To dynamically investigate the iodine nutritional status of residents in water source high iodine areas in Hebei Province, so as to provide basis for taking targeted prevention and control measures and accurate intervention strategies.

According to the "National Monitoring Program for Water Source High Iodine Areas (2018 Edition)", water source high iodine monitoring was carried out in 5 cities and 35 counties (cities, districts, hereinafter referred to as counties) of Hebei Province. According to the survey results of drinking water iodine of residents of Hebei Province in 2017, the administrative villages with a median water iodine above 100 μg/L were sorted according to the water iodine value. The systematic sampling method was adopted. Five administrative villages were selected in each county, if there were less than 5 administrative villages, all of them were selected (if the median water iodine was > 300 μg/L, at least one village shall be selected). The iodine content in drinking water of residents among the monitoring sites, salt iodine, urinary iodine and thyroid volume of children aged 8 - 10, as well as salt iodine and urinary iodine of pregnant women were tested. Water iodine was detected by the "Method Suitable for the Detection of Water Iodine in Iodine Deficient and High Iodine Areas" recommended by the National Iodine Deficiency Reference Laboratory of the Chinese Center for Disease Control and Prevention. Salt iodine was detected by semi quantitative method. Urinary iodine was detected by "Arsenic Cerium Catalytic Spectrophotometry Method" (WS/T 107-2006). Children's thyroid volume was detected by B-ultrasound.

A total of 239 water samples were collected in 167 villages, 35 counties, the median water iodine was 163.95 μg/L, ranging from 5.53 - 930.82 μg/L. A total of 6 772 edible salt samples were monitored, including 3 495 non-iodine salt samples and the rate of non-iodine salt was 51.61% (3 495/6 772). A total of 6 101 urine samples of children were tested, the median urinary iodine was 328.00 μg/L. A total of 6 103 children aged 8 - 10 were carried out B-ultrasound detection of thyroid volume in 35 counties. The goiter rate of children was 5.01% (306/6 103), and the rate of nodules was 0.56% (34/6 103). A total of 713 urine samples of pregnant women were tested, and the median urinary iodine was 221.70 μg/L.

The iodine nutrition of children in water source high iodine areas of Hebei Province is at an excess level, and the iodine nutrition of pregnant women is at an appropriate level. In addition to stopping the supply of iodized salt, we should further expand the coverage of water improvement and iodine reduction projects in high iodine areas, and strengthen the monitoring of iodine nutrition status of key populations.

Iodine; Drinking water; Edible salt; Urine; Goiter