Water Fluoridation: A Cornerstone of Public Health

How a Simple Mineral Transformed the Way We Protect Our Teeth and Health

How a small scientific discovery reshaped global dental health and continues to influence modern public policy. It provides valuable insight into the science behind fluoride’s protective role in preventing tooth decay, the regulations ensuring its safe use, and the nuanced debates about its risks and ethics.

Key Takeaways

• Exploring the history and discovery of fluoride’s benefits on dental care

• Examining the scientific reasoning behind fluoride’s anticariogenic properties

• Detailing water fluoridation’s benefits, regulations, and associated health risks

• Assessing future areas of policy and research interests regarding community water fluoridation

Introduction

It seems like common knowledge nowadays that fluoride is helpful in preventing tooth decay. After all, we find it in our toothpaste, mouthwash, and even our drinking water. However, this modern day awareness was not always apparent, and it took decades to uncover both the benefits and risks associated with fluoridation that we now take for granted. In this article, we will examine several facets of water fluoridation.

History of Water Fluoridation

The remarkable discovery of fluoride’s capabilities was first pioneered by an early 20th century dentist named Frederick McKay. It all started when McKay opened up his first private dental practice in Colorado Springs, Colorado, in 1901. There, he became awestruck by the sheer volume of locals with brown, chocolate-colored stains on their teeth, colloquially referred to as the Colorado Brown Stain at the time. Since then, McKay took it upon himself to uncover the etiology behind such a mysterious condition.

In the following years, while collaborating with Dr. G.V. Black, a dental scientist, he made two key discoveries: first, that the condition of ‘mottled enamel’, which resulted from excess fluoride exposure, began at childhood before children developed their secondary teeth and, second, that, ironically, teeth afflicted with the Colorado Brown Stain were resistant to tooth decay. In 1923, McKay traveled to Oakley, Idaho, where he made another crucial discovery: that a water pipeline was responsible for the brown stain observed in children’s teeth. He noticed this by observing that once the pipeline was shut, children sprouted healthier teeth.

Dr. Grover Kempf, who worked with McKay, then published a report of their findings, which reached the ears of H.V. Churchill, Aluminum Company of America’s chief chemist. Churchill utilized photospectrographic analysis to test the water sample in Bauxite, Arkansas, where similar levels of brown stained teeth had been reported. It was then in 1931 that he discovered excess water-borne fluoride as the culprit and the condition became known as dental fluorosis.

These findings not only highlighted the harmful effects of excessive fluoridation in water systems, but underscored its dental benefits as well. In 1931, following the discovery of the root cause of fluorosis, Dr. H. Trendley Dean set out to perform more analysis on fluoride. He specifically set out to measure the varying levels of fluoridation across different drinking water sources in the United States. Specifically, he wanted to uncover the minimum level of fluoride required to instigate fluorosis. Then, leveraging McKay and Black’s discoveries, he wanted to test the hypothesis that minimum levels of fluoridation can both fight tooth decay and not lead to fluorosis.

In 1945, he undertook a study on Grand Rapids, Michigan, in which its water source was treated with safe levels of fluoride. 11 years later, the carries rate among thousands of school children dropped by 60 percent. Grand Rapids therefore became the very first city to incorporate fluoride into its drinking water. This discovery had profound impacts on both dentistry and public health implications on the use of fluoride to combat tooth decay.

The Science Behind Fluoridation

Given its remarkable implications, how exactly does fluoride act to prevent cavities and dental caries? Fluoride is a naturally occurring mineral in both rocks and soil. It acts to protect against tooth decay through three mechanisms: inhibiting tooth demineralization, promoting tooth remineralization, and inhibiting plaque bacteria.

To inhibit tooth demineralization, fluoride binds with hydroxyapatite on teeth by replacing the OH ion with a fluoride ion to form a new compound, fluorapatite Ca10(PO4)6F2. Fluorapatite forms a crystal structure that is much more acid-insoluble than teeth’s natural minerals, such as carbonated apatite and hydroxyapatite. In short, it forms a protective barrier against cariogenic (tooth decay causing) acids.

Fluoride also acts to promote tooth remineralization. Remineralization itself is a normal and healthy process for teeth to undergo. During the process, saliva acts as a natural buffer against the acidic nature of bacteria and remineralizes calcium and phosphate back into teeth, which strengthens them. Fluoride enhances this process further because fluorapatite, which fuses into teeth, attracts more calcium ions and fluoride, rendering the teeth less soluble overall to bacterial and plaque acids.

Lastly, fluoride inhibits the growth and development of plaque bacteria. At low pH levels, bacterial cell walls become permeable to fluoride ions (F-). When bacteria produce acids, they foster this low pH environment which renders it easier for fluoride, in the form of HF, to enter them. Once HF enters the bacteria, they dissolve into H+ and F- ions, respectively, which serve to acidify the bacterial internal structure and inhibit its growth and activity.

Figure 1.

 

Benefits of Community Water Fluoridation

The benefits of community water fluoridation are numerous. It has been in use in the United States since 1945 and studies have attested to its tooth protective properties, especially in developing teeth in infants and children. According to the American Dental Association (ADA), countries like Canada, where many of their municipalities report removing fluoride from their water source, have shown significant increases in the prevalence rate of tooth decay within the past decade. 

Solely relying on toothpaste alone for our fluoride source is not enough. In fact, according to the US Centers for Disease Control and Prevention (CDC), when both fluoridated water and fluoride toothpaste work together in tandem, they offer more resilience and protection against tooth decay than one source alone. Furthermore, studies also highlight its cost-effectiveness, with the amount of cost oriented towards community water fluoridation being significantly lower than dental restoration surgeries per person.

[ Studies affirm that communities who employ water fluoridation see at least a 25% reduction in tooth decay prevalence across both children and adults.]

Current Status and Recommendations

To prevent both caries and fluorosis, the US Public Health Service recommends a fluoride concentration of 0.7 mg/L of water. As of the recent available data from the CDC, only 72.7% of Americans connected to community water systems receive fluoridated water, and only 62.9% Americans in total receive fluoridated water. The World Health Organization (WHO) recommends a wider range–0.5-1.5 mg/L–simply because different countries have different environments, climates, and varying sources of fluoride for there to be a consistent concentration source across countries. As a result, countries utilize variable water fluoride concentrations depending on their circumstances. Overall, over 400 million people across 25 countries have access to community water fluoridation.

Safety and Efficacy

Water fluoridation has been demonstrated as safe for long-term use, so long as recommended guidelines are adhered to. Various studies have attested to its efficacy in reducing tooth decay. In addition, community water fluoridation is endorsed by numerous organizations and agencies, such as the WHO, CDC, FDI World Dental Federation, and various dental and health organizations.

Potential Risks and Controversies

Despite water fluoridation’s benefits, there are risks to consider as well. Taking more than the recommended amount of 0.7 mg/L of water of fluoride concentration is heavily associated with the progression of dental fluorosis, especially among children younger than six who are still developing their teeth. This is because they are still at a stage where their teeth are still calcifying.

High levels of fluoride over long periods of time, especially over 1.5 mg/L, are also linked to another condition known as skeletal fluorosis. A chronic bone disorder, skeletal fluorosis is marked by excessive fluoride accumulation in the bones, which compromises the skeletal structure’s metabolism and calcium level. As a result, symptoms can include joint stiffness, chronic pain, osteosclerosis, neurological impairments, among other symptoms.

Current research on fluoride exposure and cognitive neurodevelopment remains contested. A 2023 systematic review and dose-response meta-analysis found a significant inverse association between higher fluoride exposure and children's IQ scores, estimating an average decrease of about 2–3 IQ points per 1 mg/L increase in water fluoride above 1 mg/L, and a weaker but still negative association for urinary fluoride (see Figure 2).

While these findings suggest that higher fluoride exposure may impair cognitive function, the authors also noted that many of the studies reviewed had methodological limitations, including the presence of confounding variables and potential biases. As such, the results should be interpreted with caution.

Figure 2.

Given all of these ramifications, what we can glean from these findings is the importance of maintaining stable fluoride concentration levels in drinking water. While little to no water fluoridation is associated with an increased risk of tooth decay, high levels of exposure are linked to the development of dental fluorosis, skeletal fluorosis, and even potential cognitive decline.

Implementation and Regulation

In the United States, water fluoride levels are regulated by two principal public health agencies: the Environmental Protection Agency (EPA) and the CDC. The EPA, in accordance with the Safe Drinking Water Act of 1974, sets the maximum federal standard for water fluoride levels in community water systems; these standards include a primary, legally enforceable standard plus a secondary, non-enforceable standard.

The difference between both standards is that if the former is violated, legal action is taken against the water provider, while a public notice is issued should the secondary standard be violated. The CDC, on the other hand, provides recommendations and guidelines about safety practices regarding fluoride. In addition, the agency also collects and analyzes data regarding water fluoridation in the United States, and disseminates those findings to the public.

Water fluoridation jurisdiction extends to state and local governments as well. The federal government does not legally require state and local communities to fluoridate their water. As a result, these matters are handled by state and local legislatures. While some states require their water systems to provide fluoridated water to their state’s residents, others leave this decision entirely to individual cities, counties, or even voters via local referendums.

Future Directions

Water fluoridation still presents many prospective challenges, such as lack of or excessive water fluoridation, and research on areas related to cognition. Many countries, such as some of India’s districts, still grapple with high water fluoridation levels, while others receive an inadequate supply of fluoridated water; both outcomes result in a higher prevalence of dental fluorosis, tooth decay, and other diseases in such countries. While abundant research has confirmed fluoride’s role in managing tooth decay as well as dental and skeletal fluorosis, there is still ongoing research regarding its effects on intelligence and cognition. However, current research suggests that excessive fluoridation has adverse effects on IQ levels. Additionally, some places in America have no access to a fluoridated water system.

These challenges highlight the pressing need to address these public health issues at both a national and global level. To reduce water fluoridation disparities across the United States, what I personally recommend is relegating more public health decision-making at the federal level, rather than leave such decisions to local and state governments. This ensures that water fluoridation standards are consistent across different states. Future international collaboration can help bridge knowledge and access to information and resources regarding water fluoridation.

Frequently Asked Questions

1. What are the main sources of fluoride?

Fluoride is found abundantly in both natural and artificial sources. In nature, it is found in soil, rocks, and in many foods, although usually at very low levels in most foods. Brewed tea has the highest fluoride concentration of any food. Artificially, it is found in toothpaste, mouthwash, fluoridated water systems, medications, and some dietary supplements.

2. How can I prevent dental fluorosis?

Check your local water system’s fluoride levels to ensure it complies with the maximum recommended amount (usually around 0.7 mg/L) and avoid swallowing too much toothpaste while brushing teeth. Schedule regular dental checkups and monitor young children who are still learning how to brush. 

3. How can I prevent skeletal fluorosis?

Skeletal fluorosis results from excessive intake of fluoride over a long period. In the United States, it is an exceedingly rare condition and not associated with fluoridated public tap water whatsoever.

Works Cited

1. KFF (Kaiser Family Foundation). (2024, November 14). Water fluoridation in the U.S.: The federal role in policy and practice. https://www.kff.org/other/issue-brief/water-fluoridation-in-the-u-s-the-federal-role-in-policy-and-practice/

2. Iheozor-Ejiofor, Z., Clarkson, J. E., & Petersen, P. E. (2023). Water fluoridation for the prevention of dental caries. Community Dentistry and Oral Epidemiology, 51(5), 1019-1020.

3. Armijo-Olivo, S., Ospina, M., Elias, A., Dennett, L., Thind, A., & da Costa, B. R. (2021). Association between fluoride exposure and neurodevelopment in children: a systematic review and meta-analysis. Journal of Evidence-Based Dental Practice, 21(1), 101536.

4. Chan, B. (2017). Fluoride in drinking water: Friend and foe. Berkeley Scientific Journal, 21(2). https://berkeleysciencereview.com/article/2017/01/25/fluoride-in-drinking-water-friend-and-foe

5. National Academies of Sciences, Engineering, and Medicine. (2023). Dietary reference intakes for fluoride, vitamin D, calcium, and phosphorus. National Academies Press (US). https://www.ncbi.nlm.nih.gov/books/NBK587342/

6. National Institutes of Health, Office of Dietary Supplements. (2022, March 29). Fluoride: Fact sheet for health professionals. https://ods.od.nih.gov/factsheets/Fluoride-HealthProfessional/

7. American Dental Association Council on Scientific Affairs. (2024). Position statement on community water fluoridation. https://www.iadr.org/science-policy/position-statement-community-water-fluoridation

8. National Institute of Dental and Craniofacial Research. (n.d.). The story of fluoridation. https://www.nidcr.nih.gov/health-info/fluoride/the-story-of-fluoridation

9. Centers for Disease Control and Prevention. (2023, February 16). 2020 water fluoridation statistics. https://www.cdc.gov/fluoridation/php/statistics/2020-water-fluoridation-statistics.html

10. American Dental Association. (2024, October 4). Community water fluoridation is effective at preventing cavities. https://www.ada.org/about/press-releases/community-water-fluoridation-is-effective-at-preventing-cavities