Background: Fluoride exposure has been related to deficits in developmental outcomes in children. Animal experiments and 2 ecologic studies in humans suggest that fluoride may be associated with earlier onset of puberty in girls, but study designs limit inferences about causal relationship at an individual level. Few studies have considered relationships in boys. Taking advantage of a birth cohort study conducted in Mexico City, we examined the effect of fluoride exposure during pregnancy on pubertal onset at ages 8-14.
Methods: Fluoride in maternal urine samples from three trimesters was measured with an ion-selective electrode-based assay following acid-facilitated diffusion. Tanner stages for pubertal development (genitalia (G) and pubic hair (P) in boys; breast, pubic hair (P) and menarche (M) in girls) were obtained by self-reported questionnaire validated in Mexican adolescents. Multivariable logistic models were used to capture the association between mean value of prenatal fluoride exposure across 3 trimesters and pubertal onset (Tanner stage=2), adjusting for age, BMI-Z score and maternal education.
Results: Mean (±SD) fluoride was 0.87 ±0.46 ppm. Among 103 girls, the odds of M =2 increased by 2.01 (95%CI: 0.49-8.32) with one ppm increase in maternal urinary fluoride; the odds of P =2 increased by 2.58 (95%CI: 0.68-9.75). Among 82 boys, the odds of G =2 decreased by 0.53 (95%CI: 0.12-2.28); the odds of P =2 decreased by 0.23 (95%CI: 0.031-1.68).
Conclusions: Results were not statistically significant at p<.05, but point estimates suggest prenatal fluoride exposures may be associated with pubertal onset in boys and girls in opposite directions. We are currently collecting repeated Tanner stages measures over time from larger number of participants and analyzing physician observed measures of pubertal onset in order to have a more robust analysis.