Traffic-related air pollution and childhood acute leukemia in France: GEOCAP nationwide case-control study

Outdoor air pollution and particulate matter (PM) have been classified as carcinogenic to humans, and benzene exposure is known to increase the risk of leukemia in adults. Yet the evidence regarding childhood leukemia remains inconclusive. In this study, we sought to investigate whether traffic-related air pollution increases the risk of acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). We used data from GEOCAP, an ongoing population-based case-control study conducted in France. It includes 4611 ALL and 830 AML cases, diagnosed between 2002 and 2013 and identified through the French national registry of childhood cancer, and 60,189 contemporaneous controls representative of the French pediatric population. Annual average exposures to nitrogen dioxide (NO2), fine PM (PM2.5) and Black Carbon (BC) at the geocoded address of residence at diagnosis for cases and inclusion for controls were estimated using land-use regression models. We also evaluated major roads length within 150 m of the geocoded addresses. Polytomous logistic regression was used to derive odds ratios (ORs) and 95 % confidence intervals (CI). Increased risks of AML were found with NO2 (OR _{per 10 μg/m3} = 1.09, 95 %CI = 1.03-1.15), PM2.5 (OR _{per 5 μg/m3} = 1.09, 95 %CI = 1.01-1.18) and BC exposures (OR _{per 0.5 10-5/m} = 1.09, 95 %CI = 1.03-1.16). The length of major roads within 150 m of the residence was also associated with AML risk (OR _{per 300 m} = 1.13, 95 %CI = 1.03-1.25). These increases in risk were more pronounced in the most urbanized areas. For ALL, inverse associations were suggested. This study provides further evidence supporting a role of traffic-related air pollution in AML risk in children.