United States Nuclear Regulatory Commission - Protecting People and the Environment

Use of Potassium Iodide

In January 2001, the Commission published a rule change to the NRC emergency planning regulations to include the consideration of the use of potassium iodide. If taken properly, potassium iodide (KI) will help reduce the dose of radiation to the thyroid gland from radioactive iodines, and reduce the risk of thyroid cancer. The Food and Drug Administration (FDA) has issued guidance on the dosage and effectiveness of potassium iodide. The NRC has supplied KI tablets to States requesting it for the population within the 10-mile emergency planning zone (EPZ). If necessary, KI is to be used to supplement evacuation or sheltering in place, not to take the place of these actions. If radioactive iodine is taken into the body after consumption of potassium iodide, it will be rapidly excreted from the body. For more information, see Consideration of Potassium Iodide in Emergency Planning.

The population closest to the nuclear power plant that is within the 10-mile emergency planning zone is at greatest risk of exposure to radiation and radioactive materials. When the population is evacuated out of the area, and potentially contaminated foodstuffs are removed from the market, the risk from further radioactive iodine exposure to the thyroid gland is essentially eliminated. Beyond 10 miles, the major risk of radioiodine exposure is from ingestion of contaminated foodstuffs, particularly milk products. Both the Environmental Protection Agency (EPA) and the FDA have published guidance to protect consumers from contaminated foods. These protective actions are preplanned in the 50-mile ingestion pathway EPZ.

Remember, in the unlikely event of a nuclear power plant accident, it is important to follow the direction of your State or local government in order to make sure protective actions, such as taking potassium iodide pills, are implemented safely and effectively for the affected population.

Page Last Reviewed/Updated Friday, November 16, 2018