Tag Archives: review

Update of NZ fluoridation review timely and useful

Image credit: Kurt:S/Flickr (CC BY-SA 2.0).

An updated New Zealand scientific review of community water fluoridation (CWF) finds that CWF in New Zealand is safe and effective. The new review, Fluoridation: an update on evidence, was published by the New Zealand Prime Minister’s Chief Science Advisor Juliet Gerrard FRSNZ HonFRSC. It examines scientific findings published since the last New Zealand fluoridation review in 2014 – Eason et al (2014). Health effects of water fluoridation: A review of the scientific evidence. It states:

“Royal Society Te Apārangi published a comprehensive review in 2014 looking at the health effects of water fluoridation [Eason et al. 2014]. The review found that there were no adverse effects of fluoride of any significance arising from fluoridation at the levels used in Aotearoa New Zealand. We have considered new research on fluoridation and comprehensive reviews published subsequently, and find that the conclusions of the Royal Society Te Apārangi remain appropriate.”

So, in effect, nothing new there as far as conclusions are concerned. New Zealanders should continue to welcome CWF without any fear of negative effects. But some readers may be interested in the details – specifically the review’s conclusions about the new research which anti-fluoride activists have been promoting of late. Opponents of CWF have in the last year or so almost exclusively concentrated their campaigns on claimed harmful neurodevelopmental and cognitive impacts. The review considers this in a section “Could fluoride have possible neurodevelopmental and cognitive health effects?” and concludes:

“Recent studies continue to show that at very high levels and with chronic exposure, fluoride could potentially have negative neurodevelopmental and cognitive impacts. However, this is not a concern at levels used in fluoridation of water supplies in Aotearoa New Zealand.”

In particular, the new review considered the studies opponents of CWF claim show harmful effects at the water fluoride concentrations used in CWF. It found problems with these studies and states:

“The conclusion reached by Royal Society Te Apārangi remains appropriate. While there is some evidence that high fluoride concentrations may have an adverse effect on developing brains, there is no convincing evidence of neurological effects at fluoride concentrations achieved by fluoridation of water supplies in Aotearoa New Zealand.”

The new review could be better

Of course, the review is written for policymakers and politicians who want the conclusions but don’t want to see the detailed evidence. They will have confidence that behind the scenes proper scientific scrutiny was made of the studies discussed. But, as a scientist, I would have liked to see more details about that scrutiny. For example, a lot more could be said about the deficiencies of the Canadian study (Green et al., 2019) than:

“There was significant and valid criticism of aspects of the study by many subject-matter experts when it was released (see for example, ‘expert reaction to study looking at maternal exposure to fluoride and IQ in children’). The study used sub-group analysis to find an association that is not explained in the paper (i.e. why were only boys affected and why verbal IQ was not impacted), the effect appeared to be driven by the minority of participants that had much higher fluoride exposures (i.e. higher than those in Aotearoa New Zealand).”

I find this statement in the review a bit misleading:

“The results found in the study undertaken in Canada [56] are also in contrast to those found in the study undertaken in Aotearoa New Zealand [57], which has the advantage of more accurately reflecting local contextual factors.”

It refers to the Green et al., (2019) and Broadbent et al (2015) studies claiming their results are contradictory. But in terms of their comparison of IQ in fluoridated and unfluoridated areas this table shows their findings were exactly the same – absolutely no difference. (Till et al 2020 used essentially the same Canadian data) I think this comparison should have been made clear in the review because it is important but is most often overlooked because opponents of fluoridation, and the study’s authors,  never consider it. They remain silent about the facts in this table. This is hypocritical considering the attempts anti-fluoridation critics made to discredit the same finding reported by Broadbent et al (2015) when their paper was published.

Fluoridation opponents have instead concentrated on the relationships between maternal urinary fluoride and child IQ outcomes reported by Green et al (2019). However, all those relationships were extremely weak (explaining only a few per cent of the variation) or statistically non-significant.

The bias of the authors of the Green et al (2019) and Till et al (2020) studies is evident not only in their complete absence of discussion of their own results showing no difference between fluoridated and unfluoridated areas. It is also shown by the fact neither Green et al (2019) or Till et al (2020) referred to the findings of Broadbent et al (2015) or include that paper in their discussion or reference list. (Contrast this with the fact Green et al 2019 included four papers published in the journal Fluoride, known for its anti-fluoridation bias and poor quality).

These omissions are serious as Broadbent et al (2015) is the only other study of IQ in areas including CWF. This defect in the papers appears not to have been picked up by the publishing journals’ referees – which brings me to question the quality of the peer review used for these papers.

We really need to have a more extensive critique of these studies with proper consideration of the methodologies used (e.g. measurement of urinary fluoride and cognitive factors), the statistical relevance of the reported relationships and the quality of their literature reviews and discussions.

A timely, authoritative and useful review

This new review is timely. The NZ Parliament will soon pass legislation removing the current local body control of regional fluoridation decisions over to the Director-General of Health. Anti-fluoride activists will actively campaign against this and will be promoting misinformation about the recent research. The new review provides lawmakers and the media with up to date scientific information, presented in a popular format, which will counter the anti-fluoridation campaigners.

The backing of the office of the New Zealand Prime Minister’s Chief Science Advisor provides scientific authority. As do the 12 reputable scientists who provided peer reviews of the document.

The more science-savvy members of the public who want to see evidence rather than simply rely on recommendations will also find the review and its bibliography useful.

At this stage, it is not clear how anti-fluoride organisations will attempt to discredit the new review and its findings. In 2014 they worked hard to discredit the NZ Fluoridation Review prepared by the Royal Society of New Zealand and the Office of the Prime Minister’s Chief Science Advisor (Health effects of water fluoridation: A review of the scientific evidence.) They prepared their own critique (promoted as a critique by “international scientists “but actually written by, and “peer-reviewed” by, the usual small group of anti-fluoride scientists and activists) –  with their report Scientific and Critical Analysis of the 2014 New Zealand Fluoridation Report. I critiqued and analysed the report in NZ Community Water Fluoridation is Safe and Effective: A critique of Fluoride Free NZ’s criticisms of the NZ Fluoridation Review which can be downloaded as a pdf.

Many opponents of CWF may be distracted by other things like the Covid19 vaccination issue at the moment. However, the anti-fluoridation campaign has big financial backers locally and internationally so it is likely they will come up with something a lot more effective than the recent attempt by Fluoride Free NZ to pretend that the new review effectively supports their claims.

I look forward to analysing any substantial critique they can make of the updated NMZ Fluoridation review.

A meme promoted by Fluoride Free NZ seeks to pretend the new fluoridation review supports their claims. It doesn’t.

Similar articles

Fluoridation: New scientific review of fluoride and oral health

fluoride-oral-healthWant to get up to date on  research about community water fluoridation (CWF) and the effects of fluoride in dental health in general?

Have a read of this new review. It’s published in a special issue of  Community Dental Health devoted to the WHO approach to the prevention of dental caries through the use of fluoride. And is also deals with possible health effects of fluoridation and fluoride in general.

The Paper is:

O’Mullane et al (2016). Fluoride and Oral Health. Community Dental Health 33, 69–99.

Summary and recommendations

The paper summarises the general conclusions and recommendations about CWF as follows:

1. Community water fluoridation is safe and cost-effective and should be introduced and maintained wherever socially acceptable and feasible.
2. The optimum fluoride concentration will normally be within the range 0.5-1.0 mg/L.
3. The technical operation of water-fluoridation systems should be monitored and recorded regularly.
4. Surveys of dental caries and enamel fluorosis should be conducted periodically. For effective surveillance the World Health Organization suggests that clinical oral health surveys should be conducted regularly every five to six years in the same community or setting.

Requirements for a CWF programme

But it is interesting to read its conclusions about the requirements for implementation of water fluoridation. This gives us an idea of why some areas do not fluoridate and what the technical and social requirements are for a successful CWF programme. These are the sort of things that district health boards will need to consider under the current legislations being considered by the New Zealand parliament.

Here is their list:

1. A prevalence of dental caries in the community that is high or moderate, or firm indications that the caries level is increasing.
2. Attainment by the country (or area of a country) of a moderate level of economic and technological development.
3. Availability of a municipal water supply reaching a large proportion of homes.
4. Evidence that people drink water from the municipal supply rather than water from individual wells, rainwater tanks or other sources.
5. Availability of the equipment needed in a treatment plant or pumping station.
6. Availability of a reliable supply of a fluoride-containing chemical of acceptable quality.
7. Availability of trained workers in the water treatment plant who are able to maintain the system and keep adequate records.
8. Availability of sufficient funding for initial installation and running costs.

How many people have access to CWF internationally?

The review has an appendix providing data on worldwide totals for populations with artificially and naturally fluoridated water. This is very useful and anti-fluoride campaigners are well-known for misrepresenting this information in their attempts to claim that most countries reject CWF.

Here is the table for artificial CWF programs:


It says in summary:

“The estimated worldwide total of people supplied with artificially fluoridated water as at April 2011 is 369,226,000 in 25 countries, including the United Kingdom, the United States, Canada, Brazil, Chile, Argentina, Peru, Panama, Guyana, Guatemala, Republic of Ireland, Spain, Serbia, Australia, New Zealand, Fiji, Malaysia, Singapore, Vietnam, Brunei, China (Special Administrative Region of Hong Kong), Papua New Guinea, Republic of Korea (South Korea), Israel and Libya.”

Natural fluoridation

The review also summarises data for people receiving fluoride through the natural levels of fluoride in their drinking water:

Natural fluoridation in the 25 countries operating artificial fluoridation schemes

“In the 25 countries with artificially fluoridated water there are an estimated 18,061,000 million people drinking naturally fluoridated water at or around the optimal level. That brings the total in these 25 countries consuming optimally fluoridated water to around 387,287,000 million.”

Other countries with natural fluoridation

“In addition, there are a further 27 countries with naturally fluoridated water supplied to an estimated 239,903,000 million people. However, it should be stressed that, in many instances, the naturally occurring fluoride level is in excess of the optimum – for example, in China, India, Argentina, Tanzania, Zambia and Zimbabwe. Total worldwide population drinking optimally fluoridated water.”

In summary – 437 million have access to fluoridated water

Combining data for artificial and natural fluoridation the review concludes:

“General estimates for the number of people around the world whose water supplies contain naturally fluoridated water at the optimum level for oral health are around 50 million. This means that, when the numbers of people with artificially (369.2 million) and naturally fluoridated water supplies (50 million) at the optimum level are added together, the total is around 437.2 million.”


This review is useful for anyone wanting an up-to-date picture of CWF, possible health effects and other issues.

I recommend that anyone active in the dental health area or who needs to respond to questions about fluoridation from the public have their own copy. they will refer to it again and again.

This link goes straight to the download of the pdf.

Similar articles