Asbestos induces aberrant crypt foci in the colon of rats.

The carcinogenicity of asbestos to the gut is controversial. The aberrant crypt focus (ACF) assay is proposed as a test for colon carcinogens. We have scored ACF in the colon of rats and mice, one month after per os gavages with suspensions of asbestos fibers. Crocidolite asbestos 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 times 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 carcinogenic to the colon.