Mutagenicity of Diesel Exhaust Particles from an Engine with Differing Exhaust After Treatments

Abstract

This study was conducted to investigate the effects of engine operating conditions and exhaust aftertreatments on the mutagenicity of diesel particulate matter (DPM) collected directly in an underground mine environment. A number of after-treatment devices are currently used on diesel engines in mines, but it is critical to determine whether reductions in DPM concentrations result in a corresponding decrease in adverse health effects. An eddy-current dynamometer was used to operate naturally aspirated mechanically controlled engine at several steady-state conditions. The samples were collected when the engine was equipped with a standard muffler, a diesel oxidation catalytic converter, two types of uncatalyzed diesel particulate filter systems, and three types of disposable diesel particulate filter elements. Bacterial gene mutation activity of DPM was tested on acetone extracts using the Ames Salmonella assay. The results indicated strong correlation between engine operating conditions and mutagenic activity of DPM. When the engine was fitted with muffler, the mutagenic activity was observed for the samples collected from light-load, but not heavy-load operating conditions. When the engine was equipped with a diesel oxidation catalyst, the samples did not exhibit mutagenic activity for any of four engine operating conditions. Mutagenic activity was observed for the samples collected when the engine was retrofitted with three types of disposable filters and sintered metal diesel particulate filter and operated at light load conditions. However, those filtration systems substantially reduced the concentration-normalized mutagenic activity from the levels observed for the muffler.

The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health (NIOSH). The mention of any company names or products does not imply an endorsement by NIOSH or the Centers for Disease Control and Prevention, nor does it imply that alternative products are unavailable, or unable to be substituted after appropriate evaluation. We acknowledge support from the NIOSH Pittsburgh Research Laboratory Diesel Team and Lake Lynn Laboratory personnel for their help and assistance in the experimental phase of this study.