Category Archives: Health and Medicine

Connett misrepresents the fluoride and IQ data yet again

The video clip below shows how local body politicians can be fooled by people misrepresenting the science. The culprit (unsurprisingly for the fluoride issue) is Paul Connett, Executive Director of the anti-fluoride propagandist group Fluoride Action Network (FAN). He relies on his PhD to provide authority – and the fact that few people in his audiences have the time or background to check out his claims.

At the moment, Connett is putting a lot of effort into promoting the myth that fluoridation causes a decrease in IQ. In this very short video clip (just over 1 minute) of a recent presentation to the Denver Water Board Connett massages data reported by Xiang et al., (2003a) to pull the wool of the Board’s eyes..

The innocent victims in his audience, including the Denver Water Board members, were no doubt impressed by this graph Connet used.

It looks pretty convincing, doesn’t it? There appears to be a statistically very significant decrease in IQ with an increase in drinking water fluoride above about 1 ppm F? (Community water fluoridation [CWF] usually uses a concentration of about 0.7 ppm). All the data points are lined up in a row.

That is until you look at the original data.

This figure is from Xiang et al., (2003a).  Not so convincing, eh? Clearly, with such a wide scatter of the data,  fluoride is only part of the story – if it has any effect at all. But this is the sort of graph one needs to consider when looking at correlations. Connett obtained his figure by breaking the data up into ranges. It looks prettier – but is misleading.

One should always look at the original data.*

Although the correlation is statistically significant, urinary fluoride explains only 3% of the variance in IQ! This tells us that fluoride has very little effect on IQ and it is very likely that it would have no explanatory role at all once other factors were considered in the statistical analysis!

I think it is inhumane to make the claims Connett does on such a flimsy correlation. His biased advocacy is, in effect, denying any efforts to find the real causes of the IQ variation.

What about confounding factors?

Connett’s claim that data was “controlled for” confounding factors is just not true. Xiang did not include any of these other factors in the statistical analysis of the data in Figure 2.

He only compared average values of these factors for the two villages in the study. There were no proper correlations across all the data. Xiang reported no differences between villages for urinary iodine, family income, and parent’s education level. However, there was an average age difference between the villages and he reported that IQ was influenced by age. The drinking water arsenic concentrations were higher in the low fluoride village than the high fluoride village (Xiang et al., 2013).

Incidentally, in a later paper (Xiang et al., 2003b) presents data for blood lead. This time he did check for a correlation across all samples and found there was no statistically significant correlation with IQ. But this was separate and not incorporated into a statistical analysis together with fluoride concentrations.

There was no real checking for the effect of confounding factors on the correlation of IQ with fluoride.

Connett asks a silly question

Connett goes on to make an emotional appeal for scientists to produce convincing data showing that fluoride does not decrease IQ:

This question is disingenuous as science can never prove something can never happen – it can only consider the evidence for it happening. Evidence of the sort presented by Xiang et al. (2003a). Scientific reviews look at the evidence, consider its reliability, compare it with evidence from other studies and draw conclusions.

Connett is disparaging about scientific reviews of the fluoride literature because he does not understand that such literature requires critical and intelligent analysis. Things like the high concentrations and doses used in animals studies he refers to. And looking below surface claims to see what the data really says – as I have done here. This is what reviewers of the scientific literature do all the time.

All Connett has relied on here is his own confirmation bias – and his emotions. Policy makers should beware of such advocacy.

See also:

Connett fiddles the data on fluoride
Connett & Hirzy do a shonky risk assessment for fluoride

*Note: Observant readers might note the second figure compares IQ with urine fluoride concentration. Unfortunately, he did not give a similar figure for fluoride concentration in drinking water. However, this is well correlated with urine fluoride. And, as urine concentration is a better indicator of fluoride intake that drinking water concentration, this figure does give a useful picture of the variance in the data Xiang used.

Incidentally, I have made several attempts without success, to get the original water fluoride concentrations from Xiang (who has so far not replied to several emails) and Connett (who told me that he does not want me contacting him again!).


Xiang, Q; Liang, Y; Chen, L; Wang, C; Chen, B; Chen, X; Zhouc, M. (2003a). Effect of fluoride in drinking water on children’s intelligence. Fluoride, 36(2), 84–94.

Xiang, Q.; Liang, Y.; Zhou, M. . and Z. H. (2003b). BLOOD LEAD OF CHILDREN IN WAMIAO–XINHUAI INTELLIGENCE STUDY. Fluoride, 36(3), 198–199.

Xiang, Q., Wang, Y., Yang, M., Zhang, M., & Xu, Y. (2013). Level of fluoride and arsenic in household shallow well water in wamiao and xinhuai villages in jiangsu province, china. Fluoride 46(December), 192–197.

Similar articles

Fluoridation: Newsweek science journalism bottoms out

One of the worst pieces of distortion and misrepresentation of the Cochrane Fluoridation Review is that written by an anti-fluoridation journalist Douglas Main in Newsweek – Fluoridation May Not Prevent Cavities, Scientific Review Shows. It has, of course, been heavily promoted by anti-fluoride activists.

Dr Charles Payet*, a dentist from Charlotte, NC, USA, has debunked this Newsweek article report in his blog article More Bad Journalism on Fluoride which is also a guest blog at Making sense of FluorideOoops, [Newsweek] Did It Again.

Readers should go to these original posts to read the full article.  However, here are a few quotes from important sections:


Yes, Water Fluoridation Has Been Proven Effective

Main starts off with an awful mischaracterization of the Review by stating that “…while using fluoridated toothpaste has been proven to be good for oral health, consuming fluoridated water may have no positive impact.” Let’s take that apart quickly.

First of all, there’s no disagreement that fluoridated toothpaste has been good for oral health. However, to state that consuming fluoridated water may have no impact is to completely ignore all historical evidence as to the dramatic decrease in dental decay once standardized CWF was implemented for the first time in Grand Rapids, Michigan 80 years ago. Not only that, the Cochrane Review directly contradicts Main’s assertion:

“Data suggest that the introduction of water fluoridation resulted in a 35% reduction in [DMF] baby teeth and a 26% reduction in [DMF] permanent teeth. It also increased the percentage of children with no decay by 15%.”

How About the Quality of the Papers Included?

Next up, Main claims that the Review “…winnowed down the collection to only the most comprehensive, well-designed, and reliable papers.” Is that accurate? Sigh……no. No it’s not. Let’s turn back to the Review to see what it says [emphasis mine]:

“For caries data, we included only prospective studies with a concurrent control, comparing at least two populations, one receiving fluoridated water and the other non-fluoridated water, with at least two points in time evaluated. Groups had to be comparable in terms of fluoridated water at baseline. For studies assessing the initiation of water fluoridation the groups had to be from nonfluoridated areas at baseline, with one group subsequently having fluoride added to the water. For studies assessing the cessation of water fluoridation, groups had to be from fluoridated areas at baseline, with one group subsequently having fluoride removed from the water.”

In other words, the Review only selected what are called “prospective” studies. While these are generally considered to be of higher quality better than cross-sectional studies, (performed at one point in time) for identifying causes, they are also much more difficult, and sometimes impossible, to do.  They are especially difficult today for one important reason when it comes to fluoride: because so many communities have already been fluoridated for a long time, it is very difficult to find one or more in which to set up a prospective study today, and the regulatory hurdles in doing so are enormous.

Therefore, it is false to claim that the Review only included the “most comprehensive, well-designed, and reliable papers.” In fact, the Review included one type of study regardless of their quality. Beyond that the Review’s discussion actually noted that more recent cross-sectional studies were often of better quality because computer use enabled better statistical analysis and consideration of confounding factors.

Payet also discusses the Cochrane judgement of study quality which Main and other anti-fluoride propagandists have misrepresented:

The Review judged quality using blinded randomised controlled studies (RCTs) commonly recommended for clinical drug trials as their baseline. However, they acknowledged this criteria is usually impossible to achieve in fluoridation studies because the assignment of subjects into a treated group versus a control group is outside the control of the investigator. Instead, researchers must use observational studies. Dr John Beal noted in his response to the Cochrane Health Group’s blog The value of cross-sectional studies on the dental benefits of water fluoridation – a response from Dr John Beal to the Cochrane Oral Health Group blog, the claim that cross-sectional, observational, studies, which were all excluded, are somehow of lower quality than RCTs, is false because a previous Cochrane Review said they’re similar!

“It is interesting to observe the conclusions of a different Cochrane review published last year (Anglemyer at al) which compared a range of study designs applied in various fields and concluded that, on average, “there is little evidence for significant effect estimate differences between observational studies and RCTs, regardless of specific observational study design”.

Well now, isn’t that interesting? The previous Cochrane Review specifically found that the 2 study types yield comparable results in terms of quality, but now this one says the cross-sectional ones aren’t good enough. As usual, Douglas Main ignores the previous one because it hurts his point. Admittedly, it would be nice if the Cochrane Review would apply more consistent standards in the selection and exclusion criteria to avoid confusion.

However, Dr. Payet has some criticisms to make of the Cochrane Review itself. It’s lack of proper qualification has been a godsend for cherry-picking anti-fluoridation propagandists:

Did you notice a certain pattern there? “Our confidence…is limited…” “We did not identify any evidence…” “There is insufficient information…” “The evidence is limited…” How in the world does Douglas Main turn that into “fluoridation doesn’t work!” As the saying goes, “The absence of evidence for something is not the same evidence for the absence of that something.”

Payet drives this point home in his conclusion:

So what’s the real take-home message of this particular Cochrane Review? Here’s all they really said: “Our exclusion criteria meant that only 9 studies were reviewed. Regardless of the quality of other studies done, we ignored them. Based on the extremely small study size and the strict criteria applied, all we can say is that more contemporary RCTs prospective studies are called for, because the ones available are old and might be biased.” That’s it! Main and his interviewees, however, go straight to, “OMG IT DOESN’T WORK WE SHOULD STOP IT NOW!” Perhaps this will make the point more clearly:

*Dr. Charles D. Payet has been a full-time practicing dentist in the city of Charlotte, North Carolina since graduating from the UNC Chapel Hill School of Dentistry in 1998. He blogs on the science and art of dentistry for all ages with a skeptical eye and has recently published several articles on the safety and efficacy of fluoride in community water fluoridation, toothpaste, etc.
Similar articles

Fluoridation: “Sciencey” sounding claims ruled unacceptable


Today, “scientific” claims of advertisers and anti-fluoride propagandists can be just as misleading

Again and again I find myself getting really annoyed at the way science is used opportunistically in advertising. We are continually bombarded with claims that the effectiveness of a product is “scientifically proven.” Or that “scientists tell us” something which supports a product. Then there are those ads where actors dress up in white lab coats and wander around a fictional, but photogenic, laboratory while giving us a fairy tale explanation of the mechanism which makes their product so effective. And this misrepresentation is widespread – involving products from cosmetics and toothpaste to fertilisers.

This advertising exploits the credibility of science and scientists as trustworthy experts. Hence the use of white lab coats and sciencey sounding terminology. Even the citation of scientific literature, studies, and trials – with the full knowledge that the target audience has no way of checking these citations.

Many countries have bodies regulating what advertisers can and can’t claim. In New Zealand we have the Advertising Standards Authority(ASA). Our ASA welcomes complaints about advertising and its rulings can lead to adverts being removed. The complaint procedure is being used by members of the public. In 2014 the ASA received 871 complaints about 672 adverts – up 10% and 12% respectively from 2013.

The Society for Science Based Healthcare publicises the complaint procedure and has made many complaints itself on products like homoeopathic treatments and magnetic mattress underlays. One of their members, Mark Honeychurch, created a tool for accessing information from the ASA complaint database which provides useful information.

It turns out that one of the most complained about organisations is Fluoride Free NZ (FFNZ) – a group campaigning against community water fluoridation. It ranks 13th in  the  organisations having the most successful complaints made against them.


The data also shows that a relatively high proportion of those complaints against FFNZ have been successful. That tells me that the complainants have been able to present good arguments to support their complaints.

Anti-fluoride campaigners are well known to claim scientific support for their case. But analysis of their claims shows them to be based on misrepresentations and distortion of the science. They are a classic example of advertisers who opportunistically, but dishonestly, use science to promote their products.

I think the misrepresentation and distortion of science are widespread in advertising and the propaganda from activist groups like FFNZ. At times, the problem seems so immense it seems impossible to counter it. So it is great to see groups like The Society for Science Based Healthcare, and the many people making similar complaints, having this sort of success.

On the other hand, perhaps consumers are developing a healthy scepticism about advertising claims. That is also a good thing, as long as that scepticism doesn’t lead to denigration of the authority of science as the best way of understanding the world and testing claims.

That would be throwing out the baby with the bath water.

See alsoFluoride Free NZ ranks 13th worst NZ organisation by ASA complaints

Similar articles

Comparing the Cochrane and NZ Fluoridation Reviews

Sci Rev

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

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

Review findings agree

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

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

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

CWF efficacy

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

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

Cochrane Review

NZ Fluoridation Review

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

Health issues related to CWF

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

The Cochrane review did not consider any other health effects.

Cochrane Review

NZ Fluoridation Review

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


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

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

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

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


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

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

Similar articles

Scaremongering and chemophobia

This poster/internet meme is making the rounds at the moment. A “true believer” asked for my comments on it as he seemed to think its arguments amounted to “gospel truth.”

misleading poster

So here are some comments:

“Natural” vs “man-made”

They are comparing  crystals found in nature with a processed chemical here. But if CaF2 (the ore fluorite) was meant be used for water treatment it would have to be processed to remove impurities (the natural ore is far from pure). The most effective way of removing contaminants is conversion to hydrofluoric acid and precipitation of calcium fluoride (CaF2). Ending up with a “man-made” product!

Some anti-fluoride campaigners seem to argue that fluoridation would be OK if the fluoridating agent used was CaF2. The contaminants present and need for purification are only two of the flaws in their argument. The low solubility of CaF2 is another flaw.

Incidentally, fluorosilicic acid is effectively purified in its manufacture because of the differing melting and boiling points of heavy metal fluorides and silicon tetrafluoride.

“Safe to hold” vs corrosive

True, concentrated fluorosilicic acid is much more corrosive than CaF2. But so what – this is an issue for those manufacturing, transporting and handling the source material. It is not an issue for consumers as drinking water does not contain either CaF2 or fluorosilicic acid.

By the way, the material safety data sheet for CaF2 says this:

“Potential Acute Health Effects: Hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. Corrosive to eyes and skin. The amount of tissue damage depends on length of contact. Eye contact can result in corneal damage or blindness. Skin contact can produce inflammation and blistering. Inhalation of dust will produce irritation to gastro-intestinal or respiratory tract, characterized by burning, sneezing and coughing. Severe over-exposure can produce lung damage, choking, unconsciousness or death.”


“Precautions: Keep locked up.. Keep container dry. Do not ingest. Do not breathe dust. Never add water to this product. Wear suitable protective clothing. In case of insufficient ventilation, wear suitable respiratory equipment. If ingested, seek medical advice immediately and show the container or the label. Avoid contact with skin and eyes.”

So the advice to those manufacturing, handling and transporting CaF2 is that it is not safe to hold  with bare hands!

Sparingly soluble in water

This is one of the disadvantages of CaF2 as a fluoridating agent as a saturated solution has a fluoride concentration of about 7.5 ppm. Just imagine the size of the container required to hold the quantities of CaF2 solution required for addition to a reservoir!

The high concentration of fluoride in liquid fluorosilicic acid (and the fact that it rapidly decomposes to produce the hydrated fluoride anion on dilution with water) provides a big advantage to it as a fluoridating agent.

Fluoride toxicity reduced by calcium

Yes, high concentrations of fluoride are toxic – although the concentration in community fluoridated water (CWF) (0.7 ppm) is quite safe. The toxicity of ingested fluoride at high concentrations can be reduced by the presence of calcium – because of the low solubility of CaF2.

But let’s be realistic, in the absence of other factors the addition of the appropriate amount of calcium would reduce the fluoride concentration to about 8 ppm. Far higher than the regulated maximum for CWF.

As for some other speculated protective action the calcium in CaF2 could provide – the calcium concentration in a saturated CaF2 solution is only about 7.5 ppm – and at the fluoride concentration used for fluoridated water CaF2 would support a calcium concentration of about 0.8 ppm. Any calcium from added calcium fluoride would be irrelevant compared with the natural calcium concentrations in drinking water. The graph compares these figures for several treatment stations in New Zealand –  see Calcium fluoride and the “soft” water anti-fluoridation myth for further information.

“Man-made waste product”

I have discussed the “man-made” fallacy above. Anti-fluoride campaigners love to describe fluorosilicic acid as a “waste product.”  But Wikipedia defines a waste product as:

“unwanted or unusable materials. Waste is any substance which is discarded after primary use, or it is worthless, defective and of no use”

By definition, then, the fluorosilicic acid used in CWF is not a waste product. It would be if it were disposed of without use – then so is food.

Anti-fluoride campaigners also seem to think that a by-product is somehow evil. This is because most fluorosilicic acid is produced as a by-product of phosphate ore processing. But, come on. Surely production and use of by-products is a desirable feature in judging the conservation aspects of a manufacturing process. And would phosphate chemicals be somehow evil if they were produced as a by-product of fluoride chemical manufacturer from phosphate ores?

Toxicity of “co-contaminants”

I discussed the problem of contaminants in “natural” CaF2 above and added that contaminants in the fluorosilicic acid used for CWF are very low.

But don’t take my word for it. Water treatment chemicals are regulated and the fluorosilicic acid used for CWF must pass rigid tests for the presence of contaminants. The regulations provide for maximum concentrations of contaminants and where a certificate of analysis shows these are exceeded the material is rejected by water treatment plants.

I discussed this in my article Fluoridation – are we dumping toxic metals into our water supplies? where I debunked this claim made by Fluoride Free NZ. I also provided some data on the chemical analysis of fluorosilicic acid samples. In the article Fluoridation: emotionally misrepresenting contamination I compare the real concentration of contaminants recorded in certificates of analysis with the regulated limits. It turns out that the fluorosilicic acid manufactured in Australia and New Zealand is very low in such contaminants – see figure below.

Of course – some opponents like to claim that any amount of contaminants is too much, despite the regulations. Well, if they want to pursue that argument then they must look at all sources of contamination. In many cases, they will find that there is a larger amount of contamination coming from the original water source, natural contamination, than from the water treatment chemicals

I showed this in the article Fluoridation: putting chemical contamination in context where I compared the amount of arsenic from different sources  in the Hamilton City water supply. The figure below from that article shows that natural levels of arsenic in the water source (the Waikato River) are much higher than the recommended levels for drinking water. Even after treatment (which reduces the arsenic levels to below the recommended maximum) the contribution of arsenic from this natural source is still much greater than the calculated contribution from the fluoridating agent used.


This bit of anti-fluoride propaganda is just another example of scaremongering relying on chemophobia and lack of information, even ignorance.

Similar articles

Fluoridation: Beliefs about safety and benefits

Most people in the US believe  community water fluoridation (CWF) is safe and beneficial. Mork & Griffin (2015) report these  findings from a 2009 health survey in a new paper:

Mork, N., & Griffin, S. (2015). Perceived safety and benefit of community water fluoridation: 2009 HealthStyles survey. Journal of Public Health Dentistry.

Their analysis of the survey data, which had 4,556 respondents, indicated that:

“perceived CWF safety and benefits increased with CWF knowledge, perceived vaccine safety, and income.”

I summarise the reported results in  the following graphs.

Perceived safety

Most (55.3%) of the surveyed people agreed or strongly agreed that CWF is safe. Only 13.2% disagreed or strongly disagreed it was safe and 31.5 % were neutral on the question.


Effect of information on CWF

However, the proportion of people believing CWF is safe was much higher in the group which had knowledge about CWF – about 70%. On the other hand, 41.3% of people with no knowledge about CWF still believed it to be safe.


Unsurprisingly, the survey showed that almost half of people who claim childhood vaccination is unsafe also claim CWF is unsafe.

Perceived benefits of CWF

About 73% of the respondents believed that CWF had some benefit (57.3%) or great benefit (15.5%). Only 27% reported that CWF had no benefit.


Regression analysis of the survey data showed that perceived CWF safety and benefits increased with CWF knowledge, perceived vaccine safety and income.


These figures suggest that the recent prediction by Paul Connett, Executive Director of the Fluoride Action Network (FAN), that CWF in the US would disappear within 18 months is delusional. He appears to be carried away by FAN’s occasional victories in stopping or preventing fluoridation in local communities. He should take more notice of the overall figures which show increases in coverage of CWF in the USA in recent years.

However, there is still a sizable minority who believe CWF is harmful or has no benefit. Given that slightly over 40% of respondents in this survey reported they had no knowledge about CWF this provides scope for the misinformation and scientific distortions of anti-fluoride activists to have an effect.  There is still a need for oral health professionals, and supporters of evidence-based health policy, to campaign for CWF and counter the misinformation opponents promote.

The authors of this study concluded:

“Although only a minority of the US population perceived CWF as unsafe or providing no benefit to health, perceptions regarding CWF varied by knowledge of CWF and socio-demographic factors. Oral health promotion activities should consider these differing perceptions of CWF among groups to tailor oral health messaging appropriately.”

Similar articles


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%!


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

Similar articles

Cochrane fluoridation review. II: “Biased” and poor quality research?


Here again, the language used in the Cochrane review (Water fluoridation for the prevention of dental caries) is very misleading. Especially when cherry-picked and taken out of context. The word “bias” used in the review does not have the meaning an uninformed reader might think.

It does not mean motivated experimental design or selection of data to “prove” a predetermined outcome. Rather it has specific meaning related to common (and usually innocent) problems encountered clinical drug trials. These problems also occur in real-life epidemiological studies and trials of the sort used for evaluating social health measures like community water fluoridation (CWF) but the lack of control in such studies means they are harder to combat.. The Cochrane ideal of randomised double-blinded trials is just not realistic in these situations. As the American Academy of Pediatrics comments in their article on the Cochrane review:

“it would be a logistical nightmare to try creating a public water system that pumps fluoridated water to the first house on the block, delivers non-fluoridated water to the following two houses and then provides fluoridated water to the 4th and final house on that block.”

The review describes the types of “biases”  considered:

“Assessment of risk of bias in included studies
. . . . . The domains assessed for each included study included: sampling, confounding, blinding of outcome assessment, completeness of outcome data, risk of selective outcome reporting and risk of other potential sources of bias. . . . . .  We had identified the following factors as important confounders for the primary and secondary outcomes: sugar consumption/dietary habits, SES, ethnicity and the use of other fluoride sources.”

Unfortunately, all these sorts of “biases” are inevitable to some extent in the real world. Researchers do not always have the budget to include consideration of all confounders, or the degree of control required. There are inevitable gaps in data when families move or withdraw children from schools. Yet it is real-world studies, not idealised laboratory experiments, that give the data and other evidence reviewers and decision-makers must consider. Humans can’t be treated like experimental rats.

What “biases” did the review find

As far as “caries outcome” is concerned the review reports a  “high risk of bias overall,” but this “bias may occur in either direction.” This indicates there is not a motivated selection of data or experimental design to produce a predetermined result as that would show up as a systematic bias.

The major cause of “bias” arose from lack of control of the confounding issues of “sugar consumption/dietary habits, SES, ethnicity and the use of other fluoride
sources.” These are of course important factors which could influence results. In the real world it is difficult to control of variations in dietary intake, although socioeconomic status (SES) and ethnicity can be included in statistical analyses of data. My impression is that this is usually done in more recent studies (which the Cochrane review team had excluded from their review – see Cochrane fluoridation review. I: Most research ignored).

Most studies were at low risk of “bias” from sampling methods but on “detection bias” the reviewers report:

The majority of the studies did not blind outcome assessors. This is perhaps unsurprising when considering the efforts that may be required to blind assessors for this type of study.”

The qualification here surely indicates the inadequacy of the Cochrane criteria for using word’s like “bias” which are more fitted to clinical drug trials than evaluation of social health policies.

Most studies did not suffer from “incomplete outcome data” where some data is not measured, but some showed the “bias” of “selective reporting” where data sets reported were incomplete. Interestingly the reviewers report one study where:

“the baseline fluoridation status of the children was determined by the location of the school they attended, which may not have taken into account any children attending schools in fluoridated areas who resided outside those areas.”

This must be a common problem researchers face when they do such real-world epidemiological studies.

Inappropriate criteria used to judge quality of research

Given the nature of evaluating a social health policy like community water fluoridation (CWF) I think the criteria used by the review team to judge the quality fo available research was quite wrong. Their criteria were more fitted to judging clinical drug trials and not social health policies. They acknowledge this in their discussion section “Quality of evidence:”

“However, there has been much debate around the appropriateness of GRADE when applied to public health interventions, particularly for research questions where evidence from randomised controlled trials is never going to be available due to the unfeasibility of conducting such trials. Community water fluoridation is one such area.”


“we accept that the terminology of ’low quality’ for evidence may appear too judgmental. We acknowledge that studies on water fluoridation, as for many public health interventions, are complex to undertake and that researchers are often constrained in their study design by practical considerations. For many public health interventions, the GRADE framework will always result in a rating of low or very low quality. Decision makers need to recognise that for some areas of research, the quality of the evidence will never be ’high’ and that, as for any intervention, the recommendation for its use depends not just upon the quality of the evidence but also on factors such as acceptability and cost-effectiveness (Burford 2012).” My emphasis.

These are important qualifications which, however, did not make it into the review’s Abstract or Plain Language Summary – and certainly not into media reporting. I think the review team was irresponsible to omit such qualifications from their summaries – and many people might suggest they were irresponsible to use such inappropriate criteria for their judgements in the first place.

The scientific literature is not perfect

I keep stressing that readers should always approach scientific reports and papers critically and intelligently. The problems identified by the Cochrane reviewers are inevitable and should always be taken into account by sensible readers. Simple reliance on the abstract of a paper or report often gives a misleading interpretation of the findings. Unfortunately, even unmotivated reporters tend not to read reports in full. Motivated activists will purposely resort to cherry-picking and distortion.

Decision-makers don’t necessarily need perfect scientific papers as they have to consider far more than the abstract conclusion of a scientific paper. There are the democratically expressed views of the electorate and the real situation where social health policies are put into effect. While the Cochrane reviewers expressed “limited confidence” in the size of the effect of CWF on tooth decay. However, policy-makers are more interested in the fact that there is a positive effect on oral health than the possible “theoretical” size of that effect.After all, policy-makers have to also consider the possible role of confounding effects like alternative sources of fluoride, the quality of dental health in the area, socioeconomic status of the population and school health programmes when making decisions about local CWF programmes.


1: The Cochrane reviewers’ use of terms like “bias” and judgment of studies as being of poor quality is inappropriate for evaluation of a social health policy. According to them:

“The main areas of concern were confounding and lack of blind outcome assessment. The evidence was additionally downgraded for indirectness due to the fact that about 71% of the caries studies that evaluated the initiation of water fluoridation were conducted prior to 1975.”

Yet they qualify this by acknowledging such judgement of “bias” and poor quality is inappropriate for a social health policy. And it was their own criteria for rejecting studies that produced a paucity of more recent studies (see Cochrane fluoridation review. I: Most research ignored).

2: These qualifications were not mentioned in the review’s Abstract or Plain Language Summary. I believe this was irresponsible of the authors. especially  given the controversial nature of the subject and the well-understood fact that media reporters rarely read beyond abstracts and summaries.

Such inappropriate and unqualified language provides a godsend to anti-fluoridation propagandists who are already cherry-picking and misrepresenting the review’s main findings.

3: We can remove the inappropriate and judgmental language and still accept that many of the problems identified in the review are inevitable for studies of social health measures. The review actually acknowledges that.

However, the sensible reader of scientific literature is surely aware of these problems. Any research paper must be assessed intelligently and critically – especially regarding the treatment of confounding factors. This is a point I have continually stressed in my posts on this subject.

In my experience, it has been the confirmation bias of anti-fluoride activists which leads them to ignoring such advice. One need only consider their use of studies related to IQ and fluoride in areas of endemic fluorosis, or their recent promotion of poor quality papers claiming a relationship between CWF and Attention-Deficit Hyperactivity Disorder (see ADHD linked to elevation not fluoridation) or hypothyroidism (see Paper claiming water fluoridation linked to hypothyroidism slammed by experts). 

I urge readers to follow this same advice with the Cochrane review. Don’t accept media reports or a limited reading of its Abstract or Plain Language Summary.

Read the whole review – intelligently and sceptically.
See also:

Cochrane fluoridation review. I: Most research ignored
Cochrane fluoridation review. III: Misleading section on dental fluorosis

Similar articles

Cochrane fluoridation review. I: Most research ignored

With the publication of the new Cochrane Fluoridation Review (Water fluoridation for the prevention of dental caries) we have, once again,  both fluoridation supporters and opponents claiming it as evidence for their contradictory positions. They surely both cannot be right.

The reality is that any such review is going to have its own complexities and limitations which allow committed believers on either side to confirm their biases. Unfortunately, this confirmation bias is promoted by inadequate reporting relying on “sound bites” from the executive summary.  Real understanding of the review and its results requires more thoughtful analysis, a reading of the full review and not just media reports and a bit of thinking about its limitations.

The post is the first of three articles looking a bit more deeply at the Cochrane fluoridation review. Here I discuss the strict criteria used by the review team for selecting the studies they considered,  the limitations this has caused for their findings and the misinterpretation of the review results this has produced.

97% of fluoridation research ignored

This seems amazing – why ignore so much of the research? We can understand the need to filter poor research or poorly reported claims. But 97%?

Yet, that is what the review reports – and summarises in their Figure 1:


The high exclusion rate was caused by the review teams decision to only consider studies which conformed to strict criteria:

“For caries data, we included only prospective studies with a concurrent control, comparing at least two populations, one receiving fluoridated water and the other non-fluoridated water, with at least two points in time evaluated. Groups had to be comparable in terms of fluoridated water at baseline. For studies assessing the initiation of water fluoridation the groups had to be from nonfluoridated areas at baseline, with one group subsequently having fluoride added to the water. For studies assessing the cessation of water fluoridation, groups had to be from fluoridated areas at baseline, with one group subsequently having fluoride removed from the water.
For the purposes of this review, water with a fluoride concentration of 0.4 parts per million (ppm) or less (arbitrary cut-off defined a priori) was classified as non-fluoridated.”

This criteria requiring measurements at several time periods and the inclusion of data from before the commencement of fluoridation was probably the main reason for excluding studies. In the review’s Table “Characteristics of excluded studies” the most often mentioned reason was “Evaluated caries in a single time point cross-sectional study.”

OK, you can sort of see the logic behind these strict criteria:

“The cross-sectional studies, whilst able to provide information on whether water fluoridation is associated with a reduction in disparities, are not able to address the question of whether water fluoridation results in a reduction in disparities in caries levels.”

But this inevitably resulted on consideration of only a small part of the available research:

“155 studies (162 publications) met the inclusion criteria for the review. However, only 107 studies (15 caries studies; 92 studies reporting data on either all fluorosis severities or fluorosis of aesthetic concern) presented sufficient data for inclusion in the quantitative syntheses.”

Inability to comment does not mean no effect

Exclusion of so many important studies meant the review was unable to come to any conclusions about important aspects like the effect of community water fluoridation (CWF) on socioeconomic difference in tooth decay,  the effect of stopping CWF programmes on later tooth decay and the effectiveness of CWF in reducing adult tooth decay.   Yet, in the review’s discussion they did make note of research which did draw some conclusions in these areas – research they refused to consider. (And it is rather ironic that one of the review’s authors, Helen V. Worthington, has co-authored several papers which conclude that CWF does reduce socioeconomic differences in dental health).

Of course, anti-fluoride propagandists have chosen to misrepresent the review – reporting its inability to draw conclusion on these questions as evidence that CWF does not influence socioeconomic differences, is not effective for adults and tooth decay does not increase when CWF is stopped!  (See Misrepresentation of the new Cochrane fluoridation review). Clear misrepresentation – but helped by the combination of exclusion of most research and the  vague language used in the review summary.

And you do sort of wonder at ignoring so much evidence when considering issues related to community health. Was Cochrane throwing away the baby with the bathwater?

Confirmation fluoridation is effective

The strict exclusion criteria enabled the review team to winnow studies down to a small number which could be analysed quantitatively. They were able to confirm from analysis of 9 studies that CWF:

“resulted in a 35% reduction in decayed, missing or filled baby teeth, and 26% reduction in decayed, missing and filled permanent teeth.”

But the strict exclusion criteria, specifically rejection of cross-sectional studies, is still a fly in the ointment. Recent studies of situations where fluoridation has been in operation for a long time did not fall within the strict selection criteria because pre-fluoridation data would not realistically be available in most cases. The review consequently did not consider properly the recent evidence – 71% of the research considered occurred before 1975!

The review, therefore, raised the issue of how applicable their findings are to the current situation in developed countries because of improved dental care and use of fluoridated toothpaste. A reasonable proviso which could have been discussed properly using the research they had excluded. But again a proviso which enables misrepresentation by anti-fluoride propagandists who imply that their findings are irrelevant to our current situation.

The review authors acknowledge that exclusion of such data presents a problem for their conclusions:

“In the past 20 years, the majority of research evaluating the effectiveness of water fluoridation for the prevention of dental caries has been undertaken using cross-sectional studies with concurrent control, with improved statistical handling of confounding factors (Rugg-Gunn 2012). We acknowledge that there may be concerns regarding the exclusion of these studies from the current review. A previous review of these cross-sectional studies has shown a smaller measured effect in studies post-1990 than was seen in earlier studies, although the effect remains significant. It is suggested that this reduction in size of effect may be due to the diffusion effect (Rugg-Gunn 2012); this is likely to only occur in areas where a high proportion of the population already receive fluoridated water.”

Of course, the review team was correct to raise the question of the possible reduced efficacy of CWF in modern developed societies. But doesn’t that suggest they should not have used such restrictive criteria in selecting studies to consider? And isn’t it irresponsible to leave the impression that CWF is no longer effective when they excluded the studies which could have provided better answers?


The Cochrane fluoridation review suffers from the fact that only 3% of available studies were considered. The restrictive selection criteria enable quantitative estimates showing  CWF is effective for children but excluded the possibility of answering questions related to the effectiveness for adults, the ability of CWF to reduce socioeconomic differences in oral health,  the effect of stopping fluoridation on later tooth decay and whether improved availability of dental treatments and use of fluoridated toothpaste has reduced the efficacy of CWF in modern developed societies.

The language of the review report itself encourages misinterpretation – and this is even worse in their blog post about the review – Little contemporary evidence to evaluate effectiveness of fluoride in the water.” Here they repeatedly refer to lack of evidence but only explain this is due to their exclusion of such evidence in a few places. What is the uninformed reader, who does not bother to read the full document, make of points in the summary such as:

  • “There is insufficient evidence to determine the effect of water fluoridation on disparities in caries levels across socio-economic status
  • There is insufficient evidence to determine the effect of water fluoridation on caries levels in adults
  • There is insufficient evidence to determine the effect of removing water fluoridation programmes from areas where they already exist”

Finally, anti-fluoride propagandists are motivated enough to misrepresent the findings in any fluoridation review or other documents. The very restricted selection criteria used by the Cochrane review and the language of its summary and news reporting of the review is a bit of a godsend to such propagandists.

Expect to see a lot of cherry-picked quotes from the Cochrane review. Twisted to turn the lack of evidence of effects (due to the exclusion of studies) into evidence for no effect.

My next article on the Cochrane review deals with its discussion of “bias” and poor quality in the studies it considered. See Cochrane fluoridation review. II: “Biased” and poor quality research.

See also:
Misrepresentation of the new Cochrane fluoridation review
Cochrane fluoridation review. II: “Biased” and poor quality research
Cochrane fluoridation review. III: Misleading section on dental fluorosis

Similar articles

Misrepresentation of the new Cochrane fluoridation review

A new fluoridation review was published this week – Water fluoridation for the prevention of dental caries from the Cochrane Oral Health Group. It’s main message is:

“Data suggest that the introduction of water fluoridation resulted in a 35% reduction in decayed, missing or filled baby teeth and a 26% reduction in decayed, missing or filled permanent teeth. It also increased the percentage of children with no decay by 15%. These results indicate that water fluoridation is effective at reducing levels of tooth decay in both children’s baby and permanent teeth.”

So, of course, we now have to put up with anti-fluoridation propagandists as they scurry to misrepresent the review’s findings.

I have written before about how Stan Litras, a New Zealand anti-fluoride propagandist,  indulges in cherry-picking, misinformation and outright distortion  of the science (see for example  Cherry-picking and misinformation in Stan Litras’s anti-fluoride article). Well, he has been at it again – this time putting his talents for misrepresentation to use on the new Cochrane Review.

Stan has issued a press release, using his astroturf vanity project (Fluoridation Network for Dentists) – Gold Standard Fluoride Review Contradicts NZ Advice. He claims that the new review’s:

“findings are completely at odds with last year’s Royal Society review, which our government refers to as justification for promoting fluoridation.”

In fact just not true!

Let’s compare his claims with what the Cochrane review actually reported.

Adult benefits

Stan claims the review “finds the science does not support claims that water fluoridation is of any benefit to adults.” Of course, Stan is implying that the review investigated the situation for adults and found no benefit.

Completely wrong.

The review says:

“No studies met the review’s inclusion criteria that investigated the effectiveness of water fluoridation for preventing tooth decay in adults, rather than children.”

And later:

“Only one of these studies examined the effect of water fluoridation on adults (Pot 1974); the reported outcome for this study was the percentage of participants with dentures. There are no data to determine the effect of water fluoridation on caries levels in adults.”

The Cochrane reviewers just did not have any suitable studies fitting their strict criteria for analysis so they could draw no conclusion on this specific question. However, in the review’s discussion they do mention a comprehensive systematic review (Griffin et al., 2007) which attributed a 34.6% reduction of tooth decay in adults to community water fluoridation. The corresponding figure for studies published after 1970 was 27.2%

Social inequalities

Stan implies the review found that fluoridation did not “reduce social” inequalities.

Completely wrong again.

The review was not able to draw any conclusion related to social inequalities because it just did not have that information. it says:

“There was insufficient information available to find out whether the introduction of a water fluoridation programme changed existing differences in tooth decay across socioeconomic groups.”

The review team did find 3 studies reporting effects of water fluoridation on disparities in caries across social class. However, there were problems with all 3 studies meaning the data was not suitable for further analysis and this  prevented them drawing any conclusions.

Benefits when toothpaste used

Stan claims, or at least strongly implies,  the review indicates that community water fluoridation does not “provide additional benefits over and above topically applied fluoride (such as in toothpaste).”

Again, completely wrong.

The review specifically says:

“Data suggest that the introduction of water fluoridation resulted in a 35% reduction in decayed, missing or filled baby teeth and a 26% reduction in decayed, missing or filled permanent teeth. It also increased the percentage of children with no decay by 15%. These results indicate that water fluoridation is effective at reducing levels of tooth decay in both children’s baby and permanent teeth.”

It goes on to say:

“However, since 1975 the use of toothpastes with fluoride and other preventive measures such as fluoride varnish have become widespread in many
communities around the world. The applicability of the results to current lifestyles is unclear.”

So, it raises the possibility that the current efficacy of community water fluoridation in industrialised countries could be lower. However, they could not draw a conclusion on this because only 30% of the included studies took place after 1975.

The review team did attempt to look at factors such as sources of fluoride “(potential confounders of relevance to this review include sugar consumption/dietary habits, SES, ethnicity and the use of other fluoride sources)” but found this not to be possible:

“However, due to the small number of studies and lack of clarity in the reporting within the caries studies, we did not undertake these sub-group analyses.”

Stopping fluoridation

Stan claims (or at least strongly implies) the review shows claims “that tooth decay increases in communities when fluoridation is stopped” are incorrect.

Wrong again.

The review says:

“There was insufficient information available to understand the effect of stopping water fluoridation programmes on tooth decay.”


“No studies that met the inclusion criteria reported on change in dmft or proportion of caries-free children (deciduous/permanent dentition) following the cessation of water fluoridation.”

The only study the review discussed was that of Maupome et al., (2001). This paper is often quoted by anti-fluoridation propagandists but those authors themselves commented on the difficulty of drawing conclusions from their data:

“Our results suggest a complicated pattern of disease following cessation of fluoridation. Multiple sources of fluoride besides water fluoridation have made it more difficult to detect changes in the epidemiological profile of a population with generally low caries experience, and living in an affluent setting with widely accessible dental services.”

Dental fluorosis

Stan claims the review “found that 40% of children in fluoridated areas have dental fluorosis.” However, the review does not compare the prevalence of dental fluorosis in fluoridated areas and unfluoridated areas. It simply draws conclusions about the likely prevalence of dental fluorosis at different fluoride intakes. This lack of comparison is unfortunate, although the omission may be due to the lack of suitable studies that survived their strict criteria.

So Stan’s claim is misleading because, without considering dental fluorosis in the non-fluoridated, areas it is not possible to attribute any responsibility to community water fluoridation. He has simply taken the reported estimate of dental fluorosis for a fluoride intake of 0.7 ppm (the concentration in fluoridated drinking water in NZ) without taking into account the prevalence of dental fluorosis in unfluoridated areas. Very misleading!

The review does, however, calculate estimates of dental fluorosis for different drinking water concentrations and we can draw some proper conclusions from these.

Total dental fluorosis. The review defines this as all the forms of dental fluorosis according to the Dean Index – from questionable to serious. (See Water fluoridation and dental fluorosis – debunking some myths for a discussion of the different forms of dental fluorosis). The graph below shows the reviews findings for the effect of fluoride exposure (drinking water fluoride concentration) on any dental fluorosis.

DF-2True, at 0.7 ppm (the usual concentration for CWF, this shows an estimated prevalence of 40%. But we can calculate the increase due to CWF by subtracting 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).

So Stan is quite wrong to imply CWF causes a total dental fluorosis in 40% of people – it is only 10% or less. However, even that figure is misleading.

Most dental fluorosis is not of aesthetic concern – in fact, the milder forms are often viewed positively from the point of view of the quality of life. So the review also considers dental fluorosis of aesthetic concern – which they define as the serious, moderate and mild forms of dental fluorosis (their inclusion of mild forms here is questionable). The graph below illustrates their findings for these forms of dental fluorosis.

So, if we consider only those forms of dental fluorosis the review considers of aesthetic concern  then calculated prevalence due to CWF amount 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.

This is a huge difference to the 40% claimed by Stan.

The review acknowledges that their inclusion of mild forms of dental fluorosis in their definition of dental fluorosis of aesthetic concern is questionable, saying “mild fluorosis may not even be considered an unwanted effect.” Most studies do not consider the mild forms undesirable. It is likely that most of the increase in “dental fluorosis of aesthetic concern” arising from community water fluoridation occurs in the mild forms.  So my suggestion of a 2 or 3% increase in “dental fluorosis of aesthetic concern” will be an overestimation.

It is unsurprising, then, that some cross-sectional studies do not detect any increase in undesirable dental fluorosis attributed to community water fluoridation. The figure below illustrates an example reported in the New Zealand in the 2009 New Zealand Oral health Survey (see Our Oral Health).


Once again this anti-fluoridation propagandist has been caught misrepresenting the scientific literature on this issue. And his misleading press release is being touted as gospel truth by anti-fluoridation groups in NZ and the USA.

It is pathetic such people have to resort to misrepresentation in this way. Surely it is a sign of desperation to use statements that no conclusions were possible on specific details (adult benefits, social inequalities, influence of toothpaste, and what happens when fluoridation is stopped) because no studies fitted the selection criteria as “evidence” that there is no effect.


Griffin SO, Regnier E, Griffin PM, Huntley V. (2007). Effectiveness
of fluoride in preventing caries in adults. Journal of Dental
Research 2007;86(5):410–5.

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

Maupomé, G., Clark, D. C., Levy, S. M., & Berkowitz, J. (2001). Patterns of dental caries following the cessation of water fluoridation. Community Dentistry and Oral Epidemiology, 29(1), 37–47.

Similar articles