Research Projects

Project at a Glance

Title: Lifetimes and fates of toxic air contaminants in California's atmosphere

Principal Investigator / Author(s): Atkinson, Roger

Contractor: University of California, Riverside

Contract Number: 93-307

Research Program Area: Atmospheric Processes, Health & Exposure

Topic Areas: Chemistry & Reactivity, Health Effects of Air Pollution, Toxic Air Contaminants


The staff of the California Air Resources Board (CARB) and the Office of Environmental Health Hazard Assessment (OEHHA) compiled summary sheets on each of the 244 substances on the CARB Toxic Air Contaminant Identification List as pan of the State of California's air toxic program Assembly Bill (AB) 1807. As one specific task of this contract, the atmospheric chemists at the Statewide Air Pollution Research Center, University of California, Riverside, reviewed the draft data sheets and commented specifically on the atmospheric persistance of the Toxic Air Contaminants. The second task of this contract was to provide ambient concentration measurements for selected compounds including polycyclic aromatic hydrocarbons (PAH) and nitro-PAH for which potency equivalency factors (PEF) have been established by the OEHHA and for which few ambient measurements have been reported. In general, the PAH concentrations measured were significantly below those measured approximately 10 years ago at several locations throughout California (Final Report, CARB Contract No. A5-185-32, May 1988). A large range of ambient concentrations of PAH occur in California, varying geographically and seasonally. Because, unlike the nitro-PAH, there is no in situ formation of the PAH, maximum exposures occur in areas of maximum emission sources under meteorological conditions favoring atmospheric inversions. In contrast to the PAH data, the nitropyrene and 2-nitrofluoranthene concentrations measured in Riverside were within the range previously observed throughout California. An elevated nighttime level of 2-nitrofluoranthene, compared to 1- and 2-nitropyrene suggested nighttime formation of 2-nitrofluorathene from the NO3 radical-initiated reaction.


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

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