Long-term health effects of atomic bombs dropped on Japan not as dire as perceived

GSA says that this massive data set has been uniquely useful for quantifying the risks of radiation because the bombs served as a single, well-defined exposure source, and because the relative exposure of each individual can be reliably estimated using the person’s distance from the detonation site. The data has been particularly invaluable in setting acceptable radiation exposure limits for nuclear industry workers and the general public.

Cancer rates among survivors was higher compared to rates in those who had been out of town at the time. The relative risk increased according to how close the person was to the detonation site, their age (younger people faced a greater lifetime risk), and their sex (greater risk for women than men). However, most survivors did not develop cancer. Incidence of solid cancers between 1958 and 1998 among the survivors were 10 percent higher, which corresponds to approximately 848 additional cases among 44,635 survivors in this part of the study. However, most of the survivors received a relatively modest dose of radiation. In contrast, those exposed to a higher radiation dose of 1 Gray (approximately 1000 times higher than current safety limits for the general public) bore a 44 percent greater risk of cancer over the same time span (1958-1998). Taking into consideration all causes of death, this relatively high dose reduced average lifespan by approximately 1.3 years.

Although no differences in health or mutations rates have yet been detected among children of survivors, Jordan suggests that subtle effects might one day become evident, perhaps through more detailed sequencing analysis of their genomes. But it is now clear that even if the children of survivors do in fact face additional health risks, those risks must be very small.

Jordan attributes the difference between the results of these studies and public perception of the long-term effects of the bombs to a variety of possible factors, including historical context.

People are always more afraid of new dangers than familiar ones,” says Jordan. “For example, people tend to disregard the dangers of coal, both to people who mine it, and to the public exposed to atmospheric pollution. Radiation is also much easier to detect than many chemical hazards. With a hand-held geiger counter, you can sensitively detect tiny amounts of radiation that pose no health risk at all.”

Jordan cautions that the results should not be used to foster complacency about the effects of nuclear accidents or the threat of nuclear war. “I used to support nuclear power until Fukushima happened,” he says. “Fukushima showed disasters can occur even in a country like Japan that has strict regulations. However, I think it’s important that the debate be rational, and I would prefer that people look at the scientific data, rather than gross exaggerations of the danger.”

— Read more in B. R. Jordan, “The Hiroshima/Nagasaki Survivor Studies: Discrepancies Between Results and General Perception,” Genetics 203, no. 4 (August 2016): 1505-12 (DOI: 10.1534/genetics.116.191759)