Carcinogenicity and cocarcinogenicity of chromium carbonyl in heterotopic tracheal grafts

Tracheal grafts, implanted s.c. on syngeneic rats, were used as a bioassay for carcinogenicity or cocarcinogenicity of chromium carbonyl (CC). After a period of revascularization, the lumens of 22 grafts were filled with an agar suspension of 2.5 mg of CC. Twenty-two grafts were filled wit a suspension of 2.5 mg of benzo(a)pyrene (BP) and a mixture of the two chemicals was placed in 24 other grafts. Four controls were exposed to the vehicle only. Eight squamous cell carcinomas developed in the tracheas treated with BP alone and 10 similar neoplasms arose in the CC-BP treated group, but 3 of those induced by CC-BP had metastasized by 9 months. CC alone induced carcinomas in two grafts. The data indicate that this metal carbonyl is a carcinogen that can act synergistically with BP and demonstrate the utility of the technique as an efficient tissue-specific bioassay.