Investigation of a Potential Cotumorigenic Effect of the Dioxides of Nitrogen and Sulfur, and of Diesel-Engine Exhaust, on the Respiratory Tract of Syrian Golden Hamsters

This report describes a study by Dr. Heinrich and colleagues to investigate the effects of exposure to NO2 and SO2 or diesel engine exhaust on tumor formation in hamsters. Hamsters were exposed for 6, 10.5, 15, or 18 months to whole diesel exhaust, diesel exhaust without particles, or a mixture of NO2 and SO2. Additional groups of animals exposed to each test atmosphere were also injected with 3 or 6 mg of diethylnitrosamine/kg body weight to evaluate any enhancing effect of diethylnitrosamine on exposure-related changes. Morphological changes in the respiratory tract were evaluated and any differences in tumor rates were compared between groups.