Tag Archives: IQ

Yet another fluoride-IQ study

As with most of these fluoride-IQ studies this one is only relevant to areas of endemic fluorosis (This is from a UNESCO paper and has been corrected for New Zealand. Identification of fluorosis in a country does not imply the whole country is high fluoride).

Yes, it’s a bit like groundhog day. Another fluoride-IQ study – and we expect this to be followed by another round of claims by anti-fluoride propagandists that this is the death knell to community water fluoridation. That this study provides the “irrefutable proof” that fluoride is a “neurotoxin.”

But that interpretation is completely wrong. This new study does nothing of the sort – in fact, quite the opposite.

The new study is:

Duan, Q., Jiao, J., Chen, X., & Wang, X. (2017). Association between water fluoride and the level of children’s intelligence: a dose-response meta-analysis https://doi.org/10.1016/j.puhe.2017.08.013

Now, why is this study absolutely useless for those opposing community water fluoridation?

It is not relevant to community water fluoridation

Because it is about a problem in areas of endemic fluorosis – where fluoride dietary intakes are much higher than where community water fluoridation exists.

From its first sentence it concentrates on fluorosis:

“Fluorosis is a progressive degenerative disease that causes skeletal fluorosis and dental fluorosis.”

And

“Currently, about 500 million people are exposed to environments high in fluoride content, while the incidence of fluorosis has already reached 200 million people worldwide.”

It’s not new research – it’s a meta-analysis of existing studies. Only studies dealing with areas of endemic fluorosis are considered in the meta-analysis. For example, the New Zealand (Broadbent et al., 2014) and Canadian (Barberio et a., 2017) papers which actually studied effects on IQ of community water fluoridation are not included. Nor is the Swedish study (Aggeborn & Öhman, 2016) which considered drinking water fluoride concentrations similar to that used in community water fluoridation.  So far these are the only reliable studies which considered low fluoride concentrations and they all show no effect of fluoride on IQ.

It is concerned with health effects in areas of endemic fluorosis

The meta-analysis includes 26 published studies in the meta-analysis. Most of the papers refer to “high fluoride water,” “fluorosis areas,” “endemic fluorosis” or similar terms in their titles. Low fluoride areas were only considered in the studies as “controls” and studies from areas of community water fluoridation were excluded.

Most of the considered studies simply compared IQ levels in “low fluoride” areas and “high fluoride” areas.  The mean drinking water fluoride concentration in the low fluoride levels of these studies was 0.6 mg/L (0.25 – 1.03 mg/L) and in the high fluoride areas, the mean drinking water concentration was  3.7 mg/L (0.8 – 11 mg/L).

As you can see the control or low fluoride areas, where the studies assumed there were no effects on IQ, have drinking water concentrations similar to that used in community water fluoridation (usually about 0.7 or 0.8 mg/L).

Yes, these studies did show statistically significant differences in IQ levels between the low and high fluoride areas. This is something for health authorities in areas of endemic fluorosis to be concerned about. And this, together with a range of other known health effects of excessive dietary fluoride intake, is the reason why attempts are made to reduce the fluoride levels in drinking water supplies in those areas.

People in high fluoride areas where fluorosis is endemic suffer a range of health problems. Credit: Xiang (2014)

Duan et al (2018) were able to present an overall estimate of the IQ difference between high and low fluoride areas – see figure. This is expressed as a standardised mean difference (SMD) – a necessary measure for a meta-analysis of a range of studies with different variability. The SMD = (difference in mean outcome between groups/standard deviation of outcome among participants) (see Cochrane Handbook).

All of the studies show a lower IQ in high fluoride areas than in low fluoride areas with the overall SMD being 0.52 (-0.62, -0.42 95% confidence interval).

To be clear – this is not 0.52 IQ points but can be interpreted as 0.52 x the standard deviation of IQ  in a population. Unfortunately, the authors do nothing to explain this, leaving readers to make the same mistake many did with a previous IQ meta-study (see Did the Royal Society get it wrong about fluoridation?).

Attempt to derive a dose-response relationship

The authors went on to attempt to derive an overall response curve relating SMD to drinking water fluoride concentration. Unfortunately, their results as presented in their  Fig 4 are confusing and the figure is not properly explained. Also, the modeling methods used to derive the response curve is not well explained.

However, the linear relationship they derived was not statistically significant. (They were able to derive a significant non-linear relationship, but again their methods and reason for doing this were not explained.)

I got the relationship shown in the figure below using the data provided in the paper without further modeling. This relationship is also not statistically significant (p=0.77).

The authors do suggest the possibility that lower intelligence may be associated with medium fluoride concentrations and “that very high fluoride concentration in water was associated with higher intelligence level than
medium fluoride.” However, although the figure above implies that IQ increases at higher fluoride concentrations, I do not think such conclusions are warranted with this data and its variability.

What causes the cognitive deficits?

Authors of these studies often seem to assume a direct chemical fluoride toxicity cause for the cognitive deficit. That also appears to be an assumption behind the desire to produce a dose-response relationship. Of course, anti-fluoride propagandists also prefer this mechanism because it enables them to argue that the effects also occur at low concentrations – they just haven’t been measured yet.

Although a dose-response relationship would be expected for a chemical toxicity mechanism this study did not produce a reasonable dose-response relationship. Some individual studies have claimed such a relationship but these claims are often not supported or the reported relationship is of only minor significance (see my discussion of Xiang et al., 2003 in Perrott, 2018).

The poor or non-existent relationship of cognitive deficits to drinking water fluoride concentration makes me suspect that there is not a direct effect. Rather the real causes of the cognitive deficits observed are dental or skeletal fluorosis or other health effects common in areas of endemic fluorosis. I suggested this in comments on Choi et al.,(2015) who observed a relationship with severe dental fluorosis but not water concentration (see Perrott 2015 – Severe dental fluorosis and cognitive deficits).

There I suggested consideration of the effects of severe dental fluorosis on quality of life and learning difficulties on cognitive deficits.  Another factor could be premature births and low birth weights which are known to influence cognitive development (see Premature births a factor in cognitive deficits observed in areas of endemic fluorosis?)

Duan et al., (2018) in their paper also allude to such possible mechanisms:

“Skeletal fluorosis is another very common and very serious side-effect of high fluoride intake, characterized by changes in the bone density, skeletal deformation, rickets, paralysis, disability, and even death. Patients with skeletal fluorosis have been reported to show neuronal nuclear vacuoles formations, cell loss in the spinal cord, and loss or solidification of Nissl bodies. Moreover, patients experience fatigue, sleepiness, headache, dizziness, and other symptoms related to the nervous system.”

Conclusions

The meta-analysis does confirm that there may be a problem with reduced of intelligence in children in areas of endemic fluorosis. This difference in IQ levels between high and low water fluoride levels is statistically significant.

However, this finding is of absolutely no relevance to community water fluoridation where the drinking water levels are similar to that in the low fluoride areas in the studies used for the meta-analysis.

The summarised data does not appear to be of sufficient quality to determine a reliable dose-response relationship. At least, the derived relationships are not statistically significant. An alternative explanation is that the observed reduced intelligence may not be directly related to drinking water concentration and instead related to dental or skeletal fluorosis, or other health effects common in areas of endemic fluorosis.

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Anti-fluoridation campaigners often use statistical significance to confirm bias

I was pleased to read this Nature article – Five ways to fix statistics – recently as it mirrors my concern at the way statistical analysis is sometimes used to justify or confirm a bias and not reveal a real causal relationship. Frankly these days I just get turned off by media reports of studies showing statistically significant relationships as evidence for or against the latest health or other fads.

As the Nature article says, statistical significance tests often amount “to uncertainty laundering:”

“Any study, no matter how poorly designed and conducted, can lead to statistical significance and thus a declaration of truth or falsity. NHST [null hypothesis significance testing] was supposed to protect researchers from over-interpreting noisy data. Now it has the opposite effect.”

No matter how good a relationship appears, or how significant the statistical analysis shows it to be, it is simply a relationship and may have no mechanistic or causal backing.  An example often used to illustrate this is the close relationship between the prevalence of autism and sales of organic produce.

Clearly statically significant but we don’t find those activists claiming autism is related to one thing or another ever citing this one. I am picking these activists may well have a bias towards organic produce.

Here are several examples I have discussed before which illustrates how “statistical significance” is sometimes used to confirm bias in fluoridation studies. I think these are very relevant as anti-fluoridation campaigners often cite statistical significance as if it is the final proof for their claims.

Ignoring relevant confounders

This is an easy trap for the biased researcher (and let’s face it, most of us are biased – it’s only human). Just ignore other confounders or risk-modifying factors that may be more important. Or ignore the fact that the risk-modifying factor one is interested in (in this case fluoride) may just be acting as a proxy for (and therefore is related to) something else which is more relevant.

This why all credible risk-modifying factors should be considered in correlation studies. They should be included in the statistical analyses.

It’s amazing how many researchers either ignore the possible risk-modifying factors besides their pet one – or pay lip-service to the problem by limiting their consideration to only a small range of such factors.

Examples of studies promoted by anti-fluoride campaigners where this is a problem include:

Peckham et al., (2015) hypothyroidism paper:

Peckham, S., Lowery, D., & Spencer, S. (2015). Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water. J Epidemiol Community Health, 1–6.

This has been widely condemned for a number of reasons – one of which is that iodine deficiency, a known factor in hypothyroidism, was not included in the statistical analysis.

(See Paper claiming water fluoridation linked to hypothyroidism slammed by experts and Anti-fluoride hypothyroidism paper slammed yet again).

The  Takahashi et al., (2001) cancer paper:

Takahashi, K., Akiniwa, K., & Narita, K. (2001). Regression Analysis of Cancer Rates and Water Fluoride in the USA based Incidence on IACR / IARC ( WHO ) Data ( 1978-1992 ). Journal of Epidemiology, 11(4), 170–179.

These authors reported an association between fluoridation and a range of cancers. Problem is, they did not consider any other risk-modifying factors. When some geographical parameters were included in the statistical analyses there were no statistically significant relationships of cancer with fluoridation.

(see Fluoridation and cancer).

The Malin & Till (2015) ADHD paper:

Malin, A. J., & Till, C. (2015). Exposure to fluoridated water and attention deficit hyperactivity disorder prevalence among children and adolescents in the United States: an ecological association. Environmental Health, 14.

This reported an association of ADHD prevalence with the extent of fluoridation in the US. Anti-fluoride campaigners have cited this paper a lot because it is the only study indicating any effect of fluoridation on cognitive ability. All other studies they rely on were from areas of endemic fluorosis where the natural levels of fluoride are higher than that used in community water fluoridation.

Malin & Till (2015) considered only household income as a possible risk-modifying factor. No consideration was given to residential elevation which other researchers had around the same time reported as associated with ADHD prevalence.

I repeated their statistical analysis but included residential elevation and a range of other risk-modifying factors. This showed there was no statically signficant association of ADHD with fluoridation when other risk-modifying factors, particularly elevation, were included. My critique of Malin and Till (20215) is now published:

Perrott, K. W. (2017). Fluoridation and attention deficit hyperactivity disorder – a critique of Malin and Till ( 2015 ). Br Dent J.

(See ADHD linked to elevation not fluoridationADHD link to fluoridation claim undermined again and Fluoridation not associated with ADHD – a myth put to rest).

Ignoring the lack of explanatory power

I think this is where the over-reliance on statistical significance, the p-value, can be really misleading. Researchers desperately wishing to confirm their bias will proudly claim  a statistically significant relationship, a p-value less than 0.05, etc., as if that is the final “proof.” These researchers will often hide the real meaning of their relationship by not making the actual data available or limiting their report of their statistical analysis to p-vlaues and, maybe, a mathematical relationship.

However, if the reported relationship actually explains only a small part of the observed variation in the data it may be meaningless. Concentration on such a relationship means that other more signficant risk-modifying factors which would explain more of the variation are ignored. Anyway, where a factor explains only a small part of the variation it is likely a more complete statistical analysis would show that its contribution was not actually statistically signficant.

Some examples:

The prenatal fluoride exposure and IQ study of Bashash et al (2017):

Bashash, M., Thomas, D., Hu, H., Martinez-mier, E. A., Sanchez, B. N., Basu, N., … Hernández-avila, M. (2016). Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6 – 12 Years of Age in Mexico.Environmental Health Perspectives, 1, 1–12.

These authors reported a statistically significant association of Child IQ with the prenatal fluoride exposure of their mothers. However, their figures showed a very wide scatter in the data indicating very little explanation of the variation in child IQ by the association with prenatal fluoride. (see below left). This must be why the Fluoride Action Network removed the data points from the figure when reproducing it for their promotion of the paper (see below right).

Bashash et al., (29017) did not give the complete statistical analysis of their data. However, I was able to digitally extract the data from their figure and my analysis showed that prenatal fluoride expose was only able to explain a little over 3% of the variation in child IQ. So, despite the statistical significance of their observed relationship prenatal fluoride exposure is unlikely to be a real factor in child IQ. In fact, concentration on this minor (even if statistically significant) factor will only inhibit the discovery of the real causes of IQ variation in these children.

Yes, anti-fluoride campaigners will protest that this study did consider some other possible risk-modifying factors. However the very low-level of explanation of the variation in the data indicates they did not consider enough.

(see Premature births a factor in cognitive deficits observed in areas of endemic fluorosis? Fluoride, pregnancy and the IQ of offspring and Maternal urinary fluoride/IQ study – an update).

The Xiang et al., (2003) water fluoride and IQ study:

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

Anti-fluoride campaigners rely a lot on this and other papers from this group.  Even though this research involved areas of endemic fluorosis it, in a sense, provides some of their best evidence because they reported a dose-dependent relationship of IQ to water F. Xiang et al., (2003) claimed a statistically signficant association of child IQ to fluoride water levels.  Other anti-fluoride campaigners, and some other researchers, have cited Xiang et al., (2003) to support such an association.

I don’t question these researchers found a significant association – but there is a problem. Nowhere do they give a statistical analysis or the data to support their claim! Very frustrating for critical readers (and we should all be critical readers).

They did, however, give some evidence from a statical analysis of the relationship of IQ with urinary fluoride. They did not give a complete statistical analysis but they included the data in a figure  (see below) – so I did my own statistical analysis of data digitally extracted from the figure.

The figure shows a high scatter of data points so this is another case of a statistically significant relationship explaining only a small part of the variability. My analysis indicates the relationship explains only about 3% of the variability in IQ value. Another case where researchers have concentrated on their own pet relationship and in the process not properly searched for more reasonable risk-modifying factors capable of explaining a larger proportion of the variation.

I have made a more detailed critique of Xiang et al.  (2015) and Hirzy et al., (2016) which relies on this data (see Does drinking water fluoride influence IQ? A critique of Hirzy et al. (2016)). A paper based on this has been submitted to a journal for publication and is currently undergoing peer review..

(see Anti-fluoride authors indulge in data manipulation and statistical porkiesDebunking a “classic” fluoride-IQ paper by leading anti-fluoride propagandists,  Connett fiddles the data on fluorideConnett & Hirzy do a shonky risk assesment for fluoride and Connett misrepresents the fluoride and IQ data yet again).

Conclusion

This  briefly outlines the statistical problems of a number of papers anti-fluoride campaigners rely on. Two common problems are:

  • Insufficient consideration of confounders or other risk-modifying factors – indicating a bias towards a “preferred” cause, and
  • Reliance on a relationship that, although statistically significant, explains only a very small fraction of the observed variation – again indicating bias towards a “preferred” cause

I don’t for a minute suggest that only those researchers publishing “anti-fluoride” research are guilty of these errors. They are probably quite common. Authors will generally responsibly warn that “correlation does not prove causation” and suggest more work needs to be done including  consideration of a wider number of confounders or risk-modifying factors. However, bias is only human so researcher advocacy for their own findings is understandable. The published research may even be of general value if readers interpret it critically and intelligently.

However, in the political world such critical consideration is very rare. Activists will use published research in the way a drunk uses a lamppost – more for support than for illumination. This makes it important that the rest of us be more objective and critically assess the claims they are making. Part of this critical assessment must include an objective consideration of the published research that is being cited.

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Endemic fluorosis and its health effects

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

 

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

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

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

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

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

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

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

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

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

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

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

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

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Maternal urinary fluoride/IQ study – an update

Model of a fetus in the womb. Photo credit: CP PHOTO/ Alliance Atlantis/ HO) 

The maternal urinary fluoride/IQ study  (Bashash et al., 2017) continues to get attention – but mainly from anti-fluoride organisations. The scientific community will evaluate the published report after giving it due consideration and there have already been criticisms. But anti-fluoride campaigners consider it the best thing since sliced bread. The Fluoride Action Network (FAN) describes it as “a cannon shot across the bow of the 80 year old practice of artificial fluoridation” and Fluoride Free NZ insist that it “must spell an end to fluoridation in New Zealand.”

We expect confirmation bias from the anti-fluoride organisations. But the misrepresentations in the propaganda from these organisations are of more concern because they are blatantly meant to scaremonger.

Misrepresentation by anti-fluoride organisations

These people have worked hard to stress the respectability of the authors of the Bashash et al., (2017) paper and claim the study is impeccable. They are not interested in a critical analysis of the data and the conclusions. And they are completely silent about the evidence from the study showing no association of children’s urinary fluoride levels and IQ – normally they are quick to criticise authors reporting such a lack of association.

But this time as well as their normal misrepresentations they have actually manipulated a figure from the paper. I wonder what copyright law would say about this.

I provided the relevant figures from the paper my earlier article (see   Fluoride, pregnancy and the IQ of offspring) and commented on the large amount of scatter in the data.  This scatter should be a warning to any sensible reader – so FAN simply overcomes that problem by deleting the data points in their presentation of the figure.

Here is the original Figure 2 and the FAN misrepresentation of it:

Notice 2 things:

  1. The original figure showed the data for GCI – general cognitive index. It is not IQ and not presented as IQ in the original paper. But it is a measure  of “verbal, perceptual performance, quantitative, memory, and motor abilities of preschool-aged children.” Perhaps a fine point and FAN may be excused for inserting the more popularly understood term IQ. Or perhaps they decided not to use the real figure for IQ (Figure 3A) because it implied no effect at normal urinary fluoride levels (see figure 3A in Fluoride, pregnancy and the IQ of offspring);
  2. FAN removed all the data points in their presentation of the figure. I am sure FAN would argue this was to “simplify” the figure. But in doing so they have removed what is the most important information in Figure 2 – the wide scatter of the data points. That scatter suggests that even though the reported association is “statistically significant” it explains very little of the observed variation and is therefore not important (and may not even be real).

Association of maternal urinary F with child IQ poor and probably misleading

In Fluoride, pregnancy and the IQ of offspring I estimated that “the reported relationships with maternal urinary fluoride could explain no more than a few percent of the variation in the data.” Purely an estimation because I did not have the data to analyse myself and the authors did not give the relevant statistical information.

I have since used a plot digitiser programme to extract the data for these figures and performed my own statistical analysis.

These are the results:

For Figure 2:

Yes, a “statistically significant” relationship (p = 0.002) but it explains only 3.3% of the variation in GCI (R-squared = 0.033)

For Figure 3A:

Again, “statistically significant” (p = 0.006) but explaining only 3.6% of the variation in IQ (R-squared = 0.0357).

So my estimate was pretty good. And my evaluation is valid:

“In this case, I would expect that other risk-modifying factors that explain the variation more completely could be found. And if these were included in the multiple regressions there may not be any observable relationship with urinary fluoride.”

Considering that this work was unable to explain about 97% of the variation in CGI and IQ I really question its publication. Certainly, scientific evaluations will conclude that this paper should not have any influence on policymakers.

It’s a pity that with all the data the authors had they did not seek out, or properly evaluate, other possible risk-modifying factors.

Other work by group showing no association ignored

Strangely, the Bashash et al., (2017) paper did not include relevant IQ information from the PhD thesis of one of their team Deena B. Thomas. This is her thesis citation:

Thomas, D. B. (2014). Fluoride exposure during pregnancy and its effects on childhood neurobehavior: a study among mother-child pairs from Mexico City, Mexico. PhD thesis, University of Michigan.

It can be downloaded from the full-text link.

The data in chapter 2 of this thesis – Urinary and Plasma Fluoride Levels During Pregnancy and Determinants of Exposure Among Pregnant Women from Mexico City, Mexico – was published. The citation is:

Thomas, D. B., Basu, N., Martinez-Mier, E. A., Sánchez, B. N., Zhang, Z., Liu, Y., … Téllez-Rojo, M. M. (2016). Urinary and plasma fluoride levels in pregnant women from Mexico City. Environmental Research, 150, 489–495.

Bashash et al., (2017) did reference this paper – after all, it dealt with the data they used for estimating fluoride exposure. But they did not reference the thesis itself – and two other chapters in that thesis are directly relevant to the relationship of fluoride exposure to child IQ.

Chapter 3 – Prenatal fluoride exposure and neurobehavior: a prospective study – is directly relevant except that where Bashash et al., (2017) reported data for the children when 4 years old and 6-12 years old Thomas reported data for child neurobehavioral outcomes at ages 1, 2 and 3.

She concluded:

“that maternal intake of fluoride during pregnancy does not have a strong impact on offspring cognitive development in the first three years of life.”

OK – perhaps the difference is purely due to age. But surely it is part of the picture and should at least been mention in the Bashash et al., (2017) discussion.

Chapter 4 – Concurrent Fluoride and Total WASI in 6-15 year old children from Mexico City, Mexico – is also directly relevant because Bashash et al., (2017) did include that data in their paper. They concluded that:

“there was not a clear, statistically significant association between contemporaneous children’s urinary fluoride (CUFsg) and IQ either unadjusted
or adjusting for MUFcr.”

This differs a little from the findings in Thomas’s thesis:

“In the overall population, urinary fluoride appears to have no significant impact on total WASI scores (β =1.32, p=0.33), but this association changes once the models are separated by male and female children. Male children showed a significantly positive trend (β=3.81, p=0.05), and females showing a negative trend that was not significant (β= -1.57, p=0.39).” [WASI score is a measure of IQ]

And she wrote:

“analysis suggests concurrent urinary fluoride exposure has a strong positive impact on cognitive development among males aged 6-15 years.”

She concludes:

“These results were surprising in that they show opposite trends to what has been reported in the literature so, more studies with similar reliable methodology, which account for plasma fluoride, diurnal variations in urinary fluoride and children’s SES, are needed. If these results are substantiated, different fluoride interventions may be needed for male children versus female
children.”

I would have thought these findings and conclusions were worthy of discussion by Bashash et al., (2017). It’s not as if the authors were unaware of their colleague’s findings.

Maybe internal politics are involved. but that does not justify the omission.

Conclusion

The anti-fluoride people, and particularly FAN, are misrepresenting the study and have manipulated a figure to hide information in an unethical way. The data presented in the Bashash et al., (2017) study shows maternal urinary fluoride can only explain 3 – 4 % of the variation in General Cognitive Index and IQ of the children. The inclusion of a more viable risk-modifying factor would probably remove even that small amount explanation.  Bashash et al., (2017) also neglected to discuss relevant information from a colleague which contradicted their conclusions.

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Fluoride, pregnancy and the IQ of offspring

Anti-fluoride campaigners don’t agree. Image credit:Dental Care Tips for Mom and Baby” presentation

What’s the story about this new IQ-fluoride study? The one that claims fluoride intake by pregnant women could endanger their children’s IQ?

Whatever the truth, it has certainly got the anti-fluoride activists going. Mary O’Brien Byrne, leader of the local anti-fluoride group is even suggesting people check if their mothers lived in fluoridated areas. And they are busy promoting the newspaper articles on this. For example Fluoride exposure in utero linked to lower IQ in kids, study saysChildren’s IQ could be lowered by mothers drinking tap water while pregnant, and Higher levels of fluoride in urine linked to lower IQ scores in children.

Best not rely on those media reports, though – you know how unreliable they can be. The original paper is available – this is the citation:

Bashash, M., Thomas, D., Hu, H., Martinez-mier, E. A., Sanchez, B. N., Basu, N., … Hernández-avila, M. (2016). Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6 – 12 Years of Age in Mexico. Environmental Health Perspectives, 1, 1–12.

And here is a link to the full text. Download it and see what sense you make of it. I warn you it is a difficult paper to read.  A lot of information is lacking and the information that is included is hard to find. The statistical analysis is incomplete.

A new twist on the tired old fluoride/IQ story

Basically, it is the old drinking water fluoride causes lowering of IQ story. This time it relates to a supposed association of fluoride intake by pregnant mothers with cognitive deficits in their children. Interesting, only one other similar study (involving fluoride exposure while pregnant) has been reported – in January this year, and also in Mexico. I wrote about that study of Valdez Jiménez et al., (2017), In utero exposure to fluoride and cognitive development delay in infants,  in the article Premature births a factor in cognitive deficits observed in areas of endemic fluorosis?

Briefly, the Valdez Jiménez et al., (2017) study was from Mexican areas of endemic fluorosis with very high fluoride concentrations in drinking water so the results are not applicable to areas where community water fluoridation is used. However, the high incidence of premature births, and low birthweights for the children, for mothers with high urinary fluoride levels does suggest that problems of birth in areas of endemic fluorosis could provide a biological mechanism to explain the IQ deficits. Rather than a direct chemical toxicity mechanism.

What about the Bashash, et al. (2017) paper?

Generally, the paper concludes that “higher prenatal fluoride exposure . . . .was associated with lower scores on tests of cognitive function in the offspring.”

So here are some concerns I have about the paper

1: An association is not evidence of, or proof for, causation. Yes, that is the normal and obvious qualification for such studies and authors tend to repeat it – even if they might still attempt to argue the case that it is evidence. A lot of confirmation bias goes on with these sort of correlational studies.

2: The information about the mothers is scant. My first question, given it was Mexico, was did they come from areas of endemic fluorosis? The women were recruited from three hospitals in Mexico city but this says nothing about their current or former residential areas. No information on drinking water fluoride is presented nor any biological assessment, such as dental fluorosis, given which could help estimate the role of endemic fluorosis.

3: Assessment of fluoride exposure relied completely on urine fluoride concentration measurements. With between one and three samples for each mother-child pair! (Of the total sampled there was only one sample for 217, two for 224 and three for 71 mothers). I believe that is completely inadequate for estimating exposure – especially as fluoride levels in urine vary markedly during the day and with diet. Besides the extremely low sample numbers,  the World Health Organisation has warned that while urinary fluoride can be useful for monitoring populations “Urinary fluoride excretion is not suitable for predicting fluoride intake for individuals.”  (see Contemporary biological markers of exposure to fluoride). They further warn that 24 hr collection is preferred to the spot sampling used in this study.

4: The statistical information presented is confusing – and insufficient to estimate how relevant the reported statistically significant associations are. I believe the best idea of the data can be gleaned from the following figures presented in the paper.

Figure 2 displays the data and association of maternal urinary fluoride (MUFcr) with a general cognitive index (CGI) for the 4 yr old offspring.

Figure 3A displays the data and association of maternal urinary fluoride (MUFcr) with IQ of the offspring at age 6 -12.

While linear regression analysis showed statistically significant associations of the CGI and IQ of offspring’s with maternal urinary fluoride levels the large scatter indicates these associations will explain only a small part of the variations observed. In such situations, reliance on p values can be misleading. As a reader, I would be more interested in the R2 values which indicate the amount of variation explained by the association.

I estimate the reported relationships with maternal urinary fluoride could explain no more than a few percent of the variation in the data. In this case, I would expect that other risk-modifying factors that explain the variation more completely could be found. And if these were included in the multiple regressions there may not be any observable relationship with urinary fluoride.

I discussed this issue more fully in my article Fluoridation not associated with ADHD – a myth put to rest which showed that a published relationship of ADHD with fluoridation extent disappeared completely when altitude was included as a risk-modifying factor. And that relationship showed less scatter of the data points than in the figures above.

5: The absence of any association of child IQ to child urine fluoride was also reported in this paper. This conflicts with other researchers working in areas of endemic fluorosis who have reported such associations. It could be that the urine fluoride measurements used in the present study were not suitable. But I am picking that the anti-fluoride campaigners will be very silent about that information, given the importance they give to other studies showing a relationship in their propaganda.

Conclusions

it is a very unsatisfying paper. I couldn’t determine if areas of endemic fluorosis were implicated – as they were for the Valdez Jiménez et al., (2017) study. Urinary fluoride is an inadequate measure of fluoride exposure – especially for individuals and spot samples – and its variability does not allow comparison with other studies and other regions. I couldn’t evaluate if the reported results were relevant to New Zealand which does not have any endemic fluorosis.

Finally, I believe aspects of the statistical analysis were inadequate. But on the positive side, I am pleased the authors did display the actual data in their figures. The information in those figures forced me to conclude that maternal urinary fluoride may not have the influence the authors suggest. If it does have an influence its contribution can only be minor and other more important risk-modifying factors will be involved.

Mind you – I am sure anti-fluoride campaigners will see it differently. They are currently heavily promoting the study and anti-fluoride guru Paul Connett sees it as the best thing since sliced bread. He has gone on record to say this means the end of community water fluoridation!

Update

I think the anti-fluoride people are aware of weaknesses in this study. The local Fluyodie Free NZ has put out a press release including a figure which they have doctored to remove the data points which show how little variation is explained. Compare their figure with the Fiugure 2 above.

Fluoride Free NZ doctors figure from paper to hide the scatter in data points showing how little of the variability the relationship explains

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

epa-meeting-sept5-2014

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

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

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

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

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

bruce-spittle

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

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

The authors are:

david-c-kennedy

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

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

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

xiang-Endemic fluorosis

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

Critique of the paper

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

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

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

In my critique I deal with the following issues:

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

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

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

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

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

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

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

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

Conclusion

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

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More nails in the coffin of the anti-fluoridation myths around IQ and hypothyroidism

thyroid_fluoride

Large Canadian study finds no effect of fluoridation on thyroid health

A new Canadian study shows no relationship of cognitive deficits or diagnosis of hypothyroidism with fluoride in drinking water. This work is important because it counters the claims made by anti-fluoride campaigners. While the campaigners cite scientific studies to support their claims, those studies are usually very weak, or irrelevant because they involve areas of endemic fluorosis where drinking water fluoride concentrations are much higher than in situations where community water fluoridation (CWF) is used.

The study is reported in:

Barberio, A. M. (2016). A Canadian Population-based Study of the Relationship between Fluoride Exposure and Indicators of Cognitive and Thyroid Functioning; Implications for Community Water Fluoridation. MSc Thesis, University of Calgary

This new study is important as it has the advantages of using a large representative sample of the Canadian population, with extensive data validation and quality control measures. It also uses individual-level estimates of fluoride exposure on the one hand, and thyroid health and cognitive problems on the other.

Fluoride exposure was measured both by concentration in tap water for selected households and concentration in urine samples from individuals.

Thyroid health

The Canadian study found:

“Fluoride exposure (from urine and tap water) was not associated with impaired thyroid functioning, as measured by self-reported diagnosis of a thyroid condition or abnormal TSH level.”

This contradicts the conclusions from the population-level study of Peckham et al., (2015) which reported that fluoridation was correlated with the prevalence of hypothyroidism. That study is quoted extensively by anti-fluoridation activists but has been roundly criticised because it did not include the influence of confounders – particularly iodine which is known to influence thyroid health.

Barberio (2016) also suggests that the different recommended fluoride concentrations used for CWF in Canada and the UK, and the fact that the Peckham et al (2015) study did not involve individual measures, could also be factors in the different findings.

Cognitive functioning

The Canadian study reported:

“Fluoride exposure (from urine and tap water) was not associated with self-reported diagnosis of a learning disability.”

Barberio (2016) did also investigate a more detailed diagnosis for cognitive problems and found:

“Higher urinary fluoride was associated with having ‘some’ compared to ‘no’ cognitive problems . . . . however, this association:

  • Was weak;

  • Was not dose-response in nature; and

  • Disappeared when the sample was constrained to those for whom we could discern fluoride exposure from drinking water.”

I guess anti-fluoride activists might latch on to this last point regarding urinary fluoride but, at least as far as tap water fluoride is concerned, there was no relationship with learning difficulties.

Conclusion

So – yet another large-scale study contradicts anti-fluoridationist claims. It shows that CWF has no influence on cognitive problems or thyroid health.

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Anti-fluoride IQ claims are false

false-claims
Anti-fluoridation campaigners’ claims that community water fluoridation reduces IQ are simply false. That is the conclusion of  Alex Kasprak – and he says why in his new Snopes.com article (see Fact Check -Fluor-IQ).

These days anti-fluoridation activists use this claim as their main argument – and they often cite scientific articles to back it up. But, Kasprak says, this claim  is based on “either willful or negligent misreading of actual science.” The claim that  studies have “linked” fluoride to reduced intelligence “is a textbook-ready case of bait-and-switch:”

” the topic has surreptitiously been shifted from the act of water fluoridation as a public health measure to the broader concept of fluoride toxicity in children. Many otherwise benign chemicals can also be harmful in high concentrations. Thiocyanate, a chemical found in kale, may kill you at high doses, for example.”

Scale and context

Kasprak critiques the way anti-fluoride campaigners so often use and cite the Choi et al., (2012) study. This was a meta-analysis of 27 mostly poor quality Chinese studies from areas of endemic fluorosis where drinking water fluoride levels are much higher than that used in community water fluoridation.

Citing neuroscientist Steven Novella Kasprak points out:

“There was a lot of variability across the studies, but generally the high fluoride groups were in the 2-10 mg/L range, while the reference low fluoride groups were in the 0.5-1.0 mg/L range […]”

In other words – fluoridated water in the US has the same level of fluoride as the control or low fluoride groups in the China studies reviewed in the recent article, and the negative association with IQ was only found where fluoride levels were much higher – generally above EPA limits.

Note: The optimum level of fluoridated water in the US is 0.7 mg/L.

Anti-fluoride campaigners sometimes concentrate on those studies in the meta-review which did focus on concentrations close to that considered optimum. But:

“Of those eight studies, half of them co-investigated fluoride and iodine together (Lin et al 1991, Xu et al 1994, Yang et al 1994, Hong et al 2001) making it hard or in some cases impossible to separate out the combined effects, and two of those four studies reached conclusions that are counter to the hypothesis that fluoridation levels alone are the main driver of a lower IQ.”

And:

“Two of those eight studies use a control group with fluoride values that are literally the same or higher than the target range of fluoridation efforts in the United States (Xu et al 1994, Hong et al 2001), seemingly ceding the point that those levels do not affect children’s IQ.”

So, as far as scale is concerned, Kasprak concludes:

“Collectively, this demonstrates that most of the IQ variance presented in the Harvard study still stems from exposures to extremely high levels of fluoride that would already be considered dangerous in the US, and those studies finding effects on a smaller scale are not sufficient to demonstrate the effects those groups opposed to fluoridation claim they demonstrate.”

As far as context is concerned none of these 27 studies were relevant to community water fluoridation:

“Literally none of the studies involved tested populations of individuals exposed to drinking water that was artificially supplemented with fluoride as a public health measure. Instead, all of the studies come from China or Iran, both of which have areas of naturally occurring (endemic) high fluoride pockets of groundwater.

That means that studies utilized in its analysis are wholly irrelevant to the question that advocates claim they are answering. This is significant, as the use of these very specific studies introduces a veritable Homerian epic of confounding details, some of which came up in our analysis of the eight low-level fluoride studies discussed above. Among the most pressing of these are a lack of information on other confounding variables and the quality of the studies they utilized. These issues are noted by the authors of the Harvard study themselves”

The authors of the Choi et al (2012) meta-review also:

“explicitly state that the results cannot be used to estimate the possible limits of fluoride exposure with respect to developmental damage, due to lack of data – ‘Our review cannot be used to derive an exposure limit, because the actual exposures of the individual children are not known.'”

Other mechanisms

Kasprek disagrees with the unsubstantiated claim of Choi et al., (2012) that other neurotoxicants are unlikely to be present in the groundwater of the studied areas. Rightly so because all those studies suffer from insufficient consideration of confounding factors. As Choi et al., (2012) said: “Most reports were fairly brief and complete information on covariates was not available.” 

In fact, statistical analysis of the data in one of the better papers the anti-fluoride campaigners rely on shows that fluoride can explain only about 3% of the measured variance in IQ. It is extremely likely that inclusion of sensible confounders in the statistical analysis would have shown any relationship of IQ with fluoride is not statistically signficant (see Connett misrepresents the fluoride and IQ data yet again).

Kasprek briefly considered arsenic as a possible confounder but with subjects like cognitive ability or IQ there are many other physical and social factors that could be imnportant.contaminants. Parental income and education as well as the psychological consequences of deformities resulting from dental and skeletal fluorosis. I discussed this last aspect in my peer-reviewed article Perrott (2015), Severe dental fluorosis and cognitive deficits and my post- Severe dental fluorosis the real cause of IQ deficits?

Fallacy of publication journal

I think Kasprek’s argument about the journal used for publishing some of these papers is fallacious:”

“Finally, four of these eight papers (Yang et al 1994, Lu et al 2000, Hong et al 2001, Xiang et al 2003a) are either published (or republished) in the allegedly peer-reviewed journal Fluoride, a publication of the “International Society for Fluoride Research Inc.” — an anti-fluoridation group whose editor-in-chief is a psychiatrist in private practice, with no academic background on the topic of fluoride toxicity.”

I am very much opposed to using the place of publication as an argument against the scientific veracity of a paper. True, Fluoride is a very poor quality journal. True, is has an ant-fluoride agenda. And true, it shows no evidence of proper peer review. However, it is disingenuous to use these facts to argue against the scientific content of these papers. Critique of the papers should rest on an analysis of their scientific content – not the place of publication.

This lazy approach is doubly worse because it carries the implication that if these papers had been published in a reputable journal with good peer review then that would be sufficient to guarantee the veracity of the science. It is not.

On the fluoride issue, there are plenty of examples of papers involving poor science that are published in reputable journals. I have discussed some of these in my articles – for example ADHD linked to elevation not fluoridationAnti-fluoride hypothyroidism paper slammed yet againPoor peer review – and its consequencesDoes community water fluoridation reduce diabetes prevalence?, The Harvard study and the Lancet paperControversial IQ study hammered in The Lancet and Repeating bad science on fluoride.

The lazy judgmentalism based on place of publication, and not content, is particularly relevant at the moment with the public concern about “false news” and efforts to introduce mechanisms of “fact checking.” Some people are advocating reliance on websites like Snopes.com – yet this site can be blatantly biased on political matters. And its bias can rest on the lazy approach of condemning a news article by its place of publication.

[A recent example was a Snopes.com article which cast aspersions on an independent journalist, Eva Bartlett, because – “She is also a contributor at RT, a news site funded by the Russian government.” OK, you may not see how lazy that argument is but try replacing the words RT and Russian by “Al Jazeera” and Qatar” or “BBC” and “British.” And, I also think describing the fact that Bartlett had been interviewed by an RT reporter, and participated in a debate aired by RT, as being a “contributor” shows a bias]

The good science

Despite delving into the details of the poor quality papers the anti-fluoride IQ argument relies on Kasprak is quite right to stress:

“This should not function as a distraction from the larger point that studying naturally occurring pockets of high fluoride and the assessing the risks of supplementing public drinking water in an effort to have it reach a concentration of 0.7 mg/L are two completely different beasts.”

So, my other criticism of Kasprak’s article is that he could have said more about the studies which are relevant to community water fluoridation.  He does briefly refer to the New Zealand study of Broadbent et al (2014) in a quote from  Ireland’s Health Research Board:

“There was only one study carried out in a non-endemic or CWF [community water fluoridation] area that examined fluoride and IQ. This was a prospective cohort study (whose design is appropriate to infer causality) in New Zealand. The study concluded that there was no evidence of a detrimental effect on IQ as a result of exposure to CWF.”

However, he missed the 2016 study of  Aggeborn & Öhman (perhaps it was too recent for him) which I discussed in my article Large Swedish study finds no effect of fluoride on IQ. The results of this study were so precise and the sample numbers used are so large it should be seriously considered by anyone looking at this issue.

Conclusion

Kasprak’s article is useful in exposing the false claim of activists that fluoride lowers IQ – especially when used in arguments against community water fluoridation. But he could have said more – and he could have avoided the fallacious argument based on place of publication which is so easily reversed to support poor quality science in reputable journals.

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Large Swedish study finds no effect of fluoride on IQ

sweden-f

Fluoride levels in Swedish drinking water (mg/L). Variation between municipalities. Source: Aggeborn & Öhman (2016)

A significant new Swedish study shows fluoride in drinking water, at the concentrations used for community water fluoridation, has no effect on IQ or other measures of cognitive ability. Similarly, it has no effect on diagnosis or prescription of medicines for ADHD, depression, psychiatric illnesses, neurological illnesses or muscular or musculoskeletal diseases.

On the other hand, the study showed positive effects of fluoride on income and employment status – most probably because better dental health is beneficial in the labour market.

This work is reported in:

Aggeborn, L., & Öhman, M. (2016). The Effects of Fluoride In The Drinking Water.

The study covers most of the health effects that anti-fluoride campaigners complain about. It really should put all these complaints to rest as the quality of this new study is much better than anything the campaigners rely on for the following reasons:

  • It involved a much large sample. Over 700,000 individuals were involved. The numbers included in specific measurements varied but they were much greater than those used in the studies cited by anti-fluoride campaigners. For example, almost 82,000 were involved in the cognitive ability comparisons – compared with a few hundred at the most in the comparable studies cited by anti-fluoride campaigners.
  • Estimates of effects were much more precise (as expected with large numbers of subjects) than for previous studies. The effect of fluoride on cognitive ability was always close to zero and for practical purposes was zero.
  • Statistical analyses were based on continuously varying fluoride levels – a much better approach than the simple comparison of data for low and high fluoride villages used in the studies cited by anti-fluoride campaigners.

Sweden is an ideal country for studying effects of fluoride at these low concentrations. It does not have artificial water fluoridation but its drinking water contains naturally occurring fluoride. The fluoride concentration in drinking water depends on the geology of the region so different Swedish communities consume water with different fluoride concentrations.

This graphic from the paper shows the number of people drinking water with various concentrations of fluoride. Note – the steps are 0.1 mg/L and although concentrations above 2.0 mg/L occur they are relatively rare. Sweden makes no attempt to remove excess fluoride until the concentrations exceed 1.5 mg/L – the maximum recommended by the World Health Organisation. For comparison, the recommended optimum concentration in  New Zealand is 0.7 mg/L.

sweden-f-01

Histogram of numbers people drinking water containing naturally occurring fluoride at different concentrations. Source: Aggeborn & Öhman (2016)

Effects of fluoride on dental health

The Swedish data showed positive effects of fluoride on oral health. For example, the share of dentists visits “decreased by approximately 6.6 percentage points if fluoride is increased by 1 mg/l. This should be considered as a large effect.” Tooth repairs are closely related to fluoride. “If fluoride would increase with 1 mg/l, the share of 20-year-olds that had a tooth repaired would be decreased approximately 3.4 percentage points considering the 2013 sample. Again, this effect is large, especially for this cohort.”

Cognitive ability

Relevant data was used from national education tests and psychological tests during the years of the Swedish military conscription. The statistical analysis produced estimates which were all very small and often not statistically significant. The estimates were sometimes negative and sometimes positive. For example, an estimate including covariates showed that “cognitive ability is increased by 0.045 Stanine points [equivalent to about 0.3 IQ points] if fluoride is increased by 1 mg/l (a large increase in fluoride). This should be considered as a zero-effect on cognitive ability.”

Other possible health effects

The authors considered the effects of fluoride on the prescription of medicines for ADHD, depression, and psychoses. They also looked at psychiatric and neurological diagnoses from outpatient and inpatient registers, as well as diagnoses of muscular and skeletal diseases. Anti-fluoride campaigners often claim fluoride has a harmful effect on these health problems.

The was no effect of fluoride on the possibilities of being prescribed any of these medicines.  For example “the probability of receiving ADHD medicines is decreased by 0.2 percentage points if fluoride is increased by 1 mg/l. In economic terms, this effect is a zero-effect.”

It was the same for all the diagnoses considered –  “The estimated effects are small and often statistically insignificant.”

According to the authors:

“In conclusion, we do not find that fluoride has any effects on these health outcomes. This further strengthens our argument that fluoride does not have any negative effects for levels below 1.5 mg/l on human capital development or health outcomes related to human capital development. It is also interesting that we do not find any effects on diagnoses for muscular and skeleton diseases, which has been a question also discussed in connection to fluoride.”

Annual income and employment status

The lack of any effect of fluoride on IQ and other psychological and non-psychological estimates suggest that fluoride would have no effect on long-term outcomes like income and employment status. However, the authors suggested that it could have a positive influence on these outcomes because of better dental health.

And this was the case. Estimates of the effect of fluoride on income were always positive and usually statistically significant. The authors estimated that “income increases by 4.2 percent if fluoride increases by 1 mg/l. This is not a negligible effect and the estimate should be considered as economically significant.”

Similarly for employment status. “If fluoride is increased by 1 mg/l, then the probability that the person is employed is increased by 2 percentage points. This result thus point in the same direction as the results for log income where both these results are significant in economic terms.”

Further analysis indicated “that when dental repairs increases by 1 percentage point, income decreases by 2 percent on the same aggregate level. This effect is clearly economically significant. This indicates that fluoride improves labor market outcomes through better dental health.”

Conclusions

This is an important study. It involved large numbers of people, estimated outcomes were far more precise than in previous studies, it used continuously varying concentrations of fluoride instead of simply comparing high fluoride and low fluoride villages, and it considered possible long-term outcomes like income and employment chances.

The advantages of this study compared with the generally poor quality studies cited by anti-fluoride campaigners should put to rest arguments used by those campaigners. In particular, it should make the current campaigns relying on to IQ and cognitive effects irrelevant.

The authors comment that their data shows there is no need to consider negative health effects on consideration of the cost-effectiveness of community water fluoridation. I wonder if, in fact, these results will encourage policy makers to consider the cost benefits of improved income and employment chances in future calculations of the cost-effectiveness of fluoridation programmes.

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Anti-fluoridationists now scaremonger about silica in your drinking water

orthosilicic-acid

Orthosilicic acid exists in drinking water. This is an idealised presentation because of polymerisation reactions. In practice, analysts measure “reactive silica.”

Well – that’s what we can infer from a new campaign of the Fluoride Action Network (FAN).

But what is the link with fluoride – the whole reason for FAN’s existence? Well, they base this campaign on the well-known hydrolysis of the fluorosilicates used in community water fluoridation to form the hydrated fluoride anion and silica. (Although these campaigners are confused here as they will also often claim fluorosilicates do not hydrolyse and survive to come out of your tap and poison you).

Then they claim that “silicic acid” (silica in solution) dissolves lead from the pipes and fittings and this lead causes brain damage. A double-barreled danger as they also claim the fluoride also damages your brain. What’s more – they also claim that “silicic acid” may dissolve your teeth!

But there are two problems with this:

  1. Your drinking water contains silica whether it is fluoridated or not. So their warnings about the silica in fluoridated water should also be valid for “fluoride-free” water which they promote!
  2. They do not have a viable chemical mechanism for silica dissolving your pipes (and there are plenty of other mechanisms which can result in corrosion of pipes anyway). The same for your teeth. This claim is just not supported by the chemical literature.

I will just concentrate here on the “evils” of silica (or “orthosilicic acid”) that are being promoted by FAN and leave the lead story for another day. These “evils” all come down to concepts being promoted by Richard Sauerheber who FAN describes as “the ultimate citizen chemist.” (OK, he is their ultimate citizen chemist). His argument is presented in Silicic Acid – How Does Fluorosilicic Acid Leach Lead? Why Does Fluorosilicic Acid Leach Lead So Much More Than Sodium Fluoride?

Is silicic acid the bogy Sauerheber claims?

His article is confused and convoluted. But it starts with the assumption that silica in drinking water (silicic acid or orthosilicic acid) is bad. He declares:

“Neither fluoride nor silicic acid are constituents of normal pristine human or mammalian blood, but rather are contaminant materials, . . “

And he states:

“The mass treatment of public fresh drinking water with industrial fluorosilicic acid to produce fluoride ion at 1.0 ppm also produces approximately 6 ppm sodium ion and .7 ppm orthosilicic acid. None of these is found in or belongs in fresh drinking water.”

Let’s stop right there and check out his claim that sodium and “orthosilicic acid” are not found in fresh drinking water.

Here is some data for drinking water in fluoridated and unfluoridated areas of Auckland, New Zealand, taken from the WATERCARE ANNUAL WATER QUALITY REPORT 2013. The data are for 15 unfluoridated treatment plants and 8 fluoridated treatment plants.

silica-sodium

These are average figures over all the plants. But values for silica as high as 64 mg/L in the unfluoridated plants and 44 mg/L in the fluoridated plant were recorded. The corresponding figures for sodium were 140 and 22 mg/L.

So Sauerheber is completely wrong. Unfluoridated water does contain silica and sodium. And at concentrations much higher than could be accounted for by added fluoridating chemicals – he calculated 0.7 mg/L – 0.7 ppm) for silica. In fact, the values are higher for the unfluoridated treatment plants in these examples.

Fluoridation makes a minuscule contribution to the concentration of these chemical species in drinking water.

Forget about fluoridation. If silica (and sodium) are such problems then Sauerheber should be campaigning against unfluoridated water as well. Even the “pristine” water in his local river or spring – silica is a normal and natural component of surface and bore waters.

But Sauerheber is also wrong about the dangers of silica in drinking water. Of course silica is present in “normal pristine human or mammalian blood” because it is part of our diet (Bisse et al 2005). It is a component of many of our foods. Sauerheber is simply attempting to confuse the issue because of the current lack of knowledge about the role of silica in the body.

But Jugdaohsingh et al., (2015) say:

“Silicon (Si) is a natural trace element of the mammalian diet and although it has not been demonstrated unequivocally that mammals have a requirement for Si there is increasing evidence to suggest that it may be important for the normal health of bone and the connective tissues. Indeed, severe dietary Si deprivation in growing animals appears to cause abnormal growth and defects of the connective tissues”

Given that silica appears to be important the presence of it in our drinking water is as an advantage. According to Jugdaohsingh (2007):

“Drinking water and other fluids provides the most readily bioavailable source of Si in the diet, since silicon is principally present as Si(OH)4, and fluid ingestion can account for ≥ 20% of the total dietary intake of Si.”

One trick Sauerheber uses is to cite reports of the danger of inhaled silica dust – which can cause cancers and silicosis. Completely irrelevant because of its different chemical form. This is equivalent to the trick often used by anti-fluoride campaigners of citing reports of results of industrial pollution or studies from areas of endemic fluorosis to support their attacks on community water fluoridation.

Will silica dissolve your teeth?

This claim is completely unsupported – no citations and purely a figment of Sauerheber’s imagination. He claims:

“Orthosilicic ‘weak’ acid has been long used in agriculture to break down solid calcium phosphate Ca3(PO4)2, thereby releasing soluble phosphate ion in soils even at neutral pH, for uptake by plant life. The reaction of silicic acid with calcium phosphate under neutral pH conditions is:

H4SiO4 + Ca3(PO4)2 →  HPO4-2 + 3Ca2+ + PO4-3+ H3SiO4.

This reaction occurs at a pH where any strong acid would have been neutralized. Orthosilicic acid is reluctant to dissociate and can break down calcium phosphate. This reaction is relevant not only to calcium phosphate in soil but also to calcium phosphate in teeth enamel. By means of orthosilicic acid, enamel is subject to slow and progressive degradation. “

This is a new one on me – and I spent many years researching the dissolution of apatite (the natural calcium phosphate) in soil and the factors influencing that. This arose because unacidulated phosphate rocks were being used in New Zealand agriculture. These material contain insoluble phosphate – in contrast to superphosphate which contain soluble phosphate.

The phosphate rocks used are mainly apatites and are complex (because of isomorphous substitution). A specific chemical equation for their dissolution depends on composition and environmental pH. But, in general, acid (H+) reacts with the apatite to produce Ca2++ H2PO4, H2O, F, Cl, CO2, etc.

H+ + Ca10(PO4)6(OH,F,Cl)2 → Ca2+ + H2PO4 + H2O + Cl + F + CO2

Dissolution is promoted by the presence of acid (H+) and removal of dissolution products (particularly Ca2+). The calcium in soil solution can inhibit apatite dissolution – it drives the equation above to the left. The later is important because New Zealand agricultural soils have relatively high levels of calcium. On the other hand, our research showed that when soils are leached to remove calcium this can promote dissolution of the natural fluorapatite in the soil. (Perrott and Kear 2004). Removal of calcium from solution drives the above equation to the right.

Apatite particle size, fluoride content and substitution of other species in the apatite structure can also influence the dissolution rate of these materials in soil. But silica, or silica in soil solution – that is a new one on me!

Pity Sauerheber didn’t give a citation to support his claim that silica “has been long used in agriculture to break down solid calcium phosphate Ca3(PO4)2, thereby releasing soluble phosphate ion in soils even at neutral pH, for uptake by plant life.” I would be very interested to see the evidence – but I cannot find anything in the scientific literature to support Sauerheber’s statement. It appears to be a figment of his imagination and anti-fluoride bias.

In the same unsupported manner, Sauerheber is suggesting silica (“orthosilicic acid”) may be dissolving our teeth. He even provides a chemical equation for it:

2H4SiO4 + Ca3(PO4)2 → 2HPO4-2 + 2H3SiO4 + 3Ca2+

First,  the primary mineral in teeth is a bioapatite (Ca10(PO4)6(OH,F,Cl)2) not Ca3(PO4)2. And H3SiO4 is not stable at the pH of drinking water or saliva so his idea is destroyed by the immediate reaction:

H+ + H3SiO4→ H4SiO4

In other words, Sauerheber’s equation above is driven to the left at the neutral and acid pH values of saliva and drinking water.

Incidentally, it is the presence of Ca2+, H2PO4 and F in our saliva (derived from food and drink) that drives the dissolution equation for apatite to the left. It prevents dissolution (acid attack or demineralisation) and promotes remineralisation. This the surface or “topical” mechanism that reduces decay in existing teeth when fluoridated water is used.

Sauerheber’s confusion

Sauerheber’s arguments are chemically confused – probably because he is driven by a wish to find anything connected with fluoride to be bad. He is confused by terminology because the silica in solution is often called orthosilicic acid, or silicic acid. But the point is that this species (whatever it is – the chemistry of silica in water is very complex) is not dissociated at neutral pH values near 7.  (more correctly only 0.18% of it is – Belton et al., 2012). It is a very weak acid -significant dissociation to form the anion only occurs at higher pH values according to the equation:

OH + H4SiO4 → H3SiO4 + H2O

Enamel attack is caused by acid (H+) not an unionized silica species or silicate anion. At these high pH values, dissociation of silicic acid at high pH does not produce H+. It actually removes OH.

The same confusion is behind Sauerheber’s assertion that leaching of lead from pipes and plumbing is caused by “orthosilicic acid.” He says:

“it is the intact orthosilicic acid, the predominant form present over the pH range 7-10 (sic) that is leaching lead or lead salts from pipes and plumbing fixtures.”

In fact, acid in drinking water is one of the causes of lead leaching. The chemical species responsible is H+ and that is why treatment plants adjust pH levels to reduce acidity. Silica in  solution does not make a contribution to the (H+) concentration.

But if it did then we should be concerned about all water as fluoridating chemicals make only a minuscule contribution to silica in water.

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