The Mutagenicity of Mineral Fibers

Abstract

Asbestos fibers are carcinogenic to both man and experimental animals. At present the cellular and molecular mechanisms for fiber carcinogenesis, however, are not entirely clear. Various in vitro and in vivo studies have identified several factors that may influence the biological effects of mineral fibers. Fibers that are long and thin are more carcinogenic than fibers that are short and thick (Stanton et al, 1977). In vitro studies using oncogenic transformation as an endpoint have demonstrated that asbestos fibers can induce malignantly transformed foci in certain rodent cells (Hesterberg et al, 1984) and that asbestos fibers, in combination with either benzo[a]pyrene (Brown et al, 1983) or radiation (Hei et al,1985, 1989) can synergistically enhance the oncogenic transforming activity of these agents. Although several types of asbestos fibers have been shown to induce chromosomal aberrations and sister chromatid exchanges in both rodent and human cells (Jaurand et al, 1986; Lechner et al, 1985), reports on the mutagenicity of asbestos fibers have largely been negative. Huang et al (1978) reported the only positive mutagenic studies of asbestos fibers, using Chinese hamster lung cells at the hypoxanthine guanine phosphoribosyl transferase (HGPRT) locus with 6-thioguanine as the selective agent.