In Japan, Relief at Radiation's Low Toll

By YUKA HAYASHI, PHRED DVORAK and ROBERT LEE HOTZ

Wally Santana/Associated Press

A young evacuee is screened at a shelter on March 24, 2011, for leaked radiation in Fukushima, Japan.

A year after the Fukushima nuclear accident, the emerging consensus among scientists is that its effects on physical health and the environment have so far been minimal. There have been no reported radiation-related deaths or illnesses from the accident, even among workers who faced very high exposure. That's a stark contrast with the world's last major nuclear accident, in Chernobyl in 1986, when 28 workers died of acute radiation syndrome within the first year.

"From a radiological perspective, we expect the impact to be really, really minor," said Kathryn Higley, a specialist in tracking radiation in the environment at Oregon State University.

Those studying the accident warn, however, that the early, reassuring conclusions may understate the extent of exposure for certain people. They add that scientists still know very little about the effect on the human body of extended exposure to low-level radiation. There also have been some disturbing developments?a reduction in the bird population near the plant, high levels of radiation in local fish?that biologists say they will continue to watch.

"The most important thing is to monitor everyone's health carefully over the longer term," said Shunichi Yamashita, vice president at Fukushima Medical University and a longtime researcher on the impact of radiation on human health.

Toshiso Kosako, a Tokyo University expert on radiation protection, estimated that, over the long run, Fukushima Daiichi will increase the incidence of thyroid problems, including cancer, for 300 to 500 people. Chernobyl, by contrast, resulted in 5,000 to 6,000 cases of thyroid illness, mostly among children, he said. A global group created to study the health effects of Chernobyl expects a total of 4,000 fatal cancers among those most highly exposed.

Mr. Kosako drew international attention in April when he tearfully resigned as an adviser to then-Prime Minister Naoto Kan, blaming the government for failing to protect communities. Though he still has complaints, he also credits the low toll to the government's relatively quick effort to control food and water supplies after the meltdowns. In Chernobyl, contaminated milk was a major cause of illness among children.

One government survey of 10,468 people from three towns at high risk?Namie, Iitate and Kawamata?was released in late February. Among them, 58% are estimated to have received less than one millisievert of exposure, and 95% less than five millisieverts. Just 23 people, including 13 nuclear workers, were assumed to have been subjected to more than 15 millisieverts.

By comparison, the U.S. Environmental Protection Agency estimates that Americans are exposed, on average, to three millisieverts of radiation per year from natural and man-made sources. Japanese safety rules allow a nuclear worker up to 100 millisieverts a year?a level that was temporarily raised to 250 millisieverts as workers tried to contain the stricken plant.

The exposure figures were based on surveys of where residents were at certain times and the radiation levels in those areas. Separately, Fukushima prefecture offers testing by whole-body scanners to directly measure internal radiation exposure. By the end of January, 15,408 people had been tested, but none 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.

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.

?'From a radiological perspective, we expect the impact to be really, really minor,' said one specialist.?

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.

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 an eerie quietness," he said. "The environment is just quieter."

Write to Yuka Hayashi at yuka.hayashi@wsj.com, Phred Dvorak at phred.dvorak@wsj.com and Robert Lee Hotz at sciencejournal@wsj.com

A version of this article appeared Mar. 10, 2012, on page C3 in some U.S. editions of The Wall Street Journal, with the headline: In Japan, Relief at Radiation's Low Toll.

Source: http://feeds.wsjonline.com/~r/wsj/xml/rss/3_7013/~3/etBPe1UlumE/SB10001424052970203961204577271152728725214.html

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