Quality and selection counts in fluoride research

I think the paper most quoted by anti-fluoridation activists must be Choi et al (2012), Developmental fluoride neurotoxicity: A systematic review and meta-analysis. I say quoted but, I suspect, not read. It is always coming up in articles on natural health web sites and continually thrown into blog and Facebook discussions. Often as a link without explanation.

It is also heavily promoted on Twitter. The same tweet is often sent from the same account daily, or more often. Here are examples.

Harvard Study: #Fluoride Lowers Children’s Intelligence By Seven IQ Points
Harvard Study Confirms Fluoride Reduces Children’s IQ huff.to/111fe5o via @HealthyLiving
Harvard Study Confirms Fluoride Reduces Children’s IQ: articles.mercola.com/sites/articles…

The paper also gets a lot of mention when anti-fluoride activists petition local bodies to prevent or stop fluoridation. It was one of the papers that had a big effect on the Hamilton City Council during the hearings they held last year (see When politicians and bureaucrats decide the science).

I recently reread the paper – this time paying special attention to the selection and quality of the papers reviewed. I think both of these are important to anyone attempting to understand the significance of this review.


Choi et al (2012) selected 27 papers for their review. Their selection was clearly not random – 25 of these are Chinese studies with 2 Iranian. Very few of these papers are directly available to western readers. One of the Iranian papers has an English abstract and 3 of the Chinese studies were published in English (guess which journal – you are right – Fluoride). 

The authors do not give any details of translation of the papers but 8 of them seem to have been translated under the auspices of Paul Connett’s Fluoride Alert (FAN) activist group (FAN describes them as the “FAN English translation”). Copyrights for these English translations are held by the International Society for Fluoride Research (ISFR) and included in their journal Fluoride. They are also available on FAN. (It is sort of difficult to locate the boundaries between FAN, ISFR and Fluoride. And did you know the ISFR has charity status in New Zealand. Yes, as taxpayers we are subsidsing them through their tax exemption!).

The authors acknowledge the reviewed studies were selected and give several reasons:

1: Studies from rural China had not been included in earlier reviews:

“We specifically targeted studies carried out in rural China that have not been widely disseminated, thus complementing the studies that have been included in previous reviews and risk assessment reports.”

2: High fluoride concentrations in drinking water are not common in the west:

“Opportunities for epidemiological studies depend on the existence of comparable population groups exposed to different levels of fluoride from drinking water. Such circumstances are difficult to find in many industrialized countries, because fluoride concentrations in community water are usually no higher than 1 mg/L, even when fluoride is added to water supplies as a public health measure to reduce tooth decay.”

Well, I can understand the logic behind that selection – provided readers don’t think they are seeing a balanced, representative review of all the existing literature. And the reasons given for this selection makes nonsense of Paul Connett’s charge that the lack of material in the industrialised countries indicates at least an unwillingness to research problems or at worst a conspiracy not to do the research and/or hide the results.


Here I will just take the size of the reviewed reports as a possible indicator of their quality. Not that I am against short papers, far from it. But in this cases most of the papers were very short – basically because they reported only a simple relationship found between IQ and fluoride in drinking water. Very few papers consider confounding factors like family education, schooling, breast-feeding, etc. Factors known to influence IQ. Nor did they discuss their results in any depth.

The authors acknowledge the brevity of the reports reviewed:

“In regard to developmental neurotoxicity, much information has in fact been published, although mainly as short reports in Chinese that have not been available to most expert committees.”


“Although most reports were fairly brief and complete information on covariates was not available, the results tended to support the potential for fluoride-mediated developmental neurotoxicity at relatively high levels of exposure in some studies.”

The histogram below gives an idea of the size of these reports – obviously some were extremely short –  19 of the 26 considered were of 3 pages or less!


Another reason for brevity is that most papers give hardly any discussion, let alone critical assessment, of the reported results. I wonder if this is because of the well-known problem of excessive levels of fluoride in many Chinese well waters and the associated incidence of dental and bone fluorosis. Perhaps this encourages researchers to simply consider fluoride as a factor in other problems when we might think it more rational to look at factors traditionally related to IQ. Like education and breastfeeding.

Even Paul Connett has conceded the poor quality of many of the studies considered in this review (while of course still scare-mongering that fluoridation is somehow going to make us all dumb). The authors of the study itself warned their paper was not relevant to the fluoridation issue (see Harvard scientists: Data on fluoride, IQ not applicable in U.S):

“Two of the scientists who compiled the Harvard study on fluoride said it really doesn’t address the safety of fluoridation levels typical of American drinking water.

“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.,” the researchers said in an e-mail response to questions from The Eagle. “On the other hand, neither can it be concluded that no risk is present.”

The researchers noted that the fluoride levels they studied were much higher than what is found in fluoridated water in the United States and recommended “further research to clarify what role fluoride exposure levels may play in possible adverse effects on brain development, so that future risk assessments can properly take into regard this possible hazard.””

I guess this paper, and its continual promotion, must impress many anti-fluoridation activists and even some local body councillers and staff. But scientists and other experts familair with the subject are not so impressed.  The NZ National Fluoridation Information service last year reviewed  literature on possible effects of fluoridation on IQ (see A review of recent literature on potential effects of CWF programmes on Neurological ):

“The available evidence raises the possibility that high levels of fluoride in drinking water may have subtle effects on children’s IQ. However all of these studies have limitations in design and analysis, a clear dose-response relationship between DWFCs and assessed IQ are often not evident. The study authors are frequently very cautious in their comments, and several noted that any indicated negative effect applied only to high DWFCs. An hypothesis of fluoride neurotoxicity would also be supported by some experimental animal studies, however the great majority of these have only considered high fluoride intakes.
However collectively the data described are not robust enough to draw a firm conclusion that high fluoride levels in drinking water supplies contribute to retarded development of children’s brains. Also there is no clear evidence to suggest an adverse effect on IQ at lower fluoride intakes such as that likely to occur in New Zealand, where fluoridated water supplies contain fluoride in the 0.7 to 1.0 mg/L range.”

Since then a local New Zealand study has failed to find any relationship between fluoridation and IQ (see Dunedin fluoride-IQ study finds no ill-effect). The study did find a positive influence of education and breast feeding on IQ though – just as we would expect.

In a typical sour grapes comment Paul Connett, who was told of this research by a reporter, quipped “rather convenient.”

Confirmation bias in action! I guess he won’t be promoting the New Zealand research in the way he does the poor quality research in the Choi et al (2012) review.

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31 responses to “Quality and selection counts in fluoride research

  1. It will be interesting to see how the University of Otago study by Dr. Broadbent measured individual lifetime exposure to fluoridated water of the subjects, in order to conclude that this exposure had no negative effect on IQ. It appears that all the 1037 children in the study were all born in the same hospital, and all lived in Otago at age 3:

    “All those born at Queen Mary Hospital between 1 April 1972 and 31 March 1973, and whose mothers lived within the Dunedin Metropolitan Health District boundaries at the time of their child’s birth and were still living in the Otago region at the time of the age 3 assessment, were eligible for inclusion.”


    Who is this cohort compared with, in order to reach the IQ conclusion? Alternatively, if the comparison is between children living in different areas of Otago, how did they control for the halo effect? Everyone knows that the halo effect makes local comparisons within mixed fluoridated and non-fluoridated areas nearly impossible.

    I look forward to seeing the “quality” of this study that Ken has already endorsed (apparently without having read more than a newspaper article on the study). Is the quality of the study dependent on whether you agree with the conclusion, Ken?


  2. Joseph. I guess you will also take the line that Connett has without seeing the details of the NZ study?

    No, I do not judge quality in the basis of conclusion. In this article I specifically limited judgement on quality of the papers to length of the report and the statements of Choi et al about their quality. Even Connett admits quality is a problem.

    With the NZ study I have not made a judgment on quality. But having seen a draft of the paper which has now been accepted by a reputable scientific journal I was aware of the inclusion of important confounding factors like education and breast-feeding ignored by the Chinese studies.

    Perhaps you should do the sensible thing and stop passing judgement on the NZ study until you read the paper, or alternatively investigate the study more carefully than relying in a newspaper report.

    In the a time, do you have any comments to make on my analysis of the papers reviewed by Choi et al.


  3. Ken-

    I remain agnostic about the strength of the findings of the studies in the meta-analysis by Choi et al. Due to the relatively high doses of fluoride supposedly ingested by the subjects in some of those studies, direct comparisons with children drinking fluoridated water in the U.S., Australia, or N.Z. is of perhaps limited use. They had to make suppositions about the relationship between drinking water fluoride concentrations and actual dose consumed by children. Any study of this sort, including the upcoming Broadbent one, has to make broad assumptions about the concentration/dose relationship (unless intake is strictly controlled and directly measured, but this is nearly impossible to do in the long-term study context).

    But as you know, high doses of any drug or substance under examination are regularly used in lab studies to test possible harmful effects. Similarly, as there is nothing glaringly improper in the study design and methods used in the Choi et al. studies, they should serve at least as a warning signal for lower doses. As you quote the Harvard researchers, it “raises the possibility that high levels of fluoride in drinking water may have subtle effects on children’s IQ.” You may not find this alarming, but it certainly calls for further study.

    (Good luck getting parents to sign their children up for a long-term high-dose fluoride/IQ study, though. Perhaps children who have been given high-dose fluoride supplements anyhow would be a good substitute. Just give children some measured fluoride drops every day for ten years or so, and compare them with a control group with a placebo dose. Make sure to tell them you’re measuring just how beneficial ingesting fluoride is for their teeth, and you may get enough volunteers.)

    The confounding factors that you say Broadbent controlled for (education and breastfeeding) are important. So are parental IQ, nutritious diet, quality time spent with parents, disease, birth order, etc.- confounding factors in IQ studies are legion. I look forward to how Broadbent controlled for these factors and the “halo effect” in Otago. After all, only about a third of the original 1000 children (now adults) still live in Dunedin, so they have a ton of confounding factors to control.



  4. Joseph, I have not suggested anything improper in Choi et al’s study design and method (although I wish they had been up front about translations) but the way the study has been used has certainly been improper, even dishonest.

    Studies like the NZ one will go a long way to showing up the improper use of the Choi et al study. As Choi et al was published less that 2 yet as ago we will probably soon see more studies like the NZ one coming to light. Connett is dishonest to claim western researchers are ignoring the issue.

    It would be best not to bad mouth the NZ study at this stage – wait until you see the published paper or, if you alphabet serious issues,contact the authors. From my reading I am sure they will be able to correct you on some of the mistaken ideas you have of their study.



  5. The core thesis of Grandjean’s new paper (1) which needs aggressive critiquing by legitimate experts is the belief there is a “global pandemic of neurodevelopmental disorders”

    This view has enormous currency among Oregon’s environmental health community. The state annual meeting’s keynote speaker argued exactly this in 2012.

    It certainly is not reflected in the ongoing internationally documented increment (Flynn effect) of gradually elevating IQ.

    Politically we need to have a clearer view if it is reasonable to attack the entire thesis or whether we should only point out the many obvious reasons why 0.7 ppm fluoride should not be considered to be among the potential threats.

    I’ve felt that Grandjean’s call in his meta-analysis paper for additional research on the conceivable relationship between fluoride and neurodevelopment was somewhat reasonable. He obviously is annoyed that (in his view) there has been a disinclination to fund research on fluoride because of its important role in oral public health. If there is in fact harm from high fluoride exposure, presumably a threshold level could be found which would quell the anti-fluoridation propaganda his papers has spawned.

    The 2006 NAS report for the EPA specifically called for addition research focusing on a broader range of neurological function than simply IQ. (2)

    But the European Union’s SCHER committee has a formal statement that such research is not warranted.

    “Available human studies do not clearly support the conclusion that fluoride in drinking water impairs children’s neurodevelopment at levels permitted in the EU. A systematic evaluation of the human studies does not suggest a potential thyroid effect at realistic exposures to fluoride. . . . . . SCHER agrees that there is not enough evidence to conclude that fluoride in drinking water at concentrations permitted in the EU may impair the IQ of children. SCHER also agrees that a biological plausibility for the link between fluoridated water and IQ has not been established.?”

    A political reason seems sufficient to me to justify more studies on CWF and neurodevelopment. Certainly there was very little else to justify the politically critical study of thimerisol and autism. There seems very little enthusiasm for a CWF and neurodevelopment study in the US.


    Charles C. Haynie, M.D.; FACS
    Hood River, Or

    (1) Neurobehavioural effects of developmental toxicity. Philippe Grandjean, Philip J Landrigan; Lancet Neurol 2014; 13: 330-38

    (2) FLUORIDE IN DRINKING WATER: A Scientific Review of EPA’s Standards. 2006, Committee on Fluoride in Drinking Water Board on Environmental Studies and Toxicology Division on Earth and Life Studies, National Research Council of the National Academies. page 185.


  6. Dr. Haynie,

    You stated that:

    “Politically we need to have a clearer view if it is reasonable to attack the entire thesis or whether we should only point out the many obvious reasons why 0.7 ppm fluoride should not be considered to be among the potential threats.”

    and then:

    “A political reason seems sufficient to me to justify more studies on CWF and neurodevelopment. Certainly there was very little else to justify the politically critical study of thimerisol and autism. There seems very little enthusiasm for a CWF and neurodevelopment study in the US.”

    Ken pointed out in this article that there is an upcoming N.Z. study that found no effect on IQ from CWF. Have you read any other studies that have measured the effect of fluoride on IQ (other than Choi et al., which found a positive association)? If so, could you point them out to us? If not, why do you presume that the fluoride/IQ connection is in any way similar to the mercury/autism hypothesis? Are you implying that the meta-analysis we are talking about here is fraudulent in the same way as the single fraudulent autism study was? Ken has explicitly disavowed such a suggestion.

    Regardless, I find it irresponsible that you would work out a political angle, without being certain what the science will find regarding this issue. You are absolutely correct that it is better for everyone for more studies to be done, but not because you are already certain of the result, and therefore see a purely “political reason” to do the studies.

    Your political pondering is in accordance with the political strategies of Pew Center for the States, and associated entities. See in particular the “message wheel.”

    Click to access Messaging-for-Fluoridation-and-the-Dental-Workforce.jacob_.pdf



  7. Often as a link without explanation.

    Sometimes several links without explanations.
    Or some teeny-weeny comment like ” You will find this interesting” or “You have to read this”.
    In allcaps.
    ‘Cause morons do that.


  8. Charlotte Shaw

    The only things I want to know are:
    1. What is my exact daily dosage of this medication?
    2. What is the exact accumulation in my bones after being medicated daily since 1973?


  9. The only things I want to know are: …

    The “only things” ?

    That about sums it up really.

    You are not interested in how to interpret such information, because, well, you know, you already know how to do that.


  10. Christopher Atkinson

    Hi Charlotte

    I am curious – you seem to think that 0.7ppm F in water is “medication”.
    You can rest assured that it is not considered “medication” either in Law or considered so by any scientific community on the planet. The only community that I am aware that insists on this description is the “anti fluoride” community.
    Therefore when you use “medication and dosage”, you are simply using the wrong words.
    Perhaps if you asked what your level of fluoride intake is that would be more helpful. However fluoride is a naturally occurring substance and may be absorbed by the body from a great number of sources. So asking questions related to your personal fluoride intake is not possible.
    Therefore, posting a question a blog asking how much fluoride you have accumulated over the past few decades is just silly.
    If you are concerned about what is in YOUR water, perhaps you could also look at how much Trihalomethanes, Semi-Volatile Organic Compounds, Organophosphorus Pesticides, Semi-Volatile Organic Compounds — Organonitrogen Herbicides, Trace Elements, bacteria and parasites are also present. This information is often readily available. If you live in NZ this may help;


  11. Christopher Atkinson

    Ah..I see Charlotte has history with this issue, having had a tussle with Making Sense of Fluoride as well as in Canada.

    She obviously isn’t genuine when asking her questions.
    Think you’ve nailed it on the head Richard


  12. Christopher-

    You wrote:

    “I am curious – you seem to think that 0.7ppm F in water is “medication”.
    You can rest assured that it is not considered “medication” either in Law or considered so by any scientific community on the planet. The only community that I am aware that insists on this description is the “anti fluoride” community.”

    Whether one defines fluoride as a “medication,” an “essential mineral,” a “mineral,” a “contaminant,” or a “substance” is only relevant to the ethical/legal issues surrounding CWF. It is irrelevant to the effectiveness or safety of fluoride, at whatever concentration. Do you mean to say that fluoride is not a “drug” at CWF concentrations, but is a “drug” at higher concentrations? Either way, yours and the authorities’ characterization of fluoride is completely irrelevant to studies measuring safety.

    Similarly, the “concentration” of fluoride in fluoridated drinking water is related to, but not identical with, “dose” or “intake.” Do you suggest that the term “daily dose” is functionally different than “daily intake?” In any case, studies are needed that test the safety (and effectiveness) of fluoride at different levels of total exposure- making comparisons based on local water concentrations is a poor substitute, laden with assumptions. That’s one of the main reasons Choi et al. is best seen as a troubling indicator of, and not more definitive evidence of, negative IQ effects.



  13. Charlotte Shaw

    So none of you ‘geniuses’ are able to answer the simple questions posed. Fair enough. Insulting me doesn’t change the fact that not a single scientist or ‘genius’ can answer the two questions posed. Caring about my health and the health of my family makes me an idiot. Just so you are aware, I do spend the majority of my life avoiding all chemicals as our family has a history of sensitivity to them. Using a toothbrush and avoiding sugar laden foods as my personal choice to avoid tooth decay makes me an idiot. With two members of my family having stage 3 kidney disease, our kidneys do not filter fluoride the way the average person’s does. The 2 and 3 year old babies in the family have mild fluorosis, despite never having used a drop of fluoridated toothpaste, consuming pesticide free foods, and being raised in a reasonable chemical free home environment. You can all quote your superior intelligence until the cows come home. Fluoride has harmed this family. Still I am asking each of you ‘geniuses’ to answer the questions, if you are unable to do so I promise I won’t insult or mock you. Perhaps you can just direct me to a scientist, doctor, or health agency anywhere in North America that can tell me what my daily ‘intake’ is, and provide me with a medical document confirming that Fluoride has not harmed me. Until then enjoy your assault on women and children who care about their health, if it makes you feel superior, and gives you a sense of entitlement to abuse us.


  14. Christopher Atkinson

    Joseph –
    Yes I agree that the definition of community fluoridated water (not fluoride) is most relevant to the ethical/legal issues surrounding CWF. Although not completely irrelevant to investigations into effects – an accurate definition should be preferred.
    However, I have noticed that most people “anti” fluoride are unable to make these distinctions as they often promote “rights” based arguments simply because they believe with zealous fervor CWF to be a medicine or a drug.
    Arguments nearly always devolve to shrill emotional tirades which are little use in any discussion.
    Have a look at the language Charlotte has presented.
    “Do you suggest that the term “daily dose” is functionally different than “daily intake?”
    I do suggest the term dose id different to daily intake.
    Using the word “dose” is an emotionally charged word implying medicine or drug preferred by “anti” fluoridationists.
    Do you object to “daily intake” ?- It is more accurate and carries less baggage when discussing the issue within the public forum?


  15. So none of you ‘geniuses’ are able to answer the simple questions posed.

    Read English.

    … not a single scientist or ‘genius’ can answer the two questions posed.

    Yes, that’s right. No scients or genius. You have foxed them all. You are a legend in your own lunchtime. The thought that maybe you are wrong and it’s the rest of the planet that’s right never occurs to you.
    Welcome to Crackpot City.

    Caring about my health and the health of my family makes me an idiot.

    Are you demented? Stop listening to the voices in your head and focus on reality. Try and read the words in front of you. Otherwise your only friends will be strawfriends.

    The “Straw Man” Fallacy


  16. Christopher Atkinson


    “So none of you ‘geniuses’ are able to answer the simple questions posed.”
    Can you tell me how much mercury I have accumulated since 5th March 1967? I suppose that will be an easy question for you to answer.
    “Caring about my health and the health of my family makes me an idiot”. No course it doesn’t Charlotte. Asking absurd questions and expecting an answer does.
    I see that you appear to have a number of health issues. Most people are exposed in some way to any number of health issues. Community water fluoridation is a public health initiative.
    I have members in my family with severe allergies yet I don’t expect society to ban specific food products or otherwise structure health policy around them. That’s life. They have responsibility for their personal safety and do not have the right to expect society to impose unreasonable restrictions on the majority’s freedoms.
    So, as have you or do you drink fluoridated water? And if so, what problems do you believe were caused ?


  17. Cedric . (51047)

    I perhaps didn’t make myself clear re politicking and science.

    I am reasonably certain (which is all that is possible) that there is no harm done neurodevelopment from 0.7 ppm fluoride in drinking water. I do not believe the incremental fluoride ion intake from fluoridation to infants, children and adults is biologically important to neurodevelopment or any of the 100+ other health harms we have seen claimed by opponents. I have this opinion from about 12 years of active involvement in both the political and scientific aspects of community water fluoridation. I consider both important. If you have peer reviewed studies I have overlooked which show harm please post those references.

    I am not in a position to have a clear opinion whether or not Grandjean’s view that there is a “global pandemic of neurodevelopmental disorders” is credible. If there is such a pandemic, I do not know if there is a reasonable biologic plausibility that “industrial chemicals” and specifically fluoride are the cause of it. One would anticipate if fluoride can be a neurotoxicant there would be a definable threshold for that effect.

    Again with respect to optimized fluoridation, fluoride is sufficiently common naturally one would expect evolutionary acclimation to low level exposure. We know that ocean mammals who are continuously exposed to about 1.4 ppm appear to be unharmed.

    I do know that systematic reviews (I quoted the SCHER statement) have not found there to be evidence that fluoride in potable water causes neurodevelopmental injury.

    I think the international oral public health advocates have combined the known science appropriately to our political messaging. We surely must find effective ways to deflect the egregious use of Grandjean’s papers and statements by scare mongering community water fluoridation opponents. Their claims, tragically, have enormous political effect quite independent of a rational objective evaluation of their invalidity.

    It would be next to impossible for an individual like myself to reach a clear and confident decision on a complex matter like Grandjean’s larger claim of harm from a long list of suspect molecules. I am unaware of a consensus among toxicologists that a new international clearing house for chemoneurotoxicants should be created.

    Here is my statement I believe you question.

    “Politically we need to have a clearer view if it is reasonable to attack the entire thesis or whether we should only point out the many obvious reasons why 0.7 ppm fluoride should not be considered to be among the potential threats.”

    It is my present opinion that I am on solid scientific ground only with respect to the latter option. The first half of the sentence was posted in hopes that experts reading the Open Parachute Blog with knowledge and experience in toxicology might provide council.

    It is very common for environmental activists to exaggerate and overstate. If there is good science of which supports a real “pandemic” then all of human kind should endeavor to mitigate and avoid such harm as we have done with lead. If however, the science shows this to be a Chicken Little claim from start to finish then Dr. Grandjean deserves all the political resistance we can muster.



    PS . .here is an excellent reasoned evaluation of the Precautionary Principle seeking workable middle ground.

    The Ethics of Synthetic Biology: Guiding Principles for Emerging Technologies
    Amy Gutmann, Hastings Center Report 41, no. 4 (2011): 17-22.


  18. Dr. Haynie-

    Presumably you wrote in response to my comment, not Cedric’s.

    You wrote:

    “I am reasonably certain (which is all that is possible) that there is no harm done neurodevelopment from 0.7 ppm fluoride in drinking water. I do not believe the incremental fluoride ion intake from fluoridation to infants, children and adults is biologically important to neurodevelopment or any of the 100+ other health harms we have seen claimed by opponents.”

    And then:

    “It is my present opinion that I am on solid scientific ground only with respect to the latter option [the option to “point out the many obvious reasons.why 0.7 ppm fluoride should not be considered to be among the potential threats”].

    1.) It is precisely this premature misplaced certainty that I criticized you for. Because of your certainty that Choi et al. will eventually be discredited or that it has zero applicability to CWF, you feel free to preemptively “attack” the issue politically. If you “do not believe the incremental fluoride ion intake… is biologically important to neurodevelopment or ANY of the 100+ other health harms we have seen claimed by opponents,” it is remarkable that you find such extreme cariostatic effects from the same “incremental fluoride ion intake.” [emphasis added] Apparently, you think there is one and only one effect on health from CWF- and that is to prevent cavities.

    2.) Frankly, your evolutionary argument is just silly. We evolved in Africa despite [and also because of] the amount of radiation in the environment- solar and earth-based. So we certainly developed ways to deal with radiation. That doesn’t necessarily mean we should intentionally expose ourselves to more radiation- due to the harmful effects. Similarly, you can’t say that there are NO harmful effects from CWF simply because we evolved in an environment that contained some naturally occurring fluoride (thereby developing some resistance to toxicity in humans).

    3.) Your statement about mammals living in ocean water “who are continuously exposed to about 1.4 ppm appear to be unharmed” is imprecise. About half of the fluoride in ocean water (which varies from 1.2 to 1.4 ppm) is in the biologically unavailable form of a magnesium fluoride complex. Ocean mammals are in effect exposed to about .6 to .7 ppm.

    Click to access Sodium,%20potassium,%20magnesium,%20calcium%20and%20strontium%20in%20sea%20water%20(Gravimetri).pdf

    For a Canadian government survey of effects of fluoride on aquatic life generally, if you are interested in these things:


    Not that this imprecision is important- ocean mammals are no more or less analogous to humans than are rats, in which specific fluoride lethal doses have been established. In simple terms, high fluoride doses kill rats in lab studies by binding to calcium in the body. Perhaps start with that mechanism, if you are searching for a “plausible” explanation for neurodevelopmental effects at CWF doses.

    4.) I agree that it is nearly impossible to critique Grandjean’s paper as a whole. But we’re talking about Choi et al. here and the quality of the underlying studies finding an effect on IQ from fluoride exposure. It seems you have a low opinion of the meta-analysis. Ken leveled some relatively mild criticisms at it, and suggested an upcoming NZ study will refute it. His position (while motivated nevertheless by a belief in CWF) seems more reasonable than your political-cart-before-the-scientific-horse approach.



  19. *EDIT* Dr. Haynie- I mistakenly posted an incorrect link relating to the proportion of free fluoride in seawater (51%) compared with magnesium fluoride complexes (47%). Here is the 1993 study I intended to cite:

    Click to access 01.1993.01Rude.pdf


  20. Joseph – you refer to “certainty that Choi et al. will eventually be discredited or that it has zero applicability to CWF” which demonstrates an unjustifed stance on your part.

    It is not a matter of Choi et al “eventually” being discredited. It is a matter of that review not being applicable to fluoridation. It is also a matter of a very poor review – selected studies of poor quality – being promoted far beyond its value. And self-promoted as Grandjeans latest paper shows. I think their self-promotion and removal of any qualifications is ethcially questionable (see Repeating bad science on fluoride).

    You appear to want fluoride to have a negative effect on IQ. I perosnally don’t find it at all suprising that F has the observed caristatic effect without simultaneously harming IQ. Why the hell should it?

    In critiquing Grandjeans’s paper let’s not forget, regarding fluoride, we are at the sam time critiquing Choi at al’s paper, of which Grandjean was a senior author.

    I don’t think my criticisms of wither Choi et al or their recent paper is mild. I personally would have sent them back for extensive changes if I had been a reviewer.


  21. Joseph

    I think I am simply going to have to stand by what I have said previously.

    The subject of the 1993 Rude and Aller paper to which you referred is “marine pore water.” Despite the complex inorganic geochemistry discussed there I don’t see the relevance to my reference to marine mammalian adaptation to free fluoride ions.

    It is my understanding that the measurements of sea water fluoride (roughly 1.4 ppm) reflect the concentration of free fluoride ions.

    There are data which pretty clearly document that sea mammals have a significantly greater fluoride exposure than do humans.

    See for example:

    J Wildl Dis. 1999 Apr;35(2):356-60. Bone fluoride concentrations in beluga whales from Canada. Mikaelian et al. Canadian Cooperative Wildlife Health Centre, PQ, Canada.

    The Choi et al meta analysis has no implication for human effects of 0.7 ppm fluoride in drinking water. That has been debated and discussed in great detail both in the Open Parachute blog, in the larger public health and scientific community and the web. I see that Ken Perrott has again well addressed that issue here. As far as I can tell only anti-fluoridation ideologues believe there is any reasonable inferences from Choi for neurodevelopment harm assessment and the fluoride concentration associated with fewer cavities.

    A dramatic testimony to the non-applicability of Choi to community water fluoridation is the combined statement from the deans of the Harvard Public Health, Medical, and Dental Schools.

    You might like to read that here:

    Click to access Harvard-Letter-3-Deans-March-2013.pdf

    With respect to additional literature on fluoridation and neurodevelopment here is one from New Zealand:

    N Z Med J. 1986 Jun 11;99(803):416-8. Exposure to fluoridated public water supplies and child health and behaviour. Shannon FT, Fergusson DM, Horwood LJ.


    My apologies to Cedric for misreading the labeling of these posts.


  22. Stuart Mathieson

    Charlotte! Not wanting to be cruel or unkind but a calm read of the references at the bottom of the article might bear fruit for you. But I suspect you will brush aside any article or evidence that questions your fixation. Mad memes are always circulating in communities and like viruses, they flourish in vulnerable hosts.


  23. Stuart Mathieson

    “I do spend the majority of my life avoiding all chemicals as our family has a history of sensitivity to them.” you say. Im not sure what you mean by “chemicals” but it is impossible to avoid them. Your body is made up of them. The physiology that keeps you alive, and the precesses that breaks you down into your constituent “stuff” consists of chemical processes. Clearly you have managed to avoid even the most basic of science in your schooling. If you need a cause why not focus on sugar and other sweeteners added to food to make you eat (buy) more and is responsible for a host of ills including rotten teeth.


  24. Stuart Mathieson

    It seems they discontinued Fluoride in Calgary. The following article in the Lethbridge Herald documents the rapid outcomes, given the infatuation with sugar loaded cordials around these days. In spite of that the response from the usual loons beggars belief including one from our friend Charlotte who thinks like many anti F- that a few borrowed one liners can be passed off as informed comment.
    The second link explains the psychological phenomenon.




  25. Stuart Mathieson

    It’s not exposure to F- that lowers IQ, it’s exposure to Fox News and its non stop propagation of hysteria.


  26. Exposure to Fox News certainly has it’s drawbacks. I would add that exposure to Mercola, Natural News, naturopaths, homeopaths,chiropractors and companies that sell water filters also lower IQ’s. It’s funny that none of the antis mention that in developed countries IQ is actually increasing, even with fluoride in the water.


  27. Stuart Mathieson

    A prominent and outspoken city councillor critic of fluoridation in Dunedin is an agent for domestic water filters so effective it even removes the dehydrogen oxide which as we all know is highly toxic in vast quantities.


  28. Christopher Atkinson


  29. Stuart Mathieson

    Having just read a Huffington Post post (!) on the 2006 Grandjean paper on neurotoxic effects on the featus it is clear the generalising tendendency of journalistic reporting damns innocuous minerals such as fluoride by association and by the absence of qualification (different irrelevant chemical and industrial combination and formulation). As Charlotte’s responses reveal, even the word “chemical” is tainted by association.
    The other thought is the bandwagoning effect on people who are troubled by any number of “issues” (not surprising given the perpetual state of hysteria maintained by certain media for political reasons) and their vulnerability to scapegoating as persecution of millions in the name of race, politics and religion vividly attest.


  30. Stuart Mathieson

    Further to my previous posting the though arises “who has a vested interest in implicating the innocuous in a contrived generalised paranoia of contamination?”
    One could conclude “the real contaminators?”. The pollution of the environment and waterways in many industrialised communities easily springs to mind.
    One might also ask “who is threatened by the mass treatment of populations via foodstuffs and reticulated water?”.
    The answer of course, “manufacturers and distributors of health supplements.”

    Another question. “who has a vested interest in concealing the real cause of tooth decay?”
    I’ll leave you to answer that one.


  31. Jam, you comment as it stands is defamatory towards another commenter here. Consequently I will not approve it.

    You are welcome to resubmit without the defamatory content, or with evidence justifying the claim.


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