The impact of exposure to fluoride in drinking water on intelligence in school age children in Iran

The present study aimed to compare the intelligence quotient (IQ) and body mass index (BMI) of 161 school-aged children (10-12 years old) residing in two cities with different levels of fluoride (F⁻) in drinking-water: 0.02 mg/L in Lalehzar (City 1) and 1.15 mg/L, corresponding to the WHO guideline value, in Reyhanshahr (City 2), Kerman Province, southeastern Iran. Additionally, the study evaluated, for the first time in 2024, the associated non-carcinogenic health risk and investigated the potential role of aluminum (Al) in forming F-Al complexes that may cross the blood-brain barrier. IQ scores were assessed using Raven's Standard Progressive Matrices, and water samples were analyzed for aluminum and fluoride content. The mean aluminum concentrations were 0.01 mg/L in City 1 and 0.04 mg/L in City 2 (p < 0.001). The corresponding mean IQ scores were 108.55 ± 11.50 and 110.41 ± 9.53, respectively, showing no statistically significant difference (p = 0.264). Regression analysis revealed no significant association between Al concentration in drinking-water and IQ (p = 0.279). A significant inverse relationship was observed between fluoride concentration and BMI (p = 0.01). Due to the conflicting findings regarding whether fluoride is safe for children's intelligence within the WHO limits, it is not possible to make a definitive statement. However, an increase in fluoride concentration appeared to be associated with a reduction in BMI, likely due to fluoride's influence on growth parameters, particularly height development. Hazard quotient (HQ) values were below unity in both cities, indicating no potential risk associated with fluoride exposure. Although the estimated risk level in City 2 was below the safety threshold (HQ = 0.81), it was relatively close to unity, warranting attention. Therefore, it is recommended that local authorities monitor and, if feasible, reduce fluoride concentrations in drinking-water, limiting additional exposure to fluoride-containing products such as toothpaste and mouthwash. Longitudinal studies in broader age groups are needed to confirm these associations and clarify the underlying mechanisms.