Category Archives: science

Korean community water fluoridation supported by new evidence


Royal Azaleas in the mountains near Habcheon

New scientific evidence for the effectiveness of community water fluoridation (CWF) is appearing all the time. So that is hardly news – but I just thought it worth mentioning this latest example from Korea because I get told again and again that there is no evidence to show CWF is effective in improving oral health.

This latest Korean study was reported in this paper :

Jung, J., Kim, J., Kim, S., Lee, J., Kim, J., & Jeong, S. (2016). Caries-preventing effects of a suburban community water fluoridation program on permanent dentition after adjusting for the number of fissure-sealed teeth. Journal of Korean Academy of Oral Health, 40(1), 61–68.

The full text is available but only the abstract and tables are in English.

The study compares children from the fluoridated Habcheon township area with children from non-fluoridated areas.

The graphic below compares dental caries on permanent teeth for the different age groups. Clearly, children in the non-fluoridated areas have poorer dental health.


On average, the data indicates fluoridation is responsible for prevention of 24.6% of decayed, missing and filled permanent teeth (DMFT) and 29.9% of decayed missing and filled tooth surfaces (DMFS) (a more sensitive measure than DMFT).


This result is very recent but not at all surprising. Similar results have been reported before.

For example – this paper reported prevention of 27.5% of decayed, missing and filled permanent teeth (DMFT) and 24% f decayed missing and filled tooth surfaces (DMFS) for 12-year-old children in Gimhae.

Kim, H., Cho, H., Kim, M., Jun, E., Han, D., Jeong, S., & Kim, J. (2014). Caries Prevention Effect of Water Fluoridation in Gimhae , Korea. J Dent Hyg Sci, 14(4), 448–454.

Again this is full text but only the abstract and tables are in English.

There are more studies reporting a similar effectiveness of CWF in Korea.

These authors are recommending that CWF, which covers only 6% of the population in the republic of Korea, should be extended to other regions in the country.

CWF has been controversial in the Republic of Korea. Health authorities are promoting the extension of CWF but this is opposed by some groups. Surveys show  the majority of people whose children have good oral health, who are aware of fluoridation  programmes or who understand the protective role of fluoride support extension of CWF. But support is much less among people who are a=unaware of the benefits or whose children have poor oral health.

So, while health authorities support the extension of CWF they also accept there is a need for more public education about the benefits.

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Science and management – a clash of cultures


Found this while weeding out some old computer files. It certainly described the conflict between science and management I experienced while working – particularly since the reforms of the early 90s. “Science” became a dirty word while “profit” and management-speak became almost compulsory.

A man in a hot air balloon realized he was lost.

He reduced altitude and spotted a woman below. He descended a bit more and shouted,”Excuse me, can you help me? I promised a friend I would meet him an hour ago, but I don’t know where I am.”

The woman below replied, “You’re in a hot air balloon hovering approximately 30 feet above the ground. You’re between 55 and 56 degrees north latitude and between 3 and 4 degrees west longitude.”

“You must be a scientist,” said the balloonist.

“I am,” replied the woman, “How did you know?”

“Well,” answered the balloonist. “everything you told me is, technically correct, but I’ve no idea what to make of your information, and the fact is I’m still lost. Frankly, you’ve not been much help at all. If anything, you’ve delayed my trip.”

The woman below responded. “You must be in Management.”

“I am,” replied the balloonist, “but how did you know?”

“Well,” said the woman, “you don’t know where you are or where you’re going. You have risen to where you are due to a large quantity of hot air.  You made a promise which you’ve no idea how to keep, and you expect people beneath you to solve your problems.

The fact is you are in exactly the same position you were in before we met, but now, somehow, it’s my fault.”

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Anti-fluoride campaigners cherry-pick irrelevant overseas research but can’t find relevant New Zealand research


Ever seen this in New Zealand?! Example of skeletal fluorosis from an overseas study used by local anti-fluoride campaigners to argue against community water fluoridation. Image Credit: Das et al., (2016)

Yes, I know. This is getting boring. A local anti-fluoride campaigner misrepresents research on fluoridation – yet again.

Perhaps I should apologise for yet another article debunking this sort of misrepresentation. In my defense can I just say this is just such a clear example that it can help drive the message home. These people cherry-pick research from areas of endemic fluorosis in China and India – pretend they are relevant to New Zealand or the USA – and ignore those studies which are relevant to countries which carry out community water fluoridation.

Stan Litras is (yet again) the guilty party. He has disseminated a press release, FIND cites new research, which will, of course, be reproduced by the Fluoride action network and make its way into the “natural”/alternative health media. That will, in turn, be cited by other anti-fluoride campaigners as “proof” that community water fluoridation is harmful!

Stan claims that:

“New research has confirmed that increased fluoride in water results in reduced intelligence. The research, published in the journal,of environmental monitoring and assessment, found that the higher the fluoride content in water, the lower the IQ of children, . . “

The paper Stan Litras relies on reports data from an area of endemic fluorosis in India. An area quite unlike New Zealand. Here is the citation for the paper (it’s a full-text version if you wish to check it out for yourself):

Das, K., & Mondal, N. K. (2016). Dental fluorosis and urinary fluoride concentration as a reflection of fluoride exposure and its impact on IQ level and BMI of children of Laxmisagar, Simlapal Block of Bankura District, W.B., India. Environmental Monitoring and Assessment, 188(4), 218.

Whatever its findings we can see how inapplicable that research is to New Zealand by comparing its data for dental fluorosis with similar data for New Zealand, USA and China. In this graphic below I compare prevalences of the mild forms (“none,”, “questionable,” very mild,” and “mild”) with the prevalences of “moderate” and “severe” forms. Only the latter forms are of concern (the milder forms are usually considered positively by adolescents and parents – see Water fluoridation and dental fluorosis – debunking some myths).

(Note: for a discussion of how severe dental fluorosis may influence IQ see Severe dental fluorosis and cognitive deficits.)

The figure  contrasts data for prevalence of dental fluorosis in NZ and theUSA where CWF is common with data for an area of endemic fluorosis in China and data from this paper (Das).

DF severe

While there is hardly any dental fluorosis of concern in USA and New Zealand these forms are very prevalent in the region of India covered by this study and a similar region of endemic fluorosis in China.

Or perhaps we should look at some more graphic evidence. Das et al., (2016) include the photo at the head of this article as an example of skeletal fluorosis found in the subjects they studied. And the photo below as an example of dental fluorosis found in their subjects.

DF Das 2016

Example of dental fluorosis observed by das et al., (2016) in subjects studied.

Come  on Stan – how often have you seen dental and skeletal fluorosis like this in New Zealand?

It is just not honest to cite this study in any discussion of the New Zealand situation. It has absolutely no relevance here.

To make this worse, Stan completely ignored New Zealand studies on these issues. For example the 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.

These researchers found no influence of community water fluoridation on IQ – see figure below.


Data from Broadbent et al., (2014)

So yes – just one more example of how local anti-fluoride campaigners are misrepresenting research on fluoridation. But a clear example of cherry-picking overseas studies irrelevant to community water fluoridation in New Zealand while, at the same time, ignoring New Zealand studies relevant to community water fluoridation.

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Cochrane fluoridation review described as “empty”


Image credit: MSoF – Ooops, [Newsweek] Did It Again

Publication of the Cochrane fluoridation review last year caused quite a flurry. Anti-fluoridation activists launched an avalanche of cherry-picked quotations and claims that completely misrepresented the review’s findings. On the other hand, the Cochrane review was poorly written and laid itself open to this cherry picking and misrepresentation.

Now, an authoritative group of authors has published a new critique which summarises the faults of the Cochrane review and shows how it has come to be misrepresented. The paper is:

Rugg-Gunn, A. J., Spencer, A. J., Whelton, H. P., Jones, C., Beal, J. F., Castle, P., … Zusman, S. P. (2016). Critique of the review of ‘Water fluoridation for the prevention of dental caries’ published by the Cochrane Collaboration in 2015. Bdj, 220(7), 335–340.

The on-line version is full text so readers can check it out for themselves.

The authors say:

“The Cochrane Review’s conclusion that ‘there is very little contemporary evidence. that has evaluated the effectiveness of water fluoridation for the prevention of caries’ is self-fulfiling due to its omission of contemporary studies designed for surveillance of public health programmes.

So they say:

“This, it could be argued, led to what is termed ‘an empty review’.”

And this is because a key problem of the review was “the restrictive inclusion criteria  used to judge adequacy of study design and risk of bias.”

Nature of water fluoridation programmes

A problem with the Cochrane review is that its judgement criteria were more suitable for drug trials than for evaluation of a social health policy. Drug evaluation relies on randomised controlled trials (RCTs), but:

“With public health interventions things are different. There will only sometimes be RCTs demonstrating efficacy and effectiveness. There are frequently no such trials because the highly complex practical, ethical and financial factors involved mean that RCTs are not feasible. Consequently, when determining whether a public health intervention is cost effective, evidence has to be drawn from a wide variety of other scientific methods and research designs including cross-sectional ones and process evaluations. . . . .

“In many cases it is simply impossible to make recommendations for public health interventions and policy if reliance is only placed on RCTs. Further, with public health interventions, the issue is not about individual patient benefit but whether the population as a whole will benefit.”

There are also many confounding effects with fluoridation:

“variations in use of other sources of fluoride, mainly from toothpaste, and diet, particularly sugar consumption. In many societies, these are closely linked to SES, and evaluation should also measure and control for these explanatory factors and interactions.”


“Water fluoridation should be evaluated using contemporary methods which are appropriate for evaluating public health interventions with such complexities, and systematic reviews should take this into account.”

The Cochrane review failed to do this and, although these problems were aired in the review’s discussion, the abstract and main conclusions were, therefore, misleading and open to misrepresentation.

Criteria for study inclusion

This “purist” approach was also demonstrated in the review’s criteria for study selection. The Cochrane authors considered:

“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.”

But baseline data can be irrelevant when considering long-term fluoridation schemes. Rugg-Gunn et al., (2016) point out:

“Over time, in many countries, coverage of the population with water fluoridation schemes was almost complete, at least to the limits of public health requirements and technical feasibility. In such jurisdictions, the priority for health authorities was to monitor the continued effectiveness of existing schemes. Most recent evaluations of water fluoridation have been of this type, using the most appropriate design, which is a single cross-sectional survey of fluoridated and non-fluoridated groups with control for confounding factors.” One of the critical problems with the 2015 Cochrane Review is that these data have been excluded from the Review.

This, although recent evaluations have usually been of higher quality than older ones because of the availability of computer processing, use of more sophisticated statistical analysis and greater awareness of the need to taker confounding factors into account.

The authors discuss the impracticability of requiring baseline data for such long-term schemes. The Cochrane reviewers themselves stipulated baseline data should be taken within 3 years of implementing water fluoridation:

“an acknowledgement that the communities may, mainly through population change, lose comparability after three years. While this assumption of similarity may be reasonable over a short period, it becomes less tenable as the period between baseline and final examinations increases.”

This requirement looks silly when considering recent data from long-term schemes or considering possible benefits for 50-year-olds because:

“baseline information on the caries experience of people of this age would be required in the community to be fluoridated and in a comparable reference community, as well as information to be collected 50 years later on the caries experience of people from the same age group in the same communities which have continued to remain fluoridated or non-fluoridated for the whole of that very long period. Such requirements are unfeasibly stringent given the potential for community demographic characteristics to change over time, and render 50-year historical comparability of intervention and reference communities meaningless for present-day comparisons.[My emphasis]

Rugg-Gunn et al., (2016) discuss in-depth other aspects of the criteria used, exclusions if modern research by the Cochrane authors and study design.

Dental fluorosis

The Cochrane review’s inclusion of dental fluorosis seems to be “tacked on” and does not use the criteria outlined for their review and selection of caries studies. In particular, it ignored the influence of different sources of dietary fluoride – leaving the impression that the resulting data related to water fluoridation when it didn’t:

“In the Cochrane Review, the effect of water fluoridation on the prevalence of fluorosis should have been isolated from the confounding effect of other fluorides. The Cochrane Review’s analysis of fluorosis studies is silent on the possible contribution of other fluorides, such as fluoridated toothpaste, which risks leaving readers with the impression that all dental fluorosis arises from fluoride in water supplies. Research since 2000 has indicated that a greater proportion of dental fluorosis risk is due to the use (and therefore swallowing) of fluoride-containing toothpastes than to optimally fluoridated water.

Consequently, an intelligent interpretation of the fluorosis data in the Cochrane review requires some extra calculation – of the sort the reviewers themselves did for the caries studies:

“This comparison between intervention and reference communities was the method used for evaluating caries prevention in the Cochrane Review but, for an unexplained reason, not for the evaluation of dental fluorosis. For communities with lower fluoride concentrations (such as 0.5 mgF/L), their fluorosis levels should be compared with those in the corresponding reference (non-fluoridated) community.”


“The highly restrictive approach taken by the Cochrane Review in examining the effect of community water fluoridation on dental caries seems to have been abandoned for dental fluorosis. The reason for this difference is unclear.”

I attempted this “extra calculation” in my article Cochrane fluoridation review. III: Misleading section on dental fluorosis.”

When differences between “fluoridated” and “non-fluoridated” areas are considered there was no significant contribution of water fluoridation to the “dental fluorosis of aesthetic concern.” However, because  this comparison was not made in the Cochrane review anti-fluoride campaigners are claiming that fluoridation causes a prevalence of 12% “dental fluorosis of aesthetic concern!”

That is very misleading.

Anti-fluoride campaigners love to quote prevalence figures for all forms of dental fluorosis, not just the more serious – implying that even the mildest forms should concern us. Consequently, they cite the Cochrane review to claim a 40% prevalence of dental fluorosis This is for all forms from the most severe to the mildest. But, in fact, when the differences between “fluoridated” and “unfluoridated” areas are calculated the prevalence of all forms of dental fluorosis attributable to community water fluoridation is only 7%. And, remember, these will be only the mildest forms.

Again, very misleading.


The Cochrane fluoridation review agrees with all other authoritative reviews when it states:

“that water fluoridation is effective at reducing caries levels in both deciduous [primary] and permanent dentition in children.”

But its conclusions conflict with the literature on:

“the effectiveness of water fluoridation in respect of: its effectiveness in adults; its effectiveness in reducing social disparities in oral health; and the effect of cessation of water fluoridation. On these, the Cochrane Review said that there was insufficient evidence; it did not say that water fluoridation was ineffective in these regards.”

On these, the review would only say that “there is insufficient evidence.” But that is a self-fulfilling conclusion given their restrictive selection criteria. Some observers may actually say such a conclusion is irresponsible because:

“It is a fundamental premise of interpreting evidence from trials that the absence of evidence, or the existence of poor-quality evidence, should not be confused with, or taken to imply, an absence of effect. There is a risk that the Cochrane Review will be inadvertently, or deliberately, misinterpreted in this way.”

And we know this is, in fact, what has happened. Motivated anti-fluoride campaigners have chosen to present an absence of evidence (because of the restricted selection of studies) as “proof” that fluoridation is not effective.

It just shows how an “empty review” can be used to make the most unwarranted claims.

Similar articles on the Cochrane fluoridation review

Anti-fluoridationists misrepresent new dental date for New Zealand children


Another whopper from the anti-fluoridation movement in New Zealand.

They claimed yesterday that “data released by the Ministry of Health today confirm that water fluoridation is having no noticeable effect in reducing tooth decay” (see DHB Data Show No Benefit From Water Fluoridation).

Yet a simple scan of the data (which can be downloaded from the MoH website) shows this to be patently untrue.

Here is a graphical summary of the New Zealand-wide data for 5-year-olds and year 8 children. It is for 2014 and I have separated the data ethnically as well as presenting the summary for all children (“total”).

DMFT and dmft = decayed, missing and filled teeth.


214---8-yrNow – don’t these figures show the press release headline and the first sentence  are completely dishonest?

The data for all children (“total”) Maori and “other” show children in fluoridated areas have a higher percentage of caries-free teeth and a lower mean value of decayed, missing and filled teeth. The data for Pacifica are less definite – because the vast majority of Pacific children live in fluoridated areas. I discussed this further in my last post A challenge to anti-fluoridationers to justify their misrepresentation of New Zealand research.


So the headline and main message of the anti-fluoridationists press release were outright lies. However, they will fall back on the claim that the press release does contain some facts.  But these are just cherry-picked snippets taken out of context to confirm the bias of the anti-fluoride mind.

For example, comparing data for Christchurch and Nelson-Marlborough with those for  Auckland and Counties-Manukau is just disingenuous if the ethnic differences (which we know clearly play a role in oral health) are not considered. Similarly, reference to the 2o14 “overturning” of the Hamilton Council decision to stop fluoridation is just silly considering that there are no separate data for the city and the Hamilton Council fiasco over water fluoridation overlapped the period the data covers.

Of course, this press release has been processed through the international anti-fluoridation – “natural”/alternative health media channels so expect to be bombarded with international reports based on these lies.

The lesson from this little story – don’t take claims made by anti-fluoridation campaigners, or similar activists with an anti-science agenda, at face value. Always check them out.

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A challenge to anti-fluoridationers to justify their misrepresentation of New Zealand research


One of the frustrations I have with the fluoridation issue is the refusal of anti-fluoride activists to engage on the science. They will pontificate, but they won’t engage in discussion.

On the surface, one would think there is a difference of opinion or interpretation of scientific issues and that could be resolved by discussion. Yet local anti-fluoride campaigners refuse to enter into discussion. Again and again, I have offered space here to local anti-fluoride campaigners so that they could respond to my articles and they have inevitably rejected the offer. They have also blocked me, and other people discussing the science, from commenting on any of their social media pages or web sites. Even when they, themselves, call for a debate they reject specific responses I have made accepting that call.

So I am left with the only alternative of responding to their claim with an article here – or on a friendly web or blog site. At least that gives me space to present my argument – I just wish I could get some intelligent responses enabling engagement on the issues.

Misrepresentations repeated

The latest misrepresentation of the science is a claim by the Auckland Fluoride Free NZ Coordinator, Kane Titchener, that recent research proves fluoridation [is] not needed.

It repeats the same misrepresentation made by Wellington Anti-fluoride campaigner, Stan Litras, which I discussed in my article Anti-fluoridation cherry-pickers at it again. Kane has either ignored my article, chosen to ignore it or possibly not even understood it.

So here we go again.

Kane claims:

“A New Zealand study published in Bio Medical Central Oral Health last month shows dental health improved the greatest extent for children in non-fluoridated areas. There is now no difference in dental decay rates between non-Maori children who live in fluoridated areas and non-Maori children who live in non-fluoridated areas, proving that fluoridation is not needed for children to obtain good dental health.”

Although he doesn’t cite the study (wonder why), his use of two figures from the study show he is writing about the paper:

Schluter, P. J., & Lee, M. (2016). Water fluoridation and ethnic inequities in dental caries profiles of New Zealand children aged 5 and 12–13 years: analysis of national cross-sectional registry databases for the decade 2004–2013. BMC Oral Health, 16(1), 21.

His claim relies on the comparison of data for “non-Māori” children in fluoridated and fluoridated areas. No – he doesn’t misrepresent the data – he just ignores the discussion by these authors of problems with simple interpretation of the data for non-Māori because of the fact it is not ethnically uniform. In particular, he ignores the qualifications they place on the data because of the inclusion in non-Māori of data for Pacifica who have poorer dental health than the rest of this group and live predominantly in fluoridated areas. This, in effect, distorts the data by overestimating the poor oral health for “non-Māori” in the fluoridated areas.

The apparent convergence

The data used in this study were taken from the Ministry of Health’s website. This divides the total population of children surveyed into the ethnic groups Māori, Pacific and “Other.” While the “other’ group will not be completely uniform (for example including Pakeha, Asian, other groups) it becomes far less uniform when combined with the Pacific group to form the non-Māori group.

So, Kane salivates over this figure from the paper especially the plots for  non-Māori ethnicities in fluoridated (F) and non-fluoridated (NF) areas.


Fig. 1 No obvious decay experience (caries-free) percentages and mean dmft for 5-year old children over years 2004 to 2013, partitioned by Māori and non-Māori ethnicities and fluoridated (F) and non-fluoridated (NF) areas

Yes, that convergence is clear and I can see why Kane is clinging to it – who can blame him. But he completely ignores the warning from the paper:

“It is likely that a substantial driver of this convergence was due to significant changes within the dynamic and heterogeneous non-Māori groups both within and between DHB regions. In effect, the ecological fallacy – a logical flaw whereby analyses of group data are used to draw conclusions about an individual – may be operating within the non-Māori group.”

When the Pacific data is removed (as is the case for the “other” group effectively made up from non-Māori and non-Pacifica) we get the plots below.


Comparison of data for “other” (non-Māori/non-Pacifica) children in fluoridated (F) and unfluoridated (UF) areas.

Nowhere near as useful for Kane’s confirmation bias and the message he wants to promote. OK – there is still some evidence of convergence from about 2007 on between fluoridated and unfluoridated children. But the graphs do show that community water fluoridation is still having  a beneficial effect. And this apparent convergence could be explained by things like the introduction of “hub and spoke” dental clinics after 2004. One problem with this raw data is that children are allocated according to the fluoridation status of the school – rather than their residence. This will lead to incorrect allocation in some cases.

Some data for Pacifica

Just to underline the problems introduced by inclusion of Pacific in the non-Māori group of the study consider the data for Pacifica shown below.


Data for 5-year-old children. dmft = decayed, missing and filled teeth. The “other” group is non-Māori and non-Pacifica

The oral health of Pacifica is clearly poorer than that of the “other” group.

Also, Pacifica make up about 20% of the non-Māori fluoridated group. So they will influence the data for the non-Māori fluoridated group by reducing the % caries free and increasing the mean dmft.

So Kane, like Stan, is blatantly cherry-picking. He is misrepresenting the study – and its author – by ignoring (or covering up) the qualifications regarding the influence of inclusion of pacific in the non-Māori fluoridated group.

The challenge

Now, I repeat the offer I have made in the past to give a right of reply to both Kane Titchener and Stan Litras. They are welcome to comment here and if they want more space I am happy to give space for separate articles for them in the way I did for the debate with Paul Connett. Now I can’t be fairer than that, can I?

So what about it Stan and Kane? What are your responses to my criticisms of the way you have cherry-picked and misrepresented this New Zealand paper?

NOTE: I have sent emails to both Kane and Stan asking them to respond and offering them right of reply.

UPDATE 1: Great minds and all that – Stan Litras sent out a press release today calling for a nation-wide debate on this issue (see FIND calls for a national debate on fluoridation). However, the seriousness of his request is rather compromised by his reply to my offer of a right of reply to the above article. He did respond to my email very quickly. This is what he wrote:

“Thanks for the offer, Ken, but I have not visited your blog site for a long time, as I object to the way you attempt to defame and discredit me.

You play the man and not the ball, which is not the mark of a reasonable person.

I hope to address that in due course as time permits, but for now I must leave you to indulge yourself without my company.”

So much for his wish for a “national debate” when he will not front up to a critique of his claims about the science.

UPDATE 2: Kane Titchener today also posted a press release today which was the text of the article I discuss in this post (see NZ research proves fluoridation not needed). He also responded quickly to my e-mail. The full text of his response was:

Who is this?”

Rather strange – considering he often pesters me with emails.

So I guess both of them have turned down my offer.

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Fluoridation decisions to be made by District Health Boards


Image credit: Constant Contact

This has been on the cards for a while. In recent years ideologically and commercially motivated activists have played havoc with the consultations organised by local body councils. Councils have shown by their own actions they are not capable of considering the scientific and health evidence related to community water fluoridation. The political intrigues of local bodies and the lack of scientific skills have prevented sensible decisions in many cases – and resulted in reversals of decisions – sometimes within a few weeks. yet New Zealanders have in most places voted to support community water fluoridation.

Councils have asked the central government to remove decisions on fluoridation from their responsibility. And now the government has decided to do just that.

This is the text of today’s  press release from the Hon Dr Jonathan Coleman, Minister of Health, and the Hon Peter Dunne, Associate Minister of Health (see Fluoridation decision to move to DHBs):

DHBs rather than local authorities will decide on which community water supplies are fluoridated under proposed changes announced today by Health Minister Jonathan Coleman and Associate Health Minister Peter Dunne.

“New Zealand has high rates of preventable tooth decay and increasing access to fluoridated water will improve oral health, and mean fewer costly trips to the dentist for more New Zealanders,” says Dr Coleman.

“This change could benefit over 1.4 million New Zealanders who live in places where networked community water supplies are not currently fluoridated.

“Water fluoridation has been endorsed by the World Health Organization and other international health authorities as the most effective public health measure for the prevention of dental decay.”

DHBs currently provide expert advice on fluoridation to local authorities.

“Moving the decision-making process from local councils to DHBs is recognition that water fluoridation is a health-related issue,” says Mr Dunne.

“Deciding which water supplies should be fluoridated aligns closely to DHBs’ current responsibilities and expertise. It makes sense for DHBs to make fluoridation decisions for their communities based on local health priorities and by assessing health-related evidence.”

A Bill is expected to be introduced to Parliament later this year. Members of the public and organisations will have an opportunity to make submissions to the Health Select Committee as it considers the Bill.

See also: DHBs could make call on fluoridating water

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Anti-fluoridationists now scaremonger about silica in your drinking water


Orthosilicic acid exists in drinking water. This is an idealised presentation because of polymerisation reactions. In practice, analysts measure “reactive silica.”

Well – that’s what we can infer from a new campaign of the Fluoride Action Network (FAN).

But what is the link with fluoride – the whole reason for FAN’s existence? Well, they base this campaign on the well-known hydrolysis of the fluorosilicates used in community water fluoridation to form the hydrated fluoride anion and silica. (Although these campaigners are confused here as they will also often claim fluorosilicates do not hydrolyse and survive to come out of your tap and poison you).

Then they claim that “silicic acid” (silica in solution) dissolves lead from the pipes and fittings and this lead causes brain damage. A double-barreled danger as they also claim the fluoride also damages your brain. What’s more – they also claim that “silicic acid” may dissolve your teeth!

But there are two problems with this:

  1. Your drinking water contains silica whether it is fluoridated or not. So their warnings about the silica in fluoridated water should also be valid for “fluoride-free” water which they promote!
  2. They do not have a viable chemical mechanism for silica dissolving your pipes (and there are plenty of other mechanisms which can result in corrosion of pipes anyway). The same for your teeth. This claim is just not supported by the chemical literature.

I will just concentrate here on the “evils” of silica (or “orthosilicic acid”) that are being promoted by FAN and leave the lead story for another day. These “evils” all come down to concepts being promoted by Richard Sauerheber who FAN describes as “the ultimate citizen chemist.” (OK, he is their ultimate citizen chemist). His argument is presented in Silicic Acid – How Does Fluorosilicic Acid Leach Lead? Why Does Fluorosilicic Acid Leach Lead So Much More Than Sodium Fluoride?

Is silicic acid the bogy Sauerheber claims?

His article is confused and convoluted. But it starts with the assumption that silica in drinking water (silicic acid or orthosilicic acid) is bad. He declares:

“Neither fluoride nor silicic acid are constituents of normal pristine human or mammalian blood, but rather are contaminant materials, . . “

And he states:

“The mass treatment of public fresh drinking water with industrial fluorosilicic acid to produce fluoride ion at 1.0 ppm also produces approximately 6 ppm sodium ion and .7 ppm orthosilicic acid. None of these is found in or belongs in fresh drinking water.”

Let’s stop right there and check out his claim that sodium and “orthosilicic acid” are not found in fresh drinking water.

Here is some data for drinking water in fluoridated and unfluoridated areas of Auckland, New Zealand, taken from the WATERCARE ANNUAL WATER QUALITY REPORT 2013. The data are for 15 unfluoridated treatment plants and 8 fluoridated treatment plants.


These are average figures over all the plants. But values for silica as high as 64 mg/L in the unfluoridated plants and 44 mg/L in the fluoridated plant were recorded. The corresponding figures for sodium were 140 and 22 mg/L.

So Sauerheber is completely wrong. Unfluoridated water does contain silica and sodium. And at concentrations much higher than could be accounted for by added fluoridating chemicals – he calculated 0.7 mg/L – 0.7 ppm) for silica. In fact, the values are higher for the unfluoridated treatment plants in these examples.

Fluoridation makes a minuscule contribution to the concentration of these chemical species in drinking water.

Forget about fluoridation. If silica (and sodium) are such problems then Sauerheber should be campaigning against unfluoridated water as well. Even the “pristine” water in his local river or spring – silica is a normal and natural component of surface and bore waters.

But Sauerheber is also wrong about the dangers of silica in drinking water. Of course silica is present in “normal pristine human or mammalian blood” because it is part of our diet (Bisse et al 2005). It is a component of many of our foods. Sauerheber is simply attempting to confuse the issue because of the current lack of knowledge about the role of silica in the body.

But Jugdaohsingh et al., (2015) say:

“Silicon (Si) is a natural trace element of the mammalian diet and although it has not been demonstrated unequivocally that mammals have a requirement for Si there is increasing evidence to suggest that it may be important for the normal health of bone and the connective tissues. Indeed, severe dietary Si deprivation in growing animals appears to cause abnormal growth and defects of the connective tissues”

Given that silica appears to be important the presence of it in our drinking water is as an advantage. According to Jugdaohsingh (2007):

“Drinking water and other fluids provides the most readily bioavailable source of Si in the diet, since silicon is principally present as Si(OH)4, and fluid ingestion can account for ≥ 20% of the total dietary intake of Si.”

One trick Sauerheber uses is to cite reports of the danger of inhaled silica dust – which can cause cancers and silicosis. Completely irrelevant because of its different chemical form. This is equivalent to the trick often used by anti-fluoride campaigners of citing reports of results of industrial pollution or studies from areas of endemic fluorosis to support their attacks on community water fluoridation.

Will silica dissolve your teeth?

This claim is completely unsupported – no citations and purely a figment of Sauerheber’s imagination. He claims:

“Orthosilicic ‘weak’ acid has been long used in agriculture to break down solid calcium phosphate Ca3(PO4)2, thereby releasing soluble phosphate ion in soils even at neutral pH, for uptake by plant life. The reaction of silicic acid with calcium phosphate under neutral pH conditions is:

H4SiO4 + Ca3(PO4)2 →  HPO4-2 + 3Ca2+ + PO4-3+ H3SiO4.

This reaction occurs at a pH where any strong acid would have been neutralized. Orthosilicic acid is reluctant to dissociate and can break down calcium phosphate. This reaction is relevant not only to calcium phosphate in soil but also to calcium phosphate in teeth enamel. By means of orthosilicic acid, enamel is subject to slow and progressive degradation. “

This is a new one on me – and I spent many years researching the dissolution of apatite (the natural calcium phosphate) in soil and the factors influencing that. This arose because unacidulated phosphate rocks were being used in New Zealand agriculture. These material contain insoluble phosphate – in contrast to superphosphate which contain soluble phosphate.

The phosphate rocks used are mainly apatites and are complex (because of isomorphous substitution). A specific chemical equation for their dissolution depends on composition and environmental pH. But, in general, acid (H+) reacts with the apatite to produce Ca2++ H2PO4, H2O, F, Cl, CO2, etc.

H+ + Ca10(PO4)6(OH,F,Cl)2 → Ca2+ + H2PO4 + H2O + Cl + F + CO2

Dissolution is promoted by the presence of acid (H+) and removal of dissolution products (particularly Ca2+). The calcium in soil solution can inhibit apatite dissolution – it drives the equation above to the left. The later is important because New Zealand agricultural soils have relatively high levels of calcium. On the other hand, our research showed that when soils are leached to remove calcium this can promote dissolution of the natural fluorapatite in the soil. (Perrott and Kear 2004). Removal of calcium from solution drives the above equation to the right.

Apatite particle size, fluoride content and substitution of other species in the apatite structure can also influence the dissolution rate of these materials in soil. But silica, or silica in soil solution – that is a new one on me!

Pity Sauerheber didn’t give a citation to support his claim that silica “has been long used in agriculture to break down solid calcium phosphate Ca3(PO4)2, thereby releasing soluble phosphate ion in soils even at neutral pH, for uptake by plant life.” I would be very interested to see the evidence – but I cannot find anything in the scientific literature to support Sauerheber’s statement. It appears to be a figment of his imagination and anti-fluoride bias.

In the same unsupported manner, Sauerheber is suggesting silica (“orthosilicic acid”) may be dissolving our teeth. He even provides a chemical equation for it:

2H4SiO4 + Ca3(PO4)2 → 2HPO4-2 + 2H3SiO4 + 3Ca2+

First,  the primary mineral in teeth is a bioapatite (Ca10(PO4)6(OH,F,Cl)2) not Ca3(PO4)2. And H3SiO4 is not stable at the pH of drinking water or saliva so his idea is destroyed by the immediate reaction:

H+ + H3SiO4→ H4SiO4

In other words, Sauerheber’s equation above is driven to the left at the neutral and acid pH values of saliva and drinking water.

Incidentally, it is the presence of Ca2+, H2PO4 and F in our saliva (derived from food and drink) that drives the dissolution equation for apatite to the left. It prevents dissolution (acid attack or demineralisation) and promotes remineralisation. This the surface or “topical” mechanism that reduces decay in existing teeth when fluoridated water is used.

Sauerheber’s confusion

Sauerheber’s arguments are chemically confused – probably because he is driven by a wish to find anything connected with fluoride to be bad. He is confused by terminology because the silica in solution is often called orthosilicic acid, or silicic acid. But the point is that this species (whatever it is – the chemistry of silica in water is very complex) is not dissociated at neutral pH values near 7.  (more correctly only 0.18% of it is – Belton et al., 2012). It is a very weak acid -significant dissociation to form the anion only occurs at higher pH values according to the equation:

OH + H4SiO4 → H3SiO4 + H2O

Enamel attack is caused by acid (H+) not an unionized silica species or silicate anion. At these high pH values, dissociation of silicic acid at high pH does not produce H+. It actually removes OH.

The same confusion is behind Sauerheber’s assertion that leaching of lead from pipes and plumbing is caused by “orthosilicic acid.” He says:

“it is the intact orthosilicic acid, the predominant form present over the pH range 7-10 (sic) that is leaching lead or lead salts from pipes and plumbing fixtures.”

In fact, acid in drinking water is one of the causes of lead leaching. The chemical species responsible is H+ and that is why treatment plants adjust pH levels to reduce acidity. Silica in  solution does not make a contribution to the (H+) concentration.

But if it did then we should be concerned about all water as fluoridating chemicals make only a minuscule contribution to silica in water.

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Reversed responsibility and the burden of proof


This tactic often comes up in discussions related to scientific and religious issues.

It’s usually used by someone who has made a claim and then been asked for evidence to support it. Their response is to demand that you show that the claim is wrong and if you can’t, to insist that this means their claim is true.

Science or Not has a brief article on this at The reversed responsibility response – switching the burden of proof. It says:

“People use this tactic to avoid supplying supporting evidence – usually because there is none. In attempting to distract you from this lack of evidence, they try to convince you that the responsibility of supplying evidence lies with you.”

This can be relatively trivial – a person might claim that there is plenty of evidence that climate change science is a scam or that community water fluoridation (CWF) is harmful. When asked for supporting evidence they ask you to “look it up” or “google it” yourself – implying that you are lazy to even ask then for their supporting evidence.

We can’t prove the impossible

Then there is the philosophically dishonest reversal of responsibility where they demand, for example, the supporter of CWF cite  studies showing CWF  does not cause harm. Dishonest because that is not how science works – it seeks to test specific situations for harm. One might produce study after study showing no specific harm but it is impossible to design a study showing anything is “safe.” The person can, therefore, dismiss each example showing no specific harm by insisting that this does not prove it is safe in all situations.

“Reversing the burden of proof is a form of the argument from ignorance fallacy, in which it is argued that a claim must be taken as true if it hasn’t been shown to be false.”

Yet, ideologically driven activists will often use this argument – maybe dressed up as the “precautionary principle.” For example, they will make submissions to community bodies conceding that perhaps they cannot produce any decisive studies showing CWF is harmful but the “precautionary principle” means that it should not be used until research shows it to be completely safe.

This is simply using ignorance – on the part of members of the community body as well as the activist – to prevent acceptance of a policy which is recommended by experts and health authorities. It’s an attempt to destroy the authority of evidence and science which should be centrally considered in such decisions.

What to do when confronted by this tactic

The Science or Not article gives advice on how to treat such tactics:

“Don’t be tempted to take on the task of falsifying the perpetrator’s claim. And don’t succumb to the pressure to accept it as true if you don’t have the evidence to refute it. Insist that they must provide supporting evidence from real-world tests.”

On the one hand, this means that community bodies who are offered submissions in this vein should demand the submitters produce the evidence and not rely on vague statements or claims. In particular, they should be wary of the use of “the precautionary principle” – unless there is enough evidence to suggest that it is applicable.

On the other hand, it means that if submitters do produce “evidence” that it must be critically and intelligently examined and not just accepted because it is full of citations. That would be submitting to the “authority” fallacy.

Finally, community bodies should be conscious of their own limitations. If they don’t have the skills for considering presented evidence properly then they should ask for the advice and opinions of real experts about that evidence.

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Anti-fluoridation cherry-pickers at it again

Anti-fluoride campaigners seem to be a sixes and sevens on whether community water fluoridation (CWF) is effective or not. Some will accept CWF is effective in improving oral health but moan about the ethics or reports of harm. Others will simply claim CWF is not effective.Stans-lie-annot

Stan Litras is a Wellington dentist and anti-fluoride campaigner in the later camp. He continually denies that CWF is effective and claims he has science to back up his claim. However, what he actually means is that of he cherry-picks the science, holds his mouth the right way and prevents you from looking at the context and data – he can find a quote to support his position.

I have debunked his claims before in my articles – such as, Cherry-picking and misinformation in Stan Litras’s anti-fluoride article and Cherry-picking and misinformation in Stan Litras’s anti-fluoride article. But he is at it again. This time he is misrepresenting a recent New Zealand research paper in a recent letter to the Christchurch Press.

There are several misrepresentations in his letter but here I will just take issue with the highlighted text. Stan claims:

“The DHB’s Dr Martin Lee published a research paper recently which showed little or no benefit from water fluoridation, a finding consistent with the modern weight of evidence.”

It is always best to check out such claims and I have hunted down the paper Stan probably refers to. It is:

Schluter, P. J., & Lee, M. (2016). Water fluoridation and ethnic inequities in dental caries profiles of New Zealand children aged 5 and 12–13 years: analysis of national cross-sectional registry databases for the decade 2004–2013. BMC Oral Health, 16(1), 21.

This is linked to the full-text version so readers can check out the paper itself.

Far from showing “little or no benefit” from water fluoridation the abstract actually says:

“Significant and sustained differences were observed between Māori and non-Māori children, and between CWF and non-CWF exposed groups.”

Stan ignored that sentence but latches on to (or cherry-picks) the next sentence:

“However, a convergence of dental profiles between non-Māori children in CWF and non-CWF regions was observed.”

But he ignores completely the authors’ discussion of this apparent convergence. Obviously, the discussion doesn’t support Stan’s anti-fluoride bias! But that discussion is interesting and worth considering.

Is there a convergence?

I have noted this convergence before in my articles Cherry picking fluoridation data and Fluoride debate: Response to Paul’s 5th article where I used similar data to that used in Schluter & Lee (2016). That data is available on the Ministry of Health’s website.

The graphs below show the raw data for all (“total”) children and for Māori:



So, yes, there is a convergence in the sense that the differences in the oral health of children in fluoridated and unfluoridated areas appears to be reducing with time. I have speculated that the apparent convergence could have something to do with the introduction of “hub and spoke” dental clinics after 2004. One problem with this raw data is that children are allocated according to the fluoridation status of thew school – rather than their residence. This will lead to incorrect allocation in some cases.

However, this paper suggests another reason for the convergence which I hadn’t considered.

Changes in and composition of the non-Māori group

The authors say:

“Another notable feature was the apparent convergence of prevalence estimates amongst non-Māori children in CWF and non-CWF areas. It is likely that a substantial driver of this convergence was due to significant changes within the dynamic and heterogeneous non-Māori groups both within and between DHB regions. In effect, the ecological fallacy – a logical flaw whereby analyses of group data are used to draw conclusions about an individual – may be operating within the non-Māori group.”

This is interesting and is supported by the data.

First, let’s note that while I compared data for Māori children with the total data in my figures above these authors have actually compared data for Māori and non-Māori. This shows a clearer convergence for non-Māori children than for all children – see this figure for 5-year-old children from the paper (dmft = decayed, missing and filled teeth per child):


Fig. 1 No obvious decay experience (caries-free) percentages and mean dmft for 5-year old children over years 2004 to 2013, partitioned by Māori and non-Māori ethnicities and fluoridated (F) and non-fluoridated (NF) areas

The picture is similar for year 8 children.

So you can see why anti-fluoride campaigners would love to cherry pick the non-Māori data. I predict that Stan and other anti-fluoridation campaigners will be reproducing parts of this figure in their propaganda for future use.  That graph is just too good for them not to cherry-pick.

But we need to remember that the non-Māori group is not ethnically uniform. In particular, Pacifica make a large contribution to this group. That contribution is unevenly distributed between the fluoridated and fluoridated groups. And it has changed over time.

  • In 2013 about 86% of Pacific live in fluoridated areas – over the period covered by these MoH records this proportion has varied between 80 and 90%.
  • In 2013 Pacifica make up about 12% of the non-Māori group (between 2007 and 2o13 this has varied between 9.0 and 12.7%)
  • In 2013 Pacific make up about 19.3% of the non-Māori fluoridated group (between 2007 and 2013 this has varied between 14.9 and 20.7% of the non-Māori fluoridated group).

MoH data confirms problem of Pacific inclusion

So the oral health of Pacifica can have a relatively large influence on the data for the non-Māori group – particularly for the fluoridated non-Māori group where they are included. This becomes important when we realise that the oral health of Pacifica is markedly poorer than for the rest of the non-Māori group. I have illustrated this using the average of data for fluoridated 5-year-olds in the period 2007 – 2013.


Data for 5-year-old children. dmft = decayed, missing and filled teeth. The “other” group is non-Māori and non-Pacifica

So the poorer oral health of Pacifica will drag down the % caries free and drag up the mean dmft data for the fluoridated non-Māori group. However, this will have little influence on the unfluoridated non-Māori group because of the very small Pacific contribution.

We can confirm this with the raw data from the Ministry of Health website. That data is given separately for Māori, Pacifica and “other” (non-Māori/non-Pacific). The figure below shows this data for the 5-year-old children.


Comparison of data for “other” (non-Māori/non-Pacifica) children in fluoridated (F) and unfluoridated (UF) areas.

OK – there is still some evidence of convergence from about 2007 on between fluoridated and unfluoridated children. But the graphs do indicate that CWF is still having  a beneficial effect.

But I think Stan and his mates will prefer to cherry-pick the data for the non-Māori group and keep very quiet about the distorting effect that inclusion of Pacific in this group has had on the apparent convergence.

Note: I have used the raw Ministry of health data in this discussion. Schluter & Lee (2016) used standardised estimates to account for the difference in the numbers of unexamined children according to ethnicity.

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