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 long-term exposure of diesel exhaust to be 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 be a potential problem. 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 the conduct of peer-reviewed, longer-term quality scientific research to address the health hazards to miners posed by diesel exhaust. However, the recent introduction of new, more stringent diesel emission control regulations by the Mine Safety and Health Administration (MSHA) has resulted in demands on NIOSH researchers to put efforts into addressing immediate industry and labor stakeholder needs. Therefore, the current NIOSH research agenda addresses both long- and short-term efforts and goals.

The new 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 in the short term, NIOSH has established partnerships with industry and labor to accomplish 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.

NIOSH and their partners have organized diesel control technology workshops around the country. The first two of these, which were held in Cincinnati, OH, and Salt Lake City, UT, were geared toward metal/nonmetal mines. To address diesel emissions in coal mines, NIOSH sponsored a workshop in Louisville, KY. These workshops, through cooperative efforts with diesel engine and diesel control technology vendors, were designed to address questions relating to the practical aspects of introducing diesel emission control technologies onto underground mining equipment.

An important short-term mission was to determine the effectiveness of selected technologies in controlling diesel emissions in an operating underground mine. This study was organized under the auspices of the Metal/Nonmetal Diesel Partnership. The partnership agreed that a series of comprehensive field evaluations of diesel particulate filter (DPF) systems used in several underground mines was needed to determine the viability of DPF systems and establish confidence in their performance. The ultimate 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.

NIOSH and the partnership conducted the first in this series of studies in the Stillwater Mining Co.´s Nye Mine in Montana. 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.

NIOSH continues active involvement in the Diesel Emissions Evaluation Program (DEEP), a North American diesel consortium partnership involving mainly Canadian metal mines. DEEP´s goal is to reduce miners´ exposure to diesel exhaust pollutants by systematically testing and evaluating control strategies at specific mine sites. This project could have a tremendous impact on the acceptance of DPF technologies in North American underground coal and metal/nonmetal mines. The experiences gathered during this project have significantly influenced rule generation and implementation relative to the exposure of miners in U.S. mines.

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.

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.

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.