People evacuated from a danger zone around Japan's damaged Fukushima nuclear plant may need to stay away for many months, but experts say there are ways to make their return swifter and easier.
Radiation levels in the area now are higher than normal and could increase risks to long-term health, but so-called remediation methods, such as deep-ploughing the soil, removing topsoil altogether and choosing crops and ways of farming that don't pick up much radioactivity, can cut the risk of harm.
Tens of thousands of people, including farmers and their families, have been evacuated from a 20-km (12-mile) exclusion zone around the stricken Fukushima plant, and another 130,000 who live in a 10 km (6-mile) band beyond the exclusion zone have been advised either to leave or stay indoors.
Assuming no drastic worsening of leaks from the tsunami- and quake-damaged plant, there will be no long-term exclusion zone like that around Chernobyl in Ukraine, the site of the world's worst nuclear disaster in 1986.
"The worst-case scenario in terms of people re-occupying the area is that people might be able to go back within months," said Steve Jones, an independent nuclear and environmental consultant.
"There's likely to be an extended ban on food production within the affected sector - of about 20 to 30 km out - that might persist for some time. But there is then also the option of applying all sorts of remedial measures."
Experts say the key to the future of the current exclusion zone will be levels of radioactive cesium 137, which has a half-life of 30 years. That means that its radioactivity drops by 50 per cent every three decades.
Both cesium 137 and another radionuclide, iodine 131, have been detected in crops, in the soil and in milk produced in the area close to the plant. Yet experts say there is no reason this should make the area a no-go zone forever.
"The iodine problem will be over in a couple of months," said Astrid Liland of the Norwegian Radiation Protection Authority, explaining that since iodine 131 has a half-life of eight days, it will quickly dissipate.
That means that milk contaminated with iodine 131, for instance, can be safely made into long-life cheese. Consumers, however, may be reluctant to buy it.
For cesium, which lingers far longer and may present a bigger problem - especially for farmers of grazing animals - both Ms. Liland and Nick Beresford, a radioecologist at the Lancaster Environment Centre in England, say the use of a chemical compound called Prussian blue is probably the best option.
Prussian Blue binds to cesium to prevent it from being taken up during digestion by cows, goats, sheep and other animals and was widely used in the areas around Chernobyl.
"It is still used in Norway to counter the effects of Chernobyl, largely for sheep and goats," said Ms. Liland.
Other lessons learned from Chernobyl include deep-ploughing the soil to drive the radiation further down into the ground, and using potassium fertilizer, experts said.
Potassium is vital for living cells and absorbed by plants in a similar way to cesium. Since plants prefer to absorb potassium, overloading the soil with potassium can limit the uptake of cesium.
"The activity at the moment will be predominantly in the top few centimetres of the soil profile, so if you're willing to spend an unlimited amount of money you could simply remove all that, take it somewhere else and bury it," added Jones.
Jim Smith, a specialist in environmental physics at Britain's Portsmouth University who has spent years studying the radiation effects from Chernobyl, said it was important not to overplay the potential health and environmental impacts from the levels of radiation seen around the Japanese plant.
Working from data from surveys conducted by teams from the United States energy department and the International Atomic Energy Agency (IAEA), Smith said there were so far no areas in which radiation levels had exceeded 300 microsieverts per hour.
"Now - 25 years on - at Chernobyl, I've worked in areas where we can still have readings of up to 300 microsieverts per hour," he said. "So whilst this is clearly a significant contamination of the terrestrial environment, I was quite relieved to see these levels (in Japan)."
For ordinary people faced with the dilemma of whether to return to their homes in the months ahead if the exclusion zone is lifted, Smith said key would be to avoid unnecessary stress.
"We're in the range of dose rates where we should say... it's not going to kill you immediately, but you'd have an increased risk - just as many people do from natural radioactivity around the world - and it's your choice," he said. "To me this is still a bigger social, economic and psychological problem than it is a radiation problem."Report Typo/Error
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