Trump might target fluoride in tap water. Here’s what the science says.

Robert F. Kennedy Jr., the anti-vaccine activist who is poised to have significant control over health and food safety in a potential Donald Trump administration, has promised to immediately seek to remove fluoride from drinking water in the United States. Trump, when recently asked about Kennedy’s plan, said it sounded “okay to me.”

The possible reversal of a decades-long practice that has been praised as one of the great public health achievements of the 20th century has worried some experts.

Here’s what to know about Trump and Kennedy’s comments on fluoride and what the science says.

The context

What is fluoride, and why is it added to tap water?

More than 200 million Americans are on fluoridated water systems, according to the CDC, and Kennedy’s focus on removing it during his long-shot bid for the presidency puzzled many experts who see little upside in the idea.

Fluoride is a naturally occurring mineral that can be found in soil, water, plants and many foods. The practice of putting fluoride in Americans’ water began in 1945 in Grand Rapids, Michigan. In 1962, the U.S. Public Health Service recommended adding small amounts to drinking water to strengthen teeth and replace minerals lost to routine wear and tear.

The decision helped fuel wild, often baseless allegations about public health officials’ motivations. That resistance was lampooned in the 1964 satirical film, “Dr. Strangelove,” in which the film’s antagonist — a paranoid general — justifies his decision to spark nuclear war by blaming fluoridation, saying it is “the most monstrously conceived and dangerous communist plot we have ever had to face.”

Other countries also add fluoride to their drinking water, including the United Kingdom, Canada, Ireland, Spain and Brazil. According to a 2022 policy paper published by the British government’s Department of Health and Social Care, an estimated 400 million people in about 25 countries are on fluoridated water systems, and an additional 50 million people drink water with naturally occurring fluoride levels that are equal to or about the same as water in which fluoride is added.

What are the health benefits and potential risks of fluoride?

Fluoride acts as a protector for teeth. The sugar consumed in food and drinks causes plaque bacteria in the mouth to create acid, which in turn weakens the protective mineral layer on teeth. This makes people more likely to develop cavities, tooth decay and tooth loss. Fluoride helps to reverse this process and strengthen teeth.

When fluoride was first introduced in water supplies in some Western countries, it caused “really, really big reductions” in tooth decay, said Michaela Goodwin, a senior lecturer in public health at the University of Manchester in England. For decades after that, community water fluoridation was proven to be safe and effective, according to the CDC.

Since the widespread adoption of fluoridated toothpaste around the 1960s and ’70s, water is no longer the only source of fluoride for many Americans. “In recent years, there have been some discussions around whether we’re still seeing that same kind of beneficial effect,” said Goodwin, who also noted overall advancement in oral health in recent decades. Still, a recent review of available studies published by the Cochrane Library said that contemporary evidence suggests that community water fluoridation “may lead to a slightly greater reduction in decayed, missing or filled primary teeth … and may lead to a slightly greater increase in the proportion of caries‐free children, but with smaller effect sizes than earlier studies.”

U.S. health officials in 2015 lowered the recommended amount of fluoride in drinking water, saying that it was less necessary given the other sources of fluoride, such as toothpastes and mouthwashes.

Some researchers have raised concerns about fluoride’s effects, such as whether the mineral has a harmful effect on developing brains. A study led by researchers at the University of Southern California and published in JAMA Network Open in May suggested that fluoride exposure during pregnancy was linked to an increased risk of childhood neurobehavioral problems. “More studies are urgently needed to understand and mitigate the impacts in the entire U.S. population,” Tracy Bastain, a USC associate professor and author of the study, said in a statement in May.

Other researchers have dismissed the USC study, and public health officials have frequently played down worries about fluoridation of water, saying that some Americans wrongly believe in myths and conspiracy theories about its risks.

What are the potential risks of fluoride overexposure?

Goodwin said the only “recognized” risk of consuming fluoride in drinking water at levels mandated in countries such as the United States is dental fluorosis, which is when teeth become discolored or damaged as a result of over-mineralization.

According to the World Health Organization, exposure to too much fluoride over time has also been associated with “crippling skeletal fluorosis,” or bone damage — but experts say this applies to levels of fluoride far exceeding those allowed in the United States.

The National Institutes of Health says that this is “extremely rare in the United States and no evidence indicates that it is caused by the recommended level of fluoride in public tap water.”

Some local lawmakers and communities around the country continue to push back against the practice of putting fluoride in water, and anti-fluoride activists have turned to the courts. In September, a federal judge ordered the Environmental Protection Agency to further regulate fluoride in drinking water, saying there was potential risk to children’s developing brains. The judge noted that his finding “does not conclude with certainty that fluoridated water is injurious to public health.”

Is there fluoride in bottled water?

According to NIH, bottled drinking water does not typically contain fluoride.

However, some bottled water does contain added fluoride, and some water naturally contains fluoride. Added fluoride must be indicated in the ingredients. In 2022, the U.S. Food and Drug Administration lowered the amount of fluoride that can be added to domestically packaged and imported bottled water from to 0.8-1.7 milligrams per liter to 0.7 mg/L. This, the FDA said, “will balance prevention of tooth decay and the risk of fluoride overexposure.”

What have Kennedy and Trump said about fluoride?

Kennedy has argued that the federal judge’s recent ruling on fluoride in the EPA case is evidence that the mineral is dangerous and should be removed from the water. (Experts say the judge’s ruling does not provide a scientific basis to end the practice. The president of the American Dental Association said that there is still “clear and compelling” evidence to put fluoride in drinking water.)

Pollsters have suggested that the unconventional — and generally unpopular — public health policy stances embraced by Kennedy, the Trump campaign and its surrogates, including the fluoride pledge, could be a strategy to reach skeptical, antiestablishment voters in what is expected to be a close election against Vice President Kamala Harris.

Trump told podcaster Joe Rogan last month that he would let Kennedy “go wild” on health, food, medicines and other issues. Trump was asked about Kennedy’s fluoride pledge in an interview with NBC and said: “I haven’t talked to him about it yet, but it sounds okay to me. You know, it’s possible.”

The Trump campaign declined to comment on Kennedy’s pledge. “While President Trump has received a variety of policy ideas, he is focused on Tuesday’s election,” spokeswoman Danielle Alvarez told The Washington Post in a previous statement.