I remembered that iodine was introduced in table salt to prevent health issues related to iodine deficiency. The deficiency was experienced by people living away from seas and oceans. Those living near seas and oceans ingested the needed iodine by eating seafood. Modern methods of packaging and shipping have made seafood more available to non coastal regions. There is still the cost factor. Adding iodine to salt is a very inexpensive way to provide the needed iodine.
Anyway - this is what Wikipedia has to say
Iodised salt (
also spelled iodized salt) is
table salt mixed with a minute amount of various salts of the element
iodine. The ingestion of iodine prevents
iodine deficiency. Worldwide, iodine deficiency affects about two billion people and is the leading preventable cause of
intellectual and developmental disabilities.
[1][2] Deficiency also causes
thyroid gland problems, including "endemic
goitre." In many countries, iodine deficiency is a major public health problem that can be cheaply addressed by purposely adding small amounts of iodine to the
sodium chloride salt.
Iodine is a
micronutrient and
dietary mineral that is naturally present in the food supply in some regions, especially near sea coasts, but is generally quite rare in the Earth's crust, since iodine is a so-called "heavy" element and
abundance of chemical elements generally declines with greater atomic mass. Where natural levels of iodine in the
soil are low and the iodine is not taken up by vegetables, iodine added to salt provides the small but essential amount of iodine needed by humans.
An opened package of table salt with
iodide may rapidly lose its iodine content through the process of oxidation and iodine
sublimation.
[3]
