Detection of mineral fibre carcinogenicity with the intraperitoneal test--recent results and their validity

The general experimental design of intraperitoneal (i.p.) carcinogenicity studies with inorganic fibres in rats is described. In a current study, in addition to glass microfibres, size-separated fine respirable fractions of commercial insulation wools (MMVF-11 and MMVF-21) also induced mesotheliomas after i.p. injection of 0.4 x 10(9) fibres. These fibre samples were also tested in inhalation studies. A special glass fibre type (B-01), which is of interest because of its low biodurability, induced tumours with 25- and 50-fold higher doses. The i.p. model has been proved to be much more specific and sensitive for testing the carcinogenicity of inorganic fibres than the inhalation model. Objections to this conclusion are cited and discussed with alternative arguments.