A 2014 review paper in The Lancet Neurology identified a number of potential development neurotoxins in children, including manganese, fluoride, chlorpyrifos, tetrachloroethylene, dichlorodiphenyltrichloroethane and the polybrominated diphenyl ethers. One of these, fluoride, has continued to fuel a discussion since the article’s publication, as the water supplies of approximately 74% of the U.S. population have fluoridation. While the debate hasn’t yet risen to the same level as those over vaccines or global warming, some U.S. municipalities are reassessing the amount of fluoride in their water sources — or whether to fluoridate at all.
Journalists and communicators of kinds would be well advised to review the best research and the history of misinformation on the topic, and to avoid false balance — “he said, she said” characterizations — where the science remains definitive. In particular, not examining the dose in question — levels of fluoridation proposed or studied — can lead to faulty reporting.
History and state of the field
U.S. towns and cities started adjusting the amount of fluoride in their water approximately 70 years ago when research linked increased fluoride levels to improved dental health. Supporters of fluoridation state that it leads to healthier communities — and is economical and easy. While recognizing the important balance of effectiveness, dose and safety, the leading scientific and health groups are overwhelmingly pro-fluoridation, with the CDC calling fluoridation “one of the greatest public health achievements of the 20th century.” The groups supporting fluoridation include the American Dental Association, the American Medical Association, the World Health Organization and the last six U.S. Surgeon Generals.
The CDC usefully summarizes the chronology of the leading research by the U.S. National Academy of Sciences. The American Association of Dental Research held a special session during their 2014 annual meeting titled “Water Fluoridation: Safety, Efficacy and Value in Oral Health Care.” Outcomes from this meeting include general consensus that no scientific evidence exists to support any of the claimed negative health effects of fluoridation other than fluorosis — a very mild mottling of tooth enamel — which can be avoided by adhering to current recommended intake levels.
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Opposition background
Despite the evidence supporting the safety and efficacy of fluoridation, anti-fluoride critics have managed to extend their influence and challenge public health experts. They claim that fluoride in drinking water has led to rising levels of fluorosis and can increase the risk of cancer. Some communities even reject fluoridation — voters in Portland, Ore., did so in 2013, the fourth time in almost 60 years — overruling the city’s commissioners, who had agreed to fluoridate the city’s water supply. (Portland is the only one of America’s 30 largest cities to do so currently.)
Anti-fluoride groups have effectively used social media to convey their message, and some are planning to lobby the EPA’s Office of Water to “determine a scientifically based (not politically influenced) MCLG (maximum contaminant level goal) for fluoride.” However, the EPA and the Department of Health and Human Services base their current fluoridation recommendations on their own rigorous scientific assessments and on those of the National Academy of Sciences, all of which take into account the balance of dose, risk and health benefits.
The “Harvard study” and its limitations
In 2012, a review of studies linking high fluoridation levels with reduced IQ scores was published in Environmental Health Perspectives. Nicknamed the “Harvard study,” this report combined the results of 27 studies and found that “children in highfluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas.” The review concluded that the “results support the possibility of an adverse effect of high fluoride exposure on children’s neurodevelopment.” Experts writing in The Lancet criticized the study for a variety of serious flaws, however. Media outlets such as the Wichita Eagle dug into the research, and found that 25 of studies analyzed took place in China, where natural fluoride levels were much higher than those in controlled U.S. public water systems. But that did not stop Witchita officials and groups from using the study to help persuade voters to reject fluoridation.
In any discussion of the “Harvard study,” it might be noted that the Deans of the Harvard Medical School, Harvard School of Dental Medicine and Harvard School of Public Health have publicly expressed their support for fluoridation.
Useful studies for background
The following are authoritative research studies and accounts of fluoride; they serve as useful citations for communicators reporting on related issues:
- The National Research Council 2006 review “Fluoride in Drinking Water: A Scientific Review of EPA’s Standards.” This report suggests slightly lowered levels of fluoride but supports the use of fluoride for public health reasons.
- A 2009 paper in the European Archives of Paediatric Dentistry, “Water Fluoridation,” presents decisive evidence for preventing tooth decay among children and states that “no association between adverse effects and water fluoridation has been established.”
- A 2014 study in the American Journal of Public Health, “Community Water Fluoridation and Intelligence: Prospective Study in New Zealand,” seeks to clarify the fluoride-intelligence issue. It states that previous studies supporting the “lowered IQ” hypothesis have likely been subject to methodological errors, or “confounding.”
- A 2007 study in the Journal of Dental Research, “Effectiveness of Fluoride in Preventing Caries in Adults,” finds evidence that fluoridation prevents cavities (caries) “among adults of all ages.”
- A 1996 study in the Journal of Public Health Dentistry, “The Effectiveness of Community Water Fluoridation in the United States,” notes that the “data on effectiveness and safety are compelling.”
- A 2000 research review by the University of York (U.K.) also presents a useful summary of academic literature.
