aggregated form when it can be examined as
part of a larger sample of plants and mines.
However, there is specific value to these
findings as well. Careful study and review of
the contour plots revealed “hot spots” of higher
noise levels. These can be the starting points for
applying engineering and administrative

controls in an attempt to reduce noise and
worker exposures.

REFERENCES

AIHA, American Industrial Hygiene
Association [1986]. “Noise & Hearing
Conservation Manual.” Fourth Edition,
(Chapter 10: Responding to Warnings And
Indicator Sounds), edited by Berger, E.H., W.D.
Ward, J.C. Morrill and L.H. Royster, p 368.

ANSI [1991]. American National Standard
Specification for Personal Noise Dosimeters.
$1.25-1991 (R1997).

Bartholomae, R.C., and J.A. Burks [1995].
Occupational Noise Exposures in Underground
Coal Mines. Proceedings of Inter-Noise 95,
Newport Beach, CA, July 10-12, pp. 833-836.

Berger, E.H. [1983]. Using the NRR to
estimate the real-world performance of hearing

protectors, Sound and Vibration, Jan, pp. 12-18.

30 CFR [1997]. Code of Federal
Regulations (CFR) governing noise exposure in
mining. CFR 30, Subchapter O, Part 70,
Subpart F: Noise Standards for Underground
Coal Mines; Subchapter O, Part 71, Subpart D:
Noise Standards for Surface Work Areas of
Underground Coal Mines and Surface Coal
Mines; Subchapter O, Part 55, Section 55.5:
Metal and Nonmetal Open Pit Mines; Section
56.5: Sand, Gravel, and Crushed Stone
Operations and 57.5: Metal and Nonmetal
Underground Mines.

Federal Register [1999]. Health
Standards for Occupational Noise Exposure;
Final Rule. Department of Labor, Mine Safety

and Health Administration, 30 CFR Parts 56 anc_,
57 et al., Vol. 64, No. 176, September 13, pp.
49548-49634,

Franks, J.R. [1996]. Analysis of
audiograms for a large cohort of noise-exposed fj
miners. Internal Report, National Institute for
Occupational Safety and Health, Cincinnati,

OH, pp. 3-8.

Giardino, D.A., and G. Durkt, Jr. [1996].
Evaluation of Muff Type Hearing Protectors as
Used in a Working Environment. ATHA
Journal, 2.57 No. 3, March.

Greskevitch, M.K. et al. [1996]. “Results
from the National Occupational Health Survey
of Mining (NOHSM).” IDHHS (NIOSH)
Publication No. 96-136, September, pp. 17-18.

NIOSH [1996]. National Occupational
Research Agenda (NORA). National Institute
for Occupational Safety and Health, Publication
No. 96-115, p. 14.

NIOSH [1976]. Survey of Hearing Loss in
the Coal Mining Industry. National Institute fo
Occupational Safety and Health, Publication
No. 76-172, June, 70 pp.

O'Malley, A., and T. O’Beirne [1993].
Managing Noise Emissions and Exposures in
Underground Coal Mines. Australian Coal
Association Research Program End of Grant
Report, NERDD&DP No. 1628, Worksafe
Australia No. 91/948, Riverview QLD 4303,
Australia, September, 97 pp.

Seiler, J.P., M.P. Valoski, and M.A. Crivai
[1994]. Noise Exposure in U.S. Coal Mines.
USS. Dept. of Labor, Mine Safety and Health
Administration, Informational Report IR 1214,

46 pp.


miner in an HCP if, during any work shift, the
miner’s noise exposure equals or exceeds the
action level. Moreover, the new rules
establishes the primacy of engineering and
administrative noise controls, and explicitly
eliminates credit for the use of personal hearing

protection, Additional criteria include, a dual
hearing protection level of 105 dBA TWAg, and
no miner is permitted to be exposed to sound
levels exceeding 115 dBA. Specific details of
the new regulations are listed in Table II.

Table II - Details of Part 62 - Occupational noise exposure measurements.
Sound levels
TWAg, . Exchange aan
Type dBA Dose | integrated, rate, dB Weighting | Response
Action level 85 50% 80 to 130 5 A Slow
Permissible 90 | 100% | 90 to 140 5 A Slow
exposure level

CROSS-SECTIONAL SURVEY OF NOISE
EXPOSURE

Methods

NIOSH is conducting a study to obtain
multi-shift worker noise exposure and
equipment noise levels to develop an up-to-date
comprehensive profile of miners’ noise
exposures as a function of equipment and
activity-specific measures. This study is a
crucial component in the effort to develop noise
controls because it will define the sources of
miners’ dosages and the characteristics of those
sources. Once this information is available,

efforts can focus on the development and
application of appropriate engineering and
administrative control measures that will result
in reduced exposures for mine workers. Data
collection will be performed at underground and
surface coal and metal/nonmetal mines and in
mineral processing plants, Although an exact
study population has not been defined at this
time, it is necessary to survey all segments of
the mining industry because workers across the ,
industry continue to have a significant risk of
hearing impairment, as illustrated by the MSHA
inspector noise survey data published in the
Federal Register (1999) (see Table III).


Px)
v4 Reverberant
fo%,
*
-
<

a SS

Source

Receiver

!
Sereno Ser ewer tran iromstecrromermagrasrd 1
!
!
Key 1
— Wes
A - Airborne
5 - Struttureborne Sabet
SEE ——

Figure 5: | Example of airborne (A) and structureborne (S) noise paths.


The plan of research is comprehensive and
is designed to include all workers at each site
investigated. The data collected will include
worker noise dose, equipment noise, and other
worker, mine, and equipment-specific
information necessary for characterizing the
noise sources. At each site, mine workers will
wear time-resolved dosimeters. During the
shift, a task-based exposure assessment methods
(T-Beam) approach studies will be used to
correlate each mine worker’s tasks, the noise
dose received, and the noise source responsible
for that incremental contribution to the miner’s
total exposure. Noise profiling of mine
machinery will be conducted using hand-held
sound level meters. This will consist of A-
Weighted Equivalent Continuous Sound Levels

(Leq) measurements on a uniform grid pattern
to develop detailed noise contours and “area
sweeping” of mine machinery to calculate sound
power. The instruments that will be used to
make these measurements include Quest
Technologies Model Q 400, Noise Dosimeters,
and Quest Model 2900, Integrating and Logging
Sound Level Meters (fig. 2). Finally, site-
specific parameters, such as characteristics of
the mine plan, will be documented to support
subsequent analyses. The bulk of the data
Collection activities are completed over five
shifts. Typically, one or two site visits are made
in advance of the data collection to gather
information for the design of the site-specific
data-collection activities.

Figure 2: Dosimeter and sound level meter for conducting noise surveys.

Results

Progress to date includes completion of
pilot studies at an underground coal mine and
underground limestone mine, and a full-scale
study conducted at a coal preparation plant. The
pilot studies served both as training exercises
for the field crews and for refining the data
collection and analysis procedures. The study at
the preparation plant included surveying the
noise on all eight floors and a contro! room (fig.
3). The data collected included A-Weighted
Leq , as well as Linear 1/3rd Octave Band
Sound Pressure Levels (SPL’s) around all major
picces of processing equipment.

The plant was a modern/multicircuit coal
preparation plant. It was constructed of steel I-
beams for internal support with corrugated steel .
walls (fig. 4), except for the first floor, which
had walls constructed from concrete block. All
floors were constructed of 4 inches:of concrete,
except on the second and sixth floors, which
were made of open steel grating. In addition,
there were many open spaces that extended
from one floor to the next, or in some cases,
from the ground floor to the top floor. The
processing equipment included classifying
cyclones, sieve bends, magnetic separators,
flotation cells, banana screens, heavy media
cyclones, D&R screens, coal spirals,
centrifuges, clean coal and refuse conveyors,
and pumps.


Table III - MSHA inspector noise samples exceeding specified TWAg sound levels.

90-dBA 80-dBA
threshold threshold
Mining i Number Percent of
sector Occupation of Percent of
samples samples >90 OBA ta ie
action
dBA (PEL) level)
Front-End-Loader Oper. 12,812 12.9 67.7
Truck Driver... 6,216 13.1 73.7
Crusher Oper. 5,357 19.9 65.1
Bulldozer Oper 1,440 50.7 86.2
Bagger... 1,308 10.2 65.0
Sizing/Washing Plant Ope 1,246 13.2 59.7
Dredge/Barge Attendan 1,124 272, 78.7
Clean-up Person. 927 19.3 713
Metal/ | Dry Screen Oper. 871 11.7 57.6
Nonmetal | 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 Oper. 583 34.0 82.5
Backhoe Oper.... 546 8.4 52.6
Dryer/Kiln Oper. 517 10.5 55.5
Rotary Drill Oper. (electric/hydraulic).... 543 39.6 83.1
Rotary Drill Oper. (Pneumatic). 489 64.4 89.0
Continuous Miner Helper. 68 33.8 88.2
Continuous Miner Oper. 262 49.6 96.2
Roof Bolter Oper. (Single 234 21.8 85.5
Roof Bolter Oper. (Twin). 92 31.5 98.9
Shuttle Car Oper. 260 13.5 78.5
Scoop Car oper.. 94 18.1 74.5
Cutting Machine Oper. 22 36.4 63.6
Coal Headgate Oper... 20 40.0 100.0
Longwall Oper.. 34 70.6 100.0
Jack Setter (Longwall). 25 23.0 68.0
Cleaning Plant Oper. 107 36.4 71.6
Bulldozer oper....... 225 48.9 94.2
Front-End-Loader Oper 244 16.0 76.6
Highwall Drill Oper.. 83 21.7 771
Refuse/Backfill Truck Driver 162 13.6 78.4
Coal Truck Driver............ 28 17.9 64.3



The measured Leg levels ranged from 83
to 115 dBA, with most floors averaging in the
upper 80s and above (see Table IV). Although
Table IV lists the dominant noise sources,
characterization of noise sources in the plant
was a complicated task for several reasons.
First, the sheer number of pieces of equipment
and their close proximity to each other made
separating specific noise sources extremely
difficult, and process considerations made it
impossible to operate equipment independently.
Next, the openness of the building allowed noise
to propagate between floors, as did the floor-to-
floor connections of the equipment. Finally, the

measured noise came from several sources,
most often a combination of airbome and
structure-borne noise paths (fig. 5). Airborne
noise was present as direct sound, generated by
the equipment, the process, and motors, and as
Teverberant sound reflected by the building’s
walls and floors. Structure-borne noise paths
resulted from equipment vibration and transfer
of that vibration to the building’s structural
components. The vibrant energy was then
radiated as airborne sound into the surrounding
area, An example of a contour plot of the noise
levels is illustrated in Figure 6.

Table IV - Summary of Leq levels,

Floor beg Range Major equipment Dominant noise source (Leq, dA)
1 91-99 pumps, pump motors classifying cyclone pump (99.4 dBA)
2 92-96 Conveyors clean coal and refuse conveyors (93.5
dBA)
dewatering screens, centrifuges, | fine refuse dewatering screen (101.6
3 93 - 103
mag separators, dBA)
4 94-101 sieve bends, D&R screens, coal | clean coal and tefuse D&R screens
spirals (100.4 dBA)
heavy media cyclones, banana
5 91-101 screens, flotation cells, sieve raw coal banana screens (99.8 dBA)
bend
6 89-115 sieve bends, cyclones fine clean coal sieve bends (104.6 dBA)
7 89-92 raw coal conveyor, sieve bends, None
mag separator
. 15-inch dia. Classifying
8 88-91 Cyclones cyclones (91 dBA)
Control | 74 (Inside) | plant controls, monitors, etc. None
Room | 90 (Outside)



CROSS-SECTIONAL SURVEY OF NOISE EXPOSURE IN THE MINING INDUSTRY

Eric R. Bauer, Mining Engineer
Jeffery L. Kohler, Laboratory Director

National Institute for Occupational Safety and Health
Office of Mine Safety and Health Research
Pittsburgh Research Laboratory

ABSTRACT

Prolonged exposure to noise over a period
of years generally causes permanent damage to
the auditory nerve and/or its sensory
components. This irreversible damage, known
as noise-induced hearing loss (NIHL), is the
most common occupational disease in the
United States today. Workers suffering from
NIHL have difficulty understanding human
speech and hearing other workplace cues.
Despite the use of regulations and efforts by
government and industry to reduce NIHL, the
problem today is as prevalent as it was more
than two decades ago. Recently, the Mine
Safety and Health Administration (MSHA)
promulgated a new regulation that is designed to
reduce NIHL in the mining industry. One of
the more significant provisions is the
elimination of MSHA’s past practice of giving
“credit” for the use of personal hearing
protection, thereby reestablishing the primacy of
engineering and administrative controls.

However, there is a knowledge gap that is
impeding the development and implementation
of engineering and administrative controls.
Although significant data exist on the exposure
to noise by occupational code, little is known
about the noise sources that contribute the most
to the worker’s dose. This is problematic in a

workplace with multiple noise sources and
workers who travel among noise sources. Yet
without this knowledge, it is difficult to focus
control efforts in any practical manner. Thus, it
is important to characterize noise sources
sufficiently well so that the sources most
hazardous to hearing are identified and those
conditions of exposure that are most amenable
to engineering controls are pinpointed as well.
The Pittsburgh Research Laboratory (PRL) of
the National Institute for Occupational Safety
and Health (NIOSH) is conducting a cross-
sectional survey of noise sources and worker
noise exposures in the mining industry to
address this deficiency. The initial effort,
conducted at a coal preparation plant and results
are described in this paper. Preliminary .
analyses indicate that the noise levels on all
floors exceeds 90 dBA in most areas, and that
levels as high as 115 dBA were recorded. In
addition, the one worker whose responsibility is
to monitor the equipment and “house clean” the
plant is slightly overexposed, even though he
spends only half the shift in the plant. General
information on the hearing loss problem in
mining, a review of hearing protection use and
noise regulations in mining, and other
background materials are also presented.


Table V - Location of Plant Controls Man
. Duration, Time, | Percent
Location .
min. pet. Dose

Control Room 210.20 51 2!
Plant 189.25 46 88
Traveling between plant and 11.50 3 ND*
control room

Total 411 100 100

"Although no control room was under 80 dBA, some higher noise levels occurred
because of equipment and the door being opened.

°ND - Not determined. Since time period was small and because the old plant

was not running, the dose is included in the Control Room dose

Table VI - Projected 8-Hour Dose for Plant Controls Man (one shift)

MSHA . . .
Designation Projected Dose, pct Time Weighted Average (TWAg), dBA
Action Level 159.96 93.4
Permissible
Exposure 152.36 93.0
Level



36

Figure 6: Example of noise contours in prep plant.

A few general observations of the noise
levels on all floors can be made. (1) Although
the highest noise levels were recorded on floor
6, floors 3 and 4 are considered to be the
noisiest floors overall because the noise was
consistent throughout the entire floors. (2)
Vibration is certainly a factor in generation of
noise throughout the plant. (3) Reverberant
noise from the building walls is likely a
significant component of the noise throughout
the plant. (4) The openness and construction of
the plant is conducive to noise propagation
between floors. This likely resulted in
“smearing” or “blending” of the noise from
floor to floor.

In addition, several man-shifts were spent
following the Plant Controls Man, documenting
his work activities while he wore a personal
dosimeter. He wore a personal dosimeter for
parts of two shifts (8 a.m. to 3 p.m.), while a
NIOSH Researcher performed a time and

motion study as he traveled throughout the
plant. Table V summarizes the Plant Control
Man’s location throughout the shifts. Table VI
presents the projected dose and time-weighted
average. The projected dose, in percent, is
computed by measuring the dose for a specified
time period (in this case, approximately 7 hrs)
and extrapolating it to a different time period (8
hrs). The time-weighted average is the average
sound level computed over an 8-hour time
period.

Figure 7 is a plot of the cumulative dose for
the measurement period. The sections of the
graph with the steepest slope indicate the
periods that the Plant Controls Man was in the
plant and receiving most of his measured noise
dosage. In contrast, the flat slope sections of the
graph are the minimal dosages accumulated
while he was in the control room or traveling
between the control room and plant.


Figure 3: Noise measurement being made with a sound level meter.

Figure 4: Example of wall and building construction including open s;



an interim or secondary noise control solution
and that engineering and/or administrative
controls should be first employed. There are
several reasons for this. First, earplugs and
carmuffs generally do not provide the same
degree of protection in the mining workplace as
they do in the laboratory or other types of
workplaces (NIOSH, 1996; and Giardino and
Durkt, 1996). The use of personal hearing
protection (PHP) was studied by Stewart and
Burgi (1980) and Berger (1983), who found that
earmuffs have serious limitations when worn
under mine conditions. These include much less
real work noise attenuation than that measured
under laboratory conditions and the possibility
of reduced hearing causing a safety hazard
(AIHA, 1986). The effectiveness of PHP can be
improved through proper fit, but the possible
hazard from overprotection while wearing PHPs
is unresolved.

Second, miners often refuse to wear hearing
protectors because they are uncomfortable,
annoying, or prevent them from perceiving
signals such as the sounds that precede a roof
fall (“roof talk”) or backup alarms on moving
equipment (NIOSH, 1996). Often miners
simply do not appreciate the risk presented by
excessive noise, nor do they believe that using
PHPs will protect them.

Finally, spot surveys have shown that
miners believe that they are wearing hearing
protectors more than they really are. For
example, a research group in New South Wales,
Australia, surveyed one mine where 75% of the
miners stated that they used hearing protectors
“regularly” (55%) or “all the time” (20%). In
fact, the investigators found that only 40% of
the miners wore hearing protectors regularly and
20% wore them some of the time (O’Malley and
O’Beirne, 1993).

The limitations of PHPs underscore the
importance of using engineering and
administrative controls to the fullest extent
practicable. At the same time, however, PHPs
can offer some reasonable measure of
protection, especially when fit and worn

correctly. As such, their importance in an =
overall hearing loss prevention program should
not be underestimated. h

HIGHLIGHTS OF NOISE REGULATION:
IN MINING I

Regulation of noise in mining is covered in
Title 30 of the Code of Federal Regulations (30
CFR). The Federal Coal Mine Health and
Safety Act of 1969 established requirements for
protecting coal miners from excessive noise
and, subsequently, the Federal Mine Safety and
Health Act of 1977 broadened the scope to
include all miners, regardless of mineral type
(CFR 30 1977). The regulations allowed a
permissible exposure level PEL) of 90 dBA
TWA over 8 hours (TWAg). Exposure below
the criterion of 90 dBA is unregulated, while
continuous exposure to levels greater than 115
dBA is not permitted. Many noise sources are
not continuous, and movement by the worker
generally results in exposure to various levels of
noise for differing periods of time. This
problem of exposure versus duration of
exposure is evaluated using the well-known
noise exposure index (NEI); the worker is out o
compliance if the NEI exceeds unity. In
practice, the dose received is most often
determined using a type 2 personal noise
dosimeter, as defined by American National
Standards Institute (ANSI) $1.25-1991(R1997)
American National Standard for Personal Noise
Dosimeters (ANSI, 1991). Despite allegations
that personal noise dosimeters are not as
accurate as sound level meters or that they read
erroneously with impulse noises, research has
found that they are as accurate as sound level
meters (Valoski et al., 1995); moreover, they
correctly weigh impulse levels (Evans et al.,
1991).

The new rulemaking efforts undertaken by
MSHA, adopted in September 1999 and
scheduled to go into effect in September 2000,
retain the PEL of 90 dBA TWAsg, and include a
new action level which is a noise dose of 50%,
or equivalently a TWAg of 85dBA. The new
regulation requires the mine operator to enroll a


Seiler, J.P., and D.A. Giardino [1994]. The
Effect of Threshold on Noise Dosimeter
Measurements and Interpretation of Their
Results. U.S. Dept. of Labor, Mine Safety and
Health Administration, Informational Report IR
1224, 16 pp.

Stewart, K.C., and E.J. Burgi [1980].
Noise-attenuating properties of earmuffs worn
by miners. Final Report, Vol. 1 on BOM
Contract JO188018, NTIS PB 83-257063, 46 pp.

Valoski, MLP., J.P. Seiler, M.A. Crivaro,
and G. Durkt [1995]. Comparison of noise
exposure measurements conducted with sound
level meters and noise dosimeters under field
conditions. MSHA Report, 26 pp.


Thus, the number of miners overexposed to
noise, as defined by federal regulations, still
exceeds their overexposure to all other health
since the 1970s, although the percentage of
mincrs overexposed to current MSHA noise
regulations remains high (Seiler, et al. 1994).
MSHA found that the percentage of coal miners
with noise exposures exceeding federal
regulations, and unadjusted for the wearing of
hearing protection, was 26.5% and 21.6% for

hazards. Data from more than 60,000 full-shift
MSHA noise surveys show that the noise
exposure of selected occupations has decreased
surface and underground mining, respectively.
Table I lists recently published data from
MSHA noise surveys of exposures in the coal
and metal/nonmetal mining industries (Federal
Register, 1999),

Table I - MSHA noise samples exceeding specified TWAg sound levels,
90-dBA threshold 80-dBA threshold
Industry TWAs sound
segment level, dBA! Number of | Percent of | Number of | Percent of
samples samples samples samples
90 (PEL)? 1075 Oe
Coal
85 (Action Level) | -------------- | -------------- 3268 76.9
Metal) | 90 (PEL) 7360 17.4
Nonmetal | 95 (Action Level) | ------------~ 28,250 66.9

ITWAg is the sound level, if constant over 8 hours, would result in the same noise dose as

measured.
?Pel-Permissible exposure level

Despite the extensive work done in the
1970s and 1980s, NIHL is still a pervasive
problem. MSHA has published new Noise
Health Standards for Mining (Federal Register,
1999). One of the changes will be the adoption
of a provision similar to OSHA's Hearing
Conservation Amendment. MSHA concluded
in a recent survey that if an OSHA-like hearing
conservation program (HCP) were adopted,
hypothetically 78% of the coal miners surveyed
would be required to be in a hearing
conservation program (Sciler and Giardino,
1994). Based on full-shift time-resolved
dosimeter measurements at six U.S. longwall
operations, Bartholomae and Burks (1995)
found that all the longwall face workers
surveyed in these mines would be required to be

ina hearing conservation program. These data
are corroborated by data collected in the
National Occupational Health Survey of Mining -
(NOHSM) during the 1980s (Greskevitch et al.,
1996). Based on this survey, the projected mine
workers potentially overexposed to noise was
approximately 200,000 workers, or 73% of the
workforce.

PERSONAL HEARING PROTECTION

At first glance, personal hearing protection
devices (earplugs, earmuffs, etc.) seem to be a
relatively cheap and simple solution to almost
any noise problem. However, good industrial
hygiene and safety practices suggest that
hearing protectors should be considered only as


INTRODUCTION

Noise is often regarded as a nuisance rather
than as an occupational hazard. However,
overexposure to noise can cause serious hearing
loss. In 1996, NIOSH reported that
occupational hearing loss is the most common
occupational disease in the United States today,
with 30 million workers exposed to excessive
noise levels (NIOSH, 1996). The problem is
particularly severe in all areas of mining
(surface, processing plants, and underground),
with studies indicating that 70% to 90% of
miners have a NIHL large enough to be

classified as a hearing disability (NIOSH, 1976; =
Franks, 1996). This alarming prevalence of
hearing loss among miners is shown in Figure 1. h
For example, the median hearing threshold of
retired miners was 20 decibels (dB) greater than
that of the general population. By age 60, over
70% of miners had a hearing loss of more than

25 dB, and about 25% had a hearing loss of

more than 40 dB. Franks (1996) review of a
private company's 20,022 audiograms indicated
that the number of miners with hearing
impairments increased exponentially with age
until age 50, at which time 90% of the miners

had a hearing impairment.

ed i
a
ef
a Hearing loss
z 60 greater than 25 dB 4
E€ L 4
2
2 40h 4
=z
ri
= Pm
5 20 ; 4
Hearing loss

2 + —-~Y greater than 7
y “— jl 40 dB
= -, :

o 20 30 40 50 60

MINERS AGE
Figure 1: Hearing loss as a function of age (NIOSH, 1976).

Since the passage of the Federal Coal Mine
Health and Safety Act of 1969, there has been
some progress in controlling mining noise.
Machinery manufacturers have incorporated

design changes to reduce noise levels. At the
same time, however, many of these gains have
been diminished by the use of ever larger, more
powerful, and sometimes noisier machines.


CUMULATIVE DOSAGE - PLANT CONTROLS MAN

Sr

140 4
130
10
ne =
100 4
90!
a0 4
704

DOSAGE (%4}

IN CONTROL ROOM

seem 20 d8 crterion,
80 d8 threshold

+ 9008 criterion,
90 8 threshold

TIME (HOURS)

Figure 7:

SUMMARY

Noise-induced hearing loss is a concern in
the mining industry. One study revealed that
more than of 90% of miners have a hearing
impairment by the age of 50 (Franks, 1996). In
addition, based on thousands of inspector noise
samples, MSHA has suggested that miners in all
sectors of mining and occupations continue to
have a significant risk of NIHL over a working
lifetime. Despite government and industry
efforts over the past three decades, hearing loss
remains relatively unchanged in the industry. It
is apparent that it is a complex problem that will
require an understanding of its underlying
causes. Although engineering and
administrative controls represent the desired

Plot of cumulative noise dose for plant controls man.

means of protecting workers from excess
exposure, it will be necessary to understand
where mine workers receive their exposure and
the specific characteristics (frequency, duration,
level) of the offending noise sources. The
NIOSH cross-sectional survey project will
establish valid worker noise exposure and
equipment noise level data for formulating
intervention strategies that target high-risk
equipment and activities with the noisiest
exposures for mine workers.

The coal preparation plant study
highlighted in this paper illustrates the nature of
the study and the complexities of the data
analysis. The ultimate value and application of
the findings from this plant will be in