Comparison of Nitro-Aromatic Content and Direct-Acting Mutagenicity of Passenger Car Engine Emissions

Abstract

Particulate emissions from internal combustion engines are a very complex mixture of carbonaceous matter containing absorbed and/or condensed organic components from the combustion of fuel and lubricants. The organic solvent extractable fraction of these particulates is extremely complex and has been reported to contain hundreds of individual compounds. A number of studies have reported that these solvent extracts are mutagenic as determined by the Ames Salmonella microbial assay. The greatest activity which has been found in certain compound class fractions within these extracts does not require metabolic activation and is called direct mutagenic activity. Chemical characterization studies have been used in an attempt to identify the compound classes or specific compounds present in these fractions. Polynuclear aromatic hydrocarbons (PAH), particularly pyrene, have been reported to readily react with nitrogen oxides to form nitrated derivatives which are powerful direct-acting mutagens. Both the PAHs and nitrogen oxides are present in engine emissions and thus the formation of nitroaromatics may indeed be possible. These results have prompted increased attention to the characterization of particulate extracts to identify the compounds or compound classes which are responsible for the direct acting biological activity. Identification of specific mutagens or classes of mutagens is important to determine whether these components are present in the effluent which is emitted to the atmosphere or are formed as a result of the particulate collection and analysis procedures. This information must be established before potential effects of these compounds on the environment can be addressed.