While we’re on the subject of top 10 lists, Dr. Paul Connett sent out a keeper just before Christmas: “Ten Key Papers that Challenge the Pro-Fluoride Mantra.” That “mantra,” of course, is “that fluoridation is ‘safe,’ ‘effective’ and ‘cost effective.”
The 10 papers below provide a strong, science-based counterpoint to pro-fluoridation claims. Notably, several of these were authored by pro-fluoride researchers.
We include some of Dr. Connett’s comments on their significance, as well. For most of the papers he lists, the full text is freely available online.
- Brunelle and Carlos. 1990. Recent trends in dental caries in US children and the effect of water fluoridation. Journal of Dental Research, 69 (Special Issue): 723-727. Full text .
Connett: This was the largest survey of dental decay in children in the US (the authors studied 39,000 children in 84 communities). The study was organized by the pro-fluoridation National Institute for Dental Research (NIDR). These NIDR authors found an average difference of only 0.6 of one tooth surface between children (aged 5-17) who lived all their lives in a fluoridated community compared to a non-fluoridated community. This result was NOT shown to be statistically significant. The pro-fluoridation bias of the authors becomes apparent in the way they present these unimpressive results in their abstract. They do not report the difference in tooth decay as an absolute value (i.e. 0.6 of one tooth surface) but as a relative % difference. This value of 18% looks more impressive than an absolute saving of 0.6 of about 100 tooth surfaces in a child’s mouth (there are 128 when all the teeth have erupted). Nor did the authors admit that they had not shown that this result was statistically significant.
- Featherstone JD. 2000. The science and practice of caries prevention. Journal of the American Dental Association (JADA), 131(7): 887-99. Full text .
Connett: In this article, which was a cover story in JADA edition of July 2000, Featherstone reached the same conclusions that many prominent dental researchers had reached over the previous 20 years: Namely, that the predominant mechanism of fluoride’s beneficial action is topical not systemic. The CDC acknowledged the same thing in 1999. In other words you don’t have to swallow fluoride to protect your teeth and therefore there is no need to force it on people who don’t want it via their drinking water.
- Warren JJ, et al. 2009. Considerations on optimal fluoride intake using dental fluorosis and dental caries outcomes: A longitudinal study. Journal of Public Health Dentistry, 69(2): 111-15. Full text.
Connett: If the Brunelle and Carlos (1990) paper was the largest US government funded study, the Warren et al (2009) paper was the most precise. This investigation was conducted as part of the “Iowa study,” which has been examining tooth decay in a cohort of children since birth. Warren et al. examined tooth decay as a function of daily ingestion of fluoride in mg/day (i.e. they examined individual exposure rather than the traditional way of comparing dental decay rates between communities with different concentrations of fluoride in water). The authors could not determine a clear relationship between caries experience and daily dose in mg/day. The authors’ state: “These findings suggest that achieving a caries-free status may have relatively little to do with fluoride intake, while fluorosis is clearly more dependent on fluoride intake.”
- Ko L, Thiessen KM. 2014. A critique of recent economic evaluations of community water fluoridation. International Journal of Occupational and Environmental Health. Full text .
- Luke J. 2001. Fluoride deposition in the aged human pineal gland. Caries Research 35(2): 125-128. Full text . See also Luke’s PhD thesis here .
Connett:Luke showed that fluoride accumulates on the calcified deposits in the human pineal gland and lowers melatonin production in animals. No health agency in any fluoridating country has attempted to repeat Luke’s work despite the fact that melatonin levels have been related to many health problems.
- Xiang Q, et al. 2003a. Effect of fluoride in drinking water on children’s intelligence. Fluoride 36(2):84-94, and Xiang Q, et al. 2003b. Blood lead of children in Wamiao-Xinhuai intelligence study [letter]. Fluoride 36(3):198-199. Full text [article] , full text [letter] .
Connett: Of the 42 (out of 49) studies (as of Dec 2014) that have found a relationship between fluoride exposure and lowered IQ, the Xiang study is one of the most important.
In the Xiang study, the authors controlled for key confounding values such as lead, and iodine (and arsenic retrospectively), parental income and educational status. In addition to comparing the mean IQ of children between the high-fluoride and low-fluoride village (a drop of 5-10 IQ points across the whole age range) they also sub-divided the children in the high-fluoride village into 5 groups with mean fluoride concentrations ranging from 0.7 to 4.3 ppm (see Table 8 in their study).
By focusing on one village they eliminated any other environmental differences between the two villages. They found that as the fluoride concentration in the five sub-groups increased two things happened: 1) the mean IQ systematically decreased and 2) the percentage of children with an IQ less than 80 (borderline mentally handicapped) dramatically increased from 0% to 37.5%.
- National Resource Council of the National Academies. 2006. Fluoride in Drinking Water: A Scientific Review of EPA’s Standards. Full text access .
Connett: A landmark report on the toxicology of fluoride, [this] is one of the very few reviews of fluoride for which the panel was balanced. It contained both pro and anti-fluoridation scientists. The report concluded that the current U.S. maximum contaminant level for fluoride (4 ppm) in drinking water is an unsafe level for human health. The panel recommended that the EPA conduct a new risk assessment to establish a goal for a safe level of fluoride in drinking water (Maximum Contaminant Level Goal, MCLG) and thence a new Federally enforceable standard (or MCL). After over 8 years the EPA has not completed this determination and so for 8 years the US continued to operate under unsafe standards for fluoride in water.
- Bassin EB, et al. 2006. Age-specific fluoride exposure in drinking water and osteosarcoma (United States). Cancer Causes and Control, May;17(4):421-8. Abstract .
Connett: This is the only study of osteosarcoma (a frequently fatal bone cancer in children), which studied the age at which exposure to fluoride was experienced. The authors write: “We observed that for males diagnosed before the age of 20 years, fluoride level in drinking water during growth was associated with an increased risk of osteosarcoma, demonstrating a peak in the odds ratios from 6 to 8 years of age. All of our models were remarkably robust in showing this effect, which coincides with the mid-childhood growth spurt.” The finding that there may a critical window of vulnerability in young men has never been refuted – or even investigated – since Bassin’s paper was published in 2006.
- Choi AL, Grandjean P, et al. 2012. Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis. Environmental Health Perspectives, 120(10):1362–1368. Full text .
Connett: This meta-analysis of 27 IQ studies was conducted by a team from Harvard including world-famous neuroscientist Philippe Grandjean (an expert on mercury and author of the recent book Only One Chance). This team acknowledged weaknesses in many of the studies but also noted the remarkable consistency of the finding that IQ was lowered in 26 out of the 27 studies reviewed. The average lowering was 7 IQ points, which is substantial, considering that at the population level even an average lowering of one IQ should be avoided.
- Choi AL, et al. 2015. Association of lifetime exposure to fluoride and cognitive functions in Chinese children: A pilot study. Neurotoxicology and Teratology, 47:96–101. Abstract .
Connett: This pilot study in China was carried out at fluoride levels, which overlap levels used in US fluoridation programs. They didn’t measure IQ specifically in this study but reported the results of a very simple test: the child’s ability to repeat a sequence of numbers both forwards and backwards. Even children with very mild dental fluorosis performed less well on this specific mental development test, than children without fluorosis. One of the experts involved in this study was Dr. David Bellenger who is world famous for his studies on lead’s neurotoxicity.
Image by Selena NBH , via Flickr