one showed levels that would lead to "health effects," the prefecture said. Among those tested, only 25 people showed exposure levels of one millisievert or higher, with the highest number, three millisieverts, found in two people.
The prefecture has also conducted thyroid tests on children, including 3,765 children tested in October and November. Medical advisers concluded that none in that group had problems related to radiation exposure.
Foreign correspondents were taken on a tour of the blasted Fukushima Daiichi nuclear reactors. The WSJ's Phred Dvorak tells Yumiko Ono what she saw at Fukushima.
One year after Japan's March 11 disaster, WSJ's Yumiko Ono talks to reporter Yuka Hayashi about the fate of Fukushima evacuees from the town of Namie who are still living in temporary housing.
Recovery workers at Japan's crippled Fukushima nuclear plant still fear for the future, one year after the country's worst ever nuclear accident. (Video: Reuters/Photo: AP)
Still, reports on population exposure are as much guesswork as science. Experts from Hirosaki University did their own thyroid tests on evacuees and found exposure levels higher than the government figures. Shinji Tokonami, a professor who helped to run the study, said that his group used different assumptions than the government about whether evacuees faced high exposure immediately or whether it was spread out over two weeks.
And it's hard to know just how much exposure people really had. Minoru Kamata, a physician at Suwa Chuo Hospital in Nagano, said that officials belatedly discovered that contaminated pebbles had been used to make the foundation of apartment buildings that housed evacuees—a fact revealed only because a teenager in the housing came from one of the few communities requiring children to wear dosimeters.
Workers at the plant have received considerably higher levels of exposure, according to data from Tokyo Electric Power Co., the operator of Fukushima Daiichi. Of the 20,115 people who have worked there since last March, 167 were exposed to 100 millisieverts or more, including six subjected to at least 250 millisieverts. The highest number was 679 millisieverts, for a worker who helped to prepare venting as rising pressure threatened an explosion. A Tokyo Electric spokesman said that none of those workers has developed health problems so far, adding that the company is closely monitoring their conditions.
Dr. Yamashita, of Fukushima Medical University, said that, though radiation exposure for the general population has likely been low, evacuations and fear of radiation could lead to problems such as increased consumption of alcohol and stress-related illnesses. Tens of thousands of residents remain uprooted.
“ 'From a radiological perspective, we expect the impact to be really, really minor,' said one specialist. ”
For days after the March 11 accident, tons of radioactive waste were dumped into the Pacific. But it has been well dispersed by ocean currents, according to marine chemist Ken Buesseler at the Woods Hole Oceanographic Institution in Massachusetts. By June, the levels of radioactive cesium-137 between 18 and 300 miles offshore were safe for human exposure, he said.
Since cesium binds to the sediment on the ocean floor, the radiation has likely had the biggest effect on bottom-dwelling fish and other animals—though the consequences still aren't clear, said Tatsuo Aono, a specialist at Japan's National Institute of Radiological Sciences. Scientists have found cesium levels in those fish up to 1,000 times higher than the previous norm.
Ecologists and biologists who toured Fukushima prefecture earlier this year found that the radiation release appeared to have had a dramatic impact on birds in the region. Biologists led by radio-ecologist Timothy Mousseau at the University of South Carolina studied 300 locations around Fukushima last July and found that local bird populations had dropped by about a third. "The response was about twice as much as after Chernobyl," said Dr. Mousseau. "We don't know why yet."
Their absence was noticeable. "It is 