Studies find little health risk from radiation exposure in Japan

On March 11, 2011, a tsunami killed more than 20,000 people and caused $200 billion in property damage in Japan. The nuclear power plant Fukushima Daiichi was one of its victims. Although no one was killed at the power plant, the media coverage quickly shifted from the larger damage caused by the tsunami to reports about the dangerous health risks the Japanese people were facing from the radioactive material emitted from the damaged reactor.

New evidence shows that the emphasis on a health risk was wrong and has caused unnecessary and damaging psychological stress worldwide. While Fukushima Daiichi is an economic disaster, it has not produced a health crisis.

Two comprehensive independent analyses have concluded: “Few people will develop cancer as a consequence of being exposed to the emitted radiation – and those who do will never know for sure what caused their disease.” That’s because the increase in cancer risk over the risk from other causes is so small that it will be statistically undetectable.

The United Nations Scientific Committee on the Effects of Atomic Radiation and the World Health Organization conducted the new studies and reported their results in the May 24 issue of Nature. From the day of the tsunami until the recent stabilization of the Fukushima reactors, both UNSCEAR and WHO have been analyzing all the available data on radiation exposure by Japanese residents of Fukushima prefecture and neighboring regions in the first year after the accident.

One hundred millisieverts (mSv) per year is universally acknowledged as the level where there begins to be a slight increase in cancer risk. A sievert is a measure of how much radiation a person has received from exposure to radioactive material. The UNSCEAR study found that residents and nuclear workers in the region adjacent to the Fukushima plant received a yearly dose of between 1 and 15 mSv. The residents of two villages that were not evacuated until months after the accident, received between 10 and 50 mSv, still much below 100 mSv.

As for the 20,115 workers and contractors employed by the Tokyo Electric Power Co. that runs the plants, the UNSCEAR analysis found that 146 workers and 21 contractors received more than 100 mSv. Six received 250 mSv and two received 600 mSv. While they have a slightly elevated risk of cancer, to date, none have suffered ill effects from their exposure.

The other study, conducted by the WHO, estimated that the yearly dose of the residents of Fukushima prefecture and the neighboring regions were below 10 mSv. David Brenner, a radiologist at Columbia University in New York City explains that because normally, 40 percent of the population will get cancer from other causes, “it doesn’t seem that it’s possible to do an epidemiological study that will show any increase risk.” Still, he adds, it may be valuable to conduct studies to reassure the population that they are not being misled.

Such reassurance will not be easy to achieve. A survey conducted by Fukushima Medical University showed that people are “utterly fearful and deeply angry. There’s nobody that they trust any more for information.” Several analysts have concluded that the psychological stress created by the nuclear accident is a greater health risk than the emitted radiation.

For that increased psychological stress the press must share much of the blame. The reporters assigned to the coverage lacked an understanding of nuclear science and what the different radiation measures meant, which resulted in misleading, exaggerated or wrong interpretations. Their most damaging mistake was to assume that the amount of radiation emitted from the reactors, was inextricably linked to cancer risk for people in the surrounding region. The UNSCEAR and WHO analysis shows that is not how radiation works.

It is unlikely that the new findings will change minds. The misleading coverage shifted the blame for the accident from the tsunami to nuclear energy itself. A majority of the Japanese are now against the use of nuclear power, and the government is talking about limiting the future use at 15 percent from the previous goal of 35 percent. As MIT professor Jacopo Buongiorno quipped, “That is like giving up driving because a friend crashed a car on a dangerous road.”

Some people in Europe, and to a lesser degree in the United States, also have placed the blame for the accident on nuclear energy rather than the tsunami and are agitating for a reduction or elimination in its use. But both they and the Japanese will have to embrace more nuclear power if they expect their governments to compete effectively against countries such as China and Russia in future global markets.

Garth Buchanan holds a doctorate in applied science and has 35 years of experience in operations research. Reach him at