| TOKYO/HONG KONG
TOKYO/HONG KONG Millions of Tokyoites are worried about radiation in tap water or in the air, but the thousands of people living in the shadow of Japan's stricken nuclear plant have another fear: it may force them to abandon their homes for years, if not forever.
More than 70,000 people have already been evacuated from an area within 20 km (12 miles) of the plant, and another 130,000 are within a zone extending a further 10 km (6 miles) in which residents are recommended to stay indoors. They too could be forced to leave their homes if the evacuation is extended due to worsening radiation levels.
Nobody in government has yet touched on the issue directly, but given growing worries about soil contamination in the largely rural area and bans on shipping and sales of local milk and vegetables, many residents fear the worst.
"Nobody wants to say it out loud, but I think that in their hearts everybody worries that they won't be able to go home for years at least," said Yoichi Azuma, principal of Koriyama Commercial High School, not far west of the 30-km (18-mile) zone, whose gymnasium has been turned into an evacuation center.
"People here have suffered three disasters: the quake, the tsunami and the invisible danger of radiation, which is a man-made disaster. We feel a lot of anger about the last one."
Though some experts say the crisis at the Fukushima Daiichi nuclear plant, 240 km (150 miles) north of Tokyo, will likely turn out to be less serious than the Chernobyl disaster of 1986, the radioactive substances being emitted are the same -- iodine 131, caesium-134 and caesium-137.
The radioactivity in iodine-131 fully disintegrates in 80 days, but it can find its way rapidly into people through the air and through milk and leafy vegetables, lodging in the thyroid gland, where it can cause DNA damage and raise the risk of cancer, particularly in young children.
Caesium is more troubling as it remains radioactive for over 200 years, threatening people with longer-term exposure through food and from external exposure as it settles on the ground.
"The length of time these areas will remain contaminated depends on the radionuclide composition," said Jim Smith, Reader in Environmental Physics at the University of Portsmouth in southern England.
"If a significant proportion is radiocaesium, food bans and, potentially, evacuation may be long-term."
Food contamination levels in Fukushima, which is known for its peaches, nashi Japanese pears, apples and strawberries as well as milk and vegetables, have risen sharply over the past week, opening up the logical option of extending the exclusion zone.
The United States as early as last week said its citizens should stay out of a broader 50 mile zone, but the Japanese government has not spoken of extension -- a view backed by experts such as Kenji Kamiya, director of the Institute for Radiation Biology and Medicine at Hiroshima University.
"We must consider the impact of radiation on human health, but at this point I think the government's decision is correct given the radiation levels," he said.
A Fukushima prefectural official said there are no firm numbers on how many people remain within the 20-30 km radius but added that many appear to have already left voluntarily, whether from worry or just the growing difficulty of life within an area running out of food and other goods. Media reports say some truck drivers, wary of radiation, refuse to enter the zone.
Chief Cabinet Secretary Yukio Edano touched on this on Thursday, noting that "social needs" might have to be dealt with over the longer term.
"But we must be careful not to send the wrong message that danger is getting bigger if we were to issue such a direction (to evacuate)," he said.
In addition, experts said, the practical issues are huge.
"There is a limit to extend the zone because Japan is an island and one thing we have to face is we have to provide shelter, prepare enough housing and schools for these people," said Lam Ching-wan, a chemical pathologist at the University of Hong Kong and member of the American Board on Toxicology.
Some Fukushima towns and cities have laid on buses for citizens who want to leave, in some cases to nearby prefectures.
At present, Azuma's school hosts 150 people ranging in age from infants to 97 years old. Some had homes destroyed by the tsunami, but many were fleeing the radiation.
Some have chronic health issues, such as kidney problems requiring dialysis, and there are several pregnant women. There are enough blankets to go round, and enough food -- barely.
"People really want to go home, but since many of them grow things or are dairy farmers, they're really worried about what might happen and what the experts might say," Azuma said.
"Foreigners might be told to leave a wider area, but all we have is what we have here."
(Editing by John Chalmers and Michael Watson)