Future Studies of the Prenatally Exposed Survivors

A Review of Forty-Five Years Study of Hiroshima and Nagasaki Atomic Bomb Survivors III. FUTURE PERSPECTIVE

Abstract

It is axiomatic in radiation biology that mitotically active cells are more vulnerable to ionizing radiation than differentiated ones that are not dividing, or do so only rarely. This belief has made studies of individuals exposed to irradiation prenatally, when cellular growth is so rapid, of substantial theoretic and general interest. As a result, over the years, the Atomic Bomb Casualty Commission (ABCC) and its successor, the Radiation Effects Research Foundation (RERF), have initiated a variety of studies designed to characterize the effects of exposure to ionizing radiation on the developing human embryo and fetus. Thus far, this research has centered largely on attempts i) to describe the risk to the developing human brain of exposure to ionizing radiation, ii) to set out the evidence bearing on a threshold level for this risk in the low dose region, iii) to examine physical growth and development of individuals prenatally exposed, iv) to ascertain the risk of premature death and morbidity from cancer or other causes among the in utero exposed survivors, v) to evaluate possible radiation-related reproductive damage, and, finally, vi) to assess, through routine biennial examinations, the late effects of exposure on menarche and menopause of individuals who were in utero at the time of the bombing.
Although there is much still to be learned epidemiologically, the studies that have occurred suggest collectively that this is an advantageous time to initiate a program of coordinated experimental and observational studies that will address directly the biological mechanisms involved in the findings that have been seen to date. Before we speculate on the form this program might take, however, it seems appropriate to describe briefly what the studies in Hiroshima and Nagasaki have revealed.