Water Fluoridation in the U.S.: The Federal Role in Policy and Practice
Introduction
Fluoridating water has been a long-standing public health practice in most communities across the U.S. and has been supported and recommended by the federal government for decades. Even so, ever since the first U.S. community began fluoridating its water in 1945 there have also been concerns raised about this practice and many communities choose not to fluoridate. In recent years, in fact, there has been growing scrutiny of the practice, and debates in many parts of the country about whether to continue fluoridation. President-elect Trump’s announced nomination of Robert F. Kennedy Jr. to be the Secretary of Health and Human Services has raised questions about the potential for the federal government to influence water fluoridation practices across the country. Kennedy has long been critical of water fluoridation and has said the incoming Trump administration will recommend that fluoride be removed from public water on day one. Meanwhile, key professional associations, public health experts, and many policymakers continue to support fluoridation as an important tool for improving dental health in the U.S., and perhaps one of the most important public health interventions ever implemented.
To help inform policy discussions about this topic, this brief provides an overview of the role of the federal government in water fluoridation decisions and the current status of water fluoridation in the U.S. While the federal government cannot require communities to fluoridate their water or remove fluoridation already in place, it does regulate maximum levels and provides guidance to state and local communities on optimal levels of fluoride. If guidance were to change – for example, suggesting that fluoride was not recommended — it could have ripple effects across the country.
The Federal Government’s Role and Current Recommendations for Water Fluoridation
The federal government does not have legal authority to require state and local communities to fluoridate their water, nor to remove fluoridation in areas where it is already policy. Instead, these decisions – just like many public health policy decisions in the U.S. – are made at the state and local levels. There are some states (for example: California, Delaware, Georgia, Illinois, Kentucky, Louisiana, Minnesota, Mississippi, Nebraska, Nevada, Ohio and South Dakota) that require water systems of a certain size within their state to provide fluoridated water, while others leave this decision to city, county, or other officials or leave the choice up to voters who decide via local referendums. At the same time, the federal government – specifically the Environmental Protection Agency (EPA) – does have the primary authority to set and regulate the maximum level of fluoridation in public water systems.
The federal government reviews data and other evidence about the safety and effectiveness of fluoridation and issues recommendations and guidance on best practices for state and local decision-makers to consider. The Department of Health and Human Services (HHS), in particular the Centers for Disease Control and Prevention (CDC), provides recommendations about best practices for achieving public health benefits from fluoridation. The first federal guidelines regarding fluoridation of water systems came from the U.S. Public Health Service (USPHS) in 1945, with a recommended maximum concentration level. Updated guidelines in 1962 revised this maximum, and included, for the first time, a recommended fluoride level, citing its ability to prevent dental caries; the most recent update to these federal guidelines was in 2015.
The federal government also sets and enforces nationwide standards for maximum allowable fluoridation levels. The EPA, acting via the authority provided through the Safe Drinking Water Act of 1974, is responsible for setting federal standards for maximum fluoridation levels in water systems to protect against risks from excessive exposure to fluoride. This includes setting a primary, legally enforceable standard for water fluoridation levels, and a secondary “non-enforceable” standard. If a water system’s fluoridation levels exceed the primary enforceable standard, legal action can be taken against the water provider; if levels exceed the secondary, non-enforceable standard, it does not trigger legal or federal action, but public notice of the exceedance must be provided to persons served by the system no later than 12 months after the levels were exceeded. EPA delegates this regulatory and enforcement authority to states that meet certain capacity requirements. States may also set their own maximum fluoride levels, as long as they are at least as stringent as federal standards.
Current HHS/USPHS guidelines (last updated in 2015) recommend an optimal fluoride concentration of 0.7 mg per liter (mg/L) in community water systems (CWS) while EPA regulations set the primary standard for the maximum level of fluoride in water systems at 4.0 mg/L and the secondary, non-enforceable standard at 2.0 mg/L. Both HHS/CDC and the EPA have discretion to update their guidance and recommendations and have done so in the past. Updating the USPHS guidelines involves a years-long, interagency and multi-stakeholder process that is likely to include review and input from external experts and a period for public comment and discussion. For example, following an internal process that developed its initial updated fluoridation recommendations, HHS published its proposed changes in 2011. After further review and public comment periods, the final updated recommendations were published in 2015, and included a change to the recommended fluoride concentration in CWS, from 1.2 mg/L to 0.7 mg/L. The EPA set its 4.0 mg/L primary standard for fluoride in 1986, and by law the agency is required to review of drinking water standards (including fluoridation standards) at least every six years. The EPA’s most recent review of drinking water standards, released in July 2024, concluded that the current maximum fluoride level guideline is “not a candidate for revision at this time.” In the future, the EPA could decide to initiate a new review and assessment process for its fluoride guidelines.
Benefits and Risks from Water Fluoridation
Water fluoridation has been found to be effective in reducing the risk and severity of dental caries (tooth decay) in children (as well as adults). According to CDC, a review of the best available evidence shows water fluoridation reduces tooth decay by about 25% in children and adults, and evidence also shows that children living in communities where water is fluoridated have, on average, more than two fewer decayed teeth compared to similar children living in non-fluoridated communities. A comprehensive review of relevant studies, updated in 2024, concluded that evidence shows that initiation of water fluoridation reduces dental caries in children. A study from Juneau, Alaska found that cessation of fluoridation in that community was associated with increases in the number of dental caries, and the number of related procedures and treatments among Medicaid-eligible children.
At the same time, questions have been raised about health risks from exposure to high levels of fluoride concentrations, beyond current federal standards. Extended exposure to high levels of fluoride may have negative effects, such as contributing to dental fluorosis, a discoloration of teeth in young children. Recently, there have been more concerns raised about high levels of fluoride exposure and potential links to other conditions. For example, a 2024 U.S. National Toxicology Program (NTP) monograph suggests a potential link between high fluoride levels (above 1.5 mg per liter, more than double the USPHS recommended amounts for community water fluoridation) and lower IQ in children, but studies reviewed for that publication were from areas outside the U.S. with naturally high fluoride concentrations in their water. The monograph concludes that more studies are needed to fully understand the potential for lower levels (under 1.5 mg/L) of fluoride exposure to affect children’s IQ. Based in part on these findings, in September 2024, a US district judge ordered the EPA to take further regulatory action on fluoride, citing the potential risks to children’s neurological development; the EPA says it is reviewing the court decision, but no additional regulatory actions have been taken to date.
Status of Water Fluoridation in the U.S.
As of 2022, the CDC estimates that 72.3% of the U.S. population that is connected to community water systems (CWS) receives fluoridated water, or 62.8% of the U.S. population overall. Not all people are connected to CWS, as a proportion of the population accesses water through wells or other private sources. The overall percentage of the U.S. population with access to fluoridated water has barely changed over the last two decades: in 2006, CDC reported that 61.5% of the population was connected to fluoridated water, compared with 62.8% in 2022. Sometimes, naturally occurring fluoride exists in water systems, and in fact, can be higher than government benchmarks, including maximum recommended levels. According to CDC, as of 2020 about 1 million people in the U.S. (0.31% of the U.S. population) were connected to CWS that had naturally occurring fluoride levels equal to or greater than the EPA’s recommended limit of 2 mg/L.
Access to fluoridated water varies significantly across the country. As of 2022, data from 51 jurisdictions (50 states and Washington, D.C.) show there are seven jurisdictions where over 95% of the population is connected to fluoridated CWS (D.C., Kentucky, Minnesota, Illinois, North Dakota, Virginia, and Georgia) (Figure 1). However, in nine states less than 50% of the population is connected to fluoridated CWS (Hawaii, New Jersey, Oregon, Idaho, Montana, Louisiana, Alaska, Utah, New Hampshire, and Mississippi). These data largely reflect state and local statutes and regulations on fluoridation. Some states require fluoridation for communities above a certain population (including Kentucky, Minnesota, and Illinois), and have relatively high fluoridation rates as a result. Other states leave these decisions up to localities, many of which have decided not to fluoridate their water supplies. In Hawaii, the state with the lowest fluoridation coverage, no locality fluoridates their water systems (with the exception of military bases). Similarly, In New Jersey and Oregon, the states with the second and third lowest coverage rates, local fluoridation decisions have been contentious. More generally, localities are revisiting existing fluoridation policies and considering ending the practice, which typically has to be voted on by water supply recipients.
Rural areas and smaller communities are less likely to have access to fluoridated drinking water. People who live in rural areas are more likely to rely on private wells, which are not usually treated with fluoride, as opposed to public treated water systems. Additionally, smaller communities may face financial barriers that limit their ability to adequately treat their CWSs, decreasing access to fluoridated water for their residents.