Effects of drinking water with high iodine concentration on the intelligence of children in Tianjin, China

Abstract

ObjectiveThis study aimed to investigate the effects of drinking water with high concentrations of iodine on the intelligence of children in Tianjin, China.MethodsIt was a population-based health survey utilizing a random cluster sampling design conducted in June 2005. Participants were recruited from the total population of primary school children attending years 1-4 with ages ranging from 8 to 10 years. Intelligence quotient (IQ) was assessed using the combined Raven's test, second edition. Linear regression analyses were applied to test for any association between water iodine concentration and IQ.ResultsA total of 1229 students were recruited with a mean IQ of 105.8 (95 CI: 104.2-107.3). Water analyses indicated iodine concentrations were high in one rural region and exceedingly high in another with median values of 137.5 and 234.7 g/l, respectively. There was a significant association between residing in the very high water iodine region and a reduction of IQ by an average of about nine points (P = 0.022), after adjusting for the potential confounding factors.ConclusionExposure to high iodine concentrations in drinking water has detrimental effects on the intelligence of children.