Named “iode” by Joseph Louis Gay-Lussac as the Latin word to identify its characteristic violet-colored vapor, iodine has become a familiar chemical for health applications from the low-tech to the high-tech.
Iodine’s disinfectant properties have led to several different uses. Although less commonly used now, tincture of iodine was historically an important supply in a home medicine cabinet since it could be used to disinfect cuts. Iodine is also often used by hikers to disinfect water for drinking and cooking since it eliminates the need to boil the water, which requires fuel and time. Considering that water weighs eight pounds per gallon and an average hiker requires a minimum of a gallon of water per day, the ability to disinfect water along the way for a long distance hike drastically reduces the load that a hiker must carry.
Iodine is the heaviest element required for life and is concentrated in the thyroid gland where it is used to produce the essential thyroxin hormones. A lack of iodine in the diet is the largest worldwide cause of preventable mental retardation and may also lead to goiter, an enlargement of the thyroid. To ensure that humans consume their daily requirement of iodine, in most countries table salt is iodized; small amounts of iodine-containing salts are added to the sodium chloride.
Medical science has taken advantage of the thyroid’s unique property of accumulating large quantities of iodine, and radioactive isotopes of iodine are used extensively in the diagnosis and treatment of thyroid problems. For example, to diagnose a thyroid issue, the short-lived isotope, I-128, with a half-life of only eight hours, may be taken as a pill. It will rapidly accumulate in the thyroid, and since radioactive elements expose film, an image of the thyroid may be generated to establish if areas of the gland are over- or under-active. The short half-life of I-128 ensures that it is cleared rapidly from the body. In cases of an overactive thyroid, the isotope, I-131, with a longer half-life of eight days, may be used strategically to reduce the function of part of the gland. By taking advantage of these isotopes, thyroid issues can be diagnosed and treated all without any invasive surgery or procedures.
More information about iodine and its health effects may be found at http://lpi.oregonstate.edu/infocenter/minerals/iodine/