By Sarabeth Lowe, MPH

Ms. Lowe is a Communication Specialist at the University of Delaware Disaster Research Center.

The benefits of fluoride (pronounced floor-eyed) were established nearly a century ago when scientists discovered that children who consumed naturally fluoridated water had fewer cavities.^1,2 What started as a simple observation set a plan into motion that would become one of the Centers for Disease Control and Prevention’s (CDC) 10 greatest public health achievements of the twentieth century.³ The plan was a relatively simple one: intentionally fluoridating the community water supply. Grand Rapids, Michigan, became the first United States (US) city to test this intervention in 1945, and the results were astounding. Rates of tooth decay in the city’s children had plummeted by more than 60 percent.^1,2,4–6 This groundbreaking success revolutionized dental care and pushed dentistry to the forefront of preventive medicine.² In 2022, nearly 70 percent of the US population—more than 200 million Americans—was using public water systems that had access to fluoridated water.^2,4–9

From the get-go, however, community water fluoridation—the careful and controlled adjustment of fluoride to a recommended level for preventing tooth decay—was entrenched in controversy.^3–8 Opposition and skepticism have been spurred on by conspiracy theories, the demand for further study, and misconceptions about its safety. As it turns out, the debate about this conventional public health intervention is anything but settled, and new research shows that there is more nuance to this picture.^9–11 Here’s what you need to know.

What is Fluoride? 

Fluoride is a naturally occurring mineral found in water, soil, plants, and certain foods.^7,8,12–18 While most water sources contain fluoride, its concentration is typically at levels too low to effectively strengthen and protect teeth. That’s why the US Public Health Service recommended adding small amounts to drinking water in 1962.^2,7 Today, the agency recommends a minimum level of 0.7mg of fluoride per liter, or about three drops in a 55-gallon barrel, to protect and strengthen your teeth.^7,19

Fluoride’s main benefit is its ability to strengthen enamel, the durable, semitranslucent outer covering of your teeth that protects them from cavities and everyday wear and tear. Even though it is incredibly durable—it’s the hardest substance in the human body—enamel can break down over time.^14,20,21 This happens when acids from bacteria and plaque in your mouth attack this outer layer, causing your teeth to leach important minerals. Notably, tooth enamel cannot grow back, but fluoride promotes remineralization, the natural tooth repair process that strengthens teeth by adding minerals back into tooth enamel. This mechanism inhibits bacteria that produce acid in the mouth, which prevents and even reverses tooth decay.^7,14,21 It also helps prevent cavities, a pervasive problem that remains widespread.

An Equitable Intervention

Decades of research have shown the benefits of fluoride. According to the CDC, community water fluoridation reduces cavities by about 25 percent across all age groups.^7,19,22–25 This is a public health measure that works passively. Nevertheless, it is a powerful one that is practical, cost-effective, and equitable.^{2,6–8,17–19,23}

Community water fluoridation is especially important for vulnerable and low-income communities, which might face barriers to accessing dental care or purchasing fluoride-fortified products.^7,25 A 2021 study published in the Journal of Public Health Dentistry called dental cavities “the most prevalent chronic disease that disproportionately affects lower socioeconomic status communities,” and data from the CDC showed that about one in four children living below the federal poverty level experience untreated cavities.^24,26,27 Community water fluoridation levels the playing field by providing a safety net.⁷ Regardless of age, income, or socioeconomic status, all people benefit simply by sipping water from their tap. Without this intervention, low-income communities would bear the brunt of increased dental disease.^2,6–8 

Public Health Impact

Good oral health is often taken for granted. Still, tooth decay and dental cavities are common problems. More than 80 percent of Americans will have at least one cavity by the time they enter their mid-30s.²⁸ While these conditions are both preventable and treatable, their impact on health and quality of life is considerable. Untreated cavities can become a chronic painful, debilitating condition that leads to permanent damage and likely tooth loss. If left unchecked, a deep cavity can cause an infection in the tooth, called an abscess, that can spread into the surrounding tissue. In rare cases, this infection can travel into the bloodstream and spread to other parts of the body, which can become life-threatening.^8,28 

In addition to preventing needless infection, pain, suffering, and tooth loss, community water fluoridation also saves money.^3,7,29,30 Chronic tooth decay and cavities often require costly treatments, such as fillings, extractions, and emergency dental visits.^7,8 Research shows that for every dollar spent on fluoridation, communities save about $20 in dental treatment costs alone.^7,29,30 Tooth decay has also led to significant economic loss in the US. Children with cavities often miss more school and receive lower grades than those without cavities, and billions of dollars in productivity are lost annually in the US due to untreated oral disease.^8,31–34 

Opposition to Community Fluoridation

Despite its proven benefits, community water fluoridation is still entrenched in controversy.^{1,5–7,9–11,13} While nearly all public health, medical, and dental organizations, including the American Academy of Pediatrics, American Dental Association, American Public Health Association, CDC, and World Health Organization, endorse this practice, people have long been skeptical of it.^35–38 Not all of this resistance was unreasonable. Opposition to fluoride dates back as early as the 1940s, when people demanded further study to more firmly establish the safety of the practice.^1,7,13 At the same time, misinformation and unfounded conspiracies, such as fluoridation being a communist plot to harm Americans, spread.^1,7,29 This distrust still exists today, driven by unclear health communication, lack of transparency, and distrust in science’s role in public policy.^10,11,39 

Some of this resistance, however, comes down to well-founded concerns about its potential harm on human health, especially as they relate to excessive fluoride exposure. Many of these risks occur where community water fluoridation levels are either at or above 1.5mg/L, more than twice the optimal level recommended by the US Public Health Service.^7,30 This is a valid concern because nearly three million Americans live in areas with tap water fluoride levels at or above this threshold.^10,40 Additionally, a boon of fluoride-fortified products, such as toothpaste, on the market has made excessive fluoride consumption more common.^7,10,11,34 

Multiple studies in reputable, prestigious journals have proven the harms of chronically ingesting too much fluoride. A commonly cited concern is dental fluorosis, which happens when a child consistently ingests too much fluoride while their permanent teeth are still forming.^41,42 However, most of these cases are innocuous and only cause tooth discoloration, which can be corrected with cosmetic treatment. High levels of fluoride can lead to more serious health concerns though, such as bone deformities, thyroid disease, and brain development. 

A recent review paper published in JAMA Pediatrics made headlines when a team of researchers from the National Institutes of Health found an association between higher levels of fluoride exposure and lower intelligence quotient (IQ) scores.^1,4,10,11,43 The analysis, which looked at 74 studies on prenatal and childhood fluoride exposure, concluded that exposure to drinking water with a fluoride concentration of 1.5mg/L or higher was consistently associated with lower IQ in children.⁴³ Even the findings from this paper, though, are clouded in controversy. The paper’s authors acknowledged that many of the studies included in the review had a “high risk of bias” and said their work was not meant to address the public health implications of water fluoridation in the US.^43–47 Furthermore, not all researchers have found this relationship between children’s intellectual ability and fluoride levels replicated in their analyses, and there have been no large longitudinal studies conducted on this relationship in the US. These contradictory results have continued to fuel an ongoing and contentious debate between experts.¹

The Future of Fluoride 

The controversy surrounding community water fluoridation is also exemplified in the various policies surrounding its implementation. The US 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. Like many public health policies, these decisions are made at the state and local levels.⁴⁸ Often, voters themselves make the decision to adjust fluoride water levels. Only one state, Hawaii, has banned community water fluoridation, but towns in North Carolina, Florida, Pennsylvania, and Texas have made efforts to stop the practice.^10,48,49 Outside of the US, most Western countries, including Denmark, France, Italy, the Netherlands, Germany, Norway, and Sweden, have ended community water fluoridation.¹⁰

Bottom Line

Both those for and against community water fluoridation have valid concerns. The acceptance of public health policies often comes down to weighing its tradeoffs, and a 2024 Cochrane review—considered the gold standard of medical reviews—shows how new data will impact this debate as it continues to unfold. The study’s authors concluded that fluoridating water today “may” lead to “slightly less” decay in kids’ teeth but that future benefits may be minimal due to the widespread addition of fluoride to toothpaste.^1,13,50,51 

Trust in science has improved in recent years, but agencies need to maintain this trend by being clear about the potential harms and risks of fluoride.^52,53 No matter which side of the debate you fall on, the historical and current ethos surrounding community water fluoridation should point us toward a consensus: conventional wisdom around public health policies can and should be revisited.^10,11 It also should serve as a reminder for experts, lawmakers, and the general public to stick to the science. 

Sources

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