Tenei, Japan - For seven generations, Yoshitoshi Sewa and his ancestors have tilled this farm in a gently curving valley filled with green rice paddies. But now he will not let his young grandchildren play outside their tile-roofed home for fear of an invisible and potentially long-lasting threat, radiation.
“Even if the government says it’s O.K., no one here wants to take the risk of radiation,” said Mr. Sewa, 63, whose farm sits about 40 miles west of Japan’s stricken Fukushima Daiichi nuclear power plant — well beyond the zone where residents have been told to leave or remain indoors.
Since an earthquake and tsunami on March 11 crippled the plant, spewing radioactive particles into the air and sea, Tokyo has ordered the evacuation of a 12-mile radius, and some villages beyond that. But those living outside the evacuation zones have felt left in limbo, exposed to levels of radiation that are several times the normal level, though not high enough to cause observable health risks. Still, experts admit that there is a lack of knowledge about the health effects of lower doses of radiation, especially over an extended period of time. Japan’s plant has been dispersing radioactive material for nearly two months and counting, far longer than the 10 days during which the Chernobyl plant released a much larger burst of radioactive particles in 1986.
It is difficult for Japanese experts to even agree on clear-cut numerical levels of radiation for deciding which areas are safe to inhabit — decisions that might affect hundreds of thousands of people living in hundreds of square miles of this densely population nation.
“This is an unprecedented situation, to which none of our textbooks apply,” said Shigenobu Nagataki, former chairman of the Nagasaki-based Radiation Effects Research Foundation, which studied victims of the World War II atomic bombings. “Decisions are being made now that will have a huge impact on Japan’s future.”
The disagreements came to the forefront on Friday, when a government adviser on radiation safety quit, calling on Japan to lower the permissible radiation dose of 20 millisieverts per year that the Education Ministry has set for schools for younger children, including elementary and junior high, in affected areas.
Other Japanese critics point out that the figure comes from the International Commission on Radiological Protection, which sets it as the upper limit of radiation exposure in inhabited areas after a nuclear accident, and thus too high for schools because children are more vulnerable. Government officials and some experts retort that the level was still low enough not to pose a health risk. They also said that radiation levels would fall over the next two months with the disappearance of short-lived iodine 131, which accounts for about half of the radioactive material emitted by the plant. Other measures are being taken to clean up the remaining radioactive matter, mainly cesium 137, which can last for generations.
Acting on its own, the city of Koriyama, about 35 miles west of the plant, will change the topsoil at 15 elementary schools where the city detected radiation doses above 20 millisieverts per year, and at 13 kindergartens where it found slightly lower radiation levels.
The Education Ministry has also found similarly high levels At 13 elementary schools, kindergartens and preschools in Fukushima Prefecture. In the city of Fukushima, 35 miles northwest of the plant, some schools have barred students from playing outside while at school. At least one school also requires children to wear hats and surgical masks, and to avoid contact with playground equipment.
The Education Ministry’s guidelines take into account the child’s exposure to radiation during the entire day, both at home and school, and experts say clean-up will have to happen all over towns, not just on school grounds. The radiation levels at schools is just one of the many decisions that Japan must make, whether on farm produce or the safety of entire towns. In Fukushima Prefecture, where the nuclear plant is located, the authorities conduct 50 tests a day on vegetables and milk, as much to reassure consumers as to find contaminated products.
Even so, Mr. Sewa, the farmer in Tenei, said that he had to destroy this spring’s crop of 880 pounds of cucumbers because he could find no buyers.
“Fukushima products are seen as tainted,” he said.
Experts say the fact that the Japanese government has not evacuated more areas reflects the balance it has struggled to strike between public safety and a desire to limit the size of affected areas in a cramped nation with little space to spare. “Fleeing is simply not an option,” said Gen Suzuki, an expert on radioactivity at the International University of Health and Welfare in Otawara, Japan. “The debate now should not be whether 10 millisieverts is safer than 20, but what steps we should be taking to decrease radiation levels.”
Mr. Suzuki and others say the risks are not as high as some people fear. But they admit that there is a lack of hard data about the health effects of lower radiation doses delivered over extended periods. Most knowledge about radiation’s health effects comes from Japan and studies on the survivors of the atomic bombs in Hiroshima and Nagasaki. Researchers calculated the exposure levels of survivors and then waited for decades to see what they died from.
They then compared the data with death rates and causes of death in other, unexposed parts of Japan.
The results showed elevated cancer rates from high levels of radiation released during atomic blasts, said Mr. Nagataki, who did such studies. But researchers are left to rely on educated guesses in trying to extrapolate those results down to lower doses, he said.
Mr. Nagataki and other experts agreed that whatever additional cancer stemmed from the radiation levels seen in many of the evacuation zones around the Fukushima plant would probably be very low, even if residents remained in them. They said that a dose of 20 millisieverts per year would likely raise the rate of cancer deaths by far less than one percent, though the radiation levels in some of the evacuated areas are much higher than that, especially near the plant.
With health risks so low, Mr. Nagataki said that evacuation was not only unnecessary, but potentially more dangerous than the radiation. He said they could face the same risks as survivors of Japan’s tsunami, who have been put into crowded school gymnasiums and other makeshift shelters where he said they are vulnerable to contagious diseases and emotional problems like depression.
The Japanese authorities moved early to evacuate about 78,000 people within 12 miles of the Daiichi nuclear plant, and told another 62,000 people between 12 and 19 miles away to stay indoors. But Tokyo proved reluctant to expand evacuation areas, despite the urgings of the International Atomic Energy Agency and recommendations by the United States that its citizens stay 50 miles from the plant.
Late last month, the authorities finally ordered the evacuation of another 7,000 people from the village of Iitate, 25 miles northwest of the plant, and a few nearby areas that showed readings in excess of 20 millisieverts per year.
“The fact is that no one knows for sure what the risks are,” said Mr. Nagataki, “but that doesn’t stop many people from saying ‘Scary! Scary!’ ”