Coalinga Chrysotile: A Short Fibre, Amphibole Free, Chrysotile: Part V - Lack of Amphibole Asbestos Contamination

Abstract

Exposure to asbestos in the indoor built environment has been a concern for many years. The most common exposures in that setting are to short ultra-thin, naturally defibrillated form of fibrous asbestiform chrysotile and possibly trace amounts of short, non-asbestiform amphibole. Coalinga chrysotile is a short fibre mineral that was mined from a large ore body in California. It has been investigated in considerable detail since, although it is widely believed to be amphibole free, evidence for this has not hitherto been summarised. Analytical results from investigations that directly searched for amphiboles and geological studies from which the presence or absence of amphibole can be inferred, have indicated that Coalinga chrysotile is free of amphibole asbestos. Indeed, numerous investigations, performed over almost half a century, using a variety of techniques including the most sensitive methods, and studying many thousands of samples have failed to find any amphibole asbestos in Coalinga chrysotile. Only very rarely have non-asbestiform, “non-friable” amphibole (so-called cleavage fragment) minerals been found in the New Idria serpentine body but away from the ore zone. A large body of animal and human evidence indicates such cleavage fragments lack biological potential.