[Study on iodine nutritional status of target population due to different iodine concentrations in drinking water after stopped iodized salt].

Objective: To investigate the iodine nutritional status of key population living areas with iodine excess in drinking water before and after stopped iodized salt supply to provide strategies of control excessive iodine.

Methods: The levels of iodine in drinking water, edible salt of household and urine of school-age children and child-beard age women were investigated at four villages A, B, C and D which iodine concentrations of 50-100, 100-150, 150-300 and more than 300microg/L. The results of iodine in water, edible salt, urine and thyroid goiter were observed before stopping iodized salt. The levels of urinary iodine in four groups were tested after stopped iodized salt one or two month later.

Results: The medians of iodine concentration in inhabitants from four groups A, B, C and D were 93.20, 143.23, 194. 10 and 805.85microg/L of drinking water, in edible salt 25.38, 28.21, 30.01 and 32.87mg/kg. Goiter rate was 15.9%, 5.9%, 12.7% and 24.0%, respectively. The median of urinary iodine (MUI) was 384.60, 374.85, 439.90 and 1260.10microg/L. The proportion of urinary iodine level of 100-300microg/L was 32.3%, 28.3%, 13.6% and 1.0%, of more than 300microg/L was 67.7%, 70.8%, 86.4% and 99.0% with iodized salt supply. MUI of all groups with non-iodized salt decreased significantly after two month, especially in group A and B. The proportion of urinary iodine levels of 100-300microg/L was obviously more than before, but group more than 300microg/L was less than before. The similar changes of MUI were in children and women, but degree of change was obviously in group A. Their MUI were in normal after two month. There were significant difference in MUI of denizens including children and women before and after intervene. There was no difference of MUI in group C and D at the same time. There were significant correlations between urinary iodine and water iodine concentration (P < 0.001). MUI in group C, D was more than 300microg/L, but evident differences were found among 4 groups under different levels of water iodine (P < 0.001). The nutritious status of iodine was markedly excessive in group B, C and D of objects.

Conclusion: Iodine nutritional status in inhabitants drinking water iodine concentration about 90microg/L was in normal, iodized salt supply could be safely stopped at the regions. Regardless iodized or non-iodized salt supply, there was inefficient in those areas with water iodine much more than 100microg/L. It is suggested that iodized salt must be stopped for controlling excessive iodine in the areas.