Chronic Inhalation Toxicity of Fibrous Glass in Rats and Monkeys

Abstract

Numerous reports have shown that fibrous glass has the potential to cause fibrogenic and carcinogenic responses in test animals. The experiments producing significant response have, however, used unrealistic routes of exposure. The increased demand for fibrous glass for insulating purposes where respirable fibers may exist presents considerable concern for potential health problems. Therefore, a long-term inhalation study was conducted with F344 rats and cynomolgus monkeys exposed in treatments characterized by fibers of varying geometry and mass concentrations. A workweek type of exposure (7 hours/day, 5 days/week) was maintained for 18 months with monkeys and 21 months with rats, which were subsequently held to 80% mortality. The evaluation of response included life table analysis, body weights, clinical signs, hematological testing, respiratory function, ophthalmic examinations, clinical biochemical analysis, and gross and microscopic pathological examinations. Both species demonstrated pulmonary macrophage aggregates and granulomas containing fibrous glass. The rats had grossly visible pleural plaques, which were not seen in the monkeys. There was no evidence of pulmonary or mesothelial carcinogenicity or fibrogenicity in either species. There were no other significant responses with the exception of a statistically increased mononuclear cell leukemia in each fiber-exposed rat group.