Mutagenic Potential of Particulate Matter from Diesel Engine Operation on Fischer-Tropsch Fuel as a Function of Engine Operating Conditions and Particle Size

Further growth of diesel engines in the light-duty and heavy-duty vehicular market is closely linked to the potential health risks of diesel exhaust. The California Air Resources Board and the Office of Environmental Health Hazard Assessment have identified diesel exhaust as a toxic air contaminant. The International Agency for Research on Cancer concluded that diesel particulate is a probable human carcinogen [1]. Cleaner burning liquid fuels, such as those derived from natural gas via the Fischer-Tropsch (FT) process, offer a potentially economically viable alternative to standard diesel fuel while providing reduced particulate emissions. Further understanding of FT operation may be realized by investigating the differences in toxicity and potential health effects between particulate matter(PM) derived from FT fuel and that derived from standard Federal diesel No. 2 (DF). The present effort investigates the mutagenicity of particulate matter derived from FT and DF fuel combustion in a single-cylinder diesel engine by relating the in-vitro mutagenic activity of the PM to engine operating conditions and particle size. Total particulate matter samples were gathered using glass fiber filters in a mini-dilution tunnel from engine operation on each fuel at seven steady state engine operating conditions. Particulate matter samples from two engine conditions were also gathered on greased aluminum foil substrates using a Micro-Orifice Uniform Deposition Impactor (MOUDI) for size selective mutagenic analysis using the Ames Typhimurium bioassay method. Toxicity effects are reported but screened from the dose-response analysis using a method similar to that set forth by Bernstein [2]. Results indicate mutagenic response differences in the particulate matter as functions of engine operating conditions, fuel type and particle size. Large particles exhibit a significantly greater mutagenic effect than their smaller counterparts.