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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

3.1c) Improve Measurement and Controls to Reduce Coal Mine Dust Exposure

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Issue

For attainment of the respirable coal mine dust PEL set by Congress in 1969, substantial work was needed to provide improved dust assessment and controls, including cleaner coal cutting technology, better ventilation methods, and generally enhanced dust suppression methods in coal mines.

Approach

In collaboration with the Mining Research Program, we developed and fostered the adoption of new and improved coal cutting and processing machinery, dust suppression techniques, and dust-measuring instruments, with these objectives to:

  • Develop better means of assessing coal mine dust in and around mines
  • Develop better means of controlling dust levels in and around mines

RDRP researchers use conventional gravimetric samplers and instantaneous light-scattering instruments to monitor dust levels at various locations throughout mining operations. Typically, stationary and mobile sampling strategies are employed. These instruments and techniques are used to identify major dust sources and their contribution to miner exposures. Our researchers then develop control technologies that are economically viable and mine-worthy to protect miners from exposure. Generally, these controls are developed and tested in full-scale simulated laboratory mine conditions to optimize their performance and then are taken into actual mines to further demonstrate their capabilities. The instrumentation discussed above is employed to carry out these in-mine evaluations.                  

Traditional exposure assessment methods have important limitations (9, A3-20). Gravimetric samplers only provide an average dust concentration over the sampling period with no indication of significant dust events, and thus do not detect peak exposures. In addition, results of gravimetric sampling may not be available for days or weeks, by which time the results may be irrelevant to taking effective action on the immediate source of the problem. Instantaneous light scattering instruments offer another approach to exposure assessment. Unfortunately, they only provide a relative measure of dust and performance and can be biased by particle size distribution, composition of the dust cloud, and moisture in the air-stream.

Given these limitations, our researchers recognized the need for a real-time, person-wearable dust monitor. The “Personal Dust Monitor” has now been developed and reached the implementation stage. It promises better assessment of coal mine dust in and around mines, providing the means for real-time monitoring of exposures by the miners themselves. Real-time monitoring permits identification of trouble spots, enabling miners to immediately avoid, reduce, or eliminate exposures, leading directly to disease prevention. The real-time features of the personal dust monitor provides a leading measure of dust control as opposed to the conventional methods, which are lagging measures that cannot contribute to a swift intervention.

Following the successful demonstration of new technologies for monitoring and controlling coal mine dust, our researchers then transfer the technologies to the industry, labor, and MSHA via publications, workshops, conference presentations, partnership meetings, and in-mine demonstrations of the technologies. 

Outputs and Transfer

Between 1996 and 2005, 97 publications on dust measurement and control have been published by researchers in the Respiratory Diseases and Mining Research Programs, including NIOSH numbered publication, “Performance of a New Personal Respirable Dust Monitor for Mine Use”(A3-21). These have consisted of 16 NIOSH numbered publications, 35 peer-reviewed journal publications, eight other journal articles, and 38 conference presentations (A3-22). 

In 2003, all of the dust-control technologies that the Respiratory Diseases and Mining Research Programs have developed and that were currently in use in mines were compiled and published in the “Handbook for Dust Control in Mining,” also available on NIOSH Web site (A3-23). This handbook, which provides a single information source to help mine operators control dust levels, has been widely accepted by and has received positive feedback from industry, labor, and regulatory agencies. MSHA has played a valuable role in promoting these dust control technologies. For example, in 1999, MSHA placed a “Longwall Dust Control Toolbox” on its Web site to guide longwall operators in their efforts to control respirable dust. The Respiratory Diseases and Mining Research Programs developed most of the control technologies (28 of 32 references) that were included in the MSHA toolbox (A3-24). For example, our research on longwall mining has identified optimum water-spray types and locations in cutting drums, developed directional water-spray systems for the longwall shearer, identified optimum operating pressures for different water-spray types, demonstrated methods to control dust from crusher/stageloader units, and improved operating practices such as worker positioning and cutting practices. These controls are especially important because of increasing production levels. During operator dust sampling, average production of continuous miner sections more than doubled from 310 tons of coal per shift in 1971 to 770 tons per shift in 2003. Likewise, average longwall production increased nearly 10-fold from 590 tons per shift in 1971 to 5,600 tons per shift in 2003. All else being equal, higher production means more dust generation but the development and commercial adoption of enhanced dust controls has largely coped with the increased generation of dust in coal mining.

Information on the personal dust monitor has been shared with coal mine operators, labor representatives, and MSHA, and widespread adoption of the instrument in workplaces is anticipated (A3-25).

Intermediate Outcomes

RDRP and the Mining Research Program have collaborated to develop and disseminate improved means of controlling coal mine dust in and around mines. These controls have contributed to a major reduction in dust levels in underground coal mines. For continuous miner workers, the percentage of dust samples exceeding the 2 mg/m3 PEL dropped from 49 percent in 1971 to nine percent in 2003. For longwall workers, the percentage dropped from 44 percent to 12 percent over the same time period. These declines in dust exposures have been accomplished despite large concomitant increases in production in both continuous miner and longwall sections. In spite of increased coal production over the years, compliance with MSHA PELs continued to improve (A3-26).

Motivation and direction to disease prevention efforts have been provided by the three major RDRP long-term initiatives (3.1a-c above): a) verification that the enacted coal mine dust standard protects miners; b) tracking disease occurrence in miners; and c) improve measurement and controls to reduce coal mine dust exposure. Together with the work of MSHA in enforcing current PELs, and the actions of worker organizations and employers, these initiatives have contributed to a substantial reduction in disease levels (Figure 6). Between 1970 and 1999, the percentage of examined underground coal miners with CWP (category 1/0+) declined about seven-fold (from 11 percent to 1.6 percent). Among those with 25 years or longer tenure in mining, the percentage of examined miners with CWP in 1997-99 was below five percent compared to a high of nearly 35 percent in 1973-78 (A3-27).

What’s Ahead

An important focus during the next few years will be the development of effective training materials and health communications for coal miners and mine managers on how the personal dust monitor can be used to reduce workers’ exposure to respirable dust. To form the basis for developing these materials, human factors researchers will collect data to identify how personal dust monitor use affects miners’ exposures to respirable dust. First, researchers will identify several specific examples of how miners use information about the monitors to discover which parts of their jobs and/or which aspects of their work environment may cause them to be overexposed to respirable dust. Second, they will identify the types of changes that miners and mine managers could implement to reduce their exposure. Researchers will then develop material for communicating this important information to miners and mine managers. They will also develop training modules to 1) explain the capabilities and use of personal dust monitors to coal miners and 2) explain how to download data, clean the monitor unit, and program it for the next shift of dust sampling to mine health and safety technicians. In addition, geographically focused efforts to improve awareness and utilization of both conventional and newer approaches to coal mine dust exposure assessment and control will be implemented based upon the surveillance activities already described in chapter 3.1b.

Intermediate Goals and Objectives Moving Forward

The intermediate goal of RDRP research on lung diseases induced by coal mine dust is to prevent and reduce pneumoconiosis among coal miners. To accomplish this, the following objectives have been developed:

  • Improve technologies for dust assessment and dust control in coal mining
  • Monitor and evaluate the occupational extent, severity, and characteristics of CWP
  • Increase awareness of the occupational contribution to the burden of CWP
  • Research the nature and causes of "hot spots" of CWP
  • Develop better tools for  identification, evaluation, and prevention of CWP
  • Develop recommendations for dust reduction, digital x-rays, B readers
NIOSH Program:

Respiratory Diseases

Evidence Package