Communities across the United States first began adding fluoride to water systems eight decades ago. While the EPA sets regulatory levels based on recommendations from the CDC and other health experts, local communities themselves choose whether to fluoridate their water. Currently, almost three-quarters of the U.S. population live in areas with fluoridated water.

While water fluoridation has indisputably reduced the individual and societal burden of dental caries, it has also provoked controversy. Over the years, some opponents have accused the fluoridation movement of being part of a communist conspiracy to control or poison the American population. At the same time, concerns have long been raised about potential negative effects of fluoride, including discoloration and pitting of teeth, potential disruptions of thyroid function, and lower intelligence.

Most recently, an analysis of 74 studies from 10 other countries, published in JAMA Pediatrics earlier this year, reported that high levels of fluoride are associated with a lower IQ in children. However, in the U.S., the currently recommended concentration of 0.7 mg/L is significantly lower than the levels found in those studies and is not associated with any poor health outcomes. Meanwhile, the new secretary of the Department of Health and Human Services, Robert F. Kennedy, Jr., has expressed opposition to fluoridated water.

Given the ongoing debate, the Wellness Letter asked UC Berkeley water expert Charlotte Smith, PhD, a lecturer in environmental health sciences at the School of Public Health, about the history of fluoridation, the recent attention over a potential impact on intelligence, and why this is an environmental justice issue. 

Wellness Letter: Can you explain why water started to be fluoridated?

Charlotte Smith: The relationship between cavity prevention and fluoride has been well known for a long time. It had been observed that people in communities with higher levels of naturally occurring fluoride in the water had fewer dental carries. That benefit was seen throughout the life course—not only in children but adolescents and adults as well. The evidence is clear.

Water fluoridation is considered one of the greatest public health achievements of the 20th century. In the U.S., fluoride was first added to water in some communities in the 1940s. Once the trend began, the number of communities adding fluoride to the water continued increasing and became more and more prevalent over the decades.

WL: One problem is that most people today don’t remember the situation before fluoridation.

CS: Exactly. I grew up in a community with a fluoridated water system. People I knew didn’t have serious tooth decay, nor did they lose most of their teeth as they got older. If fluoride is removed from water systems, we could be going back to a time when many more people will have a lot more cavities, especially if they don’t have good dental care.

Water is obviously a good vehicle for exposing teeth to fluoride. It really is an environmental justice issue. Some members of a community might not have access to dental care, but everyone would have access to fluoride through the community’s water system.

WL: Can you elaborate on that aspect?

CS: If a community water system is fluoridated, there’s complete equity. Everyone drinking water in the community has access to the benefits of that public health intervention. In contrast, there are a lot of reasons that people in more disadvantaged circumstances might lack access to dental care. Not everyone can afford it. Many have no dental insurance. It can be hard to take time off from work to schedule a dental visit, or maybe no one can watch the kids.

WL: But don’t some areas already have enough naturally occurring fluoride in the water?

CS: Yes, fluoride is found naturally in soil, in most places at low levels. From the soil, it gets into the well water. It also gets into crops, and therefore food. In some places, like in parts of the southwest, there are much higher levels of fluoride in the water, just like there are some places with higher levels of arsenic. Those communities wouldn’t be candidates for adding fluoride to the water on top of the natural levels.

WL: Is it possible to get enough fluoride by brushing your teeth with fluoride toothpaste?

CS: Some argue that people should receive their fluoridation through toothpaste. While it’s true that you can get fluoride by brushing your teeth with fluoridated toothpaste, that doesn’t have the same impact as adding fluoride to water. The studies show that communities with fluoridated water have better dental outcomes, even though many people in all communities brush their teeth with fluoridated toothpaste. In other words, being exposed to fluoride through toothpaste is the baseline.

WL: What about the argument that adding fluoride to water is forcing people to ingest it against their will?

CS: Well, a key aspect of fluoridation is that there’s a technical solution for people who might object to it, for whatever reason, although it isn’t free. A reverse osmosis filter under their sink or on the countertop, which can cost several hundred dollars, can remove the fluoride from the water.

WL: What concerns have there been in the past about fluoridation?

CS: Some of the historical concerns were that fluoride could cause dental fluorosis and skeletal fluorosis. Dental fluorosis is when the teeth get mottled and stained and sometimes pitted. Skeletal fluorosis is the weakening of the bone structure. These are legitimate concerns, but they only happen when the fluoride level in the water is very high, not at the levels used in U.S. communities that fluoridate the water.

But there were also right-wing political concerns. In the movie Dr. Strangelove [released in 1964], one of the characters is obsessed with the idea that fluoridated water is a communist plot, which was a common conspiracy theory at the time. So there have always been people of the opinion that fluoridation is bad policy. The intensity of that debate has waxed and waned over the years.

WL: Now we have recent reports raising questions about the impact of fluoride on children’s IQs. Can you put this debate in context?

CS: That discussion was most recently spurred by a report in JAMA Pediatrics that looked at several dozen studies from other countries and concluded that high levels of fluoride were associated with lower IQ scores in children. The authors stated that the conclusions don’t apply to water systems with lower levels of fluoride, like in the U.S.

Unfortunately, many people stop reading after headlines like “Fluoride associated with low IQ.” They don’t go beyond that to find out that the association is dependent upon higher levels of fluoride, and that the authors themselves were clear that their findings are not relevant in systems with lower levels, like in the U.S.

WL: Last fall, RFK, Jr., wrote in a social media post that “fluoride is an industrial waste associated with arthritis, bone fractures, bone cancer, IQ loss, neurodevelopmental disorders, and thyroid disease.” What do you anticipate from any reviews of the evidence by the administration?

CS: Well, there are two things wrong with that statement. First, as I said earlier, fluoride occurs naturally on our planet. The other issue is that health outcomes are always dose dependent. Anything can be toxic at high levels—salt, aspirin, alcohol, you name it. It will be interesting to see what the new administration says and does if it actually looks at the data and receives public comment on any proposed regulations.

The arguments against fluoridation are generally based on hype, and the actual regulations are based on data, so we’ll have to wait and see how this plays out. But the evidence is clear that water fluoridation at the low concentrations used in the U.S. prevents dental caries and does not have negative health impacts. The evidence also shows lower overall costs of dental care in communities with fluoridation. Removing fluoride from water systems is just a bad idea.