Even studies from endemic fluorosis areas show fluoride is not harmful at levels used in fluoridation

Most of the claims made by anti-fluoride propagandists are simply wrong. Image source: Fluoridation and the ‘sciency’ facts of critics

Anti-fluoride propagandists continually cite studies from areas of endemic fluorosis in their arguments against community water fluoridation (CWF). But if they critically looked at the data in those papers they might get a shock. Invariably the published data, even from areas of endemic fluorosis, shows fluoride is safe at the concentrations relevant to CWF.

I have completed a detailed analysis of all the 65 studies the Fluoride Action Network (FAN) lists as evidence that community water fluoridation (CWF) is harmful to child IQ. The full analysis is available for download as the document Analysis of FAN’s 65 brain-fluoride studies.

In this article, I discuss the studies in the FAN’s list (see FLUORIDE & IQ: THE 65 STUDIES”) which report relationships between child IQ and fluoride exposure in areas of endemic fluorosis. There are eleven such studies in the FAN list but only six of them provide sufficient data to enable independent statistical analysis.

While those six studies do show a statically significant (p<0.05) negative relationship of IQ with fluoride intake those results are not relevant to CWF because the fluoride as exposure levels are much higher than ever occurs with CWF.

However, it is possible to investigate if the relationships are significant at lower concentrations more relevant to CWF. I have done this with these six studies and illustrate the result obtained with these graphs below using the data extracted from Xiang et al (2003). (This study is often used by anti-fluoride campaigners).

The red data points in the figures below are for lower concentrations of urinary F or creatinine adjusted urinary F. The range for the red points is still quite a bit larger than urinary F levels measured for children in areas where CWF is used. However, we can see that the relationships at these lower ranges are not statistically significant (results from regression analyses cited in figures).


This was also the case with the other studies from FAN’s list which provided sufficient data for regression analyses. I summarise the results obtained for five of these studies in the figure below.

This show that none of the studies found statistically significant relationships with fluoride exposure for the low fluoride concentration relevant to CWF. The situation is basically the same for the sixth study, Mustafa et al (2018), which reports average school subject performances for a range of subjects for children in Khartoum state, Sudan. However, it is hard to know what the safe limit for fluoride exposure is in that climate (for climatic reasons the upper permissible F level in drinking water is set at 0.33 ppm for Khartoum state) and the sample numbers are low. Interested readers should consult my report – Analysis of FAN’s 65 brain-fluoride studies.


Anti-fluoride campaigners often cite FAN’s list (FLUORIDE & IQ: THE 65 STUDIES”) in their attempts to argue that fluoridation is bad for the child’s brain. But in these series of articles Anti-fluoride 65 brain-fluoride studies not evidence against fluoridation, I have shown that their arguments are false.

In Child IQ in countries with endemic fluorosis imply fluoridation is safe I showed that while IQ and other health problems may occur where fluoride exposure is very high in areas of endemic fluorosis the reports themselves implicitly assume that the low fluoride exposure in the “low fluoride” areas is safe. It is the data from these areas, not the “high fluoride” areas, that are relevant to CWF. So despite the heavy use of these articles by FAN and anti-fluoride activists these studies do not prove what they claim. If anything these studies show CWF is safe.

In this article, I considered a few of these studies which included data relevant to low fluoride exposure. When the low fluoride exposure data (relevant to CWF)  from these studies were statistically analysed none of them showed significant relationships of child IQ to fluoride exposure. That confirms the implicit assumption from these studies that there is no negative effect of fluoride exposure on child IQ at these low levels.

Finally, in Canadian studies confirm findings of Broadbent et al (2015) – fluoridation has no effect on child IQ I summarise results from the only three studies where comparisons of IQ for children living in fluoridated and unfluoridated areas are compared. These studies were made in New Zealand and Canada and the results were the same. No statistically significant differences in child IQ were found.

However, the authors of the Canadian studies ignored this result and instead used questionable statistical methods to search for possible relationships between fluoride exposure and child IQ. Most of the relationships they report were not statistically significant but, nevertheless, they and their supporters have simply ignored this and concentrated on the few statically significant relationships.

Anti-fluoride activists currently rely strongly on these studies and heavily promote them. I will discuss these few studies further in my next article.

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5 responses to “Even studies from endemic fluorosis areas show fluoride is not harmful at levels used in fluoridation

  1. Water fluoridation is UNNECESSARY (brush and spit with fluoridated toothpaste if you wish), UNSAFE (neurotoxic Fluoride is bio-accumulative in the human body over time), INEFFECTIVE (purportedly works primarily by topical application, not by ingesting it) and UNETHICAL without informed consent.


  2. Barry, I really do expect more from commenters here.

    This article is part of a series where I show the studies used by FAN mostly show or at least simplicity assume, that fluoridation is actually safe. that there is no neurological effect.

    Now, Barry, I may be wrong. I may have made mistakes. But I welcome commenters who can engage with my arguments, show me where I am wrong and where I have made mistakes.

    This is what makes rational discussion possible.

    But you have instead come here to bombard me with tired slogans.

    If you think fluoridation is UNSAFE then explain why – with evidence. And show me where my arguments in this article are mistaken.

    If you think it is INEFFECTIVE then engage with the studies showing that it is effective. (Yes, the main mechanism with existing teeth is the reaction at the tooth surface, the common ion effect. And that works because ingestion of food and beverages containing fluoride, phosphate and calcium maintains the concentration of these ions at the tooth surface and this prevents mineralisation. if your disagree then provide your evidence).

    If you think it is UNETHICAL then at least engage with the facts. In New Zealand communities do give informed consent – fluoridation is not imposed on unwilling communities. Yet in my city, Hamilton, anti-fluoride activists managed to capture councillors and get fluoridation stopped – despite clear support for it. It took campaigns from angry voters plus a new referendum showing support for fluoridation for councillors to correct their silly mistake.

    So when people like you preach ethics while attempting to deny a safe and effective health measure that people want then I call hypocrisy.


  3. Obviously, I have no direct knowledge of the circumstances of purported “informed consent” for the medical intervention of water fluoridation in Hamilton, New Zealand.

    So the rather rude comment, “people like you … etc.” is uncalled for in your last paragraph. Surely, you can do better.

    But I do know there are thousands of municipal jurisdictions in the USA and Canada where residents are being forced to drink (CWF) fluoridated tap water or pursue costly and inconvenient alternatives, without any consent whatsoever, let alone the higher standard of informed consent.

    The reason being, the ballot question regarding water fluoridation was voted on several decades BEFORE most of the municipality’s electors were either born or of voting age.

    For example, where I live, the ballot question was first put to local electors in 1966, 54 years ago.

    Little wonder people and their respective locally elected officials are revisiting this issue and rejecting this archaic, unnecessary practice.

    And yes, it should remain a locally determined matter, not an edict from a higher level of government, as some fluoridationists have proposed.

    (Obtaining informed consent re: fluoridation should include: (1) accurately describing the proposed intervention, including where the Fluoride comes from and what it and the required equipment will cost, (2) accurately describing the individual’s role in decision-making and whether the ballot vote is binding, (3) accurately discussing viable alternatives to the proposed intervention, (4) accurately discussing the risks of the proposed intervention and (5) eliciting the individual’s preference.)

    Finally, I notice you neglected to address the following in your response:

    “Water fluoridation is UNNECESSARY (brush and spit with fluoridated toothpaste if you wish).”

    In any event, I stand by my original comment. Sorry you don’t like it.

    “Water fluoridation is UNNECESSARY (brush and spit with fluoridated toothpaste if you wish), UNSAFE (neurotoxic Fluoride is bio-accumulative in the human body over time), INEFFECTIVE (purportedly works primarily by topical application, not by ingesting it) and UNETHICAL without informed consent,” with the additional provisos that people are often ingesting Fluoride from multiple sources daily, not just their public drinking water and that people drink varying amounts of water while also having unique medical conditions aggravated by this needless chemical addition to the public drinking water.


  4. Barry, you obviously don’t get my point. You make claims without any substantiation except bald and tired old slogans.

    Putting things in capital letters is not providing evidence.

    As I said, I expect more than this from my commenters here. I expect rational discussion, evidence and principled debate. Not tired old slogans.

    If you wish to argue that a health policy accepted by experts as safe and effective is not – then provide your evidence.

    The rest is really a matter of democratic decision. In New Zealand communities decide such matter for themselves and it is simply unethical for a minority to attempt to impose their dogmatic policies on the majority. Especially in this case as such dogma only contributes to the suffering of innocent children.

    Don’t forget – you came to this discussion because of an article which described specific scientific facts. You are not debating those. I think it is unethical for you to enter a discussion simply to spout tired old slogans without engaging with the issues the article describes.

    In essence, put up or shut up. Engage in good faith scientific discussion. Deal with the issues presented here and stop opportunistically repeating tired old slogans.


  5. Barry,

    54 years of fluoridation?

    So, you have 54 years of data from your own jurisdiction backing your statement that CWF is both “UNSAFE” and “INEFFECTIVE”?

    How about providing that data? If it actually supports your beliefs then it will be interesting to find out why your jurisdiction appears to contradict worldwide data since 1945


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