[16] The WHO, FDI World Dental Federation, and Centers for Disease Control and Prevention endorse fluoridation as safe and effective at recommended levels.
[29] Although it is rarely life-threatening, tooth decay can cause pain and impair eating, speaking, facial appearance, and acceptance into society,[30] and it greatly affects the quality of life of children, particularly those of low socioeconomic status.
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.
[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.
[10] A 2016 review found variable quality evidence that, overall, stopping of community water fluoridation programs was typically followed by an increase in cavities.
[37] In 2024, the National Toxicology Program (NTP), a division of the U.S. Department of Health and Human Services, published a systematic review evaluating fluoride exposure's impact on neurodevelopment and cognition.
The strongest evidence emerged from areas with drinking water fluoride concentrations exceeding 1.5 mg/L, the World Health Organization's guideline for safe consumption.
Notably, the analysis identified prenatal and early childhood exposure as periods of heightened vulnerability, with findings indicating that maternal fluoride intake during pregnancy was significantly correlated with reduced IQ in offspring.
These findings suggest that cumulative fluoride exposure, encompassing sources such as drinking water, food, and dental products, could contribute to adverse neurodevelopmental outcomes.
Even at urinary fluoride concentrations below the WHO’s 1.5 mg/L guideline, the review found consistent IQ reductions, even when restricting to studies with low risk of bias.
The authors noted that even small IQ shifts at the population level, as seen with other neurotoxicants, can significantly increase the number of individuals classified as intellectually disabled, with a 5-point drop nearly doubling this figure.
[66] More recently, a 2023 study extended these findings by identifying significant IQ reductions at maternal urinary fluoride concentrations as low as 0.45 mg/L, with effects evident even at levels below the WHO's guideline of 1.5 mg/L.
[84] 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.
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.
High fluoride levels have been found in other foods, including barley, cassava, corn, rice, taro, yams, and fish protein concentrate.
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.
[11] The European Commission review states "No obvious advantage appears in favour of water fluoridation compared with topical prevention".
[93] Milk fluoridation is practiced by the Borrow Foundation in some parts of Bulgaria, Chile, Peru, Russia, Macedonia, Thailand and the UK.
[100] 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.
[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.
[103] 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.
[104] 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 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.
[110] In 1874, the German public health officer Carl Wilhelm Eugen Erhardt recommended potassium fluoride supplements to preserve teeth.
[111][112] 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".
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.
[115] 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.
[115] 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.
[11][55] 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][130][131][132] and presents a moral conflict between the common good and individual rights.