A review of experimental evidence for the carcinogenicity of man-made vitreous fibers.

This paper reviews experimental studies on the carcinogenicity of man-made vitreous fibers. Long-term inhalation studies using several animal species and dust preparations of fibrous glass, rock wool or slag wool have produced little evidence of pulmonary fibrosis or pulmonary tumors. While some intratracheal injection studies found almost no pathological changes in lung tissue, some showed that pulmonary fibrosis can occur. Only one intratracheal injection study has reported that vitreous fibers can be carcinogenic; in contrast, many workers have reported that, following intrapleural or intraperitoneal injection, man-made vitreous fibers are highly carcinogenic, and tumor production appears to be closely related to fiber size. In vitro tests confirm that vitreous fibers can be toxic and can cause neoplastic transformation of cultured cells. The discrepancies between some experimental studies probably result from the relatively high solubility of most vitreous fibers. It seems likely that, while these fibers can survive in body cavities long enough to cause tumor production, they dissolve in lung tissue fast enough to have relatively little harmful effect. Rock-wool fibers appear more durable than glass- or slag-wool fibers, and, with similar fiber numbers and sizes in any dust cloud, this material is the most likely to have harmful potential.