Mining Topic: Respirable Dust

Continuous mining machine equipped with wet head technology

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.

Noteworthy Publications & Products

A New Leak Test Method for Enclosed Cab Filtration Systems (2012-08)
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.
Benchmarking Longwall Dust Control Technology and Practices (2012-08)
Results from the NIOSH underground dust surveys and current longwall dust control technology and operating practices are discussed.
Best Practices for Dust Control in Coal Mining (2013-03)
This handbook was developed to identify available engineering controls that can help the industry reduce worker exposure to respirable coal and silica dust.
Best Practices for Dust Control in Metal/Nonmetal Mining (2013-03)
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.
Coal Dust Exposure and Mortality From Ischemic Heart Disease Among a Cohort of U.S. Coal Miners (2012-08)
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.
Continuous Miner Spray Considerations for Optimizing Scrubber Performance in Exhaust Ventilation Systems (2012-08)
This paper describes lab experiments to examine the effect of spray type, 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.
Dust Control Handbook for Industrial Minerals Mining and Processing (2013-03)
Mined ore undergoes crushing, grinding, cleaning, drying, and product sizing as it is processed, generating harmful dust. This handbook reviews technologies for lowering dust levels below the permissible or recommended occupational exposure limits.
Equivalency of a Personal Dust Monitor to the Current United States Coal Mine Respirable Dust Sampler (2011-09)
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 (2012-08)
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 (2012-08)
Dust surveys determined if deep-cut mining expose face workers to higher levels of respirable dust. Study findings indicate that levels on bolting faces did not appear to be affected by longer cycles associated with deep-cut mining practices.
Evaluation of the Approach to Respirable Quartz Exposure Control in U.S. Coal Mines (2012-08)
The performance of the current regulatory approach was found to be lacking due to the use of a variable property - quartz content in airborne dust - to establish a standard for subsequent exposures.
Evaluation of the Wet Head Continuous Miner to Reduce Respirable Dust (2012-08)
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 (2012-08)
Field tests confirm that an air-blocking shelf installed in the inside perimeter of a blasthole drill shroud substantially improves dust control. This modification reduced respirable dust by 66%–81% in the immediate vicinity of the shroud...
Investigation into Dust Exposures and Mining Practices in Mines in the Southern Appalachian Region (2012-08)
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 (2012-08)
NIOSH experimentally investigated various factor effects on cab air filtration system performance.
Laboratory and Field Performance of a Continuously Measuring Personal Respirable Dust Monitor (2012-08)
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.
Reducing Dust Exposure from Contaminated Work Clothing with a Stand-Alone Cleaning System (2012-08)
An alternative method to the original system developed by NIOSH and Unimin Corp to provide for a stand-alone clothes cleaning system.