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.