Benefits and risks from the national strategy for improvement of iodine nutrition: a community-based epidemiologic survey in Chinese schoolchildren.

OBJECTIVE: Mild to severe iodine deficiency has been documented in China since 1960. To eliminate this persisting iodine deficiency, legislation on universal salt iodization was introduced in 1995 as a long-term public health intervention strategy. We examined the urinary iodine excretion and the iodine content of drinking water and salt samples to assess the benefits and risks of this national strategy.

METHODS: We examined the urinary iodine excretion of 1594 schoolchildren 8 to 10 y old from the 16 counties of China. The iodine content of 1097 drinking water and 4501 table salt samples also was assessed in these counties. The study was conducted from April 2009 through October 2010. Urinary iodine excretion and iodine levels in drinking water and table salt samples were measured based on the Sandell-Kolthoff reaction. Data were interpreted according to World Health Organization criteria.

RESULTS: The median urinary iodine levels of the schoolchildren were 198.2, 277.2, 336.2, and 494.8 μg/L in areas with iodine levels lower than 10, 10 to 150, 150 to 300, and higher than 300 μg/L in the drinking water, respectively. The mean iodine level in the table salt specimens was 30.4 mg/kg, the coverage rate was 98.6%, and the qualified rate was 96.7%. The goiter prevalence was 8.0% in the areas with an iodine level higher than 150 μg/L in the drinking water.

CONCLUSION: In each area, the median urinary iodine of schoolchildren was nearly or above 200 μg/L, which confirmed the effectiveness of the iodization strategy. However, in areas with an iodine content higher than 150 μg/L in the drinking water, the schoolchildren had more than adequate or excessive iodine intake, which was associated with the prevalence of goiter. Therefore, it is important to adjust the strategy of universal salt iodization control in China.