Studies of the mortality of A-bomb survivors. 5. Radiation dose and mortality, 1950--1970

During 1950-1970 mortality from disease, especially from leukemia and other cancer, was high among survivors with large radiation doses. There were minor variations in mortality from causes other than neoplasms but little evidence of radiation effect. Despite observed differences, variation in relative risk among the cancers cannot be stated with certainty because of sampling variability. Survivors who were children under ten when irradiated had the highest relative risks for cancer. Radiation effects decreased with increasing age at the time of the bombs. The data are too sparse to support exact statements as to the shape of the dose-response curves for leukemogenesis or carcinogenesis, but are consistent with linear relationships. Leukemia rates in the high dose groups declined persistently with time but had not yet reached normal levels by 1965-1970. The rates for other cancers, however, increased during the study period. An RBE of neutrons, compared with gamma radiation, of about five fits the leukemi...