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Potassium iodide (KI) pills should be available to everyone age 40 or younger—especially children and pregnant and lactating women—living near a nuclear power plant, according to a new report from a government-mandated expert panel of the National Academy of Sciences.

The panel, which is made up of nine members, including Dr. David V. Becker of NewYork-Presbyterian Hospital/Weill Cornell Medical Center, also finds that potassium iodide can prevent thyroid cancer caused by exposure to radioactive iodine, a substance that could be released during a severe accident at a nuclear power plant. Potassium iodide will not protect the body against other types of radioactive isotopes released during nuclear-reactor incidents or those likely to be used in a so-called "dirty bomb," adds the committee that wrote the report.

According to the report, for potassium iodide to be most effective, it must be taken within a few hours before or after exposure to radioactive iodine. Further protection from risk should be accomplished by evacuation and by control of contaminated milk and food. The report also calls on states and municipalities to decide how to stockpile, distribute, and administer potassium iodide tablets for their particular situation.

"Potassium iodide, if taken in appropriate dosage in a timely manner, can block the thyroid gland's uptake of radioactive iodine and thus help prevent the appearance of radio-iodine-induced thyroid cancer and other thyroid disorders," says Dr. Becker, Professor of Radiology and Medicine at Weill Cornell Medical College and Attending Radiologist and Physician at NewYork-Presbyterian Hospital/Weill Cornell Medical Center. Radioactive iodine is also used in small amounts for diagnostic and therapeutic procedures. KI works by flooding the thyroid's iodine binding sites, thus preventing the accumulation of subsequent radioactive iodine.

"While KI has limitations, it is still potentially valuable. Infants and young children would be most in need of protection from radioiodine exposure due to the comparatively smaller size of the thyroid gland in children and the greater radiosensitivity of growing tissues," says Dr. Becker. "While thyroid cancer, a rare disorder, is curable in most cases, taking actions that reduce the chance of exposure is still preferable."

Regarding its limitations, Dr. Becker says, "KI would only be useful against certain kinds of nuclear terrorism, such as an incident involving an operational nuclear power plant in which large amounts of radioactive iodines could be released. KI would not be effective against a so-called 'dirty bomb' since KI only protects against radioactive iodine, not other radioactive isotopes—such as plutonium, uranium, cesium, or cobalt 60—that might be found in a 'dirty bomb' blast."

"Additionally, KI only protects the thyroid gland—not other organs or tissues—against exposure to I-131 radiation," adds Dr. Becker. "And, to be effective, KI must be taken just before or shortly after exposure."

According to the new report, KI pills are not recommended for people over 40 because epidemiological studies have not demonstrated a significant risk of radiation-induced thyroid cancer in this age group, while their risk of side effects from potassium iodide is increased.

Stockpiles of KI for public distribution already exist. The U.S. Nuclear Regulatory Commission has supplied some states with KI sufficient for one or two doses for every person living or working within ten miles of a nuclear power plant. Additionally, the U.S. Department of Health and Human Services (HHS) has purchased KI tablets for a stockpile.

Scientists, including Dr. Becker, have studied previous environmental releases of radioiodines and their medical consequences, most particularly the 1986 reactor fire and explosion in Chernobyl in the former Soviet Union that has been found responsible for causing thyroid cancer in more than 2,000 children exposed to the resulting fallout.

Dr. Becker contributed a section in the new report on iodine physiology and the effects of the Marshall Island's Bikini accident of 1954. Dr. Becker is an authority on the accident, having studied that area in the 1960s as part of a Department of Energy team organized by the Brookhaven National Laboratories. He was also Chairman of the National Cancer Institute's Chernobyl Fallout Joint Study group, and is now a member of the Thyroid Advisory Oversight Group for U.S.-Belarus and U.S.-Ukraine cooperative studies of post-Chernobyl thyroid disease. Additionally, Dr. Becker founded the Nuclear Medicine Department at New York Hospital (now NewYork-Presbyterian Hospital/Weill Cornell Medical Center) in 1955.

Recent legislation (Public Health Security and Bioterrorism Preparedness and Response Act of 2002, Section 127) requested that the President of the United States—in consultation with various individuals representing appropriate federal, state, and local agencies—establish guidelines for the stockpiling of KI tablets and for the distribution and utilization of KI tablets in the event of a nuclear incident. Prior to establishing those guidelines, the President was requested by Congress to enter into agreement with the National Academy of Sciences to conduct a study to determine the most effective and safest means to distribute and administer KI tablets on a mass scale. As a result, the Centers for Disease Control and Prevention (CDC) asked their Board on Radiation Effects Research to convene a panel to assess the distribution and administration of KI in the event of a nuclear incident. The study began on March 27, 2003.