Background gamma radiation and childhood cancers within ten miles of a US nuclear plant.

In light of some recent reports concerning childhood leukaemia near nuclear installations, we examined rates of cancer in children in relation to background gamma ray exposure. Data from a national monitoring programme around nuclear facilities were used to map the distribution of background gamma radiation for 69 small geographical subunits (average population 2300) within ten miles of one US nuclear plant. An association was found for incidence of childhood cancers as a whole (odds ratio (OR) = 2.4; 95% confidence limits (CL) 1.2, 4.6). For leukaemias specifically, the odds ratio was also elevated but confidence limits were very wide (OR = 2.4; 95% CL 0.5, 12.9). Analyses adjusting for sociodemographic characteristics of study tracts (population density and income) gave similar results; data on other risk factors were unavailable. Conventional risk models would not predict a detectable increase in childhood cancer from background gamma radiation, particularly not an increase of this magnitude. The large effect for solid tumours as well as leukaemias is also somewhat counter to expectation. Since a priori the association we observed was unlikely, it is important to know if similar trends in childhood cancer with background radiation are seen in other areas before rejecting chance or bias as an explanation for the result.