Laryngeal cancer risks in workers exposed to lung carcinogens: Exposure-effect analyses using a quantitative job exposure matrix

Background Various occupational agents are suspected risk factors for laryngeal cancer. However, individual studies are often inadequate to investigate how such exposures relate to this relatively rare outcome. Important limitations include small sample sizes, lack of detail on exposure, and inadequate adjustment for confounders. Methods This study applied quantitative estimates via SYN-JEM for four established occupational lung carcinogens to case-control data from five (Western European and Latin American) studies within the International Head and Neck Cancer Epidemiology Consortium. Participant job histories for n=2256 laryngeal cancer cases and n=7857 controls recruited from 1989-2007 were linked with quantitative SYN-JEM estimates via ISCO-68 codes. Logistic regression models were applied to assess the effects of occupational exposure to asbestos, respirable crystalline silica (RCS), chromium-VI, and nickel on laryngeal cancer risk while controlling for tobacco and alcohol consumption. Results Increased ORs were observed for all agents evaluated. In males, a positive exposure-effect relationship was observed with duration of RCS exposure (p-value for trend 90%ile: OR=2.21, 95% CI=1.13-4.33) and career-average exposure (>90%ile: OR=2.96, 95% CI=1.51-5.79), and in the highest category of career-cumulative nickel/chromium-VI combined exposure (>90%ile: OR=1.51, 95% CI=1.01-2.26). These relationships weakened in analyses restricted to blue collar workers but interpretations remained unchanged. Conclusions These results support causal links between exposure to known lung carcinogens and laryngeal cancer. Measures to reduce such exposures in workplaces could decrease the risk of both laryngeal and lung cancers.