On the 70th anniversary of the atomic bomb, experts consider the enduring radiologic and psychological impact of nuclear disasters and how this information can be used for public health planning in the case of future events. The reviews are part of a three-part series published in the Lancet.
The first atomic bomb, dropped during World War II on the Japanese city of Hiroshima, is believed to have immediately killed 80,000 people, and tens of thousands more would soon succumb from radiation exposure. A second bomb dropped 3 days later on Nagasaki killed another 40,000 people.
Although there have not been any further wartime detonations of nuclear weapons, since that time there have been five severe nuclear accidents ― Kyshtym (Russia, 1957), Windscale Piles (United Kingdom, 1957), Three Mile Island (United States, 1979), Chernobyl (Russia, 1986), and Fukushima (Japan, 2011).
In the first Lancet article, Kenji Kamiya, MD, PhD, vice-president of Hiroshima University, Japan, and colleagues examine the long-term health impact of radiation exposure and report on findings from the Japanese atomic bombings and the largest of the nuclear disasters, which was in Chernobyl.
Radiation exposure increases the risk for cancer throughout life, so continued follow-up of exposed individuals is essential, note the authors. The late-onset effects of radiation exposure have been identified by long-term, large-scale epidemiologic studies, the most reliable source being the cohort study of Japanese survivors of the atomic bombings of Hiroshima and Nagasaki (the Life Span Study).
The Life Span Study is valuable because of its large size, the fact that the cohort is a general population of people of all ages and both sexes, and the wide range of individually assessed doses. It has followed 94,000 atomic bomb survivors from 1950 to the present and clearly reveals an increased lifetime risk for cancer in survivors.
The risk was found to be proportional to dose for solid cancers, and a higher risk was found in those exposed as children or young adults, the investigators point out.
Similarly, after the Chernobyl disaster, an increased risk for childhood thyroid cancer was observed among children who had experienced internal exposures from consuming radioactivity in food.
However, much still remains unknown about radiation exposure. "The dose–response relation for cancer at low doses is assumed, for purposes of radiological protection, to be linear without a threshold, but has not been shown definitively," write Dr Kamiya and coauthors.
Cancer risk increases after exposure to moderate and high doses of radiation (more than 0.1 to 0.2 Gy), but it is yet unclear whether the risk is increased by acute low doses (0.1 Gy or lower) or low dose rates.
"This outstanding issue is not only a problem when dealing appropriately with potential health effects of nuclear accidents, such as at Fukushima and Chernobyl, but is of growing concern in occupational and medical exposure," they say. "Therefore, the appropriate dose–response relation for effects of low doses of radiation needs to be established."
Noncancer health concerns also need to be studied. At high doses, and possibly lower ones as well, radiation might increase the risk for cardiovascular, respiratory, and other diseases. But whether a "radiation-induced excess risk of circulatory disease persists at low doses is the subject of much debate and research," they note.
Children exposed in utero to high doses of atomic bomb radiation suffered adverse effects on the development of the central nervous system, and the risk for cancer increased with maternal dose. Hereditary effects in the children of atomic bomb survivors have not been detected to date.
In the second article, Koichi Tanigawa, MD, Fukushima Medical University, in Japan, and his team looked at an aspect of nuclear disasters that often gets buried amid the more pressing medical issues — the psychological burden of living in an affected region.
The effects of nuclear power plant accidents can vary substantially, ranging from short-term to long-term health effects and from physical health to social and psychological effects, the authors note.
But amid all of the issues involved, "major psychological effects are the most commonly observed effects after a nuclear power plant accident," they write.
The 2006 Chernobyl Forum reported that studies of adults affected by the disaster showed that the incidence of posttraumatic stress disorder and other mood and anxiety disorders doubled. On the basis of these findings, they concluded that the accident's most serious public health issue was the adverse effects on mental health, an effect made worse by poor communication about the health risks associated with reported radiation levels.
Similar problems were seen after Fukushima, with the Fukushima Health Management Survey reporting that the proportion of adults with psychological distress (14.6%) was almost five times higher among disaster evacuees compared with the general population (3%), note the authors. Repeated evacuation and long-term displacement has resulted in severe healthcare problems for the most vulnerable populations, such as the elderly, in whom mortality increased threefold in the first 3 months following evacuation.
"Although the radiation dose to the public from Fukushima was relatively low, and no discernible physical health effects are expected, psychological and social problems, largely stemming from the differences in risk perceptions, have had a devastating impact on people's lives,” said Dr Tanigawa in a statement.
Thus, the effects of a major accident are not limited to those caused by radiation. Psychological disorders reported by the people affected by the Chernobyl accident and the Fukushima Daiichi accident "highlighted the importance of issues not related to radiation, such as evacuation and long-term displacement of vulnerable people, and mental, psychological, and social factors," the authors point out.
What's Ahead for the Future?
In the third article, Akira Ohtsuru, MD, PhD, professor, Department of Radiation Health Management, Fukushima Medical University School of Medicine, Japan, and his coauthors discuss planning for the future.
Specifically, there 437 nuclear power plants operating around the world, and at least one third are located in areas more densely populated than Fukushima Daiichi. Measures must be taken to protect the millions of individuals who might be exposed to radiation in the aftermath of another nuclear accident, they write.
Effective plans must be developed to protect the public and minimize negative effects, as well as to protect emergency workers from exposure to high-dose radiation. In addition, research is needed to help decision makers avoid premature deaths among vulnerable groups, such as hospitalized patients, during evacuation.
Lessons from the Fukushima disaster need to be learned, the authors write. "One of the key tasks of the health services is to reliably communicate that in most nuclear accidents very few people are exposed to a life-threatening dose of radiation," Dr Ohtsuru and his team said in a statement.
"Physicians must play a key role in helping residents understand the health risks. Evacuation of a large population of vulnerable people in nursing homes and hospitals will also need careful planning and adequate medical support. Additionally, screening for mental illness in residents relocated from their homes and providing mental health care will be essential," they comment.
In Japan, steps have been taken to prepare for future disasters. A disaster medical system was developed in 1995, more than a decade before Fukushima, after the devastating Great Hanshin-Awaji earthquake, which killed 6434 people and injured 44,000 others. There are more than 600 hospitals throughout the country designated disaster medical centers as of January, 2015.
More recently, the authors point out, the Fukushima accident created an impetus to update the medical curriculum. New innovative training programs have been established to provide physicians with the knowledge and skills needed to deal with the medical and social effects of a nuclear accident. These include training modules in radiation medicine for medical students at Fukushima Medical University and a science and technology studies module to enrich the existing medical program. In addition, a leadership program at Hiroshima University has also been established, with the goal of training future leaders in nuclear disasters and of addressing medical, environmental, and social factors.
First Step in Right Direction
In an accompanying commentary, Michael R. Reich, PhD, from the Harvard T H Chan School of Public Health, Boston, and Aya Goto MD, MPH, PhD, from Fukushima Medical University, note that in the 4 years that have passed since the nuclear power plant accident at Fukushima, the problems have moved from an "acute nuclear disaster to a chronic environmental disaster, with multiple social, psychological, economic, and political consequences."
As described in these articles, a large number of people continue to experience multiple losses, both tangible and intangible, at the individual, family, and community levels, they note.
"More efforts are needed, both inside and outside Japan, to share the lessons learned from Fukushima around the world," they write. "This special issue of the Lancet is a first step in that direction."
Several of the authors had competing interests, as noted in the articles. Dr. Reich and Dr Goto have disclosed no relevant financial relationships.
Medscape Medical News © 2015 WebMD, LLC
Send comments and news tips to firstname.lastname@example.org.
Cite this: Looking Backward and Forward: Impact of Nuclear Disasters - Medscape - Aug 06, 2015.