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Nuclear Meltdown in Japan: What's the Risk of Radiation?

FAQ on Radiation Risk From Tsunami-Damaged Nuclear Plants

Could radiation from Japan's nuclear plants affect the U.S.?

No significant radiation from the Japan disaster is expected to hit the U.S., say experts from the Oregon State University department of radiation health physics.

"Any radioactive contaminants released will end up raining out of the atmosphere into the Pacific Ocean, where they will be diluted and absorbed, or in the very near vicinity of the plants," Kathryn Higley, PhD, says in a news release. "This is not Chernobyl."

Royal says there is no danger of radiation affecting any of the United States -- not even Alaska or Hawaii, which are much closer to Japan than is California.  Yet he says he's already received panicked calls from pregnant women in California, asking whether they should have a therapeutic abortion to avoid giving birth to radiation-damaged children.

State radiation detectors in the U.S. have picked up signals that appear to be from the Fukushima plant.  But the U.S. Environmental Protection Agency (EPA) notes that the amount of radiation is far from harmful.

"The levels we're seeing coming from Japan are 100,000 times lower than what you get from taking a round-trip international flight," the EPA said in a March 22 news release.

The EPA maintains the RadNet system, made up of more than 100 monitors that give continuous, real-time radiation readings. The system also has 40 deployable monitors capable of reading the body dose of radiation a person would receive in the vicinity of the monitor. Just to be on the safe side, the EPA has sent extra monitors to Guam, Hawaii, and Alaska. 

The EPA noted on March 28 that levels of radioactive iodine found in Massachusetts rain water exceed the maximum contamination limit (MCL) for drinking water. However, the MCL is calculated on the effects of drinking contaminated water for 70 years. The radioactive iodine in Massachusetts rainwater likely did come from Japan -- but it won't be there for long, as it has a half life of days rather than years.

Because there's no risk to the U.S., Royal scoffs at people who are stockpiling potassium iodide pills. These pills can prevent radioactive iodine from collecting in the thyroid gland and causing thyroid cancer -- but Royal says there's no U.S. risk of radioactive iodine from the Japan nuclear emergency. Fortunately, if people panic and take the pills, they won't do any harm as long as they are taken as directed.

Royal notes that even if a person received enough radiation to cause radiation sickness -- 1,000 milisieverts -- the dose would increase their risk of cancer by 40%. To put this in perspective, smoking cigarettes increases cancer risk by 1,000% to 2,000%.

Here's some more perspective. From normal background radiation, a person who lives in Denver is exposed to 1 millisievert more radiation per year than is a person living in St. Louis. Royal says that the people living in the 18-mile zone around Chernobyl were exposed to 3 millisieverts of radiation in the years following the disaster. "That is less than the difference from living a few years in Denver rather than St. Louis," he says.

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