A full meltdown has been avoided so far at Japan's 40-year-old Fukushima Daiichi nuclear plant. Neverless, as far away as Tokyo, 240 kilometers to the south, the city government says small amounts of the radioactive iodine and cesium have been detected in the air. Higher levels of radioactive materials have been monitored closer to the plant, prompting the government to order the evacuation of residents within a 20-kilometer radius.

As a precautionary measure against radiation exposure, the Japanese have also distributed 230,000 units of potassium iodide tablets, comprising a stable form of iodine, to evacuation centers in the area around the Fukushima Daiichi and Fukushima Daini nuclear power complexes, according to the International Atomic Energy Agency (IAEA). Potassium iodide, which is available in the U.S. in 130- and 65-milligram doses (smaller doses are given to children), has been shown to protect the thyroid gland from the radioactive form of iodine released by nuclear accidents or emergencies that could lead to thyroid cancer.

Thyroid cancer ended up being the biggest negative health impact caused by the Chernobyl nuclear reactor disaster, according to a report issued last month by the United Nations Scientific Committee on the Effects of Atomic Radiation. The report (pdf) specifies that more than 6,000 Russian, Ukrainian and Belarusian residents who were children at the time of the disaster had been diagnosed with thyroid cancer as of 2006, the disaster's 20th anniversary. Fifteen of these people had died as of 2005. The incidence of thyroid cancer in contaminated areas of the Ukraine and Belarus was triple that of normal thyroid cancer incidence in the area, although the study's authors acknowledge that more attention was paid to medical examinations and improved record-keeping in those areas affected by the Chernobyl event.

As Japan struggles regain control of the Fukushima Daiichi plant, demand for potassium iodide is growing even 8,000 kilometers away on North America's west coast. Anbex, Inc., based in Williamsburg, Va., announced on its Web site Tuesday that it has sold out of its iOSAT brand of potassium iodide. Other makers of the substance have announced similar shortages.

Scientific American spoke with John Boice, a professor at Vanderbilt University's Vanderbilt-Ingram Cancer Center and a cancer epidemiologist with the International Epidemiology Institute in Rockville, Md., to better understand why potassium iodide is in demand as well as what it can (and cannot) do.

[An edited transcript of the interview follows.]

Why is potassium iodide administered to people who have been exposed to radioactive iodine?
The thyroid is like a sponge for iodine. It's been known from the 1970s that if you administer normal iodine the thyroid will absorb it and then block the uptake of subsequent exposures to radioactive iodine. Therefore, if you take potassium iodide and then are exposed to radioactive iodine, there won't be any place for it to go because your thyroid is all filled and the radioactive material will be excreted from the body.

One pill is good for 24 hours, but then you have to take another pill. You don't take two pills at once, because having too much potassium iodide isn't good for you either. Like anything else, it's not 100 percent effective, but it appears to be quite a benign thing to take, and it does block the uptake of radioactive iodine.

Is thyroid cancer the foremost risk when radioactive iodine is in the air?
With regard to radioactive iodine, it's just the thyroid gland that you're worried about; you're not concerned about anything else. Of course, in an event like Chernobyl where the reactor's containment vessel did not hold everything a number of other radioactive elements were also released, including cesium and strontium as well as some of the reactor fuel—the uraniums and plutoniums. Still, the two main elements of concern from a radiation leak would be radioactive iodine and cesium, [the latter of] which has a half-life of 30 years, so it stays around for a little while.

Would potassium iodide protect a person from other forms of cancer?
No, this is unique. These potassium iodide pills are not magic pills. They protect against thyroid cancer but they don't protect you against other possible cancers.

Assuming there is more than radioactive iodine in the air, what can people do to protect themselves?
There is no protective agent against other cancers. The protective measures are to evacuate, get as far away from the radiation exposure as you can so that your dose is much lower. Stay inside, don't go out and breathe contaminated air. If you do get some exposure to radioactive elements, take a shower and wash them off immediately.

The radiation leak at Fukushima Daiichi appears to have increased demand for potassium iodide in the U.S. Is this a necessary precaution?
I have experience studying the effects of radioactive iodine on adults and, based on that, it actually looks like the adult thyroid gland is not very sensitive to the cancer-producing effects of radiation. One of the things we have learned about studying the after-effects of Chernobyl is that the kids who lived in areas of radioactive fallout who drank contaminated milk had a huge increase in thyroid cancer related to radioactive iodine. Something on the order of 6,000 extra cases of thyroid cancer occurred among the children that had been exposed to increased radioactive iodine.

That's sort of the concern and the reason why the Japanese are distributing potassium iodide. That's why around our own nuclear power plants we have stockpiles of potassium iodide. Still, it's not recommended that adults over the age of 40 take potassium iodide. The benefit is miniscule because our thyroid glands are not that sensitive.

8 Comments

1. 1. EyesWideOpen 05:52 PM 3/16/11

   IOSAT is the government stockpiled iodine approved by the FDA and available to the public through pharmacies for around $10.00 for a pack of 14 (you don't want to take more because this is a mega-dosage for fallout only).
   
   On eBay, sellers have bought up supplies at $10.00 per 14-pack (or less due to volume purchases), and have each 14-pack IOSAT at just under $2,000.
   
   That's right, they likely bought it for under $10.00 in volume, and resell each one for $2,000 ... with an astronomical profit. (Do the math, buy 100 packs at $10.00 for $1,000, and sell 100 packs at $2,000 for $200,000; and pay-off your mortgage by exploting the misery of others in a global crises.)
   
   Sadly this is the ugly underbelly of capitalism and free markets that created the most illustrious standards of living in recorded history.

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2. 2. jack.123 05:53 PM 3/16/11

   I keep a surplus for myself and my family,if you are exposed to high levels of radiation you are most certainly protected.Let those who did not protect themselves deal with the cancers that follow.Hope you have insurance that covers acts of God.

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3. 3. EyesWideOpen 06:34 PM 3/16/11

   They say that Beta Glucan is now proven by science to perhaps become the holy grail of cancer prevention for the entire body:
   
   http://en.wikipedia.org/wiki/Beta-glucan
   
   A fascinating quote from this article:
   
   "Radiation Exposure
   
   Specific hematopoietic activity was first demonstrated with β-glucan in the mid-1980s in an analogous manner as granulocyte monocyte–colony stimulating factor (GM-CSF).[17] Research was carried out initially with particulate β-glucan and later with soluble β-glucans, all of which were administered intravenously to mice.[18][19][20] Mice exposed to 500-900 cGy (500-900 mrads) of gamma radiation exhibited a significantly enhanced recovery of blood leukocyte, platelet and red blood cell counts when given i.v. β-glucan.[21] Other reports showed that β-glucan could reverse the myelo-suppression produced with chemotherapeutic drugs such as fluorouracil,[15] carboplatinum or cyclophosphamide.[22] Moreover, the anti-infective activity of β-glucan combined with its hematopoiesis-stimulating activity resulted in enhanced survival of mice receiving a lethal dose of 900-1200 cGy of radiation.[13] In vitro studies showed that β-glucan could enhance granulocyte and megakaryocyte colony formation by hematopoietic stem progenitor cells when used in combination with GM-CSF and interleukin-3 (IL-3), respectively."
   
   It gets better reading on! I have just stockpiled this amazing supplement from the Shiitake mushroom and the cell wall of baker’s yeast (Saccharomyces cerevisiae), by NOW Foods, in light of this radiation crisis.

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4. 4. ormondotvos 06:24 PM 3/17/11

   However, in certain circumstances, excessive consumption of iodine can actually inhibit the synthesis of thyroid hormones, thereby leading to the development of goiter (enlargement of the thyroid gland) and hypothyroidism. Excessive iodine intake may also cause hyperthyroidism, thyroid papillary cancer, and/or iodermia (a serious skin reaction).
   In an attempt to prevent these symptoms of iodine toxicity, the Institute of Medicine established the following Tolerable Upper Intake Levels (TUL) for iodine:
   • 1-3 years: 900 mcg
   • 4-8 years: 300 mcg
   • 9-13 years: 600 mcg
   • 14-18 years: 900 mcg
   • 19 years and older: 1,100 mcg
   • Pregnant women 14-18 years: 900 mcg
   • Pregnant women 19 years and older: 1,100 mcg
   • Lactating women 14-18 years: 900 mcg
   • Lactating women 19 years and older: 1,100 mcg
   It is important to note that if you have an autoimmune thyroid disease (for example, Grave's disease or Hashimoto's disease) or if you have experienced an iodine deficiency at some point in your life, you may be more susceptible to the dangers of excessive iodine consumption, and may, therefore, need to monitor your intake of iodine more carefully.
   
   
   Look up foods with iodine and save your money. Kelp is likely the best, and available widely at Asian and health food stores.

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5. 5. EyesWideOpen 07:13 PM 3/17/11

   Iodine dosage for 19 years and older: 1,100 mcg:
   
   That is exactly what I figured (where 1,100 mcg = 1.1 mg or milligrams).
   
   IOSAT in packets of 14 tablets (approved by the FDA and distributed by the military in out of control situations) contains, get this, 130 mg of Potassium Iodine per tablet! (One tablet to be taken every day for no more than 14 days in a radiation emergency.)
   
   Based on your healthy dosage of 1.1 mg for adults per day, the government is expecting us to take over 118x that dosage in a single IOSAT pill if a nuclear cloud passes over our homes... for up to 14 days. Mindboggling.
   
   I'm a little confused, however, when you say excessive iodine (which of course is toxic) causes goiter. For example, birds (such as budgies) get goiter due to a deficiency of iodine in their diets; adding iodine to their water in trace amounts can prevent goiter. Based on what you're saying, people could end up with goiter (swollen necks) by taking the full 14 day dosage of IOSAT in a nuclear emergency.

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6. 6. tranquility15 in reply to jack.123 07:51 PM 3/21/11

   Really.....

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7. 7. EyesWideOpen 08:11 PM 3/21/11

   If we're to believe Ann Coulter, we're denying ourselves the health benefits of radiation by taking iodine in a nuclear emergency.
   
   As the cloud passes, just go to your local park, run across the grass and get a natural high breathing in those sweet radioactive particles. (Picture that famous aerial view of Julie Andrews running across the field ecstatically singing "the hills are alive to the sound of music!..." then imagine she is enshrouded in a cloud of radiation, only it's YOU running across that field as Ann Coulter awaits you with open arms...)

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8. 8. drhugh 12:42 PM 3/27/11

   I would be interested to know what radioactive salts are dissolved in the reactor coolant water in sufficient quantity to burn those two workers who got a boot-full.

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