Povidone-iodine in people with thyroid problems. Povidone-iodine is a chemical complex of povidone, hydrogen iodide, and elemental iodine. It contains from 9% to 12% available iodine. It works by releasing iodine which results in the death of a range of microorganisms. Povidone-iodine came into commercial use in 1955. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. Povidone-iodine is available over the counter. The wholesale cost in the developing world is about 3.30 to 11.40 per liter of 10% solution. This amount in the United Kingdom cost the
Iodine be primordial. As such, iodine is monoisotopic and its atomic weight is known to great precision, as it is a constant of nature. The longest-lived of the radioactive isotopes of iodine is iodine-129, which has a half-life of 15.7 million years, decaying via beta decay to stable xenon-129. Some iodine-129 was formed along with iodine-127 before the formation of the Solar System, but it has by now completely decayed away, making it an extinct radionuclide that is nevertheless still useful in dating the history of the early Solar System or very old groundwaters, due to its mobility in the environment.