Coal workers’ pneumoconiosis 
 

prevalence disparity between Australia 
 

and the United States



by G.J. Joy, J.F. Colinet and D.D. Landen 

Abstract Although rates of pneumoconiosis in coal miners have declined substantially in the 

United States since the passage of the Federal Coal Mine Health and Safety Act of 1969, new 

cases continue to occur, including cases of rapidly progressive disease. In contrast, Australia’s 

underground coal mining industry has reported few new cases of pneumoconiosis for more 

than 20 years. Mortality from coal workers’ pneumoconiosis in official health statistics and the 

prevalence of pneumoconiosis among miners screened in X-ray surveillance programs are also 

lower in Australia. The U.S. National Institute for Occupational Safety and Health (NIOSH) was 

requested by both industry and labor stakeholders to examine this issue, with the ultimate aim 

of reducing the rate of pneumoconiosis among U.S. coal miners. A number of factors, including 

coal dust exposure, silica exposure and coal rank were examined as potential contributors to 

the above noted differences. Comparison of coal rank data from each country did not illuminate 

the issue. Air sample data from the coal mining industries in both countries show that coal 

dust levels in Australian mines are somewhat higher than those reported in similar U.S. mines; 

however, quartz exposure for Australian miners is lower than for many U.S. miners. If quartz 

is contributing to the greater number of cases of pneumoconiosis in the United States, more 

effective dust control measures, as well as an independent exposure standard for respirable 

quartz in coal mining, should be implemented to reduce this potentially disabling condition. 

Introduction 

Australia has an active underground 

coal mining industry in two states — 

New South Wales and Queensland 

— but has maintained a low rate of 

pneumoconiosis for more than 20 years. 

By comparison to the United States, 

mortality from coal workers’ pneu

moconiosis (CWP) in official health 

statistics and the prevalence of pneu

moconiosis among miners screened in 

X-ray surveillance programs are also 

lower in Australia. Clouding the dif

ference in disease rates between the 

two countries is the fact that the oc

cupational exposure standard for the 

respirable fraction of coal mine dust 

(RCMD) in the above two Australian 

states is higher than the regulatory ex

posure standard in the United States. 

The U.S. National Institute for Oc

cupational Safety and Health (NIOSH) 

was requested by stakeholders from 

both U.S. industry and labor to inves

tigate the disparity in pneumoconiosis 

rates between Australia and the United 

States. 

Pneumoconiosis is a disease of the 

lung parenchyma caused by deposition 

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of dust particles and the reaction of lung 

tissue to the dust. The inhaled dust par

ticles responsible for the disease must 

be small enough to pass through the 

upper airways and into the lung, with 

these particles generally smaller than 

10 μm (10-5 m) aerodynamic equivalent 

diameter. Dust of this size is considered 

to be within the respirable dust fraction. 

Coal miners are susceptible to two 

types of pneumoconiosis, CWP and sili

cosis.The two conditions are difficult to 

distinguish on chest X-rays (Laney et 

al., 2009), but they show different tissue 

patterns on pathologic diagnosis and 

may have different clinical presenta

tions as well. The likelihood of CWP 

development is directly related to the 

magnitude and duration of exposure to 

coal mine dust, as well as to the quartz 

content of the respirable dust and to the 

rank of the coal. Coal rank represents a 

measure of the geologic maturity of the 

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coal, with coals of differing ranks having differing physical 

and chemical characteristics. CWP may progress in severity 

from nonsymptomatic simple CWP to complicated CWP, 

which is also called progressive massive fibrosis (PMF), a debilitating condition. The presence of simple CWP increases 

the risk of developing PMF (NIOSH, 1995). Coal miners are 

also susceptible to silicosis, due to inhalation of respirable 

quartz from cutting or drilling rock, and silicosis may also 

progress to PMF. In miners found to have simple CWP, re-

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moval from or substantial reduction to exposure 

can prevent progression to PMF. Silicosis, how

ever, may progress to PMF even after cessation 

of exposure. 

This investigation is subject to limitations, in

cluding little comparable exposure and surveil

lance data. These limitations are due in part to 

differing regulatory and surveillance schemes under which the data is generated and collected. As 

a result, this investigation adopted the ecological 

approach, and is presented as a hypothesis-gener

ating work, rather than as a definitive resolution 

of the question. 

Background 

At the beginning of the 20th century, pneu

moconiosis prevalence and mortality among coal 

miners were very high in the United States and 

Australia. Following implementation of legislative 

standards for coal dust exposure in the United 

States, prevalence dropped substantially. Nev

ertheless, new cases have continued to occur in 

the United States over the last 20 years, while 

reported CWP mortality rates in Australia are 

close to zero, supported by disease surveillance 

data from New South Wales. Further compound

ing the problem, the U.S. cases have sometimes 

resulted in rapid progression and death from 

PMF in young miners with apparently low levels 

of coal dust exposure (CDC, 2006; CDC, 2007). 

CWP mortality rates for the United States and 

Australia are shown in Fig. 1.

Figure 1 

Mortality from coal workers pneumoconiosis, United States and Australia, 

by year. 

1 

1 Rates of CWP mortality for the U.S. population over age 15 for the years 1968-1999 were obtained from the 2002 edition of 

the Work-Related Lung Disease Surveillance Report (NIOSH, 2003). Rates of CWP mortality for the Australian population over 

age 15 for the same years were calculated from data in the General Record of Incidence of Mortality database (AIHW, 2005). 

Rates for both the United States and Australia include the International Classification of Disease (ICD) code appropriate to 

the year of death: ICD-8 code 515.1 (Anthracosilicosis) for the years 1968-1978, ICD-9 code 500 (Coal Workers’ Pneumoconiosis) for the years 1979-1998, and ICD-10 code J-60 (Coal Workers’ Pneumoconiosis) for deaths 1999 forward (ILO, 2002). 

The rates presented have not been adjusted for age or gender. 

The prevalence of pneumoconiosis among 

coal miners in the United States and New South 

Wales from 1970 through 2006 is presented in Fig. 

2.

Figure 2 

Prevalence of pneumoconiosis, ILO category 1/0 or greater among U.S 

underground coal miners and New South Wales coal industry employees, by year. 

2

2 The authors were unable to obtain prevalence data from the Queensland surveillance program. 

As shown, U.S. CWP prevalence among under

ground coal miners was 3.6% during 2000-2004 

(NIOSH, 2008). For New South Wales, the rates 

shown in Fig. 2 represent both surface and under

ground miners (Coal Services, 2008). 

Pneumoconiosis rates have been near zero for 

the past decade, which represents a substantial 

reduction from earlier years (Glick et al., 1972; 

Griffits, 1990). The prevalence of pneumoconio

sis reported in New South Wales has been lower than that 

reported among underground miners in the United States 

since the early 1980s. 

To give further context to the data in Fig. 2, in the United 

States, underground coal miners have been screened since 

1970 in an X-ray surveillance program mandated under the 

Federal Coal Mine Health and Safety Act of 1969. In this 

program, called the Coal Workers’ X-ray Surveillance Pro
 

Table 1 

Mean dust concentrations with standard deviation, adjusted to the MSHA sampling convention for all jurisdictions. U.S. 

occupation description is stated first, followed by the corresponding Australian job title. Missing data are unavailable. 

United States New South Wales Queensland Queensland 

Occupation 1995-2000 1985-1999 1999-2001 1995-2000 

N mg/m3

 (sd) N mg/m3 (sd) N mg/m3 (sd) N mg/m3 (sd) 

Jack setter-longwall/ 

chock operator 3,305 1.28 

(0.80) 3,831 1.94§

 (1.25) - 2.86 205 2.52§ (2.21) 

Longwall operator/ 

shearer operator 6,560 1.40 

(0.83) 3,799 2.12§

 (1.33) - 2.63 187 2.37§ (1.20) 

Headgate operator/ 

maingate operator 1,584 0.80 

(0.67) 447 1.67§

 (1.55) - 1.83 54 1.94§ (1.96) 

Return-side face 

worker/ face operator 8,156 1.55 

(0.97) 247 2.05§

 (1.33) - 2.44 - -

Significantly different values are indicated in Table 1 by the superscript §. 

gram (CWXSP). The cost of X-rays is borne by employers, 

but the overall program is managed by NIOSH, which sets 

standards for obtaining the films and for their interpretation. 3 

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3 The current surveillance program is titled the Enhanced Coal Workers’ X-Ray Surveillance Program (ECWXSP). 

By contrast, in New South Wales, all medical surveillance 

is performed by Coal Services Pty Limited, an organization 

composed of labor and industry representatives. Data on 

pneumoconiosis prevalence are published in annual reports; 

however, no published information is available on the meth

ods used to conduct the screening, nor on how the prevalence 

rates are generated. 

To further expand on the above differences, participation 

in pneumoconiosis screening programs in both the United 

States and New South Wales is voluntary. Initial participa

tion in the CWXSP was estimated at 90%, but it has dropped 

over time. In fact, during the period from 2000 to 2004, the 

participation rate was estimated at 48% (NIOSH, 2008). No 

published data are available on current participation rates 

among New South Wales miners; however, participation has 

been estimated at about 40% of all eligible industry employ

ees (Delaney, 2008). 

Approach to this study 

In this study, two factors were postulated that might con

tribute to different disease rates in Australia and the United 

States: (1) dust exposure limits and dust-control-related is

sues and (2) physicochemical properties of coals (coal rank). 

These factors were compared as far as practicable between 

the two nations to identify any significant differences. The 

methods applied were a review of the relevant literature, 

published data on coal dust exposure and coal rank data; 

consultations with members of industry, labor and academia; 

and visits to operating underground coal mines in Australia 

to observe operating practices and dust control methods. 

Comparison of dust exposure limits. The current regula

tory standards for respirable coal mine dust (RCMD) in the 

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three jurisdictions studied are substantially different. In the 

United States, the exposure level enforced by Mine Safety 

and Health Administration (MSHA) (excluding Part 90 min

ers with diagnosed CWP) is 2.0 mg/m3, (Federal Register, 

1970). In New South Wales, the standard is 2.5 mg/m3 and 

in Queensland, the standard is 3.0 mg/m3. The Australian 

standards are based on AS-2985, an International Standards 

Organization (ISO)-compliant sampling method (Standards 

Australia, 2004), which differs from the MSHA method, pri

marily in the sampler flow rate value (1.7 L/min in the AS

2985 method and 2.0 L/min in the MSHA method). Using 

the conversion factor (1.23) (Page and Volkwein, 2009) to 

account for the effect of the different sampling flow rates, the 

standards for the two Australian jurisdictions may be adjust

ed to allow comparison to the MSHA sampling convention. 

Thus, the adjusted exposure standards are 3.1 mg/m3 for New 

South Wales and 3.7 mg/m3 for Queensland. The Queensland 

limit is reduced for shifts longer than eight hours, so that the 

cumulative exposure does not exceed 24 mg·hr/m3 ISO mass 

basis over the extended shift duration. 

The United States and Queensland sample portal-to

portal, meaning that the sampling starts when the miner en

ters the portal of the mine, including travel time to and from 

the working face, and continues until the miner exits the 

mine portal. However, in New South Wales, samples are not 

collected during this travel time, but only during the miner’s 

underground work period, denoted crib-room-to-crib-room 

— that is, from underground areas within the mine. The dif

ference between the crib-room-to-crib-room and portalto-portal methods in New South Wales and Queensland, 

respectively, has been estimated to increase the measured 

concentration of New South Wales samples by approximately 

10% (Cliff and Kizil, 2002). All three jurisdictions collect 

dust on the most highly exposed occupations, but the par

ticular occupations included differ, and similar job titles in 

the United States and Australia may not include identical 

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job responsibilities. 

Further differences relate specifically to quartz expo

sure. New South Wales and Queensland regulate exposure 

to quartz separately from respirable coal dust, with specific 

exposure limits (New South Wales: 120 μg/m3; Queensland: 

100 μg/m3 — both ISO mass basis). In the United States, 

MSHA regulates exposure to quartz through reduction of 

the permitted RCMD concentration, according to the rela

tionship 10 divided by the percentage of quartz found in the 

sample (Federal Register, 1994). This method is intended to 

limit quartz exposures at or below 100 μg/m3. Finally, while 

New South Wales and Queensland assess compliance via 

individual sample results, MSHA uses an average of multiple 

samples to assess compliance with the standard. 

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Comparison of coal rank. In the literature, 

one factor that has been associated with CWP is 

coal rank (Bennett et al., 1979; Attfield and Seixas, 

1995), which is a measure of the geologic matura

tion of the coal. The risk of incidence and progres

sion of CWP increases with coal rank, although 

the exact properties of higher-rank coal that are 

responsible for the increased hazard to the lungs 

are not known. 

Study results 

Dust exposure limit data. Among the three ju

risdictions, directly comparable dust exposure data 

are limited. Table 1 shows a comparison between 

dust levels for several longwall occupations in the 

three jurisdictions. 

The U.S. Longwall Operator description in

cludes headgate- and tailgate-side longwall shear

er operators. The data for the United States are 

from the MSHA Standardized Information System 

(MSIS) database (MSHA, 2010). New South Wales 

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data and Queensland 1999-2001 data are from Cliff and Kizil, 

2002. Queensland 1995-2000 data are from Ham et al., 2001. 

Where the available data included sample number (N), 

mean and standard deviation information, the dust concen

tration means for the United States and the two Australian 

states were tested for equivalence using the SAS® TTEST 

procedure. Associated testing of variance showed unequal 

variances for all groups; therefore, the t-test results incorpo

rating the Satterthwaite approximation were used. Where 

the t-test could be applied, the U.S. mean dust concentrations 

were all significantly less than the related Australian means 

at p < 0.01. 

Among the three jurisdictions, data regarding exposure 

to respirable quartz are even more limited. The Queensland 

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respirable quartz exposure limit is 100 μg/m3 mea

sured according to AS-2985; this equates to 123 

μg/m3 on an MSHA basis. Quartz exposure sam

ples from Queensland were compared to MSHA 

inspector samples for the same set of occupations 

during the same time period. No respirable quartz 

exposure data for New South Wales were avail

able. 

In Queensland, 10.4% (103/986) of samples 

collected by Queensland Mines Department per

sonnel from 1995 to 2000 to measure respirable 

quartz exposure exceeded the 100 μg/m3 expo

sure limit (Ham et al., 2001). In the United States, 

for the same set of miner occupations, 22.1% of 

MSHA inspector samples collected in the cen

tral Appalachian region, which includes southern 

West Virginia, western Virginia and eastern Ken

tucky, exceeded 123 μg/m3

. This area is included 

in MSHA coal districts 4, 5, 6 and 7. The fraction 

of samples exceeding 123 μg/m3 in the western 

United States (MSHA coal district 9), where coal 

seams tend to be similar in thickness to those in 

Australia, was 7.2%, and the fraction for the re

maining MSHA coal districts (excluding the an

thracite operations of district 1) was 7.4% (Fig. 3). 

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Figure 3 

Proportion of respirable dust samples exceeding 123 μg/m3 quartz in 

Queensland and U.S. MSHA bituminous coal districts, 1995 through 

2000.
	

Figure 4 

ECWXSP pneumoconiosis prevalence rates and mean respirable quartz 

concentrations by MSHA coal district. 
 

Pneumoconiosis prevalence rates from the NIOSH EC

WHSP and the mean respirable quartz concentration of 

MSHA inspector samples from 2000 through 2009 for MSHA 

coal districts 2 through 11 are illustrated in Fig. 4 (NIOSH, 

2010; MSHA, 2010). As shown, districts with the higher silica 

exposures generally have higher rates of CWP. The correla

tion (Spearman’s rho) between these two variables is 0.68, 

p < 0.05. 

Coal rank data. Table 2 presents data on coal rank from 

various sources in the United States and Australia as mea

sured by fixed carbon content by proximate analysis. 

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Table 2 

Values for mean fixed carbon content for coals from 

Australian and U.S. sources. 

Percent fixed carbon (proximate analysis)

 Source Mean N Std. Dev. 

New South Wales 53.90 80 6.31 

Queensland 62.48 97 10.53 

MSHA District 4 58.87 455 8.73 

MSHA District 5 58.04 456 6.01 

MSHA District 6 49.76 350 5.15 

MSHA District 7 51.37 397 3.91 

Colorado 44.75 292 7.41 

New Mexico 38.49 175 7.57 

Utah 39.03 153 8.41 

Wyoming 36.80 549 6.75 

Coal 

data for Australian coals was extracted from a commercial 

Coal Quality database (Wood Mackenzie, 2008). Data for 

U.S. coals was extracted from the U.S Geological Survey 

COALQUAL database (USGS, 1997). 

The mean fixed carbon content of coal samples from 

New South Wales and Queensland were compared to coal 

samples from the United States using the t-test. The mean 

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fixed carbon content of coal samples from Queensland was 

significantly higher than that of coal samples from all U.S. 

sources, all p < 0.001. Coal samples from New South Wales 

were significantly higher in fixed carbon content than coals 

from U.S. sources, except for MSHA districts 4 and 5, all p < 

0.001. The mean fixed carbon content of coals from MSHA 

districts 4 and 5 was significantly higher than for coals from 

New South Wales, p < 0.001. 

Discussion 

The difference in CWP prevalence and mortality between 

the United States and Australia is significant and of long du

ration. However, in interpreting this difference, analysis of 

prevalence data among the United States, New South Wales 

and Queensland is limited by the lack of directly comparable 

exposure data at the occupation level and, also, by the lack 

of information on job tenure from New South Wales and 

Queensland. The occurrence of CWP is related to cumulative exposure, so information on job tenure is important in 

interpreting rates — i.e., a low incidence of CWP may simply 

reflect a population of miners who have not been exposed 

long enough to develop disease. However, if Australian coal 

miners do, in fact, have lower job tenures than U.S. miners, 

note that for the past 20 years, even the lowest tenure group 

in the United States has a higher rate of CWP than miners 

in New South Wales, so this potential difference appears 

unimportant (Table 3). 

Table 3 

CWP prevalence for U.S. miners with 0-4 years’ tenure, and miners in New South Wales. 

CWP prevalence % > 1/0 

Surveillance period*				 United States New South Wales 

1990-1994	 	 0.8 

1995-1999	 

2000-2004 

0.6 

< 0.5 

1.2	 

2005-2009		 0.5 

* Surveillance periods apply to the United States. New South Wales prevalence is reported 

annually by Coal Services Pty Ltd. 

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seam thickness. Australian coal 

mining involves less disturbance 

of roof or floor rock to produce 

coal than does mining in the Ap

palachian regions of the United 

States, where the coal is found in 

thin seams. The average coal seam 

thickness in New South Wales for 

mines operating in 2004 was 3.2 m 

(10.5 ft), and in Queensland for 

mines operating in 2003 it was 4 

m (13.2 ft). By comparison, seam 

heights in U.S. mines range from 

1.2 m (4 ft) in MSHA coal district 

1.8-2.3 m (6-8.5 ft) in district 9. In 

the central Appalachian region, 

where rapidly progressive CWP 

has been documented, the average 

seam height is 1.4 m (4.5 ft). 

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Of note, longwall mining, with its generally higher dust 

exposures, began in Queensland in the mid-1980s. Given 

the latency of CWP, new cases among the cohort of miners 

who worked on these longwalls may begin to be discovered 

through an effective surveillance program in the current 

timeframe. 

The coal rank data presented allow this potential factor 

to be discarded. If coal rank were an important factor, rank 

in Australia would be expected to be substantially lower than 

U.S. ranks. Additionally, New South Wales experienced high 

pneumoconiosis rates in the mid-20th century, and, while 

mining still occurs in the same coal formations – with similar 

coal rank – today, disease prevalence is very low. 

Another possible explanation for the differences be

tween the two countries is illuminated by examining coal 
 

Although the impact of the above geologic difference 

may not be immediately apparent, it may result in higher 

exposure to respirable quartz among U.S. miners.To evaluate 

this argument, a selection of 63 mines in the central Appala

chian region (MSHA coal districts 4, 5, 6 and 7), was exam

ined to evaluate how much rock was actually being cut. The 

amount of rock cut was assessed using notes made by MSHA 

inspectors as part of their normal activities. For 16 mines 

in district 4, an average of 26% of the total material height 

extracted was rock (46 of 175 cm); in district 5 (20 mines), 

25% (43 of 173 cm) was rock; in district 6 (13 mines), 19% 

(28 of 147 cm) was rock; and in district 7 (14 mines), 31% (53 

of 173 cm) was rock (Pollock et al., 2009).4 

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4 It should be noted that these mines are not representative of all mines in the districts, having been selected based on high measured RCMD 

concentrations, and the inspector’s notes described conditions encountered on particular days. However, this information demonstrates that 

Appalachian mines sometimes cut a significant amount of rock. 

Australian coal 

mines, with substantially thicker seams, would be able to eco

nomically extract coal without disturbing roof or floor rock at 

anywhere near these quantities, with a coincident reduction 

of respirable quartz generated. 

A final potential explanation for the differences between 

the two countries relates to the sampling methods employed. 

The regulatory systems in New South Wales and Queensland 

evaluate compliance by comparing each dust sample individ

ually to the applicable dust standard, described as a “singlesample” method. In the United States, MSHA evaluates 

compliance by averaging multiple samples collected on one 

occupation over successive (up to five) shifts or days. MSHA 

has reported that multiple sample averaging methods are 

not protective for all miners (Federal Register, 1998). In fact, 

MSHA has attempted to adopt a single-sample approach to 

compliance assessment on three occasions — in 1991, 1998 

and 2000. The first two attempts involved changes to sam

pling policy, but these were reversed subsequent to legal 

challenges. Following extended public comment, a revised 

proposed rule was published in 2003, and that rulemaking 

activity remains ongoing.The authors note that the proposed 

rule to lower miners’ exposure to respirable coal mine dust 

published on Oct. 19, 2010 (FR 75 64412) includes a provision 

to adopt a single-sample, full-shift approach for exposure 

determination. 

Conclusions 

Objective exposure data directly applicable to condi

tions in both countries is limited; however, analysis of avail

able data and the commonality of mining technologies in 

Australia and the United States offers directions for further 

research on this important issue. 

As evidenced by data from the last 20 years, the rate of 

pneumoconiosis in underground coal miners in New South 

Wales is lower than rates in U.S. miners. Based on the available information, exposure to respirable coal mine dust is 

higher in Australian underground coal mines than in the 

United States; however, Australian miners appear to be ex

posed to lower respirable quartz dust. Differences in coal 

rank do not explain the difference in CWP prevalence. 

A potential explanation for this apparent paradox in

volves two factors. The first is that the thicker coal seams in 

Australia permit mines to cut much less rock than in U.S. 

mines, particularly compared to the central Appalachian 

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area, where coal seams are thin. This leads to the possibility 

of Australian miners having lower quartz exposures than U.S. 

miners who work in thinner seam deposits. This argument is 

bolstered by the association between the rapid development 

and progression of simple CWP in U.S. underground coal 

miners exposed to relatively low overall RCMD concentra

tions but to RCMD with elevated quartz content. 

The second factor to explain the paradox may be the 

procedure used in the United States to measure exposure to 

RCMD and quartz in coal mines. MSHA’s own analysis of 

its sampling data has shown that using the average of several 

samples to assess compliance can obscure individual samples 

that are substantially above the exposure limit. Further, this 

assessment method is not protective of all miners on all work 

shifts, and, as recommended in the1995 NIOSH Criteria Doc

ument, should be revised to enhance protection of miners’ 

health. Finally, regarding the argument that quartz exposure 

may be responsible for some of the elevated pneumoconiosis 

prevalence in the United States compared to Australia, it 

should also be recognized that it is not the only factor con

tributing to the higher U.S. disease rates.This is demonstrated 

by the observed pneumoconiosis rates in MSHA coal dis

tricts with the low sample quartz content (see Fig. 4, district 

10), which still exceed rates in New South Wales. 

Other factors that could impact the differing CWP preva

lences involve physical and operational characteristics of 

underground coal mines in Australia and the United States. 

Mines in Australia on average are larger, in terms of employment,than mines in the United States.This difference follows 

from the larger proportion of longwall mines in Australia 

compared to the United States, particularly in the Appala

chian region. In 2006, the average Australian underground 

coal mine employed more than 200 miners (Australian Coal 

Association, 2008). In the United States, underground coal 

mines, excluding anthracite mines, employed an average of 

40 employees in MSHA district 6, to 277 in MSHA district 

11 (MSHA, 2008). Larger mines may have higher levels of 

financial resources for installation of dust controls, and for 

maintenance of dust controls and production equipment. 

The effect of mine size was examined, and mines with fewer 

than 50 employees were found to have higher rates of CWP 

(Laney and Attfield, 2010). 

Operational differences were observed to exist between 

the two nations. An example is the U.S. practice of roof bolt

ers working downwind of the continuous miner, potentially 

exposing them to high dust concentrations. This practice is 

rare in Australia. Another aspect is the use of respiratory 

protection, which appears higher in Australian mines. These 

observations at this time have not been systematically ex

amined, but could have some effect on dust exposure. A 

difficulty with comparing current practices is rooted in the 

latency of CWP. The differing practices would have had to 

have been established decades ago to be reflected in today’s 

CWP rates. 

Based on this analysis, it seems possible that some of the 

cases identified as CWP in the United States — particularly 

those in the central Appalachian region — may be due to 

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quartz exposure. If this is the case, emphasis should be placed 

on quantifying quartz exposure in U.S. coal miners and on re

ducing that exposure where necessary. The authors reiterate 

the sampling methodology recommendations for respirable 

coal mine dust and quartz found in the 1995 NIOSH Criteria 

Document — the establishment of an independent exposure 

standard for respirable quartz in coal mining — and recom

mend a targeted program to assess the exposure of coal min

ers to quartz in thin seam underground mines. 

Finally, CWP is not the only disease caused by exposure 

to coal dust. Considerable morbidity from other respira

tory diseases such as chronic obstructive pulmonary disease 

(COPD) can result, negatively affecting the health of coal 

miners, which makes prevention even more important. Fore

casted increases in production and the expected long-term 

duration of coal utilization worldwide make enhanced pre

ventive measures urgent. 

Acknowledgments 

The authors acknowledge and thank the following for the 

assistance they provided during the performance of this re

search: Coal Services Pty Limited, the Coal Services Standing 

Committee on Dust Research and Control, Peabody Energy 

Australia, Xstrata Coal, and the Mining + Energy Division of 

the Construction, Forestry, Mining and Energy Union. 

Disclosure 

The findings and conclusions in this report are those of 

the authors and do not necessarily represent the views of the 

National Institute for Occupational Safety and Health. 

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