Association Between Maternal Fluoride Exposure During Pregnancy and IQ Scores in Offspring in Canada

Abstract

IMPORTANCE The potential neurotoxicity associated with exposure to fluoride, which has generated controversy about community water fluoridation, remains unclear. OBJECTIVE To examine the association between fluoride exposure during pregnancy and IQ scores in a prospective birth cohort. DESIGN, SETTING, AND PARTICIPANTS This prospective, multicenter birth cohort study used information from the Maternal-Infant Research on Environmental Chemicals cohort. Children were born between 2008 and 2012; 41% lived in communities supplied with fluoridated municipal water. The study sample included 601 mother-child pairs recruited from 6 major cities in Canada; children were between ages 3 and 4 years at testing. Data were analyzed between March 2017 and January 2019. EXPOSURES Maternal urinary fluoride (MUF SG), adjusted for specific gravity and averaged across 3 trimesters available for 512 pregnant women, as well as self-reported maternal daily fluoride intake from water and beverage consumption available for 400 pregnant women. MAIN OUTCOMES AND MEASURES Children's IQ was assessed at ages 3 to 4 years using the Wechsler Primary and Preschool Scale of Intelligence-III. Multiple linear regression analyses were used to examine covariate-adjusted associations between each fluoride exposure measure and IQ score. RESULTS Of 512 mother-child pairs, the mean (SD) age for enrollment for mothers was 32.3 (5.1) years, 463 (90%) were white, and 264 children (52%) were female. Data on MUF SG concentrations, IQ scores, and complete covariates were available for 512 mother-child pairs; data on maternal fluoride intake and children's IQ were available for 400 of 601 mother-child pairs. Women living in areas with fluoridated tap water (n = 141) compared with nonfluoridated water (n = 228) had significantly higher mean (SD) MUF SG concentrations (0.69 [0.42] mg/L vs 0.40 [0.27] mg/L; P = .001; to convert to millimoles per liter, multiply by 0.05263) and fluoride intake levels (0.93 [0.43] vs 0.30 [0.26] mg of fluoride per day; P = .001). Children had mean (SD) Full Scale IQ scores of 107.16 (13.26), range 52-143, with girls showing significantly higher mean (SD) scores than boys: 109.56 (11.96) vs 104.61 (14.09); P = .001. There was a significant interaction (P = .02) between child sex and MUF SG (6.89; 95% CI, 0.96-12.82) indicating a differential association between boys and girls. A 1-mg/L increase in MUF SG was associated with a 4.49-point lower IQ score (95% CI, −8.38 to −0.60) in boys, but there was no statistically significant association with IQ scores in girls (B = 2.40; 95% CI, −2.53 to 7.33). A 1-mg higher daily intake of fluoride among pregnant women was associated with a 3.66 lower IQ score (95% CI, −7.16 to −0.14) in boys and girls. CONCLUSIONS AND RELEVANCE In this study, maternal exposure to higher levels of fluoride during pregnancy was associated with lower IQ scores in children aged 3 to 4 years. These findings indicate the possible need to reduce fluoride intake during pregnancy.

Effects of Fluoride Long-Term Exposure over the Cerebellum: Global Proteomic Profile, Oxidative Biochemistry, Cell Density, and Motor Behavior Evaluation

“…Its high electronegativity allows the conversion of the fluoride ion into hydrogen fluoride (HF), facilitating its cellular interaction and distribution through the bloodstream [ 2 , 31 , 32 ]. The ability to cross different types of cell membranes, including the blood–brain barrier, is conFigured as one of its toxicity mechanisms, being related to changes in the metabolism and physiology of neurons and glia, modifying the memory and learning process of individuals [ 20 , 30 , 33 ]. Our data demonstrate that fluoride at high concentrations is able to cross the cerebellar blood–brain barrier, once the fluoride levels observed in the tissue of animals exposed to the concentration of 50 mg F/L were significantly higher than those found in control animals.…”

Maternal and fetal exposures to fluoride during mid-gestation among pregnant women in northern California

“…The importance of this early cerebral spinal fluid in brain development is demonstrated in Xenopus embryos, where exposure to a mixture of ubiquitous chemicals at concentrations found in human amniotic fluid affect thyroid hormone-dependent transcription, gene expression, brain development and behaviour in early embryogenesis [38]. While our analyses were done on midtrimester amniotic fluid, given recent population based correlations between systemic fluoride exposure and neurotoxicity [8], further studies of how fluoride may also affect early brain development in concert with other environmental stressors, are warranted.…”

“…This concentration of community water fluoridation in the US is higher than in Canada, where approximately one-third of Canadian communities fluoridate their water supply, and Europe, where only 3% of Europeans have fluoridated water [2,3]. Recent studies of the potential effects of fluoride on neurodevelopment from prenatal exposures [4][5][6][7][8], and the onset of puberty in boys [6], suggest the need to evaluate fluoride concentrations in communities in the US and their relationship to fluoride concentrations in pregnant women.…”

La sphère orale, cible et marqueur de l’exposition environnementale

“…En plus de ses propriétés extracellulaires qui sont bien documentées, des données récentes rapportent des effets intracellulaires du fluor, avec la modulation d'expression de gènes dans l'épithélium dentaire, mais aussi dans d'autres tissus (Figure 1). L'exposition au fluor a ainsi été associée à des effets dépassant le cadre buccal et les tissus minéralisés, dont des effets neurotoxiques et une diminution du quotient intellectuel [33,34], des perturbations de l'axe androgénique [35] (le fluor est répertorié comme un PE dans la TEDX List), et une augmentation des processus inflammatoires [36]. L'implication des récepteurs des hormones stéroïdiennes (progestérone et androgènes) dans les mécanismes d'action du fluor sur les améloblastes [37] laisse ainsi suspecter de fortes interactions entre fluor et PE.…”