The EPA is stepping up efforts to monitor radiation levels in the United States following reports of elevated levels across the country as a result of Japan's nuclear reactor meltdown. Two states—Washington and California—reported finding trace amounts of radiation in milk this week. However, federal officials and nuclear experts have repeatedly assured the public that individuals in the United States do not face increased risk of radiation poisoning.
After the jump, we explore some common questions about the risks of radiation exposure both in the day-to-day and during a nuclear disaster.
How did radiation from Japan make its way into milk produced on the West coast?
Radioactive particles traveled through the atmosphere to the United States, where they settled on grass and in water that was consumed by some cows. The radiation passed through the cows and into the milk.
Should I be worried about radiation exposure from dairy products?
According to both the Environmental Protection Agency and the Food and Drug Administration, no. The milk samples taken in Washington and California contained radioactive particles at concentrations 5,000 times lower than the limit that the FDA has deemed safe for human consumption. FDA senior scientist Patricia Hansen told CNN that the radiation levels found in recent milk samples are "miniscule" compared to the exposure that people face in their daily lives. What's more, the particles found in the samples come from an isotope known as radioactive iodine, or iodine-131, which has a relatively short lifespan.
Should I be worried about food imported from Japan?
The FDA has banned all imports of fruits, vegetables and dairy products from the area of Japan near the Fukushima Daiichi nuclear plant. Food products from Japan make up less than 4 percent of all U.S. imports, and the FDA has said that the risks to human health are still low if radiation-tainted products are consumed in moderation. Americans only face risk, the agency says, if they consume excessive amounts of such products.
How much radiation am I exposed to in my daily life?
As Peter Caracappa, a radiation safety officer and professor of nuclear engineering at Rensselaer Polytechnic Institute pointed out on NPR recently, radiation is a part of nature. "Everything that's living has some amount of radiation coming from it," noted Caracappa. "Plus there's radiation in the ground and the air."
Where might I encounter radiation in the course of an ordinary day?
Well, bananas, as Caracappa points out, contain radioactive potassium. And as this handy, tongue-in-cheek infographic shows, even sharing a bed with someone for a night will expose you to some radiation (about half the amount found in a single banana).
Is there a type of radiation that's particularly harmful to humans?
Ionizing radiation—the type of radiation people get exposed to in small doses when they receive an X-ray and in much larger doses via a nuclear catastrophe like the one in Japan—is able to alter the chemical makeup of human cells. Cellphones and microwave ovens produce much less harmful forms of non-ionizing radiation (though there has been much discussion about the possibility that radiation from cell phones can affect the brain). Most people are exposed to ionizing radiation through radon gas in the air we breathe.
What is radon?
Radon is a radioactive gas that can cause cancer. According to the EPA, it causes many thousands of deaths each year. It is odorless, has no taste, and is found all over the U.S. It comes from the natural breakdown of uranium in soil, rock and water.
Americans are most at risk of radon exposure at home, particularly in basements, where it can seep in through cracks and holes in a home's foundation. The EPA encourages everyone to test their home for radon, and says that inexpensive radon reduction systems can reduce radon levels in a home by up to 99 percent.
What could exposure to high doses of ionizing radiation do?
Despite conservative firebrand Ann Coulter's recent claims—that exposure to radiation is good for the body, meaning the Japanese will actually benefit from the nuclear meltdown—the biological effects of high levels of radiation exposure are quite severe. The United States Nuclear Regulatory Commission (USNRC) notes that just about every form of cancer imaginable has been linked to exposure to ionizing radiation.
Is there a level of exposure to ionizing radiation that is considered to be most deadly?
Because everyone reacts to radiation in different ways, the USNRC says that it's "not possible to indicate what dose is needed to be fatal." The most extreme examples of mass exposure to ionizing radiation were the bombings of Hiroshima and Nagasaki in Japan in 1945 and the 1986 Chernobyl disaster.
Many of the victims in those incidents who were exposed to extremely high doses of ionizing radiation died within days, weeks, or months of radiation poisoning. Such poisoning essentially leads to the bodily organs shutting down one by one. The Mayo clinic chart shown at left illustrates what such radiation poisoning can do to the body.
Is there any chance of someone in the United States contracting radiation poisoning from Japan?
No. Every expert on the subject has unequivocally ruled out such a risk. Americans do face a possible risk of future cancers related to minimal exposure, but even that appears to be an extremely remote possibility at this point. The EPA is seeking to prevent such exposure via increased monitoring of radiation levels in potential sources such as milk, rain, and drinking-water supplies.
(Photo: Petar Petrov/AP)

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