Iodine-131 Basic Information from EPA

The Environmental Protection Agency provides various information about Iodine-131 on their website. They answer questions about Iodine-131 properties, where it comes from, affects on the body and environment, and most importantly how to know if you are exposed and how to protect yourself. As seen in earlier posts, this radioactive isotope comes from nuclear reactors, weapons, or medicine (imaging or radiation therapy). It can be released into the environment through urine of a patient being treated with Iodine-131 or is released from nuclear reactors and weapons. It can either be absorbed into water or released as a gas in the air, so people can either be exposed by breathing or drinking it.

Iodine-131 is a non-metalic, purplish-black crystalline solid, or deep violet vapor. It is able to be sublimed, change directly from a solid to a vapor, and dissolves in alcohol and water. It will irritate the eyes, nose and throat when exposed. Also, as noted earlier, the half-life of this radioactive isotope is short in comparison to others, being about 8 days. However, this half-life changes in different parts of the body. For example, the half-life in the thyroid gland is 100 days, in bones is 14 days, and in the kidney, spleen, or reproductive organs is 7 days.

When the body is exposed to Iodine-131, it will collect the radionuclide in the thyroid gland. Chronic exposure can cause thyroid cancer, and lower doses cause various thyroid problems like making it overactive, or slowing its activity. What is strange about the treatment of this is that Iodine-131 is used to treat itself through different doses. However, it is risky because it can either help by slowing the process of production of cancer cells or may favor the formation of them.

So how will you know if you are exposed radioactive iodine? Being near a nuclear power plant can increase exposure, and tests are available in most major medical centers. In the event of a nuclear accident, the government may give out non-reactive iodine so your body will absorb that instead of the radioactive iodine because it cannot tell the difference. However, this should only be done in emergency situations as there are health risks with this iodine as well.

http://epa.gov/radiation/radionuclides/iodine.html