Determination of Asbestos in Bulk Materials by Polarized Light Microscopy

— analysis of asbestos in labware in Kyoto University —

Abstract

   Preliminary research on the determination of asbestos in bulk materials by polarized light microscopy was carried out both to assess the current status of the asbestos content of labware in Kyoto University and to validate analytical techniques for asbestos measurement. We detected asbestos (chrysotile, amosite, tremolite) in 14 of 31 samples investigated. Fibrous particles very similar to chrysotile were identified in a sample of heat-resistant material. Because this sample was found to be formed of the natural mineral sepiolite, and also because its optical properties may have changed due to its thermal history, there is a risk of a false positive for asbestos on ordinary observation. Therefore we examined the relationship between heat-treatment temperature and dispersion staining as well as the extent of color changes in multiple immersion liquids for chrysotile and sepiolite. On this basis, we carried out discriminant analysis for asbestos and non-asbestos by polarized light microscopy. We conclude that the fibrous chrysotile-like particles in the heat-resistant sample were sepiolite partially changed by heating.