Tag Archives: Royal Society of NZ

Should we trust science? – Wellington talk


Naomi Oreskes is Professor of the History of Science and Affiliated Professor of Earth and Planetary Sciences at Harvard University, and an internationally renowned geologist, science historian, and author.

If you are in Wellington next Tuesday this should be an interesting talk. I would certainly be in the audience if I was able.

Should we trust science?

Perspectives from the history and philosophy of science

Naomi Oreskes

Professor of History of Science at Harvard University.

6pm Tuesday 24 November 2015
Paramount Theatre, 25 Courtenay Place, Wellington

In this talk Professor Naomi Oreskes offers perspectives from the history and philosophy of science, argues that we should trust science and explains why.

Many readers will know Professor Oreskes as one of the authors, together with Eric M. Conway, of 
Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming
I highly recommend this excellent book.

These two authors have also written a science-based book of fiction The Collapse of Western Civilization: A View from the Future. I haven’t read it yet, but it’s certainly on my list (and in my eReader).

The Royal Society of NZ has organised the event – for more information see Should we trust science? « At Six « Events « Royal Society of New Zealand.

For those of us who can’t make Professor Oreskes talk there is a video of a similar talk she gave at Virginia Tech recently at Distinguished Lecture 2015: Dr. Naomi Oreskes, Harvard University

About Naomi Oreskes

Naomi Oreskes is Professor of the History of Science and Affiliated Professor of Earth and Planetary Sciences at Harvard University, and an internationally renowned geologist, science historian, and author.

Oreskes is the author of many scholarly and popular books and articles on the history of earth and environmental science. She has lectured widely and won numerous prizes, including the 2009 Francis Bacon Medal for outstanding scholarship in the history of science and technology, the 2011 Climate Change Communicator of the Year, and the 2014 American Geophysical Union Presidential Citation for Science and Society.

For the past decade, Oreskes has been primarily interested in the science and politics of anthropogenic climate change. Her 2010 book, Merchants of Doubt, How a Handful of Scientists Obscured the Truth on Issues from Tobacco to Global Warming, co-authored with Erik M. Conway, was shortlisted for the Los Angeles Times Book Prize and won the Watson-Davis Prize from the History of Science Society. The film version was released in late 2014.

Oreskes’s current research projects include completion of a scholarly book on the history of Cold War oceanography.

Naomi Oreskes is brought to New Zealand by History of Science 2015 conference in partnership with the Royal Society of New Zealand.

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Fluoride Free NZ report disingenuous – conclusion

This is the third and last article in a series critiquing contributions to the Fluoride Free NZ report Scientific and Critical Analysis of the 2014 New Zealand Fluoridation Report which is aimed at discrediting the recent review Health Effects of Water Fluoridation: a Review of the Scientific Evidence produced by the Royal Society of NZ together with the Office of the Prime Minister’s Chief Science Advisor (hereafter refered to as the Royal Society Review).

My first article, Peer review of an anti-fluoride “peer review” discussed Kathleen Theissen’s contribution. (It also discussed a draft contribution by Chris Neurath which does not appear in the final version). The second article, Cherry-picking and misinformation in Stan Litras’s anti-fluoride articlecritiques Stan Litras’s contribution. This one discusses H. S. Micklem’s contribution.

See The farce of a “sciency” anti-fluoride report for an analysis of the close relationships between the authors and peer reviewers of the Fluoride Free NZ report and anti-fluoride activist groups.

There are a few smaller articles by Paul Connett and Mark Atkins. They do not deal with the contents of the Royal Society Review so I will not comment on them here.

This article below completes my critique of the Fluoride free NZ report.

H. S. Micklen, who wrote the second article in the Fluoride Free NZ report, is one of the coauthors, together with Paul Connett, of the book  The Case against Fluoride which anti-fluoride activists treat as gospel. His article was “peer-reviewed” by James Beck, the other co-author of the book.

In my comments I use the section headings used by H. S. Micklem.

Dental fluorosis

I think Micklen’s comments on dental fluorsis are quite muddled. He confuses the relevance of the different grades of dental fluorosis and unfairly attributes the more severe forms to community water fluoridation (CWF). Consequently he calculates a cost of dental treatment which is wrong.

Recently I put dental fluorosis, its different grades and its contribution to oral health satisfaction into context with the image below (see Water fluoridation and dental fluorosis – debunking some myths):

Dental fluorosis of grades none, questionable, very mild and mild are common in countries suitable for CWF – in both fluoridated and unfluoridated areas. Fluoridation may cause a small increase in mild grades. But these first 4 grades (none – mild) are judged purely “cosmetic. In fact children and parents often judge the grades “questionable – mild” more highly than “none.” Research finds these milder forms of dental fluorosis often improve dental health related quality of life (Do and Spencer, 2007; Chankanka et al., 2010; Peres et al., 2009; Biazevic et al., 2008; Büchel et al., 2011; Michel-Crosato et al., 2005).

Micklem is straw-clutching to take one reference used by the Royal Society Review out of context to imply that these studies are wrong because “subjects liked the appearance of a complete set of artificially white teeth.” He says “they did not like the whiteness associated with fluorosis.”  But the authors actually say:

“The ranking of images of teeth with a fluorosis score of TF 1 may lead to the inference this sample of 11 to 13 year olds do not consider milder presentations of fluorosis to be aesthetically objectionable. The very white teeth represented an unnatural presentation that could only be achieved by cosmetic procedures. . . . This is consistent with previous work related to dental aesthetics [18,19] whereby teeth with mild forms of fluorosis (TF 1, TF2) were rated similarly.”

Micklem raises the bogey of the cost of veneers (up to $1750 per tooth) but this is just scaremongering as veneers would not be used for teeth with these mild grades of fluorosis.

Moderate and severe grades of dental fluorosis are common in areas where fluorosis is endemic, but relatively rare where CWF is used. Occurences in the later case, despite the low concentrations of fluoride in treated drinking water, will have other causes – high natural levels in well water, industrial pollution, excessive consumption of toothpaste, etc.

Treatment of moderate and severe cases of dental fluorosis using veneers may well be appropriate for a very few young people in countries like New Zealand and the US but it is misleading to attribute this to CWF. Interestingly, Micklem’s misattribution mirrors that of Ko and Thiessen (2014). They also assumed all moderate and  severe dental fluorosis was caused by CWF thereby enabling them to declare no cost benefit to CWF because of the required dental treatments.

Micklem has simply continued the anti-fluoride propagandist tradition of confusing data for the relative amounts of different grades of dental fluorosis and attributing problems with the rare moderate and severe forms to the more common questionable and mild forms.

Neurotoxicity and IQ

In this section Micklem attempts to contrast the Choi et al (2012) metareview with the Broadbent et al (2014) study. He erroneously refers to both as being relevant to CWF and “the case that water fluoridation poses a development risk to human intelligence.”

Let’s make this clear. The Choi et al (2012) review did not include studies of CWF. The authors made clear that their results should not be seen as relevant to CWF. Most of the brief reports they reviewed studied areas of endemic fluorosis and Xiang (2014) (one of the authors of an included study) gives some idea of how this is manifested in a title slide to a recent talk.

The only study Micklem comments on that involved CWF was that of Broadbent at al (2014).  Micklem describes this as “inconclusive” but does not say why. Do I detect some bias there?

Given the available studies I think the Royal Society review was justified in concluding “that on the available evidence there is no appreciable effect on cognition arising from CWF.”

Passing on to the question of the Choi et al (2012) metareview, which is not relevant to CWF. Micklen concedes that included studies were individually  “not strong” but argues “the existence of so many studies almost all saying the same (important) thing” should be treated with attention and respect. I agree – but lets not allow that attention and respect to be blind. Let’s be aware of the limitations and attempt to understand what the results might mean.

The authors of that metareview have extended their work to making their own measurements in a pilot study (Choi et al., 2014). In this new paper they did not find a significant relationship between cognitive deficit measurements and drinking water fluoride. We need to accommodate this finding in our assessment of the metareview.

Choi et al (2014) did find a significant association of cognitive deficits with severe dental fluorosis.  Perhaps we need to respect that finding and give it some attention. Rather than the assuming the mechanism of such cognitive deficits is the speculated but unproven neurotoxic activity of fluoride we should be open to other possible mechanisms (Perrott 2015)..

I have done so with my article  and would welcome any feedback Micklem could give on this. I feel that the effects of a physical deformity like severe dental fluorosis on learning is a more realistic mechanism (for which there is a lot of published evidence) than some sort of vague chemical toxicity which has never been noted at these low concentrations.

Incidentally, Micklem attempts to discredit the Royal Society’s understanding of the Choi et al (2012) saying it suggested that the measured IQ reduction was “arguably negligible.” The Royal Society review actually said:

“Setting aside the methodological failings of these studies, Choi et al. determined that the standardised weighted mean difference in IQ scores between “exposed” and reference populations was only -0.45. The authors themselves note that this
difference is so small that it “may be within the measurement error of IQ testing”.[172]”

Choi et al., (2012) said:

“The estimated decrease in average IQ associated with fluoride exposure based on our analysis may seem small and may be within the measurement error of IQ testing.”

And their abstract reported the “standardized weighted mean difference in IQ score between exposed and reference populations was –0.45 (95% confidence interval: –0.56, –0.35).”

There has been some confusion because Choi et al., (2012) used a standardised weighted mean difference to accommodate the different IQ scales used in the studies they reviewed. But their warning about the small size of the calculated difference and its relationship to measurement errors in IQ testing is relevant.

The Royal Society Review did indeed make a mistake in the executive summary where it referred to a claimed IQ shift of “less than one IQ point” when it should have said “less than one standard deviation.” I discussed this in Did the Royal Society get it wrong about fluoridation? and noted that even Harvard University made the same mistake in its inital press release of the Choi et al (2012) work.

I think the Authors of the Royal Society Review should correct that mistake, as Harvard University did – but it does not change the fact there is no mistake in the review’s evaluation of the Choi et al (2012) paper.


In this section Micklem attempts to cast doubt on the Royal Society Review’s comments on the form of fluoride in drinking water and a possible role of fluoride in releasing lead from pipe fittings.

The hydrolysis of fluorosilicic acid when diluted during water treatment may not be completely understood (nothing ever is) but recent high quality research (Urbansky & Schock 2000; Urbansky 2002; Finney et al., 2006) has confirmed the review’s statement it is “effectively 100% dissociated to form fluoride ion under water treatment conditions.” Despite acknowledging the need for more and better research Urbansky (2002) concluded “all the rate data suggest that equilibrium should have been achieved by the time the water reaches the consumer’s tap if not by the time it leaves the waterworks plant.”

This debate only exists among anti-fluoride propagandists because of selective and motivated reliance on old and poor quality research, together with confirmation bias. For example, the report by Crosby (1969) that “evidence from specific-ion electrode and conductivity measurements at 25° confirms that sodium fluorosilicate, at the concentration normally present in public water supplies, is dissociated to at least 95%” is interpreted by Coplan et al., (2007) as “proof” the fluorosilicate is 5% unhydrolysed!

Micklem relies on then papers of Master et al., (2000), Copelan et al 2007 and Mass et al., (2007) to argue that fluoride treatment chemical enhances lead release from pipes. However, I think an objective assessment of these paper would conclude the authors argue determinedly for a preconceived hypothesis and that many of their arguments are irrelevant and faulty. This is not to dismiss their finding on lead levels in drinking water – but as Masters et al., (2000) themselves point out – “statistical association should not be confused with causation.” 

Similarly, I suggest that Micklen’s reliance on Sawan et al., (2010) to support Copelan’s hypothesis amounts to special pleading as those workers used drinking water concentration of 100 mg/L of fluoride and 30 mg/L of lead.


Micklem uses the old anti-fluoride activist trick of fixating on a cherry-picked paper which fits his agenda and downplaying or attempting to discredit papers which don’t. He concentrates on Bassin et al (2006), despite its description by its authors as “an explanatory study” requiring “further research” to “confirm or refute” its conclusions. That paper fits Micklem’s agenda because it found a statistically increased risk of osteosarcomas in male boys exposed to water fluoridated at 1.2 mg/L F.

In such a complex area, for a cancer with such a low incidence, a balanced overall consideration of research reports is necessary. All papers have their advantages and drawbacks so conclusions should be derived from proper consideration of the total research findings – as the Royal Society review appears to have done.

The Bassin (2006) findings have not been confirmed by any later work – despite a range of such studies (Kim et al., 2011; Comber et al., 2011; Levy and Leclerc 2012; Blakey et al., 2014). The Royal Society Review pointed out previous reviews had all concluded that “based on the best available evidence, fluoride could not be classified as carcinogenic in humans.” And that “more recent studies have not changed this conclusion.”

Micklem hasproduced nothing to counter that conclusion.

Cardiovascular and renal effects

Micklen attempts to use the paper, Martín-Pardillos et al., (2014), cited by the Royal Society Review, against the reviews conclusions. The review presents the paper this way:

“A number of studies indicate that fluoride may reduce aortic calcification in experimental animals and humans.[199] This preventive effect was recently confirmed by in vitro experiments, but in vivo findings from the same studies showed the opposite result – that phosphate-induced aortic calcification was accelerated following exposure of uremic rats to fluoride in water at around 1.5 mg/L.[200] The authors suggested that chronic kidney disease could be aggravated by relatively low concentrations of fluoride, which (in turn) accelerates vascular calcification. However, further studies are required to test this hypothesis.”

Martín-Pardillos et al., (2014) proceeded from the hypothesis that fluoride did not initiate calcification but because it is attracted to calcified deposits it may influence subsequent crystallisation of the calcified material.

Their in vitro results indicated a protective effect against calcification. While the opposite was observed with the 5/6 nephrectomised rats with induced calcification they still concluded:

“The direct inhibition of ectopic calcification could still occur in vivo when the renal function is correct, such as during aging or even the initial stages of diabetes, and this possibility deserves further research.”

This is relevant to healthy humans without chronic kidney disease (CKD).

The acceleration of induced vascular calcification with the 5/6 nephrectomised rats does raise the need for further studies, and monitoring the situation with humans suffering CKD. But let’s not forget the rat model was extreme. Rats had all of one kidney and 2/3 of the other kidney removed. They were also fed a phosphate enriched diet and the induced CKD was clearly indicated by urea and creatine blood concentration.

Of course these findings are relevant when considering ongoing research and monitory the situation of CKD human patients. As the authors say “the effects of fluoride on renal function and vascular health are more complicated than expected.”

However, the current advice of the National Kidney Foundation is that:

“Dietary advice for patients with Chronic Kidney Disease (CKD) should primarily focus on established recommendations for sodium, calcium, phosphorus, energy/calorie, protein, fat, and carbohydrate intake. Fluoride intake is a secondary concern.”

Given that such patients are already monitory their diet and more advanced cases also probably regularly monitory blood indicators  any possible effect of fluoride for individuals should be detected. It is likely that by the time any problem with fluoride in drinking water is indicated other problems will also have occurred and patients will be taking steps such as water filtering and careful dietary management to handle their situation.

In fact individually directed management of food and drinking water appears to be a sensible way of handling problems if they do occur with a few people.

Micklem’s “call for CKD sufferers to be warned to avoid tap water” is too extreme and alarmist. Already the advice is that persons with CKD should be notified of the potential risk of fluoride exposure and be kept up to date with new research. Any patients who are particularly worried can then take steps like using filtered water for their own peace of mind. This seems more appropriate than denying the rest of the population access to a simple, effective and safe (for them at least) social policy like CWF.


This completes my critique of the Fluoride Free NZ report.

The original Royal Society review, Health Effects of Water Fluoridation: a Review of the Scientific Evidence, was prepared in response to a request from councils for a summary of the current science on CWF. This is because over the last few years activists political groups, like Fluoride Free NZ (and its international associate Fluoride Action Network) have bombarded New Zealand councils with misinformation and distortion of the science in campaigns to prevent CWF or get it removed

Councils do not have the expertise to critical consider claims made by such activist groups and have adopted a policy of requesting central government take over their responsibilities on the issue. Until that happens, however, councils will continue to have such decisions forced upon them.

The Royal Society review provides a timely and authoritative source of information for councils. Understandably Fluoride Free NZ feels somewhat trumpted by the review. So it is understandable this activist groups, and the international associate will use their media influence to try to discredit it.

This report is an attempt to fool councils by pretending to be objective and international. Yet, as my articles in this series show, it is simply a put-up job. It is not objective – all the authors and “peer reviewers” are working for or associated with the Fluoride Action Network or its associates. The articles follow the typical cherry-picking and confirmation bias of such activist organisations.

See The farce of a “sciency” anti-fluoride report for an analysis of the close relationships between the authors and peer reviewers of the Fluoride Free NZ report and anti-fluoride activist groups.

The Fluoride Free report is simply disingenuous – a sham aimed at fooling councils.


Bassin, E. B., Wypij, D., Davis, R. B., & Mittleman, M. a. (2006). Age-specific fluoride exposure in drinking water and osteosarcoma (United States). Cancer Causes & Control : CCC, 17(4), 421–8.

Biazevic, M. G. H., Rissotto, R. R., Michel-Crosato, E., Mendes, L. A., & Mendes, M. O. A. (2008). Relationship between oral health and its impact on quality of life among adolescents. Brazilian Oral Research, 22(1), 36–42.

Blakey, K., Feltbower, R. G., Parslow, R. C., James, P. W., Gómez Pozo, B., Stiller, C., … McNally, R. J. (2014). Is fluoride a risk factor for bone cancer? Small area analysis of osteosarcoma and Ewing sarcoma diagnosed among 0-49-year-olds in Great Britain, 1980-2005. International Journal of Epidemiology, 43(1), 224–34.

Broadbent, J. M., Thomson, W. M., Ramrakha, S., Moffitt, T. E., Zeng, J., Foster Page, L. A., & Poulton, R. (2014). Community Water Fluoridation and Intelligence: Prospective Study in New Zealand. American Journal of Public Health, 105(1), 72–76.

Büchel, K., Gerwig, P., Weber, C., Minnig, P., Wiehl, P., Schild, S., & Meyer, J. (2011). Prevalence of Enamel Fluorosis in 12-year-Olds in two Swiss Cantons. Schwiz Monatsschr Zahnmed, 121(7/8), 652–656.

Chankanka, O., Levy, S. M., Warren, J. J., & Chalmers, J. M. (2010). A literature review of aesthetic perceptions of dental fluorosis and relationships with psychosocial aspects/oral health-related quality of life. Community Dentistry and Oral Epidemiology, 38(2), 97–109. x

Choi, A. L., Sun, G., Zhang, Y., & Grandjean, P. (2012). Developmental fluoride neurotoxicity: A systematic review and meta-analysis. Environmental Health Perspectives, 120(10), 1362–1368.

Choi, A. L., Grandjean, P., Sun, G., & Zhang, Y. (2013). Developmental fluoride neurotoxicity: Choi et al. Respond. Environmental Health Perspectives, 121(3), A70.

Choi, A. L., Zhang, Y., Sun, G., Bellinger, D., Wang, K., Yang, X. J., … Grandjean, P. (2014). Association of lifetime exposure to fluoride and cognitive functions in Chinese children: A pilot study. Neurotoxicology and Teratology, 47, 96–101.

Comber, H., Deady, S., Montgomery, E., & Gavin, A. (2011). Drinking water fluoridation and osteosarcoma incidence on the island of Ireland. Cancer Causes & Control : CCC, 22(6), 919–24.

Coplan, M. J., Patch, S. C., Masters, R. D., & Bachman, M. S. (2007). Confirmation of and explanations for elevated blood lead and other disorders in children exposed to water disinfection and fluoridation chemicals. Neurotoxicology, 28(5), 1032–42.

Crosby, N. T. (1969). Equilibria of fluorosilicate solutions with special reference to the fluoridation of public water supplies. Journal of Applied Chemistry, 19(4), 100–102.

Do, L. G., & Spencer, A. (2007). Oral Health-Related Quality of Life of Children by Dental Caries and Fluorosis Experience. Journal of Public Health Dentistry, 67(3), 132–139.

Eason, C., & Elwood, JM. Seymour, Thomson, WM. Wilson, N. Prendergast, K. (2014). Health effects of water fluoridation : A review of the scientific evidence. Royal Society of New Zealand and Office of the Prime Minister’s Chief Science Advisor, Wellington.(p. 74).

Finney, W. F., Wilson, E., Callender, A., Morris, M. D., & Beck, L. W. (2006). Reexamination of hexafluorosilicate hydrolysis by 19F NMR and pH measurement. Environmental Science & Technology, 40(8), 2572–7.

Kim, F. M., Hayes, C., Williams, P. L., Whitford, G. M., Joshipura, K. J., Hoover, R. N., & Douglass, C. W. (2011). An assessment of bone fluoride and osteosarcoma. Journal of Dental Research, 90(10), 1171–6.

Ko, L., & Thiessen, K. M. (2014). A critique of recent economic evaluations of community water fluoridation. International Journal of Occupational and Environmental Health

Levy, M., & Leclerc, B.-S. (2012). Fluoride in drinking water and osteosarcoma incidence rates in the continental United States among children and adolescents. Cancer Epidemiology, 36(2), e83–e88.

Maas, R. P., Patch, S. C., Christian, A.-M., & Coplan, M. J. (2007). Effects of fluoridation and disinfection agent combinations on lead leaching from leaded-brass parts. Neurotoxicology, 28(5), 1023–31.

Martín-Pardillos, A., Sosa, C., Millán, A., & Sorribas, V. (2014). Effect of water fluoridation on the development of medial vascular calcification in uremic rats. Toxicology, 318C, 40–50.

Masters, RD; Coplan, MJ; Hone, BT; Dykes, J. (2000). Association of silicofluoride treated water witrh elevated blood lead. NeuroToxicology, 21(6), 1091–1100.

Michel-Crosato, E., Biazevic, M. G. H., & Crosato, E. (2005). Relationship between dental fluorosis and quality of life: a population based study. Brazilian Oral Research, 19(2), 150–155.

Peres, K. G., Peres, M. a, Araujo, C. L. P., Menezes, A. M. B., & Hallal, P. C. (2009). Social and dental status along the life course and oral health impacts in adolescents: a population-based birth cohort. Health and Quality of Life Outcomes, 7, 95.

Perrott, K. W. (2015). Severe dental fluorosis and cognitive deficits. Neurotoxicology and Teratology. In press.

Sawan, R. M. M., Leite, G. A. S., Saraiva, M. C. P., Barbosa, F., Tanus-Santos, J. E., & Gerlach, R. F. (2010). Fluoride increases lead concentrations in whole blood and in calcified tissues from lead-exposed rats. Toxicology, 271(1-2), 21–6.

Urbansky, E. T. (2002). Fate of fluorosilicate drinking water additives. Chem. Rev., 102, 2837–2854.

Urbansky, E. T., & Schock, M. R. (2000). Can Fluoridation Affect Water Lead Levels and Lead Neurotoxicity ? In American Water Works Association Annual Conference (pp. 1–31).

Xiang, Q. (2014) Keynote Address on IQ studies published in China. Fluoride Action network.

Did the Royal Society get it wrong about fluoridation?

Health Effects of Water Fluoridation: a Review of the Scientific EvidenceDid the Royal Society of NZ and the Office of the NZ Prime Minister’s Chief Science Advisor make a big mistake in their report Health Effects of Water Fluoridation: a Review of the Scientific Evidence)? Did they misrepresent a scientific paper which reported an effect of fluoride on the IQ of children?

This is what “Connett’s Crowd,” anti-fluoridation activists and propagandists, are saying in their attempts to discredit the review. So, did this review make the mistake its critics claim?

Well, no. It’s just a beat up. But there is a small mistake in the review’s executive summary which the anti-fluoridationists are pouncing on.

The issue

Most critics of community water fluoridation rely heavily on this paper:

Choi, A. L., Sun, G., Zhang, Y., & Grandjean, P. (2012). Developmental fluoride neurotoxicity: A systematic review and meta-analysis. Environmental Health Perspectives, 120(10), 1362–1368.

This was a metareview of mainly obscure and brief reports (see Quality and selection counts in fluoride research) indicating the possibility the fluoride intake by children living in high fluoride areas of China and Iran may suffer IQ deficits. Choi et al., (2012) used a statistical analysis to determine the possible size of the IQ drop averaged over all the studies. They found a small drop and said:

“The estimated decrease in average IQ associated with fluoride exposure based on our analysis may seem small and may be within the measurement error of IQ testing.”

Their abstract reported the:

“standardized weighted mean difference in IQ score between exposed and reference populations was –0.45 (95% confidence interval: –0.56, –0.35).”

(Their use of “standardised weighted mean difference” was poorly explained and has caused confusion with many readers. See below for a brief explanation of the term).

What did the Royal Society Review say about this?

The review discusses the question of possible neurotoxic effects on page 49-50. Their comment relevant to Choi et al., (2014) appears below (click to enlarge):


And this is what is in the executive summary (click below to enlarge). It makes a very small mistake by referring to “less than one IQ point” when it should have said “less than one standard deviation.”


So, the review reported the Choi et al., (2012) findings accurately but made a small mistake in the executive summary. This is really of no consequence because the overall message of the small size of the estimated IQ drop (described by the authors as “small and may be within the measurement error of IQ testing”) is not really altered.

What do the anti-fluoride critics say?

Such mistakes are inevitable and authors will universally say they usually find them only after publication when no correction is possible. I remember picking up 5 mistakes in one of my papers – mainly incorrect spelling of my own name several times and a mistake in the address of my institution – those were the early days of word processing! Of course no one used my mistakes to cast doubts on the scientific content of the paper.

Still, “Connett’s crowd” have been merciless in their criticism. Here is an example from the big man himself (see Water Fluoridation: The “Healthy” Practice That Has Deceived the World):

Gluckman and Skegg (sic)* mistakenly claim “a shift of less than one IQ point” in the 27 studies reviewed by Choi et al. (2012). What they have done here is to confuse the drop of half of one standard deviation reported by the authors with the actual drop in IQ, which was 6.9 points. Such an elementary mistake would not have been made by Gluckman and Skegg (sic)* if they had actually read the report, instead of relying on what fluoridation propagandists were saying about it.

* Of course Gluckman and Skegg – who Connett calls The ‘Hollow Men’ of New Zealand –  did not author this review.

H.S. Micklem, in the Fluoride Free NZ report on the Royal Society review, snipes:

“It is hard to imagine how this mistake could have been made by anyone who had actually read the papers that are disparaged so casually.”

I guess critics should read carefully before indulging in such snaky comments. All they have demonstrated is that they did not read past the executive summary of the review (and certainly did not read the relevant section in the review). Or, more seriously, that they wish to misrepresent the review by highlighting the mistake and ignoring what the review actually says.

(At Least Kathleen Thiessen was more honest in her comments in the FFNZ report because she did refer to page 49 as well as the mistake. However she still concluded “The RSNZ report is not accurate in its characterization of the Choi et al. (2012) article on effects of fluoride on children’s IQ.”)

Update: One of my commenters, picker22, has brought this to our attention – it puts the mistake mentioend above into context.

“The original press release from Harvard School of Public Health News service made the same error stating that the difference was .5 IQ points. This error on the part of Harvard led to more that a couple of mis-statements by fluoridation advocates in the US.

The current web page notes that the sentence reporting the magnitude of IQ change was “updated” Sept 5, 2012. Sadly, I didn’t copy the original.


Is Choi et al (2012) relevant to fluoridation?

Not really.

The only study specific to community water fluoridation (CWF) the Royal Society review mentions is Broadbent, et al., (2014). Community Water Fluoridation and Intelligence: Prospective Study in New Zealand.

The Choi et al., (2012) paper reviews reports mainly from areas of endemic fluorosis where fluoride intake is much higher than areas using CWF. Subsequently the same authors  made their own measurements in a similar area of China and did not find a significant relationship of drinking water fluoride to IQ (see Choi et al., 2014. Association of lifetime exposure to fluoride and cognitive functions in Chinese children: A pilot study).

The did, however, find a relationship of IQ to severe dental fluorosis. I discuss their findings in my article 

What is this “standardised weighted mean difference”

This term caused a lot of confusion with readers and critics. Choi et al., (2012) used this statistical device because they were attempting to estimate the average decrease in  IQ associated with fluoride exposure based on the difference in IQ between children from high fluoride villages and low fluoride villages in a large number of studies. Further, different IQ scales and measurement methods were used in the different studies which had different levels of variation in the data.

They therefore standardised the differences by expressing them as a fraction of the standard deviation for each study. A mean value over all studies was determined, weighting the contribution from each study according to the precision of the IQ measurements.

The standardised weighted mean difference value of 0.45 has meaning because we know it represents less than half of one standard deviation so it gives us an indication of how it compares with measurement error. But a value of 6.9 as used by Paul Connett is meaningless – until we are told the standard deviation. Choi et al. (2012)  did not report a difference of 6.9 implied by Paul Connett who appears to have obtained that value from a response to a letter to the editor where they use a hypothetical example to explain the meaning:

“For commonly used IQ scores with a mean of 100 and an SD of 15, 0.45 SDs is equivalent to 6.75 points (rounded to 7 points).”

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Anti-fluoride activists define kangaroo court as “independent”

A kangaroo court is a mock or illegal court that is set up in violation of established legal procedure

The international anti-fluoride movement seems somewhat pre-occupied with thew situation in New Zealand.  In the last few months they have unleashed their “big guns” to attack two publications from local scientific researchers.  First was their attempt to discredit the paper Broadbent, J. M., Thomson, W. M., Ramrakha, S., Moffitt, T. E., Zeng, J., Foster Page, L. A., & Poulton, R. (2014). Community Water Fluoridation and Intelligence: Prospective Study in New Zealand. American Journal of Public Health. Now they have produced an International Peer Review of the  review Health Effects of Water Fluoridation: a Review of the Scientific Evidence. This was commissioned by Sir Peter Gluckman, the New Zealand Prime Minister’s Chief Science Advisor and Sir David Skegg, President of the Royal Society of New Zealand at the request of Auckland City on behalf of several local Councils.

Fluoride Free NZ pretends that the Royal Society Review “was sent out for review by five independent international experts” and a press release from their astroturf organisation the NZ Fluoridation Information Service repeats the independent claim (see NZ fluoridation report trashed by international reviewers).

Well let’s have a look. How independent are the authors of the critique?

An “independent” peer review?

I don’t think so. Here are the authors – chosen by the anti-fluoride movement, of course – together with affiliations and a little history

Kathleen Theissen, Environmental Risk Scientists. I don’t know what the affiliation “environment Risk Scientists,” is. Perhaps a consultancy. However, she is still listed as an affiliate on the Oak Ridge Center for Risk Analysis web site. Theissen was one of the minority* anti-fluoride members on the National Research Council Committee on Fluoride in Drinking Water which produced the NRC reviewFluoride in Drinking Water: A Scientific Review of EPA’s Standards.” She frequently writes articles and submissions opposing community water fluoridation

Chris Neurath, Research Director, American Environmental Health Studies Project. Neurath is also the “Research Director,” of Paul Connett’s Fluoride Action Network (FAN). The American Environmental Health Studies Project is really just the Fluoride Action Network in drag with a couple of other similar organisations tied in.

Hardy Limeback, Head of Preventive Dentistry, University of Toronto. Limeback was also an anti-fluoride minority member of the  National Research Council Committee on Fluoride in Drinking Water which produced the NRC review Fluoride in Drinking Water: A Scientific Review of EPA’s Standards.” He is also an anti-fluoride activist who writes often on the issue and a member of the Advisory Board of Paul Connett’s Fluoride Alert Network.


James Beck, a co-author together with Paul Connett of the anti-fluoridation book The Case against Fluoride.

Spedding Micklem, also a co-author together with Paul Connett of the anti-fluoridation book The Case against Fluoride.

So, definitely not independent

This is a serious distortion of the truth by Fluoride Free NZ because they have continual described the authors of the Royal Society Review as not independent. They wrote, for example (see Fluoridation review ‘Dirty Science’ – Fluoride Free NZ):

“The NZ “expert panel” included only people who were already known to be ardently in favour of fluoridation and not one single person who is known to be opposed, or even someone neutral. It was therefore already a foregone conclusion.”

So, I can only conclude that these people define “independent” to mean that they agree with them – they have an anti-fluoride political stance. And they define anyone whose scientific work produces an objectively determine conclusion favourable to the consensus understanding of the effectiveness and safety of community water fluoridation as not independent!

I can only repeat, how do these hypocritical people sleep straight in their bed’s at night.

How valid are their criticisms

OK, so these people are not independent – but how valid are their criticisms. That is another issue. I am preparing a detailed analysis of the claims made in this critique and will post it in the next few days. So, watch this space.

*Three of the 12 members of the committee expressed disagreement with some fo the committee’s conclusions.

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