Ames assay chromatograms of extracts of diesel exhaust particles from heavy-duty trucks on the road and from passenger cars on a dynamometer

Particles from diluted exhaust of heavy-duty diesel trucks were collected on filters in the Allegheny Mountain Tunnel on the Pennsylvania Turnpike. Dichloromethane extracts of these particles were separated into 65 fractions by normal-phase high-performance liquid chromatography, and Ames assays (TA98 without activation) were carried out on each fraction. The Ames assay chromatograms for the Allegheny Tunnel sample had the same general shape as the chromatograms of dilution tube samples from diesel-powered passenger cars run on a dynamometer. This suggests that the direct-acting mutagens in Allegheny Tunnel samples from heavy-duty diesels are mainly the same as those in laboratory samples from diesel-powered passenger cars and that the relative proportions of these compounds are similar in the two types of samples. If so, then the implication is that differences in the direct-acting Ames assay mutagenicities of unfractionated extracts reflect differences in the absolute concentrations of all of the mutagens and not in the distribution of mutagens.