Why Potassium Iodide?

By Kim Smiley

In addition to evacuating the people near the nuclear plants in crisis, the Japanese government has distributed potassium iodide.  There has also been a run on potassium iodide on the West Coast of the United States.


Why would pills protect against radiation?  The first part of the answer lies in the thyroid gland.  The thyroid contains some of the only cells in the body that can absorb iodine.  The thyroid needs iodine in order to produce thyroid hormones which are used by nearly every cell in the body and help regulate important functions such as metabolism.  The second part of the answer is that iodine-131 is a common isotope produced by the fission of uranium atoms during the operation of nuclear reactors.  When fission products are released into the environment and consumed by humans, the thyroid can absorb radioactive iodine, just like it absorbs stable iodine.  Exposure from radioactive iodine can lead to thyroid cancer.

When exposure to radiation is possible, potassium iodide is used because the thyroid has a limit to how much iodine it needs.  If the thyroid has been flooded by stable iodine, it decreases the chance that radioactive iodine will be absorbed.  Any unneeded iodine should be passed through the body relatively quickly, limiting the amount of exposure to the radiation emitted by the iodine-131.

History has shown us that the threat of thyroid cancer is very real following a nuclear reactor accident.  There has been an epidemic of thyroid cancer in the area affected by the Chernobyl accident in 1986.  Experts believe that distribution of iodide potassium could have largely prevented this long term health consequence.  Additionally, the majority of iodine exposure came from drinking milk produced by cows living in the area contaminated by the accident.  If people had avoided drinking contaminated milk in the months following the accident, the effects of radioactive iodine would have greatly been diminished.  Another possible solution that could be applied to help prevent thyroid cancer following a reactor accident would be to test all food and drink for contamination.

There are a few other important facts to consider about potassium iodide.  It is not recommend for low levels of radiation.  The U.S. Nuclear Regulatory Committee has stated that very low levels of radiation may reach the United Stations, but that the amount is well below any harmful limit.  Officials have repeatedly stated that there while use of the potassium iodide is an appropriate precaution for individuals near the accident site in Japan, there is no need for people within the US to take potassium iodide to protect against the effects of radiation.  There are also a number of unpleasant side effects associated with potassium iodide and it is recommended that you speak to your doctor before taking the supplement.

Click on the “Download PDF” button above to view a Process Map of how the body absorbs iodine and a high level Cause Map of the thyroid epidemic following Chernobyl.