Biological activity of exhaust emissions from two after‐treatment device‐equipped light‐duty diesel engines

Abstract

Whole diesel exhaust has recently been classified as a probable carcinogen, and particulate exhaust, known to contain mutagenic and carcinogenic chemicals, has clearly shown to be mutagenic in several genotoxicity studies. The goal of this study was to determine whether, and to what extent, the installation of some exhaust aftertreatment‐devices on two light‐duty diesel engines (1930 cc and 2500 cc) EGR‐valve equipped may reduce mutagenic activity associated to particles collected during both U.S.A. and European driving cycles. Exhaust particles collected onto Teflon‐coated filters were sonicated and Soxlhet extracted (benzene and acetone) and the mutagenicity of the SOF was analysed using Salmonella/microsome test system (TA98 and TA100 strains ‐/+S9 fraction). In accordance with literature data, the strongest mutagenicity was revealed by TA98 strain without enzymatic activation, suggesting a direct‐acting mutagenicity prevalence in diesel particulate. The relationship between this mutagenic activity and NOx concentration suggests that this finding is perhaps attributable to the existing nitroarenes fraction even using EGR‐valve. The 2500 cc engine revealed a two‐fold mutagenic activity compared to the 1930 cc engine both EGR‐valve equipped, while an opposite result was found in particulate matter amount The use of non‐catalytic ceramic trap induces a decrease of the 2500 cc car particle mutagenic activity, while an enhancement in the 1930 cc engine was shown. The catalytic converter and the electrostatic filter installed on the 2500 cc engine yield to a light particle amount and SOF mutagenicity decrease. A greater engine stress was obtained using European driving cycle, which caused the strongest mutagenicity /Km with respect to U.S.A. cycle. These preliminary results point out the usefulness of mutagenicity tests in the research of even new more efficient automotive emission aftertreatment devices.