Contribution of 1-nitropyrene to direct-acting Ames assay mutagenicities of diesel particulate extracts

Abstract

Projections of future increases in the number of diesel powered U.S. passenger cars have raised concerns about potential adverse human health effects associated with diesel engine particulate exhaust (Pepelko et al., 1980). One concern has been carcinogenic polycyclic aromatic hydrocarbons (PAH), known for many years to be associated with diesel exhaust particles. A more recent concern, raised by experiments with the Ames Salmonella mutagenesis assay, has been the discovery that PAH may not be the only potential carcinogens in the diesel exhaust particles (Huisingh et al., 1978; Wang et al., 1978; Pepelko et al., 1980). These experiments have shown that organic solvent extracts of diesel exhaust particles are directly mutagenic (i.e., mutagenic without activation by mammalian tissue homogenate), whereas the predominant PAH identified in the extracts are mutagenic in the Ames assay only with activation (Searle, 1976; McCann and Ames, 1976; Gibson et al., 1978). We (Schuetzle et al., 1981) and others (Erickson et al., 1979) have identified many oxygenated derivatives of PAH in these extracts. Many of these derivatives could be direct-acting mutagens, but little is known yet about their mutagenicities or their concentrations in the extracts. One of the PAH derivatives identified was l-nitropyrene (I-NP) (Schuetzle et al., 1982), recently shown to be an extremely potent direct-acting mutagen in the Ames assay (Wang et al., 1980; LOfroth et al., 1980, Rosenkranz et al., 1980). Herein we report a rigorous determination of the percentage contribution of 1-NP to the direct-acting Ames assay mutagenicities of extracts of exhaust particles collected from 3 different diesel powered passenger vehicles. The percentage contribution, P, of 1-NP is given by: