Intratracheal instillation of automobile exhaust condensate in Syrian golden hamsters.

Male Syrian golden hamsters were intratracheally instilled with automobile exhaust condensate at dose levels of 0.306, 0.613, 1.25, 2.5, and 5.0 mg/hamster once a fortnight for 78 weeks. While a total of six tumors were found in the trachea and lung, hamsters treated with the vehicle only showed no respiratory tract neoplasms. Bronchiogenic adenomatous proliferations and hyperplastic nodules in the lung occurred in all groups, with a significant difference in incidence being seen between the high-dose groups and the controls.