Joint Effects Of Excessive Fluoride And Iodine In Drinking Water On Children’s Thyroid And Intelligence Development

ObjectivesResearch on effects of thyroid damage and intelligence of children by chronic exposure of excessive fluoride and excessive iodine alone and by joint-effect of excessive fluoride and iodine. To elucidate the toxicity and mechanism of excessive fluoride and iodine, and to provide theoretical evidences for early stage biomarkers research.MethodsAccording to the concentration of fluoride and iodine in drinking water, four villages in two counties of TianJin were classified to three groups as high fluoride and iodine, high fluride and control area. Ninty eight children who were born and grew in the four areas were chosen for dental flurosis examination with Dean’s method and were evaluated intelligence level by CRT-RC. Drinking water and salt samples were collected from homes and schools of every child. The morning Urine was collected and venous blood was taken from the objectives before breakfast. The concentrations of T3, T4, TSH, FT3and FT4in serum were detected with radioimmunoassay method. MDA content was measured by TBA chromatometry method. Superoxide Dismutase (SOD) activity was determined by xanthine oxidase method. Reactive oxygen species (ROS) level was determined by ELISA.Results1Qualified iodized salt coverage rate in high fluoride and iodine, high fluride group were higher than control group (P<0.05). There was no significant difference in drinking water among these three groups (P>0.05).2Significant raise of urinary fluoride and iodine were observed in high fluoride and iodine, and high fluoride groups compared to control group. Thyroid hormone T4in high fluoride and iodine group was higher than high fluoride group (P<0.05), but there were no significant differences of other Thyroid hormone(T3, FT3, FT4and TSH) among the three groups (P>0.05). 3The difference of prevalence of dental fluorosis in high fluoride group was higher than high fluoride and iodine group (P<0.05), and prevalence of dental fluorosis was tended to increase with age.4The difference of children’s IQ was statistically significant among the groups, and in the abilities of series relationship, differences were statistically significant lower in high fluoride and iodine group (P<0.05).5ROS in high fluoride and iodine group was higher than high fluoride group (P<0.05), but activities of SOD was inverse. The difference of MDA wasn’t statistically significant among the groups (P>0.05).6The content of urinary iodine had a positive correlation with ROS, and a negative correlation with SOD.Conclusions1The exposure of high fluoride alone or combination with iodine has a definite impact on children’s thyroid function, and there were no significant differences of other Thyroid hormone except T4.2The combined exposure of high fluoride and iodine impact intelligence development of children, mainly involving abstract reasoning abilities such as series of relations, analogy, graphics sets.3Oxidative stress status are closely related to urinary iodine and fluoride. ROS and SOD may be early biomarkers of damage caused by high fluoride and high iodine.This work was supported by grants from TianJin Medical and Health Research Project Foundation (2010)(No.10KG215).