RESUMO
The United States government established the Atomic Bomb Casualty Commission (ABCC) in Hiroshima and Nagasaki in 1947 and 1948, respectively, under the auspices of the National Academy of Sciences. The purpose was to study late health effects in the people exposed to the atomic bomb radiation. To attain this purpose smoothly, branch laboratories of the Japanese National Institute of Health were attached to ABCC in 1948. This arrangement continued for 28 years until it was replaced in 1975 by the Radiation Effects Research Foundation (RERF) which is equally funded by the two governments of Japan and the United States. The authors summarize the research activities of ABCC and RERF. Epidemiological method for assessing the health risks of radiation exposure is to identify a numerator of those with health abnormalities among a denominator population defined by exposure dose. In Hiroshima and Nagasaki, the identification of the denominator was delayed because of the confusion after the war, but a greater delay has occurred in Chernobyl and, so far, only the numerator has been emphasized. It concludes that in the studies of the late health effects of atomic bomb survivors, it is important to clarify not only positive findings showing the presence of abnormalities but also negative findings indicating the absence of abnormalities
