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Water fluoridation
Water fluoridation
Water fluoridation
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Clear water pours from a spout into a drinking glass.
Fluoridation does not affect the appearance, taste or smell of drinking water.[1]

Water fluoridation is the controlled addition of fluoride to public water supplies to reduce tooth decay. Fluoridated water maintains fluoride levels effective for cavity prevention, achieved naturally or through supplementation.[2] In the mouth, fluoride slows tooth enamel demineralization and enhances remineralization in early-stage cavities.[3] Defluoridation is necessary when natural fluoride exceeds recommended limits.[4] The World Health Organization (WHO) recommends fluoride levels of 0.5–1.5 mg/L, depending on climate and other factors.[5] In the U.S., the recommended level has been 0.7 mg/L since 2015, lowered from 1.2 mg/L.[6][7] Bottled water often has unknown fluoride levels.[8]

Tooth decay affects 60–90% of schoolchildren worldwide.[9] Fluoridation reduces cavities in children, with Cochrane reviews estimating reductions of 35% in baby teeth and 26% in permanent teeth when no other fluoride sources are available, though efficacy in adults is less clear.[10][needs update] In Europe and other regions, declining decay rates are attributed to topical fluorides and alternatives like salt fluoridation and nano-hydroxyapatite.[3][11][12][13]

The United States was the first country to engage in water fluoridation, and 72% of its population drinks fluoridated water as of 2022.[14][15] Globally, 5.4% of people receive fluoridated water, though its use remains rare in Europe, except in Ireland and parts of Spain.[16] The WHO, FDI World Dental Federation, and Centers for Disease Control and Prevention endorse fluoridation as safe and effective at recommended levels.[17][18] Critics question its risks, efficacy, and ethical implications.[19][20][21]

Goal

[edit]
Molar viewed from the top, with a cavity in the central pit, and a small amount of blood in nearby fissures.
A cavity starts in a tooth's outer enamel and spreads to the dentin and pulp inside.

The goal of water fluoridation is to prevent tooth decay by adjusting the concentration of fluoride in public water supplies.[2] Tooth decay (dental caries) is one of the most prevalent chronic diseases worldwide.[22] Although it is rarely life-threatening, tooth decay can cause pain and impair eating, speaking, facial appearance, and acceptance into society,[23] and it greatly affects the quality of life of children, particularly those of low socioeconomic status.[22] In most industrialized countries, tooth decay affects 60–90% of schoolchildren and the vast majority of adults; although the problem appears to be less in Africa's developing countries, it is expected to increase in several countries there because of changing diet and inadequate fluoride exposure.[9] In the U.S., minorities and the poor both have higher rates of decayed and missing teeth,[24] and their children have less dental care.[25] Once a cavity occurs, the tooth's fate is that of repeated restorations, with estimates for the median life of an amalgam tooth filling ranging from 9 to 14 years.[26] Oral disease is the fourth most expensive disease to treat.[27] The motivation for fluoridation of salt or water is similar to that of iodized salt for the prevention of congenital hypothyroidism and goiter.[28]

The goal of water fluoridation is to prevent a chronic disease whose burdens particularly fall on children and the poor.[22] Another of the goals was to bridge inequalities in dental health and dental care.[29] Some studies suggest that fluoridation reduces oral health inequalities between the rich and poor, but the evidence is limited.[3] There is anecdotal but not scientific evidence that fluoride allows more time for dental treatment by slowing the progression of tooth decay, and that it simplifies treatment by causing most cavities to occur in pits and fissures of teeth.[30] Other reviews have found not enough evidence to determine if water fluoridation reduces oral-health social disparities.[10]

Health and dental organizations worldwide have endorsed its safety and effectiveness at recommended levels.[3] Its use began in 1945, following studies of children in a region where higher levels of fluoride occur naturally in the water.[31] Further research showed that moderate fluoridation prevents tooth decay.[32]

Implementation

[edit]
Large water pipes next to monitoring equipment.
Fluoride monitor (at left) in a community water tower pumphouse, Minnesota, 1987

Fluoridation does not affect the appearance, taste, or smell of drinking water.[1] It is normally accomplished by adding one of three compounds to the water: sodium fluoride, fluorosilicic acid, or sodium fluorosilicate.

  • Sodium fluoride (NaF) was the first compound used and is the reference standard.[33] It is a white, odorless powder or crystal; the crystalline form is preferred if manual handling is used, as it minimizes dust.[34] It is more expensive than the other compounds, but is easily handled and is usually used by smaller utility companies.[35] It is toxic in gram quantities by ingestion or inhalation.[36]
  • Fluorosilicic acid (H2SiF6) is the most commonly used additive for water fluoridation in the United States.[37] It is an inexpensive liquid by-product of phosphate fertilizer manufacture.[33] It comes in varying strengths, typically 23–25%; because it contains so much water, shipping can be expensive.[34] It is also known as hexafluorosilicic, hexafluosilicic, hydrofluosilicic, and silicofluoric acid.[33]
  • Sodium fluorosilicate (Na2SiF6) is the sodium salt of fluorosilicic acid. It is a powder or very fine crystal that is easier to ship than fluorosilicic acid. It is also known as sodium silicofluoride.[34]

These compounds were chosen for their solubility, safety, availability, and low cost.[33] A 1992 census found that, for U.S. public water supply systems reporting the type of compound used, 63% of the population received water fluoridated with fluorosilicic acid, 28% with sodium fluorosilicate, and 9% with sodium fluoride.[38]

Occurrences

[edit]
World map with several land areas highlighted, especially in China, India, east Africa, southwest U.S., and Argentina.
Geographical areas associated with groundwater having over 1.5 mg/L of naturally occurring fluoride, which is above recommended levels[11]
Southern Arizona map with a jumble of regions colored gray, white, and blues of various shades.
Detail of southern Arizona. Areas in darker blues have groundwater with over 2 mg/L of naturally occurring fluoride.

Fluoride naturally occurring in water can be above, at, or below recommended levels. Rivers and lakes generally contain fluoride levels less than 0.5 mg/L, but groundwater, particularly in volcanic or mountainous areas, can contain as much as 50 mg/L.[39] Higher concentrations of fluorine are found in alkaline volcanic, hydrothermal, sedimentary, and other rocks derived from highly evolved magmas and hydrothermal solutions, and this fluorine dissolves into nearby water as fluoride. In most drinking waters, over 95% of total fluoride is the F− ion, with the magnesium–fluoride complex (MgF+) being the next most common.[citation needed] Because fluoride levels in water are usually controlled by the solubility of fluorite (CaF2), high natural fluoride levels are associated with calcium-deficient, alkaline, and soft waters.[40]

Some bottled waters contain undeclared fluoride, which can be present naturally in source waters, or if water is sourced from a public supply which has been fluoridated.[41] The FDA states that bottled water products labeled as de-ionized, purified, demineralized, or distilled have been treated in such a way that they contain no or only trace amounts of fluoride, unless they specifically list fluoride as an added ingredient.[41]

Recommendations

[edit]

Target level

[edit]

Authorities such as the World Health Organization publish recommendations for the amount of fluoride in piped water. The lower bound is set to reduce the incidence of dental caries and the upper bound is set to prevent harms such dental fluorosis. Levels below this range can be increased by water fluoridation and levels above this range should be reduced using treatment technology. The WHO upper limit ("guideline value") of 1.5 mg/L has been repeatedly reaffirmed since 1984.[5]: 371  The WHO mentions that the upper limit may need to be reduced in setting some national standards to keep the consumption below 6 mg/day. This can happen in case of higher piped water consumption such as in warmer climates, or when other sources of fluoride (e.g. food, air and dental preparations) are present.[5]: 371  In 2011, the WHO reports that protection against dental caries begin at 0.5 mg/L[5]: 372  and that most fluoridation standards target a range of 0.5–1.0 mg/L. The WHO itself does not give a target for fluoridation.[5]: 370 

The European Food Safety Authority's Panel on Dietetic Products, Nutrition and Allergies (NDA) considers fluoride not to be an essential nutrient, yet, due to the beneficial effects of dietary fluoride on prevention of dental caries they have defined an Adequate Intake (AI) value[a] for it. The AI of fluoride from all sources (including non-dietary sources) is 0.05 mg/kg body weight per day for both children and adults, including pregnant and lactating women.[42] Applying the 60 kg adult assumption, this is equivalent to 3 mg/day. (This assumption is repeatedly used in the 2011 WHO report to derive limits for non-fluoride substances, with 74 total occurrences.)[5] The EFSA has an upper legal limit for fluoride content in water at 1.5 mg/L. In 2024 it prepared a draft for the tolerable upper intake levels (UL) for daily fluoride consumption in children.[43]

In 2011, the U.S. Department of Health and Human Services (HHS) and the U.S. Environmental Protection Agency (EPA) lowered the recommended level of fluoride to 0.7 mg/L.[6] In 2015, the U.S. Food and Drug Administration (FDA), based on the recommendation of the U.S. Public Health Service (PHS) for fluoridation of community water systems, recommended that bottled water manufacturers limit fluoride in bottled water to no more than 0.7 milligrams per liter (mg/L; equivalent to parts per million).[44]

A 2007 Australian systematic review recommended a range from 0.6 to 1.1 mg/L.[11]

Historical USA recommendations
[edit]

Pre-2011 US recommendations were based on evaluations from 1962, when the U.S. specified the optimal level of fluoride in water to range from 0.7 to 1.2 mg/L, depending on the average maximum daily air temperature; the optimal level is lower in warmer climates, where people drink more water, and is higher in cooler climates.[45]

Between 1974 and 1989, fluoride was listed as an essential nutrient by the U.S. National Research Council. In 1989, it removed this designation due to the lack of studies showing it is essential for human growth, though still considering fluoride a "beneficial element" due to its positive impact on oral health. Studies in the late 1980s and the early 1990s indicate that childhood fluoride intake is around 0.05 mg/kg body weight per day when fluoridated and 0.03 mg/kg/day when not.[46]

Methods to reach target level

[edit]

In the United States, the Centers for Disease Control and Prevention developed recommendations for water fluoridation that specify requirements for personnel, reporting, training, inspection, monitoring, surveillance, and actions in case of overfeed, along with technical requirements for each major compound used.[47]

The WHO recommends reaching the adequate level of fluoride intake through fluoridation of low fluoride water (or of milk or salt) as well as topical fluoride preparations including fluoridated toothpastes, silver diamine fluoride varnish, and glass ionomer cement. The WHO also recommends that excess intake be avoided by switching to an alternative water source if possible, or through defluoridating techniques.[48]

Defluoridation is needed when the naturally occurring fluoride level exceeds recommended limits. It can be accomplished by percolating water through granular beds of activated alumina, bone meal, bone char, or tricalcium phosphate; by coagulation with alum; or by precipitation with lime.[4] Clay can also be used for defluoridation, but one must first ensure it contains no toxic chemicals or other pollutants.[48]

Pitcher or faucet-mounted water filters do not alter fluoride content; the more-expensive reverse osmosis filters remove 65–95% of fluoride, and distillation removes all fluoride.[8]

Evidence

[edit]

Existing evidence suggests that water fluoridation reduces tooth decay. Consistent evidence also suggests that it can cause dental fluorosis, most of which is mild and not usually of aesthetic concern.[10][11] No clear evidence of other adverse effects exists, though almost all research thereof has been of poor quality.[49]

Effectiveness

[edit]

Reviews have shown that water fluoridation reduces cavities in children.[10][50][51] A conclusion for the efficacy in adults is less clear with some reviews finding benefit and others not.[10][51] Studies in the U.S. in the 1950s and 1960s showed that water fluoridation reduced childhood cavities by fifty to sixty percent, while studies in 1989 and 1990 showed lower reductions (40% and 18% respectively), likely due to increasing use of fluoride from other sources, notably toothpaste, and also the 'halo effect' of food and drink that is made in fluoridated areas and consumed in unfluoridated ones.[2]

A 2000 UK systematic review (York) found that water fluoridation was associated with a decreased proportion of children with cavities of 15% and with a decrease in decayed, missing, and filled primary teeth (average decreases was 2.25 teeth). The review found that the evidence was of moderate quality: few studies attempted to reduce observer bias, control for confounding factors, report variance measures, or use appropriate analysis. Although no major differences between natural and artificial fluoridation were apparent, the evidence was inadequate for a conclusion about any differences.[49] A 2007 Australian systematic review used the same inclusion criteria as York's, plus one additional study. This did not affect the York conclusions.[52] A 2011 European Commission systematic review based its efficacy on York's review conclusion.[19] A 2015 Cochrane systematic review estimated a reduction in cavities when water fluoridation was used by children who had no access to other sources of fluoride to be 35% in baby teeth and 26% in permanent teeth.[10] The evidence was of poor quality.[10] A 2020 study in the Journal of Political Economy found that water fluoridation significantly improved dental health and labor market outcomes, but had non-significant effects on cognitive ability.[53]

Fluoride may also prevent cavities in adults of all ages. A 2007 meta-analysis by CDC researchers found that water fluoridation prevented an estimated 27% of cavities in adults, about the same fraction as prevented by exposure to any delivery method of fluoride (29% average).[54] A 2011 European Commission review found that the benefits of water fluoridation for adult in terms of reductions in decay are limited.[50] A 2015 Cochrane review found no conclusive research regarding the effectiveness of water fluoridation in adults.[10] A 2016 review found variable quality evidence that, overall, stopping of community water fluoridation programs was typically followed by an increase in cavities.[55]

Most countries in Europe have experienced substantial declines in cavities without the use of water fluoridation due to the introduction of fluoridated toothpaste and the large use of other fluoride-containing products, including mouthrinse, dietary supplements, and professionally applied or prescribed gel, foam, or varnish.[3] For example, in Finland and Germany, tooth decay rates remained stable or continued to decline after water fluoridation stopped in communities with widespread fluoride exposure from other sources. Fluoridation is however still clearly necessary in the U.S. because unlike most European countries, the U.S. does not have school-based dental care, many children do not visit a dentist regularly, and for many U.S. children water fluoridation is the primary source of exposure to fluoride.[29] The effectiveness of water fluoridation can vary according to circumstances such as whether preventive dental care is free to all children.[56]

Fluorosis

[edit]
Closeup of a smiling mouth with teeth showing minor white streaks on one tooth.
A mild case of dental fluorosis, visible as white streaks on the subject's upper right central incisor

Fluoride's adverse effects depend on total fluoride dosage from all sources. At the commonly recommended dosage, the only clear adverse effect is dental fluorosis, which can alter the appearance of children's teeth during tooth development; this is mostly mild and is unlikely to represent any real effect on aesthetic appearance or on public health.[11] In April 2015, recommended fluoride levels in the United States were changed to 0.7 ppm from 0.7–1.2 ppm to reduce the risk of dental fluorosis.[57] The 2015 Cochrane review estimated that for a fluoride level of 0.7 ppm the percentage of participants with fluorosis of aesthetic concern was approximately 12%.[10] This increases to 40% when considering fluorosis of any level not of aesthetic concern.[10] In the US mild or very mild dental fluorosis has been reported in 20% of the population, moderate fluorosis in 2% and severe fluorosis in less than 1%.[57]

The critical period of exposure is between ages one and four years, with the risk ending around age eight. Fluorosis can be prevented by monitoring all sources of fluoride, with fluoridated water directly or indirectly responsible for an estimated 40% of risk and other sources, notably toothpaste, responsible for the remaining 60%.[58] Compared to water naturally fluoridated at 0.4 mg/L, fluoridation to 1 mg/L is estimated to cause additional fluorosis in one of every 6 people (95% CI 4–21 people), and to cause additional fluorosis of aesthetic concern in one of every 22 people (95% CI 13.6–∞ people). Here, aesthetic concern is a term used in a standardized scale based on what adolescents would find unacceptable, as measured by a 1996 study of British 14-year-olds.[49] In many industrialized countries the prevalence of fluorosis is increasing even in unfluoridated communities, mostly because of fluoride from swallowed toothpaste.[59] A 2009 systematic review indicated that fluorosis is associated with consumption of infant formula or of water added to reconstitute the formula, that the evidence was distorted by publication bias, and that the evidence that the formula's fluoride caused the fluorosis was weak.[60] In the U.S. the decline in tooth decay was accompanied by increased fluorosis in both fluoridated and unfluoridated communities; accordingly, fluoride has been reduced in various ways worldwide in infant formulas, children's toothpaste, water, and fluoride-supplement schedules.[30]

Safety

[edit]

Fluoridation has little effect on risk of bone fracture (broken bones); it may result in slightly lower fracture risk than either excessively high levels of fluoridation or no fluoridation.[11]

There is no clear association between water fluoridation and cancer or deaths due to cancer, both for cancer in general and also specifically for bone cancer and osteosarcoma.[61] Series of research concluded that concentration of fluoride in water does not associate with osteosarcoma. The beliefs regarding association of fluoride exposure and osteosarcoma stem from a study from the NTP in 1990, which showed uncertain evidence of association of fluoride and osteosarcoma in male rats. But there is still no solid evidence of cancer-causing tendency of fluoride in mice.[62] Fluoridation of water has been practiced around the world to improve citizens' dental health. It is also deemed as major health success.[63] Fluoride concentration levels in water supplies are regulated, such as United States Environmental Protection Agency regulates fluoride levels to not be greater than 4 milligrams per liter.[64] Actually, water supplies already have natural occurring fluoride, but many communities chose to add more fluoride to the point that it can reduce tooth decay.[65] Fluoride is also known for its ability to cause new bone formation.[66] Yet, further research shows no osteosarcoma risks from fluoridated water in humans.[67] Most of the research involved counting number of osteosarcoma patients cases in particular areas which has difference concentrations of fluoride in drinking water.[68] The statistic analysis of the data shows no significant difference in occurrences of osteosarcoma cases in different fluoridated regions.[69] Another important research involved collecting bone samples from osteosarcoma patients to measure fluoride concentration and compare them to bone samples of newly diagnosed malignant bone tumors. The result is that the median fluoride concentrations in bone samples of osteosarcoma patients and tumor controls are not significantly different.[70] Fluoride exposures of osteosarcoma patients are also proven to be not significantly different from healthy people.[71] More recent studies have disputed any relationship to consumption of fluoridated drinking water during childhood.[72]

Fluoride can occur naturally in water in concentrations well above recommended levels, which can have several long-term adverse effects, including severe dental fluorosis, skeletal fluorosis, and weakened bones; water utilities in the developed world reduce fluoride levels to regulated maximum levels in regions where natural levels are high, and the WHO and other groups work with countries and regions in the developing world with naturally excessive fluoride levels to achieve safe levels.[73] The World Health Organization recommends a guideline maximum fluoride value of 1.5 mg/L as a level at which fluorosis should be minimal.[74]

In rare cases improper implementation of water fluoridation can result in overfluoridation that causes outbreaks of acute fluoride poisoning, with symptoms that include nausea, vomiting, and diarrhea. Three such outbreaks were reported in the U.S. between 1991 and 1998, caused by fluoride concentrations as high as 220 mg/L; in the 1992 Alaska outbreak, 262 people became ill and one person died.[75] In 2010, approximately 60 gallons of fluoride were released into the water supply in Asheboro, North Carolina in 90 minutes—an amount that was intended to be released in a 24-hour period.[76]

Like other common water additives such as chlorine, hydrofluosilicic acid and sodium silicofluoride decrease pH and cause a small increase of corrosivity, but this problem is easily addressed by increasing the pH.[77] Although it has been hypothesized that hydrofluosilicic acid and sodium silicofluoride might increase human lead uptake from water, a 2006 statistical analysis did not support concerns that these chemicals cause higher blood lead concentrations in children.[78] Trace levels of arsenic and lead may be present in fluoride compounds added to water, but no credible evidence exists that their presence is of concern: concentrations are below measurement limits.[77]

The effect of water fluoridation on the natural environment has been investigated, and although some claim that no adverse effects have been established, other items find evidence of harm or of concern. Issues studied have included fluoride concentrations in groundwater and downstream rivers; lawns, gardens, and plants; consumption of plants grown in fluoridated water; air emissions; and equipment noise.[77] [79] [80]

Mechanism

[edit]

Fluoride exerts its major effect by interfering with the demineralization mechanism of tooth decay. Tooth decay is an infectious disease, the key feature of which is an increase within dental plaque of bacteria such as Streptococcus mutans and Lactobacillus. These produce organic acids when carbohydrates, especially sugar, are eaten.[81] When enough acid is produced to lower the pH below 5.5,[82] the acid dissolves carbonated hydroxyapatite, the main component of tooth enamel, in a process known as demineralization. After the sugar is gone, some of the mineral loss can be recovered—or remineralized—from ions dissolved in the saliva. Cavities result when the rate of demineralization exceeds the rate of remineralization, typically in a process that requires many months or years.[81]

Carbonated hydroxyapatite enamel crystal is demineralized by acid in plaque and becomes partly dissolved crystal. This in turn is remineralized by fluoride in plaque to become fluorapatite-like coating on remineralized crystal
Demineralization and remineralization of dental enamel in the presence of acid and fluoride in saliva and plaque fluid[81]

All fluoridation methods, including water fluoridation, create low levels of fluoride ions in saliva and plaque fluid, thus exerting a topical or surface effect. A person living in an area with fluoridated water may experience rises of fluoride concentration in saliva to about 0.04 mg/L several times during a day.[3] Technically, this fluoride does not prevent cavities but rather controls the rate at which they develop.[83] When fluoride ions are present in plaque fluid along with dissolved hydroxyapatite, and the pH is higher than 4.5,[82] a fluorapatite-like remineralized veneer is formed over the remaining surface of the enamel; this veneer is much more acid-resistant than the original hydroxyapatite, and is formed more quickly than ordinary remineralized enamel would be.[81] The cavity-prevention effect of fluoride is mostly due to these surface effects, which occur during and after tooth eruption.[84] Although some systemic (whole-body) fluoride returns to the saliva via blood plasma, and to unerupted teeth via plasma or crypt fluid, there is little data to determine what percentages of fluoride's anticavity effect comes from these systemic mechanisms.[85] Also, although fluoride affects the physiology of dental bacteria,[86] its effect on bacterial growth does not seem to be relevant to cavity prevention.[87]

Fluoride's effects depend on the total daily intake of fluoride from all sources.[39] About 70–90% of ingested fluoride is absorbed into the blood, where it distributes throughout the body. In infants 80–90% of absorbed fluoride is retained, with the rest excreted, mostly via urine; in adults about 60% is retained. About 99% of retained fluoride is stored in bone, teeth, and other calcium-rich areas, where excess quantities can cause fluorosis.[73] Drinking water is typically the largest source of fluoride.[39] In many industrialized countries swallowed toothpaste is the main source of fluoride exposure in unfluoridated communities.[59] Other sources include dental products other than toothpaste; air pollution from fluoride-containing coal or from phosphate fertilizers; trona, used to tenderize meat in Tanzania; and tea leaves, particularly the tea bricks favored in parts of China. High fluoride levels have been found in other foods, including barley, cassava, corn, rice, taro, yams, and fish protein concentrate. The U.S. Institute of Medicine has established Dietary Reference Intakes for fluoride: Adequate Intake values range from 0.01 mg/day for infants aged 6 months or less, to 4 mg/day for men aged 19 years and up; and the Tolerable Upper Intake Level is 0.10 mg/kg/day for infants and children through age 8 years, and 10 mg/day thereafter.[88] A rough estimate is that an adult in a temperate climate consumes 0.6 mg/day of fluoride without fluoridation, and 2 mg/day with fluoridation. However, these values differ greatly among the world's regions: for example, in Sichuan, China the average daily fluoride intake is only 0.1 mg/day in drinking water but 8.9 mg/day in food and 0.7 mg/day directly from the air due to the use of high-fluoride soft coal for cooking and drying foodstuffs indoors.[39]

Alternatives

[edit]
A tube applying toothpaste to a toothbrush.
Fluoride toothpaste is effective against cavities. It is widely used, but less so among the poor.[89]
Fluoridated iodized salt sold in Germany

The views on the most effective method for community prevention of tooth decay are mixed. The Australian government review states that water fluoridation is the most effective means of achieving fluoride exposure that is community-wide.[11] The European Commission review states "No obvious advantage appears in favour of water fluoridation compared with topical prevention".[50] Other fluoride therapies are also effective in preventing tooth decay;[22] they include fluoride toothpaste, mouthwash, gel, and varnish,[90] and fluoridation of salt and milk.[89] Dental sealants are effective as well,[22] with estimates of prevented cavities ranging from 33% to 86%, depending on age of sealant and type of study.[90]

Fluoride toothpaste is the most widely used and rigorously evaluated fluoride treatment.[89] Its introduction is considered the main reason for the decline in tooth decay in industrialized countries,[3] and toothpaste appears to be the single common factor in countries where tooth decay has declined.[91] Toothpaste is the only realistic fluoride strategy in many low-income countries, where lack of infrastructure renders water or salt fluoridation infeasible.[92] It relies on individual and family behavior, and its use is less likely among lower economic classes;[89] in low-income countries it is unaffordable for the poor.[92] Fluoride toothpaste prevents about 25% of cavities in young permanent teeth, and its effectiveness is improved if higher concentrations of fluoride are used, or if the toothbrushing is supervised. Fluoride mouthwash and gel are about as effective as fluoride toothpaste; fluoride varnish prevents about 45% of cavities.[90] By comparison, brushing with a nonfluoride toothpaste has little effect on cavities.[59]

The effectiveness of salt fluoridation is about the same as that of water fluoridation, if most salt for human consumption is fluoridated. Fluoridated salt reaches the consumer in salt at home, in meals at school and at large kitchens, and in bread. For example, Jamaica has just one salt producer, but a complex public water supply; it started fluoridating all salt in 1987, achieving a decline in cavities. Universal salt fluoridation is also practiced in Colombia and the Swiss Canton of Vaud; in Germany fluoridated salt is widely used in households but unfluoridated salt is also available, giving consumers a choice. Concentrations of fluoride in salt range from 90 to 350 mg/kg, with studies suggesting an optimal concentration of around 250 mg/kg.[89]

Milk fluoridation is practiced by the Borrow Foundation in some parts of Bulgaria, Chile, Peru, Russia, Macedonia, Thailand and the UK. Depending on location, the fluoride is added to milk, to powdered milk, or to yogurt. For example, milk powder fluoridation is used in rural Chilean areas where water fluoridation is not technically feasible.[93] These programs are aimed at children, and have neither targeted nor been evaluated for adults.[89] A systematic review found low-quality evidence to support the practice, but also concluded that further studies were needed.[94]

Other public-health strategies to control tooth decay, such as education to change behavior and diet, have lacked impressive results.[30] Although fluoride is the only well-documented agent which controls the rate at which cavities develop, it has been suggested that adding calcium to the water would reduce cavities further.[95] Other agents to prevent tooth decay include antibacterials such as chlorhexidine and sugar substitutes such as xylitol.[90] Xylitol-sweetened chewing gum has been recommended as a supplement to fluoride and other conventional treatments if the gum is not too costly.[96] Two proposed approaches, bacteria replacement therapy (probiotics) and caries vaccine, would share water fluoridation's advantage of requiring only minimal patient compliance, but have not been proven safe and effective.[90] Other experimental approaches include fluoridated sugar, polyphenols, and casein phosphopeptide–amorphous calcium phosphate nanocomplexes.[97]

A 2007 Australian review concluded that water fluoridation is the most effective and socially the most equitable way to expose entire communities to fluoride's cavity-prevention effects.[11] A 2002 U.S. review estimated that sealants decreased cavities by about 60% overall, compared to about 18–50% for fluoride.[98] A 2007 Italian review suggested that water fluoridation may not be needed, particularly in the industrialized countries where cavities have become rare, and concluded that toothpaste and other topical fluoride are the best way to prevent cavities worldwide.[3] A 2004 World Health Organization review stated that water fluoridation, when it is culturally acceptable and technically feasible, has substantial advantages in preventing tooth decay, especially for subgroups at high risk.[9]

Worldwide prevalence

[edit]
Main article: Water fluoridation by country
World map showing countries in gray, white and in various shades of red. The U.S. and Australia stand out as bright red (which the caption identifies as the 60–80% color). Brazil and Canada are medium pink (40–60%). China, much of western Europe, and central Africa are light pink (1–20%). Germany, Japan, Nigeria, and Venezuela are white (<1%).
Percentage of population receiving fluoridated water, including both artificial and natural fluoridation, as of 2012:[14]
  80–100%
  60–80%
  40–60%
  20–40%
  1–20%
  < 1%
  unknown

As of November 2012, a total of about 378 million people worldwide received artificially fluoridated water. The majority of those were in the United States. About 40 million worldwide received water that was naturally fluoridated to recommended levels.[14]

Much of the early work on establishing the connection between fluoride and dental health was performed by scientists in the U.S. during the early 20th century, and the U.S. was the first country to implement public water fluoridation on a wide scale.[99] It has been introduced to varying degrees in many countries and territories outside the U.S., including Argentina, Australia, Brazil, Canada, Chile, Colombia, Hong Kong, Ireland, Israel, Korea, Malaysia, New Zealand, the Philippines, Serbia, Singapore, Spain, the UK, and Vietnam. In 2004, an estimated 13.7 million people in western Europe and 194 million in the U.S. received artificially fluoridated water.[14] In 2010, about 66% of the U.S. population was receiving fluoridated water.[100]

Naturally fluoridated water is used by approximately 4% of the world's population, in countries including Argentina, France, Gabon, Libya, Mexico, Senegal, Sri Lanka, Tanzania, the U.S., and Zimbabwe. In some locations, notably parts of Africa, China, and India, natural fluoridation exceeds recommended levels.[14]

Communities have discontinued water fluoridation in some countries, including Finland, Germany, Japan, the Netherlands, and Switzerland.[101] Changes have been motivated by political opposition to water fluoridation, but sometimes the need for water fluoridation was met by alternative strategies. The use of fluoride in its various forms is the foundation of tooth decay prevention throughout Europe; several countries have introduced fluoridated salt, with varying success: in Switzerland and Germany, fluoridated salt represents 65% to 70% of the domestic market, while in France the market share reached 60% in 1993 but dwindled to 14% in 2009; Spain, in 1986 the second West European country to introduce fluoridation of table salt, reported a market share in 2006 of only 10%. In three other West European countries, Greece, Austria and the Netherlands, the legal framework for production and marketing of fluoridated edible salt exists. At least six Central European countries (Hungary, Czechia, Slovakia, Croatia, Slovenia, Romania) have shown some interest in salt fluoridation; however, significant usage of approximately 35% was only achieved in the Czech Republic. The Slovak Republic had the equipment to treat salt by 2005; in the other four countries attempts to introduce fluoridated salt were not successful.[102][103] Additionally, concerns regarding potential overexposure to fluoride and the varying effectiveness of fluoridation methods have led some countries to reassess their approaches. Recent evaluations highlight a preference for topical fluoride applications, which are considered more effective and safer, especially given the limited systemic benefits of fluoridation beyond early childhood.[16] When Israel implemented the 2014 Dental Health Promotion Program, that includes education, medical followup and the use of fluoride-containing products and supplements, it evaluated that mandatory water fluoridation was no longer necessary, stating "supply of fluoridated water forces those who do not so wish to also consume water with added fluoride. This approach is therefore not accepted in most countries in the world.".[104]

History

[edit]
See also: History of water supply and sanitation
Faded, grainy image of three men in the outdoors, holding up a boy. The man on the left has a short white beard and mustache, a hat, and a three-piece suit.
1909 photograph by Frederick McKay of G.V. Black (left), Isaac Burton and F.Y. Wilson, studying the Colorado brown stain[105]

The history of water fluoridation can be divided into three periods. The first (c. 1801–1933) was research into the cause of a form of mottled tooth enamel called the Colorado brown stain. The second (c. 1933–1945) focused on the relationship between fluoride concentrations, fluorosis, and tooth decay, and established that moderate levels of fluoride prevent cavities. The third period, from 1945 on, focused on adding fluoride to community water supplies.[32]

In the first half of the 19th century, investigators established that fluoride occurs with varying concentrations in teeth, bone, and drinking water. In the second half they speculated that fluoride would protect against tooth decay, proposed supplementing the diet with fluoride, and observed mottled enamel (now called severe dental fluorosis) without knowing the cause.[106] In 1874, the German public health officer Carl Wilhelm Eugen Erhardt recommended potassium fluoride supplements to preserve teeth.[107][108] In 1892, the British physician James Crichton-Browne suggested that the shift to refined flour, which reduced the consumption of grain husks and stems, led to fluorine's absence from diets and teeth that were "peculiarly liable to decay". He proposed "the reintroduction into our diet ... of fluorine in some suitable natural form ... to fortify the teeth of the next generation".[109]

The foundation of water fluoridation in the U.S. was the research of the dentist Frederick McKay (1874–1959). McKay spent thirty years investigating the cause of what was then known as the Colorado brown stain, which produced mottled but also cavity-free teeth; with the help of G.V. Black and other researchers, he established that the cause was fluoride.[110] The first report of a statistical association between the stain and lack of tooth decay was made by UK dentist Norman Ainsworth in 1925. In 1931, an Alcoa chemist, H.V. Churchill, concerned about a possible link between aluminum and staining, analyzed water from several areas where the staining was common and found that fluoride was the common factor.[111]

Head and shoulder of a 60-ish man with a flattop haircut and in a coat and tie, looking directly at camera with head tilted to his right and a slight smile.
H. Trendley Dean set out in 1931 to study fluoride's harm, but by 1950 had demonstrated the cavity-prevention effects of small amounts.[112]

In the 1930s and early 1940s, H. Trendley Dean and colleagues at the newly created U.S. National Institutes of Health published several epidemiological studies suggesting that a fluoride concentration of about 1 mg/L was associated with substantially fewer cavities in temperate climates, and that it increased fluorosis but only to a level that was of no medical or aesthetic concern.[113] Other studies found no other significant adverse effects even in areas with fluoride levels as high as 8 mg/L.[114] To test the hypothesis that adding fluoride would prevent cavities, Dean and his colleagues conducted a controlled experiment by fluoridating the water in Grand Rapids, Michigan, starting 25 January 1945. The results, published in 1950, showed significant reduction of cavities.[31][115] Significant reductions in tooth decay were also reported by important early studies outside the U.S., including the Brantford–Sarnia–Stratford study in Canada (1945–1962), the Tiel–Culemborg study in the Netherlands (1953–1969), the Hastings study in New Zealand (1954–1970), and the Department of Health study in the U.K. (1955–1960).[111] By present-day standards these and other pioneering studies were crude, but the large reductions in cavities convinced public health professionals of the benefits of fluoridation.[29]

Fluoridation became an official policy of the U.S. Public Health Service by 1951, and by 1960 water fluoridation had become widely used in the U.S., reaching about 50 million people.[114] By 2006, 69.2% of the U.S. population on public water systems were receiving fluoridated water, amounting to 61.5% of the total U.S. population; 3.0% of the population on public water systems were receiving naturally occurring fluoride.[116] In some other countries the pattern was similar. New Zealand, which led the world in per-capita sugar consumption and had the world's worst teeth, began fluoridation in 1953, and by 1968 fluoridation was used by 65% of the population served by a piped water supply.[117] Fluoridation was introduced into Brazil in 1953, was regulated by federal law starting in 1974, and by 2004 was used by 71% of the population.[118] In the Republic of Ireland, fluoridation was legislated in 1960, and after a constitutional challenge the two major cities of Dublin and Cork began it in 1964;[111] fluoridation became required for all sizeable public water systems and by 1996 reached 66% of the population.[14] In other locations, fluoridation was used and then discontinued: in Kuopio, Finland, fluoridation was used for decades but was discontinued because the school dental service provided significant fluoride programs and the cavity risk was low, and in Basel, Switzerland, it was replaced with fluoridated salt.[111]

McKay's work had established that fluorosis occurred before tooth eruption. Dean and his colleagues assumed that fluoride's protection against cavities was also pre-eruptive, and this incorrect assumption was accepted for years. By 2000, however, the topical effects of fluoride (in both water and toothpaste) were well understood, and it had become known that a constant low level of fluoride in the mouth works best to prevent cavities.[119]

Economics

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Fluoridation costs an estimated $1.36 per person-year on the average (range: $0.32–$14.38; all costs in this paragraph are for the U.S.[2] and are in 2024 dollars, inflation-adjusted from earlier estimates[120]). Larger water systems have lower per capita cost, and the cost is also affected by the number of fluoride injection points in the water system, the type of feeder and monitoring equipment, the fluoride chemical and its transportation and storage, and water plant personnel expertise.[2] In affluent countries the cost of salt fluoridation is also negligible; developing countries may find it prohibitively expensive to import the fluoride additive.[121] By comparison, fluoride toothpaste costs an estimated $11–$23 per person-year, with the incremental cost being zero for people who already brush their teeth for other reasons; and dental cleaning and application of fluoride varnish or gel costs an estimated $125 per person-year. Assuming the worst case, with the lowest estimated effectiveness and highest estimated operating costs for small cities, fluoridation costs an estimated $21–$32 per saved tooth-decay surface, which is lower than the estimated $123 to restore the surface[2] and the estimated $208 average discounted lifetime cost of the decayed surface, which includes the cost to maintain the restored tooth surface.[26] It is not known how much is spent in industrial countries to treat dental fluorosis, which is mostly due to fluoride from swallowed toothpaste.[59]

Although a 1989 workshop on cost-effectiveness of cavity prevention concluded that water fluoridation is one of the few public health measures that save more money than they cost, little high-quality research has been done on the cost-effectiveness and solid data are scarce.[2][45] Dental sealants are cost-effective only when applied to high-risk children and teeth.[122] A 2002 U.S. review estimated that on average, sealing first permanent molars saves costs when they are decaying faster than 0.47 surfaces per person-year whereas water fluoridation saves costs when total decay incidence exceeds 0.06 surfaces per person-year.[98] In the U.S., water fluoridation is more cost-effective than other methods to reduce tooth decay in children, and a 2008 review concluded that water fluoridation is the best tool for combating cavities in many countries, particularly among socially disadvantaged groups.[30] A 2016 review of studies published between 1995 and 2013 found that water fluoridation in the U.S. was cost-effective, and that it was more so in larger communities.[123]

U.S. data from 1974 to 1992 indicate that when water fluoridation is introduced into a community, there are significant decreases in the number of employees per dental firm and the number of dental firms. The data suggest that some dentists respond to the demand shock by moving to non-fluoridated areas and by retraining as specialists.[124]

Controversy

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Main article: Opposition to water fluoridation

The water fluoridation controversy arises from political, moral, ethical, economic, and safety concerns regarding the water fluoridation of public water supplies.[101][125] For impoverished groups in both developing and developed countries, international and national agencies and dental associations across the world support the safety and effectiveness of water fluoridation.[3] Authorities' views on the most effective fluoride therapy for community prevention of tooth decay are mixed; some state water fluoridation is most effective, while others see no special advantage and prefer topical application strategies.[11][50]

Those opposed argue that water fluoridation has no or little cariostatic benefits, may cause serious health problems, is not effective enough to justify the costs, is pharmacologically obsolete,[2][126][127][128] and presents a moral conflict between the common good and individual rights.[129]

See also

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Notes

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Water fluoridation

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Water fluoridation is the deliberate adjustment of fluoride concentration in public drinking water supplies, typically to around 0.7 milligrams per liter, by adding compounds such as hexafluorosilicic acid to reduce the incidence of dental caries through mechanisms including enamel remineralization and bacterial inhibition. The practice originated in the United States in 1945, following epidemiological observations of lower caries rates in areas with naturally fluoridated water, and has since been implemented unevenly globally, with approximately 63% of Americans on community water systems receiving fluoridated water in 2022, while most European countries rely instead on alternative fluoride delivery methods like toothpaste. Proponents cite systematic reviews showing modest caries reductions, such as a slight decrease in decayed, missing, or filled teeth in children, though these effects are smaller in contemporary settings amid pervasive topical fluoride exposures from dentifrices. Opposition highlights risks including cosmetic dental fluorosis from overexposure and potential neurodevelopmental effects, with a 2024 National Toxicology Program monograph concluding moderate confidence in an association between fluoride levels exceeding 1.5 mg/L in drinking water and 2-5 point IQ decrements in children, alongside ethical critiques of non-voluntary mass medication infringing on informed consent and bodily autonomy.

Definition and Purpose

Overview of Water Fluoridation

Water fluoridation is the controlled adjustment of fluoride ion concentration in public drinking water supplies to an optimal level of 0.7 milligrams per liter (mg/L) for the purpose of reducing the incidence of dental caries. This process typically involves the addition of fluoride compounds such as fluorosilicic acid, sodium fluoride, or sodium fluorosilicate to municipal water systems where naturally occurring fluoride is below the target concentration. Fluoride levels are continuously monitored and adjusted to maintain the recommended range, accounting for variations in water consumption and other dietary fluoride sources. The practice originated from epidemiological observations in the early 20th century of mottled enamel (dental fluorosis) alongside reduced tooth decay in communities with naturally high fluoride in groundwater, such as in Colorado Springs, leading to controlled trials. The first community-wide implementation occurred in , on January 25, 1945, marking the inception of artificial fluoridation as a public health measure. In the United States, approximately 73% of individuals served by public water systems—nearly 210 million people—receive fluoridated water as of 2025. Globally, water fluoridation reaches over 370 million people across roughly 25 countries, with highest coverage in nations like the United States and Australia, where 60-80% of the population benefits, compared to minimal adoption in Europe and Asia. Proponents cite decades of data showing 25-40% reductions in caries prevalence, though efficacy varies with total fluoride exposure from toothpaste and other sources, and debates persist over risks like fluorosis at higher concentrations.

Intended Public Health Goals

The primary intended public health goal of water fluoridation is to prevent dental caries by adjusting fluoride concentrations in public water supplies to optimal levels, typically 0.7 milligrams per liter as recommended by the U.S. Public Health Service since 2015. This adjustment aims to deliver low-dose fluoride exposure to the population, promoting enamel remineralization and reducing demineralization from bacterial acids, thereby decreasing cavity incidence across all age groups. Public health authorities, including the Centers for Disease Control and Prevention, position fluoridation as a community-wide intervention to improve oral health equity, particularly for children and underserved populations with limited access to dental services or fluoridated products. Fluoridation seeks to achieve these outcomes cost-effectively, with proponents estimating reductions in tooth decay by 20 to 40 percent and associated savings from fewer dental treatments. The approach targets systemic fluoride benefits during tooth development in children while providing ongoing protection for adults, independent of individual behaviors like brushing. The World Health Organization endorses maintaining fluoride levels sufficient for caries prevention while avoiding excess that could lead to dental fluorosis, aligning with global guidelines for safe drinking water quality.

Historical Development

Early Observations and Natural Fluoride

In 1901, dentist Frederick McKay established a practice in , where he observed an endemic condition of permanent brown staining and mottling on the enamel of teeth among native residents, particularly children born and raised locally. This "Colorado brown stain" affected up to 90% of native children, presenting as chalky white areas progressing to brown discoloration, yet these teeth exhibited remarkable resistance to dental caries compared to unaffected teeth. McKay documented similar mottling in other regions with distinct water sources, such as , and parts of , hypothesizing a factor in the local drinking water as the cause after ruling out local habits or diet. McKay collaborated with dental pathologist G.V. Black in 1909, confirming the enamel defects were hypoplastic but noting the caries immunity, which prompted further investigation into water composition. Chemical analyses in the 1920s by McKay and others, including H.V. Churchill, identified elevated fluoride concentrations—around 12 parts per million (ppm) in Colorado Springs water—as the culprit, linking high natural fluoride from geological sources in groundwater to the mottling. These findings established that naturally occurring fluoride in water, derived from minerals in soil and rocks, could induce dental fluorosis at excessive levels while potentially conferring protection against decay at lower concentrations. In 1931, H. Trendley Dean of the U.S. Public Health Service began systematic epidemiological studies on fluorosis, surveying over 7,000 children across 25 U.S. cities to correlate water fluoride levels with enamel mottling severity, developing the Dean's fluorosis index. Dean's research in the 1930s confirmed that fluoride thresholds above 1.5–2.0 ppm caused mild to severe fluorosis, but levels around 1.0 ppm yielded substantial caries reductions—up to 60% in some studies—without significant cosmetic damage. By mapping endemic fluorosis areas, Dean demonstrated an inverse relationship between natural fluoride exposure and caries prevalence, providing the foundational evidence for controlled fluoride's dental benefits from natural sources.

Pioneering Trials and Adoption

In the early 20th century, dentists Frederick McKay and G.V. Black investigated endemic brown staining on teeth in Colorado Springs residents, later identified as dental fluorosis linked to high natural fluoride levels in local water supplies exceeding 2 parts per million (ppm). McKay observed that affected individuals exhibited unusually low rates of tooth decay despite the cosmetic discoloration. H. Trendley Dean, a U.S. Public Health Service epidemiologist, expanded this research in the 1930s by surveying 21 U.S. cities and correlating fluoride concentrations in water with enamel mottling and caries prevalence. Dean established that fluoride levels around 1 ppm prevented mottling while inversely associating with caries rates, proposing this as an optimal concentration for public water supplies. The first controlled community trial commenced on January 25, 1945, in , where sodium fluoride was added to achieve 1 ppm, with Muskegon serving as a non-fluoridated control; preliminary five-year data in 1950 indicated significant caries reductions in children. Concurrently, , initiated fluoridation in May 1945 against Kingston as control, yielding a 30% drop in child caries after five years by the early 1950s. These trials, sponsored by the U.S. Public Health Service, demonstrated caries reductions of 50-60% in primary teeth and 40% in permanent teeth after 10-15 years, prompting endorsements from health authorities. Adoption accelerated post-1950, with , and Brantford, Ontario, following suit; by 1960, over 50 million Americans received fluoridated water, driven by empirical trial outcomes despite emerging public debates.

Expansion and Policy Milestones

Following endorsements from key health authorities, community water fluoridation expanded from demonstration projects to widespread adoption in the United States during the mid-20th century. In 1950, the American Dental Association, United States Public Health Service, and U.S. Surgeon General endorsed the practice based on early trial data showing reduced caries rates without significant adverse effects. This spurred implementation in additional municipalities, serving 1.5 million Americans by that year. The 1950s marked accelerated growth, with the U.S. Public Health Service formalizing fluoridation as policy in 1951, recommending adjustment of water fluoride concentrations to about 1.0–1.2 mg/L in low-fluoride areas to mimic naturally protective levels observed in endemic fluorosis regions. By 1952, the number of people receiving fluoridated water reached 13.3 million, reflecting the third-largest single-year expansion in U.S. history. Expansion continued robustly into the 1960s, driven by state and local public health initiatives; the largest annual increase occurred in 1965, adding 13.5 million people, including 8 million from 's adoption. By 1980, fluoridation reached approximately 112 million Americans, or 50% of the population on public water systems. Cumulative U.S. population served grew to over 200 million by 2010, covering 66.2% of those on community systems. Internationally, adoption followed U.S. trials, with Canada implementing in Brantford, Ontario, as a parallel 1945 demonstration that confirmed efficacy. Australia began trials in the early 1950s, leading to Newcastle's full implementation in 1953 and eventual coverage for about 90% of the population by the 2000s. Other nations, including and (1959), adopted similar programs, though uptake varied; many European countries opted against mandatory fluoridation, favoring alternatives like salt or milk fortification due to concerns over centralized dosing and natural fluoride variability. The acknowledged fluoridation's potential in basic water quality guidelines but did not issue binding endorsements, emphasizing site-specific assessments over uniform policy.
YearApproximate U.S. Population Served (millions)Key Policy or Expansion Note
19501.5Endorsements by , ,
195213.3Third-largest annual expansion
1965+13.5 (incremental)Largest annual expansion, including
198011250% of population on public systems

Recent Policy Shifts and Challenges

In September 2024, a U.S. federal judge in the U.S. District Court for the Northern District of California ruled in Food & Water Watch v. EPA that the Environmental Protection Agency (EPA) must regulate fluoride in drinking water to address its unreasonable risk to children's neurodevelopment, specifically lower IQ scores, based on substantial evidence from epidemiological studies linking exposure at or near the recommended 0.7 mg/L level to cognitive deficits. The ruling, stemming from a lawsuit under the Toxic Substances Control Act, did not mandate an end to community water fluoridation but required the EPA to eliminate the identified risk through rulemaking, prompting criticism from dental organizations like the American Dental Association (ADA), which maintains that fluoridation at 0.7 mg/L remains safe and effective for caries prevention without conclusive evidence of harm at those levels. The National Toxicology Program (NTP) bolstered these challenges with its August 2024 monograph, concluding with moderate confidence that fluoride exposures exceeding 1.5 mg/L in drinking water are associated with reduced IQ in children, based on systematic review of human studies primarily from regions with naturally high fluoride; however, the report explicitly avoided assessing risks at U.S. optimal levels (0.7 mg/L) or weighing benefits against potential harms, and a pre-release draft suggesting associations at lower exposures was revised amid scientific debate over study quality and confounders like socioeconomic factors. In response, the EPA announced in April 2025 an expedited review of this new science alongside its July 2024 reaffirmation of the 4.0 mg/L maximum contaminant level, while Congress introduced legislation in July 2025 requiring independent scientific review of federal fluoridation guidelines to strengthen evidence-based policy. In 2025, the Trump administration, through Health and Human Services Secretary Robert F. Kennedy Jr., advised public water systems to remove fluoride, citing health risks such as neurological effects on children, and directed the Centers for Disease Control and Prevention (CDC) to cease recommending community water fluoridation, without issuing a federal mandate. Public health organizations including the CDC and ADA continued to support fluoridation for cavity prevention despite the directive and ongoing debate. State-level policy diverged markedly, with Utah enacting the first statewide ban on public water fluoridation through House Bill 81, signed in March 2025 and effective May 7, 2025, prohibiting addition of fluoride to municipal systems and funding alternatives like school-based programs, driven by concerns over neurodevelopmental risks cited in NTP findings and local advocacy; Florida followed as the second state, influenced by the federal advisory, with Governor Ron DeSantis signing Senate Bill 700 in May 2025 and effective July 2025, imposing similar restrictions, marking a shift from decades of promotion by health agencies. These actions contrast with projections estimating that nationwide cessation could increase childhood caries incidence by up to 20-30% and raise healthcare costs by billions annually, as modeled in peer-reviewed analyses emphasizing fluoridation's net benefits in caries reduction. Public and scientific challenges persist, including ballot initiatives in communities like Telluride, Colorado (2024), where voters ended fluoridation citing ethical concerns over mass medication without consent, and ongoing litigation alleging violations of informed consent; critics, including groups referencing NTP data, argue for individual choice amid evidence of dose-dependent risks, while proponents highlight methodological flaws in neurotoxicity studies (e.g., reliance on high-exposure cohorts in China and Mexico) and robust meta-analyses affirming caries benefits without IQ effects at optimal doses. Rural areas face amplified vulnerabilities, with low fluoridation coverage exacerbating dentist shortages and caries disparities, as documented in 2025 assessments.

Scientific Mechanism

Biochemical Action on Teeth and Enamel

Dental enamel primarily consists of hydroxyapatite crystals, with the chemical formula Ca₁₀(PO₄)₆(OH)₂, which can undergo demineralization when exposed to acids produced by cariogenic bacteria in plaque, lowering the oral pH below approximately 5.5 and leading to dissolution of the mineral phase. Fluoride ions counteract this process by adsorbing onto the enamel surface and partially dissolving crystals, where they inhibit further demineralization by forming a protective layer and promoting the repair of early lesions through remineralization. During remineralization, fluoride substitutes for hydroxyl ions in the apatite structure, yielding fluorapatite, Ca₁₀(PO₄)₆F₂, which has a lower solubility in acidic conditions than hydroxyapatite, with a critical dissolution pH around 4.5 compared to 5.5 for the latter. This fluorapatite formation enhances enamel resistance to acid attacks by reducing the rate of mineral dissolution, as evidenced by in vitro studies showing decreased enamel loss in fluoride-exposed samples under acidic challenge. Additionally, fluoride facilitates the precipitation of calcium fluoride (CaF₂)-like deposits on enamel surfaces, which act as reservoirs releasing fluoride ions during subsequent acid exposure, thereby sustaining local concentrations that support ongoing remineralization and surface hardening. The biochemical efficacy relies on sufficient fluoride availability at the tooth-plaque interface, where even low concentrations from sources like fluoridated water contribute primarily through topical effects rather than systemic incorporation into developing enamel.

Systemic vs. Topical Effects

Topical fluoride effects on dental caries prevention occur primarily post-eruption, through direct interaction with enamel surfaces in the oral environment. Fluoride ions in saliva, plaque fluid, or applied agents inhibit enamel demineralization by competing with hydroxyl ions during acid attacks from plaque bacteria, forming a protective fluorapatite-like layer that is more resistant to dissolution than hydroxyapatite. This mechanism also promotes remineralization of early carious lesions by facilitating calcium and phosphate deposition in the presence of fluoride, reducing net mineral loss over time. Additionally, fluoride exerts antibacterial effects by penetrating bacterial cells as hydrogen fluoride, lowering intracellular pH and disrupting metabolic processes in cariogenic species like Streptococcus mutans. Systemic fluoride effects involve ingestion and subsequent incorporation into developing tooth structures pre-eruption, where fluoride substitutes for hydroxide in to form during enamel mineralization. This process theoretically enhances the acid resistance of unerupted teeth, as fluorapatite has a lower solubility product (Ksp ≈ 10^{-60}) compared to hydroxyapatite (Ksp ≈ 10^{-58}). However, clinical evidence for a substantial pre-eruptive systemic benefit remains limited, with reviews indicating no direct demonstration of improved caries resistance from such incorporation alone. In water fluoridation at 0.7 mg/L, systemic intake elevates salivary fluoride concentrations to approximately 0.016–0.038 mg/L, enabling sustained low-level topical exposure via oral fluids rather than high-dose applications. Empirical studies and reviews consistently show that caries reduction from fluoridated water correlates more strongly with post-eruptive topical mechanisms than pre-eruptive systemic ones, as benefits persist in erupted teeth and diminish when topical sources like dentifrice are absent. Systemic supplementation trials, such as those with tablets or drops, yield inconsistent additional caries prevention beyond topical fluoride, supporting the predominance of surface-level actions. While early epidemiological data from natural fluoride areas suggested systemic roles, methodological critiques and modern in situ analyses attribute most observed declines to posteruptive effects.

Implementation Practices

Methods and Chemicals Used

The principal chemicals used for artificial water fluoridation are sodium fluoride (NaF), sodium fluorosilicate (Na₂SiF₆), and fluorosilicic acid (H₂SiF₆, also known as hydrofluorosilicic acid or hexafluorosilicic acid). Sodium fluoride, a white powder, was the initial compound employed in early fluoridation programs and remains suitable for smaller water systems due to its straightforward handling in dry form. In contrast, fluorosilicic acid, a liquid byproduct of phosphate fertilizer production, predominates in larger municipal systems for its cost-effectiveness and ease of injection via liquid metering pumps. Sodium fluorosilicate, another powder, serves as an alternative for systems preferring solid additives. Fluoride addition occurs at water treatment facilities, typically after filtration and sedimentation but before final disinfection, or directly into distribution reservoirs to achieve a target concentration of 0.7 milligrams per liter (mg/L) in the United States. Dry chemicals like sodium fluoride and sodium fluorosilicate are fed using gravimetric or volumetric feeders that dissolve into solution for proportional dosing based on water flow rates. Liquid fluorosilicic acid is introduced through corrosion-resistant pumps calibrated to inject precise volumes, with pH adjustments often required to mitigate acidity impacts on infrastructure. Automated control systems integrate flow meters and chemical feed rates to maintain consistent dosing, minimizing over- or under-fluoridation. Ongoing monitoring ensures compliance with optimal levels, involving daily sampling from multiple points in the distribution system to capture representative fluoride concentrations. Operators employ ion-selective electrodes, colorimetric test kits, or laboratory analysis via methods like ion chromatography for verification, with results compared against regulatory standards such as the U.S. Environmental Protection Agency's maximum contaminant level of 4.0 mg/L. Continuous online analyzers may supplement manual checks in advanced setups, alerting to deviations for immediate corrective action. Public water systems report data periodically to health authorities, facilitating oversight and adjustment of fluoridation practices. The U.S. Public Health Service (PHS), under the Department of Health and Human Services, established an optimal fluoride concentration of 0.7 milligrams per liter (mg/L) for community water fluoridation in 2015, down from the prior range of 0.7–1.2 mg/L adopted in 1962, to account for increased fluoride exposure from sources like toothpaste while minimizing dental fluorosis risk. This level aims to provide sufficient topical and systemic fluoride for caries prevention without exceeding benefits relative to risks. The U.S. Environmental Protection Agency (EPA) sets a primary maximum contaminant level (MCL) of 4.0 mg/L to protect against skeletal fluorosis and a secondary standard of 2.0 mg/L for cosmetic dental fluorosis effects. Internationally, the (WHO) guidelines recommend fluoride levels not exceeding 1.5 mg/L in drinking water, with optimal ranges often cited as 0.5–1.0 mg/L adjusted for climate and total intake, emphasizing avoidance of naturally high concentrations linked to endemic fluorosis. In April 2025, the U.S. HHS Secretary directed cessation of the federal fluoridation recommendation and initiated EPA review of related standards, reflecting emerging concerns over neurodevelopmental risks at levels above 1.5 mg/L as assessed by the National Toxicology Program (NTP). Water systems implementing fluoridation maintain target concentrations through automated feeders dosing hydrofluorosilicic acid or other compounds, with adjustments based on flow rates and consumption patterns. Monitoring typically involves daily manual sampling and analysis via ion-selective electrodes or colorimetric methods, supplemented by continuous online analyzers for real-time data in larger utilities. Regulations require systems to notify users if levels deviate significantly, with states reporting aggregated data to the CDC's Water Fluoridation Reporting System for quality assurance and compliance tracking. Over-adjustment risks are mitigated by targeting within ±0.1–0.3 mg/L of the optimum, though variability from groundwater blending or seasonal demand necessitates vigilant oversight.

Global and Regional Variations in Practice

Community water fluoridation is practiced in about 25 countries, providing artificially fluoridated water to roughly 400 million people worldwide, though this represents less than 6% of the global population and coverage percentages differ markedly across regions. High-adoption nations typically target concentrations of 0.7 mg/L, aligning with U.S. Public Health Service guidelines, while others adjust based on local climate or natural fluoride levels. In contrast, many countries forgo water fluoridation in favor of alternatives like fluoridated salt, milk, or toothpaste, citing concerns over consent, overexposure risks, or sufficient dental hygiene advancements. In the Americas, fluoridation is widespread in the United States, where approximately 63% of the population on public water systems—about 209 million people—receives fluoridated water as of 2025, though recent state-level restrictions, such as Utah's ban in March 2025, signal emerging challenges. Canada achieves 44% national coverage, concentrated in Ontario and Alberta, while Brazil serves 40-60% through targeted urban programs. Chile and Argentina maintain moderate implementation at 70% and 19%, respectively, often integrated with school-based fluoride programs. Europe exhibits low and patchwork adoption, with most nations— including , , , , and the Netherlands—opting against community water fluoridation due to ethical objections to mass medication and preferences for voluntary fluoride sources. Only covers 73% of its population, the about 10% (primarily in the West Midlands and Northeast England), and limited areas in , totaling under 5% continent-wide. The 's 2025 assessment highlighted risks at levels above 1.5 mg/L, influencing minimal uptake and calls for stricter monitoring in naturally high-fluoride areas. Asia and Africa show negligible artificial fluoridation, with Singapore and Hong Kong at 100% coverage as exceptions amid broader regional reliance on naturally occurring fluoride, which often exceeds optimal levels in groundwater from , , and East African rift valleys. No major Asian countries like , , or implement it nationally, while African programs are virtually absent, affecting fewer than 1% systematically, though natural excesses pose endemic fluorosis risks in nations like and . In Oceania, reaches 80-89% coverage and 61%, supported by long-standing public health policies despite periodic referenda debates.
RegionApproximate CoverageKey Countries and Notes
North America60-70% averageUS (63%), Canada (44%); recent US state bans emerging.
South America20-50% variableBrazil (40-60%), Chile (70%); urban-focused.
Europe<5%Ireland (73%), UK (10%); most countries reject it.
Asia<5%Singapore/Hong Kong (100%); natural fluoride issues prevalent.
Africa<1%Minimal programs; high natural fluoride in groundwater.
Oceania70-80%Australia (89%), New Zealand (61%); policy-supported.

Empirical Evidence on Effectiveness

Reduction in Dental Caries Incidence

Early controlled trials demonstrated substantial reductions in dental caries incidence following the introduction of community water fluoridation. In the Grand Rapids study, initiated in 1945 as the first U.S. city to fluoridate its water supply, caries prevalence decreased by 48% to 70% among children and adolescents aged 12-14 after 13-15 years of fluoridation, compared to non-fluoridated control areas. Similar findings emerged from contemporaneous trials in , and other locations, with initial reductions ranging from 50% to 65% in primary and permanent teeth over five years. Systematic reviews of these and subsequent observational studies have quantified average caries reductions attributable to fluoridation at 25% to 35% in the decayed, missing, and filled teeth (DMFT) index for both children and adults. For instance, a meta-analysis estimated a 26% relative reduction in caries following fluoridation initiation across 10 studies involving nearly 40,000 participants. The Community Preventive Services Task Force reported a median increase of 14.6 percentage points in the proportion of caries-free children after fluoridation began, based on 11 studies. Contemporary evidence, however, indicates smaller incremental benefits due to widespread availability of fluoridated toothpaste and improved dental hygiene since the mid-20th century. The 2024 Cochrane review update, analyzing post-1975 studies, found low-certainty evidence of a mean reduction of 0.24 in dmft (deciduous teeth) among children—equivalent to about 0.25 fewer affected tooth surfaces—with uncertain effects on permanent teeth (DMFT). No qualifying studies assessed adults, and pre-1975 data showed larger effects, underscoring the diminished marginal impact in modern contexts with multiple fluoride exposures. Despite these limitations, observational data from upper-middle-income countries continue to associate community fluoridation with lower caries incidence in children under 13 years, even alongside topical fluoride use. Sources promoting fluoridation, such as public health agencies, often emphasize higher historical estimates, while independent reviews like Cochrane highlight evidential uncertainties and reduced contemporary efficacy.

Comparative Studies and Long-Term Outcomes

The Grand Rapids-Muskegon study, initiated in 1945 as the first controlled trial of community water fluoridation in the United States, compared caries rates in fluoridated Grand Rapids with non-fluoridated Muskegon and other control areas over 15 years. After 11 years, caries prevalence in permanent teeth among 12- to 14-year-olds in Grand Rapids decreased by approximately 50% compared to baseline and control communities, with reductions persisting into adolescence. By the fifteenth year, the study reported sustained but moderated benefits, with about 40-60% fewer decayed, missing, or filled surfaces in fluoridated cohorts versus non-fluoridated peers, though confounding factors such as improved overall dental hygiene were noted as potential influencers. A 2021 comparative analysis of (fluoridated since 1956) and (non-fluoridated after cessation in 2011) in Canada examined primary dentition in children aged 2-5 years using standardized clinical exams. Edmonton children exhibited 20-30% lower prevalence of caries experience (mean dmfs scores) and severe early childhood caries compared to Calgary counterparts, after adjusting for socioeconomic status and access to care; the difference was most pronounced in low-income groups. Similar patterns emerged in a 2020 New Zealand cross-sectional study of 4-year-olds, where residence in fluoridated areas correlated with 40% lower odds of severe caries (adjusted odds ratio 0.59), based on national oral health surveys controlling for ethnicity and deprivation indices. Long-term outcomes from decades-long implementations, such as New Zealand's variable fluoridation coverage since the 1950s, indicate persistent but diminishing absolute caries reductions over time. Longitudinal data from birth cohorts followed into adulthood show fluoridated communities maintaining 15-25% lower lifetime caries increments compared to non-fluoridated ones, though effect sizes halved between mid-20th century and recent decades, attributable to widespread fluoride toothpaste use and dietary shifts. Cessation studies provide counterfactual evidence: in Junee, Australia, discontinuing fluoridation in 2009 led to a 25% rise in child caries rates within five years versus sustained fluoridated controls, underscoring reversibility of benefits. Systematic reviews of such long-term comparisons, synthesizing over 50 ecological and cohort studies, estimate median caries reductions of 12-15% in permanent teeth for lifelong exposure at 0.7 ppm, with greater relative efficacy in high-risk populations but challenges in isolating fluoridation from concurrent hygiene improvements. These findings highlight causal contributions to caries prevention via sustained enamel strengthening, yet underscore the need for adjusted analyses to account for secular trends in oral health.

Influence of Modern Dental Hygiene Practices

The widespread adoption of fluoridated toothpaste since the 1970s has coincided with substantial declines in dental caries across populations, independent of community water fluoridation (CWF) status. Systematic reviews attribute much of the post-1970s caries reduction to regular toothbrushing with fluoride dentifrices, which provide topical fluoride concentrations far exceeding those from ingested water. In non-fluoridated regions, caries prevalence has fallen comparably to fluoridated areas, underscoring the dominant role of these modern practices over systemic fluoride sources. Contemporary studies conducted after 1975, when fluoride toothpaste use became prevalent, demonstrate diminished marginal benefits from CWF compared to earlier trials. A 2024 Cochrane systematic review of randomized and non-randomized studies found that CWF initiation post-1975 yields a mean difference of -0.24 (95% CI -0.03 to -0.52) in decayed, missing, or filled primary teeth (dmft) index among children, based on two studies involving 2,908 participants (low-certainty evidence). This contrasts sharply with pre-1975 studies, which reported larger reductions averaging -2.10 dmft (very low-certainty evidence), reflecting higher baseline caries rates and limited alternative fluoride exposures at the time. The review explicitly notes that the smaller contemporary effect sizes likely stem from confounding by ubiquitous fluoride toothpaste, which saturates topical benefits and minimizes additive systemic effects. Post-1980s surveys further illustrate this trend, with fluoridated communities showing only 9-25% lower caries occurrence than non-fluoridated ones, a narrowing gap attributable to improved hygiene behaviors and over-the-counter fluoride products. Fluoride toothpaste alone reduces caries by 15-30% in short-term studies of children, with effects persisting amid broader hygiene advancements like flossing and professional cleanings. Consequently, in eras of optimized personal oral care, CWF's public health impact appears incrementally modest, primarily benefiting those with inconsistent hygiene adherence rather than population-wide prevention.

Evidence on Safety and Risks

Dental Fluorosis and Aesthetic Concerns

Dental fluorosis manifests as alterations in tooth enamel appearance due to excessive fluoride ingestion during the developmental period from birth to approximately age 8, when enamel mineralization occurs. It presents as opaque white lines, streaks, or spots on the teeth, with severity ranging from very mild (barely noticeable fine lines) to severe (brown discoloration and pitting). The condition is assessed using Dean's Fluorosis Index, which categorizes changes on a scale from 0 (normal) to 4 (severe), with scores of 2 or higher (mild and above) often raising aesthetic considerations. In communities with water fluoridation at the recommended level of 0.7 mg/L, the prevalence of dental fluorosis of potential aesthetic concern is approximately 12%, primarily in mild forms that do not impair tooth function but may affect appearance. Systematic reviews indicate that even low-level fluoride exposure from drinking water correlates with increased fluorosis risk, though severe cases remain rare in optimally fluoridated areas. U.S. national surveys show a rise in fluorosis prevalence from the 1980s onward, with about 23% of adolescents affected by 2000–2004, attributed to cumulative intake from fluoridated water, toothpaste, and other sources rather than water alone exceeding optimal levels. Aesthetic impacts are subjective but documented in studies where mild fluorosis on anterior teeth influences perceptions of smile attractiveness among adolescents and parents, potentially affecting self-esteem and social interactions. While very mild cases (Dean's score 1) are often imperceptible and deemed inconsequential, mild to moderate fluorosis (scores 2–3) can lead to dissatisfaction with tooth appearance, prompting cosmetic treatments like microabrasion or veneers in affected individuals. Research emphasizes that fluorosis does not cause pain or increase caries susceptibility but highlights the need to monitor total fluoride exposure to minimize visible enamel changes.

Neurodevelopmental and Other Health Risks

Studies have investigated potential neurodevelopmental effects of fluoride exposure, primarily focusing on children's intelligence quotient (IQ). The U.S. National Toxicology Program's 2024 monograph concluded with moderate confidence that fluoride exposures above 1.5 mg/L in drinking water are associated with lower IQ scores in children, based on 19 high-quality studies involving over 7,000 participants, where 18 showed significant inverse associations. However, confidence drops to low for exposures below 1.5 mg/L due to limited data, reliance on cross-sectional designs limiting causality, potential confounders such as arsenic or iodine deficiency, and exposure misclassification from spot urine samples. At levels approximating community water fluoridation (around 0.7 mg/L), findings are inconsistent. A 2025 systematic review and meta-analysis of 74 studies reported an overall inverse association (standardized mean difference -0.45 IQ points), persisting in low-bias subgroups even below 1.5 mg/L for urinary fluoride, though null for water fluoride under that threshold; however, 52 of the studies carried high risk of bias, and many originated from high-exposure endemic areas with methodological limitations. Conversely, a 2023 meta-analysis restricted to low exposures (≤1 mg/L) found no significant IQ reduction (standardized mean difference 0.07, 95% CI -0.02 to 0.17), attributing prior signals to high-dose dominance and confounders. Prospective cohorts like Green et al. (2019) in Canada reported stronger effects in boys (-4.49 IQ points per 1 mg/L increase at ~0.7 mg/L), but critics highlight small samples and unadjusted variables. Evidence for other neurological outcomes, such as attention-deficit/hyperactivity disorder (ADHD), remains sparse and inconclusive at fluoridation levels, with no meta-analytic support for associations below 1.0 mg/L. Beyond neurodevelopment, risks like skeletal fluorosis—characterized by bone hardening and joint pain—are negligible at 0.7 mg/L, occurring only with chronic intakes exceeding 10-20 mg/L, far above U.S. fluoridation practices. Thyroid disruption shows potential at high exposures (>2-4 mg/L), with some reviews noting elevated TSH in children, but population-level studies at 0.7 mg/L detect no impairment in hormone levels or prevalence. Bone fracture risk and cancer incidence lack consistent links to low-dose fluoridation, per epidemiological reviews. Overall, while high-dose poses documented risks, data at community levels indicate minimal to no adverse effects, though ongoing research addresses residual uncertainties in vulnerable subgroups.

Dose-Response Relationships and Thresholds

The dose-response relationship between water fluoride concentration and dental caries reduction exhibits a positive association at low to moderate levels, with epidemiological data indicating approximately 25-40% fewer decayed, missing, or filled surfaces (DMFS) in children exposed to 0.7-1.2 mg/L compared to unfluoridated , based on systematic reviews of studies. This benefit arises primarily from enhanced remineralization of enamel and inhibition of demineralization during early development, though the incremental caries prevention plateaus beyond 1.0 mg/L as systemic exposure yields diminishing returns relative to topical sources like . Higher concentrations, such as 2-4 mg/L, show no proportional increase in efficacy and correlate with elevated risks of enamel defects, underscoring a narrow therapeutic window. For safety thresholds, the U.S. Public Health Service and CDC recommend 0.7 mg/L as the optimal concentration to balance caries prevention against risk, with an upper limit of 2.0 mg/L to avoid moderate to severe cosmetic fluorosis in children under 8 years, when enamel is forming. The WHO guideline value is 1.5 mg/L, beyond which very marked fluorosis may occur in a significant proportion of the population, based on epidemiological thresholds from endemic areas. , a rarer outcome involving changes and pain, requires chronic intake equivalent to >4-8 mg/L in water for adults, with no established risk at community fluoridation levels. The EPA's maximum contaminant level remains 4.0 mg/L, reflecting a margin against but secondary standards at 2.0 mg/L for aesthetic concerns. Regarding neurodevelopmental outcomes, some dose-response meta-analyses report an inverse linear association between maternal or childhood urinary (>0.8 mg/L) and IQ scores, estimating a 1.6-3.0 point decrement per 1 mg/L increase, drawing from cohort studies in regions with naturally high (1-10 mg/L). However, these findings derive largely from high-bias observational data prone to confounders like , , and lead exposure, with limited applicability to controlled low-dose (0.7 mg/L) fluoridation; counter-analyses of lower-exposure studies find no significant IQ effects. Thresholds for potential remain unestablished below 1.5 mg/L in rigorous, low-exposure designs, highlighting the need for beyond .
Fluoride Concentration (mg/L)Caries Reduction EffectPrimary Risk Threshold
0-0.7Minimal systemic benefit; relies on topical sourcesNegligible fluorosis
0.7-1.2Optimal: 25-40% DMFS reductionLow cosmetic fluorosis risk
1.5-2.0Plateaued benefitIncreased mild-moderate fluorosis
>4.0No added benefit possible; EPA MCL
This table summarizes epidemiological thresholds from dose-response models, emphasizing that benefits accrue systemically in primary dentition while risks escalate nonlinearly with total intake including diet and dentifrice.

Controversies and Debates

Opponents of community water fluoridation argue that it represents mass therapeutic administration without individual informed consent, infringing on personal autonomy and bodily integrity. Fluoride added to water acts pharmacologically to alter dental health outcomes, distinguishing it from non-therapeutic public health measures like chlorination, and thus qualifies as compulsory medication delivered indiscriminately to all users regardless of age, health status, or preference. This bypasses core medical ethics principles requiring voluntary, informed agreement for interventions, as consumers cannot feasibly opt out without alternative water sources, which impose disproportionate burdens on low-income households. Critics, including bioethicist Paul Connett, further contend that silicofluorides used in fluoridation—industrial byproducts never licensed as medicines by regulators like the U.S. FDA or subjected to pharmaceutical-grade toxicity testing—constitute unlicensed experimentation on populations, contravening human rights standards such as the Nuremberg Code's prohibition on non-consensual medical procedures. Proponents invoke ethics frameworks, asserting that collective beneficence justifies overriding individual when evidence demonstrates net population benefits, such as caries reductions of 25-40% in fluoridated communities, particularly aiding underserved children. They analogize to other interventions like iodized salt or vaccinated requirements, where proxy via elected representatives or democratic referenda substitutes for personal agreement, prioritizing justice in addressing health disparities—e.g., in , where 32% of residents lack and lower-income groups suffer higher decay rates. However, these parallels are contested, as salt fortification allows consumer avoidance and labeling, whereas water fluoridation affects all involuntarily, including infants via formula and those with contraindications like renal impairment, potentially violating non-maleficence if risks like mild fluorosis (affecting 23% of U.S. children at optimal levels) or debated thresholds materialize unevenly. The reliance on democratic processes for legitimacy raises concerns, as votes often reflect incomplete information or institutional biases favoring fluoridation, sidelining minority views and failing to incorporate updated risk data from studies post-1950s implementation. Ethical analyses, including scoping reviews of literature from onward, reveal persistent tensions between deontological respect for —rooted in —and utilitarian calculations of aggregate welfare, with no resolution amid polarized debates. Recommendations for include enhanced public , transparency on dose variability from sources, and exploration of less coercive alternatives like targeted topical applications, though these do not fully address the foundational deficit in mass systems.

Scientific Disputes and Study Interpretations

Scientific disputes surrounding water fluoridation center on the interpretation of epidemiological studies assessing its cariostatic effects and potential health risks, with contention over study quality, variables, and applicability to low-dose exposures. The 2000 York systematic review, commissioned by the Department of Health, analyzed 3200 studies and concluded that fluoridation reduces decayed, missing, and filled teeth (DMFT) by approximately 15% on average, but rated the evidence quality as low to moderate due to reliance on non-randomized, ecological designs prone to . Critics of the review, including proponents of fluoridation, argued it underestimated benefits by including studies from high-caries baseline populations where relative reductions appear smaller, and by not fully accounting for the shift toward topical effects in modern contexts. Conversely, skeptics highlighted the review's failure to demonstrate unequivocal , noting that observed caries declines in fluoridated areas often paralleled improvements in overall dental hygiene and widespread fluoride toothpaste use, confounding attribution. Recent meta-analyses have intensified debates on effectiveness. A 2024 Cochrane review of 58 studies found community water fluoridation (CWF) slightly reduces caries in primary teeth (mean difference -0.24 DMFT; 95% CI -0.36 to -0.12) but showed inconsistent effects in , with high risk of bias in included trials due to lack of blinding and adjustment for confounders like (SES). Pro-fluoridation interpretations emphasize absolute caries prevention (e.g., 0.2-0.3 fewer decayed teeth per child), while opponents contend the small effect size—often below amid declining baseline caries rates—does not justify population-level intervention, especially given evidence of in high-hygiene eras. These disputes underscore methodological challenges: most evidence derives from observational data susceptible to the , with few high-quality randomized controlled trials feasible for ethical and logistical reasons. On safety, interpretations diverge sharply regarding neurodevelopmental risks, particularly IQ. The National Toxicology Program's (NTP) August 2024 monograph, reviewing 72 studies primarily from China and India, concluded with moderate confidence that fluoride exposures above 1.5 mg/L in drinking water are associated with lower IQ in children (typically 2-5 points), based on consistent dose-response patterns across prospective cohorts. However, the report expressed low confidence for exposures at or below 1.5 mg/L—the range encompassing U.S. CWF levels of 0.7 mg/L—citing insufficient data and potential confounders like urinary fluoride measures capturing total intake rather than water-specific sources. Defenders of fluoridation, including agencies like the CDC, argue that associations at lower doses reflect residual confounding from SES, nutrition, or co-exposures (e.g., lead, iodine deficiency), and that no causal mechanism is established for optimal levels; they criticize NTP for over-relying on methodologically weak foreign studies with high natural fluoride variability. Opposing views assert that even community-level exposures pose risks, pointing to a January 2025 JAMA Pediatrics of 59 studies linking maternal or childhood urinary fluoride to IQ decrements (e.g., -2.9 points per 1 mg/L increase), including some U.S. and Canadian data below 1.5 mg/L, and invoking preclinical evidence of fluoride's via and endocrine disruption. Disputes arise over causality: skeptics demand fulfillment, noting inconsistent replication and failure to control for reverse causation or favoring null safety results in pro-fluoridation institutions. A 2021 similarly found IQ associations but highlighted study heterogeneity and reliance on spot urinary measures, which may overestimate water's contribution amid multifactorial exposures. These interpretive rifts reflect broader tensions, with pro-fluoridation sources often affiliated with bodies prioritizing aggregate benefits, while independent reviews reveal evidential gaps warranting precaution at current doses. In the United States, community water fluoridation began as a policy initiative with the adjustment of fluoride levels in Grand Rapids, Michigan, on January 25, 1945, following epidemiological studies linking naturally occurring fluoride to reduced dental caries. Subsequent adoption accelerated through endorsements by public health bodies, including the American Public Health Association in 1950, which affirmed it as a safe measure, leading to fluoridation in over 90% of large U.S. public water systems by the 1960s. Federal involvement grew with the U.S. Public Health Service's 1962 recommendation for optimal levels of 0.7–1.2 mg/L, later revised to 0.7 mg/L in 2015 by the Department of Health and Human Services to minimize fluorosis risks while maintaining benefits. Legal challenges to fluoridation have persisted since the 1940s, framed primarily as violations of , bodily autonomy, or under the U.S. , yet courts have consistently rejected these claims, classifying it as a rational measure akin to chlorination rather than . Over 108 lawsuits filed through the late uniformly failed, with appellate courts upholding municipal authority; for instance, a 1996 ruling affirmed fluoridation under police powers without requiring individual consent. Opposition often invoked ethical concerns over non-voluntary administration, but judicial deference to prevailed until recent shifts. A pivotal development occurred on September 24, 2024, when the U.S. District Court for the Northern District of , in Food & Water Watch v. EPA, ruled that fluoride at 0.7 mg/L presents an "unreasonable risk" to children's IQ under the Toxic Substances Control Act, based on substantial from studies linking exposure to neurodevelopmental effects, though stopping short of deeming it outright harmful. The court mandated the Agency to initiate to address risks, prompting EPA plans to appeal on procedural grounds without contesting the risk finding. This marked the first federal judicial acknowledgment of significant health risks from standard fluoridation levels, potentially influencing future regulations amid ongoing litigation. Politically, momentum against fluoridation has intensified in the 2020s, with state-level actions overriding local decisions. enacted a statewide ban via House Bill 81, signed in March 2025 and effective May 2025, prohibiting fluoride addition to public water systems and superseding prior local vote requirements, despite a Heber City referendum in April 2025 favoring retention by 53%. followed as the second state, with Senate Bill 700 signed by Governor on May 15, 2025, eliminating fluoridation mandates and shifting to voluntary local opt-ins, effective July 1, 2025. In 2025, Health and Human Services Secretary Robert F. Kennedy Jr. announced plans to direct the Centers for Disease Control and Prevention to cease recommending community water fluoridation, citing neurodevelopmental risks to children such as lowered IQ. Public health organizations including the CDC and American Dental Association continue to support fluoridation for cavity prevention. advanced similar legislation in April 2025, passing a committee vote to restrict additions unless approved by supermajority referenda, reflecting broader conservative skepticism of federal guidelines. These moves contrast with historical local rejections, such as Portland, Oregon's 2013 ballot measure defeating fluoridation by 61%, and highlight decentralizing trends amid debates over centralized interventions. Internationally, policy adoption has been uneven, with limited uptake outside the ; for example, the has no harmonized fluoridation policy, and countries like and the discontinued programs in the 1970s–1990s after ethical reviews favoring individual choice and topical alternatives. In , a 2014 Ontario court dismissed a class-action challenge claiming fluoridation as battery, upholding it as administrative policy. Recent global trends show stagnation, with only about 5% of the world's population receiving fluoridated water, per 2020 estimates, as nations prioritize alternatives like fluoridated salt in or milk in parts of .

Public Opposition and Conspiracy Claims

Public opposition to water fluoridation has persisted since the practice's inception in the mid-20th century, often manifesting through local referendums and ballot initiatives where voters have rejected or repealed fluoridation mandates. , over 50 referendums since the have resulted in the defeat of fluoridation proposals, with opposition frequently citing concerns over individual consent, potential health risks, and government overreach. Recent examples include Union County and Lincoln County in , where commissioners voted in 2024 and early 2025 to cease adding fluoride to public water supplies, reflecting growing localized resistance amid broader debates on interventions. Similarly, Miami-Dade County commissioners approved an 8-2 vote on April 2, 2025, to halt fluoridation, driven by commissioner concerns over emerging studies on neurodevelopmental effects. At the state level, and enacted laws in 2024 banning fluoride addition to municipal water, while at least 21 states introduced prohibitive bills during the 2025 legislative sessions. Organized anti-fluoridation efforts are led by groups such as the Fluoride Action Network (FAN), founded by chemist Paul Connett, which advocates for ending water fluoridation based on ethical objections to compulsory medication and critiques of safety data. Prominent figures like Robert F. Kennedy Jr. have amplified opposition, arguing that fluoridation represents an outdated and risky public policy, particularly in light of studies suggesting IQ reductions at levels near U.S. standards. Opposition draws from diverse ideological sources, including libertarians emphasizing personal autonomy and some conservative activists viewing it as bureaucratic imposition, though mainstream public health bodies maintain majority support in national polls, with a July 2025 CareQuest Institute survey finding 57% approval among Americans. Voter turnout in referendums often correlates with lower health literacy, as explored in a 2019 study of U.S. communities, where confusion over fluoridation's mechanisms contributed to rejection rates exceeding 50% in several cases. Conspiracy claims surrounding water fluoridation trace to the , originating in Cold War-era narratives alleging it as a communist plot to weaken populations or a Nazi-derived method for mind control, purportedly tested in concentration camps to induce docility. These assertions, popularized by figures like Charles E. Perkins in correspondence claiming industrial was repurposed from poison gas production for , lack empirical substantiation and have been propagated through fringe publications rather than peer-reviewed evidence. Modern variants, echoed in some online discourse, allege deliberate depopulation agendas or ties to aluminum industry waste disposal, but such claims fail causal scrutiny, as fluoridation's adoption stemmed from epidemiological observations of naturally occurring 's dental benefits in Springs by 1901 and controlled trials in Grand Rapids starting 1945. While these theories have marginalized legitimate ethical debates by associating opposition with unsubstantiated paranoia, they persist in pockets of public skepticism, particularly amid recent high-profile endorsements like Kennedy's calls for federal cessation. No verifiable evidence supports intentional maleficence in fluoridation programs, which were developed through research rather than covert agendas.

Alternatives and Complementary Approaches

Topical Fluoride Applications

Topical fluoride applications deliver fluoride ions directly to tooth surfaces, primarily acting at the enamel-plaque interface to inhibit demineralization and enhance remineralization without significant systemic exposure. This localized effect contrasts with water fluoridation's reliance on ingested incorporation into developing teeth. Fluoride ions adsorb to crystals, forming fluorapatite during remineralization, which resists acid dissolution at lower pH levels than native enamel minerals. Additionally, elevated plaque concentrations suppress cariogenic by interfering with metabolic processes like enzyme activity, reducing acid production. Common forms include toothpastes containing 1000–1500 ppm (typically or stannous fluoride), used twice daily for brushing, which systematic reviews indicate reduce caries increment by approximately 24% in primary and . rinses (0.05–0.2% ) provide supplementary benefits, particularly for high-risk individuals, with evidence from meta-analyses showing additional caries prevention when combined with . applications encompass gels or foams (1.23% acidulated , applied for 1–4 minutes quarterly), varnishes (5% , reapplied every 3–6 months), and silver diamine for arresting active lesions. varnishes demonstrate 33–46% caries reduction in systematic reviews of children and adults, with higher efficacy in prevention when applied biannually. Efficacy data from Cochrane and other systematic reviews affirm topical fluorides' role in caries control across populations, with preventive fractions ranging 20–40% depending on baseline risk and application frequency; for instance, 0.9% difluorosilane every 3 months yields substantial reductions in preschoolers. In high-caries-risk adults, combinations of professional gels and daily toothpastes outperform single modalities, arresting lesions and preventing new ones per longitudinal analyses. These interventions are recommended by dental guidelines for targeted use, especially where systemic is absent or suboptimal. Safety profiles favor topical over systemic routes, as absorption is minimal when not swallowed, though acute ingestion risks or at high doses. In children under 6, improper use—such as swallowing toothpaste—contributes to mild , a cosmetic enamel mottling affecting but not function, with risks mitigated by pea-sized amounts and supervision per CDC and ADA advisories. No robust evidence links standard topical applications to neurodevelopmental or skeletal effects, unlike debates around chronic systemic overexposure.

Dietary and Supplemental Options

Dietary sources of occur naturally in varying trace amounts in many foods, though they typically contribute less to overall intake than fluoridated or . High- foods include , which can contain 0.3–6.0 mg/L in brewed form depending on source and time; such as with edible bones (e.g., sardines, providing 0.5–1.0 mg per serving); and certain produce like (approximately 0.07 mg per cup) or grapes and raisins. These levels vary based on , , and , and empirical data indicate that natural dietary alone rarely achieves the systemic exposure needed for optimal caries prevention without supplementation or . Fortified dietary options, such as fluoridated salt, have been implemented in programs in countries including , , and parts of to deliver systemic at controlled levels of 250–300 mg/kg in salt, yielding daily intakes of 0.5–0.75 mg for average consumers. These initiatives demonstrate caries reductions comparable to water fluoridation in community studies, with minimal fluorosis risk when total exposure remains below thresholds (e.g., not combined with fluoridated water), as evidenced by longitudinal data from and showing 20–40% fewer decayed surfaces in children. Safety margins are wide due to voluntary consumption, allowing self-regulation unlike mandatory water sources. Dietary fluoride supplements, primarily sodium fluoride tablets or lozenges, are recommended by the (ADA) and Centers for Disease Control and Prevention (CDC) for children in areas with water fluoride below 0.3 mg/L, starting at age 6 months with dosages escalating by age: 0.25 mg/day for ages 6 months–3 years, 0.5 mg/day for 3–6 years, 1.0 mg/day for 6–16 years. These provide systemic benefits by incorporating into developing enamel pre-eruption and maintaining circulating levels for remineralization, with meta-analyses confirming efficacy equivalent to water fluoridation in reducing caries by 25–40% when adhered to, though compliance challenges limit population-level impact compared to passive water delivery. Prescriptions should limit supply to 4 months to monitor intake and prevent excess, as risks arise above 5 mg/kg body weight, and chronic over-supplementation correlates with mild in 10–20% of users exceeding guidelines. Unlike broad fluoridation, supplements enable targeted use for high-risk groups, aligning with causal mechanisms where inhibits demineralization primarily via topical effects post-eruption but supports pre-eruptive strengthening systemically.

Natural and Low-Fluoride Strategies

Dietary modifications emphasizing reduced intake of fermentable carbohydrates, particularly , represent a foundational low-fluoride strategy for caries prevention, as frequent sugar exposure promotes acid production by oral bacteria like , leading to enamel demineralization. Studies indicate that replacing with non-fermentable alternatives such as or in diets significantly lowers caries incidence, with evidence from controlled trials showing up to 50% reduction in decay rates among children adhering to low-sugar regimens. Adequate intake of calcium and supports enamel remineralization, as these minerals constitute crystals in tooth structure; deficiencies correlate with increased caries risk across age groups. Vitamin D supplementation or exposure enhances calcium absorption and enamel formation, with meta-analyses linking higher maternal and childhood levels to 20-40% lower in offspring. A 2024 nationwide study confirmed that serum below 20 ng/mL independently predicts elevated caries odds ratios of 1.5-2.0, even after adjusting for confounders like . Similarly, serum calcium levels inversely associate with decay severity in pediatric populations, underscoring nutritional remineralization without reliance. Xylitol, a naturally occurring five-carbon found in , inhibits bacterial adhesion and acidogenesis when consumed in chewing gums or lozenges at 5-10 grams daily, yielding 35-60% caries reductions in randomized trials. A 2022 meta-analysis of 10 studies found gums most effective post-meals, with pure products outperforming mixtures, and no adverse effects beyond mild laxation at high doses. This approach targets plaque without systemic , suitable for communities opting out of water fluoridation. Hydroxyapatite (HAP), a biomimetic mirroring enamel composition, enables fluoride-free remineralization by filling micro-lesions and buffering ; clinical trials demonstrate HAP toothpastes prevent caries as effectively as 500-1000 ppm fluoride varnishes, with superior outcomes in early enamel repair. A 2023 randomized study reported 20-30% greater remineralization in HAP users versus fluoride controls, attributed to direct crystal deposition rather than fluorapatite conversion. Nano-HAP variants enhance penetration into demineralized zones, reducing sensitivity and halting progression in 70-80% of initial lesions without risks associated with fluoride overexposure. These topical agents align with low-fluoride paradigms by leveraging endogenous mineral dynamics.
  • Key dietary targets: Limit added sugars to <5% of caloric intake; prioritize phosphorus-rich foods (, nuts) and sources (fatty fish, fortified non-dairy).
  • Xylitol protocols: 3-5 exposures daily via gum, totaling 6-10g, for high-risk groups like children in non-fluoridated areas.
  • HAP application: Twice-daily brushing with 10-15% HAP pastes, monitored via annual radiographs for lesion arrest.
Such strategies emphasize individualized, consent-based prevention over mass intervention, with efficacy substantiated in longitudinal cohorts where fluoride avoidance coincided with stringent and .

Economic Analysis

Cost-Benefit Assessments

water fluoridation is frequently assessed as cost-effective in peer-reviewed economic evaluations, with benefits from reduced dental caries typically exceeding and maintenance costs. A of 23 studies found that the economic benefits, primarily through averted dental treatments, ranged from $1.10 to $135 in savings per $1 invested, depending on location, population demographics, and caries prevalence. , fluoridation is estimated to save an average of $32 per person annually by preventing 25% of cavities and associated restorative procedures. These savings accrue from fewer fillings, extractions, and orthodontic interventions, with lifetime benefits accumulating across populations served. Operational costs for fluoridation programs are relatively low, averaging $0.50 to $3 per year in the U.S., covering compound purchases, equipment, monitoring, and personnel. Capital investments for initial setup, such as feeders and piping modifications, vary by system size but are amortized over decades, yielding benefit-to-cost ratios often exceeding 20:1 in high-burden areas. For instance, a U.K. analysis projected a £21.98 return per £1 spent over 10 years for adults, driven by 0.2 fewer decayed, missing, or filled surfaces per person annually. Cost-effectiveness is higher in communities with baseline high caries rates, limited access to dental care, and low preexisting exposure, as topical alternatives like provide partial overlap but less equitable reach. Critiques of these assessments highlight omissions in potential adverse effects, such as treatment for , which can add $8 to $41 per person per year in net costs when included, potentially negating benefits in low-caries settings. Methodological flaws have also been identified, including defective cost estimations and assumptions, as critiqued by Ko and Thiessen (2015). A scoping review of economic evaluations noted that while all concluded fluoridation's favorability, many relied on older data predating widespread fluoride toothpaste use, which diminishes marginal gains from systemic exposure. Recent evidence, such as the 2024 Cochrane systematic review update indicating low-certainty evidence for small caries reductions (mean difference of 0.24 dmft) in contemporary settings with topical fluoride availability, and the LOTUS study reporting modest 2-3% reductions in dental treatments, further suggests limited additional benefits that may impact net savings calculations. Sensitivity analyses indicate that at optimal 0.7 ppm levels, net savings hold, but exceedances or individual overexposure inflate harm costs without proportional caries reductions. agencies like the CDC maintain that benefits persist despite alternatives, yet independent reviews urge incorporating full risk profiles for updated valuations.
Study/SourceBenefit per $1 InvestedKey AssumptionsLimitations Noted
U.S. (2016)$6–$20 average25% caries reduction; excludes harmsPrevalent topical fluoride use may lower marginal benefits
U.K. Adult Model (2021)£21.98 over 10 years0.2 DMFT reduction; lifetime horizonFocuses on adults; ignores severe fluorosis rarity
Global Scoping Review (2020)Cost-saving in all casesCompares to non-fluoridated areasHeterogeneity in methods; older studies dominant
Risk-Inclusive Analysis (2024)Negative if harms costedIncludes fluorosis treatment at $8–$41 PPPYCalls for alternatives promotion

Projections from Discontinuation Scenarios

A modeling study published in JAMA Health Forum in May 2025 projected that cessation of community water fluoridation across U.S. public water systems would result in a 7.5% increase in the of decayed, missing, or filled tooth surfaces among children aged 2–17 years over five years, leading to approximately 25.4 million additional decayed primary and 1.9 million additional decayed . This analysis, which incorporated data from the National Health and Nutrition Examination Survey (NHANES) and national treatment cost estimates, indicated that the greatest burden would fall on publicly insured children, with low-income and Medicaid-enrolled populations facing up to a 9.2% rise in decay . Over a longer 10-year horizon, the model forecasted 53.8 million damaged , exacerbating disparities in oral health outcomes. Economically, the same study estimated that discontinuing fluoridation would generate $9.8 billion in additional U.S. costs over five years, primarily from elevated dental treatment expenditures for caries restoration, with costs rising by $20–$30 annually depending on status. These projections accounted for both direct restorative procedures (e.g., fillings at $150–$200 per surface) and indirect effects like emergency visits, but did not factor in potential offsets from reduced fluoridation infrastructure maintenance, estimated at $0.50–$3.00 per person-year in operational savings. Critics of such models argue they may overestimate caries reversion by assuming static behavioral factors like topical use, citing historical discontinuations (e.g., in , , post-1992) where caries increases were modest or absent due to compensatory measures. Empirical data from prior cessations support variable but often adverse projections. A 2024 Israeli study of preschoolers after 2014 fluoridation halt found caries prevalence rose from 23.7% to 35.4% over four years, with decayed teeth per child increasing by 0.28 surfaces, projecting annualized national treatment costs in the millions if unmitigated. Similarly, Calgary, Alberta's 2011 discontinuation correlated with a 1.2-surface caries increase in adolescents by 2013–2014, implying potential municipal dental care expenditures exceeding CAD $10 million annually without alternatives. However, not all cases show uniform deterioration; a review of 13 cessation studies found inconsistent caries rebounds, attributed to baseline fluoride exposure from dentifrice and diet, suggesting projections could be tempered by 20–50% in high-compliance scenarios. In scenarios emphasizing alternatives like school-based topical applications or supplements, projected caries offsets might reduce net increases to 3–5%, but implementation costs could add $5–$15 per child-year, potentially negating savings and straining public budgets in underserved areas. Overall, discontinuation models consistently forecast net economic losses from heightened restorative demands, with benefit-cost ratios inverting from fluoridation's typical 1:20–1:40 return to deficits exceeding $10 over a , though long-term data gaps on adult cohorts limit precision.

Adoption Rates by Region

In , community water fluoridation covers approximately 73% of the population served by public water systems as of 2022, equating to about 63% of the total U.S. population when accounting for those on private wells. In , adoption varies significantly by province, with higher rates in (around 75%) and (near 100%), but near-zero in and ; national coverage is estimated at 40-45% of the population. Europe exhibits low adoption rates overall, with most countries rejecting widespread fluoridation due to ethical concerns over mass medication and preferences for topical alternatives. Only fluoridates at a national level, covering about 73% of its population, while limited schemes exist in parts of the (about 10% coverage) and (around 12% in certain regions like Basque Country and ); this results in fewer than 3% of Western Europeans receiving fluoridated water. In , maintains high coverage, with over 90% of the population accessing fluoridated across all states and territories as of 2023, though implementation varies slightly by jurisdiction (76-100%). has more patchy adoption, with approximately 51% of the population receiving fluoridated water in 2025, primarily through territorial authority decisions following legislative changes in 2021 that centralized but did not mandate fluoridation. Asia shows sparse and localized adoption, concentrated in city-states like and (both 100% coverage) and (95%), but negligible in populous nations such as , , and , where natural fluoride levels or alternative delivery methods predominate; overall regional prevalence remains under 5% due to demographic weights. has variable implementation, with achieving about 70% coverage, fluoridating in select urban areas serving roughly 40-50% of its population despite legal mandates, and limited programs in and ; many countries rely instead on naturally occurring fluoride or salt fluoridation, keeping continent-wide rates below 20%. Africa and the Middle East generally lack systematic fluoridation programs, with adoption near 0% in most nations, though some areas in and have implemented or trialed it at low percentages (<10%); high natural in affects certain regions but does not constitute deliberate . Globally, only about 25 countries maintain programs serving over 400 million people, representing roughly 5% of the world's .

Recent Declines and Reversals

In the United States, Utah enacted the first statewide ban on community water fluoridation in March 2025, with House Bill 81 signed by Governor Spencer Cox prohibiting the addition of fluoride to public water supplies effective May 7, 2025. Florida followed with its own statewide ban later in 2025, marking the second U.S. state to implement such a policy amid debates over health risks highlighted in a 2024 federal court ruling acknowledging potential neurodevelopmental effects in children from excessive fluoride exposure. Several municipalities discontinued fluoridation between 2023 and 2025, often citing concerns over safety data from recent studies and court decisions. In , at least 14 communities, including Palm Bay (January 2025) and Miami-Dade County (April 2025 vote by 8-2 margin), ceased adding fluoride, affecting over 900,000 residents and contributing to broader regional pullbacks in . In , Abilene and Brushy Creek (2023) halted the practice, while , also stopped in 2023 following local votes or policy shifts. Additional discontinuations occurred in Yorktown and , and the Weber Basin Water Conservancy District serving parts of , prompted by the same 2024 ruling. Internationally, recent cessations remain limited compared to historical discontinuations in during the –, with no major country-wide reversals reported post-2020 beyond localized actions. In , Alrass City discontinued fluoridation, leading to a 2025 study documenting subsequent changes in caries and fluorosis prevalence among children. , , ended fluoridation in 2011 amid cost concerns, resulting in documented increases in pediatric dental procedures; while reinstatement efforts were debated into the , full reversal to addition has not been uniformly implemented as of mid-2025. These U.S.-centric trends reflect growing legislative scrutiny, with at least 16 states introducing anti-fluoridation bills in 2025, though most did not pass. Empirical post-cessation data from affected areas, such as elevated caries rates in prior studies from and U.S. locales like (discontinued 2007 but analyzed recently), underscore causal links to reduced preventive benefits, independent of source biases favoring continuation.

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  202. https://pmc.ncbi.nlm.nih.gov/articles/PMC12009762/
  203. https://nextcity.org/urbanist-news/calgary-remove-water-fluoridation-reinstating-dental
  204. https://www.wbaltv.com/article/what-states-have-considered-fluoride-bans/64855417
  205. https://publichealth.jhu.edu/2024/why-is-fluoride-in-our-water
  206. https://www.history.com/articles/fluoride-water-teeth-health
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