Research Projects

Project at a Glance

Project Status: complete

Report Published November 1981:

Title: Geographical and temporal distribution of atmospheric mutagens in California.

Principal Investigator / Author(s): Pitts, James N., Jr.

Contractor: Statewide Air Pollution Research Center, UC Riverside

Contract Number: A9-077-31


Research Program Area: Atmospheric Processes


Abstract:

The Statewide Air Pollution Research Center continues to assess the mutagenic potency, as determined by the Ames Salmonella/mammalian-microsome assay, of suspended particulate matter in the South Coast Air Basin (SCAB). This program was designed to reveal factors influencing the diurnal variation and geographical distribution of the mutagenicity associated with airborne particles and to establish current "baseline" levels of this mutagenicity for future reference. The current year of this program involves identification of the chemical species responsible for this observed mutagenicity.

Most studies to date have determined the mutagenicity for sampling periods of 24 hours or more. Unfortunately, a collection period of this length averages any mutagenicity peaks which might have occurred. Furthermore, such data may not have sufficient time-resolution to permit assessments of the nature of the mutagen sources (i.e., mobile vs. stationary emissions or primary vs. secondary pollutants). Therefore, investigations were conducted on diurnal variations in the mutagenicity of ambient particles collected simultaneously at several sites across the SCAB. These collections were made every twelve hours for a 72-hour period in winter 1980 and very three hours for a 24-hour period, on two late summer days in 1980 and an early spring day in 1981.

The following conclusions can be drawn from this program:

* Levels of particulate mutagenicity are highly variable, ranging over nearly two orders of magnitude during the sampling periods used in this work.
* Both direct-acting and activatable mutagens are present in the organic extracts from suspended particles collected in the SCAB.
* Average mutagen density is generally higher during the nighttime hours than during the day.
* The diurnal variation exhibited by particulate mutagenicity is similar to that expected of a primary pollutant, with the levels responding to emission rates and atmospheric mixing heights. Significant positive correlations are observed between the mutagen parameters and NO, NO2, and CO levels, while secondary pollutants such as ozone and peroxyacetyl nitrate correlate negatively.
* Nitroarenes may contribute substantially to the mutagenicity of ambient particulate organic matter in the SCAB.
* No clear evidence for or against atmospheric transformations which may affect particulate mutagenicity is apparent from our data.


 

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