Tess Robertson-Neel, MPH, National Center for Health Research
The debate over fluoride in water has percolated for years but took center stage in 2024 and 2025. This article looks at the research evidence, which tends to be more nuanced than a simple “Yes or No” view of fluoride.
Why add fluoride to water?
Fluoride has been added to municipal tap water in the U.S. since the late 1940s[1], and as of 2022, more than 200 million Americans drank tap water with fluoride added.[2] Fluoride is a naturally occurring mineral that is found in small amounts in soil, plants, and water. Fluoride is not needed to keep the water clean, so it is added for one reason only: to protect our teeth. In the early 1900s, dental cavities and tooth decay were very common even in developed countries like the United States and there were very few methods of treatment or prevention.[3] Around this time, researchers started to notice that certain communities had much healthier teeth than others and eventually determined that the natural fluoride in their water sources was strengthening their teeth and preventing cavities.[1] They learned that fluoride helps strengthen enamel, the hard protective coating on our teeth.[4] As a result, small amounts of fluoride were added to community water systems.
Negative impacts of fluoride exposure
Oral health has drastically improved over the last 100 years, thanks to fluoride in water and toothpaste and improvements in dental hygiene, but it is possible to have too much of a good thing. Exposure to too much fluoride, especially during childhood, can cause a condition known as dental fluorosis,[5] which can lead to discoloration of teeth and uneven tooth surfaces. In extreme cases, it can damage the protective enamel layer and require treatment. When exposed to extremely high amounts of fluoride over longer periods of time, people can also develop skeletal fluorosis which can lead to bone fractures, bone and spinal deformities, and more. This severe fluorosis is extremely rare in the U.S., but more cases are seen in countries like India and China where the amount of fluoride in the water is much higher.[5]
In recent years, the impact of fluoride on IQ has raised new concerns. A systematic review of 74 large studies comparing people living in communities with or without fluoride in their water[6] found that in more than 85% of the studies, children’s IQ scores were lower in communities with more fluoride in their drinking water. There were two ways fluoride had an impact: children’s IQs were lower in communities with fluoride added to the water, and the more fluoride that was in the water, the lower the IQ scores. However, it’s important to emphasize that the estimated impact on IQ scores across the studies used in the analysis was small, just a few points out of the typical IQ score, which averages 100 points. Scores on IQ tests can change by about 5 points each time a person takes the test, and those small differences aren’t considered meaningful to individuals. Nevertheless, an average decrease of a few points can have an impact on the community level. In addition, all of the studies took place outside of the United States (where fluoridation levels are easier to study), and many were done in countries that have higher levels of fluoride in the water than the U.S.[6] The results could have been different if the studies were conducted in the U.S., where fluoride in water supplies are lower and more children may drink bottled water or other beverages.
When evaluating the impact of fluoride exposure on IQ or any other health issue, it can be difficult, if not impossible, to consider the impact of other factors, such as education, cultural differences that affect IQ scores (but not intelligence), and test-taking ability. Those can be very influential, in addition to fluoride levels in the water.
Of course, fluoride exposure can also be affected by habits and behaviors. For example, although the amount of fluoride in most community water systems in the U.S. would be unlikely to cause problems, if a child is also being exposed to substantial amounts of fluoride through toothpaste, mouthwash, or prescription fluoride treatments, their dose could be too high. Additionally, young children or pregnant women could be more vulnerable to the negative health effects of fluoride exposure. To be cautious, we recommend that you gather more information about the level of fluoride in your community water system.
How much is good, how much is too much?
The US Public Health Service’s current recommended amount of fluoride in a community water system is 0.7 mg/L and the EPA requires public water systems to keep the concentration of fluoride below 4.0 mg/L. The World Health Organization recommends that drinking water should have no more than 1.5 mg/L of fluoride, which is more than twice the recommended level in the U.S. but less than half of the U.S. enforceable maximum.[7]
It’s important to know that the amount of fluoride in municipal water is very low compared to dental products like toothpaste. However, people usually consume more water than toothpaste or mouthwash. Most kinds of toothpaste have a concentration of around 1,000 mg/L, but it is estimated that we only ingest between 0.1 mg and 0.3 mg (depending on how well a person can control what they swallow). To get the dental health benefits without risking fluorosis, the current guidelines from the American Dental Association recommend the following toothbrushing practices for children:
- Children younger than 2 years old: brush only with water and consult with a health professional before using fluoride toothpaste
- Children 2-6 years old: a pea-sized amount (approximately 0.25 g of toothpaste or 0.25 mg of fluoride).[8]
The National Academies of Sciences, Engineering, and Medicine set the tolerable upper limit of daily fluoride intake at 10 mg/day for people ages 9+. For younger children and infants, they set the maximum tolerable levels much lower.[9] The adequate intake, the recommended amount to see a positive impact on dental health of fluoride from all sources, is calculated as 0.05 mg of fluoride/ kilogram that a person weighs/ day. [10] Since young children do not weigh very much, they should consume less fluoride to get only the desired dental benefit with fewer additional risks. According to the EPA, the typical daily intake of fluoride from food, water, and other fluoride-containing products is only around 2.9 mg for adults. For infants and toddlers, it is between 1.2 and 1.6 mg a day.[11]
The upper limits for fluoride intake were set decades ago, before experts were aware of some of the risks, so it is time to re-evaluate how much fluoride in water or other products is too much.
The Bottom Line
Removing all fluoride from water could have drastic consequences for dental health if people are not getting enough fluoride from toothpaste or other sources. On the other hand, research suggests that too much fluoride can also be detrimental. Better research is needed and it is equally important for everyone to understand what is a good amount of fluoride and what is too much, and to calculate the total from drinking water, tooth paste, and other sources for children and adults of different ages.
All articles are reviewed and approved by Dr. Diana Zuckerman and other senior staff.
The National Center for Health Research is a nonprofit, nonpartisan research, education and advocacy organization that analyzes and explains the latest medical research and speaks out on policies and programs. We do not accept funding from pharmaceutical companies or medical device manufacturers. Find out how you can support us here.
References
[1] CDC. (2024, May 23). Timeline for Community Water Fluoridation. Community Water Fluoridation. https://www.cdc.gov/fluoridation/timeline-for-community-water-fluoridation/index.html
[2] CDC. (2024, November 19). 2022 Water Fluoridation Statistics. Community Water Fluoridation. https://www.cdc.gov/fluoridation/php/statistics/2022-water-fluoridation-statistics.html
[3] CDC. (1999, October 22). Achievements in Public Health, 1900-1999: Fluoridation of Drinking Water to Prevent Dental Caries. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm4841a1.htm
[4] NIH. (2025, February). Fluoride & Dental Health | National Institute of Dental and Craniofacial Research. https://www.nidcr.nih.gov/health-info/fluoride
[5] Cleveland Clinic. (2024, October 14). Fluorosis: What’s the Right Amount of Fluoride? Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/23227-fluorosis
[6] Taylor, K. W., Eftim, S. E., Sibrizzi, C. A., Blain, R. B., Magnuson, K., Hartman, P. A., Rooney, A. A., & Bucher, J. R. (2025). Fluoride Exposure and Children’s IQ Scores: A Systematic Review and Meta-Analysis. JAMA Pediatrics, 179(3), 282–292. https://doi.org/10.1001/jamapediatrics.2024.5542
[7] Associated Press (2024, August 23). Fluoride in drinking water at twice safe limit linked to lower IQ in children. The Guardian. https://www.theguardian.com/society/article/2024/aug/23/fluoride-water-study
[8] American Dental Association Council on Scientific Affairs. (2014). Fluoride toothpaste use for young children. Journal of the American Dental Association, 145(2), 190–191. https://doi.org/10.14219/jada.2013.47
[9] Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. (1997). Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. National Academies Press (US). http://www.ncbi.nlm.nih.gov/books/NBK109825/
[10] NIH. (2024, June 26). Office of Dietary Supplements—Fluoride Fact Sheet. https://ods.od.nih.gov/factsheets/Fluoride-HealthProfessional/
[11] U.S. Environmental Protection Agency. (2010). Fluoride: Exposure and relative source contribution analysis. Health and Ecological Criteria Division, Office of Water. https://www.epa.gov/sites/default/files/2019-03/documents/fluoride-exposure-relative-report.pdf