Fluoride & the Developing Brain

For decades, community water fluoridation has been promoted as one of dentistry’s great public-health achievements. We were taught that adding fluoride to drinking water would strengthen teeth, reduce cavities, and improve oral health across entire communities. For many of us in dentistry, that message was presented almost as settled science.

But when I began looking more closely at the research, I found that the story was far less settled than I had been taught.

The contemporary evidence for community water fluoridation is surprisingly weak. In its 2024 systematic review, Cochrane found that, in contemporary studies, starting community water fluoridation was associated with an average difference equivalent to approximately 0.24 fewer decayed, missing, or filled primary teeth per child. The evidence was rated low certainty, and the confidence interval included the possibility of no benefit. For permanent teeth, the contemporary evidence was considered very uncertain.

That matters because there is an important difference between saying that fluoride can interact with enamel chemistry and saying that adding fluoride to an entire community’s drinking water has been demonstrated to meaningfully reduce dental caries. I am no longer comfortable treating those statements as interchangeable.

And now another question has become even more important.

If the contemporary evidence for meaningful dental benefit from water fluoridation is uncertain or modest, what should we do when a growing body of research is simultaneously raising concerns about prenatal fluoride exposure and the developing brain?

That is the question I want to explore here.

A New U.S. Study Changes the Conversation

In August 2026, researchers led by Katrina Simon, PhD, published a study in the American Journal of Epidemiology examining prenatal exposure to fluoride in regulated public drinking water and later cognition in 2,514 U.S. children from the NIH Environmental influences on Child Health Outcomes, or ECHO, program.

The children were born between 2006 and 2019 across 17 study sites in 23 states. Researchers linked maternal residential addresses during pregnancy with fluoride concentrations reported by public water systems and later assessed childhood cognition using the NIH Toolbox. What they found deserves our attention.

The association between prenatal water fluoride and fluid cognition was nonlinear. Fluid cognition includes abilities such as working memory, attention, cognitive flexibility, problem solving, and learning new information. Using a change-point statistical model, the researchers identified approximately 0.675 mg/L as the best-fitting point at which the relationship changed. Above that concentration, every additional 0.1 mg/L of prenatal water fluoride was associated with a 0.67-point lower fluid-cognition score.

Why does 0.675 mg/L immediately get my attention? Because the U.S. Public Health Service recommends approximately 0.7 mg/L fluoride for community water fluoridation. We need to be scientifically precise about what this means. A second statistical approach used in the same study did not find a statistically significant inverse association until approximately 1.1 mg/L. Therefore, 0.675 mg/L should not be presented as a proven toxicity threshold. Nor does this study prove that fluoridated water causes irreversible brain damage. It is an observational study. It found an association with cognition; it did not demonstrate damaged brain tissue, establish causation, or determine that the cognitive differences are permanent.

Those distinctions matter. But so does the signal.

It Is Not Just One Study

The ECHO study becomes more important when we look at it alongside other prospective pregnancy studies.

In 2019, Green and colleagues published a Canadian birth-cohort study in JAMA Pediatrics. Unlike the ECHO study, researchers measured fluoride directly in maternal urine during pregnancy, providing a biomarker of the mother’s internal exposure. A 1 mg/L increase in maternal urinary fluoride was associated with a 4.49-point lower full-scale IQ among boys; that urinary-fluoride association was not observed in girls. Using a separate measure of estimated maternal fluoride intake, a 1 mg/day increase was associated with a 3.66-point lower IQ across boys and girls.

In 2024, Malin and colleagues examined 229 mother-child pairs in the Los Angeles MADRES cohort. A 0.68 mg/L increase in specific-gravity-adjusted maternal urinary fluoride measured during the third trimester was associated with 1.83 times the odds that a child’s total neurobehavioral-problems score at age three would fall in the borderline-clinical or clinical range. The article was corrected in June 2024 for labeling and scaling errors in a figure; the correction did not change the reported effect estimates or conclusions. An important limitation is that the primary exposure assessment relied on a single third-trimester spot urine sample, strengthening the case for future studies using repeated urinary fluoride measurements throughout pregnancy.

These studies did not measure exactly the same thing.Malin examined neurobehavior. Green examined IQ. Simon and the ECHO investigators examined fluid cognition. They also used different exposure measures, populations, and research teams.

Yet their findings point in a similar direction. That matters. In science, confidence can grow when a question is approached through different methodologies and related findings emerge. This is sometimes referred to as triangulation of evidence. No single one of these studies proves that fluoride causes brain injury. But when maternal urinary fluoride is associated with neurobehavior in one prospective study, prenatal fluoride exposure is associated with childhood IQ in another, and prenatal public-water fluoride is associated with fluid cognition in a large U.S. cohort, it becomes increasingly difficult to dismiss every study as “junk science.”

What Do Benchmark-Dose Analyses Tell Us?

Benchmark-dose analyses provide another way of looking at the prenatal fluoride question. Rather than asking simply whether an association is statistically significant, researchers can estimate the exposure level associated with a predefined change in outcome. Grandjean and colleagues applied this approach to prospective pregnancy cohorts from Canada and Mexico and calculated a lower-bound benchmark concentration of approximately 0.2 mg/L maternal urinary fluoride for a modeled 1-point decrease in childhood IQ. When a third prospective cohort from Denmark was added, the combined analysis produced a BMCL of 0.28 mg/L maternal urinary fluoride. Importantly, the Danish cohort alone did not show a significant fluoride–IQ association, highlighting the uncertainty that remains at lower exposures.

A 2024 systematic review by Taher and colleagues went one step further and modeled what Grandjean’s urinary benchmark might correspond to in drinking water. Using assumptions about maternal water consumption and fluoride excretion, they estimated approximately 0.179 mg/L. That is not a directly observed toxicity threshold, and the authors emphasized substantial uncertainty in extrapolating urinary fluoride to drinking-water concentrations. Nevertheless, these benchmark analyses raise an important question about how much margin exists between estimated points of departure for prenatal neurodevelopment and the 0.7 mg/L concentration intentionally maintained in U.S. fluoridated water.

Then Came the National Toxicology Program

In 2024, the National Toxicology Program completed a major systematic review of fluoride exposure and neurodevelopment.

NTP concluded with moderate confidence that higher fluoride exposure—particularly exposures around or above 1.5 mg/L in drinking water—is associated with lower IQ in children. NTP also clearly stated that there were insufficient data to determine whether the 0.7 mg/L concentration recommended for U.S. community water supplies adversely affects children’s IQ. That is an important limitation. But “insufficient evidence to determine harm” is not the same statement as “proven safe.”

A 2025 systematic review and meta-analysis by NTP researchers evaluated 74 epidemiologic studies. Among studies with individual-level urinary fluoride measurements, each 1 mg/L increase was associated with an average 1.63-point lower IQ score. When the analysis was restricted to studies rated at low risk of bias, the estimated decrease was smaller—1.14 points—but remained statistically significant. The researchers emphasized that evidence remains limited and uncertain at drinking-water concentrations below 1.5 mg/L, and there were insufficient data to determine whether drinking water at 0.7 mg/L affects children’s IQ.

The Study I Want to See Next

One weakness in the new ECHO study is that researchers knew the fluoride concentration in the public water associated with the mother’s residence, but they did not know precisely how much fluoride actually entered each mother’s body. Water fluoride tells us something about the source of exposure. Maternal urinary fluoride tells us more about internal exposure from multiple sources. The ideal next-generation study would measure both.

I want researchers to measure the fluoride concentration in the mother’s actual drinking water, document how much water she consumes, collect repeated maternal urinary fluoride measurements throughout pregnancy, account for major dietary and supplemental fluoride sources, evaluate renal function and fluoride clearance, document infant feeding practices, and then follow children long-term with standardized neurodevelopmental testing.

Why repeated urine measurements? Because a single urine sample is only a snapshot. Exposure varies from day to day with fluid intake, diet, physiology, and other sources.

Water concentration + actual consumption + repeated maternal urinary fluoride would give us a much clearer understanding of biological exposure.

For Me, the Developing Brain Changes the Equation

I want to be extremely clear about what the science does and does not currently show.

The existing studies do not prove that community water fluoridation at 0.7 mg/L causes irreversible neurological injury.

They do not prove that every fetus or child exposed to fluoride will experience cognitive harm.

They do not yet identify a completely safe prenatal exposure threshold.

But taken together, they represent a converging neurodevelopmental signal that deserves serious investigation. We do not need to claim more than the evidence supports. What the evidence already shows is enough to ask difficult questions.

And my own position is simple. If fluoridated water prevented dental caries 100%, but high-quality evidence ultimately demonstrated that the prenatal exposure necessary to achieve that benefit caused irreversible neurodevelopmental injury, I would consider that trade unacceptable.

The brain wins.

• Science asks questions.
• Science attempts replication.
• Science improves exposure measurements.
• Science identifies vulnerable populations.
• Science compares risks with benefits.

And science changes recommendations when the evidence changes.

While we wait for better answers, we also have to decide what degree of uncertainty we are willing to accept.

My position is that when an exposure is intentionally delivered population-wide, when pregnant women and infants cannot realistically be excluded from that exposure, and when a growing body of research raises legitimate questions about fetal and childhood neurodevelopment, the precautionary response should be to halt community water fluoridation unless and until high-quality evidence establishes an adequate margin of safety for the developing brain at the concentrations and total exposures people actually experience.

We should not require proof of irreversible neurological injury before reconsidering an intervention.

Absence of definitive proof of harm should not be treated as proof of safety.

Stay tuned for next week’s part II. Today was a lot of science—but wait, there’s more! Fluoride is far more complex than it may seem, my friends. It’s not just about tooth decay prevention. Know the science and make your own informed decisions.

Warmly,

Barbara Tritz

Queen of Dental Hygiene and Protector of Brains

References

1. Simon KR, et al. Prenatal exposure to fluoride in public water and child cognition in the US ECHO cohort, 2006–2019. American Journal of Epidemiology. Published August 14, 2026. doi:10.1093/aje/kwag186.
2. Green R, Lanphear B, Hornung R, et al. Association Between Maternal Fluoride Exposure During Pregnancy and IQ Scores in Offspring in Canada. JAMA Pediatrics. 2019;173(10):940–948. doi:10.1001/jamapediatrics.2019.1729.
3. Malin AJ, Eckel SP, Hu H, et al. Maternal Urinary Fluoride and Child Neurobehavior at Age 36 Months. JAMA Network Open. 2024;7(5):e2411987. doi:10.1001/jamanetworkopen.2024.11987. The article was corrected June 28, 2024, for errors in the figure; the reported effect estimates and conclusions were not changed.
4. Grandjean P, Hu H, Till C, et al. A Benchmark Dose Analysis for Maternal Pregnancy Urine-Fluoride and IQ in Children. Risk Analysis. 2022;42(3):439–449. doi:10.1111/risa.13767.
5. Grandjean P, Meddis A, Nielsen F, et al. Dose dependence of prenatal fluoride exposure associations with cognitive performance at school age in three prospective studies. European Journal of Public Health. 2024;34(1):143–149. doi:10.1093/eurpub/ckad170.
6. Taher MK, Momoli F, Go J, et al. Systematic review of epidemiological and toxicological evidence on health effects of fluoride in drinking water. Critical Reviews in Toxicology. 2024;54(1):2–34. doi:10.1080/10408444.2023.2295338.
7. National Toxicology Program. NTP Monograph on the State of the Science Concerning Fluoride Exposure and Neurodevelopment and Cognition: A Systematic Review. NTP Monograph 08. Research Triangle Park, NC: National Toxicology Program; 2024. doi:10.22427/NTP-MGRAPH-8.
8. Taylor KW, Eftim SE, Sibrizzi CA, et al. Fluoride Exposure and Children’s IQ Scores: A Systematic Review and Meta-Analysis. JAMA Pediatrics. 2025;179(3):282–292. doi:10.1001/jamapediatrics.2024.5542.
9. Iheozor-Ejiofor Z, Walsh T, Lewis SR, et al. Water fluoridation for the prevention of dental caries. Cochrane Database of Systematic Reviews. 2024;10:CD010856. doi:10.1002/14651858.CD010856.pub3.
10. U.S. Department of Health and Human Services Federal Panel on Community Water Fluoridation. U.S. Public Health Service Recommendation for Fluoride Concentration in Drinking Water for the Prevention of Dental Caries. Public Health Reports. 2015;130(4):318–331. doi:10.1177/003335491513000408.