Special pleading by Philippe Grandjean on fluoride

Scientists are as human as anyone else. They aren’t immune to jumping on bandwagons, getting bees in their bonnets, special pleading or selectively interpreting their data to support a pet hypothesis or an obsession. The scientific peer review process restrains this human failing somewhat during  normal scientific publishing, but it can get out of hand when there is no such restraint.

Unfortunately Philippe Grandjean demonstrates this failing in a recent post – Mottled fluoride debate on his blog Chemical Brain Drain. This relates to a recent paper of which he is a junior author – . Association of lifetime exposure to fluoride and cognitive functions in Chinese children: A pilot study. I discussed this paper in my article Severe dental fluorosis the real cause of IQ deficits?

So what is wrong with the blog article?

1: Backgound claims about Choi et al (2012) (another paper Grandjean was also a junior author of.

He claims of this paper “children in the high-fluoride areas showed an average IQ 7 points below the controls.” That’s a bit of spin because that paper reported  an IQ deficit of only 0.45 of a standard deviation (7 IQ points is a hypothetical value mentioned in a later explanation). The authors themselves commented:

“The estimated decrease in average IQ associated with fluoride exposure based on our analysis may seem small and may be within the measurement error of IQ testing.”

2: He mentions work reported in the 2014 paper on “exposure assessment and cognitive testing of 51 children.” However, the data for only 43 of these children were actually used (and 3 groups of n=8, n=9 and n=26 compared).

3: He claims that for this group “lifetime exposures to fluoride from drinking water covered the full range allowed in the US.” He is attempting to make the finding relevant to the practice of community water fluoridation (CWF). The usual target for optimum fluoride concentration in CWF is 1 ppm or less. I guess their study covered this range because the lowest drinking water concentration was 1 ppm. As no cognitive defects or other effects were found at that concentration it is stretching things to claim the study (and especially the negative effects observed) is relevant to CWF.

4: He claims the measure cognitive defects were more common than actually reported. He says:

“children with fluoride-induced mottling of their teeth – even the mildest forms that appears as whitish specks on the enamel – showed lower performance on some neuropsychological tests.”

Yet what they specifically reported is that:

  • No statistically significant relationship of measured cognitive defects to drinking water fluoride concentration.
  • A statistically significant relationship of one cognitive deficit measure to moderate and severe dental fluorosis.

5: He indulges in further special pleading with statistical results claiming:

“a New Zealand study that “found that fluoridation is not neurotoxic for either children or adults, and does not have a negative effect on IQ”. This interpretation is rather optimistic, as the statistical confidence limits suggest that a loss of 2-3 IQ points could not be excluded by their findings.”

Well, of course this result doesn’t exclude the possibility – but it is completely inappropriate to use that argument to somehow claim the result proves there is an IQ difference.

Dental fluorosis and cognitive deficits


This photo accompanies Grandjean’s blog post. Could it be that severe dental fluorosis could contribute to learning difficulties and hence IQ deficits just because of appearance?

The Choi et al (2014) study did find a statistically significant relationship of cognitive deficit to moderate/severe dental fluorosis and I discussed this in my article Severe dental fluorosis the real cause of IQ deficits?

Although the numbers in the study were small that conclusion does seem reasonable because moderate/severe dental fluorosis is known to negatively affect the quality of life of children just because of the physical anomaly. That in itself could explain the observed results without needing to invoke some unknown mechanism of chemical neurotoxicity at low fluoride concentrations.

Sixty percent of the children in the Choi et al., (2014) study had moderate/severe dental fluorosis. The graphic below demonstrates that situation is very different to what exists in countries using CWF. The areas reviewed (Choi et al., 2012) and studied (Choi et aql., 2014)  are areas of endemic fluorosis. There results are of course relevent to those situations but should not be naively extrapolated to areas using CWF.

Unfortunately Grandjean and Choi et al., (2014) seem unprepared to consider the possible effect of negative appearance connected with severe dental fluorosis on learning and hence IQ of children. They seem unwilling to consider any hypothesis except their favoured one of chemical toxicity. For example, Choi et al., (2014) are “planning a larger scale study to better understand the dose–effect relationships for fluoride’s developmental neurotoxicity.” Surely that is a blinkered approach.

Similarly Grandjean and Landrigan (2014), in the Lancet paper which anti-fluoride propagandists love to promote, were on thin ice to declare fluoride a neurotoxic element. The only evidence they used for this was the Choi et al., (2014) study where non-chemical factors like negative appearance could be involved. This paper was subsequently criticised in a later issue of the journal. However, its original publication, despite its special pleading, indicates faults in the journal’s peer review process (see and Repeating bad science on fluoride and Controversial IQ study hammered in The Lancet).

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13 responses to “Special pleading by Philippe Grandjean on fluoride

  1. I wish that all the scientific information would be collected and presented to show, conclusively (is that possible?) that fluoride is either the white knight, black evil or something in between (used correctly, it is fine).

    My old world view was to simply believe well presented and/or written claims.
    Now I wish to see the original evidence (advice from Dr Ben Goldacre’s blog ‘Bad Science’). Despite all the debate, the NZ health Department appears unable to collect and present this evidence. Surely SOMEONE has done this? If so, then all debate would cease.

    Rhetoric and blind crowd thinking such as: ‘Everyone knows fluoride is good/bad’ simply won’t do’, as there is no complete evidence & therefor, nothing is settled.

    It sounds simple to me, how about the rest of you?


  2. Chris, reviews gather together the relevant evidence and some of them attempt to discuss the quality of the original research.

    Why not have a read of the most recent one from the Royal Society of NZ and the Office of the PM’s Chief Scientific Advisor.

    See Review finds community water fluoridation safe and effective for download links.


  3. Chris, once you’ve read this so called ‘review’ have a read of the Critique here. http://fluoridefree.org.nz/nz-review/nz-review-critique/nz-fluoridation-review-timeline/


  4. And Chris, when you have looked at the attack on the Royal Society Review produced by Kane’s organisation, FFNZ, have a read of the critiques of the FFNZ document here.

    Specifically you might want to read:

    Peer review of an anti-fluoride “peer review”

    Cherry-picking and misinformation in Stan Litras’s anti-fluoride article, and

    Did the Royal Society get it wrong about fluoridation?


  5. Chris, after you’ve read that non-sense supplied by Ken have a read of his colleagues (Alison Campbell’s) incorrect answers at the Waikato University Google Hang Out.


    Then read these two books from your local library.


    Then sign up to come and listen to Dr Paul Connett in February.


  6. Chris, it might be worth you judging for yourself the calibre of the anti-fluoride propagandist Paul Connett. He claims to be a world expert on fluoridation. He has done no original research on the topic and has no peer reviewed scientific papers on it. However, he is head of a political activist (Fluoride Action Network) group financed by the “natural” health industry. Kane is one of his fanboys and the highlight of Kane’s year is the annual holiday Paul takes to NZ.

    A year ago I had an on-line debate with Paul which you can find at Fluoride Debate. You can also download a PDF file of the debate.

    Paul does not publicise the debate – I think he feels he did not do too well. But it is worth reading it if you have the time as I spent some time outlining the techniques Paul uses to distort the science and provide misleading information.


  7. Ken, can you please provide your submission to the Hamilton City Council Tribunal in 2013? You live in Hamilton, are a leading expert in fluoridation and take a keen interest in local politics. Where is it?


  8. Kane, this is the submission I made to the Hamilton City Council last year on behalf of Making Sense of Fluoride – https://openparachute.files.wordpress.com/2014/05/0062.pdf

    I don’t claim to be a leading expert in fluoridation although I have worked as a research chemist and done some research on fluoride and fluorosilicic acid. I do not have a keen interest in either local or national politics. Still, I guess accuracy was never your strong point.

    Now for some light relief perhaps you could post your submission to the Hamilton City Council – the video link was rather amusing.


  9. By the way, Steve has also provided information on Paul Connett here recently


  10. Riddled with lies Ken.

    “Strong teeth reduces the wear and damage which can, indirectly, lead to decay. However, the
    mechanism directly initiating decay occurs at the tooth surface and is inhibited by fluoride
    present in saliva and biofilms on the tooth surface. Opponents of CWF claim this surface
    mechanism means that ingested fluoride plays no role and fluoride is only effective when
    topically applied – as with toothpaste. This is a gross simplification and distortion.”

    I’m actually after your 2013 submission during the tribunal. Can you please post.



  11. I notice you are unable to find and justify any fault with my submission, Kane,

    I also notice you are refusing to provide links to your submission and video or your oral presentation. Come on, don’t be shy. I found them quite funny the first time I saw them.

    But I can understand if you no longer want to stand by them. After all, your organisation appears to have decided to give up on a science and legal advisor he was so ineffective.


  12. It’s unclear who wrote the above article and so it’s hard to judge what the ulterior motive would be, other than to support continued fluoridation and to discredit Choi and Grandjean. The silly notion that dental fluorosis causes loss of IQ is presented as a straw man argument. Of course dental fluorosis does not cause loss of IQ, but fluorosis as a bio marker of toxicity represents the degree to which individuals have been over-exposed to the neurotoxic chemical fluoride. A not so subtle difference. As for the graph showing low levels of moderate to severe fluorosis in the U.S., this graph is behind the times. The CDC’s own graph shows that if the 41% of kids with fluorosis, 8.6% have moderate and 3.6% have severe. Whatever happened to “first do no harm”? Doctors and dentists who continue to support and even promote fluoridation are concerned only with the harm to their own reputations if they dare admit they’ve been wrong.


  13. Barbara, I wrote the article – as the owner of the blog anything not written by me is identified as such.

    There was no ulterior motive – simply an attempt to analyse Grandjean’s claims critically and intelligently. The normal scientific approach.

    My article on severe dental fluorosis and cognitive deficits was accepted by the journal – the reference is:
    Perrott, K. W. (2015). Severe dental fluorosis and cognitive deficits. Neurotoxicology and Teratology, 48, 78–79. You can download it here.

    Perhaps you should read it before being so dismissive.

    This is not a “straw man” argument – but is does put forward a credible hypothesis to explain the results in their paper. After all, while they found a link between severe dental fluorosis and IQ they did not identify a link between water fluoride concentration and IQ.

    There is absolutely no evidence that fluoride is toxic, let alone neurotoxic, at concentrations used in community water fluoridation.

    Here is the CDC presentation of the distribution of different forms of dental fluorosis. Your figures seem wrong. But if you have anything more recent please provide a link or citation.
    US DF

    But even that data is dishonestly quoted as the fact is that the figures are very similar for fluoidated and unfluodiated areas. Community water fluodiation at the most has only a small effect – and then only on the mildest forms of dental fluoiodis. Here is some data for New Zealand.


    Anti-fluoride campaigners always distort and misrepresent this data – one shouild always check out their claims. Read this for example.


    AS for “first do no harm” – I suggest you should do a bit of self-analysis with this in mind as tooth decay does a lot of harm to kids.


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