Diesel emissions are known to contain mutagenic and carcinogenic chemicals. Reduction of diesel emissions may be accomplished through installation of various kinds of catalytic traps or oxidizers in the exhaust train. This project examined two relevant aspects of this problem. The first objective was to determine whether, and to what extent such traps may reduce the emission of mutagenic chemicals into the environment. The second objective was to examine the effect of fuel formulation on mutagenic activity associated with the particulate phase of diesel exhaust. In the studies of the effectiveness of particulate trap oxidizers, exhaust particles were collected from diesel automobiles, with and without traps, at the Southwest Research Institute (SwRI) at San Antonio, Texas. Mutagenesis tests were conducted using the Ames Salmonella bacterial test system on extracts of the particles. The mutation rate was calculated in terms of mutants per mile of travel during a set of standard test cycles. The results indicated a two to twenty-fold reduction in particle-associated mutagenic activity present in the exhaust, which could be attributed to a reduction by the traps of particulate emission. There was no change in the specific mutagenic activity (revertants / microgram of soluble organic fraction, SOF) of the material extracted from particles collected with or without the oxidizer traps. Since most of the mutagenic and carcinogenic activity in diesel exhaust has been shown to be associated with the particulate phase, these studies indicate that installation of exhaust traps on diesel powered vehicles may substantially reduce the emission of carcinogenic materials into the environment. For the studies of the effect of fuel formulation on emission of mutagenic material by diesel engines, particles were collected from a heavy-duty engine (Cummins NTCC 400) on a test stand at the SwRI. Fuel variables were percent aromatic content, weight-percent sulfur and 90% boiling point. The results indicated a positive correlation between the aromatic content of the fuel and the emission of particle-associated mutagenic material, calculated as mutants/hp-hr, but no such association between either sulfur content or 90% boiling point of the fuels tested. A limited number of samples were also collected from the automobiles while burning high or low aromatic fuels but the data were not sufficient to draw any conclusions.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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