Tag Archives: fluoridation

Another study used by anti-fluoride activists actually shows community water fluoridation OK

Another study comparing effect in children from nonendemic areas (Dagang) and endemic fluorosis area (Jinghai) about 80km apart in the Tianjin area of China. Hardly sampling the same population.

Anti-fluoride campaigners still use studies from endemic fluorosis area of China in their campaign against community water fluoridation (CWF). This misrepresents the situation. While the control areas they use (non-endemic fluorosis areas where there are no health effects) are relevant to CWF the data from the endemic fluorosis areas where fluoride intake is high are simply not relevant to CWF.

However, some of these studies provide enough information to enable checking for health effects in the control, non-endemic fluorosis areas. I discuss one of these studies below – Cui et al (2018) – and show it finds no health effects at the low fluoride concentration relevant to CWF. The use of this study in anti-fluoride campaigns is therefore misleading.

I also show how even in his misrepresentation of this study the “Research Director” of the Fluoride Action Network (FAN), Chris Neurath, makes basic mathematical mistakes.

The citation for this study is:

Cui, Y., Zhang, B., Ma, J., Wang, Y., Zhao, L., Hou, C., … Liu, H. (2018). Dopamine receptor D2 gene polymorphism, urine fluoride, and intelligence impairment of children in China: A school-based cross-sectional study. Ecotoxicology and Environmental Safety, 165(August), 270–277.

The study used school children (7 to 12 years old) from the districts of Jinghai and Dagang in Tianjin of China (see map above). The endemic fluorosis area had drinking water fluoride concentrations of 1.52–2.49 mg/L and the nonendemic fluorosis area had drinking water fluoride concentrations of 0.20–1.00 mg/L.

Of course, the results for children in the endemic fluorosis area are simply not relevant to CWF where the drinking water concentrations are usually less than 0.8 mg/L.


Child IQ values were compared with urinary fluoride levels and regression analysis used to determine if there was any relationship. The children were also tested for the presence of different genes and each of three different genetic groups was considered separately.

Skewed data

The data from both endemic and non-endemic fluorosis areas were combined. That for urinary F was skewed and had to be transformed to provide the normal data distribution required for linear regression analysis. Consequently, the authors report linear regression results for the relationship of child IQ to the logarithm of urinary F [Log(UF)].

No statistically significant relationships were found for two of the genotypes (designated CC & CT) but there was a significant relationship for the genotype designated TT. Less than 14% of the children had this gene.

Figure from Cui et al (2018) showing a negative relationship of child IQ with the logarithm of urinary fluoride. Equation of fitted line is IQ = 117.48 – 9.75*Log(UF). R-squared = 0.142, p = 0.012. 95% CI for coefficient -17.21,-2.29

So, of course, the anti-fluoride campaigners simply go with the results for the children with the TT gene and ignore the results for the other 86% of children.

Nothing new here – they always ignore results that they can not use in their campaigns to confirm their biased presentations.

Analysis of the data for the low fluoride levels relevant to CWF doesn’t support activist claims

Here I will just consider the data relevant to CWF. After digitally extracting the data from the figures in the paper I restricted linear regression analysis to the children with urinary F values of less than 2 mg/L (which is still rather high for areas where CWF is used). The figure below displays that data, together with the results of linear regression analysis. Untransformed values were used because data for urine fluoride concentrations less than 2 mg/ml is normally distributed.

Linear regression analysis for the relationship of child IQ with urinary F. Children with TT gene about 44% of the sample. Children with CC and CT genes about 86% of the sample.

There were no statistically significant (p < 0.05) relationships, either for the TT variant (red triangle) or for the other variants (open circle) (CC & CT combined in this figure).

So, once again we see that if the appropriate data from these studies are used they confirm that there is no relationship of child IQ with measures of fluoride exposure at concentrations relevant to CWF (see also New study touted by anti-fluoridation campaigners actually indicates fluoridation is safe).

FAN’s “Research Director” makes simplistic mistakes

FAN plans to use studies like Ciu et al (2018) in their upcoming case against the US Environmental Protection Agency. Their aim is to attempt to establish cognitive effects as the main harms from CWF and then use studies like these to argue against CWF. Even though studies like this simply establish that there is no harm from fluoride concentration used for CWF. One hopes that the experts testifying for the EPA show how these studies are misrepresented by FAN.

FAN has provided a presentation by their “Research Director,” Chris Nerath, which they claim summarises their arguments. It’s a “pretty” PowerPoint presentation (FAN describes it as “powerful“) and may fool some people, but it just does not stand up to scientific scrutiny.

Quite apart for the misrepresentation of these scientific studies, and use of studies like Cui et al (2018) which are not relevant to CWF, Neurath simply makes basic scientific mistakes.

For example, in his slide 33, he claims that Cui et al (2018) showed a 10 point IQ loss for a 1 mg/L increase in urinary F. But that is simply not true – his mistake is that he ignored the fact that the linear relationship reported by Cui et al 2018) [IQ = 117.48 – 9.75*Log(UF)] is based on log values of urinary F where the value of the coefficient is -9.75. In other words, the 10 point loss is for an increase of urinary by a log value of 1 is equivalent to an increase from a concentration of 1 mg/L [Log(1) = 0] to a urinary F concentration of 10 mg/L ([log(10)=1].

Slide 33 from the presentation by Chris Neurath, FAN’s “Research Director” displaying an embarrassing mathematical mistake.

Let’s do the correct calculation for him. The Cui et al (2018) relationship shows an IQ value 117.48 for a urinary F concentration of 1 mg/L [Log(1)=0] and 114.55 for a urinary F concentration of 2 mg/L [Log(2)=0.301]. So the loss is only 2.9 IQ points.

Neurath thinks it sounds much better for his case to say a loss of 10 IQ points but all he has done is shown either he did not read Cui et al (2018) properly or does not understand a simple mathematical relationship.

However, I should stress Neurath’s argument is irrelevant to CWF, as well as being mathematically wrong because its analysis includes data from endemic fluorosis areas. In fact, there is no statistically significant relationship between child IQ and urinary fluoride either for the overall group or for the separate genetic groups considered.

“Safety threshold”

The graph in Neurath’s slide is adapted from Cui et al (2018) which made an attempt to determine a “safety threshold of urine fluoride levels for IQ
impairment” for the children with the TT gene. They defined this “safety threshold” as the urinary fluoride value corresponding to the mean IQ for the group. This seems arbitrary to me and the authors make no attempt to justify the definition.

They then divided the data into quintiles according to urinary fluoride values. Quintile 4 was the first quintile where the mean IQ value is below the mean IQ for the whole group so they assumed to mean log(UF) for that quintile to represent the “safety threshold.”

It all seems quite hairy to me – but I suppose the method produces a few data points which Neurath was able to plot on a graph and make to appear impressive. But look at the spread of the data (Neurath does not show this) in the graph below where the bars represent the spread of data for each quintile and the dotted line is the mean IQ value for the group. The spread is hardly surprising – the overall data is very scattered and only about 9 data points were used for each quintile.

I frankly think this method of determining a “safety threshold” is meaningless. We could do exactly the same with the data where urinary fluoride is less than 2 mg/L – much more relevant to CWF. This is the result – using quartiles of about 8 data points each.

Quite meaningless.

There are many other misrepresentations and mistakes in Chris Neurath’s Powerpoint presentation and I may return to some of them later. However, let’s hope the court recognises these and rejects FAN’s attempts.


Anti-fluoride activists continually use studies from areas of endemic fluorosis in their campaigns against CWF. However, when the actual data relevant to community water in these studies are considered they usually show no health effect.  There is no doubt that people living in endemic fluorosis areas suffer a range of health problems. But where these studies provide complete data they almost always could be used to support CWF.

Activists like FAN and their “Research Director” simply clutch on to any study they can finds which appears to show harmful effects of fluoride and ignore the fact that they are hardly ever relevant to the fluoride concentration used in CWF. They cherry-pick and ignore, or cover-up, any information not supporting their bias.

This approach is hardly scientific. It is not objective and never undertakes a critical review of the studies used. These activist display a thoughtless approach to scientific research when they opportunistically use scientific studies like this. Their approach is unthinking and it is hardly surprising that they make simple mathematical and statistical errors like the one described here and made by Paul Connett recently (see and Author confirms anti-fluoridation activist misrepresentation of her work).

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When scientists get political: Lead fluoride-IQ researcher launches emotional attack on her scientific critics

age credit: Science and Politics – Skeptically.org

It seems impossible to keep politics out of science. It’s a pity because politics can end up forcing science to produce the results desired by politicians. When this happens the ideal aim of science – the pursuit of objective knowledge – can get lost.

We rightly disapprove of external political and commercial influences on science. But there is another insidious form of politics derived from ego, personal ambition and the promotion of research by institutes and individual researchers. This is very often driven by the competition for research funding – the loudest researcher gets the grant. These days this is a real problem – the classical introverted scientist, no matter how bright, is often at a complete disadvantage when it comes to the fight over research funding.

In my own career, I have seen excellent researchers driven to redundancy simply because they did not have the political skills to fight for research funds. And at the same time, I have seen mediocre scientists, often producing poor quality or even misleading science, get those funds – simply because of their ambition and political skills.

These thoughts came flooding back to me as I read the new opinion piece by Christine Till, the leader of the research group that published several of the recent fluoride-IQ/ADHD and similar papers that I have critiqued here. Papers that have been heavily promoted by the authors and Till’s institute as well as the anti-fluoride/anti-vaccination crowd and, at the same time, extensively critiqued by the scientific community.

The citation  for her article is:

Till, C., & Green, R. (2020). Controversy: The evolving science of fluoride: when new evidence doesn’t conform with existing beliefs. Pediatric Research.

Unfortunately, the article is not a reply to critics or a good faith scientific engagement with the scientific issues. It is simply an attack on those who have made honest and respectful critiques. An attack which attributes unjust motives to her critics and comes close to personal.

Attempt to close down science by personal attacks

I discussed some of these issues before in my articles Scientific integrity requires critical investigation – not blind acceptance and Fluoridation science and political advocacy – who is fooling who?

In this case, I was concerned about the way  Dr William Ghali, one of the promoters of  Christine Till’s work, attacked and attempted to belittle scientific colleagues who were indulging in the normal peer-review process of critiquing published papers which they considered had faults. Nothing new about that scientific critique – it goes on all the time. It is expected by authors and, in the end, it helps to improve the science. I Personally think such critique should be welcomed by researchers.

If the opponents of scientific exchange like Dr Ghali are successful in their attempt to prevent such scientific debate then we are all losers. How can we trust scientific findings that are protected from scrutiny?

This is what is wrong with the opinion piece by Till and Green cited above. Instead of entering into a good-faith scientific exchange with their critics they attribute motives and biases to them. Even accusing them of attempting to prevent the progress of science. They accuse critics of a “tendency to ignore new evidence,” of  “overt cognitive bias” and of promoting  a “polarized fluoride debate.”

But, in fact, these critiques have come because the “new evidence” is not being ignored but is being evaluated. It is being critically considered. The article more or less admits this when it says “critics attacked the methodology of the study [Green et al (2019] and discounted the significance of the results.

True, the so-called “fluoride debate” is polarised. After all, it is being promoted by anti-fluoride/anti-vaccination activists who are attempting to prevent or remove, a health policy known to benefit children. Till & Green may be unhappy that they have not been able to win over the scientific community with their paper but it is hardly honest to reject the critiques of the paper by calling them “attacks” or by claiming they “ignore” the evidence.

An admission the paper had difficulties

The article admits the  Green et al (2019) paper had difficulties right from the beginning. It took three attempts before a journal would accept it for consideration. Even then it ended up having “several additional rounds of review by the JAMA editors until we eventually reached a compromise.” This gives some substance to my speculation of problems in the review process which lead to the unprecedented publication of an editor’s note – a political action  I have never seen before (see If at first you don’t succeed . . . statistical manipulation might help).

They acknowledge that even their colleagues in environmental epidemiology “were initially sceptical.” And so they should have been – all new research should be reviewed sceptically and critically.

Refusing to engage scientifically

But the annoying thing is that these authors attempt to write off the scepticism and critical review of the wider scientific community as being due to “experts” (yes in quotes), “who held strong beliefs . .” This despite the fact that in the published critiques it is not “strong beliefs” which were presented, but detailed consideration of the methodology and statistical analyses used in the original paper.

All these critiques were made respectfully – and often with thanks to the Green et al (2019) for their new work. Yet Till and Green accuse these reviewers of making “vitriolic comments and claims with little scientific basis” – a comment which is, in itself, disrespectful to those who took time to make their critiques. They resort to smearing two of the reviews (by the UK-based Science Media Centre and Dr Berezow, a specialist from the American Council on Science and Health) by accusations these bodies are “both heavily funded by the pharmaceutical and food and beverage industries.” This funding smear is commonly used by anti-science activists who attempt to discredit scientific findings or analysis but refuse to consider the science itself.

They say of these two reviews that they claim “the results are driven by outliers” – yet a simple search shows that this comment simply does not appear in the cited reviews.  The critique of Dr Berezow from the American Council on Science and Health does not include either of the words “outlier” or “driven.”

The only reference to “outliers” in the Science Media Centre review was by Dr Oliver Jones, Associate Professor of Analytical Chemistry, RMIT University who wrote:

“The authors state that an increase of 1 milligram per liter (1 mg/L) increase in fluoride was associated with a 4.49 point lower IQ score but fluoride intake appears to have been below 1 mg/L for most people in the study, even for those with fluoridated water, and nearly everyone (bar a few outliers) had a fluoride intake of less than 2 mg/L (which multiple previous studies have shown is safe) . There is also a Lot of variation in the data – which makes drawing firm conclusions/ predictions from it difficult.”

A valid criticism which needed a response – not a smear.

My search for the word “driven” produced these two comments:

Dr Joy Leahy, Statistical Ambassador, Royal Statistical Society, wrote:

“if a woman is living in an area with fluoridated water during pregnancy, then her child is likely to grow up drinking this same fluoridated water. Therefore, it is difficult to say whether any association found is driven by the fluoride consumption in pregnancy, or an assumed fluoride consumption in the infant after birth.”

Prof Rick Cooper, Professor of Cognitive Science, Birkbeck, University of London, said:

“a significant decrease in IQ was found only in boys – girls showed a non-significant increase in IQ. The negative effect was driven by a small number of boys whose mothers had extreme levels of fluoride exposure, but even these children had IQ in the normal range.”

These are valid points that again deserve a scientific response yet Till & Green describe them as “vacuous claims exemplify attempts to manipulate the scientific evidence and manufacture doubt.”

We all support using new knowledge to adjust policies

Till & Green attempt to claim the high moral ground by asserting:

“Science advances by continuously challenging old ideas and adjusting our beliefs as new knowledge emerges, even if this new evidence conflicts with conventional wisdom or is inconvenient.”

Of course, this is true and I think it is dishonest of them to pretend this is not also the position of those who critiqued their paper. These reviewers were interested in looking at the new results, evaluating them and seeing how relevant they are. Seeing if they do indeed require us to adopt new thinking.

After all, look at what Dr Berozow, one of the critics they smeared by implying he was influenced by industry funding  and was falling back on “vitriolic comments” and “vacuous claim”, says in introducing his critique:

“The investigation by Green et al into the effect of maternal consumption of fluoride on the IQ of children is important. It is always wise to constantly evaluate and reevaluate long-standing public health practices in the light of new evidence.”

Till & Green are simply resorting to attributing motive and asserting their critics are not open to new knowledge as a way of avoiding facing up to the valid criticisms made by experts who reviewed and critiqued their work.

Confirmation bias – the pot calls the kettle black

We all suffer from confirmation bias and scientists (including Till & Green) are not immune. It is well understood that scientists are the last people to recognise problems in their own work. That is why peer review and open critique of scientific reports is so essential. But, in line with the whole approach of this opinion piece, Till & Green attempt to present a picture that only their critics suffer from this problem. They say:

“We typically fret about subtle biases, like recall bias and unmeasured confounding, but confirmation bias, the tendency to ignore or debunk data that does not conform to what we believe, is arguably a much larger problem.”

I find their attempt to belittle concerns about “unmeasured confounding” rather ironic. After all, this was the problem with Till’s original fluoride-ADHD work (which she used to win research grants for her later fluoride research) that I highlighted in Perrott (2018) Fluoridation and attention deficit hyperactivity disorder – a critique of Malin and Till (2015).

I am aware that Till has read my paper in its pre-publication and published forms but studiously ignores it. For example, the ADHD paper of Riddell et al (2109), which she co-authored, simply does not include Perrott (2018) in its discussion and continues to present Malin & Till (2105) as authoritative despite the obvious flaw that it ignored important confounders, and when these are considered their claim of a relationship between fluoridation and ADHD prevalence proved to be false.

So much for her attribution of confirmation bias to others – when she is obviously guilty of it in this case by ignoring “data that does not conform, to what [she] believes.”

The Till & Green opinion piece is unwise

Till & Green seem to have simply reacted emotionally to the reviews and critiques the Green et al (2019) paper received. They, of course, had the right – even the obligation – to respond scientifically to the reviews. But I believe their response in this article is unwise, maybe even professionally damaging,  and they should not have committed these emotional outbursts to print. After a cooling down period, it is possible they will withdraw the article – and that would be best for them in the end.

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New study touted by anti-fluoridation campaigners actually indicates fluoridation is safe

Children used in this study were from Lintingkou town (a normal-fluoride/control area) and Dakoutun town (a high-fluoride area) in Baodi district of Tianjin, China. The towns are 25 km apart.

Anti-fluoridation activists on social media seem to cite any scientific article about fluoride which they think will show it harmful. They usually rely only on information in the article title or abstract. This means they are often wrong as the articles may not be at all relevant to the low fluoride concentrations used in water fluoridation. Perhaps they should stop for a minute and actually read the articles they cite.

The other day @NYSCOF, the twitter account for the New York State Coalition Opposed to Fluoridation, Inc (a small antifluoridation activist group in New York) promoted a new Chinese study as part of its campaign against community water fluoridation (CWF). It claimed: “Children’s IQ was lower when water and urinary fluoride levels were high compared to a low fluoride group.” But the fact this is a Chinese study should have warned the honest reader that the “high” fluoride group lived in an area of endemic fluorosis and data for them is irrelevant to CWF.

In fact, some of the data in their paper are relevant to CWF – the data for the “low fluoride” control group where children were exposed to drinking water concentrations less than 1 mg/L (CWF aims to maintain a drinking water fluoride concentration of about 0.7 or 0.8 mg/L). It’s worth looking at that data to see if child IQ is related to fluoride exposure at that level.

The take-home message is that it isn’t.

Here is the citation for the new study:

Zhao, Q., Tian, Z., Zhou, G., Niu, Q., Chen, J., Li, P., … Wang, A. (2020). SIRT1-dependent mitochondrial biogenesis supports therapeutic effects of resveratrol against neurodevelopment damage by fluoride. Theranostics, 10(11), 4822–4838.

Two different communities

The children (8-12 year-olds) in this study came from two different communities in the Baodi district of Tianjin, China – see the map above. They are Lintingkou town, where drinking water fluoride concentrations were “normal,” and Dakoutun town, which is in an area of endemic fluorosis and the drinking water fluoride concentrations are high (about 1 to 3.5 mg/L). The towns are about 25 km apart and will clearly have a number of differences which could be relevant to the IQ of children. Possible confounders like this were not considered in the study.

People living in areas of endemic fluorosis suffer a range of health and socioeconomic effects which could influence child IQ

The figure below from the paper illustrates the ranges of drinking water F and urinary F for the children studied (30 in each of the “low” and “high” fluoride groups).

Only the data for the “control” group are relevant to CWF. Unfortunately, the authors chose to plot the IQ data for the two groups on the same graph and concluded that this showed a “fluoride-caused intellectual loss in children” – see their graph below.

But, their conclusion is wrong. When we look at the data for the “control” and “high fluoride” groups separately that simple conclusion is clearly unwarranted.  In fact, there is no statistically significant relationship (p<0.05) of child IQ with urinary F for either the “low” or the “high” group – see the graph below which uses digitally extracted data from the above figure. Data points for the”low” fluoride group are green and those for the “high” fluoride group are red.

This shows how statistical analyses like regression analyses can produce misleading results if the data is not considered properly. It is simply misleading to include two separate populations like this in a regression analysis without considering the whole range of possible confounders.

There is no relationship between child IQ and urinary fluoride in either population. All the regression analysis shows is that there is a difference between the two towns – and that is simply shown by the average values of IQ in those towns. The average child IQ in Lintingkou town is 112.4 while in Dakoutun town it is 98.5.

While these IQ values seem pretty good (usually the average IQ for a population is 100) the lower value for Dakoutun town is not surprising considering that the population living in areas of endemic fluorosis suffer a whole range of health and social problems.

The biochemical data has the same problem

The paper itself is a real hodgepodge of separate studies involving child IQ, levels of mitochondrial biogenesis signalling molecules, experiments with rats and with in vitro cell cultures. I do not have the expertise to critique the biochemical, cell culture and rat behavioural techniques used. However, the presentation of the biochemical data for the children suffers the same problems as the presentation of the IQ data.

The authors claim that there is a significant positive relationship between the silent information regulator 1 (SIRT1) and child urinary F, and significant negative relationships of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) and mitochondrial transcription factor A (TFAM) with child urinary F. But they simply lumped the data for the two towns together. When the data for the two groups are considered separately there are no statistically significant relationships for these biochemical measures in either of the two groups – see figures below. Again, data points for the “low” fluoride group are green and those for the “high” fluoride group are red.


Yet against anti-fluoride campaigners are promoting a study that they probably haven’t even bothered reading. They are using results for an area of endemic fluorosis to argue against CWF. Worse, they are completely ignoring the data in this and similar studies which show no relationship between child IQ and fluoride exposure at fluoride levels relevant to CWF.


The Twitter account @NYSCOF promoting this specific study is very active and is connected with the Fluoride Action Network (FAN) through Carol Kopf –  the media officer for both the New York State Coalition Opposed to Fluoridation, Inc. (NYSCOF) and FAN. Ironically, she uses the slogan “I Am a Force for Science” on her Twitter image.

Sometimes I drop a reply to her posts – in this case pointing out: “And no loss of IQ at F concentrations relevant to community water fluoridation. These studies show CWF safe.”

My comment will not change Carol Kopf’s mind, of course, but others may read it and understand. Mind you, it’s inevitable that other anti-fluoride activists see my comments and react in stupid ways. For example, one of the Fluoride Free NZ leaders, Kane Kitchener, posted this reply:

“Ken, you’ve been exposed too long by Hamilton’s Fluoridated water. Too much reduction in IQ to see it.”

It really is pointless attempting to discuss science with these people.

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No relationship of bone cancer to fluoridation – another new study the anti-fluoride brigade will attempt to ignore

Anti-fluoride activists claim that water fluoridation causes nine cancer proved wrong, yet again. Image credit: Four myths about water fluoridation and why they’re wrong

A new study confirms, yet again, that osteosarcoma, a type of bone cancer, is not associated with community water fluoridation (CWF). This the seventh such study since a 1990 report of an animal study suggested such a link.

The 199o study exposed rats to very high concentrations of fluoride so the results were not relevant to CWF. But, of course, this did not stop anti-fluoride campaigners using the study to argue that CWF causes osteosarcoma.

The citation for this new study is:

Kim, F. M., Hayes, C., Burgard, S. L., Kim, H. D., Hoover, R. N., Osteosarcoma, N., … Couper, D. (2020). A Case-Control Study of Fluoridation and Osteosarcoma. Journal of Dental Research 1.

This was a hospital-based study where patients diagnosed with osteosarcoma were compared with control patients diagnosed with other bone tumours or different conditions. This figure summarises the findings.

The only statistically significant effects show a reduced likelihood of osteosarcoma diagnosis for people living in fluoridated areas – compared with those living in non-fluoridated areas (the red triangles in the figure). These were for people who never drank water and people who had lived in fluoridated areas for 0% to 50% of their lives. It is likely the effects for people who did drink bottles water and those who had lived in fluoridated areas for 50% to 100% or 100% of their lives are not statistically significant because of the smaller numbers involved (The green circles in the figure).

It’s been a bad week for the anti-fluoride crowd – the science keeps proving them wrong. Perhaps that is why they are silent about these new studies.

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New review finds fluoride is not a developmental neurotoxicant at exposure levels relevant to fluoridation

Proper consideration of the best science shows community water fluoridation does not have a negative effect on child IQ. Image credit: Africa Studio / Shutterstock.com

A new extensive review of the scientific literature has concluded that fluoride is not a human developmental neurotoxicant at the current exposure levels in Europe. This is of course just as valid for New Zealand, the USA and other countries which use community water fluoridation (CWF).

Forty-one pages long, it’s a very extensive and detailed review. The full text can be downloaded  and its citation is:

Guth, S., Hüser, S., Roth, A., Degen, G., Diel, P., Edlund, K., … Thomas, H. (2020). Toxicity of fluoride: critical evaluation of evidence for human developmental neurotoxicity in epidemiological studies, animal experiments and in vitro analyses. Archives of Toxicology. 2020 May 8.

The anti-fluoridation crowd won’t be happy with this review. They have tended to have things their own way as they have argued that fluoridation is harmful to child IQ using irrelevant studies from endemic fluorosis areas where people suffer a range of health effect from overexposure to fluoride and other contaminants. Anti-fluoride campaigners have also misrepresented and misused recent studies from areas where fluoride exposure is lower.

So this review is timely because it critically examines all the recent studies and identifies their limitations. It identified 23 relevant epidemiological studies published between January 2012 and August 2019. One of these examined an association between fluoride exposure and school performance. The other 22 examined possible relationships with IQ.

Limitations of fluoride-IQ studies

The authors reported that:

“So far, almost all studies investigating the effect of fluoride intake on intelligence were performed in relatively poor, rural communities, e.g., in China, Iran, and Mongolia, where drinking water may contain comparatively high levels of fluoride (‘exposed population’), whereas the ‘reference populations’ often had access to water that was fluoridated at the recommended level.”

Figure 1: People in endemic fluorosis area sufferer a range of health problems – studies from these areas are not relevant to CWF

This means that anti-fluoride campaigners usually rely on studies which actually show no effect at F intake levels relevant to CWF. They base their arguments on the known negative health effects at high fluoride intake (people in areas of endemic fluorosis suffer a range of health problems) but ignore, or cover-up the fact the data actually does not show any harmful effects at levels similar to that experienced by people in areas of CWF.

Figure 2: Drinking water concentrations reported by Duan et al. (2018) from “high F” and “low F” villages compared with tap water F in areas of CWF

Figure 2 above shows this using data from 26 studies reported in the review of Duan et al. (2018). Here the blue range represents the drinking water concentration range for the control groups where no health problems were reported, or it was assumed none occurred (that is why it was a control group). The green range represents drinking water fluoride concentration common in areas of CWF.

We should be drawing our conclusions about the possible effects of CWF from the blue range of data – not the red range.

Confounding effects

Guth et al (2020) stress that most studies they considered ignored many confounding effects.  For example:

” . .rural regions with unusually high or unusually low fluoride in drinking water may be associated with a less developed health-care system, as well as lower educational and socioeconomic status. Furthermore, in these regions the overall nutritional status and the intake of essential nutrients may be lower and the exposure to environmental contaminants such as lead, cadmium, mercury, or manganese may be higher—factors that are also discussed to have a potential impact on intelligence”

Only two of the studies were from areas using CWF – Broadbent et al (2015) and Green et al (2019) – and their conclusions were different. Guth et al (2020) considered these two studies in detail.

Both studies were limited by the lack of IQ data for mothers – parental IQ is a strong confounder for child IQ studies. But Guth et al (2020) are quite critical of the lack of consideration of confounders in the Green et al (2019) study:

Green et al. (2019) did not consider breastfeeding and low birth weight as possible confounders (both factors significantly associated with IQ in the study of Broadbent); they considered some of the relevant confounders (city, socioeconomic status, maternal education, race/ethnicity, prenatal secondhand smoke exposure), but did not adjust for others (alcohol consumption and further dietary factors, other sources of fluoride exposure, exact age of children at time point of testing). Furthermore, the study (Green et al. 2019) did not include assessment of children’s postnatal fluoride exposure via, e.g., diet, fluoride dentifrice, and/or fluoride tablets, which is considered to be a noteworthy limitation.”

Problems like poor consideration of confounders, contradictory results and the vague results reported by Green et al (2019) (no overall effect of fluoridation on child IQ, a statistically significant relationship of drinking water F concentration with male child IQ but not with female child IQ) caused Guth et al (2020) to conclude:

“The available epidemiological evidence does not provide sufficient arguments to raise concerns with regard to CWF in the range of 0.7–1.0 mg/L, and to justify the conclusion that fluoride is a human developmental neurotoxicant that should be categorized as similarly problematic as lead or methylmercury at current exposure levels.”

To repeat – this review is very detailed and thorough. Unlike the recent review of Grandjean (2019) (Developmental fluoride neurotoxicity: an updated review) which was superficial and somewhat biased (Grandjean is well known for his opposition to CWF) it made a detailed assessment of problems like the poor consideration of confounders or important risk-modifying factors and the concentration on poor quality studies from areas of endemic fluorosis.

Hopefully, policymakers will read this new review and take its conclusions into account.

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Anti-fluoride campaigners still rely on irrelevant studies


Despite Paul Connett’s claim that one only has to read four studies, anti-fluoride campaigners waste so much time promoting irrelevant studies to support there claims one could say they end up drowning in their own irrelevance. Image Credit: Ian Mcewan Quotations

Anti-fluoride activists simply can’t help it. They will post on social media citations to anything they think shows that fluoride is harmful – even if the studies are completely irrelevant to community water fluoridation (CWF). This despite Paul Connett, director of the Fluoride Action Network (FAN), claiming “You only have to read four studies…” to come to the conclusion that CWF is bad for your health.

Connett claims that he has it all sewed up with these four studies from areas where CWF is used or fluoride exposure values are similar to that for CWF. So I thought this would mean activists would give up citing studies from areas of endemic fluorosis where fluoride exposure is much larger. But no – here we go again with FAN returning to the reliance on endemic fluorosis studies with the claim:

“NEW STUDY: Each 1.0 mg/L increment in [urinary fluoride] concentration corresponded with an increase in the prevalence of psychosomatic problems.”

The local fluoride Free NZ activist group (FFNZ) simply repeats the claim. Anti-fluoride activists have a consistent habit of simply repeating these sort of claims, together with citation, without bothering to actually check what the cited papers say or how relevant the study really is to their cause. These activists seem to make a hobby of this – one can see their work every day on Twitter and Facebook. If nothing else one has to admire their dedication to the cause, if not there understanding of what they cite.

In this case, the study is not at all relevant to CWF. Here is its citation.

Wang, A., Duan, L., Huang, H., Ma, J., Zhang, Y., & Ma, Q. (2020). Association between fluoride exposure and behavioural outcomes of school-age children: a pilot study in China. International Journal of Environmental Health Research, 00(00), 1–10.

Briefly, it reports results for a comparison of six behavioural scores for 325 resident school-age children (7–13 years old) living in Tongxu County of Henan Province in China with a measure of fluoride exposure  (urinary fluoride using a single morning collected sample). There was no statistically significant relationship with of five of these behavioural scores (conduct problems, learning problems, Impulsive-hyperactive, anxiety or ADHD index) with urinary fluoride but there was with one – Psychosomatic problems.

It’s a very weak relationship – one has only to look at how the data is scattered in the figures in the paper to see this:


Notice that the urinary fluoride concentration (Fluoride in the graphs) cover a range much higher than is typical for areas where CWF is used – usually much less than 2 mg/L. Not surprising, as it is from an area of endemic fluorosis. Also noticeable is that some of the high fluoride value data points are outliers which of course will influence the statistical analysis.

Not all the data is available but extraction of the data from the figure for Psychosomatic Problems enabled me to check the effect of outliers at high urinary fluoride concentrations. When only the data for urinary fluoride concentrations below 3 mg/L are considered there is no statistically significant relationship. This is even more true when only the data for urinary fluoride concentrations below 2.5 mg/L is considered. And these concentrations are still higher than found for children living in areas where CWF is used.


This study is completely irrelevant to CWF. In fact, if only the low urinary fluoride concentrations more relevant to CWF are considered the study shows absolutely no negative effect of fluoride on child behaviour. If anything, the study actually could be used to support CWF.

But this does not stop anti-fluoride campaigners from promoting the study on social media as if it supported their arguments. I guess the promotion of irrelevant work like this is simply a result of the way they mine citations – promoting anything that could appear to indicate problems with fluoride -even when the studies are completely irrelevant. It’s also a result of the thoughtless way citations are used and studies are promoted by people who don’t understand or even bother to read the studies they cite and promote.

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Author confirms anti-fluoridation activist misrepresentation of her work

Anti-fluoride activists like Paul Connett often distort scientific findings and misrepresent studies. Authors should not give him a free pass and should expose such misinformation about their findings. Image credit: World Congress for freedom of scientific research

Paul Connett, director of the Fluoride Action Network (FAN),  claims “You only have to read four studies…” to come to the conclusion that community water fluoridation (CWF) is bad for your health. One of the studies he refers to is that of Riddell et al (2019) and Connett claimed that this study found “a staggering 284% increase in the prevalence of ADHD among children in fluoridated communities in Canada compared to non-fluoridated ones.”

I commented on this claim in my article Anti-fluoridation propaganda now relies on only four studies. 3: Riddell et al (2019) saying:

“This is just so wrong – Connett has misinterpreted the findings in this paper and completely covered up the fact that the results were dependent on age. He may well be “staggered” but he has made a bad mistake.”

Now, the senior author of this paper has confirmed that Connett was mistaken. She has confirmed that Connett is misrepresenting her work.

I emailed Julia Riddell to check if the Table 4 in her paper was mislabeled because some of the results were from linear regression analyses rather than logical regression analyses (see Anti-fluoridation propaganda now relies on only four studies. 3: Riddell et al (2019)). I also took the opportunity to ask her about Connett’s claim.

In her response she writes:

“I agree with you that the statement “a staggering 284% increase in the prevalence of ADHD among children in fluoridated communities in Canada” is a misinterpretation of our results, . . “

Riddell gives two reasons for saying this:

“First, a percentage should only be used to calculate values that are part of a whole, and thus a percentage is not an appropriate descriptive statistic to discuss these results. Further, and more importantly, I believe this interpretation of the odds ratio is incorrect. Odds is not probability nor is it likelihood of a ADHD diagnosis. Instead, odds = probability(ADHD dx) / probability(no ADHD dx).

In order to calculate a percent increase in the prevalence of ADHD, we would need to know the base rate probability of an ADHD diagnosis in the absence of water fluoridation (that is, what is the prevalence of ADHD ONLY in non-fluoridated communities).”

She writes: “To my knowledge, there has never been a national prevalence rate of ADHD calculated only for non-fluoridated regions, which is why we didn’t interpret the results in this way in our paper.” However, she provides an estimate using a postulated ADHD base rate of 0.08 (8% prevalence). According to her the Odds Ratios she reported in her paper would mean fluoridation would increase ADHD prevalence from 8% to 10%.

This is very different from Paul Connett’s claim. He should withdraw his claim and apologise for his mistake.

Two questions

Paul Connett’s little fiasco raises two questions for me:

1: Will Paul Connett now withdraw his claim and apologise for his mistake/misrepresentation?

I guess the answer is “when Hell freezes over.” He is not known for such apologies – neither is the anti-fluoride movement he leads. It continually misrepresents scientific findings and has never, in my experience, apologised for that misrepresentation when it has been exposed.

In fact, the anti-fluoride movement’s main propaganda thrust relies on citing any scientific work it can present, or misrepresent, as harmful to the case for community water fluoridation. This way it pretends to have the backing of science while relying on the unwillingness or inability of policymakers they bombard with the propaganda to factually check out these claims.

2: Why are researchers not more proactive in countering misrepresentation of their findings like this?

Yes, I know, researchers and especially their institutions do not like to enter into public debates with activists. There is some logic in this – after all, there is the old adage that it is not worth wrestling a pig because the pig enjoys it and both sides end up covered in dirt.

But this particular case is an example of misrepresentation which is being promoted to health policymakers who mainly do not have the scientific skills to check out the claims. It’s not a matter of entering into an unsavoury fight – but of correctly informing these policymakers when such misrepresentation occurs.

The other concern I have is that some anti-fluoride activists, including some well-known members (sometimes paid members) of Paul Connett’s FAN, have developed links with researchers and appear to be influencing publications through the journal peer-review process. In my article Anti-fluoridation propaganda now relies on only four studies. 6: Incestuous relationship of these studies I show how incestuous the publication and peer review process is for some of the scientific papers currently being promoted by anti-fluoride activists. Perhaps this is not too uncommon in science publication (many scientists complain about this sort of thing happening). But the participation of FAN members in the journal peer-review process is worrying as it suggests a relationship which FAN can use to get information about upcoming papers and prepared their propaganda and misinformation claims accordingly.

On the one hand, this may mean authors are hesitant to criticism FAN members and their claims because this could rebound on them during the publication process. On the other hand, it surely means that these people should be treated as valid science commentators and therefore open to challenge by researcher without the stigma of entering into an activist debate.

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Anti-fluoridation propaganda now relies on only four studies. 6: Incestuous relationship of these studies

A Fluoride Action Network (FAN) propaganda video where Paul Connett urges listeners to consider only four studies when considering the possible harmful effects of fluoridation.

Paul Connett, director of the Fluoride Action Network (FAN), now claims “You only have to read four studies…” to come to the conclusion that community water fluoridation (CWF) is bad for your health. He wants you to ignore all the other research – which is just bad science.

But this is even worse than it looks because these four studies are hardly independent. They basically represent the work of one or two groups and weaknesses in the studies indicate the groups are basically “torturing” data to produce relationships which confirm their likely biases against CWF. The same researchers appear as authors on most of the published papers from these studies.

But that is not all. There is evidence of an “old boy/girl network” operating within these research groups where journal peer reviewers are selected from the same groups.

It’s called “taking in each other’s laundry.”

For earlier articles in this series see:

In this article, I discuss the incestuous relationship of the studies promoted by Connett and show these researchers have links to anti-fluoride activism.

Links between the four studies

One indication of the lack of independence of these studies is the fact that the papers have common authors. The figure below reveals these links between the studies via their authors with the names in red being authors on more than one of the papers.

The above diagram indicates the four studies came from no more than 2 groups.

Martinez-Meir is common to both groups – probably because her laboratory was responsible for the analysis of maternal urinary fluoride.

Christine Till has been responsible for several of these studies as she obtained funding on the back of the flawed Malin & Till (2015) study (see Leader of flawed fluoridation study gets money for another go).

Till and Lanphear appear to have responsibility for formulating and designing these studies.

So it is wrong to see these as completely independent studies. They will all be influenced by the biases of the groups involved and the links shown in the figure above suggest coordination in publishing their research findings.

This becomes more apparent when we look at the journals involved in publishing some of this work and the peer reviewers used.

Links with peer reviewers

Unfortunately, very few journals make available the names of peer reviewers or the contents of their reviews. A pity, as I would like to understand better the controversy that seemed to erupt during the journal review of the Green et al (2019) paper, for example. (This controversy resulted in an unprecedented brief statement from the Editor and an opinion piece by David Bellinger promoting the paper – see If at first you don’t succeed . . . statistical manipulation might help).

However, some of the researchers have published their fluoride work in the journal Environmental Health which in recent years has published peer reviewer names and the contents of their reviews. So let’s look at papers published by the authors Connett is promoting where this peer review information is available. They were all published in Environmental Health and are:

This diagram illustrates some of the papers and the reviewers and links the authors and reviewers.

Note: The extra papers considered in the figure are:

Yes, it’s a real network and perhaps it’s not necessary to follow the details of each link. We can see, though, that authors on these papers often appear as journal peer reviewers of other papers from these research groups.

I suspect this situation may be more common in science publishing than we realise – especially as journals now often ask authors to suggest possible reviewers and to specifically name researchers they do not want to review their work.

I think that is bad for the quality of published research. It’s easy to see that in a network like this peer review is done within the groupthink (or bias) that exists in such a network. I raised this problem when commenting on the peer review of an earlier paper from the network – Malin & Till (2015) – in my articles Poor peer-review – a case study and Poor peer review – and its consequencesIn this case, the reviewers were fixated on chemical toxicity as the reason for health problems so did not consider all the other possible factors that might be responsible for the prevalence of ADHD diagnoses. They, therefore, missed completely possible regional effects which were at the time shown as important (see Perrott 2018).

This author/peer-reviewer network is particularly bad in situations like this where a controversial or even flawed paper gets approval simply because of the common biases of authors and peer reviewers.

Links with anti-fluoride campaigners

Notice in the figure above that two of the reviewers for Grandjean’s paper are members of FAN – senior members at that. While their contribution to improving the paper was probably minimal (Spittle’s comment – “The review capably considers recently available information and is highly pertinent to the public health” was worthless) the fact these reviewers were selected by the journal (and possibly by the author who is also the Chief Editor of the journal) indicates some influence.

These links indicate some sort of “under the table” influence and linking of researcher with FAN which probably explains why FAN often seems to have early information about upcoming publications which enable them to launch timely propaganda pieces.

Journals used for publication

Environmental Health is open access and a pay-to-publish journal. Pay-to-publish is becoming more common but many researchers steer away from these journals because they tend to have a reputation that payment encourages publication of bad research. On the positive side (as I said above) the open access policy, in this case, helps us see when the peer reviewers are and understand the problems I have discussed.

A relevant aspect of the author-peer-reviewer network, in this case, is the involvement of journal editors in the network as shown by this diagram.

NOTE: See notes for previous figure.

Phillipe Grandjean is also the author of Grandjean et al (2019) which appeared in the previous figure. I have written about his specific biases regarding fluoride in the past (see Special pleading by Philippe Grandjean on fluoride) and it is notable that as Editor in Chief of Environmental Health he refused to even consider for publication my paper critiquing Malin & Till (2015) (see Fluoridation not associated with ADHD – a myth put to rest).

David Bellinger is linked to the Bashash et al (2018a) study, not as an author, but as the note in the paper says:

“David Bellinger collaborated on the design and execution of this study’s cognitive testing.”

So it’s not surprising to see him authoring a promotion of the Green et al (2019) paper – although the inclusion of that promotion and the special note from the journal’s editor in that issue of the journal is very unusual.


The lack of independence in these four studies really reinforces the danger of limiting one’s reading. It’s not just a matter of restricting reading to four papers – its a matter of restricting information sources to one (or perhaps two) research groups influenced by the same groupthink and biases.

Group thinking and bias within research groups are not new. Nor is it a surprise that journals can be influenced by such group thought and bias and that this influences their acceptance of papers for publication. But if you are aware of the problem then you realise the need not to restrict your reading in the way that Connett is suggesting.

If anything, Connett’s statement is an admission that the overall findings of scientific studies on this issue do not support his case. He admits that all the studies anti-fluoride activists had been relying on in the past suffer from relating only to high fluoride concentrations. His plea people now restrict their reading to only four studies which really limits information sources to one or perhaps two research groups with a bias against CWF, is aimed at censoring the wider information availble.

Even more reason for readers to beware. One should never restrict information sources in the way Connett is suggesting.

See also:

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Anti-fluoridation propaganda now relies on only four studies. 5: Don’t censor yourself

The anti-fluoride movement wants to restrict your reading to “just four studies.” They actively ignore or attempt to discredit other relevant studies. Image credit: Censorship in media.

For earlier articles in this series see:

Part 1: Anti-fluoridation propaganda now relies on only four studies. 1: Bashash et al (2018).

Part 2: Anti-fluoridation propaganda now relies on only four studies. 2: Green et al (2019).

Part 3: Anti-fluoridation propaganda now relies on only four studies. 3: Riddell et al (2019).

Part 4: Anti-fluoridation propaganda now relies on only four studies. 4: Till et al (2020).

Paul Connett, director of the Fluoride Action Network (FAN), admits in his Fluoride Action Network (FAN) Bulletin from March 24, 2020:  “You only have to read four studies…” that “Many of the earlier studies were in places with elevated natural fluoride levels.” Yes – they are overwhelmingly from areas of endemic fluorosis, mainly in China, where health problems are very common and obvious. They have no relevance to community water fluoridation (CWF) – but this did not stop Connett, FAN and the whole anti-fluoride movement using them in their propaganda opposing a safe, effective and economic health policy known to reduce child tooth decay.

But he now claims “You only have to read four studies…” to come to the conclusion that community water fluoridation (CWF) is bad for your health. As I said in the first article in this series that is simply bad science. One should not ignore all the other relevant studies – and anyway, these four studies do not say what Connett claims.

Oh, but what about Santa-marina et al (2019)

In this article, I discuss a study Connett purposely ignored. The whole anti-fluoride activist movement has avoided discussing this study. It’s citation is:

Santa-Marina, L., Jimenez-Zabala, A., Molinuevo, A., Lopez-Espinosa, M., Villanueva, C., Riano, I., … Ibarluzea, J. (2019). Fluorinated water consumption in pregnancy and neuropsychological development of children at 14 months and 4 years of age. Environmental Epidemiology, 3.

Of course they ignore it, pretending it doesn’t even exist because it doesn’t confirm their bias!

As Table 7 below shows, Santa-marina et al (2019) reported statistically significant POSITIVE relationships of child cognitive measures with drinking water-fluoride. The red triangle indicates the relationship was statistically significant and the bars represent the 95% confidence interval

Table 7: Relationships of cognitive measures with exposure to fluoride for children reported by Santa-marina et al (2019)

I have already commented on the likelihood that this study suffers from many of the same weaknesses as the other studies discussed in this series – the four studies Paul Connett is actively promoting. The large confidence intervals indicate that the reported relationships will explain only a small percentage of the variance in cognitive measurements.

But, the point is this is another study that has as much right to be considered as the ones used by Connett. And there are others. Connett and other anti-fluoride campaigners purposely exclude studies they cannot use to support their anti-fluoride bias. Studies like those of Broadbent et al (2015), Aggeborn & Öhman (2016), Barberio et al (2017) and Perrott (2018).

The important thing is that the results reported in all the four studies promoted by Connett are contradictory. They lack consistency. Different measures of cognitive ability and fluoride exposure are required to find significant relationships. All the reported associations are weak and there are many statically non-significant associations Connett, and the authors themselves, just don’t discuss.

The critical and intelligent reader needs to take these factors into account instead of cherry-picking results which fit their agenda.

One does not make changes to health policy based on such weak evidence.

Taking in each other’s laundry

Tomorrow I will discuss the links between the four papers Connett is promoting to show that they are not independent. These authors also tend to act as journal reviewers for each other’s papers. To a large extent, the researchers involved are taking in each other’s laundry. See Anti-fluoridation propaganda now relies on only four studies. 6: Incestuous relationship of these studies.

See also:

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Anti-fluoridation propaganda now relies on only four studies. 4: Till et al (2020)

Paul Connet, head of the anti-fluoride propaganda group, Fluoride Action Network, claims that the IQ of children bottle-fed in fluoridated areas drops by 9 points. But he misrepresented the research. There is no observable effect.

For earlier articles in this series see:

Part 1: Anti-fluoridation propaganda now relies on only four studies. 1: Bashash et al (2018).

Part 2: Anti-fluoridation propaganda now relies on only four studies. 2: Green et al (2019).

Part 3: Anti-fluoridation propaganda now relies on only four studies. 3: Riddell et al (2019).

Paul Connett, director of the Fluoride Action Network (FAN), now claims “You only have to read four studies…” to come to the conclusion that community water fluoridation (CWF) is bad for your health. As I said in the first article in this series that is simply bad science. One should not ignore all the other relevant studies – and anyway, these four studies do not say what Connett claims.

In this article, I discuss the fourth study Connett recommends. It’s citation is:

Till, C., Green, R., Flora, D., Hornung, R., Martinez-mier, E. A., Blazer, M., … Lanphear, B. (2020). Fluoride exposure from infant formula and child IQ in a Canadian birth cohort. Environment International, 134(September 2019), 105315.

Till et al (2020)

Finally, according to Connett:

“The fourthcame in 2020, when it was reported that children who were bottle-fed in fluoridated communities in Canada lost up to 9 IQ points compared to those in non-fluoridated communities.”

This claim is just not true as Table 5 below shows. There is no significant difference in IQ (FSIQ) of children, who had been bottle-fed as babies, between fluoridated (mean IQ 106.1) and unfluoridated (mean IQ 106.8) areas. The only difference Till et al (2020) saw between fluoridated and unfluoridated areas was a significant increase of verbal IQ (VIQ – a subset of FSIQ) for breastfed children in fluoridated areas compared with non-fluoridated areas, and a significant decrease in performance IQ (PIQ a subset of FSIQ) for formula-fed babies in fluoridated areas compared with non-fluoridated areas.

Table 5. Influence of fluoridation on the IQ, VIQ and PIQ of children breastfed or formula-fed as babies found by Till et al (2020)(* indicates statistically significant difference)

Connett appears to have not read the Till et al (2020) paper, or misunderstood it. Perhaps his misunderstanding is derived from the relationships of cognitive measurements with drinking water F – although the relationships are not statistically significant for IQ (FSIQ) (see Table 6 below).

Then perhaps he is grasping at the straws offered by separating the IQ measurements into subsets – VIQ and PIQ. There were no significant relationships for VIQ but there are for the relationships of PIQ to drinking water F for both breastfed and formula-fed children. In fact a decrease of almost 8 PIQ points per 0.5 mg/L water fluoride concentration increase (which the authors argue is the increase seen with fluoridation).

Table 6: Relationships of cognitive measures with exposure to fluoride for children breastfed or formula-fed as babies reported by Till et al (2020)

This study has all the hallmarks of a desperate search for significant relations by using other measures of cognitive ability and fluoride exposure when the main relationship (that of FSIQ and CWF) proves not to be statistically significant. This approach, which statisticans are critical of, is common with most of the studies Connett relies on for his current claims.

There is also the problem that the authors in  their abstract, and of course the anti-fluoride activists promoting the paper, basically ignore most of the relationships because they are not statistically significant and report only the significant ones – and even then often incorrectly (as does Connett who uses the term IQ inappropriately).

Connett is wrong. His claim that “bottle-fed in fluoridated communities in Canada lost up to 9 IQ points compared to those in non-fluoridated communities” is just plain wrong. In fact, the mean IQ values for bottle-fed children in fluoridated areas of Canada was 106.1 and in non-fluoridated areas was 106.8 according to this study.

Tomorrow I will discuss other studies Connett purposely ignores and attempts to cover up because he cannot construe them as supporting his anti-fluoride narrative – see Anti-fluoridation propaganda now relies on only four studies. 5: Don’t censor yourself.

See also:

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