Because iodine concentrates in the thyroid gland (it is essential for the synthesis of thyroid hormones), exposure to radioiodine by inhalation of contaminated air or ingestion of contaminated food or milk can lead to radiation injury to the thyroid, including increased risk of thyroid cancer and other thyroid disorders.

Radiation to the thyroid from radioiodine can be limited by taking nonradioactive iodine (stable iodine) such as potassium iodide (KI).1 Fetuses, infants, children, and pregnant and lactating women are most in need of protection from radioiodine exposure and most likely to benefit from KI. To be most effective, KI must be taken within a few hours before or after exposure to radioiodine. KI does not protect other organs or tissues from external exposure to radiation or from internal exposure to other radioactive isotopes, such as strontium, cesium, or cobalt.

To ensure that KI will be available in the event of an incident at a nuclear power plant that causes release of radioiodine, the US Nuclear Regulatory Commission has supplied participating states with KI sufficient for two dosages for every person who lives or works within 10 miles of a nuclear power plant. In addition, the US Department of Health and Human Services has purchased KI tablets for the national pharmaceutical stockpile. Some local agencies have developed their own plans for stockpiling and distributing KI (see Chapter 6 and Appendix C for details).

To establish a coordinated program based on the latest scientific advice, Public Law 107-188, the Public Health Security and Bioterrorism Preparedness and Response Act of 2002, Section 127 (see Appendix A), requested that the president—in consultation with representatives of appropriate federal, state, and local agencies—establish guidelines for the stockpiling of KI tablets and for their distribution and use in the event of a nuclear incident. Before establishing the guidelines, the president was requested to enter into an agreement with the National Academy of Sciences to conduct a study to recommend the most effective and safest way to distribute


Potassium iodide is a chemical compound that contains iodine that can be used to protect the thyroid from possible radiation injury by blocking subsequent accumulation of radioiodine, thereby reducing the radiation to the thyroid that could result from the inhalation or ingestion of radioiodine.

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