The extensive use of heavy-duty diesel engines in underground mines has raised concerns about the potential adverse health effects arising from exposure of miners to diesel exhaust. Of particular concern is exposure to diesel particulate matter (DPM) which contains mutagenic and carcinogenic organic compounds. Potential exposure to vapor phase diesel emissions such as carbon monoxide (CO), nitrogen dioxide (NO2) and mutagenic and carcinogenic compounds is also of some concern. A variety of emission controls have been developed for use in reducing DPM emissions, in particular. The long-term objective of this research project is to evaluate the effects of several DPM emission control systems on the chemical and mutagenic character of emissions from diesels intended for in- mine use to assess relative health risks. The specific aims of this proposed research project are the: 1) collection of DPM and vapor phase material from laboratory tests of underground mine diesel engines operated in steady-state and transient conditions, with and without emission control devices and fuel additives; 2) extraction and quantitation of the organic material associated with the DPM and vapor phase samples; 3) determination of the mutagenicity associated with these extracts using the Ames assay; 4) quantitation of key mutagenic and carcinogenic polynuclear aromatic hydrocarbons (PAH) in the extracts; and 5) determination of the engine operating conditions which most contribute to exhaust mutagenicity and levels of key PAH. If possible, in-mine ambient air samples will be collected while the same emission control devices are in use in order to assess actual contributions of the controlled diesel emissions to in-mine air quality. A variety of typical mining diesel engines will be tested using DPM emission devices such as dry exhaust conditioners with and without uncatalyzed ceramic traps and fuel additives. Extracts of the organic material from both DPM and vapor phase samples will be analyzed. Eight mutagenic and carcinogenic PAH known to be present in diesel exhaust will be quantitated by gas chromatography (GC) and GC/mass spectrometry techniques. The mutagenic response of the DPM and vapor phase organic extracts will be determined using the Ames Salmonella typhimurium/microsomal mutagenicity bioassay. The chemical and mutagenicity data obtained from this study along with other emission data such as DPM, CO, and NO2 will be converted to estimated in-mine concentrations. These data will then be used to assess the relative effect of each DPM emission control system on each engine tested in terms of contribution to potential health hazards in underground mines.