Endemic fluorosis and its health effects

Much of the anti-fluoridation propaganda used by activists rely 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.

 

The public debate in New Zealand might convince the casual reader that all the science related to fluoride revolves around tooth decay and IQ. But that is certainly not the case on a world scale.

The World Health Organisation gives guidelines for the concentration of fluoride in drinking water recommending it should be in the range 0.5 – 1.5 mg/L. OK, above 0.5 mg/L because of the positive effect it has on oral health, in reducing dental decay. That interests us in New Zealand because our drinking water is more likely to be deficient in fluoride.

But on the world scale, many people are far more interest in the higher limit – or at least in attempting to reduce their drinking water fluoride concentration to below this limit. This is because large areas of the world suffer from the health effects of endemic fluorosis due to the excessive dietary intake of fluoride and the high concentration in their drinking water.

There are significant health effects from endemic fluorosis – effects we don’t’ have here but are important to many countries. So there is plenty of research – both on the health effects and on reducing drinking water concentrations and dietary intake.

In fact, the anti-fluoride campaigners get all the scientific reports they use in “evidence” to oppose community water fluoridation from studies in countries where fluorosis is endemic. Not only is this misrepresenting the science. It is also unbalanced because scientific studies on IQ in areas of endemic fluorosis represent only a small proportion of such health-related studies.

To illustrate this I have done a number of searches on Google Scholar using the terms “endemic fluorosis” and one other term related to a health effect. Here is the resulting table.

“endemic fluorosis” and “?”	Hits in Google Scholar
Alone	8810
And “dental fluorosis”	3570
And “bone”	3570
And “skeletal fluorosis”	2910
And “cancer”	1690
And “death”	1180
And “birth”	1170
And “osteoporosis”	1130
And “body weight”	936
And “gastrointestinal”	808
And “Osteoclerosis	697
And “diabetes”	642
And “cardiovascular”	633
And “reproduction”	592
And “IQ”	480
And “cognitive”	331
And “heart disease”	327
And “hypothyroidism”	297
And “Renal failure”	292
And “obesity”	230
And “infertility”	216
And “non-skeletal fluorosis”	183
And “muscoskeletal”	178
And “birth weight”	135
And “birth defects”	86
And “premature birth”	29

40% of the hits related to “dental fluorosis” and another 40% to “bone” while 33% related to “skeletal “fluorosis.” Obviously, these are of big concern in areas of endemic fluorosis so receive a lot of research attention. In fact, the prevalence of these is used to define an area as endemic.

But only 5% of hits related to IQ – clearly of much less concern to researchers. Yet it seems to be all we hear about here and this illustrates how unbalanced most of the media reports we get here are.

To start with, these health effects do not occur in countries like New Zealand using community water fluoridation. They occur in regions where drinking water contains excessive fluoride and where the dietary intake of fluoride is excessive.

But the other fact is that IQ effects receive relatively little attention in health studies from those areas compared with the more obvious, and more crippling, effects like dental and skeletal fluorosis.

Mind you, that doesn’t stop activists making sporadic claims of all sorts of health effects from fluoridation and relying on studies from areas of endemic fluorosis. But the most frequent claims made by activists at the moment relate to IQ. Perhaps this is because it is harder to hide the fact that we don’t see cases fo skeletal fluorosis or severe dental fluorosis in New Zealand. IQ changes are not so obvious and this might make them a more useful tool for anti-fluoride campaigners to use in their scaremongering.

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Facts about fluorosis – not a worry in New Zealand

This sort of serious dental fluorosis does not occur in New Zealand

A recent issue of the Fluoride Exposed Newsletter gives us the facts about dental fluorosis – a subject very often misrepresented by opponents of community water fluoridation.

Fluoride Exposed also explores what U.S. Surgeon Generals have done to promote prevention of both tooth decay and fluorosis in an article on their website, Is fluoride good for your teeth?:

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Ever notice how words ending with “-osis” sound a bit scary?  That’s because “-osis” is a suffix (from the Greek) commonly used to describe disorders or abnormal states. Tuberculosis, multiple sclerosis…no fun. Those are serious.

Dental fluorosis is one of those things that sounds scarier than it actually is… at least if you live in a country like the good old U.S. of A., where public health and environmental protection agencies and organizations have made the scary kind of dental fluorosis (severe dental fluorosis) exceedingly rare.

Dental fluorosis is a little like blood pressure.  When it’s low, you’re good – in fact, mild dental fluorosis can protect your teeth from cavities.  Moderate dental fluorosis describes the appearance of tooth enamel when kids get exposed to a bit too much fluoride.  Changes range from barely visible white spots or streaks (in most cases) to white spots that are a cosmetic concern.  Severe forms involve staining and pitting.  These severe forms of fluorosis are super rare in the U.S. – because we have those protections we mentioned. In the States, we make sure fluoride isn’t too low or too high in drinking water.  It’s only in regions such as rural India, China, and the African Rift Valley, where severe dental fluorosis commonly reaches an actual disease state and affects tooth health and function.  But in the U.S., fluorosis is one of those things that’s not as scary as it sounds.

As you may already know, fluoride gets into your tooth enamel during the remineralization process and forms a super compound called fluoroapatite that resists decay.  For this reason, our dentists want us to get fluoride, ideally through drinking water and fluoride toothpaste.  Or if you’re in a community without fluoridated water, there are dental treatments and dietary supplements you can get.

But if a child who’s still developing teeth gets too much fluoride, dental fluorosis can occur while the teeth are still forming under the gums.  Data from the National Health and Nutrition Examination Survey (1999-2004) tells us that less than one-quarter of persons aged 6-49 in the United States had some form of dental fluorosis.

They even made a chart that shows the severity level of those affected:

Note: One interesting factoid: In this study, the rate of fluorosis for teenagers aged 12-15 was forty percent! That’s significantly higher than the rate for all age groups taken together.  It’s a data point we’ll be keeping an eye on in future studies.

According to the American Dental Association (ADA), the mild and moderate forms of dental fluorosis we have in the U.S. do not negatively affect the health of your teeth. It’s actually even correlated with some good things.  For example, rates of dental fluorosis are higher in kids whose teeth are more resistant to tooth decay.  Makes sense, right?

That said, we can make sure a child’s amount of fluoride is “just right” – enough to provide cavity protection, but not enough to cause visible changes in the tooth enamel.
5 ways to prevent kiddos from ingesting too much fluoride:

1. 1. Don’t give kids fluoride supplements if your drinking water is already at or above the recommended fluoride concentration of 0.7 mg/L.  You can find out if your water system fluoridates and at what level from this cool site from the CDC: https://nccd.cdc.gov/DOH_MWF/Default/Default.aspx.  Or call your water utility provider.
   2. If your drinking water contains greater than 2 mg/L of fluoride, children 8 years and younger should use an alternative source of drinking water.  A little less than 1% of Americans on public water systems have fluoride above this level.
   3. If you have well water, have it tested for fluoride levels, and again, use an alternative source for kids if fluoride is more than 2 mg/L.  Use an alternative source for everyone in the family if it tests at or above 4 mg/L.
   4. Use only a rice-grain-sized amount of fluoride toothpaste to brush kids’ teeth if they’re younger than 3.
   5. For kids who are 3-6 years old, use a pea-size amount of fluoride toothpaste, and supervise these preschool kids when they brush so they don’t swallow too much fluoride toothpaste.

So that’s it! Dental Fluorosis: it’s a scary name, but not a big worry in the U.S.

Whew! One less “-osis” to freak out about!

Subscribe to the Fluoride Exposed newsletter.

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

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.

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:

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.

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 fluoride, Connett & 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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Fluoridation: New scientific review of fluoride and oral health

Want to get up to date on  research about community water fluoridation (CWF) and the effects of fluoride in dental health in general?

Have a read of this new review. It’s published in a special issue of  Community Dental Health devoted to the WHO approach to the prevention of dental caries through the use of fluoride. And is also deals with possible health effects of fluoridation and fluoride in general.

The Paper is:

O’Mullane et al (2016). Fluoride and Oral Health. Community Dental Health 33, 69–99.

Summary and recommendations

The paper summarises the general conclusions and recommendations about CWF as follows:

1. Community water fluoridation is safe and cost-effective and should be introduced and maintained wherever socially acceptable and feasible.
2. The optimum fluoride concentration will normally be within the range 0.5-1.0 mg/L.
3. The technical operation of water-fluoridation systems should be monitored and recorded regularly.
4. Surveys of dental caries and enamel fluorosis should be conducted periodically. For effective surveillance the World Health Organization suggests that clinical oral health surveys should be conducted regularly every five to six years in the same community or setting.

Requirements for a CWF programme

But it is interesting to read its conclusions about the requirements for implementation of water fluoridation. This gives us an idea of why some areas do not fluoridate and what the technical and social requirements are for a successful CWF programme. These are the sort of things that district health boards will need to consider under the current legislations being considered by the New Zealand parliament.

Here is their list:

1. A prevalence of dental caries in the community that is high or moderate, or firm indications that the caries level is increasing.
2. Attainment by the country (or area of a country) of a moderate level of economic and technological development.
3. Availability of a municipal water supply reaching a large proportion of homes.
4. Evidence that people drink water from the municipal supply rather than water from individual wells, rainwater tanks or other sources.
5. Availability of the equipment needed in a treatment plant or pumping station.
6. Availability of a reliable supply of a fluoride-containing chemical of acceptable quality.
7. Availability of trained workers in the water treatment plant who are able to maintain the system and keep adequate records.
8. Availability of sufficient funding for initial installation and running costs.

How many people have access to CWF internationally?

The review has an appendix providing data on worldwide totals for populations with artificially and naturally fluoridated water. This is very useful and anti-fluoride campaigners are well-known for misrepresenting this information in their attempts to claim that most countries reject CWF.

Here is the table for artificial CWF programs:

It says in summary:

“The estimated worldwide total of people supplied with artificially fluoridated water as at April 2011 is 369,226,000 in 25 countries, including the United Kingdom, the United States, Canada, Brazil, Chile, Argentina, Peru, Panama, Guyana, Guatemala, Republic of Ireland, Spain, Serbia, Australia, New Zealand, Fiji, Malaysia, Singapore, Vietnam, Brunei, China (Special Administrative Region of Hong Kong), Papua New Guinea, Republic of Korea (South Korea), Israel and Libya.”

Natural fluoridation

The review also summarises data for people receiving fluoride through the natural levels of fluoride in their drinking water:

Natural fluoridation in the 25 countries operating artificial fluoridation schemes

“In the 25 countries with artificially fluoridated water there are an estimated 18,061,000 million people drinking naturally fluoridated water at or around the optimal level. That brings the total in these 25 countries consuming optimally fluoridated water to around 387,287,000 million.”

Other countries with natural fluoridation

“In addition, there are a further 27 countries with naturally fluoridated water supplied to an estimated 239,903,000 million people. However, it should be stressed that, in many instances, the naturally occurring fluoride level is in excess of the optimum – for example, in China, India, Argentina, Tanzania, Zambia and Zimbabwe. Total worldwide population drinking optimally fluoridated water.”

In summary – 437 million have access to fluoridated water

Combining data for artificial and natural fluoridation the review concludes:

“General estimates for the number of people around the world whose water supplies contain naturally fluoridated water at the optimum level for oral health are around 50 million. This means that, when the numbers of people with artificially (369.2 million) and naturally fluoridated water supplies (50 million) at the optimum level are added together, the total is around 437.2 million.”

Conclusion

This review is useful for anyone wanting an up-to-date picture of CWF, possible health effects and other issues.

I recommend that anyone active in the dental health area or who needs to respond to questions about fluoridation from the public have their own copy. they will refer to it again and again.

This link goes straight to the download of the pdf.

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Anti-fluoride claims often not relevant to New Zealand

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?”

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.

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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Cochrane fluoridation review. III: Misleading section on dental fluorosis

The Cochrane review did not look at the effect of community water fluoridation (CWF) on dental fluorosis. It simply reviewed data on the prevalence of dental fluorosis at different fluoride drinking water concentrations – up to 7.6 ppm which is well outside the optimum concentration used for CWF.

This is strange for a review specifically about CWF. Strictly speaking, as it stands  this section should have been a separate review on dental fluorosis itself. However, this review did calculate a probable dental fluorosis prevalence at 0.7 ppm (the usual concentration used in CWF) which is misleading because it can be misinterpreted as due completely to CWF when it isn’t. And, of course, anti-fluoridation propagandists have cherry-picked and misinterpreted this.

The forms of dental fluorosis. Questionable, Very Mild and Mild forms are usually considered positively whereas the Moderate and Severe forms are considered negatively. See Water fluoridation and dental fluorosis – debunking some myths

Confusing language

I think is was a serious mistake for the reviewers to include this section in a review on CWF as this can imply the calculated prevalences quoted are caused by CWF. They aren’t.

Strictly, their calculations were reported correctly in the abstract:

“There is a significant association between dental fluorosis (of aesthetic concern or all levels of dental fluorosis) and fluoride level.”

And also in the Plain Language Summary:

“The researchers calculated that, in areas with a fluoride level of 0.7 ppm in the  water, approximately 12% of the people evaluated had fluorosis that could cause concern about their appearance.”

However, in their blog post on the review (see “Little contemporary evidence to evaluate effectiveness of fluoride in the water”) they inappropriately claim:

“There is an association between fluoridated water and dental fluorosis.”

Quite wrong – the association was with fluoride concentration (and most studies were of natural fluoride levels) – not with CWF.

They also use the term “water fluoridation” incorrectly in their comment on other possible harm from fluoride:

“Five studies that reported on dental fluorosis also presented data on the association of water fluoridation with skeletal fluorosis (Chen 1993; Jolly 1971; Wang 2012), bone fracture (Alarcon-Herrera 2001), and skeletal maturity (Wenzel 1982), in participants between the ages of six and over 66 years. Four of the studies included a total of 596,410 participants (Alarcon-Herrera 2001; Chen 1993; Wang 2012; Wenzel 1982), and fluoride concentration in all four studies ranged from less than 0.2 ppm to 14 ppm.”

Their use of the term “water fluoridation” to cover natural fluoride concentrations up to 14 ppm is irresponsible and misleading.

What the review did on dental fluorosis

It simply attempted to find a quantitative relationship between “fluoride level” (concentrations of naturally derived fluoride in drinking water) and dental fluorosis prevalence. It did this for all grades of dental fluorosis from “questionable” to “severe” (see figure above for illustrations fo the different grades). It also did this for “dental fluorosis of aesthetic concern” (which they arbitrarily defined as the mild, moderate and severe forms – they acknowledge inclusion of “mild” forms here is debatable). The figure below gives an idea of the data they were working with.

Using this data they produced tables of the probability of any forms of dental fluorosis, and of dental fluorosis of aesthetic concern at fluoride concentrations from 0.1 to 4 ppm. In the figures below I have converted their probability values to a calculated prevalence of dental fluorosis at concentrations up to 0.7 ppm.

As you can see from these figures the calculated prevalence of dental fluorosis at “fluoride exposures” less than the 0.7 ppm is only slightly less that at the 0.7 ppm used in CWF. So  it is very misleading to interpret the review’s statement below as indicating anything about CWF:

“The researchers calculated that, in areas with a fluoride level of 0.7 ppm in the  water, approximately 12% of the people evaluated had fluorosis that could cause concern about their appearance.”

Why should the review have considered differences between fluoridated and unfluoridated areas for its conclusions about tooth decay – but ignore the differences between fluoridated and unfluoridated areas in its consideration of dental fluorosis?

Estimating possible effect of CWF on dental fluorosis

In Misrepresentation of the new Cochrane fluoridation review I estimated what the possible effects of CWF is from the calculated probabilities in the Cochrane review. I am surprised the reviewers do not do this themselves as their review was meant to be about CWF and not natural fluoride levels in general.

At 0.7 ppm (the usual concentration for CWF), the calculated prevalence of all forms of dental fluorosis is 40%. But to calculate the prevalence due to CWF we must subtract the prevalence for non-fluoridated water. So dental fluorosis due to CWF would be 40% – 33% = 7 % of people  (using the review’s concentration for non-fluoridated water of 0.4 ppm) or 40% – 30% = 10 % of people (using a more realistic concentration of 0.2 ppm).

Similarly, if we consider only those forms of dental fluorosis the review considers of “aesthetic concern,”  then calculated prevalence due to CWF amounts to only 12% – 10% = 2% of people (using the reviews definition of non-fluoridated) or 12% – 9% = 3%  of people using a more realistic concentration of 0.2 ppm for non-fluoridated.

Defining “dental fluorosis of aesthetic concern”

The milder forms of dental fluorosis are usually judged positive from the point of view of the quality of life. That is why the review also considered dental fluorosis of aesthetic concern – which they define as the severe, moderate and mild forms of dental fluorosis. But, their inclusion of mild forms here is questionable and they acknowledge that:

“Within the context of this review dental fluorosis is referred to as an ’adverse effect’. However, it should be acknowledged that moderate fluorosis may be considered an ’unwanted effect’ rather than an adverse effect. In addition, mild fluorosis may not even be considered an unwanted effect.”

It is not surprising (considering the data in the figures above) that surveys  usually find no changes in the severe and medium forms of dental fluorosis (usually considered of “aesthetic concern”) due to CWF.

I think the Cochrane reviewers were irresponsible to quote calculations which did not include the difference between fluoridated and non-fluoridated areas. This has enabled anti-fluoridation propagandists to use the authority of the Cochrane name to imply, as they often do, that CWF causes a dental fluorosis prevalence of 40%!

Conclusions

The review section on dental fluorosis should not be read as information on the effects of CWF – although the presented data can be used to calculate possible effects. These calculations confirm findings of published surveys that CWF has no effect of the forms of dental fluorosis of aesthetic concern.

However, the conclusions presented in this section of the review are open to misrepresentation and distortion just as they are with the reviews comments on “bias” and poor quality of research (see Cochrane fluoridation review. II: “Biased” and poor quality research) and their selection criteria (see Cochrane fluoridation review. I: Most research ignored). Misrepresentation and distortion of the review are already happening. Anti-fluoridation activists are heavily promoting this review, together with their distortions and misrepresentations, opportunistically using  the Cochrane name to give “authority.”

Sensible readers will not rely on such misrepresentation or brief media reports. Nor will they rely on the Abstract or Plain Language Summary – which have problems. They will read the whole document – critically and intelligently. This is the only way to find out what the true content of this review is.

See also:

Misrepresentation of the new Cochrane fluoridation review
Cochrane fluoridation review. I: Most research ignored
Cochrane fluoridation review. II: “Biased” and poor quality research

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