One of the most common elements on Earth, fluoride is naturally present in human bodies and water, and common in toothpaste and mouthwash. And for decades, the mineral has been added to the water supplies of thousands of communities across the United States to help prevent dental cavities and decay. Dental professionals believe this practice is an effective and affordable approach to oral well-being, and consider it among the country’s 10 most significant public health achievements of the 20th century.

Fluoride’s long-standing presence in many public water systems has not gone uncontested, but questions about its safe ingestion have been rekindled with the election of Donald Trump. Former presidential candidate and anti-vaccine activist Robert F. Kennedy Jr., named by Trump last week to lead the U.S. Department of Health and Human Services, has vowed to ban the practice on the federal level.

Kennedy has called fluoride “industrial waste” and linked it to a variety of negative health outcomes — some of which anti-fluoridation advocates have highlighted for decades but many dental professionals say have been debunked.

“I’d say all of those claims have either been soundly refuted or he is exaggerating what the evidence really shows,” said Scott Tomar, associate dean of prevention and public health sciences in the College of Dentistry at the University of Illinois Chicago. “Water fluoridation — one of the nice things about it is it doesn’t require any special behavior on people’s part. Just drinking water or preparing your food with fluoridated water confers prevention benefits. And it’s one of incredibly few public health measures that actually saves money.”

Dental professionals say several studies show the amount of fluoride normally added to water is safe for human ingestion and effective in reducing tooth decay by 25%. Proponents of fluoridation also point to research findings that it saves $6.5 billion nationally and more than $30 per person in dental treatment costs each year. Public health officials also say it is a measure that addresses oral health disparities among racial and ethnic minority groups.

For the most part, it has been up to states and municipalities to decide whether to add the mineral to their water supply. Illinois is one of at least 12 states that have made it mandatory, and 1,634 of 1,811 water systems serving over 98% of its population were fluoridated as of November 2023, according to data from the Centers for Disease Control and Prevention.

After Kentucky and Minnesota, Illinois ranks third — and fourth if counting No. 1 Washington, D.C. — with the most people served by community water supplies receiving fluoridated water.

In a statement to the Tribune, the Illinois Department of Public Health talked about the benefits of fluoride and did not address whether it would consider reversing the state’s 1967 fluoridation mandate.

“The effectiveness, safety, and practicality of fluoridation at the optimal level has been established by decades of careful scientific study and research. Fluoridation has the support of virtually every leading health and scientific organization,” the statement said. “In fact, research has confirmed that fluoride is an important trace element in human nutrition and is a natural part of the human environment, present in the soil and rocks, seawater, groundwater, plants, and in human and animal bones and teeth.”

Michael Danner, president of the Illinois State Dental Society, said in a statement the nonprofit supports evidence-based education and advocacy for the oral health of residents. Thousands of dentists and hundreds of dental hygienists across the state are members of the organization.

“We remain focused on educating patients, communities, and policymakers about the proven benefits of fluoride,” Danner said.

The U.S. Department of Health and Human Services has since 2015 recommended an optimal concentration of 0.7 milligrams of fluoride per liter of drinking water which it says “maximizes (its) oral health benefits while minimizing potential harms.” According to the CDC, this amount equals three drops of water in a 55-gallon barrel. The U.S. Environmental Protection Agency has set a maximum limit of 4 milligrams of fluoride per liter of water in public systems.

However, critics of water fluoridation argue that even these optimal levels can be dangerous and lead to a variety of medical consequences including neurodevelopmental issues, which have been the focus of recent efforts to discourage the practice nationwide.

“So we’re happy that it’s risen to a presidential discourse, and it certainly has increased awareness of the subject,” said Stuart Cooper, executive director of the Fluoride Action Network, a national nonprofit that has advocated for ending water fluoridation since 2000. “All we’re doing at this point … is over-exposing people. We no longer gain a benefit from it.”

In 2017, the U.S. EPA denied a petition led by the organization seeking to ban the addition of fluoride to water, as the agency claimed the petitioners did not present sufficient scientific evidence that it had caused anyone to suffer neurotoxic harm. In September, however, a federal judge for the U.S. District Court for the Northern District of California ruled that it posed an “unreasonable risk of reduced IQ in children” and ordered the EPA to conduct a risk assessment.

Rethinking the role of water fluoridation in the United States might’ve been underway before Kennedy’s declarations earlier this month. But whether the Trump administration will intervene in a public health measure long left to the discretion of state governments and local municipalities remains to be seen, as he has often stated a commitment to protect states’ rights and to reverse, revise and slash regulations.

“In terms of fluoridation, and more broadly in public health, there’s certainly lots of anxiety about what the new administration might mean in terms of many areas,” Tomar said. “This is a measure that’s almost entirely administered at the local level. … Even if the EPA were to issue some type of advisory, this is really a local issue and this seems to be an administration that favors state and local rights. So, I don’t know how this may play out.”

A little goes a long way

In the early 20th century, scientists observed that communities with a higher prevalence of a certain type of tooth discoloration — which looks like flecks or spots on the enamel of the teeth — also experienced lower rates of tooth decay and cavities. They discovered fluoride was causing both, a condition that would later be called dental fluorosis.

“This is not a new condition. The history of community water fluoridation started out as an investigation of fluorosis,” Tomar said. “But the risk factors for more severe fluorosis are not community water fluoridation — a lot of it is inappropriate use of other types of fluoride products.”

For instance, when young kids brush their teeth they are not always able to spit out large dollops of toothpaste, which they end up ingesting. FDA-approved toothpaste with fluoride has an average level of 1,100 milligrams per liter, but people use a tiny portion of that every time they brush their teeth.

A pea-sized amount of toothpaste, the recommended amount per brushing for children between 3 and 6 years old, contains 0.25 milligrams of fluoride — that’s around 0.5 milligrams daily. Adults typically use a quarter teaspoon of toothpaste each time they brush their teeth, which contains about 1.3 milligrams of fluoride. Most of the product is spit out, though estimates indicate infants and children typically ingest between 0.1 and 0.3 milligrams and adults ingest 0.1 milligrams of fluoride from toothpaste in a day. The optimal concentration levels in drinking water are 0.7 milligrams of fluoride per liter.

But it was only in the 1940s that the scientific community began to understand the benefits of fluoridated water over non-fluoridated water, as researchers tried to ascertain whether the natural presence of the mineral had different effects than when it was manually added to water supplies. Three Illinois cities played crucial roles in these studies.

Aurora was one of two cities used as a baseline, given its naturally occurring fluoride content of almost 1 milligram per liter of water. The trials compared four pairs of similarly sized cities, including Evanston and Oak Park. The North Shore suburb had fluoride added to its water while Oak Park remained without fluoride. In a span of 15 years, the prevalence of cavities in children was reduced by 50% to 70% in the communities with fluoridated water, regardless of whether it had been added or occurred naturally.

In 1967, Illinois enacted a mandate that required all community water systems to adjust their fluoride to optimal levels between 0.9 and 1.2 milligrams per liter. The law was amended in 2016 requiring all community water systems to adjust fluoride to 0.7 milligrams per liter, based on updated analyses of different sources of fluoride including toothpaste and mouth rinses.

According to the most current data from the Illinois Department of Public Health, 1,658 of 1,842 community water systems fluoridate in the state.

“There are several reasons why some are not required to do so, including that they have naturally occurring levels within the optimal safe range, serve a small population or are privately owned,” a department spokesperson said.

Throughout his career, Tomar has spoken at countless county commissions and city councils as they weigh the benefits of implementing community water fluoridation. Having been involved for years in school-based prevention programs, he has also met children whose families don’t have consistent access to toothpaste or who don’t own a toothbrush — “some things that so many of us take for granted.”

It’s a big reason why, Tomar argues, community water fluoridation is essential.

“It reaches every member of the community, regardless of socioeconomic status and access to dental care,” Tomar said. “In fact, it benefits members of lower socioeconomic communities most greatly because often they don’t have as ready access to other forms of fluoride like professionally applied fluorides in a dental office or even relative regular use of fluoride-containing toothpaste.”

Concerns about possible connections between fluoride and bone cancer or osteoporosis, as well as developmental issues such as lower IQ levels have long been the focus of many studies — including one from the National Toxicology Program which preceded the most recent federal ruling against water fluoridation.

The August report from the National Toxicology Program, part of the federal health department that Kennedy is expected to lead, found that fluoride in drinking water at more than twice the recommended limit was associated with lower IQ in children.

“Everybody was making a big deal over (it), but if you actually read what they say, it does not apply to the levels of fluoride involved in community water fluoridation,” Tomar said, pointing to how the report was based on twice the recommended limit. “Almost every substance, at a high enough level, could have potential adverse effects. The small amount of chlorine that’s in our water protects us from waterborne diseases, but we wouldn’t think to drink a cup of bleach. So, you know, we try to find the right concentration to maximize the benefit and minimize the risk.”

The fate of fluoridation

Unfortunately, Cooper said, most of the focus on anti-fluoride advocacy gets conflated with conspiracy theories peddled in the 1960s by a far-right group called the John Birch Society which claimed water fluoridation was part of a communist plot concocted by the government to use for mind control on large swaths of populations.

Even now, the spread of erroneous and exaggerated information can be detrimental, he said: “Anytime misinformation is repeated, that’s upsetting, and it does impact any movement.”

Cooper said that the Fluoride Action Network came about as a way for medical and scientific professionals — including physicians and dentists — to fight fluoridation with facts.

“That was our mission,” he added, “to bring science into the debate.” But the organization, he clarified, “is not anti-fluoride.”

“We’re anti-overexposure to fluoride, anti-ingestion of fluoride,” Cooper said. “We understand the science shows that topical use of that toothpaste can reduce dental decay, but the studies show that ingestion does not reduce dental decay and actually comes with risk.”

In 2016, the group filed a petition with the U.S. EPA saying there was scientific evidence that optimal levels of water fluoridation posed an “unreasonable risk” under the Toxic Substances Control Act like the chemicals it has long regulated including asbestos, radon and lead-based paint. The EPA rejected the petition, so the group took the agency to federal court — and, after eight years, a federal judge ruled the practice a hazard.

Now, the EPA can comply and either issue a warning on the product and its use, he said, or prohibit companies from selling the chemical for use in drinking water supplies. Or it can appeal.

A U.S. EPA spokesperson said the agency is in the process of reviewing the district court’s decision.

Those opposed to water fluoridation also saw a major win in new research suggesting its benefits might be waning. A Cochrane systematic review — which synthesizes relevant health care research and evidence — was published in October analyzing 157 studies, comparing some that were conducted before fluoride toothpaste became available in 1975 with others conducted after.

The review found that studies before 1975 indicated fluoridated water systems decreased the number of decayed teeth by an average of 2.1 per child. But modern studies, after 1975, estimated a lower benefit of 0.24 fewer decayed teeth per kid — about a quarter of a tooth.

Fluoride toothpaste, professional applications and proper nutrition to prevent cavities and tooth decay are so widely available nowadays, Cooper said, that “if there was a small benefit from fluoridation, we’re no longer getting it.”

However, Tomar said modern-day comparison studies such as those included in the Cochrane review are limited because very few communities in the United States are completely unexposed to fluoridated water, even if their supply is not fluoridated.

“If you buy processed beverages or foods manufactured in a fluoridated area, that probably has fluoride in the product,” he explained. “So to claim that your comparison group is truly unexposed is probably not true.”

In any case, it is that overexposure that concerns Cooper, especially in childhood when permanent teeth are still forming under the gums and when too much fluoride can combine with dental enamel, developing discoloration or fluorosis. Older people cannot develop this condition.

Cooper said fluorosis in young people has skyrocketed in recent decades, according to CDC data from National Health and Nutrition Examination Surveys each sampling 5,000 people. In the mid-2000s, 41% of American teenagers aged 12-15 had discoloration in their teeth. That percentage went up to 65% in 2012. However, a 2016 survey showed that 70% of children and adolescents had some level of fluorosis.

This concerns him especially because it means youth are being exposed to fluoride during a critical time of childhood development, which could affect their brains. It’s why in the last decade, over 1,500 communities have ended water fluoridation, he said, a trend that has increased in recent years.

Earlier this year lawmakers in Georgia, Kentucky and Nebraska filed bills to reverse their respective state mandates and leave the decision up to a local voter referendum or local water system governing bodies. But even in the last few weeks, Cooper said, he has been fielding calls from state legislatures and city council members every day as they read up on recent studies and the federal ruling.

So far, no legislators in Illinois have reached out to him.

Local views could be changing in other parts of the country, however.

Cooper has heard from water directors in different U.S. cities who say they will take their cue if the EPA does not appeal the federal judge’s decision.

“They will view that as a concession that this is neurotoxic, and there will be this huge domino effect across the country of ending water fluoridation,” Cooper said.

Regardless of who won the presidential election and who was chosen to lead the country’s health and environmental agencies, he added, his organization expected someone to take notice of the issue. And despite reluctance from the dental establishment to change course, Cooper feels optimistic.

“We’re happy that it’s risen to a presidential discourse, and it certainly has increased awareness of the subject,” he said. “Fluoridation was already, is already dying. … Our ruling put the nail in the coffin.”

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