GUEST BLOG: Ian Powell – Very good fluoridation political call, Dr Verrall

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Infectious diseases specialist Dr Ayesha Verrall was a surprise cabinet appointment being a first-time MP. Despite the rarity she’s not mucking around. This is evidenced by her legislative proposal, as Associate Minister of Health, to shift decision-making over water fluoridation from local authorities to the Director-General of Health (in effect the Ministry of Health).

The issues behind Verrall’s initiative are nicely discussed in an ‘explainer’ article (20 March) by Stuff journalist Hannah Martin.

When working for the Association of Salaried Medical Specialists I would often come across despair and frustration from specialists discussing gut-wrenching cases of poor tooth decay. This wasn’t just dental and public health specialists. They also included those in emergency departments where these cases often presented themselves and anaesthetists where surgery was required (the latter also play an important role pre and post-operative care).

What is fluoridation

Fluoride is a mineral found in our bones and teeth. It also naturally exists in water, soil, plants, rocks, air and many foods. Fluoride makes teeth more resistant to decay by strengthening the tooth surface. It also interferes with the growth of cavity-causing bacteria and helps repair the early stages of tooth decay. But there is not enough fluoride in water and food to help prevent tooth decay.

Consequently fluoridation is the process used to adjust the level of fluoride in drinking water, consistent with World Health Organisation safety advice, to achieve prevention. All of us on reticulated supply drink fluoridated water but not all at a level to address tooth decay.

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Fluoridation first began in New Zealand in 1955. Around 50% of New Zealanders presently receive fluoridated water (about 60% of those on reticulated water supplies). Reportedly only one-third of local authorities have authorised fluoridation. This apparently discrepancy is reflected in the fact that most of Auckland with a single council is fluoridated.


The most recent New Zealand oral health study, conducted in 2009, revealed that there was 40% less tooth decay among children and adolescents where water was fluoridated compared with those where it wasn’t. Fluoridation isn’t a magic bullet for preventing tooth decay. But, along with brushing twice daily, eating healthy foods and regular dental check-ups, it is the most effective.

Water fluoridation is also cost effective according to experts. This expertise was reinforced by a 2015 Sapere Research Group study which concluded that for every dollar spent on water fluoridation, $9 is saved in dental care costs, some in the health system but largely by individuals.

There are genuinely held concerns over fluoridation believing that it causes or contributes to a number of health conditions such as cancer, Down’s syndrome, renal disease, allergic conditions, repetition strain injury, and that it causes interference with enzyme function. But they haven’t been substantiated by experimental studies or epidemiological analyses.

It is true that if consumed in large amounts fluoride can be toxic. But, according to the Health Ministry, a person would need to drink thousands of glasses of water in a single sitting to obtain anything near a lethal dose (and an awful amount peeing I might add).

Verrall proposal

The Associate Health Minister is using a less known but acceptable legislative means to achieve her objective. She is amending the stalled Health (Fluoridation of Drinking Water) Amendment Bill introduced by the National Party to transfer decision-making on water fluoridation from local authorities to district health boards.

There was good sense behind National’s bill but Verrall is improving its efficiency by centralising decision-making through transferring the responsibility to the Director-General of Health. Her mechanism will be by means of what is called a Supplementary Order Paper.

National Party concerns

National is concerned. While agreeing with the science behind fluoridation, its Deputy Leader and health spokesperson Dr Shane Reti​ has called it an “overreach” worried that the centralisation of power would stir up more resentment by those who are against fluoridation. He makes a reasonable point but there are at least four counters.

First, the scientific evidence about the benefits (and risks) of fluoridation is overwhelming. The public accepted that the Government was following the best available science in its Covid-19 elimination of community transmission strategy. Providing that the science behind fluoridation is communicated as effectively as it was over Covid-19, there is no reason why the public wouldn’t similarly accept it, particularly if it focusses on those who might be understandably hesitant.

Second, it will be important that the Associate Minister ensures that there is plenty of opportunity for the public to make submissions that are then considered by Parliament’s relevant select committee. Third, the logic behind decentralising fluoridation decisions to DHBs is about as consistent as doing the same with decisions over which Covid-19 vaccines should be purchased.

Finally, increased resentfulness from already aggressive opponents should not be allowed to govern what we do. That resentfulness would exist regardless of who make the decision. Just imagine how much less the progress in combating homophobia would be if those behind the homosexual law reform bill of 1986 had backed down in fear of making more resentful the bill’s vociferous opposition.

Social determinants of health

Social determinants of health are both external to our health system and the biggest driver of poor health. Serious tooth decay is driven by social determinants. Safely adjusting the level of fluoridation doesn’t address the causes of social determinants of health but should go a long way to reducing bad oral health consequences.

It is overstating to say that Ayesha Verrall is brave to promote this initiative although she is likely to be subjected to personal abusive attacks from some fanatical quarters. But, as a first-time MP cabinet member, she has made an early astute political call that if legislated should make a positive difference in the lives of many (perhaps even transformational).


Ian Powell was Executive Director of the Association of Salaried Medical Specialists, the professional union representing senior doctors and dentists in New Zealand, for over 30 years, until December 2019. He is now a health systems, labour market, and political commentator living in the small river estuary community of Otaihanga (the place by the tide). First published at Otaihanga Second Opinion.


  1. The minute you equate legislation around a person’s sexuality and whether or not it is okay to force fluoride in water onto people that may not want it, your argument deserves to be rejected. If the government would step in and prevent advertising junk food, fix diet advice away from refined carbs, and promote/give high dose vitamin c to everyone there would be little tooth decay.

    • You missed the bit where the evidence support using fluoride. That would lead to the conclusion that those holding anti-fluoride views are just imagining that it causes harm.
      While I can live with whatever moral decisions society agrees to there is a real lack of evidence (genetic, chemical, biological) concerning sexuality which would be my reason for questioning why the good doctor linked the 2 issues.

      • Bonnie: “…..there is a real lack of evidence (genetic, chemical, biological) concerning sexuality which would be my reason for questioning why the good doctor linked the 2 issues.”

        But he doesn’t link the two issues. I’ve reread his post for just this reason. He does say that parliament shouldn’t let opposition stand in the way of passing Verrall’s legislation, just as it didn’t over the Homosexual Law Reform Act, all those years ago. And I well remember the viciousness of the opposition to that Bill!

        The HLR Act’s purpose was to legalise consensual sex between men aged 16 and older. It removed the provisions of the Crimes Act 1961 that criminalised this behaviour.

        It had nothing to do with the gender issues currently occupying the attention of many people.

    • Left Sceptical: “The minute you equate legislation around a person’s sexuality and whether or not it is okay to force fluoride in water onto people…..”

      I was puzzled by your comment, so I reread the post. The author doesn’t do that. Here’s what he actually wrote:

      “Just imagine how much less the progress in combating homophobia would be if those behind the homosexual law reform bill of 1986 had backed down in fear of making more resentful the bill’s vociferous opposition.”

      He’s arguing that we shouldn’t allow anti-fluoride sentiments to stand in the way of passing Verrall’s piece of legislation. Just as anti-gay activism didn’t deter parliament from passing the Homosexual Law Reform Act.

      I was a voter back in the days of the Homosexual Law Bill being presented to parliament by Fran Wilde. And I can tell you that the opposition to it was vicious. It’s difficult to imagine now, and difficult to see what opponents were so afraid of.

  2. Anti vac will join with antifloride and court cost will fall on the taxpayer rather than the rate payer and any ruling will cover the whole country

  3. The anti-science brigade will revolt against fluoridation and chlorination of water and against vaccination too. They choose tooth decay, water borne diseases and exposure to pathogens. Those responsible for Public Health have to make tough calls to combat lunacy.

    • Steven Nichols: “The anti-science brigade will revolt against fluoridation and chlorination of water and against vaccination too.”

      I’m reminded of the folate nonsense, a few years back.

      Folate (folic acid) is vitamin B9. All of us need it for proper nutrition. It’s especially important for women in the first stages of pregnancy, given that B9 deficiency is linked by research to neural tube defects in infants (spina bifida). Neural tube development happens in the first trimester: often before a woman realises that she’s pregnant.

  4. This to me is an example of when our system of government works well. The writer states that National originally put up a bill that had good sense behind it. The bill has stalled. The government’s Associate Minister of Health has picked it up and improved its efficiency. National’s health spokesperson has raised some concerns which it is the whole purpose of an opposition – to ensure that proposals are tested and subject to rigour. The writer concedes that he makes a reasonable point and then outlines the counters. So if this goes ahead there is science behind it and the government and opposition have both been involved constructively. Would that there could be a lot more of this and that the hard core supporters of each party would not see it as an opportunity for cheap shots or point scoring. One can only wish.

  5. Maybe we can get fluoride added to all those sugary drinks kids consume, or perhaps toothpaste. Hang on it’s already in toothpaste isnt it.

    Comments by Philippe Grandjean, adjunct professor of environmental health, Harvard T.H. Chan School of Public Health:

    “We should recognize that fluoride has beneficial effects on dental development and protection against cavities. But do we need to add it to drinking water so it gets into the bloodstream and potentially into the brain? To answer this, we must establish three research priorities.

    “First, since dental cavities have decreased in countries both with and without water fluoridation, we need to make sure we are dosing our water with the proper amount of fluoride for dental medicine purposes, but no more.

    “Second, we need to make sure fluoridation doesn’t raise the risk of adverse health effects. In particular, we need basic research on animals that would help us understand the mechanisms by which fluoride may be toxic to the developing brain.

    “Third, we need to find out if there are populations highly vulnerable to fluoride in drinking water—bottle-fed infants whose formula is made with tap water, for example, or patients undergoing dialysis. If these individuals are at risk, their water must come from a source that is lower in fluoride.”

    • Grandjean is a known opponent of community water fluoridation and often acts and a scientific spokesperson for the Fluoride Action network.

      I question his scientific ethics because as Chief Editor of the journal Environmental Health he refused to allow my submitted article to be considered. My article was a response to a previous article in that journal and ethically any response should have been published in Environmental Health.

      My article was eventually published elsewhere (see Perrott, K. W. (2018). Fluoridation and attention deficit hyperactivity disorder a critique of Malin and Till (2015). British Dental Journal, 223(11), 819–822.

      Unfortunately, this sort of scientific censorship and partisanship is not too uncommon in the scientific world. In Grandejan’s case, he actively works with other authors promoting and anti-fluoride agenda and consequently the peer review process in his journal is farcical.

      The moral of this take is don’t rely on personal quotes and personal endorsements on so-called authorities. Look at the evidence for oneself.

  6. Pedro: “Maybe we can get fluoride added to all those sugary drinks kids consume…”

    If said drinks are manufactured in an area where water supplies are fluoridated, they’ll already have fluoride in them.

    As the author of this post notes, fluoride isn’t a silver bullet, but it does help to smooth out the differences between low-income and higher-income populations.

    I note the comments of Philippe Grandjean. It must be pointed out that the issues you quote above have been raised in the past.

    It’s a long time since I worked in the health sector, but my memory of the debate over water fluoridation goes back to the 1960s. And of course there was debate before that. I’ve heard it all before.

    Given that fluoride is ubiquitous in the environment, including in water, there’s a deep history of people drinking it. Though it’s relatively recently that it was found to be the fluoride element which was reducing tooth decay prevalence in some communities.

    In this country, and for reasons of geology (broadly conceived), fluoride levels in the environment are lower than has been found desirable for optimum dental health. Hence the adjustment upwards of existing fluoride levels in our water supplies.

  7. Fluoridating the currently unfluoridated areas of NZ will make very little difference to the numbers of “gut-wrenching cases of poor tooth decay” described by Ian Powell. A study, “Association between community water fluoridation and severe dental caries experience in 4-year-old New Zealand children”, led by pro-fluoridation Professor Philip Schluter of Canterbury University, analysed Ministry of Health data for 4-year-old children from the years 2010-2015. Published in the journal JAMA Pediatrics, it found that the incidences of severe tooth decay in the fluoridated areas of NZ were higher than in the unfluoridated. Thus fluoridation cannot solve the problem. The primary cause is sugar. A serious, sustained campaign to reduce its consumption is the only way it can be solved.

    • John Christie: “….it found that the incidences of severe tooth decay in the fluoridated areas of NZ were higher than in the unfluoridated.”

      This is misleading. What you’re talking about here is unadjusted data. Here’s the abstract:

      The authors note the following:

      “Severe caries were identified for 24 226 children (15.8%) in fluoridated and 17 135 children (14.0%) in unfluoridated areas, yielding an unadjusted odds ratio of 0.93 (95% CI, 0.90-0.95). However, in the adjusted analyses, children residing in areas without fluoridation had higher odds of severe caries compared with those within fluoridated areas (odds ratio, 1.21; 95% CI, 1.17-1.24).”

      The differential effect of water fluoridation on the oral health of children generally, and low-income children in particular, is well-known to anybody who’s worked in that area of healthcare. Adults also experience the beneficial effects of water fluoridation.

      But – as Powell points out above – it isn’t a silver bullet. Even in fluoridated areas, children can develop tooth decay, if the diet is high in sugar (without the buffering effects of foods and drinks which aren’t sugar-rich) and tooth-brushing isn’t regular.

      However. Children’s health status is never their fault; they are dependent upon the adults who look after them. Water fluoridation gives every child – no matter their SES – a leg-up in the oral health stakes.

  8. D’Esterre, my comment is not misleading. Read again the first sentence in the text you have quoted. It states quite plainly that severe tooth decay rates in the fluoridated areas of NZ are higher (15.8% of 4-year-old children) than in the unfluoridated (14.0%). That is the reality on the ground. No amount of statistical adjustment can change that fact.

    The purpose of Schluter et al.’s adjusted analyses is to create a mathematical model that can explain this reality. Table 4 in the paper shows that the main determinants of children’s dental health are level of deprivation and ethnicity. Factors that directly affect tooth decay rates such as diet, dental hygiene practices and affordability of professional dental care were not included in the model.

    The finished model predicts that fluoridating all of NZ would reduce the overall rate of severe tooth decay in 4-year-old children by 5.6%.

    There are about 60,000 4-year-olds in NZ. A reasonable estimate of the overall rate of severe decay is 15% (it is 15.0% if the 60,000 are divided into fluoridated and unfluoridated in the same proportion as in the Schluter sample). 15% of 60,000 is 9,000. 5.6% of 9,000 is 504, say 500. That leaves 8,500 with “gut-wrenching cases of poor tooth decay”. What is the plan for these children?

    Social deprivation and ethnicity (probably a surrogate for racism in the model) are drivers for poor diet, poor dental hygiene and the unaffordability of dental care. Diet is probably the main factor: many historical studies have shown that dental decay was not a public health problem before the introduction of sugar. In Tristan da Cuhna introduction of sugar led to an 8 to 10-fold increase in decay rates; in Japan during World War 2, tooth decay rates fell by 90% when sugar imports fell by the same percentage [Rugg-Gunn, A.J. et al., ‘The role of sugar in the aetiology of dental caries. 2. The epidemiological evidence’, Journal of Dentistry 11, 190 (1983)].

    These facts suggest a plan for all, adults as well as children, one with much greater potential than fluoridation. It requires facing down big food and implementing programmes such as Childsmile in Scotland, along with serious, ongoing programmes to tackle inequality and racism. We should be aiming for a 100% reduction, not 5.6%.

    Much of the Schluter paper is written in rather opaque language, so confusion in reading it is understandable. The Guardian has published a guide to reading statistics, “Without learning to think statistically, we’ll never know when people are bending the truth” by statistician, Paul Goodwin. It includes the memorable quotation, “people use statistics like drunks use lamp-posts – for support rather than illumination” and advises, “common sense should be our first line of defence”.

    Take the figure 5.6%. Is that reasonable? Fluoride-tooth enamel chemistry suggests water fluoridation should reduce dental decay rates [Featherstone, J.D.B., ‘Dental caries: a dynamic disease process’, Aust. Dent. J. 53, 286 (2008)] but inter-country comparisons indicate that the reduction is small – see the OECD data in Decay rates in fluoridated and unfluoridated countries are indistinguishable, and the lowest rate, in unfluoridated Denmark, is less than half that in NZ. From the Schluter analysis we could predict Denmark has lower levels of inequality and racism than NZ.

    For those who read the Schluter paper (or its abstract), “population attributable fraction” (the 5.6% figure) is the expected reduction in the number of cases due to an intervention, divided by the total number of cases, and expressed as a percentage. Here “case” means severe dental decay and “intervention” means fluoridating all of NZ

    • Your comment is misleading – you simply are ignoring the fact that proper detection of differences must use an analysis where data is adjusted for things like ethnicity. The motive for this is proper analysis of the data, is not the construction of a model

      A big problem is cherry-picking adjusted data, in this case, is that most Pacific Islanders (who ethnically have high rates of tooth decay) are contracted in fluoridated areas. This distorts the results when there is no adjustment.

      Schluter et al discuss this problem as I do also in my article on the way anti-fluoride activists misrepresent studies like this.

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