Radioactive iodine, also known as radioiodine or Iodine 131, is a radioactive isotope of the element iodine. It is created by nuclear reactions. A radioactive isotope, also called a radioisotope, is a form of an element which is unstable due to a slightly different atomic makeup. Specifically, it will have a different number of neutrons and therefore a different atomic weight than its stable counterpart.
The unstable nature of radioisotopes makes them to decay over time, releasing radiation. The time it takes a particular isotope to decay is measured in terms of its half life - the amount of time it takes for that element to degrade to half of its original amount. Iodine-131 has a half life of about 8 days. If you started with one milligram of Iodine-131, in 8 days you would have 1/2 milligram, in 16 days 1/4 milligram.
Accidental exposure to radioactive iodine is a leading cause of thyroid cancer.
Radioiodine is produced by nuclear reactions.
You can receive an unintentional or excessive dosage to iodine-131 due to:
It can be ingested, inhaled or absorbed from open wounds or through the skin.
People who have been exposed to radioactive iodine are at an increased risk of developing disorders of the thyroid gland - especially thyroid cancer. The degree of risk depends upon the amount of contamination and the length of exposure. Because they are still developing, the greatest danger is to children, infants and unborn babies. It can take as long as 38 years to develop thyroid cancer after exposure, so older adults are considered to be at somewhat lesser risk.
There may also be an elevated risk of leukemia in those who have had therapeutic radioiodine treatment.
Taking potassium iodide (KI) within 3-4 hours of exposure will block your thyroid from absorbing radioactive iodine for 24 hours. The sooner to the incident you take it, the less radioactive iodine your thyroid will be able absorb.
Note: You can buy Potassium Iodide online without a prescription from sites like Nukepills.com - a major supplier of FDA-approved Potassium Iodide (KI).
Yes. Iodine-131 is used in the treatment of several disorders in both human and veterinary medicine, most notably hyperthyroid (caused by thyrotoxicosis or Graves Disease) - a condition where the thyroid gland has become overly active. It is also used to treat some forms of thyroid cancer. Radioiodine therapy is used when doctors need to destroy abnormal or malignant thyroid tissue.
Patients treated with iodine-131 therapy have to exercise precaution afterwards to avoid contaminating their environment or exposing others to second-hand radiation. While most of this radiation will have dissipated within several weeks, if you have had radioiodine therapy, you could still register a false positive on airport radiation detectors for up to 3 months!
According to the American Cancer Society, therapeutic treatment with radioactive iodine can cause:
More information: Nuclide Safety Data Sheet - Iodine-131 (pdf)