The Effects of Oxidation on the Chemistry and Toxicity of Two-stroke Engine Exhaust Particles

ROBERT D. MCWHINNEY(1), Jay G. Slowik(1), Jonathan P.D. Abbatt (1)

(1) Dept. of Chemistry and SOCAAR, University of Toronto

     Abstract Number: 284
     Last modified: November 9, 2009

Abstract
Inhalation of particulate matter (PM) is well known to cause numerous adverse health effects. Oxidative stress responses have been measured in biological systems exposed to PM and are strongly implicated in the toxic mechanism of PM inhalation. One chemical mechanism by which PM can induce oxidative stress is through redox cycling, in which a component of the particle acts to catalytically transfer electrons from biological reducing agent to oxygen, generating reactive oxygen species in the cell. A metric of redox cycling, the dithiothreitol (DTT) assay, has been correlated to biological measures of toxicity. Quinones have been indentified as particularly active as redox cycling agents, and are generated from the heterogeneous oxidation of PAHs. PAH-rich diesel exhaust particles, upon dark reaction with ozone, have been demonstrated to increase in toxicity as measured by the DTT assay.
Exhaust from a two-stroke gasoline engine is exposed to ozone in a flow tube. Filter samples of fresh and oxidised engine particles are obtained to monitor particle toxicity using the DTT assay. Unique to this study is the real-time characterisation of PM chemical composition with an Aerodyne Time-of-Flight Aerosol Mass Spectrometer (ToF-AMS). Chemical and toxicity changes are compared to uncover what changes in the organic aerosol chemistry are resulting in the associated changes in PM toxicity.