Is adjustment for smoking needed in a cohort study of cancer mortality among chrysotile asbestos factory and mine workers?

Introduction A retrospective cohort study of 35 840 employees is currently being conducted in a chrysotile mine and its processing facilities in Asbest, the Russian Federation. The primary aim is to quantify exposure-response relationships for cancers potentially associated with chrysotile exposure. Some of those cancers are also tobacco-related; however individual-level information on tobacco use is not available for the full cohort. To address this gap, a cross-sectional study of current and retired workers from JSC Uralasbest was conducted to assess the relationship between smoking status and workers' exposure to chrysotile. Methods Self-administered questionnaires were completed by current workers during meetings organized by occupational safety specialists. Retired workers filled in questionnaires during Veterans' meetings or were interviewed via telephone or at home. Estimates of exposure to chrysotile were available for 999 current and 3795 retired workers who were linked to the cohort study. Results Among the 7451 respondents (n=3698 men and n=3753 women), 66% of men and 9% of women were ever-smokers. Smoking prevalence was stable across birth decades in men, but increased from