Mutagenicity of used crankcase oils from diesel and spark ignition automobiles

The Salmonella mutagenicity assay was used to compare the mutagenic activity of used crankcase oil (UCO) from diesel and spark-ignition (gasoline) engine passenger cars. UCO samples were obtained during periodic oil changes from 9 spark-ignition and 10 diesel-powered vehicles. Five samples of unused motor oil were also tested. Direct tests of UCO did not detect mutagenic activity in Salmonella typhimurium strain TA-98. Therefore, an extraction procedure was used to concentrate the mutagens and remove interfering chemicals. Extracts were tested both with and without Aroclor-1254-induced rat liver homogenate fraction (S-9). Dose-dependent mutagenicity with and without S-9 was observed in both diesel and spark-ignition engine UCO extracts. Mutagenic activity was also found in unused oil extracts, but it was lower than that in UCO extracts and generally required addition of S-9. The mutagenic potency of diesel UCO extracts was similar to that of gasoline UCO extracts, both with and without addition of S-9. This indicated that potential health risks associated with disposal, handling, and recycling of diesel UCO may not be significantly different from those of UCO from gasoline engines.