Drinking water contributes to excessive iodine intake among children in Hebei, China

In Hebei province, China, over six million people are potentially exposed to excessive iodine through consumption of high iodine underground drinking water and consumption of iodized salt. The aim of this study is to evaluate the contributions of drinking water and iodized salt on children's iodine nutrition in one area of Hebei province in order to refine strategies to correct the excessive iodine intake in these areas.

To investigate the relationships between iodine content in water, iodized salt and urinary iodine content (UIC) in children (8-10 years), we randomly sampled three towns with a known median water iodine (MWI) of 150-300 μg/l in Hengshui City, Hebei province and collected water, salt and urine samples.

The median UIC was 518.1 μg/l, the overall MWI was 247.0 μg/l, and 83% of children sampled were found to have urinary iodine concentrations higher than the WHO criterion of 300 μg/l. There was a significant and positive correlation between the median UIC of the children and the MWI in the 12 villages where the children lived (Spearman R=0.79, P=0.002), but the UIC was not significantly correlated with the median salt intake (MSI) (Spearman R=-0.17, P=0.6). A multiple linear regression analysis indicated that 68.7% of the variability in median UIC is associated with variability in MWI in the 12 villages.

Iodine in drinking water was identified to be the key contributor to this excessive iodine in children indicating that in these areas, intervention should focus on providing alternative drinking water supplies.