The Long-Term Effects of Radiation Exposure

March 15, 2011

Reporters and the public are scrambling to understand the health effects of the low-level radiation being absorbed by Japanese civilians and rescue workers from the crippled reactors in Fukushima province. The sad fact is that Japan already is the world’s first and longest running natural history experiment in such exposures. The populations that survived the Hiroshima and Nagasaki bomb blasts have been studied for nearly 65 years. As survivors pass away, their initial exposures and their causes of death are duly noted. That database has provided researchers with a wealth of information for documenting the long-term effects of radiation exposure.

Here, for instance, is an abstract that appeared in 2009 in the Journal of Radiological Protection of a review of the literature written by Dr. Mark Little, who is the senior scientist in the radiation epidemiology branch at the National Cancer Institute:

The survivors of the atomic bombings in Hiroshima and Nagasaki are a general population of all ages and sexes and, because of the wide and well characterized range of doses received, have been used by many scientific committees . . . as the basis of population cancer risk estimates following radiation exposure. Leukemia was the first cancer to be associated with atomic bomb radiation exposure, with preliminary indications of an excess among the survivors within the first five years after the bombings. An excess of solid cancers became apparent approximately ten years after radiation exposure. With increasing follow-up, excess risks of most cancer types have been observed, the major exceptions being chronic lymphocytic leukemia, and pancreatic, prostate and uterine cancer. . .

In general, the relative risks per unit dose among the Japanese atomic bomb survivors are greater than those among comparable subsets in studies of medically exposed individuals. . .  Risks among occupationally exposed groups such as nuclear workforces and underground miners are generally consistent with those observed in the Japanese atomic bomb survivors. In general, consistent patterns of variation of risk with age at exposure are also seen in all studies-risks for all cancer types diminish with increasing age at exposure.

There are also excess risks of various types of non-malignant disease in the Japanese atomic bomb survivors, in particular cardiovascular, respiratory and digestive diseases. . .  In the absence of a convincing mechanistic explanation of epidemiological evidence, at present a cause-and-effect interpretation of the reported statistical associations for cardiovascular disease is unreliable but cannot be excluded. Further epidemiological and biological evidence will allow a firmer conclusion to be drawn.

Recent epidemiological studies of the population surrounding Chernobyl have shown increased cancer rates, with some estimates going as high as 2,000 cancer deaths attributable to that 1986 nuclear power plant disaster in the former Soviet Union.

As of this writing, the radiation exposure in Japan is greater than Three Mile Island (essentially nil) and less than Chernobyl. What it ultimately might become remains to be seen, and is largely in the hands of the Japanese government and electric utility officials struggling to get the situation at the three reactors at the Fukushima Daiichi complex under control. When that finally occurs, and physicians and scientists try to figure out how much long-term damage there will be to the local population and rescue workers, they will undoubtedly go to the comprehensive databases created over the past half century from the survivors of Hiroshima and Nagasaki. A repository of the information can be found at the website of the Radiation Effects Research Foundation, which is a joint project of the Japanese and U.S. governments.

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One Response to The Long-Term Effects of Radiation Exposure

  1. Pete on March 22, 2011 at 2:41 am

    Is it appropriate to compare the outcomes from the Fukushima releases to exposure to nuclear weapon explosions? Are the radiation, isotope and intensity profiles similar, or is there a degree of extrapolation going on which may, or may not, be relevant?
    I am saddened but not surprised by the media jumping on the news and comparing to Hiroshima/Nagasaki and Chernobyl creating alarm but not taking the opportunity to really investigate and explain the detail of the risks and the probability of certain results – worst case ‘sky’s gonna fall’ seems to be their default.
    I was interested by your comment on radiation exposure in miners, I suspect airline pilots and staff get significant cosmic radiation exposures, and people living in radon emitting granite area are also probably at risk. The relative risks compared to folk living within 30km of the Japanese reactors would be interesting to know.

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