Fallout, radiation doses near Dounreay, and childhood leukaemia.

Possible explanations for the recently reported increased incidence of childhood leukaemia around Dounreay were examined in the light of changes in the national incidence of leukaemia that occurred during the period of exposure to fallout from international testing of nuclear weapons in the atmosphere. It was concluded that the increase could not be accounted for by an underestimate of the risk of leukaemia per unit dose of radiation at low doses and low dose rates, nor by an underestimate of the relative biological efficiency of high as compared with low linear energy transfer radiation. One possible explanation was underestimation of doses to the red bone marrow due to the discharges at Dounreay relative to the dose from fallout, though investigation of ways in which this might have occurred did not suggest anything definite. Other possible explanations included a misconception of the site of origin of childhood leukaemia, outbreaks of an infectious disease, and exposure to some other, unidentified environmental agent. These findings weigh heavily against the hypothesis that the recent increase in childhood leukaemia near Dounreay might be accounted for by radioactive discharges from nuclear plants, unless the doses to the stem cells from which childhood leukaemia originates have been grossly underestimated.