In 1982, the U. S. Food and Drug Administration approved potassium iodide to protect thyroid glands from radioactive iodine involving accidents or fission emergencies.  In an accidental event or attack on a nuclear power plant, or in nuclear bomb fallout, volatile fission product radionuclides may be released. Of these products, 131I is one of the most common and is particularly dangerous to the thyroid gland because it may lead to thyroid cancer.  By saturating the body with a source of stable iodide prior to exposure, inhaled or ingested 131I tends to be excreted, which prevents radioiodine uptake by the thyroid. According to one 2000 study "KI administered up to 48 h before 131I exposure can almost completely block thyroid uptake and therefore greatly reduce the thyroid absorbed dose. However, KI administration 96 h or more before 131I exposure has no significant protective effect. In contrast, KI administration after exposure to radioiodine induces a smaller and rapidly decreasing blockade effect. " For optimal prevention, KI must be dosed daily until a risk of significant exposure to radioiodine by either inhalation or ingestion no longer exists.