Childhood cancer and nuclear power plants in Switzerland: a census-based cohort study via International Journal of Epidemiology

Since Black reported a cluster of children with leukaemia near Sellafield in 1984,1 numerous studies investigated cancer incidence near nuclear power plants (NPP), with conflicting results. Some found an increased risk also at places where NPPs were planned but not built, concluding that factors other than radiation might be responsible.2^,3 A recent case–control study from Germany, which reported odds ratios (ORs) of 1.61 for all cancers and 2.19 for leukaemia in 0–4 year olds living <5km from a NPP, refuelled the debate on a possible link between NPPs and childhood cancer.4^,5

Most previous analyses were ecological and may have been affected by exposure misclassification and confounding.6–11 The German case–control study was criticized for potential selection and participation bias.4^,5^,12^,13 A recent Finnish study combining ecological, cohort and case–control analyses was small, with no children living <5km from NPPs.14 All previous studies analysed residence at diagnosis. Given the higher vulnerability to radiation of fetuses and infants and the latency between radiation exposure and cancer development, residence at birth might be more relevant.15

We investigated the risk of childhood leukaemia and all childhood cancers in the vicinity of Swiss NPPs, using a cohort approach with person-years derived from the Swiss censuses 1990 and 2000 and incident cases from the Swiss Childhood Cancer Registry (SCCR). We analysed distance of residence at birth to the nearest NPP in the main analysis, and distance to residence at diagnosis in a secondary analysis. Outcomes of interest were leukaemia and all cancers diagnosed at ages 0–4 (<5) and 0–15 (<16) years. We adjusted for confounders, included other nuclear installations (research reactors and storage sites), and locations where NPPs were planned but not built, and assessed the robustness of the results in sensitivity analyses.

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