Objective Within the SYNERGY project, we evaluated the exposure-response relation between occupational exposure to respirable crystalline silica (RCS) and the risk of lung cancer in pooled analyses of community-based studies.

Methods RCS was estimated using a quantitative general population job-exposure matrix (‘SYNJEM’) for 16 786 lung cancer cases and 20 818 matched population or hospital controls. 34.2% of the men were ever exposed to RCS, while 8.6% of the women were ever exposed. Odds ratios (ORs) and 95% confidence intervals (95% CI) were estimated stratified by gender using unconditional logistic regression models adjusted for age, study centre, cigarette pack-years, time-since-quitting smoking, and ever employment in an occupation with known lung cancer risk.

Results We observed a monotonic increase in risk of lung cancer associated with occupational exposure to RCS among men (unexposed versus 4^th quartile among exposed 1.45 (95%CI, 1.31–1.60). Result did not differ by smoking status and remained significantly elevated among non-smokers. The association was stronger in squamous cell carcinoma and small cell lung cancer as compared to adenocarcinoma of the lung especially among former and current smokers. The effect of RCS on lung cancer in women was not detectable likely related to small numbers.

Conclusions The SYNERGY results show that occupational silica exposure is associated with an increased risks of all lung cancer types in a pooled analyses of community-based studies.