A review on potassium iodide in radiological disasters

By: Victoria Hom, PharmD Candidate c/o 2018

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This year marked the 31^st anniversary of Chernobyl, the worst nuclear disaster in history due to a malfunctioned reactor operated by inadequately trained staff. The accident’s explosion released a large plume of iodine-131, one of many radioactive substances, into the atmosphere, which prompted an evacuation around the Belarus-Russia and Ukraine region. Within ten days, about thirty-one clean-up workers died with thousands more expected from the high levels of radiation.¹ Studies suggest that the radioiodine exposure led to a striking increase of thyroid cancer in young children – as much as a hundred-fold increase when compared to pre-disaster rates.² Additionally, despite being far from the disaster site, high levels of radioactive material were detected over other parts of Northern Europe.

Poland was a country that responded quickly to the thyroid cancer crisis by dispensing a nationwide supply of potassium iodide (KI). The rationale was to saturate the thyroid gland with non-radioactive iodine, thereby preventing the uptake of radioactive iodine. However, the evidence in support of this use of potassium iodide was arguably indirect and controversial. Critics questioned the spike in thyroid cancer shortly after the Chernobyl incident, challenging that the dramatic increase in rates may have resulted from intensive screening.³ Other studies presented evidence that the risk of thyroid cancer increases with increasing doses of radiation – suggesting that Poland’s dose was lower, hence a lower incidence of thyroid cancer was recorded.⁴ The distance factor of Poland from Chernobyl coupled with restriction of possibly radioactive-infected milk and vegetables also undermined the association between low incidence of thyroid cancer in Poland and KI administration. In fact, there was higher reduction in radioiodine exposure attributed to the diet restriction compared to the reduction by potassium iodide administration.⁵ Studies also stated that there was no significant increase in thyroid cancer occurrences in Polish children that did not receive the drug. However the difference in occurrence when compared to Belarus in Russia remained significantly high.⁵ A more thorough literature review into thyroid cancer incidences and the results of potassium iodide use may help shed more light on these controversies.

Regardless of the controversy associated with the use of potassium iodide after Chernobyl, its widespread administration demonstrated its safety and tolerability during radiological emergencies. It was even shown to be safe in children and pregnant or lactating women. Its safety coupled with its low cost makes it an ideal drug to stockpile for these situations.² Some common side effects including rashes and swelling of the salivary glands proved to be mild and not clinically significant.²

Over 30 years after Chernobyl, we are better prepared for nuclear disasters. Since potassium iodide is most efficacious when administered within three to four hours after exposure to radioiodine, local city governments are sure to keep a sufficient supply ready near nuclear power plants.⁶      In fact, New York State has a supply of potassium iodide for people living within a 10-mile radius of nuclear power plants. More information on its availability and distribution is usually provided in annual emergency planning booklets distributed by local governments and power companies.⁶ These protocols were also established for the Fukushima Daiichi Nuclear Power Plant prior to its nuclear disaster in March 2011. Unfortunately, Japanese government officials failed to organize for the potassium iodide distribution until five days after the accident; at that point, the pills had little effect.⁷ Luckily, the dose of radiation was not nearly as high as that of Chernobyl so there were less casualities.⁸ But regardless of the levels of radiation, countries should do as Poland did. Be proactive and not reactive.

SOURCES:

1. Chernobyl Disaster: Ukraine Marks 30th Anniversary. British Broadcasting Company (BBC). http://www.bbc.com/news/world-europe-36136286. Published 04/26/2016.
2. Guidance Potassium Iodide as a Thyroid Blocking Agent in Radiation Emergencies. United States Nuclear Regulatory Commission (US NRC). http://www.nrc.gov/docs/ML1233/ML12339A632.pdf. Published 12/01/2001. Last Updated 03/30/2012.
3. Astakhova LN, Anspaugh LR, Beebe GW, et al. Chernobyl-related thyroid cancer in children of Belarus: a case-control study. Radiat Res. 1998;150(3):349-56. D: 9728663 [PubMed – indexed for MEDLINE].
4. Davis S, Stepanenko V, Rivkind N, et al. Risk of thyroid cancer in the Bryansk Oblast of the Russian Federation after the Chernobyl Power Station accident. Radiat Res. 2004;162(3):241-8. D: 15332999 [PubMed – indexed for MEDLINE].
5. Robbins J, Schneider AB. Chernobyl and the KI controversy in the United States. Nat Clin Pract Endocrinol Metab. 2008;4(3):117. doi: 10.1038/ncpendmet0779.
6. Use of Potassium Iodide During Radiological Emergencies: Information for the Public. New York State Department of Health. https://www.health.ny.gov/environmental/radiological/potassium_iodide/information_for_the_public.htm. Published 03/01/2011.
7. Hayashi Y. Japan officials failed to hand out radiation pills in quake’s aftermath. The Wall Street Journal. http://www.wsj.com/articles/SB10001424052970204010604576596321581004368. Published 09/29/2011.
8. FAQs: Fukushima Five Years On. World Health Organization. http://www.who.int/ionizing_radiation/a_e/fukushima/faqs-fukushima/en/. Published 2016.