Use of Potassium Iodide

Potassium iodide, also known by its chemical symbol "KI", is a salt. In fact, it is commonly added to table salt to make it "iodized." In the event of a radiological emergency, if taken properly, KI may reduce how much radioactive iodine the thyroid gland is able to absorb, potentially reducing an increase in the risk of developing thyroid cancer.

The NRC's regulations on the use of potassium iodide for radiological emergencies requires States (including Tribal governments) that have populations in the 10-mile emergency planning zone (EPZ) of a commercial nuclear power plant to consider including KI in emergency plans as a protective measure.

The U.S. Food and Drug Administration (FDA) issued guidance on the dosage and effectiveness of KI. The NRC supplies KI tablets, in accordance with FDA dosing guidelines, to States that request it for populations within the 10-mile EPZ of a nuclear power plant. The population within the 10-mile EPZ is at the greatest risk of exposure to radioactive iodine. Evacuation, along with removing potentially contaminated food products from the market, essentially eliminates the risk from further radioactive iodine exposure to the thyroid. However, prophylactic use of KI may be recommended by States as a supplement to evacuation or sheltering in place.

For populations outside of the 10-mile EPZ 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, and can be implemented in a timely and effective manner. Therefore, supplemental KI is not recommended for populations outside of the 10-mile EPZ but within the 50-mile ingestion pathway EPZ.

Remember, in the unlikely event of a nuclear power plant accident, follow instructions from your State or local government in order to make sure protective actions, such as evacuation, shelter-in-place, or taking potassium iodide pills (if applicable), are implemented safely and effectively for the affected population.

For additional information on KI, please see Frequently Asked Questions about Potassium Iodide.

Page Last Reviewed/Updated Monday, April 19, 2021