Exposure to environmental tobacco smoke in childhood and incidence of cancer in adulthood in never smokers in the European Prospective Investigation into Cancer and Nutrition.

The association between childhood environmental tobacco smoke (ETS) exposure and adult cancer risk is controversial; we examined this relationship in never smokers within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Over an average of 10 years, 8,372 cases of cancer were diagnosed in 112,430 never smokers in EPIC. Childhood ETS was self-reported by participants at baseline, along with other lifestyle factors. Hazard ratios (HR) for ETS exposure in childhood and their 95% confidence intervals (CI) were estimated by Cox proportional hazards models stratified by age, sex, and study center and adjusted for education, alcohol drinking, body mass index, physical activity, non-alcoholic energy intake, fruit and vegetable intake, and adulthood ETS exposure. Models were further adjusted for reproductive factors for female cancers, for meat intake for digestive system cancers, and for diabetes status for pancreatic cancer. No association was observed between childhood ETS exposure and overall cancer risks (HR = 0.97, 95% CI = 0.92-1.02), and for selected sites. The only exception was pancreatic cancer, as previously reported by Vrieling et al., among those who had been exposed daily in childhood (overall HR = 2.09, 95% CI = 1.14-3.84). In conclusion, childhood ETS exposure might not be a major risk factor for common cancers in adulthood.