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NIOSH Respiratory Diseases Research Program

Evidence Package for the National Academies' Review 2006-2007

NIOSH Programs > Respiratory Diseases > Evidence Package > 3. Interstitial Lung Diseases > 3.1 Respiratory Diseases Induced by Coal Mine Dust

3.1b) Tracking Disease Occurrence in Coal Miners

previous 3.1a) Verification that the Enacted Coal Mine Dust Standard Protects Miners | 3.1c) Improve Measurement and Controls to Reduce Coal Mine Dust Exposure next


The Federal Coal Mine Health and Safety Act called for, and RDRP instituted, monitoring efforts directed towards pneumoconiosis detection and prevention. Anticipated inadequacies of prevention, solely through mandated dust reduction, necessitated implementation of a program to eliminate or limit disease progression by allowing transfers to lower-dust jobs for miners with signs of early disease.

Population-based surveillance of CWP was needed for ongoing assessment of disease levels so that the impact of the concurrent reduction in dust levels could be reliably evaluated over time, by region, and mining occupation, mine type, and process.


RDRP operates a secondary disease prevention program, the Coal Workers’ X-ray Surveillance Program, which is a medical monitoring program for underground coal miners intended to identify those with signs of pneumoconiosis and grant them the right to work in a low-dust environment. Through early detection of disease and resulting reduction in dust exposure, the likelihood of progression of disease to the more severe categories of simple pneumoconiosis is reduced, thereby limiting the risk of development of the frequently disabling progressive massive fibrosis. The information gathered is principally intended for monitoring the health of individual miners, but also provides critical data on disease occurrence and its distribution over time and place.

The objectives for this activity are to:

  • Contribute to the prevention of CWP progression by means of a worker monitoring program
  • Assess disease prevalence by person, time, and place on an ongoing basis to evaluate the success of prevention efforts
  • Use the monitoring and surveillance information to guide prevention efforts
  • Maintain, develop, and evaluate existing and new technologies for CWP detection

RDRP has operated the Coal Workers’ X-ray Surveillance Program in ‘rounds’ of surveys each lasting three to five years, including every operating underground coal mine in each round. Our administrative procedures include ensuring that mines post examination plans at the mine site, certifying examination facilities, obtaining second (and any necessary subsequent) x-ray readings, processing examination results, notifying miners of their x-ray findings, and, on behalf of MSHA, notifying affected miners of their right to transfer to a low-dust occupation.

Between 1970 and 1999, RDRP processed over 300,000 radiographs of underground coal miners. We maintained an x-ray reading program intended to ensure unbiased reading and a high level of quality control. Miner participation is voluntary. In an effort to increase program participation, our staff now assures that all underground coal mine operators comply with the requirement to arrange and post plans for periodic chest x-ray examinations for their employees (in the past, some operators did not comply with this requirement and their miners would not have been offered examinations).

From 1999 to 2002, RDRP personnel worked with MSHA to operate a special x-ray examination program (Miners’ Choice Program) that was an adjunct to the routine Coal Workers’ X-ray Surveillance Program. This program involved enhanced publicity, incentives, and other activities focused on motivating miners to obtain a chest x-ray. Participants in this program came from 586 surface coal mines and 444 underground coal mines, and were able to avail themselves of information on their health status, and, in the case of the underground coal miners, receive job transfer letters if pneumoconiosis was detected.

Recently, our workforce surveillance efforts among coal miners have been increasing. The Enhanced Coal Workers’ Health Surveillance Program gives more attention to focusing on identifying ‘hotspots’ of disease occurrence by geographic region, with plans to extend it to consider other factors (e.g. coal rank and job-specific exposure characteristics). The critical issue here is to identify miners with rapid progression of disease, since those cases can serve as ‘sentinels’ indicating inadequate control of dust exposure. We then work with our partners in labor, industry, and government to investigate the causes, and then to work to remediate identified problems. 

RDRP is now operating a mobile examination unit (Figure 7), recently purchased by MSHA for NIOSH and equipped by NIOSH, enabling convenient examination of miners in any coal mining region. This unit includes facilities for both conventional and digital radiography, as well as lung function testing and interviewing. Starting in March 2006, we initiated surveys in regions of the coal fields with apparent clusters of rapid progression of CWP. We also employed intense publicity and outreach efforts and situated the mobile van at convenient locations in a concerted effort to increase participation by miners. Preliminary findings support the surveillance data indicating that miners in certain regions may be at excessive risk of severe pneumoconiosis. In addition, in collaboration with NIOSH’s Mining Research Program and MSHA, RDRP is promoting targeted assessments of risk factors and interventions to reduce risk in these areas.

The need for reliable tools and methods for the assessment of CWP has driven a number of RDRP initiatives. One of these, arising from evidence that x-ray readers suffered from excessive variability in their classifications, led to RDRP’s creation of the B Reader Certification Program in the 1970s. The B Reader Certification Program provides education to physicians about the pneumoconioses and the International Labour Office (ILO) classification system for the pneumoconioses and administers tests to determine competency in use of the classification system. The usefulness of this program now extends far beyond CWP to pneumoconioses in general, providing a pool of knowledgeable and skilled readers for worker monitoring programs, research, and other applications.

Figure 7:New mobile examination unit for the Enhanced Coal Workers’ Health Surveillance Program.

Figure 7

RDRP is active in maintaining and enhancing the B Reader Certification Program. We have revised aspects of the program to comply with recent changes in the international classification system. We have also worked to improve the methodology for assessment of readings from individual readers. To do that, we assessed the logical structure of the current certification test, searched for better radiographs to include in the test, and conducted workshops with other experts to obtain feedback. In addition, through extramural activities, the program is engaged in moving from conventional radiography to digital radiography.

In addition, RDRP staff have maintained involvement in the ILO system itself, ensuring that NIOSH remains a center of excellence in film reading techniques. A recent and significant part of this activity was a collaborative multi-national film reading trial led by RDRP scientists that provided the scientific basis for the recent ILO 2000 revision of the classification system. This involved six readers from each of twelve countries and resulted in the ILO revising the standard films they distribute worldwide. Our scientists were also key participants in revising the methods used in using those films for better recognition of CWP and other dust diseases of the lungs.

Outputs and Transfer

Thirty-four peer-reviewed publications, book chapters, and reports were published by RDRP authors on surveillance aspects of CWP and associated methodology. Of these, 13 were published after 1995, demonstrating the current emphasis on ongoing surveillance and prevention (A3-14). Although all of these publications were of importance in notifying the public and NIOSH stakeholders of disease status in the U.S., a recent paper showing the extent and location of cases of rapid progression emphasizes our current focus on disease prevention (6, 7, A3-15, A3-16). As evidence of the importance of the B Reader Certification Program nationally and internationally, one critical paper has been cited 49 times (8, A3-17).

RDRP periodically disseminates information on CWP morbidity and mortality in our series of “WoRLD Surveillance Reports.” The most recent of these is the “WoRLD Surveillance Report 2002” (see also chapter 8.1). Following widespread dissemination of this report, requests for this report have come from 12 countries, 14 state and county organizations, and 37 universities, and the report has been cited in more than 140 publications (further information on public interest in our surveillance outputs is provided in chapter 8).

Recently, RDRP improved the accessibility of occupational respiratory surveillance data and information about our surveillance programs via the Internet by converting the “WoRLD Surveillance Report 2002” to accessible and user-friendly files, including downloadable data, charts, tables, and figures. This includes information on CWP morbidity and mortality and coal mine dust exposures. In addition, we have developed on-line query system—the National Occupational Respiratory Mortality System (NORMS)—permitting interested parties to obtain mortality data, including pneumoconiosis mortality information, stratified by year, state, and other factors (further information, including statistics on usage, is provided in chapter 8).

RDRP has held a variety of workshops, including two major meetings involving the B Reader Certification Program, 1998 and 2003 (A3-18). Each involved a large group of stakeholders from labor, industry, and the medical profession, as well as researchers from academia. Recommendations from these workshops are contained in a NIOSH topic page on “Chest Radiography” (

Intermediate Outcomes

Table 7: Participation and Disease Rates, Coal Workers’ X-ray Surveillance Program

Time Period


Number of X-Rays Processed by NIOSH[1]

Average Number of Underground Coal Miners for the Period[2]

Participation Rate

Number of X-Rays Showing Evidence of CWP[1]

CWP Disease Rate











































  1. Data provided by NIOSH Underground Coal Mine System
  2. Average calculated using the MSHA Address and Employment Data Sets


Over the 35 years since inception of RDRP’s Coal Workers’ X-ray Surveillance Program, over 18,000 of the more than 300,000 examinations were found to indicate signs of pneumoconiosis. Receipt of notification letters concerning their health status empowered these 18,000 coal miners to either exercise their right to job transfer or otherwise voluntarily alter their work practices (including respirator use) to reduce further dust exposure. Over the past two decades, nearly 20 percent of notified miners exercised formal job transfer to reduce their exposures (Table 7). An unknown percentage of the remaining 80 percent take other measures to reduce their exposures. This secondary prevention approach helps protect underground coal miners who, for one reason or another, have developed disease despite the dust control mandate.

Information from the monitoring program is employed in assessing trends in pneumoconiosis, and was consulted by the Secretary of Labor’s Advisory Committee on the Elimination of Pneumoconiosis among Coal Miners in 1996. This committee compiled a report with 20 main recommendations consisting of 100 direct action items. A3-19 provides a summary of MSHA’s responses to these recommendations.

RDRP efforts have raised employer awareness of their obligation to post plans to and administer x-rays through the Coal Workers’ X-ray Surveillance Program. Thus, employer compliance has increased from 90 percent to 98 percent of coal mine operators over the last three years (2003-2006). Likewise, miner participation in examinations offered through the Coal Workers’ X-ray Surveillance Program has increased from between 20 and 30 percent for three rounds from 1985-1999 to nearly 50 percent for the 2000-2004 round of examinations (Table 7).

Progress Towards End Outcomes

Workforce surveillance of coal miners by RDRP provides evidence of the reduction in pneumoconiosis in the mining industry. Through the activities, outputs, and intermediate outcomes described above, RDRP has contributed to the decline.

What’s Ahead

Ongoing monitoring and surveillance of lung disease among coal miners will continue, along with continued efforts to enhance these activities for improved prevention. Our newly acquired mobile examination unit will be undertaking an intensive schedule of surveys with emphasis on those locations where miners appear to be at increased risk. Tabulation of existing surveillance data has provided sufficient information to identify apparent high-risk areas; each of these areas will be visited at least once (depending on the number of miners in the area) and through community outreach and personal contact, miners will be invited to have a chest x-ray and breathing test. Information will be gathered about the individual miners’ exposures, including information about the mines in which the participants work for use in identifying risk factors (e.g. type of coal, mining method, characteristics of job- or task-specific exposures) for disease development. Results of surveillance will then be used to geographically target efforts to improve awareness and use of measures to monitor and control dust exposures. Overall, this approach employs both primary and secondary disease prevention measures in a coordinated effort to reduce disease development in coal miners. The success of the program will be quantified in part by continued monitoring of annual adjusted and/or stratified pneumoconiosis rates.

Also, we are actively working on issues relating to the use of newer chest imaging technologies such as digital radiography and computerized tomography in the recognition and assessment of CWP. Digital radiography is an especially important priority. It is rapidly replacing conventional film technology, but brings with it certain questions relating to its comparability with conventional methods, as well as issues of intra-reader and inter-reader variability.

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