Objectives Firefighters are potentially exposed to a wide variety of chemical compounds during the course of their work and inhalation is considered to be the major source of exposure. A large number of human carcinogens have been detected in smoke at fires. The aim was to investigate the risk of lung cancer among firefighters, while controlling for smoking habits.

Methods We used data from the SYNERGY project including pooled information on lifetime work histories and smoking habits for 14,748 male lung cancer cases and 17,543 controls from 14 case-control studies conducted in Europe, Canada, New Zealand and China. There were 190 men who had ever worked as a firefighter (based on ISCO-68), among them 86 cases and 104 controls. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by unconditional logistic regression, adjusted for study, age, smoking, and ever employment in an occupation with established lung cancer risk.

Results We observed no increased risk of lung cancer in firefighters, neither before (OR = 1.03, 95% CI: 0.77–1.38) nor after (OR = 0.95, 95% CI: 0.68–1.32) adjustment for smoking and exposure to other occupational lung carcinogens. There was no evidence of a trend of increasing lung cancer risk with increasing duration of work as a firefighter (p = 0.58) and no significant heterogeneity in lung cancer risk among firefighters across the studies. None of the major histological subtypes of lung cancer was associated with work as a firefighter.

Conclusions We found no evidence of an excess lung cancer risk related to occupational exposure as a firefighter, when lifetime history of tobacco smoking and exposure to other occupational lung carcinogens was taken into account.