Childhood cancer and traffic-related air pollution in Switzerland

Abstract

TPS 684: Long-term health effects of air pollutants 1, Exhibition Hall, Ground floor, August 26, 2019, 3:00 PM - 4:30 PM Background: A number of studies have investigated an association between childhood leukaemia and traffic-related air pollution, often using NO2 concentration as a proxy measure. However, few studies have accounted for the drop in NO2 levels over recent decades. We aimed to investigate whether the incidence of childhood cancer and the diagnostic groups of leukaemia, lymphoma, and central nervous system (CNS) tumours is associated with mean annual ambient NO2 concentration at children’s homes. Methods: We included all children aged <16 years from the Swiss national census of 1990 to 2014 and identified all incident cancer cases from the Swiss Childhood Cancer Registry. We used land use regression models combining the results of a nationwide dispersion model for NO2 with spatial covariates on road network, traffic intensity, population density, and land cover to estimate current exposure at children’s precisely geocoded place of residence. Cancer incidence was investigated in time-to-event analyses using Cox proportional hazards models with time-varying covariates, adjusting for level of urbanization, socio-economic factors, and background ionising radiation. Results: In time-to-event analyses based on 2,871 cases, the adjusted hazard ratio comparing children with NO2 exposure above the 90th percentile with those below the median was 1.59 for all cancers combined (95%-CI 1.40, 1.81). We observed an increased hazard ratio for leukaemia (HR 1.65; 95%-CI 1.31, 2.09) with indication of a dose-response relationship, in particular for the diagnostic subgroup of acute myeloid leukaemia (AML) (2.51; 1.38, 4.54) and, to a lesser extent, acute lymphoid leukaemia (1.52; 1.17, 1.99). We also found evidence of an increased hazard ratio for lymphoma (1.60; 1.17, 2.18) and CNS tumours (1.42; 1.08, 1.86). Conclusion: This nationwide study suggests that exposure to high levels of traffic-related air pollution is associated with an increased risk of childhood leukaemia, most notably AML.