Iodine in waters: possible links with endemic goitre

Iodine analyses of surface watersfrom various areas of the U.K. (0.40-15.6 μg/l I) and N. America (0.47-13.3μg/l I) reveal considerable regional differences. Some variation is due to contaminant I deriving from urban, industrial and agricultural sources and drainage from abandoned metalliferous mines. However, it is significant that the geology of the areas with higher I levels is dominated by limestone bedrocks. The I content of domestic supplies reflect their source, sub-surface waters containing appreaciably more than those from surface sources; in addition, I in waters for domestic use is reduced during purification treatment. It is unlikely that drinking waters provide more than 10% of the daily human I requirement. Whereas the I content of surface waters can give a general indication of the I status of the local environment, the highest levels were recorded for Missouri (x = 8.03 μg/l) and northern England (x=3.71), areas where endemic goitre was prevalent and soil I is generally low.