Coalinga Fibre - A Short, Amphibole-Free Chrysotile Part 1: Evidence for a Lack of Fibrogenic Activity

Abstract

Controversy continues to surround the biological activity of short fibre chryso tile. This is largely due to a lack of studies in which there has been 'pure expo sure' to this material. Most of the exposures studied, whether in humans or animals, have been confounded by the additional presence of long fibre chry sotile and/or amphibole. This report presents the morphological and morpho metric findings of a lifetime inhalation study of F344 rats exposed to three types of chrysotile. The first, from Coalinga, Calif., is comprised of fibres that are almost all less than 5 μm in length and is not contaminated with amphi bole. The other two, the Jeffrey fibre and the UICC/B standard, are both Canadian long fibre preparations with a minor degree of amphibole contami nation. Exposed animals displayed no fibrosis following exposure to Coalinga chrysotile but showed fibrogenic responses with both Canadian fibres.