How the public’s knowledge, attitudes, and practice intersect with scientific evidence about fluoride

Abstract

For over 75 years, community water fluoridation has been implemented as a public health strategy to reduce dental caries. While early studies suggested dramatic reductions in dental caries, recent evidence indicates that the benefits of community water fluoridation are more modest. Concurrently, concerns have grown over rising rates of enamel fluorosis and possible links between fluoride intake and lowered intelligence in children and thyroid hormone disruption, even at exposure levels found in fluoridated regions. This first part of this paper discusses the historical context and current scientific evidence on the effectiveness of community water fluoridation and safety of systemic fluoride. The second part presents findings from a fluoride survey conducted with 8011 adults in Canada and the U.S. The survey assessed knowledge about fluoride, public perceptions of the risks and benefits of community water fluoridation, and fluoride use with young children. Overall, 60 % of respondents correctly identified why fluoride is added to drinking water. Knowledge of community water fluoridation was higher among older, more educated, and White participants. Among those familiar with community water fluoridation, 51 % expressed support, 27 % opposed it, and 25 % were neutral. Support was primarily driven by confidence in its safety and benefits, while opposition was driven by safety concerns and perceived violations of personal freedom. Trust in public health officials was higher among supporters (87 %) compared with non-supporters of community water fluoridation (52.1 %). When presented with hypothetical risk-benefit scenarios, participants consistently prioritized the prevention of potential health risks, such as reduced IQ, over the relatively modest dental benefit of preventing one cavity. The survey also revealed that most parents report using more fluoride toothpaste for young children than recommended, suggesting a gap in adherence to safe fluoride use guidelines. Our findings highlight mixed public views on community water fluoridation and knowledge gaps surrounding fluoride toothpaste use with children, underscoring the need for clear, evidence-based communication about fluoride exposures.

Introduction

In some communities, fluoride is added to drinking water to reach a concentration of 0.7 mg/L, which is considered optimal for preventing dental decay. Currently, 73 % of Americans and 37 % of Canadians on public water supplies have fluoridated water.¹ In contrast, water fluoridation was ended in most of Europe between the 1970s and 1980s when topical fluoride alternatives (e.g. toothpaste) became widely available. Delivery of systemic fluoride was replaced with more targeted strategies, such as adding fluoride to milk or salt.

Community water fluoridation (CWF) was first introduced in the 1940s. Since then, substantial scientific evidence has examined both its effectiveness in preventing dental caries (i.e. tooth decay) and the safety of fluoride exposure. This paper reviews the historical context of CWF and examines how the evidence regarding its benefits and potential risks has evolved over time. Growing scientific evidence, including a 2024 systemic review of the literature conducted by the National Toxicology Program,² has raised concerns about adverse health effects of high fluoride exposure and reignited debate over the ethics of mandatory fluoridation and safe dosage, particularly for vulnerable populations. In addition, a ruling from a federal lawsuit by consumer groups against the U.S. Environmental Protection Agency concluded in September of 2024 that

“Plaintiffs have proven, by a preponderance of the evidence, that water fluoridation at the level of 0.7 mg/L— the prescribed optimal level of fluoridation in the United States—presents an unreasonable risk of injury to health or the environment, without consideration of costs or other non-risk factors, including an unreasonable risk to a potentially exposed or susceptible subpopulation under the conditions of use.” ³

With evidence of neurotoxicity at fluoride concentrations of 1.5 mg/L or higher, the judge reasoned that a twofold margin is not sufficient for ensuring the safety of vulnerable populations.

Fluoride hesitancy appears to be growing,⁴ driven in part by increased media coverage⁵ and vocal opposition towards CWF from public figures including the U.S. Department of Health and Human Services Secretary Robert F. Kennedy, Jr. In early 2025, Utah and Florida became the first U.S. states to ban fluoridation of public water systems. In contrast, numerous dental, medical, and public health organizations continue to support CWF as a safe, equitable, and cost-effective population level strategy for preventing caries. Amid these sharply divided perspectives, it remains unclear whether the public views fluoridated drinking water as a critical public health concern.

In the second part of this paper, we present results of an 8000-person fluoride survey conducted in Canada and the United States examining the public’s current knowledge and attitudes towards topical and systemic fluorides. The survey was developed to understand reasons why people may support or oppose fluoridation and explore how beliefs about perceived risks and benefits of fluoride intersect with current scientific evidence and trust of public health agencies. Finally, using data collected from parents of young children, we examine what parents know about fluoride and offer recommendations for safe use of fluoride with young children.

PART 1. Historical context and scientific evidence regarding the effectiveness and safety of community water fluoridation

The origin of community water fluoridation

The dental benefits of fluoridated water were identified in the early 1900s following a serendipitous discovery. Dr. Frederick McKay, a dentist in Colorado Springs, began to investigate why residents with distinctively brown-stained teeth or “mottled enamel” (later termed enamel fluorosis) had remarkably healthy teeth. These observations sparked investigations into local water supplies. Over the next few decades, public health researchers confirmed that excess fluoride caused discoloration of tooth enamel and made teeth less susceptible to decay.

In 1942, Dr. H. Trendley Dean of the U.S. Public Health Service (PHS) showed that a water fluoride concentration of approximately 1.0 part per million (ppm) provided significant protection against caries while causing only minimal and almost imperceptible enamel fluorosis.⁶ Because the findings of reduced dental decay were so profound, the U.S. PHS began to consider the possibility of testing artificial water fluoridation in select communities. At this time, scientific consensus about the toxicity of fluoride had not been achieved and experts called for rigorous scientific scrutiny before widespread implementation.⁷ In 1944, Dr. L. Pierce Anthony, editor of the Journal of the American Dental Association, wrote an editorial acknowledging the potential benefits of fluoridated water, but also raised concerns about its safety. In a strikingly cautious editorial, he warned:

“Because of our anxiety to find some therapeutic procedure that will promote mass prevention of caries, the seeming potentialities of fluoride appear speculatively attractive, but, in light of our present knowledge or lack of knowledge of the chemistry of the subject, the potentialities for harm outweigh those for good.”⁸

Other scientists warned that existing studies examining the toxicity of fluoride were “fraught with uncertainties”⁹ or were influenced by industry, including the Sugar Research Foundation or the aluminum and fertilizer companies.¹⁰

The first artificial water fluoridation trials began in 1945 in the United States and in 1946 in Canada. Sodium fluoride started to be added to public water supplies in Grand Rapids, Michigan with the aim of reducing dental caries. Cross-sectional surveys of almost 30,000 school children involved in these trials demonstrated that dental caries were reduced by up to 60 % from fluoridated water.¹¹ The findings were so striking that the American Dental Association (ADA) and the U.S. PHS endorsed CWF as a safe and effective way to prevent dental caries long before the trials had even been completed.

CWF was promptly adopted as a public health strategy to prevent dental caries, a disease that became increasingly prevalent with the rise of industrial sugar production and increased sugar consumption.¹² At the time, dental caries was considered a major public health issue, with 10 % of young men drafted for military service being rejected due to dental disease. Medical, dental, and public health bodies were highly optimistic that CWF could serve as a “magic bullet” to prevent tooth decay.^6,13 Although some critics voiced concerns about potential health risks of CWF, their objections were dismissed and pushed to the margins as fringe viewpoints.^14,15

By 1950, fluoride was added to the public water supplies serving over 20 million Americans. By 1975, water fluoridation reached over 100 million Americans. From 1950 to 2015, the U.S. PHS recommended that fluoride be added to public water supplies to reach a target level of 0.7 to 1.2 mg/L; fluoride concentrations in the lower end of this range were recommended for warmer climates where water consumption rates were thought to be higher than in colder climates. In 2015, the U.S. PHS revised its guidelines to recommend a uniform concentration of 0.7 mg/L. This change was driven by the widespread availability of fluoride in dental care products, as well as evidence of rising enamel fluorosis trends. Sodium fluoride (a byproduct produced by the aluminum industry) was the main fluoridation compound used until 1968. Since then, fluorosilicic acid, a byproduct of the phosphate fertilizing industry, has been used to fluoridate water because it is cheaper, more abundant, and easier to mix into water because of its liquid form.⁶ Today, fluoride is added to drinking water in approximately 25 countries, reaching over 370 million people worldwide.¹⁶

Fluoride sources

Fluoridated water is the main source of fluoride intake. For adults, fluoridated water and beverages and foods made with fluoridated water account for 70–75 % of total dietary fluoride intake.¹⁷ In the U.S., most caregivers use tap water to mix powdered formula. When the water is fluoridated at 0.7 mg/L, fluoride concentration in the prepared formula can range from 0.76–0.83 mg/L depending on formula brand and type (i. e. milk-based, soy, etc.).¹⁸ Infants drinking powdered formula made with fluoridated water can have a 70-fold higher fluoride intake than exclusively breastfed infants; breastmilk contains minimal amounts of fluoride (<0.02 μg/L).^17,19,20

Other dietary sources include tea, soybean beverages, seafood that contains shells or edible bones (e.g. sardines), processed foods (e.g. chicken nuggets due to the deboning process), gelatins, and fruits and vegetables due to pesticide residues or if grown in soil containing fluoride.^21–25 Tea plants absorb fluoride from soil and can have very high levels of fluoride (1.6–6.1 mg/L) if grown in regions where soil levels are naturally high.^26,27 In a U.S. study, children who drank black or green tea had 42 % higher plasma fluoride concentrations than non-tea drinkers.²⁸ Fluoride can be found in juice, pop, and any other beverage that is made with fluoridated water.^29,30 Fluoride also can be found in air through industrial emissions and can be released by certain pharmaceuticals, including fluorinated anesthetics.³¹

Fluoride also is a main component of most dental hygiene products. These topical sources of fluoride (e.g., toothpastes, mouthwashes, and professionally applied or prescribed gels, etc.) have high concentrations of fluoride (typically around 1000 to 1500 ppm) and are thus an important source of exposure in young children, who are more likely to inadvertently ingest these products.³² Among children aged 18–30 months, an average of 64 to 84 % of toothpaste is swallowed^33,34 with more appealing toothpaste flavours linked to higher intake.³⁵ The European Food Safety Authority estimated that average intake of fluoride from toothpaste is approximately eight times higher in children compared with adults on a per body weight basis (11.5 μg/kg/day versus 1.4 μg/kg/day).³⁶ Careful monitoring of young children using topically applied fluorides is required because of their inadequate control of the swallowing reflex.³⁷

Depending on geographic locations, the natural concentration of fluoride in groundwater can be elevated (i.e. >2 mg/L), most commonly in geothermal regions, volcanic rock areas, and arid zones, such as in some parts of China, India, East African Rift Valley, U.S., and Mexico. In such areas, measures for de-fluoridation of drinking water are necessary to reduce adverse health risks, including severe dental and skeletal fluorosis.³⁸

Fluoride absorption, distribution, and excretion

In the absence of calcium, approximately 80 % of fluoride is absorbed in the gastrointestinal tract, with peak plasma levels typically reached within 20 to 60 min after oral intake.³⁹ When fluoride is consumed in a soluble form—such as sodium fluoride found in drinking water or toothpaste—absorption is highly efficient, approaching 100 %. In contrast, fluoride from less soluble sources, like calcium fluoride or certain foods, is absorbed less completely due to lower bioavailability.⁴⁰ Dietary factors can further reduce fluoride absorption; for example, calcium and magnesium can bind with fluoride to form insoluble compounds that limit its uptake. Additionally, absorption decreases when gastric pH is elevated.⁴¹

Once absorbed, fluoride enters the bloodstream and is either eliminated by the kidney or retained in the body; only a small fraction is excreted in feces.⁴² In adults, about 50 % of absorbed fluoride is bound to hard or soft tissues and the other 50 % is excreted in urine.³⁹ In contrast, about 80–90 % is retained in infants and young children. Approximately 99 % of the body’s fluoride is found in mineralized tissues (mainly bone) where it is strongly, but not irreversibly bound; about 1 % is found in soft tissues, including calcified parts of the pineal gland. From bone stores, fluoride can be mobilized from the resorption associated with the process of bone remodelling.

Effectiveness of CWF in caries prevention

CWF has long been viewed as one of the top ten greatest health achievements in the 20th century. Currently, the CDC reports that CWF is associated with a 25 % relative reduction in dental caries. The benefit tends to be most pronounced in primary teeth of children^43,44 but it also is found in adults.^43,45

Recent data, including a Cochrane review, has found a much smaller caries reduction benefit when examining studies conducted from 1975 onwards.^46,47

After the widespread adoption of fluoride-containing toothpaste in the 1970s, the benefits of CWF in preventing dental caries are estimated to lie somewhere between 0 and 4 %.

CWF was associated with an average of 0.24 fewer decayed, missing, and filled primary teeth (dmft) (95 % CI: −0.03 to 0.52), equating to about one-quarter of a tooth with fewer dmft. Thus, while studies initiated pre-1975 found that CWF resulted in substantial reductions in caries prevalence (i.e. up to a 60 % reduction), evidence from contemporary studies shows a much smaller benefit (i.e. absolute risk reduction of ~4 %). The shift in the effectiveness of CWF over time likely reflects the introduction of fluoride toothpaste, better access to dental care, and other factors such as nutrition.

Data compiled by the WHO from the 1970s onwards show almost uniform decline in caries prevalence across several developed countries regardless of whether the country implements CWF or not (Fig. 1). Despite widespread availability of fluoride and advances in caries prevention over the past 75 years, untreated dental caries in permanent teeth is the most prevalent health condition globally, affecting 2.4 billion people.^48,49 In the U.S., 59 % of 12- to 19-year-olds have a least one documented cavity⁵⁰ with disproportionately higher risk found among socioeconomically disadvantaged, minority populations, and those with greater health care needs.^51,52 Thus, while the prevalence of dental caries has declined, these declines in caries levels have not occurred equally across socio-economic groups.

Fig. 1.

Dental caries trends as indicated by the Decayed, Missing, or Filled Permanent Teeth (DMFT) Index for 12-year-olds in (a) eight fluoridated countries (Australia, Canada, Hong Kong, Ireland, Israel, New Zealand, Singapore, United States) and (b) sixteen nonfluoridated countries (Austria, Belgium, Denmark, Finland, France, Germany, Greece, Italy, Japan, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom). Figure based on Country/Area Profile Program data accessed from the World Health Organization Collaborating Centre for Education, Training, and Research in Oral Health, Malmö University, Sweden. Reprinted from⁵⁸.

CWF is often reported to reduce health inequalities^53,54 and to improve dental and general health more so for socially-disadvantaged children for whom access to dental care and adherence to oral health routines is low.⁵⁵ However, evidence for this claim is weak. One of the first systematic reviews of CWF known as the York Review⁵⁶ concluded that “the evidence about reducing inequalities in dental health was of poor quality, contradictory, and unreliable” .⁵⁶ More recently, two Cochrane reviews^46,47 did not find conclusive evidence regarding CWF’s impact on reducing socioeconomic disparities in oral health. A recent study conducted in the UK⁵⁷ reported data according to disparities and also found no evidence that deprivation influences the relationship between CWF and the severity of caries. That is not to say that access to fluoridated water does not reduce oral health inequalities, but that support for the claim that fluoridation addresses health disparities is weak.

Rising enamel fluorosis trends

Fluorosis occurs when excessive fluoride is ingested while tooth enamel is being mineralized. High fluoride exposure before tooth eruption affects amelogenesis (enamel formation) by disrupting the formation of hydroxyapatite crystals and causing hypomineralization of the enamel subsurface. The window of susceptibility for enamel fluorosis in permanent central incisors (the most aesthetically relevant teeth) is from birth to age 4 years, with the most susceptible period being the first two years of life. Susceptibility to enamel fluorosis can continue up to eight years, when enamel maturation is completed and before the final permanent teeth finish erupting. After teeth are formed, enamel fluorosis can no longer develop or worsen.

Enamel fluorosis can vary in severity. In mild fluorosis, the tooth enamel can have small white striations or opaque areas. In moderate fluorosis, there are larger white areas. In severe fluorosis, brown discoloration and pitting can be present. Severity of enamel fluorosis relates to the dose, frequency and timing of fluoride exposure as well as individual susceptibility factors.⁵⁹ Most fluorosis is mild to very mild, which may only be visible to dentists under certain lighting and is considered a cosmetic defect. In contrast, moderate and severe fluorosis is more visible and can disfigure the teeth.

Exposure to excessive fluoride levels in drinking water (>2 mg/L) increases risk of enamel fluorosis, though low levels of water (or plasma) fluoride have also been associated with enamel fluorosis.⁶⁰ Other risk factors include infant formula reconstituted with fluoridated water,^61,62 fluoridated toothpaste if swallowed among young children,^33,61 and dietary fluoride supplements when taken from birth or soon after.^63,64

When CWF was initiated, the ‘optimal’ level of fluoride in drinking water aimed to achieve maximum protection against dental caries, while minimizing the likelihood of enamel fluorosis. Over the past three decades, however, increases in the prevalence and severity of enamel fluorosis have been observed among adolescents in the U.S.,^65–68 suggesting that children may be ingesting more fluoride today than when fluoride was first introduced to public water supplies. In 1986–1987, 22.6 % of adolescents aged 12–15 years had enamel fluorosis that was very mild or greater compared with 40.7 % in 1999–2004.⁶⁵ More recent oral health surveys have reported an even higher prevalence of enamel fluorosis. In 2001–2002, 29.7 % of American youth evaluated as part of the National Health and Nutrition Examination Survey (NHANES) had enamel fluorosis that was very mild or greater compared with 61.3 % of youth evaluated in 2011–12;⁶⁸ (Fig. 2) the prevalence was even higher (69 %) in the NHANES 2015–2016 survey, though the CDC expressed concern about how fluorosis was evaluated in this survey.

Fig. 2.

Percent (weighted) enamel fluorosis severity levels, based on person-level Dean’s Fluorosis Index (DFI) among youth 6–9 years. Data from National Health and Nutrition Examination Surveys (NHANES) conducted between 1999–2004 and 2011–2016. *Data obtained from 1999–2004 NHANES Survey **Data obtained from 2011–2016 NHANES Survey. Adapted with permission from https://wwwn.cdc.gov/Nchs/Data/Nhanes/Public/2014/DataFiles/FLXC_H_R.htm.

The striking increase in enamel fluorosis parallels the expansion of water fluoridation and possible increases in ingestion of fluoride from various sources in childhood, including toothpaste, ready-to-drink (bottled) tea or iced tea, processed foods, infant formula, mechanically deboned meats, and fluoride pesticide residues on foods. Changes in the indices and technologies used to measure enamel fluorosis must also be considered when assessing trends in fluorosis prevalence.⁶⁹

How and when fluoride works to prevent dental caries

Fluoride prevents dental caries by improving resistance to the effect of acids. Specifically, it exerts anti-cariogenic action by promoting enamel remineralization and reducing enamel demineralization. Additionally, fluoride inhibits bacterial metabolism and acid production, thus disrupting the process of glycolysis.⁷⁰ When fluoride ions are present in the oral environment, such as from fluoridated water or toothpaste, they are absorbed into the crystal structure of the enamel surface, providing protection against the dynamics of caries formation (i.e. topical effect).

Fluoride has been shown to work both systemically and topically, but there is consensus that its main effect in preventing dental caries is exerted through topical action

(i.e. from direct contact with tooth surfaces).^71,72 Even when fluoride is ingested in drinking water, its protective mechanism is predominantly due to being absorbed into the bloodstream and eventually secreted into saliva (i.e. topical effect).

It is possible to obtain significant caries protection without ingestion of fluorides.⁷³ A meta-analysis of 70 placebo-controlled fluoride toothpaste trials involving over 42,000 children found a preventive fraction (i.e. caries increment when comparing differences between the treatment and control group) of 24 % for dmft through the use of fluoride toothpaste.⁷⁴ The benefits of fluoride toothpaste were similar between trials conducted in fluoridated and nonfluoridated communities. Hydroxyapatite (HAP)-based (i.e., fluoride-free) toothpaste are also gaining popularity as an effective alternative to fluoride toothpaste.^75–77 Thus, there is strong evidence for preventing caries using toothpaste, which can provide additional caries reduction over and above the benefits provided by CWF, but this requires compliance by the individual.

Historically, it was believed that fluoride’s primary benefit came from being incorporated into the developing enamel before teeth erupted. However, rat studies from the 1980s showed that fluoride’s main anti-caries effect was topical and after the teeth erupt. Consistent with the post-eruptive cariostatic benefit of fluoride, a randomized, double-blind trial conducted in the late 1990s⁷⁸ showed that fluoride supplementation (i.e. tablets, drops, lozenges) in pregnant women did not benefit their offspring. Professional organizations, like the ADA, the American Academy of Pediatrics, and the CDC, no longer recommend fluoride supplements for pregnant women or for infants from birth to 6 months. In contrast, prescription dietary fluoride supplements continue to be recommended by dental and medical organizations for children who live in areas without CWF, though this recommendation has recently been challenged under the leadership of Health & Human Services Secretary Robert F. Kennedy, Jr.

Developmental fluoride neurotoxicity

The developing brain is especially vulnerable to environmental neurotoxicants. During gestation and infancy, the brain undergoes rapid growth and complex neurodevelopmental processes, making it especially particularly susceptible to neurotoxicants.⁷⁹ Formula-fed infants can be at increased risk of excessive fluoride intake, especially when formula is reconstituted with fluoridated water during the first six months of life.

On a body weight basis, formula-fed infants ingest 3 to 4 times more fluoride than an adult who drinks fluoridated water.³¹

For pregnant women, fluoride intake can vary depending on factors such as body weight, the fluoride concentration in drinking water, water consumption habits, and the intake of fluoride-rich foods and beverages like black tea. Additionally, fluoride stored in a woman’s bones can be released back into the bloodstream during specific life stages, including menopause and pregnancy. This means that even if a pregnant woman stops consuming fluoridated water, her fetus may still be exposed to fluoride released from bone stores.

Fluoride can readily cross the placenta through passive diffusion.⁸⁰ In one study of pregnant women, fluoride supplements (1.5 mg/day) were found to increase fetal blood concentrations by approximately twofold.⁸¹ Animal studies have found that fluoride exposure may contribute to placental abnormalities, including inflammation and variations in vascular density and concentrations of vascular endothelial growth factor-A, which can have significant effects on pregnancy and fetal development.⁸² Fluoride also crosses the blood-brain-barrier into the brain. Animal studies have shown that fluoride can cause oxidative stress,⁸³ alterations in neurotransmitters,^84,85 decreases in certain neural receptors⁸⁴ and stunted neuronal development.⁸⁰ These considerations underscore the importance of carefully assessing total fluoride intake during pregnancy and infancy.

When the fluoridation trials began in the mid-1940s, David Ast, Chief of the New York State Health Department Dental Bureau, assured the public that “special attention will be given to the questions of … mental development and emotional stability” in children (pp. 43). However, human studies investigating the effects of fluoridation on mental development, Intelligence Quotient (IQ), or behavior were not conducted until about 70 years later. The results of these studies are summarized below.

Fluoride and child IQ

Much of the literature on fluoride neurotoxicity in humans has been published over the past 20 years, with higher-quality studies being published in the past decade. Most of the early epidemiologic studies were conducted in countries like China and India where high levels of naturally occurring fluoride are found at concentrations of 1.5 mg/L or higher. These studies consistently reported associations between higher water fluoride concentrations and lower IQ in children. Results from two meta-analyses^86,87 showed that 4 to 16-year-old children living in areas with high fluoride exposure had significantly lower IQ scores compared to those living in low-fluoride areas. In one of these studies,⁸⁶ the standardized weighted mean difference in IQ was −0.45, which corresponds to a decrement of roughly 6.8 IQ points per 1 mg/L increase in water fluoride concentration. However, these findings were largely dismissed because some of the studies included in the meta-analyses were considered to have methodological limitations and were viewed as not being relevant to areas with water fluoridation where levels are lower (0.7 mg/L).

In 2024, the National Toxicology Program (NTP) at the U.S. Department of Health and Human Services published a monograph reviewing all scientific evidence pertaining to fluoride and neurodevelopment. Consistent with prior meta-analyses, they concluded – with moderate confidence – that higher levels of fluoride exposure (e.g., drinking-water fluoride levels >1.5 mg/L) are associated with adverse cognitive outcomes in children.² The NTP conducted a subsequent meta-analysis of 59 studies that compared children exposed to higher versus lower fluoride levels. Results showed statistically significant reductions in child IQ in 88 % of the studies with losses averaging roughly 7 IQ points. The association was attenuated but remained significant when examining only the 12 high-quality studies; the overall pooled standardized mean effect difference (SMD) was −0.19, reflecting a decrement in child IQ of approximately 3 IQ points when comparing high exposed groups to low exposed groups in this mean-effects analysis.⁸⁸ However, the SMD should be interpreted with caution given that the “high” (exposure) and “low” (reference) groups can vary dramatically from study-to-study (i.e. the effect size will vary depending on the spread of the individual study data).

Regarding dose-response relationships, the NTP found a statistically significant association between urinary fluoride concentrations and child IQ when restricting exposure levels to less than 1.5 mg/L (pooled change in SMD for high quality studies: β= −0.08; 95 % CI= −0.15, −0.002), equivalent to an IQ decrement of 1.2 points.⁸⁸ The association with water fluoride concentration when restricting to levels below 1.5 mg/L remained negative (pooled change in SMD for high quality studies: β= −0.32; 95 % CI= −0.91, 0.26) but was not significant. The discrepancy between the urinary fluoride and water fluoride findings may reflect the fewer high-quality studies investigating water fluoride (3 studies; N = 879 observations) as an exposure metric compared with urinary fluoride (4 studies; N = 4179 observations). Another potential reason for this discrepancy is that water fluoride concentration does not capture the amount of water ingested nor other potential sources of fluoride intake. In contrast, urinary fluoride concentration captures total fluoride exposure from dietary intake and from bone stores and is therefore considered a more optimal exposure metric than water fluoride concentration for risk assessment.

The NTP report, which reviewed studies up to October 2023, concluded that “confidence in the associations at lower fluoride levels could be increased by additional prospective cohort studies with individual fluoride exposure measures.” Prospective cohort studies have now been conducted across nine cohorts in six countries.^89–97 Apart from the U.S.-based study,⁹⁵ which examined child behavioural outcomes in preschool-aged children, all other cohort studies examined whether prenatal fluoride exposure poses a risk to child IQ or mental development. Among the fluoride-IQ studies, significant inverse associations between higher levels of gestational fluoride exposure and lower IQ in children were reported in 5 of the 8 cohort studies.^{89,90,92,96,97} Among the 5 studies showing an inverse association between prenatal exposure to fluoride and lower IQ, three were conducted in areas where fluoride is added to drinking water or salt to reach “optimal” levels (i.e., water fluoride levels of 0.7 mg/L),^89,92,98 one was conducted in an area with low levels (<0.75 mg/L) of naturally-occurring fluoride in drinking water,⁹⁶ and one was conducted in an endemic fluorosis area in Mexico.⁹⁷ Among the studies that did not find an inverse association between prenatal exposure to fluoride and IQ, two were conducted in regions that do not add fluoride to drinking water (Denmark and Sweden)^91,94 and one was conducted in the Spanish region of Gipuzkoa where some women received fluoridated drinking water.⁹³

Findings from these prospective cohort studies have raised legitimate concerns about potential neurodevelopmental effects of fluoride.

However, the precise level at which fluoride becomes hazardous remains intensely debated. Moreover, further research is needed to examine potential susceptibility factors, including iodine deficiency⁹⁹ and genetic risk factors,¹⁰⁰ which may exacerbate fluoride neurotoxicity.

Fluoride and child behavior

Comparatively fewer studies have assessed the impact of prenatal or childhood fluoride exposure on neurobehavioral outcomes, but the emerging evidence raises concern. An early ecological analysis of U.S. data linked community water fluoridation with ADHD prevalence¹⁰¹: drawing on the National Survey of Children’s Health and the CDC fluoridation records, it was estimated that each 1 % rise in artificial fluoridation in 1992 corresponded to roughly 67,000–131,000 additional parent-reported ADHD diagnoses over the subsequent decade, even while controlling for socioeconomic status. While such population-level findings cannot establish causality, they spurred more detailed, individual-level investigations.

Recent prospective birth-cohort studies conducted in areas with optimal fluoridation have found largely consistent findings. In the ELEMENT cohort in Mexico¹⁰²; (n = 213), higher creatinine-adjusted maternal urinary fluoride (MUF) across trimesters (mean MUF = 0.85 mg/L) was associated with more ADHD-like symptoms – particularly inattention – on the Conners’ Rating Scale-Revised in children aged 6–12. Similarly, in the MADRES cohort in Los Angeles;⁹⁵ (n = 263; median MUF = 0.75 mg/L) higher MUF exposure in the third trimester roughly doubled the odds that 3-year-olds would score in the borderline/clinical range for total, internalizing, and externalizing problems on the Child Behavior Checklist. The NICE cohort in Sweden (n = 341; median MUF = 0.72) also found that higher specific gravity adjusted MUF exposure in the third trimester was associated with increased externalizing problems and ADHD raw scores as measured by the Child Behavior Checklist at age 4.⁹⁴ In contrast with these findings, in the INMA cohort in Spain,¹⁰³ higher creatinine-adjusted MUF across pregnancy (n = 255; mean MUF = 0.62 mg/L) predicted a lower risk of inattention at age 11, suggesting possible population differences in vulnerability.

Cross-sectional studies also reveal associations between childhood fluoride exposure and behavioral problems. In the Canadian Health Measures Survey with children and youth ages 6–17 (n = 1877; mean tap-water fluoride 0.23 mg/L, specific gravity adjusted urinary fluoride 0.62 mg/L), higher water fluoride concentration (but not urinary fluoride) was linked to more than a sixfold greater odds of an ADHD diagnosis, and increased hyperactivity/inattention scores on the Strengths and Difficulties Questionnaire.¹⁰⁴ Furthermore, a U.S. cohort in Cincinnati (Cincinnati Childhood Allergy and Air Pollution Study; n = 334; mean urinary fluoride 0.88 mg/L), found that 12-year-olds with higher specific gravity adjusted urinary fluoride levels exhibited greater somatization and internalizing symptoms, with boys nearly seven times more likely than girls to reach the “at-risk” threshold for internalizing problems.¹⁰⁵ Similarly, in China, a cross-sectional study of 325 school-children (aged 9–13; mean urinary fluoride 1.54 mg/L) linked higher unadjusted urinary fluoride to elevated psychosomatic problems on the Conners’ Rating Scales-Revised.¹⁰⁶ However, in an Australian cohort (n = 2682), percent-lifetime exposure to fluoridated water (0 %, >0–<100 %, 100 % from birth to age 5) was not significantly related to behavioral outcomes on the Strengths and Difficulties Questionnaire at ages 5–14.¹⁰⁷

Taken together, these findings underscore a generally adverse pattern of early life fluoride exposure on neurobehavioral outcomes including both internalizing and externalizing problems, with some inconsistencies possibly driven by differences in timing and method of exposure assessment, developmental windows, outcome measures, and population susceptibility.

Mechanisms of fluoride neurotoxicity and endocrine disruption

Toxicologic studies have found that fluoride can disturb synaptic plasticity,¹⁰⁸ reduce brain-lipid or phospholipid content, and the enzymes that metabolize them, inhibit cholinesterase activity, and reduce acetylcholine.³¹ Experimental studies have shown that fluoride can induce mitochondrial dysfunction,¹⁰⁹ enhance oxidative stress⁸³ and inhibit metalloproteins.^110,111 Another potential mechanism relates to fluoride’s effects on immune function, which has received some attention in experimental studies.^31,112 Neurotoxicity of fluoride also has been associated with disruption of the thyroid gland, a mechanism that underlies various other endocrine disrupting chemicals.^31,113 In fact, sodium fluoride was used as a medical treatment for hyperthyroidism up until the 1950s, at which time medications were developed to reduce thyroid gland overactivity.¹¹⁴

Fluoride and thyroid hormone disruption

While the mechanisms explaining fluoride’s neurotoxic effects remain unclear, accumulating evidence suggests thyroid toxicity may play a role. Some studies of children and non-pregnant adults in Southeast Asia have reported associations between higher drinking water- and urine-fluoride concentrations and elevated serum thyroid stimulating hormone (TSH), lower serum free and total thyroxine (T4) and triiodothyronine (T3) concentrations, and increased thyroid gland volume; all of which have been observed in those with hypothyroidism.^115–117 Alterations in thyroid structure¹¹⁸ and function^117,119 have been reported among children living in fluoride endemic areas (i.e., water fluoride concentration range: 1.23 – 5.8 mg/L) of China and India. In children aged 7–12 years, thyroid volume was found to increase by 0.22 cm³ (95 % CI: 0.14, 0.31) per 0.88 mg/L increase in urinary fluoride. Elevations in serum TSH levels have also been observed among 7–13-year-old children, whereby every 1 mg/L increase in water and urinary fluoride concentration was associated with a 0.13 and 0.11 μIU/mL increase in TSH, respectively.¹¹⁷ Similarly, an ecologic study from England found a higher prevalence of hypothyroidism in areas with higher levels of fluoride in drinking water.¹²⁰

Other studies have reported opposite results, linking higher water-fluoride levels to elevated serum total T4 and T3 levels.¹²¹ Differences in findings across these studies may be attributed to variability in study design, methodological rigor, level and duration of fluoride exposure, as well as age at exposure. Fluoride-thyroid associations have been examined through experimental work as well, with one study reporting lower free T4 (FT4) and T3 (FT3) levels in Wistar rat offspring whose mothers were exposed to higher doses of fluoride (i.e., 20 mg/kg of body weight and >100 ppm) in gestation.^122,123 Comparable findings were reported in adult Wistar rats at lower, prolonged fluoride exposure levels.¹²⁴

Thyroid disruption is of particular concern in pregnancy because the developing fetus relies exclusively on maternal thyroid hormones during the first 10–12 weeks of gestation, and to a lesser extent throughout the second and third trimesters.¹²⁵ Considering thyroid hormones are critical for optimal fetal growth and neurodevelopment, gestational hypothyroidism has been associated with adverse outcomes in offspring, including preterm birth, increased risk of neurodevelopmental disorders, and lower IQ.^126–128 A prospective birth cohort study from Denmark (i.e., Danish National Birth Cohort) found that elevated maternal TSH (≥ 10 mIU/L) and low FT4 (<10 pmol/L) were associated with an 8 to 13-point reduction in child verbal IQ.¹²⁷ Similar findings were reported in a meta-analysis.¹²⁹ Primary (i.e., clinical) hypothyroidism in pregnancy has also been linked with increased risk of autism spectrum disorder (ASD; adjusted hazard ratio: 1.31–1.80)¹³⁰ and ADHD (adjusted odds ratio: 1.2)¹³¹ among mother-child pairs in the U.S., Denmark, and Norway. Importantly, even mild reductions in maternal thyroid hormone levels (including subclinical hypothyroidism) during gestation have been associated with adverse neurodevelopment.^132–134 There also is some evidence to suggest that the adverse outcomes associated with maternal thyroid dysfunction in pregnancy can persist throughout childhood and adolescence.¹³⁵

Until recently, little was known about the potential impact of fluoride exposure on maternal thyroid function in pregnancy, especially in areas with optimally fluoridated water. Using data from a Canadian pregnancy cohort (MIREC), results indicated a significant association between maternal fluoride exposure and hypothyroidism in pregnancy; a 0.5 mg/L increase in drinking water fluoride concentration was associated with a 65 % increase in the odds of having a diagnosis or meeting criteria for primary hypothyroidism (adjusted OR = 1.65, 95 % CI: 1.04, 2.60).¹³⁶ The association was strengthened when restricting the sample to only women who lived in the same residence for a year or longer (adjusted OR = 1.80, 95 % CI: 1.07, 3.01).¹³⁷ Males born to women with hypothyroidism were also found to have significantly lower Full-Scale IQ scores.¹³⁶

In a second study conducted in the MIREC cohort, higher levels of fluoride exposure were associated with alterations in maternal thyroid hormone levels; the magnitude of which varied by fetal sex.¹³⁸ In particular, a 1 mg/L increase in MUF concentration was associated with a 35 % increase in TSH levels among those pregnant with female fetuses. These results suggest that maternal thyroid disruption may play a role in fluoride-induced developmental neurotoxicity observed in a previous study of this same cohort,⁹² though further research is needed.

Fluoride may impact thyroid function by several potential mechanisms. It may inhibit the deiodinase enzymes that are necessary for thyroid hormone production, resulting in decreased blood-T3 and T4 levels and increases in circulating TSH.^139,140 Fluoride also may induce structural and functional changes to the follicular epithelial cells of the thyroid gland (e.g., decline in the colloidal content and damage to the endoplasmic reticulum) resulting in insufficient secretion of Tg, and thus disruption to thyroid hormone synthesis more broadly.^122,141 Further, fluoride may interfere with iodine to exert its negative effects on thyroid function, perhaps by inhibiting the expression and activity of sodium iodide symporters that are necessary for mediating active iodide transport into the thyroid, resulting in lower iodine availability and the indirect suppression of thyroid hormone production.^142–144

It is unknown whether prenatal exposure to fluoride could impact offspring thyroid functioning in childhood. Studies investigating other endocrine-disrupting chemicals (EDCs) have reported significant associations between maternal exposure to phthalates,^145,146 parabens^145,147 organochlorine compounds,¹⁴⁸ and per- and polyfluoroalkyl substances^149,150 in gestation, and alterations in neonatal TSH, T4, and T3 levels; with some changes in thyroid function persisting throughout childhood (i.e., 8–9 years of age).¹⁴⁶ Maternal hypothyroidism in pregnancy, with and without autoimmune etiology, has also been associated with elevated TSH levels in neonates¹⁵¹ and adolescents,¹⁵² suggesting that maternal thyroid dysfunction in pregnancy may impact thyroid system functioning in the offspring. This is especially important considering the findings linking fluoride exposure to increased risk of maternal hypothyroidism in pregnancy.¹³⁶

Fluoride, sex hormones, and pubertal outcomes

Associations between fluoride exposure and reductions in children’s sex hormone levels¹⁵³ and changes in pubertal onset^95,154 have also been reported. In one U.S. study,¹⁵³ testosterone levels were significantly lower among males (aged 6–19 years) with plasma fluoride concentrations in the second (%change= −8.08; 95 % CI: −17.36, 2.25) and third tertiles (%change= −21.65; 95 % CI: −30.44, −11.75) relative to those with plasma fluoride concentrations in the first tertile. Similar findings were reported for females with respect to estradiol (%change for those with plasma fluoride in the third relative to first tertile= −9.87; 95 %CI: −18.59, −0.22).¹⁵³ Another U.S. based study found a significant association between higher water fluoride levels and younger age at first menstrual period (B for an IQR increase= −0.28; 95 %CI: −0.54, −0.02) among 16–19-year-old females, such that a 0.53 mg/L increase in tap-water fluoride was associated with a 3.3-month earlier menarche. Non-Hispanic Black adolescents were found to be especially vulnerable to fluoride’s potential impact on age at menarche (B for an IQR increase in plasma fluoride= −0.42; 95 %CI: −0.61, −0.23). While fluoride has been linked with early puberty among females, the opposite has been reported for males. In particular, higher urinary fluoride concentrations have been associated with greater odds of delayed genital development [OR for an IQR (0.31 mg/L) increase= 0.71; 95 %CI: 0.53, 0.95] and pubic hair growth [OR for an IQR increase= 0.71; 95 %CI: 0.51, 0.98 in Mexican males aged 10–17 years].¹⁵⁴

Early and delayed puberty have been linked to numerous adverse mental and physical health outcomes in childhood and adolescence. Studies from North America, Europe, Asia, and Australia have reported associations between early or delayed pubertal onset (assessed via parent- and self-report or physical examination) and increased risk of anxiety, depression, and substance use,^155–157 externalizing behaviors,¹⁵⁸ poor sleep, lower quality of life,¹⁵⁹ reduced academic performance,¹⁶⁰ less physical activity, and poor physical health.^159,161 Many of these studies also highlight sex as a key moderator, with female youth noted to experience more severe and long-lasting mental health difficulties related to early pubertal onset.^155,156 This is consistent with the early timing hypothesis, which links early pubertal adjustment with risk of negative outcomes among early maturing females.¹⁶²

Conclusion and implications for science and policy

Fluoridation was first introduced in the 1940s and officially endorsed by the U.S. PHS in the 1950s. Over the past 75 years, fluoridation has been implemented in the U.S. and many other countries. From the outset, however, fluoridation has sparked vigorous debate over its benefits, safety, and ethics.¹⁶³ This debate continues today with many claims and counterclaims similar to discussions that took place when CWF was first adopted, but now within the context of more knowledge about fluoride’s mechanisms of action, effectiveness, and safety. The debate over CWF remains highly polarized and has become increasingly politicized in recent years, highlighting the need to better understand public views and preferences on this issue.

Much has changed since fluoridation was first introduced. Contemporary evidence suggests the benefits of CWF may not be as substantial today as compared to 75 years ago, in part, due to the significant influx of fluoride sources. While early studies conducted in the 1950s and 1960s found that adding fluoride to drinking water could lower cavity rates by up to 60 %, more recent controlled studies suggest far smaller benefits than in the past.⁴⁷ Moreover, mechanistic studies from the 1980s and 90 s demonstrated that fluoride’s effects are mainly topical, which contrasted with earlier beliefs that its benefits were primarily systemic. Further, mounting scientific evidence has emerged regarding rising rates of enamel fluorosis,^65–68 and potential adverse health effects of fluoride exposure, including risk of diminished child IQ, behavioral problems, and endocrine disrupting effects. While adverse health effects of fluoride at higher dosage levels have long been known, evidence now suggests potential effects at lower exposure ranges, particularly among vulnerable populations.⁸⁸

When high-quality, prospective studies began to suggest that fluoride exposure might affect cognitive outcomes in children living in fluoridated areas, proponents of fluoridation dismissed these findings on the grounds that the research was conducted outside the United States, specifically in Canada and Mexico. However, the fluoride exposure levels measured in these studies (in both urine and water) were comparable to those found in U.S. populations, underscoring their relevance. Other critics argued that findings stemming from urinary fluoride or water fluoride levels at or above 1.5 mg/L are not relevant for informing discussion about fluoridation safety because the hazardous level is approximately twice that found in fluoridated communities. But a twofold margin is not sufficient for ensuring the safety of vulnerable populations from a hazard level. A tenfold safety margin is typically used by the U.S. Environmental Protection Agency. Thus, if 1.5 mg/L is identified as a hazardous level, then water fluoride concentrations would need to be closer to 0.15 mg/L to adequately protect the most vulnerable populations given differences in individual sensitivity. But not everyone agrees, raising questions about why normal safety margins are not applied to water fluoridation. Other proponents of CWF deny the evidence and instead label the research suggesting adverse health effects of fluoride as being “flawed”,^164,165 despite the NTP report considering the research to be of high quality.

Reaching consensus on controversial topics like CWF is challenging when organized efforts actively dispute scientific findings that conflict with deeply held beliefs.¹⁶⁶ Overcoming such skepticism obviously demands robust, trustworthy, and compelling evidence. Scientific consensus emerges when independent researchers, using diverse approaches to address different aspects of a problem, consistently reach the same conclusions. More research is therefore urgently needed, particularly for populations with low fluoride exposure levels. We need to address the effects of cumulative fluoride exposure across the lifespan, understand dietary sources, susceptibility factors, and how to best assess total fluoride intake. In order to justify population-wide exposure to fluoride in drinking water, a thorough risk-benefit assessment is needed that includes vulnerable populations, such as infants, pregnant women, and those with kidney disease or high water intake. Animal studies using fluoride exposure levels that are analogous to current human exposure levels also will be important.

Public health interventions should be continuously evaluated to ensure that their benefits outweigh any potential risks. CWF has been widely implemented for over 75 years, but evolving scientific evidence and diversification of fluoride sources necessitate ongoing re-evaluation. Achieving this goal demands a critical and objective evaluation of emerging research and an openness to considering alternative methods of delivering fluoride to prevent caries and reduce disparities in oral health. As scientific evidence evolves over time and new strategies to prevent adverse dental health outcomes emerge, our understanding must adapt accordingly. This ongoing evolution in our understanding of the risks and benefits of CWF is a fundamental aspect of public health decision making.

PART 2. Public knowledge, attitudes, and behaviors about fluoride

Public perception of CWF is undergoing a notable shift, driven by emerging scientific research, increased media attention, and growing political debate, which may contribute to increased fear of fluoride. By studying public perceptions of water fluoridation, we can examine the factors that drive support or opposition for this public health practice. Understanding contemporary perceptions of CWF is essential for informing policymaking and risk communication moving forward. This information is especially critical today given changes in scientific literacy, the enabling of information to spread quickly on social media, and declining levels of trust in medical and public health professionals in the wake of the COVID-19 pandemic.¹⁶⁷

Previous studies have explored public support for CWF in various countries, including Australia,^168–170 Japan,¹⁷¹ Canada,^172,173 Scotland,¹⁷⁴ and the U.S.¹⁷⁵ Some surveys have investigated how socio-demographic groups may hold distinct and nuanced views on CWF.^170,176 However, much of the existing data on public attitudes is outdated, uses convenience samples in small geographic regions, or lacks depth in capturing the complexities of today’s increasingly polarized discourse. Prior studies tend to focus on fluoride’s dental health benefits,¹⁷⁷ while giving limited consideration to perceived risks and ethical concerns – factors that now feature prominently in opposition to CWF.¹⁷⁸ With a growing body of research suggesting potential neurotoxic effects of fluoride, there is a need for updated, comprehensive surveys that reflect contemporary public perceptions. Such efforts should aim to understand how evolving evidence on both the risks and benefits of fluoridation shapes opinion, particularly in a context where public trust in health guidance is increasingly contested.

In early 2025, we conducted a nationally representative survey to understand what adults living in Canada and the U.S. know about topical and systemic fluoride use, and to explore concerns about safety, trust in public health officials, and perceived benefits of fluoride in the public water supply. Given the evolving landscape surrounding the risks and benefits of CWF, we further explored how individual-level support for water fluoridation may shift under certain hypothetical risk-benefit scenarios. Finally, among participants who reported having children under 6 years of age, we explored what parents know about safe fluoride use with children.

Methods

Participants

We recruited adults aged 18 years and older living in Canada or the U.S. The survey was conducted in English and all participant information was de-identified. Participants who identified as parents were asked to answer additional questions related to their children’s oral health habits. Prior to completing the survey, all individuals were provided with a detailed consent form outlining the study’s objectives, procedures, potential risks, and benefits. Participants were informed that their participation was entirely voluntary, their results would be kept anonymous, and that they could withdraw at any time without penalty. The study received ethics approval from the Human Participants Review Committee at York University.

The survey was initiated on December 30, 2024, and was completed on February 22, 2025, after achieving our pre-determined target sample sizes for Canadian (n = 2000) and U.S. (n = 6000) respondents. Approximately 50 % of responses from each country were collected in the first wave of the survey between December 30, 2024, to January 6, 2025, and the remaining 50 % were collected in the second wave of the survey between January 7 and February 22, 2025. We created these two waves to control for potential effects of fluoride-related media attention occurring over the course of data collection. For each wave of our survey, recruitment was stratified by U.S. state and Canadian province to create a sample distribution similar to the national distribution of both countries. The Canadian territories were not represented in our survey, as there were less than ten respondents from these regions. Age and gender characteristics were matched across all the sampled geographic regions.

Survey

Survey data were collected using CloudResearch Prime Panels, an online platform designed to facilitate high-quality research by providing access to a diverse pool of respondents. Prime Panels recruits participants from multiple sources, including online research panels, to enhance a representative sample. Its proprietary SENTRY^® system maintains data quality by detecting inattentive responses, failed CAPTCHAs, and ineligible participants. To further ensure data integrity, we excluded responses if they were completed in less than 300 s due to concerns about validity based on pilot data. The survey included questions assessing several different domains as described below.

Demographic characteristics were collected, including information about educational attainment, age, gender, annual household income, marital status, ethnicity, number of children, political affiliation (left versus right), place of residence (major city, mid-size city, small town, rural area), personal fluoride use, as well as views on common childhood vaccines. Respondents were given the optional response of ‘prefer not to answer’ for questions pertaining to educational attainment, gender, income, marital status, place of residence, ethnicity. American states were categorized by census region (Northeast, Midwest, South, and West).

Survey aims

The first part of the survey examined what participants know about topical and systemic fluoride use. Knowledge about CWF was assessed by asking participants to select the most accurate response to “Why is fluoride added to drinking water?” from a list of four possible reasons; they could also select “I don’t know” or provide their own response in an open field. We then assessed self-rated knowledge by asking participants to describe their awareness regarding water fluoridation, using a 4-point scale ranging from ‘I have never heard of water fluoridation’ to ‘I know a lot about water fluoridation’, and whether fluoride is currently being added to the water supplying their home (Yes, No, or I don’t know). We explored differences in responses to these questions by specific demographics in both the Canadian and American samples, including by gender, age, household income, highest level of education, and parental status.

The second part of the survey assessed public opinions about CWF. Participants were asked: “Do you think your tap water should be fluoridated?” (Yes, No, I don’t know). Responses were summarized by key demographic variables only for participants who had endorsed that they had at least heard of CWF (n = 7173); the remaining 838 respondents who endorsed that they had never heard of CWF were excluded. Using this subsample, we examined belief statements about CWF to gain insights into why participants think tap water should or should not be fluoridated. Specifically, we asked participants to indicate whether they agree or disagree (or did not know enough to respond) with justifications that are commonly made for or against fluoridation. Justifications included: “The benefits of water fluoridation outweigh any risks.”; “Fluoridation of drinking water is safe.”; and “Water fluoridation imposes on personal rights or freedoms.” Results are summarized only for participants who reported having at least some knowledge of CWF.

Finally, participants were presented with five hypothetical risk-benefit scenarios and asked to indicate their level of support for adding fluoride to drinking water by selecting one of the following responses: strongly support, somewhat support, neutral, somewhat oppose, and strongly oppose.

Results

A total of 9270 participants were initially recruited with 7043 from the U.S. (76 %) and 2227 from Canada (24 %). CloudResearch’s SENTRY^® system automatically excluded 40 participants (0.4 %) who did not meet the study’s minimum age of 18 years, as well as 816 participants (8.8 %) who failed at least two out of three attention checks or did not pass the reCAPTCHA verification process. Additional data cleaning was conducted to remove 403 participants (4.3 %) who completed the survey in under 300 s (5 min) as responses below this threshold were deemed unreliable. After exclusions, the final sample consisted of 8011 participants, of which 6011 were from the U.S. (75 %) and 2000 were from Canada (25 %). Participants completing the survey in the first and second wave of data collection were comparable on demographic characteristics. For the purpose of the current study, we combined responses collected over the entire recruitment period. Among the 8011 participants, 1025 were parents of a child under the age of 6 years.

Knowledge about CWF

Among the 8011 respondents, 4771 (59.6 %) correctly identified the purpose of community water fluoridation (CWF) as “to prevent tooth decay”. The most common incorrect response was “to sanitize water”, which was selected by 20.4 % of the total sample; 20 % endorsed “I don’t know” or selected another incorrect response.

We found substantial variability in fluoride knowledge by age, education, and other socio-demographic determinants (Table 1). Specifically, individuals aged 65 and older were most likely to know why fluoride is added to drinking water (84.5 % responded correctly), while young adults aged 18–29 were the least likely to answer the question correctly (36.5 %). Respondents with higher educational attainment demonstrated greater accuracy; 73.1 % of those with a postgraduate degree selected the correct answer compared to 50.8 % of those with a high school education or less. Notably, correct responses were also more common among participants identifying as White or Caucasian (67.9 %) compared to Black or African American (39.4 %) or other ethnic backgrounds (49.3 %). Political orientation showed modest differences, with those identifying on the political right (63.1 %) and left (65.1 %) slightly outperforming centrists (54.6 %). A similar proportion of U.S. and Canadian participants answered the knowledge question correctly (59.2 % vs. 60.7 %, respectively).

Table 1.

Proportion of responses to why fluoride is added to drinking water. Results reported by demographics.

	n	To build strong bones	To keep pipes from rusting	To prevent tooth decay	To sanitize the water	I don’t know/other
Total sample	8011	313 (3.9)	353 (4.4)	4771 (59.6)	1634 (20.4)	940 (11.7)
Country
Canada	2000	64 (3.2)	73 (3.7)	1213 (60.7)	444 (22.2)	206 (10.3)
United States	6011	249 (4.1)	280 (4.7)	3558 (59.2)	1190 (19.8)	734 (12.2)
Parent of a child under 6	1025	79 (7.7)	91 (8.9)	440 (42.9)	295 (28.7)	120 (11.7)
Gender
Man	3918	157 (4.0)	203 (5.2)	2216 (56.6)	938 (23.9)	404 (10.3)
Woman	3925	147 (3.7)	138 (3.5)	2490 (63.4)	650 (16.6)	500 (12.7)
Non-Binary	71	5 (7.0)	4 (5.6)	31 (43.7)	19 (26.8)	12 (16.9)
Prefer not to answer	95	4 (4.2)	8 (8.4)	33 (34.7)	26 (27.4)	24 (25.3)
Age
18–29	1560	85 (5.4)	152 (9.7)	570 (36.5)	467 (29.9)	286 (18.3)
30–44	1995	105 (5.3)	125 (6.3)	967 (48.5)	520 (26.1)	278 (13.9)
45–64	2716	95 (3.5)	66 (2.4)	1766 (65.0)	492 (18.1)	297 (10.9)
65+	1738	28 (1.6)	9 (0.5)	1468 (84.5)	155 (8.9)	78 (4.5)
Household Income
<$30,000	1410	60 (4.3)	87 (6.2)	719 (51.0)	326 (23.1)	218 (15.5)
$30,000 – $60,000	1904	78 (4.1)	83 (4.4)	1141 (59.9)	381 (20.0)	221 (11.6)
$60,001 – $100,000	1844	58 (3.1)	76 (4.1)	1188 (64.4)	344 (18.7)	178 (9.7)
$100,001 – $150,000	1447	61 (4.2)	58 (4.0)	892 (61.6)	316 (21.8)	120 (8.3)
>$150,000	1003	45 (4.5)	39 (3.9)	652 (65.0)	180 (17.9)	87 (8.7)
Prefer not to answer	401	11 (2.7)	10 (2.5)	178 (44.4)	86 (21.4)	116 (28.9)
Education
Highschool or less	2979	126 (4.2)	181 (6.1)	1512 (50.8)	671 (22.5)	489 (16.4)
College degree/diploma	2192	75 (3.4)	83 (3.8)	1343 (61.3)	469 (21.4)	222 (10.1)
University degree	1615	61 (3.8)	53 (3.3)	1072 (66.4)	311 (19.3)	118 (7.3)
Postgraduate degree	1107	48 (4.3)	27 (2.4)	809 (73.1)	156 (14.1)	67 (6.1)
Prefer not to answer	116	3 (2.6)	9 (7.8)	34 (29.3)	26 (22.4)	44 (37.9)
Ethnicity
White or Caucasian	5094	171 (3.4)	161 (3.2)	3459 (67.9)	825 (16.2)	478 (9.4)
Black/African American	1279	83 (6.5)	90 (7.0)	504 (39.4)	383 (29.9)	219 (17.1)
Other	1638	59 (3.6)	102 (6.2)	808 (49.3)	426 (26.0)	243 (14.8)
Political Status
Left	1999	93 (4.7)	84 (4.2)	1301 (65.1)	369 (18.5)	152 (7.6)
Center	3810	136 (3.6)	179 (4.7)	2080 (54.6)	856 (22.5)	559 (14.7)
Right	2202	84 (3.8)	90 (4.1)	1390 (63.1)	409 (18.6)	229 (10.4)

Regarding self-rated knowledge about CWF, most respondents endorsed ‘I have heard of water fluoridation, but know little about it’ (46.3 %) or ‘I have some knowledge about water fluoridation’ (37.1 %). Few respondents endorsed having never heard of CWF (10.4 %) or knowing a lot about CWF (6.1 %). When asked whether fluoride is currently being added to the water supplying their home, 47.9 % endorsed yes, 16.9 % endorsed no, and 35.2 % reported ‘I don’t know’.

Public opinions about CWF

Among the 7173 participants with at least some awareness of CWF, 50.8 % responded that their tap water should be fluoridated, 26.9 % responded “no,” and 22.2 % reported that they did not know (Table 2). Support for fluoridation was higher among older adults, with 59.8 % of those aged 65 and older responding “yes,” compared to 45.8 % and 47.8 % of those aged 30–44 and 18–29, respectively. Support also varied by education level: 62.9 % of those with a postgraduate degree supported fluoridation, compared to 44.7 % of participants with a high school education or less. Regarding political orientation, 64.2 % of left-leaning participants supported fluoridation compared to 47.3 % of those identifying as centrist and 44.5 % of those identifying as right-leaning. Opinions about whether tap water should be fluoridated showed less variability as a function of income and ethnicity. Finally, supporters of CWF were more likely to report “a great deal” or “a fair amount” of trust in public health officials (86.7 %) compared with non-supporters of CWF (52.1 %).

Table 2.

Proportion of individuals who answered yes, no, or I don’t know to the question “Do you think your tap water should be fluoridated?”. Responses shown by socio-demographic variables and are only reported for participants with at least some awareness of CWF.

	n	Yes	No	I don’t know
Total sample that has heard of CWF	7173	3646 (50.8)	1935 (26.9)	1592 (22.2)
Parent of a child under 6	886	442 (49.8)	280 (31.6)	164 (18.5)
Country
Canada	1820	969 (53.2)	436 (24.0)	415 (22.8)
United States	5353	2677 (50.0)	1499 (28.0)	1177 (22.0)
Gender
Man	3557	1908 (53.6)	957 (26.9)	692 (19.5)
Woman	3495	1684 (48.2)	943 (27.0)	868 (24.8)
Non-Binary	50	27 (54.0)	11 (22.0)	12 (24.0)
Prefer not to answer	70	26 (37.1)	24 (34.3)	20 (28.6)
Age
18–29	1254	599 (47.8)	361 (28.8)	294 (23.4)
30–44	1748	801 (45.8)	540 (30.9)	407 (23.3)
45–64	2482	1237 (49.8)	673 (27.1)	572 (23.0)
65+	1688	1009 (59.8)	360 (21.3)	319 (18.9)
Household Income
<$30,000	1189	540 (45.4)	350 (29.4)	299 (25.1)
$30,000 – $60,000	1722	865 (50.2)	485 (28.2)	372 (21.6)
$60,001 – $100,000	1705	881 (51.7)	460 (27.0)	364 (21.3)
$100,001 – $150,000	1332	752 (56.5)	325 (24.4)	255 (19.1)
>$150,000	925	499 (53.9)	237 (25.6)	189 (20.4)
Prefer not to answer	299	108 (36.1)	78 (26.1)	113 (37.8)
Level of Education
Highschool or less	2523	1129 (44.7)	768 (30.4)	626 (24.8)
College degree/diploma	2013	968 (48.1)	572 (28.4)	473 (23.5)
University degree	1512	873 (57.7)	347 (22.9)	292 (19.3)
Postgraduate degree	1035	651 (62.9)	214 (20.7)	170 (16.4)
Prefer not to answer	89	24 (27.0)	34 (38.2)	31 (34.8)
Ethnicity
White or Caucasian	4731	2430 (51.4)	1265 (26.7)	1036 (21.9)
Black/African American	1056	568 (53.8)	276 (26.1)	212 (20.1)
Other	1386	648 (46.8)	394 (28.4)	344 (24.8)
Political Status
Left	1846	1185 (64.2)	313 (17.0)	348 (18.9)
Center	3312	1565 (47.3)	898 (27.1)	849 (25.6)
Right	2015	896 (44.5)	724 (35.9)	395 (19.6)

Among the 3646 individuals who indicated that tap water should be fluoridated, 82.9 % agreed that the benefits of CWF outweigh any risks and 87.0 % agreed that fluoridation of drinking water is safe (Fig. 3). In contrast, among the 1935 individuals who do not think tap water should be fluoridated, only 17.8 % agreed that the benefits of CWF outweigh any risks and only 22.6 % agreed that fluoridation of drinking water is safe. In general, nonsupporters of CWF were about two to three times more likely to endorse “I don’t know” compared with supporters of CWF on questions related to effectiveness and safety of CWF. Finally, the majority (66.2 %) of supporters of CWF do not see this public health practice as imposing on personal rights or freedoms, whereas the majority of nonsupporters are more likely to think that water fluoridation imposes on personal rights and freedoms (61.3 %).

Fig. 3.

Percentage of those who agree, disagree, or don’t know (DK) whether (A) the benefits of water fluoridation outweigh any risks, (B) fluoridation imposes on personal rights or freedoms, and (C) fluoridation of drinking water is safe. Results shown for individuals who endorse support (n = 3646) or non-support for CWF (n = 1935).

Participants were also asked to indicate how concerned they are about exposure to lead, per- and polyfluorinated substances (PFAS), and plastics in drinking water. Concern (either “very concerned” or “somewhat concerned”) about each of these contaminants was similar among both supporters of CWF [lead (77.5 %), PFAS (64.7 %), plastics (76.7 %)] and non-supporters [lead (75.9 %), PFAS (67.9 %), plastics (77.3 %)].

Responses to hypothetical trade-offs between risks and benefits

Support (either strongly or somewhat) for adding fluoride to drinking water was high (70.3 %) if it can reduce tooth decay (Fig. 4). However, when the preventive benefit was quantified to a saving of one cavity per person over a lifetime, support for adding fluoride to drinking water declined to 49.0 %. When potential health risks were introduced, participants’ level of support declined even more. For example, if adding fluoride to drinking water was associated with a 1 % increase in the number of children with intellectual disability, then support for CWF was only endorsed by 24.1 %. Likewise, if adding fluoride to drinking water was associated with increased risk of thyroid problems, then support for CWF was only endorsed by 19.9 %. Finally, when the hypothetical scenario included both risks (i.e. reduced IQ) and benefits (i.e. prevents one cavity), participants were less supportive of adding fluoride to drinking water (23.0 %) as compared to when benefits of preventing one cavity was reported in the absence of any adverse health effects (49.0 %).

Fig. 4.

Percentage of respondents who endorsed strongly or somewhat supporting the addition of fluoride to drinking water when presented with different hypothetical scenarios. Based on a sample of 8011 Canadian and American respondents.

Caregiver knowledge, attitudes, and behaviors about fluoride

To better understand fluoride-related knowledge, attitudes, and behaviors among caregivers, we analyzed responses from 1025 participants who reported being a parent or legal guardian of a child under the age of six. We examined self-reported use of fluoride toothpaste, timing and quantity of use, brushing frequency, caregiver knowledge of fluoride sources and recommended guidelines for toothpaste use, and support for CWF.

Caregiver knowledge about fluoride.

Knowledge of fluoride’s purpose and sources was mixed. While 42.9 % of caregivers correctly identified “preventing tooth decay” as the reason for why fluoride is added to drinking water, 45.4 % responded incorrectly and 11.7 % were uncertain. Regarding infant formula, 32.1 % agreed with the statement that it should be mixed with fluoridated water to prevent cavities, whereas 45.9 % disagreed and 22.0 % were unsure. Knowledge about early life fluoride exposure was also variable, with 41.1 % agreeing that ingesting fluoride before tooth eruption reduces cavity risk, nearly 30 % disagreeing, and 28.9 % indicating uncertainty.

Self-rated knowledge about CWF among caregivers was comparable to the overall sample. The majority of caregivers endorsed ‘I have heard of water fluoridation but know little about it’ (44.8 %) or ‘I have some knowledge about water fluoridation’ (32.4 %). Few respondents endorsed ‘I have never heard of water fluoridation’ (13.6 %) or ‘I know a lot about water fluoridation’ (9.3 %).

Fluoride toothpaste use.

Across the total sample of caregivers with a child under the age of six, 60.4 % reported that their child currently uses fluoride toothpaste, 31.8 % reported non-use, and 7.7 % reported “I don’t know.” As expected, use increased with age: 50.0 % among children under two years old, 60.1 % among those aged 2 to 4 years, and 70.3 % among five-year-olds. Caregivers were asked to indicate how much toothpaste their child uses when brushing their teeth using the following visual as a guide (Fig. 5).

Fig. 5.

Survey question asked to parents and caregivers of children under the age of six.

While the recommended amount of fluoride toothpaste for children under three years of age is a “rice-grain” size,¹⁷⁹ 78.8 % of caregivers with children under three reported using more than the recommended amount: 43.8 % reported using a pea-sized amount, 26.6 % reported using a half-load, and 8.4 % a full-load. Only 21.2 % reported usin the recommended rice-sized amount. Among children aged three to five (3–5.9 years), the recommended amount is a “pea-size”. However, 53.2 % of caregivers reported using more than the recommended amount: 42.4 % of caregivers reported using a half-load and 10.7 % reported using a full-load. Only 39.0 % reported using the recommended pea-sized amount.

Toothpaste was introduced at one year of age among 32.4 % of caregivers and at age 2 years among 26.1 % of caregivers. A minority of parents (11.3 %) reported that their child did not use toothpaste. Brushing twice daily was the most frequently reported behavior across all age groups: 52.1 % of children under two years, 63.9 % of those aged 2 to 4 years, and 73.2 % of five-year-olds. Fewer than 10 % of children under the age of six were reported to brush their teeth three or more times.

Fluoride toothpaste use also differed by perceived safety of water fluoridation. Among parents who responded that water fluoridation is safe, 72.2 % reported fluoride toothpaste use for their child. In contrast, among parents who responded that water fluoridation is not safe, 43.5 % reported use. Among those who were uncertain, 53.4 % reported use of fluoride toothpaste.

Caregivers who reported avoiding fluoride varnish with their child in the past year were more likely to oppose CWF (43.8 %) than those who did not avoid fluoride varnish (26.5 %). Similarly, caregivers who avoided fluoride toothpaste were more likely to oppose CWF (50.2 %) compared to those who did not (24.9 %).

Survey discussion

Despite increased media coverage of CWF over the past year, public understanding of its purpose remains relatively low in both Canada and the U.S. In our survey, about 60 % of adults correctly identified the reason fluoride is added to drinking water. The most common misconception was that fluoride is used to sanitize water. For comparison, a 2009 U.S. HealthStyle survey found that just 48 % of respondents accurately identified the purpose of CWF.¹⁷⁵ Heightened media attention in recent years may have contributed to the modest increase in public awareness observed in our survey relative to this 2009 U.S. survey. However, substantial knowledge gaps remain. More than half of respondents reported having limited or no knowledge about CWF, and only a small minority (6 %) said they knew “a lot” about the topic. Nearly half were unsure whether their household water was fluoridated. These findings align with a recent 2025 IPSOS poll, which found that 48 % of Americans were unsure whether fluoride is currently added to their home water supply.¹⁸⁰

Familiarity and support for CWF varied by demographic characteristics. Older individuals (i.e. 65+ years) had the highest accuracy (85 %) when asked about the purpose of CWF, while those under 30 years had the lowest accuracy (37 %). Knowledge about the purpose of CWF was similarly low (43 %) among parents of young children, consistent with the trend that younger-aged adults have little knowledge of CWF. Studies conducted in the U.S.¹⁷⁵ and South Africa¹⁸¹ also found better knowledge among older and more educated people, though demographic differences were not found in a study conducted across several European countries.¹⁷⁸ In addition to more knowledge about CWF, older adults were more likely to endorse support for CWF compared with younger adults. Higher education and income levels also were associated with more familiarity and support for CWF.

Older individuals likely lived through the initial implementation and promotion of CWF during the mid-20th century, when it was widely publicized as a major public health initiative. Public messaging was more prominent then, so they may have a stronger memory or awareness of its purpose relative to younger adults. Moreover, older adults may have personally experienced the shift from higher rates of tooth decay before CWF to improved dental health afterward, reinforcing their beliefs about its intended benefits. This generational gap in knowledge may reflect both a fading emphasis on fluoridation in public discourse and changing patterns in health communication.

Perceptions about the safety and effectiveness of CWF were mirror images of each other when comparing endorsements made by supporters and non-supporters. Unsurprisingly, supporters of CWF tend to believe it is both safe and effective; 82.9 % say the benefits outweigh the risks, and 87.0 % agree it is safe. Most supporters (66.2 %) do not view it as an infringement on personal rights or freedoms, likely because of perceived benefits. In contrast, only 17.8 % of nonsupporters believe the benefits of CWF outweigh the risks, and just 22.6 % think it is safe. Non-supporters also are more likely to be uncertain about CWF safety and more likely to view fluoridation as an infringement on individual rights (61.3 %). In short, support for fluoridation is largely driven by confidence in its safety and benefits, while opposition stems from safety concerns and perceived violations of personal freedom.

Support for CWF is influenced by how its risks and benefits are framed

Public support for community water fluoridation (CWF) varies significantly depending on how its benefits and risks are presented. When only the general benefit of reducing tooth decay was mentioned, 70 % of participants expressed support for CWF; the 30 % who did not express support may consider access to topical sources, such as toothpaste, as sufficient. However, support declined to 49 % when the benefit was specified as preventing just one cavity per person over a lifetime. Introducing potential health risks further decreased support. When fluoridation was hypothetically linked to a 1 % increase in intellectual disability among children, support dropped sharply to 24 %. A similar scenario involving a potential increase in thyroid disorders saw support fall to 20 %. When both a minimal benefit (preventing one cavity) and a health risk (reduced IQ) were presented together, support remained low at 23 %. These findings suggest that, when faced with a trade-off, the public prioritizes the prevention of neurodevelopmental disorders over dental health benefits.

Overall, the hypothetical scenarios demonstrate that support for CWF diminishes considerably when potential health risks are introduced or when perceived benefits are minimal. These findings underscore the significance of recent scientific findings concerning fluoride and lower IQ and the EPA lawsuit in shaping public opinion about CWF. The findings also highlight the importance of communicating both the risks and benefits of CWF using evidence-based information about the actual magnitude of its preventive effects in order for the public to make informed decisions.

Caregiver knowledge gaps highlight the need for improved fluoride education

Our survey revealed significant gaps in caregiver knowledge about fluoride and its appropriate use, with important implications for public health. Notably, 58 % of caregivers did not know why fluoride is added to drinking water, indicating a widespread lack of awareness about CWF and its intended purpose. Moreover, nearly one-third of caregivers (32 %) incorrectly believed that infant formula should be mixed with fluoridated water to prevent cavities, while an additional 22 % were unsure. Although fluoride can help prevent cavities after teeth have erupted, ingesting it before this stage offers little to no dental benefit. In fact, unlike breastmilk, which naturally contains very low levels of fluoride,^19,20 infant formula mixed with fluoridated water can contribute to overexposure,¹⁸ raising this risk of enamel fluorosis.⁶¹ Over two-thirds of U.S. children and adolescents have enamel fluorosis,^65–68 making it critical to monitor fluoride exposure during infancy and early childhood.

Professional organizations like the American Academy of Pediatric Dentistry,¹⁸² the American Dental Association,¹⁸³ and the American Academy of Pediatrics¹⁸⁴ recommend using fluoride-free or low-fluoride water when preparing infant formula. However, the finding that one-third of caregivers believe fluoridated water is beneficial for infants (i.e. before teeth erupt) points to a clear communication gap.

To protect children’s health, public health agencies and healthcare providers must prioritize more effective education for parents and caregivers about when fluoride is beneficial and when it may pose a risk.

At the same time, guidance recommending the use of low-fluoride water also must consider practical realities. Since tap water is most commonly used to prepare infant formula, caregivers living in fluoridated areas may feel compelled to seek alternative water sources to reduce the risk of enamel fluorosis. Yet not all families have equal access to such options. For many, obtaining low-fluoride water may require extra financial resources, transportation, or access to specific retail outlets—barriers that are not feasible for all households. This underscores the need for both clear guidance and equitable public health solutions that support informed and accessible decision-making for all families.

Equally concerning is the finding of excess fluoride toothpaste use with young children. While health authorities recommend a rice-grain-sized amount of fluoride toothpaste for children under age three,¹⁸⁵ nearly 79 % of caregivers reported using more than this amount. Similarly, for children between ages 3 to 6 years, over half (53 %) of caregivers reported using more than the recommended pea-sized amount. Our findings are consistent with a recent U.S. study showing that nearly 40 % of children aged 3–6 years used more than the “pea-size” amount of toothpaste recommended by health authorities.¹⁸⁶ A pea-sized amount of fluoride toothpaste (250 mg) with 1000 ppm of fluoride contains 0.25 mg of fluoride. If a 3-year-old child brushes their teeth twice a day and ingests 50 % of fluoride toothpaste each time, they would ingest 0.25 mg of fluoride per day from toothpaste alone. The Adequate Intake level for a 3-year-old is 0.7 mg/day (equivalent to drinking 1 L of water fluoridated at 0.7 mg/L); the tolerable upper intake level is 1.3 mg/day.³⁹ Thus, if excess toothpaste is used (such as from using a full load of fluoride toothpaste) and swallowed, this would increase the risk of excess fluoride exposure. Several respected health authorities and professional organizations have issued guidelines on the safe use of fluoride in toothpaste, supplements, and infant formula preparation.^37,183,185

Conclusion

Our findings reveal that CWF remains a polarized issue based on public opinion. Differing beliefs about its effect in preventing tooth decay, its potential for adverse health effects, and reduced trust in health authorities have contributed to mixed perceptions of this public health practice. Survey results also underscore a critical need for targeted public health communication about CWF and parental education on age-appropriate fluoride use. Clear, evidence-based messaging from clinicians and public health agencies is essential to ensure that caregivers understand both the benefits and risks of fluoride, especially in the context of infant feeding and inadvertent ingestion of fluoride toothpaste. Pregnant women may also take steps to minimize fluoride intake (e.g. avoiding foods and beverages with high fluoride levels) while maintaining the topical benefits of fluoride. Educational campaigns should clearly convey not only the recommended quantities of fluoride toothpaste for different age groups but also the potential consequences of overuse. Fluoride-free toothpaste that includes an effective anti-caries agent could be a viable option for the oral care of young children too. Health professionals – such as pediatricians and dentists – play a vital role in reinforcing messages about oral health promotion and safe fluoride use during routine visits. Visual aids and packaging labels that illustrate the correct amount of toothpaste may also help caregivers apply guidelines more accurately. Addressing this knowledge gap is essential to balancing the preventive benefits of fluoride with the need to minimize the risk of harm, particularly in vulnerable populations like infants and young children.