Several U.S. communities are debating whether to remove fluoride from their water supplies in the wake of comments by President-elect Trump’s Health and Human Services nominee Robert F. Kennedy Jr., who called the mineral an “industrial waste,” looking to remove it from water systems across the nation once Trump takes office.
Local journalists who may find themselves covering this topic will likely hear arguments from both sides. A good question to ask to inform your reporting is, “What does the research say?”
To be sure, there are still unanswered questions about water fluoridation in modern times and many researchers have called for better studies. At the same time, there’s little evidence that fluoride is harmful at low levels.
We have unpacked five recent studies, including systematic reviews, followed by a list of additional research.
Before selecting these studies, we read through dozens of published research papers, which paint a complex and evolving picture of the water fluoridation debate. Here are some of the main takeaways from recent studies:
- The prevalence of dental cavities has decreased in recent decades, thanks to the widespread use of fluoride toothpaste and mouthwash, so the benefit of water fluoridation may be less pronounced today than it was in years after the programs were implemented in 1945.
- Evidence for the benefits of water fluoridation is largely based on older studies, many of which were conducted before the widespread use of fluoride toothpaste. But this doesn’t mean that fluoride is harmful or should be removed from water supplies, researchers note. The per-person cost of fluoridating a water system is a fraction of the cost of one dental filling.
- Water fluoridation leads to reductions in dental cavities, especially in children, both in baby and permanent teeth, research finds, especially in earlier studies. But evidence for adults is limited.
- The main negative effect of fluoride in water is dental fluorosis, where white streaks appear on teeth.
- Some studies show an association between fluoride and harmful health effects, but most of those studies are conducted in areas of the world with exceptionally high fluoride levels, which is not relevant to the U.S., where the fluoride levels in community water supplies are generally low.
- Long-term exposure to very high levels of fluoride can lead to adverse health effects, including noticeable discoloration and pitting of teeth, and skeletal fluorosis, a condition that affects bones and joints. Some studies have also shown an association between high fluoride levels with lower IQ in children.
- Water fluoridation may reduce dental health disparities, especially for children in lower-income households, although more recent studies have been inconclusive.
- The studies consistently identify the consumption of sugary foods and drinks as a leading cause of dental cavities. They highlight how frequent and excessive sugar intake creates an environment in the mouth that favors the growth of bacteria responsible for tooth decay.
- There is a need for more, high-quality research on the cost-effectiveness of water fluoridation and the limitations of previous research to produce more robust evidence for policymakers.
This is a companion piece to 15 common questions about fluoride in drinking water.
Some of the journals may be behind a paywall, so be sure to check out our 2023 tip sheet on how to access academic research for free.
Research Roundup
Water Fluoridation For the Prevention of Dental Caries
Zipporah Iheozor-Ejiofor, et al. Cochrane Database of Systematic Reviews, October 2024.
The study: This paper reviews 157 studies from 1946 to 2023, to evaluate the effectiveness of water fluoridation in preventing dental cavities in people of all ages. To be included, the studies’ baseline of fluoridation levels had to be comparable and the studies had to report at least two time points to assess the impact of fluoridation.
The findings:
- Water fluoridation reduced the average number of decayed, missing, or filled children’s primary teeth by 35%. It reduced the average number of decayed, missing or filled permanent teeth by 26%. Most of the studies (71%) were conducted before 1975 and the widespread use of fluoride toothpaste.
- At 0.7 mg/L, the optimal fluoride level in the water, about 12% of people in the included studies showed dental fluorosis.
- There is not enough information to determine if water fluoridation reduces socioeconomic disparities in tooth decay.
- There’s not enough information to understand how stopping water fluoridation affects tooth decay levels.
- No studies on the effectiveness of fluoridation for preventing adult cavities made the researchers’ inclusion criteria.
The takeaway: More studies evaluating the effectiveness of water fluoridation for the prevention of cavities are needed, the authors note.
“The implementation or cessation of community water fluoridation requires careful consideration of the current evidence alongside the broader context of a population’s oral health, oral health behaviors, diet and consumption of tap water, movement or migration, and the availability and uptake of other caries prevention strategies,” they write. “In addition, factors such as acceptability, cost-effectiveness and the feasibility of the implementation and monitoring of a community water fluoridation program should be taken into account.”
2015 United States Public Health Service Optimal Fluoride Level Adherence and Operation Among Adjusting Water Systems in 40 States: 2016–2021
Theresa j. Boehmer, et al. AWWA Water Science, October 2024.
The study: This study evaluates how well U.S. water systems adhere to the 2015 U.S. Public Health Service recommendation for optimal fluoride levels in drinking water of 0.7 mg/L. Using data from the Water Fluoridation Reporting System, the study examines adherence, data quality and the precision of fluoride level maintenance across 40 states, from 2016 to 2021. The U.S. Public Health Service is part of the Department of Health and Human Services.
The findings:
- Most water systems operated near the USPHS target of 0.7 mg/L, with a mean monthly fluoride level of 0.71 mg/L.
- About 76% of fluoride readings fell within ±0.1 mg/L of the target.
- Larger water systems serving over 200,000 people showed less fluctuation, with average fluoride levels closer to the target and with fewer deviations. Smaller systems serving 25 to 3,300 people had greater variability, with 29.8% of readings exceeding the upper limit of 0.8 mg/L.
- About 16% of reported readings were below the recommended 0.6 mg/L, potentially compromising dental health benefits.
The takeaway: “These findings demonstrate that adjusting water systems are operating consistently and at a greater accuracy,” the authors write. “Water fluoridation recommendations are reviewed as additional research becomes available, particularly on minimum therapeutic dose, balance of benefits and potential harms, user acceptance and satisfaction, and cost-effectiveness.”
How Effective and Cost-Effective is Water Fluoridation for Adults and Adolescents? The LOTUS 10-Year Retrospective Cohort Study
Deborah Moore, et al. Community Dentistry and Oral Epidemiology, August 2024.
The study: The LOTUS study investigates the effectiveness and financial costs of community water fluoridation in preventing dental treatments and improving oral health among adults and adolescents 12 years and older in England. The research spans 2010 to 2020 and examines outcomes like fillings and extractions; decayed, missing or filled teeth; and treatment costs.
The findings:
- Invasive dental treatments were 3% lower in the optimally fluoridated group (0.7 mg/L) compared with the non-optimally fluoridated group.
- Decayed, missing or filled teeth were 2% lower in the fluoridated group.
- The National Health Service dental treatment costs were 5.5% lower for fluoridated individuals. (NHS is the publicly funded health care system of the U.K.)
- Reductions in dental treatments varied minimally across socioeconomic groups, with no meaningful impact on reducing health inequalities.
The takeaway: “Receipt of optimal water fluoridation 2010–2020 resulted in very small positive health effects which may not be meaningful for individuals,” the authors write. “Our results support the hypothesis that water fluoridation appears to be producing less dramatic impacts on oral health in contemporary UK populations than in historical studies.”
They add: “The discovery of water fluoridation made an unparalleled contribution to oral health in the 20th century. In the 21st century, greater impact may be achieved by advocating for upstream, policy-level action to address the commercial determinants of health and create supportive food environments.”
Related commentary: Investigating the Effectiveness of Water Fluoridation
Darshini Ramasubbu, Jonathan Lewney and Brett Duane. Dental Public Health, July 2024.
Community Water Fluoridation Levels To Promote Effectiveness and Safety in Oral Health — United States, 2016 – 2021
Theresa J. Boehmer, Srdjan Lesaja, Lorena Espinoza and Chandresh N. Ladva. Morbidity and Mortality Weekly Report, June 2023.
The study: This study examines trends in community water fluoridation levels across the U.S. from 2016 to 2021. It evaluates how fluoridation levels align with federal recommendations of 0.7 mg/L to prevent cavities while ensuring safety.
The findings:
- More than 70% of the U.S. population served by public water systems had access to optimally fluoridated water during this period. A total of 4,080 community water systems safely fluoridated water 99.99% of the time with levels below the secondary safety standard of 2.0 mg/L, a level set by the Environmental Protection Agency to protect public health. Meanwhile, suboptimal water systems in which fluoride concentrations are below 0.6 mg/L are ineffective in supporting the oral health of their communities.
- Fluoridation levels varied by state and region, with some states achieving significantly higher rates than others.
- Many communities maintained fluoride concentrations consistent with the federal recommendation of 0.7 mg/L for balancing effectiveness and safety in preventing tooth decay.
The takeaway: Community water fluoridation remains a widely adopted and effective public health strategy for preventing tooth decay.
Evaluation of Water Fluoridation Scheme in Cumbria: the CATFISH Prospective Longitudinal Cohort Study
Michaela Goodwin, et al. Public Health Research, Nov. 2022.
The study: This study evaluates the impact of reintroducing water fluoridation in Cumbria, England, on children’s dental health, and its cost-effectiveness. Researchers followed two cohorts: Children born between 2014 and 2015, who were exposed to fluoridated water from birth until age 5. And children who were 5 years old in 2013 and 2014 and were followed until they were 11 years old.
The children were either in a control group or an intervention group. The control group included children who lived in East Cumbria and did not receive fluoridated water. The intervention group included children who lived in West Cumbria and received fluoridated water through their water treatment plants.
The findings:
- Among the birth cohort, 17.4% of children in fluoridated areas had tooth decay compared with 21.4% in non-fluoridated areas, indicating a modest benefit.
- For the older cohort, decay rates were slightly lower in fluoridated areas — 19.1% vs. 21.9%.
- Fluoridation is likely cost-effective because it decreases the need for expensive dental treatments.
- There were no significant differences in the effect of fluoridation observed across socioeconomic groups.
The takeaway: “We suggest that, where prevalence is low, consideration should be given to targeted approaches that may be as or more effective, as this may attract less criticism from those who believe that [water fluoridation] is an inappropriate intervention,” the authors write. “Such targeted approaches may include modification of known risk factors, such as sugar consumption, rather than relying on the biopharmaceutical effect of fluoride alone.”
They add: “The ‘silver bullet’ approach that was effective in the 1950s is failing to address dental caries in the most deprived populations and, hence, a hybrid approach with behavioral elements should be considered.”
Additional reading
A Systematic Review of Fluoride Contamination in Water Resources of Iran from 2016 to 2023: Spatial Distribution and Probabilistic Risk Assessment
Danial Nayeri, Hadis Elyasi, Ali Jafari and Mohammad Rezvani Ghalhari. Biological Trace Element Research, October 2024.
Association Between Fluoride Intake From Drinking Water and Severity of Dental Fluorosis in Northern and Western Mexico: Systematic Review and Meta-Analysis
José Gamarra, et al. BMC Oral Health, June 2024.
Oral Health of Women and Children: Progress, Challenges, and Priorities
Jayanth Kumar, James J. Crall and Katrina Holt. Maternal and Child Health Journal, July 2023.
Debater Water Fluoridation Before Dr. Strangelove
Catherine Carstairs. American Journal of Public Health, August 2015.
Dental Caries (Cavities): Community Water Fluoridation. Systematic Review
The Community Preventive Services Task Force, April 2013.
Effectiveness of Fluoride in Preventing Caries in Adults
S. O. Griffin, E. Regnier, P. M. Griffin and V. Huntley. Journal of Dental Research, May 2007.
Dental Caries and Dental Fluorosis at Varying Water Fluoride Concentrations
Keith E. Heller, Stephen A. Eklund, Brian A. Burt. Journal of Public Health Dentistry, April 2007.
Systematic Review of Water Fluoridation
Marian S. McDonagh, et al. The BMJ, October 2000.
Achievements in Public Health, 1900-1999: Fluoridation of Drinking Water to Prevent Dental Caries
MMWR, October 1999.
Expert Commentary