The fluoride debate
The nuance you may be looking for
Fluoride has sprung into the national spotlight in the past few weeks, and many people have great questions. Here’s the nuance to equip yourself for evidence-based discussions.
Fluoride is important for our teeth
Fluoride is a naturally occurring mineral found in water, soil, air, and some foods. Our bodies need minerals for many things, including strengthening our bones and teeth. Just like our bones need enough calcium, our teeth benefit from getting enough fluoride. Specifically, fluoride strengthens enamel—the thin, hard layer that covers our teeth—which helps prevent bacteria from causing cavities. Preventing cavities is good for many things, including cardiovascular health.
The value of fluoride isn’t controversial—it’s good for our teeth. This is why toothpaste contains fluoride, and dentists apply it directly to teeth, too. The question being debated is whether we should add it to our public water supplies.
Fluoride in our water supply is effective
Since 1945, local communities have been putting fluoride in drinking water. Currently, about 3 in 4 Americans receive fluoridated water. This is largely a hyperlocal decision—your city or county decides—but some states, like Hawaii, have banned it.
Water fluoridation has been an effective population-level intervention to reduce tooth decay. As the chart below shows, fluoride was added to water supplies in the mid-1940s, and tooth decay declined. It also has an impressive return on investment—for every dollar spent on fluoridation, $20 is saved in preventing dental procedures.
Of course, correlation doesn’t equal causation. So scientists have studied what happens once we remove fluoride in water. Tooth decay increases across the population. For example:
In 2011, Calgary’s city council banned fluoridation. In five years, cavities among elementary school children increased almost twofold, and IV antibiotics (to mitigate harm from bacteria) increased eightfold. They ended up putting fluoride back in in 2021.
In 2007, Juneo, Alaska, voted to stop adding fluoride. Afterward, the average number of cavity procedures per child increased to almost one more procedure per year (1.55 versus 2.52) among children under six.
The benefit from fluoridated water became more modest when we added fluoride to toothpaste. A 2024 Cochrane review—the gold standard of medical reviews that pooled 21 studies—found studies conducted earlier than 1975 showed a clear and important effect on preventing tooth decay in children. After 1975, there may be less robust benefits.
Fluoridation is especially important in low-resource areas
Because the public water system reaches everyone equally, fluoridation mitigates the impact of disparities in access to dental care in the United States. This is one of the beauties of public health—a mainly invisible population intervention, helping the most vulnerable.
Lower-income families still struggle to find dentists who take their insurance. In 2023, the American Dental Society found that only one in three dentists nationally accept Medicaid. This helps explain the CDC report that children in lower-income families have nearly three times higher rates of untreated cavities than children in higher-income families.
The impact of this goes well beyond preventing cavities. Poor dentition can be an important source of stigma and shame for a child and can serve as a visible sign of poverty. Studies show that children with poor dentition are more likely to withdraw from social participation, hide their smiles, and have higher rates of school absenteeism. These early life experiences can be a barrier to a sense of confidence and social belonging that can have lifelong effects.
Is it safe? The dose makes the poison
The U.S. Public Health Service recommends a fluoride concentration of 0.7 parts per million in drinking water, a level carefully chosen to prevent cavities. However, some places in the U.S. (~0.6% of the total population) have natural fluoride in their water that reaches up to 1.5 parts per million.
Very high levels of fluoride can be dangerous. Fluoride toxicity first impacts the skeletal bones, beginning at an exposure of 5 mg/kg of body weight per day. If we do the math, the average child (40 kg) must drink 286 liters of fluoridated water daily to reach toxicity. At that point, they would die from water overconsumption.
Rumors have also circulated about a link between fluoride and thyroid function. But again, the dose makes the poison. A meta-analysis—pooling 27 studies on this topic—found that hormone levels started increasing at fluoride levels of 2.5 parts per million—about 3.5 times higher than what is added to our water systems.
In the past five years, a few studies have questioned whether safety signals exist in children’s cognitive development. However, the studies have important limitations that call into question their applicability:
Studies in Mexico, Iran, China, and other countries measured fluoride levels far higher than what’s added to U.S. drinking water.
A recent controversial study in the U.S. found a correlation between maternal fluorinated water consumption and a lower IQ in 3- and 4-year-old boys. However, fluoride levels were more than double that of what most receive in the U.S., and conducting IQ tests at ages 3 and 4 is questionable, given that most children cannot read at this age.
Some, including RFK Jr., have also raised concerns about a link between fluoride and osteosarcoma (a rare bone cancer) in childhood and adolescence. While a rat study suggested a link, several human studies refuted this, as they did not find a link (here, here). In 2022, the American Cancer Society conducted an extensive review and concluded that there was “no strong evidence.”
While it is important to follow ongoing safety carefully, several factors need to be considered to establish causality that we don’t have in the case of fluoridated drinking water in the U.S. These include biological plausibility (there is no real mechanism to link fluoride to IQ), the relationship between fluoride dose in U.S. water and observed human health effects (called dose-response relationships), and whether we see consistency across many human studies and different populations, particularly at the exposure levels that we see in America.
Why have other countries removed it from their water?
Most Western European countries have ended public water fluoridation. There are a few reasons why:
Other countries have free dental care for kids.
They get fluoride from other sources, like fluorinated salt, especially in communities without centralized water systems.
Different approaches to assessing health risk. Europe, for example, uses a precautionary hazard approach. If a study shows a substance can be toxic, they aim to eliminate the hazard completely. A risk approach, which the United States uses, begins with identifying a hazard but takes it one step further by assessing the probability of the exposure doing harm. This approach requires more data, time, and multidisciplinary expertise at one table to determine risk assessments and, thus, policy. Neither approach is necessarily wrong, but it can lead to contradictory actions.
Bottom line
Water fluoridation is one of the century’s top 10 public health achievements and is still supported by organizations like the American Dental Association and the American Academy of Pediatrics. While the benefit now may be more modest, thanks to toothpaste, it’s important to consider the benefits to all Americans, including our neighbors with fewer financial resources.
Love, YLE
Your Local Epidemiologist (YLE) is founded and operated by Dr. Katelyn Jetelina, MPH PhD—an epidemiologist, wife, and mom of two little girls. YLE reaches more than 280,000 people in over 132 countries and has a team of 11 whose main goal is to “translate” the ever-evolving public health science so that people will be well-equipped to make evidence-based decisions. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:
Thank you for another great article on public health issues. Many years ago, as part of a medical school rotation, I spent a month with a Family Practice physician, whose office was close to the borders of Maryland, Pennsylvania, and West Virginia. He showed me, as we saw patients, that he could tell if they were from West Virginia, as soon as the children smiled, as West Virginia had no fluoride in the water, and Pennsylvania and Maryland did. I think it was a most “Vivid”, public health lesson.
A few case reports: (1) I grew up drinking beautiful mountain spring water and have spent way too much time since in dentists' chairs, including in the era before local anesthesia was available. (2) I recently tutored an ESL student who grew up near Mexico City, where the water is naturally fluoridated. Somewhere around age 45, she had to go to a dentist for her FIRST cavity ever! She also had some of the most beautiful teeth I've seen anywhere. Of course RFKjr seems generally off-the-wall and we can hope our Senators will have the sense to see that. But thanks for the informative article, YLE!