Impact of high lodine and fluoride intake on children's IQ in rural China

Background Excessive intake of both fluorine and iodine can lead to various health effects. The potential influence of excessive fluorine and iodine intake on the intelligence of school-age children has become a notable concern. Objectives To investigate the relationship between urinary fluoride (UF) levels, urinary iodine (UI) levels, and intelligence quotient (IQ). Methods This study involved 711 children aged 8 to 12 from rural Jiangsu, China. Water iodine levels were measured using As3+-Ce4+ catalytic spectrophotometry, while UI levels were determined using inductively coupled plasma mass spectrometry. Fluoride levels in urine and drinking water were measured using the ion-selective electrode method. Children's cognitive function, evaluated through IQ scores, was assessed using the Combined Raven's Test. The results were considered significant at the P < 0.05 level. Results The average IQ score was 107.6, the median UF was 281 <mu>g/L, and the median UI was 1.39 mg/L. The correlation coefficient (beta) and confidence interval (95%CI) for UF and UI on IQ were - 3.34 (-4.14, -2.43) and - 3.31 (-4.19, -2.41), respectively (P < 0.001, P < 0.001). UF > 1.4 mg/L and UI >= 300 mu g/L were negatively correlated with IQ scores in all school-age children (P < 0.001, P < 0.001), with beta and 95% CIs of -3.59 (-5.45, -1.74), -4.06 (-5.91, -2.21), respectively. The interaction term (UF > 1.4 mg/L: UI >= 300 mu g/L) was negatively correlated with IQ scores in all (P = 0.041) and female school-age children (P = 0.007), with beta and 95%CIs of -4.43 (-8.66, -0.19) and - 8.87 (-15.16, -2.40), respectively. Conclusions High levels of both fluoride and iodine intake negatively affect the IQ of school-age children. Monitoring and regulating these elements in children's diets is essential to prevent cognitive impairment.