Category Archives: Science

“Do your own research!”

How many times have I had discussion partners on the internet say to me “Do your own research?”

Inevitably they are pushing some pseudoscientific or anti-scientific conspiracy theory – yet claiming science is their friend!

Here, one of the members of Paul Connett’s Fluoride Action Network team ( Carol Kopf, Media Director who uses the Twitter name @nyscof) tells critics to do their own research – internet research:

And if you type in fluoride adverse effects, you get 270 results

Well, I followed her advice and got this:

Fluoride adverse effects – PubMedScreenshot-fluoride

But unlike Carol Kopf I naturally didn’t stop there – I also typed in “water adverse effects” and got this:

Water adverse effects -PubMed

She has a really funny understanding of what the word research means.

Imagine if she followed her implied advice and refused to consume water because of all its adverse effects!

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Let’s rely on anecdotes instead!

Image credit: Saturday Morning Breakfast Cereal.

This satirical piece from The Shovel highlights an unfortunate way many politicians (mainly US and Australian)  and internet propagandists approach scientific matters – relying on anecdotes and not evidence. It is also true of many blog commenters.

Science To Be Replaced By Anecdotes

Australia’s scientific research programs will be cut back and replaced by a recent experience the guy down the shops had, it was revealed today. A government spokesperson said it was a move to a more common-sense approach to research and development. “Roger, who I bumped into just the other day, told a pretty pertinent story about how he’d seen first hand just how powerful anecdotes can be,” the spokesperson said. “I think it would be unwise and, frankly, disrespectful, to dismiss his opinion out of hand”.The spokesperson said the Coalition wanted to avoid the dangerous precedent set by previous Governments whereby science was left to professionals and experts. “Scientists have a right to an opinion too. But let’s not forget the various other equally valid views and opinions in the community”.

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Emotion Drives Decision


Image Credit: Gaping Void

So true.


Anti-fluoride activists unhappy about scientific research

Mark Atkin (“Science and legal advisor” for FFNZ) and Mary Byrne (“National Co-ordinator and media contact” for FFNZ) promote their “magic” fluoride free water.

These activists have a really weird understanding of science and the nature of scientific research. How’s this for press releases from the NZ Fluoride Free Science and Legal Advisor, Mark Atkin:

1: Rubbishing a planned review of the published science around fluoridation by Sir Peter Gluckman (the Prime Minister’s Chief Science advisor) and the NZ Royal society. Mark declares the review is “totally one-sided” and that Gluckman admits this (see Secret Fluoridation Review Totally One-Sided Admits Chair)!

And what is Atkin’s “evidence” for that? Well Gluckman did say:

“this is just straightforward scientists reviewing what’s in the peer reviewed literature about what we know about the safety and efficacy of fluoride in water. It is reviewing the scientific literature.”

And Atkin chose to distort that to mean:

This “‘review’ of water fluoridation will only look at research that supports fluoridationists’ belief in ‘the safety and efficacy of fluoride in water’, says Sir Peter Gluckman, co-chair of this thereby-admitted ‘kangaroo review’.
It is no wonder that scientific studies showing water fluoridation is neither safe nor effective have not been sought for this bogus ‘review’.”

Mark Atkin seems to have a serious comprehension problem.

2: Claiming Waikato University is commissioning research to obtain  predetermined conclusions.

The same day Atkin produced another press release (see Predetermined ‘research’ outcome commissioned by Waikato Uni). He certainlychurns out press releases even if their quality leaves a lot to be desired.

The specific project Atkins is upset about plans to look in detail at:

“nearly 1700 publicly accessible submissions to the Hamilton City Council on the initial decision to remove flouride from Hamilton’s city water supply with a view to tracing interests and other links to private interests and public lobbying groups.”

Rather than making assumptions about the outcome, the research is aimed at establishing if there were links and their extent. The title of the project is “Public Integrity and Participatory Democracy: Hamilton
City Council’s Water Fluoridation Decision.” Surely it is in all our interests to determined how effective our participatory democracy works at the local body level.

Given that the anti-fluoridation activists often claim our democratic processes are distorted by groups like the District Health Boards I would have thought they would welcome this research. Mind you, they may prefer to leave that particular claim unchecked by objective analysis and actually be far more scared of what an objective analysis of the process reveals about their own manipulation and links to private commercial interests and lobby groups.

Isn’t that weird. A “science advisor” who interprets a scientific review “about the safety and efficacy of fluoride in water” to mean that “scientific studies showing water fluoridation is neither safe nor effective” will be excluded! And that research aimed at tracing interests and links of submitters to commercial and lobby groups will only produce a results claiming the links exist without considering any evidence.

Perhaps this is the way Mark Atkin thinks scientific investigations should happen. Perhaps this is the way the “world fluoridation experts” he idolizes, like Paul Connett and Declan Waugh, carry out their “investigations.”

But it is certainly not the way genuine scientific investigations are done.

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“Creative” reporting of fluoridation science


I am all for genuine creativity in science, and elsewhere. But some people seem to think anything goes when the are promoting their ideology or political views.

Again and again I come across campaigners , especially in areas like “natural” health, climate change denial and promotion of creationism, who seem to think “creative embellishment – or outright distortion – is OK when claim that science is “on their side.”

Here’s a typical example from Fluoride Free NZ (FFNZ) who are attempting to deny the science indicating that fluorosilicates used for fluoridation of water supplies decompose to form the fluoride anion. They are desperate to assert that fluorosilicate species remain and these “might” be toxic.

FFNZ cites the National Toxicology Program (NTP), part of the US Department of Health and Human Services. But puts words into their mouths to create exactly the opposite conclusion to tat which should be taken from that web site.

According to FFNZ:

the NTP “says the assumption that fluoridation chemicals disassociate into free fluoride ions is not supported by experimental evidence. This is good to remember when the fluoridationists claim that fluoride, is fluoride is fluoride. They are operating on belief rather than scientific fact.”

But the NTP says nothing of the sort. The page simply lists a 1999 nomination, from a “private individual”, for research to consider possible toxicity. Yes, the “private individual” gives as grounds “lack of toxicity information; assumed complete dissociation to free fluoride under normal conditions of use not supported by experimental evidence.” But that is the view of the nominator – not of NTP.

In fact, the NTP has a statement making clear that selection of an agent for study does not imply support for the nominators views:

” Selection of an agent for a study does not imply that the agent is hazardous or a potential carcinogen in laboratory animals; likewise, an agent not selected for toxicologic study by the Program should not be taken to mean that the agent is not potentially hazardous or potentially carcinogenic in laboratory rodents.”

Interestingly the cited web page includes “The following information related to “fluorosilicates  “including history from earlier or later nominations for this same agent.” Specifically  Nomination Background a pdf document “Review of Toxicological Literature.” It is a comprehensive review, but on page 4 it says:

“In water, fluorosilicic acid readily hydrolyzes to hydrofluoric acid and various forms of amorphous and hydrated silica. At the concentration usually used for water fluoridation, 99% hydrolysis occurs and the pH drops to 4.2. As pH increases, hydrolysis increases. At the pH of drinking water, the degree of hydrolysis is “essentially 100%” (Crosby, 1969; Urbansky and Schock, 2000).

H2SiF6(aq) + 4 H2O    →    6 HF(aq) + Si(OH)4(aq)”

Exactly the opposite of what FFNZ assert!

Now who is ” operating on belief rather than scientific fact.”

A clear example of extreme confirmation bias amounting to complete distortion.

For more information on the science of the decomposition of fluorosilicates in water have a read of Declan Waugh’s misinformation on fluorosilicic acid and An open letter to Declan Waugh – new mechanism for fluoride toxicity?

Credit: Thanks to Duane for the image.

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There is research and there is “research”


I saw this image on Facebook yesterday and it really resonated with me. I had just been to the Hamilton City Council hearings on their draft annual plan. The anti-fluoride brigade dominated the session.

Many of their submitters proudly declared they had “researched” the subject and found fluoride is really nasty. They were eager to present their “research” findings to the council.

I have long been concerned that many people have cheapened the word “research” by the way they use it. Reading ideologically motivated web sites and magazines is not real research – yet it seems to drive the anti-fluoride community and provide a hubris that they are somehow doing “research.”

By the way, I presented a submission for the making Sense of Fluoride group. Download the linked pdf file if you want to read it.

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Fluoride debate: Why I support fluoridation – Response from Connett

This is Paul Connett’s response to Ken Perrott’s article – Fluoride debate: Why I support fluoridation.

I think your opening statement certainly gives us a perspective from where you are coming on this issue Ken and that is helpful.

I am very glad that you put “having an open mind” and “relying on science” as your key tools for resolving controversial issues like fluoridation. I believe that once you have got over some negative impressions that you have had with some people opposed to fluoridation, that you will find that having an open mind and relying on the best science will inevitably lead you to rejecting fluoridation and to see it as the misguided practice it is. But we shall see.

As far as the case you present I find it very, very short on science. Basically you argue that fluoride is needed to react with our bio-apatites and make them stronger, less soluble and in the case of teeth less vulnerable to tooth decay. You offer no scientific evidence that interaction with the bones is beneficial and can be achieved without damage to the bone or the connective tissue.

Your case as far as the teeth are concerned seems to boil down to the need to put fluoride in the drinking water so after passing through the whole body it ends up in our saliva and that this is the delivery system which reduces tooth decay. Two questions: 1) Why do you feel that this is more rational and suitable than treating the tooth enamel more directly with topical treatments like fluoridated toothpaste?  2) If you reject topical treatment for some reason and you insist the fluoride must be swallowed to be effective why don’t you use a more appropriate way of delivering fluoridated water, i.e. in one liter bottles at 1 ppm and prepared with pharmaceutical grade sodium fluoride?

I asked this latter question at the end of section 1A but in your response you did not answer. So may I ask it again?  Would not this delivery system provide, 1) a better control of the dose, 2) a far better control over the purity of the chemical used and 3) would not force this human treatment on people who don’t want it. Nor would it involve giving up on the central dogma of water fluoridation. Surely this would be a win-win situation for everyone?

On the ethical front, you stress the need to help disadvantaged children. No argument there from me. But what if your chosen method actually further disadvantages these children and their families? What for example are parents in low-income families supposed to do if they don’t want their children to drink fluoridated water? Haven’t you trapped these families with this policy? Moreover, are you not aware of the extensive literature from India that fluoride’s toxic effects are more serious for people with poor nutrition (low protein, low vitamins and low calcium – see the early work from Pandit et al., 1940 and the more recent animal studies from Chinoy, NJ – see the FAN bibliography for full citations, Aren’t children in disadvantaged communities more likely to have poor nutrition?

Scotland, which has no fluoridation, has found a simple and cost-effective alternative way of fighting tooth decay as this recent BBC Scotland report indicates (

 “A scheme to encourage nursery children to brush their teeth has saved more than £6m in dental costs, according to a new study.

Childsmile involves staff at all Scottish nurseries offering free supervised toothbrushing every day.

Glasgow researchers found that the scheme had reduced the cost of treating dental disease in five-year-olds by more than half between 2001 and 2010.

The programme was launched in 2001 and costs about £1.8m a year.

It emphasises the importance of toothbrushing and helps parents establish a healthy diet from the earliest stage.

A number of nurseries and schools in targeted areas also provide fluoride varnish and toothbrushing in primary one and two.

An evaluation, funded by the Scottish government and carried out by Glasgow University, found that fewer children needed dental extractions, fillings or general anaesthetics as a result of the programme.

‘Less toothache’

There was also said to be a drop in the number of children needing hospital treatment for dental problems, freeing up operating theatres.

Public Health Minister Michael Matheson said: “This is an amazing achievement and shows just how much can be saved from a very simple health intervention.

“This has seen less tooth decay in children which means less toothache, fewer sleepless nights and less time off school.

“By this simple measure, NHS costs associated with the dental disease of five-year-old children have decreased dramatically.

“More children can just be treated routinely in the dental chair because they need less invasive treatments, so fewer fillings and fewer extractions, and many more children with much better oral health than we have seen in many years.”

For the second time you state your concerns about, “Unwarranted extrapolation from studies done at high concentration” which you say are “a dime a dozen and worthless in this debate.”

Last time you brought this up I responded by showing that several human IQ studies were not done at high concentrations. For example, in nine of the 27 IQ studies  reviewed by Choi et al (2012), the high fluoride village was at 3 ppm or less. I also went into more detail on the study by Xiang et al. (2003a,b) who found a threshold at 1.9 ppm for this effect.

In my discussion on this point I stressed the difference between concentration and dose and the need to consider a margin of safety calculation to protect for the full range of expected sensitivity or vulnerability in a large population when extrapolating from a small human study of a fairly homogeneous population. Thus extrapolating from Xiang’s study we find that there is absolutely no margin of safety to protect either for the range of exposure to fluoride in an American or NZ population or for the full range of sensitivity expected in any large heterogeneous population. This latter calculation is particularly important for your major concern – disadvantaged children – because that is almost certainly where you will find the most vulnerable in this regard.

When we embarked on this exercise I thought that this was going to be an exchange between yourself and me, but I am finding that you do not want to restrict yourself to my arguments but want to argue against all the arguments thrown at you by people opposed to fluoridation. That has a place of course but it was not what I was expecting. In my view it serves to distract and muddy the waters.

I wish you had taken a more disciplined approach and focused entirely on the arguments I have put forward. In this respect it is unfortunate that when you were educating yourself on this issue you did not take advantage of reading the book I co-authored with two other scientists, James Beck, MD, PhD and Spedding Micklem, DPhil (Oxon). There we spelled out the case in a cool, calm and collected way with every argument backed up with citations to the scientific literature. As you know – but your readers may not – I sent you a pdf copy of this text. By so doing, I had hoped that we could keep this debate tightly focused; that I could defend my own arguments (and there is plenty enough of those) and not have to keep considering those of others.

Your readers might also not know that shortly after this book was published (Oct 2010) I was invited in early 2011 to meet with staff of the Ministry of Health in Wellington. About 20 people were there from the Ministry and some of their advisers. I carefully went through the arguments in the book and asked them at the end of my presentation to provide a written response to the book showing where I was wrong and providing the science that supported their critique. I added that if they could not do this with all the resources and personnel at their disposal then they should not continue to promote this practice. After nearly 3 years I still have not received that written critique.  Meanwhile, personnel from this Ministry, including the Minister himself, continue to promote the practice and even accuse opponents of distorting the scientific arguments – with no specific examples to which someone like myself could respond.

Blanket condemnation of opponents gets us nowhere. Nor does it help to keep knocking down straw dummies. The debate will only be seriously engaged when the proponents begin to put forward and defend the studies that have convinced them that fluoridation is both effective and safe – and safe for everyone. This is what opponents like myself have done. This was what I was expecting from you Ken when you got the opportunity to put forward your case. Surprisingly, you gave no scientific citations at all.  Hopefully, these will come later.

Rather than take up any more space at this point I will wait for part 2 of your case, where I hope you will present some science to support this practice.

While you are doing this I will prepare my response to your response to my section 1A.


Choi et al., 2012. Developmental fluoride neurotoxicity: a systematic review and meta-analysis. Environ Health Perspect 120:1362–1368.

Pandit et al., 1940, Endemic Fluorosis in South India, Indian Journal of Medical Research 28, no. 2: 533–58.

Q. Xiang, Y. Liang, L. Chen, et al., “Effect of Fluoride in Drinking Water on Children’s Intelligence,” Fluoride 36, no. 2 (2003): 84–94, .

Q. Xiang, Y. Liang, M. Zhou, and H. Zang, “Blood Lead of Children in Wamiao-Xinhuai Intelligence Study” (letter), Fluoride 36, no. 3 (2003):198–99, .

Anyone wanting to follow the debate and/or check back over previous articles in the debate can find the list of articles at Fluoride Debate.

See also:

Similar articles on fluoridation
Making sense of fluoride Facebook page

Fluoridation – the IQ myth

fluoride_kills_test (1)Some of the myths promoted by anti-fluoridation activists really are of the “unsinkable rubber duck” variety. No matter how many times they are debunked they keep being repeated.

If you follow the fluoridation debate at all you will have come across the “Harvard Study” “proving” fluoride makes you dumb. It is often associated with the claim that the Nazis used fluoridated water supplies in their concentration camps to distract the inmates. Some will even claim that this is the purpose for fluoridation in the US!

I haven’t dealt with this particular myth yet, but really can’t do better than repeat this post from the US Life is Better with Teeth web site. (By the way, this is an excellent source of information on the fluoridation issue). The article is Fluoride and IQs

In July 2012, anti-fluoride activists circulated an article from a journal called Environmental Health Perspectives (EHP) to support their claim that fluoride lowers IQ scores in children. There are several reasons why the claim being made by opponents lacks credibility.

  • The EHP article reviewed studies on IQ scores for children living in areas of China, Mongolia and Iran where the water supplies have unusually high, natural fluoride levels. In many cases, the high-fluoride areas were significantly higher than the levels used to fluoridate public water systems in the U.S. In fact, the high-fluoride areas in these countries reached levels as high as 11.5 mg/L — more than 10 times higher than the optimal level used in the U.S.
  • This article offers a meta-analysis, and its credibility hinges on whether good-quality studies are reviewed. Yet the article’s co-authors admit that “each of the [studies] reviewed had deficiencies, in some cases rather serious, which limit the conclusions that can be drawn.” Although the studies compared high-fluoride with low-fluoride areas, the authors acknowledge that “the actual exposures of the individual children are not known.”
  • The two Harvard researchers who reviewed these studies have distanced themselves from the way in which anti-fluoride activists have misrepresented their article. After contacting these researchers, the Wichita Eagle newspaper reported, “While the studies the Harvard team reviewed did indicate that very high levels of fluoride could be linked to lower IQs among schoolchildren, the data is not particularly applicable here because it came from foreign sources where fluoride levels are multiple times higher than they are in American tap water.”
  • The Harvard researchers wrote in their article that the average standardized mean difference (0.45) in IQ scores “may be within the measurement error of IQ testing.” Despite web pages claiming that the article ”confirms” that fluoride reduces IQ scores, the Harvard co-authors did not reach a firm conclusion, writing instead that “our results support the possibility of adverse effects …” Indeed, their article called for more and better-quality research, including more “precise” data on the children involved and assurances that other factors have been ruled out as reasons for the IQ differences.
  • Given the small difference in IQ scores, it’s possible that arsenic levels, school quality, nutrition, parents’ educational levels or other factors could have shaped the results. The authors also added that “reports of lead concentrations in the study villages in China were not available”— another factor that could not be ruled out. A Britishresearch team reviewed similar Chinese studies, found “basic errors” in them, and reported that “water supplies may be contaminated with other chemicals such as arsenic, which may affect IQ.”
  • Between the 1940s and the 1990s, the average IQ scores of Americans improved 15 points.  This gain (approximately 3 IQ points per decade) came during the same period when fluoridation steadily expanded to serve millions and millions of additional Americans.

See also:

Similar articles on fluoridation
Making sense of fluoride Facebook page
Fluoridate our water Facebook page
New Zealanders for fluoridation Facebook page

Activists peddle chemical misinformation for fluoridation referenda

The propaganda produced by anti-fluoridation activists reminds me of this cartoon.


There are just so many examples of this in a flyer produced by the Fluoride Action Network of NZ (FANNZ) for the upcoming fluoridation referenda in Hamilton, Whakatane and Hastings. Here is just one small section describing the fluoridating chemicals used in New Zealand.


They are, of course, referring to the most commonly used fluoridating, chemicals –  fluorosilicic acid and sodium fluorosilicate. I have written about these chemicals, and the FANNZ misinformation on them before – see Fluoridation – are we dumping toxic metals into our water supplies?,  Water treatment chemicals – why pick on fluoride?  and Hamilton – the water is the problem, not the fluoride! .

The claims on the flyer are just misleading, if not outright lies. Just in the extract above (only a small part of the flyer):

1: Fluorosilicic acid is a by-product of the fertiliser industry in New Zealand. There is a market for that chemical (if only a relatively small one in New Zealand because we don’t have a fluoride industry) so it is not waste.  Sure, in its concentrated form it is corrosive and toxic – as are all such chemicals. Including those used in water treatment like chlorine, sodium hydroxide, aluminium sulphate, etc. (see Water treatment chemicals – why pick on fluoride? ).

2: No, it is not food grade, neither is the chlorine, sodium hydroxide and alum used in water treatment. Because they aren’t used in foods – especially at those concnetrations.

3: Contamination with “mercury, arsenic, lead, cadmium and other heavy metals” is extremely small (see Fluoridation – are we dumping toxic metals into our water supplies?,  Water treatment chemicals – why pick on fluoride?  and Hamilton – the water is the problem, not the fluoride! ). Regulations define permissible levels of contaminants in our water supply and the chemicals used to treat it. They are based on known health risks of such chemicals and include large safety factors.  Suppliers must fulfill these requirements, and provide certificates of analysis from independent laboratories, or the material is rejected.

Here is an example of the data from a Certificate of Analysis for a batch of fluorosilicic acid supplied to the Hamilton City council earlier this year:


Those levels of heavy metals are extremely low. FANNZ has access to this information – a copy of this certificate was supplied to the local FANNZ representative by the Hamilton City Council. So why do they persist with this lie about contamination with toxic heavy metals?

4: No, it is not the same as naturally occurring calcium fluoride (CaF2). But when diluted in water fluorosilicic acid and the fluorosilicate anion decomposes to form the fluoride anion (F) and silica.


The reaction is driven to completion by removal of SiO2 from solution. The fluoride anion is exactly the same as that in calcium fluoride and a solution of dissolved CaF2. It is the F species which provides the beneficial action to teeth and bones.

5: No it has never been tested for human safety at the low concentrations used in water fluoridation – for a very good reason. You can’t prepare a solution of fluorosilicic acid at these low concentrations because of its decomposition (see equation above). But, because it is hydrolysed to form F, safety studies carried out with fluoride solutions prepared from chemicals like sodium fluoride and CaF2 are completely relevant. Remember, the fluoride anion is the fluoride anion, whatever its origin.

Chemical confabulation

Anti-fluoridation activists are nothing if not faithful to their story. They perform all sorts of difficult mental gymnastics when confronted with the facts above. Some of them will invent anything to deny these facts. For example:

Claim 1: The fluorosilicate does not decompose completely – it still gets into your drinking water and body. They will even quote Crosby et al (1969) who reported “that sodium fluorosilicate, at the concentration normally present in public water supplies, is dissociated to at least 95%.” The activists choose to interpret “at least 95%” to mean they have 5% to point to, and not representing any margin of error in the data.

There have been a number of studies specifically for checking the completion of hydrolysis of fluorosilicate anion at low concentrations. Although equilibrium measurements indicate complete hydrolysis it was necessary to make sure that kinetic factors did not inhibit the reaction.

Most of these studies were reviewed by Urbansky 2002, in his paper “Fate of Fluorosilicate Drinking Water Additives.” He concluded that all the chemical “rate data suggest that equilibrium should have been achieved by the time the water reaches the consumer’s tap if not by the time it leaves the waterworks plant.”

Similarly, Finney et al (2006) investigated fluorosilicate hydrolysis using 19F NMR and reported their results agreed with “previous findings that at pH ~ 7 and at typical drinking water formal fluoride concentration, hexafluorosilicate dissociation to produce free fluoride ions will be essentially complete.”

Claim 2: Fluoride in natural CaF2 is bound tightly to Ca and the extra Ca acts as “a partial antidote to fluoride toxicity, so, obviously, the statement ‘fluoride is fluoride is fluoride’ is misleading.”

As a chemist I find this confused but several anti-fluoridation activists have made that claim to me. Fluoride exists in solution as the hydrated F anion – not directly connected to a cation as in the solid crystal. Effectively it is independent of the cations in solution. Sure, if there is excessive Ca2+ then CaF2 crystals will precipitate. And other ions could also promote removal of other insoluble products. But in solution fluoride is fluoride is fluoride. It is not influenced by its origin.

Really, this sort of gobbledygook is just an attempt to avoid reality. It is not science.

See also:

Similar articles on fluoridation
Making sense of fluoride Facebook page
New Zealanders for fluoridation Facebook page

Topical confusion persists

I got a little leaflet from the Hamilton City Council the other day – with my rate demand. The leaflet tells me the council has stopped adding fluoride to the city’s water supply, gives some advice on alternative sources of fluoride – and then assures me their decision was all for the best. Because:

“Application by toothpaste and other means that directly affect the tooth surface are much more effective at reduing tooth decay than fluoridation of water supplies.”

Trouble is that is just wrong. I shows the council did not learn anything about the mechanism of fluoride protection against tooth decay from their recent hearings . Worse, they are confused – and are passing on their confusion to their citizens.

I discussed this issue of the topical mechanism in my article Fluoridation – topical confusion. But I guess it bears repeating because the Hamilton City Council is not the only group confused about this. And the anti-fluoridation activists are working hard to spread that confusion.

It’s a topical mechanism –  not application

When the word “topical” gets mentioned in this situation we need to understand clearly this refers to the mechanism of inhibiting mineralisation – not to the method of application. The topical mechanism is the major one preventing decay of existing teeth at all ages, it operates at the tooth surface ( and just below) and relies on having a relatively continuous low concentration of F in the saliva and biofilms on the teeth.

Fluoridated water (and fluoride in our food) participates in that mechanism of protection. Some of the fluoride in the drink and food gets transferred directly to saliva, and thence the tooth surface – during consumption.

Anti-fluoridation activists attempt to confuse the issue by talking about fluoride which is ingested, metabolised and then excreted from the salivary duct at a concentration lower than in fluoridated water. That fluoride has little effect at the tooth surface – because of its low concentration.

It is the fluoride transferred directly to saliva during the act of drinking (or consumption of food) that provides a sufficiently high concentration to have a protective effect. That is, F is transferred to the saliva, and then biofilms, during drinking and eating – something we do regularly. The concentration  in saliva spikes and then declines over an hour or so.

The US Center for Disease Control stresses this mechanism in its  report Recommendations for Using Fluoride to Prevent and Control Dental Caries in the United States:

” . . drinking fluoridated water, brushing with fluoride toothpaste, or using other fluoride  dental products can raise the concentration of fluoride in saliva present in the mouth 100-to 1,000-fold. The concentration returns to previous levels within 1–2 hours but, during this time, saliva serves as an important source of fluoride for concentration in plaque and for tooth remineralization.”

The diagram below portrays this – the fluoride is going directly from the drink and food into the saliva:


Mineralisation and remineralisation = tooth decay

Tooth decay occurs because when the pH at the tooth surface is lowered (this happens bacteria decompose sugars) some of the the calcium hydroxy apatite at the tooth  surface dissolves – mineralisation. With time the pH increases and the reaction is reversed – calcium and phosphate ions at the tooth surface reform as the solid hydroxy apatite (remineralisation).

When fluoride is present at the tooth surface a fluorohydroxy apatite is formed. This is “harder” – it doesn’t dissolve as readily. Consequently the incorporation of fluoride into the tooth surface reduces mineralisation – and enhances remineralisation. It inhibits tooth decay.

It turns out that F in fluoridated water and food does this very effectively. And, because we drink and eat often, dietary forms of fluoride help to maintain a useful concentration of saliva fluoride over time.

Topical application methods (toothpastes and dentrifices) are a supplement to fluoridated water and dietary fluoride, but not a substitute – partly because they are not applied as often (if at all). Even here it seems their mode of operation may be by the formation of CaF2 globules on the tooth surface (because if the high F concentration) which then slowly release their F over time to maintain saliva concentrations at an appropriate level (see the  review article Mechanisms of Action of Fluoride for Caries Control by Buzalaf, Pessan, Honório, and ten Cate JM (2011)).

This topical mechanism which operates with fluoridated water means that the whole population can and does access the “topical mechanism” without thinking about it. Unfortunately the anti-fluoride lobby are spreading a lot of misinformation about the word “topical.” And, now, so is our local City Council.

The dangers of consultation

Hamilton City Councillors came in for a lot of criticism after their shock decision to end fluoridation. In their defence they claim their consultation process (“The Fluoride Tribunal”) gave them then information they needed – and the process was “robust.” (That word “robust” is the latest trendy word at the council these days).

But the fact they are repeating this mistaken description of the topical mode of fluoride protection against tooth decay shows it was far from “robust.” Despite all their efforts – and the large number of submissions, the council got it wrong.

I have watched many of the videos of submissions I know that the group of experts from the Waikato District Health Board and Ministry of Health did explain this topical mechanism. I know they explained it clearly. So why did the “tribunal” get it so wrong?

Here’s a couple of reasons which come to mind:

  1. The expert submissions were swamped by the submissions from anti-fluoridation activists (about 90% of the submissions). Many of those repeated the misleading interpretation of the topical mode of action.
  2. The Council had set itself up as a “tribunal” (my dictionary describes that as a group “with the authority to judge, adjudicate on, or determine claims or disputes.”) They were assuming they had the power, knowledge and ability to make an authoritative judgement of the scientific evidence set before them.
  3. The council appeared to give at least equal credence to “both sides” – councillors often referred to hearing evidence from “eminent experts on both sides.” Apparently an academic title was enough to show credibility in the eyes of these councillors – no attention being paid to the submitters background, specialisation or research experience.
  4. Worse, some of the councillors appeared to give more credence to the anti-fluoridation submitters than the District Health Board and Ministry of Health experts. A telling comment from one councillor was his reference to attempting to balance information from “experts who do no research and non-experts who do all the research.” His concept of research seemed to be internet Google searching and listing multiple but unsubstantiated claims. I experienced hostility from several councillors who were very dismissive of any reference to science.

It seems to me the sort of consultation set up by the Hamilton City Council was poorly thought out. It should never have been seen as a “tribunal” set up to make judgments about the science of fluoridation or possible health problems. The council members just do not have the scientific ability – or indeed the necessary skills in critical thinking, to make judgements in such a complex area. They could not produce a decision reflecting the best judgment of the evidence – and indeed they didn’t. Their document purely listed common arguments presented by submitters. There was no assessment of credibility, evidential support or confirmation.

If an assessment of the current science around fluoridation was really required then this should have been done by appropriate professionals – not politicians. The council should have relied on such an expert review, or in its absence, the recommendation of the proper experts. Instead they set themselves up in judgment of the complex science – and took evidence from some of the most inappropriate sources.

In the end, a referendum at the next local boy elections was the only way to resolve the pickle they had got themselves in to. Hopefully the new council will not make the same sort of mistakes about fluoridation advice.

See also:

Making sense of fluoride Facebook page
Other Fluoridation articles