Fluoride in Drinking Water: What the Evidence Shows

Evidence reviewed November 1, 2026.

Patients have been asking about fluoride in drinking water. Two states banned it in 2025, a federal court case changed direction in 2026, and federal agencies are reviewing it now. This article sets out what the evidence shows at the level actually used in the United States, and what remains uncertain.

The short answer. At 0.7 mg/L, the level U.S. systems that fluoridate aim for, contemporary studies show a small cavity benefit, with low-certainty evidence, and the established tradeoff is dental fluorosis, which in the United States is mostly mild and cosmetic. The studies raising other concerns involve higher levels, above 1.5 mg/L, and do not settle the question at 0.7. The evidence, and what is still uncertain, is set out below.

The level used in the United States

Community water fluoridation means a water system adjusts the fluoride in its water to a set level to help prevent cavities. Fluoride also occurs naturally in water, at levels that vary by source.

Since 2015, the U.S. Public Health Service has recommended 0.7 milligrams of fluoride per liter of water (0.7 mg/L) for systems that fluoridate, a level set to prevent cavities while limiting dental fluorosis, described below. That number is a recommendation, not a legal limit. The enforceable federal limit set by the Environmental Protection Agency (EPA) is 4.0 mg/L. State and local governments decide whether a water system fluoridates. [1][2][7]

Why this is in the news

State bans. In 2025, Utah and Florida each enacted a statewide ban on adding fluoride to public water systems. Utah acted first, in March 2025. Florida followed in May 2025. [3][4]

More bills, none passed. During the 2026 state legislative season, bills to ban fluoridation or restrict it were filed in 23 states. None was approved. Those figures come from the September 22, 2026 update by the Campaign for Dental Health at the American Academy of Pediatrics, reporting legislative tracking by the CareQuest Institute. [5]

The court case. In September 2024, a federal district court judge ruled that fluoridation at 0.7 mg/L presents an unreasonable risk under the Toxic Substances Control Act and ordered the EPA to respond. On May 21, 2026, the Ninth Circuit Court of Appeals vacated and remanded the case for further proceedings on procedural grounds. The appeals court found that the trial court had taken over the case from the parties: it refused to rule on the record of the first trial and held a second trial. It did not decide whether fluoridated water is safe or unsafe. [6]

The EPA review. In April 2025, the EPA announced it would review the science on fluoride in drinking water ahead of its normal schedule. It released a preliminary assessment plan in January 2026 and an assessment protocol in August 2026. The federal enforceable limit remains 4.0 mg/L; the assessment is ongoing. [7]

Fluoride supplements. On October 31, 2025, the Food and Drug Administration (FDA) announced intended enforcement against specified unapproved ingestible fluoride products marketed for children under age 3, and for older children not at high risk of cavities. The FDA sent notices to four companies stating its intention to take enforcement action. The American Dental Association (ADA) responded that a clinician’s judgment should guide supplement use. ADA guidance still lists supplements for children at high risk of cavities whose water has low fluoride, starting at 6 months of age. The two positions now differ for young children. [8][9]

CDC guidance has not changed. In April 2025, the Secretary of Health and Human Services said he planned to direct the CDC to stop recommending fluoridation. As of this writing, CDC guidance still recommends fluoride to prevent cavities and still describes 0.7 mg/L as the level drinking water needs to reliably prevent cavities. [1]

What the evidence shows about cavity prevention

A 2024 Cochrane review combined 157 studies of water fluoridation. Only 22 of those studies addressed starting or stopping fluoridation. The other 135 addressed dental fluorosis. In studies conducted after 1975, when fluoride toothpaste was in widespread use, starting fluoridation may have reduced decay in children’s baby teeth by about one quarter of a tooth per child on average. That contemporary estimate came from two studies. The range around it included the possibility of little or no benefit, and the reviewers rated the certainty of the evidence as low. Studies from before 1975 found a much larger effect, about two fewer decayed teeth per child. The review found no eligible studies of cavity outcomes in adults. [12]

Contemporary studies suggest a small cavity-prevention benefit from water fluoridation, but its size remains uncertain. The added benefit today comes on top of fluoride toothpaste, which was not in widespread use in the earlier studies.

What the evidence shows about risk

Brain development. In August 2024, the National Toxicology Program (NTP) published a review of studies on fluoride exposure and children’s IQ. The NTP concluded, with moderate confidence, that higher fluoride exposure is associated with lower IQ in children. That conclusion describes higher exposure, including drinking water with more than 1.5 mg/L of fluoride, which is more than twice the U.S. recommended level. It does not establish that risk starts at 1.5 mg/L. Most of the studies were conducted outside the United States, and the review assessed total fluoride exposure from all sources, not fluoridated water alone. [10]

The same review stated that there were not enough data to determine whether 0.7 mg/L affects children’s IQ. For adults, the NTP described the evidence on cognition as limited, which is not the same as a finding of no effect. [10][16]

A related meta-analysis published in JAMA Pediatrics in 2025 combined 74 studies and also found associations between fluoride exposure and lower children’s IQ scores. Its data at the levels used in U.S. fluoridation were limited: when exposure was estimated from drinking water alone, the authors reported limited data and uncertainty for concentrations below 1.5 mg/L. Many of these studies measured fluoride in urine rather than in water. A urinary fluoride concentration is not equivalent to a drinking water concentration, and the two should not be read as interchangeable. [11]

Two points matter for reading coverage of this research. First, the studies behind these findings are observational. Observational studies can show that two things occur together. They cannot by themselves prove that one caused the other. Second, findings at higher exposure levels do not answer the question at 0.7 mg/L. The evidence does not establish whether drinking water fluoridated at 0.7 mg/L affects children’s IQ. The question is not closed. The data are not sufficient to settle it in either direction.

Dental fluorosis. Fluorosis is a change in the appearance of tooth enamel. It can develop only while teeth are forming, up to about age 8. In the United States, fluorosis is mostly mild and cosmetic: faint white spots or streaks that do not affect how teeth function and are not painful. Moderate and severe fluorosis, which can stain and pit enamel, are rare. The chance of fluorosis rises with a child’s total fluoride intake from all sources, which is one reason the recommended water level is set where it is. [13][1]

What this means for you

Know your water. The fluoride level at your tap depends on the water system that serves your home. Your water provider publishes an annual water quality report, also called a Consumer Confidence Report, that lists the fluoride level. The CDC also offers a lookup tool called My Water’s Fluoride. For a private well, the level can only be found by laboratory testing. [1]

Toothpaste does the most direct work. Brush twice a day with fluoride toothpaste. Water and toothpaste work together, and toothpaste delivers a higher concentration of fluoride to the teeth at the times it is used. For most patients, consistent toothpaste use is the most important fluoride habit. Fluoridated water adds to this: frequent low-level contact every day, and fluoride present while children’s teeth are still forming, as described below. [1]

If your water is not fluoridated, ask. A water level below 0.7 mg/L is a reason to discuss prevention with your dentist. It is not, by itself, an indication for supplements. The supplement decision depends on the child’s age, cavity risk, the measured fluoride concentration in the water, and fluoride from other sources. The ADA’s supplement schedule recommends no supplements when the water concentration is above 0.6 mg/L. Professional fluoride varnish is another option. Given the difference between the FDA position and ADA guidance described above, make the supplement decision with your child’s dentist or pediatrician. [1][8][15]

Benefit and risk run on different measures. Fluoride helps prevent cavities mainly through contact with tooth surfaces. Fluorosis risk depends on the amount swallowed from all sources while teeth are developing. Fluoride swallowed while teeth are developing is built into the enamel as it mineralizes. The ADA describes a significant role for that incorporation in preventing decay in the pits and fissures of molars, which are hard for toothpaste to reach. The larger effect comes after teeth erupt: fluoride present in small amounts in the mouth throughout the day slows mineral loss and helps rebuild the surface. The ADA’s current summary is that the greatest reduction in decay occurs when both effects are combined. Fluoridated water works in both ways. It is present while children’s teeth are forming, and it keeps a low level of fluoride in contact with erupted teeth every day, which fluoride toothpaste adds to at higher concentration when it is used. Fluorosis is the risk when the amount swallowed during development is too high. This does not mean children should swallow toothpaste. Fluoride comes from water, toothpaste, food, and drinks made with fluoridated water, and it is the swallowed total, not any single source, that matters for fluorosis. [14][15][17][1]

Young children should use a small amount of toothpaste, a smear about the size of a grain of rice up to age 3 and a pea sized amount from ages 3 to 6, and be supervised so they swallow as little as possible. [1]

What we recommend at Precision Dental of Windsor. We recommend brushing with fluoride toothpaste and assess whether additional protection, such as professional fluoride varnish or prescription-strength toothpaste, is appropriate based on age and cavity risk. Our guidance follows the ADA, including when to start fluoride toothpaste for children and how much to use.

Summary

Contemporary studies suggest a small cavity-prevention benefit from water fluoridation, but its size remains uncertain. The clearest risk findings in the recent literature concern higher exposure, including water above 1.5 mg/L, and the evidence does not establish whether drinking water fluoridated at 0.7 mg/L affects children’s IQ. Federal review is under way and the court case is not finished, so this could change.

Evidence matters. Individual assessment matters. If you are unsure what your water contains or what your child needs, bring your questions to your next visit, and let’s talk about your situation.

Families who are new to the practice can ask about this at their first visit.

References

1. Centers for Disease Control and Prevention. Community Water Fluoridation Frequently Asked Questions. https://www.cdc.gov/fluoridation/faq/index.html

2. 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. https://doi.org/10.1177/003335491513000408

3. American Dental Association. Utah becomes first state to ban community water fluoridation. ADA News. March 28, 2025. https://adanews.ada.org/ada-news/2025/march/utah-becomes-first-state-to-ban-community-water-fluoridation/

4. American Dental Association. Florida second state to ban community water fluoridation. ADA News. May 15, 2025. https://adanews.ada.org/ada-news/2025/may/florida-second-state-to-ban-community-water-fluoridation/

5. Campaign for Dental Health, American Academy of Pediatrics. 2026 State Legislative Season and Fluoridation. Update, September 22, 2026. https://ilikemyteeth.org/2026-state-legislative-season-fluoridation/

6. U.S. Court of Appeals for the Ninth Circuit. Food & Water Watch v. United States Environmental Protection Agency, No. 25-384. Memorandum disposition filed May 21, 2026. https://cdn.ca9.uscourts.gov/datastore/memoranda/2026/05/21/25-384.pdf

7. U.S. Environmental Protection Agency. Fluoride in Drinking Water. https://www.epa.gov/sdwa/fluoride-drinking-water

8. American Dental Association. Statement from the ADA on FDA Action to Limit Fluoride Supplements for Children 3 and Younger and Advises for High Risk of Caries in Older Children. October 31, 2025. https://www.ada.org/about/press-releases/fluoride-supplements-for-children-3-and-younger

9. U.S. Food and Drug Administration. FDA Acts to Protect Children from Unapproved Fluoride Drug Products. Press announcement, October 31, 2025. https://www.fda.gov/news-events/press-announcements/fda-acts-protect-children-unapproved-fluoride-drug-products

10. National Toxicology Program. Fluoride Exposure: Neurodevelopment and Cognition. https://ntp.niehs.nih.gov/research/assessments/noncancer/completed/fluoride

11. 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. https://doi.org/10.1001/jamapediatrics.2024.5542

12. 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. https://doi.org/10.1002/14651858.CD010856.pub3

13. Centers for Disease Control and Prevention. About Dental Fluorosis. https://www.cdc.gov/oral-health/about/about-dental-fluorosis.html

14. Centers for Disease Control and Prevention. Recommendations for Using Fluoride to Prevent and Control Dental Caries in the United States. MMWR Recommendations and Reports. 2001;50(RR-14):1-42. https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5014a1.htm

15. American Dental Association. Fluoride: Topical and Systemic Supplements. https://www.ada.org/resources/ada-library/oral-health-topics/fluoride-topical-and-systemic-supplements

16. National Toxicology Program. NTP Monograph on the State of the Science Concerning Fluoride Exposure and Neurodevelopment and Cognition: A Systematic Review. NTP Monograph 08. August 2024. https://ntp.niehs.nih.gov/publications/monographs/mgraph08

17. American Dental Association. Fluoridation Facts. 2025 edition. https://commons.ada.org/fluoridationfacts/1/