By Mary Otto
For more than 70 years, communities across the United States have been supplementing naturally occurring fluoride in water supplies to promote oral health.
Nearly 75% of Americans – more than 211 million people – are served by community water fluoridation (CWF) programs, according to the U.S. Centers for Disease Control (CDC).
The agency, which has hailed community water fluoridation as one of the 10 great public health achievements of the 20th century, credits the consumption of fluoridated water with significant reductions in tooth decay.
According to a large scale 2018 study, U.S. counties in which more than 75% of the population had access to community water fluoridation showed a 30% reduction in tooth decay in children’s primary teeth and a 12% reduction in permanent teeth compared with counties in which fewer than 75% of the population had access to publicly fluoridated water.
Around the globe, the World Dental Federation (FDI) has noted that “more than 350 million people in 30 countries receive the benefits of water fluoridation.”
And while community water fluoridation is not common in Europe, fluoride is widely available in salt in several European countries, according to the FDI’s Oral Health Atlas. The organization says, “universal access to fluoride for dental health is part of the basic human right to health.”
Since its beginnings, water fluoridation has stirred controversy, with opponents asserting that the practice amounts to forced medication and poses health risks including reduced intelligence.
“Fluoridation is not safe or cost-effective,” contended Bill Osmundson, of the Fluoride Action Network, a leading opposition group in a California Healthline piece that took careful stock of the debate in 2016.
In recent years, fluoride detractors have cited studies (including a number from China) describing an inverse relationship between fluoride exposure and intelligence in children. The quality of these studies has been widely challenged. The Wichita Eagle reported on the findings in coverage of a local fluoride debate in 2012.
Recently, a Canadian study has brought renewed attention to the fluoride/IQ controversy. The paper, subjected to “additional scrutiny” before its August 2019 publication in the prestigious JAMA Pediatrics, linked higher fluoride consumption by pregnant women to lower intelligence scores in their offspring.
“These findings indicate the possible need to reduce fluoride intake during pregnancy,” the authors concluded. While some outside experts attested to the study’s scientific merits, others were quick to point out its limitations.
The study received a measured response from several professional organizations with groups including the American Academy of Pediatrics and the American Dental Association affirming their continued support for community water fluoridation.
“This study is neither the first, nor will it be the last, to test the association between prenatal fluoride exposure and cognitive development,” predicted journal editor Dimitri A. Christakis in an editorial note that accompanied the paper.
The quest for standards
While stressing the oral health benefits of fluoridation, too much fluoride can be a bad thing, public health officials have long acknowledged.
Excess consumption can cause dental fluorosis, which manifests as mottling of the tooth enamel and may affect bone development, researchers have found. Some studies have focused on people living in areas with high levels of naturally-occurring fluoride in their water.
For years, the fluoride level long regarded by U.S. health officials as optimal for cavity prevention was set at a range of 0.7 milligrams to 1.2 milligrams per liter of water.
Officials at the U.S. Department of Health and Human Services, while continuing to stress the benefits of fluoride, proposed in 2011 that the recommended level of fluoride in drinking water be set at the lowest end of that range. The officials noted that the lower standard reflected research into changing water consumption patterns over time. They also observed that Americans now are getting fluoride from a variety of sources that did not exist in the 1940s, when community water fluoridation programs first got underway.
Public health officials in 2015 updated the recommendation for an “optimal” level of fluoride in drinking water nationwide. The new standard, 0.7 milligrams of fluoride per liter of water, was announced by the U.S. Department of Human Services.
In the years leading to the updated standard, the National Research Council, which issues independent, expert reports intended to improve government decision making and public policy, issued several reports on fluoride safety.
In a 1993 survey, “Health Effects of Ingested Fluoride,” the NRC observed that medications, as well as individual diet, metabolism and other factors, can affect the extent to which fluoride is retained in the body.
In a 2006 study, “Fluoride in Drinking Water: A Scientific Review of EPA’s Standards,” the NRC acknowledged that in developing regulatory standards for high levels of fluoride in drinking water three adverse health effects warranted consideration: severe enamel (dental) fluorosis from exposure to high levels between birth and 8 years of age; risk of bone fractures and severe forms of skeletal fluorosis (a rare condition in the United States) after lifetime exposure.
The report concluded the EPA’s water standard was too high to protect against adverse health effects.
The NRC’s 2007 report, “Earth Materials and Health: Research Priorities for Earth Sciences and Public Health,” looked at connections between earth science and public health, addressing positive and negative impacts. The report concluded that fluoride should be regarded as an element essential for human life based on its role in cellular functions involving metabolic or biochemical processes. The report went on to conclude that fluoride in drinking water has two beneficial effects: preventing tooth decay and assisting with bone mineralization and bone matrix integrity.
Fluoridation as a public health measure
Over the years, public health leaders have continued to promote fluoride’s value. As U.S. Surgeon General, David Satcher, in his 2000 report, “Oral Health in America,” detailed the importance of fluoride in fighting tooth decay across the nation’s population:
“Fluoride reduces the incidence of dental caries and slows or reverses the progression of existing lesions (i.e., helps prevent cavities). Today, all Americans are exposed to fluoride to some degree, and there is little doubt that widespread use of fluoride has been a major factor in the overall decline in recent decades in the prevalence and severity of dental caries in the United States and other economically developed countries.” The landmark report also offered this explanation of fluoride’s role in oral health:
“Fluoride is the ionic form of the element fluorine, the thirteenth most abundant element in the crust of the Earth. Because of its high affinity for calcium, fluoride is mainly associated with calcified tissues (i.e., bones and teeth). The ability of fluoride to inhibit, and even reverse, the initiation and progression of dental caries is well known. Fluoride’s mechanisms of action include incorporation of fluoride into enamel pre-eruptively, inhibition of demineralization, enhancement of remineralization, and inhibition of bacterial activity in dental plaque.”
About the same time, in a much-cited paper published in Mortality and Morbidity Weekly Report, the CDC provided an account of 20th-century water fluoridation research, beginning with the 1901 work of Colorado Springs dentist Frederick S. McKay.
“The history of water fluoridation is a classic example of clinical observation leading to epidemiologic investigation and community-based public health intervention,” the paper noted.
“Although other fluoride-containing products are available, water fluoridation remains the most equitable and cost-effective method of delivering fluoride to all members of most communities, regardless of age, educational attainment, or income level.”
The CDC has estimated that community water fluoridation yields “approximately $38 savings in dental treatment costs for every $1 invested.”
But the agency has also acknowledged that federal, state and local health departments, together with public health partners “face ongoing challenges in promoting and expanding CWF.”
Tension over fluoride endures
Most water supplies in the U.S. are controlled locally: laws and ordinances governing water fluoridation often are passed at the community level.
When fluoridation measures are considered by city councils or county officials, or when they appear on local ballots, they often face opposition from detractors.
In 2012, Wichita, Kansas voters rejected fluoridated water as they had in 1964 and 1978. That same year, in Portland, Ore., the city council approved fluoridation. But the decision was overruled by voters in 2013.
In other places, however, fluoridation efforts have moved forward.
In 2013, editors at the Tampa Bay Times were awarded the Pulitzer Prize for “their diligent campaign that helped reverse a decision to end fluoridation of the water supply for the 700,000 residents of the newspaper’s home county.”
And after years of work by oral health and children’s advocates, the Santa Clara Water District began providing fluoridated tap water to large sections of San Jose, Calif. in 2017.
Until then, the sprawling city, with a population of more than 1 million, had been known as the largest metropolitan jurisdiction in the nation that lacked a fluoridated drinking water program.
