585 research outputs found
Bacterial Mutagenicity of Urban Organic Aerosol Sources in Comparison to Atmospheric Samples
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
Seasonal and Spatial Variation of the Bacterial Mutagenicity of Fine Organic Aerosol in Southern California
The bacterial mutagenicity of a set of 1993 urban particulate air pollution samples is examined using the Salmonella typhimurium TM677 forward mutation assay. Ambient fine particulate samples were collected for 24 hr every sixth day throughout 1993 at four urban sites, including Long Beach, central Los Angeles, Azusa, and Rubidoux, California, and at an upwind background site on San Nicolas Island. Long Beach and central Los Angeles are congested urban areas where air quality is dominated by fresh emissions from air pollution sources; Azusa and
Rubidoux are located farther downwind and receive transported air pollutants plus increased quantities of the products of atmospheric chemical reactions. Fine aerosol samples from Long Beach and Los Angeles show a pronounced seasonal variation in bacterial mutagenicity per cubic
meter of ambient air, with maximum in the winter and a minimum in the summer. The downwind smog receptor site at Rubidoux shows peak mutagenicity (with postmitochondrial supernatant but no peak without postmitochondrial supernatant) during the September-October periods when direct transport from upwind sources can be expected. At most sites the mutagenicity per microgram of organic carbon from the aerosol is not obviously higher during the
summer photochemical smog period than during the colder months. Significant spatial variation in bacterial mutagenicity is observed: mutagenicity per cubic meter of ambient air, on average, is more than an order of magnitude lower at San Nicolas Island than within the urban area. The
highest mutagenicity values per microgram of organics supplied to the assay are found at the most congested urban sites at central Los Angeles and Long Beach. The highest annual average values of mutagenicity per cubic meter of air sampled occur at central Los Angeles. These findings
stress the importance of proximity to sources of direct emissions of bacterial mutagens and imply that if important mutagen-forming atmospheric reactions occur, they likely occur in the winter and spring seasons as well as the photochemically more active summer and early fall periods
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