Direct and indirect mutagenic effects of extracts from particles emitted in automobile exhaust gas.

The mutagenicities of particles in automobile exhaust gas emitted under different driving conditions, i.e. constant speed driving (20, 40, or 80 km/h) and variable speed driving according to a typical traffic pattern in Tokyo, were studied. The gasoline-engined automobile was run on a chassis dynamometer. Exhaust samples collected on glass fiber filters, which were extracted with benzene, and the extracts were tested by the Ames Salmonella assay. Strains TA 100 and TA 98 were used, with and without a metabolic activation system (S9 mix). The mutagenic activity per km driving increased with increase of the speed, and the particles produced by variable speed driving showed higher mutagenicity than those produced by constant speed driving.