Fluoridation: Whakatane teaches us something we should already know


Parliamentary Committee – proper place to discuss attitudes towards community water fluoridation?

So, the Whakatane District Council today reversed its decision to stop fluoridation (see Whakatane fluoride flip-flop). A decision made only a few weeks ago (see Fluoridation: Whakatane District Council makes the Hamilton mistake).  The new vote effectively acknowledges they had made a mistake – a mistake they would not have made if they had paid attention to what happened in Hamilton 2 – 3 years ago.

Well, really two mistakes:

1: Councils should not ignore the democratic will of the electorate without very good reasons. Sure, the referenda in Hamilton and Whakatane were non-binding. But they did represent the will of the people. And the council did not have adequate reasons for ignoring that will.

One difference in Whakatane is that only Ohope and Whakatane itself are fluoridated. The new resolution requests the council to decide whether to fluoridate other areas where the voters supported it – noticeably it effectively accepts the will of those voters opposed to fluoridation where they are a majority in a specific water treatment area.

2: Councils should not be so foolish as to think they can decide the science, or decide health matters. It amazes me that the mayor of Whakatane could acknowledge his council does not have scientific skills – yet he went ahead and got the council to make decisions about the science and health issues involved with community water fluoridation!

Perhaps he would not have done this if there had not been an ideologically and commercially motivated activist group pressuring the council. But that is no excuse.

Would this Mayor have succumbed to pressure from an activist group who disagreed with accepted science and technology of road and bridge building? Of house construction? Or any other matter the council considers. Just imagine what havoc a flat earth society or anti-gravity pressure group could play.

I would hope not. We cannot have such important issues endangered because a group with no skills in the matter takes it upon itself to think it can make decisions about the science, technology and health recommendations. Whatever pressure is coming from activist groups.

It is not the job of councils to decide such matters.

What should councils decide

Yes, they must decide on financial and operational matters involved with these issues. But they don’t get to decide the science and technology. It is hubris on their part to think they can.

Councils do have a role. As operators of water treatment plants they must decide on the financial and working matters. They must decide on the feasibility of specific water treatments.

Under current legislation, they must also take into account the attitudes of their electorate. The government and central health bodies recognise that community water fluoridation can be controversial for some people. Therefore, they encourage local communities to make the final decisions. It is noticeable that where Health Boards seek to extend community water fluoridation they use community consultation and education, including referenda, and do not impose a central demand.

In the end, no matter what the science says or what central health authorities recommend, it is up to communities to make up their minds on a controversial social policy – even if that results in a decision contrary to skilled recommendations.

But councils should not have any role in deciding the science or health policies. The appropriate bodies already do that and they make their recommendations. It is arrogant for councils to think they can, or should, rewrite those recommendations and conclusions about community water fluoridation.

Councils really have nothing to complain about

Councils complain they are being asked to make decisions they are not skilled to make – but that is up to them. If they accepted the conclusions and recommendation of the appropriate central bodies and limited their consideration to financial and working matters which are correctly within their skill set they would have nothing to complain about. Similarly, they should accept the democratic will of their voters on this issue (unless there are good financial or operational matters suggesting otherwise).

Perhaps there is need to remove councils from that assessment of community attitudes towards fluoridation. Let it be done by health boards.

As for the demand that so-called “independent”  or “alternative” groups have an input into decisions – surely the most appropriate place for that is at a central level – the parliamentary health committee or reviews by the Ministry of Health. Such considerations would be less influenced by the childish politics we often see at the local level – especially in election year (which is the case for Whakatane and was also for Hamilton).

Councils should stop sticking their noses into areas they have no authority or skills to make decisions on.

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Chemistry – “to dupe, to cheat?”


OK – these are actors – but they could be portraying a certain PhD qualified chemist presenting a submission to a local body

I was reading a few articles about Dmitri Mendeleev recently – seeing we were celebrating his 182nd birthday (see What a pleasant surprise!). One I came across (Dmitri Mendeleev: Chemistry, the hot-air balloon and vodka) set me back a bit. Initially, it offended my feeling about the noble science of chemistry (have I mentioned I am a chemist) with this little titbit:

“Mendeleev himself did not consider himself to be a chemist. And rightly so. Back in those years the word “chemist” was synonymous to conman and the expression “to do chemistry” (khimichit in Russian) meant to dupe, to cheat.”

OK, I can understand how that attitude came about in  the early days – scientists often had unsavoury links with the spiritual and industrial or economic spheres. But surely not today?

Unfortunately, it does happen today. We can all think of a few names of qualified chemists (and other scientists) who are effectively snake-oil sales persons. Or something worse – in my mind – people who use science and cherry-picking of the scientific literature to misinform the public for ideological reasons. Paul Connett, from the US anti-fluoridation activist group the Fluoride Action Network, is an obvious example.

When you think about it these sort of people – with academic degrees – are all over the place. From “creationist science,” to “intelligent design” to climate change denial, anti-vaccination and anti-GMO groups, and so on. Their presence  seems particularly strong in the alternative and “natural” health movement. And this is an area where the use of honorifics like Doctor, Professor, etc., is milked quite irrationally.

We are all consumers of scientific information so should be wary of such charlatans. We owe it to ourselves not to be swayed by such honorifics so that we don’t properly assess their claims. If we do not have the scientific skills to do our own critical analysis of the claims then we should take the advice of experts whose background rest on more than a degree. Their occupation, employment and publication history.

This is particularly true for public officials when they make decisions which can affect the health of citizens. And, yes, I must admit I have in mind the Whakatane District Council who tomorrow are to reconsider their decision a few weeks back to discontinue community water fluoridation.  On this – have a read of this open letter from one of the councillors criticising the way that decision was made (Open letter to Councillors).

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What a pleasant surprise!


I don’t normally notice the special images on Google’s search page but was pleasantly surprised this morning to see this one.

It’s great to see some people are celebrating  Dmitri Mendeleev’s 182nd birthday. He was born February 8, 1834 , in the village of Verkhnie Aremzyani, near Tobolsk in Siberia.

Mendeleev is considered the “father” of the Periodic Table. I remember as a school student being fascinated by the periodic table and the early versions of it as the researchers of the time attempted to make sense of chemistry. That fascination remained with me as my study of chemistry became more advanced Today, the table is firmly based in quantum physics and can be derived directly from quantum considerations. Yet, in  those early days, no-one had that theoretical insight and derived the table from the chemical and physical properties of the then-known elements. The fact this enabled them to predict the existence of other elements, and the fact this lead to successful searches for them, has always inspired me.

So, Dmitri Mendeleev is one of the giants whose shoulders today’s scientists stand on. Only natural then that this commemorative ruble marking the 150th anniversary of his birth is a prized souvenir I picked in up Moscow 30 years ago.


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Censorship by demonisation

I believe the demonisation of Vladimir Putin, the president of the Russian Federation, creates an obstacle to political understanding. This was obvious in the political rhetoric surrounding the shooting down of the Malaysian Flight MH17 over the Donbass region in Ukraine. But is it also obvious in the continuing rhetoric around the Ukrainian and Syrian civil wars.

This  demonisation can end up being a form of censorship as it prevents anything like an objective discussion of political issues. It can even prevent people using available news sources because they are tainted in their minds if they don’t go along with the demonisation.

In a sense, it is like the conditioning of Pavlov’s dogs. For many people the words “Putin” and “Russia” create an immediate knee-jerk reaction which prevents discussion of the issues at hand.

This video showing an attempted discussion, on Aljazeera US,  of the possibilities of the US and Russian Federation working together to counter Daesh (ISIS) in Syria and bring about a political settlement of the civil war is a rather extreme example of problems resulting from demonisation. So extreme that Aljazzera no longer hosts the video of the programme – this one was recorded off the TV screen by a separate person who has made it available.

Frankly, I cannot understand how Aljazeera US allowed their programme frontperson to behave so badly.

Thanks to: Stephen Cohen Schools Al Jazeera Buffoon on Russia


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Once more on the IQ and fluoride myth – why ignore other factors?

The “fluoride damages IQ” myth won’t go away – mainly because it is avidly promoted by campaigners against community water fluoride (CWF). This is despite the fact that no link has even been drawn between CWF and IQ (the only relevant study shows no connection). But that doesn’t stop ideologically driven campaigners who rely on poor quality studies from areas of endemic fluorosis where dietary fluoride intake is higher than in areas using CWF.

There are plenty such studies, but a more recent one illustrates their problems – and the role  confirmation bias seems to play in these studies. It is:

Kundu, H., Basavaraj, P., Singla, A., Gupta, R., Singh, K., & Jain, S. (2015). Effect of fluoride in drinking water on children′s intelligence in high and low fluoride areas of Delhi. Journal of Indian Association of Public Health Dentistry, 13(2), 116.

It’s another study where the IQ values of children from a “high fluoride” area were compared with those for children from a “low fluoride area.” There was a statistically significant difference and the paper goes on to claim:

“High F concentration in the drinking water was found to have marked systemic effects on the IQ of children. Though the precise mechanism by which F crosses the blood brain barrier is still not clean‑cut; enough evidence survives for the influence of F intake via drinking water and low IQ of the child.”

However they do acknowledge:

“Apart from fluoride there are other factors which also affect IQ of children. In the present study, mothers diet during pregnancy also significantly affected the IQ of the children.”

The supporting data is poorly presented and described – for example, no indication is given of the fluoride concentration in the drinking water of the “high fluoride and “low fluoride” areas used. Although they do cite areas in Delhi (where the study was located) with fluoride concentration as high as 32.5 ppm!. And I cannot find any details on “mothers diet during pregnancy” (except perhaps division into two groups – “routine” or “special diet as suggested by the doctor during pregnancy”).

Those confounding factors

These sorts of studies almost always rely on finding a statistically significant difference in the IQ values of children in two different areas or villages. But that statistical significance says nothing about the causal factors involved – it may have nothing to do with differences in fluoride levels.

Kundu et al., (2015) do at least include some data on confounding factors which is often missing from such studies. These show significant difference between the groups from the “high fluoride” and “low fluoride” areas which have no connection with fluoride in drinking water – such as father’s occupation, mother’s education and father’s education) – or only an indirect connection (dental fluorosis).

Here is a summary of the data for the various factors. I have selected the data so to show as two values – equal to “high fluoride” and “low fluoride.”


You get the picture. The areas were chosen according to the concentrations of fluoride in drinking water (whatever they were), but they could equally have been chosen on the basis of parental education, father’s occupation or prevalence of the more severe forms of dental fluorosis.

In fact, rather than concluding drinking water fluoride has a “marked systemic effects on the IQ of children” we could equally have concluded:

  • “The father’s occupation has a marked effect on the IQ of children with the children of unskilled fathers having a lower IQ.”
  • “The mother’s and father’s education has a marked effect on the IQ of children with the children of parents with a higher education having a higher IQ.”
  • “Diet of mothers during pregnancy has a marked effect on the IQ of children.” (The paper did not include data suitable for plotting for this.)

The dental fluorosis factor interests me as I have suggested that, in areas of endemic fluorosis, the physical appearance of defective teeth could lower quality of life and cause learning difficulties which are reflected in lower IQ values (see Severe dental fluorosis the real cause of IQ deficits?Severe dental fluorosis and cognitive deficits – now peer reviewed and Free download – “Severe dental fluorosis and cognitive deficits”).

I think that this is more reasonable as a mechanism than the chemical toxicity mechanism that almost all authors of these sorts of papers assume – but never support with any evidence. Even when dental fluorosis is considered it is usually treated as an indicator of lifetime intake of fluoride (which it is) rather than and independent cause of low IQ.


Most studies like this seem to be motivated by confirmation bias. Despite the possibility of a range of factors being involved, and some of these such as parental education being a more obvious cause, there appears to be an urge to interpret data as evidence of a chemical toxicity mechanism involving fluoride. And there is never any experimental work to confirm this preferred mechanism.

To my mind, if fluoride is implicated in the low IQ values the mechanism involving effects of dental fluorosis on quality of life and learning difficulties appears more credible than an unproven chemical toxicity.

Note: None of this is directly relevant to areas where CWF is used. The prevalence of more serious forms of dental fluorosis is very small in these areas and not related to CWF. Also, no study has yet found an effect of CWF on IQ. Given the higher levels of fluoride used in the studies from areas of endemic fluorosis, and the higher levels of serious forms of dental fluorosis, extrapolation of the results to areas where CWF is used is completely unwarranted.

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January ’16 – NZ blogs sitemeter ranking

Blog-Post-Checklist (1)

Image credit: 29-Point Blog Post Checklist: How to Seduce Your Readers to Buy

There are about 300 blogs on the list, although I am weeding out those which are no longer active or have removed public access to sitemeters. (Let me know if I weed out yours by mistake or get your stats wrong).

Every month I get queries from people wanting their own blog included. I encourage and am happy to respond to queries but have prepared a list of frequently asked questions (FAQs) people can check out. Have a look at NZ Blog Rankings FAQ. This is particularly helpful to those wondering how to set up sitemeters. Please note, the system is automatic and relies on blogs having sitemeters which allow public access to the stats.

Here are the rankings of New Zealand blogs with publicly available statistics for January 2016. Ranking is by visit numbers. I have listed the blogs in the table below, together with monthly visits and page view numbers. Meanwhile, I am still keen to hear of any other blogs with publicly available sitemeter or visitor stats that I have missed. Contact me if you know of any or wish help adding publicly available stats to your bog.

You can see data for previous months at Blog Ranks

Subscribe to NZ Blog Rankings Subscribe to NZ blog rankings by Email Find out how to get Subscription & email updates Continue reading

Fluoridation: Whakatane District Council makes the Hamilton mistake


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.”


“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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“Crusade Against Multiple Regression Analysis” – don’t throw baby out with bathwater


Richard Nisbett is a professor of psychology and co-director of the Culture and Cognition Program at the University of Michigan.

Edge has an interesting talk  about the problems of research relying on regression analyses (see The Crusade Against Multiple Regression Analysis).  Unfortunately, it has some important faults – not the least is his use of the term “multiple regression” when he was really complaining  about simple regression analysis.

Professor Richard Nisbett quite rightly points out that many studies using regression analysis are worthless, even misleading – even, as he suggests, “quite damaging.”  Damaging because these studies gets reported in the popular media and their faulty conclusions are “taken as gospel” by many readers. Nisbet says:

“I hope that in the future, if I’m successful in communicating with people about this, there’ll be a kind of upfront warning in New York Times articles: These data are based on multiple regression analysis. This would be a sign that you probably shouldn’t read the article because you’re quite likely to get non-information or misinformation.

Knowing that the technique is terribly flawed and asking yourself—which you shouldn’t have to do because you ought to be told by the journalist what generated these data—if the study is subject to self-selection effects or confounded variable effects, and if it is, you should probably ignore them. What I most want to do is blow the whistle on this and stop scientists from doing this kind of thing. As I say, many of the very best social psychologists don’t understand this point.

I want to do an article that will describe, similar to the way I have done now, what the problem is. I’m going to work with a statistician who can do all the formal stuff, and hopefully we’ll be published in some outlet that will reach scientists in all fields and also act as a kind of “buyer beware” for the general reader, so they understand when a technique is deeply flawed and can be alert to the possibility that the study they’re reading has the self-selection or confounded-variable problems that are characteristic of multiple regression.”

I really hope he does work with a statistician who can explain to him the mistakes he is making.  The fact that he raises the issue of “confounded-variable problems” shows he is really talking about simple regression analysis. This problem can be reduced by increasing the types and numbers of comparisons performed in an analysis – by the use of multiple regression analysis, the very thing he makes central to his attack!

The self-selection problem

Nisbett gives a couple of examples of the self-selection problem:

“A while back, I read a government report in The New York Times on the safety of automobiles. The measure that they used was the deaths per million drivers of each of these autos. It turns out that, for example, there are enormously more deaths per million drivers who drive Ford F150 pickups than for people who drive Volvo station wagons. Most people’s reaction, and certainly my initial reaction to it was, “Well, it sort of figures—everybody knows that Volvos are safe.”

Let’s describe two people and you tell me who you think is more likely to be driving the Volvo and who is more likely to be driving the pickup: a suburban matron in the New York area and a twenty-five-year-old cowboy in Oklahoma. It’s obvious that people are not assigned their cars. We don’t say, “Billy, you’ll be driving a powder blue Volvo station wagon.” Because of this self-selection problem, you simply can’t interpret data like that. You know virtually nothing about the relative safety of cars based on that study.

I saw in The New York Times recently an article by a respected writer reporting that people who have elaborate weddings tend to have marriages that last longer. How would that be? Maybe it’s just all the darned expense and bother—you don’t want to get divorced. It’s a cognitive dissonance thing.

Let’s think about who makes elaborate plans for expensive weddings: people who are better off financially, which is by itself a good prognosis for marriage; people who are more educated, also a better prognosis; people who are richer; people who are older—the later you get married, the more likelihood that the marriage will last, and so on.”

You get the idea. But how many academic studies rely on regression analysis of data from a self-selected sample of people? The favourite groups for many studies are psychology undergraduates at universities!

Confounded variable problem

I have, in past articles, discussed some examples of this related to fluoride and community water fluoridation.

See also: Prof. Nisbett’s “Crusade” Against Regression


Simple regression analyses are too prone to confirmation bias and Nisbett should have chosen his words more carefully, and wisely. Multiple regression is not a silver bullet – but it is far better than a simple correlation analysis. Replication and proper peer review at all research and publication stages also helps. And we should always be aware of these and other limitation in exploratory statistical analysis. Ideally, use of such analyses should be limited to a guide for future, more controlled, studies.

Unfortunately, simple correlation studies are widespread and reporters seem to see them as easy studies for their mainstream media articles. This is dangerous because it has more influence on readers, and their actions, than such limited studies really warrant. And in the psychological and health fields there are ideologically motivated groups who will promote such poor quality studies because it fits their own agenda.

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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.


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).




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.


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.


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