Chronic inhalation of cobalt oxide and cigarette smoke by hamsters.

Exposure of hamsters to CoO aerosol (10 g/L, 7 hrs./day, 5 days/week) caused pneumoconiosis but affected neither the life span nor the incidence of other than pneumoconiotic lesions. No carcinogenic effects of CoO were observed. While cigarette smoke exposures significantly increased the incidence of certain types of other than pneumoconiotic lesions including tumors, they also increased the life span of the smoke-exposed animals significantly. The latter phenomenon may account for the higher tumor incidence in the smoke-exposed animals. No effect of the smoke exposures on incidence and degree of pneumoconiosis was observed. The mean body weights of the smoke-exposed groups were significantly reduced.