Co-exposure between asbestos and inorganic particles and risk of lung cancer in the ARDCO study

For lung cancer, there is evidence of a joint effect between smoking and asbestos. However, little is known about a possible joint effect between asbestos and other inorganic particles. The objective was to study the association between lung cancer and occupational asbestos exposure in the abscence or presence of additional exposure to inorganic particles. A 12-year follow-up study was conducted to analyse lung cancer incidence in a cohort of 13,814 retired workers previously exposed to asbestos and volunteering to participate in a multiregional survey program (Asbestos Related Diseases Cohort, ARDCO) from October 2003 and December 2005. From complete work histories, occupational exposure to asbestos, mineral wools, refractory ceramic fibers, crystalline silica and cement dust were assessed by job-exposure matrices. Association between lung cancer and occupational asbestos exposure was estimated by Cox model, adjusted for smoking, in the presence or absence of additional exposure to inorganic particles. At the end of follow-up (April 2015), 364 incident lung cancer cases were diagnosed. The association between lung cancer and asbestos exposure was statistically significant (HR=2.3 [95% CI=1.0-5.4]), but it seemed increased in the presence of additional exposure to mineral wools (HR=3.1 [95% CI=1.4-7.2]). However, at equal asbestos exposure level, the association was no longer different in the presence of additional exposure to mineral wools. Other inorganic particles did not modify the association between asbestos and lung cancer. Mineral wools may modify the association between lung cancer and asbestos. However, subjects exposed to both factors seemed also to be more exposed to asbestos.