Mutagenicity of diesel exhaust particles from two fossil and two plant oilfuels

Particulate matter of diesel engine exhaust from four different fuels was s tudied for content of polynuclear aromatic compounds and mutagenic effects. Two so-called biodiesel fuels, rapeseed oil methylesters (RME) and soybean oil methylesters (SME), were compared directly with two fossil diesel fuel s with the normal (DF) and a low sulfur content (LS-DF), Diesel exhaust par ticles were sampled on filters from the diluted and cooled exhaust of a tes t engine at five different speeds and loads. Filters were weighed for total particulate matter, Soxhlet extracted with dichloromethane and the content of insoluble material determined. The soluble organic fraction was analyse d for polynuclear aromatic compounds. Mutagenicity was determined using the Salmonella typhimurium/mammalian microsome assay with strains TA98 and TA1 00, Compared with DF, the exhaust particles of LS-DF, RME and SME contained less insoluble material, which consisted mainly of the carbon cores of die sel exhaust particles, The concentrations of individual polynuclear aromati c compounds varied widely among the different exhaust extracts, but total c oncentrations of the compounds were approximately double for DF and SME com pared with LS-DF and RME, In TA98 significant increases in mutation rates w ere obtained for the soluble organic fractions of all fuels for engines run ning at full speed (load modes A and D), but for DF revertants were 2- to 1 0-fold more frequent as compared with LS-DF, RME and SME, Revertant frequen cies for DF and partly for LS-DF were also elevated in TA100, while RME and SME gave no significant increase in mutations. The results indicate that d iesel exhaust particles from RME, SME and LS-DF contain less black carbon a nd total polynuclear aromatic compounds and are significantly less mutageni c in comparison with DF. A high sulfur content of the fuel and high engine speeds (rated power) and loads are associated with an increase in mutagenic ity of diesel exhaust particles.