By Mary Otto
For more than 65 years, communities across the United States have been supplementing naturally occurring fluoride in water supplies to promote oral health. At what are considered optimum levels, numerous studies have shown fluoride reduces cavities. But too much fluoride can be a bad thing, public health officials have acknowledged. Consumption at excess levels may cause fluorosis and skeletal deformities, research has found.
The fluoride level long regarded by health officials as optimal for cavity prevention was set at a range of 0.7 milligrams to 1.2 milligrams per liter of water. But in January 2011, officials at the U.S. Department of Health and Human Services, while continuing to stress the benefits of fluoride, proposed that the recommended level of fluoride in drinking water be set at the lowest end of that range. They noted that the lower standard reflected research into changing water consumption patterns over time. In addition, they observed that Americans are now getting fluoride from a range of sources that did not exist in the 1940s when community water fluoridation programs first got underway.
UPDATE: Stressing that community water fluoridation remains an important tool in fighting tooth decay, on April 27, 2015, public health officials updated their recommendation for the “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 2010, 73.9 percent of the U.S. population on community water systems, or about 204.3 million people, had access to fluoridated water, according to the U.S. Centers for Disease Control. The CDC has a tool that allows the public to check the fluoridation status of its water.
The World Dental Federation (FDI) has noted that “more than 350 million people in 30 countries receive the benefits of water fluoridation.” While community water fluoridation is not common in Europe, fluoride is widely available in salt in a number of 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.”
Former U.S. Surgeon General David Satcher, in his 2000 report, “Oral Health in America,” detailed the importance of fluoride in fighting tooth decay:
“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.”
“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 preeruptively, inhibition of demineralization, enhancement of remineralization, and inhibition of bacterial activity in dental plaque.”
Photo by Neal Jennings.
In the Mortality and Morbidity Weekly Report for Oct. 22, 1999, the CDC offered a much-cited paper explaining scientific thinking about the effectiveness of water fluoridation.
“Fluoridation of community drinking water is a major factor responsible for the decline in dental caries (tooth decay) during the second half of the 20th century. The history of water fluoridation is a classic example of clinical observation leading to epidemiologic investigation and community-based public health intervention. 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 piece also offered a useful history of the development of the science behind community fluoridation efforts concluding:
“Since the early days of community water fluoridation, the prevalence of dental caries has declined in both communities with and communities without fluoridated water in the United States. This trend has been attributed largely to the diffusion of fluoridated water to areas without fluoridated water through bottling and processing of foods and beverages in areas with fluoridated water and widespread use of fluoride toothpaste. Fluoride toothpaste is efficacious in preventing dental caries, but its effectiveness depends on frequency of use by persons or their caregivers. In contrast, water fluoridation reaches all residents of communities and generally is not dependent on individual behavior.”
The National Research Council, which issues independent, expert reports intended to improve government decision making and public policy, also has produced several reports on fluoride.
In its 1993 report, “Health Effects of Ingested Fluoride,” the NRC observed that that medications, as well as individual diet, metabolism and other factors, can affect the extent to which fluoride is retained in the body. The report also identified additional studies to address fluoride intake, dental fluorosis, bone strength and carcinogenicity.
The NRC’s 2006 report, “Fluoride in Drinking Water: A Scientific Review of EPA’s Standards,” 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
- 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.
The American Dental Association notes that “an individual can have a lifetime of fluoridated water for less than the cost of one dental filling.”
“The American Dental Association continues to endorse fluoridation of community water supplies as safe and effective for preventing tooth decay. This support has been the Association’s position since policy was first adopted in 1950. The ADA’s policies regarding community water fluoridation are based on the overwhelming weight of peer-reviewed, credible scientific evidence. The ADA, along with state and local dental societies, continues to work with federal, state and local agencies to increase the number of communities benefiting from water fluoridation.”
Despite scientific evidence, debate remains
Yet fluoride has remained a source of controversy as evidenced by debates over fluoridation in a number of communities in recent months. A Phoenix, Ariz., panel voted in late 2012 to continue fluoridating its water while fluoridation was voted down in Wichita, Kan. In Portland, Ore., the city council approved fluoridation in September 2012 only to be overruled by voters in May 2013.
The Fluoride Action Network (FAN) is one group that strongly opposes water fluoridation. On its website, FAN describes the workings of fluoride this way:
“Fluoride — a powerful poison of enzymes — works topically, in part, by poisoning enzymes in the bacteria. While poisoning enzymes in oral bacteria may lead to a desirable result vis-a-vis teeth, poisoning enzymes elsewhere in the body could lead to a host of undesirable results.”
That description offers a sharp contrast to the CDC’s summary of how fluoride is believed to prevent decay:
“Enamel and dentin are composed of mineral crystals (primarily calcium and phosphate) embedded in an organic protein/lipid matrix. Dental mineral is dissolved readily by acid produced by cariogenic bacteria when they metabolize fermentable carbohydrates. Fluoride present in solution at low levels, which becomes concentrated in dental plaque, can substantially inhibit dissolution of tooth mineral by acid.
“Fluoride enhances remineralization by adsorbing to the tooth surface and attracting calcium ions present in saliva. Fluoride also acts to bring the calcium and phosphate ions together and is included in the chemical reaction that takes place, producing a crystal surface that is much less soluble in acid than the original tooth mineral.
“Fluoride from topical sources such as fluoridated drinking water is taken up by cariogenic (cavity-causing) bacteria when they produce acid. Once inside the cells, fluoride interferes with enzyme activity of the bacteria and the control of intracellular pH. This reduces bacterial acid production, which directly reduces the dissolution rate of tooth mineral.”
Fluoride opponents also cite studies that link fluoride to lower IQ and other adverse health outcomes.
In the days leading up to a vote on water fluoridation in Wichita, Kan., members of Wichitans Opposed to Fluoridation cited a group of studies reviewed by Harvard scientists that indicated that high levels of fluoride could be linked to lower IQs among schoolchildren.
The Harvard scientists told The Wichita Eagle that the data was not particularly applicable in the United States because it came from foreign sources where fluoride levels were many times higher than they are in American tap water.
“The Harvard scientists did not gather the original data for the paper they published in July, titled ‘Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis,’ wrote Eagle reporter Dion Lefler.
“The Harvard paper was a compilation of 27 other studies, 25 of which were done in China.
“On average, children with higher fluoride exposure showed poorer performance on IQ tests,” the Harvard researchers wrote. “Fluoride released into the ground water in China in some cases greatly exceeded levels that are typical in the U.S. In general, complete information was not available on these 27 studies, and some limitations were identified.”
“One of the Chinese studies that has been translated into English, “Research on the intellectual abilities of 6- 14- year-old students in an area with endemic fluoride poisoning,” gave a glimpse of what the study limitations are.
“The students in the study were drinking well water containing seven parts per million of fluoride – 10 times the amount proposed for Wichita water.
“The study compared children in a control group with those whose water had high levels of fluoride.
“The children in the control group were drinking water with up to .8 parts per million of fluoride, a slightly higher level than .7 parts per million that will be in Wichita water if the ballot issue passes.
“The Chinese researchers found children using the high-fluoride water had IQs about a point lower than the control group,” Lefler wrote. “But the researchers also found the IQ differential didn’t appear to last to adulthood.”
In the November election, Wichita voters rejected fluoridated water as they did in 1964 and 1978.
Related resource: Fluoride in water in the United States and public health misinformation: Research review
Mary Otto, AHCJ’s topic leader on oral health, is writing blog posts, editing tip sheets and articles and gathering resources to help our members cover oral health care. If you have questions or suggestions for future resources on the topic, please send them tomary@healthjournalism.org.
