Activities and future plans of the radiation effects research foundation

The Radiation Effects Research Foundation (RERF) was established in 1975 as a binational research foundation supported by Japan and the United States. It continues the work of the Atomic Bomb Casualty Commission (ABCC) which was established in 1974. ABCC-RERF studies focus on several fixed cohorts of survivors and their children: the Life Span Study (LSS) cohort (120,000 survivors); the In-Utero cohort (3,300 people born within 9 months of the bombings); the F1 cohort (88,000 people born between mid-1946 and 1984), and the Adult Health Study (AHS) cohort (an ongoing clinical study of 17,000 LSS survivors and 1,100 people exposed in-utero). Epidemiological data have shown increased risks of leukemia and solid cancers by radiation exposure among the survivors. Excess leukemia risks, especially for children, were markedly elevated 5 to 10 years after exposure and have continued at reduced levels. Excess solid cancer rates became apparent within 10 years after exposure, increasing throughout life in rough proportion to background rates. For doses of interest in radiation protection excess leukemia risks exhibit an upward curving dose response pattern while the solid cancer excess appears to be linear by dose with no apparent threshold. In addition to malignancy, AHS data has shown dose-related increased risk for various non-malignant diseases; radiation cataracts, benign tumors of uterus, thyroid and parathyroid (hyperparathyroidism), and autoimmune thyroid diseases. Persons exposed in-utero exhibit a broad range of dose-related effects including delayed growth and development and higher rates of microcephaly. Studies of birth defects, chromosome aberrations, childhood mortality, and genetic variants of serum or erythrocyte proteins have provided no indication of heritable mutations in the F1 cohort. Continued follow-up of survivors exposed as children (90% are still alive) is essential to understanding the temporal pattern of excess risks and lifetime risks, and may provide useful insights into the biological mechanisms by which radiation causes cancer. Further studies including DNA sequencing and clinical screening for adult-onset diseases, as well as ongoing mortality follow-up will be carried out in the F1 cohort. Advances in molecular biology and genetics are making biological samples from RERF cohort members an extremely valuable resource for research on the basic mechanisms leading to radiation effects. Blood cells obtained from AHS participants together with autopsy tissues stored at RERF are a potential source of DNA that will serve to immortalize the survivors. Furthermore, cancer tissues accessible through the Hiroshima and Nagasaki Tissue Registries (more than 90% of LSS cohort members) are the most important sources of material for molecular studies. The research findings of RERF have long been used by numerous international bodies as a principal basis for establishing radiation protection standards. Continued research at RERF is important for extending our understanding of radiation health effects and for enhancing the health and welfare of atomic-bomb survivors and all people in the world. (author)