Fluoride in Tap Water: What the Science Says in 2026

Many Americans on public water drink water that contains fluoride, either added on purpose or occurring naturally. The US Public Health Service has recommended 0.7 mg/L for community water fluoridation since 2015. EPA’s enforceable maximum is 4.0 mg/L, with a non-enforceable secondary standard of 2.0 mg/L to prevent tooth discoloration. The debate today is mainly about whether fluoride affects children’s brain development. A 2024 federal toxicology review found an association with lower IQ at exposures above 1.5 mg/L, but said there wasn’t enough data to judge the 0.7 mg/L level. EPA is now re-examining the science, and its limit has not changed as of October 2026.

This post lays out the numbers, the evidence on both sides, what has happened in the courts and in Washington since 2024, and how to find out how much fluoride is in your own water. It is not medical advice. If you have questions about fluoride for an infant, during pregnancy, or for a health condition, talk to your doctor or dentist.

The numbers that matter

Value	What it is	Enforceable?
0.7 mg/L	US Public Health Service recommended level for community fluoridation (2015)	No, a recommendation
1.5 mg/L	Level above which NTP found, with moderate confidence, an association with lower IQ in children (2024)	No, a research finding
2.0 mg/L	EPA secondary standard, to prevent cosmetic dental fluorosis	No, but systems above it must notify customers
4.0 mg/L	EPA maximum contaminant level (MCL) and goal (MCLG), set in 1986	Yes

The 0.7 mg/L figure replaced an older range of 0.7 to 1.2 mg/L that dated to 1962. The Public Health Service lowered it partly because Americans now get fluoride from other sources, such as toothpaste, and to reduce the risk of dental fluorosis (faint white marks on teeth that form when children take in too much fluoride while teeth are developing).

Whether to fluoridate is decided by states and local governments, not the federal government. CDC states that it does not mandate fluoridation and that the 0.7 mg/L level is not an enforceable standard.

The case for fluoridation

Public health agencies and dental groups have supported fluoridation for decades because it reduces tooth decay.

CDC says fluoridation at the recommended level reduces cavities by about 25% in children and adults, and continues to list 0.7 mg/L as the level needed to reliably prevent cavities.
The American Dental Association and American Academy of Pediatrics continue to support community water fluoridation. After the 2024 NTP report, the ADA said the monograph did not provide new or conclusive evidence that should change current fluoridation practice.
Dental fluorosis risk is low at 0.7 mg/L. A 2023 CDC analysis of 2016–2021 data found that only 0.01% of population-weighted monthly fluoride measurements in fluoridating systems exceeded 2.0 mg/L.

The evidence on benefits has also gotten more nuanced. A 2024 Cochrane review found that in modern studies, starting fluoridation may lead to a slightly greater reduction in tooth decay in children, but with smaller effects than in studies from before 1975, and rated that evidence low certainty. Cochrane attributed the decline mainly to the spread of fluoride toothpaste. It found no eligible studies on adults and not enough evidence to judge what happens when communities stop fluoridating.

The case for concern

The main concern is neurodevelopment, especially for babies and young children.

The NTP monograph (August 2024). The National Toxicology Program, part of the National Institutes of Health, concluded with moderate confidence that higher fluoride exposures, such as drinking water above 1.5 mg/L, are associated with lower IQ in children. Key limits, in NTP’s own words: it found insufficient data to determine whether 0.7 mg/L affects children’s IQ, said more research is needed at low exposures, found no evidence of effects on adult cognition, and did not assess fluoride’s dental benefits. The finding is an association, not proof of cause.

The JAMA Pediatrics meta-analysis (January 2025). A review co-authored by NIEHS scientists pooled 59 studies and found an inverse association between fluoride exposure and children’s IQ. When the drinking water analysis was limited to levels below 1.5 mg/L across all studies, the inverse association did not hold; among the studies rated at low risk of bias, it did. The authors said the relationship below 1.5 mg/L was uncertain. Other researchers published critiques of the data and methods, and the authors published a response, so this remains an active scientific debate.

It’s worth being precise about what these studies did and didn’t find. Neither NTP nor the meta-analysis concluded that 0.7 mg/L lowers IQ. Neither concluded that it is proven safe for neurodevelopment either.

The court case

In 2016, Food & Water Watch and other groups petitioned EPA under the Toxic Substances Control Act (TSCA) to ban adding fluoride to drinking water. EPA denied the petition and the groups sued.

September 24, 2024: US District Judge Edward Chen of the Northern District of California ruled that fluoridation at 0.7 mg/L presents an “unreasonable risk” to health under TSCA and ordered EPA to take regulatory action. He also wrote that the finding did not conclude with certainty that fluoridated water harms public health, and left the choice of response to EPA.
May 21, 2026: The Ninth Circuit Court of Appeals vacated that ruling and sent the case back. The appeals court did not decide whether fluoride is safe. It held that the district court abused its discretion by holding the case for a year and a half to wait for new studies and running a second trial, when both sides had asked for a decision on the first trial record. It told the lower court to decide the case based only on that first record, and to reconsider standing.

As a result, the 2024 order requiring EPA to act under TSCA is no longer in effect, and the case is back before the district court.

What has changed in 2025 and 2026

These are the confirmed developments as of October 2026:

April 7, 2025: EPA committed to an expedited review of new science on fluoride in drinking water. The same week, HHS Secretary Robert F. Kennedy Jr. said he would tell CDC to stop recommending fluoridation. As of this writing, CDC’s fluoridation pages still list 0.7 mg/L as the recommended level.
May 7, 2025: Utah’s HB 81 took effect, prohibiting the addition of fluoride to public water systems.
July 1, 2025: A Florida law (SB 700) took effect that prohibits additives in public water systems unless they are used to meet drinking water standards, remove contaminants or improve water quality, which ended fluoridation in the state.
October 31, 2025: FDA announced it intends to take enforcement action against unapproved ingestible fluoride prescription products (drops and tablets) labeled for children under 3, or for older children who aren’t at high risk of tooth decay. This concerns supplements, not tap water.
January 22, 2026: EPA released a preliminary assessment plan and literature survey for its fluoride review, focusing on two endpoints in children: dental fluorosis and neurodevelopmental effects such as IQ.
August 3, 2026: EPA released the protocol it will use to write the fluoride human health assessment. EPA says a draft will go out for public comment once complete, and that the final assessment will inform any revision to drinking water rules. It has not given a date.

The federal limit of 4.0 mg/L has not changed. Any new limit would require a separate rulemaking after the assessment is finished.

How to find your fluoride level

Check your Consumer Confidence Report. Every community water system must publish an annual report, and fluoride appears in the table of detected contaminants. Our guide to reading your water quality report shows where to look. You can also look up your utility for its EPA compliance record.

Try CDC’s My Water’s Fluoride tool. About 40 states share data there. CDC notes it’s voluntary, isn’t real-time, and may show the utility’s target level rather than measured values.

Call your utility if neither source answers your question.

Private well? Fluoride occurs naturally in some groundwater, sometimes above 2.0 mg/L. Add it to your lab test. See our well water testing guide.

If you want less fluoride

You don’t need to take any action if your water meets federal standards. If you’d still prefer to reduce fluoride, these are the options agencies describe:

Reverse osmosis. CDC lists fluoride among the substances RO systems may reduce. Look for certification to NSF/ANSI 58 with a specific fluoride reduction claim. Our reverse osmosis vs. carbon filters guide explains the trade-offs, including wastewater.
Standard carbon pitchers and faucet filters generally are not certified for fluoride. Check the certification listing for a fluoride claim before assuming.
Bottled water. CDC says water labeled de-ionized, purified, demineralized or distilled contains no or only trace fluoride unless fluoride is listed as added.
For infants. CDC says formula mixed with fluoridated water can raise the chance of mild dental fluorosis if formula is the baby’s main food, and that using low-fluoride bottled water some of the time lowers that risk. Ready-to-feed formula contains little fluoride. Talk to your pediatrician, and see our guide on tap water for baby formula.

CDC also notes that fluoride isn’t absorbed through skin, so showering and bathing aren’t a fluoride exposure concern. If you reduce fluoride in drinking water, ask your dentist whether you or your children need fluoride from other sources.

Bottom line

At 0.7 mg/L, fluoridation still has the support of CDC, the ADA and the AAP, and the federal limit is still 4.0 mg/L. Federal toxicologists have found an association with lower IQ at higher exposures but couldn’t say whether 0.7 mg/L has an effect. EPA’s review is underway with no end date. Know your number, follow the review, and make decisions about infants and children with your pediatrician or dentist.