Biological effects of naturally occurring and man-made fibres: in vitro cytotoxicity and mutagenesis in mammalian cells

Abstract

Cytotoxicity and mutagenicity of tremolite, erionite and the man-made ceramic (RCF-1) fibre were studied using the human– hamster hybrid A L cells. Results from these fibres were compared with those of UICC Rhodesian chrysotile fibres. The A L cell mutation assay, based on the S1 gene marker located on human chromosome 11, the only human chromosome contained in the hybrid cell, has been shown to be more sensitive than conventional assays in detecting deletion mutations. Tremolite, erionite and RCF-1 fibres were significantly less cytotoxic to A L cells than chrysotile. Mutagenesis studies at the HPRT locus revealed no significant mutant yield with any of these fibres. In contrast, both erionite and tremolite induced dose-dependent S1 − mutations in fibre-exposed cells, with the former inducing a significantly higher mutant yield than the latter fibre type. On the other hand, RCF-1 fibres were largely non-mutagenic. At equitoxic doses (cell survival at ∼ 0.7), erionite was found to be the most potent mutagen among the three fibres tested and at a level comparable to that of chrysotile fibres. These results indicate that RCF-1 fibres are non-genotoxic under the conditions used in the studies and suggest that the high mesothelioma incidence previously observed in hamster may either be a result of selective sensitivity of hamster pleura to fibre-induced chronic irritation or as a result of prolonged fibre treatment. Furthermore, the relatively high mutagenic potential for erionite is consistent with its documented carcinogenicity. © 1999 Cancer Research Campaign

Genetic Predisposition to Fiber Carcinogenesis Causes a Mesothelioma Epidemic in Turkey

“…Erionite is a chemical carcinogen and mutagen (11) and animal experiments have shown that erionite is more potent than crocidolite in causing malignant mesothelioma (12). It has been suggested that erionite increases the balance between cell proliferation and apoptosis and that a lower amount of erionite compared with crocidolite asbestos is required to induce c-Jun mRNA, a mechanism that has been linked to fiber carcinogenesis (13).…”

Evaluation of hazardousness of refractory fibers by cell magnetometry

“…It is thought that exposure to harmful substances causes delayed relaxation through their physical and chemical effects on the cytoskeleton (Cohen, 1973;Brain et al, 1988;Nemoto et al, 1989). Okayasu et al (1999) conducted cytotoxicity and mutagenicity studies of RF and erionite, tremolite and chrysotile fibers. The system under study, the human-hamster hybrid AL cell mutation, is known to be more sensitive than conventional assays in detecting specific mutations.…”

The health risk of chrysotile asbestos

“…No indication was provided of the number or size distribution of fibers in the test samples. Using data presented for UICC chrysotile [14], the dose was estimated to be 50 000 fibers/cell in the culture. In humans, even at high exposures, one fiber would be deposited in every 2000 alveoli per day [12 && ].…”