Research on potential radiation risks in areas with nuclear power plants in Japan:leukaemia and malignant lymphoma mortality between 1972 and 1997 in 100 selectedmunicipalities

Abstract

The results of a geographical correlation study using Poisson regression analysis arereported for leukaemia and malignant lymphoma mortality between 1972 and 1997 in 100selected Japanese municipalities with or without a nuclear power plant (NPP). The datadid not support social concerns of an increased risk of malignant lymphoma in the vicinityof Japanese NPPs. However, some estimates of overall excess relative risk (ERR; relativerisk minus one) were statistically significantly positive for leukaemia mortality in 20 NPPmunicipalities compared with mortality in the remaining 80 control areas, taking intoaccount a minimum two-year latency following the start of commercial operation.One estimate was 0.228 (95% CI: 0.074–0.404) from a simple area adjustmentusing the mortality in all Japan as the external baseline rate. This superficialincrease is not due to leukaemia among young people, aged less than 25 years atdeath. The ERR estimate for ages at death of 50–74 years was confounded to bepositive for leukaemia and distorted to be negative for malignant lymphoma. Forleukaemia, a positive ERR estimate was seen, especially for females and duringspecific periods. Confounding of the ERR estimate for two causes was also seen insome NPP areas including a high adult T-cell leukaemia (ATL) area. Temporalarea variations associated with ATL misclassification and a temporal increasingtrend of leukaemia mortality in the elderly caused the confounding effects. Ourfindings do not support the hypothesis of a leukaemogenic impact of NPPs inJapan.