Study of Adolescents Exposed in Utero to the Atomic Bomb, Nagasaki, Japan

With the increasing use of atomic energy in our society, the effects of ionizing radiation, particularly those that are delayed, have become a matter of great concern. Since 1947 the Atomic Bomb Casualty Commission (ABCC) has conducted continuing medical studies among survivors of the atomic bombing in Hiroshima and Nagasaki, including since 1951 a group of children who were irradiated in utero.1 Fetal tissues being particularly sensitive to ionizing radiation,"' this latter group is of special interest. Information on the effects of ionizing radiation during prenatal development has been gathered mainly from animal experiments."' These studies have shown that irradiation early in gestation results in increased pre-natal deaths, and later irradiation in gross abnormalities or delayed effects.