Physical examinations on atomic bomb survivors and their succeeding generations by means of twin study

During the past 10 years, health questionnaire surveys and medical and physical examinations were carried out on twins who were exposed to atomic bombing and their siblings born to exposed parents. In addition, fetal autopsies for the 1st and 2nd generation of offspring (F1, F2) of exposed parents were performed during the same period. None of the aforementioned examinations yielded results demonstrating a higher frequency of abnormal findings when exposed at ≤ 2 km from the hypocenter than when exposed at >2 km. Since nothing brought a greater environmental change, except for atomic bombing, for the survivors, atomic bombing may have been a source of serious genetic change in the filial generations. Research is being conducted to determine the effects of atomic bomb exposure on the generation which was its victim and on their filial generations. Although exposure distance and doses should be considered in studying the circumstances of exposure, sensitivity and resistance to radiation and morbidity triggered by these factors are heterogeneous for individuals whose genetic backgounds differ. This paper summarizes the results of a pilot case study on the disease conditions of twins exposed to atomic bombing and their siblings of atomic-bomb exposed generation which was done within a limited budget and with limited manpower. (N.K.)