Long-term health effects in hamsters and rats exposed chronically to man-made vitreous fibres.

Abstract

As part of a comprehensive inhalation study, groups of Osborne-Mendel rats and Syrian golden hamsters were exposed to several types of airborne man-made vitreous fibres (MMVF). Exposure protocols were ‘nose-only’ 6 h per day, 5 days a week for 24 months, with surviving animals maintained for the rest of their lives. Challenge aerosols consisted of four types of fibrous glass, one refractory ceramic fibre (RCF) and one mineral (slag) wool fibre. UICC crocidolite asbestos and clean air served as positive and negative controls for the inhalation groups. Groups of additional controls were unmanipulated caged animals, intraperitoneally (IP) injected animals, and intratracheally (IT) instilled animals. Animals, after their deaths, were examined macroscopically and microscopically. Fibre lung burdens were significant for the inhalation exposures and related to the mean diameters of the fibrous challenge aerosols. The inhalation exposures with MMVF did not result in any adverse effects except for a mesothelioma of the lung in one hamster exposed to the RCF, not a statistically significant finding. Consistent with other reported work, abdominal mesotheliomas were induced in the groups of hamsters and rats injected IP with 0.45-μm mean diameter fibrous glass, RCF and crocidolite asbestos. With IT instillations, primary lung tumours were found only in hamsters and rats receiving UICC crocidolite; no lung tumours occurred in animals instilled IT with two types of MMVF.