INVESTIGATION INTO DUST EXPOSURES AND MINING PRACTICES IN MINES IN THE SOUTHERN APPALACHIAN REGION 

D. E. Pollock, NIOSH, Pittsburgh, PA 

J. D. Potts, NIOSH, Pittsburgh, PA 

G. J. Joy, NIOSH, Pittsburgh, PA 

ABSTRACT 

Recent NIOSH published information has shown an increase of 

rapidly progressive coal workers’ pneumoconiosis (CWP) in the 

southern Appalachian coal region (SAR) of the U.S., despite the fact 

that compliance data indicates that most coal miners have been 

exposed to coal mine dust concentrations below the statutory limit of 

2.0 mg/m3. While the exact cause of these elevated CWP levels in the 

SAR has not been established, several factors may be contributing to 

the increase in occupational lung disease among coal miners. The 

mining of high rank coal is known to lead to higher CWP rates, and this 

type of coal is mined in a portion of this region. Also, a high 

percentage of the mines in the region are on reduced dust standards 

because of the high silica content of the airborne dust resulting in 

miners possibly being exposed to excessive amounts of respirable 

silica dust. Exposure to excessive amounts of respirable silica dust 

can lead to silicosis, a disabling and potentially fatal lung disease. 

NIOSH's Respiratory Hazards Control Branch has been investigating 

the possible causes that would account for the observed higher trends 

in disease progression through literature review, data analysis, and inmine surveying. 

The investigation to date has revealed that underground mines 

are faced with cutting large amounts of rock in order to maintain 

haulage clearances. Cutting rock not only increases the potential for 

silica exposure, it increases the requirement for machine maintenance 

which was a concern observed during dust surveys conducted by 

NIOSH. Over half of the mines operating in the SAR are on reduced 

standards due to high silica content. Adequate face ventilation of the 

continuous miner and roof bolter and limited down-wind operations 

from the miner are also issues of concern and items which require the 

constant attention of miners operating in these conditions. 

Disclaimer: Mention of any company or product does not constitute 

endorsement by the National Institute for Occupational Safety and 

Health. 

INTRODUCTION 

The Federal Coal Mine Health and Safety Act of 1969 was 

passed to protect the safety and health of coal miners. It included 

provisions to mitigate the harmful effects of respirable coal mine dust 

by mandating airborne respirable dust standards. Therefore, since 

December 30, 1972, the amount of respirable coal mine dust allowed 

in the mine air that miners breathe has been limited to 2.0 mg/m3 for a 

working shift. This standard is further reduced when the respirable 

dust contains more than 5 percent quartz since this presents an 

additional health hazard. If the silica content on the filters exceeds 5% 

by weight as determined by MSHA’s P7 infrared method, the 2.0 

mg/m3 standard is reduced using the formula 10 ÷ % quartz (Parobeck 

and Tomb, 2000; U.S. Code of Federal Regulations, 2008). The 

Federal Coal Mine Health and Safety Act of 1969 also established the 

U.S. National Coal Workers’ X-ray Surveillance Program (CWXSP) to 

screen underground coal miners for coal workers’ pneumoconiosis 

(CWP) and to document the general trends and patterns in the 

prevalence of x-ray evidence of pneumoconiosis among working coal 

miners. Under this medical monitoring program, administered by 

NIOSH, coal mine operators are required to offer a free chest x-ray to 

each underground miner at the time of hire and again three years later; 

and in the event the second x-ray shows evidence of the development 

of CWP, the miner, if still engaged in mining, must be offered an 

additional x-ray two years later. This program also provides miners an 

opportunity to participate voluntarily in subsequent health screenings 

every five years following the initial screenings. 

Data was combined with the latest round of x-rays in this 

surveillance program and from the Miners’ Choice Program, a special 

program sponsored by MSHA which offered targeted free health 

screenings to both surface and underground coal miners between 

1996 - 2002. Analysis by the NIOSH Division of Respiratory Disease 

Studies showed that from 1970 - 1995, the tenure-related prevalence 

of CWP was on the decline, however from 1999 - 2008; the tenurerelated prevalence of disease has doubled. (WoRLD Report, 2008) 

New cases of CWP are still occurring among miners who have worked 

exclusively under current dust exposure limits (Antao et al., 2004). 

The study by Antao et al. identified 886 cases of CWP among 29,521 

miners examined from 1996 - 2002, or approximately one in 20 miners 

with CWP. Among these, 35.4% were identified with rapidly 

progressive CWP, which included 41 miners with pulmonary massive 

fibrosis. When comparing the rapidly progressive CWP cases against 

the cases without the progression, Antao et al. discovered that the 

miners with the rapidly progressive CWP had reported to have worked 

at the mining face longer, were younger, and had worked at smaller 

(fewer than 50 employees) mines. Also observed was the clustering of 

the CWP “hotspots” in the SAR. The CWP hotspots include counties 

located in western Virginia, eastern Kentucky and southern West 

Virginia, which include MSHA coal districts 4, 5, 6, and 7. MSHA 

district 4 is made up of counties in southern West Virginia. District 5 

comprises the entire state of Virginia. District 6 is the counties of 

eastern Kentucky and district 7 is made up of counties in central 

Kentucky and the states of North Carolina, South Carolina and 

Tennessee. 

For this investigation, we sought to identify mining conditions and 

exposures which may explain the increased CWP prevalence that has 

been observed among underground coal miners from the SAR. 

METHODS 

NIOSH researchers utilized Mine Safety and Health 

Administration (MSHA) inspector compliance sampling data in the 

MSHA Standardized Information System (MSIS) database to identify 

mines of interest. An analysis of the MSIS database was conducted 

for each MSHA district in the SAR region. The data were filtered to 

only include compliance samples from underground coal mines. An 

analysis of all sampled occupations was conducted for the calendar 

years 2000 - 2005. Also, a separate analysis of only the continuous 

miner operator was performed since this occupation may be exposed 

to high concentrations of dust. The data were filtered to tabulate the 

number of compliance samples over the 2.0 mg/m3 standard. The 

number of samples exceeding the reduced dust standard due to high 

silica content was also calculated. A ratio comparing the frequency the 

2.0 mg/m3 standard was exceeded to the overall number of data 

entries for the particular mine was calculated. A second ratio was 

calculated to determine the number of times the mine exceeded the 

reduced dust standard. The percentage of samples that exceeded the 

dust standards were compared with other mines percentages in the 
district to determine the targeted mines for this study. Figure 1 is an 

example of an MSIS graph for district 4. This example identifies the 

mines exceeding the current applicable standards. 

Figure 1. MSIS graph showing target mine percentages of samples 

exceeding the standards. 

The mines targeted for this study not only consisted of mines with 

high percentage exceeding the applicable standard but also those

mines with low percentages of samples that exceeded the applicable 

standard. A 5% criterion was utilized to identify a number of mines 

from each district for further evaluation. Those mines that had 5% or 

above incidences where they exceeded the applicable standard were 

listed as target mines. The MSIS analysis proved to be a useful 

method to identify targeted mines for this study; however difficulty in 

finding active mines for follow-up presented a problem. Initial runs of 

the database included data from calendar years 1990-2005 however, 

upon further research of targeted mines, many of the subject mines 

were no longer operating. A subsequent analysis of the MSIS 

database for the calendar years 2000-2005 resulted in an increase in 

active mines. In addition to identifying active mines, the rationale 

behind the 2000-2005 timeframe was to target mines utilizing current 

dust control technology and methods. A list of targeted mines was 

compiled for each MSHA district. 

NIOSH researchers also included the mines listed on MSHA’s 

Respirable Dust Emphasis Program (RDEP). The RDEP list identifies 

mines experiencing compliance problems having been cited at least 

two or more times during the previous fiscal year for excessive dust. 

Several of the mines identified through the MSIS analysis were on the 

RDEP list. 

MSHA DOCUMENTATION REVIEW 

The next step in the investigation involved visits to selected 

MSHA District Offices to examine the inspector reports and dust 

control plans for the targeted mines. These reports contained detailed 

information regarding the mine’s operation, equipment, and dust 

control practices that were observed at the time of the sampling 

inspection. The most recently completed MSHA Form 2000-86, 

Respirable Dust Sampling and Monitoring Data, was examined for 

each of the targeted mines. These completed forms contain 

information such as the mine conditions, mining equipment utilized, the 

number of times that the mine entity or the mine was cited for 

excessive dust, water spray pressures, ventilation types, air 

measurements and equipment maintenance schedules. Many of the 

targeted mines had more than one mechanized mining unit (MMU) 

report in their files. Each MMU report for the particular mine was 

reviewed. 

RESULTS OF MSIS DATA AND MSHA DOCUMENTATION REVIEW 

Table 1 shows the number of mines identified in each selection 

category for each MSHA district. Antao et al. stated that the miners 

who had developed the rapidly progressive CWP were more likely to 

have worked in “small mines” with fewer than 50 employees (Antao et 

al., 2004). MSHA defines a “small mine” as one having fewer than 20 

employees. While the MSIS study does show a higher percentage of 

mines with number of employees below 50, it should be noted there 

were several large operations that exceeded the applicable dust 

standards and there were several small mines with low employment 

numbers that had very few occurrences where their dust samples 

exceeded the applicable dust standards. It should be noted that small 

mines (<50 employees) are the majority of the active underground coal 

mines in districts 4, 5, 6, and 7. Table 2 shows the number of active 

underground small mines and the total number of active underground 

mines for each district. 

Table 1. Number of mines per category for each MSHA district.

MSHA Coal 

District 

Mines Exceeding the 

Applicable Standards RDEP Mines 

Mines in Compliance 

with the Applicable 

Standards 

4 7 (43%<50 employees) 7 (57%<50 employees) 7 (43%<50 employees) 

5 5 (90%<50 employees) 3 (50%<50 employees) 8 (50%<50 employees) 

6 6 (83%<50 employees) 4 (50%<50 employees) 8 (75%<50 employees) 

7 4 (66%<50 employees) 3 (33%<50 employees) 5 (80%<50 employees) 

Table 2. Number of active small (<50 employees) and total number of 

active underground coalmines in MSHA districts 4, 5, 6, and 7. 

Source: MSHA Oracle database December, 2008 

MSHA Number of Small Total Active 

District Underground Mines Underground Mines 

4 85 148

5 39 53 

6 88 105

7 50 70 

Total 262 373 

The documents reviewed at MSHA district offices revealed some 

interesting information concerning mining conditions in the SAR. The 

documents listed the dust control parameters in the approved mine 

ventilation plan, ventilation measurements, curtain setback, machine 

maintenance, operational sprays, and scrubber airflows at the time of 

the MSHA sampling inspection. What did stand out was the amount of 

rock being cut at these mines. On average, MSHA inspectors 

recorded a ratio of 20 to 30 percent rock to overall roof height. Figure 

2 shows the average percentages of rock cut as compared to the roof 

height for each MSHA district targeted mine category. 

Figure 2. Percentage of rock cut to mine roof height for targeted 

mines. 

It should be noted that according to MSHA’s compliance data, 

several of the mines were successfully meeting the applicable 

standards under the same difficult mining conditions. Many of these 

mines also had fewer than 50 employees; suggesting that some 

“small” mines are capable of maintaining dust concentrations within 

applicable standards even with limited equipment and personnel 

resources. Table 3 lists the number of active mines in each of the 

MSHA districts and those on a reduced standard as of April 2, 2008. 

Districts 4, 5, 6, and 7 clearly have more active mines than the other 

MSHA districts. Also, these districts account for the highest 

percentage of mines on reduced standards. 
Table 3. Mines on Reduced Standards for MSHA districts as of April 

2, 2008. Source: US Department of Labor, Mine Safety and Health 

Administration, Program Evaluation and Information Resources, MSHA 

Standardized Information System, Arlington, VA.

Underground1

District w/Reduced Stds Active Status 

# % 

1 10 3 30% 

2 31 14 45% 

3 31 5 16% 

4 130 73 56% 

5 57 38 67% 

6 86 39 45% 

7 62 36 58% 

8 16 5 31% 

9 22 6 27% 

10 9 1 11% 

11 7 6 86% 

All 461 226 49% 1

 Mines with one or more MMUs/Roof Bolter Designated Areas on a 

reduced dust standard. 

MSHA data shows that operations mining an extended cut utilized 

flooded-bed scrubbers. All of the MMUs reviewed in district 4 were 

using scrubbers. Besides utilizing flooded-bed scrubbers, mines may 

also use continuous ripper miners equipped with directional spray 

systems or spray fan systems utilizing hollow cone water spray 

manifolds. However, MMUs with spray fan systems are prohibited from 

taking extended cuts. The water sprays become effective air movers 

as the water pressure increases, but this airflow can create turbulence 

that can push dust towards the miner operator and increase the 

operator’s exposure (Jankowski et al., 1987). There were four MMUs 

in district 5 utilizing fan spray systems, two of which were at mines 

exceeding the applicable standards. One was on the RDEP list, and 

the other was at a mine in compliance with their applicable standard. 

The other 14 MMUs examined in district 5 were utilizing scrubbers. 

District 6 had only one MMU listed as using a fan spray system which 

was at a mine on the RDEP list. The other 24 MMUs examined in 

district 6 had miners equipped with scrubbers. District 7 had two 

MMUs listed as using a fan spray systems at a mine in compliance 

with their applicable standard. The other 19 MMUs examined were 

using scrubber equipped miners. 

Table 4 lists the face ventilation types used by the mines in this 

study. While exhaust curtain appears to be the preferred method, 

there were numerous MMUs operating with both exhaust and blowing 

face ventilation. A clear pattern of face ventilation types versus mines 

exceeding their applicable standard or mines in compliance with their 

applicable standard was not readily apparent. 

Table 4. Face ventilation types utilized in targeted mines.

MSHA 

District 

Mines Exceeding 

Their Applicable 

Standard 

RDEP Mines 

Mines in 

Compliance With 

Their Applicable 

(13 MMUs) (10 MMUs) (12 MMUs) 

4 8 Exhaust Curtain 

2 Blowing Curtain 

7 Exhaust Curtain 

1 Blowing Curtain 

9 Exhaust Curtain 

1 Blowing Curtain 

3 Both 2 Both 2 Both 

5 (10 MMUs) 

10 Exhaust Curtain 

(2 MMUs) 

2 Exhaust Curtain 

(6 MMUs) 

6 Exhaust Curtain 

6 

(12 MMUs) 

6 Exhaust Curtain 

1 Blowing 

5 Both 

(7 MMUs) 

2 Blowing 

5 Both 

(6 MMUs) 

1 Blowing 

5 Both 

7 

(5 MMUs) 

1 Blowing 

4 Both 

(6 MMUs) 

6 Both 

(9 MMUs) 

9 Both 

DUST SURVEYS 

Mine dust and ventilation surveys were scheduled at cooperative

mines to investigate and confirm findings from the district reports, as 

well as, to indentify operating conditions not obvious in the reports. 

Surveys focused on measuring the dust exposure of the continuous 

miner operators, roof bolters, and shuttle car operators and area 

sampling of the intake and return of continuous miner and roof bolter. 

The surveys typically consisted of three consecutive days of sampling 

and observation during normal production. Time studies were 

conducted to track continuous miner cuts, shuttle car and roof bolter 

locations, and various other operations which may influence dust 

exposure readings. Curtain setback and configuration were noted for 

each cut. Face ventilation measurements were taken with a vane 

anemometer at the beginning of all cuts. 

Thermo MIE Personal Data RAMs (pDRTM) were utilized to record 

dust concentrations during the surveys. The pDR is a real-time 

aerosol monitor with logging capability. The typical sampling package 

consisted of a pDR and two MSA1 ElfTM sampling pumps (calibrated to 

2 liters per minute) with pre-weighed 37-mm MSA1 filters and 10-mm 

nylon cyclones. The pDR provided a relative measure of dust levels 

and by utilizing two gravimetric samplers on the sampling rack, a 

correction factor was calculated for the pDR measurements. The MSA 

filters were post-weighed for dust concentration and then sent to an 

independent laboratory for silica analysis. Prior to each cut, the 

sampling packages were set in the intake and return of the targeted 

machine(s). The sampling pumps were run for the duration of the cut 

or operation of the machine and placed on hold during the move to the 

next cut. The pDR monitors were left in logging mode since they had 

real-time capability. This procedure enabled the NIOSH researchers to 

analyze dust generation on a cut by cut basis and observe real-time 

dust levels at the specified sampling locations. Utilizing time study 

observations, researchers were able to associate dust levels with the 

machine/individual operations. 

A personal dust monitor (PDM) (Thermo Fisher Scientific 

Corporation, Franklin, MA)1 was placed on the miner and bolter 

operator(s) and the shuttle car operator(s) to provide end-of-shift 

measurements of their dust exposure. Various maintenance tasks 

such as bit replacement, scrubber maintenance, bolter dust box 

cleaning, and spray maintenance were observed and noted. Also, 

water spray types were noted and water spray pressures were 

measured at the spray nozzle. 

SURVEY RESULTS AND DISCUSSION 

NIOSH has completed six surveys to date at targeted mines in 

MSHA districts 4, 5, 6, and 7. The mines varied in size from very small 

operations with crew sizes of approximately 8 men to large operations 

utilizing super sections where two continuous miners were operating 

sequentially and were developing panels for longwall mining. On a 

super section, only one miner was operating at a given time. 

While these mines varied as far as crew size, equipment types 

and sizes, and production rates, all mined through substantial rock 

layers. Rock thickness for 5 of the mines surveyed varied from 15.2 

cm (6 in.) to 30.48 cm (1 ft.). One mine was cutting 0.9 m (3 ft.) of 

sandstone in order to maintain the roof height. The roof rock 

conditions encountered at this mine changed the status of this mine 

from a mine in compliance with their applicable standard to a mine 

exceeding their applicable standard and faced with complying with a 

reduced standard. Figure 3 is a box and whisker plot of the PDM 

gravimetric sampling concentration ranges obtained from the dust 

surveys. While the median values are below 2.0 mg/m3 for all of the 

occupations, the higher ranges of the continuous miner operator may 

have been due to operator positioning or dust roll-back. There are two 

points on the plot of the shuttle car operator which are shown as 

outliers. 

MSHA P7 silica analysis results have been received on the area 

sampler filters of four of the six mines surveyed. Figure 4 is a box and 

whisker plot of the percent alpha quartz results from four of the mines 

surveyed. 

Mining through rock requires not only controlling respirable dust at 

lower concentrations, but also increased maintenance of extraction 

equipment due to the hardness of rock compared to coal. Cutting bit 

life is drastically reduced whenever severe rock conditions are 
encountered. As the bits wear, more dust is generated (Khair et al., 

1999) and scrubber maintenance soon becomes an issue. Figure 5 is 

a picture of two continuous miner bits. The bit on the left was retrieved 

after a bit change on a continuous miner during a recent dust survey. 

The bit on the right is a new bit which clearly shows the carbide cutting 

tip. 

Figure 3. Box and whisker plot of the end-of-shift PDM gravimetric 

sampling concentrations. 

Figure 4. Box and whisker plot of the percent alpha quartz from the 

continuous miner return, bolter intake, and bolter return area samplers. 

When bits become worn below the carbide tip, they no longer cut, 

they grind. Grinding generates more airborne dust, often in quantities 

that the sprays and scrubber cannot keep up with, leading to increased 

exposure of miners. Attention to bit wear is critical when mines are 

cutting rock. Bit changes, clearing clogged water sprays and scrubber 

maintenance may be required every time the miner relocates to 

another cut. While this may seem excessive, it is necessary to 

adequately control dust when mining in the conditions observed during 

these six surveys. 

Another common observation during these mine surveys was the

frequency of roof bolters working downwind of the continuous miner. 

In these conditions, roof bolters may very easily be exposed to 

unacceptable dust concentrations. Mines must minimize if not 

eliminate downwind bolting where results from respirable dust samples 

demonstrate high quartz percentages as seen in Figure 4. 

Also common to the bolter operations of the mines surveyed was 

inadequate ventilation of the bolter faces. The dust control plans for 

these mines listed the minimum airflow to the bolter face to be 84.96 

m3/min. (3,000 cfm.). There were numerous periods noted where the 

bolting face had very limited if any airflow to the face. The use of line 

curtains to direct the air through the working area and reduce the dust 

concentrations was recommended during these surveys. There were 

several mines observed that took the time and effort to properly install 

and anchor the line curtains and as a result, had lower dust exposure 

to the miners. 

Figure 5. Comparison of worn miner bit to a new bit. 

SUMMARY 

A majority of mines located in the SAR are faced with difficult 

mining conditions that may be contributing to an increase in rapidly 

progressive CWP. The “easy” coal of yesterday has already been 

mined. The mines of today are faced with mining thick layers of 

quartz-bearing rock, which rapidly wears miner bits and creates 

maintenance problems for the machine and dust control systems. 

MSHA inspector reports that were reviewed have shown the mining of 

rock to be a common occurrence in the mines identified through the 

MSIS study. As a result, MSHA districts 4, 5, 6, and 7 account for the 

highest percentage of mines on reduced standards due to the 

presence of high quartz levels in the working environment. 

Dust surveys were conducted at six targeted mines to observe 

their operations and examine their dust control equipment and 

methods to determine commonalities or note any differences that were 

not evident from the inspector reports. The surveys to date have 

confirmed the findings of the inspector reports concerning the amounts 

of rock that the mines are cutting. As the proportion of rock cut 

increases, a corresponding increase in machine preventative 

maintenance must occur. An increase of bit, scrubber, and spray 

maintenance will likely be required to control the dust levels 

encountered by these mines operating in these conditions. 

Another common occurrence noted during the surveys was the 

lack of proper ventilation at the bolting faces. This deficiency is made

more critical given the frequency of bolter crews working downwind of 

the continuous miner. The ventilation of the bolting face is often 

overlooked because high volumes of dust are not visible as compared 

to a continuous miner face. Thus, a false sense of security may exist. 

Bolting face ventilation and maintenance of the bolter’s dust control 

system is critical to protect the miners working in these areas. Dust 

samples with high quartz percentages are prevalent in the SAR. 

Efforts must be made to protect the workers who are drilling into 

quartz-bearing strata and are working directly in the continuous miner 

return air path. 

NIOSH is continuing this study at other targeted mines throughout 

the SAR and in the interim, mines must be cognizant of the increased 

health hazards which follow mining excessive amounts of rock. Mines 

overall, must be aware that maintenance of their dust control systems, 

worn bit replacements, scrubber maintenance, proper ventilation, and 

the reduction of down-wind operations is crucial in order to protect their 

miners from dust related illnesses and stop this increasing CWP trend. 
REFERENCES 

1. Antao, V.C. dos S., Petsonk, E.L., Sokolow, L.Z., Wolfe, A.L., 

Pinheiro, G.A., Hale, J.M., Attfield, M.D. (2004), “Rapidly 

Progressive Coal Workers’ Pneumoconiosis in the United States: 

Geographic and Other Factors”, Occupational Environmental 

Medicine 2005; 62, pp.670-674. 

2. Federal Coal Mine Health and Safety Act. Public Law no. 91-173 

(1969). 

3. Jankowski, R.A., Jayaraman, N.I., and Babbitt, C.A., “Water 

Spray Systems for Reducing the Quartz Dust Exposure of the 

Continuous Miner Operator”, Proceedings of the 3rd U.S. Mine 

Ventilation Symposium, University Park, PA, pp.605-611. R.V. 

Ramani (ed.). Society of Mining, Metallurgy, and Exploration, 

Littleton, CO., 1987. 

4. Khair, A. W., Xu, D., and Ahmad, M., “Principles of Bit Wear and 

Dust Generation”, Proceedings if New Technology in Mine Health 

and Safety. SME Littleton, CO, February 1999, pp. 175-183. 

5. Parobeck, P.S., and Tomb, T.F., 2000, “MSHA’s Programs to 

quantify the crystalline silica content of respirable mine dust 

samples,” Preprint 00-159, presented at the SME Annual 

Meeting, February 28-March 1, 2000, Salt Lake City, Utah, 5pp. 

6. U.S. Code of Federal Regulations, 2004, “Title 30 – Mineral 

Resources; Chapter 1 – Mine Safety and Health, Parts 56 through 

58; Subchapter O – Coal Mine Safety and Health, Parts 70 

through 74, “U.S. Gov. Printing Office, Office of Federal 

Regulations, July. 

7. Work-Related Lung Disease (WoRLD) Surveillance System 

Report, http://www2a.cdc.gov/drds/WorldReportData