Evidence that water can be an important contributor to total
iodine intake comes from studies in Denmark, South Africa,
China, and refugee populations in Algeria (20–24). Although
iodine intake from water sources may be important in preventing
deficiency, it may also contribute to excessive intakes and adverse
effects (1,2). An association has also been found between high
iodine concentrations in drinking water and reduced intelligence
quotient in China (25). Despite these data, WHO has not yet
defined a guideline value for iodine in drinking water (19).