Risk Of Exposure To Radioiodine From Japan

You probably know that a major earthquake and tidal wave hit Japan a few weeks ago.  One of the many problems associated with this catastrophe was damage to several nuclear reactors with leakage of radioactive materials, including radioiodine (I-131).   You may or may not know that exposure to radioiodine is associated with increased risk of developing thyroid cancer.  The risk is directly related to the exposure (i.e., radiation dose) and is highest in young children and pregnant women.   Much of what we know about the association between radio iodine and cancer risk comes from the experience at the  Chernobyl power plant  in Russia in 1984.  We know that exposure from breathing contaminated air confers greatest risk,  followed by ingestion of contaminated milk and fresh vegetables.  Children under age 10 years are at greatest risk.  Risks are also related to the distance from the radiation source- the damaged nuclear plants in Japan are more that 5000 miles from the west coast of the U.S.- that’s a long distance.  Risk is also related to time.  For radioiodine, the half-life is about a week, so that the exposure risks decrease rapidly over time.

What should people in the U.S. do to prevent/minimize risks for the development of thyroid cancer ?

Last week, the Pediatric Endocrine Society (formerly named in honor of Lawson Wilkins) published a letter summarizing the risk of exposure to radioiodine from Japan.  The letter was written by Andrew Bauer, a pediatric endocrinologist at Walter Reed Army Medical Center in Washington, D.C.    Dr. Bauer reviewed the situation and offered advice regarding the use of potassium iodine (KI) to high risk populations in the U.S. (i.e., young children and pregnant women).  Oral KI is highly effective in preventing radioiodine from being taken up by the thyroid, thereby effectively eliminating the risk of developing thyroid cancer from the exposure.  Dr. Bauer made clear in his letter, that at present, there is no reason to consider KI prophylaxis anywhere in the U.S.  I think it would be worthwhile for both pediatric endocrinologists and primary care doctors to read Dr. Bauer’s letter, but I haven’t yet figured out how to provide a link to the letter, unless you are a member of the Pediatric Endocrine Society, but I will try to do so.  Meanwhile, a number of other professional societies have published statements on-line (e.g., Radiation Risks to Health: a joint statement from the American Association of Clinical Endocrinologists, the American Thyroid Association, The Endocrine Society, and the Society of Nuclear Medicine, March 18, 2011).  So far all the experts are saying we should stay cool and avoid the temptation to stock up on KI.

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