STUDIES OF MORTALITY OF A-BOMB SURVIVORS .6. MORTALITY AND RADIATION-DOSE, 1950-1974

Followup through 1974 adds 3402 deaths to the previously reported 16,828 among the 82,000 A-bomb survivors since 1950, 762 from cancer. With 14,405 deaths from natural causes other than cancer, there is still no real evidence that diseases other than cancer are involved in the late mortality effect of the nuclear radiation. In addition to leukemia and cancer of thyroid, breast, and lung, now cancer of the esophagus, stomach, and urinary organs, and the lymphomas, should be included among the forms of cancer caused by the ionizing radiation from the 1945 atomic explosions. Evidence of a general carcinogenic effect is increasing. Evidence of radiation carcinogenesis is much stronger for Hiroshima than for Nagasaki victims of the bombs. The leukemogenic effect still seems present in the 1970-1974 period, but greatly reduced, and the average absolute risk for other malignant neoplasms now exceeds that for leukemia. The minimal latent period for most of the carcinogenic effects was under 15 yr and depends on age and site of cancer. Age in 1945 plays an important but variable role in the carcinogenic effect, but one that cannot be fully understood without further observation. Only for leukemia in Hiroshima are the data numerous enough to permit confident statements to be made about the form of the dose-response curve.