Intraperitoneal injection studies for the evaluation of the carcinogenicity of fibrous phyllosilicates

A review of the inhalation studies performed with crocidolite shows that, in the case of mineral fibres, realistic exposure can lead to irrelevant (false negative) results. The intraperitoneal test with mineral dusts in rats is much more sensitive and the qualitative analogy to the carcinogenicity found in the lung is good. Evaluation of the carcinogenicity of different fibre types according to their activity after intrapertioneal injection may be justified. New measurements of fibres tested in earlier experiments indicate that at least 0.5 to 1 x 10 high 9 fibres longer than 5 mym should be injected for a negative result to become valid. About 10 high 9 fibres of chrysotile Calidria did not show a clear carcinogenic effect in contrast to 4 x 10 high 7 fibres of UICC chrysotile from Canada which induced tumours in about 30 per cent of the rats.