Childhood cancer and nuclear power plants in Switzerland: a census-based cohort study

Abstract

Background: Previous studies on childhood cancer and nuclear power plants (NPPs) produced conflicting results. We used a cohort approach to examine whether residence near NPPs was associated with leukaemia or any childhood cancer in Switzerland.

Methods: We computed person-years at risk for children aged 0-15 years born in Switzerland from 1985 to 2009, based on the Swiss censuses 1990 and 2000 and identified cancer cases from the Swiss Childhood Cancer Registry. We geo-coded place of residence at birth and calculated incidence rate ratios (IRRs) with 95% confidence intervals (CIs) comparing the risk of cancer in children born <5 km, 5-10 km and 10-15 km from the nearest NPP with children born >15 km away, using Poisson regression models.

Results: We included 2925 children diagnosed with cancer during 21 117 524 person-years of follow-up; 953 (32.6%) had leukaemia. Eight and 12 children diagnosed with leukaemia at ages 0-4 and 0-15 years, and 18 and 31 children diagnosed with any cancer were born <5 km from a NPP. Compared with children born >15 km away, the IRRs (95% CI) for leukaemia in 0-4 and 0-15 year olds were 1.20 (0.60-2.41) and 1.05 (0.60-1.86), respectively. For any cancer, corresponding IRRs were 0.97 (0.61-1.54) and 0.89 (0.63-1.27). There was no evidence of a dose-response relationship with distance (P > 0.30). Results were similar for residence at diagnosis and at birth, and when adjusted for potential confounders. Results from sensitivity analyses were consistent with main results.

Conclusions: This nationwide cohort study found little evidence of an association between residence near NPPs and the risk of leukaemia or any childhood cancer.

Figure 1

Maps showing sites of nuclear facilities and population density in Switzerland. Locations of NPPs, research facilities, the interim storage facility and sites where NPPs were planned but never built (upper map) and population density in 2000 in quintiles (lower map) NPP, nuclear power plant; EPFL, École Polytechnique Fédérale de Lausanne; Uni, University; PSI, Paul Scherrer Institute

Figure 2

Flow chart of selection of children with childhood cancer

Figure 3

Results for birth cohort. Incidence rate ratios adjusted for sex, age and year at diagnosis and 95% CIs comparing children living in the inner 5 km, 5–10 km and 10–15 km zones with children outside the 15 km zone. Results for nuclear power plants (NPPs); any nuclear facility including NPPs, research and storage facilities; and sites of planned but not built NPPs are shown

Figure 4

Results for resident cohort. Incidence rate ratios adjusted for sex, age and year at diagnosis and 95% CIs comparing children living in the inner 5 km, 5–10 km and 10–15 km zones with children outside the 15 km zone. Results for nuclear power plants (NPPs); any nuclear facility including NPPs, research and storage facilities; and sites of planned but not built NPPs are shown

Figure 5

Comparison of results of main and sensitivity analyses. Incidence rate ratios adjusted for sex, age and year at diagnosis and 95% CIs comparing children living <5 km with children living >15 km from a nuclear power plant. Results are shown for the birth cohort and are adjusted for sex, age and year at diagnosis. Analyses numbered as in Box 1