I think we can all agree that “Look, Mom – no cavities!” is good news. But we continue to disagree about the best way to achieve that. Fluoridation of public water sources remains controversial as a public health measure despite the strong evidence that fluoride prevents tooth decay. Public debates can become quite heated, with one side praising water fluoridation as an essential preventive and the other side demonizing it as coerced ingestion of a poison. Recently fluoridation has faced new accusations that it lowers IQ. Which side is right? Let’s see how the evidence and the arguments on both sides hold up to scrutiny.
Optimal level of fluoride in drinking water
The natural fluoride content of drinking water varies widely by geographic location. Studies have shown that people whose water is low in fluoride are more likely to develop cavities. If the fluoride content is too high, they can develop fluorosis, with tooth discoloration and other problems. The EPA has set maximum levels of fluoride at 2 ppm to prevent enamel fluorosis and 4 ppm to prevent skeletal fluorosis. The World Health Organization has set the recommended maximum level at 1.5 ppm. In 2015, the U.S. Department of Health and Human Services updated the optimal fluoride level in drinking water to 0.7 mg of fluoride per liter of water (equivalent to 0.7 parts per million or ppm). This was based on extensive research and consideration of other sources of fluoride. If the natural fluoride content of drinking water is lower than 0.7 ppm, water fluoridation can raise it to 0.7. If it is over the recommended maximum level, there are ways to lower it. Estonia had levels as high as 7 ppm (10 times the optimum), and they were able to successfully lower the fluoride exposure of their citizens by using reverse osmosis technology and drilling new wells.[i] Fluorosis should not occur at currently recommended levels of water fluoridation.
Fluoride reduces cavities
Fluoride is the key to preventing and controlling tooth decay. There is a clear scientific consensus: the evidence shows fluoride is effective, both at the individual and at the community level. Individual measures include taking fluoride supplements and getting various professional fluoride treatments by dentists.[ii]Community measures include water fluoridation, educational programs, and fortification of foods such as table salt. Few people would deny that fluoride is effective; the disagreements are about how fluoride should be supplied.
Water fluoridation is safe and effective
Over a hundred studies in various countries have shown consistent results. Early studies showed that water fluoridation cut the risk of tooth decay by around 50%. Current estimates are lower, because today’s public is exposed to many more sources of fluoride, like fluoride toothpaste. Recent studies have confirmed the benefit. For instance, a 2018 study in Australia[iii] found consistent associations between low lifetime exposure to fluoridated water and childhood caries. The current estimate by the American Dental Association is that it reduces tooth decay by at least 25% in both children and adults.
From the American Dental Association (ADA) to the World Health Organization (WHO), around a hundred national and international professional medical societies, research organizations, and health agencies around the world have endorsed water fluoridation as safe and effective. International scientific reviews show no link between any adverse health effects and drinking water with fluoride levels that do not exceed 1.5 ppm. After evaluating the evidence, the CDC dismissed claims that fluoride increased the risk of cancer, Down syndrome, heart disease, osteoporosis, bone fracture, AIDS, low intelligence, Alzheimer’s disease, allergic reactions, and other health conditions. And there is no evidence that water fluoridation has ever harmed the environment.
Fluoridation is the most cost-effective way to prevent tooth decay. Every $1 invested in fluoridation saves $38 in treating dental problems.[iv]
Alternatives to fluoridation
In some areas fluoridation is not feasible, for cost or logistical reasons. It is banned in China where naturally high fluoride levels in water are a serious problem. In 2010, 66% of U.S. residents had access to fluoridated water, compared to 70% in Australia and 70.5% in Chile. When some countries that had previously practiced fluoridation discontinued it, they saw a rise in tooth decay. Currently only about 5.7% of the world’s population, in only 24 countries, get added fluoride in their water. The rest of the world has preferred other methods of reducing tooth decay, like topical application, fluoride toothpaste, and adding fluoride to milk or table salt. These methods are effective too.
Opposition to water fluoridation is not based on science
The opposition to water fluoridation is not based on any credible scientific evidence that properly regulated fluoridation causes harm, but on philosophical and ethical concerns that value individual rights over the common good. It is seen as mass medication without individual consent. Legal challenges in the courts have mostly been unavailing. Conspiracy theories have been invoked, as parodied in the movie Dr. Strangelove, where General Jack D. Ripper orders a nuclear strike against the Soviet Union to counteract what he imagines is a nefarious Communist plot to fluoridate our water and thereby “impurify our precious bodily fluids.” The communists were not the only ones blamed; it has also been called a capitalist ploy and a way for the aluminum industry to dispose of toxic fluoride wastes and make a profit.
It seems to me the opposition to fluoridation often originates as a poorly informed knee-jerk emotional reaction. (Ain’t no dang gummint gonna make me put nasty chemicals in my body!) Once people feel uncomfortable about fluoridation, it is a simple matter to cherry-pick the scientific literature and find rationalizations to reject it. And there is a small minority of dissenting scientists who find reasons to reject the scientific consensus. You can find a PhD to support any belief.
The Fluoride Action Network has a list of “50 reasons to oppose fluoridation.”[v] I find them far from persuasive.
- “Fluoride is the only chemical added to water for the purpose of medical treatment.” (It’s not for treatment, but for prevention. Being the only one would not be a reason to reject something: it might be the only one where adding it is indicated. There is precedent: we add iodine to table salt to prevent goiter.)
- It’s unethical because they don’t get informed consent from individuals. (They don’t get informed consent from every user of iodized table salt, either. And others have argued that it is unethical to deny this public health benefit to our children.)
- The dose can’t be controlled. (Here they have a good point. Some people drink large amounts of water; others avoid water or replace tap water with bottled water that may not contain fluoride. People get fluoride from other sources like toothpaste, supplements, and dental treatments. Similarly, we can’t control the dose of iodine, since some people use non-iodized salt. No one considers that a problem; certainly not a reason to stop adding iodine to salt.)
- Fluoride is not an essential nutrient. (That’s beside the point.)
- Fluoride accumulates in the body. (But there’s no evidence that water fluoridation leads to accumulations of fluoride that cause health consequences.)
- Countries that don’t fluoridate their water have seen similar declines in dental decay. (That’s because they provide fluoride in other ways, like adding it to table salt.)
- Fluoride causes arthritic symptoms. (No, it causes skeletal fluorosis, but only in much higher doses than people get from water fluoridation.)
That’s enough of a sample to give you an idea of the quality of their arguments. Mostly speculation, misdirection, animal studies, and logical fallacies.
Does water fluoridation decrease IQ?
The Fluoride Action Network claims that 33 studies have shown an association between fluoride exposure and reduced IQ. These studies, mostly out of China, did not address water fluoridation at all. They compared areas with very high levels of fluoride in natural water sources to areas with lower levels. The levels associated with lower IQ were far higher than the amounts in fluoridated water. Their low-fluoride group got a similar amount to what is in fluoridated water.
Even Snopes has debunked this claim:
“the claim that there are scientific studies that support the notion that water fluoridation can cause developmental problems in children that result in lower IQs is false.”[vi]
Which is unfair – fluoridating or not fluoridating?
Very few of the arguments against water fluoridation hold up to scrutiny, but some do. If you are an elderly person with dentures, you can argue that fluoridation will not benefit you personally and that it is an arbitrary, unfair government imposition. It will only cost you tax dollars you did not choose to spend, and you didn’t give informed consent. You can argue that we can’t be 100% certain it won’t cause harm.
Water fluoridation is a cost-effective, efficient way to reduce tooth decay in populations, but it is not the only way. Where it is not available, parents have to be educated to know that their children need fluoride supplements, and poor families may not be able to afford supplements or dental treatment. If opponents of fluoridation cared about the welfare of children, they would advocate other ways of getting fluoride to children, like adding fluoride to table salt, or they would offer to subsidize free supplements and free dental care for poor children. Instead, they seem to be selfishly fixated on their own freedom.
What to do?
The CDC considers water fluoridation “one of the 10 great public health achievements of the 20th century.” Dentists recommend it (even though you might think they would want to increase their business by encouraging cavities!). If you reject it, aren’t you obligated to find another way of protecting poor children?
This article was originally published as a SkepDoc column in Skeptic magazine.