Fluoridation: Beliefs about safety and benefits

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

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

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

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

I summarise the reported results in  the following graphs.

Perceived safety

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


Effect of information on CWF

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


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

Perceived benefits of CWF

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


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


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

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

The authors of this study concluded:

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

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Climate change: Our time really is running out

This video features Professor Peter Wadhams, leading Arctic scientist Cambridge University, interviewed by Judy Sole, the University of Earth. It is very topical and very important.

Professor Wadhams argues that politicians are dragging their feet on the climate change issue. The approach of trying to limit CO2 emissions just won’t work. We have to put serious money into research methods of removing CO2 from the atmosphere and countering methane emissions from seabed permafrost.

He discusses the radical reduction of arctic ice due to global warming and warns that this is leading to release of methane gas from underwater seabed permafrost and this could have relatively rapid effects on global warming.

via Our time is running out – The Arctic sea ice is going! – YouTube.

Thanks to Richard for bringing my attention to this video.

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Cochrane fluoridation review. III: Misleading section on dental fluorosis

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

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

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

Confusing language

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

Strictly, their calculations were reported correctly in the abstract:

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

And also in the Plain Language Summary:

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

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

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

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

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

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

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

What the review did on dental fluorosis

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


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


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

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

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

Estimating possible effect of CWF on dental fluorosis

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

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

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

Defining “dental fluorosis of aesthetic concern”

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

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

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

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


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

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

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

See also:

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

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June ’15 – NZ blogs sitemeter ranking


Big problems with Sitemeter

The problems with SiteMeter are even worse this month. No data could be obtained for about 50 blogs using SiteMeter. People have also reported strange results. So if you wish to query the information in the table I suggest you check out the data in the SiteMeter pages.

If you are using SiteMeter, and especially if you find you page isn’t included this month, I suggest you consider transferring to a more reliable counter like StatCounter. Have a look at the NZ Blog Rankings FAQs if you need help with this.

There are now over 300 blogs on the list, although I am weeding out those which are no longer active or have removed public access to sitemeters. (Let me know if I weed out yours by mistake, or get your stats wrong).

Every month I get queries from people wanting their own blog included. I encourage and am happy to respond to queries but have prepared a list of frequently asked questions (FAQs) people can check out. Have a look at NZ Blog Rankings FAQ. This is particularly helpful to those wondering how to set up sitemeters. Please note, the system is automatic and relies on blogs having sitemeters which allow public access to the stats.

Here are the rankings of New Zealand blogs with publicly available statistics for June 2015. Ranking is by visit numbers. I have listed the blogs in the table below, together with monthly visits and page view numbers. Meanwhile I am still keen to hear of any other blogs with publicly available sitemeter or visitor stats that I have missed. Contact me if you know of any or wish help adding publicly available stats to your bog.

You can see data for previous months at Blog Ranks

Subscribe to NZ Blog Rankings Subscribe to NZ blog rankings by Email Find out how to get Subscription & email updates Continue reading

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


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

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

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

The review describes the types of “biases”  considered:

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

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

What “biases” did the review find

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

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

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

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

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

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

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

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

Inappropriate criteria used to judge quality of research

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

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


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

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

The scientific literature is not perfect

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

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


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

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

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

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

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

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

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

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

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

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

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

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Cochrane fluoridation review. I: Most research ignored

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

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

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

97% of fluoridation research ignored

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

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


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

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

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

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

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

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

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

Inability to comment does not mean no effect

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

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

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

Confirmation fluoridation is effective

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

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

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

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

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

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

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


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

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

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

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

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

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

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

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What is causing warming of the earth?

Bloomberg has a great article showing why climate change deniers have it all wrong when they argue that the observed global warming is explained by natural causes. It just isn’t. The article is What’s Really Warming the World? Climate deniers blame natural factors; NASA data proves otherwise.

Here are the main points and graphics which compare the observed changes in earth’s temperature  with the changes expected from individual factors:

Natural factors

Changes in the earth’s orbit around the sun (blue line) have had a negligible effect on warming:


Changes in the sun’s temperature (orange line)have also had a negligible effect:


Volcanos influence the earth’s temperature, usually causing decreases,(red line) but cannot explain the observed warming:


Natural factors combined (earth’s orbit, sun temperature and volcanoes) (green line) cannot explain the observed warming:


Human factors

Changes in land use, like deforestation, (light green line) actually have a cooling effect:


Ozone level changes (light blue line) have only a slight warming effect:


Aerosol pollution (purple line) has had a marked cooling effect:


Greenhouse gas concentration increases (green line) have had a marked warming effect – it is clearly the main factor responsible for global warming:


When all the human factors, ozone, land use, aerosols and greenhouse gases, are combined the models (blue line) show a good agreement with observed temperature changes (black line):


Natural and human factors combined

When all the natural and human factors are combined (red line) agreement between the modelling and observed earth temperatures is even better.



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New science bloggers wanted for Sciblogs 2.0

Sciblogs 2.0 coming soon

After nearly six years in operation, Australasia’s largest blog network is getting a facelift and some fresh voices.

Sciblogs features commentary from around 30 scientists and science writers and is consistently ranked among the country’s top 10 blogs based on Sitemeter statistics.

But the platform is well overdue for a revamp and will soon be relaunched with a new look, new additions to the blogging line-up and a remit of appealing to a wider audience.

Among the changes will be:

  • A more visual look and refreshed blog homepages
  • Mobile-friendly design so Sciblogs looks good on smartphones and tablets
  • Some new bloggers covering everything from drones to psychology
  • News content drawing from sources such as our new Scimex.org research news portal.

Become a Scibling

We are on the lookout for new science bloggers to join our lively stable of bloggers and as well as writers, videographers and social media gurus who are passionate about science communication and who are keen to collaborate on Sciblogs.

“The likes of Iflscience, Science Alert and the science blog networks of Scientific American and Scienceblogs shows there’s strong appetite for science news and commentary,” said Sciblogs editor and SMC Director, Peter Griffin.

“We want to grow the Sciblogs community featuring the best, most interesting science from New Zealand and around the world. We’ll improve our mobile and social media presence so Sciblogs content is easier to browse and share.”

The new Sciblogs will go live by the end of August – contact Sciblogs editor Peter Griffin if you would like to get involved.

Gagging of scientists – a common problem?


A recent NZ Association of Scientists survey indicates that 40% of NZ scientists report they feel gagged from communicating their scientific findings to the public. Management policies and funding problems were blamed and there are issues around “embarrassing the government.”

The Science and Innovation Minister, Stephen Joyce, is not convinced by the survey results but is unwilling to accept there is a problem without  “a heck of a lot more evidence than we’ve got from one write-in survey.” (See Call for closer look at scientists’ claims | Radio New Zealand News.)  You can be sure he won’t go out of his way to look for such evidence.

Wider than direct censorship

Despite Joyce’s attempts to “turn a blind eye,” I think there is a problem and can certainly remember examples from my time working in a Crown Research Institute (these problems may not be as bad in the Universities). But the problem is wider than direct censorship – limiting publication because of commercial sensitivity, protection of intellectual property,  fear of scaring away or offending potential funders and succumbing to legal action – or just threats of legal action – from commercial interests.

There is also the gagging effect arising from the institutional culture, the attitudes and perceived interests of management bureaucracy, the old-boy network (which these days incorporates people from the commercial  sectors as well as the government and political system). I experienced an example of the old-boy network when a National MP attempted to get my director to “discipline” me because I had made a public statement on nuclear disarmament! I am sure this sort of “behind the scenes” pressure is exerted all the time on research institute managements by commercial and political figures. And how often do management figures consider the interests of freedom of expression and information, or the responsibility of science to communicate with the public, when subjected to such pressure with its implied threats to the funding or “name” of the institute?  Or to the career of the management figure themselves?

Wider than one’s own research

The issues, for and against, may be fairly clear when the findings being gagged are the research results of the scientists themselves. But scientists do have the responsibility to speak up about science itself, and about general findings which may not be directly linked to the narrow field of specialisation of the scientist concerned.

This is especially true today when so much pseudoscience and outright distortion of science is promoted in the public sphere. Very often the promotion is done in the interests of business so managements may feel the need to prevent staff from fulfilling such responsibilities so as to avoid commercial pressures on the institute.

A common example is the scientific misinformation peddled by the “natural”/alternative health industry, which today is a big and profitable business – despite attempting to present itself as the “David” challenging the “Goliath” of “Big Pharma.”

Institutional management may pressure staff not to face up to their responsibility to fight this misinformation – especially if they believe there may be possibilities of research contracts from businesses within that industry. Maybe management will express this in relatively bland terms such as the need to protect the “name” and “reputation” of the institute. Or express the concept that the institute should not be seen to be “taking sides” as this undermines its credibility and appearance of objectivity.

Becoming a “street fighter” or abdicating scientific responsibility?

Then, of course, there is just the outright viciousness of some anti-science campaigners. Getting into public fights with some ideologically motivated activists can be like participating in a pub brawl. Responsible management cannot be happy about staff being seen as “street fighters.”

Management also has a responsibility not to expose their staff to danger. In New Zealand District Health Boards have tended not to take part in public meetings which are stacked with anti-fluoride activists – partly for the safety reason. And recent reports of attacks on health spokespersons and city council leaders, by anti-fluoride activists, show this is a reasonable concern (see  Lismore mayor assaulted in broad daylight by fluoride-hater, and Beware the violent antis – Lismore Mayor physically assaulted).

33618It is a complex issue. On the one hand engagement with those who are misrepresenting science can sometimes end up like fighting a pig – one’s opponent is so slimy they can escape from any rational debate and the expert ends up just a dirty as the pig in the end. In the other hand not to take part in the public debate  results in the abdication of our scientific responsibilities and handing over the public issue to those who promote misinformation and pseudoscience. (In NZ anti-fluoride propagandists are continually claiming  the refusal of district health boards to front up to their meetings as evidence that science does not support fluoridation!)

Social media

Social media can be just as nasty to pro-science people who attempt to challenge misrepresentation and pseudoscience (have a look at the abuse rendered by the Australian anti-fluoride propagandist Dan Germouse here). There is little point in engaging extremists on social media – unless one is sure there are other readers, or “lurkers,” who may learn something from the exchange.

But one thing is sure, advocates of science do not use social media as often or as effectively as they should. Studies do show that pseudoscientific groups and those peddling scientific misinformation tend to dominate social media like Facebook and Twitter. Social media can be effective in creating opinions – and anyway it is a popular forum which we ignore at our peril.  Scientists need to find ways to effectively take part in social media – if we don’t we are abdicating our responsibility to society to defend science and oppose misinformation.


Gagging of scientists is much wider than the few cases where publication of individual research findings is restricted.Unfortunately institutional culture, its conservatism, authoritarianism and bureaucracy, inhibit the freedom of scientists to take part in the public debate around scientific issues. They inhibit participation in social media where much of the public debate occurs (see Science and social media in new Zealand). Institutional culture can therefore restrict a scientist’s ability to fulfill his or her responsibility to communicate science to the public and to oppose widespread misinformation and pseudoscience.

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