Category Archives: Science and Society

In the end, it came down to the science in Denver


Denver Board of Water Commissioners listen to information at the July 2015 fluoride information session.

In my update to the post Subverting democratic consultation on the fluoride issue I reported that Denver Water has voted unanimously to continue community water fluoridation.  They have now produced a web article explaining their decision – see  The “why” behind our fluoride policy.

I think this comment sums it up:

“In the end, it came down to the science. And there’s a lot of it.On Aug. 26, the Denver Board of Water Commissioners voted to continue its practice of community water fluoridation.”

That decision came after a thorough review where both supporters and opponents of community water fluoridation presented their cases to the board.

“After reviewing the presentations, the extensive research on this issue, and the advice of public health and medical professionals in Colorado, the board announced there would be no change in its water fluoridation policy.

The resolution the board adopted at its meeting stated: “Nothing we heard through the presentations or learned in research would justify ignoring the advice of the public health agencies and medical organizations or deviating from the thoroughly researched and documented recommendation of the U.S. Public Health Service.””

And that is how it should be. Public officials should listen to the experts – scientific and health. Of course, they must also listen to criticism of expert recommendations, but such critical opinions must be carefully and critically weighed up. Denver Water board members appear to have done this.

The board said:

“Notably, every public health agency operating in our service area urged us to continue our practice of managing fluoride concentrations in our drinking water.”

This is supported by the list of presentations they considered as described in Denver Fluoride Fight Pits Activists Against Long-Standing Health Policy:

Number of comments in favor of fluoridation: 101

Organizations in favor of fluoridation:

  • Denver Public Health Department
  • Denver Health
  • Denver Environmental Health
  • Tri-County Health Department (Adams, Arapahoe, Douglas)
  • Jefferson County Public Health
  • Colorado Department of Public Health and Environment
  • Colorado Dental Association
  • American Dental Association
  • Colorado Academy of Pediatric Dentistry
  • Colorado Medical Society
  • Colorado Academy of Family Physicians
  • Deans of the University of Colorado Dental, Medical and Public Health Schools
  • Various community organizations

Number of comments opposed to fluoridation: 1,078
Organizations opposed to fluoridation:

  • Fluoride Action Network
  • New York State Coalition Opposed to Fluoridation
  • Concerned Residents of Peel to End Fluoridation
  • We Are Change Colorado”

Similar articles

Subverting democratic consultation on the fluoride issue


Credit: Making Sense of Fluoirde

Denver Water, which as Colorado’s largest water provider, has been reviewing its water fluoridation policy. It will announce its decision in the next few days but I found its description of the consultation process interesting.

[Update: Denver Water has now voted unanimously to continue community water fluoridation (see Good News – Denver Water Votes to Continue Community Water Fluoridation!). A complete failure for the anti-fluoride campaigners who worked hard to defeat fluoridation in Denver.]

A spokeswoman for the board, Stacey Chesman said Denver Water had received nearly 1,200 comments, from as far away as New Zealand, with 1,078 opposed to fluoridation, and 663 of those submitting their comments on postcards created by We Are Change Colorado. Every public health agency in Denver Water’s service area urged it to continue fluoridating water (See Water systems sink teeth into debate over drinking it).

Pretty impressive, eh? Twelve hundred submissions and about 90% oppose community water fluoridation (CWF). But look again – over 60% of the opposing submissions were on postcards provided by the anti-fluoride propagandist group “We are Change Colorado.”

Manipulating council consultations

That reminds me of the Hamilton City Council’s fluoride considerations two and a half years ago. That Council’s  summary of submissions reported:

“Of the 1,557 submissions received 1,385 (89%) seek Council to stop the practise of adding fluoride to the Hamilton water supply. 170 (10.9%) seek Council to continue the practise of adding fluoride and 2 (0.1%) submitters did not indicate a stance.”

The Hamilton numbers are so similar to those in Denver that one might wonder if the same people or organisations organised many of the submissions. And, I suspect, the Denver number of 90% opposed is just as unrepresentative of the public’s view as the Hamilton 90% – as shown by the subsequent Hamilton referendum where 70% of voters supported CWF! (See When politicians and bureaucrats decide the science).

The postcard tactic used in Denver is also much the same as the New Zealand Fluoride Free organisation providing submission templates  (templates A, B, C, D, were used in Hamilton) and submission guides. And the comment that Denver water received submissions “from as far away as New Zealand” also rings a bell – many of the submissions received by the Hamilton City Council were from as far away as the USA. And, in fact, video links were used to enable oral submissions by anti-fluoride propagandists from the USA!

What we have seen in these two cases – and many others in New Zealand, the USA, Canada and Australia – is a highly efficient organised campaign from “out-of-towners” intent on subverting the consultation process and the democratic rights of local citizens. A process which one might think mature and sensible civil leaders could easily recognise and discount. However, some of these leaders are easily fooled. In Hamilton, the local council gave the high numbers of anti-fluoride submissions they got as one of the main reasons for deciding to stop CWF. This seemed to them more important than the real referenda results!

A fluoride referendum in Thames

In New Zealand, the small town of Thames will hold a referendum on fluoridation of their water supply in November (see Thames fluoride referendum set for 5 November). Campaigning will start soon and no doubt we will see the same circus of whirlwind visits from out-of-towners, propaganda from overseas anti-fluoride propagandists (who promote themselves as “world experts” on the subject), and billboard, newspaper and radio advertising – probably paid for by the “natural”/alternative health industry.

I hope the people of Thames will be rightly suspicious of these “out-of-towners,” and ideologically and commercially motived propagandists, and instead listen to the advice of their own social health and dental experts.

Similar articles

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.

Similar articles

What is life?


I am being purposely provocative here – and who else provokes better that Richard Feynman.

Similar articles

Anti-fluoride propagandists get creative with statistics


According to a recently published survey, only 15% of New Zealanders are opposed to community water fluoridation (CWF).

Only 15% – yet anti-fluoride propagandists are using the same survey (or their limited reading of it) to claim that 58% of New Zealanders are opposed to (or do not support) CWF! (See Fluoridation problem for New Zealand, Most NZers do not support fluoridation, study saysFLUORIDATION’S FALLING POPULARITY NO SURPRISE, and Fluoridation’s Falling Popularity No Surprise.) That’s a huge difference. Someone must be using statistics in a creative way – or just outright lying.

The survey results were published in this paper:

Whyman, R. A., Mahoney, E. K., & Børsting, T. (2015). Community water fluoridation: attitudes and opinions from the New Zealand Oral Health Survey. Australian and New Zealand Journal of Public Health.

So anyone can check it out – although I recommend, as always, to read the full text. Often abstracts do not give the full information you want.

This survey reports data for various questions, but Table 2: “Estimates of ‘how in favour of water fluoridation’ (unweighted n, weighted percentage with 95% CI) opinions among adults (>=18 years of age)” is the relevant one here. The graphics below summarise the overall message (vertical bar is the 95% CI):


Or simplifying further into “for,” “against,” “neutral” and “do not know:”


So you can see the cherry-picking Mary Byrne from Fluoride Free NZ indulged in for her press release Most NZers do not support fluoridation, study says where she claims:

“This is the finding of a new survey carried out by Hawke’s Bay District Health Board: 58% of people did not support fluoridation even “somewhat”. This shows that people are really clear – New Zealanders do not agree with adding an industrial by-product, classified as hazardous, to our drinking water.”

She, no doubt would be offended by a claim that 85% of people support (or do not oppose) fluoridation – strongly or somewhat. Yet, her cherry picking is just as bad.

The real message from this survey for the anti-fluoride campaigners is that only 15% are opposed to community water fluoridation (CWF) – and then only 10% are strongly opposed.

As for the “creative license” of Mary Byrne and her fellow anti-fluoride propagandists, this message I picked up from a statistician’s cartoon sums it up:

You’ve heard of ‘Lies, Damn Lies, and Statistics.’ Well, apparently, they WERE lying about the statistics.”

The real message from the survey

The authors of this report did concentrate on the figure for those supporting CWF, or more importantly, the large proportion of people who are neutral (20%) or feel they just do not know enough to decide (22%). Interestingly, if these are excluded (as probably happens in referenda where a yes or no answer is required so that the neutral and undecided may not vote) the survey’s data translate into about 74% of the population supporting CWF and 26% opposing it. Not too different to recent referenda results (ranging from 58.1% support in Whakatane to 76.4% support in South Waikato).

However, health authorities are right to be concerned about the relatively large number of neutral and undecided people. The 15% who are opposed to CWF may largely be a “lost cause” because of their ideological stubbornness. But the data does show a need for more information on CWF and oral health in general.  It is likely that a better-informed population on this issue would lead to lower numbers of neutral and “do not know” people – and, very likely, a larger number of those who support CWF.

I have simply mentioned here the overall figures for support of, and opposition to, CWF but the study goes into a lot more detail and identifies sectors of the population requiring better education on the subject. Hopefully, we will see suitable oral health education programmes in future and a reduction in the neutral and “don’t know” numbers.

That can only be a good thing.

Similar articles

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

Similar articles

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.

Christmas reading

Christmas isn’t far away. Perhaps some of you are already thinking of presents for the scientifically minded in your family. You could do a lot worse that gifting one of the books on the shortlist for the 2015 Royal Society Winton Prize for Science Books.

The list is now public – see Royal Society Winton Prize for Science Books. And if you must wait to see which one wins the prize then the judges will announce this at a public event on 24 September 2015, hosted by Professor Brian Cox OBE, Royal Society Professor for Public Engagement in Science.

The books on the shortlist are below, together with the judges comments and a link to discover more about the book. There is also a link to the first chapter of each book for those careful buyers who would like to read a bit before deciding on that gift.

Man Who Couldn’t Stop: OCD and the True Story of a Life Lost in Thought by David Adam

The judges said: “An amazingly gripping and informative look inside someone’s head, told with a depth of knowledge and genius turn of phrase that only an expert and gifted writer could wield.”

Download the first chapter of this book (PDF).

Alex Through the Looking-glass: How Life Reflects Numbers and Numbers Reflect Life  by Alex Belos

The judges said: “Bellos fizzes with enthusiasm, and his genuine love for the subject shines through and makes mathematics engaging and non-threatening even for math-phobes.”

Download the first chapter of this book (PDF).

Smashing Physics by Butterworth, Jon (2015) Paperback by Jon Butterworth

The judges said: “With his unique insider perspective, Butterworth has humanized a classic science story that we all thought we knew. His writing is so engaging that he makes some of the most advanced science around seem within our grasp.”

Download the first chapter of this book (PDF).

Life’s Greatest Secret: The Story of the Race to Crack the Genetic Code by Matthew Cob

The judges said: “A brilliantly written account of one of the most important scientific discoveries of the century, with a fresh perspective that also dispels the myths popularised by previous reports.”

Download the first chapter of this book (PDF).

Life on the Edge: The Coming of Age of Quantum Biology by Johnjoe Mcfadden and Professor Jim Al-Khalili

The judges said: “A topic that could have been incomprehensible to the average reader becomes unexpectedly enthralling in the hands of these skilled communicators. A controversial work that deserves its already wide audience.”

Download the first chapter of this book (PDF).

Adventures in the Anthropocene: A Journey to the Heart of the Planet We Made by Gaia Vince

The judges said: “Vince’s passion and strong voice grabs you instantly and the story she tells is truly original. A finely-crafted book on an important, urgent topic.”

Download the first chapter of this book (PDF).

Similar articles


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.

Similar articles

Fluoridation: Newsweek science journalism bottoms out

One of the worst pieces of distortion and misrepresentation of the Cochrane Fluoridation Review is that written by an anti-fluoridation journalist Douglas Main in Newsweek – Fluoridation May Not Prevent Cavities, Scientific Review Shows. It has, of course, been heavily promoted by anti-fluoride activists.

Dr Charles Payet*, a dentist from Charlotte, NC, USA, has debunked this Newsweek article report in his blog article More Bad Journalism on Fluoride which is also a guest blog at Making sense of FluorideOoops, [Newsweek] Did It Again.

Readers should go to these original posts to read the full article.  However, here are a few quotes from important sections:


Yes, Water Fluoridation Has Been Proven Effective

Main starts off with an awful mischaracterization of the Review by stating that “…while using fluoridated toothpaste has been proven to be good for oral health, consuming fluoridated water may have no positive impact.” Let’s take that apart quickly.

First of all, there’s no disagreement that fluoridated toothpaste has been good for oral health. However, to state that consuming fluoridated water may have no impact is to completely ignore all historical evidence as to the dramatic decrease in dental decay once standardized CWF was implemented for the first time in Grand Rapids, Michigan 80 years ago. Not only that, the Cochrane Review directly contradicts Main’s assertion:

“Data suggest that the introduction of water fluoridation resulted in a 35% reduction in [DMF] baby teeth and a 26% reduction in [DMF] permanent teeth. It also increased the percentage of children with no decay by 15%.”

How About the Quality of the Papers Included?

Next up, Main claims that the Review “…winnowed down the collection to only the most comprehensive, well-designed, and reliable papers.” Is that accurate? Sigh……no. No it’s not. Let’s turn back to the Review to see what it says [emphasis mine]:

“For caries data, we included only prospective studies with a concurrent control, comparing at least two populations, one receiving fluoridated water and the other non-fluoridated water, with at least two points in time evaluated. Groups had to be comparable in terms of fluoridated water at baseline. For studies assessing the initiation of water fluoridation the groups had to be from nonfluoridated areas at baseline, with one group subsequently having fluoride added to the water. For studies assessing the cessation of water fluoridation, groups had to be from fluoridated areas at baseline, with one group subsequently having fluoride removed from the water.”

In other words, the Review only selected what are called “prospective” studies. While these are generally considered to be of higher quality better than cross-sectional studies, (performed at one point in time) for identifying causes, they are also much more difficult, and sometimes impossible, to do.  They are especially difficult today for one important reason when it comes to fluoride: because so many communities have already been fluoridated for a long time, it is very difficult to find one or more in which to set up a prospective study today, and the regulatory hurdles in doing so are enormous.

Therefore, it is false to claim that the Review only included the “most comprehensive, well-designed, and reliable papers.” In fact, the Review included one type of study regardless of their quality. Beyond that the Review’s discussion actually noted that more recent cross-sectional studies were often of better quality because computer use enabled better statistical analysis and consideration of confounding factors.

Payet also discusses the Cochrane judgement of study quality which Main and other anti-fluoride propagandists have misrepresented:

The Review judged quality using blinded randomised controlled studies (RCTs) commonly recommended for clinical drug trials as their baseline. However, they acknowledged this criteria is usually impossible to achieve in fluoridation studies because the assignment of subjects into a treated group versus a control group is outside the control of the investigator. Instead, researchers must use observational studies. Dr John Beal noted in his response to the Cochrane Health Group’s blog The value of cross-sectional studies on the dental benefits of water fluoridation – a response from Dr John Beal to the Cochrane Oral Health Group blog, the claim that cross-sectional, observational, studies, which were all excluded, are somehow of lower quality than RCTs, is false because a previous Cochrane Review said they’re similar!

“It is interesting to observe the conclusions of a different Cochrane review published last year (Anglemyer at al) which compared a range of study designs applied in various fields and concluded that, on average, “there is little evidence for significant effect estimate differences between observational studies and RCTs, regardless of specific observational study design”.

Well now, isn’t that interesting? The previous Cochrane Review specifically found that the 2 study types yield comparable results in terms of quality, but now this one says the cross-sectional ones aren’t good enough. As usual, Douglas Main ignores the previous one because it hurts his point. Admittedly, it would be nice if the Cochrane Review would apply more consistent standards in the selection and exclusion criteria to avoid confusion.

However, Dr. Payet has some criticisms to make of the Cochrane Review itself. It’s lack of proper qualification has been a godsend for cherry-picking anti-fluoridation propagandists:

Did you notice a certain pattern there? “Our confidence…is limited…” “We did not identify any evidence…” “There is insufficient information…” “The evidence is limited…” How in the world does Douglas Main turn that into “fluoridation doesn’t work!” As the saying goes, “The absence of evidence for something is not the same evidence for the absence of that something.”

Payet drives this point home in his conclusion:

So what’s the real take-home message of this particular Cochrane Review? Here’s all they really said: “Our exclusion criteria meant that only 9 studies were reviewed. Regardless of the quality of other studies done, we ignored them. Based on the extremely small study size and the strict criteria applied, all we can say is that more contemporary RCTs prospective studies are called for, because the ones available are old and might be biased.” That’s it! Main and his interviewees, however, go straight to, “OMG IT DOESN’T WORK WE SHOULD STOP IT NOW!” Perhaps this will make the point more clearly:

*Dr. Charles D. Payet has been a full-time practicing dentist in the city of Charlotte, North Carolina since graduating from the UNC Chapel Hill School of Dentistry in 1998. He blogs on the science and art of dentistry for all ages with a skeptical eye and has recently published several articles on the safety and efficacy of fluoride in community water fluoridation, toothpaste, etc.
Similar articles