Tumour induction after intraperitoneal injection of fibrous dusts.

I.p. injection of glass fibres to rats of different strains resulted partly in different tumour rates. Young rats showed more marked coalescence and earlier growth of tumours but also earlier mortality without tumours, as compared with older rats. Haemorrhagic ascites from tumour-bearing rats induced tumours after i.p. injection. Tumours were also obtained after i.p. injection of fibres in European hamsters and rabbits, but these species are less susceptible than rats. Histological studies in rats show that fibrosis is not an absolute requirement for the development of a fibre-induced mesothelioma. After intratracheal instillation of either crocidolite or glass fibres in European hamsters, the respective fibres showed up in the diaphragm and in the spleen.