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Thyroid-Blocking Potassium Iodide in Growing Demand

Threat of radiological attack drive desire for Cold War era treatment

4 min read

17 October 2001–It’s suddenly very, very busy in Shane Connor’s warehouse. Since 1999, this small-town Texas businessman has maintained an e-commerce business selling two main products: surplus Geiger counters from the Cold War era, and bottles of a compound called potassium iodide (KI). Before 11 September, Connor filled about a dozen orders a day for KI, which blocks uptake by the thyroid gland of certain highly carcinogenic nuclear fission products. Since the attacks on New York City’s World Trade Center and the Pentagon in Washington, D.C., however, 150—200 people have clicked on his site every day, seeking to stock up on KI.

Connor isn’t the only one on the receiving end of inquiries about potassium iodide. At the Rockville, Md., headquarters of the U.S. Nuclear Regulatory Commission (NRC), calls are coming in from town councils and private citizens alike, asking where they, too, can get their supply. As it happens, after two decades of debate, the commission ruled last January that states containing nuclear power plants must at least consider stockpiling potassium iodide or distributing it to the public.

The commission had batted the KI question around ever since a panel investigating the 1979 Three Mile Island accident urged the government to set up potassium iodide reserves. Pressure for storage or distribution mounted in the 1990s, when evidence accumulated that the prompt distribution of KI in Poland immediately after the 1986 Chernobyl accident may have helped protect children there.

Yet U.S. authorities remained reluctant to take action, even as Canada, Japan, and France stockpiled KI. In part they were concerned that some people might mistake the substance for a panacea, forgetting it protects only against radioactive iodine. In part they were worried about costs, logistics, and–not least–the negative message it might transmit to the public about nuclear reactor safety.

"When you propose a program for treating the consequences of radiation exposure, you inevitably raise people’s concerns about the level of hazard," commented risk analyst James Flynn of Decision Science Research Institute in Eugene, Ore.

Not in dispute: KI’s effectiveness

KI is undoubtedly an effective antidote against radioactive iodine, if promptly administered to the right people in the proper doses. The thyroid gland is a sponge for iodine, but one that does not discriminate between stable and radioactive iodine isotopes. It will absorb whatever source happens to be available, including the radioactive I-131 likely to be released in large quantities in any nuclear reactor accident that breaches the containment. Infants and children are at highest risk because their glands are so small and active.

Flood the thyroid with the stable variety of iodine, and it will have no room for the radioactive kind. Because the half-life for I-131 is short–about eight days–only temporary saturation of the thyroid is necessary. The catch is that KI must be taken soon after a nuclear accident release; wait more than 12 hours, and it’s relatively useless.

Nuclear industry trade groups like the Washington, D.C.—based Nuclear Energy Institute argue that sheltering and evacuation are enough to protect the public and that the costs and possible misuse of KI make its distribution a financial and logistical nightmare. Confusion about the appropriate dosage, and the level of radiation exposure at which to administer it, are other points of contention.

Consequently, the NRC is not requiring states to adopt a specific KI policy. Rather, the onus is on the states to show that they have considered issues of stockpiling or distribution for anyone living within a nuclear power plant’s 16-km-radius emergency preparedness zone. States are already required to stockpile some KI supplies for emergency workers and people that would be unable to evacuate, such as those in nursing homes and hospitals. Illinois, for example, stockpiles about 10 000 seven-day supplies for these groups.

Some states, like Tennessee, Alabama, Arizona, and New Hampshire, have stockpiled for the general public. Tennessee has also dabbled in public distribution, an experience authorities there say has not been positive. Potassium iodide has a shelf life of about five years. Tennessee distributed it for the first time in the early 1980s, from door to door within a plant’s emergency preparedness zone; but only a small percentage of families returned for a replacement batch five years later. Despite media campaigns, public response in picking up replacement KI had been low.

Are emergency zones too small?

By the 10th anniversary of Chernobyl, in 1996, as IEEE Spectrum reported ["Unforeseen Health Findings," November 1996, p. 27], it was clear that children exposed to Chernobyl radiation suffered from higher rates of thyroid cancer than expected. (To be sure, more vigilant medical surveillance may have elevated apparent incidence rates somewhat.) But in the following year, a paper published in the journal Environmental Health Perspectives raised some troubling questions about the general effectiveness of emergency preparedness zones here in the United States.

The paper was based on work done in the mid-1990s by Cham E. Dallas, director of the interdisciplinary toxicology program at the University of Georgia College of Pharmacy, in Athens, Ga. Focusing on the geographic distribution of thyroid cancers in the region most affected by the Chernobyl accident, Dallas naturally expected rates to be highest where most of the fallout was deposited. But instead, his study showed that cancers clustered in the population centers along the Ukrainian railways leading from Kiev to Moscow.

Beyond fallout

Dallas and his fellow investigators hypothesize that the railway cars–along with the vegetables, milk, and other foodstuffs they transported–carried, stirred up, and deposited radionuclides in a so-called ingestion zone along the rail lines. Because there was a three-day interval between the accident and warning by Soviet authorities, people continued to buy contaminated food, suggesting that ingestion, not inhalation, could have been the main absorption mechanism of I-131.

Though such theories are open to challenge, the study does raise questions about the adequacy of the circular emergency preparedness zones that play a big role in planning for nuclear accidents. The fallout plume may not be the only important transport mechanism. Hence, the stockpiling or distribution of KI in only a given area could leave people elsewhere at greater risk, wholly unprotected, and with a false sense of security to boot.

Some notice of the situation is being taken. There is currently a U.S. House bill that would require stockpiling of KI for everyone within an 80-km radius of a nuclear power plant.

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