Metal carcinogenesis. I. Observations on the carcinogenicity of a refinery dust, cobalt oxide, and colloidal thorium dioxide.

Abstract

Summary A metallurgical dust obtained from the dust flue of a nickel refinery was shown to be a locally acting carcinogen in both rats and mice. Sarcomas were induced in two strains of rats at about 45 per cent of the sites of intramuscular injection, with most of the tumors being demonstrably of striated muscle cell origin. Average latent periods approximated 6 months, and metastases occurred frequently. Mice proved less responsive than rats, showing significantly longer latent periods and an absence of metastases. A majority of the mouse tumors appeared to be fibrosarcomas. Similar experiments utilizing single intramuscular injections of cobalt oxide powder gave a 50 per cent local incidence of rhabdomyosarcomas in rats but proved completely negative in the mice tested. Single intramuscular injections of “Thorotrast” failed to induce a local tumor response in either rats or mice. Four out of 50 “Thorotrast”-treated mice developed malignant lymphomas in an average of 457 days. No sarcomas or malignant lymphomas were observed in control animals given injections of Procaine Penicillin G.