The purpose for this study was to determine the fibrogenicity of silica (7631869), bentonite (1302789), kaolin (1332587), talc (14807966), vermiculite (1318009), feldspar, and coal in animals by nose only exposures. The cytotoxicity of the same minerals was to be determined in in-vitro tests and an evaluation was to be made regarding the data to provide comparative cytotoxic correlations on fibrogenicity and to develop information which would be useful in interpreting human exposure effects. In-vitro studies showed that bentonite, kaolin, silica, and vermiculite had the greatest hemolytic activity and talc, coal, and feldspar the least. Significant release of the cytosolic enzyme, lactate-dehydrogenase, was observed in-vitro with kaolin, silica, and vermiculite. Two lysosomal enzymes, beta-glucuronidase and beta-N- acetylglucosaminidase, were significantly released after in-vitro treatment with kaolin, silica, vermiculite, and talc. In-vivo studies showed that silica, kaolin, bentonite, vermiculite, and feldspar all induced an initial acute pulmonary response; however, there appeared to be no correlation between this acute response in-vivo and the chronic pulmonary affects of these minerals. These studies also indicated that the initial pulmonary response reflected in in-vitro studies was not correlated with the chronic response of the dust.
Division of Respiratory Disease Studies, NIOSH, U.S. Department of Health and Human Services, Morgantown, West Virginia