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Little Health Risk Seen From Fukushima’s Radioactivity


“Two independent reports show that the public and most workers received only low doses of radiation following last year’s meltdowns at the Fukushima Daiichi nuclear power plant in Japan. Nature reports that the risks presented by the doses are small, even though some are above guidelines and limits set by the Japanese government. Few people will develop cancer as a result of the accident, and those that do may never be able to conclusively link their illness to the meltdowns. The greatest risk lies with the workers who struggled in the early days to bring the reactors under control. So far no ill-effects have been detected. At Chernobyl, by contrast, the highest exposed workers died quickly from radiation sickness.”

Few people will develop cancer as a consequence of being exposed to the radioactive material that spewed from Japan’s Fukushima Daiichi nuclear power plant last year — and those who do will never know for sure what caused their disease. These conclusions are based on two comprehensive, independent assessments of the radiation doses received by Japanese citizens, as well as by the thousands of workers who battled to bring the shattered nuclear reactors under control.

The first report, seen exclusively by Nature, was produced by a subcommittee of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) in Vienna, and covers a wide swathe of issues related to all aspects of the accident. The second, a draft of which has been seen by Nature, comes from the World Health Organization (WHO) in Geneva, Switzerland, and estimates doses received by the general public in the first year after the accident. Both reports will be discussed at UNSCEAR’s annual meeting in Vienna this week.

The UNSCEAR committee’s analyses show that 167 workers at the plant received radiation doses that slightly raise their risk of developing cancer. The general public was largely protected by being promptly evacuated, although the WHO report does find that some civilians’ exposure exceeded the government’s guidelines. “If there’s a health risk, it’s with the highly exposed workers,” says Wolfgang Weiss, the chair of UNSCEAR. Even for these workers, future cancers may never be directly tied to the accident, owing to the small number of people involved and the high background rates of cancer in developed countries such as Japan.

Scientists involved in producing the UNSCEAR report hope that their independent summary of the best available data could help to dispel some of the fear about fallout that has grown over the past year (see Nature 483, 138–140; 2012). As well as providing a preliminary assessment of workers’ exposure, the UNSCEAR report concludes that the Japanese government’s estimate of the radiation released was correct to within a factor of ten, and that further study is needed to fully understand the impacts of the accident on plants, animals and marine life near the power station. When a final version of the report is approved by the full UNSCEAR committee next year, it should provide a useful baseline for future studies.

The Fukushima crisis began on 11 March 2011, when a magnitude-9.0 earthquake triggered a tsunami off the coast of Japan. A 14-metre wave flooded four of the six reactors at the Fukushima Daiichi plant, knocking out emergency cooling systems and leading to meltdowns and explosions that released radioactivity into the air and ocean. In the year since the accident, the plant has been stabilized, and radioactive emissions have largely stopped.

From last autumn, UNSCEAR has been reviewing all the available data on Fukushima’s radiation — just as it did to produce what was then the definitive report on the 1986 Chernobyl nuclear accident. In particular, it scoured anonymized medical data for 20,115 workers and contractors employed by the Tokyo Electric Power Company, which runs the plant. It found that 146 employees and 21 contractors received a dose of more than 100 millisieverts (mSv), the level at which there is an acknowledged slight increase in cancer risk. Six workers received more than the 250 mSv allowed by Japanese law for front-line emergency workers, and two operators in the control rooms for reactor units 3 and 4 received doses above 600 mSv, because they had not taken potassium iodide tablets to help prevent their bodies from absorbing radio­active iodine-131 (see ‘In the zone’). So far, neither operator seems to have suffered ill effects as a result of their exposure.


Most of the workers who received high doses were exposed in the early days of the crisis. In those first hours, they were huddled in darkened control rooms, while small teams made forays inside the reactor buildings to survey the damage and manually operate valves and other equipment. Often, they did not know how much radiation was present — the report says that an automated system designed to monitor their radiation levels was not operating properly. By mid-April, basic access control and monitoring had been restored on the site.

Experts agree that there is unlikely to be a detectable rise in thyroid cancer or leukaemia, the two cancers most likely to result from the accident. “There may be some increase in cancer risk that may not be detectable statistically,” says Kiyohiko Mabuchi, who heads Chernobyl studies at the National Cancer Institute in Rockville, Maryland. In Chernobyl, where clean-up workers were exposed to much higher doses, 0.1% of the 110,000 workers surveyed have so far developed leukaemia, although not all of those cases resulted from the accident.

The risk to the roughly 140,000 civilians who had been living within a few tens of kilometres of the plant seems even lower. Because detailed radiation measurements were un­available at the time of the accident, the WHO estimated doses to the public, including radiation exposure from inhalation, ingestion and fallout. The agency concludes that most residents of Fukushima and neighbouring Japanese prefectures received a dose below 10 mSv. Residents of Namie town and Iitate village, two areas that were not evacuated until months after the accident, received 10–50 mSv. The government aims to keep public exposure from the accident below 20 mSv per year, but in the longer term it wants to decontaminate the region so that residents will receive no more than 1 mSv per year from the accident.

The WHO’s calculations are consistent with several health surveys conducted by Japanese scientists, which found civilian doses at or below the 1–15-mSv range, even among people living near the plant. One worrying exception is that infants in Namie town may have been exposed to enough iodine-131 to receive an estimated thyroid dose of 100–200 mSv, raising their risk of thyroid cancer. But data collected from 1,080 children in the region found that none had received a thyroid dose greater than 50 mSv. Chernobyl’s main cancer legacy in children was thyroid cancer.

Fearful and angry

The large population involved could mean that the eventual number of radiation-induced cancers among the public will actually be higher than among workers, even though the risk to each individual civilian is tiny, says David Brenner, a radiologist at Columbia University in New York city. But he doubts a direct link will ever be definitively made. Under normal circumstances, “40% of everybody will get cancer”, he says. “It doesn’t seem to me that it’s possible to do an epidemiological study that will see an increased risk.” Still, it may be valuable to conduct studies to reassure the population that they are not being misled, he adds.

A far greater health risk may come from the psychological stress created by the earthquake, tsunami and nuclear disaster. After Chernobyl, evacuees were more likely to experience post-traumatic stress disorder (PTSD) than the population as a whole, according to Evelyn Bromet, a psychiatric epidemiologist at the State University of New York, Stony Brook. The risk may be even greater at Fukushima. “I’ve never seen PTSD questionnaires like this,” she says of a survey being conducted by Fukushima Medical University. People are “utterly fearful and deeply angry. There’s nobody that they trust any more for information.”

Overall, the reports do lend credibility to the Japanese government’s actions immediately after the accident. Shunichi Yamashita, a researcher at Fukushima Medical University who is heading one local health survey, hopes that the findings will help to reduce stress among victims of the accident. But they may not be enough to rebuild trust between the government and local residents. Tatsuhiko Kodama, head of the radioisotope centre at the University of Tokyo and an outspoken critic of the government, questions the reports’ value. “I think international organizations should stop making hasty reports based on very short visits to Japan that don’t allow them to see what is happening locally,” he says.

UNSCEAR’s working committee of roughly 70 scientists still has much to do before the final report is completed. Committee members will continue to independently validate sources of data from the accident and work on models of the flow of radio­isotopes from the reactors into the environment. For the workers, “individual medical follow-up is more important than the statistical follow-up”, Weiss says. “People want to know whether what we say is true.”


15 Comments on "Little Health Risk Seen From Fukushima’s Radioactivity"

  1. DC on Thu, 24th May 2012 3:01 pm 

    Nature is a respteced journal, but this….all sounds a little too good to be true. Not to suggest those that are saying world-wide death is imminent either have the whole story, but this report sounds like its trying to blow radiation up everyones butt and calling it sunshine. As far as there bland assertions that only .000000000001% of people around Chernobyl got sick, there is a great deal of evidence to suggest a lot of people got sick, many have died, and are still dieing.

    I mean, if Fukishima was such a minor ‘accident’, why are they scraping playground topsoil in Tokyo and hauling it away? Really like to know what Nature has to say about that…

  2. Hugh Culliton on Thu, 24th May 2012 3:15 pm 

    Next, ‘independent’ reports will start to claim that not only is there little risk of cancer, but the Fukushima radiation will clear up acne and make your teeth whiter! Even though we’re only 7 Richter away from a massive dump of radiation into the ocean, it’s all double plus good according to the folks who built a nuke plant on top of one of the most seismically active zones on the planet.

  3. Kenz300 on Thu, 24th May 2012 5:06 pm 

    It was previously reported that both TEPCO and the Japanese government have unreported the dangers and radiation from the very first day of the disaster. It would be interesting to see what data was used and if it can be relied on. Independent data collection and reporting needs to be done.

  4. MrBill on Thu, 24th May 2012 7:16 pm 

    This quote-“”Under normal circumstances, “40% of everybody will get cancer”, he says. “It doesn’t seem to me that it’s possible to do an epidemiological study that will see an increased risk.””–OK, you simply measure for any increases in radiation related cancers within the appropriate populations and timelines. It was done in Japan before after WWII and did measure increases in these cancers…I had respect for “Nature”, I’m surprised they would print this ignorant quote.

  5. RICHARD RALPH ROEHL on Thu, 24th May 2012 11:11 pm 

    All is well, comrade sheep! Nothing to worry about. Go back to sleeeeeep! Nuclear fission technology is more safe than ‘Freddie’ with a butcher’s knife. It is also “too cheap to meter”.

    Yeah! Saaaaaaaaaafe! Too cheap to meter! Okay! Great! Let’s build more of these nuclear bomb monsters… starting with Waikiki Beach, Martha’s Vineyard, Beverly Hills… and in Manhattan!

  6. James on Fri, 25th May 2012 12:59 am 

    Lies, Lies, Lies. I wonder who paid to have this stuff put out? Maybe the Nuclear Industry? We’ll see in the next few years when the rate of cancer and leukemia skyrocket. Maybe the nuclear Industry will keep that a secret too.

  7. BillT on Fri, 25th May 2012 1:40 am 

    “Nature” is owned by MacMillan Publishers and is one of the few corporations that control information that is given to the people. If you think they are totally independent of the control of the nuclear industry, you are kidding yourself. I have been following this problem since it happened and NOTHING tells me that it is as harmless as they are portraying.

    If it was not bad, why have they looked at evacuating Tokyo if #4 goes? W@hy isn’t there work being done to correct the problem instead of a 10 year time line? Why is radiation in the US at multiples of what it should be?

    Cancer takes 10 to 20 years to show up. When many millions start dieing in the future, will they blame it on something else like they did with tobacco for so many years, buying doctors to claim it was safe? The nuclear industry needs to be shut down now!

  8. BillT on Fri, 25th May 2012 1:46 am 

    BTW: “… That mainstream media have been powerful advocates for nuclear

    power comes as no surprise. “The media are saturated with a skilled, intensive, and effective advocacy campaign by the nuclear industry, resulting in disinformation” and “wholly counterfactual accounts .. widely believed by otherwise sensible people,” states the 2010-2011 World Nuclear Industry Status Report by Worldwatch Institute. [3] What is less well understood is the nature of the “evidence” that gives the nuclear industry its mandate, Cold War science which, with its reassurances about low-dose radiation risk, is being used to quiet alarms about Fukushima and to stonewall new evidence that would call a halt to the industry. …”

  9. Norm on Fri, 25th May 2012 2:24 am 

    Interesting how you can blow up 6 reactors and nobody get hurt. With these rosy conclusions, the ‘independent’ scientists got to keep their jobs. They will still have a paycheck, healthcare, their 3 bedroom house, and can get groceries at Safeway. If they had drawn any other conclusion, no more house, no more healthcare, no more groceries.

  10. MrEnergyCzar on Fri, 25th May 2012 2:44 am 

    Did Japan raise the acceptable exposure limits?


  11. BillT on Fri, 25th May 2012 3:54 am 

    They are scraping soil off of Tokyo playgrounds and hauling it to dumps where it is buried, but not mentioning why. It would be considered toxic waste here in the US under old standards. But, the standards are constantly being ‘up graded’ as the levels climb. Buy a Geiger counter and test your own food and see what you are putting into your bodies. They are cheaper than an Ipad and much more important to your life.

  12. beamofthewave on Fri, 25th May 2012 4:14 am 

    This makes me think it may be an ELE, why else would they put such blatant propaganda out unless it was really, really bad. Did they post some of the pictures of the deformed kids from Chernobyl also?

  13. musbrad on Fri, 25th May 2012 11:52 am 

    More industry propaganda. I am disappointed that Nature would publish such trash. I am with BillT on this one-buy a dosimeter-and get familiar with it.

  14. Kenz300 on Sat, 26th May 2012 2:13 pm 

    All 54 nuclear reactors in Japan are shut down. Now Japan needs to keep them shut down and move to safe, clean alternative energy sources. Wind, solar, wave energy, geothermal and second generation biofuels can all be produced locally and provide local jobs. With increased energy efficiency, energy conservation and alternative energy sources Japan can move closer to ending their nuclear nightmare.

  15. Welch on Sun, 27th May 2012 2:22 am 

    “I have been following this problem since it happened and NOTHING tells me that it is as harmless as they are portraying.”

    With respect, this has just told you that. It may be the case.

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