Cause-specific mortality among workers in asbestos mining and enrichment factories (Asbest Chrysotile Cohort Study) compared with the general population of Sverdlovsk Oblast, Russian Federation

Objectives: Complementing the previously published cohort-internal comparison we hereby compare the cause-specific mortality in workers of the Asbest Chrysotile Cohort study (ACC) with the general population of Sverdlovsk Oblast where the mine and factories are located. Methods: The ACC cohort database and the regional Federal State Statistic Service for the Sverdlovsk Oblast population were used. We calculated sex-specific standardized mortality ratios (SMRs) and 95% confidence intervals (CI) for the main ICD-10 disease groups and for selected cancer sites for the populations ≥ 15 years from 1980 to 2015. In relation to exposure, we applied the Sverdlovsk rates to the person-years in each exposure category to obtain expected numbers of lung cancer deaths. For comparing types of ACC workers (mine, enrichment factories, both), we calculated lung cancer SMRs in men by duration of employment (< 5 years, 5–14 years, and ≥ 15 years) and start of employment (before or after 1975) with miners as reference in each stratum. Results: Overall mortality of men in the ACC was reduced by 14%, mainly because of the most common cause of death, circulatory disease; this effect was much weaker in women. Elevated mortality was observed for both sexes from diseases of the digestive system (10–30%) and blood and blood forming organs (121–181%). Lung cancer mortality in men was increased from the 3rd quartile of chrysotile containing dust and in the highest quartile with SMR 1.30, 95% CI 1.07–1.57, while the increase in high exposed women was not reaching statistical significance (SMR 1.69, 95% CI 0.87–2.96). No increased SMRs were seen for laryngeal, stomach or ovarian cancers. Male factory workers first employed before 1975 had higher lung cancer mortality compared to miners, but not when employed after 1974. Conclusions: The observed excess in lung cancer confirms previous observations in the ACC. Risk management measures in the enrichment factories may have reduced the lung cancer risk to the level of the miners in recent decades.