Influence of rat lung and liver homogenates on the mutagenicity of diesel exhaust particulate extracts

Abstract

Diesel exhaust particles collected from an automobile operated on a chassis dynomometer were extracted with dichloromethane and evaluated for mutagenicity in Salmonella typhimurium. The extracts were mutagenic to strains TA-100, TA-98, TA-1538, and TA-1537 and contained both direct and indirect-acting mutagens. The promutagens in the extract were activated by the addition of Aroclor 1254 induced and uninduced rat liver S-9, but not uninduced lung S-9. All three S-9 preparations, as well as Aroclor induced liver S-9 without NADP, bovine serum albumin, and fetal calf serum, significantly decreased the direct mutagenicity in TA-100 suggesting that protein binding of mutagenic components was at least partially responsible. Results of studies using the mixed-function oxidase inhibitor SKF 525-A suggest a minor role of metabolism in detoxifying mutagens in the extract. The inability of lung S-9 to activate promutagens in the extract and protein binding of direct-acting mutagens may be important modifying factors to consider in estimating the potential human inhalation health hazards of diesel particulate exhaust emissions.