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February 2008

Key Points

• Potassium iodide (KI) is an option as a secondary protective measure within the 10-mile emergency planning zone (EPZ) around a nuclear power plant. KI can protect the thyroid gland against radioactive iodine if taken within a limited time before, during or after exposure. KI provides no protection against other radionuclides or for other organs in the body.
• In the unlikely event of a radioactive release from a nuclear power plant, the most probable radiation exposures would come from radioactive noble gases, not from radioactive iodine. Noble gases do not concentrate in the body. The primary protective actions in the event of a nuclear plant accident are evacuation or sheltering, which protect the whole body from any type of radioactive exposure. 
• The most likely pathway for exposure to radioactive iodine is from ingesting contaminated food or milk. However, emergency plans in regions with nuclear power plants include provisions for protecting the food chain.
• A 2002 law states that the federal government will provide KI to state and local governments should they wish to distribute the compound in the area 10 to 20 miles from a nuclear power plant.  The law also includes an option to waive the KI program if the federal government concludes there is a more effective way to protect the thyroid gland from radioactive iodine.  The White House Office of Science and Technology Policy (OSTP) invoked this waiver in January 2008, saying interdiction of any contaminated food, along with the consideration of evacuation and sheltering, are more effective protective measures to use in the very unlikely event that people beyond 10 miles of a nuclear plant could be exposed to radioactive iodine.

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¹ Public Health Security and Bioterrorism Preparedness and Response Act of 2002, Public Law 107-188, June 12, 2002.

² Ibid, Section 127(f).