How does KI work?
For people exposed at close range to large amounts of radioactive material, taking potassium iodide tablets can be very important. Radioactive iodine is one of the materials released after a nuclear accident. The thyroid gland actively takes up and stores iodine, including radioactive forms of the mineral, and exposure to large amounts of radioactive iodine can increase the risk of developing thyroid cancer.
Taking a large amount of nonradioactive iodine (in the form of KI) prior to massive radiation exposure saturates the thyroid gland with iodine and thereby prevents radioactive iodine from entering the gland. This protective effect lasts about 24 hours, so the drug has to be taken daily during a period of intense radiation exposure in order to be effective.
Potassium iodide does not protect against the adverse effects of other radioactive compounds released during a nuclear accident, such as radioactive cesium.
What is the current radiation danger?
So far, health officials report an insignificant amount of radiation reaching the West Coast of the US. For example, the radiation dose a person normally receives from rocks, bricks, and the sun is 100,000 times the amount coming from Japan.
In contrast, the risks associated with daily use of large doses of potassium iodide are not insignificant. Long-term use of high doses of this compound can cause acne, headaches, and other side effects, and occasionally leads to thyroid abnormalities such as hypothyroidism or hyperthyroidism. Because the amount of radioactive iodine currently reaching the US from Japan is so small, the risks associated with taking potassium iodide for radiation protection probably outweigh the benefits.
What about taking extra iodine in the form of iodized salt?
The amount of iodine added to table salt is so small that it would be physically impossible to consume enough salt for it to protect against radiation. Further, high salt intake carries its own risks of adverse effects, so eating more salt is not recommended as a method of protecting against radioactive iodine.
When should I use it?
According to all of the available evidence, the reactor accident in Japan is not a threat to the US population, and the use of KI tablets is not currently recommended. People should only take KI for radiation protection if they live in contaminated areas and have been instructed to do so by health officials. The adult dose of KI for protection against radiation is 130 mg per day, which is nearly 700 times the Recommended Dietary Allowance for iodine.
Are there other protections against radiation?
In areas exposed to dangerous radiation levels, authorities will recommend that people stay indoors with all the doors and windows closed and sealed until the threat passes. The walls of buildings provide some degree of protection against radiation, especially those that are tightly sealed, as this prevents radioactive particles from the passing air from entering the house.