WASHINGTON — Concerns about radiation sickness in Japan are focused for now on the area about 20 miles around the quake-struck Fukushima nuclear plant, where the public has been evacuated but some workers are still fighting off a nuclear disaster.
If the worst happens — a full core meltdown and a large release of radiation — people living within hundreds of miles of the plant could have a somewhat higher risk of developing cancer over decades to come. Experts say the risks depend on how much radiation is released, how much exposure people get to it and over how long a period, and how the winds blow.
There's very little risk for people in the United States most atmospheric scientists say, because any plume would disperse widely, said Thomas Tenforde, president of the National Council on Radiation Protection and Monitoring. Fallout spreading after being blown thousands of miles would probably be below the level of concern for elevated cancer risk, he said.
There were reports of radiation levels of 40 rem on Monday at the nuclear plant — an extraordinarily high degree that would cause radiation sickness after an exposure of just two and one-half hours. U.S. safety rules limit workers to exposure of 5 rem per year. But the Japanese site rates later went down, said Edwin Lyman, a physicist and expert on the health effects of radiation at the Union of Concerned Scientists, a nuclear-safety watchdog group.
The severity of radiation sickness depends on the amount of radiation the body absorbs. It usually begins with nausea and vomiting, and can be followed by other symptoms — including headache and fever. The symptoms are more severe and hit faster when exposure levels are higher and sustained.
If the doses are high enough, the results can lead to gastrointestinal diseases and death, Tenforde said.
In addition, low doses of radiation over the long term can increase a person's risk of cancer over a period of 20-to-30 years or longer, he said. The risk is small but "non-negligible," he said.
Tenforde said he couldn't predict the risks in Tokyo, about 100 miles from the nuclear plant, if there was a core meltdown. That would depend on the amount of radiation, how quickly it was released and other factors, he said.
Potassium iodide pills build up non-radioactive iodine in the body. This lowers the chance that radioactive iodine will enter the thyroid cells, Tenforde said.
Lyman said that the pills have to be taken at the right time, several hours in advance of exposure.
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