Information icon.svg Results for the 2023 RationalWiki Moderator Election have now been posted. Thank you for participating in this election, and congratulations to the winners!

Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis

From RationalWiki
Jump to navigation Jump to search
How Jesus made wine
Water woo
Icon water.svg
Suckers getting soaked

"Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis" is a 2012 study published in Environmental Health Perspectives by four well-qualified researchers (Anna L. Choi,[note 1] Guifan Sun,[note 2] Ying Zhang,[note 3] and Philippe Grandjean[note 4])[1] that has been mis-cited by anti-fluoridists for years.

In short: They were studying fluoride poisoning in China, and it's irrelevant to any debate over intentional water fluoridation.[1]

Media attention[edit]

In June of 2012, some news organizations[2] transmitted a press release by the "NYS Coalition Opposed to Fluoridation, Inc." which suggested that a 2012 Harvard meta-study on the effects of water fluoridation and child IQs found "significantly lower IQ" in children. What a ghastly thing to see coming from real scientists, doing real science!

The study has been repeatedly cited by anti-fluoridation groups (which include bastions of science like Joseph Mercola and NaturalNews) as slam-dunk evidence.[3][4]

Genuine results[edit]

However, if you actually read the paper and look at Table 1, the study compared children in areas with recommended levels of fluoride in water — the same levels that are introduced in the process of water fluoridation (0.5 to 1.5 mg/L) — to children in areas with high fluoride levels (above 1.5 mg/L). In other words, and yet again, this paper documents the risks of chronic fluoride toxicity, not water fluoridation.[1]

The authors of the original 2012 meta-analysis published an updated statement on the study in September of that year,[5] underscoring this:

Our study summarized the findings of 27 studies on intelligence tests in fluoride-exposed children; 25 of the studies were carried out in China.

In general, complete information was not available on these 27 studies, and some limitations were identified.

So not only were the studies lacking complete information and seriously limited in scope (both of which greatly harm scientific replicatability), they were also all conducted in China, a country which not only has an extensive record of government interference in academia (as well as a "prevalence of fraud and plagiarism"),[6] but is also a place where natural fluoride levels in the groundwater often exceed the amount that is considered safe for consumption by the World Health Organization (an "upper limit of 1.5 mg/litre").[7]

Fluoride released into the ground water in China in some cases greatly exceeded levels that are typical in the U.S.

That the fluoride levels in the Chinese studies had at times been elevated directly by industrial spills into the ground water supply means that other compounds could possibly have leaked into the water which were not even looked for by the fluoride studies ("such as arsenic")[7] and which may just as well — or better — explain the apparent reduction in IQ. Furthermore, these studies "also failed to take into account other sources of fluoride intake, from coal used for indoor fires and contaminated grain, practices not seen in many developed countries."[7]

When considering the risks and benefits of fluoride exposure, the level of intake needs to be considered.

These results do not allow us to make any judgment regarding possible levels of risk at levels of exposure typical for water fluoridation in the U.S. On the other hand, neither can it be concluded that no risk is present.

That is to say, pro-fluoridation science does not recommend massive amounts of fluoride being added to water supplies. As with anything, the dose makes the poison. What is literally concluded by the study authors about their meta-analysis of the Chinese research is that it cannot be used to say anything about U.S. water fluoridation. Neither can it be used to demonstrate the harmful effects (or complete safety, to be fair) of municipal fluoridation as the study is better used to examine the effects of fluoride poisoning. So when this paper is quoted, let the authors of said paper have the last word — it is not relevant to the U.S. or to the supposed dangers of artificial fluoridation.

External links[edit]


  1. Department of Environmental Health, Harvard School of Public Health, Boston
  2. School of Public Health, China Medical University, Shenyang
  3. School of Stomatology, China Medical University, Shenyang
  4. Institute of Public Health, University of Southern Denmark, Odense


  1. 1.0 1.1 1.2 Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis by Anna L. Choi et al. (2012). Environ. Health Perspect. 120(10): 1362–1368. doi:10.1289/ehp.1104912. Full text of the paper.
  2. What the fuck is wrong with you, Reuters?(broken link)
  3. Mercola, J. (January 18, 2013). Harvard Study Confirms Fluoride Reduces Children’s IQ. The Huffington Post. Retrieved March 20, 2017.
  4. Seriously, even Wikipedia editors are sick of seeing that study and that Lancet one too, since they constantly say "refer to the archives" whenever those studies are brought up.
  5. Statement on Fluoride Paper by Anna Choi (September 11, 2012).
  7. 7.0 7.1 7.2