The bacterial mutagenicity of a comprehensive set of urban
particulate air pollution source samples is examined using
the Salmonella typhimurium forward mutation assay.
Each of the combustion source samples examined, including
the exhaust from catalyst-equipped autos, noncatalyst
autos, heavy-duty diesel trucks, plus natural gas, distillate oil, and wood combustion sources, is mutagenic in this assay, with a response per microgram of organic carbon in these samples generally greater than that of cigarette smoke aerosol. The noncombustion source samples tested generally are not mutagenic at the levels examined. The specific mutagenicity (mutant fraction per microgram of
organic carbon) of ambient aerosol samples collected in
southern California is compared to a weighted average of
the specific mutagenicity of the primary source samples
assembled in proportion to their emission rates in the Los
Angeles area. In most cases where a comparison can be
made, the specific mutagenicity of the source composites
and the ambient samples are of similar 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 higher than can be explained by direct
emissions from the sources studied here
