Geochemistry of iodine in relation to iodine deficiency diseases

Seawater is the most important reservoir for terrestrial iodine; this is a major influence on iodine distribution in the secondary environment. Volatilization of iodine from the oceans, possibility as elemental iodine or as an organically-bound species, is the main source of the element in the environment. The distribution of iodine in the secondary environment is, therefore, largely controlled by proximity to the oceans, with rainwater and surface run-off relatively enriched in iodine in near-coastal regions. Soil iodine content is also strongly influenced with coastal soils being much enriched and central continental soils being depleted. The soil's ability to retain iodine is also an important factor. Organic matter together with iron and aluminium oxides and clays are the important sinks of soil iodine.