Does fluoride in drinking water affect children's IQ?

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1. 1

   Fluoride Exposure and Children’s IQ Scores

   Archives of Pediatrics and Adolescent Medicine (Taylor et al.)Published Jan 6, 2025Checked Sep 30, 2026

   “Of 74 studies included (64 cross-sectional and 10 cohort studies), most were conducted in China (n = 45); other locations included Canada (n = 3), Denmark (n = 1), India (n = 12), Iran (n = 4), Mexico (n = 4), New Zealand (n = 1), Pakistan (n = 2), Spain (n = 1), and Taiwan (n = 1). Fifty-two studies were rated high risk of bias and 22 were rated low risk of bias. Sixty-four studies reported inverse associations between fluoride exposure measures and children's IQ. Analysis of 59 studies with group-level measures of fluoride in drinking water, dental fluorosis, or other measures of fluoride exposure (47 high risk of bias, 12 low risk of bias; n = 20 932 children) showed an inverse association between fluoride exposure and IQ (pooled SMD, -0.45; 95% CI, -0.57 to -0.33; P < .001). In 31 studies reporting fluoride measured in drinking water, a dose-response association was found between exposed and reference groups (SMD, -0.15; 95% CI, -0.20 to -0.11; P < .001), and associations remained inverse when exposed groups were restricted to less than 4 mg/L and less than 2 mg/L; however, the association was null at less than 1.5 mg/L.”

2. 2

   Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis

   Environmental Health Perspectives (Choi et al.)Published Jul 20, 2012Checked Sep 30, 2026

   “The standardized weighted mean difference in IQ score between exposed and reference populations was -0.45 (95% confidence interval: -0.56, -0.35) using a random-effects model. Thus, children in high-fluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas. Subgroup and sensitivity analyses also indicated inverse associations, although the substantial heterogeneity did not appear to decrease. The results support the possibility of an adverse effect of high fluoride exposure on children's neurodevelopment. Future research should include detailed individual-level information on prenatal exposure, neurobehavioral performance, and covariates for adjustment.”

3. 3

   Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6–12 Years of Age in Mexico

   Environmental Health Perspectives (Bashash et al.)Published Sep 22, 2017Checked Sep 30, 2026

   “We had complete data on 299 mother-child pairs, of whom 287 and 211 had data for the GCI and IQ analyses, respectively. Mean (SD) values for urinary fluoride in all of the mothers (n=299) and children with available urine samples (n=211) were 0.90 (0.35) mg/L and 0.82 (0.38) mg/L, respectively. In multivariate models we found that an increase in maternal urine fluoride of 0.5mg/L (approximately the IQR) predicted 3.15 (95% CI: -5.42, -0.87) and 2.50 (95% CI -4.12, -0.59) lower offspring GCI and IQ scores, respectively. In this study, higher prenatal fluoride exposure, in the general range of exposures reported for other general population samples of pregnant women and nonpregnant adults, was associated with lower scores on tests of cognitive function in the offspring at age 4 and 6-12 y. https://doi.org/10.1289/EHP655.”

4. 4

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

   Archives of Pediatrics and Adolescent Medicine (Green et al.)Published Aug 19, 2019Checked Sep 30, 2026

   “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 MUFSG 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) MUFSG 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. 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.”

5. 5

   Fluoride exposure and cognitive neurodevelopment: Systematic review and dose-response meta-analysis

   Environmental Research (Veneri et al.)Published Jan 10, 2023Checked Sep 30, 2026

   “Dose-response analysis showed a substantially linear IQ decrease for increasing water fluoride above 1 mg/L, with -3.05 (95% CI -4.06; -2.04) IQ points per 1 mg/L up to 2 mg/L, becoming steeper above such level. A weaker and substantially linear decrease of -2.15 (95% CI -4.48; 0.18) IQ points with increasing urinary fluoride emerged above 0.28 mg/L (approximately reflecting a water fluoride content of 0.7 mg/L). The inverse association between fluoride exposure and IQ was particularly strong in the studies at high risk of bias, while no adverse effect emerged in the only study judged at low risk of bias. Overall, most studies suggested an adverse effect of fluoride exposure on children's IQ, starting at low levels of exposure. However, a major role of residual confounding could not be ruled out, thus indicating the need of additional prospective studies at low risk of bias to conclusively assess the relation between fluoride exposure and cognitive neurodevelopment.”

6. 6

   Developmental fluoride neurotoxicity: an updated review

   Environmental Health (Grandjean)Published Dec 1, 2019Checked Sep 30, 2026

   “Fourteen recent cross-sectional studies from endemic areas with naturally high fluoride concentrations in groundwater supported the previous findings of cognitive deficits in children with elevated fluoride exposures. Three recent prospective studies from Mexico and Canada with individual exposure data showed that early-life exposures were negatively associated with children's performance on cognitive tests. Neurotoxicity appeared to be dose-dependent, and tentative benchmark dose calculations suggest that safe exposures are likely to be below currently accepted or recommended fluoride concentrations in drinking water. The recent epidemiological results support the notion that elevated fluoride intake during early development can result in IQ deficits that may be considerable. Recognition of neurotoxic risks is necessary when determining the safety of fluoride-contaminated drinking water and fluoride uses for preventive dentistry purposes.”

7. 7

   Water fluoridation (Wikipedia)

   WikipediaPublished Sep 29, 2026Checked Sep 30, 2026

   “Water fluoridation is the controlled addition of fluoride to public water supplies to reduce tooth decay. Fluoridated water maintains fluoride levels effective for cavity prevention, achieved naturally or through supplementation. In the mouth, fluoride slows tooth enamel demineralization and enhances remineralization in early-stage cavities. Defluoridation is necessary when natural fluoride exceeds recommended limits. The World Health Organization (WHO) recommends fluoride levels of 0.5–1.5 mg/L, depending on climate and other factors. In the U.S., the recommended level has been 0.7 mg/L since 2015, lowered from 1.2 mg/L. Bottled water often has unknown fluoride levels. Tooth decay affects 60–90% of schoolchildren worldwide. Fluoridation reduces cavities in children, with Cochrane reviews estimating reductions of 35% in baby teeth and 26% in permanent teeth when no other fluoride sources are available, though efficacy in adults is less clear. In Europe and other regions, declining decay rates are attributed to topical fluorides and alternatives like salt fluoridation and nano-hydroxyapatite.”

8. 8

   Public Health Impacts of Water Fluorides: Current Evidence from a Rapid Systematic Review.

   Advances in nutrition (Bethesda, Md.) (Zohoori et al.)Published Oct 22, 2025Checked Oct 4, 2026

   “The most common risk of bias was insufficient control of confounders. Health outcomes studied included blood pressure, neurological outcomes, bone cancers, thyroid function, skeletal outcomes, low birth weight/preterm birth, and metabolic outcomes. In children, some evidence of adverse effects on neurological outcomes and thyroid function was observed. In adults, some evidence was identified of adverse effects on blood pressure, thyroid function, and skeletal structure. In general, these effects occurred at drinking water fluoride concentrations >1.5 mg/L. No evidence of adverse effects was found at concentrations <1.0 mg/L in both children and adults. The nature of study designs and methodological limitations precluded causal inference. No convincing evidence of harm was identified from community water fluoridation at concentrations between 0.7 and 1.0 mg/L, whereas uncertainty remains at higher concentrations. Significant methodological limitations highlight the need for more rigorous future studies. A protocol was developed a priori and registered on the Open Science Framework (Registration DOI: https://doi.org/10.17605/OSF.IO/JH245).”

9. 9

   Addressing Critiques of the Evidence Linking Fluoride and Children's IQ.

   Annals of global health (Taylor et al.)Published Dec 12, 2025Checked Oct 4, 2026

   “This inverse association persisted when analyses were restricted to the best evidence, the high‑quality studies, and was consistent across subgroups defined by sex, age, country, outcome assessment method, timing of exposure, and exposure matrix (e.g., urine or drinking water). Notably, among the high‑quality evidence, inverse associations were still observed at fluoride exposure levels below 1.5 mg/L, based on both urinary and drinking‑water measurements. These publications have received considerable public and media attention, prompted healthy scientific discourse, and have been cited by public health decision‑makers. Many scientific comments were carefully considered and resolved during development and peer review, which contributed to the rigor of the final documents. However, some recurrent critiques continue to be raised. This viewpoint provides a high‑level summary of these key critiques and corresponding responses to help the public, media, and the scientific community better understand the strength and implications of the scientific evidence on fluoride exposures and neurodevelopment and cognition.”

10. 10

    Fluoride and Neurodevelopmental Hazard Modelling: An Assessment of Concentration-Response Analysis.

    Community dentistry and oral epidemiology (Kumar et al.)Published Oct 31, 2025Checked Oct 4, 2026

    “mental Protection Agency (EPA) benchmark dose modelling was utilised to determine the association between fluoride concentrations and cognition scores.ResultsAll four maternal urinary fluoride (MUF) studies did not meet the standards for acceptable quality, as identified by the EPA data quality criteria, which are necessary for combining data from different studies for dose-response analysis. The pooled estimate was not statistically significant (βMUF = -1.06, 95% CI: -3.63, 1.50; p = 0.42; I2 = 62%). A meta-analysis of five studies conducted in fluoridated areas showed a pooled SMD effect size of 0.04 (95% CI: -0.06, 0.14; p = 0.42; I2 = 0%), favoring higher fluoride. The benchmark dose models did not reveal a functional relationship between MUF or water fluoride concentration and cognitive outcomes (Goodness-of-fit p ConclusionsThe data quality assessment revealed serious flaws that render the maternal urinary studies unacceptable for hazard assessment and benchmark dose modelling. Therefore, more appropriate studies in endemic fluorosis areas are needed to accurately determine whether fluoride is associated with adverse cognitive outcomes in populations with meaningful exposure.”

11. 11

    Childhood fluoride exposure and cognition across the life course.

    Science advances (Warren et al.)Published Nov 19, 2025Checked Oct 4, 2026

    “How are children's fluoride exposures associated with cognitive test performance in adolescence and midlife? Whereas most prior research has estimated effects of exposure to extremely high levels of fluoride, we consider exposure to levels of fluoride within the range typical in most places and of greatest relevance to policy debates about government water fluoridation. We use data from the nationally representative (United States) High School and Beyond cohort, characterize fluoride exposure from drinking water across adolescence, adjust for confounders, and observe cognitive test performance in both secondary school and at age ~60. We find that children exposed to recommended levels of fluoride in drinking water exhibit modestly better cognition in secondary school, an advantage that is smaller and no longer statistically significant at age ~60.”