Commentary and Review Series 3-09
Atomic Bomb Survivors: Long-term Health Effects of Radiation
Mabuchi K, Fujiwara S, Preston DL, Shimizu Y, Nakamura N, Shore REDennis C. Shrieve, Jay S. Loeffler, eds. Human Radiation Injury.
Philadelphia: Lippincott, Williams & Wilkins; 2010, pp 89-113
Summary
This review summarizes what has been learned regarding the health effects of radiation exposure to the atomic bombs in Hiroshima and Nagasaki and the potential for further insights. A major effect has been the increased incidence and mortality risks of hematopoietic and solid cancers that adversely affect the longevity and quality of life of the exposed survivors. There also is emerging evidence of dose-related increases in risks of cardiovascular and several other late-onset non-cancer diseases. The apparent life-long radiation-related risk for solid cancer and non-cancer diseases is a matter of public-health concern and scientific importance.
Much has been learned about the dose response for solid cancers and how it is modified by gender, age and time. Much more, however, needs to be learned about organ-specific cancer risks and their potential risk modifiers, e.g., smoking, female reproductive factors, viral infection, nutrition, etc. Further knowledge in this area will help in extrapolating the risk data from the Japanese population to others with differing disease background. Importantly, biological samples for many of the survivors offer opportunities for learning more about radiation carcinogenesis at more fundamental levels. New insights into the nature of the radiation-related risk will undoubtedly come from further follow-up investigations.
Radiation effects on cardiovascular and other late-onset diseases were recently identified and will become clearer as young survivors become older. The longitudinal clinical examination program (Adult Health Study) has effectively identified a number of specific diseases associated with radiation (e.g., thyroid nodule, hyperthyroidism, hypertension, liver disease) and shed light on radiation-related changes suggestive of possible biological mechanisms involved. More advances can be expected from this approach.
The RERF cohort of the children exposed to the bomb inutero is small but very unique. The RERF data have shown a radiation-related increase for solid cancers occurring in early adult years, accompanied by an emerging trend of a radiation-related risk of non-cancer diseases. More follow-up is needed to determine the long-term potential for late neurological effects in this population.
Early reports of possible genetic effects revealed no demonstrable adverse effects on birth defects, other undesirable pregnancy outcomes, or molecular indicators of genetic effects. Given the relatively low parental dose distribution, the negative results do not necessarily indicate that there is no effect, but do provide an upper bound limit on risk estimates. Additional data on adult-onset multifactorial disease (such as diabetes and circulatory disease) are expected to provide additional information unavailable elsewhere, as will data on late-onset Mendelian diseases.
The studies of the atomic bomb survivors and their children have contributed a great deal of scientific knowledge on the health effects of radiation exposure. The atomic bomb cohort studies are widely acknowledged as the “gold standard“ in studies of radiation health effects and radiological protection. This is a result of the availability of well-characterized radiation dose estimates and well-defined populations that have been followed up with remarkable effectiveness. The atomic bomb survivor studies do not provide the full answer regarding radiation effects, as they represent responses to a single acute external radiation exposure, but not protracted exposures. Nevertheless, these studies provide by far the strongest foundation available for human radiation risk assessment.
This review summarizes what has been learned regarding the health effects of radiation exposure to the atomic bombs in Hiroshima and Nagasaki and the potential for further insights. A major effect has been the increased incidence and mortality risks of hematopoietic and solid cancers that adversely affect the longevity and quality of life of the exposed survivors. There also is emerging evidence of dose-related increases in risks of cardiovascular and several other late-onset non-cancer diseases. The apparent life-long radiation-related risk for solid cancer and non-cancer diseases is a matter of public-health concern and scientific importance.
Much has been learned about the dose response for solid cancers and how it is modified by gender, age and time. Much more, however, needs to be learned about organ-specific cancer risks and their potential risk modifiers, e.g., smoking, female reproductive factors, viral infection, nutrition, etc. Further knowledge in this area will help in extrapolating the risk data from the Japanese population to others with differing disease background. Importantly, biological samples for many of the survivors offer opportunities for learning more about radiation carcinogenesis at more fundamental levels. New insights into the nature of the radiation-related risk will undoubtedly come from further follow-up investigations.
Radiation effects on cardiovascular and other late-onset diseases were recently identified and will become clearer as young survivors become older. The longitudinal clinical examination program (Adult Health Study) has effectively identified a number of specific diseases associated with radiation (e.g., thyroid nodule, hyperthyroidism, hypertension, liver disease) and shed light on radiation-related changes suggestive of possible biological mechanisms involved. More advances can be expected from this approach.
The RERF cohort of the children exposed to the bomb inutero is small but very unique. The RERF data have shown a radiation-related increase for solid cancers occurring in early adult years, accompanied by an emerging trend of a radiation-related risk of non-cancer diseases. More follow-up is needed to determine the long-term potential for late neurological effects in this population.
Early reports of possible genetic effects revealed no demonstrable adverse effects on birth defects, other undesirable pregnancy outcomes, or molecular indicators of genetic effects. Given the relatively low parental dose distribution, the negative results do not necessarily indicate that there is no effect, but do provide an upper bound limit on risk estimates. Additional data on adult-onset multifactorial disease (such as diabetes and circulatory disease) are expected to provide additional information unavailable elsewhere, as will data on late-onset Mendelian diseases.
The studies of the atomic bomb survivors and their children have contributed a great deal of scientific knowledge on the health effects of radiation exposure. The atomic bomb cohort studies are widely acknowledged as the “gold standard“ in studies of radiation health effects and radiological protection. This is a result of the availability of well-characterized radiation dose estimates and well-defined populations that have been followed up with remarkable effectiveness. The atomic bomb survivor studies do not provide the full answer regarding radiation effects, as they represent responses to a single acute external radiation exposure, but not protracted exposures. Nevertheless, these studies provide by far the strongest foundation available for human radiation risk assessment.