BACTERIAL MUTAGENICITY OF URBAN ORGANIC AEROSOL SOURCES IN COMPARISONTO ATMOSPHERIC SAMPLES

The bacterial mutagenicity of a comprehensive set of urban particulate air pollution source samples is examined using the Salmonella typhimu rium forward mutation assay. Each of the combustion source samples exa mined, including the exhaust from catalyst-equipped autos, noncatalyst autos, heavy-duty diesel trucks, plus natural gas, distillate oil, an d wood combustion sources, is mutagenic in this assay, with a response per microgram of organic carbon in these samples generally greater th an that of cigarette smoke aerosol. The noncombustion source samples t ested generally are not mutagenic at the levels examined. The specific mutagenicity (mutant fraction per microgram of organic carbon) of amb ient aerosol samples collected in southern California is compared to a weighted average of the specific mutagenicity of the primary source s amples assembled in proportion to their emission rates in the Los Ange les area. In most cases where a comparison can be made, the specific m utagenicity of the source composites and the ambient samples are of si milar magnitude, with the exception that the -PMS mutagenicity of the aerosol at Long Beach, CA, during the first half of the calendar year 1982 and at Azusa, CA, during the April-June 1982 period is much highe r than can be explained by direct emissions from the sources studied h ere.