Dental Fluorosis, IQ, and Urinary Fluoride in Peruvian Schoolchildren

Objectives: To explore dose-response relationships between urinary fluoride levels, intelligence quotient (IQ), and dental fluorosis in schoolchildren from a district in Arequipa, Peru, characterized by high fluoride exposure from groundwater and proximity to a major mining center at an average altitude of 2300 m above sea level.
Methods: A total of 737 schoolchildren aged 8 to 16 years (mean 11.54±2.47) from Uchumayo (a semi-rural area near the mining center) and Yanahuara (an urban area with better access to services) were included, following parental consent and assent. Dental fluorosis was assessed using the modified Dean’s Index, and IQ was measured using the Toni 2 test, designed to evaluate problem-solving ability in abstract graphical tasks. Urinary fluoride concentrations (mg/L) were determined using a Seven Direct SD50 potentiometer (Mettler Toledo) and a fluoride ion-selective electrode (ISE). Water fluoride concentrations were also measured at random points in both districts over three months.
Results: Of the students evaluated, 386 were from Uchumayo and 352 from Yanahuara; 58.48% were female and over 70% were aged 8 to 13. The average fluoride concentration in water was significantly higher in Uchumayo (0.76±0.16mg/L) compared to Yanahuara (0.19±0.03mg/L). Higher urinary fluoride level was not associated with increased odds of greater dental fluorosis severity. A negative dose-response relationship between urinary fluoride levels and IQ scores was observed; however, confidence interval overlaps limited the strength of this association. Notably, IQ scores ≤89 were exclusively observed in children with moderate or severe fluorosis.
Conclusions: While trends suggest an association between fluoride exposure, dental fluorosis severity, and IQ scores, the results are limited by overlapping confidence intervals. Further studies, are necessary to confirm these findings and establish causality.