Detection and evaluation of UI

The UI content detection was conducted as follows: urine samples were collected randomly once during the day. The UI content was determined by arsenic-cerium catalytic spectrophotometry in WS/T 107-2006 standard issued by the Ministry of Health of China. Iodine intake status assessment method was based on the recommended method in the Guidelines for the Assessment of Iodine Deficiency Disorders and Their Elimination issued by the World Health Organization, UNICEF, and the Global Iodine Intake Alliance in 2001. Iodine intake assessment was based on UI: <100 µg/L, insufficient; 100–199 µg/L, moderate; 200–299 µg/L, mild overdose; and >300 µg/L, excessive.