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3094564 
Technical Report 
The Carcinogenicity of Chrysotile Asbestos 
Nicholson, WJ; Landrigan, PJ 
1994 
NIOSH/00224028 
Asbestos and Cancers 
Asbestos and Cancers 
The carcinogenic effects of chrysotile (12001295) asbestos were examined in this review. Studies on the carcinogenic effects of individual asbestos fiber types have been complicated by the fact that few, if any, exposures have been to asbestos purely of one fiber type. Studies have demonstrated that the major Canadian chrysotile ore body was contaminated by a relatively small amount of tremolite (77536686). Amphibole fibers such as tremolite have been found to persist in their native conformation in the lungs years after exposure while chrysotile fibers are easily dissolved in body fluids. Such differences complicate exposure studies of chrysotile based on lung burden data and may have resulted in erroneous conclusions. The latency of cancer development among asbestos exposed individuals has also complicated studies as has the inability of lung burden data to represent actual chrysotile deposition in pleural tissue. Several studies have linked exposure to chrysotile asbestos to the development of mesothelioma and increased mortality from lung cancer has been reported in asbestos workers primarily exposed to chrysotile asbestos. Analysis of data from a cohort of asbestos workers exposed to different asbestos fiber types at different times indicated that the number of predicted cases of mesothelioma increased by 64% based upon exposures to both amosite (12172735) and chrysotile compared with the number calculated based upon exposure to amosite alone. Animal data supporting the human observations were reviewed. The authors conclude that chrysotile asbestos is a human pulmonary carcinogen and presents a substantial risk of mesothelioma as well.