Tag Archives: Connett

Mary Byrne’s criticism is misplaced and avoids the real issues

Image credit: BuildGreatMinds.Com

First, thanks to Mary Byrne and FFNZ for this response (see Anti-fluoride group coordinator responds to my article). Hopefully, this will help encourage some good faith scientific discussion of the issues involved in my original article (Paul Connett’s misrepresentation of maternal F exposure study debunked). I am pleased to promote such scientific exchange.

I will deal with the issues Mary raised point by point. But first, let’s correct some misunderstandings. Mary claimed I am a “fluoride promoter” and had “sought to discredit the study via his blog posts and tweets.”

  1. I do not “promote fluoride.” My purpose on this issue has always been to expose the misinformation and distortion of the science surrounding community water fluoridation (CWF). I leave promotion of health policies to the health experts and authorities.
  2. I have not “sought to discredit the study.” The article Mary responded to was a critique of the misrepresentation of that study by Paul Connett – not an attack on the study itself. This might become clear in my discussion below of the study and how it was misrepresented.

The study

The paper we are discussing is:

Bashash, M., Thomas, D., Hu, H., Martinez-mier, E. A., Sanchez, B. N., Basu, N., … Hernández-avila, M. (2016). Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6 – 12 Years of Age in Mexico.Environmental Health Perspectives, 1, 1–12.

Anti-fluoride activists have leaped on it to promote their cause – Paul Connett, for example, claimed it should lead to the end of community water fluoridation throughout the world! But this is not the way most researchers, including the paper’s authors, see the study. For example, Dr. Angeles Martinez-Mier, co-author and one of the leading researchers,  wrote this:

1. “As an individual, I am happy to go on the record to say that I continue to support water fluoridation”
2. “If I were pregnant today I would consume fluoridated water, and that if I lived in Mexico I would limit my salt intake.”
3.  “I am involved in this research because I am committed to contribute to the science to ensure fluoridation is safe for all.”

Was the reported association statistically significant?

Mary asserts:

“Perrott claims that the results were not statistically significant but his analysis is incorrect.”

That is just not true. I have never claimed their reported association was not statistically significant.

I extracted the data they presented in their Figures 2 and 3A and performed my own regression analysis on the data. This confirmed that the associations were statistically significant (something I never questioned). The figures below illustrating my analysis were presented in a previous article (Maternal urinary fluoride/IQ study – an update). These results were close to those reported by Bashash et al., (2017).

For Fig. 2:

My comment was – “Yes, a “statistically significant” relationship (p = 0.002) but it explains only 3.3% of the variation in GCI (R-squared = 0.033).”

For Fig 3A:

My comment was – “Again, “statistically significant” (p = 0.006) but explaining only 3.6% of the variation in IQ (R-squared = 0.0357).”

So I in no way disagreed with the study’s conclusions quoted by Mary that:

” higher prenatal fluoride exposure, in the general range of exposures reported for other general population samples of pregnant women and nonpregnant adults, was associated with lower scores on tests of cognitive function in the offspring at age 4 and 6–12 y.”

I agree completely with that conclusion as it is expressed. But what Mary, Paul Connett and all other anti-fluoride activists using this study ignore is the real relevance of this reported association. The fact that it explains only about 3% of the IQ variance. I discussed this in the section The small amount of variance explained in my article.

This is a key issue which should have been clear to any reader or objective attendee of Paul Connett’s meeting where the following slide was presented:

Just look at that scatter. It is clear that the best-fit line explains very little of it.  And the 95% confidence interval for that line (the shaded area) does not represent the data as a whole. The comments on the statistical significance and confidence intervals regarding to the best-fit line do not apply to the data as a whole.

Finally, yes I did write (as Mary quotes) in my introductory summary that “the study has a high degree of uncertainty.” Perhaps I should have been more careful – but my article certainly makes clear that I am referring to the data as a whole – not to the best fit line that Connett and Mary concentrate on. The regression analyses indicate the uncertainty in that data by the low amount of IQ variance explained (the R squared values) and the standard error of the estimate (about 12.9 and 9.9 IQ points for Fig 2 and  Fig 3A respectively).

The elephant in the room – unexplained variance

Despite being glaringly obvious in the scatter, this is completely ignored by Mary, Paul Connett and other anti-fluoride activists using this study. Yet it is important for two reasons:

  • It brings into question the validity of the reported statistically significant association
  • It should not be ignored when attempting to apply these findings to other situations like CWF in New Zealand and the USA.

Paul Connett actually acknowledged (in a comment on his slides) I was correct about the association explaining such small amount of the variance but argued:

  • Other factors will be “essentially random with respect to F exposure,” and
  • The observed relationship will not be changed by the inclusion of these other factors.

I explained in my article Paul Connett’s misrepresentation of maternal F exposure study debunked how both these assumptions were wrong. In particular, using as one example the ADHD-fluoridation study I have discussed elsewhere (see Perrott, 2017). I hope Mary will refer to my article and discussion in her response to this post.

While ignoring the elephant in the room – the high degree of scattering, Mary and others have limited their consideration to the statistical significance and confidence intervals of the reported association – the association which, despite being statistically significant, explains only 3% of the variation (obvious from the slide above.

For example, Mary quotes from the abstract of the Bashash et al., (2017) paper:

“In multivariate models we found that an increase in maternal urine fluoride of 0.5mg/L (approximately the IQR) predicted 3.15 (95% CI: −5.42, −0.87) and 2.50 (95% CI −4.12, −0.59) lower offspring GCI and IQ scores, respectively.”

I certainly agree with this statement – but please note it refers only to the model they derived, not the data as a whole. Specifically, it applies to the best-fit lines shown in Fig 2 and Fig 3A as illustrated above. The figures in this quote relate to the coefficient, or slope, of the best fit line.

Recalculating from 0.5 mg/L to 1 mg/L this simply says the 95% of the coefficient values, or slopes, of the best fit lines resulting from different resampling should be in the range  -10.84 to -1.74 CGI (Fig 2) and -8.24 to 1.18 IQ (Fig 3A).

[Note – these are close to the CIs produced in my regression analyses described above – an exact correspondence was not expected because digital extraction of data from an image is never perfect and a simple univariate model was used]

The cited CI figures relate only to the coefficient – not the data as a whole. And, yes, the low p-value indicates the chance of the coefficient, or slope, of the best-fit line being zero is extremely remote. The best fit line is highly significant, statistically. But it is wrong to say the same thing about its representation of the data as a whole.

This best-fit line explains only 3% of the variance in IQ – and a simple glance at the figures shows the cited confidence intervals for that line simply do not apply to the data as a whole.

The misrepresentation

That brings us back to the problem of misrepresentation. We should draw any conclusions about the relevance of the data in the Bashash et al., (2017) study from the data as a whole – not just from the small fraction with an IQ variance explained by the fitted line.

Paul Connett claimed:

“The effect size is very large (decrease by 5-6 IQ points per 1 mg/L increase in urine F) and is highly statistically significant.”

But this would only be true if the model used (the best-fit line) truly represented all the data. A simple glance at Fig 2 in the slide above shows that any prediction from that data with such a large scatter is not going to be “highly statistically significant.” Instead of relying on the CIs for the coefficient or slope of the line, Connett should have paid attention to the standard error for estimates from the data as a whole given in the Regression statistics of the Summary output. – For Fig. 2, this is 12.9 IQ points. This would have produced an estimate of “5-6 ± 26 IQ points which is not statistically significantly different to zero IQ points,”  as I described in my article

Confusion over confidence intervals

Statistical analyses can be very confusing, even (or especially) to the partially initiated. We should be aware of the specific data referred to when we cite confidence intervals (CIs).

For example, Mary refers to the CI values for the coefficients, or slopes, of the best fit lines.

Figs 2 and 3A in the Bashash et al., (2017) paper include confidence intervals (shaded areas) for the best fit lines (these take into account the CIs of the constants as well as the CIs of the coefficients). That confidence interval describes the region of 95% probability for where the best-fit line will be.

Neither of those confidence intervals applies to the data as a whole as a simple glance at Figs 2 and 3A will show. In contrast, the “prediction interval” I referred to in my article, does. This is based on the standard error of the estimate listed in the Regression statistics. Dr. Gerard Verschuuren demonstrated this in this figure from his video presentation.

Mary is perfectly correct to claim “it is the average effect on the population that is of interest” – but that is only half the story as we are also interested in the likely accuracy of that prediction. The degree of scatter in the data is also relevant because it indicates how useful this average is to any prediction we make.

Given the model described by Bashash et al., (2017) explained only 3% of the IQ variance, while the standard error of the estimate was relatively large, it is misleading to suggest any “effect size” predicted by that model would be “highly significant” as this ignores the true variability in the reported data. When this is considered the effect size (and 95% CIs) is actually “5-6 ± 26 IQ points which is not statistically significantly different to zero IQ points,”

Remaining issues

I will leave these for now as they belong more to a critique of the paper itself (all published papers can be critiqued) rather than the misrepresentation of the paper by Mary Byrne and Paul Connett. Mary can always raise them again if she wishes.

So, to conclude, Mary Byrne is correct to say that the model derived by Bashash et al., (2017) predicts that an increase of “fluoride level in urine of 1 mg/L could result in a loss of 5-6 IQ points” – on average. But she is wrong to say this prediction is relevant to New Zealand, or anywhere else, because when we consider the data as a whole that loss is “5-6 ± 26 IQ points.”

I look forward to Mary’s response.

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Anti-fluoride activist commits “Death by PowerPoint”

We have all sat through boring, and counterproductive, PowerPoint presentations. Boring because the presenter breaks all the rule relevant to the preparation of visual displays. And counterproductive because, in the end, the audience does not remember any of the information the presenter attempts to convey.

David JP Phillips gives some relevant advice on PowerPoint preparation in the video above and similar advice is available online.  All this advice is very helpful for anyone preparing a presentation – although constant reminders of the points and frequent practice or experience are needed to take it on board. The PowerPoint programme seems to tempt even the best presenter to make fundamental mistakes which can reduce the effectiveness of their visual material.

Learning from bad examples

Examples of bad PowerPoint presentations are ubiquitous – but I urge readers to critically consider this recent example. The PowerPoint presentation the anti-fluoride campaigner, Paul Connett, prepared for his recent presentation to a meeting in the NZ Parliament buildings. Fluoride Free NZ (FFNZ) has provided a link to Connett’s presentation – Prof Paul Connett Power Point Presentation to Parliament 22nd Feb 2018.

It has 155 slides for presentation with another 24 extra slides to be held in reserve if he had time. Just the sheer number of slides, let alone the extreme detail on individual slides, violates a basic presentation rule to start with.

Well, I say “prepared” but the recent Fluoride Free NZ newsletter describes it as “The Power Point presentation that Prof Connett showed” to the MPs meeting. I find that hard to believe as only three MPs turned up to the meeting. In such situations, a reasonable person gives up on a detailed presentation and resorts to having a chat with the people who did turn up.

An example of what not to do in a PowerPoint presentation – source  Prof Paul Connett Power Point Presentation to Parliament 22nd Feb 2018

I urge interested readers to download it and have a look. Critique it from the point of view of the advice given by David JP Phillips above. It really is a bad presentation and I don’t believe any objective person could have taken anything meaningful from it. Treat this as a learning exercise.

Mind you, these presentations are usually simply “singing to the choir” – presented to true believers. All indications are that the three MPs who attended that meeting can be described that way. Other MPs were probably well aware that Connett’s presentations given on his recent speaking tour had no relevance to their work – and probably most were aware of his bias and unreliability as a source of scientific information, anyway.

Second reading of fluoridation bill

Parliament will shortly undertake the second reading of the Health (Fluoridation of Drinking Water) Amendment Bill. It is currently 15th on the order paper.  This bill does not deal with the science of fluoridation – parliament wisely leaves that to the experts who can advise them when necessary. The bill simply concerns the procedure for decision-making – specifically suggesting transferring the decision from councils to District Health Boards. The Parliamentary Health Committee has already consulted widely on this – and FFNZ and Paul Connett have had every opportunity to present their views. In fact, Paul Connett and other opponents of fluoridation gerrymandered the system to get much longer presentation times than other submitters. I guess they have plenty of experience of making submissions and know all the tricks.


Here I am simply treating Paul Connett’s PowerPoint presentation as an example of how not to use PowerPoint. Later I will probably return to his presentation and deal with specific areas where he misrepresents the science.

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New fluoride debate falters

Characters debate the “fluoride conspiracy” in Kubrick’s Dr Strangelove

What is it with these anti-fluoride campaigners – and particularly their leaders? They make a song and dance about having “science on their side.” They will heavily promote the latest research and papers if they can argue that they confirm their bias. And they will email politicians or make submissions to local bodies making scientific claims – often with citations and long lists of references.

But we simply can not get them to enter into a good faith scientific discussion of the sort I suggested in Do we need a new fluoride debate?

I thought this was going to happen. Bill Osmunson, the current Direct of the Fluoride Action Network (FAN), had agreed and even produced an initial article for posting. But he has now pulled out and asked me not to post his article. Apparently, my critique of a recent paper by him and his colleagues from FAN (see Flaw and porkie in anti-fluoride report claiming a flaw in Canadian study) was the straw that broke the camels back as far as he was concerned.

Talk about tiptoeing around a discussion partner. How can one have a discussion with someone this sensitive?

Excuses, excuses!

This is the explanation he gives for his withdrawal from the planned exchange:

“I have second thoughts about a discussion with you.  Do not publish my comments.*

After reading your comments in response to Neurath, it became obvious that you have no interest in discovering the truth or protecting the public.  Nor do you have reasonable judgment to evaluate research.

You do have good mechanical skills, but not judgment.

You correctly take weaker arguments and point out they are weak.  But you do not comment or appreciate the main more powerful issues.  Your comments make it sound like there is no value because some points have lower value.  Only a person who carefully rereads McLaren and Neurath, and then your comments understands some of your points are valid and you have missed others which are powerful.

In addition, you use derogatory, unprofessional mocking terms to attack the person instead of the issues.  I’m not interested in being your porky or sparky or pimp.

You are unprofessional and are not worth the time.”

  • The “comments” Bill refers to are a 55-page pdf file he sent me as the first post in our exchange. We were discussing a shorter form more suitable for a blog post when he decided to back out.

Mind you, in a previous email he had acknowledged that his mates (presumably in FAN) were unhappy about him participating in this good-faith scientific exchange. He wrote:

“Several people have told me not to respond to you, because you are unprofessional with your statements and comments.  You attack the messenger instead of the message and you have such severe bias and faith in fluoride that you must have worked for the tobacco companies to learn your strident blind bias.  
OK, I gave you a try once before and found you to be violent with your personal attacks and lack of judgment.”
 Sounds like “excuses, excuses,” to me. Surely I am not such a horrible person? I asked Bill to identify anything in my exchange with Paul Connett (see The Fluoride Debate) where I had behaved in the way he charged. He couldn’t. And I challenge anyone else to identify such behaviour on my part in that exchange.

Bill Osmunson and his mates claim I behaved badly in this exchange with Paul Connett – but they refuse to give a single example

 I can only conclude that the people at FAN are unable to provide good scientific arguments to support their case. They may well produce documents with lists of citations and references with “sciency” sounding claims. But they will not allow their claims to undergo the sort of critique normal in the scientific community.
Still – I am willing to be proven wrong. if Bill feels that he doesn;t have the scientific background for this sort of exchange perhaps Chris Neurath, Harvey Limeback or one of the other authors from FAN of the article I critiqued in Flaw and porkie in anti-fluoride report claiming a flaw in Canadian study) could take his place.
The offer is open.

Debunking a “classic” fluoride-IQ paper by leading anti-fluoride propagandists


Three of the paper’s authors – Quanyong Xiang (1st Left), Paul Connett (2nd Left) and Bill Hirzy (far right) – preparing to bother the EPA.

Anti-fluoride groups and “natural”/alternative health groups and websites are currently promoting a new paper by several leading anti-fluoride propagandists. For two reasons:

  1. It’s about fluoride and IQ. The anti-fluoride movement recently decided to give priority to this issue in an attempt to get recognition of possible cognitive deficits, rather than dental fluorosis,  as the main negative health effect of community water fluoridation. They want to use the shonky sort of risk analysis presented in this paper to argue that harmful effects occur at much lower concentrations than currently accepted scientifically. Anti-fluoride guru, Paul Connett, has confidently predicted that this tactic will cause the end of community water fluoridation very soon!
  2. The authors are anti-fluoride luminaries – often described (by anti-fluoride activists) as world experts on community water fluoridation and world-class scientists. However, the scientific publication record for most of them is sparse and this often self-declared expertise is not actually recognised in the scientific community.

This is the paper – it is available to download as a pdf:

Hirzy, J. W., Connett, P., Xiang, Q., Spittle, B. J., & Kennedy, D. C. (2016). Developmental neurotoxicity of fluoride: a quantitative risk analysis towards establishing a safe daily dose of fluoride for children. Fluoride, 49(December), 379–400.


Co-author Bruce Spittle – Chief Editor of Fluoride – the journal of the International Society for Fluoride Research

I have been expecting publication of this paper for some time – Paul Connett indicated he was writing this paper during our debate in 2013/2014. FAN newsletters have from time to time lamented at the difficulty he and Bill Hirzy were having getting a journal to accept the paper. Connett felt reviewers’ feedback from these journals was biased. In the end, he has lumped for publication in Fluoride – which has a poor reputation because of its anti-fluoride bias and poor peer review. But, at last Connett and Hirzy have got their paper published and we can do our own evaluation of it.

The authors are:


Co-author David C. Kennedy – past president of the International Academy of Oral Medicine and Toxicology – an alternative dentist’s group.

Bill Hirzy, Paul Connett and Bruce Spittle are involved with the Fluoride Action Network (FAN), a political activist group which receives financial backing from the “natural”/alternative health industry. Bruce Spittle is also the  Chief Editor of Fluoride – the journal of the International Society for Fluoride Research Inc. (ISFR). David Kennedy is a Past President of the International Academy of Oral Medicine and Toxicology which is opposed to community water fluoridation.

Quanyong Xiang is a Chinese researcher who has published a number of papers on endemic fluorosis in China. He participated in the 2014 FAN conference where he spoke on endemic fluorosis in China.

xiang-Endemic fluorosis

Much of the anti-fluoridation propaganda used by activists relies on studies done in areas of endemic fluorosis. Slide from a presentation by Q. Xiang to an anti-fluoride meeting organised by Paul Connett’s Fluoride Action Network in 2014.

Critique of the paper

I have submitted a critique of this paper to the journal involved. Publication obviously takes some time (and, of course, it may be rejected).

However, if you want to read a draft of my submitted critique you can download a copy from Researchgate – Critique of a risk analysis aimed at establishing a safe dose of fluoride for children.  I am always interested in feedback – even (or especially) negative feedback – and you can give that in the comments section here or at Researchgate.

(Please note – uploading a document to Researchgate does not mean publication. It is simply an online place where documents can be stored. I try to keep copies of my documents there – unpublished as well as published. It is very convenient).

In my critique I deal with the following issues:

The authors have not established that fluoride is a cause of the cognitive deficits reported. What is the point in doing this sort of risk analysis if you don’t actually show that drinking water F is the major cause of cognitive deficits? Such an analysis is meaningless – even dangerous, as it diverts attention away from the real causes we should be concerned about.

All the reports of cognitive deficits cited by the authors are from areas of endemic fluorosis where drinking water fluoride concentrations are higher than where community water fluoridation is used. There are a whole range of health problems associated with dental and skeletal fluorosis of the severity found in areas of endemic fluorosis. These authors are simply extrapolating data from endemic areas without any justification.

The only report of negative health effects they cite from an area of community water fluoridation relates to attention deficit hyperactivity disorder (ADHD) and that paper does not consider important confounders. When these are considered the paper’s conclusions are found to be wrong – see ADHD linked to elevation not fluoridation, and ADHD link to fluoridation claim undermined again.

The data used by the Hirzy et al. (2016) are very poor. Although they claim that a single study from an area of endemic fluorosis shows a statistically significant correlation between IQ and drinking water fluoride that is not supported by any statistical analysis.

The statistically significant correlation of IQ with urinary fluoride they cite from that study explains only a very small fraction of the variability in IQ values (about 3%) suggesting that fluoride is not the major, or maybe not even a significant, factor for IQ. It is very likely that the correlation between IQ and water F would be any better.

Confounders like iodine, arsenic, lead, child age, parental income and parental education have not been properly considered – despite the claims made by Hirzy et al. (2016)

The authors base their analysis on manipulated data which disguises the poor relations of IQ to water fluoride. I have discussed this further in Connett fiddles the data on fluorideConnett & Hirzy do a shonky risk assessment for fluoride, and Connett misrepresents the fluoride and IQ data yet again.

Hirzy et al. (2016) devote a large part of their paper to critiquing Broadbent et al (2014) which showed no evidence of fluoride causing a decrease in IQ  using data from the Dunedin Multidisciplinary Health and Development Study. They obviously see it as a key obstacle to their analysis. Hirzy et al (2016) argue that dietary fluoride intake differences between the fluoridated and unfluoridated areas were too small to show an IQ effect. However, Hirzy et al (2016) rely on a motivated and speculative estimate of dietary intakes for their argument. And they ignore the fact the differences were large enough to show a beneficial effect of fluoride on oral health.


I conclude the authors did not provide sufficient evidence to warrant their calculation of a “safe dose.” They relied on manipulated data which disguised the poor relationship between drinking water fluoride and IQ. Their arguments for their “safe dose,” and against a major study showing no effect of community water fluoridation on IQ, are highly speculative and motivated.

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Rejection of scientific studies in online discussions


Sometimes the on-line discussion of scientific issues  looks like a citation battle. People take sides, battle lines are drawn and struggle commences. Each side fires barrages of citations “proving” their own argument.

The battle progresses in real-time – the proferred citations are immediately rejected and alternatives offered. One would think the other side would take time out to actually read the offered citations – but no they are usually quickly rejected as unreliable.  I also get the impression that in many cases the side offering the citation  has also not bothered to read it – usually relying on its use by an ally or its coverage in a friendly on-line magazine.

OK, it natural to be lazy but wouldn’t we all learn a lot more by actually reading the citations being thrown around. And doesn’t it discredit one’s position to reject a citation out of hand for unjustified reasons?

The Logic of Science recently posted an analysis of the bad reasons people use for rejecting citations – 12 bad reasons for rejecting scientific studies. It is well worth a read – we will recognise these 12 reasons and hopefully learn not to use them ourselves in future.

Here are the 12 bad reasons:

Bad reason #1: Galileo/Columbus

“When faced with results that they don’t like, many people will invoke Galileo or Columbus and claim that they defied the mainstream view and people thought that they were crazy, but they turned out to be right. . . [However] no one thought that Galileo was crazy. He presented facts and careful observations, not conspiracies and conjecture. He did not blindly reject the science of his day, rather he made meticulous observations and presented data that discredited the common views. That is not in any way shape or form the same as arrogantly and ignorantly rejecting a paper just because you disagree with it.”

Yes, the Galileo claim always come across to me as very arrogant and crazy – yet it’s a common excuse. An Australian climate change denial group even incorporated Galileo into its title – poor old Galileo must be turning in his grave.

Bad reason #2: science has been wrong in the past

“[P]eople often make the broad claim that science shouldn’t be trusted because it has been wrong before. . . . . First, it is true that science has been wrong, but it has always been other scientists who have figured out that it was wrong. Further, it is logically invalid to blindly assume that it is wrong just because it has been wrong before.

Additionally, although there have been plenty of minor hypotheses which have been discredited, there have been very few core ideas that have been rejected in the past century. In other words, ideas which are supported by thousands of studies have rarely been rejected, and very few central ideas have been overthrown in recent decades.

Finally, attacking science by asserting that it has been wrong before is utterly absurd because science is inherently a process of modifying our understanding of the world. In other words, science is self correcting. This is one of it’s greatest strengths. . . . . It constantly replaces erroneous ideas as new evidence comes to light (the same can’t be said for anti-science views which rigidly cling to their positions no matter how much evidence opposes them). Therefore, the fact that science has been wrong is actually a good thing, because if there were no instances where we had discovered that a previous idea was wrong, that would mean that science hadn’t advanced.”

Scientific knowledge is always incomplete – with time it becomes more and more correct in its description of reality, but there is always room for improvement, for deepening of specific knowledge and refinement of theories.

It seems to me very crass to use this inherent property of good science against science itself.

Bad reason #3: it’s all about the money

Ironically, this excuse is commonly used by people allied with movements funded by big business who are campaigning against scientific findings they feel challenged by.

“This is probably the most common response to papers on climate change, vaccines, GMOs, etc., and it’s often simply untrue. The scientific community is massive, and there are thousands of independent scientists doing research. Further, all scientific publications require authors to declare any conflicts of interest, so you can actually check and see if a paper was paid for by a major company, and if you did that, you would find that many of the papers supporting GMOs, vaccines, etc. have no conflicts of interest. Anti-scientists, of course, have no interest in actually looking at the paper. They would rather just assume that it was paid off because that fits with their world-view.

. . . even if a paper does have a conflict of interest, that doesn’t give you carte blanche to ignore it. The fact that someone works for a pharmaceutical company, for example, does not automatically mean that they biased or falsified their data. If a paper has a conflict of interest, then you should certainly give it extra scrutiny, and you should be suspicious if it disagrees with other papers or has questionable statistics, but you cannot automatically assume that it is flawed.”

Wise words. We should always read scientific papers critically and intelligently – especially when there may be a conflict of interest. But it is neither critical or intelligent to reject them out of hand in this way.

Bad reason #4: there are other results that I disagree with

Someone will say, “I reject the science of X because science also says Y and I disagree with Y.” We can rephrase this as, “I reject science because I reject science.” I would not, for example, accept water fluoridation as evidence that it’s ok to reject the science of vaccines unless I had already rejected the science of fluoridation. In other words, you have to justify your rejection of the science of Y before you can use it as evidence that we shouldn’t trust the science of X. Further, even if you could demonstrate that the science of Y (in this example fluoridation) was wrong, that still would not in any way shape or form prove that the science of X (in this example vaccines) is wrong. In fact, this entire line of reasoning is just a special case of the logical fallacy known as guilt by association. If are going to say that a scientific result is incorrect, you have to provide actual evidence that the specific result that you are talking about is incorrect.”

Yes, this tactic is a red-herring, often used as a diversionary device, and very lazy as it shows an unwillingness to consider properly the issue at hand.

Bad reason #5: gut feelings/parental instincts

know I am right

” . . . .  show someone the scientific evidence for vaccines, and they respond with, “well as a parent only I know what is best for my child.” Similarly, when I show people the evidence for GMOs, they often respond with something like, “well I just have a gut feeling that manipulating genes is bad.” I do not give a flying crap about your instincts or gut feelings. The entire reason that we do science is because instincts and feelings are unreliable. When someone presents you with a carefully conducted, properly controlled study, you absolutely cannot reject it just because you have a gut feeling that it’s wrong. Doing that makes no sense whatsoever. It is the most blatant form of willful ignorance imaginable. Don’t get me wrong, intuition is a good thing, and gut feelings can certainly help you in many situations, but they are not an accurate way to determine scientific facts.”

Our feelings and instincts are very strong and will often divert our attempts at rational considerations. I think such factors are  often behind the rejection of scientific studies – even when this reason is not given. But:

“Gut feelings simply aren’t reliable. That’s why we do science.”

Bad reason #6: I’m entitled to my opinion/belief

“This is another very common response, and it is very similar to #5. Science deals with facts, not opinions or beliefs. When multiple scientific studies all agree that X is correct, it is no longer a matter of opinion. If you think that X is incorrect, that’s not your opinion, you’re just wrong. Think about the relationship between smoking and lung cancer again. What if someone said, “well everyone is entitled to their opinion, and my opinion is that it’s safe.” Do you see the problem? Scientists don’t have an opinion or belief that smoking is dangerous; rather, it is a scientific fact that it is dangerous, and if you think that it is safe, you are simply in denial. Similarly, you don’t get to have an “opinion” that the earth is young, or vaccines don’t work, or climate change isn’t true, or GMOs are dangerous, etc. All of those topics have been rigorously tested and the tests have yielded consistent results. It is a fact that we are changing the climate, a fact that vaccines work, a fact that the earth is old, etc. If you reject those, you are expressing willful ignorance, not an opinion or belief.”

Hear, hear!

Bad reason #7: I’ve done my research/an expert agrees with me

” . . . . . if your “research” disagrees with properly conducted, carefully controlled studies, then your research is wrong (or at the very least, must be rejected pending future data). There, it’s that simple. The only exception would be if your research is actually a large set of properly controlled studies which have directly refuted the study in question (e.g., if you have a meta-analysis vs. a single study, then, all else being equal, go with the meta-analysis). It’s also worth pointing out that having a few people with advanced degrees on your side does not justify your position (that’s a logically fallacy known as an appeal to authority). No matter what crackpot position you believe, you can find someone somewhere with an advanced degree who thinks you’re right.”

This appeal to authority is commonly used – nothing seems to offend an anti-fluoride campaigner more than to refer to their ideological leader, Paul Connett, without reference to his degree of former university title! Such people also often show the converse – refusing to use titles when referring to the work of someone they disagree with.

Bad reason #8: scientific dogma

“This response basically states that all scientists are forced to follow the “dogma” of their fields, and anyone who dares to question that dogma is quickly ridiculed and silenced. . . . .  In short, that’s simply not how science works. Nothing makes a scientist happier than discovering that something that we thought was true is actually false. In fact, that is how you make a name for yourself in science. No one was ever considered a great scientist for simply agreeing with everything that we already knew. Rather, the great scientists are the ones who have shown that our current understanding is wrong and a different paradigm provides a better understanding of the universe. To be clear, if you are going to defeat a well established idea, you are going to have to have some very strong evidence.”

A related claim is that the “scientific establishment” prevents publication -often used to explain why many of the authorities used by people rejecting scientific studies do not have a credible publication record.

I would be the last person to deny human jealousies and defense of peer-reviewers and scientific editors can be a problem with specific journals – but there is many alternative journals willing to accept papers.

But this does raise another issue to be wary of – there are some journals which have incredibly poor peer review and often accept papers because of the authors’ willingness to pay a publication fee. Publication in such journals should definitely be seen as a warning sign – but as in all other cases judgment should be based on a critical and sensible analysis of the paper  itself.

Bad reason #9: distrust of governments/media

” Many people, however, take it even a step further. On numerous occasions, I have shown someone a study which was not in anyway affiliated with a government agency, yet they still responded with a lengthy rant about corrupt governments or the media. The basic idea of their argument seems to boil down to, “the government/media agree with these results, therefore they must be false.” This line of reasoning is, however, clearly fallacious (in fact it’s a logical fallacy known as guilt by association). Governments and the media will lie to push their own agendas, I’m certainly not denying that, but that fact does not automatically mean that everything that they say is a lie. . . . . . . It’s fine to be skeptical of what you are told by the government/media. In fact it is a good thing, but when you are presented with scientific evidence, then it’s not a matter of trusting the government/media. Rather, it is a matter of whether or not you accept science. In other words, I don’t need to trust the government or media in order to accept the results of a carefully controlled study.”

A related reason is to imply that any scientific study is not independent because the researcher are paid. Rather silly, considering we all have to live and researchers are no different. These people will instead cite articles written by activists or journalists working for magazines financed by an industry like the “natural”/alternative health industry. Or claim the financing of activist organisation is by “donation” so it doesn’t count

Bad reason #10: it’s a conspiracy

“This one is very closely related to #8 and 9, but it takes things a step further. It proposes that there is a massive conspiracy and scientists are being paid by governments/big companies to falsify results. . . . . the scope of this conspiracy would be impossibly huge. The scientific community consists of millions of people from all over the world working out of thousands of universities, institutes, non-profits, corporations, agencies, etc. It includes people from countless religions, cultures, political ideologies, etc. There is no way that you could possibly get that many people to agree on a massive deception like this. Just think about what is being proposed here. Do you honestly think that nearly all of the world’s climate scientists have been bought off? . . . . . .  Do you honestly think that all of those different organizations (many of whom compete with each other and have different goals and purposes) have all managed to come together to make one unified conspiracy? That’s just nuts. The same problems exist for governments. . . . . Honestly ask yourself the following question: which is more plausible, that countless governments, companies, non-profits, etc. have all come together to create the world’s largest conspiracy and buy off virtually every scientist on the planet, or that the thousands of independent scientists who have devoted their lives to science are actually doing real research?”

Personally I think this reason should be considered as an immediate acceptance that the commenter has lost or that they have disqualified themselves – like Godwin’s law for the first person to bring up Hitler or the Nazis.


Bad reason #11: anecdotes

“Anecdotes do not matter in science, because anecdotes don’t allow us to establish causation. Let me give an example. Suppose that someone takes treatment X and has a heart attack 5 minutes later. Can we conclude from that anecdote that treatment X causes heart attacks? NO! It is entirely possible that the heart attack was totally unrelated to the treatment and they just happened to coincide with one another. Indeed, I once heard a doctor describe a time where he was preparing to vaccinate a child, and while preparing the vaccine, the child began having a seizure (to be clear, he hadn’t vaccinate the child yet). He realized that if he had given the vaccine just 60 seconds earlier, it would have looked for all the world like the vaccine had caused the seizure when in fact the kid just happened to have a seizure at the same time that a vaccine was being administered.

. . . . it should be clear that anecdotes are worthless because they cannot establish causal relationships (in technical terms, using them to establish causation is a logical fallacy known as post hoc ergo propter hoc fallacies [i.e., A happened before B, therefore A caused B]). Properly controlled studies, however, do allow us to establish causation.”

Yet commenters again and again fall back on anecdotes – even after launching a citation attack the anecdotal evidence seems to have much more relevance than anything reported in scientific studies.

Bad reason #12: a scientific study found that most scientific studies are wrong

“This argument is fascinatingly ironic because it uses a scientific paper to say that we shouldn’t trust scientific papers, but let’s look closer because this argument actually has some merit. The paper being references is, “Why most published research findings are false” by John Ioannidis, and it is actually a very useful and informative work, but it often gets misused.”

The Ioannidis paper describes several reasons why individual papers may be wrong. Issues like small sample size and publication bias in its many forms.

Researcher who often search the literature are aware of these problems and they are aware of the advice to approach all papers critically and intelligently – even the ones which present results you find favourable.

But as the article points out:

“. . .all of that may sound very bleak, but it should not make you lose all confidence in the scientific process because of a very important component of scientific inquiry: replication. Ioannidis’s work applies mostly to single paper studies. . . . .  So, this paper shouldn’t make you question the safety of vaccines, the effects we are having on the climate, etc. It should, however, make you skeptical of the one or two anti-vaccine papers that you occasionally see, or the one paper supporting some “miracle cure,” or the occasional paper on homeopathy, acupuncture, etc. Those studies almost always have tiny sample sizes and countless other studies have failed to replicate their results. This is why it is so important to look at the entire body of literature not just a single study.”


The Logic of Science article concludes:

” . . . no matter how you cut it, many of you wouldn’t be alive today if it wasn’t for science. Science clearly works and you need an extremely strong justification for rejecting scientific results.

To be fair, some scientists are corrupt and bad science does occasionally get published, but bad research tends to be identified and discredited by other researchers. In other words, there may be a high probability of a single paper being wrong, but when lots of different studies have all arrived at the same conclusion, you can be very confident in that conclusion. Perhaps most importantly, you cannot simply assume that a paper is bad just because you disagree with its results. You need to present actual evidence that it is flawed or biased before you can reject it.”

Good advice. When you enter a discussion you should actually read the citations you use – and insist you discussion partner readers theirs. And read them critically and intelligently.

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Alternative reality of anti-fluoride “science”

Paul Connett made many unsupported claims in his presentation against community water fluoridation (CWF) to Denver Water. Here I debunk a claim where he rejects most scientific studies on the cost-effectiveness of CWF.

Different grades of dental fluorosis

Connett asserted two things in his presentation:

  1. Previous research showing the cost effectiveness of community water fluoridation (CWF) has been made obsolete by a single new paper.
  2. Something about this new paper (Ko & Theissen, 2014) makes it more acceptable to him than previous research – and he implies you

Plenty of research shows CWF is cost-effective

Connett has cherry-picked just one paper, refused to say why and, by implication, denigrated any other research results. And there are quite a few studies around.

Here are a just a few readers could consult:

Of course, the actual figures vary from study to study, and various figures are used by health authorities. But generally CWF is found cost-effective over a large spectrum of water treatment plant sizes and social situation.

Connett relies on a flawed study

Connett relies, without justification,  on a single cherry-picked study:

Ko, L., & Thiessen, K. M. (2014). A critique of recent economic evaluations of community water fluoridation. International Journal of Occupational and Environmental Health, 37(1), 91–120.

This is a very long paper which might impress the uninitiated. To give it credit, it does make lengthy critiques of previous studies on cost effectiveness. But it has a huge flaw – its treatment of the cost of dental fluorosis.

It rejects warranted assumptions made by most studies that the adverse effects of CWF on dental fluorosis are negligible: They say:

“It is inexplicable that neither Griffin et al. nor other similar studies mention dental fluorosis, defective enamel in permanent teeth due to childhood overexposure to fluoride. Community water fluoridation, in the absence of other fluoride sources, was expected to result in a prevalence of mild-to-very mild (cosmetic) dental fluorosis in about 10% of the population and almost no cases of moderate or severe dental fluorosis. However, in the 1999–2004 NHANES survey, 41% of U.S. children ages 12–15 years were found to have dental fluorosis, including 3.6% with moderate or severe fluorosis.”

Two problems with that statement:

  1. The prevalence of “cosmetic” dental fluorosis may be about 10% but this cannot be attributed to CWF as non-fluoridated areas have a similar prevalence. For example, in the recent Cochrane estimates show “cosmetic” dental fluorosis was about 12% in  fluoridated areas but 10% in non-fluoridated areas (see Cochrane fluoridation review. III: Misleading section on dental fluorosis).This is a common, probably intentional, mistake made by anti-fluoride campaigners – to attribute the whole prevalence to CWF and ignore the prevalence in non-fluoridated areas. This highly exaggerates the small effect of CWF on the prevalence of “cosmetic” dental fluorosis – which in  any case does not need treatment. “Cosmetic” dental fluorosis is often considered positively by children and parents.
  2. The small numbers of children with moderate and severe dental fluorosis (due to high natural fluoride levels, industrial contamination or excessive consumption of fluoridated toothpaste) is irrelevant as CWF does not cause these forms. Their prevalence is not influenced by CWF.

So Ko and Theissen (2014) produce a different cost anlaysis because :

“. . . the primary cost-benefit analysis used to support CWF in the U.S. assumes negligible adverse effects from CWF and omits the costs of treating dental fluorosis, of accidents and overfeeds, of occupational exposures to fluoride, of promoting CWF, and of avoiding fluoridated water.”

We could debate all the other factors, which they acknowledge have minimal effects, but they rely mainly on the dental expenses of treating dental fluorosis:

“Minimal correction of methodological problems in this primary analysis of CWF gives results showing substantially lower benefits than typically claimed. Accounting for the expense of treating dental fluorosis eliminates any remaining benefit.”

They managed to produce this big reduction in cost-effectiveness by estimating costs for treating children with moderate and severe dental fluorosis – finding:

“the lifetime cost of veneers for a child with moderate or severe fluorosis would be at least $4,434.”


“For our calculations, we have assumed that 5% of children in fluoridated areas have moderate or severe fluorosis.”

See the  trick?

They attribute all the moderate and severe forms of dental fluorosis to CWF. Despite the fact that research shows this is not caused by CWF and their prevalence would be the same in non-fluoridated areas!

The authors’ major effect – which they rely on to reduce the estimated benefits of CWF – is not caused by CWF.

Connett is promoting an alternative “scientific” reality

The Ko & Theissen (2014) paper is one of a list of papers anti-fluoridation propagandists have come to rely on in their claims that the science is opposed to CWF. In effect, this means they exclude, or downplay, the majority of research reports on the subject – treating them like the former Index Librorum Prohibitorum, or “Index of Forbidden Books,” an official list of books which Catholics were not permitted to read.

The Ko & Theissen (2014) paper is firmly on the list of the approved studies for the anti-fluoride faithful. A few others are Peckham & Awofeso (2014), Peckham et al., (2015)Sauerheber (2013) and, of course, Choi et al., (2012) and Grandjean & Landrigan (2014).  You will see these papers cited and linked to on many anti-fluoride social media posts – as if they were gospel – while all other studies are ignored.

These papers make claims that contradict the findings of many other studies. They are all oriented towards an anti-fluoridation bias. And most of them are written by well-known anti-fluoride activists or scientists.

In effect, by considering and using studies from their own approved list and ignoring or denigrating studies that don’t fit their biases, they are operating in an alternative reality. A reality which may be more comfortable for them – but a reality which exposes their scientific weaknesses.

Lessons for Connett

I know Paul Connett is now a lost cause – he will continue to cite these papers from his approved list and make these claims no matter how many times they are debunked. But, in the hope of perhaps helping others who are susceptible to his claims, here are some lessons from this exercise. If anti-fluoride activists wish to support their claims by citing scientific studies they should take them on board.

Lesson 1: Make an intelligent assessment of all the relevant papers – don’t uncritically rely on just one.

Lesson 2: Don’t just accept the findings of each paper – interpret the results critically and intelligently. How else can one make a sensible choice of relevant research and draw the best conclusions.

Lesson 3: Beware of occupying an alternative reality where credence is given only to your own mates and everyone else is disparaged. That amounts to wearing blinkers and is a sure way of coming to incorrect conclusions. It also means your conclusions have a flimsy basis and you are easily exposed.

Lessons for everyone susceptible to confirmation bias.

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Fluoridation: Connett’s criticism of New Zealand research debunked


Paul Connett, Executive Director of the Fluoride Action Network recently made a presentation to Dever Water opposing community Water Fluoridation (CWF). Many of his claims were just wrong – he seriously distorted the science and used this to misinform the board members.

I am posting a series of articles debunking his claims. But Daniel Ryan from Making Sense of Fluoride has also entered the fray with his article Dr Connett distorts the Dunedin IQ fluoride study. I urge readers to check out the article.

Daniel is debunking claims made by Connett about the New Zealand research paper:

Broadbent, J. M., Thomson, W. M., Ramrakha, S., Moffitt, T. E., Zeng, J., Foster Page, L. A., & Poulton, R. (2014). Community Water Fluoridation and Intelligence: Prospective Study in New Zealand. American Journal of Public Health, 105(1), 72–76.

That study is a thorn in Connett’s side because it completely refutes his claims that CWF causes a drop in IQ. It is an excellent paper (as well as being a New Zealand one) – which is another thorn in Connett’s side as he relies on poor quality studies made in areas of endemic fluorosis for his claims.

Daniel goes through Connett’s assertions about the New Zealand study and debunks each of them in turn.

The Broadbent et al. (2014) study investigated a situation where low fluoride concentrations were used. It is the only in-depth study of IQ at these low concentrations. However, I did make a brief investigation of the situation in the USA comparing the average IQ for each state with the percentage fluoridation coverage of the population in each state. I reported that in IQ not influenced by water fluoridation.

The figure below shows the data – and there is no statistically significant correlation of IQ with CWF (the dotted lines show the 95% confidence boundaries)..

Connett debunked once again.

See also:

Connett misrepresents the fluoride and IQ data yet again
Fluoridation: Connett’s naive use of WHO data debunked

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Fluoridation: Connett’s naive use of WHO data debunked

Paul Connett is the Executive Director of the anti-fluoride propagandists group, the Fluoridation Action Network (FAN). His recent presentation to the Denver Water Board’s fluoridation forum was full of scientific misrepresentations and distortions.

I debunked his claims on fluoridation and IQ in the article Connett misrepresents the fluoride and IQ data yet again. Here I debunk his claim that WHO data shows community water fluoridation (CWF) is not effective.

This video clip shows his claim:

1: Is there a difference between fluoridated and unfluoridated countries?

Connett waves around graphs showing declines in tooth decay in  some countries but does nothing to support his claim that there is no input from fluoridation to this improvement in oral health. After all, oral health depends on a number of factors so any serious claim needs adjustment for these factors and a proper quantitative comparison.

The data in these graphs is just not suitable for this – but lets humour people like Connett who place so much faith in the graphs. I took this graph from Connett’s book The Case against Fluoride (Chapter 6, page 38).


It is easy enough to do a ballpark comparison of the average rate of decline of dental decay  for the four nonfluoridated countries and compare that to the average rate for the four fluoridated countries. I did this and found the average decline in dmft (decayed, missing and filled teeth) for non-fluoridated countries was 1.4/decade and for fluoridated countries 1.6/decade. On the face of it the decline in tooth decay was more rapid in the fluoridated countries – the opposite to Connett’s claim.

Of course, Connett would laugh at such a comparison and claim the data is just not good enough to make such comparisons.  And I agree – but isn’t that exactly what he was trying to do?

He was simply waiving around a poor set of data which he thinks supports his claim that CWF is ineffective – it doesn’t. He should know that, and he should be ashamed, as someone with scientific training, to make these claims using such evidence.

The huge influence of inter-country differences on these data, irrespective of fluoridation, surely sticks out like a sore thumb in Connett’s graphs. That doesn’t require a scientific training to see. These differences introduce so much noise into the data that no conclusion is possible about the influence on fluoridation.

Robyn Whyman pointed this out in his report for the National Fluoridation Information Service – Does delayed tooth eruption negate the effect of water fluoridation?:

“Studies that appropriately compare the effectiveness of water fluoridation do not compare poorly controlled inter-country population samples. They generally compare age, sex, and where possible ethnicity matched groups from similar areas. Inter-country comparisons of health status, including oral health status, are notoriously difficult to interpret for cause and effect, because there are so many environmental, social and contextual differences that need to be considered.”

2: Comparison within countries

The WHO data includes New Zealand and Ireland where there are fluoridated and unfluoridated areas. Cornett’s graphs do not differentiate – the just use the averages for these two countries.  Yet, even that sparse WHO data set  shows clear benefits of community water fluoridation on oral health. Consider the differences in tooth decay between fluoridated and unfluoridated areas of  Ireland.

I showed this graph to Connett at the beginning of our debate on fluoridation. throughout the next few months he continued to confuse the issue and I kept coming back to it. Finally, he said in his closing statement, “My apologies. I should have checked back.”

An acknowledgment, of sorts, that his use of the WHO data is wrong in his graphs – but he continues to misrepresent it in this way!

The data in the graphs below shows a similar situation for New Zealand – this time using data from the NZ Ministry of Health (which is much more extensive than the WHO data).dmft

3: CWF still effective when fluoridated toothpaste used.

Paul Connett’s claim that CWF is unnecessary when fluoridated toothpaste is used was based on a naive interpretation of the graphs he was waving around. The data above for Ireland and New Zealand show that, even where the use of fluoridated toothpaste is widespread, there is still a difference in the oral health of children living in fluoridated and unfluoridated areas of a country.

Other research also shows CWF is still effective, even though its effectiveness may, these days, be less than observed in the past when fluoridated toothpaste was not used. But, in contrast to what Connett appears to think, fluoridated toothpaste in not the only factor involved. There is the general improvement in dental health treatments and diet in recent years. Rugg-Gunn & Do (2012)  also refer to the “halo” effect – a diffusion of beneficial fluoride from fluoridated area into unfluoridated areas via food and beverages and consumption of water away from the place of residence.

The recent data can also be influenced by differences in residence and place of dental treatment. For example, dental treatment and record taking may occur at a school or dental clinic in a non-fluoridated area but the child may live in a fluoridated area. This effect could explain the apparent reduction of differences for New Zealand children from fluoridated and non-fluoridated areas after 2006 in the above graph. In 2004 a “hub and spoke” dental clinics system was introduced where one school dental clinic could serve several areas – both fluoridated and non-fluoridated.



Paul Connett’s use of the graphs showing improvement in oral health in countries independent of fluoridation, is on the surface, naive because no conclusion about the effectiveness of CWF can be drawn from this sparse data involving comparison between countries with so many political, social and environmental differences. Connett is presumably aware of this, and of the fact the same WHO data shows a beneficial effect for Ireland and New Zealand.

This is another case of Connett using a scientific academic title (his PhD), to give “authority” to his misrepresentation and distortion of the science to local body politicians.


Connett, P., Beck, J., & Micklem, H. S. (2010). The Case against Fluoride: How Hazardous Waste Ended Up in Our Drinking Water and the Bad Science and Powerful Politics That Keep It There.

Ministry of Health (2014) Age 5 and Year 8 oral health data from the Community Oral Health Service.

National Fluoridation Information Service (2011): Does Delayed Tooth Eruption Negate The Effect of Water Fluoridation? National Fluoridation Information Service Advisory June 2011, Wellington, New Zealand.

Rugg-Gunn, A. J., & Do, L. (2012). Effectiveness of water fluoridation in caries prevention. Community Dentistry and Oral Epidemiology, 40, 55–64.


Connett misrepresents the fluoride and IQ data yet again

The video clip below shows how local body politicians can be fooled by people misrepresenting the science. The culprit (unsurprisingly for the fluoride issue) is Paul Connett, Executive Director of the anti-fluoride propagandist group Fluoride Action Network (FAN). He relies on his PhD to provide authority – and the fact that few people in his audiences have the time or background to check out his claims.

At the moment, Connett is putting a lot of effort into promoting the myth that fluoridation causes a decrease in IQ. In this very short video clip (just over 1 minute) of a recent presentation to the Denver Water Board Connett massages data reported by Xiang et al., (2003a) to pull the wool of the Board’s eyes..

The innocent victims in his audience, including the Denver Water Board members, were no doubt impressed by this graph Connet used.

It looks pretty convincing, doesn’t it? There appears to be a statistically very significant decrease in IQ with an increase in drinking water fluoride above about 1 ppm F? (Community water fluoridation [CWF] usually uses a concentration of about 0.7 ppm). All the data points are lined up in a row.

That is until you look at the original data.

This figure is from Xiang et al., (2003a).  Not so convincing, eh? Clearly, with such a wide scatter of the data,  fluoride is only part of the story – if it has any effect at all. But this is the sort of graph one needs to consider when looking at correlations. Connett obtained his figure by breaking the data up into ranges. It looks prettier – but is misleading.

One should always look at the original data.*

Although the correlation is statistically significant, urinary fluoride explains only 3% of the variance in IQ! This tells us that fluoride has very little effect on IQ and it is very likely that it would have no explanatory role at all once other factors were considered in the statistical analysis!

I think it is inhumane to make the claims Connett does on such a flimsy correlation. His biased advocacy is, in effect, denying any efforts to find the real causes of the IQ variation.

What about confounding factors?

Connett’s claim that data was “controlled for” confounding factors is just not true. Xiang did not include any of these other factors in the statistical analysis of the data in Figure 2.

He only compared average values of these factors for the two villages in the study. There were no proper correlations across all the data. Xiang reported no differences between villages for urinary iodine, family income, and parent’s education level. However, there was an average age difference between the villages and he reported that IQ was influenced by age. The drinking water arsenic concentrations were higher in the low fluoride village than the high fluoride village (Xiang et al., 2013).

Incidentally, in a later paper (Xiang et al., 2003b) presents data for blood lead. This time he did check for a correlation across all samples and found there was no statistically significant correlation with IQ. But this was separate and not incorporated into a statistical analysis together with fluoride concentrations.

There was no real checking for the effect of confounding factors on the correlation of IQ with fluoride.

Connett asks a silly question

Connett goes on to make an emotional appeal for scientists to produce convincing data showing that fluoride does not decrease IQ:

This question is disingenuous as science can never prove something can never happen – it can only consider the evidence for it happening. Evidence of the sort presented by Xiang et al. (2003a). Scientific reviews look at the evidence, consider its reliability, compare it with evidence from other studies and draw conclusions.

Connett is disparaging about scientific reviews of the fluoride literature because he does not understand that such literature requires critical and intelligent analysis. Things like the high concentrations and doses used in animals studies he refers to. And looking below surface claims to see what the data really says – as I have done here. This is what reviewers of the scientific literature do all the time.

All Connett has relied on here is his own confirmation bias – and his emotions. Policy makers should beware of such advocacy.

See also:

Connett fiddles the data on fluoride
Connett & Hirzy do a shonky risk assessment for fluoride

*Note: Observant readers might note the second figure compares IQ with urine fluoride concentration. Unfortunately, he did not give a similar figure for fluoride concentration in drinking water. However, this is well correlated with urine fluoride. And, as urine concentration is a better indicator of fluoride intake that drinking water concentration, this figure does give a useful picture of the variance in the data Xiang used.

Incidentally, I have made several attempts without success, to get the original water fluoride concentrations from Xiang (who has so far not replied to several emails) and Connett (who told me that he does not want me contacting him again!).


Xiang, Q; Liang, Y; Chen, L; Wang, C; Chen, B; Chen, X; Zhouc, M. (2003a). Effect of fluoride in drinking water on children’s intelligence. Fluoride, 36(2), 84–94.

Xiang, Q.; Liang, Y.; Zhou, M. . and Z. H. (2003b). BLOOD LEAD OF CHILDREN IN WAMIAO–XINHUAI INTELLIGENCE STUDY. Fluoride, 36(3), 198–199.

Xiang, Q., Wang, Y., Yang, M., Zhang, M., & Xu, Y. (2013). Level of fluoride and arsenic in household shallow well water in wamiao and xinhuai villages in jiangsu province, china. Fluoride 46(December), 192–197.

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Connett & Hirzy do a shonky risk assesment for fluoride

Paul Connett, executive director of the Fluoridation Action Network (FAN), told me, during our fluoride debate, that he was writing a scientific paper defining a lower safety limit for fluoride than currently accepted. Nothing has been published yet – although a recent FAN newsletter did refer to a risk assessment paper by him and Bill Hirzy currently under review. I look forward to reading this paper, but I am not holding my breath as neither author has an impressive publication record.

Connett described his risk assessment for fluoride in the debate (see Fluoride debate: Paul Connett’s Closing statement) and he and Hirzy have also made comments on this lately. They are rejecting the current risk assessment, based on the incidence of severe dental fluorosis, and using the incidence of IQ deficits instead. To this end, they are heavily promoting the work of Choi et al., (2012) and Xiang et al., (2003) (which reported IQ deficits in areas where fluorosis is endemic). They are also attempting to rubbish published research (such as Broadbent et al., 2014) which show no significant IQ deficits at fluoride concentrations used in community water fluoridation.

Connett and Hirzy have also organised campaigns to congressional representatives in their effort to force a downward revision of the Environmental Protection Agency’s (EPA) standards for fluoridation.

Connett’s approach is a desk study – these guys are not going  to dirty their hands by doing their own research to get useful data. They are taking a value which they claim represent the lowest concentration of fluoride in drinking water below which no IQ deficit was found. They then apply “safety factors” to effectively conclude the only safe concentration is zero (see Scientist says EPA safe water fluoride levels must be zero)!

I will be a bit surprised if they manage to squeeze their paper though a decent review process because their approach is shonky. Look at the way they use the data from Xiang et al., (2003). (I have used the presentations by Connett and Hirzy at last February’s Sydney anti-fluoride conference as sources here). As I pointed out in Connett fiddles the data on fluoride, this data actually does not show a strong relationship between IQ and fluoride. The figure (from Xiang et al., 2003) shows the relationship between IQ and urinary fluoride and, in this case, the fluoride explains only about 3% of the variance in IQ.

Despite being statistically significant (p=0.003) this is certainly not evidence for a causative relationship. Clearly other, unconsidered, factors contribute to the variance and if these were considered the relationship with fluoride may be non-significant.

(Readers may notice the figure uses data for urinary not drinking water fluoride. Unfortunately, Xiang did not give a similar figure for fluoride concentration in drinking water. I have contacted him requesting the similar data for drinking water but so far have not had a meaningful response. Xiang did report drinking water fluoride is well correlated with urine fluoride so the above figure probably gives a good idea of the variability in drinking water fluoride as well).

Connett and Hirzy effectively ignore the high variability in the data and rely on a trick to get this  second graph. By splitting the concentration range into groups and taking the mean IQ for each group they make the situation look a lot more respectable. Who would guess from this trick that fluoride only explained about 3% of the IQ variance?

Connett illustrates his next step with this slide.


He then claims that IQ deficits occur at a fluoride concentration of 1.26 ppm – he appears to have simply subtracted the value of one standard deviation from the mean of the lowest concentration group associated with a significantly different mean IQ to that of Xiang’s “control” group – Xinhaui village. That is strange because surely the first figure indicates  that low IQ values occur even for children with very low urinary fluoride, and most probably drinking water fluoride.

Connett then uses a safety factor of 10 (“to account for the wide range of sensitivity expected for any toxic substance in a large population”). Of course, this produces a maximum “safe” concentration of 0.13 ppm – which rules out all fluoridated water – and most natural water sources!

Sydney Feb 21 B Australia,  2015Connett goes on to promise his offsider, Bill Hirzy, will elaborate on the method they issued. Hirzy’s presentation did mention fluoride intake from other sources besides water. He then presents his conclusion on what the “safe daily dose” is fluoride – but no explanation of why! All the preceding slides in his presentation where self-justifying descriptions of his qualifications, employment history and how great his organisation, FAN, is.



Connett and Hirzy are claiming IQ deficits are more important than dental fluorosis for setting of maximum fluoridation levels in drinking water. They are campaigning to get this accepted by legislators and the EPA.

Connett has been promising publication in a scientific journal for several years and recently implied that a paper is under review. If their publication efforts are successful a more critical assessment of their approach will be possible.

Available information indicates Connett and Hirzy have no original data but are relying on data from a study of children in an area of endemic fluorosis in China. They are refusing to accept published information from areas where community water fluoridation exists.

Their analysis also appears to rely on a tricky processing of the data to obscure the fact that fluoride probably only explains about 3% of the variance in IQ measured by the Chinese researchers! Legislators and policy makers would be foolish indeed to make changes to fluoridation standards on the basis of such data and poor analysis.

I could, of course, be wrong so eagerly await the Connett & Hirzy (2016?) paper.

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