Iodine is a naturally occurring element found in sea water and in certain rocks and sediments. There are non radioactive and radioactive forms of iodine. Iodine is used as a disinfectant for cleaning surfaces and storage containers and is used in skin soaps and bandages, and for purifying water. Iodine is also added to some table salt to ensure that all people in the United States have enough iodine in their diet. Most radioactive iodine is manmade. It is used in medical tests and to treat certain diseases. Most radioactive forms of iodine change very quickly (seconds to days) to stable elements that are not radioactive. However, 129I (read as iodine 129) changes very slowly (over millions of years)