The available studies therefore provide indirect evidence of a lower risk of mesothelioma from  exposure to chrysotile compared to exposure to amphibole, or to mixed commercial asbestos fibers which likely included amphibole asbestos. One approach we have used to address in part these methodological limitations of SMR/SIR-based studies of mesothelioma is a systematic review of the ratio between deaths from mesothelioma (or pleural cancers for studies conducted before the use of the 10th version of the International Classification of Diseases (WHO, 1993)) and total deaths in the asbestos-exposed occupational cohorts (McCormack et al., 2012). Given the long latency of mesothelioma, such a ratio should be adjusted for age at death, but this information is not available from the published reports of relevant studies. Nevertheless, the results of 56 cohorts occupationally exposed to commercial asbestos, of which 22 were comprised of workers exposed (uniquely or predominantly) to chrysotile, 8 of workers exposed to amphiboles, and 26 of workers exposed to mixed or unknown type of fiber, show a strong correlation between fiber type and proportion of pleural cancer deaths over the total (Fig. 1, p-value of difference=0.00003). Where the ratio falls below 1% the majority of commercial asbestos-exposed occupational cohorts were chrysotile exposed, whereas the majority of amphibole and mixed exposure cohorts had ratios above 1% (ref).

• By Paolo Boffetta, Kenneth A. Mundt, William J. Thompson
• For more inforamtion, please visit  https://www.sciencedirect.com/science/article/pii/S0041008X18304277