DESCRIPTION: The global objective of the proposed study is to accurately measure and control the genotoxic respirable particulate matter (PM) produced by diesel engine powered mining equipment. This study is aimed at highlighting differences between the engine out PM emissions measured in a laboratory in accordance with the new Mine Safety and Health Administration (MSHA) regulations, and the actual "real-world" PM exhaust emissions emitted by mining engines operating over normal duty cycles in mine atmospheres. This study proposes to employ a portable real-time particulate matter mass monitor to quantify the genotoxic exposures by measuring diesel particulate matter (DPM) emissions from tailpipes of mining engines. It is proposed that an integrated APPROACH be adopted that will involve a critical assessment of DPM exhaust emissions measured in the laboratory as well as direct on-board DPM emissions measured from engines operating in the mines. The inability of the adequate on-board PM measurement technology that could consistently and accurately measure DPM in underground mines resulted in MSHA requiring only in-laboratory engine tests. However, very recent developments in PM mass measurement systems may now enable in-field PM exhaust emissions measurements from diesel engines. This would provide researchers with the ability to evaluate the real-world contribution of particulate matter from diesel engines operating in the close confines common to mining environments. Moreover, this technology would provide a means of verifying in-use performance of proposed emissions curtailing devices and identifying emissions control system failures in the field. The proposing team's experience has highlighted the imperative need to measure in-mine diesel PM exposures, since prior work for the West Virginia Diesel Commission had shown that engines and exhaust aftertreatment systems that have passed certification tests in the laboratory may not only malfunction in the field, but the emission levels may be significantly greater than the certification standards. Such technology is imperative in order to accurately assess in-mine diesel PM exposures so that the mining industry can effectively safeguard the health and safety of miners while enhancing the productivity and efficiency of mining operations.