Timeline for Community Water Fluoridation

At a glance

Listed below are key events from the history of the use of fluoride to protect a community's oral health.


  • Portrait of Frederick S. McKay

    Dentists in the United States and Italy separately observe lower rates of dental decay in populations with distinctively stained teeth. Dr. Frederick S. McKay of Colorado Springs, Colorado, notes that many residents have what locals call “Colorado brown stain” and devotes his career to investigating the phenomenon he labels “mottled enamel.” This description is later changed to “dental mottling.”

  • 1912

    The Marine Hospital Service, formerly dedicated to caring for ill and disabled mariners, becomes responsible for improving the health of the general population and is renamed as the U.S. Public Health Service (USPHS). In the future, the USPHS will grow to include the National Institute of Health (NIH) and the Centers for Disease Control and Prevention (CDC).

  • 1914

    U.S. drinking water standards are enacted. Even though the federal standards only apply to interstate carriers (mainly railways), many state regulators adopt them too.

  • Portrait of Greene Vardiman Black

    G.V. Black, dean of Northwestern University Dental School, joins McKay in Colorado to study dental mottling. McKay grows more and more certain that something in the drinking water is the cause. However, analysis of water samples from stricken communities in half a dozen states reveal nothing out of the ordinary. McKay’s and Black’s collaboration spans decades, and they jointly publish five seminal papers on dental mottling.

  • 1916

    The first of McKay’s and Black’s papers reveals a paradox at the heart of their investigation: “Contrary to what might be expected [mottling] does not seem to increase the susceptibility of the teeth to decay.”

  • 1925

    A dentist in Essex, England, determines that children living where mottled enamel is most common in the UK tend to have much less dental decay than other children. Meanwhile, McKay convinces the residents of an Ohio town where mottling is widespread to spend $35,000 to switch to a new water supply.

  • Mural of fluoride

    In the 1920s, Dr. F.L. Robertson, based in Bauxite, Arkansas, notices an unusual number of cases of mottled enamel in local children born after 1909. This coincides with the community’s adoption of a new well for water supply. The prevailing misconception attributes the mottling to aluminum in the town’s namesake bauxite ore. Consequently, the well is abandoned in 1927. Interestingly, during a 1927 trip to Italy, McKay discovers that children in a Neapolitan suburb, born after a shift to a new water source, do not exhibit the dental staining characteristic of their parents—a local trait with roots dating back to Roman times.

  • 1928

    McKay learns of the situation in Bauxite and requests water samples from the town’s wells. McKay’s analysis again proves inconclusive.

  • 1930

    H.V. Churchill, a chemist associated with the Aluminum Company of America (now Alcoa), the owner of Bauxite and its mines, employs new technology to examine water from the discarded well. His analysis reveals a fluoride concentration significantly exceeding normal levels. At the same time, McKay sends water samples to Churchill for further scrutiny. Churchill confirms that McKay’s samples also exhibit exceptionally elevated fluoride concentrations.

  • Portrait of Trendley Dean

    Dr. H. Trendley Dean, USPHS officer and founder of the Dental Hygiene Unit at the recently established NIH, determines that mottled enamel is caused by too much fluoride intake. He renames the condition “dental fluorosis.” Dean begins a long-running series of epidemiologic studies exploring the relationship between fluoride intake, dental fluorosis, and tooth decay.

  • 1932

    McKay returns to Oakley, Ohio, which switched to a new water supply at his urging in 1925. He finds that the children born since then have no dental mottling.

  • 1934

    Dean publishes detailed criteria for diagnosing dental fluorosis.

  • 1935

    Dean declares fluorosis “an acute and urgent public health problem.”

  • 1936

    Dean concludes that people who drink water with a fluoride concentration of 1.0 ppm or lower have extremely low risk of developing even cosmetic fluorosis. Subsequently, he investigates whether drinking water with fluoride at levels too low to cause fluorosis might provide resistance to cavities, similar to that observed in visibly mottled teeth.

  • 1938

    Analyzing data collected by others on rates of fluorosis and dental decay among children in 26 states, Dean notes “a strong inverse relation” between the conditions.

  • 1939

    Dr. Gerald J. Cox and a team of scientists from the Mellon Institute at the University of Pittsburgh publish a paper proposing the controlled addition of fluoride to drinking water to prevent tooth decay.

  • 1942

    21 Cities Study: Dean publishes the findings of an NIH study of 7,200 children aged 12 to 14 from 21 cities in Colorado, Illinois, Indiana, and Ohio. Children tended to have fewer cavities and less severe decay in cities with more fluoride in the community water supply. This effect plateaued at concentrations greater than 1.0 ppm. Building on his 1936 findings, Dean concludes that 1.0 ppm fluoride in drinking water reduces rates of tooth decay with negligible risk of fluorosis. Dean also updates his diagnostic criteria for dental fluorosis. His revised fluorosis index remains in clinical use to this day.

  • Masthead of the Reader's Digest Magazine for February 1943
    Feb 1943

    “The Town Without a Toothache,” an article originally featured in the December 19, 1942, edition of Collier’s magazine, gains widespread attention when Reader’s Digest republishes it. The piece highlights the remarkable cavity-preventing attributes of naturally fluoridated water in Hereford, Texas. Parts of the article also appear in newspapers nationwide.

  • Aug 2, 1944       

    Grand Rapids City Commission votes to approve a pilot fluoridation project.

  • Oct 1944

    An editorial published in the Journal of the American Dental Association (JADA) warns against rushing to fluoridate drinking water.

  • Dec 1944

    JADA walks back its criticism of fluoridation in a follow-up editorial, but it reiterates the need for more research before fluoridation can be considered an acceptable public health intervention.

  • 1945

    Fluoridation trials: A planned 15-year trial of community water fluoridation is launched in four cities. Each fluoridating city is paired with a “control,” a nearby city of similar size and demographic makeup, with a low-fluoride water source similar to that of the trial city. Fluoridating Grand Rapids, Michigan, is paired with neighboring Muskegon; Newburgh, New York, with Kingston; Evanston, with Oak Park; and—in Canada—Brantford, Ontario, with nearby Sarnia. Two other cities with water having a natural fluoride content near 1.0 ppm serve as fluoridated controls. The study included these two cities to see whether fluoride-adjusted water performs differently than naturally fluoridated water. Aurora, Illinois, is the naturally fluoridated control for the Grand Rapids–Muskegon trial, and Stratford, Ontario for Brantford–Sarnia. Schoolchildren in all participating cities receive annual dental exams throughout the trial. By year’s end, 232,000 Americans are receiving fluoridated tap water from their community water system.

  • The waterworks at Grand Rapids, Michigan. An historic site for community water fluoridation
    Jan 25, 1945

    At 4:00 p.m., Grand Rapids, Michigan, achieves a historic milestone by becoming the inaugural city to implement water fluoridation. Engineers at the Monroe Avenue Water Filtration Plant begin adding a carefully controlled amount of sodium fluoride to the city’s water supply.

  • 1946

    The Evanston–Oak Park fluoridation trial begins. It is more intricate than the other U.S. trials. A few smaller, institutional-scale fluoridation projects unrelated to NIH’s grand long-term trials also are launched. This raises the total number of Americans receiving fluoridated tap water to 328,000 by the end of the year.

  • 1948

    577,683 Americans receive fluoridated tap water.

  • Historical newspaper clipping on fluoridation shows a dental exam and a worker treating water with fluoride.

    The first children to drink fluoridated water since infancy begin reaching school age. Dental examiners in Grand Rapids, Newburgh, and Brantford report a sharply lower number of cavities among the children starting school in 1949. Cities and small towns across Michigan, Texas, and Wisconsin begin fluoridation programs of their own. The number of Americans receiving fluoridated tap water nearly doubles in just 1 year, with the total number climbing to just under 1 million.

  • Collection saliva samples from students in Grand Rapids

    Upon reaching the 5-year mark, the Grand Rapids–Muskegon and Newburgh–Kingston trials undergo formal review, which determines that “controlled fluoridation displayed the same effects as natural fluoridation.”

  • June 1950

    The American Dental Association, Association of State and Territorial Dental Directors, and USPHS all issue statements endorsing community water fluoridation. The U.S. Surgeon General declares that any community wishing to fluoridate its water supply should be “strongly encouraged” to proceed. By year’s end, another half-million Americans are receiving fluoridated tap water, raising the total number to 1.5 million.

  • July 1951

    Muskegon withdraws from the fluoridation trial and begins fluoridating its water. With the loss of its control city, the Grand Rapids trial is technically finished. However, schoolchildren in both cities continue receiving annual dental exams for another decade, and by 1960 rates of tooth decay are roughly equal among children in Muskegon and Grand Rapids. The total number of Americans receiving fluoridated tap water leaps to 4.85 million in 1951, a threefold increase over the previous year.

  • 1952

    The total number of Americans receiving fluoridated tap water nearly triples again, reaching 13.3 million. With an increase of 8.4 million people served, 1952 marks the third-largest expansion of community water fluoridation in history.

  • 1954

    The number of Americans receiving fluoridated tap water passes 20 million.

  • Advertisement for fluoride toothpaste

    Crest, the world’s first fluoride toothpaste, is released nationally. Fluoride toothpastes become very common in developed countries by the mid-1960s, and many other fluoridated oral care products are created over the next few decades.

  • 1962

    Federal drinking water standards are updated, now including fluoride guidelines with recommended and maximum levels. The standards incorporate a sliding scale to account for higher water consumption in warmer weather, adjusting fluoride levels accordingly. The optimal fluoride concentration ranges from 0.7 ppm to 1.2 ppm, contingent on the local climate.

  • 1963

    A USPHS fluoridation team publishes Manual of Water Fluoridation Practice, the first fluoride engineering handbook.

  • 1965

    Another 13.5 million Americans begin receiving fluoridated tap water, marking the largest annual expansion of community water fluoridation ever. Nearly 8 million people gain access to fluoridated drinking water in New York City alone.

  • 1967

    Another 9.5 million Americans begin receiving fluoridated tap water, marking community water fluoridation’s second-largest annual expansion.

  • 1969

    As the U.S. population surpasses 200 million, 43.7% of Americans now have access to fluoridated tap water. A survey by the USPHS examines over 1,000 community water supplies, revealing inadequate state oversight of public water systems and inconsistent water quality.

  • 1970

    The U.S. Environmental Protection Agency (EPA) is created, combining federal pollution control and environmental oversight responsibilities into a single agency with regulatory authority.

  • 1972

    The Clean Water Act gives EPA responsibility for developing mandatory standards to control water pollution and authority to enforce those standards.

  • 1974

    The Safe Drinking Water Act (SDWA) grants EPA authority over drinking water quality, enforcing legally binding standards for all U.S. public water supplies. It shifts from the USPHS goal of “healthy water” to EPA-set thresholds for toxicologically “safe water.” SDWA clarifies that EPA can’t mandate adding substances for health benefits, only requiring additives necessary for safe water. Consequently, the Act designates drinking water fluoridation as a state, not federal, responsibility.

  • 1975

    Over 100 million Americans receive fluoridated tap water.

  • 1978

    The U.S. Surgeon General moves the National Fluoridation Program to the Centers for Disease Control (CDC). The CDC continues to oversee and offer guidance, along with technical support, to state and territorial fluoridation programs up to the present day.

  • 1980

    Half of the total U.S. population receives fluoridated tap water.

  • Michigan Fluoride monument

    Grand Rapids celebrates “Fifty Years of Fluoridation” with a symposium and a massive marble monument, featuring a drinking water fountain. Due to new construction in 2007, the monument is relocated and currently stands on the Delta Dental corporate campus in Okemos, Michigan.

  • 2002

    The former Monroe Avenue Water Filtration Plant in Grand Rapids, the site where the 1945 fluoridation trials originated, is now listed on the National Register of Historic Places.

  • 2008

    The U.S. population passes 300 million, and 64.3% of the population receives fluoridated tap water.

  • Grand Rapids, Michigan historic marker "The Beginning of Water Fluoridation"

    More than 200 million Americans (66.2% of the population) have access to fluoridated tap water. In acknowledgment of the pivotal role played by the former Monroe Avenue Water Filtration Plant in Grand Rapids, a Michigan Historical Marker is erected, recognizing it as “the beginning of water fluoridation.”

  • 2012

    Fluoridated water is supplied to three-quarters of Americans (74.6%) through public water systems, while 67.1% of the overall U.S. population has access to fluoridated tap water.

  • 2015

    Based on the widespread availability of fluoride in drinking water and oral care products, along with considerations of dental fluorosis trends and evidence on fluid intake in diverse climates, the USPHS simplifies recommendations for optimal fluoride concentration. The new guidance advises community water systems to adopt a uniform concentration of 0.7 mg/L of fluoride in drinking water, ensuring cavity prevention benefits while minimizing the risk of dental fluorosis. Consequently, public water systems nationwide commence fluoridation at the recommended 0.7 ppm level.

  • 2020

    Building upon 75 years of demonstrated safety and effectiveness, the U.S. Department of Health and Human Services enhances its Healthy People 2030 objectives. The updated goal is to elevate “the proportion of people with the recommended amount of fluoride in their water systems” to 77.1%.