What is the hazard? The extraction, crushing, and transport of coal in mining operations can generate significant amounts of airborne respirable coal dust. In metal, nonmetal, stone, and sand and gravel mining operations and for select occupations in coal mines, the generation of respirable silica dust during mining is the primary concern. How are mineworkers affected? Inhalation of respirable coal dust can lead to coal workers' pneumoconiosis (CWP), a disabling and potentially fatal lung disease. Inhalation of excessive levels of silica dust can lead to silicosis, another disabling and potentially fatal lung disease. Recent surveillance data indicates that the prevalence of CWP is on the rise following a 30-year downward trend. Also, mining accounted for approximately 23% of the reported silicosis deaths in the 1990s. What is OMSHR's approach to the problem? Reducing respiratory diseases in miners is one of the top level goals of the Office of Mine Safety and Health Research's (OMSHR) strategic plan. To achieve this objective, we conduct research to develop improved dust control technologies, which can be used to reduce the mine workers' respirable dust exposure. Four key components of this dust research program include: intramural engineering control research; technology transfer; funding of extramural research projects; and improved dust monitoring capabilities. OMSHR's ongoing intramural research addresses dust control problems in both the coal and metal/nonmetal mining industries. MSHA compliance sampling data is analyzed to identify occupations at high risk for exposure to elevated dust levels. Laboratory and/or mine-site research is then conducted to identify and evaluate dust control technologies for these high-risk occupations. The unique, full-scale dust laboratories in Pittsburgh are used by OMSHR dust researchers to evaluate technologies under controlled conditions that are not present at operating mine sites. Control technologies proven successful in the laboratory then undergo final evaluation at operating mine sites. Specific details of the dust control research currently being conducted in our intramural research program are provided at the OMSHR website. Publications as part of our technology transfer efforts include two recently published handbooks "Best Practices for Dust Control in Coal Mining" and "Best Practices for Dust Control in Metal/Nonmetal Mining." Mine operators can use these handbooks to identify successful control technologies that can be implemented at their respective mines to reduce worker exposures. Our researchers have also conducted a series of "best practices" workshops in mining regions around the country. Videos of the presentations related to dust controls for coal mining and slide presentations for metal/nonmetal mining are available for download from the NIOSH Mining website. We have recently partnered with the Industrial Minerals Association-North America (IMA-NA) to produce a dust control handbook that summarizes control technologies addressing all phases of mineral processing operations. OMSHR funds extramural research in areas that can have a direct impact on the reduction of dust levels in mining operations. In addition to ventilation research, basic research examines concepts such as the potential of utilizing particle charging and the wetting characteristics of respirable dust particles to improve their capture. Real-time monitoring of respirable dust exposures enables mine operators to identify potential overexposures and implement interventions to prevent these overexposures. The personal dust monitor (PDM) is a real-time dust monitor that was developed by NIOSH through intramural and extramural research over the last decade. Extensive NIOSH testing has demonstrated that the PDM is an accurate dust sampler, and MSHA has specified that the PDM will be used for compliance dust sampling in its proposed respirable dust regulations, which are in the final stages of the rulemaking process. The PDM is a research-to-practice success story and demonstrates the impact of NIOSH research. See the list of spotlighted publications below and also our program highlights page for more information. The work in this topic area is supported by the NIOSH Mining Dust Monitoring and Control and Ventilation programs. See the NIOSH Mining Products page for software, guides, training materials or other items related to this topic.

Tools and Resources

Guides

Best Practices for Dust Control in Coal Mining (PDF, 4468 KB, 2010-01)
In light of the ongoing severity of these lung diseases in coal mining, this handbook was developed to identify available engineering controls that can help the industry reduce worker exposure to respirable coal and silica dust. The intent was to identify the best practices that are available to control respirable dust levels in underground and surface coal mining operations.

Best Practices for Dust Control in Metal/Nonmetal Mining (PDF, 3040 KB, 2010-05)
This handbook was developed to identify available engineering controls that can assist underground and surface metal/nonmetal mining operations in reducing worker exposure to respirable silica dust. The controls discussed in this handbook range from long-used controls which have developed into industry standards, to newer controls, which are still being optimized.

Dust Control Handbook for Industrial Minerals Mining and Processing (PDF, 14308 KB, 2012)
Throughout the mining and processing of minerals, the mined ore undergoes a number of crushing, grinding, cleaning, drying, and product sizing operations as it is processed into a marketable commodity. These operations are highly mechanized, and both individually and collectively these processes can generate large amounts of dust. If control technologies are inadequate, hazardous levels of respirable dust may be liberated into the work environment, potentially exposing workers. Accordingly, federal regulations are in place to limit the respirable dust exposure of mine workers. Engineering controls are implemented in mining operations in an effort to reduce dust generation and limit worker exposure.

Diseases, injuries & disorders

Coal Dust Exposure and Mortality From Ischemic Heart Disease Among a Cohort of U.S. Coal Miners (PDF, 249 KB, 2011)
Particulate exposure from air pollution increases the risk of ischemic heart disease (IHD) mortality. Although coal miners are highly exposed to coal dust particulate, studies of IHD mortality risk among coal miners have had inconsistent results. Previous studies may have been biased by the healthy worker effect. Methods: We examined the dose-response relationship between cumulative coal dust exposure, coal rank, and IHD mortality among a cohort of underground coal miners who participated in the National Study of Coal Workers' Pneumoconiosis.

Measurement & analysis

Equivalency of a Personal Dust Monitor to the Current United States Coal Mine Respirable Dust Sampler (PDF, 228 KB, 2008-01)
The work presented in this paper focuses on the relationship between the PDM and respirable dust concentrations currently measured by a coal mine dust personal sampler unit utilizing a 10 mm Dorr Oliver nylon cyclone.

Evaluating Portable Infrared Spectrometers for Measuring the Silica Content of Coal Dust (PDF, 2012)
Miners face a variety of respiratory hazards while on the job, including exposure to silica dust which can lead to silicosis, a potentially fatal lung disease.

Evaluation of Face Dust Concentrations at Mines Using Deep-Cutting Practices (PDF, 4319 KB, 2011)
Data collected for this study indicate that 20-mesh screens should be cleaned for every 40 ft of advance because 22% of the deep-cut sequences surveyed for this study experienced a 20% to 35% decrease in scrubber airflow over the course of the cut. For blowing face ventilation, field and laboratory data indicate that maintaining a proper curtain-to-scrubber airflow ratio of 1.0 and a curtain setback distance that allows the miner operator to stand at the mouth of the curtain helps control dust. Curtain airflows should be measured before activation of the scrubber regardless of ventilation type (exhausting or blowing) to avoid erroneously overinflating the ratio. The curtain setback variance should be greater than the maximum cutting depth to allow miner operators to maintain their position at the mouth of the curtain when the miner is fully extended into the cut. Greater curtain setback distances associated with deep-cutting methods may result in cuts that do not require ventilation curtain, such as the initial heading developments beyond the last open crosscut. For these cuts, dust levels were generally lower during development of deep cuts when compared to regular cuts. However, adequate ventilation of cuts without ventilation curtain is dependent on a properly functioning scrubber. Dust levels on the bolting faces did not appear to be affected by the longer cycles associated with deep-cut mining practices when curtain airflow was measurable and the curtain was periodically advanced in sync with the bolting machine.

Evaluation of the Approach to Respirable Quartz Exposure Control in U.S. Coal Mines (PDF, 258 KB, 2012)
Occupational exposure to high levels of respirable quartz can result in respiratory and other diseases in humans. The Mine Safety and Health Adminstration (MSHA) regulates exposure to respirable quartz in coal mines indirectly through reductions in the respirable coal mine dust exposure limit based on the content of quartz in the airborne respirable dust.

Investigation into Dust Exposures and Mining Practices in Mines in the Southern Appalachian Region (PDF, 241 KB, 2009)
This paper presents the results to date of a NIOSH investigation into the possible causes that would account for the observed higher trends in CWP disease progression through review, data analysis, and in-mine surveying.

Key Design Factors of Enclosed Cab Dust Filtration Systems (PDF, 900 KB, 2008-11)
NIOSH experimentally investigated various factor effects on cab air filtration system performance. This paper describes the laboratory experiments which were performed on an enclosed cab test stand examining the independent factor effects of intake filter efficiency, intake filter loading (airflow resistance), intake air leakage around the filter, recirculation filter use, and wind on cab performance.

A New Leak Test Method for Enclosed Cab Filtration Systems (PDF, 2012)
AbstractA new test method has been developed by the National Institute for Occupational Safety and Health (NIOSH) and Clean Air Filter (CAF) for quantifying the outside air leakage into environmental cab filtration systems.

Engineering controls

Benchmarking Longwall Dust Control Technology and Practices (PDF, 1003 KB, 2011)
The National Institute for Occupational Safety and Health (NIOSH) conducted a series of benchmark surveys at longwall operations across the country to identify current operating practices and the types of controls being used. Gravimetric and instantaneous dust sampling was completed to quantify the dust levels generated by major sources on the longwall section and to identify different control technologies in use today. Substantial reductions in dust levels were realized at sampling locations on the face when compared with longwall surveys conducted in the 1990s. Results from the underground dust surveys and current longwall dust control technology and operating practices will be discussed.

Continuous Miner Spray Considerations for Optimizing Scrubber Performance in Exhaust Ventilation Systems (PDF, 150 KB, 2010)
This paper describes NIOSH conducted laboratory experiments to examine the effect of spray type, spray pressure, machine body blocking sprays, and scrubber airflow on dust and gas levels while using a 12.2 m (40 ft) exhaust ventilation curtain setback from the face.

Evaluation of the Wet Head Continuous Miner to Reduce Respirable Dust (PDF, 163 KB, 2010)
This paper describes field tests conducted by NIOSH to evaluate the effectiveness of a wet head continuous mining machine for reducing dust exposure for continuous miner operators.

Field Evaluation of Air-blocking Shelf for Dust Control on Blasthole Drills (PDF, 443 KB, 2011)
In previous studies, an air-blocking shelf has been shown to be successful in reducing respirable dust leakage from the drill shroud in a laboratory setting. Dust reductions of up to 81 percent were achieved with the shelf under operating conditions consisting of a 1.9:1 collector-to-bailing airflow ratio and a 5.1-cm gap between the shroud and ground. Recent research focused on evaluating the shelf on two actual operating blasthole drills, in much more severe environments. In the field, the shelf reduced dust levels in the areas surrounding one operating blasthole drill by 70 percent. Dust reductions measured in the immediate vicinity of the shroud were reduced by 66 percent at one mine and 81 percent at the other mine. These field tests confirm that the air-blocking shelf is useful for reducing respirable dust generation from blasthole drills.

Reducing Dust Exposure from Contaminated Work Clothing with a Stand-Alone Cleaning System (PDF, 268 KB, 2008)
An alternative method to the original system developed by NIOSH and Unimin Corporation to provide for a stand-alone clothes cleaning system has been developed to quickly, effectively, and safely remove dust from the clothing of a worker without dust exposure to the worker, the work environment, or co-workers during the cleaning process.

Administrative controls

Laboratory and Field Performance of a Continuously Measuring Personal Respirable Dust Monitor (PDF, 1128 KB, 2006-09)
This report includes the theory of operation, description, and the performance of the Personal Dust Monitor (PDM) compared to gravimetric-based reference dust sampling methods and laboratory verification of the instruments accuracy. There is also a detailed underground evaluation that includes measurement of the instruments precision, durability under mine use conditions, and the functionality of the instrument when used by miners.

Information gateways

Silica

Silicosis: Learn the Facts!