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COAL WORKERS’ PNEUMOCONIOSIS IN U.S. COAL MINES: A REVIEW OF EXPOSURES, INTERVENTIONS, AND OUTCOMES
by
Timothy William Beck
B.S., Mining Engineering, University of Missouri-Rolla, 2000
Submitted to the Graduate Faculty of
Graduate School of Public Health in partial fulfillment
of the requirements for the degree of
Master of Public Health
University of Pittsburgh
2014
UNIVERSITY OF PITTSBURGH
GRADUATE SCHOOL OF PUBLIC HEALTH
This essay is submitted
by
Timothy William Beck
on
April 4, 2014
and approved by
Essay Advisor:James Peterson, PhD ______________________________________Associate ProfessorEnvironmental and Occupational HealthGraduate School of Public HealthUniversity of Pittsburgh
Essay Reader:Anthony Iannacchione, PhD ______________________________________Associate ProfessorMining EngineeringSwanson School of EngineeringUniversity of Pittsburgh
Copyright © by Timothy W. Beck
2014
ABSTRACT
Despite nearly forty-five years of protective dust rules, U.S. coal miners still experience an
alarming level of coal workers’ pneumoconiosis, a debilitating and deadly lung disease. For
miners that have worked entirely under these dust rules, the probability of developing the second
level of disease or greater should be zero for a 35 year career. Recent surveillance has pegged the
number at over two percent, with eight percent of experienced miners exhibiting some evidence
of the disease. Nearly 1,000 miners and former miners succumb to the disease annually,
establishing it as a serious public health issue, and making it the deadliest mining-related hazard
in the U.S., far ahead of widely publicized roof falls, fires, and explosions.
The National Institute for Occupational Safety and Health and other research
organizations have suggested a series of possible causes for the continued prevalence of coal
workers’ pneumoconiosis, including extended shift lengths, increased mining of higher quartz-
bearing coal and rock seams, and insufficient dust rule enforcement. This paper presents many of
the broader risks for developing coal workers’ pneumoconiosis as well as a discussion of the
impact of specific exposure characteristics.
In the coal dust regulations developed in 1969, a seemingly comprehensive approach to
control exposures was employed: regulation and enforcement, dust control research, medical
surveillance, and worker compensation. While the present system addresses several of the risk
James Peterson, PhD
COAL WORKERS’ PNEUMOCONIOSIS IN U.S. COAL MINES: A REVIEW OF EXPOSURES, INTERVENTIONS, AND OUTCOMES
Timothy W. Beck, MPH
University of Pittsburgh, 2014
factors leading to coal workers’ pneumoconiosis, it fails to account for the disparity between
current documented dust exposures and expected rates of the disease, especially in localized
regions. This paper briefly discusses the activities of each component, noting the successes and
shortcomings experienced. The current approach to worker exposure control is reviewed along
with the prospects of reducing the prevalence of this deadly and debilitating disease.
Recommendations are presented to suggest improved approaches to control exposure to coal
mine dust and prevent the resulting diseases.
TABLE OF CONTENTS
1.0 INTRODUCTION.........................................................................................................1
1.1 EXPOSURE TO AIRBORNE PARTICULATE MATTER............................3
1.2 U.S. COAL MINING OVERVIEW....................................................................4
1.3 COAL MINE PARTICULATE EXPOSURES..................................................4
1.4 COAL WORKERS’ PNEUMOCONIOSIS.......................................................5
2.0 FACTORS ASSOCIATED WITH CWP..................................................................10
2.1 ENVIRONMENTAL FACTORS......................................................................10
2.2 INDIVIDUAL RISK FACTORS.......................................................................17
3.0 REDUCING CWP IN U.S. COAL MINES..............................................................23
3.1 PRIMARY PREVENTION OF CWP..............................................................23
3.2 SECONDARY PREVENTION OF CWP........................................................30
3.3 TERTIARY PREVENTION OF CWP............................................................32
4.0 RECOMMENDATIONS............................................................................................37
4.1 IMPROVED DUST MONITORING AND CONTROL.................................37
4.2 TARGETED INTERVENTIONS.....................................................................38
4.3 MINER ENGAGEMENT AND PARTICIPATION.......................................40
4.4 INSTITUTIONAL REFORM...........................................................................41
5.0 CONCLUSIONS.........................................................................................................42
APPENDIX A: DEVELOPMENT OF THE TERMINOLOGY OF COAL WORKERS’
OCCUPATIONAL LUNG DISEASES......................................................................................45
APPENDIX B: BRIEF HISTORY OF U.S. MINING HEALTH AND SAFETY
REGULATION TO 1969............................................................................................................47
BIBLIOGRAPHY........................................................................................................................50
LIST OF TABLES
Table 1. Occupational exposure limits for respirable coal mine dusts worldwide (adapted from
[77])...............................................................................................................................................25
Table 2. Respirable coal dust regulatory and recommended exposure limits (adapted from [80])
.......................................................................................................................................................26
LIST OF FIGURES
Figure 1. Wood-cut diagram from Agricola’s De Re Metallica depicting a miner exposed to
“fetid vapors” [3].............................................................................................................................2
Figure 2. CWP morbidity in U.S. underground coal miners by tenure, 1970-2012 [25]................8
Figure 3. Percentage of evaluated miners with rapidly progressive coal workers’ pneumoconiosis
by county [30]..................................................................................................................................9
Figure 4. Probability of a miner being classified as 2/1+ after a 35 year career of exposure to
various coal dust concentrations [31]............................................................................................11
Figure 5. Prevalence of CWP (ILO 1/0+) among U.S. coal miners by estimated exposure [43]..18
Figure 6. Hours worked annually by U.S. underground coal miners, 1978-2007 [17].................19
Figure 7. Operator and inspector coal mine dust measurements, 1979-2003 [14]........................28
Figure 8. NIOSH CWXSP mobile examination unit.....................................................................31
Figure 9. Fatalities at U.S. coal mines, 1900-1969 [17]................................................................48
1.0 INTRODUCTION
Mining in all its forms provides a range of materials that contribute to the wellbeing of society
and advancements in a range of fields. From the familiar metals and stones that build the world
around us to the fuels that power our modern technologies, mining plays an important role in the
world’s prosperity and quality of living. Mining has long been recognized as a distinctly
dangerous occupation. It appears that nearly all historical records of mining afford at least some
mention of the dangers faced by miners. Hippocrates supplied one of the first known
acknowledgements of the hazards in circa 400 BC, when he observed the toxic effects of lead
exposure in miners [1]. Nearly 400 years later, Strabo encountered and described the effects of
sickening mine air in his 7 BC work, Geographica [2]:
“the air in the mines is both deadly and hard to endure on account of the grievous
odor of the ore, so that the workmen are doomed to a quick death. What is more,
the mine is often left idle because of the unprofitableness of it, since the workmen
are not only more than two hundred in number, but are continually spent by
disease and death.”
Though it was widely known that foul air in mines could cause sickness and death, a connection
between the mine environment contaminated with dust and the detrimental effects on the lungs is
described in Georgius Agricola’s 1556 mining treatise De Re Metallica [3]:
1
“the dust which is stirred and beaten up by digging penetrates into the windpipe
and lungs, and produces difficulty in breathing, and the disease which the Greeks
call asthma. If the dust has corrosive qualities, it eats away the lungs and implants
consumption in the body… Women are found who have married seven husbands,
all of whom have this terrible consumption has carried off to a premature death.”
This toxic air is even depicted in the original engraved plates that demonstrate primitive mining
methods, using fire to break rocks and develop tunnels (Figure 1). While Agricola may have
attributed other mining hazards to supernatural subterranean gnomes, he no less recognized that
miners frequently suffered respiratory disease due to their labors underground.
Figure 1. Wood-cut diagram from Agricola’s De Re Metallica depicting a miner exposed to “fetid vapors”
[3].
2
1.1 EXPOSURE TO AIRBORNE PARTICULATE MATTER
Over the past many years, a growing body of evidence has demonstrated associations between
the inhalation of particulate matter and an extensive list of negative health effects. The exposure
to such aerosols, in both workplace and ambient environments, is expressed as a mass per unit
volume of air, or mass concentration (or simply “concentration”). Studies have shown that
increases in the concentration of inhalable particulate matter results in increased deaths from
respiratory illnesses, increased cardiovascular deaths, increased rates of lung cancer and
increased risk of premature births and infant mortality [4], [5], [6], [7]. These small particles are
easily inhaled and not effectively filtered by the nose or upper respiratory system [8]. Produced
by many natural and anthropogenic processes, fine particulate may deeply penetrate the lungs,
causing extensive damage.
Until recently, ambient particulate matter was ubiquitous in industrial areas, playing a
main role in the choking “fog” that claimed several lives during notable mid-20 th century
episodes in Meuse Valley, Belgium, Donora, Pennsylvania, and London, England [9]. Efforts
across the U.S. following the passage of the Clean Air Act of 1970 have significantly reduced
these hazardous ambient particulate concentrations. Between 1990 and 2012, national
concentrations of PM10 (particulate matter with a 50% cut-point of aerodynamic diameter less
than 10 microns) have decreased 39 percent to a 24-hour time-weighted average (TWA) of 63.8
µg/m3, as measured by the U.S. Environmental Protection Agency at hundreds of strategically
located sites [10].
3
1.2 U.S. COAL MINING OVERVIEW
Coal is an abundant mineral resource in the U.S. and provides a relatively inexpensive source of
energy for electric power generation. The production of coal has historically provided substantial
employment, with over 800,000 miners working at the nation’s mines in 1923 [11]. Though
current employment in U.S. underground coal mines has declined to 54,426 in 2012 [12], mining
remains the primary industry in the coalfields of several U.S. states, including West Virginia,
Kentucky, and Illinois [13]. This regional concentration localizes the impact of both economic
and health effects resulting from coal mining on a population with few employment alternatives.
1.3 COAL MINE PARTICULATE EXPOSURES
The level of ambient particulate contamination in U.S. coal mines is measured by both coal mine
operators and inspectors for the Mine Safety and Health Administration (MSHA) and is
presented by the National Institute for Occupational Safety and Health (NIOSH) in their annual
Work-Related Lung Disease Surveillance System report [14]. NIOSH reports that the average
coal miner’s 8-hour TWA exposure to respirable dust was 0.458 mg/m3 in 2012. It should be
noted, however, that as recently as 1995, 42 percent of these individual samples exceeded the
MSHA permissible exposure level of 2.0 mg/m3 [15]. With these elevated exposures in coal
mines come many of the associated health impacts, most notably coal workers’ pneumoconiosis.
4
1.4 COAL WORKERS’ PNEUMOCONIOSIS
Following recent mine disasters at the Sago and Upper Big Branch underground coal mines, in
2006 and 2010, respectively, the U.S. coal industry redoubled their safety efforts, setting record
lows for both injury rates and fatalities in 2012 [16]. These recent successes however may
obscure the fact that thousands of miners continue to succumb to preventable occupational lung
diseases. From 1996 to 2007, coal mining accidents claimed the lives of 415 workers, both on
the surface and underground [17]. During the same time period, coal worker’s pneumoconiosis
(CWP) played a role in the death of over 8,000 individuals, being identified as the primary cause
of death in 40 percent of these cases [18]. This tremendous human cost comes with a
considerable financial burden as well—over $39 billion in federal CWP compensation benefits
have been paid to coal miners over the 25 years from 1980 to 2005 [19].
Coal workers’ pneumoconiosis (CWP), also commonly known as “black lung disease,” is
a progressive lung disease resulting from exposure to high levels of respirable dust that can be
disabling and fatal in its most severe form. CWP is defined as the accumulation of coal dust in
the lungs and the resulting reaction of tissue to its presence [20]. Once contracted, there is no
cure for CWP. The goal, therefore, is to limit worker exposure to respirable dust to prevent
development of the disease. The disease may have a very long latency period, extending into
decades, and be asymptomatic with many of the physical effects remaining hidden until detection
and diagnosis through medical examination [19]. This is in contrast to many other mining
hazards, which manifest themselves in immediate and visible ways. The development of the
terminology used to label and describe this occupational respiratory disease is explored in .
5
1.4.1 Detection and diagnosis
Unlike many other respiratory exposures, the effects of exposure to coal mine dust and initial
development of CWP do not typically manifest in sudden shortness of breath or other ailments.
Instead, living miners must rely on chest radiographs (or x-rays) and functional breathing tests to
identify the presence of this lung damage.
There are two types of CWP: simple and complicated. In chest x-rays, simple CWP
appears as small opacities (10 mm and smaller in diameter) in the lungs, while complicated CWP
presents as larger opacities and fibrotic masses. These chest x-rays are classified by International
Labour Organization (ILO) standards based on the following procedures [21]: lung images
demonstrating simple CWP are grouped based on severity as major category 1, 2, or 3, with
those showing no apparent damage classified as 0. The major category determination may list
other categories if the additional category was “seriously considered” during the classification.
For example, an ILO classification of subcategory 1/0 is reported for x-rays classified as
category 1 after having been seriously considered as category 0 as an alternative. NIOSH uses
the subcategory 1/0 as the lowest possible presentation of the disease for their surveillance work.
Simple CWP may result in minimal functional impairment [22]. While categories 2 or 3 may be
associated with reductions of the maximum ventilatory rates and a slightly lower level of oxygen
in the bloodstream, these irregularities are not enough to cause disability.
The names complicated CWP and progressive massive fibrosis (PMF) are used to
describe the singular condition of exhibiting one or more opacities with diameters exceeding 10
mm on radiograph. Images demonstrating PMF are grouped based on severity as category A, B,
or C, with those showing the least damage classified as A. This condition is most likely to
develop in miners already affected by simple CWP, though it has been found in miners with no
6
previous CWP diagnosis. Another characteristic of this condition is that it may continue to
progress without continued dust exposure. Functional impairments associated with PMF include
breathlessness, chronic bronchitis, and occurrence of right-sided heart failure. PMF is also
associated with decreased oxygen-diffusing capacity and increased mortality [23].
1.4.2 Recent increase in CWP prevalence
Today, CWP continues to be a persistent and significant health threat to underground coal mine
workers. Until recently, the prevalence of CWP in U.S. coal mines had been declining. For
underground coal miners with 25 or more years of experience, the prevalence of CWP had
dropped from over 30 percent in 1970 to a low of 4.2 percent in 1999 [24]. This rate has doubled
to nearly eight percent for the same demographic in the most recent NIOSH surveys conducted
in 2012 [25]. Figure 2 shows this recent increase in CWP (as defined by ILO category 1/0 or
greater) as measured by NIOSH’s Coal Workers’ X-ray Surveillance Program (CWXSP) for
those miners with the most tenure underground.
7
Figure 2. CWP morbidity in U.S. underground coal miners by tenure, 1970-2012 [25].
After the Upper Big Branch disaster in 2010, 24 of the 29 deceased miners were examined by the
West Virginia Medical Examiner for evidence of CWP [26]. Evidence of CWP was found in 17
of the 24 victims (or 71 percent), with four others having “anthracosis”, which is a term that may
be used in place of CWP or to describe an earlier, milder form of the disease. This rate compares
very unfavorably to the NIOSH-documented rate of 10.0 percent for the rest of the miners in the
state of West Virginia [27]. Most startling is that one of the victims with CWP was just 25 years
of age and five of the miners with CWP had worked less than 10 years as coal miners.
Recent NIOSH published reports have shown that a recent increase in rapidly progressing
CWP can be localized to the Central Appalachian Region [28], [29], [30]. These areas have been
referred to as black lung or CWP “hot spots” in the associated literature. Figure 3 shows a map
of the locations experiencing rapidly progressing CWP at rates much higher than expected. In
these black lung hot spots, up to 80% of evaluated miners had evidence that their cases of CWP
8
were advancing at alarming rates. It is apparent that despite numerous attempts to reduce the
incidence of CWP in these areas, the disease remains a significant public health issue and may
require new approaches or more stringent controls to protect miners’ health.
Figure 3. Percentage of evaluated miners with rapidly progressive coal workers’ pneumoconiosis by
county [30].
9
2.0 FACTORS ASSOCIATED WITH CWP
For CWP, many exposure characteristics have been studied extensively with connections
established to resulting disease, while some have been hypothesized, but may lack supporting
evidence. For many of these factors, epidemiological evidence provides a strong link or
association and toxicological studies have demonstrated the plausible biological mechanisms
responsible for the development of CWP pathologies. These factors can be grouped into general
properties of the work environment and individual characteristics that may transform the various
environmental exposures into personal negative health effects.
2.1 ENVIRONMENTAL FACTORS
2.1.1 Mass concentration
Much of the CWP literature has focused on the mass concentration of respirable coal dust as a
measure of occupational dust exposure. Early studies of British miners were used by Jacobsen et
al. to produce one of the first quantitative exposure-response relationships for coal dust
exposures by mass concentration [31]. This exposure-response curve, shown in Figure 4,
illustrates that as one is exposed to increasing concentrations of respirable coal mine dust, the
predicted risk of developing CWP increases. This same relationship compares favorably to
10
studies of U.S. coal miners, demonstrating the increasing risk of developing CWP classified as
ILO category 1/0 or greater after working for 45 years in increasingly dusty mine atmospheres
[32]. As further evidence that lower occupational exposures to mass concentrations of respirable
dust may reduce disease burden, studies of former U.S. miners at autopsy have shown that
working under the reduced dust standards from the Federal Coal Mine Health and Safety Act of
1969 (the Coal Act) has reduced both the prevalence and severity of lung damage associated
with CWP. Progressive massive fibrosis (PMF), the most severe stage of CWP, has been
identified in 9.6 percent of miners who worked prior to 1969, while for those who worked post-
1970, 1.2 percent [33]. Although additional exposure characteristics are frequently integrated
into the epidemiological analysis, mass concentration has consistently been associated with the
prevalence and progression of disease [30].
Figure 4. Probability of a miner being classified as 2/1+ after a 35 year career of exposure to various coal
dust concentrations [31].
11
2.1.2 Particle size
Particulate concentrations have been typically measured as a mass-based concentration because
mass is relatively easy to measure with current techniques and health-effects have been shown to
be well-correlated with the mass of respired particles [34]. Many epidemiological studies support
this approach, showing increasing adverse health effects with increasing particulate mass
concentrations [4], [5], [6], [7].
Recent advances in nanotechnology have allowed the measurement of increasingly
smaller particles with corresponding increases in surface area per unit mass. Toxicological
studies have followed, showing that smaller particles can cause stronger adverse biological
reactions, especially inflammation and release of reactive oxygen species (ROS), than the same
mass concentration of larger particles [35]. While several coal mine particle size studies have
been undertaken in response to associations between coal dust exposure and chronic obstructive
pulmonary disease, this research has mainly focused on thoracic particles, larger than those of
respirable size [36], [37]. Currently, there is little published field data on the size distribution of
coal mine dusts in the submicron to micron range. For this reason, the toxicology of small
particles have not been adequately studied in coal miner populations, though this has been
suspected to impact current rates of disease by NIOSH [15].
2.1.3 Coal and coal dust composition
Coal is a complex heterogeneous mixture of more than 50 different possible elements [38]. Many
of these elements are oxidized producing many more potential compounds. Composed primarily
of organic matter, the amount of inorganic compounds can range from nearly zero to 50 percent
12
by weight. These “contaminants” can include phyllosilicates, quartz, carbonates, sulfides,
sulfates, and other minerals [39]. The main metals are iron and aluminum, with arsenic,
cadmium, cobalt, copper, nickel, and zinc representing trace fractions. The composition of coal
varies widely from coal seam to coal seam, and frequently within the same seam [40].
The dust found in underground coal mines has been estimated to be between 40 and 95
percent coal [15]. The remainder consists of dusts from the surrounding strata or from rock
(limestone) dust applied to prevent both the occurrence and the propagation of explosions. While
coal dust composition may not mimic that of bulk coal, studies have suggested that using bulk
coal data can provide a good approximation of the potential makeup of coal mine dust [41].
Many studies have established connections between these components of coal and coal dust and
resulting incidence of CWP, with the most frequently discussed contents being carbon, quartz,
and iron [42].
2.1.3.1 Carbon content
Coal rank is the common term used to differentiate between the carbon content of different coal
deposits. High rank coals are considered to contain 89–90 percent carbon, while medium/low
rank coals contain 80–89 percent carbon [43]. Epidemiological studies have linked a higher risk
of developing PMF over a working lifetime to miners exposed to similar levels of respirable dust
of high rank coal [43]. Another study looking at functional impairments found that miners in the
high-rank coal mines of the Midwestern and eastern U.S. had greater loss of lung function than
miners from the western U.S., where low-rank coals are common [44]. These studies corroborate
the findings of the Mining Research Establishment in Great Britain. Based on exposure to a 2.0
mg/m3 respirable dust concentration of coal with 86.2 percent carbon content, the resulting risk
of developing PMF after a 40-year working career has been calculated at 1.19 percent and 7.75
13
percent for simple CWP [45]. For coals with carbon content of 83 percent, in the middle of the
medium/low rank range, the risks decreased to 0.71 percent for PMF and 6.49 percent for simple
CWP. Because of the influential effect that coal rank has on the occurrence of CWP and PMF,
some groups, including American Conference of Governmental Industrial Hygienists (ACGIH)
have called for exposure limits to be established based on the rank of coal being mined [46].
2.1.3.2 Quartz content
For many years, respirable quartz (also referred to as crystalline silica) dust was considered the
active agent in the development of CWP. While quartz dust “dose and composition do not appear
to account wholly for changes in the prevalence of CWP” [47], the fibrogenic properties of
quartz are well connected to lung pathology and respiratory impairment. Research has shown a
wide variation in the risk of quartz exposure in U.S. coal mines, based on the origin of the quartz
content or its interaction with other chemicals and minerals in the airborne dust. For this reason,
epidemiological studies have produced divergent results with different dose-response curves for
CWP with similar quartz exposures [32]. These relationships have been especially challenged to
predict CWP at low quartz concentrations, though it is expected that coal dust exposures are the
dominant toxic hazard in these situations [48].
As the thicker coal seams in the U.S. are depleted, mines are left with thinner seams to
exploit. In order to mine these thinner seams while maintaining equipment clearance, some
operations will intentionally remove portions of the rock above and below the seam [28]. Pollock
et al. report that in these cases, from 20 to 30 percent of the mined material is pure rock. These
modern coal seams also tend to be less continuous and contain more rock partings. Rock partings
within the coal and areas where the coal is not present typically contain much more quartz than
the coal itself [49]. There is some epidemiological connection between these quartz exposures
14
and CWP, with U.S. research finding a significant relationship between the mining of thinner
seams of coal and rock and the occurrence of CWP [50]. For those miners working in seams less
than sixty inches in height, the risk of being located within a black lung hot spot region is 8.6
times higher than that for miners working seams five feet or taller. These results are consistent
with British research that associated increases in CWP prevalence with cutting of rock [51].
2.1.3.3 Iron content
One of the long-recognized contaminants within coal is iron pyrite, chemical formula FeS2.
While pyrite is frequently connected to the risk of spontaneous combustion in coal mines,
exposure to iron-bearing dusts may be relevant to the development of CWP. Researchers have
noted accumulations of iron in the lung tissue of CWP victims, suggesting that iron’s ability to
catalyze oxidant production may contribute to the onset of pneumoconiosis [52]. A recent
toxicological study demonstrated that coals with the highest pyritic sulfur and available iron
generate the greatest inflammatory stress response, an indicator of lung distress, and a potential
precursor to the development of CWP [53]. This agrees with a post-mortem study that found that
lung iron content correlated well with the degree of CWP [54].
Huang et al. have extensively examined the incidence of CWP and numerous components
in coal, finding a strong positive correlation between both sulfur and bioavailable iron, though
they did not identify a similar effect for coal rank or crystalline silica/quartz [41]. Because the
levels of iron are much higher for eastern coals than for those in the West, this result may be an
artifact of the demonstrated regional concentration of CWP (Section 1.4.2). Because of the
complex nature of coal dust and interactions between compounds, separate effects for the range
of coal constituents can be difficult to establish [48].
15
2.1.4 Mine size and location
While rates of CWP are currently increasing in mines of all size, NIOSH researchers have shown
that both CWP and PMF are much more prevalent among worker from small mines (those with
fewer than 50 employees) [55]. These small mines also have a 10 times greater likelihood of
being in a black lung hot spot region than larger mines with 500 or more employees [50]. A
robust analysis of MSHA citation and noncompliance data from 1999 to 2002 indicates that there
is no clear relationship between an increased number of citations issued and a mine’s likelihood
of being located in a CWP hot spot region [50]. In fact, the research found that fewer than seven
percent of mines in the hot spot regions received citations pertaining to the permissible dust
limits, while twenty percent in other regions received similar citations. By contrast, when
considering violations due to excessive concentrations of quartz dust, the hot spot mines
exhibited a significantly higher proportion of citations than those mines in other areas, indicating
a higher exposure to coal dusts containing hazardous levels of respirable quartz dust. This
analysis suggests that small mines may not have the resources to effectively provide protection
for workers, including integration of state-of-the-art approaches to dust suppression and
acquisition of personal protective equipment, such as respirators.
16
2.2 INDIVIDUAL RISK FACTORS
2.2.1 Age and total lifetime dust burden
Age has been shown to be a risk factor for the development of CWP [45]. This likely stems from
the increased cumulative dust exposure for older individuals compared to younger workers.
Chronic dust exposures, even at levels below the current 2.0 mg/m3 standard, can produce
substantial accumulation in the macrophages of the lung. Because lung clearance rates are
reduced by lung burden [56], high exposure intensities, even for just five years, can result in
clearance times that extend for another 25 years [57]. This extended residence time of inhaled
particles in the lungs provides an increased opportunity for immunological response, such as
chronic inflammation and fibrogenesis.
Cumulative dust exposure has been shown to be a strong predictor of CWP risk [58].
Figure 5 shows this relationship for U.S. coal miners [43]. As indicated in the figure, exposures
over a 45 year career at a concentration of 2.0 mg/m3 result in rates of CWP ranging from 14 to
24 percent, depending on coal rank. Because many of the samples collected for compliance
exceed the 2.0 mg/m3 value, miners are achieving their permissible lifetime accumulation in
fewer years of tenure and accumulating much higher amounts of dust over a working career than
permitted by the law [15].
17
Figure 5. Prevalence of CWP (ILO 1/0+) among U.S. coal miners by estimated exposure [43].
Note: Exposure to 2.0 mg/m3 for 45 years is equivalent to 90 mg--years/m3 as shown.
2.2.2 Shift length and time between work shifts
U.S. coal miners continue to work more hours annually, working both longer and more frequent
shifts [17]. The increase since 1978 in annual time worked can be seen in Figure 6. Case studies
of workers at two British mines have indicated that working extended hours may cause an
increase in CWP prevalence [51]. Although only weak epidemiologic connections have been
established between miners working extended shifts and rates of CWP, miners working 12 hours
are theoretically exposed to 50 percent more dust than workers with 8 hour shifts. As has been
discussed in the previous section, this increase in cumulative dust burden over a career will
increase the risk of developing CWP. Longer shifts also pose the problem of reduced lung
clearance times for workers who work consecutive shifts. This can overwhelm lung clearance
mechanisms and result in significant accumulations of dust particles, reduced breathing capacity,
and development of CWP [56]. Unfortunately information about shift lengths is not miner-
18
specific in the U.S., but rather mine- or industry-specific. This makes it increasingly difficult to
make a formal epidemiologic analysis for workers in U.S. coal mines.
1978 1983 1988 1993 1998 20031500
1600
1700
1800
1900
2000
2100
2200
Year
Hour
s wor
ked/
unde
rgro
und
min
er
Figure 6. Hours worked annually by U.S. underground coal miners, 1978-2007 [17].
2.2.3 Use of respirators and personal protective equipment
Because CWP results from exposure to coal dust, it is largely preventable through the use of
respirators. A common, inexpensive half-face respirator typically provides a protection factor of
10, reducing the wearer's concentration to 10 percent of the workplace concentration [59].
Though this application would greatly reduce the occurrence of CWP, barriers are present which
inhibit respirator use.
On the individual level, coal miners may neglect to use respirators during their activities
because there may be a lack of awareness about the hazards and consequences, a lack of
knowledge on the proper fit and use of respirators, or even a perceived lack of personal control
over their health and wellbeing. Tobacco use may also limit respirator use, with strong inverse
relationships observed between smokers and duration and frequency of respirator use [60]. A
19
recent study of U.S. coal miners has shown that miners may modulate their respirator use to
target dusty tasks, with higher levels of dust exposure being associated with increased respirator
use [61]. An earlier study of U.S. miners found the same effect, with observations and
measurements showing that respirator use is intermittent and that the respirator was not worn
when dust was not visible [62]. This is an important finding, suggesting that information about
the possibly unseen hazards presented by certain activities can increase self-protective behaviors.
For those workers that would wear a respirator, there is the issue at smaller mines of
unavailability of required fit tests and even respirators themselves [63]. Research has also shown
that respirator use is related to establishment size, increasing from 11.5 percent at the smallest
establishments to 56.5 percent at the largest [64]. Because size of mine and respirator use are
closely linked, efforts to improve awareness and access to fit tests, especially among smaller
mines, are needed to reduce the development of CWP.
2.2.4 Smoking status
Although both smoking and dust exposure may be responsible for the development of chronic
obstructive pulmonary disease and loss of lung function, smoking does not appear to increase the
prevalence of CWP or affect an individual’s development of CWP [31]. When U.S. researchers
produced a logistic model of pack-years on CWP and compared it to the same model of age and
dust exposure on CWP, smoking was found to be unable to predict the prevalence of the disease
[43]. This is consistent with earlier British research showing that smoking does not increase the
potency of coal dust [65].
20
2.2.5 Individual immunological factors and health status
Chronic inflammatory diseases, like CWP, are multi-factorial and affected by both
environmental and genetic factors. The underlying immunologic mechanisms and potential
genetic susceptibilities leading to the development of CWP are not clearly understood [66]. Coal
dust has been shown to stimulate an inflammatory and fibrotic response through the release of
cytokines [67]. Investigations into polymorphisms within genes related to these cytokines have
found divergent results in relation to CWP status. A recent study of Turkish miners has
demonstrated a differential distribution in polymorphisms relevant to pro- and anti-inflammatory
cytokines in victims of CWP and control subjects [67]. This finding is in contrast to that of a
similar study by many of the same researchers that no significant difference exists between
control subjects and those with complicated CWP [68].
In addition to cytokines, inflammatory cells secrete reactive oxygen species (ROS) during
the immunological response to dust particles. Imbalances between ROS and antioxidant enzymes
can be used as a marker of oxidative stress. In a study of miners with CWP, levels and activities
of various antioxidant enzymes were elevated, suggesting the presence of oxidative stress due to
free radical formation [69]. This may explain the effects observed for coal miners exposed to
higher levels of bioavailable iron from pyrite (see Section 2.1.3.3) [53].
Other health effects have been shown to be connected to CWP. For example, CWP and
tuberculosis have historically co-existed in the mining workforce. Though CWP does not cause
an increased risk for tuberculosis, the presence of tuberculosis appears to be related to both CWP
incidence and progression [70], [58]. Wiener et al. describe atypical reactions to tuberculosis that
may contribute to the development of PMF from simple CWP [71].
21
Another complication related to CWP is the presence of rheumatoid arthritis (RA), an
autoimmune disease that causes damage through an inflammatory response. In miners with
rheumatoid factor, the autoantibody that contributes to the autoimmune disease process of RA,
rheumatoid pneumoconiosis can develop. This rare condition, also called Caplan syndrome, is
characterized by multiple rounded nodules forming in the lungs over a short period of time, and
may occur in one percent of CWP victims [72]. While there is no evidence that coal mining
predisposes workers to RA, it is unclear whether RA changes the lung’s response to coal dust.
22
3.0 REDUCING CWP IN U.S. COAL MINES
The passage of the Federal Coal Mine Health and Safety Act of 1969 (the Coal Act) established
respirable dust exposure limits, dust sampling requirements for inspectors and mine operators, an
engineering research program to develop and disseminate dust control technologies, a voluntary
chest x-ray surveillance program to identify CWP in underground coal miners, and a benefits
program to provide compensation to affected workers and their families. In an approach first
described by Leavell and Clark in 1965, preventive medicine and associated efforts to prevent
and control disease can be divided into three levels of intervention: primary, secondary, and
tertiary [73]. The approach adopted by the U.S. government to reduce incidence and prevalence
of CWP can likewise be divided into the same categories.
3.1 PRIMARY PREVENTION OF CWP
Primary prevention techniques are most critical in preventing disease by eliminating exposures
that lead to development of the disease. Regulatory and engineering controls are examples of
primary prevention efforts because if implemented properly they can reduce or eliminate
exposures and prevent the disease from occurring. Because there are no effective therapies for
the treatment of CWP, disease prevention through exposure reductions is the only way to
improve miners’ occupational health. Limiting exposure to coal dust through various
23
underground control measures and the appropriate enforcement of permissible limits, the Coal
Act places a strong emphasis on controlling exposures to control disease.
3.1.1 Compliance with a regulatory dust standard
Prior to federal regulations limiting coal mine dust concentrations, the average coal miner was
exposed to respirable dust in concentrations exceeding 6 mg/m3 [74]. The Coal Act established
the most stringent permissible coal dust concentration in the world at 2.0 milligrams per cubic
meter of mine air [75]. An interim standard of 3.0 mg/m3 was put into effect from 1969 to 1972,
before the two milligram standard became effective. The final standard was based primarily on
studies of United Kingdom coal miners, with the intent being the prevention of PMF by stalling
the progression of simple CWP [76]. Table 1 lists current occupational exposure limits for
respirable coal mine dust in various countries worldwide. Though there are differences in
sampling and measurement methodologies between countries, it can be seen that limit-setting
and enforcement are core principles in the primary prevention of workplace diseases worldwide
[77].
24
Table 1. Occupational exposure limits for respirable coal mine dusts worldwide (adapted from [77])
Country Dust Concentration* (mg/m3)
Australia –
Queensland
3.0
Australia - New
South Wales
2.5
Belgium 5.0
Brazil 4.0
Canada 2.0
China 6.0
Finland 2.0
Germany 4.0
India 3.0
Italy 3.3
Netherlands 2.0
Russia 2.0
South Africa 2.0
United Kingdom 3.8
United States 2.0
Turkey 5.0
* Respirable dust concentrations shown for zero silica/quartz content.
In the U.S., MSHA is responsible for establishing and enforcing the permissible exposure limit
of 2.0 mg/m3 for respirable coal mine dust (30 CFR §70.100) [78]. This dust concentration is
25
measured gravimetrically as an 8-hour TWA with a reduced standard when the respirable quartz
content exceeds 5 percent (30 CFR §70.101) [78]. Due to continued evidence of CWP in the U.S.
coal mining workforce, MSHA has recently proposed a reduction in the allowable respirable dust
concentration to 1.0 mg/m3 [79]. While this rule was first presented in 2010, MSHA has yet to
publish the final rule. Table 2 below lists these proposed regulatory exposure limits and other
recommended limits from various U.S. organizations.
Table 2. Respirable coal dust regulatory and recommended exposure limits (adapted from [80])
Exposure
Limit
mg/m3
Limit type Notes/Adjustments
MSHA (1969-1972) 3.0 8-hour TWA, PEL If SiO2 > 5%, 10 / %SiO2
MSHA (1972-
present)
2.0 8-hour TWA, PEL If SiO2 > 5%, 10 / %SiO2
MSHA (proposed) 1.0 8-hour TWA, PEL Separate standard for SiO2
ACGIH 0.9 8-hour TWA, TLV® Bituminous or lignite, separate
limit for SiO2
ACGIH 0.4 8-hour TWA, TLV® Anthracite, separate limit for
SiO2
NIOSH 1.0 10-hour TWA, REL Separate REL for SiO2
OSHA 2.4 8-hour TWA, PEL If SiO2 > 5%, 10 / (%SiO2 + 2)
CalOSHA 0.9 8-hour TWA, PEL If SiO2 > 5%, 0.1 mg/m3
Note: PEL = Permissible Exposure Limit, TLV® = Threshold Limit Value®, REL = Recommended Exposure Limit
26
Several issues are evident with the current enforcement program, most notably the lack of
cooperation between industry and government agencies. This longstanding issue can be
evidenced in the long and arduous process of developing basic regulations during the early 20 th
century as described in . Additional issues arise due to the fact that operators share responsibility
for periodic sampling of occupational dust concentrations. When collecting their samples,
operators are allowed to reduce production rates to 50 percent of the average production for the
last 5 valid samples [78]. As production has been closely linked to resulting dust concentrations
[79], this affords the mine operator the ability to intentionally reduce production during sampling
periods rather than measure dust exposures during a typical shift [81].
Weak penalties may also provide inadequate incentive for companies to take protective
measures to prevent CWP. A 2005 study found that when MSHA fines a company for violating
the relevant dust regulation, the average fine levied is only $387.85 [82]. For companies
producing millions of tons of coal annually, at an average price of $66 per ton [83], small fines
may have little financial impact.
MSHA has made efforts to address inaccurate samples and weak enforcement measures.
In 1991, MSHA revealed possible intentional mine operator tampering of dust sampling filters,
producing what were called “abnormal white centers”, so named because of the appearance of
the white filter medium in the center of the filter where black coal dust would typically be
deposited. Robert Weissman, the president of Public Citizen, called this “The Great Coal Dust
Scam” at the time [84]. Peabody Coal Company ultimately pleaded guilty to concealing the true
level of exposure to respirable dust with a $500,000 fine for tampering with dust sampling filters.
While MSHA observed a 6.5 percent proportion of invalid samples due to AWC, this reduced to
1 percent following citations and litigation [75]. As can be seen in Figure 7, the difference
27
between operator and MSHA dust concentrations was much wider in the earlier years under the
Coal Act, with the gap reduced significantly after the 1998 ruling in the case Secretary of Labor
v. Keystone Coal Mining Corp. [85].
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Coal
Min
e Du
st C
once
ntra
tion
(mg/
m3)
Figure 7. Operator and inspector coal mine dust measurements, 1979-2003 [14].
Even when unbiased measurements are made, infrequent sampling may allow a potentially
hazardous environment during the time between sampling events. Sampling for coal dust is only
required for five sequential shifts four times per year [78]. This frequency of sample collection is
inadequate when the variability of exposures is high. In these cases, the frequency of sample
collection must be increased to adequately estimate occupational exposure [86]. Continuous dust
sampling methods have been proposed to increase the frequency of sampling and limit the
amount of time spent under hazardous conditions. In rules proposed in 2010, MSHA requires the
use of a newly developed continuous personal dust monitor (PDM 3600) by Thermo Scientific
Inc. [79].
28
― Inspector Samples
--- Operator Samples
3.1.2 Research to develop engineering controls
The Coal Act directs a federal initiative to research means to control the dusts in underground
coal mines. The primary method to control worker exposure to coal dusts underground is to
apply ventilation and water [81]. Previously, research advancing these techniques was
undertaken by USBM, within the Department of the Interior. With the defunding and closing of
USBM in 1995 and 1996, respectively, these functions have been integrated into NIOSH’s
Office of Mine Safety and Health Research.
The research program begins at the point of dust generation and works to break the chain
leading ultimately to miner exposure. While this approach has shown to be sufficient to control
dust below permissible limits, the continuing rate of excessive exposures indicate that there are
failures in either the design or application of these controls. The NIOSH’s National Occupational
Research Agenda – Mining Sector Council has developed research objectives suggesting that
researchers develop new or improved methods of reducing miners’ exposure to dust [87].
As recently as 2005, 34 full-time employees were responsible for engineering dust
controls, developing dust monitoring techniques and instruments, and researching the monitoring
and control of diesel emissions, with a discretionary research budget of about $1.1 million [88].
A smaller portion of this workforce is dedicated to developing dust control measures for the
entire coal mining industry, with a total of 8 employees focused on continuous mining, longwall
mining, and surface coal mining. These researchers are spread among three research projects,
with a combined research budget of under $140,000 [89]. This lack of resources severely limits
the ability of researchers to devise new controls and effectively increase industry awareness to
the proper application of these controls.
29
3.2 SECONDARY PREVENTION OF CWP
Medical examinations to detect asymptomatic disease are considered to be secondary level
prevention as they allow victims to be diagnosed and treated before symptoms develop. In the
case of CWP control, screening chest x-rays and lung function tests are important to identify
disease, to evaluate the efficacy of the primary exposure control efforts, and to plan tertiary
prevention efforts of medical care and compensation.
3.2.1 Medical surveillance to track incidence and progression of CWP
Under the Coal Act, the Coal Workers’ Health Surveillance Program at NIOSH is tasked with
conducting epidemiological research to monitor the progression of CWP in the U.S. labor force.
This approach to disease control can be termed secondary prevention, with the goal being to
identify and treat the disease before symptoms develop. The Coal Act specifies that each coal
mine operator offer an initial chest radiograph to every newly employed underground miner and
then again approximately every five years. When a U.S. coal miner dies, the Coal Act also
allows for families to arrange for a free autopsy to both help support a potential benefit claim and
to provide scientists with more detailed information about CWP.
At the onset of the National Study of Coal Workers’ Pneumoconiosis in 1969, the
prevalence of CWP in bituminous miners was estimated to be 47 percent [20]. Subsequent work
by NIOSH technicians in the Coal Workers’ X-ray Surveillance Program (CWXSP) observed
lung damage in 30 percent of examined individuals [24]. As discussed previously, until recently
the rate of CWP in the U.S. workforce was declining. First noted around 2000, NIOSH
researchers have observed an increased prevalence of CWP, especially in localized regions of the
30
Appalachian coalfields. These findings caused NIOSH to augment coal worker surveillance
efforts through enhanced surveillance, called the Enhanced Coal Workers’ Health Surveillance
Program (ECWHSP). This program, in addition to a similar initiative by MSHA, sought to
increase levels of participation in “hot spot” regions by deploying mobile examination units
(Figure 8).
Figure 8. NIOSH CWXSP mobile examination unit.
Some issues have been raised with the current approach to surveillance. For example, because of
the voluntary nature of these exams, various forms of ascertainment bias may be present, with
some members of the miner population being more, or less, likely to be included than others. As
an example of a self-selection bias, workers who are experiencing symptoms or fears of
respiratory distress may be more likely to seek medical examination than those that are non-
symptomatic. This could result in rates of CWP being skewed higher than reality. Another
potential issue is a healthy worker effect, in which some workers, who have become disabled or
died, cannot or do not participate in the screening process. These sick or deceased individuals are
not included in the official tally. While the recruitment efforts by the ECWHSP have increased
participation rates, concerns about oversampling in certain regions have led some researchers to
suggest that the results from the ECWHSP be separated from the base findings of the CWXSP
31
[90]. NIOSH has acknowledged these biases, finding that these tended to underestimate the true
burden of disease among underground coal miners [91].
Not all miners exercise their right to free examinations when they are available. Though
the rate of participation has been continuously increasing over each five-year sampling period
since 1990, less than half of all miners receive medical screening at least once during the period
[24]. This poor participation rate may be attributed to external factors that influence the miners’
willingness to take advantage of voluntary medical exams. For example, in Kentucky, there is a
short period of time available following diagnosis for miners to seek compensation for their
work-related illness, with compensatory claims required to be filed within three years after
diagnosis. Many workers, who are not experiencing any symptoms from their disease and are not
permitted to receive benefits while they are still employed may not want to seek these benefits
and possibly lose their much larger mining paychecks [92]. Finally, although 30 CFR §90
provides job reassignments without loss of regular pay to miners exhibiting CWP (described in
more detail in 3.3.2), many miners are reluctant to submit to the medical surveillance and
potentially lose the overtime income that regular miners frequently earn.
3.3 TERTIARY PREVENTION OF CWP
Tertiary prevention targets victims of the disease and attempts to slow progression of the disease.
This can include treatment, job reassignment, compensation, and rehabilitation to improve
quality of life and prevent complications from the disease. The Coal Act aims to achieve this by
providing access to care and financial benefits through a worker compensation scheme while
also offering reassignment to less hazardous work locations.
32
3.3.1 Compensation for disease and disability
In 1946 contract negotiations, following a long strike and ultimate government seizure of the
nation’s coal mines, John L. Lewis, the president of the United Mine Workers of America
(UMWA), pushed for direct compensation of occupational diseases. He made this demand with
the realization that proposed prevention efforts would likely never be achieved. Eventually
signed at the White House, the new contract established the Welfare and Retirement Fund (now
UMWA Health and Retirement Funds), providing for miners in the cases of sickness, disability,
death, or retirement. This fund was initially financed by a royalty of 5 cents per ton of coal
produced, increasing to 10 cents in the subsequent National Bituminous Coal contract of 1947.
This fund would not only change the way in which miners and their diseases were viewed by the
medical community and the public at large, this approach to compensation would change the
way that employees in other industries were repaid for harm caused by their occupational
exposures [93].
Continuing the compensation movement begun in the 1940’s and bowing to efforts from
the newly formed Black Lung Association [94], the federal government mandated a federal
system of worker’s compensation in the 1969 Coal Act. Title IV of the Coal Act established the
Federal Black Lung Benefits Program, providing relief to state workers’ compensation programs
and the estimated 125,000 miners, both UMWA-affiliated and non-union, suffering from
pneumoconiosis at the time [94]. The program, initially administered by the Social Security
Administration, provided compensation with public funds for those victims of coal mine dust
exposure.
By the early 1970’s, with the number of claims far exceeding expectations, changes were
made by the Black Lung Benefits Act of 1972 in eligibility criteria to streamline the claim
33
process. Further changes were made in the Black Lung Benefits Reform Act of 1977 to help to
resolve the ongoing problem of outstanding and unapproved claims.
The Black Lung Disability Trust Fund (BLDTF), established by the Black Lung Benefits
Revenue Act of 1977, was created to provide initial benefits, financed by excise taxes on coal
produced by both surface and underground methods, at rates of $0.50 and $1.10 per ton,
respectively. These taxes continue to provide revenues of approximately $566 million annually
[95]. Currently, over 25,000 beneficiaries receive monthly federal payments ranging from about
$625 to $1,250 for their disability [96], [97], with the BLDTF reporting a negative balance of
$6.1 billion [98].
Despite the availability of federal benefits, miners face substantial barriers to accessing
compensation from the BLDTF. One major hurdle is initially proving that the miner has black
lung, as defined by the law. A recent Government Accounting Office (GAO) report showed that
for 2008, the Department of Labor (DOL) denied 87 percent of claims [99]. This rate of denial is
attributed to the influence on DOL administrative law judges by the weight of evidence
presented by mining companies, whose doctors have much more familiarity with the disease than
individual miners’ doctors. The same GAO report found that 4 percent of the 763 miners who
gained black lung benefits between 2001 and 2008 waited up to 8 years for their awards. While
the bulk of the awards (73 percent) were received within three years, nearly one quarter of the
cases took between three and six years. This delay and denial in receiving benefits brings into
question the efficiency of the compensation program.
The credibility of the program has been challenged by a 2013 joint investigation by ABC
News and the Center for Public Integrity. The investigators found that Dr. Paul Wheeler, a doctor
and professor of radiology at Johns Hopkins Hospital, had not once observed the severe form of
34
the disease since 2000, despite reviewing over 1500 CWP x-rays [100]. Although Johns Hopkins
subsequently suspended their x-ray review program, Dr. Wheeler’s findings have resulted in the
denial of benefits to numerous miners and their families [101].
3.3.2 Medical removal and job reassignment
Part 90 of the Coal Act establishes an occupational reassignment program to identify miners with
medical evidence of CWP and remove them to less dusty environments (30 CFR §90) [78]. This
was the first mandated medical removal protection program proposed by the federal government
[102]. The dust exposure limit is reduced to 1.0 mg/m3 for those participating in the voluntary
program, with more frequent sampling required (30 CFR §90.100 and 30 CFR §90.208,
respectively) [78]. Acknowledging that the disease may continue to progress following transfer,
this reduction in dust exposure is intended to slow the progression of disease while still
providing wage and job protection [30]. The Coal Act specifies that a Part 90 miner “shall
receive compensation for such work at not less than the regular rate of pay received by him
immediately prior to his transfer.” Despite these protections, less than 15 percent of eligible
miners exercise their medical removal rights [103]. This lack of participation calls into question
both the framework and execution of the system in achieving worker protection in the U.S. coal
mines.
Both lack of awareness and confusion about the program have been cited as reasons for
poor participation rates [104]. As previously discussed, less than fifty percent of coal miners
participate in the CWXSP. Because individuals eligible for Part 90 transfer are notified following
examination by NIOSH’s CWXSP, those miners that do not participate in the CWXSP will not
be informed to participate in the Part 90 program. While it is possible for a miner to be examined
35
independently at an approved facility, at his own expense, this is likely a barrier to participation
in the program.
Another factor in low participation rates may be the lack of economic diversity in the
nation’s coalfields. As alternative well-paying employment opportunities are scarce, workers are
less inclined to call attention to themselves by asserting their rights under the Coal Act. Although
Part 90 miners must be moved to jobs with lower dust concentration, this transfer itself may keep
some from participating. For example, upon exercising the option for relocation, “a Part 90
miner is not entitled to dictate to the operator or otherwise specify the particular position to
which the transfer must be made.” [105]. This lack of choice in assignment may result in the
miner being assigned to what may be considered to be an inferior position, losing the opportunity
for production incentives and overtime pay. Until more eligible miners are engaged in this
program, the positive impact on disease progression and overall health status will be limited.
36
4.0 RECOMMENDATIONS
Although rates of CWP have declined substantially following the 1969 passage of the Coal Act,
recent evidence shows that the decline has ended. In order to fully eliminate the disease, renewed
efforts and alternative approaches may be necessary. To this end, MSHA published a proposed
rule in 2010 to reduce the permissible dust exposure limit and modify sampling strategies. Even
with these proposed changes, the new dust rules overlook some issues in preventing new cases of
CWP.
The current system of CWP control in U.S. coal mines employs a diversified approach of
enforcement, engineering, medical surveillance, and compensation. Upon critical review, several
components of this system have significant flaws that may detract from the goal of protecting
coal miners. A recent increase observed in the rate of CWP in coal miners is likely multifactorial
and indicates possible failures in one of more parts of the system. Possible explanations include
excessive exposures and undetected toxicities associated with these exposures. The following
recommendations arise due to the continued risk of CWP in the nation’s mines.
4.1 IMPROVED DUST MONITORING AND CONTROL
The current MSHA sampling regime generates over 100,000 personal samples each year. NIOSH
has questioned if these samples could be better collected to ensure that the exposure of every
37
coal miner is below the dust limit for every shift [15]. Even with demonstrated compliance to the
current regulations, the opportunity exists for miners to be overexposed for long intervals
between sampling activities. Increasing the sampling frequency and requiring representative
rates of coal production will improve the link between sample results and true coal dust
exposures. Increased sampling frequency will also prevent mine operators from temporarily
modifying the mine environment to produce lower dust levels, through ventilation changes or
other transitory conditions. These frequent samples will also provide rapid assessment of the
mine atmosphere to identify when significant changes in either dust generation or exposure
controls occur. This is especially important in working areas of underground coal mines where
conditions can change very quickly.
When mines identify conditions that present a hazard to miners that may result in
overexposure to coal dust, engineering controls or modified work practices must be implemented
promptly. For operators and miners to make these changes, proven and reliable interventions
must be available. Continued research into engineered dust controls, safe work practices,
respiratory protections, dust characteristics, and health effects is essential to developing state-of-
the-art technologies and controls. Sufficient resources, in terms of both personnel and funding,
are needed to advance current designs and promote new approaches to dust control.
4.2 TARGETED INTERVENTIONS
In order to reduce the burden of CWP, interventions must address the factors tied most closely to
the incidence of disease. Controlling exposures to excessive concentrations of coal mine dust and
minimizing total lifetime dust burdens appear to be the best means to preventing CWP. As has
38
been shown by many epidemiological studies, when there is little exposure to dust, there is a low
probability of respiratory illnesses, including CWP. Efforts to reduce overall dust concentrations
will have the direct effect of lowering exposures and reducing rates of CWP. This should be the
primary focus of all parties involved: regulators, operators, miners, and researchers.
A targeted approach would also focus on coal mines that have a history of violations and
are associated with risk factors for CWP. As the rates of CWP appear to be higher in smaller
mines and in mines located in the Central Appalachian Region, resources may be best allocated
to these operations. Although the mines located in the Central Appalachian Region demonstrate
lower levels of non-compliance to current dust regulations, they are associated with rates of
CWP far in excess to the rest of the coal mining industry. Efforts by NIOSH and MSHA to
enhance worker surveillance in this region address only secondary prevention to CWP.
Engineering controls, work plans, and enforcement practices should be specifically developed
for the potentially unique mining conditions to prevent hazardous exposures.
Efforts must also be focused on improving protections at small mines. Elevated rates of
CWP and PMF at small mines demonstrate higher levels of exposure. Improved surveillance and
sampling in this region should work to quantify exposures and identify the presence of any
unique toxicities. If small mines lack the resources to provide effective worker protection,
technical assistance may help in identifying cost-effective dust controls and improving
management of respiratory protection programs.
While the current regulations strive to reduce exposures to dust, there remain apparent
excess risks when exposed to current dust levels. As has been suggested by ACGIH, different
dust concentration limits for different dust compositions may be appropriate. In areas with coal
39
dust exhibiting especially toxic qualities due to coal rank or iron content, interventions may be
developed to address these conditions.
4.3 MINER ENGAGEMENT AND PARTICIPATION
In order to realize Congress’s stated goal to “adequately assure that no miner would suffer
material impairment of health or functional capacity even if exposed to the regulated substance
or hazard regularly for the period of his working life” [102], individual miners must play a role
in engaging in protective behaviors and participating in medical surveillance programs.
Improved communication about the hazards, including the potential health effects and modern
tools to measure exposure should be included in both new miner training (30 CFR §48.5) and in
annual refresher training of miners (30 CFR §48.8) [78]. NIOSH has developed education and
training materials to be used in these settings. One particular product, “Faces of Black Lung”,
provides first-hand accounts from two victims of CWP, showing how the disease has changed
their lives and their relationships with loved ones [106].
There continues to be a disconnection between behaviors and health effects due to the
delay between dust exposure and onset of CWP. Recent efforts by NIOSH and MSHA have
increased participation in medical surveillance programs, but still fail to engage about half of all
coal miners. NIOSH has emphasized continued communication about “the purposes of the
medical screening and surveillance program, the health-protection benefits of participation, and a
description of the procedural aspects of the program” [15]. While this may be effective, this
information may be best delivered to miners by other miners using their own words, as in the
40
video “Faces of Black Lung”. It is suggested that current and former miners be enlisted to
provide this information to fellow miners for maximum impact.
New dust measuring instruments can provide miners with more prompt feedback about
exposures and cues for action than prior methods, like gravimetric measurements, which provide
results days later. Following introduction and training, the continuous feedback from the PDM
3600 personal dust monitor has been shown to encourage miners to modify their behaviors and
lower dust exposures [107]. Although first priority should be given to implementing engineering
controls for coal dust, this PDM feedback may also increase respirator usage for miners in work
areas contaminated by coal dust.
4.4 INSTITUTIONAL REFORM
Another issue with the current approach to CWP prevention in U.S. coal mines is the lack of
incentives afforded to mine operators for innovation. For example, the current disease
compensation program fails to reward innovation or implementation of industry-accepted best
practices for worker dust protection. Developing an incentive system for mines that take
proactive steps and thereby reduce their liability to coal excise taxes would reward proactive
behaviors that address the primary means of CWP prevention. A similar, comprehensive risk-
based framework to mine safety and health has been proposed by the National Mining
Association [108].
41
5.0 CONCLUSIONS
When miners enter the U.S. coal mining workforce, they should expect to work a full career with
no negative health effects. Although the prospects are better than they were forty years ago, this
is not currently the case for CWP. Improvements of many aspects of the current respirable dust
control program have been proposed: reduced respirable dust concentration limits [15], targeted
research [87], improved enforcement and compliance [79], [81], and overhauled compensation
and benefits programs [99]. To date, few of these suggestions have been effectively
implemented, with CWP rates increasing in recent health surveys.
Evidence from Australia’s coal fields indicates that a very low level of disease incidence
can be attained even with a higher permissible dust concentration and associated dust exposures
[109]. This has implications for the U.S., suggesting that a unique property of U.S. coal exposure
is responsible for causing observed rates of CWP. NIOSH researchers have proposed that quartz
exposures, extended shift lengths, and potential bias in compliance sampling may be key factors
in the recent resurgence of CWP [30]. The present analysis bears this out, showing that
environmental factors such as mass concentration and mine location can have major effects on
individual risks of CWP.
Any effort to reduce the rates of CWP must first focus on improving the work
environment. The Federal Coal Mine Health and Safety Act of 1969 established environmental
dust standards for underground coal mines, requiring that the concentration of respirable dust in
42
the mine atmosphere not exceed 2.0 mg/m3 for a working shift [78]. Coal mine operators
currently demonstrate a high level of compliance to these dust regulations. In the face of
continued evidence of CWP in the workforce, MSHA has published a proposed dust rule that
contains several changes including lowering the coal mine dust standard to 1.0 mg/m3, increasing
the frequency of compliance dust sampling, utilizing a single sample to determine compliance,
and requiring the use of a continuous personal dust monitor for compliance sampling [79]. This
approach by MSHA acknowledges that simply choosing a lower allowable dust concentration
does not ensure that CWP will be reduced or eliminated. By modifying the associated sampling
strategy, MSHA hopes to reduce bias in sampling and time spent exposed to elevated dust
concentrations. MSHA’s risk assessment estimates that these changes will significantly reduce
the risks of CWP and other respiratory diseases [79].
External factors, including geography and mine size, also play a role in a miner’s lifetime
risk of developing CWP. The distribution of CWP occurrence is not distributed uniformly across
the nation and all coal mining operations. Small mines and mines located in the Central
Appalachian region present higher risks of CWP. Current and proposed dust rules do not contain
provisions for small mines or specific regions. If permissible dust concentrations are reduced,
this omission may have potential effects similar to those seen for the Coal Act, with the resulting
closure of numerous small or marginal coal mines [110]. While this will eliminate some of the
smaller mines associated with high rates of CWP, it will also produce a concentrated regional
economic impact in the nation’s coal fields.
Finally, miners are integral parts of any dust control program. They should be aware of
the hazards of overexposure to respirable coal dust, engineering controls to mitigate these
hazards, and medical interventions available for their benefit. Training should focus on providing
43
plain language explanations and encouragement to participate in surveillance efforts. As the
beneficiaries of the dust program and ultimate bearers of potential negative health effects from
any failures, miners must avail themselves of protections underground (i.e. engineering controls
and respirators) and early detection of disease and take an active role in protecting their personal
health status. Through these interventions, the promise of a fulfilling career with no health
impairments may be realized.
What’s on your face, you can wash off, but what’s on your lungs, you can’t.
– Carl L. Bailey, “Face of Black Lung”
44
APPENDIX A: DEVELOPMENT OF THE TERMINOLOGY OF COAL WORKERS’
OCCUPATIONAL LUNG DISEASES
Exposure to airborne particulate matter has long been known to be a serious health threat to
workers in many industries. In coal mining, overexposure to respirable coal mine dust particles
can lead to the breathing distress that comes by many names: black lung, miners’ asthma,
miners’ consumption, coalworkers’ cough, anthracosis, or pneumoconiosis [111]. Most of these
terms can be traced back to a specific time period, where doctors and the miners themselves
classified the disease using the “terminology of the day” [112].
One of the first modern medical reports to comment on the unusual respiratory disease
burden of coal miners was brought by Dr. W. Marshall in 1825 [113]. Described as “phthisis
melatonica,” this “pigmented wasting disease” was observed in the lungs of Welsh coal miners
who “attributed the commencement of ailments to having wrought for some time in a very
impure atmosphere.” In 1831, the specific lung diseases of coal miners in Great Britain were
termed “Miners’ Black Lung” by physician Dr. J.C. Gregory, who arrived at this term from the
black masses found in the lungs of a deceased miner [114]. Shortly thereafter, in 1838, a Scottish
doctor by the name Dr. Thomas Stratton suggested the use of the term “anthracosis” to describe
the same condition [115]. The more general term “pneumoconiosis” was later introduced by
German pathologist and physician Friedrich von Zenker in 1866 to describe “dusty lungs” that he
observed over a range of occupations, not just coal mining [116].
Official governmental terminology for the miners’ unique and debilitating disease
condition developed in the 1940s when a national British compensation program, the Coal
Mining Industry (Pneumoconiosis) Compensation Scheme, 1943, provided disability
45
determinations of “coal miner’s pneumoconiosis” to disabled workers. This phrase was later
updated to “coal workers’ pneumoconiosis”, taking into consideration that many other coal
handlers and processors were succumbing to the disease, not just those that toiled in the mines.
This is the term adopted by the U.S. medical establishment for disease detection, diagnosis, and
treatment [117].
In the U.S., the phrase “black lung” is both colloquial and legal in nature, not a strict
medical diagnosis or classification of respiratory dysfunction. Barbara Ellen Smith extensively
describes the social and political struggle to control and widen the definition of “black lung”
[118]. The late 1960’s movement fostered by the Black Lung Association was a direct challenge
to the medical establishment which had previously attributed the disease to weak constitution,
poor living conditions, individual habits (e.g. smoking), and fear of the mines rather than a
contaminated work atmosphere. By defining the nature of the disease as both occupational and
abnormal, miners and their advocates played a considerable role in the approach to control and
prevent dust exposures, and compensate affected victims. The Federal Mine Safety and Health
Act of 1977 (Public Law 91-173) broadly defined the term “black lung” as “a chronic dust
disease of the lung arising out of employment in an underground coal mine.” Miners falling
under this definition may be compensated for their disability by the Black Lung Disability Trust
Fund. This compensation program is explored in section 3.2. Even today, the definition of black
lung continues to be debated, with some coal companies asserting a narrow view that applies
only to the classical presentation of the lung disease as opacities appearing on x-ray film and not
one of the other medically-recognized manifestations of disease, like loss of lung capacity,
emphysema, or chronic bronchitis [100].
46
APPENDIX B: BRIEF HISTORY OF U.S. MINING HEALTH AND SAFETY
REGULATION TO 1969
From the early years of the United States, coal miners have been subjected to occupational
hazards that have tragically shortened their lives, in both sudden and prolonged manners. From
the major mine fires and explosions where over 400 men and boys perished to the working air
frequently contaminated with coal dust and noxious gases, history is replete with stories of the
risks encountered by those who extracted, processed, and used coal. Prior to the first Federal
safety regulations in 1910, states were largely independent in their oversight of the mining
industry, with some states enacting their own legislation to ensure safer working conditions.
Most of these controls were put into place to protect the miners from explosion and fire, rather
than to specifically prevent occupational injuries and diseases.
Following a string of major mine disasters, most notably the Monongah disaster of
December 6, 1907, where 361 miners died from a coal dust-fueled explosion, Congress
established the U.S. Bureau of Mines (USBM). In the years from 1910 to 1941, the USBM had
minimal influence on the health and safety at individual mines, due to a lack of authority and
insufficient funding. In 1940, with a staggering 1,388 miners killed in numerous disasters and
accidents, public pressure mounted for improved working conditions [17]. The Federal Coal
Mine Safety Act of 1941 (Public Law 49) attempted to improve federal oversight by providing
inspectors with the right of entry to the nation’s coal mines, though they did not yet have any
specific health or safety standards to enforce.
47
The USBM would continue in this advisory role until 1952, when the Federal Mine
Safety Act (Public Law 82-522) would allow federal inspectors to issue notices of violation and
orders of withdrawal to mines employing more than 15 underground miners. Unfortunately, this
change produced very little effect on the rate of fatalities in U.S. coal mines with the rates
continuing to stagnate (Figure 9). The mines in the U.S. remained the most dangerous in the
developed world, with death rates far exceeding those in other developed countries, like France,
Belgium, Great Britain, and Netherlands. Only once from 1951 to 1965 did another nation’s
fatality rate exceed that of the U.S., with West Germany suffering 1.60 fatalities per 100,000
hours worked in 1962 [110]. This anomalous rate in West Germany was the result of the horrific
Luisenthal Mine disaster, a series of explosions killing 299 of the 433 miners underground [119].
1900 1910 1920 1930 1940 1950 19600
500
1,000
1,500
2,000
2,500
3,000
3,500
0
1
2
3
4
5
6
Fatalities
Rate
Num
ber o
f Fat
aliti
es
Fata
lity
Rate
Figure 9. Fatalities at U.S. coal mines, 1900-1969 [17].
In a recurrence of the past, a major U.S. disaster in 1968 renewed the call for increased mine
safety regulations. A November 20th blast killed seventy-five miners and three federal inspectors
48
in Farmington, West Virginia. A hoard of news media traveled to the area, investigating the
background for their stories. Though they gained little insight from the mining company officials
during this time, they did observe widespread respiratory disorders in those they contacted in the
industry. To capitalize on the attention and to elevate health issues to the same level as other
safety issues, the Black Lung Association was formed in January 1969. Concern with the lack of
protections and benefits for those suffering from black lung disease frequently resulted in
“wildcat strikes” (work stoppages not sanctioned or sponsored by the United Mine Workers of
America) and demonstrations throughout the U.S. coal fields [94]. These decidedly political
actions would have a profound effect on the resulting legislation, the Federal Coal Mine Health
and Safety Act of 1969 (the Coal Act), especially in the establishment of compensatory benefits.
The Coal Act is detailed in greater detail beginning in Chapter 3.0 .
49
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