Objective To explore the changes of children's iodine nutritional status before and after water improvement in water-borne high iodine areas in Xuzhou, China.

Methods The systematic sampling method was used to select administrative villages with a median water iodine >100 μg/L in seven counties and districts in Xuzhou before (2018) and after water improvement measures (2024), and the terminal water was collected to determine water iodine. A stratified random sample of forty children aged 6 to 12 years were selected from the primary school in each administrative village to determine their urinary iodine content and salt iodine content at home and examine their thyroid using B-ultrasound.

Results After water improvement measures, the median water iodine in the monitored villages decreased from 262.4 μg/L to 28.4 μg/L (Z=6.94, P < 0.001), and the water iodine value in all villages was < 100 μg/L. The consumption rate of uniodized salt significantly decreased from 76.99% (900/1 169) to 71.07% (1 086/1 528) (χ²=11.94, P < 0.001). The median urinary iodine in children decreased from 453.3 μg/L to 335.2 μg/L (Z=9.58, P < 0.001), and the proportion of high urinary iodine decreased from 71.94% (841/1 169) to 56.02% (856/1 528) (χ²=76.53, P < 0.001). The prevalence of goiter decreased from 4.96% (58/1 169) to 3.34% (51/1 528) (χ²=4.50, P < 0.05), and the rate of nodules with a diameter >5 mm decreased from 2.14% (25/1 169) to 0.26% (4/1 528) (χ²=21.93, P < 0.001).

Conclusion After the implementation of the water improvement project in Xuzhou, the water iodine levels in the monitored villages decreased significantly; children's iodine nutritional status improved compared with that before water improvement, although the median urinary iodine level remained excessive.