Hiroshima and Nagasaki: the survivors. The puzzle of absent effects

It is argued that the method of basing estimates of the risks of populations exposed to radiation under normal, peace-time activities, on the results obtained from A-bomb survivors may not be justified. Among the survivors there is a definite dose-related increase in the number of malignancies but other radiation effects such as increase in the incidence of leukaemia in children exposed in utero, genetic effects in children conceived by survivors and general increase in mortality, are conspicuously absent. It is felt that estimates of radiation effects on survivors indicate a difference in response to radiation, as far as leukaemia is concerned, between persons exposed to radiation alone, and those who were also subject to mechanical injuries and heat burns. Together with the absence of other expected effects of radiation, and the lower cancer incidence, this indicates that A-bomb victims cannot be assumed a priori to behave in response to radiation in the same way as those exposed to radiation alone, without accompanying physical, psychological and social traumata. Estimates of radiation risk based on observations on the A-bomb survivors may thus turn out to be too low, by a considerable margin. (U.K.)