Pleural and Parenchymal Responses in Rats to Short-Term Inhalation Exposures to Erionite, Crocidolite, Chrysotile, Silica and Titanium Dioxide

Abstract

The ultimate assay for determining the pathogenicity of respirable fibrous materials is a rodent 2-year inhalation lifetime study. Under these circumstances, asbestos exposure gives rise to lesions in rats which are similar to those seen with human occupational exposures, i.e., interstitial fibrosis, primary lung cancer, and mesothelioma (Wagner et al., 1974). This assay presents the fibrous material in a physiological manner and in relevant doses. However, the assay is costly and time consuming, and it would be impractical to test all the fibrous materials available commercially or being developed for commercial exploitation in this manner. Alternative assays are in vitro cell systems and implantation or inoculation studies in animals. These approaches have limitations. In vitro cell systems monitor cell/fiber interactions over a short period, thus neglecting the important effects of residence in lung tissue and interactions with host factors such as the immune system. These cell systems do provide a practical method for alerting one to the overall potential pathogenic nature of the material, but it is frequently difficult to relate this activity in terms of fibrogenicity or carcinogenicity.

Copyright for this contribution: U.S. Government