Tag Archives: endemic fluorosis

Debunking a “classic” fluoride-IQ paper by leading anti-fluoride propagandists

epa-meeting-sept5-2014

Three of the paper’s authors – Quanyong Xiang (1st Left), Paul Connett (2nd Left) and Bill Hirzy (far right) – preparing to bother the EPA.

Anti-fluoride groups and “natural”/alternative health groups and websites are currently promoting a new paper by several leading anti-fluoride propagandists. For two reasons:

  1. It’s about fluoride and IQ. The anti-fluoride movement recently decided to give priority to this issue in an attempt to get recognition of possible cognitive deficits, rather than dental fluorosis,  as the main negative health effect of community water fluoridation. They want to use the shonky sort of risk analysis presented in this paper to argue that harmful effects occur at much lower concentrations than currently accepted scientifically. Anti-fluoride guru, Paul Connett, has confidently predicted that this tactic will cause the end of community water fluoridation very soon!
  2. The authors are anti-fluoride luminaries – often described (by anti-fluoride activists) as world experts on community water fluoridation and world-class scientists. However, the scientific publication record for most of them is sparse and this often self-declared expertise is not actually recognised in the scientific community.

This is the paper – it is available to download as a pdf:

Hirzy, J. W., Connett, P., Xiang, Q., Spittle, B. J., & Kennedy, D. C. (2016). Developmental neurotoxicity of fluoride: a quantitative risk analysis towards establishing a safe daily dose of fluoride for children. Fluoride, 49(December), 379–400.

bruce-spittle

Co-author Bruce Spittle – Chief Editor of Fluoride – the journal of the International Society for Fluoride Research

I have been expecting publication of this paper for some time – Paul Connett indicated he was writing this paper during our debate in 2013/2014. FAN newsletters have from time to time lamented at the difficulty he and Bill Hirzy were having getting a journal to accept the paper. Connett felt reviewers’ feedback from these journals was biased. In the end, he has lumped for publication in Fluoride – which has a poor reputation because of its anti-fluoride bias and poor peer review. But, at last Connett and Hirzy have got their paper published and we can do our own evaluation of it.

The authors are:

david-c-kennedy

Co-author David C. Kennedy – past president of the International Academy of Oral Medicine and Toxicology – an alternative dentist’s group.

Bill Hirzy, Paul Connett and Bruce Spittle are involved with the Fluoride Action Network (FAN), a political activist group which receives financial backing from the “natural”/alternative health industry. Bruce Spittle is also the  Chief Editor of Fluoride – the journal of the International Society for Fluoride Research Inc. (ISFR). David Kennedy is a Past President of the International Academy of Oral Medicine and Toxicology which is opposed to community water fluoridation.

Quanyong Xiang is a Chinese researcher who has published a number of papers on endemic fluorosis in China. He participated in the 2014 FAN conference where he spoke on endemic fluorosis in China.

xiang-Endemic fluorosis

Much of the anti-fluoridation propaganda used by activists relies on studies done in areas of endemic fluorosis. Slide from a presentation by Q. Xiang to an anti-fluoride meeting organised by Paul Connett’s Fluoride Action Network in 2014.

Critique of the paper

I have submitted a critique of this paper to the journal involved. Publication obviously takes some time (and, of course, it may be rejected).

However, if you want to read a draft of my submitted critique you can download a copy from Researchgate – Critique of a risk analysis aimed at establishing a safe dose of fluoride for children.  I am always interested in feedback – even (or especially) negative feedback – and you can give that in the comments section here or at Researchgate.

(Please note – uploading a document to Researchgate does not mean publication. It is simply an online place where documents can be stored. I try to keep copies of my documents there – unpublished as well as published. It is very convenient).

In my critique I deal with the following issues:

The authors have not established that fluoride is a cause of the cognitive deficits reported. What is the point in doing this sort of risk analysis if you don’t actually show that drinking water F is the major cause of cognitive deficits? Such an analysis is meaningless – even dangerous, as it diverts attention away from the real causes we should be concerned about.

All the reports of cognitive deficits cited by the authors are from areas of endemic fluorosis where drinking water fluoride concentrations are higher than where community water fluoridation is used. There are a whole range of health problems associated with dental and skeletal fluorosis of the severity found in areas of endemic fluorosis. These authors are simply extrapolating data from endemic areas without any justification.

The only report of negative health effects they cite from an area of community water fluoridation relates to attention deficit hyperactivity disorder (ADHD) and that paper does not consider important confounders. When these are considered the paper’s conclusions are found to be wrong – see ADHD linked to elevation not fluoridation, and ADHD link to fluoridation claim undermined again.

The data used by the Hirzy et al. (2016) are very poor. Although they claim that a single study from an area of endemic fluorosis shows a statistically significant correlation between IQ and drinking water fluoride that is not supported by any statistical analysis.

The statistically significant correlation of IQ with urinary fluoride they cite from that study explains only a very small fraction of the variability in IQ values (about 3%) suggesting that fluoride is not the major, or maybe not even a significant, factor for IQ. It is very likely that the correlation between IQ and water F would be any better.

Confounders like iodine, arsenic, lead, child age, parental income and parental education have not been properly considered – despite the claims made by Hirzy et al. (2016)

The authors base their analysis on manipulated data which disguises the poor relations of IQ to water fluoride. I have discussed this further in Connett fiddles the data on fluorideConnett & Hirzy do a shonky risk assessment for fluoride, and Connett misrepresents the fluoride and IQ data yet again.

Hirzy et al. (2016) devote a large part of their paper to critiquing Broadbent et al (2014) which showed no evidence of fluoride causing a decrease in IQ  using data from the Dunedin Multidisciplinary Health and Development Study. They obviously see it as a key obstacle to their analysis. Hirzy et al (2016) argue that dietary fluoride intake differences between the fluoridated and unfluoridated areas were too small to show an IQ effect. However, Hirzy et al (2016) rely on a motivated and speculative estimate of dietary intakes for their argument. And they ignore the fact the differences were large enough to show a beneficial effect of fluoride on oral health.

Conclusion

I conclude the authors did not provide sufficient evidence to warrant their calculation of a “safe dose.” They relied on manipulated data which disguised the poor relationship between drinking water fluoride and IQ. Their arguments for their “safe dose,” and against a major study showing no effect of community water fluoridation on IQ, are highly speculative and motivated.

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Premature births a factor in cognitive deficits observed in areas of endemic fluorosis?

premature

Could the increased incidence of premature births explain cognitive deficits observed in areas of endemic fluorosis? Image credit: New Kids-Center.

Anti-fluoridation activists are soon likely to be promoting a new paper reporting a study which found a relationship between maternal (in utero) exposure to fluoride and cognitive development delay in infants. Of course, they will be unlikely to mention the study occurred in an area of endemic fluorosis where drinking water fluoride concentrations are much higher than used in community water fluoridation (CWF). They are also unlikely to mention the possible role of premature births in cognitive development delay observed in the study.

The paper is:

Valdez Jiménez, L., López Guzmán, O. D., Cervantes Flores, M., Costilla-Salazar, R., Calderón Hernández, J., Alcaraz Contreras, Y., & Rocha-Amador, D. O. (2017). In utero exposure to fluoride and cognitive development delay in infants . Neurotoxicology

Valdez Jiménez et al., (2017) studied 65 mother-baby pairs in an area of endemic fluorosis in Mexico. The mothers had high levels of fluoride in their urine and this was negatively associated with cognitive functions (Mental Development Index – MDI) in the infants.

The concentration of fluoride in the tap water consumed by the mothers ranged from 0.5 to 12.5 mg/l, with about 90% of water samples containing fluoride above the World Health recommended maximum of 1.5 mg/l.

Fluoride in the mothers’ urine was also high – with the mean concentration for all the mothers of 1.9 mg/l  for the 1st trimester, 2.0 mg/l for the 2nd and 2.7 mg/l for the 3rd trimester. Urinary fluoride concentrations as high as 8.2 mg/l were found. This compares with a mean value of F in urine of 0.65 mg/L) for pregnant women residents in areas with low levels of F in drinking water (0.4 to 0.8 mg/l – similar to that recommended in community water fluoridation).

The MDI test used evaluates psychological processes such as attention, memory, sensory processing, exploration and manipulation, and concept formation. This was negatively associated with maternal urine fluoride concentrations – the association explaining about 24% of the variance.

Room of other influences

This data suggests that other confounding factors which weren’t measured could also contribute to the variation of the MDI results, and if such confounders were included in the statistical analysis the contribution from urinary fluoride may be much less than 24%.

However, I am interested in the data for premature births that were, unfortunately, not included in the statistical analysis. The paper reports “33.8% of children were born premature i.e. between weeks 28-36 and had a birth weight lower than 2.5 kg.” This is high for Mexico – as they say:

“The World Health Organization (WHO) in Mexico reported a rate of 7.3 cases per 100 births; compared with 33.8% of cases per 100 births that we observed in our study. We have 26.5% more cases than expected.”

According to their discussion, other researchers have also reported higher premature births in areas of endemic fluorosis, compared with non-endemic areas.

Is premature birth a mechanism explaining cognitive deficits?

This study differs from many others in that fluoride exposure to the pregnant mother, rather than the grown child, was investigated. While the authors tended to concentrate on possible chemical toxicity effects on the cognitive development of the child in utero it is also possible that indirect effects could operate. For example, premature birth and low birth weights could themselves be a factor in child cognitive development.

In fact, a quick glance a the literature indicates this may be the case. For example, Basten at al., (2015) reported that preterm birth was associated with “decreased intelligence, reading, and, in particular, mathematics attainment in middle childhood, as well as decreased educational qualifications in young adulthood.” It was also associated with decreased wealth at 42 years of age.

The influence of endemic fluorosis on premature births and birth weights may not involve fluoride directly. Health problems abound in endemic areas – as well as the obvious dental and skeletal fluorosis complaints also involve muscles, blood vessels, red blood cells, the gastrointestinal mucosa and other soft tissues. It is easy to see such health problems influencing the prevalence of premature births and birth weights.

Not relevant to CWF

Of course, none of this is relevant to community water fluoridation. Such fluoridated areas do not have the health problems of areas with endemic fluorosis where drinking water concentrations are much higher. But, of course, this does not stop opponents of CWF claiming that similar problems occur at the lower concentrations.

In case anyone attempts to use this suggestion as an argument against CWF I should mention the only study I could find that makes the link between CWF and fluoridation. Often cited by anti-fluoride campaigners it is a poster paper:

Hart et al., (2009). Relationship between municipal water fluoridation and preterm birth in Upstate New York.

Presented at an Annual Meeting of the American Public Health Association the study appears not to have been published in a peer-reviewed journal. While the authors claim to have found a small, but statistically significant, increase in premature births in fluoridated areas this could be due to a number of possible confounding factors.With only a brief abstract to go on it is impossible to critically assess the study  – in fact, I suspect the non-publication is probably an indication of poor quality.

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Water fluoridation – what to expect in the near future

drinking-water-glass-wiki

Community water fluoridation (CWF) will persist in science news for the foreseeable future – not for any valid scientific reason but because of reaction to political pressures against it. This is particularly so in New Zealand where our parliament will be discussing legislative changes to fluoridation decision-making this year.

This is not to say that all the relevant news will be political. There is still ongoing research into the efficacy, cost-effectiveness and possible health effects of fluoridation. Although much of this is a response to pressure from opponents of this social health policy.

So what scientific and political news about CWF should we expect to see in the coming years?

The legislation

In the immediate future, this will be dominated by the new parliamentary legislation [Health (Fluoridation of Drinking Water) Amendment Bill– at least in New Zealand. However, US anti-fluoride campaigners are following this legislation very closely, and will probably become involved in submission on it, so I expect this will also get coverage internationally. At least in the alternative health media which has stong links to the US anti-fluoride activist organisation, Fluoride Action Network (FAN), and which routinely carry their press releases.

The NZ Parliamentary Health Committee is currently taking written submissions on the fluoridation bill. The deadline for these is February 2. Readers interested in making their own submission can find some information on the submission process in my article Fluoridation: members of parliament call for submissions from scientific and health experts.

The bill itself simply transfers the decision-making process for fluoridation from local councils to District Health Boards. But most submissions will inevitably be about the science and not the proposed changes to decision-making – and, considering the promise of the local anti-fluoride group to shower the committee with “thousands and thousands of submissions,” will misrepresent that science. I will be interested to see what allowance the committee chairman makes for such irrelevant submissions when it comes to the public hearings, which could begin as early as February.

The bill has support from all the parliamentary parties, except the small NZ First which apparently wants councils to keep responsibility for fluoridation decisions, but wants to make binding referendums obligatory. So, I predict the bill will be passed this year. However, there will probably be attempts at the committee stages to amend it to transfer decision-making to central government, probably the Ministry of Health. Such an amendment appears to be supported by the Labour Party, but not by the National Party.

The “IQ problem” – a current campaign

There will be some news about research on the question of possible cognitive effects of fluoride in drinking water in the next few years. Not because there is any concern about this among health professionals. But because the claim that fluoride causes a drop in IQ is pushed very strongly by anti-fluoride activists. While they have a long list of claimed negative health effects of fluoridation the IQ claim is currently central to their political campaigns.

The campaigners claim scientific support for this claim. But that support comes mainly from a number of poor quality papers outlining research results from areas of endemic fluorosis (where drinking water concentrations of fluoride are much higher than the optimum levels used for CWF), mainly in China. FAN has a lot invested in this claim because it financed the translation of many of these otherwise obscure papers into English.There is general agreement among health specialists that these studies are not relevant to CWF. Investigation of areas where CWF is used, and where natural fluoride levels are similar to those used in CWF have not shown any neurological effects due to fluoride.

There is general agreement among health specialists that these studies are not relevant to CWF. Investigation of areas where CWF is used, and where natural fluoride levels are similar to those used in CWF have not shown any neurological effects due to fluoride.

However, FAN is strongly pushing the idea that cognitive effects of fluoride (rather than very mild dental fluorosis) should be the main criteria used in determining the recommended maximum levels of fluoride in drinking water. They currently have a petition in front of the US Environmental Protection Agency (EPA) promoting this claim. This may make the news in the near future as the EPA must respond this month and the likely rejection of the petition will no doubt cause a flurry of press releases.

Paul Connett, who with other members of his family runs FAN, has also attempted to use the scientific publication path to promote this claim. His arguments and calculations defining an extremely low maximum concentration, are very naive and his draft paper has already been rejected by journals several times. However, he no doubt lives in hope for its eventual acceptance somewhere. If he is successful this will be trumpeted to the high heavens by his supporters because while they describe Paul Connett as the international authority of water fluoridation he actually has no proper scientific publications in that area.

Research on neurological effects

We expect some research publications in the next year or so from the current US National Toxicity Program research on claims that fluoride at the concentrations used in drinking water fluoridation could have neurological effects. This research is basically a systematic review – according to the proposal:

an “evaluation of the published literature to determine whether exposure to fluoride is associated with effects on neurodevelopment, specifically learning, memory, and cognition.”

The motivation for this work, apart from the political pressure arising from activist claims, is to attempt to evaluate possible effects at concentration relevant to CWF. (Most published animal and human studies have involved higher concentrations). As the proposal says:

“Previous evaluations have found support for an association between fluoride exposure and impaired cognition; however, many of the studies included exposure to high levels of fluoride. Most of the human evidence was from fluoride-endemic regions having high background levels of fluoride, and the animal studies typically included exposure during development to relatively high concentrations of fluoride (>10 mg/L) in drinking water. Thus, the existing literature is limited in its ability to evaluate potential neurocognitive effects of fluoride in people associated with the current U.S. Public Health Service drinking water guidance (0.7 mg/L).”

I discuss the background to the US National Toxicity Program fluoride research in my article Fluoride and IQ – another study coming up.

Canadian Professor Christine Till will soon start a study looking at cognitive and behavioral factors using a data set for pregnant women exposed to contaminants. She intends to investigate the possibility of relationships with markers for fluoride consumption (see ). Anti-fluoride campaigners hold out great hope for results from this study because Till’s previous research is widely used by them to claim that fluoridation causes increased prevalence of attention-deficit hyperactivity disorder (ADHD). However, that research was flawed because potential confounders were not considered properly. In fact, her reported statistically significant correlations disappears when the confounders are included (see  ADHD linked to elevation not fluoridation).

Problems in areas of endemic fluorosis

Health effects including cognitive deficits: The World Health Organisation recommends that drinking water fluoride concentrations should not be higher than 1.5 mg/L because of negative health effects of high concentrations. Many areas of the world do have high drinking water fluoride concentrations and those areas suffer from endemic fluorosis – dental and skeletal fluorosis. This is, of course, a serious problem and there is a continuous stream of research papers devoted to these areas.

This research is not relevant to CWF (where the optimum concentration of 0.7 mg/L or similar levels is used). But, of course, anti-fluoride campaigners will continue to cite these papers as “evidence” against CWF. We may even see an expert on endemic fluorosis being toured in New Zealand to provide scientific credibility to the anti-fluoride campaign. Dr. Ak.K. Susheela, who works on endemic fluorosis in India and has links with FAN, has been speaking at meetings organised by the anti-fluoride movement in North America and has been suggested as a speaker the local anti-fluoride campaigners should bring to New Zealand.

I expect there will be more papers reporting IQ deficits in areas of endemic fluorosis and these will most probably continue to use a chemical toxicity model to explain their results. I personally am interested in the possibility of researchers considering other models, such as the psychological effects of dental and physical deformities like dental and skeletal fluorosis (see Perrott et al. 2015. Severe dental fluorosis and cognitive deficits). Unlikely, considering how research can get locked into pet paradigms, but one can but hope.

Defluoridation: Another big issue in areas of endemic fluorosis is the need to lower drinking water fluoride concentrations. This if often done by finding alternative sources but there is continuing research on treatment methods to do this.

Again, not relevant to CWF – but I do follow this research and find some of it interesting chemically. Perhaps it reminds me of my own research many years ago.

Conclusions

The controversy around CWF is not going to go away. The opposition is strongly grounded in the “natural”/alternative health industry. It has plenty of financial and ideological resources and its message appeals to a significant minority of the population.

Most of the public interest this year will relate to the new legislation – expect plenty of press releases from the anti-fluoride groups as they organise to make and advertise their submissions, and express their anger at the probably inevitable decision that will go against them.

However, there will be a continuing dribble of research reports of relevance to CWF and to the claims advanced by anti-fluoride campaigners. While it is normal for a social health policy to be continually monitored and its literature reviewed, some of this research is a direct result of concerns raised by campaigners and activists.

Many in the scientific community find this sort of political activity annoying. But it does have its up side. CWF has been one of the most hotly contested social health programmes. Consequently is has received more than its fair share of literature reviews and new research.

And that is a good thing. Anti-fluoride activists often claim there is little research on the health effects of CWF. But that is just not true. Ironically it is the very political activity of such campaigners which has led to CWF being one of the most thoroughly researched social health policy.

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Anti-fluoride claims often not relevant to New Zealand

xiang-Endemic fluorosis

Much of the anti-fluoridation propaganda used by activists relies on studies done in areas of endemic fluorosis. Slide from a presentation by Q. Xiang to an anti-fluoride meeting organised by Paul Connett’s Fluoride Action Network in 2014.

As we head towards the parliamentary consideration of new legislation on fluoridation in New Zealand the anti-fluoride groups are building a campaign to oppose the transfer of responsibilities from local councils to District Health Boards. So, their Facebook pages are promoting myths that fluoridation is dangerous to health – and we expect this to intensify as parliament moves into its Health Committee hearings on the bill.

Also expect that the local anti-fluoridation groups, and their backers, will bring out tame “experts” to make presentations to the parliamentary Health Committee and to public meetings.

Has Connett lost his effectiveness in New Zealand campaigns?

Maybe (once again) Paul Connett or Bill Hirzy who are paid propagandists from the US Fluoride Action Network. An activist group financed by the US “natural”/alternative health industry. But perhaps these two are “old hat.” Connett has been making regular visits to Australia and New Zealand during the Southern Hemisphere summers for some time now and the locals have got a bit tired of him. Bill Hirzy accompanied him on last years summer vacation and really didn’t contribute much to the campaign. Thames overwhelmingly supported fluoridation in their referendum last year (see Thames voters decisively support fluoridation) – despite the highly publicised opposition by Connett and Hirzy).

A possible new anti-fluoridation “expert?”

susheela

Poster for an anti-fluoride meeting in Region of Peel, Canada. Image credit: Reiki with Christine

Perhaps local activists recognise this because they are floating ideas of bringing out a new “expert” – Dr A. K. Susheela. She might also have more credibility than either Hirzy or Connett – because, unlike them, she has actually published scientific papers on fluoride. In fact, she is the executive director of India’s Fluorosis Research and Rural Development Foundation – a small non-government organisation based in Delhi. The purpose of the foundation is to encourage awareness of fluorosis in both medical and local Indian communities to curb the spread of this crippling skeletal disease in India.

Susheela has also been doing  the circuit of anti-fluoride campaign meetings in North America (see, for example, ‘Fluoride is a deadly poison’ Peel’s water fluoridation committee has heard). As the poster above indicates, she is being promoted as an expert on fluoride toxicity and fluorosis.  But please note – this does not make her an expert on community water fluoridation.  All her work has concentrated on areas of endemic fluorosis – where dietary intake of fluoride is much higher than in fluoridated areas of New Zealand.

In a 1999 article for UNICEF (Susheela, A. K., Mudgal, A. (1999). Fluoride in water : An overview. UNICEF WATERfront, (13), 11–13.) she admitted:

“According to 1984 guidelines published by the World Health Organization (WHO), fluoride is an effective agent for preventing dental caries if taken in ‘optimal’ amounts.”

She went on to described the WHO recommendations for fluoride in drinking water:

“Water is a major source of fluoride intake. The 1984 WHO guidelines suggested that in areas with a warm climate, the optimal fluoride concentration in drinking water should remain below 1 mg/litre (1ppm or part per million), while in cooler climates it could go up to 1.2 mg/litre. The differentiation derives from the fact that we perspire more in hot weather and consequently drink more water. The guideline value (permissible upper limit) for fluoride in drinking water was set at 1.5 mg/litre, considered a threshold where the benefit of resistance to tooth decay did not yet shade into a significant risk of dental fluorosis.”

For comparison, the target fluoride concentration for community fluoridation in New Zealand is about 0.7 – 1.0 mg/litre. The natural levels of fluoride in New Zealand’s drinking water are even lower. There is no significant risk of skeletal or dental fluorosis of concern due to CWF, or natural levels of fluoride,  in New Zealand.

Dr Susheela has no expertise in the area of community water fluoridation – or areas of the world where drinking water fluoride levels are similarly very low. Perhaps this is why she made the mistake of including Australia and New Zealand among countries where fluorosis is endemic in the above article which included the map below.

susheela-unicef

Dr Susheela is mistaken about fluoride in New Zealand and Australia. Map from her article 

Fluoride Freee NZ disingenuously used this mistake to claim that New Zealand suffered from endemic fluorosis – and cited UNICEF in support.  I would hope that Dr Susheeela, if she does come to New Zealand to campaign against the upcoming fluoridation bill, publicly admits and apologises for this  mistake.

Conclusion

We are used to anti-fluoride campaigners misrepresenting the scientific research on the efficacy and possible health effects of community water fluoridation. But we should also be wary of their claims derived from research in areas of endemic fluorosis where dietary intake of fluoride is much higher than in New Zealand. This includes studies on possible IQ effects and skeletal fluorosis.

The research may be respectable – but the findings are just not relevant to countries like New Zealand where the drinking water fluoride concentrations (in fluoridated and unfluoridated areas) is much lower.

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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.”

Kundu

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.

Conclusions

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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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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Special pleading by Philippe Grandjean on fluoride

Scientists are as human as anyone else. They aren’t immune to jumping on bandwagons, getting bees in their bonnets, special pleading or selectively interpreting their data to support a pet hypothesis or an obsession. The scientific peer review process restrains this human failing somewhat during  normal scientific publishing, but it can get out of hand when there is no such restraint.

Unfortunately Philippe Grandjean demonstrates this failing in a recent post – Mottled fluoride debate on his blog Chemical Brain Drain. This relates to a recent paper of which he is a junior author – . Association of lifetime exposure to fluoride and cognitive functions in Chinese children: A pilot study. I discussed this paper in my article Severe dental fluorosis the real cause of IQ deficits?

So what is wrong with the blog article?

1: Backgound claims about Choi et al (2012) (another paper Grandjean was also a junior author of.

He claims of this paper “children in the high-fluoride areas showed an average IQ 7 points below the controls.” That’s a bit of spin because that paper reported  an IQ deficit of only 0.45 of a standard deviation (7 IQ points is a hypothetical value mentioned in a later explanation). The authors themselves commented:

“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 testing.”

2: He mentions work reported in the 2014 paper on “exposure assessment and cognitive testing of 51 children.” However, the data for only 43 of these children were actually used (and 3 groups of n=8, n=9 and n=26 compared).

3: He claims that for this group “lifetime exposures to fluoride from drinking water covered the full range allowed in the US.” He is attempting to make the finding relevant to the practice of community water fluoridation (CWF). The usual target for optimum fluoride concentration in CWF is 1 ppm or less. I guess their study covered this range because the lowest drinking water concentration was 1 ppm. As no cognitive defects or other effects were found at that concentration it is stretching things to claim the study (and especially the negative effects observed) is relevant to CWF.

4: He claims the measure cognitive defects were more common than actually reported. He says:

“children with fluoride-induced mottling of their teeth – even the mildest forms that appears as whitish specks on the enamel – showed lower performance on some neuropsychological tests.”

Yet what they specifically reported is that:

  • No statistically significant relationship of measured cognitive defects to drinking water fluoride concentration.
  • A statistically significant relationship of one cognitive deficit measure to moderate and severe dental fluorosis.

5: He indulges in further special pleading with statistical results claiming:

“a New Zealand study that “found that fluoridation is not neurotoxic for either children or adults, and does not have a negative effect on IQ”. This interpretation is rather optimistic, as the statistical confidence limits suggest that a loss of 2-3 IQ points could not be excluded by their findings.”

Well, of course this result doesn’t exclude the possibility – but it is completely inappropriate to use that argument to somehow claim the result proves there is an IQ difference.

Dental fluorosis and cognitive deficits

DentalFluorosis

This photo accompanies Grandjean’s blog post. Could it be that severe dental fluorosis could contribute to learning difficulties and hence IQ deficits just because of appearance?

The Choi et al (2014) study did find a statistically significant relationship of cognitive deficit to moderate/severe dental fluorosis and I discussed this in my article Severe dental fluorosis the real cause of IQ deficits?

Although the numbers in the study were small that conclusion does seem reasonable because moderate/severe dental fluorosis is known to negatively affect the quality of life of children just because of the physical anomaly. That in itself could explain the observed results without needing to invoke some unknown mechanism of chemical neurotoxicity at low fluoride concentrations.

Sixty percent of the children in the Choi et al., (2014) study had moderate/severe dental fluorosis. The graphic below demonstrates that situation is very different to what exists in countries using CWF. The areas reviewed (Choi et al., 2012) and studied (Choi et aql., 2014)  are areas of endemic fluorosis. There results are of course relevent to those situations but should not be naively extrapolated to areas using CWF.

Unfortunately Grandjean and Choi et al., (2014) seem unprepared to consider the possible effect of negative appearance connected with severe dental fluorosis on learning and hence IQ of children. They seem unwilling to consider any hypothesis except their favoured one of chemical toxicity. For example, Choi et al., (2014) are “planning a larger scale study to better understand the dose–effect relationships for fluoride’s developmental neurotoxicity.” Surely that is a blinkered approach.

Similarly Grandjean and Landrigan (2014), in the Lancet paper which anti-fluoride propagandists love to promote, were on thin ice to declare fluoride a neurotoxic element. The only evidence they used for this was the Choi et al., (2014) study where non-chemical factors like negative appearance could be involved. This paper was subsequently criticised in a later issue of the journal. However, its original publication, despite its special pleading, indicates faults in the journal’s peer review process (see and Repeating bad science on fluoride and Controversial IQ study hammered in The Lancet).

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