Coalinga fibre: A short-fibre, amphibole-free chrysotile - Part 4: Further evidence for a lack of fibrogenic and tumorigenic activity

Coalinga chrysotile is a short-fibre, amphibole-free asbestos from California. It is prototypic of many other short-fibre chrysotiles found elsewhere in the world. Since short-fibre chrysotile is the most common form of asbestos, a deeper understanding of the biological effects of Coalinga chrysotile should provide important insights into what many regulatory agencies are now calling a major health hazard, the reasoning behind this being that these agencies consider all fibre types to be biologically equivalent. Previously the potential fibrogenicity of Coalinga chrysotile had been assessed in two inhalation bioassays. The first was conducted in 1978 at the National Institutes of Environmental Health and Sciences (NIEHS) in the United States. Our earlier analysis of this investigation demonstrated that Coalinga chrysotile was not fibrogenic. The second inhalation bioassay was conducted in 1983 at the Fraunhofer Institute in Germany by Muhle et al. Unfortunately, in their final analysis, data were presented in a way that did not allow one to determine whether Coalinga chrysotile was fibrogenic or not. Because of this, the slides have been re-examined using the Wagner scoring system, which is designed specifically to assess fibrosis. The findings of this re-evaluation clearly demonstrate, yet again, that Coalinga chrysotile is not fibrogenic in these assays. Copyright (C) 2002 S. Karger AG, Basel.