• Fluoride is a naturally occurring mineral found in most water sources.

• Water fluoridation is simply the process of adjusting the amount of fluoride in drinking water to the recommended level for optimal oral health.

• Fluoridation remains a safe and effective tool for oral health, especially where oral health care access (including dental visits, fluoride varnish and fluoride toothpaste or mouth rinse) may be limited.

• Drinking water and toothpaste with fluoride each provide important and complementary benefits.

• Studies show that adding fluoride to community water can help reduce cavities in children and increase the number of kids who stay cavity-free.

• No studies show neurocognitive or IQ effects on humans at fluoride levels at or below 0.7 mg/L—the level typically found in U.S. drinking water.

• The National Toxicology Program (NTP) report i and the 2024 federal court ruling require the EPA to reassess its recommended fluoride levels in drinking water but did not recommend a ban on CWF.

• Most fluoride-IQ studies lack peer review and robust study design, have a high risk of bias, rely on convenience sampling and use cross-sectional designs, making the evidence insufficient to determine if fluoride causes IQ deficits.

• Fluoride-IQ studies that concluded a link between fluoride levels and lower IQ scores were conducted in countries with high endemic fluoride levels, far exceeding the optimal level used in U.S. public water systems and there is no evidence of adverse impacts of fluoride at 0.7 mg/L or lower.

• The 2025 JAMA Pediatricsii study suggests a potential association between higher fluoride exposure and reduced IQ scores in children, particularly at concentrations above 1.5 mg/L. However, the study’s conclusions are limited by methodological weakness, including the high risk of bias in many included studies and the absence of U.S.-based populations.

• The NTP Monographi and the JAMA Pediatricsii study identified associations between fluoride levels above 1.5 mg/L and lower IQ levels but concluded, “This Monograph and Addendum do not address whether the sole exposure to fluoride added to drinking water in some countries (i.e., fluoridation, at 0.7 mg/L in the United States and Canada) is associated with a measurable effect on IQ. "

• Ongoing high-quality research conducted within the U.S. at recommended fluoridation levels is important to continuously inform public health policy.

• Fluoridation is supported by numerous health organizations, including the World Health Organization (WHO), Centers for Disease Control (CDC), American Medical Association (AMA), American Academy of Pediatrics (AAP), American Academy

​of Pediatric Dentistry (AAPD), American Dental Association (ADA) and the California Dental Association (CDA).

• There is evidence of the impact of stopping CWF from places like Juneau, Alaskaiii, and Israel. In fact, on June 30, 2025, Calgary, reintroduced fluoride in its public water systems due to the sharp increase in dental treatments requiring antibiotics and general anesthesia since fluoride was removed.

• ​Fluoride is a naturally occurring mineral found in soil and in varying concentrations in water sources—such as rivers, lakes and oceans—as well as in certain foods and beverages.

• Fluoride provides both systemic and topical protection. Before teeth emerge through the gums, fluoride from foods, beverages, dietary supplements and fluoridated water helps strengthen developing tooth enamel—making it more resistant to decay. This is known as a “systemic” benefit.

• Once teeth have erupted, water with fluoride in the body also offers a “topical” benefit by becoming part of saliva, where it continuously bathes the teeth in small amounts, aiding in the repair of weakened enamel and helping to prevent cavities.

• Fluoride is introduced during a controlled process within the water treatment plant.

• Public water systems purchase bulk fluoride in various forms, including liquid and dry compounds.

• The selected fluoride compound is carefully added at the final stage of the treatment process, with multiple control systems and safeguards in place to maintain optimal levels.

• California water systems operate under stringent regulatory oversight to ensure fluoride levels remain within safe, approved limits.

​• State Regulations on Fluoridation is found in Title 15 California Code of Regulations Section.​

• The Division of Drinking Water (DDW), a branch of the State Water Resources Control Board, serves as the primary regulatory authority overseeing fluoride levels in public water systems (PWSs).
• DDW is responsible for ensuring that water fluoridation is implemented safely and effectively to protect public health.
• Robust engineering safeguards and routine performance reviews help maintain system integrity and safeguard consumers.
• Fluoride levels are rigorously monitored by DDW on a daily, monthly and annual basis to ensure compliance with regulatory standards.
• Health and Safety Code 116410 (a) mandates that each PWS with at least 10,000 service connections and a natural level of fluoride that is less than the minimum shall be fluoridated.
• The recommended fluoride level in drinking water is 0.7 mg/L. The Environmental Protection Agency (EPA) sets the maximum allowable fluoride level at 4 mg/L; California enforces a stricter limit of 2 mg/L.​

•The American Dental Association's Health Policy Institute released a research brief, State-Level Costs of Removing Fluoride from Community Water Systems, which was a cost-effective analysis on ceasing fluoridation in public water systems for children ages 0–19 in the United States. Using Choi and Simons' estimates of the cost of dental treatment associated with removing fluoride from community water systems, the analysis determined that California would be the most impacted state.

​
• Estimated 5-Year Increase in Dental Care Costs for California due to the Removal of Fluoride from Community Water Systems: $4,8 billion.

• After Calgaryiii discontinued water fluoridation in 2011, the city saw a steady rise in severe dental issues, evidenced by increased rates of treatment under general anesthesia and hospital admissions for intravenous antibiotics.

• In contrast, Edmonton, which maintained its fluoridation program, experienced little to no change in these treatment rates over the same period.

• Recognizing the public health implications, Calgary reintroduced community water fluoridation on June 30, 2025.

• Nine years after Juneauiii halted community water fluoridation, the average cost of cavity treatment per child increased by 47%.

• In contrast, Anchorage (where water remains fluoridated) saw only a 5% increase in the same timeframe.

• Discontinued CWF in 2013 due to concerns over individual health autonomy.

• In 2017, the rate of children requiring urgent dental care for cavities had surged by 51% and the percentage of children with urgent dental needs was double in Windsor-Essex County.v

​• The average annual cost of emergency dental visits is approximately $508,259 for the local health system, in response to these outcomes.

• In 2022, Windsor reinstated CWF as a preventive public health measure.

• For children to exceed a safe amount of fluoride, they would need to drink significantly more water than normal or ingest large quantities of toothpaste regularly.

• Children and adults who consume a typical diet, drink optimally fluoridated water, and use U.S. regulated fluoridated dental products as directed should not exceed the maximum levels for fluoride.

• The biggest risk of fluoride over-exposure in California comes from children drinking well water, which can often exceed 0.7 mg/L and is not regulated or monitored as closely as public water systems.

• Other countries like India and China have higher endemic levels of fluoride in their groundwater and, in some regions, may also use coal products that release additional fluoride.

• Some countries also use fluoridated salt as a safe and effective caries‑prevention strategy, particularly in regions where water systems may not have the infrastructure to support community water fluoridation. In these settings, fluoridated salt serves as an alternative method to achieve the same cavity‑prevention benefits at recommended intake levels.

• Californians do not have those exposures; while it is possible for well water to have higher levels of fluoride than recommended, Californians on municipal water systems have their fluoride level in water controlled to a safe level, as per the EPA.

• Severe fluorosis, which can cause visual discoloration and weaken teeth due to excessive exposure to fluoride, is extremely rare when fluoride levels are kept within recommended guidelines. We do not see cases of severe fluorosis in lifelong residents of California, thus there has not been a concern of over-exposure among Californians.

• Systemic and Topical Protection: Drinking fluoridated water helps strengthen developing teeth from the inside —especially in children— and mixes with saliva to provide continuous, low-level topical protection for all ages.

• Widespread Reach: It serves entire communities, including those with limited access to regular dental care, by offering passive, daily protection.

• Long-Term Prevention: Research shows that water fluoridation reduces tooth decay in both children and adults by approximately 25vivii

• Mild to moderate dental fluorosis, which can occur if individuals are exposed to higher than recommended quantities of fluoride, is mainly a cosmetic concern and does not compromise tooth strength.

• Surface Shield: topical fluoride strengthens the tooth surface by encouraging remineralization, making enamel more resilient against acids produced by plaque and sugar.

• Time-limited: This topical application significantly increases the amount of fluoride in saliva and dental plaque for 1–2 hours after brushing.

• Targeted Use: Beneficial for individuals at a higher-risk of tooth decay – such as those with orthodontic appliances, reduced saliva flow, or a history of cavities.

• Flexible Formulations: Available over the counter and prescription-strength options to match individual needs for added cavity prevention.

• Water fluoridation and topical fluoride work together to deliver comprehensive protection against cavities. Fluoridated water provides a steady, passive defense by maintaining low levels of fluoride in the mouth throughout the day, while fluoride toothpaste offers a concentrated boost at critical times, like bedtime, when targeted protection is most effective.

​​Objective:

• To examine whether CWF is associated with adolescent IQ and cognitive functioning across the life course, using population-representative data from Wisconsin.

Study Design:

• ​Retrospective longitudinal cohort study using data from the Wisconsin Longitudinal Study (WLS) to estimate the impact of fluoride exposure on adolescent IQ while observing geographic mobility across childhood.

Data Source:

• ​Wisconsin Longitudinal Study (WLS): a random one‑third sample of the 1957 Wisconsin high‑school graduating class (n=10,317) and historical records on CWF from CDC Fluoridation Census U.S and naturally occurring fluoride levels in wells.

​Limitations:

• Inability to directly quantify adolescents’ consumption of fluoride (e.g., urine fluoride).

• Lack of data on dental care in adolescents or non-water sources of fluoride exposure.

Conclusion:

• ​Across all models and cognitive measures, the study finds no evidence that CWF at optimal U.S. levels is associated with lower adolescent IQ or cognition later in life.

Implications:

• The findings reinforce that community water fluoridation at recommended levels is not associated with adverse cognitive outcomes in adolescence or later life.

• Provides population‑representative U.S.‑based evidence, directly relevant to fluoridation policy debates.

• Counters recent policy decisions to end CWF in some states that cited studies of limited relevance (extremely high fluoride exposures, non‑U.S. samples, or unrepresentative populations).

• Strengthens the scientific basis for maintaining or initiating CWF as a safe and valuable public health measure for dental health without measurable cognitive risk.

Objective:

•​ Determine whether childhood fluoride exposure from drinking water at U.S. recommended levels (0.7 mg/L) affects academic achievement in the 12th grade during adolescence and midlife.

Study Design:

• ​Prospective, longitudinal U.S. cohort study that observes cognitive performance, in both secondary school and at age ~60.

​​Data Source:

The study used the High School and Beyond (HSB:80) nationally representative longitudinal cohort, which began in 1980 with 58,270 U.S. 10th‑ and 12th‑grade students, with 26,820 followed through 2021.

• Adolescent outcomes (12th grade) included standardized measures of reading achievement, mathematics achievement, vocabulary/verbal ability, and general academic aptitude.

• Midlife outcomes (ages ~50–60) included validated assessments of episodic memory, executive functioning, processing speed, verbal fluency, and a composite global cognition score.

• Adolescent outcome data came from NCES-administered standardized academic tests, and midlife outcomes came from HSB follow‑up neuropsychological assessments conducted in person or online.

• Cognition was assessed using objective, validated tools at both life stages—academic tests in adolescence and multi‑domain cognitive batteries in midlife.

• Results: Fluoride exposure at U.S. community water fluoridation levels (0.0–1.2 mg/L, typically 0.7 mg/L) was not associated with differences in adolescent academic performance or midlife cognitive functioning.

• Effect sizes were small and statistically nonsignificant, with confidence intervals crossing the null, indicating no meaningful association.

Limitations:

• ​The study was unable to directly measure individual fluoride intake and instead relied on community water chemistry as a proxy for exposure. Given fluoride’s short biological half‑life, this approach is likely the most practical option in a community-based study, though it remains an imperfect substitute.

Conclusion:

• At U.S. exposure levels, and across all analytic models, no evidence of harm to cognition; if anything, slight early-life cognitive benefit was observed.

• Adolescent cognitive test performance.

• Adult cognitive outcomes.

• Trajectories of cognitive aging.

​• Adolescents exposed to recommended fluoride levels showed modestly better cognitive performance in secondary school.

• This advantage was smaller and not statistically significant by midlife (~age 60)

I​mplications:

• Supports the position that community water fluoridation at U.S. recommended levels does not reduce IQ and may even correlate with slight early cognitive advantages.

• This study is highly relevant for U.S. policy debates, as it examines fluoride exposure at U.S.- recommended levels.

• Previous studies linking fluoride to IQ reductions involved much higher fluoride levels (>1.5-22 mg/L), were studies performed outside of the U.S. and were often in regions with endemic fluorosis (see below for details on these studies).

​Objective:

• ​To perform a systematic review and meta-analysis of epidemiological studies investigating children’s IQ scores and prenatal or postnatal fluoride exposure.

Study Design:

• ​Systematic review and meta-analysis.

Data Source:

• ​74 cross-sectional and prospective cohort studies.

Limitations:

• ​52 studies were rated at high risk-of-bias from various countries (45 in China, 12 in India, 4 in Iran, 4 in Mexico, 3 in Canada, 2 in Pakistan, 1 in Denmark, New Zealand, Spain and Taiwan, none from the United States). Calls out the need for more rigorous research.

Conclusion:

• The analysis found a statistically significant inverse relationship between fluoride exposure and children’s IQ scores. Specifically in spot urine tests, for every 1 mg/L increase in urinary fluoride concentration, there was an average decrease of 1.63 IQ points. In studies with a low risk of bias, the decrease was 1.14 IQ points per 1 mg/L increase.

• “Among the subset of low risk-of-bias studies, there were inverse associations when exposed groups were restricted to less than 4mg/L, less than 2mg/L and less than 1.5mg/L for analyses of fluoride measured both in water and in urine.” For reference, the U.S. Public Health Service recommends an optimal fluoride concentration of 0.7 mg/L.

​Implications:

• The study calls for further investigation into potential cognitive effects.

Objective:

• To assess the effects of initiation or cessation of CWF for the prevention of dental caries.

• To evaluate the association of water fluoridation (artificial or natural) with dental fluorosis.

​Study Design:

• ​Systematic review and meta-analysis of existing epidemiological studies.

Data Source:

• ​157 studies, All ages.

Limitations:

• Many included studies used non‑random, deliberately selected communities, introducing potential differences between populations that may bias results.

• Findings were inconsistent across studies, with some showing benefit and others showing no effect, lowering confidence in overall conclusions.

• Much of the evidence comes from older studies conducted before the widespread use of fluoride toothpaste and modern caries‑prevention practices, limiting relevance to current U.S. conditions.

• Found no eligible studies on outcomes for adults.

• Older findings may still apply to countries with high tooth decay and limited access to fluoride toothpaste, but less so to contemporary settings.

• Evidence on caries outcomes was updated through August 2023, but evidence on dental fluorosis remains older, current only through February 2015.

Conclusion:

• Due to very low-certainty evidence, the Cochrane Systematic Reviews could not determine if the cessation of CWF affected cavities in children.

• At a fluoride level of 0.7 mg/L, approximately 12% of participants exhibited fluorosis of aesthetic concern and about 40% showed fluorosis of any degree; however, the strength of this evidence is limited due to the study design quality and incomplete reporting.

• Recent studies suggest that CWF can result in a slightly greater reduction in dental decay among children and a modest increase in the number of children who remain cavity-free.

Implications:

​• A co-author of the study, Dr. Anne-Marie Glenny, was quoted as saying, “…no evidence to stop fluoridation programs.”

• Contemporary evidence shows that initiating CWF leads to small reductions in decayed, missing, filled, total teeth affected (dmft) and slight increases in caries‑free children, with low‑certainty evidence and insufficient data on cessation, disparities, or adult outcomes.

• Dental fluorosis risk increases with higher fluoride levels, though overall certainty is limited due to study bias and potential inconsistency.

• Decisions about implementing or discontinuing CWF should consider population oral health, behaviors, tap‑water consumption, availability of other preventive strategies, and factors such as acceptability, cost‑effectiveness, and feasibility of implementation and monitoring.

Objective:

• To evaluate the evidence on whether fluoride exposure is associated with neurodevelopmental and cognitive outcomes, primarily in children.

• The NTP review was designed to evaluate total fluoride exposure from all sources and was not designed to evaluate the health effects of fluoridated drinking water alone.

Study Design:

• Systematic review under the Office of Health Assessment systematic framework, integrating human epidemiological, experimental animal and mechanistic studies.

Data Source:

• Published, peer-reviewed studies and non-English databases identified through systematic literature searches up to May 1, 2020:

• Human Data: Epidemiological studies that reported fluoride exposure (via drinking water, urinary fluoride, or other biomarkers) and neurodevelopmental outcomes (IQ, cognition), from multiple countries outside the U.S.:

• China: large number of studies in areas with naturally high fluoride in water

• India: several cross-sectional studies from various regions

• Iran: High- and low-exposure population studies

• Mexico: assessed children in regions of endemic fluoride exposure

• Canada, Pakistan and others

• Animal Data: Experimental studies on rodents from previously published research assessing learning and memory at different fluoride doses.

• Mechanistic Data: Laboratory-based studies (in vitro and animal) from published sources exploring fluoride’s potential neurotoxic mechanisms.

Limitations:

​• The measurement of IQ in most fluoride studies was not standardized and the studies frequently failed to control for key contextual factors such as age, sex, socioeconomic status, parental education/IQ, nutrition, iodine status, co-exposures to arsenic and lead and aspects of the caregiving environment. These methodological weaknesses contribute to a high risk of bias and limit the reliability of the evidence (Levy, 2025).

​Conclusion:

• The NTP determined with only moderate confidence that higher estimated fluoride exposures (exceeding the World Health Organization Guidelines of 1.5 mg/L) are consistently associated with lower IQ in children.

• The NTP did not confirm this association exists at lower fluoride levels typical in the U.S. (0.7 mg/L).

• The NTP Report did not include their typical risk assessment because the data was not considered reliable by external expert reviewers.

Implications:

•​​ Further research is needed to assess the effects of lower levels of fluoride exposure, especially the levels that are maintained in the U.S. water supply, on IQ.

• Longitudinal studies are considered highly reliable because they track the same individuals over time and measure exposure prior to the occurrence of outcomes. This design establishes temporal order, minimizes recall bias and provides stronger control of confounding compared to cross-sectional studies. Well-designed longitudinal studies represent one of the most robust forms of non-experimental evidence.

• National Academics of Sciences, Engineering and Medicine (NASEM) recommended that the NTP “emphasize that much of the evidence presented

​comes from studies that involve relatively high fluoride concentrations and that the monograph cannot be used to draw conclusions regarding low fluoride exposure concentrations.”

• Studies claiming that fluoride affects IQ generally exhibit weak methodology, characterized by lack of peer review, reliance on convenience sampling and cross-sectional designs that limit causal inference.

• When researchers use a cross-sectional study design or a cross-sectional analysis of cohort studies to report the association between fluoride and IQ, the results are not appropriate or sufficient to determine causation of IQ deficits.

• Many of the studies with concerns were done in other countries where they have higher levels of fluoride in their water, drink more water daily (up to 2.5x more) and have ongoing exposure to fluoride through environmental sources such as burning coal indoors.

• Spot urine samples are collected at random times and results can vary based on recent fluoride exposure, hydration status and intake of food or beverages. Compared to 24-hour urine collections, spot samples are not considered reliable biomarkers for fluoride concentration. Both the NTP Monograph and the JAMA Pediatrics study relied on spot urine testing methodologies.

• The Proceedings of the National Academy of Sciencesviii above retrospective longitudinal cohort study examined fluoride exposure at U.S. recommended drinking water levels and found no evidence that CWF is associated with lower adolescent IQ or adverse cognitive outcomes later in life. The study provided population-representative U.S. evidence directly relevant to current policy debates, countering decisions to end CWF based on studies involving extremely high exposures or non-representative populations and reinforces that CWF remains a safe and effective public health measure that improves dental health.

• The Science Advancesix prospective, longitudinal cohort study examined fluoride exposure at recommended levels in drinking water to determine whether these

​levels influence cognitive development and inform policy discussions on water fluoridation. The study found children exposed to recommended fluoride levels showed slightly better cognitive performance in secondary school compared to children who were not exposed to recommended levels of fluoride in drinking water. A smaller cognitive benefit was observed in adults around age 60.

• The JAMA Pediatricsii systemic review and meta-analysis examined fluoride exposure and children's IQ, finding inverse associations at levels below 1.5 mg/L, but not consistently at 0.7 mg/L or lower.

• NTPi reviewed studies on fluoride exposure and cognition, concluding that higher fluoride levels (above 1.5 mg/L) are associated with lower IQ in children. However, they found insufficient data to determine whether fluoride at 0.7 mg/L—the level recommended for U.S. community water supplies—has negative effects on children's IQ. Some studies have suggested potential risks at lower levels, but findings are not conclusive.

• Kumar JV, Moss ME, Liu H, Fisher-Owens S. Association between low  fluoride exposure and children's intelligence: a meta-analysis relevant to community water fluoridation. Public Health. 2023 Jun; 219:73-84. doi: 10.1016/j.puhe.2023.03.011. Epub 2023 Apr 28. PMID: 37120936.

• Antoon JW, Kumar JV. Concerns About Data and Analyses Used in Assessing Fluoride Exposure and Children's IQ Scores. JAMA Pediatr. 2025;179(7):803–804. doi:10.1001/jamapediatrics.2025.0932

• Pollick H. The Role of Fluoride in the Prevention of Tooth Decay. Pediatr Clin North Am. 2018 Oct;65(5):923-940. doi: 10.1016/j.pcl.2018.05.014. PMID: 30213354.

• Zokaie T, Pollick H. Community water fluoridation and the integrity of equitable public health infrastructure. J Public Health Dent. 2022 Jun;82(3):358-361. doi: 10.1111/jphd.12480. Epub 2021 Oct 14. PMID: 34647624; PMCID: PMC9544072.
  

• American Academy of Pediatrics

• American Academy of Family Practitioners

• American Medical Association

• American Nurses Association

• American Osteopathic Association

• American Public Health Association

• American Water Works Association

• Centers for Disease Control and Prevention

• Department of Defense—fluoridates military bases around the world

• Mayo Clinic

• National Academy of Medicine

• World Federation of Public Health Associations

• World Health Organization

​·     +250 other leading health organizations

​References

i  National Toxicology Program. NTP Monograph on the State of the Science Concerning Fluoride Exposure and Neurodevelopment and Cognition: A Systematic Review. 2024. Accessed August 20, 2024. https://ntp.niehs.nih.gov/sites/default/files/2024-08/fluoride_final_508.pdf

ii  Taylor KW, Eftim SE, Sibrizzi CA, et al. Fluoride Exposure and Children's IQ Scores: A Systematic Review and Meta-Analysis. JAMA Pediatr. 2025;179(3):282–292. doi:10.1001/jamapediatrics.2024.5542

iii  Anderson O. JAMA releases study on elimination of community water fluoridation. ADA News.

May 30, 2025. https://adanews.ada.org/ada-news/2025/may/jama-releases-study-on-elimination-of-

community-water-fluoridation-7/. Accessed March 3, 2026.

iv  Choi SE, Simon L. Projected Outcomes of Removing Fluoride From US Public Water Systems. JAMA Health Forum. 2025;6(5):e251166. doi:10.1001/jamahealthforum.2025.1166.

v  WindsorEssex County Health Unit. Oral Health Report, 2018 Update. Windsor, Ontario; April 2018. https://www.wechu.org/sites/default/files/edit-resource/em-oral-health-report-2018/comm-e-e-psi-data-oral-health-report-2018-update-accessible-521822018-id-36792.pdf. Accessed March 3, 2026.

vii  Centers for Disease Control and Prevention. (n.d.). About community water fluoridation. https://www.cdc.gov/fluoridation/about/index.html

viii  J.R. Warren, G. Rumore, K. Sicinski, P. Herd, & M. Engelman, Municipal water fluoridation,  adolescent IQ, and cognition across the life course: Evidence from the Wisconsin Longitudinal Study, Proc. Natl. Acad. Sci. U.S.A. 123 (16) e2536005123, https://doi.org/10.1073/pnas.2536005123 (2026).

ix  John Robert Warren et al. Childhood fluoride exposure and cognition across the life course. Sci.

Adv.11, eadz0757(2025). DOI: https://www.science.org/doi/10.1126/sciadv.adz0757

x  Iheozor-Ejiofor Z, Walsh T, Lewis SR, Riley P, Boyers D, Clarkson JE, Worthington HV, Glenny A-M, O'Malley L. Water fluoridation for the prevention of dental caries.

Cochrane Database of Systematic Reviews 2024, Issue 10. Art. No.: CD010856. DOI: 10.1002/14651858.CD010856.pub3. Accessed 02 March 2026