Documents Kohyama, Norihiko 1 results

The mineral phases and chemical and physical characteristics of the chrysotile-A (12001295), chrysotile-B, crocidolite (12001284), amosite (12172735), and anthophyllite (17068789) samples prepared by the International Union Against Cancer (UICC) in 1966 were examined in this study. Mineral phases were determined through the use of X-ray diffraction (XRD). Anthophyllite, talc (14807966), and nonfibrous minerals were detected in samples of chrysotile-A. The quantity of anthophyllite in chrysotile-A was estimated at 2%. The proportions of chrysotile in chrysotile-A and chrysotile-B were 94% and 92%, respectively. Amosite and crocidolite samples each contained about 1% quartz (14808607). The anthophyllite sample contained about 5% each of chlorite and mica, and about 20 to 30% talc. Overall, the chemical compositions of the samples indicated high purity. Chrysotile-B contained higher concentrations of some constituents than chrysotile-A, while anthophyllite contained high concentrations of oxides, indicating an impurity. Thermal analysis of the chrysotiles and anthophyllite indicated dehydroxidation and recrystallization. No mineral impurities were detected in the amosite and crocidolite samples by thermal analysis. Analytical transmission electron microscopy revealed that the chrysotiles consisted of thin, curly fibrils, fiber bundles, and platy materials, while amosite, crocidolite, and anthophyllite consisted of wider, rectangular fibers. The mean lengths of the chrysotile and crocidolite fibers were shorter and exhibited less variability than those of the amosite and anthophyllite samples. The mean fiber widths of the chrysotiles were less than those of amosite, crocidolite, and anthophyllite. The authors conclude that further study is necessary, since the characteristics of the UICC asbestos samples measured with modern equipment and techniques differ from those that were established years ago.