Results from a Long-Term Carcinogenicity Study in Rats with Intraperitoneal Injection of Soluble Fibrous Dusts

Abstract

This long-term study evaluated the potential carcinogenic effects (mesotheliomas) of various man-made vitreous fibres, when administered intraperitoneally (2–20 injections) in rats. Four new insulation wool fibres (designated M, O, P and V), considered as highly soluble, were tested at dose-levels up to 5000 × 106 WHO fibres. They were compared to crocidolite (dose-level up to 1000 × 106 WHO fibres) and to reference, highly soluble fibre (fibre B, dose-levels up to 5000 × 106 WHO fibres). The tested fibres did not produce notable adverse effects on the basis of mortality, clinical signs and body weight, except at high dose-levels. Histopathological investigations distinguished the various fibres: (i) fibres M and O did not induce mesotheliomas at dose-levels up to 5000 × 106 fibres; (ii) fibres P and V induced up to 16% and 28%, respectively, of mesotheliomas at the same dose-level, i.e. in the same range as for the reference fibre B (18% of animals with mesotheliomas); (iii) 90% of the crocidolite-treated animals displayed mesotheliomas at a dose-level of 1000 × 106 fibres.