Detection and average content levels of carcinogenic and mutagenic compounds from the particulates on diesel and gasoline engine mufflers

Carcinogenic and mutagenic compounds, which were extracted from the particulates that adhered to inner surfaces of diesel and gasoline engine mufflers, were quantified by the series method of Soxhlet extraction, liquid-liquid partition, thin-layer chromatography, and spectrofluorometry. Mutagenic activity of their neutral and acidic fractions was tested in the improved Ames assay by the preincubation method with Salmonella typhimurium TA98 in the presence and absence of metabolic activation system (S-9 mix). The average content levels (μg/g tar) of polycyclic aromatic hydrocarbons from gasoline engine cars were greater than those from diesel engine vehicles. However, the levels of nitro derivatives of PAHs and polycyclic quinones from the diesel engines were greater than from the gasoline engines. Mutagenic activity of the diesel acidic fraction was the highest among the diesel and gasoline fractions, and was significantly higher in the absence of the S-9 mix. Furthermore, the relative value (R_{c = 0}) of infrared absorption of carbonyl stretching vibration to that of methylene asymmetric stretching vibration of the diesel acidic fraction was the highest among the diesel and gasoline fractions. These results strongly suggest that highly direct-acting mutagens in the acidic fraction are at higher levels in diesel emission particulates than those from gasoline, and that these mutagens are carboxylic acid, aldehyde, and alcohol derivatives of PAHs and NPAHs.