Cancer incidence in the vicinity of Finnish nuclear power plants: an emphasis on childhood leukemia.

The objective of this paper was to study cancer incidence, especially leukemia in children (<15 years), in the vicinity of Finnish nuclear power plants (NPPs). We used three different approaches: ecological analysis at municipality level, residential cohorts defined from census data, and case-control analysis with individual residential histories. The standardized incidence ratio of childhood leukemia for the seven municipalities in the vicinity of NPPs was 1.0 (95% CI 0.6, 1.6) compared to the rest of Finland. The two cohorts defined by censuses of 1980 and 1990 gave rate ratios of 1.0 (95% CI 0.3, 2.6) and 0.9 (95% CI 0.2, 2.7), respectively, for childhood leukemia in the population residing within 15 km from the NPPs compared to the 15-50 km zone. The case-control analysis with 16 cases of childhood leukemia and 64 matched population-based controls gave an odds ratio for average distance between residence and NPP in the closest 5-9.9 km zone of 0.7 (95% CI 0.1, 10.4) compared to > or =30 km zone. Our results do not indicate an increase in childhood leukemia and other cancers in the vicinity of Finnish NPPs though the small sample size limits the strength of conclusions. The conclusion was the same for adults.