Residential Proximity to Agricultural Herbicides during Pregnancy and Childhood Leukemia in the Danish National Birth Cohort

BackgroundThe majority (61%) of Denmark’s land cover is agricultural. Cereals and grains are the major crops, and almost all acres of these crops are treated with herbicides. Based mostly on case-control studies, parental exposure to pesticides during pregnancy has been associated with increased risk of childhood cancer.MethodsThe Danish National Birth Cohort (DNBC) enrolled over 100,000 pregnant women 1996-2003. For childhood leukemias (diagnosed <15 years) through 2014 and 10% of the cohort (N=9,362, excluding non-singleton births and children with Down Syndrome), we linked addresses during the pregnancy to crop maps and crop-specific pesticide sales data to estimate the amount (g) of herbicides applied at distances within 100, 250, 500, 1000m of homes. We used Cox proportional hazard models to estimate hazard ratios (HR) and 95% confidence intervals (95%CI) for 18 herbicides with the highest use.ResultsThere were 191 children diagnosed with childhood cancer, including 61 leukemia cases. So...