Data from short-term tests on motor vehicle exhausts

Abstract

The mutagenicity of motor vehicle exhausts has been studied by using Salmonella typhimurium strains TA 98 and TA 100. Acetone extracts of the particulate phase and the gas phase have been tested in the presence and absence of a metabolizing system (S9). The particulate phases from medium- and heavy-duty diesel vehicles were tested. The vehicles were driven according to a modified 13 mode test, and the particulate phase was sampled at mode 6 (maximum load and intermediate engine speed) and mode 12 (10% load and rated speed). In mode 6 all vehicles gave approximately the same mutagenicity in strain TA 98 (50,000-90,000 revertants/kW-hr) as well as in TA 100 (200,000-360,000 revertants/kW-hr). A higher mutagenic effect, in some cases up to 10 times, was seen with mode 12.Light-duty vehicles of different year models were tested using different fuel/engine combinations. The vehicles were driven according to FTP 72 or ECE driving cycle. Cold starts at two different temperature levels, approx. 0 degrees C and 23 degrees C, respectively, were also compared. Based on the mutagenicity of the particulate extracts (given as revertants per km), the light-duty vehicles could be divided into three main groups. The first group, the high mutagenicity group, giving 100,000-700,000 revertants/km, consists only of diesel cars. In the medium mutagenicity group, giving between 20,000 and 100,000 revertants/km, different gasoline fuels are placed, i.e., leaded and lead-free gasoline as well as alcohol/gasoline fuels. Two other fuels, methanol (M95) and propane (LPG), constitute the low mutagenicity group, giving less than 20,000 revertants/km. Fuels from the medium effect group will produce a particulate phase with low mutagenicity if the vehicle is equipped with a three way catalyst with closed loop, or fuel injection. The cold start temperature did not change this classification, since all samples gave a somewhat higher mutagenic effect at the low temperature. With the ECE driving cycle, much lower mutagenicity was noted with the diesel cars than in the tests with the FTP-72 driving cycle, at least with tester strain TA 98. On strain TA 100 the diesel exhaust samples still showed a much higher mutagenicity than other samples. Acetone extracts of the gas phase from diesel and gasoline exhaust (trapped in ice/water condensers and CO(2)/ethanol condensers) also gave mutagenic effects. The contribution of the gas phase to the mutagenic effects seems to be more important in the absence of S9 and more important in the case of gasoline exhausts.