Rationale: Occupational coexposure to asbestos and other fibers or particles could modify the carcinogenicity of asbestos with regard to pleural mesothelioma.
Objectives: To estimate associations between pleural mesothelioma and occupational mineral wool and silica exposure and to study the impact of occupational coexposure on the risk of pleural mesothelioma.
Methods: A total of 1,199 male cases and 2,379 control subjects were included in a French pooled case-control study. Complete job histories were collected, and occupational exposure to asbestos, mineral wool (MW), and silica were assessed by three French job exposure matrices. Unconditional logistic regression models adjusted for age, birth date, and occupational asbestos exposure were used to estimate odds ratios (OR) and 95% confidence intervals (CIs).
Measurements and main results: A significant association between mesothelioma and MW exposure was observed after adjustment for occupational asbestos exposure. OR for subjects exposed to less than 0.01 fibers·ml(-1)·yr(-1) was 1.6 (95% CI, 1.2-2.1) and increased to 2.5 (95% CI, 1.8-3.4) for subjects exposed to more than 0.32 fibers·ml(-1)·yr(-1). All ORs for silica exposure were around the null. Coexposure to either asbestos and MW or asbestos and silica seemed to increase the risk of pleural mesothelioma. ORs were 17.6 (95% CI, 11.8-26.2) and 9.8 (95% CI, 4.2-23.2) for subjects exposed to both asbestos and MW and for subjects exposed to both asbestos and silica, respectively, compared with 4.3 (95% CI, 1.9-9.8) for occupational asbestos exposure alone.
Conclusions: Our results are in favor of an increased risk of pleural mesothelioma for subjects exposed to both asbestos and MW or asbestos and silica.