ASBESTOS INDUCES ABERRANT CRYPT FOCI IN THE COLON OF RATS

The carcinogenicity of asbestos to the gut is controversial. The aberr ant crypt focus (ACF) assay is proposed as a test for colon carcinogen s. We have scored ACF in the colon of rats and mice, one month after p er os gavages with suspensions of asbestos fibers. Crocidolite asbesto s induced ACF in the colon of rats in two independent experiments (P = 0.02 and P < 0.01 compared to controls given water), and was ten time s less effective than the carcinogen azoxymethane. Chrysotile asbestos also induced ACF in rats. Neither crocidolite nor chrysotile induced ACF in mice. The data suggest that ingested asbestos may be carcinogen ic to the colon.