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Fluoridated Water: Should You Be Worried?

  • Writer: FibonacciMD
    FibonacciMD
  • Jun 9
  • 9 min read

The debate over fluoridated water has resurfaced amid new legislation.

This article explores fluoride sources, its effects on oral health, the history and current state of water fluoridation, and potential risks, particularly to children's cognitive development.


Fluoridated Water, fluoride

In 1999 the Centers for Disease Control and Prevention declared fluoridation of drinking water one of the ten great public health achievements of the 20th century.[1] Twenty six years later, in March of 2025, the Governor of Utah signed a law banning the addition of fluoride to drinking water.[2] Bills to ban fluoridation have also been introduced in several other states. Controversy around the safety of water fluoridation has existed since its inception but has intensified recently due to research suggesting a link between high intakes of fluoride and IQ.[3,4]


Where Do We Get Fluoride?

Fluoride is a mineral found in small amounts in almost all soil, water, and foods, including tea and marine fish consumed with their bones.[5] Tea contributes significantly to fluoride intake in cultures where large amounts are consumed. In the United States however, most of the ingested fluoride comes from fluoride in toothpaste and other dental products and from fluoride added to the water supply. Because food readily absorbs fluoride from cooking water, the fluoride content of foods can be significantly increased when it is prepared using fluoridated water. Based primarily on studies done in the 1970s and 80s, the typical fluoride intake in the U.S. from food and beverages, including fluoridated water, is estimated to be 2.2 mg/day for young children and 2.9 mg/day for adults.[5] Swallowed toothpaste adds - depending on how much is swallowed - about 0.1 mg per day in adults and over twice this in young children. [5,6]


Fluoride and Oral Health

While fluoride is not an essential nutrient, nutrition guidelines do make daily intake recommendations based on the amount consumed by healthy individuals that benefits oral health. This amount is 0.05 mg/kg body weight/day for everyone over 6 months of age, or about 1.1 mg/day for a 6-year-old and 3.8 mg/day for an adult. [7]  Because fluoride has a high affinity for calcium most of the fluoride in the human body is found in bones and teeth, where it strengthens bone and makes teeth more resistant to decay. Tooth decay, also known as cavities or dental caries, is the most common noncommunicable disease in the world. It occurs when bacteria in the mouth form colonies, known as plaque, on the surface of the teeth. If not removed, the bacteria in the plaque metabolize dietary carbohydrates, producing acids that dissolve tooth enamel and the underlying tooth structures.


Cavities may seem like a minor issue, but left untreated, they can cause incapacitating pain, reduce the ability to eat, lead to tooth extraction, and cause systemic infection. [8,9] Fluoride consumed early in life, during tooth development, is incorporated into tooth enamel, making it more resistant to the acid that causes decay. After the teeth are formed, fluoride is no longer incorporated into the enamel, but ingested fluoride is secreted in saliva. This continually bathes the teeth reducing the amount of acid produced by bacteria, inhibiting the dissolution of tooth enamel by acid, and increasing enamel remineralization after acid exposure.[10] Fluoride in toothpaste and mouth rinses has the same topical effect but remains in the mouth for only a few hours after use.


Fluoridation of Drinking Water

Fluoride is added to community water supplies to reduce the risk of tooth decay. This intervention had its beginnings in the early 1900s, when it was observed that people in areas with naturally high levels of fluoride in the water had fewer cavities, but also often had stained teeth, a condition originally called Colorado Brown Stain and now known as dental fluorosis. [9] By the 1940s, studies that added low levels of fluoride to drinking water found tooth decay to be reduced by 50 to 70% among children in communities where fluoride was added to the water compared to those in communities without added fluoride. [9] By 1950, the American Dental Association and the U.S. Public Health Service endorsed fluoridation of community water supplies.


Continued evidence of the benefits of fluoridated water to dental health led to the development of the first guidelines for the addition of fluoride to water in 1962. [11] Currently, the U.S. Public Health Service recommends an optimal water fluoride concentration of 0.7 mg/L; an amount that maximizes dental health and minimizes the risk of fluorosis. This is not a mandate but a guideline for state and local governments to use in deciding whether to implement water fluoridation.[12] To reach this level, communities add fluoride when water fluoride levels are low, remove fluoride where levels are too high, or just monitor the concentration when the water already contains the recommended amount of fluoride.[12]

Currently about 63% of Americans are served by community water systems that fluoridate their water.[13] When compared to non-fluoridated communities, these fluoridation programs have been estimated to reduce tooth decay by about 25%.[12] The difference in effectiveness between current studies and those reported in the 1940s has been attributed to the consumption of foods and beverages processed or bottled with fluoridated water in areas without fluoridated water and to the widespread use of fluoride toothpaste, which was first marketed in 1956 and now accounts for about 95% of the toothpaste sales in the U.S.[9,11,14]


Is Fluoride Harmful?

The potential for fluoride to cause harm depends on the amount that is consumed. Single doses in the range of 3 to 5 grams are fatal, although this has only been reported from accidental poisoning.[15]  Much smaller fluoride doses, such as might be obtained from water that exceeds 4 mg/L, carries a risk for changes in bone structure. [16] This amount is uncommon in natural water supplies, and 4 mg/L has been set as the limit allowed by the Environmental Protection Agency in public water systems.[16] The most common adverse effect, dental fluorosis, occurs at even lower doses.[15]


During tooth development, which takes place in children 8 years and younger, fluoride intakes of only a few milligrams per day can cause the symptoms of dental fluorosis, which range from white or brown stains on the teeth to pitting of the tooth enamel. To prevent dental fluorosis, nutrient guidelines recommend that fluoride intake be limited to no more than 1.3 mg/day for children ages 1 to 3 years and no more than 2.2 mg/day for those 4 through 8 years.  Dental fluorosis does not occur in those older than 8 years but an upper limit of 10 mg/day has been set to protect bone health.[7] While these recommendations set clear guidance for protecting dental and bone health, they do not address some of the newer research suggesting a link between higher fluoride intakes and lower IQs in children.


Several recent large studies have evaluated the impact of fluoride intake on IQ in children. A National Toxicology Program Monograph and corresponding systematic review and meta-analysis concluded with moderate confidence that at fluoride exposures that exceed 1.5 mg/L of drinking water there is a dose response association between higher fluoride level and lower IQ in children.[17,18] When childhood exposure to fluoride levels below 1.5 mg/L of drinking  water was examined, no association was found.[18] Thus far, however, studies examining fluoride and IQ have only looked for an association between the two. An association does not mean that high fluoride is the cause of lower IQ; a mechanism whereby fluoride might affect IQ has not been determined. Factors other than, or in addition to fluoride, could be contributing to the reductions in IQ. Questions have also been raised about the impact of fluoride on the gut microbiome, but reviews of the current literature show that fluoride at levels typically consumed (less than 2mg/L) have no impact on the gut microbiome. [26]


Weighing the Risks and Benefits

The risk that high fluoride intake in children may result in reductions in IQ is the focus of current concerns.  Data from populations around the world have found lower IQ scores in children exposed to fluoride levels above 1.5mg/L of drinking water.[18,19]   But in the United States, where water is a major dietary source of this mineral, fluoride is added to water at a level that is less than half of the lowest amount associated with IQ reductions.[12] Based on this, it could be assumed that the risk to children is low. However, there is no recent data on total fluoride intake in U.S. children and no studies have examined the relationship between fluoride intake and IQ in the United States, so it is difficult to accurately evaluate risk. 


We do know that there are areas in the U.S. where the natural water supply contains fluoride levels greater than 1.5 mg/L.[18]  Individuals whose water comes from a community water supply can request information on the fluoride in their drinking water by contacting the supplier. Those whose water comes from a well can have it tested for fluoride content.


Another major source of fluoride in the U.S. is fluoride-containing toothpaste and dental rinses. The American Dental Association recommends fluoridated toothpaste but also recognizes that the ingestion of too much fluoride while teeth are developing can cause dental fluorosis. [20] Therefore, it is recommended that children begin using fluoride toothpaste at age 2 years, and until age 3 should use just a smear the size of a rice grain. Children aged 3 to 6 years should use no more  than a pea-sized amount. Following these standards and making sure older children do not swallow fluoride-containing toothpaste or dental rinses can help maximize the benefits and minimize the risks. [20]


A majority of Americans consume fluoridated water and use a fluoride-containing toothpaste. Researchers have expressed concern that for some, particularly children, total fluoride intake may reach levels comparable to that associated with reduced IQ [21]. But is the solution to end water fluoridation for everyone? There is evidence that cessation of fluoridation will cause a decline in dental health, particularly in those without the resources to access fluoridated oral care products or good dental care.  Seven to eight years after the city of Calgary stopped water fluoridation the incidence of tooth decay was 10% greater than in Edmonton, where fluoridation remained in place; the lack of fluoride had a greater impact in those without dental insurance. [22,23]


Bottom Line

Fluoridation of community drinking water is the most cost-effective method of delivering fluoride to the American public. The recommended level of fluoride in drinking water in the United States reduces the risk of tooth decay and saves billions of dollars in annual dental costs; and there is no evidence that it affects children’s IQ.[24] However, more research is needed to determine the actual intake of fluoride in U.S. children including that in the food and water supply as well as that ingested in swallowed toothpaste and dental rinses.[18]   More research is also needed on how and if fluoride affects brain development, its effect on the microbiome, and the oral health impact of stopping water fluoridation. [25]



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