Comparative studies with natural and man-made mineral fibres in vitro and in vivo

Several types of fibrous dusts have caused lung tumours and mesotheliomas in humans and/or in laboratory animals. In order to study the effects of the fibrous dusts, cell toxicity and transformation were investigated. The cell systems used included epithelial lung cells from the Syrian golden hamster, human bronchoepithelial cells and mesothelial cells from the rat. In general, the natural mineral fibres showed a higher cytotoxic and transforming potency per fibre than did the man-made fibres. Nickel powder and nickel oxide were used as well known chemically carcinogenic dusts and titanium dioxide as a negative non-fibrous dust control. The extent of the biological fibre mass, whereas among the natural mineral fibres, crocidolite was more active on the basis of fibre numbers. Corresponding with intraperitoneal carcinogenicity studies, the in vitro studies demonstrated a clear transforming capacity of the naturally occuring mineral fibres. This effects was much less for the glass microfibres, silicon carbide fibres and nickel dusts. In the reaction of the different cell systems to fibre treatment, no systematic differences could be observed.