Occupational exposure to chlorinated solvents and lung cancer: results of the SYNERGY case-control study

OBJECTIVE: The association between occupational exposure to chlorinated solvents and lung cancer remains inconclusive. This study investigated this relationship using data from the internationally pooled SYNERGY study.

METHODS: Data from 14 case-control studies conducted in 13 European countries and Canada were pooled, including 28 048 participants (12 329 cases and 15 719 controls). Lifetime occupational exposure to chlorinated solvents was assessed using the ALOHA+job-exposure matrix. ORs and 95% CIs were estimated using unconditional logistic regression, adjusted for study centre, age, sex, smoking (pack-years and cessation), cumulative exposure to five occupational lung carcinogens (asbestos, hexavalent chromium, polycyclic aromatic hydrocarbons, respirable crystalline silica and diesel engine exhaust), cumulative benzene exposure and employment in high-risk occupations ('List A' jobs). Associations were estimated across categories of exposure levels, durations and analyses stratified by smoking status and lung cancer subtypes.

RESULTS: We found no evidence of an association between ever exposure to chlorinated solvents and lung cancer risk (OR 1.03; 95% CI 0.96 to 1.10). Among exposed individuals, a positive trend with cumulative exposure was observed (p=0.031), but not when non-exposed individuals were included (p=0.173). Positive trends were found with exposure duration (p=0.005 for exposed; p=0.048 overall); risks were modestly elevated (OR 1.11) in those exposed for 20 or more years. No increased risk was observed across smoking strata or lung cancer subtypes.

CONCLUSIONS: This pooled analysis provides limited evidence of an association between occupational exposure to chlorinated solvents and lung cancer, though exposure-response trends were noted among exposed individuals.