Potassium Iodide (KI)

What is it?

Potassium Iodide is a salt, similar to sodium chloride (NaCI), normal table salt. KI is available in pill form or dissolved in water as a supersaturated potassium iodide (SSKI) solution. The pills contain a daily adult (children’s doses range from 16-65 mg depending on their size and age) dosage of 130 milligrams (mg).

What is KI used for?

The thyroid gland needs iodine to carry out its hormone production function. The gland is constantly removing iodine from the bloodstream. Iodine normally enters the bloodstream from the food we eat. For decades it has been known that 130 mg KI was enough iodine to totally satisfy an adult’s thyroid gland’s desire for iodine for a day or so. If 130 mg KI is taken shortly before radioactive iodine enters the body, the thyroid gland will have already been totally satisfied and will not absorb radioactive iodine from the bloodstream. Thus, the body will eliminate the radioactive iodine, primarily by way of the urine, over a period of a week or two and the thyroid will not absorb and store the radioactive iodine. Taking KI is a method of shutting down the thyroid absorption of iodine (a process called “blocking”) until the body rids itself of any radioactive iodine.

Where does radioactive iodine come from?

Radioactive iodine is a fission product, one of about 200 different radioactive atoms (radionuclides) that can be produced when uranium atoms fission or split apart upon being struck by a neutron. For example, radioactive iodine is created through the process of using nuclear reactors to supply the heat used to produce electricity or as a result of the detonation of an atomic bomb. The major isotopes of radioactive iodine produced in the fissioning process have a short half-life. Therefore, they only exist while the nuclear reactor is operating and producing electricity or for a few days following the reactor shutdown or atomic bomb detonation. It is not a concern, for example, in spent fuel from nuclear reactors.

Radioactive iodine is also made for medical purposes under controlled conditions using an accelerator.

Is radioactive iodine hazardous?

Radioactive iodine can be hazardous if we are exposed to enough of it. Radioactive iodine undergoes radioactive decay, releasing both beta and gamma rays. If we are close to radioactive iodine or if we take radioactive iodine into our bodies, our bodies will be exposed to its beta and gamma rays. If radioactive iodine is removed from the bloodstream and stored in the thyroid gland, the thyroid gland and the rest of the body will receive higher radiation doses than they would if the radioactive iodine simply passed through the body. This removal and storage can be prevented by the appropriate use of KI.

Are there any beneficial uses of radioactive iodine?

Radioactive iodine has been used for the past half century for diagnostic and therapeutic purposes in medicine.

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