environmental Quality. The Agency has not
received any new information or comments that would affect its previous
determination. As a result of the Agency's review of the final noise
rule, MSHA has concluded that the rule will not have significant
environmental impacts, and therefore neither an environmental
assessment nor an environmental impact statement is required. In
addition, MSHA believes that the final rule will indirectly aid the
environment since many of the engineering controls which control noise,
such as mufflers and curtains, also aid in controlling environmental
pollutants.
Executive Order 13084 (Consultation and Coordination With Indian Tribal
Governments)
MSHA certifies that the final rule does not impose substantial
direct compliance costs on Indian tribal governments. Further, MSHA
provided the public, including Indian tribal governments which operated
mines, the opportunity to comment on the proposal and to participate in
the public hearing process. No Indian tribal government applied for a
waiver or commented on the proposal.
Executive Order 12612 Federalism
Executive Order 12612, regarding federalism, requires that
agencies, to the extent possible, refrain from limiting state policy
options, consult with states prior to taking any actions which would
restrict state policy options, and take such actions only when there is
clear constitutional authority and the presence of a problem of
national scope. Because this final rule does not limit state policy
options, it complies with the principles of federalism and with
Executive Order 12612.
Unfunded Mandates Reform Act of 1995
MSHA has determined that, for purposes of Sec. 202 of the Unfunded
Mandates Reform Act of 1995, this final rule does not include any
Federal mandate that may result in increased expenditures by State,
local, or tribal governments in the aggregate of more than $100
million, or increased expenditures by the private sector of
[[Page 49557]]
more than $100 million. Moreover, the Agency has determined that for
purposes of Sec. 203 of that Act, this final 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 final Regulatory Economic
Analysis, the annualized cost of this final rule is approximately $8.9
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 final regulation. The final
rule will impact approximately 15,299 coal and metal and nonmetal
mining operations; however, increased costs will be incurred only by
those operations (approximately 10,476 mines) where noise exposures
exceed the allowable limits. MSHA estimates that approximately 187 sand
and gravel or crushed stone operations are run by state, local, or
tribal governments and will be impacted by this rule.
When MSHA issued the proposed rule, the Agency affirmatively sought
input of any state, local, and tribal government which may be affected
by the noise rulemaking. This included state and local governmental
entities who operate sand and gravel mines in the construction and
repair of highways and roads. MSHA mailed a copy of the proposed rule
to these entities. No state, local or tribal government entity
commented on the proposed rule. When the final rule is published, MSHA
will mail a copy to all 187 entities.
IV. Miscellaneous
Permissible Exposure Level
The final rule affirms MSHA's initial determination, set out in the
proposal, that there is a significant risk for miners of material
impairment from noise exposures at or above an 8-hour time-weighted
average of 85 dBA. However, the final rule also comports with MSHA's
initial conclusion that it would not be either technologically or
economically feasible at this time for the mining industry to implement
a reduced permissible exposure level for noise, including a reduction
in the exchange rate. For these reasons the final rule does not reduce
the permissible exposure level, but it does require mine operators to
take a number of other actions that will substantially reduce miners'
risk of occupational noise-induced hearing loss.
MSHA will continue to examine closely the feasibility of a
reduction in the permissible exposure level for miners' noise exposure.
This will include, but is not limited to, assessment of the
availability and suitability of equipment retrofits for noise control,
evaluation of the state of existing noise control technology
appropriate for mining applications, and the availability of
alternative, and less noisy, equipment for various mining tasks. MSHA
intends to work closely with all segments of the mining community in
its continuing assessment of feasibility.
NIOSH Criteria Document
In March 1996, the National Institute for Occupational Safety and
Health (NIOSH) released for peer review a draft Criteria Document for
Occupational Noise Exposure, which was intended to update an earlier
NIOSH Criteria Document for Noise that had been issued in 1972. MSHA
summarized the recommendations of the draft Criteria Document in the
preamble to the proposed rule (61 FR 66369-66370), and considered the
draft Criteria Document recommendations, as well as comments that
addressed the draft Criteria Document, in developing this final rule.
In June 1998 NIOSH issued the final Criteria Document for
Occupational Noise Exposure, which in large part adopts the
recommendations of the 1996 draft Criteria Document, which, as
mentioned above, were considered as part of this rulemaking. However,
the final Criteria Document does include several recommendations which
differ from recommendations in the 1996 draft Criteria Document. The
main differences between the draft and the final Criteria Documents are
as follows:
1. Action level. In the draft document, NIOSH proposed what was
essentially an ``action level'' that would trigger establishment of
a Hearing Loss Prevention Program. The ``action level'' would have
been an 8-hour TWA of 85 dBA. The final Criteria Document does not
adopt the ``action level'' concept, and instead would trigger
establishment of a Hearing Loss Prevention Program at the
recommended exposure limit of an 85 dBA TWA8. Under
MSHA's final rule, a miner's noise exposure at 85 dBA
TWA8 requires enrollment of the miner in a Hearing
Conservation Program.
2. Ceiling Level. The NIOSH draft Criteria Document recommended
a ceiling at a 115 dBA sound pressure level. The final Criteria
Document recommends a 140 dBA sound pressure level ceiling limit for
continuous, varying, intermittent, or impulsive noise.
3. Dual Hearing Protection Level. The draft Criteria Document
did not make a recommendation for such a level. However, the final
Criteria Document recommends the use of dual hearing protection at
exposures exceeding a TWA8 of 100 dBA.
4. Quiet Period. The draft Criteria Document recommended a 14-
hour quiet period prior to a baseline audiogram, and would not
permit the use of hearing protectors as a substitute. The final
Criteria Document recommends a quiet period of 12 hours, and still
would not permit the use of hearing protectors in lieu of the quiet
period.
Rule Format
In the preamble to the proposed rule MSHA solicited comments on the
appropriate format for the final rule, providing examples for
commenters of alternate approaches. There was no clear consensus among
commenters to the proposal that the traditional format of MSHA's
regulations should be changed. As a result, the final rule adopts the
format of existing MSHA regulations.
Unlike the proposal the final rule does not include a question and
answer section. Instead, after publication of the final rule, MSHA will
develop and issue a compliance guide for the mining community to
facilitate its understanding of and compliance with the requirements of
the final rule. Additionally, MSHA is receptive to submission by the
mining community of suggestions for issues that should be addressed in
the compliance guide.
V. Material Impairment
Section 101(a)(6) of the Federal Mine Safety and Health Act of 1977
(Mine Act) provides that, in dealing with toxic materials or harmful
physical agents, standards set by the Secretary shall:
* * * 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.
MSHA has determined that there is a significant risk of material
impairment of health and functional capacity to miners from exposure to
workplace noise despite the existing noise standards, and the Agency's
rulemaking evidence supports this. MSHA anticipates that the final rule
will reduce, by approximately two-thirds, the number of miners who will
suffer a material impairment due to exposure to
[[Page 49558]]
occupational noise under the existing regulations.
MSHA's conclusion that there is a significant risk of material
impairment of health for workers exposed over their working lifetimes
to sound levels of 85 dBA is based on the Agency's definition of
material impairment, which is referred to in this preamble as the OSHA/
NIOSH-72 definition. Under the OSHA/NIOSH-72 definition, the excess
risk of a hearing impairment from occupational noise exposure is 15% or
one-hundred fifty-in-a-thousand miners at an 85 dBA TWA8
exposure for a working lifetime. The Supreme Court has indicated, in
discussing significant risk in the context of litigation under section
6(f) of the OSH Act, that OSHA is free to use conservative assumptions
in interpreting data so long as they are supported by reputable
scientific concepts, and that a one-in-a-thousand risk is significant.
Industrial Union Department, AFL-CIO v. American Petroleum Institute,
448 U.S. 607, 655 (1980) (the Benzene Case). If the Mine Act were to
impose the same risk-finding requirement as the OSH Act, MSHA's
determination of a significant risk of material impairment of health
falls well within the Supreme Court's direction to OSHA in the Benzene
Case.
Exposure to hazardous sound levels results in noise-induced hearing
loss. Noise-induced hearing loss is often described in terms of the
relationship between the sound level to which a person is exposed and
the duration of the exposure. Exposures to noise at sound levels equal
to or greater than the 8-hour average sound level of 85 dBA have been
shown to lead to hearing loss, which can be temporary or permanent.
Noise-induced hearing loss causes difficulty in hearing and
understanding speech. People suffering from significant noise-induced
hearing loss require even nearby persons to speak loudly and clearly to
be understood, and they are often frustrated by missing vital
information. Also, background noise affects the person's ability to
distinguish meaningful sounds from ambient noise. Little benefit can be
derived from the use of a hearing aid because it amplifies sound
indiscriminately, without increasing clarity, decreasing distortion, or
screening out unwanted sounds. Noise also produces secondary, non-
auditory effects.
Although the secondary effects of noise-induced hearing loss are
more difficult to identify, document, and quantify than the hearing
loss itself, recent laboratory and field studies have found an
association between noise and cardiovascular problems and other
illnesses such as hypertension. Studies also suggest that holding
exposure below a time-weighted average of 85 dBA will significantly
improve both psychological and physiological stress reactions.
Safety risks at the workplace may arise as a result of noise-
induced hearing loss. Workers suffering from noise-induced hearing loss
may not hear safety signals because of reduced hearing sensitivity to
higher frequencies. In addition, noise-induced hearing loss results in
the loss of the ability to distinguish between many pairs of
consonants, which makes speech incomprehensible. As a result, miners
suffering from noise-induced hearing loss may have trouble
understanding directions or warnings given by their supervisors or co-
workers.
Definition of Material Impairment
MSHA has determined that a 25 dB hearing level averaged over 1000,
2000, and 3000 Hz in both ears is the most appropriate gauge of a
miner's risk of developing significant noise-induced hearing loss. MSHA
therefore considers such a loss to constitute a material impairment in
hearing. MSHA's definition of material impairment is based on one
developed in 1972 by NIOSH and subsequently adopted by OSHA in its
noise standard for general industry, referred to below as the OSHA/
NIOSH-72 definition. (As noted by a commenter, the preamble to the
proposed rule incorrectly stated that the OSHA/NIOSH-72 definition
included the phrase ``in either ear.'' This mistake is corrected here
and in the final rule.) In addition, as discussed elsewhere in this
preamble, MSHA notes that it has not adopted the revised definition of
material impairment set forth in the final NIOSH Criteria Document
issued in June 1998. Throughout this preamble, therefore, MSHA will
continue to refer to the definition of material impairment developed by
NIOSH in 1972.
In nearly all studies of risk, material impairment from exposure to
noise is defined as a 25-dB hearing level. Hearing level is the
deviation in hearing sensitivity from audiometric zero. Positive values
indicate poorer hearing sensitivity than audiometric zero, while
negative values indicate better hearing. Audiometric zero is the lowest
sound pressure level that the average, young adult with normal hearing
can hear. Because of the widespread use of this definition in the
scientific community, MSHA has used it in the final rule.
Most definitions of hearing impairment are based solely on pure
tone audiometry, in which an audiometer is used to measure an
individual's threshold hearing level the lowest level of discrete
frequency tones that he or she can hear. The test procedures for pure
tone audiometry are relatively simple, widely used, and standardized.
Although there is little debate in the scientific community about the
usefulness of pure tone audiometry in assessing hearing loss, there is
some disagreement about the range of audiometric frequencies that
should be used in determining hearing loss.
When OSHA initially published its noise standard establishing noise
exposure limits for employees, 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 definition (AAOO 1959) of hearing impairment is a hearing
level exceeding 25 dB, referenced to audiometric zero, averaged over
500, 1000, and 2000 Hz in either ear. 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) modified the 1959 criteria in 1979 by adding the hearing
level at 3000 Hz to the 500, 1000, and 2000 Hz frequencies. The AAOO
1959 and AAO-HNS 1979 definitions cover all types of hearing loss and
were designed for hearing speech under relatively quiet conditions. The
NIOSH-72 definition includes the higher frequencies, which are crucial
to the comprehension of speech under everyday conditions.
In its draft 1996 Criteria Document for occupational noise
exposure, NIOSH indicated that it was considering a new definition for
material impairment of a 25 dB or greater hearing loss at 1000, 2000,
3000, and 4000 Hz in both ears. This definition was a recommendation of
a Task Force to the American Speech-Language-Hearing Association (ASHA)
in 1981. In 1997, NIOSH conducted a reanalysis of the NIOSH-
Occupational Noise and Hearing Survey data and reevaluated the excess
risk of material hearing impairment incorporating the 4000 hertz
audiometric frequency in the definition of material impairment. (Excess
risk is defined by NIOSH as the percentage with material impairment of
hearing in an occupational noise exposed population after subtracting
the percentage who would normally incur such impairment from other
causes in a population not exposed to occupational noise.) In 1998,
NIOSH published the results of this reanalysis in its final Criteria
Document. The excess risk of developing occupational noise induced
[[Page 49559]]
hearing loss under the reassessment is 8%. The excess risk of
developing occupational noise induced hearing loss under the 1972 NIOSH
definition of material impairment is 15% for average noise exposure
level of 85 dBA. The final Criteria Document recommends that the
reanalysis reaffirms support for the 85 dBA NIOSH recommended exposure
limit.
The final rule does not adopt the revised NIOSH definition for
hearing impairment. Several commenters noted that this definition has
not been adopted by the scientific community, and no state workers'
compensation agency awards compensation for hearing impairment based
upon the current NIOSH hearing impairment criterion. Despite the fact
that noise-induced hearing loss usually first becomes detectable at
4000 Hz, MSHA finds that the scientific evidence does not, as yet,
support including 4000 Hz in the frequencies used for calculating
hearing impairment. Inclusion of test frequencies above 2000 Hz,
however, is necessary to show the effect of noise below 90 dBA on
hearing, so MSHA continues to include the 3000 Hz frequency. Several
commenters suggested that MSHA use the AAO-HNS 1979 definition of
material impairment. There were relatively few commenters in favor of
using the AAO-HNS 1979 definition. MSHA has excluded the 500 Hz
frequency from the definition of hearing impairment because it is not
as critical for understanding speech and is least affected by noise.
MSHA chose the hearing levels at 1000, 2000, and 3000 Hz on which to
base its definition of material impairment because high frequency
hearing is critically important to the understanding of speech, which
often takes place in noisy conditions. The Agency's determination is
consistent with OSHA's reasoning for its noise standard, and many
comments and studies cited support this approach.
Risk of Impairment
The risk of developing a material impairment becomes significant
over a working lifetime when workplace exposure to noise exceeds sound
levels of 85 dBA. Data reviewed by the Agency indicate that lowering
exposure from 90 dBA to 85 dBA does not eliminate the risk, it reduces
the risk by approximately half.
Typically, noise-induced hearing loss occurs first at 4000 Hz and
then progresses into the lower and higher frequencies. MSHA notes that
because noise does not affect hearing sensitivity equally across all
frequencies, the population defined as impaired will differ according
to the frequencies that are used in the measurement criteria. For
example, AAOO 1959 is weighted toward the lower frequencies, because it
was developed to determine an individual's ability to communicate under
quiet conditions. AAO-HNS, which includes 3000 Hz, is weighted toward
the higher frequencies. Because OSHA/NIOSH-72 is weighted even more
towards the higher frequencies due to the elimination of the hearing
level at 500 Hz, the population of those impaired due to noise exposure
will be greater than under the AAOO 1959 and AAO-HNS 1979 definition.
MSHA has found that there is no reliable mathematical relationship
among the three ways of assessing hearing impairment, so that direct
comparisons of their results are not possible. That is, it is not
possible to accurately predict the values computed using one definition
from values computed using either of the other two methods. In
addition, most of the raw data that would allow conversion from one
definition to another are no longer available. Nonetheless, the results
from all three approaches tend to demonstrate the same result.
Measuring Risk
MSHA could not determine an individual miner's risk from exposure
to particular levels of noise because at any given noise exposure, some
miners will suffer harm long before others, and a miner's
susceptibility cannot be measured in advance of exposure. However, as
MSHA noted in the proposal, risks can be determined for entire
populations. 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 percentage of an exposed population meeting the selected
criteria; and
(3) The percentage of an exposed population meeting the selected
criteria minus the percentage of a non-noise exposed population meeting
the same criteria, provided both populations are similar, apart from
their occupational noise exposures.
MSHA has determined that the third method, commonly known as
``excess risk,'' 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
noise standard (46 FR 9739, 1983). This method allows the
differentiation of the population expected to develop a hearing
impairment due to occupational noise exposure from the population
expected to develop an impairment from non-occupational causes, such as
aging or medical problems.
Although studies of hearing loss in the rulemaking record
consistently indicate that exposure to increased sound levels or
increased duration results in increased hearing loss, the reported risk
estimates of occupational noise-induced hearing loss vary considerably
from one study to another. The variation is due to three factors:
(1) The definition of ``material impairment'' used (discussed
above);
(2) The screening of the control (non-noise-exposed) group; and
(3) The sound level below which material impairment from noise
exposure is not expected to occur.
In some of the data used by MSHA, researchers did not screen their
study and control populations, while in others they used a variety of
screening criteria. Theoretically, screening does not have a
significant impact on the magnitude of occupational noise-induced
hearing loss experienced by given populations as long as the same
criteria are used to screen both the noise-exposed and the non-noise-
exposed populations being compared. However, failure to take into
account any non-occupational noise exposure, loss of hearing
sensitivity due to aging, or both, can have a profound effect when
considering whether the subjects have exceeded an established
definition of material impairment. For example, if both the exposed and
control populations are screened to eliminate persons with a history of
military exposure, use of medicines harmful to the ear, noisy hobbies,
and conductive hearing loss from acoustic trauma or illness, the excess
risk would be significantly different from that determined using
unscreened populations.
The studies used by MSHA for the final as well as the proposed rule
generally assumed exposures below 80 dBA to be nonhazardous. Although a
few researchers--Kryter (1970) and Ambasankaran et al. (1981)--have
reported hearing loss from exposure to sound levels below 80 dBA, most
scientists believe that the risk of developing a material impairment of
hearing from exposure to such low 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''
[[Page 49560]]
control group. Thus, 80 dBA has become the lower sound level against
which other noise exposures are compared to determine the ``excess
risk.'' This position was adopted by OSHA in its evaluation of the risk
of hearing loss for its existing standard on hearing conservation.
Review of Study Data
As noted in the preamble to the proposed rule, Table 1 is derived
from the preamble to OSHA's noise standard (46 FR 4084). It displays
the percentage of the population expected to develop a hearing
impairment meeting the AAOO 1959 definition if exposed to the specified
sound levels over a working lifetime of 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 based on
the AAOO 1959 definition, which was used by the original researchers.
Table 1.--OSHA Risk Table
----------------------------------------------------------------------------------------------------------------
Excess risk (%)
---------------------------------------------------
Sound level (dBA) NIOSH
ISO (1975) EPA (1973) (1972) Range
----------------------------------------------------------------------------------------------------------------
80.......................................................... 0 5 3 0-5
85.......................................................... 10 12 15 10-15
90.......................................................... 21 22 29 21-29
----------------------------------------------------------------------------------------------------------------
The excess risk of material impairment under the 1997/1998 NIOSH reanalysis is discussed earlier in this
preamble under Definition of Material Impairment.
Table 1 shows that the excess risk of material impairment after a
working lifetime at a noise exposure of 80 dBA is low. On the other
hand, a noise exposure of 85 dBA indicates a risk ranging from 10% to
15%. At a noise exposure of 90 dBA, the risk ranges from 21% to 29%.
Table 2 presents additional information on the risk assessments
calculated by NIOSH (Table XVII, Criteria Document, 1972), one portion
of which was included in Table 1. Table 2 is based on both the AAOO
1959 and the OSHA/NIOSH-72 definitions. It shows that NIOSH's risk
assessment found little difference between using the OSHA/NIOSH-72
definition and using the AAOO 1959 criteria.
Table 2.--NIOSH Risk Table
------------------------------------------------------------------------
Excess risk (%)
-------------------------
Sound level (dBA) OSHA/NIOSH-
72 AAOO 1959
------------------------------------------------------------------------
80............................................ 3 3
85............................................ 16 15
90............................................ 29 29
------------------------------------------------------------------------
Regarding how adjustments to the definitions used would affect the
excess risk figures above, MSHA agrees with several researchers
referred to by commenters. Suter (1988) estimates that the excess risk
would be somewhat higher if 500 Hz were excluded and 3000 Hz were
included in the definition of material impairment. Sataloff (1984)
reports that the effect of including hearing loss at 3000 Hz in the
AAOO 1959 definition of hearing impairment would dramatically increase
the prevalence of hearing impairment, as follows. 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. confirmed that the
exclusion of 500 Hz and the inclusion of 3000 Hz increased the number
of hearing impaired individuals in their study of potential workers'
compensation costs for hearing impairment (Royster et al., 1978). Using
an average hearing loss of 25 dB as the criterion, 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 the
OSHA/NIOSH-72 definition.
MSHA included the following three tables in the preamble to the
proposed rule in order to show data regarding the working lifetime risk
of material impairment based upon the three different definitions
commonly used for material impairment. Table 3 is based on AAO 1959,
Table 4 is based on AAO-HNS 1979, and, Table 5 is based on the OSHA/
NIOSH-72 definition. 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 are taken from summary graphs in that
report. The noise-exposed population was 65 years old, with 40 years of
noise exposure. Because the control group was not screened for the
cause of hearing loss, a high level of non-occupational hearing loss
may undervalue the excess risk from occupational noise exposure. The
researchers (Melnick et al., 1980) added the component of noise-induced
permanent threshold shift (the actual shift in hearing level due only
to noise exposure) to the control data.
MSHA did not receive any comments on the three tables reflecting
the predictable fact that, for any given population, the excess risk of
material impairment due to noise exposure will be greater using the
AAO-HNS 1979 definition than using the AAOO 1959 definition. Likewise,
the excess risk of material impairment due to noise exposure will be
greater using the OSHA/NIOSH-72 definition than using the AAO-HNS 1979
definition. All three tables show a smaller excess risk than did the
data presented in Table 1.
Table 3.--Risk of Impairment Using AAOO 1959 Definition of Impairment
and Using Melnick et al., 1980 Data
------------------------------------------------------------------------
Excess risk
Percent (percent)
Exposure with 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 4.--Risk of Impairment Using AAO-HNS 1979 Definition of Impairment
and Using Melnick et al., 1980 Data
------------------------------------------------------------------------
Excess risk
Percent (percent)
Exposure with with noise
impairment exposure
------------------------------------------------------------------------
non-noise..................................... 41.6 0.0
80 dBA........................................ 41.8 0.2
[[Page 49561]]
85 dBA........................................ 44.4 2.8
90 dBA........................................ 50.0 8.4
------------------------------------------------------------------------
Table 5.--Risk of Impairment Using OSHA/NIOSH-72 Definition of
Impairment and Using Melnick et al., 1980 Data
------------------------------------------------------------------------
Excess risk
Percent (percent)
Exposure with 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
------------------------------------------------------------------------
The excess risk in Table 1 represents the risk assessments
conducted by ISO, EPA, and NIOSH in three different years during the
early 1970's. All three agencies used the same definition of impairment
(AAOO 1959) in evaluating available studies. Their results are similar.
MSHA applied three different definitions of hearing impairment to
the same data (Melnick 1980) to show that the excess risk of impairment
varies depending on how you define impairment. Tables 3, 4, and 5
present the results of this analysis. Because Melnick did not screen
his control group for the cause of the hearing loss (could be non-
occupational noise exposure), the amount of hearing loss in the
supposed non-noise exposed group is high. By subtracting the value for
the non-noise exposed (control) group from the values determined for
groups with different levels of occupational noise exposure, we
determined the excess risk for populations exposed at that level.
Tables 6 and 7 were also included in the preamble to the proposed
rule to show data derived by Melnick in Forensic Audiology (1982) for
risk of impairment due to noise exposure. These tables show the results
of applying the AAO-HNS 1979 method to a population that is 60 years
old with 40 years of exposure to the specified sound levels. In both
tables, the data represent the noise-induced permanent threshold shift
calculated by Johnson, but the screening criteria used in the two
tables are different. Melnick's data in Table 6 are based upon the
screened age-induced hearing loss data (that is, they are screened for
non-occupational hearing loss) of Robinson and Passchier-Vermeer,
whereas Table 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 1 than to that in Tables 3, 4, and 5, but still
differs. Tables 6 and 7 directly illustrate the effect of screening
populations in determining excess risk due to occupational noise
exposure. Comparison of these tables shows that the percentage of
workers with hearing impairment is greater in the table constructed
with an unscreened population as the base.
Table 6.--Risk of Impairment Using Age-induced Hearing Loss Data of
Passchier-Vermeer and Robinson
------------------------------------------------------------------------
Excess risk
Percent (percent)
Exposure with with noise
impairment exposure
------------------------------------------------------------------------
75 dBA........................................ 3 0
80 dBA........................................ 5 2
85 dBA........................................ 9 6
90 dBA........................................ 21 18
------------------------------------------------------------------------
Table 7.--Risk of Impairment Using Non-occupational Hearing
------------------------------------------------------------------------
Excess risk
Percent (percent)
Exposure with with noise
impairment exposure
------------------------------------------------------------------------
75 dBA........................................ 27 0
80 dBA........................................ 29 2
85 dBA........................................ 33 6
90 dBA........................................ 40 13
------------------------------------------------------------------------
Chart 1 incorporates the risk assessment results of Tables 3, 4, 5,
6, and 7.
[[Page 49562]]
[GRAPHIC] [TIFF OMITTED] TR13SE99.000
Note that the data from both Table 6 and Table 7 used the AAO-HNS 1979
definition. The exact numbers of those at risk varies with the study
because of the definition of material impairment used, the screening
criteria used, and the selection of the control group. Despite 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 sound levels
of 85 dBA; and
(3) Lowering the exposure from 90 dBA to 85 dBA reduces the excess
risk of developing a material impairment by approximately half.
Related Studies of Worker Hearing Loss
The preamble to the proposed rule indicated that MSHA examined a
large body of data on the effects of varying industrial sound levels on
worker hearing sensitivity, including studies that specifically
addressed the mining industry. Regardless of the industry in which the
data were collected, MSHA found that exposures to similar sound levels
results in similar degrees of material impairment in workers. These
studies support the conclusions reached in the previous section about
the risk of impairment at different sound levels.
NIOSH (Lempert and Henderson, 1973) published a report in which the
relationship of noise exposure to noise-induced hearing loss was
described. NIOSH studied 792 industrial workers whose daily noise
exposures were 85 dBA, 90 dBA, and 95 dBA. The noise-exposed workers
were compared to a control group whose noise exposures were lower than
80 dBA. The exposures were primarily to steady-state noise, but the
exposure levels fluctuated slightly in each category. Both groups were
screened to exclude non-occupational noise exposure or medical
complications. The subjects ranged in age from 17 to 65 years old. The
report clearly shows that workers whose noise exposures were 85 dBA
experienced more hearing loss than the control group. In addition, as
the noise exposures increased to 90 dBA and 95 dBA, the magnitude of
the hearing loss increased.
NIOSH reanalyzed these data in a report, ``Reexamination of NIOSH
Risk Estimates'' (Prince et al., 1997), which was published after
MSHA's proposed rule. The authors reanalyzed the data from NIOSH's
report (Lempert and Henderson, 1973) that had established a dose-
response relationship for noise. In the original study, Lempert and
Henderson had interpreted response to be proportional to dose. Prince
interpreted the relationship to be a more complex one, and this
analysis resulted in a better fit with the data. Prince's approach also
consistently yielded a slightly lower excess risk. Thus, Prince
concluded that there is an excess risk of developing a hearing
impairment from a noise exposure of 85 dBA and above.
NIOSH (1976) published the results from a study on the effects of
prolonged exposure to noise on the hearing sensitivity of 1,349 coal
miners. From this study, NIOSH concluded that coal miners were losing
their hearing sensitivity 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 (only 12% of the
noise exposures exceeded a TWA8 of 90 dBA), the measured
hearing loss of the older coal miners was indicative of noise exposures
between a TWA8 of 90 dBA and 95 dBA. NIOSH 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 experienced a higher
incidence of hearing impairment than the non-occupational-noise-exposed
group (control group) at each age. Using the OSHA/NIOSH-72 definition
of material impairment, 70% of 60-year-old coal miners were impaired
while only a third of the control group were. This would correspond to
an excess risk of 37%.
NIOSH also sponsored a study, conducted by Hopkinson (1981), on the
[[Page 49563]]
prevalence of middle ear disorders in coal miners. In this study, the
hearing sensitivity of 350 underground coal miners was measured. The
results of this study supported the results of the 1976 NIOSH study on
the hearing sensitivity of underground coal miners (i.e., coal miners
had worse hearing than the controls); the measured median hearing
levels of the miners were the same in the two studies.
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.
Neither the control group nor the noise-exposed groups were screened
for anatomical abnormalities of the ear.
Baughn used this data to estimate 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, 43% of 58-year-old workers exposed
for 40 years to noise at 85 dBA would meet the AAOO 1959 definition for
hearing impairment. Thirty-three percent of an identical but non-noise
exposed population would be expected to meet the same definition of
impairment. The excess risk from exposure to noise at 85 dBA would
therefore be 10%. Using the same procedure, the excess risk for 80 dBA
is 0% and for 90 dBA 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 workers with unknown exposure histories. Also
excluded were people with ear disease or abnormalities and language
difficulty. 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 those of 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 the Burns and Robinson mathematical model, MSHA constructed
Chart 2. The chart shows that a noise exposure of 85 dBA over a 40-year
career is clearly hazardous to the hearing sensitivity of 60-year-old
workers. Chart 2 compares the same three definitions of impairment to
the Burns-Robinson Model as used in Tables 3, 4, and 5 with the Melnick
data. Chart 2 confirms the relationship between the definition of
impairment and the computation of excess risk.
[GRAPHIC] [TIFF OMITTED] TR13SE99.001
The prevalence of hearing loss in a group of 228 Canadian steel
workers, ranging in age from 18 to 65 years of age, was compared to a
control group of 143 office workers in a study conducted by Martin et
al. (1975). 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 these workers
would be at risk of incurring a hearing impairment with a
TWA8 90 dBA permissible exposure level compared to 4% with a
TWA8 85 dBA permissible exposure level. Both the noise-
exposed and the control groups were screened to exclude workers with
non-occupational hearing loss.
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
[[Page 49564]]
above 90 dBA caused considerable hearing loss in a large percentage of
employees and 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.
Berger, Royster, and Thomas (1978) studied 42 male and 58 female
workers employed at an industrial facility and a control group of 222
persons who were not exposed to occupational noise. Of the 322
individuals included in the study, no one was screened for exposures to
non-occupational noise such as 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
(Leq is an average sound level computed on a 3-dB exchange
rate). According to the researchers, the measurable loss was in close
agreement with the predictions of Burns and Robinson, Baughn, NIOSH,
and Passchier-Vermeer.
Studies of Impact of Lower Sound Levels
Table 8 reproduces the most recent data on the harm that can occur
at lower sound levels, found in the International Standards
Organization's publication ISO 1999 (1990). The noise exposures for the
population ranged between 75 dBA and 100 dBA. Table 8 presents the mean
and various percentages of the hearing level of a 60-year-old male
exposed to noise for 40 years. The noise-induced permanent threshold
shift in hearing was combined with the age-induced hearing loss values
to determine the total hearing loss. The age-induced hearing loss
values were from an unscreened population representing the general
population.
Table 8.--Hearing Level Resulting From Selected Noise Exposures
----------------------------------------------------------------------------------------------------------------
Hearing level in dB
Sound level in dBA ---------------------------------------------------
500 Hz 1000 Hz 2000 Hz 3000 Hz
----------------------------------------------------------------------------------------------------------------
80.......................................................... 12 6 10 30
85.......................................................... 12 6 11 33
90.......................................................... 12 6 16 42
----------------------------------------------------------------------------------------------------------------
Information about the effects of lower noise exposures on hearing
are especially valuable in attempting to identify 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 reaffirmed many of the earlier findings of the
Committee. Based on temporary threshold shift (TTS) studies, the report
suggests that to prevent noise-induced hearing loss, exposures must
remain below 76 dBA to 78 dBA. Based on field studies, the report
suggests that, to guard against any permanent hearing loss at 4000 Hz,
the sound level should be less than 85 dBA, and possibly less than 80
dBA. Finally, the report suggests that therapeutic drugs, such as
aminoglycoside antibiotics and salicylates (aspirin), can interact
synergistically with noise to yield more hearing loss than would be
expected by either stressor alone.
Few current studies of unprotected U.S. workers exposed to a
TWA8 between 85 and 90 dBA are available, because the
hearing conservation program of OSHA's noise standard requires
protection at those levels for most industries (the exception being
employers engaged in oil and gas well drilling and servicing
operations). The difficulty in constructing new retrospective studies
of U.S. workers has been noted by Kryter (1984) in his chapter entitled
``Noise-Induced Hearing Loss and Its Prediction.'' He states that due
to the global trend in the last decade to institute noise control and
hearing conservation programs, new retrospective studies are no longer
feasible. Kryter believes that the retrospective studies of Baughn,
Burns and Robinson, and the U.S. Public Health Service are thus the
best available on the subject of noise-induced permanent threshold
shift. Kryter developed a formula to derive the effective noise
exposure level for damage to hearing from the earlier studies and
determined the noise-induced permanent threshold shift at different
percentiles of sensitivity at various audiometric test frequencies for
a population of workers.
Studies of workers in other countries can provide valuable
information in assessing the consequences of workplace noise exposure
between 85 dBA and 90 dBA. Differences in socioeconomic factors such as
recreational noise exposure, use of medicines harmful to the ear, and
inflammation of the middle ear (otitis media) make it difficult to
directly apply the results of studies of workers from other countries.
However, MSHA has determined that these studies can be used as further
support for 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 on average
exposures. Assuming that exposure to sound levels less than 80 dBA did
not cause any hearing loss, they assigned workers exposed to these
levels to the control group. The researchers 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 whose exposure was between
80 dBA and 103.5 dBA, hearing loss tended to increase steadily during
their careers but leveled off after 15 years. In contrast, for workers
exposed to sound levels above 103.5 dBA, hearing loss continued to
increase beyond 15 years.
A statistical method for predicting hearing loss was developed
using the data collected in the Rop study. 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%. The study concluded that exposure to sound levels at or above 85
dBA damaged workers' hearing.
A study (Schwetz et al., 1980) of 25,000 Austrian workers 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. The study further
[[Page 49565]]
concluded that at 85 dBA there is no hearing recovery, ultimately
causing noise-induced hearing loss. Schwetz, therefore, recommended 85
dBA as the critical intensity--the permissible exposure limit.
Stekelenburg (1982) calculated age-induced hearing loss according
to Spoor and noise-induced hearing loss according to Passchier-Vermeer.
Based upon these calculations, Stekelenburg suggested 80 dBA as the
acceptable level for noise exposure over a 40 year work history. At
this exposure, Stekelenburg calculates that socially impaired hearing
due to noise exposure would be expected in 10% of the population.
A study of 537 textile workers by Bartsch et al. (1989), which
defined socially significant hearing loss as a 40 dB hearing level at
3000 Hz, found that the hearing loss resulting from exposures below 90
dBA mainly occurs at frequencies above 8000 Hz (these frequencies are
not normally tested during conventional audiometry). Even though the
study concluded that the hearing loss was not of ``social importance,''
it did support a reduced hearing loss risk criterion of 85 dBA be used
to protect the workers' hearing.
With the exception of the Bartsch study, the results of the foreign
studies are generally consistent with those of U.S. workers. The
Bartsch conclusion that the hearing loss is not of ``social
importance'' is not supported by the many studies, discussed earlier,
that point to the importance of good hearing sensitivity at 3000 Hz in
order to understanding speech in everyday, noisy environments. Based on
experience, MSHA has found that people will encounter hearing
difficulty before their hearing loss level reaches 40 dB at 3000 Hz.
One commenter stated that the studies cited by MSHA in justifying
the risk of material impairment at exposures below 90 dBA were based on
sound levels determined using older instrumentation. Assuming that MSHA
would be using more modern instrumentation for compliance purposes, he
suggested that the Agency should not use the old data and studies. The
commenter suggested that MSHA either raise or retain the criterion
level of a TWA8 of 90 dBA or have the studies re-done with
newer instrumentation before proceeding with rulemaking. MSHA maintains
that the studies remain valid, however, because they were conducted
using methodologies based on sound level meters. The studies, like the
final rule, were based on the standardized definitions of A-weighting
network and slow response and usually measured steady-state noise.
Therefore, the studies are reliable and applicable. MSHA's risk
assessment is based upon the best scientific data available to the
Agency, as required by the Mine Act.
Reported Hearing Loss Among Miners
To confirm the magnitude of the risks of noise-induced hearing loss
among miners, MSHA examined the following evidence of reported hearing
loss among miners.
Audiometric Databases
Audiometric testing is not currently required in metal and nonmetal
mining and is offered in coal mining only after a determination of
overexposure to noise. However, in connection with its ongoing
assessments of the effectiveness of the current standards in protecting
miner health, MSHA has obtained two audiometric databases consisting of
20,022 audiograms conducted on 3,439 coal miners and 42,917 audiograms
conducted on 9,050 metal and nonmetal miners. The audiometric
evaluations on the coal miners were conducted between 1971 and 1994,
mostly during the latter years. The audiograms on metal and nonmetal
miners were collected between 1974 and 1995. Each audiogram in the data
set contained a miner identification number, age, date of test, and
audiometric thresholds for each ear at 500, 1000, 2000, 3000, 4000, and
6000 Hz. Supplemental data such as dates of employment, noise
exposures, use of protective equipment, and training histories were not
provided. MSHA asked NIOSH to examine the audiometric data and both
MSHA and NIOSH (Franks, 1996) have performed analyses of the coal miner
database.
Coal Miner Audiometric Data
Franks used a computer expert system to screen the data for year-
to-year consistency of the audiograms, test-room background noise, and
asymmetry in hearing that might indicate a unilateral loss of hearing
(which is not characteristic of occupational noise-induced hearing
loss). More than 2,500 questionable audiograms were reviewed by NIOSH
audiologists.
The final screened database consisted of 17,260 audiograms
representing 2,871 coal miners. It was compared to the database in
Annex A of ``ISO-1999.2 Acoustics--Determination of Occupational Noise
Exposure and Estimation of Noise-Induced Hearing Loss.'' NIOSH's report
entitled ``Analysis of Audiograms for a Large Cohort of Noise-Exposed
Miners'' (NIOSH, 1996) indicates that 90% of these coal miners had a
hearing impairment (defined as an average 25-dB hearing level at 1000,
2000, 3000, and 4000 Hz) by age 51 compared with only 10% of the
general population. Even at age 69, only 50% of the non-noise-exposed
population acquire a hearing impairment.
By age 35 the average miner has a mild hearing loss, and 20% of
miners have a moderate loss. By age 64, fewer than 20% of the miners
have marginally normal hearing, while 80% have moderate to profound
hearing loss. In contrast, 80% of the non-noise-exposed population will
not acquire a hearing loss as severe as the average miner's, regardless
of how long they live. Further, Franks concluded that miners, after
working 20 to 30 years, could find themselves in life-threatening
situations resulting from their inability to hear safety signals and
roof talk.
Metal and Nonmetal Miner Audiometric Data
NIOSH used a computer expert system to screen the audiometric data
on metal and nonmetal miners. The data were screened for year-to-year
consistency of the audiograms, test room background noise, and
asymmetry in hearing that might indicate a loss of hearing in only one
ear (not characteristic of an occupational noise-induced hearing loss).
The expert system identified 20,429 questionable audiograms, and a
subset of 1000 were reviewed by an audiologist.
The final screened database consisted of 22,488 audiograms
representing 5,244 metal and nonmetal miners. The data were compared to
those in Annex A of ``ISO-1999.2 Acoustics--Determination of
Occupational Noise Exposure and Estimation of Noise-Induced Hearing
Loss.'' NIOSH's report, entitled ``Prevalence of Hearing Loss for
Noise-Exposed Metal/Nonmetal Miners'' (NIOSH, 1997), supports the
conclusions of earlier scientific studies that metal and nonmetal
miners are losing their hearing sensitivity faster than the general
population. It indicates that, ``At age 20, approximately 2% have
hearing impairment, rising to around 7% at age 30, 25% at age 40, 49%
at age 50, and 70% by age 60. By contrast, 9% of the non-occupationally
noise-exposed have hearing impairment at age 50.'' Franks noted a
difference in the increase of hearing loss between men and women. He
also noted that, due to the NIOSH definition of hearing impairment used
in the study (inclusion of 4,000 Hz.), there was a sufficient degree of
hearing impairment in the population to cause communications problems,
because miners would have difficulty in understanding some consonants
whose
[[Page 49566]]
frequency is between 3,000 and 4,000 Hz.
MSHA received comments on both NIOSH studies. One commenter
asserted that Franks used an incorrect screening process for the
audiograms as well as the incorrect control group (ANNEX A of ISO R-
1999) and alleged other deficiencies in the studies. This commenter
stated that he reanalyzed the data using minimal screening of
audiograms, and compared it to the ``correct'' control group (Annex C
of ANSI S3.44-1996, ``Acoustics--Determination of Occupational Noise
Exposure'') estimating that the hearing impairment of the miners was
caused by noise exposure. The commenter concluded that both the coal
and metal and nonmetal audiometric data suggest that typical
occupational noise exposures are on the order of lifetime time-weighted
exposures of about 89 dBA. This commenter thus suggests that there is
no need for MSHA to continue with rulemaking, as the current
regulations are adequate in protecting miners' hearing sensitivity.
Some commenters concurred with the re-analysis of the NIOSH studies
performed by this commenter. MSHA notes, however, that there was no
significant difference between the control groups, as the International
Standards Organization 1999.2 standard and the American National
Standards Institute S3.44 standard are virtually identical--the ANSI
document having been adapted from the ISO document.
However, MSHA also received a great deal of support for the NIOSH
studies, which showed that the use of the Annex A control group--highly
screened audiometric data was appropriate and the use of Annex B or C
in the reanalysis was inappropriate.
One commenter stated, ``The use of Annex B * * * is questionable
because these data were not screened to exclude persons with
occupational noise exposure.''
MSHA agrees with Dr. Franks in that Annex A was the most
appropriate database for the analysis conducted because it is the only
database in ISO 1999 for which year-to-year changes in hearing and
prevalence of hearing impairment could be calculated. MSHA also
received support from commenters for the NIOSH studies. Additionally,
MSHA conducted its own research and determined that miners are still
losing more of their hearing sensitivity than non-noise-exposed
workers. Annex A is a more stringent screening method than Annex C
which was used by Dr. Clark. Annex A was selected because it represents
a highly screened sample, free from ``undue noise exposure'' and ear
disease.
Several researchers who studied the health status of miners
provided testimony based on numerous research reports. Their conclusion
was that miners have incurred a greater loss of hearing sensitivity
than the general population has. MSHA believes that the NIOSH studies
are valid evidence that supports the rule.
MSHA conducted a separate analysis of the audiometric data for coal
miners, using the 25 dB hearing level at 1000, 2000, and 3000 Hz
definition of material impairment of hearing. In order to reflect
current trends, the percentage of current coal miners (whose latest
audiogram was taken between 1990 and 1994) with material impairment of
hearing was compared to NIOSH's study on coal miners published in 1976.
The results are shown in Chart 3, along with NIOSH's 1976 results for
both the noise-exposed miners and the non-noise-exposed controls.
The data points for Chart 3 represent the mean hearing loss of both
ears at 1000, 2000, and 3000 Hz relative to audiometric zero. The top
line represents the 1976 (pre-noise-regulation) group, the middle line
represents the 1990-1994 (noise-regulated) group, and the bottom line
represents the non-noise-exposed group. Although there has been some
progress under the existing regulations, miners are still losing more
of their hearing sensitivity than non-noise-exposed workers. This is
true even if the analysis is limited to miners under 40 years of age
(that is, those who have worked only under the current coal noise
regulations).
[GRAPHIC] [TIFF OMITTED] TR13SE99.002
MSHA also analyzed the audiometric data for the number of standard
threshold shifts and reportable hearing loss cases. In the preamble to
the proposal, MSHA defined a standard threshold shift 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 final rule adopts this
definition. The importance of a standard threshold shift is that it
reveals that a permanent loss in hearing sensitivity
[[Page 49567]]
has occurred. When the change from the baseline averages 25 dB or more
at the same frequencies, the hearing loss must be reported to MSHA.
``Standard threshold shift'' and ``reportable hearing loss'' are
discussed in greater detail below.
For the second analysis, the first audiogram of each miner was
assumed to be the baseline. The last audiogram of each miner was
compared to the baseline. Neither audiogram was corrected for age-
induced hearing loss. Also, because of the lack of supporting data, it
was not possible to exclude non-occupational standard threshold shifts,
resulting in a greater number of standard threshold shifts. The results
of the 3,102 coal miners audiograms analyzed are presented in Chart 4.
[GRAPHIC] [TIFF OMITTED] TR13SE99.003
Chart 4 clearly shows that many of the coal miners were found to
have a standard threshold shift. The likelihood of acquiring a standard
threshold shift generally increases with advancing age. The MSHA
analysis was conservative in that only the first and last audiograms
were included, resulting in each miner having only one standard
threshold shift. In fact, a miner may have experienced multiple
standard threshold shifts.
In addition to the above audiometric data, two NIOSH studies
mentioned in the section of this preamble on risk of impairment support
MSHA's conclusion that miners are at risk of noise-induced hearing
loss. In the 1976 NIOSH study, although the majority of noise exposures
were less than 90 dBA, approximately 70% of the 60-year old coal miners
had experienced a material impairment of hearing using the OSHA/NIOSH-
72 definition. The Hopkinson (1981) NIOSH study also supports the
earlier NIOSH results.
Data Provided by Commenters
Two commenters to the proposed rule provided information on the
hearing sensitivity of miners. The first commenter estimated that 45 to
50% of employed miners have experienced a standard threshold shift (at
least 25% if corrected for age-induced hearing loss). 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. Corrected for
age-induced hearing loss, the percentage of miners with this level of
hearing loss decreased to about 15%.
The second commenter referred to an oral presentation by Smith et
al. at the 1989 Alabama Governor's Safety and Health Conference. (MSHA
notes that the Smith presentation itself is not part of the rulemaking
record, although Smith verified that the comment was correct via letter
(December 5, 1994). MSHA believes that the Smith paper is valid
evidence which supports the rule.) 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. The authors found that 15% of
these workers would have some degree of hearing impairment using the
AAO-HNS 1979 definition. They also reported that at least 26% of the
mining population would have some degree of hearing impairment using
the same definition.
In response to MSHA's request for additional specific information
regarding hearing loss among miners, some commenters stated that they
had no workers' compensation awards for miners' hearing loss at their
operations. No commenters supplied information regarding the cost of
compensation awards. Some commenters supplied specific information on
miner's age, occupation, and degree of hearing loss. Several commenters
submitted data, some in conjunction with an analysis of the data, in
support of their position that hearing protectors can be effective as
the primary means of protecting miners against occupational noise-
induced hearing loss.
The NIOSH (Franks) analysis of the two databases cited by MSHA and
the three analyses conducted by Clark and Bohl under the auspices of
the National Mining Association (the first a report summarizing a
reanalysis of the NIOSH Coal Miner Study, the second a report
containing a reanalysis of the NIOSH Metal and Nonmetal Miner Study,
and the third a report containing an analysis of two data bases from
the National Mining Association) indicate that miners are developing
hearing losses to a degree that constitutes material impairment. These
analyses also indicate that the amount of hearing loss and the
percentage of the population that is impaired is highly variable.
Further, some individual miners received a substantial hearing loss.
The differences in the conclusions of these studies are attributable to
the different baselines used in the analyses for comparison of the
exposed populations. The NIOSH analysis included detailed screening of
the data and used a control group (described in Appendix A of
[[Page 49568]]
ANSI S3.44, ``American National Standard Determination of Occupational
Noise Exposure and Estimation of Noise-Induced Hearing Impairment'')
where the hearing losses of the group are strictly due to aging. In
contrast, the Clark-Bohl analyses and conclusions did not include
screening of the data and used for comparison the control group
(described in Appendix C of ANSI S3.44) where the control group's
hearing losses included those due to exposures to less than two weeks
of occupational noise, exposures to non-occupational noise, otological
abnormalities, as well as those due to aging. There is insufficient
information in the studies to allow a determination of which method of
analysis is more appropriate or superior. As a result of the
differences in approach between these analyses, the analyses arrive at
different conclusions regarding the magnitude of the hearing losses
exhibited by miners, although all of these analyses do indicate that
some miners are developing a material impairment of hearing in varying
degrees. Additionally, these analyses do not support the conclusion
that a hearing conservation program that relies primarily or
exclusively on the use of hearing protectors effectively protects all
miners from noise-induced occupational hearing loss.
Other studies and data were submitted by other commenters in
support of their position that a hearing conservation program that
relies primarily or soley on the use of hearing protectors can
adequately protect miners' hearing. These studies and data are
discussed later in the preamble.
Reported Hearing Loss Data
Under MSHA's existing regulations at 30 CFR part 50, mine operators
are required to report cases of noise-induced hearing loss to MSHA when
it is diagnosed by a physician or when the affected miner receives an
award of compensation. Between 1985 and 1997, mine operators reported a
total of 2,590 cases of noise-induced hearing loss. In a substantial
number of these cases, the occupational noise exposures occurred after
the implementation of the current noise regulations.
Coal mine operators reported 674 cases among surface miners, 1,098
cases among underground miners, and 14 cases among miners whose
positions were not identified. According to coal mine operators, 710 of
the 1,786 cases began working at a mine after the implementation of the
noise regulations for coal mines--1972 for underground coal mining and
1973 for surface coal mining. Workers with no reported mining
experience were excluded from the analysis.
Metal and nonmetal mine operators reported 650 cases among surface
miners and 154 cases among underground miners, a total of 804 cases.
According to mine operators, 172 of the 804 cases began working at a
mine after the implementation of noise regulations for metal and
nonmetal mines in 1975. Again, workers with no reported mining
experience were excluded from the analysis.
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 reported of workers
who began working after the implementation of the current standards.
This is despite the fact that, at present, there are more metal and
nonmetal miners than coal miners employed in the United States. A
possible explanation of the difference between reported cases of noise-
induced hearing loss among coal and metal and nonmetal miners may be
that there is more frequent use of engineering noise controls in metal
and nonmetal mining. Because the occupational noise standards for coal
mines allow inspectors to take into account the use of hearing
protectors in determining compliance, most coal mines use hearing
protectors for compliance unless the engineering controls are
inexpensive or come with the equipment. Metal/nonmetal mines are not
allowed to use hearing protectors for compliance unless they have
implemented all feasible engineering and administrative controls. Other
possible reasons include differences in the severity of the noise
exposures, variations among states' criteria for workers' compensation
awards, continual use of hearing protectors, and the effectiveness of
selected hearing protectors.
MSHA reviewed the narrative associated with each case of noise-
induced hearing loss to determine the average degree of hearing loss.
Although many narratives included reasons for reporting the noise-
induced hearing loss, others only listed the illness as ``hearing
loss.'' Approximately half the cases had no information on the severity
of the hearing loss. Some contained designations such as standard
threshold shift, OSHA reportable case, or percent disability. The
narratives did not contain enough information with which to determine
an average severity for cases of noise-induced hearing loss.
At least 40% of the reported cases in coal mining resulted in the
miner being compensated for noise-induced hearing loss. Another 7% of
the reported cases indicated that a workers' compensation claim for
noise-induced hearing loss had been filed. In metal and nonmetal mines,
at least 21% of the reported cases resulted from the miner being
compensated for noise-induced hearing loss. Nearly another 4% of the
reported cases indicated that a workers' compensation claim for noise-
induced hearing loss had been filed.
The low number of cases reported to the Agency are believed to be
due to either:
(1) The lack of a specific definition of a noise-induced hearing
loss in MSHA's part 50 regulations and the resulting confusion on the
part of mine operators about which cases to report;
(2) The lack of consistency among state requirements for awarding
compensation for a noise-induced hearing loss and among physicians in
diagnosing what constitutes a hearing loss caused by noise; or
(3) The lack of required periodic audiometric testing in the mining
industry.
In sum, the hearing loss currently reported to MSHA under part 50
cannot be used to accurately characterize the incidence, prevalence, or
severity of hearing loss in the mining industry. However, the data
clearly show that miners are experiencing noise-induced hearing loss.
Workers' Compensation Data
The preamble to the proposal reviewed a study by Valoski (1994) of
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 databases, Valoski was
unable to obtain data for all states, including those with significant
mining activities. 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, excluding
rehabilitation or medical costs.
In a letter to MSHA, NIOSH cited the Chan et al. (1995)
investigation for NIOSH of the incidence of noise-induced hearing loss
among miners using information from the Bureau of Labor Statistics'
(BLS) Supplementary Data System. In the 15 states that participated in
the BLS program between 1984 and 1988, a total of 217 miners (93 coal
miners and 124 metal and nonmetal miners) were awarded workers'
compensation for noise-induced hearing loss. During those
[[Page 49569]]
years, mine operators from all states reported 873 cases of noise-
induced hearing loss among coal miners and 286 cases among metal and
nonmetal miners. Chan et al. stated that because of differing state
workers' compensation requirements, it is not possible to directly
compare noise-induced hearing losses among the states. These factors
limit the usefulness of the data obtained.
MSHA reviewed reports on workers' compensation in Canada and
Australia in the preamble to the proposed rule. The noise regulations
and mining equipment used in these countries are similar to those in
the United States. A recent report on workers' compensation awards to
miners in Ontario, Canada (1991) showed that between 1985 and 1989,
noise-induced hearing loss was the second leading compensable
occupational disease. Approximately 250 claims for noise-induced
hearing loss involving miners were awarded annually during that time.
Lescouflair et al. (1980) studied 278 metal and asbestos miners
working in Quebec, Canada who claimed compensation for hearing loss.
After excluding 28.7% (80) cases of non-mining noise-induced hearing
loss, approximately 50% (99) of those diagnosed as having noise-induced
hearing loss were shown to have a hearing impairment, based on the AAOO
1959 definition. An estimated 63% (125) showed an impairment based on
AAO-HNS 1979 definition. 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 noise-induced hearing loss between
those miners exposed to a combination of intermittent and continuous
noise and those exposed to 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 noise-induced hearing loss made up 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 noise-induced hearing loss. 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.
Although the compensation data are incomplete and cannot be used
for estimating the prevalence of noise-induced hearing loss in the
mining industry, the limited data available show that numerous cases
are being filed each year, at considerable cost. Furthermore, according
to the data reported by mine operators, many miners who developed
noise-induced hearing loss worked in mining only after the
implementation of the current noise regulations. This evidence of
continued risk, although limited, supplements and supports the data
previously presented from scientific studies.
Exposures in the U.S. Mining Industry
Miners in the U.S. are at significant risk of experiencing material
impairment as a result of exposure to noise. Exposure levels remain
high in all sectors of the mining industry, even though noise
regulations have been implemented for some time. Exposures are
particularly high in the coal mining sector, where hearing protectors,
rather than engineering or administrative controls, remain the primary
means of protection against noise-induced hearing loss.
Inspection Data
Noise exposure data has been collected by MSHA inspectors from
thousands of samples gathered over many years. Table 9 indicates
samples which present readings exceeding the permissible exposure
level, (TWA8 of 90 dBA) and also shows noise dose trends in
metal and nonmetal mines based on over 232,500 full-shift samples
collected using personal noise dosimeters by MSHA from 1974 through
1997.
Table 9.--MNM Mines Noise Dose Trends CYs 1974-97 *
------------------------------------------------------------------------
Number
Number of samples Percent
Fiscal year samples exceeding exceeding
90 dBA TWA8 90 dBA TWA8
------------------------------------------------------------------------
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
1996............................. 16,686 2,228 13.4
1997............................. 10.731 1,989 14.3
------------------------------------------------------------------------
* From USBM's MIDAS data base. Italicized data not included in chart 9a.
[[Page 49570]]
Table 10 shows samples with readings exceeding the permissible
exposure level (TWA8 of 90 dBA) and noise dose trends in
coal mines based on 75,691 full-shift samples collected by MSHA from
1986 through 1997 using personal noise dosimeters. MSHA began routine
sampling in coal mines in 1978 but did not begin building the database
until 1986.
Table 10.--Coal Mine Noise Dose Trends, FYs 86-97
------------------------------------------------------------------------
Number
Number of samples Percent
Fiscal year samples exceeding exceeding
90 dBA TWA8 90 dBA TWA8
------------------------------------------------------------------------
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
1996............................. 6,064 1,256 20.7
1997............................. 6,542 1,388 21.2
------------------------------------------------------------------------
The inspection data for the coal and metal and nonmetal mining
sectors have been graphed in Charts 9a and 10a, which indicate that the
metal and nonmetal sector shows a gradual but consistent downward trend
in the percentage of samples exceeding the current permissible exposure
level. However, there was no such clear trend for coal mines during the
same period. MSHA attributes this difference to the established use of
engineering and administrative controls in metal and nonmetal mines.
[[Page 49571]]
[GRAPHIC] [TIFF OMITTED] TR13SE99.004
MSHA notes that the interaction of two factors in the data
represented in these charts may offset each other. First, the database
is made up of samples collected in noisier mines and occupations.
Second, the database includes both initial overexposure and the results
of any resampling to determine compliance after the mine operator has
utilized engineering or administrative controls (in the case of an
overexposure found during an initial survey).
Dual Survey Data
MSHA conducted a special survey to compare noise exposures at
different threshold levels, because the final rule requires integration
of sound levels between 80 dBA and at least 130 dBA for the action
level and between 90 dBA and at least 140 dBA for the permissible
exposure level. The survey, referred to as the dual-threshold survey,
involved the collection by MSHA inspectors of data in coal, metal, and
nonmetal mines. Each sample was collected using a personal noise
dosimeter capable of collecting data at both thresholds simultaneously.
All other dosimeter settings were the same as those used during normal
compliance inspections (the 90 dBA criterion level, 5-dB exchange rate,
and A-weighting and slow response characteristics). The noise doses
were mathematically converted to their corresponding TWA8.
Tables 11 and 12 display the dual-threshold data in metal and
nonmetal mines and in coal mines. Table 11 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 11.--M/NM Dual-Threshold Noise Samples Equal to or Exceeding Specified TWA8 Sound Levels--March 1991
through December 1994
----------------------------------------------------------------------------------------------------------------
90 dBA threshold 80 dBA threshold
---------------------------------------------------
TWA8 sound level (in dBA) Number of Percent of Number of Percent of
samples samples samples samples
----------------------------------------------------------------------------------------------------------------
90 (PEL).................................................... 7,360 17.4 ........... ...........
[[Page 49572]]
85 (action level)........................................... ........... ........... 28,250 66.9
----------------------------------------------------------------------------------------------------------------
As indicated in Table 11, 17.4% of all samples collected by MSHA in
metal and nonmetal mines during the specified period equaled or
exceeded the permissible exposure level (a TWA 8 of 90 dBA
using a 90-dBA threshold)--slightly less than the results of the
inspectors' samplings in Table 9. Under the final rule feasible
engineering and administrative controls are required to be implemented
in such instances in all mines to reduce the noise exposure to the
permissible exposure level. Furthermore, 67% of the samples in metal
and nonmetal mines exceeded the action level (a TWA8 of 85
dBA using an 80-dBA threshold).
MSHA's dual-threshold sampling data for coal mines is presented in
Table 12. These data consist of over 4,200 full-shift samples collected
from March 1991 through December 1995 using personal noise dosimeters.
Table 12.--Coal Dual-Threshold Noise Samples Equal to or Exceeding Specified TWA8 Sound Levels
[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 (PEL).................................................... 1,075 25.3 ........... ...........
85 (action level)........................................... ........... ........... 3,268 76.9
----------------------------------------------------------------------------------------------------------------
As indicated in Table 12, 25.3% of all samples collected by MSHA in
coal mines during the specified period equaled or exceeded the
permissible exposure level (a TWA8 of 90 dBA using a 90-dBA
threshold). Furthermore, almost 77% of the survey samples from the coal
industry showed noise exposures equaling or exceeding a TWA8
of 85 dBA using an 80-dBA threshold (the action level).
Tables 13 and 14 present some of the MSHA dual-threshold sampling
data by occupation for the most frequently sampled occupations in metal
and nonmetal and coal mines, respectively.
Table 13.--Percentage of MSHA M/NM Inspector Noise Samples Exceeding Specified TWA8 Sound Levels, by Selected
Occupation
----------------------------------------------------------------------------------------------------------------
90 dBA 80 dBA
threshold threshold
-------------------------------
Number of Percent of
Occupation samples Percent of samples 90 thn-eq>85 dBA
dBA (PEL) (action level)
----------------------------------------------------------------------------------------------------------------
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
----------------------------------------------------------------------------------------------------------------
These occupations comprise about 87 percent of the 42,206 MSHA dual-threshold samples collected at
metal/nonmetal mines from March 1991 through December 1994 using a personal noise dosimeter over a miner's
full shift
[[Page 49573]]
Table 14.--Percentage of MSHA Coal Inspector Noise Samples Exceeding Specified TWA8 Sound Levels, by Selected
Occupation
----------------------------------------------------------------------------------------------------------------
90 dBA 80 dBA
threshold threshold
-------------------------------
Number of Percent of
Occupation samples Percent of samples 90 thn-eq>85 dBA
dBA (PEL) (action level)
----------------------------------------------------------------------------------------------------------------
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
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These occupations comprise about 71 percent of the 4,247 MSHA dual-threshold samples collected at coal
mine from March 1991 to December 1995 using a personal noise dosimeter over a miner's full shift
As shown in these tables, the percentage of miners exceeding the
specified noise exposures varied greatly according to occupation. For
example, Table 13 shows that only 8.4% of the ba
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