The Chemical Toxicology of Ambient Air Pollutants

Many of the adverse effects of ambient air pollution have been attributed to reactions of chemical species generated from fossil or biogenic fuel combustion. This review focuses on two reactions: ( a ) a prooxidant reaction, in which oxygen is reduced to hydrogen peroxide, and ( b ) covalent bond formation between electron-rich centers on biological targets with reactive compounds called electrophiles. Prooxidants were found to be concentrated in the particulate matter (PM) fraction of ambient air in the Los Angeles Basin with electrophiles concentrated in the volatile organic compound (VOC) fractions. Actions on mouse macrophages indicated the adverse effects to be mostly attributed to the PM, with anti-inflammatory actions to the VOC fraction. The latter observation does not include, however, the adverse effects of VOCs associated with the transient receptor potential (TRP) calcium channels on epithelial cells, a perspective that needs further investigation.