Respiratory tract tumors in hamsters induced by benzo(a)pyrene.

Summary Benzo( a )pyrene (BP), prepared as a colloid suspension of fine particles in 0.5% gelatin-0.9% NaCl solution, was administered by intratracheal instillation to 50 male and 50 female syrian golden hamsters. The control group, which consisted of 25 males and 25 females, received 0.5% gelatin-0.9% NaCl solution. The hamsters were treated weekly for 8 weeks and received a total dose of 111 mg of BP. BP induced respiratory tumors in 26 of the 65 hamsters examined. These tumors included squamous cell and anaplastic carcinomas, adenocarcinomas, fibrosarcomas, adenomas, polyps, and papillomas. Each segment of the respiratory tract, with the exception of the bronchi, had a similar incidence of tumors. Only two tumors were diagnosed in the bronchial region. Of 47 control hamsters, 1 animal carried a tracheal polyp. Rate of clearance of BP from lung after a single administration was dependent on the dose of carcinogen. Low doses of BP were cleared rapidly while the weekly dose instilled in this study was retained for a long time.