Mutagenicity of particulates in small engine exhaust

Abstract

Air pollution, largely from automobile traffic, has been worsening in the developed countries, especially in urban areas. Since environmental mutagens and carcinogens have come under scrutiny (Menck et al., 1974; Bridges, 1976), a rapid microbial mutation test (Ames et al., 1975) has been applied to the study of air pollution (Chrisp and Fisher, 1980). We reported that the airborne particulates collected in residential and industrial urban areas showed 7-445 h i s + revertants/plate/m 3 of air from tester strain TA98 incubated along with rat-liver extract in the Ames test (Tokiwa et al., 1977). Although we did not know the exact sources of mutagens in the residential area, we pointed out that automobile-exhaust emissions might be the greatest contributor (Ohnishi et al., 1980). In Japan some kinds of pollutants from cars, such as NOx, CO, and hydrocarbons, are subject to control. We also reported that exhaust emissions from an unregulated 1972 car provoked about 12000 h i s + revertants/plate/m 3 of exhaust gas, whereas those from a 'regulated' 1975 passenger car showed about 4000 h i s + rever tants /plate/m 3 from strain TA98 in the presence of S9 mix (Ohnishi et al., 1980). Furthermore, compared to these gasoline engines, automobile exhaust from old diesel engines showed very high mutagenic potency: more than 20000 h i s + rever tants /plate/m 3 (Ohnishi et al., 1980). In West-Germany it has been estimated that 1.85 ton of benzo[a]pyrene was produced by gasoline engines of passenger cars in 1973 (Grimmer and Hildebrandt, 1975). Even when the most restrictive minima were in force on gasoline engines of passenger cars in Japan in 1978, exhaust emissions from a 1978 passenger car (equipped with a catalyst) showed about 1000 h i s + revertants /plate/m 3 in the Salmonella/microsome test (unpublished data); and the emissions of small engines used to generate electric power or to run agricultural machinery are not regulated at all. In this paper we report that particulate exhaust