Parental occupational exposure to benzene and the risk of childhood cancer: A census-based cohort study

Background: Previous studies on occupational exposures in parents and cancer risks in their children support a link between solvents and paints with childhood leukaemia. Few studies have focused specifically on benzene. Objectives: To examine whether parental occupational exposure to benzene is associated with an increased cancer risk in a census-based cohort of children. Methods: From a census-based cohort study in Switzerland, we included children aged < 16 years at national censuses (1990, 2000). We retrieved parental occupations reported at census and assessed exposure to benzene using a job exposure matrix. We identified incident cancer cases through record linkage with the Swiss Childhood Cancer Registry. We fitted Cox proportional-hazards models to assess associations between exposures and the following outcomes: any cancer, leukaemia, acute lymphoid leukaemia (ALL), acute myeloid leukaemia (AML), lymphoma, non-Hodgkin lymphoma, central nervous system (CNS) tumours, and glioma. We adjusted models for a range of socio-economic, perinatal and environmental factors. Results: Analyses of maternal (paternal) exposure were based on 9.0 (13.2) million person years at risk and included 1004 (1520) cases of cancer, of which 285 (438) had leukaemia, 186 (281) lymphoma, 227 (339) a CNS tumour. Maternal exposure was associated with an increased risk of childhood leukaemia (hazard ratio 1.73, 95% CI 1.12-2.67) and ALL (1.88, 1.16-3.04). We found little evidence of an association for other outcomes or for paternal exposure. Adjusting for potential confounders did not materially affect the results. Conclusions: This nationwide cohort study suggests an increased risk of leukaemia among children whose mothers were exposed to benzene at work.