Giving Perspective on the Recent Report on Water Fluoridation and Cognitive Impairment

By
Spring Hatfield, RDH, BSPH
-
© Brian Jackson / Adobe Stock

The Centers for Disease Control and Prevention (CDC) has named water fluoridation one of the top 10 great public health interventions of the 20th century.1 However, it has taken a serious hit recently.

The Department of Health and Human Services National Toxicology Program released a report, “Monograph on the State of Science Concerning Fluoride Exposure and Neurodevelopment and Cognition,” on August 22, 2024.2 Then, in September, a ruling came out of the U.S. District Court of the Northern District of California that implied water fluoridation could potentially pose a risk to cognitive function via lower IQ.3

What does this mean for water fluoridation? In short, nothing. However, these documents will most certainly be obstacles for many hygienists providing clinical care. This is a familiar scenario in dentistry. We have combatted multiple claims, such as the recent study on xylitol and cardiovascular events and previous reports indicating that flossing isn’t beneficial.4,5

Nonetheless, these obstacles can be quite frustrating. Let’s discuss what these documents say and how we can discuss these findings with patients. The common endpoint in both documents is the concern for lowered IQ associated with fluoride ingestion. This endpoint is a problem, so let’s start there.

IQ is a Poor Endpoint

Acknowledging that IQ is a poor measure of intelligence or cognitive function is important. Do you know what your IQ is? Likely not, and if you do, it was probably tested in elementary school, which is not an accurate measure for your current IQ. This is because IQ can change.6

Since IQ varies during different life stages, it is a poor endpoint because adjustments would need to be made depending on the individual’s age and life experiences.6

Nevertheless, let’s pretend IQ is a perfectly acceptable endpoint. If fluoride ingestion affected IQ levels at a population level, the Flynn Effect may have never been observed. The Flynn Effect is a phenomenon that “IQ has increased over successive generations throughout the world during most of the past century, at least since 1930.”7

Current research evaluating the Flynn Effect indicates an average of 2.2-point increase in IQ every decade. This research assessed IQ over 70 years. Accordingly, one could safely assume that if fluoride exposure was a significant factor, a decrease in IQ would have been indicated since water fluoridation has been an ongoing effort for over 50 years.8

The Monograph

The Monograph made big headlines and reignited fears associated with fluoride exposure. However, were the findings all that significant? Absolutely not. The Monograph told us nothing new.

The report states that drinking water with fluoride levels twice the recommended dose was consistently associated with lower IQ scores in children.2,9 This information is not new. We have been aware of this for quite some time. Additionally, the concern for dental fluorosis prompted the U.S. Public Health Service to adjust the recommended level of water fluoridation in 2015 from 1 ppm to 0.7 ppm, creating a more significant margin of safety.10,11

The Monograph offers no new information that would change the current recommendations regarding water fluoridation.

The Court Ruling

The good news is that health care and science are not determined in a courtroom, and sound evidence supports the safety and efficacy of community water fluoridation for caries prevention.12 However, this ruling will undoubtedly raise some concerns. Therefore, it is important that dental professionals understand what the ruling means.

The ruling calls for the Environmental Protection Agency (EPA) to “engage with a response since the court found an unreasonable risk of injury.” However, what that response should be was not well defined.3,9

This ruling is unlikely to affect current water fluoridation practices. Though it does require the EPA to “take action,” it does not ban or limit community water fluoridation. It is essentially smoke and mirrors.3,9

Of interest, Judge Chen admitted his ruling “does not conclude with certainty that fluoridated water is harmful to public health.” Yet, that statement will likely be omitted when the mainstream media reports on the ruling.9

Talking Points to Overcome This Obstacle

It is unlikely that you will change the minds of those staunchly opposed to the use of fluoride. However, when patients present with genuine curiosity or need for clarity, there are points that can be made that may help alleviate their concerns.

Dose

The dose is the first thing I would discuss with patients concerned about the health effects of fluoride exposure. Most substances have a safe or nontoxic dose, a toxic dose, and a fatal dose. This is true for almost every substance on earth, including essential chemicals required for proper biological functions to sustain life, such as water and oxygen.13,14

A toxic dose of fluoride has been established at 5 to 10 mg/kg of body weight, with fatal doses being 5 to 10 g/kg of body weight.15 With this in mind, let’s consider how much fluoride one might be exposed to through fluoridated water.

Water fluoridation in the United States is set at 0.7 ppm, which equals 0.7 mg/L of water. Therefore, an adult weighing 150 lbs must drink approximately 485 liters of water to reach a toxic dose of fluoride. That amount of water would be fatal, as the estimated toxic dose of water is between one to three liters per hour. Thus, you would easily experience water intoxication and or death from water intoxication well before reaching a toxic dose of fluoride through water fluoridation.16,17

However, this is assuming the water supply is fluoridated. You might be surprised that your community water is not fluoridated. If you or your patients are interested in determining if the water in your community is fluoridated, the CDC offers a resource, My Water’s Fluoride, which allows you to look up your community water provider.18

Considering topically applied fluoride such as fluoridated toothpaste, the amount ingested is negligible. The typical amount of fluoride in a single dose of over-the-counter toothpaste (adult dose or approximately a quarter teaspoon) is 1.3 mg. Therefore, if you swallow the entire dose, you will be exposed to 1.3 mg, well below the amount needed for a toxic dose. Generally, adults are better at expectorating toothpaste, and the estimated ingested amount from daily brushing is 0.1 mg.16

Children are more likely to swallow toothpaste during brushing. Therefore, the recommended dose is smaller and more specific for children. Children under three should use a smear or no more than a grain of rice, while children three to six should use a pea-sized amount of toothpaste.19

The estimated amounts of fluoride ingestion from toothpaste for children vary by age: 0.1 to 0.25 mg for infants and children 0 to 5 years of age and 0.2 to 0.3 mg for children 6 to 12 years of age. These doses are well below any toxic level or level of concern.16

Systemic vs. Topical

It is also imperative for patients to understand the difference between a topically applied fluoride and a systemic fluoride exposure. Generally, topical fluoride applied by dental professionals has a limited impact on systemic fluoride. Systemic fluoride is based on water fluoridation, dietary habits, and medication use. While some systemic exposure could occur from toothpaste and other topically applied fluoride products, the amount is negligible.16

Consider the amount of fluoride one is exposed to through certain dietary choices versus what one is exposed to from the use of fluoridated toothpaste:16

  • 1 cup of brewed coffee = 0.22 mg
  • 1 cup of brewed tea = 0.07 to 1.5 mg
  • 3 ounces of canned shrimp = 0.17 mg
  • 1/2 cup of cooked oatmeal = 0.08 mg
  • 3/4 cup of grapefruit juice = 0.08 mg

With these estimates, it may be better to avoid drinking coffee or tea rather than avoiding the use of fluoridated toothpaste or even community fluoridated water for those looking to reduce fluoride exposure.

Certain medications contain fluoride or some form of fluorine, often organo-fluorine, though it is not the active ingredient in most cases. The fluoride added to drinking water or what is usually found in toothpaste is sodium fluoride, which has a fluorine-sodium bond. In contrast, the organo-fluorine used in medications has a fluorine-carbon bond. Therefore, they differ, but they both still contain a fluorine molecule, and metabolism is the same.16,20-23

Some of the most popular drugs that have organo-fluorine as an ingredient include:20

  • Lipitor
  • Advair Discus
  • Prevacid
  • Lexapro
  • Crestor
  • Vytorin
  • Celebrex
  • Levaquin
  • Risperdal
  • Zetia

I sincerely doubt patients are giving their medical providers pushback when they prescribe these medications based on the presence of organo-fluorine. Maybe people concerned about fluoride exposure are only concerned when the fluorine atom is bound to a sodium atom and not so much when it is bound to a carbon atom. Or maybe they simply are unaware of the use of organo-fluorine in medications.

Nonetheless, this is an example of why the uproar over water fluoridation and the use of fluoride toothpaste is so confounding. In most cases, patients are unaware of all the different ways they are exposed to fluoride-containing substances and make very little change to their lifestyle. Yet they do not hesitate to discontinue the use of fluoride toothpaste, one of the most minor contributors to fluoride exposure.

Simply put, the belief that fluoridated toothpaste or professionally applied topical varnish significantly contributes to systemic fluoride exposure is wildly inaccurate.

Fluoride varnish is the only professionally applied fluoride treatment approved for children under six. This is because varnishes are the least likely to expose an individual to a high bolus of fluoride, reducing the risk of adverse effects.16,24

Metabolism, Distribution, and Elimination

In addition to the dose and route of exposure, fluoride’s metabolism, distribution, and elimination are considerable factors in safety.

Fluoride metabolism is straightforward. Fluoride enters the body through the GI tract, mainly the small intestines. As soon as fluoride is absorbed, plasma levels increase. This increase occurs around 10 minutes after ingestion and reaches peak levels around one hour after ingestion or absorption. A return to basal levels is achieved within 11 to 15 hours, meaning fluoride is eliminated from the plasma.25

Once fluoride reaches the plasma, it is quickly absorbed by the skeleton or excreted via the kidneys. The amount of fluoride retained in the skeleton depends on the individual’s age.25

Also of important note is that fluoride is not cumulative. Studies show when water fluoridation is halted, the half-life of fluoride is 120 weeks for adults and 70 weeks for children. When fluoride exposure is halted, the retained fluoride in bone is released slowly into the blood plasma, where the metabolic process begins, slowly eliminating accumulated fluoride over time.25

Approximately 80% of ingested fluoride is absorbed, and the remaining 20% never reaches central circulation. Of the 80% absorbed, approximately 50% is retained in hard tissues, and the other 50% is excreted via the kidneys. In children, typically, more fluoride is retained in hard tissues than in adults, which is one reason systemic fluoride is more effective at preventing caries in children. However, when fluoride exposure is halted, fluoride is more quickly eliminated from the hard tissues of children than adults, potentially increasing dental caries risk.16,25

In Closing

At the current doses, water fluoridation has single-handedly lowered dental caries rates with no evidence of toxicity or health effects. Water fluoridation is often the only “dental care” some children receive. Yet it remains a target for certain activist groups as they arbitrarily claim it is “toxic.” Toxicity is determined by multiple factors, one of which is the dose. Doses of fluoride in water and oral care products are designed to be beneficial while also remaining safe when used properly.

The recent court ruling will be an obstacle for many clinicians, as patients will undoubtedly be concerned about their fluoride exposure. The judge who ruled admitted there was uncertainty in the ruling because there was no conclusive evidence that water fluoridation poses a risk to public health.

The Monograph published by the Department of Health and Human Services added little to what we already know about fluoride consumption. We know and have known for years that doses two times higher than what is used in the United States are associated with a one to three-point lowered IQ in children. But again, IQ measures are not a suitable endpoint, especially in children, because IQ is not constant throughout all life stages.

We have decades of high-quality studies that support the use of fluoride, both topically and systemically, to prevent dental caries. These studies have contributed to determining the proper beneficial and safe dose.

Though it is unlikely to change the minds of individuals staunchly opposed to using fluoride, providing quality information on the benefits of fluoride and how it can be safely used to reduce dental caries may be helpful for patients on the fence due to the recent headlines.

No one will ever be able to eliminate fluoride entirely; it is too abundant. However, we know that fractioned low doses can be beneficial both topically and systemically. Personally, I will continue to use fluoride and recommend it. These findings have not changed the decades of knowledge we have on its benefits and safety.

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References

  1. About Community Water Fluoridation. (2024, May 15). Centers for Disease Control and Prevention. https://www.cdc.gov/fluoridation/about/index.html
  2. NTP Monograph on the State of the Science Concerning Fluoride Exposure and Neurodevelopment and Cognition: A Systematic Review [NTP Monograph 8]. (2024, August). National Toxicology Program. https://ntp.niehs.nih.gov/sites/default/files/2024-08/fluoride_final_508.pdf
  3. Food & Water Watch, Inc. v. Environmental Protection Agency, 3:17-cv-02162, (N.D. Cal. Sep 24, 2024) ECF No. 445. https://www.courtlistener.com/docket/6201332/445/food-water-watch-inc-v-environmental-protection-agency/
  4. Witkowski, M., Nemet, I., Li, X.S., et al. Xylitol is Prothrombotic and Associated With Cardiovascular Risk. European Heart Journal. 2024; 45(27): 2439-2452. https://doi.org/10.1093/eurheartj/ehae244.
  5. Tossing Flossing. (2016, August 17). Harvard Health Publishing. https://www.health.harvard.edu/blog/tossing-flossing-2016081710196
  6. Klemm, W.R. (2018, May 27). No, Your IQ Is Not Constant. Psychology Today. https://www.psychologytoday.com/us/blog/memory-medic/201805/no-your-iq-is-not-constant
  7. Sternberg, R. J., & Kaufman, J. C. (2002). Intelligence. In V. S. Ramachandran (Ed.), Encyclopedia of the Human Brain (Vol. 2, pp. 587-597). Academic Press. https://books.google.com/books?id=TbVzoCw2-vAC&printsec=frontcover
  8. Wongupparaj, P., Wongupparaj, R., Morris, R.G., Kumari, V. Seventy Years, 1000 Samples, and 300,000 SPM Scores: A New Meta-Analysis of Flynn Effect Patterns. Intelligence. 2023; 98: 101750. https://www.sciencedirect.com/science/article/abs/pii/S0160289623000314
  9. Anderson, O. (2024, September 26). Judge Orders EPA to Address Impacts of Fluoride in Drinking Water. American Dental Association. https://adanews.ada.org/ada-news/2024/september/judge-orders-epa-to-address-impacts-of-fluoride-in-drinking-water/
  10. Saxena, S., Sahay, A., Goel, P. Effect of Fluoride Exposure on the Intelligence of School Children in Madhya Pradesh, India. Journal of Neurosciences in Rural Practice. 2012; 3(2): 144-149. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3409983/
  11. Timeline for Community Water Fluoridation. (2024, May 15). Centers for Disease Control and Prevention. https://www.cdc.gov/fluoridation/timeline-for-community-water-fluoridation/index.html
  12. Draft Information Paper: Effects of Water Fluoridation on Dental and Other Health Outcomes [NHMRC Publication Reference EA 15]. (2016, September). National Health and Medical Research Council. https://www.scimex.org/__data/assets/file/0017/106523/16399-NHMRC-Fluoride-Information.pdf
  13. Cooper, J.S., Phuyal, P., Shah, N. (2023, August 1). Oxygen Toxicity. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK430743/#
  14. Peechakara, B.V., Gupta, M. (2023, June 26). Water Toxicity. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK537231/
  15. Ly, J. (2024, January 17). Fluoride Toxicity. Medscape. https://emedicine.medscape.com/article/814774-overview
  16. Fluoride: Fact Sheet for Health Professionals. (2024, June 26). NIH: Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Fluoride-HealthProfessional/
  17. Water Intoxication. (2024, September 17). Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/water-intoxication
  18. My Water’s Fluoride. (n.d.). Centers for Disease Control and Prevention. https://nccd.cdc.gov/doh_mwf/default/default.aspx
  19. Wright, J.T., Hanson, N., Ristic, H., et al. Fluoride Toothpaste Efficacy and Safety in Children Younger Than 6 Years: A Systematic Review. Journal of the American Dental Association. 2014; 145(2): 182-189. https://jada.ada.org/article/S0002-8177(14)60225-7/fulltext
  20. O’Hagan, D. Fluorine in Health Care: Organofluorine Containing Blockbuster Drugs. Journal of Fluorine Chemistry. 2010; 131(11): 1071-1081. https://www.sciencedirect.com/science/article/abs/pii/S0022113910000722
  21. Hori, H., & Honma, R. (2020). Decomposition of Fluoropolymers by Their Mineralization in Subcritical Water. In B. Ameduri & S. Fomin (Eds.), Opportunities for Fluoropolymers: Synthesis, Characterization, Processing, Simulation, and Recycling (pp. 303-331). Elsevier. https://www.sciencedirect.com/science/article/abs/pii/B9780128219669000110
  22. PubChem Compound Summary for CID 5235, Sodium Fluoride. (2024). National Center for Biotechnology Information. https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-Fluoride#section=NCI-Thesaurus-Code
  23. Kyzer, J.L., Martens, M. Metabolism and Toxicity of Fluorine Compounds. Chemical Research in Toxicology. 2021; 34(3): 678-680. https://pubs.acs.org/doi/10.1021/acs.chemrestox.0c00439
  24. Weyant, R.J., Tracy, S.L., Anselmo, T., et al. Topical Fluoride for Caries Prevention. Journal of the American Dental Association. 2013; 144(11): 1279-1291. https://jada.ada.org/article/S0002-8177%2814%2960659-0/fulltext
  25. Martínez-Mier, E.A. Fluoride: Its Metabolism, Toxicity, and Role in Dental Health. Journal of Evidence-Based Complementary and Alternative Medicine. 2012; 17(1): 28-32. https://journals.sagepub.com/doi/full/10.1177/2156587211428076

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