Interaction between fibrous dust and cells in vitro.

Studies carried out jointly with macrophages, fibroblasts and epithelial cells in vitro, have shown that the long fibers of asbestos or glass are incorporated in a special way. Phagocytosis of the long fibers is delayed and/or remains incomplete. Incomplete incorporation of the fiber causes a localized discontinuity in the cell membrane. There results continuous liberation of intra-cellular enzymes, which is compensated for by an increasing glycolytic metabolism. The effect of fibrous dusts cannot be compared with those of granular SiO2-dusts. Fibrous dusts, e.g. asbestos and glass fibers, induce the formation of polykaryotic giant cells by way of fusion; asbestos possibly also causes the interspecific fusion of cells. There are indications that in the process of asbestos induced cell fusioning integrated virus genomes are activated and infectious virus are released. The interaction between the cell and fiber causes a chronic irritation of the cell, which is discussed as a factor for tumour induction. There seems to be a causal relationship between the fibrogenic and carcinogenic effects of anorganic dusts and their shape, i.e. their length and diameter, regardless of their chemical composition. Thus the fibrogenic and carcinogenic effect is limited by a minimal length and a maximal diameter.