8288448 Joint effects of occupational exposure to hexavalent chromium and tobacco smoking on lung cancer risk

<h3>Objective</h3> To provide refined information on joint effects of occupational exposure to hexavalent chromium (Cr(VI)) and smoking on lung-cancer risk. <h3>Material and Methods</h3> This analysis in men included 13,605 lung-cancer cases and 16,451 controls from 14 European and Canadian case-control studies. Job histories were linked to the SYN-JEM assigning occupational exposure to Cr(VI). Various smoking-related metrics and ever/never occupational exposure to Cr(VI) were investigated in relation to lung cancer risk using unconditional logistic regression. Odds ratios (ORs) and 95% confidence intervals (CIs) were adjusted for study centre, age group, and recognized high-risk occupations. Joint effects were evaluated on the additive scale by calculating the relative excess risk due to interaction (RERI) and corresponding 95% CIs using the delta-method. <h3>Results</h3> Ever occupational exposure to Cr(VI) occurred in 30% of cases and 23% of controls. Light and moderate smokers (&lt;20 cigarettes/day) showed OR 13.4, CI 11.9–15.1 not exposed to Cr(VI) and OR 17.4, CI 15.2–20.0 with exposure to Cr(VI), with RERI 3.79, CI 2.12–5.47. Heavy smokers (≥20 cigarettes/day) not exposed to Cr(VI) had OR 27.6, CI 24.2–31.6 and with Cr(VI) OR 33.6, CI 28.3–39.9; with RERI 5.72, CI 0.79–10.66. In recent quitters of smoking (1-15 years), the OR was 9.15, CI 8.09–10.4 when not exposed to Cr(VI) and with exposure to Cr(VI) OR 10.8, CI 9.35–12.50 with RERI 1.44, CI 0.20–2.67. After 15 years of smoking cessation, the joint effect was weakened, with a RERI of 0.35, CI -0.16–0.85. <h3>Conclusion</h3> Occupational Cr(VI) exposure augments smoking-related lung-cancer risk beyond additivity. The RERI remains elevated for up to 15 years after tobacco cessation. These results support integrated control of workplace exposure to Cr(VI) and tobacco control.