Effects of high fluoride and iodine combined exposure on thyroid nodules and goiter in school-age children in Jiangsu, China

With advancements in detection equipment and an increase in the frequency of examinations, thyroid nodules and goiter in children have garnered attention. This study aims to determine the effects of high iodine and fluoride exposure on thyroid nodules and goiter in school-aged children. We recruited children aged 8 to 12 from rural Jiangsu, China, based on the concentrations of iodine and fluoride in local drinking water and urine. Participants were divided into four groups: a group with high fluoride and iodine (HFHI), a group with high fluoride (HF), a group with high iodine (HI), and a control group (CONTROL). Fluoride levels in both drinking water and urine samples were measured using the ion-selective electrode method. Urinary iodine (UI) was assessed using inductively coupled plasma mass spectrometry, and children's thyroids were examined with portable ultrasound equipment equipped with a linear 7.5-MHz probe. The detection rates of thyroid nodules in the HFHI, HF, HI, and CONTROL groups were 10.4 %, 6.5 %, 7.7 %, and 2.8 %, respectively. The goiter detection rates were 3.8 %, 2.9 %, 3.8 %, and 1.1 %, respectively. In the HFHI group, statistically significant correlations were found between urinary fluoride (UF) and thyroid nodules (P = 0.011, adjusted OR and 95 % CIs were 2.29 [1.21, 4.32]), as well as between UI and thyroid nodules (P = 0.038, adjusted OR and 95 % CIs were 1.58 [1.04, 2.40]), and between UI and goiter (P = 0.014, adjusted OR and 95 % CI were 2.31 [1.19, 4.48]). In the HI group, there was a statistically significant link between UI and goiter (P = 0.005, adjusted OR and 95 % CI were 2.45 [1.31, 4.58]). Combined high iodine and fluoride exposure may have an adverse effect on thyroid nodules in school-age children.