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Thursday, March 8, 2012
QUEST FOR RECOVERY
Tohoku fears nuke crisis evacuees gone for good
By MIZUHO AOKI
Second in a series
KAWAUCHI, Fukushima Pref. — During a visit in late February to Shidamyo, less than 30 km from the Fukushima No. 1 nuclear plant, a few elderly residents could be seen ambling around the tranquil rural district, but there were no signs of any children.
Radiation readings in the area have been high since three reactors at the power plant melted down, and are currently between 1 to 3 microsieverts per hour — about 20 to 60 times higher than levels in Tokyo.
Shidamyo, however, was never designated as an emergency evacuation preparation area since it is part of the city of Iwaki, Fukushima Prefecture, where low hourly radiation readings of around 0.1 to 0.2 microsievert have been recorded in most districts.
But residents alarmed about radioactive fallout still urged parents with children to evacuate anyway, and about 50 of Shidamyo's 140 inhabitants fled the area, including all the children.
"They moved to different places, some to other parts of Iwaki, while others moved outside Fukushima Prefecture altogether. We — the elderly — are the remaining residents," said Chuhei Sakai, a 62-year-old maker of "tsukemono" pickles and a farmer in Shidamyo.
As of Feb. 23, Fukushima had seen 62,674 residents evacuate from the prefecture, a massive increase from the 38,896 evacuees estimated last June, according to the prefectural government. The total includes residents who notified authorities that they were evacuating, but still remain officially registered in the prefecture.
So far, there have been no reported cases of Fukushima residents suffering health problems as a result of radiation exposure since the nuclear crisis started. Data show exposure from radioactive materials emitted by the crippled nuclear plant has been small, but experts say the data are too limited to draw any conclusions yet about the impact on residents' health. Continuous monitoring of their health and diet remains crucial, they say.
"If the current radiation dose estimates are correct, (cancer-related deaths) likely won't increase," said Michiaki Kai, professor of radiation protection at Oita University of Nursing and Health Sciences."If there is any health impact from radiation, it would be too small to detect, and in any case it would be masked by other, much larger factors, such as smoking and diet," Kai said.
According to a prefectural health survey of 9,747 residents in the three highly contaminated municipalities of Iitate, Kawamata and Namie, about 58 percent of them were externally exposed to less than 1 millisievert in the first four months of the nuclear crisis.
The survey also showed that only 71 residents were exposed to 10 millisieverts, although the dosage of one person was as high as 23 millisieverts, the prefecture said.
A cumulative dosage of 100 millisieverts over a person's lifetime increases the risk of dying from cancer by 0.5 percent, according to the International Commission of Radiological Protection, a body of scientists that makes nuclear regulatory recommendations worldwide, including Japan.
In terms of internal exposure from radioactive cesium, the dosage Fukushima residents received was found to be even smaller.
According to a separate prefectural government examination of 15,408 residents across 18 municipalities, including Iitate and Namie, conducted from June 27 to Jan. 31, internal exposure levels were below 1 millisievert in most cases. The highest level detected was about 3 millisieverts, but only two residents were found to have received such a dosage.
However, concerns remain over the amount of radioactive iodine residents' thyroid glands were exposed to when the nuclear disaster erupted in March, releasing massive quantities of iodine-131 into the atmosphere.
Iodine-131 is known to accumulate in the thyroid gland when inhaled or ingested, and experts say it may possibly cause thyroid cancer. Particular caution is necessary when it comes to children, who are two to three times more vulnerable to radiation, experts stress.
Last year, the central government conducted thyroid screenings only on 1,080 children up to age 15 in the municipalities of Iwaki, Kawamata and Iitate, between March 26 and 30.
According to the screenings, the highest exposure detected was 0.1 microsievert, equivalent to an annual dose of 50 millisieverts for a 1-year-old, experts say.
While this is a relatively high dosage, it is unlikely to increase a child's chances of developing cancer, said Makoto Akashi, executive director of the National Institute of Radiological Sciences.
Still, Akashi added that as current data are limited, it's difficult to provide a conclusive answer.
Because the half-life of iodine-131 is only eight days, emissions of the isotope from the Fukushima No. 1 plant have decayed and it is no longer possible to measure the dosage children were exposed to.
"We haven't checked all the children (in Fukushima), so we don't know (their exposure levels). We can only estimate their dosages from the data compiled to date," Akashi said.
Fukushima is currently carrying out thyroid exams on about 360,000 people aged under 18 at the time of last March's disasters. Prefectural authorities plan to continue conducting checkups throughout their lifetimes — every two years up to age 20, and every five years afterward.
Following the 1986 Chernobyl disaster, about 6,000 children and adolescents in what is now Ukraine and Belarus developed thyroid cancer, according to the U.N. Scientific Committee on the Effects of Atomic Radiation.
The victims were believed to have ingested the iodine isotopes through heavily contaminated food produce, including milk.
While iodine-131 remains a concern, the risk of Fukushima residents suffering internal exposure through eating food contaminated with radioactive cesium is considered low. Screening tests conducted by the central and municipal governments show that contamination in most produce has declined over the past year, except for some fish, mushrooms, produce grown in forests and wild animals.
Highly contaminated leaf vegetables such as spinach were found soon after the nuclear crisis began, in Fukushima Prefecture and other parts of the country.
Spinach grown in Ibaraki Prefecture, for example, was found to contain 1,931 becquerels of radioactive cesium per kilogram last March 20 — almost four times higher than the government's maximum limit.
But in January, all screened vegetables — excluding mushrooms and some dried vegetables — were confirmed to contain less cesium than the 500-becquerel threshold, and most produce contained no radioactive cesium, according to the health ministry.
When the No. 1 plant's crippled reactors started spewing radioactive materials last March, vegetables were heavily contaminated by isotopes that fell from the sky and stuck to their leaves, according to Yasuyuki Muramatsu, a radiochemistry professor at Gakushuin University in Tokyo.
But radioactive cesium that has fallen to the ground becomes more strongly attached to soil as time passes, and the main contamination route now is through root systems, Muramatsu said.
Contamination levels of produce have declined because it is much less likely that plants will absorb cesium through their roots, he said.
Meanwhile, decontamination efforts have become a pressing matter in both Fukushima and other highly contaminated areas outside the prefecture, to lower residents' external exposure as much as possible.
Although decontamination work has been completed at most schools in Fukushima Prefecture by removing contaminated surface soil from their grounds, little progress has been made in other areas, including residential neighborhoods. This is mainly due to difficulties in finding temporary storage sites for contaminated waste, while this winter's unusually heavy snowfall also slowed work, prefectural authorities said.
The only municipality in Fukushima that has kicked off full-fledged decontamination efforts is Kawauchi, according to prefectural official Satoshi Masuda.
Part of the village falls inside the 20-km no-go zone, while another part was declared an emergency evacuation preparation area between last April and September.
In addition to Kawauchi, the cities of Fukushima, Date and Minamisoma have just launched limited decontamination efforts, Masuda said.
The central and municipal governments plan to decontaminate all areas where the annual radiation dosage exceeds 1 millisievert, excluding naturally occurring radiation, with the long-term goal of reducing the level to below 1 millisievert. Areas outside Fukushima also will be targeted, such as Miyagi, Saitama and Chiba prefectures. There are no plans to decontaminate Tokyo, however.
Experts say decontamination can prove effective in cities, but they express doubts about whether rural areas, especially mountains and forested regions, can be adequately cleansed. To fully decontaminate forests, for instance, in theory all trees would have to be cut down and all the surface soil scraped away, they point out.
About 70 percent of Fukushima Prefecture is mountainous, forested, or both, making decontamination work especially problematic.
And even if radiation readings drop, a lot of municipalities expect that many former residents still will not return home.
Kawauchi, whose population stood at around 3,000 before March 11, is one of the municipalities that fear resident numbers will never return to predisaster levels.
According to a survey conducted by local authorities in February, more than 60 percent of the 1,817 respondents said they do not intend to return to the village or have yet to make up their mind.
The top reason cited by respondents was fear of radiation exposure, followed by concerns that municipal medical and welfare facilities are now insufficient.
Rikizo Nishiyama, a 78-year-old farmer from Kawauchi currently living in temporary housing in the city of Koriyama, also in Fukushima Prefecture, said he and his wife plan to return to the village at the end of March, but their future doesn't look bright.
"I used to farm land in Kawauchi, but it's not an option when I return" because it hasn't been decontaminated yet, Nishiyama said. "I will have to live off my pension."
Back in Iwaki, meanwhile, authorities have conducted a limited decontamination trial, but due to a lack of temporary storage sites for contaminated waste they can't proceed with full-scale efforts to cleanse the area, according to Sakai, the farmer in Shidamyo.
"Children should not come back (to Shidamyo) yet. Nothing has been done (to decontaminate the area)," he said.
In this series, we examine how the March 11 calamity changed the nation and what needs to be done to revive Japan as the first anniversary of the Great East Japan Earthquake approaches.