Potassium IodideDecember 2004
By Jon VanZile
|LE Magazine December 2004|
| Potassium Iodide |
Protecting Yourself In a Nuclear Emergency
By Jon VanZile
Chernobyl: Lessons Learned
Chernobyl was the first nuclear emergency large enough to threaten the health and well-being of millions of people. During that catastrophe, one of the main reactors of the power plant melted down, releasing an estimated 120 million curies of radioactive material. The surrounding land was heavily contaminated with plutonium and cesium, as well as with dangerous levels of radioactive iodine. Ultimately, more than 21,000 square kilometers of land were contaminated, and about 135,000 people were permanently evacuated. Experts later estimated that 17 million people were exposed to excess radiation,4 including 2.3 million children living in eastern Russia, southern Belarus, and northern Ukraine.5
At first, scientists did not appreciate the threat posed by high levels of radioiodine released during the meltdown. It did not take long, however, to start seeing the effects. Within four years, there was a sharp spike in the incidence of thyroid cancer.1 This increase occurred in children who had received less than 30 rems of radioiodine to the thyroid.6 Within 15 years, more than 1,000 cases of thyroid cancer had been reported in the affected areas, a 30- to 60-fold increase.6 All of the cases, according to the World Health Organization, were “most probably solely attributable to this single release of radioactivity to the environment.”5 Significantly, none of these areas made potassium iodide widely available.
Following the Chernobyl meltdown, Poland immediately distributed 17 million doses of potassium iodide, including 10 million to children. This was the first time scientists had an opportunity to study the side effects of potassium iodide in a large population. The news was encouraging: side effects were clinically insignificant.6
Awful as it was, the Chernobyl experience confirmed a valuable lesson: children are by far the most vulnerable to radiation exposure, even in relatively small doses.7 Children exposed to radiation suffer from higher rates of certain childhood cancers, especially leukemia and thyroid cancer, and have a greater likelihood of developing breast cancer as adults.7
Children’s greater vulnerability to radiation exposure is attributable to several factors, according to the American Academy of Pediatrics. First, children have higher minute ventilation, or a higher concentration of tiny capillaries in the lungs. This leads to greater radioactivity exposure from the same amount of radioactive material. Second, children are extra sensitive to the DNA-damaging effects of radioactive energy. Finally, children are more likely than adults to suffer from long-term psychological injury due to a radiation disaster.1
Guidelines for Protection
Significantly, however, this is only a recommendation. The final decision to stockpile potassium iodide has been left to state and local governments. Although the NRC has made free doses available to local governments, a significant number of cities and states have chosen not to participate in the program. As a result, you cannot be sure whether your local government has adequate supplies of potassium iodide. Fortunately, potassium iodide pills are available over the counter.
While the government recommends stockpiling within a 10-mile radius of a nuclear reactor, there is good reason to believe that people within a larger area should take precautions. The distribution of radioiodine is affected by wind patterns. In Chernobyl, the areas of greatest contamination were the 20-mile zone around the reactor, another region 120 miles north-northeast of the reactor, and yet another area 300 miles northeast of the reactor.1
In heavily congested areas—like southeastern New York state, which is close to five nuclear reactors—the American Academy of Pediatrics recommends stockpiling potassium iodide within a 50-mile radius. Other proposals have suggested a 200-mile radius.1
FDA-approved potassium iodide is available in 130-mg and 65-mg pills. The government has issued dosage guidelines for home use of potassium iodide, as shown in Table 1 above.
Potassium iodide can be dissolved in any liquid. Because it tastes salty, the FDA recommends dissolving it in pleasant-tasting solutions when administering it to children. Fruit beverages, including orange juice and raspberry drink, seem to hide the flavor. Chocolate milk and flat cola also can help mask the taste. Water and low-fat milk do not disguise the unpleasant taste. Each dose of potassium iodide lasts for 24 hours.
Limitations of Potassium Iodide
Potassium iodide is not entirely without side effects. In newborns, potassium iodide has been shown to decrease the blood level of thyroxine and increase the level of thyroid stimulating hormone.1 In pregnant women, potassium iodide has been shown to cause neonatal hypothyroidism. In both cases, potassium iodide should be administered only as a last resort. People with iodine allergies should avoid potassium iodide.
Potassium iodide’s effectiveness also depends on the nature of the radioactive exposure. The drug is specifically geared to thyroid protection by blocking the uptake of radioiodine, a common beta particle produced during certain nuclear reactions. However, potassium iodide offers no protective benefits against other forms of radiation, including the extremely dangerous neutrons that are released during a nuclear explosion. It is also ineffective against so-called “dirty bombs,” which are constructed from radioactive material that does not contain radioiodine.
Finally, among older people and those in iodine-deficient areas, potassium iodide use has been associated with iodine-induced thyrotoxicosis. At chronic high doses, it has been shown to cause goiter or hypothyroidism. Because of this, people with multinodular goiter, Graves’ disease, and autoimmune thyroiditis should be use caution and consult a physician before using potassium iodide.6
Despite these limitations, potassium iodide, if used quickly and correctly, is the only pharmacological approach that has ever shown specific protective effects during a nuclear emergency.1
1. Radiation disasters and children. Pediatrics. 2003 June;111(6PT1):1455-66.
2. Takamura N, Hamada A, Yamaguchi N, et al. Urinary iodine kinetics after oral loading of potassium iodine. Endocr J. 2003 Oct;50(5):589-93.
3. Available at: http://www.fda.gov/cder/guidance/5386fnl.htm. Accessed September 15, 2004.
4. Weinberg AD, Kripalani S, McCarthy PL, Schull WF. Caring for survivors of the Chernobyl disaster. What the clinician should know. JAMA. 1995 Aug 2;274(5):408-12.
5. Available at: www.who.int/ionizing_radiation/pub_meet/Iodine_Prophylaxis_ guide.pdf. Accessed September 19, 2004.
6. Available at: http://www.fda.gov/cder/guidant/index.htm. Accessed September 15, 2004.
7. Miller RW. Special susceptibility of the child to certain radiation-induced cancers. Environ Health Perspect. 1995 sep;103(Suppl 6):41-4.
8. Federal Emergency Management Agency. Federal Policy on the Use of Potassium Iodide (potassium iodide). Federal Register. 2002 Jan 10;:67(7):1355-6.
9. Available at: http://www.nrc.gov/what-we-do/regulatory/emer-resp/emer-prep/potassium-iodide.html. Accessed September 19, 2004.