Ever since the news of Japan's nuclear crisis, there have been several claims made over the Internet that have panicked people in the U.S. about potential exposure to radiation (one culprit is this viral e-mail), which has led to me being the recipient of questions about whether or not people should be taking potassium iodide supplements to avoid absorption to radioactive iodine.
Should you take potassium iodide pills? My answer has been an unequivocal, "No, it's not necessary. There is little risk of any level of radiation exposure to worry about anywhere else other than in Japan near the reactors. If you're worried about getting cancer, try thinking more about losing weight, eating more dietary fiber, and eating more fruits and vegetables."
In the process of answering questions, I did find myself interested in learning more about radiation and health. By far the best, most in-depth article I've read on "How Radiation Threatens Health" is this one written by Nina Bai and published by Scientific American. Bai's article gives readers an excellent understanding on the typical radiation levels that people are currently exposed to (0.2 to 0.3 milliSieverts), how much they are exposed to by a typical CT scan (1 milliSievert) and what kinds of levels people should really be worried about—the kind of levels that lead to symptoms of radiation sickness ("a whole body dose of 3 sieverts, that is, 3,000 times the recommended public dose limit per year") and the kind that kills people within weeks (5 to 10 sieverts).
Yes, there are concerns over low-dose radiation over time, but as Bai's article points out, the increase of cancer risk is small and basically comes out to about an increase of eight potential cancer cases per 10,000 people. And, the point is that even if any radiation made it over the ocean and to the U.S. (which is unlikely) it would be at levels too low to cause concern.
As for potassium iodide (KI) supplements (not addressed in Bai's article), there is cause for concern because I keep reading that these are "flying off the shelves" in various articles.
The way KI works is by flooding iodine into the thyroid gland to become trapped by the thyroid's receptors, which blocks the uptake and accumulation of radioiodine that could lead to possible thyroid diseases or cancer. This is particularly important in children who are more at risk for radioiodine-induced cancer (as is what happened with the Chernobyl incident because of radioiodine0contaminated milk). The doses for preventing radioidine uptake are high: 50 to 100 milligrams for adults. If exposure is pretty certain, then supplementation with these pills make sense.
But consider that the Upper Limit for adults is 1.1 milligram per day. These pharmacologic doses could be potentially detrimental since excessive iodine can actually lead to hyper- or hypothyroidism and have been known to increase risk of thyroid cancers. Taking these doses should not be considered a safe precautionary measure, as marketed. There is a risk!
My concern is this: that the irresponsible Internet claims are leading people to actually take the high doses of the KI and that retail outlets selling them (like this one with 130 milligram per tablet!) are doing so without giving people any sense of what the risks are when taking high amounts.