RESULTS OF ANIMAL-EXPERIMENTS CONCERNING CARCINOGENIC EFFECT OF FIBROUS DUSTS AND THEIR INTERPRETATION WITH REGARD TO CARCINOGENESIS IN HUMANS

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  • 1 January 1976
    • journal article
    • research article
    • Vol. 162  (5-6) , 467-505
Abstract
After reviewing hypotheses of the pathogenesis of asbestos induced malignant tumors, experimental data on animals were reported. A high incidence of tumors (most of them mesotheliomas) was induced in rats by i.p. injection of fibrous dusts (chrysotile, palygorskite, crocidolite, glass fibers, nemalite). Treatment with 8 types of granular dusts led through high dosage (50-100 mg), to neoplasms in only a small percentage of animals. After i.p. application of 2 mg of chrysotile, crocidolite or glass fibers a tumor incidence ranging from 16-38% was observed and fibrous reaction was slight; 100 mg of milled chrysotile with relatively short fibers (99.8% < 5 .mu.m, 99.5% < 3 .mu.m) caused no asbestosis, but tumors developed in 32% of the rats. I.p. injection of fibrous dusts also induced mesotheliomas in mice, but not in Syrian hamsters or guinea pigs. The fibrous shape of asbestos dust causes its carcinogenic effect and other fibrous dusts can also lead to tumors. Prerequisites are an adequate measure of the fibers and their constancy in the tissue. For these 2 parameters no exact dates exist. A fiber with a diameter < 1 .mu.m and a length < 3 .mu.m exerts a carcinogenic effect. A sequence of other factors has an importance for the dose-effect relationship of fibrous dusts. Material of the fibers plays a role in so far as it defines the effect producing amount of fibers. The relevance of the results of animal experiments to man is discussed espcially with regard to the carcinogenic effect of glass fibers.