Mesothelioma risk among those exposed to chrysotile asbestos only and mixtures that include amphibole: a case–control study in the USA, 1975–1980

Source avec lien : Occupational and Environmental Medicine, 78(3), . 10.1136/oemed-2020-106665

L’exposition professionnelle à l’amiante est liée au mésothéliome. Cependant, on ne sait pas encore si l’exposition à l’amiante chrysotile uniquement est associée au risque de mésothéliome, et l’hétérogénéité du risque selon les différents types/longueurs de fibres reste incertaine. Nous avons cherché à savoir si le risque de mésothéliome diffère entre les travailleurs exposés uniquement à l’amiante chrysotile et ceux exposés au chrysotile et aux amphiboles ≥1 (amosite, trémolite, anthophyllite et crocidolite) au cours de leur vie professionnelle.

Occupational asbestos exposure is causally linked to mesothelioma. However, whether exposure to only chrysotile asbestos is associated with mesothelioma risk, and the heterogeneity in risk by different fibre types/lengths remains unclear. We investigated whether mesothelioma risk differs among workers exposed to only chrysotile asbestos compared with chrysotile and ≥1 amphibole (ie, amosite, tremolite, anthophyllite and crocidolite) over the working lifetime. We analysed next-of-kin interview data including occupational histories for 580 white men (176 cases and 404 controls) from a case–control study of mesothelioma conducted in the USA in 1975–1980. Asbestos exposure was determined by an occupational hygienist using a job-exposure matrix and exposure categories included chrysotile only and nine chrysotile–amphibole mixtures. Logistic regression models were used to estimate the ORs and 95% CIs of mesothelioma, comparing each asbestos category to the unexposed group, adjusted for age at death and data source. Analysis of contrasts was used to assess overall heterogeneity and pair-wise differences in risk. Exposure to long and short chrysotile only was associated with increased mesothelioma risk compared with the unexposed (OR=3.8 (95% CI 1.3 to 11.2)). The complex mixture of extra-long amosite, short and long chrysotile, tremolite and anthophyllite was associated with the highest risk (OR=12.8 (95% CI 4.1 to 40.2)). There was evidence for overall heterogeneity among the asbestos exposure categories (p heterogeneity=0.02). However, the lower risk observed for exposure to chrysotile only compared with the complex mixture was not significant (p difference=0.10). Our findings suggest that policies aimed at regulating asbestos should target both pure chrysotile and mixtures that include amphibole.

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