NIOSH Mining Safety and Health Research

Short-term overexposure to diesel exhaust has been linked to health effects such as eye and nose irritation, headaches, nausea, and asthma. Based on a combination of chemical data, genotoxicity, and experimental carcinogenicity, NIOSH has determined that diesel exhaust is a potential human carcinogen. The International Agency of Research on Cancer regards diesel exhaust as a probable human carcinogen. The Environmental Protection Agency considers long-term exposure to diesel exhaust likely to cause cancer and environmental concentrations of diesel exhaust to potentially cause health problems. Underground miners can be exposed to over 100 times the typical environmental concentration of diesel exhaust and over 10 times that of other workplace exposures. About 34,000 underground miners and 200,000 surface miners are exposed to diesel exhaust, as are more than 1 million other workers in the United States.

The goal of this research program is to investigate, develop, and evaluate diesel emission monitoring and control technologies for the purpose of monitoring and reducing, in an economically viable manner, the exposure of U.S. miners to diesel emissions and their harmful health effects. We are committed to conducting long-term, peer-reviewed, quality scientific research to address the health hazards to miners posed by diesel exhaust. In addition, NIOSH researchers will continue to put efforts into addressing immediate industry and labor stakeholder needs as they arise. Therefore, the current NIOSH research agenda addresses both long- and short-term efforts and goals.

The diesel regulations introduced into both U.S. coal and metal/nonmetal mines are technology-driven. This means that, while the basic technology to control diesel emissions in mines is available, research is needed to address many engineering and logistic application problems. To address this need, NIOSH established partnerships with industry and labor to collaborate on the required research efforts. These include a Coal Mine Diesel Partnership with the Bituminous Coal Operators Association, the National Mining Association and the United Mineworkers of America, and a Metal/Nonmetal Mine Diesel Partnership with the National Mining Association, the National Stone Sand and Gravel Association, the MARG Diesel Coalition, and the United Steelworkers of America.

An example of the successful results made possible through the work of these partnerships was a NIOSH study conducted in the Stillwater Mining Co.'s Nye Mine in Montana. The goal of this study was to reduce the exposure of underground miners to diesel particulate matter (DPM) and gases and to identify technically and economically feasible controls to curtail particulate matter emissions from existing and new diesel-powered vehicles in underground metal/nonmetal mines. This study was conducted in two phases. The goal of the first phase was to establish the effectiveness of selected technologies (several DPF systems, diesel oxidation catalysts, biodiesel blends, and No. 1 and No. 2 diesel fuel) in reducing diesel emissions by using an isolated zone methodology. The goal of the second phase was to assess the effectiveness of DPF system in controlling the exposure of underground miners in actual production scenarios. The results of these efforts were published as NIOSH Reports of Investigation (RI 9667, RI 9668) and can be downloaded from the following links: RI 9667 and RI 9668.

NIOSH and their partners also continue to organize diesel control technology workshops around the country. These workshops, through cooperative efforts with diesel engine and diesel control technology vendors, are designed to address questions relating to the practical aspects of introducing diesel emission control technologies onto underground mining equipment.

Another effort involves diesel engine emission evaluations using a transportable engine dynamometer and an engine test cell emissions measurement system that will be used at Lake Lynn Lab to ascertain the actual performance of emissions control technology in a realistic mine setting having naturally occurring dusts and dilutions. Lake Lynn is providing NIOSH with the means to conduct real-world research and testing on commercial control technologies, including new engines, water-fuel emulsions, low-sulfur fuel, catalysts, and DPF systems. In addition, the results from the Lake Lynn studies can be compared with those obtained in institutional labs. It also offers a way to relate the effects of controls on customary (gravimetric filter sampling) and alternative metrics of diesel exhaust particles.

Schematic of the diesel laboratory in the D-drift of Lake Lynn Experimental Mine

NIOSH researchers have developed methods for the collection and analysis of carbon attributed to DPM. We are presently conducting detailed investigations of problematic issues with the measurement and analysis of DPM. This includes analyses on coal mine dust interferences, elemental carbon/DPM ratios, effects of control technology on diesel emissions analysis, and effects of biodiesel and fuel additives on diesel emissions analysis.

Continuous elemental carbon analyzer

Diesel emissions are a complex mixture of gases and particulate matter. Controversy has surrounded attempts by MSHA to (1) quantify the risk associated with exposure to DPM and (2) develop policies limiting exposure of underground miners. Since recent health research implicates ultrafine particles as the probable health culprit, many argue that regulations based on mass concentrations of DPM, total carbon, or elemental carbon are not addressing the effects of particle size, distribution, and chemical composition from a health perspective. Longer-term NIOSH research focuses on the size-dependent chemical characterization of DPM to provide the missing knowledge needed to elucidate the issues related to the effects on human health posed by the changing character of DPM due to the use of modern engines and control technology.