What We’ve Learned from Survivors of the Atomic Bombs

What are some of the most interesting or influential findings RERF has produced in your opinion?
Several things come to mind. Early on, RERF researchers noted that excess leukemia was the first delayed response from radiation exposure, with about 49% of the excess cases from leukemia attributable to radiation. The risk of leukemia increased with increased dose of radiation and was higher for those who were younger when exposed. Subsequent studies from RERF reported a significant linear radiation dose response for all solid cancers with dependence on sex, attained age and age at exposure. However, more recent studies indicate a possible curvature in this dose-response relationship. Another important finding is that elevated solid cancer risk is observed even at low levels of exposure (in the category 0-100mGy). RERF studies have also provided detailed site-specific risks for several cancers. More recently, studies from RERF have indicated possible effects of radiation on non-cancer diseases such as cardiovascular disease and diabetes.

What are some of the ways that the findings have been useful, for example in setting occupational exposures to radiation?
RERF’s research results have been the world’s primary guide for radiation-induced health effects, especially cancer, and have influenced most of our daily lives without our realizing it. Safety standards for common medical diagnostic procedures such as x-rays and CT (Computed Tomography) scans, as well as occupational exposures around the world, rely heavily on risk estimates generated from RERF studies. Additionally, RERF scientists and study results help to illuminate potential health effects in victims of nuclear accidents, current and former workers at nuclear facilities, citizens living in the vicinity of nuclear sites, atomic veterans and other radiation-exposed populations. 

Have most of the insights from studying this cohort already been gained?
Not at all. There is much more to learn, as almost a fifth of A-bomb survivors are still alive, including about 70% of those who were under the age of 10 years at the time of the bombings and who are now entering the age where cancer and other diseases are more common. We are still making new and surprising discoveries such as the fact that hormonal factors appear to affect the relationship between radiation dose and some cancers – for example, RERF scientists have shown that the radiation-related risk of breast cancer may be highest with exposure around menarche, while the radiation-related risk of uterine cancer appears highest with exposure prior to menarche. In addition, our results generate new questions. For example, while we still see a strong radiation dose-response for all solid cancer in survivors, the latest follow up of the atomic bomb survivor LSS cohort indicated some curvature that we need to study further to understand. Current and future studies will also focus on the unique scientific opportunity to integrate epidemiological, clinical and dose information with information from biological specimens to gain new insights into the underlying mechanisms of radiation-related disease. For example, the Trio Genome Study plans to use whole genome sequencing to examine the potential effects of parental radiation exposure on the possible occurrence of mutations in their children.

How have advances in technology helped RERF’s research?
As new technology and methods become available, RERF applies these latest tools to answer or refine important questions in radiation science. For example, one of the key questions that has concerned the survivors, their children, and the scientific community, has been whether radiation exposure to parents can affect their children. Over the decades, RERF has tried to address this question using the best technology of the time, and to date, no heritable effects have been found. We are now planning to use the latest whole genome sequencing technology to address the question of potential heritability of radiation effects. Similarly, we expect to elucidate the mechanisms of radiation-induced diseases such as cancer by analyzing the biospecimens of atomic bomb survivors using advanced technologies like omics, which enable comprehensive analysis of biomolecules. Fortunately, RERF has preserved over 2.16 million biospecimens with clinical records through long-term clinical cohort studies. We feel that the time has come to analyze these samples to uncover the detailed mechanisms of radiation effects. From a dosimetry standpoint, we are using modern mathematical phantoms similar to those used in the latest Disney films to refine our individual radiation dosimetry estimates and get more precise estimates of radiation risk. 

What are some of the biggest challenges RERF faces?
RERFs work would not have been possible without the incredible support of the survivors and their children who stepped forward to be part of the study, but communication with those in the study and with the public, has not always been enough. This was particularly true in the early years of ABCC. We have been working hard to open the line of communications. For example, we recently held two public talks explaining genetic studies in Hiroshima and Nagasaki, and requested public feedback from these talks. With efforts such as these, I think our relationship with survivors today is much better, but we need to keep a strong focus on communication of our plans and study results.

What are you most looking forward to for the future of RERF?
A very high priority is that RERF should continue our excellence as a scientific organization, leveraging expertise from collaborations around the world, and answering key questions of importance to science, and to the survivors. We are planning the Trio Genome Study (and other molecular studies) because, in addition to the scientific community, the survivors and their children want to know the answers. Next year marks RERF’s 50th anniversary, and our move in two years will not only provide infrastructure that enables cutting-edge research but also take us closer to the local community, physically and otherwise. I would like to make sure that provides us with more opportunities for engagement.

Dr. Rajaraman received her Ph.D. in Epidemiology from the Johns Hopkins Bloomberg School of Public Health. Dr. Rajaraman began her career at the Radiation Epidemiology Branch at the U.S. National Cancer Institute where her research focused on the interaction of environmental and genetic factors in cancer risk. She co-led the U.S. Radiologic Technologists Study, an occupational cohort of more than 100,000 technologists exposed to low-to-moderate doses of fractionated radiation. Recent work prior to joining RERF includes setting up regional programs for cancer research in South Asia, and serving as a U.S. Health Attaché and Regional Representative for South Asia, where she coordinated key aspects of the regional COVID-19 pandemic response and set up ongoing multinational biomedical research efforts.

Nancy Huddleston is Communications Director at the National Academy of Sciences. The article was originally posted to the website of the National Academy of Sciences.