Tag Archives: community water fluoridation

Fluoridation: Whakatane District Council makes the Hamilton mistake

Whakatane-DC-logo

Here we go again.

The Whakatane District Council has ignored the results of their own referendum and decided to stop community water fluoridation (CWF). (see Council votes to stop fluoridationand Whakatane mayor stands by fluoride decision).  This mirrors almost exactly the behaviour of the Hamilton City Council three years ago.

But are the Whakatane councillors (or, at least, the 6 who voted to stop CWF) so short of memory that they did not learn from the Hamilton experience? There the decision resulted in protests and petitions, eventually forcing the council to hold yet another referendum at the end of 2013. That showed, once again, clear support (about 70%) for CWF and the council later reversed their decision.

A thoroughly bad experience for that council and a humiliating one for the city. We had the picture of council politicians pretending to know better than the health and scientific experts and attempting to impose their own ideologically motivated position on the voters. It got so silly the council even issued their own leaflet providing oral health advice – advice which was out of step with that issued by health authorities!

Councils ignore voters wishes at their own peril. The Whakatane District Council anti-fluoridationist Mayor, Tony Bonne, justified his move by referring to the low voter turnout in the referendum. Are we to take it that if he loses the next election he will ignore that result and refuse to step down because of the low voter turnout?

Referendum results

The 2013 referendum in the Whakatane District showed that 60.5 per cent of those who voted were in favour of fluoridation, with 39.5 per cent against. However, in the only areas currently fluoridated – Whakatane City and Ohope – support for CWF was even greater – 65.8 per cent and 70.5 per cent respectively. The council is surely silly to ignore that vote without a good reason.

“We listened to the experts.”

Mayor Bonne declared “we listened to the experts” before making the decision. But who the hell were these experts?:

Supporting CWF –  Dr Neil de Wet of Toi Te Ora Public Health and local dental practitioner John Twaddle. OK, these people seem to have some qualifications to be described as “expert.”

Opposing CWF – Mary Byrne and Jon Burness of Fluoride-Free New Zealand. What expertise do these people have? – why should their word be accepted?

Well, they are both activists, belonging to the local activist group which is a chapter of the US Fluoride Action Network. That body is financed by the “natural”/alternative health industry – particularly by the Mercola on-line business.  (Local anti-fluoride actions, such as those in the High Court, have similarly been financed by the NZ health Trust – the lobby group for the local “natural”/alternative health industry. See Who is funding anti-fluoridation High Court action? and Corporate backers of anti-fluoride movement lose in NZ High Court).

Mary has no expertise I know of except her activism. Jon is an alternative health practitioner and business person. He specialises in kinesiology and is a member of the  Society of Natural Therapists and Researchers, NZ. As part of his business he runs the Whakatane Natural Health Centre.

Whakatane Natural Health Centre …… bringing together a comprehensive range of therapies for mind, body and soul. Kinesiology, Massage Therapy, Bowen Tech, Hypnotherapy, Lymphatic Drainage, Herb and Allergies, Acupuncture. – See more at:

OK, everyone has to make a living and I do not want to question the sincerity of either Mary or Jon.

But experts!! Tony Bonne is disingenuous to use that word. He should be representing his voters, not the alternative woo merchants, whatever his own personal ideological beliefs. It is a sad day when we elect councillors (or at least the six who voted for Bonne’s resolution) who cannot differentiate between acceptable scientific and health experts  on the one hand and ideologically driven activists and alternative “practitioners” using very questionable techniques on a gullible public on the other.

Councils not appropriate for fluoridation decisions

Mayor Bonne did, however, make sense with his statement that it should not be left to local bodies to make public health decisions and he would welcome stronger direction from central government. In that he actually agrees with Daniel Ryan, President of the Making sense of Fluoride group who said:

“There is just no excuse any more for John Key’s government to keep making councils juggle the expensive and diversionary hot potato. They want councils to focus on core business and be fiscally responsible – and they say they care about children’s health. With one simple measure on fluoridation they could have a really meaningful impact on all of that.”

The ball is in the government’s court on this issue – and has been for several years since local bodies formally asked central government and the Ministry of Health to take responsibility for decisions on CWF. There is really no excuse to leave this with councils whose decisions are so easily clouded by ideology and personal ambitions that they, or at least some of the council members, will happily ignore the advice of the real science and health experts and the wishes of their voters.

See also: Government considers fluoridation law change

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New study finds community water fluoridation still cost effective

Cyber-The-Vote-Cost-Benefit-Analysis-1A new report on the cost effectiveness of community water fluoridation (CWF) confirms it is still effective. The report is:

Ran, T., & Chattopadhyay, S. K. (2016). Economic Evaluation of Community Water Fluoridation: A Community Guide Systematic Review. American Journal of Preventive Medicine.

This study is a systematic review of the literature.  A total of 564 papers were identified, but after excluding studies which didn’t fit the inclusion criteria, this was whittled down to ten studies (8 peer-reviewed journal articles and 2 reports) published in the period 2001 – 2013. The studies were located in Australia, USA, Canada and New Zealand.

Intervention costs

The review found:

“Per capita annual cost ranged from $0.11 to $4.92 in 2013 U.S. dollars for communities with  >1,000 population. The variation in per capita annual cost was mainly attributable to community population size. Specifically,
per capita annual cost decreased as population size increased, after adjusting for factors such as discount rate.”

And

“per capita annual cost was the highest when population size was around 1,000. As community population size increased, per capita annual cost decreased. In particular, per capita annual cost for communities with >20,000 population was <$1.”

 

Intervention benefits

The caries reduction reported in the reviewed studies ranged from 15 – 33%.per capita annual benefits ranged

Intervention benefits included averted healthcare costs and productivity losses. The per capita annual benefits reported in these studies ranged from $5.49 to $93.19

Benefit-cost ratios

As would be expected the reported benefit-cost ratios varied with population size – ranging from 1.12 to 57.21.

So, the authors’ conclusion was:

“In summary, benefit–cost ratios were larger than 1.0 for communities of at least 1,000 people, indicating that CWF was cost beneficial for communities with no fewer than 1,000 people.”

Possible issues

The authors list a number of issues for consideration in future studies of this issue. Interestingly these include two that anti-fluoride campaigners argue have been ignored:

Cost of fluorosis: The authors say this should be included “if there is clear evidence of severe dental fluorosis.”

The only study to have included such costs is that of Ko & Theissen (2014). They included costs of repair or severe dental fluorosis – despite there being no evidence that CWF causes either moderate or severe dental fluorosis. Ko and Theissen made no attmept to justify inclusion of this cost and the “mistake” is not doubt due to the well-known anti-fluoride sympathies of Theissen (see Alternative reality of anti-fluoride “science” for a discussion of this paper).

Political costs: The authors give as an example “expenses associated with promoting CWF.”

Of course, this would also include the legal and referendum costs we have seen imposed on New Zealand local bodies over the last few years. But it should also include the private costs of those who campaign for and against CWF and the larger corporate costs of bodies like the NZ Health Trust which has initiated unsuccessful High Court action. The NZ health trust is a lobby group for the “natural”/alternative health industry and their costs no doubt eventually get passed on to the consumers of their products and services.

It would be interesting to see the breakdown of such political costs for different countries and regions. I imagine it would be hard to predict what these costs could be in an individual situation. Although I can appreciate local bodies may feel obliged to budget for such costs.

And I wonder if one should include the cost of legal justice and democratic consultation in a cost-benefit analysis. This could lead to people questioning parliamentary elections or their rights to challenge corporations and criminals in the courts.

Should anti-fluoride campaigners do their own cost-benefit analysis?

It’s a simple fact that anti-fluoride campaigners lose more of their struggles than they win – even in the USA. It’s also a fact that they see the threat of imposition of legal and consultation costs as a way of pressuring local bodies to avoid the issue. But, I wonder if they have ever undertaken a cost-benefit analysis on their own activities.

For example, given the failures of the High Court action by the campaigners over recent years and the lack of success in referenda held in New Zealand in 2013 and 2015 perhaps they should do a few “back of the envelope” calculations.

If they want to personally enjoy drinking water that is “fluoride free” then what is the most reliable intervention they could apply to achieve that benefit.

Consider two scenarios:

1: A political approach. The costs of referendum and consultation campaigns, their personal loss of income and free time in making submissions, organising Paul Connett’s Southern hemisphere holiday tours of New Zealand and Australia. Consider also the costs to the “natural”/alternative health industry in their taking and sponsoring legal actions.  Balance this against the very low likelihood of success – and possibly also consider the negative result of social criticism and discrediting that may represent a financial loss to those who run businesses or are practitioners in the “natural”/alternative health industry.

2: A personal responsibility approach. The cost of  purchasing a relatively cheap and effective water filter to lower the F concentration in their tap water. The capital cost would be a few hundred dollars per household and the annual costs would not be large. In fact, the NZ Health trust may help lower these costs by reinvesting the money they would otherwise lose in paying for unsuccessful court actions. The benefits would be immediate and clear. They would get the “fluoride free” water they have demanded. They would have a lot more free time to devote to their families and businesses. And they would not get the current condemnation they get from local body politicians and voters who resent the increased costs their actions have caused in the past.

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Fluoridation: Some simple chemistry

I often get comments about the chemistry of community water fluoridation which make clear the need for a simple explanation of some of the chemical concepts involved.  Here is an article I wrote some time ago on this but, for the life of me, I cannot remember where I put it on-line. So, I might be repeating myself – but, at least, it makes the article available. (t can also be downloaded as a pdf – just click on the title


Some chemistry issues involved in the fluoridation debate

Some claims made by critics of community water fluoridation (CWF) are chemically wrong. However, they may seem convincing to people without a chemical background.

Here I discuss some of the chemistry involved in the fluoridation debate and show how these claims are wrong.

What happens when a solid dissolves in water?

dissolving crystalIn a solid like ordinary salt (NaCl) the atoms exist as positively (Na+ cations) and negatively (Cl- anions) ions in a rigid lattice structure. This structure is generally stable as the ions are held together by electrostatic forces. But the structure can often be disrupted by water. The water molecular (H2O) is polar – it has a negatively charged end (the O atom) and a positively charged end (the H atoms).  These ends are attracted to the oppositely charged ions, surrounding them and bringing them into solution.

Once in solution, the ions are free from the rigid lattice and move about by themselves. The cations and anions are randomly mixed up through the volume of solution.

The ions are also hydrated. Depending on the chemical nature of the ion and its charge there may be different numbers of water molecules in the primary hydration shell right next to the ion. But other water molecules are also weakly associated outside the primary shell so we can think of anions and cations in solution as being sheathed by jackets of water molecules.

hydration

Can calcium fluoride exist in solution?

Some people suggest that natural forms of calcium fluoride are not toxic because the calcium modifies the fluoride. But technically there is no such thing as calcium fluoride in solution.

In nature fluoride is usually present as solid fluorite (calcium fluoride) or fluorapatite (a calcium phosphate containing fluoride and other ions). But when calcium fluoride dissolves the ions separate and the resulting solution is a random mixture of hydrated fluoride anions and hydrated calcium cations.

Fluorite (“natural” calcium fluoride) dissolves to form hydrated calcium cations and fluoride anions.

So our “natural” water containing “natural” fluoride actually does not contain calcium fluoride. Calcium fluoride does not exist as a separate species in solution. It contains a random mixture of hydrated fluoride anions and hydrated calcium cations.

We can describe this with the chemical formula:

CaF2  →  Ca2+(aq) + 2F(aq)

Where the (aq) notation identifies the ion as being hydrated in the solution.

What ions are in your drinking water?

In the real world, our “natural” water source contains more than this, though. It contains other ions which have dissolved from minerals or from other sources like rain and runoff.

In reality, our “natural” water should be considered as a solution of a range of randomly distributed anions and cations. Because of the nature of dissolved ions and the multiple ions present we cannot describe our “natural” water as containing “calcium fluoride,” “sodium chloride” or any other common chemical. These names are really only applicable to the ionic solids. Rather the water is a solution of hydrated Ca2+(aq), Na+(aq), F(aq), Cl(aq), etc. We have to characterise the water by the amounts of each ion present in solution.

The drinking water you get after treatment may contain less of some of the natural ions, or more if extra is added during (eg. F is naturally in the water source but sometimes supplementary fluoride is added to provide concentration optimum for dental health).

solution

 

 

Your drinking water contains a random mixture of hydrated anions  and cations

 

 

You may think I have missed some obvious ions. For example –  H+(aq) and OH(aq). These are usually understood as present (at extremely low concentrations) and easily derived from the H2O molecule anyway.

H2O (aq)  ↔  H+(aq) + OH(aq)

In practice, water treatment plants adjust the pH (degree of acidity or alkalinity) of your water to very near neutral where the concentration of H+(aq) and OH(aq) are approximately the same and extremely low. They may do this by adding lime (containing Ca2+), ammonia (containing (NH4+) or other chemicals.

What about Al3+(aq)?- after all, chemicals like aluminium sulphate are added to remove colloidal material? However, this procedure works because in dilute solution Al3+(aq) hydrolyses (reacts with water) to form solid Al(OH)3 – so removing Al3+(aq) from solution.

Fluoridating chemicals

These are sometimes added during water treatment. Their purpose is to increase the fluoride (F) concentration to levels which are optimum of dental health. The chemicals used are generally fluorosilicic acid, sodium fluorosilicate or sodium fluoride.

Some critics of fluoridation argue these chemicals are toxic and calcium fluoride, a “natural” form of fluoride, is safe. They have even argued that community water fluoridation would be OK if CaF2 was used. But this argument is faulty for a number of reasons.

  • The lower toxicity of CaF2 is a result of its lower solubility. This is why some studies show the toxicity of high concentrations of fluoride can be reduced by addition of calcium salts.
  • Despite its low solubility CaF2 is sufficiently soluble to maintain a fluoride concentration of about 8 ppm (mg/L) – still far higher than the optimum concentrations aimed for in CWF (0.7 ppm).
  • The low solubility of CaF2 makes it impractical as a fluoridating chemical as if added as a solid uniform equilibrium concentrations would be difficult to achieve. If added as a liquid we would need a container almost as large as the water reservoir itself to store the near saturated CaF2
  • “Natural” CaF2 would be too impure for use in water treatment. Expensive processing (involving conversion to hydrofluoric acid and precipitation of CaF2) would be required to reduce the impurities.

Sometimes critics argue that “natural” fluoride in water is in the form of CaF2 which makes it safe because of the presence of Ca. But remember that CaF2 does not exist in solution which contains a random mixture of cations and anions. The hydrated Ca2+ ion is present in water naturally because it is derived from a range of sources besides fluoride minerals. It is also often added to water during treatment. So your drinking water already contains calcium, and usually at higher concentrations than if all the fluoride had been derived from “natural” CaF2

What about fluorosilicates?

Some critics of CWF claim that fluoride is not the problem. That because the most commonly used fluoridating chemicals are fluorosilicic acid (H2SiF6) and sodium fluorosilicate (Na2SiF6) the problem is the fluorosilicate species. They will even claim that we are drinking fluorosilicic acid and claim that there has been no testing of the safety of this chemical in drinking water.

But this claim is wrong. In fact, fluorosilicates react with water when diluted. They decompose to form silica and the hydrated fluoride anion. Consequently, safety studies made with sodium fluoride are completely relevant to these fluoridating chemicals when diluted.

FSA-2

A small amount of silica is normally present in drinking water. There is a tendency for this to polymerise and end up as solid SiO2.

Because of the extreme dilution of the fluorosilicate the liberated H+(aq) does not have a measurable effect on the pH mainly because of the equilibrium:

H2O (aq)  ↔  H+(aq) + OH(aq)

Anyway, the pH of the water is adjusted during treatment to neutral values (by the addition of acids, soda ash or lime) to prevent acid attack on pipes.

Chemicals in drinking water are extremely dilute

Critics will often wave pictures of bags of chemical being added to drinking water. Often they will illustrate their claimed danger of fluoridating chemicals by referring to safety data sheets. But these data sheets provide information on the storage, handling and disposal of the concentrated chemicals and have no relevance to the extremely dilute nature of the final drinking water.

The recommended optimum concentration of fluoride in drinking water is 0.7 ppm. Humans have difficulty imagining such extreme dilutions but the following figure provides some idea in day-to-day concepts.

micro

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Responding to Tracey Brown on fluoridation

CWFwaterI appreciate Tracey Brown, Director of Sense About Science, taking the time to respond to some of the comments in my article The ugly truth about critics of “the ugly truth” in science (see “The ugly truth” – Tracey Brown ticks me off). Despite apparent differences I think Tracey and I are singing from the same hymn sheet regarding the need to confront assumptions and check the evidence supporting common claims. That was the message from her lecture and I simply expanded this to include claims of the sort Tracey herself was making.

An apology

First, I must apologise for implying Tracey relied only on the reading of the two papers that were cited to me. I of course have no idea what other reading she has done on the subject – although some of her comments did reflect the views of Peckham, a well-known anti-fluoride activist, as expressed in his misleading paper Peckham (2012).

I also did not know for sure she had based her comments on “inadequate knowledge – claims from anti-fluoride campaigners she uncritically accepted.” That should have been expressed as my view, my conclusion, drawn from her lecture – rather than a statement of fact.

I did say “even scientists, and pro-science people, can suffer from confirmation bias – just like anyone else. They can sometimes adopt a partisan position which restricts them to considering only the misinformation and distortions peddled by anti-science campaigners.” However, I was simply presenting that as  a general problem – not accusing her specifically of this. We should be able to raise these possibilities without being accused of “rudeness” or “brittleness.” This oversensitivity can be an obstacle to the necessary tasks of demanding evidence for the claims being made by anyone.

The fluoridation issue

I don’t, for a minute, think Tracey has jumped on the anti-fluoride bandwagon. But I am concerned that she seems, at this stage, to have uncritically accepted some of the claims made by people like Peckham and Connett.

Tracey’s understanding of community water fluoridation (CWF) is important. A she said in her lecture, “members of the public have asked “Sense About Science” about it.” Her organisation needs to be able to correct misunderstandings and provide an objective summary of CWF. (In this respect Sense About Science is a similar position to Making Sense of Fluoride, a group I belong to). I think, at the moment, Tracey’s comments indicate her organisation’s advice on CWF could be misleading.

Tracey’s response struck me a being largely defensive – objecting to the style of some of my specific comments rather discussing the evidence for or against CWF or its handling by health authorities and decision makers. As it stands she still appears to adhere to the claims made in her lecture which, I think, are just wrong. So, it is worth expanding on some of the comments I have already made.

Is there really no critical assessment of the evidence for CWF?

It is ironic that Tracey uses CWF as an example where evidence has not been questioned. She even says that “governments went about fluoridation in the 50s by stealth, without discussion which caused a backlash.”

But the facts are that in most jurisdictions the decisions on CWF are usually made by local bodies and water companies, not governments. These decisions usually involve consultations and often very contentious debates.  Unlike many other health measures, CWF has been countered from its very beginnings by protests and representations. Although this has usually been ideologically driven and sometimes, but not always, extreme, such opposition has guaranteed a high level of discussion, consultation and scrutiny of the evidence.

That continues to the present day. In my own city (Hamilton, New Zealand) pressure from activists to cease CWF lead to a limited consultation by the council in 2013, and a decision to stop fluoridating. Citizens, many of them quite knowledgeable on the subject, reacted because they felt they had not been properly consulted or listened to and the council had ignored previous referendums and their own polling data. A new referendum showed overwhelming support and subsequently  the council reversed their decision and CWF returned to our city in 2014.

Actually, this illustrates two features which must be taken into account in our defence or criticism of social health policies.

  1. Often the central issue is one of values – even the conflict between a social approach or a libertarian one. Decision-makers should take account of such values in their community as they may be more relevant than the science.
  2. Decision-makers often just do not have the skills to judge scientific evidence. This was particularly true for the Hamilton City Council which was effectively swamped by anti-fluoride activists promoting misinformation and distortion.

For many people involved in this process, and many citizens, CWF has been revisited so many times, the evidence scrutinised and criticised so many times, there is indeed a backlash. Citizens are not happy about their local bodies spending so much time and money on repetitive consultation and even react negatively to new referenda. New Zealand local bodies now wish to unload the whole issue onto Central government arguing, quite legitimately, they do not have the expertise to make such decisions. They have had a gutsful of the issue.

Benefits of opposition

This continual consultation and rehashing of the evidence has produced some positive outcomes – the anti-fluoride activity has a silver lining. The Royal Society of NZ, together with the Office of the PM’s Chief Scientific advisor produced a review updating the evidence relevant to the efficacy and safety of CWF to the middle of 2014. The citation is:

Eason, C., & Elwood, JM. Seymour, Thomson, WM. Wilson, N. Prendergast, K. (2014). Health effects of water fluoridation: A review of the scientific evidence.

This was partly financed by local bodies who felt thoroughly confused by the competing claims. I suggest Sense About Science people read this document, and others, in their efforts to get up to speed on CWF.

Not only does NZ now have an up-to-date review of CWF we also have several High Court decisions which put to rest some of the claims made by activists. Poetic justice perhaps – as funding  from the “natural”/alternative health industry has actually produced scientific and legal judgements supporting CWF! The opposite of what they intended.

Setting “optimum” levels

Tracey said in her response:

“I stated, briefly, that the one part per million figure originates from those old studies. Other parts of the world have rejected it in favour of different concentrations. My reading of the subsequent research on concentrations was that it was not possible to come up with a clear case for one part per million, as opposed to say 0.7 as used elsewhere, and that although the need for controls is better understood and sometimes applied, the multiple and variable sources of other contributors to dental health have made it harder to get a signal from the noise. In the lecture, I pointed out that it’s very difficult to control and measure the dose that people actually get from water. It’s not clear whether you disagree with this.”

Her original comment on “old studies” still stands. As I said before, standards are set according to the studies available at the time – this does not mean they are not revisited or changes as new studies become available. This has, in fact, happened with CWF and it is misleading to imply otherwise.

I don’t think it is a matter of “rejecting” the research. Health authorities and decision makers in each country make decisions about “optimum” levels taking into account their own specific situations, dietary intake, drinking water consumption, etc. Counties don’t “reject” decisions of other countries.

Of course it is hard to control and measure the “dose”, or intake – but that is true for any beneficial element – most of which have upper and lower bounds for recommended intake. Dietary consumption is hardly an exact science – one should not be concerned about the 0.7 or 1 ppm difference. Why should fluoride present a special problem?

Personally, I see talk about “dose” as another misleading argument promoted by anti-fluoride campaigners. Firstly, because of the implication such accuracy is required and secondly because it is painting fluoride out to be in the same class as a very active and possibly toxic drug requiring accurate control – which it isn’t. Really, fluoride is in the same class as sodium, potassium, phosphorus, magnesium and selenium. It is not a drug.

Trends of declining dental decay

No one claims CWF is a magic bullet, or that it is the only factor behind improving oral health. Yet the graphic Tracey used is promoted constantly by campaigners to “prove” CWF is ineffective by implying health authorities see fluoride as the only factor involved.  The graphic “proves” nothing except that oral health has improved over the years.

In my article I assumed Tracey used the image from Cheng et al (2007). In fact, her comments on Austria introducing gobstoppers suggest she probably used the one below from Peckham (2012). There are warning signs there as the citation was a personal communication from Chris Neurath – an activist and “research director” in the management of Paul Connett’s Fluoride Action Network. Even the journal citation should ring bells as Fluoride is a poor quality journal effectively managed by the anti-fluoride community.

Peckham image

And, as I pointed out in my original article, these images avoid showing the WHO data within countries – which do show that CWF is effective. It is extremely naive, and misleading, to suggest that the WHO data shows that it is not effective.

I am seriously concerned that inadequate review of the scientific literature will lead to Sense About Science promoting this misleading graphic in its response to public requests for information.

Real world problems for public discussion of evidence

Institutional cultures often restrict the ability of staff to comment publicly. This may be expressed as a condition of employment or it may just be informal discouragement. On the fluoridation issue, it may just be a matter of institutions preventing staff from participating in the “street-fighting” nature of many of the public discussions. In fact, some local institutions have said they are not ready to expose their staff to the threats and abuse which are often part of these public discussions. It is a health and safety issue for them.

Consequently, these discussions are often handled better by non-institutional “activist” groups like Sense About Science. The group Making Sense of Fluoride (MSoF)is effectively a sister group to Sense About Science, but concentrating on the scientific and ethical issues around community water fluoridation. It was formed precisely because institutions like District Health Boards are not able to take part fully in the public debate. Many MSoF people are not limited by institutional requirements.

Incidentally, institutional restrictions are another reason many people who discuss scientific issues publicly are retired. Such retirees often have the background knowledge and research skills necessary for this discussion but no restriction on what they can say, and where.

Tactical approaches are also important. Very often the public is not interested in the scientific details and qualifications which should be attached to evidential claims. They are often happy to leave such discussion to the “boffins.” Scientific debates may be suitable for some fora but can be a real turn off in referendums. Institutional decisions to forgo scientific debate and detailed qualifications may be completely correct in such situations.

The issue of making disagreements like this public (in the same way Tracey suggests health authorities may not be completely open about the contradictory evidence) is a real one for me with this and my previous post. I had to consider tactical questions. Tracey’s comments on CWF may have been buried within her lecture and not noticed by anti-fluoride activists who just love to publicise and promote such statements. My criticism has now brought them to the attention of the anti-fluoride community. I have handed them a bit of juicy propaganda.

However, my motive is promotion of integrity in science and the need to back up claims with evidence. This is more important to me than a specific campaign of support for CWF. Tracey provided an example which illustrates my concern – so why should I not comment on it?

The public discussion of science, which was the subject of Tracey’s lecture, is not simple and we should not neglect the social and psychological research about public opinion and the way to communicate with the public.

Conclusions

I am grateful to Tracey for responding to my article and wish her and Sense About Science the best in updating their knowledge on CWF.

I am a little disappointed her response was defensive and did not involve an in-depth discussion of CWF. This is probably natural, but it is important that groups like Sense About Science and Making Sense of Fluoride not ignore such challenges. It is also important for such groups to be ready to update their knowledge and opinions on issues when required.

In her article Can you handle the truth? Some ugly facts in science and sensibility introducing her lecture Tracey said:

“The ugly truth is that all of us – however informed, however good our intentions – end up letting things slide once in a while. We overlook, overstate or understate the evidence behind research, claims, or policies, for a number of reasons.”

So true – and something we should continually come back to.

I think Tracey was guilty of this in her claims about CWF. Granted, these were only a small part of her lecture. But to anyone with sufficient knowledge to see her mistakes the claims about CWF did detract from the authenticity of the other claims she made.

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ChildSmile dental health – its pros and cons

Childsmile-Hebrides-Today

There is some local interest in the Scottish ChildSmile dental health programme. Partly because anti-fluoride campaigners are promoting it to local bodies as an alternative to community water fluoridation (CWF). Their interest is possibly due to the opt-in nature of the programme which they see as satisfying there demands for “freedom of choice” (in this case the choice means excluding their own children from the programme which, after all, does include fluoride treatments).

However, health professionals in the UK are more balanced in their opinions. While welcoming ChildSmile they do not see it as an argument against CWF – rather as “the next best thing – a rather expensive substitute for the fluoridation schemes that have never been introduced.”

I have written about the ChildSmile programme before (see Fluoride debate: Ken Perrott’s closing response to Paul Connett?). But here is some more detail I have picked up from discussion online with health professionals.

What is the ChildSmile programme?

quote-3-1a
On the surface, the ChildSmile programme supplies children with toothbrushes and toothpaste:

“The core programme involves supervised daily toothbrushing for all Scottish three and four year olds attending nursery schools (but not those who don’t attend nurseries). This has been extended to five and six year olds in primary schools in those areas (not necessarily across entire local authorities) counted as being among the 20% most deprived in Scotland.”

Data suggest that about 82% of three and four-year-olds are participating. The children who do not take part do not benefit.

ChildSmile also includes twice-yearly application of fluoride varnish to children’s teeth.  The programme 2013/2014 targets included this:

“At least 60% of 3 and 4 year old children in each SIMD quintile to receive at least two applications of fluoride varnish per year by March 2014.”

In addition to toothbrushing and varnishing, Childsmile involves health education initiatives based principally on public health nurses and health visitors attaching themselves to particular schools in order to give oral health advice to children and parents. Subject to parental consent, they also arrange for children who are not registered with a dentist to undergo check-ups and, if necessary, treatment.

Is it a substitute for CWF?

Not really, but health professionals see it as the “next best thing.” Appropriate for situations where there is no CWF. But it only covers children – and then only those children whose parents give consent (many don’t). In contrast, CWF benefits adolescents and adults, as well as children. Families can, of course, “opt out” od CWF (by using water filters or different sources), but numbers will be lower than those excluded by “opt-in” procedures.

It is wrong to see such programmes as alternatives to, or separate from, CWF. Elements of the ChildSmile programme were already present before ChildSmile was introduced. Similar elements will also be common in countries like New Zealand.

Is it effective?

Childsmile was introduced in 2008 so it is a little early to judge its effectiveness. Scottish children’s dental health has improved and the programme most likely has assisted that.

For example, 58% of five-year-olds were free of decay in 2008, compared with 68% in 2014. The average decayed, missing and filled teeth (dmft) score for this age group has fallen over that period from 1.86 to 1.27.

CS-1

However, there does not seem to have been a reduction in dental health inequalities between children from different social groups in Scotland. In 2008, 42% of children from the most socially deprived quintile of Scottish five-year-olds were free of decay compared with 73% of those from the least deprived quintile. In 2014, 53% of five-year-olds in the most deprived quintile were free of decay compared with 83% of those from the least deprived quintile.

CS-2

According to the Scottish National Dental Inspection programme the absolute inequality between the most and least deprived children remains at 30% (comparing percentages of children without tooth decay), according to surveys conducted in 2008, 2010, 2012 and 2014.

Another concern is that children in the most deprived quintile of five-year-olds have not reached the national target set in 2010 that 60% of them should be free of decay.

Of course, the ChildSmile programme has no effect on the oral health of  current adolescents and adults.

What about the cost?

ChildSmile is far less cost-effective than CWF. Let’s compare the cost of CWF in England with the costs for the ChildSmile programme in Scotland

CWF serves 6 million people in England, costs around £2.1 million a year and is benefiting everyone with natural teeth, regardless of age, education or socioeconomic status. It benefits all children. So the cost per person of is around 35 pence per annum, although if we exclude people with no natural teeth it is likely to be a little higher than that – an average cost of about 40 pence per person benefiting.

If we take a narrow view and assume only children and adolescents aged 0 to 17 (21% of the population in England ) benefitted from CWF the cost would apply to around 1.26 million out of the 6 million supplied with fluoridated water. On that basis, the cost of CWF would be £1.67 per year for each child benefitting.

In contrast:

The total national ChildSmile budget for 2013/14 was £14,956,000, according to a statement by the Minister responsible to the Scottish Parliament in July 2013. This covers  everything attributable to Childsmile – the toothbrushing programme, plus targeted varnish applications and associated oral health education initiatives.  Assuming that around 120,000 Scottish children aged between three and six are benefiting, it works out at a cost of around £125 per child per annum.

Compare the Childsmile costs of around £125 per child per annum with the CWF costs of about 40 pence per person per annum or even £1.67 per year for each child benefitting. CWF is obviously many times less expensive that ChildSmile.

What is the attitude of Scottish dentists?

The British Dental Association supports CWF and in Scotland has come out publicly to call for communities to move towards introducing water fluoridation. That position undermines the arguments of New Zealand anti-fluoridation groups claiming that Childsmile is an adequate substitute for water fluoridation. The professional body representing dentists in Scotland does not see it that way.

The BDA in Scotland points out that CWF would be beneficial to children and elderly people. It argues that water fluoridation “would complement the Childsmile programme” by helping cut the overall burden of tooth decay and reducing dental health inequalities in the elderly. We could look at it another way and see that a Childsmile programme could complement water fluoridation. After all, we must remember that initiatives such as Childsmile rely on personal compliance and that they benefit only those taking part. They give no benefit for the rest of the population, unlike CWF.

CWF and ChildSmile are are not mutually exclusive. Children in fluoridated areas should be encouraged to brush their teeth regularly with a fluoride toothpaste and to receive dental check-ups. Bear in mind, also, that components of a ChildSmile programme, such as supervised toothbrushing, were in use in parts of Scotland before the introduction of the full programme. Elements of the ChildSmile programme will also be in current use in New Zealand.

Conclusions

Despite claims of anti-fluoride propagandists, the ChildSmile programme is not a simple alternative to CWF. And it is wrong to see it as such in New Zealand.

It is far less cost-effective – the Scottish programme costs around £125 per child per annum compared with 40 pence per person per annum (or £1.67 per year for each child benefitting when benefits to adults are excluded) and therefore far less likely to be put in place as an alternative to CWF.

ChildSmile is an “opt-in” programme so its coverage is far lower than CWF which is an “opt-out.” This is important when social differences in oral health are important.

However, the contact between children and their families on the one hand and public health nurses, health visitors and dentists on the other, is very valuable and may have wider benefits than oral health alone. (I am thinking of problems caused by child neglect and abuse).

I think these sort of programmes are socially very helpful and strongly support them. The cost is, of course, a limiting factor. However, elements of such social programmes may be possible within budget constraints that health authorities face.

Health programmes like ChildSmile, or elements of that programme, can be very effective even in areas where CWF exists. They can give that extra boost to the oral health of children and can, therefore, complement CWF.

There are many areas where CWF is not feasible because of low population density, lack of suitable water reticulation systems or local political opposition to CWF. I believe that programmes like ChildSmile, or parts of that programme, can be very helpful in those situations. Northland and particularly NZ’s Far North are obvious examples.

Finally, let’s not be diverted by the programme name. I am sure that elements of the Scottish ChildSmile programme are already in place in New Zealand, or parts of New Zealand. Given the costs of such programmes, and budget limitations, these programmes do have the advantage that they can be targeted to regions or social groups where the need is the greatest.

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Alternative reality of anti-fluoride “science”

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

Different grades of dental fluorosis

Connett asserted two things in his presentation:

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

Plenty of research shows CWF is cost-effective

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

Here are a just a few readers could consult:

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

Connett relies on a flawed study

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

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

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

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

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

Two problems with that statement:

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

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

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

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

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

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

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

And:

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

See the  trick?

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

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

Connett is promoting an alternative “scientific” reality

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

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

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

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

Lessons for Connett

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

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

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

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

Lessons for everyone susceptible to confirmation bias.

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Comparing the Cochrane and NZ Fluoridation Reviews

Sci Rev

New Zealand policy makers and health professionals should be wary about much of the current media comments on the Cochrane Fluoridation Review (Iheozor-Ejiofor 2015). Anti-fluoridation campaigners are misrepresenting it and distorting its findings. They are using cherry-picked quotes to make claims about the review which are just not true.

Some are even claiming (wrongly) that the Cochrane review findings conflict with this in the NZ Fluoridation Review (Eason et al., 2014). Or that, simply because it was published a few months after the NZ Review it somehow makes the NZ Review obsolete.

Review findings agree

Nothing could be further from the truth. The findings in the Cochrane Review do not conflict with those in the NZ  Review. And, because the Cochrane Review is much more limited than the NZ Review, policy makers and health professionals should not consider that as the only document required for their reading.

In particular, the Cochrane Review considered only questions of community water fluoridation (CWF) efficacy. It did not consider aspects related to health concerns which, of course, are always in the front of the minds of policy makers and health professionals.

I have done a side-by-side comparison of the two reviews and summarise their findings below

CWF efficacy

The Cochrane reviewers produced a quantitative estimate for the effect of CWF on dental decay, but only for children and used only studies satisfying their strict selection criteria (see Cochrane fluoridation review. I: Most research ignored). This unfortunately excluded more recent high-quality cross-sectional studies.

The NZ Reviewers did not produce an overall quantitative estimate but made more general conclusions.

Cochrane Review

NZ Fluoridation Review

Efficacy of CWF
“Data suggest that the introduction of water fluoridation resulted in a 35% reduction in decayed, missing or filled baby teeth and a 26% reduction in decayed, missing or filled permanent teeth. It also increased the percentage of children with no decay by 15%. These results indicate that water fluoridation is effective at reducing levels of tooth decay in both children’s baby and permanent teeth”. “Analysis of evidence from a large number of epidemiological studies and thorough systematic reviews has confirmed a beneficial effect of CWF on oral health throughout the lifespan. This includes relatively recent studies in the context of the overall reduced burden of caries that has resulted from the widespread use of topical fluoride products (e.g. toothpastes,  mouth rinses, and fluoride varnishes).”
Adult caries
No conclusions because of study selection limitations. “Although most studies of the effects of CWF have focused on benefits in children, caries
experience continues to accumulate with age, and CWF has also been found to help reduce the extent and severity of dental decay in adults, particularly with prolonged exposure. The long history of CWF around the world now means that many adults in late life have experienced a lifetime of fluoridation. The benefits for adult dental health include lower levels of root caries, and better tooth retention into old age.”
Socio-economic effects
No conclusions because of study selection limitations. “The burden of tooth decay is highest among the most deprived socioeconomic groups, and this is the segment of the population for which the benefits of CWF appear to be greatest. CWF appears to be most cost-effective in those communities that are most in need of improved oral health. In New Zealand, these include communities of low socioeconomic status, and those with a high proportion of children or Māori. A number of studies have suggested that the benefits of CWF are greatest among the most deprived socioeconomic groups, although the magnitude of the difference is uncertain.”
Effect of stopping fluoridation
No conclusions because of study selection limitations. “Stopping CWF leads to ~17% increase in caries experience”  cited from US Task Force on Community Preventive Services
Influence of fluoridated toothpaste, etc.
No conclusions because of study selection limitations. The beneficial effect of CWF on oral health is still shown in relatively recent studies illustrating the overall reduced burden of caries that has resulted from the widespread use of topical fluoride products (e.g. toothpastes,  mouth rinses, and fluoride varnishes). “In New Zealand, significant differences in decay rates between fluoridated and non-fluoridated communities continue to exist, despite the fact that the majority of people use fluoride toothpastes.”

Health issues related to CWF

Dental fluorosis is generally considered the only negative health results of CWF. Both Reviews did consider dental fluorosis, although the Cochrane review did not specifically compare fluoridated and unfluoridated areas – which is necessary to determine the effect of fluoridation on dental fluorosis prevalence. See Cochrane fluoridation review. III: Misleading section on dental fluorosis for a discussion of this and an estimate fo the effect of CWF on dental fluorosis calculated using the Cochrane data.

The Cochrane review did not consider any other health effects.

Cochrane Review

NZ Fluoridation Review

Dental Fluorosis
Only calculated effect of fluoride intake in dental fluorosis. The effect of CWF itself was not considered. However, this can be estimated by subtracting prevalence for unfluoridated region. These estimates indicate that dental fluorosis levels of aesthetic concern are similar in fluoridated and unfluoridated areas (see Cochrane fluoridation review. III: Misleading section on dental fluorosis).
.
“The prevalence of fluorosis of aesthetic concern is minimal in New Zealand, and is
not different between fluoridated and non-fluoridated communities, confirming that a substantial proportion of the risk is attributable to the intake of fluoride from sources other
than water (most notably, the swallowing of high-fluoride toothpaste by young children).
The current fluoridation levels therefore appear to be appropriate. It is important, however, that the chosen limit continues to protect the majority of high-exposure individuals.”
IQ effects
Not considered “We conclude that on the available evidence there is no appreciable effect on cognition arising from CWF.”
Cancer
Not considered “We conclude that on the available evidence there is no appreciable risk of cancer arising from CWF.”
Kidney
Not considered “Studies and systematic reviews have found no evidence that consumption of optimally fluoridated drinking water increases the risk of developing kidney disease. However, individuals with impaired kidney function experience higher/more prolonged fluoride exposure after
ingestion because of reduced urinary fluoride excretion, and those with end stage kidney
disease may be at greater risk of fluorosis.”

Conclusions

The Cochrane review is far more limited in its coverage than the NZ Fluoridation Review. It did not consider possible health effects (apart from dental fluorosis) which is an important aspect of the fluoridation controversy for health professionals and policy makers.

The two Reviews agree that CWF is effective for children, but the NZ Review also considered effectiveness for adults, the reduction of socioeconomic differences in oral health and effects of stopping fluoridation on tooth decay. It also considered more recent research than the Cochrane review, so was able to discuss possible reduction in the efficacy of CWF due to the use of fluoridated toothpaste in recent years.

The Cochrane review does not make the NZ Fluoridation  Review obsolete at all. Nor do its conclusions conflict with those of the New Zealand Review.

Policy makers and health professionals should pay attention to both reviews in making judgements of CWF efficacy, but will need to use the NZ Review for their judgements on possible health effects.

References

New Zealand Fluoridation Review:
Eason, C., & Elwood, JM. Seymour, Thomson, WM. Wilson, N. Prendergast, K. (2014). Health effects of water fluoridation : A review of the scientific evidence

Cochrane Fluoridation Review:
Iheozor-Ejiofor, Z., Worthington, HV., Walsh, T., O’Malley, L., Clarkson, JE., Macey, R., Alam, R., Tugwell, P., Welch, V., Glenny, A. (2015). Water fluoridation for the prevention of dental caries (Review). The Cochrane Library, (6).

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More poor-quality research promoted by anti-fluoride activists

Anti-fluoridation propagandists must think all their Christmases have come at once. They at last have a “peer-reviewed” scientific paper they can claim supports their position. What’s more, it is the second such paper to appear in the last month.

But they really are resorting to arguments of quantity (2 papers) over quality. This new paper claiming a link between community water fluoridation (CWF) and Attention-Deficit Hyperactivity Disorder (ADHD) is of just as poor quality as the earlier one claiming a link with hypothyroidism. Both papers are speculative, ignore other relevant factors, and “prove” nothing.

I discussed the hypothyroidism paper in the article Paper claiming water fluoridation linked to hypothyroidism slammed by experts. The new ADHD paper is:

Malin, A. J., & Till, C. (2015). Exposure to fluoridated water and attention deficit hyperactivity disorder prevalence among children and adolescents in the United States: an ecological association. Environmental Health, 14.

Here are my thoughts on this paper.

Exploratory investigation – correlation not causation

The authors have simply taken existing online data and searched for a statistically signficant relationship. They have explored the limited data sets used – not attempted to prove an effect. After all, correlation does not prove causation – the graph below shows an example of how correlation can often produce meaningless results.

The data sets Malin and Till (2015) used are both from the USA Centers fo disease Control (CDC).

  1. State-based attention-deficit hyperactivity disorder (ADHD) prevalence (Visser et al., 2014);
  2. Numbers of people receiving fluoridated water from public water supplies in each state obtained from the CDC.

Note, they did not use data for individual children exhibiting symptoms of ADHD  determined by  a health professional. The data was from random surveys “in which parents were contacted via telephone and asked about the emotional and physical well-being of a randomly selected child from their household.” Similarly they did not use data for dietary intake of fluoride by individual children but used “the percentage of the U.S. population on public water systems that receives optimally fluoridated drinking water.”

They have assumed these data are reliable proxies for occurrence of ADHD and fluoride dietary intake. But the data could represent other factors as well.

For example, parental reporting of ADHD could differ from state to state because of differences in parental educational levels and ideological attitudes. People in  different sates may not have the same level of knowledge, awareness or acceptance of such behaviours. Malin and Till themselves acknowledge ADHD reporting is higher for parents with a high school education than for parents who did not graduate high school (Visser (2014). Parental education levels are likely to vary from state to state.

The availability of CWF can be dependent on the size of urban areas for both technical reasons and because of  recognised willingness for innovation from large and high status city leaders (Crain, 1996) so that the state prevalence used could be acting as a proxy for the distribution of urban areas of different sizes, and the relative urban/rural distributions in different sates. A correlation may indicate nothing more than a relationship between city sizes and parental education.

The authors themselves warn their study has limitations, saying it is:

“an ecological design that broadly categorized fluoride exposure as exposed versus non-exposed rather than collecting information related to concentration of fluoride and patterns and frequency of exposure or outcome at the individual level. Future research could explore the relationship between exposure to fluoridated water and the occurrence of ADHD at the individual level.”

And, again, we should always keep in mind that correlation does not prove causation.

The starting hypothesis

Inevitably any serious exploratory investigation should start with a working hypothesis. As psychologists the authors are presumably interested in ADHD and its causes. But why investigate state prevalence of CWF instead of any of the other factors indicated in this condition. In fact they list a range of candidates from arsenic and lead to food additives and food colouring. Granted, they saw CWF as a field ripe for plucking as they say fluoride “has received virtually no attention in the ADHD literature.” But I would have expected them to at least include these other known factors as confounders in their study.

I think the answer lies with their biased reading of the literature. They start with the claim that fluoride is a “widespread environmental neurotoxin,”  but only really cite Grandjean and Landrigan (2014) and the closely-related meta-analysis of Choi et al., (2012) to support this claim. I have discussed those papers and their problems in  Repeating bad science on fluoride and Controversial IQ study hammered in The Lancet. A major problem with that work is it involved areas of endemic fluorosis where fluoride intake is high so it is not directly relevant to CW. In fact, the authors’ bias is indicated by the fact they did not cite Broadbent et al., (2014) which showed no neurotoxic effects of CWF. Broadbent et al.’s paper is directly relevant to CWF – Choi et al.’s is not. (I discussed the differences as indicated by dental fluorosis data in my article Water fluoridation and dental fluorosis – debunking some myths

I feel this omission indicates that the authors resort to the special pleading of anti-fluoride activists in the citations they used for justifying their starting hypothesis. The also rely on studies of rats fed very high levels of fluoride, such as that of  Mullenix et al., (1995), and then use her weak argument to claim relevance to CWF by comparing  rat blood plasma F levels to those for humans ingesting high levels of fluoride. (See my article Peer review of an anti-fluoride “peer review” for a discussion on this). Similarly, although acknowledging the high F intake levels of most of the studies reviewed by Choi et al., (2012), they excuse this by referring to the one study with low levels (0.88 mg/L) – ignoring the fact this was a one and a half page article in a newsletter describing measurements in an iodine deficient area. In this study (Lin, et al., 1991) children from low iodine areas were compared with a group from another area that had received iodine supplementation. About 15% of the children suffered mental retardation, 69% of these exhibited subclinical endemic cretinism. The effect of iodine supplementation was clear, the effect of fluoride not so clear. (See Peer review of an anti-fluoride “peer review” for further discussion of this).

So, I think the justification for their starting hypothesis is hardly objective

“Natural” vs “artificial” fluoride

Despite  problems with justification for their hypothesis they did find a significant positive relationship between the US state prevalence of parent-reported ADHD in children and the state proportion of water supplies with optimum levels of fluoride. Again, not a proof of their hypothesis, but interesting data to consider nonetheless. They found inclusion of socio-economic status data improved the relationship but did not consider other relevant confounding factors like parental education and exposure to relevant chemicals.

In contrast, the relationship they found between ADHD prevalence and natural fluoride prevalence (at optimum level or above) was negative and statistically signficant. This actually conflicts with their starting hypothesis of chemical neurotoxicity based on the work of Choi et al., (2014) and Grandjean and Landrigen (2014). While they concede the data really doesn’t allow a conclusion they suggest it could result from the ADHD effect being specific to “fluoridation chemicals” and not fluoride itself.

This leads them to suggest a theoretical “pathway” for CWF contributing to ADHD – the corrosion of lead-bearing plumbing by fluorosilicic acid. Trouble is this ignores the well established fact that fluorosilicates used in CWF decompose to form silica and the hydrated fluoride anion when diluted in water. Malin and Till seem oblivious to work showing this and rely instead on citation of the poor quality work of Masters and Coplan to support this “pathway.” Another example of their citation bias.

But their proposal does raise an important question. Given that lead is one suggested cause of ADHD why did they not concentrate their exploratory analysis of data for lead intake by children in different states, rather than CWF prevalence? Or at least include lead levels as confounders in their statistical analysis.

The thyroid story again

Their second suggested “pathway” is via suppression of thyroid gland activity by fluoride. But, again, this hypothesis does raise the question of other causes, in particular iodine deficiency. (See my discussion of Peckham’s paper – Paper claiming water fluoridation linked to hypothyroidism slammed by experts – for more on this). If this was part of their starting hypothesis then why not consider data for state prevalence of iodine deficient diets of children? Or or include this as a confounder in the analysis?

I find it interesting that despite declaring a starting hypothesis based on the chemical toxicity claims of Choi et al., (2012) and Grandjean and Landrigen (2014), Malin and Till have not proposed any theoretical “pathway” involving direct neurotoxicity of fluoride itself to explain their result. This makes their unwillingness to consider other relevant confounding factors even more obvious.

Conclusions

As I wrote above correlation is not causation  and this study does not “prove” anything. The observed “link”could represent a number of other relationships which are not directly associated with CWF. The analysis also suffers from a lack of consideration of obvious confounding factors.

I believe this is the sort of problem that arises when researchers have a committment to a starting hypothesis and peer review systems are inadequate. Such studies are a problems when published because ideologically motivated activists love to cherry-pick them to claim “scientific support” for their cause. This is not helped when the researchers themselves climb on the activist bandwagon and attempt to claim more for their findings that is really justified.

I think Malin and Till have done this with the press release from their department – Fluoride in tap water associated with ADHD in children, researchers find. It is one thing to say:

“Our findings showed that artificial fluoridation prevalence in 1992 predicted ADHD prevalence in 2003, 2007 and 2011 among children and adolescents in the United States, and that was after controlling for median household income.”

But the careful claim their “findings showed” a “prediction” is far too easily seen as proof in the mind of the lay-reader. Worse, they draw unwarranted conclusions from their limited work:

“As citizens of Toronto, living in an artificially fluoridated community, I think we need to ask ourselves whether this is still a worthwhile practice.”

One can only pose such questions in the context of an objective assessment of their own work together with other research of possible harmful and beneficial effects of CWF. I think their biased choice of citations in this paper shows they are not capable of doing this.

On the other hand reviews such as the recent NZ Fluoridation Review, Health effects of water fluoridation : A review of the scientific evidence, have done this. Community leaders should be going to such sources for their information and not rely on cherry-picked poor quality studies like Malin and Till (2015) which will be promoted to them by anti-fluoride propagandists and activists.

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Open letter to Lisa Hansen on NZ Fluoridation Review

Dear Lisa,

There are mistakes and misinterpretations of the scientific literature in your recent open letter to Sir Peter Gluckman and Sir David Skeggs. The letter also misrepresents the NZ Fluoridation Review (Eason et al., 2014) and the Fluoride Free NZ (FFNZ) report criticising that review. It gives the latter report more credibility and status than it deserves.

I am responding with an open letter of my own because I think the mistakes and misrepresentations need correction. I hope you receive my critique with the respect for the scientific openness,  criticism and healthy discussion you assert in the last paragraph of your letter. That certainly describes my approach and in that light I offer you a right of reply on my blog to this open letter.

First I consider some aspects of the way you present the NZ Fluoridation Review and the FFNZ report.

Citing the NZ Fluoridation Review

You generally cite Health Effect of water fluoridation: A review of the scientific evidence (Easton et al., 2014) as  the “Gluckman/Skegg report.” I realise you did this because your clients, and particularly the Fluoride Free NZ activist group, have adopted that terminology. It is however disrespectful to the real authors of the review. Such reports are not usually attributed to the heads of institutes or organisations.

Nature of the NZ Fluoridation Review

You unfairly compare Easton et al., (2014) to other major reviews in terms of cost, time taken, processes and the publication period reviewed. You are simply citing the activist FFNZ report which set out to discredit the NZ Fluoridation Review in any way possible.

The Fluoridation Review describes its approach in this way:

“Several previous rigorous systematic reviews were used as the basis for this analysis, and literature searches in Medline, EMBASE, the Cochrane library database, Scopus, and Web of Science were undertaken to identify subsequent studies in the peer-reviewed scientific literature. Alleged health effects from both the scientific and non-scientific literature were considered, and many original studies relating to these claims were re-analysed.” [My emphasis].

The Review’s purpose was not to duplicate the previous extensive reviews on this subject. It instead summarised them and reviewed later research. In other words the goals were simpler and less costly. (Costs were in any case determined by the local bodies which commissioned and, together with the Ministry of Health,  paid for the review.)

The FFNZ comparison is disingenuous.

The FFNZ Report.

You promote the inaccurate self-description of the FFNZ report (Scientific and Critical Analysis of the 2014 New Zealand Fluoridation Report) as “international peer reviewed.” That is the impression FFNZ attempts to convey  but it is dishonest – all the authors and “peer-reviewers” are connected with, or work for, Paul Connett’s Fluoride Action Network and similar activist organisations in the US or NZ. I illustrate some of the links in the figure below taken from the blog article The farce of a “sciency” anti-fluoride report.

I have provided an in-depth analysis and critique of the FFNZ report in a series of blog articles which are available in a single PDF document (Fluoridation is safe and effective: A critique of Fluoride Free NZ’s criticism of The NZ Fluoridation Review).

Now, the substantive issues you raise in your open letter.

Endemic fluorosis, community water fluoridation and IQ

Up front we must be clear about the situations behind the various scientific studies on the issue of fluoride and IQ.

So far, the only study  directly relevant to community water fluoridation (CWF) is that of Broadbent et al., (2014). This studied populations in the Dunedin region over a long time period. Notably you do not refer to this study, despite its extensive nature and relevance to the issue at hand. In  fact you seem unaware of the research as you claim in your letter that the “impact on IQ from water fluoridation at between 0.7 and 1 ppm” is “as yet unmeasured!”

The studies you do cite (mainly Choi et al., 2012) are from areas of higher fluoride consumption. Most of the studies were from areas of endemic fluorosis – mainly in China. This means that the findings cannot simply be transferred to areas like NZ.

Choi et al., (2012) are clear about the criteria used for choice of studies in their metareview. They say:

“We specifically targeted studies carried out in rural China that have not been widely disseminated, thus complementing the studies that have been included in previous reviews and risk assessment reports.”

And

“Opportunities for epidemiological studies depend on the existence of comparable population groups exposed to different levels of fluoride from drinking water. Such circumstances are difficult to find in many industrialized countries, because fluoride concentrations in community water are usually no higher than 1 mg/L, even when fluoride is added to water supplies as a public health measure to reduce tooth decay.”

This is why the Choi et al., (2012) meta review is not directly relevant to CWF.

Choi et al., (2012) not relevant to CWF.

I can illustrate the difference between that situations reviewed by Choi et al., (2012) and the New Zealand situation where CWF is common using dental fluorosis data from the recent paper of Choi et al., (2015),  Our Oral Health (2010) and Beltrán-aguilar & Barker (2010) (see Water fluoridation and dental fluorosis – debunking some myths).

There is very little severe or moderate dental fluorosis in NZ and USA. But it is very common in the area studied by Choi et al., (2015) which is probably typical of the areas reviewed by Choi et al., (2012) and the Indian paper you cite (Saxena et al., 2012). Unfortunately most of the studies reviewed by Choi et al., (2012) are of poor quality (see below) and do not include data for many possibly confounding factors like severe dental fluorosis, pesticide use, etc.).

So – clearly different situations.

The metareview of Choi et al (2012) was a metareview of studies from higher fluoride areas – not a metareview of studies from all areas, or studies from areas where CWF is common. Their review is not directly applicable to situations where CWF is considered, like NZ and USA.

The authors have stated this themselves:

“These results do not allow us to make any judgment regarding possible levels of risk at levels of exposure typical for water fluoridation in the U.S. On the other hand, neither can it be concluded that no risk is present.”

Note: I have suggested (Perrott 2015) that the small cognitive deficits report by the Choi et al., (2012) could be caused by severe dental fluorosis, and not directly caused by chemical toxicity. (I discuss this further below.) This is consistent with the results of Choi et al., (2015) who observed a significant relationship of cognitive deficits to severe/medium dental fluorosis but did not find a significant relationship with the fluoride concentration of the drinking water.

I believe researchers studying IQ effects in areas of endemic fluorosis should consider this hypothesis.

The “error” in the NZ Fluoridation Review

Your open letter concentrates mainly on an “error” in the NZ Fluoridation Review. This “error” was little more than a “typo,” occurred only in the executive summary (the body of the review reported the science correctly), and was corrected by the authors when brought to their attention. They also corrected at least one other error at the same time. I have discussed this in Did the Royal Society get it wrong about fluoridation?

Any publishing author is well acquainted with the problems of typos and similar errors. Despite the best proof-reading of drafts one inevitably finds some errors only after publication. (An example of Murphy’s Law, I guess.) This error has only become an issue because of the intention of activist organisations who wish to discredit the review.

It is worth noting that the Harvard University press release reporting the research concerned made exactly the same error and acknowledged and corrected it when pointed out. The current version now says:

“The average loss in IQ was reported as a standardized weighted mean difference of 0.45, which would be approximately equivalent to seven IQ points for commonly used IQ scores with a standard deviation of 15.*

** This sentence was updated on September 5, 2012.”

Yet, you, FFNZ and their associates do not criticise Harvard University!

Your mistaken description of error.

First, I will stress again that discussion of this “error” refers to the work of Choi et al., (2012) and areas where fluorosis is most likely endemic. That research does not deal with CWF or the situations where drinking water fluoride concentrations are that low.

The slide below, from a presentation made by Xiang (2014) at Paul Connett’s last conference in Washington, gives an idea of the situation in areas where these studies were made. Xiang is the author of several of the papers reviewed by Choi et al (2012) and commonly used by anti-fluoride activists in arguing against CWF.

This is clearly a different situation to New Zealand.

What did Choi et al (2012) actually report?

They report in their abstract “The standardized weighted mean difference in IQ score between exposed and reference populations was –0.45.” This is a standard deviation resulting from their analysis of 27 studies with different methods and quality of data. It is not a difference in IQ score.

This approach was necessary because the different studies reviewed had different IQ scales, different measurement methods and different levels of variation in the data. They standardised the differences by expressing them as a fraction of the standard deviation for each study. A mean value over all studies was determined, weighting the contribution from each study according to the precision of the IQ measurements.

Mistakenly, Harvard University and the NZ Review summary originally described this as an IQ score difference instead of SD. (Note – this mistake was not in the body of the NZ Fluoridation Review). In fact many readers were confused as the statistical process used by a Choi et al (2012) was not sufficiently well explained from a lay person’s viewpoint and they had to publish an extra explanation later (Choi et al., 2013).

Going from a standardised weighted mean difference value to a difference in IQ points.

Standard deviation is a function if variation in data so it is wrong to assume a value for all situations. It will be different for different sets of data.

The standardised weighted mean difference value of 0.45 has meaning because we know it represents less than half of one standard deviation so it indicates how it compares with measurement error. Many people have equated the difference of 0.45 to 7 IQ points. However, Choi et al., (2012)  did not report a difference of 7 you claim. This value came out of the explanation in Choi et al., (2013) in their response to a letter to the editor. They provided an example for a commonly used IQ scale normalised against a theoretical bell curve:

“For commonly used IQ scores with a mean of 100 and an SD of 15, 0.45 SDs is equivalent to 6.75 points (rounded to 7 points).”

This cannot simply be translated to any other IQ scale. For example these values would be inappropriate for the IQ scale used in Saxena et al., (2012)  study you refer to later in your letter.

The significance of the 0.45 standard deviation decrease in IQ points.

It is easy to throw around values of 7 and 15, as you do, but what is the significance of the result (for areas of endemic fluorosis – let’s not forget this study is not directly relevant to CWF). Choi et al., (2012) themselves warn that a decrease of 0.45 standard deviation “may seem small and may be within the measurement error of IQ testing.”

All this says is that many data sets, especially those with high variability, may not show a difference between children from high and low fluoride areas because the difference measured by Choi et al., (2012) is relatively small. In saying that I am not trying to deny any significance at all to their results. However, it is provisional and, as they say, it needs further confirmation. I think two points must be made here:

  1. The metareview was purposely biased towards studies from China and high fluorosis areas – many of which show endemic fluorosis. It is not directly relevant to the issue of CWF;
  2. The articles reviewed were in themselves mostly of poor quality, did not consider confounding factors and were often very brief (see figure). Not the fault of Choi et al., (2012) and hardly a surprising situation for the regions of interest, but this does help put the value of 0.45 standard deviation into context. It is, as yet, really only provisional.

Histogram showing size of the reports reviewed by Choi et al., (2012) from 

Your claim the Fluoridation Review misrepresented Choi et al (2012) in a specific quote.

Choi et al., (2012) themselves say:

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

This is a valid assessment because the mean difference they observed amounted to only 0.45 of a standard deviation which can be related to measurement error.

The Review refers to this text (and quotes as section of it) as follows:

The authors themselves note the difference is so small that “it may be within the measure tn error of IQ testing.”

I really don’t see any misrepresentation there. The authors did note that the difference was small compared with measurement error.

In summary I reject your criticisms on this issue for these reasons:

  1. You have relied for claims on a metareview of studies from areas of endemic fluorosis. A study reviewing reports of mainly poor quality and which the authors had described as not relevant to areas using CWF.
  2. You misrepresent correction of the small mistake as a change in recognition of the science or a “misreading of the available evidence.” There was no change as the science was correctly reported in the body of the review – the mistake occurred only in the summary. Others have made similar  mistakes – including Harvard University in their press release.
  3. You repeatedly refer to an IQ point differences of 7 without at any time considering how significant this value is compared with the measurement errors.
  4. You imply that this issue was not thoroughly addressed, which is wrong as it was discussed in the body of the review. Correction of the mistake in the summary is all that was required.

But, I stress again, whatever the significance of the small IQ differences reported for areas with endemic fluorosis in these studies they are not relevant to areas like NZ where no IQ deficits have been reported for CWF. In fact, quite the opposite (Broadbent et al., 2014).

Claims of neglected evidence

You  express concern “relevant evidence” was neglected by the authors of the review.

You refer to 2 papers:

1: Cheng and Lynn (2013) and a study “(referred to by Cheng and Lynn).” However, you do not attempt to explain what this paper contributes. The journal (it is in Mankind Quarterly) is not one normally considered for publishing scientific papers and is extremely difficult to access. My reading of the paper indicates nothing new – in fact it is a repetition of the data from the Choi et al., (2012) paper (which I find strange as it doesn’t even cite that paper).

Why do you wish Mankind Quarterly to be cited? Published by the Ulster Institute for Social Research (and not a scientific body), Wikipedia describes it this way:

“It has been called a “cornerstone of the scientific racism establishment” and a “white supremacist journal”, “scientific racism’s keepers of the flame”, a journal with a “racist orientation” and an “infamous racist journal”, and “journal of ‘scientific racism'”.

2: The cross-sectional study by Saxena et al., (2012). I agree this wasn’t included – but then again it is not relevant to CWF. The study considered situations where drinking water F concentration was greater than 1.5 ppm.

Unfortunately the images you reproduce could give a misleading impression. The linear plot in your figure was actually for the relationship between urine F concentration and drinking water concentration.

The plot for intelligence grade does not look so impressive (see figure).

Saxena

Saxena et al., (2012 ) do show an increase in mean intelligence grade (corresponding to a decrease in IQ) for the increasing concentration ranges. (You should perhaps note your reference to a standard deviation of 15 in such studies is clearly irrelevant to this study). They admit to several limitations in their study. We can agree with their assertion there is a “need for a more careful evaluation of the effect of fluoride on intelligence.” But given the endemic fluorosis in the area they studied, and in the areas of the studies reviewed by Choi et al., (2012) and studied by Choi et al., (2015) I suggest this is only relevant to such areas. I stress –  no such IQ differences were observed in areas where CWF is used (Broadbent et al., 2014).

I am aware of a number of other studies reporting cognitive deficits in areas of endemic fluorosis – suggesting IQ may well be a topical area of research in such areas. The NZ Fluoridation Review may not have cited these – precisely because they are not relevant to our situation.

However, I will reproduce some data from one of them (Sudhir et al., 2009) because it is directly relevant to the next topic. These authors did see increasing cognitive deficits with increasing concentration of F in drinking water. But they also saw a strong relationship between cognitive deficit and severe dental fluorosis (see figure below).

Sudhir

In this study IQ grade 5 is “intellectually impaired” and grade 3 is “intellectually average.”

Severe dental fluorosis and cognitive deficits

I stressed at the beginning of this letter that these IQ studies have all (except for Broadbent et al., 2014) concentrated on areas of endemic fluorosis. Children in these areas show high incidence of severe dental fluorosis and this is quite different to New Zealand (see the second figure in this letter). It is also noteworthy that Choi et al., (2015) chose to extend their work in an area of endemic fluorosis (in a Chinese village) and not an area of the USA where CWF is common. Maybe they recognise this is a problem for areas of endemic fluorosis and not for areas using CWF.

Unfortunately researchers like Choi et al., (2015) have limited their working hypothesis only to chemical toxicity. But, dental defects are known to cause decreased quality of life and this could be translated into learning difficulties and reduced IQ scores. In a recent article I suggested these researchers widen their considerations to including the hypothesis that severe dental fluorosis, in itself, could be a cause of cognitive deficits simply because of the effect of physical anomalies and appearance on IQ (see Perrott 2015).

This is, after all, consistent with their findings that cognitive deficits were significantly related to incidence of severe/medium dental fluorosis but not to the F concentration in the drinking water.

Other oral defects like bad dental decay are also known to cause a reduced quality of life and may lead to learning problems and cognitive deficits. While severe dental fluorosis is a problem in  areas of endemic fluorosis it is not here. I suggest you worry more about possible IQ effects of tooth decay than any due to fluoride in our drinking water.

You are just scaremongering with your flight of fancy suggesting that “institutionalizing the additional proportion of the population due to mental deficiency” should be considered as a cost against CWF. One could more sensibly say that in NZ the quality of life and possible cognitive deficits arising from dental decay should be considered as a cost against opposition to CWF.

Conclusion

Your letter is part of an ongoing campaign by New Zealand anti-fluoridation activists like FFNZ and New Health NZ to discredit the NZ Fluoridation Review. New Health NZ is part of the NZ Health Trust, a well-funded lobby group for the “natural”/alternative health industry in New Zealand. It campaigns on issues like fluoridation, vaccinations and “chemtrails” (see Who is funding anti-fluoridation High Court action? and Corporate backers of anti-fluoride movement lose in NZ High Court).

On the surface your complaint about the mistake in the summary of the NZ Fluoridation review is at least churlish. Especially as it was corrected when brought to the authors’ attention and there was no mistake in the body of the review. Despite the same mistake in the original version of Harvard University’s press release on the research neither you nor your colleagues in the NZ anti-fluoride movement have complained to Harvard University.

One would have though the correction of the mistake would have pulled the rug out from under the anti-fluoridation critics but you have unjustly tried to use the original mistake to argue that the authors of the NZ Fluoridation Review misunderstood or misrepresented the science. In fact, the misrepresentation comes from you and your anti-fluoridation colleagues as the study you seem to pin all your arguments on was made in areas of endemic fluorosis,  (mainly in China) and has no direct relevance to New Zealand CWF.

New Zealand health professionals and members of local bodies should see your complaint for what it is – part of the ongoing activist campaign against CWF. These decision makers are justified in the confidence they have in the NZ Fluoridation Review.

Yours sincerely,

Dr Ken Perrott

References

Beltrán-aguilar, E. D., & Barker, L. (2010). Prevalence and Severity of Dental Fluorosis in the United States , 1999 – 2004 (pp. 1999–2004).

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.

Cheng, H., & Lynn, R. (2013). The adverse effect of fluoride on Children’s intelligence: A systematic review. Mankind Quarterly, 53, 306–347.

Choi, A. L., Sun, G., Zhang, Y., & Grandjean, P. (2012). Developmental fluoride neurotoxicity: A systematic review and meta-analysis. Environmental Health Perspectives, 120(10), 1362–1368.

Choi, A. L., Grandjean, P., Sun, G., & Zhang, Y. (2013). Developmental fluoride neurotoxicity: Choi et al. Respond. Environmental Health Perspectives, 121(3), A70.

Choi, A. L., Zhang, Y., Sun, G., Bellinger, D., Wang, K., Yang, X. J., … Grandjean, P. (2015). Association of lifetime exposure to fluoride and cognitive functions in Chinese children: A pilot study. Neurotoxicology and Teratology, 47, 96–101.

Eason, C., & Elwood, JM. Seymour, Thomson, WM. Wilson, N. Prendergast, K. (2014). Health effects of water fluoridation : A review of the scientific evidence (p. 74).

Fluoride Free New Zealand. (2014). Scientific and Critical Analysis of the 2014 New Zealand Fluoridation Report

Hansen, L. (2015). An open letter to the Prime Minister’s Chief Science Advisor and to the President of the Royal Society of New Zealand.

Ministry of Health. (2010). Our Oral Health Key findings of the 2009 New Zealand Oral Health Survey. Wellington, Ministry of Health.

Perrott, K. W. (2015). Severe dental fluorosis and cognitive deficits. Neurotoxicology and Teratology.

Saxena, S., Sahay, A., & Goel, P. (2012). Effect of fluoride exposure on the intelligence of school children in Madhya Pradesh, India. Journal of Neurosciences in Rural Practice, 3(2), 144–9.

Sudhir, K. M., Chandu, G. N., Prashant, G. M., & Reddy, V. V. S. (2009). Effect of fluoride exposure on Intelligence Quotient ( IQ ) among 13-15 year old school children of known endemic area of fluorosis , Nalgonda District , Andhra Pradesh . JOURNAL OF THE INDIAN ASSOCIATION OF PUBLIC HEALTH DENTISTRY, 2009(13), 88–94.

Xiang, Q. (2014) Fluoride and IQ research in ChinaKeynote Address at FAN’s 5th Citizens’ Conference on Fluoride.

 

 

 

 

 

Severe dental fluorosis and cognitive deficits – now peer reviewed

peer-review-cartoon
Last May I raised the possibility that the much touted relationship of small IQ declines for children living in areas with naturally high fluoride in drinking water could be associated with severe dental fluorosis and not a chemical neurotoxicant (see Confirmation blindness on the fluoride-IQ issue). In November I repeated this argument because the recently published work by Choi et al (2015) provided evidence of a statistically significant relationship of cognitive deficits to severe dental fluorosis for Chinese children living in high fluoride areas  (see Severe dental fluorosis the real cause of IQ deficits?).
I am pleased to report the journal Neurotoxicology and Teratology (which published the Choi et al., 2015 paper) have now accepted a peer-reviewed letter to the Editor from me on the subject:

Perrott, K. W. (2015). Severe dental fluorosis and cognitive deficits. Neurotoxicology and Teratology.

Don’t limit possible hypotheses

My letter warns:

“cognitive deficits could have many causes or influences – genetic, environmental and/or social. Researchers need to be careful not to limit their possible hypotheses or research approaches. Unfortunately Choi et al. (2015) appear to be doing just this with their plans for a larger scale study targeted only at “fluoride’s developmental neurotoxicity.””

It points out:

Choi et al. (2012) did highlight the need for further research. Broadbent et al. (2014) showed no effect of fluoride on IQ at the optimum drinking water concentrations used in CWF [community water fluoridation]. However, most of the reports reviewed by Choi et al. (2012) considered data from areas of endemic fluorosis where drinking water fluoride concentrations are higher.”

“Choi et al. (2015) did not find a statistically significant association of drinking water fluoride concentration with any of the neuropsychological measurements. But they did find one for moderate and severe dental fluorosis with the WISC-R digit span subtest.”

This suggests a possible hypothesis involving the effects of negative physical appearance and not a chemical neurotxocant:

“Emotional problems in children have been related to physical anomalies, including obvious oral health problems like severe tooth decay (Hilsheimer and Kurko, 1979). Cognitive deficits can sometimes be related to emotional problems and subsequent learning and behavior problems. Quality of lifeparticularly oral health related quality of life – is negatively related to tooth decay and severe dental fluorosis. It is possible that negative oral health quality of life feelings in children could induce learning and behavior difficulties which are reflected in neuropsychological measurements.”

Difference between areas of endemic fluorosis and CWF

This hypothesis is applicable to children in areas of endemic fluorosis but is not relevant to areas where CWF is used:

“Sixty percent of the children in the Choi et al. (2015) pilot study had dental fluorosis graded as moderate or severe. This likely reflects the endemic fluorosis of the study area. Only a few percent of individuals in areas exposed to the optimum levels of drinking water fluoride used in CWF have dental fluorosis that severe. For example, a recent oral health survey in New Zealand found 2% of individual had moderate dental fluorosis and 0% had severe dental fluorosis (Ministry of Health, 2010). Similarly a US survey found only 2% of individuals exhibited moderate dental fluorosis and less the 1% severe dental fluorosis (Beltrán-Aguilar et al., 2010).”

“Tooth decay and other oral defects negatively impact a child’s quality of life as assessed by children and parents (Barbosa and Gavião, 2008; Nurelhuda et al., 2010; de Castro et al., 2011; Aguilar-Díaz et al., 2011; Biazevic et al., 2008; Abanto et al., 2012Krisdapong et al., 2012; Bönecker et al., 2012; Locker, 2007). Quality of life impacts have also been found for dental fluorosis, but there is a marked difference in physical appearance and quality of life assessments for children with moderate/severe dental fluorosis compared with those having none/questionable or very mild/mild forms.

The physical appearance of moderate and severe forms of dental fluorosis is generally considered undesirable so we could expect these forms to be associated with poor quality of life and this appears to be the case (Chankanka et al., 2010; Do and Spencer, 2007; Chikte et al., 2001). In contrast, most studies report no effect or a positive effect of questionable, very mild and mild forms of dental fluorosis on quality of life (Do and Spencer, 2007; Chankanka et al., 2010; Peres et al., 2009; Biazevic et al., 2008; Büchel et al., 2011; Michel-Crosato et al., 2005).

Given the different patterns of dental fluorosis severity in areas of endemic fluorosis and areas where CWF is practiced and fluoride intakes are likely to be optimal it seems reasonable to expect a difference in ways fluoride intake influences health-related quality of life and possibly cognitive factors.”

My purpose in this letter was to argue that other mechanisms besides chemical neurotoxicity should be considered in these studies. I hope researchers take this on board and look forward to the response of Choi and her co-workers to this suggestion.

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