Health follow-up studies of Japanese atomic bomb survivors have now been in progress for nearly 50 years, a remarkable tribute to sustained scientific cooperation between Japan and the United States since World War II. From the beginning, genetic research has received particular attention.
The first population-based work in Hiroshima and Nagasaki involved a large clinical-epidemiological investigation in which all late-term pregnancy outcomes were identified (nearly 77 000 pregnancies over a five-year period, 1948 through 1953) and then studied clinically in relation to parental exposure to bomb irradiation. No differences were found (in frequencies of birth defects, stillbirths, etc), thus allaying the immediate public concern that atomic radiation might spawn an epidemic of malformed children. Identification of the Fl generation continued thereafter for nearly the entire reproductive life of the exposed population (1945 through 1985). That work was coupled with clinical examination of all offspring of exposed parents, together with children