Studies on genotoxicity of orally administered crocidolite asbestos in rats: implications for ingested asbestos...

The early genotoxic action of oral exposure to UICC crocidolite asbestos fibres was studied in different short-term tests. Fischer-344 rats were gavaged with 50 mg/b.w.kg untreated asbestos fibres and fibres which had been allowed to adsorb benzo(a)pyrene molecules from extremely low concentration (0.25-2.5 microg/ml) aqueous solutions. This system can be considered a model for the drinking of potable water contaminated by asbestos fibres together with biologically active organic micro-pollutants. The Ames Salmonella mutagenicity assay was performed on concentrated urine and serum samples of treated animals. The formation of micronuclei and sister chromatid exchanges was also studied in the bone marrow of the exposed rats. The micronucleus analysis indicated marginal genotoxic activity only upon treatment with crocidolite prepared from the solution of 1 microg/ml. A dose-dependent increase was, however, demonstrated in the sister chromatid exchange frequency upon treatment with benzo(a)pyrene coated fibres. These experiments suggest the acute cogenotoxic activity of such fibres in orally exposed animals.