Tag Archives: Dental fluorosis

Water fluoridation and dental fluorosis – debunking some myths

Dental fluorosis is really the only “negative” side effect of community water fluoridation (CWF). It occurs in non-fluoridated as well as fluoridated areas but is often a little more common in the fluoridated areas.

However, there is a lot of rubbish about dental fluorosis spouted by anti-fluoride propagandists. It is worth putting dental fluorosis into its proper context and debunking some of the misinformation they promote.

Here are some facts.

1: Diagnosis of dental fluorosis involves grading teeth into 6 levels:

  1. No dental fluorosis
  2. Questionable
  3. Very mild
  4. Mild
  5. Moderate
  6. Severe.

Here are some photos of the different grades

2: The moderate/severe grades are rare in areas considered for CWF and fluoridation does not increase prevalence of those grades of dental fluorosis. However, those more severe forms are more common in areas where dental fluorosis is endemic like parts of China, India and north Africa.

Dental and skeletal fluorosis is a real problem in these endemic areas, but it is not a problem in the areas where CWF is used.

The figure below contrasts data for prevalence of dental fluorosis in NZ and the USA where CWF is common with data for an area of endemic fluorosis in China.


3: The 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).

In contrast research shows that the moderate/severe grades of dental fluorosis have a negative impact on health-related quality of life(Chankanka et al., 2010; Do and Spencer, 2007; Chikte et al., 2001).

4: Anti-fluoride propagandists often lump all grades together – presenting dental fluorosis as always bad. It also enables them to produce high figures to inflate the apparent problem. That is deceptive.

5: Anti-fluoride propagandists often use data from countries like India and China where fluorosis is endemic in their arguments against CWF. The figure above shows this is also deceptive.

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Severe dental fluorosis the real cause of IQ deficits?

A new study finds cognitive function defects, like IQ, in children are not significantly related to fluoride in drinking water. But they are associated with medium and severe dental fluorosis.

This interests me for two reasons:

  1. The report is by Choi and Grandjean who had also authored the 2012 meta-review often used by anti-fluoride activists to claim that community water fluoridation causes a lowering of IQ (the authors subsequently pointed out the high fluoride concentrations in the papers they reviewed meant that conclusion is not valid)
  2. The data reported is consistent with my suggestion in Confirmation blindness on the fluoride-IQ issue that reported relationships between IQ and drinking water fluoride concentration could really indicate a relationship with severe dental fluorosis, and not drinking water fluoride itself.

The new report is:

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.

Firstly – this is only a pilot study and has several acknowledged weaknesses – the small number of children studied (51) being the most obvious. However, this is what was found:

“Sixty percent of the subjects examined had moderate or severe fluorosis. These children were exposed to elevated fluoride concentrations in drinking water. Children with normal or questionable Dean Index were all from households with a water fluoride concentration of 1 mg/L and had urinary fluoride excretion levels below 1 mg/L.”

The children were placed in 3 groups according to their degree of dental fluorosis:

  1. Normal/questionable (N=8)
  2. Very mild/mild (N=9)
  3. Moderate/severe (N=26)

The high proportion of children with moderate/sever dental fluorosis indicates the study involved an area of endemic fluorosis.

And the results of neuropsychological tests:

“Results of multiple regression models show that moderate and severe fluorosis was significantly associated with lower total and backward digit span scores when compared to the reference combined categories of normal and questionable fluorosis (Table 4). Although the associations between fluoride in urine and in drinking water with digit span were not significant, they were in the anticipated direction. Motor coordination and dexterity were not significantly associated with fluoride in drinking water and fluorosis although higher levels were associated with poorer scores as well. Other outcomes did not reveal any association with the fluoride exposure.”

The authors used a number of neuropsychological tests. The digit span test results suggest a “deficit in working memory” for the children with moderate and severe dental fluorosis. None of the other tests used show any signficant relationship with indices for fluoride exposure.

So, this pilot study did not show any association of neuropsychological tests with fluoride concentration in drinking water but it did find an association with medium and severe dental fluorosis. This is consistent with my speculation in Confirmation blindness on the fluoride-IQ issue that “a physical defect like dental and skeletal fluorosis could lead to decreasing IQ.”

I argued that:

“minor physical anomalies are known to be associated with learning difficulties and emotional illness in children (seeHilsheimer & Kurko 1979). It seems entirely reasonable that a physical anomaly like severe dental fluorosis could lead to learning difficulties in children which could be seen as lower IQ values.”

There are many problems with the studies anti-fluoride activists promote relating IQ to fluoride in drinking water. But it could be that any real effect seen with the higher fluoride concentrations could simply be explained by effects of the physical anomaly of medium and severe dental fluorosis common at these higher concentrations.

Unfortunately the authors of this study still do not consider this possibility. I guess it could be that someone with a hammer only sees nails, and chemical toxicologists are only capable of considering brain damage caused by toxic chemicals. The effects of physical anomalies on learning difficulties are probably quite outside their training and experience.

Their confirmation bias and mental blockage on this meant they were considering dental fluorosis as just another indicator of dietary fluoride intake. However, even that assumption has its problems because genetic differences are also known to be involved in dental fluorosis.

I think this must be why they ended with a conclusion that could well be quite unfounded:

“This pilot study in a community with stable lifetime fluoride exposures supports the notion that fluoride in drinking water may produce developmental neurotoxicity”

Dental fluorosis and community water fluoridation

Fluorosis is endemic in many parts of China and the high prevalence of medium/severe dental fluorosis (60%) among the children in the Choi et al (2014) pilot study shows their situation is not at all similar to that in areas of New Zealand and USA using community water fluoridation (CWF).

The figures below give some context.

Here are examples of the different degrees of dental fluorosis.

The graph below shows the situation reported for New Zealand in the 2009 New Zealand Oral health Survey (see Our Oral Health). No severe and only 2% moderate dental fluorosis reported.

This figure (taken from Fluorosis Facts: A Guide for Health Professionals) shows the amount  of moderate and severe dental fluorosis in the US is also very small.

Perhaps we can now contrast the situation here, in areas where CWF is common, with the situation in China in areas with endemic fluorosis where these studies were undertaken. The figure below is a slide from a presentation by Xiang (2014) to Paul Connett’s recent anti-fluoride “get-together” (Xiang 2014). This is not the very mild dental fluorosis attributed to CWF.

(Anti-fluoride people also often single out the study of Xiang, et al (2003). Effect of fluoride in drinking water on children’s intelligence. Fluoride, 36(2), 84–94, because unlike the others it is more detailed.  Xiang’s team has studied areas where fluorosis is endemic.)


Anti-fluoride activists often promote the meta-review of Choi et al (2012) in their arguments against CWF. However, there are many problems with these studies including the fact reported IQ effects were associated with much higher drinking water fluoride concentrations than occurs with CWF.

The new study of Choi et al (2014) did not confirm any association of neuropsychiatric measurements with drinking water fluoride concentration. However, it did show association of negative neuropsychological effects with medium/severe dental fluorosis.

This is consistent with the physical anomaly of severe dental fluorosis being the real cause of IQ effects and not any direct chemical toxic effect.

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Do you prefer dental fluorosis or tooth decay?

Anti-fluoride propagandists often use the incidence of dental fluorosis as an argument against community water fluoridation. However, they exaggerate the problem by misrepresenting the issue in two ways:

1: They present the issue as if the figures for the incidence of dental fluorosis relate to the severe forms when they don’t. Most cases of dental fluorosis in areas using CWF are classified as questionable or mild. Yet the anti-fluoride people will present images of severe dental fluorosis which is never caused by CWF (see ). Severe forms are caused by excessive toothpaste consumption, high natural fluoride levels or industrial contamination. Never by CWF.

The figure below shows the incidence of the different dental fluorosis categories in New Zealand (data taken from 2009 New Zealand Oral health Survey – see Our Oral Health).

And here are some accurate images of dental fluorosis provided by the Centers for Disease Control and Prevention (CDC).


 (Double click to enlarge)

2: They will then go on to claim that dental fluorosis is disfiguring and destroys the quality of life of the afflicted. Of course this may be true in countries where severe dental fluorosis occurs,* but not in countries like New Zealand where CWF is used.

A recently published study objectively determined the effect of dental fluorosis and dental decay on 5,474 North Carolina schoolchildren and their families – Effects of Enamel Fluorosis and Dental Caries on Quality of Life. It found no statistically significant association between dental fluorosis and oral-health related quality of life scores. Probably what one would expect because the incidence of dental fluorosis was about 28% and most of this was questionable or very mild.

But what about the effect of tooth decay on quality of life? In this case the results were statistically significant showing that dental caries does decrease the quality of life.

Their overall conclusions – a child’s caries experience negatively affects oral health-related quality of life, while fluorosis has little impact.

I think many of us can relate to this from our own childhood experience.

*The mainly poor quality IQ studies anti-fluoridation activists like Paul Connett love to quote were made in areas of high natural fluoride where dental and skeletal fluorosis is endemic. Such studies are not relevant to the issue of CWF, but they do raise in my mind the effect of severe dental fluorosis on quality of life, learning problems and hence possibly IQ measurements (see my article Confirmation blindness on the fluoride-IQ issue). Personally I think any disfiguring oral defect like bad tooth decay or severe dental fluorosis would effect a child’s quality of life and potentially cause learning defects and so drop in IQ.

In countries like NZ such effects on quality of life and learning are much more likely to result from bad dental decay than severe dental fluorosis. If anything, perhaps CWF actually reduces learning problems and potentially prevents decreases in IQ.


Another study invesdtigatign the influence of tooth decay and dental fluorsis on quality of life is described in the paper by 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.

This also concluded that caries and less acceptable appearance showed a negative impact, while mild fluorosis had a positive impact on child and parental perception of oral health-related quality of life.

See also:

New report from the National Fluoridation Information Service – Dental fluorosis – is it more than an aesthetic concern? Its key findings are:

“Evidence does not indicate there are any health risks associated with CWF at the levels of 0.7 to 1.0 mg/L in New Zealand, and no severe dental fluorosis, or skeletal fluorosis, has been found. While fluoride is incorporated into teeth and bones, there is no robust evidence of toxic accumulation of fluoride in other tissues in the body. CWF in New Zealand has been found to not lead to anything more than very mild or mild dental fluorosis for a small “

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Confirmation blindness on the fluoride-IQ issue

Confirmation bias is a human problem – especially in organisations with a political or ideological agenda. Not surprising then to find it rampant among those opposing fluoridation.

It sticks out like the proverbial when opponents of community water fluoridation claim the practice causes a decline in child IQ. That debate is raging at the moment because a recent New Zealand paper (Broadbent et al 2014) showed no effect of fluoridation on IQ. Anti-fluoridationists are doing their best to discredit the study because they hang their argument on a meta review (Choi et al 2012) which they think shows that fluoride in drinking water reduces child IQ.

I will leave analysis of the arguments being used against Broadbent et al’s paper for another article. Here I just want to comment on some of the data revealed by Choi et al’s review. In Quality and selection counts in fluoride research I criticised the poor quality of the articles used in the review. However, one stood out as practically the only exception in that it did consider some confounding factors. This is Xiang et al (2003).

So I am not surprised Paul Connett falls back on this specific paper when he defends those generally poor studies. He said recently:

“In fact, several of the studies did control for these factors.  A good example is Xiang’s work, which has controlled for lead, iodine, arsenic, urban/rural, fluoride from all sources, parent’s education, and socio-economic status (SES).”

Mind you he covers up the fact that Xiang’s work considered fluoride concentrations in drinking water higher than that used in community water fluoridation. Connett’s confirmation bias in action I guess.

Still, Xiang et al 2003 did report reduced IQ for children drinking well-water with higher F concentrations – their data is summarised in the figure below.

IQ-1This may not be relevant to community water fluoridation but neither is it proof that somehow fluoride can directly affect IQ at higher concentrations. The authors did consider (to a limited extent) confounders such as child age, family income, parental education, urinary iodine and (in a later paper) blood lead and found no influence levels. But they seem to have just ignored a very obvious confounding factor – the influence of a physical defect (in this case bad teeth resulting from severe dental fluorosis) on learning.

Dental fluorosis and IQ

The same group extended their study (just 2 villages were involved) to dental and skeletal fluorosis – big problems in this region of China. Here is the data for “defect dental fluorosis” DDF, which is “severe” dental fluorosis and some “moderate” dental fluorosis form the more commonly reported Dean’s classification of dental fluorosis. This is for the same children as the IQ study but reported separately (Xiang et al 2004).


The blood serum levels correlate (R2=0.74) with fluoride in drinking water so the two graphs are consistent with the idea that IQ correlates with defect dental fluorosis. (This can be checked in a later paper – Xiang et al (2011) -which compares serum fluoride concentration with limited data for IQ)

Incidentally, these authors also looked at adult skeletal fluorosis in the same two villages and reported its occurrence (mainly the Grade II mild form) in the high fluoride village (Xiang et al 2005).

These results aren’t surprising – drinking water appears to be the main dietary source of fluoride in these villages so we should expect  severe dental fluorosis to correlate with fluoride concentration in the drinking water.

The blindness of preconception

The authors did not find a relationship of IQ with parental education, family income or serum lead levels which are known factors influencing IQ they did find it with fluoride where no clear direct mechanism is known. I suspect, though, if the authors had bothered considering a model where a physical defect like dental and skeletal fluorosis could lead to decreasing IQ they would have found a relationship. I say this because minor physical anomalies are known to be associated with learning difficulties and emotional illness in children (see Hilsheimer & Kurko 1979). It seems entirely reasonable that a physical anomaly like severe dental fluorosis could lead to learning difficulties in children which could be seen as lower IQ values.

A pity the authors just didn’t think to check for such a relationship – because they had the data. They had a preconceived model of fluoride in drinking water somehow influencing IQ directly.

Even worse, the literature has now become so contaminated with the “fluoride causing IQ decline” story it is extremely difficult to find data where research have directly considered the influence of dental and skeletal fluorosis on IQ and learning difficulties.

Oh well – this whole story is not relevant to New Zealand or the issue of community water fluoridation. We just don’t get severe dental fluorosis here and fluoridation has only been connected to the very mildest forms of dental fluorosis. However, the propaganda against community water fluoridation and the extreme claims made about the evils of fluoride have diverted attention away from what I think is a very important issue. The problems with learning faced by children with physical anomalies – or even just social anomalies common with socially and financially disadvantaged families.

Does water fluoridation improve children’s IQ?

If the real lesson of the Xiang et al’s papers is that a physical anomaly like severe dental fluorsis causes learning difficulties it turns the whole story around. The work is being used inappropriately (because of the high fluoride concentrations) as “evidence” against community water fluoridation. But it may instead actually be used to support community water fluoridation.

After all, tooth decay is very debilitating for children. It is a physical anomaly which definitely causes a lot of physical pain. But it also causes a lot of psychological pain. It is probably an important negative factor in children’s learning and behavioural problems.

I am sure community water fluoridation can make a positive contribution to dental health of our children. But, if this is reflected in reduced learning difficulties, it might also have a positive influence on their IQ.

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Dental fluorosis: badly misrepresented by FANNZ

Ideologically motivated political activists often make extreme claims. Perhaps they feel their claims will never be challenged because they are aimed at their own supporters. Sometimes I think it is because they just don’t get challenged enough by reasonable people.

I have previously shown examples of misrepresentation of science by local anti-fluoride activists (see Fluoride and heart disease – another myth , Anti-fluoridation porkies – Mullinex’s ratsFluoridation: the hip fracture deceptionAnatomy of an anti-fluoridation myth , Fluoridation – the IQ mythActivists peddle chemical misinformation for fluoridation referendaCherry picking fluoridation dataFluoride sensitivity – all in the mind?Fluoridation – topical confusionFluoridation – it does reduce tooth decayFluoridation – are we dumping toxic metals into our water supplies?).

Here’s another blatant example – their misrepresentation of dental fluorosis. In this case it involves knowingly using the wrong photographs while quoting a Ministry of Health (MoH) source on the subject. I have posted below both the official photographs used by the MoH and the photographs they were replaced with in the anti-fluoridation quote. This blatant misrepresentation occurs on the official website of the Fluoride Action Network of NZ (FANNZ).

But first, this is what I wrote about dental fluorosis in my exchange with Paul Connett. The graph illustrates the nature of dental fluorosis observed in New Zealand.

Proponents of fluoridation do acknowledge dental fluorosis in a negative, although minor, aspect of fluoridation.

Opponents of fluoridation will often quote high values of the incidence of fluorosis which ignore the fact that much of it is “questionable” and/or “very mild.” These grades are really only cosmetic and usually can only be detected by a professional. Opponents may also hide the fact that the incidence of fluorosis for children living in fluoridated may often be the same as, or only slightly greater than, the incidence for children living in non-fluoridated areas.

The graphs below shows the situation reported for New Zealand in the 2009 New Zealand Oral health Survey (see Our Oral Health).

Health experts have generally concluded that the apparent rise in the incidence of fluorosis is caused by increases in other forms of fluoride intake, such as from eating toothpaste, and not from fluoridated water.

Ministry of Health version

I am quoting here from the MoH website page – Infant formula and fluoridated water. This is the page FANNZ quoted from

Enamel fluorosis

Tooth enamel fluorosis is one of a range of changes to tooth enamel. Living in an area with fluoridated water can increase the mild white flecks or streaks in the tooth enamel.

The following photos provide examples of normal teeth and the types of mild to moderate diffuse enamel fluorosis that is most commonly associated with water fluoridation. The most recent New Zealand information indicates that about 29 percent of 9-year-old children in Southland who had always received fluoridated water had these changes to the tooth enamel. This level had not changed since several earlier studies undertaken in the 1980s. (Bold my stress)

Normal dental enamel
Mild white spots on teeth – mild diffuse enamel hypoplasia
Mild white spots on teeth – moderate diffuse enamel hypoplasia

Moderate white streaks associated with enamel fluorosis

Other defects on teeth

Severe enamel fluorosis involves brownish defects to the tooth enamel which may also be pitted.

This form of enamel defect is uncommon in New Zealand. The most recent New Zealand information from 9-year-old children in Southland indicates that about 5 percent of children had similar defects.

These defects were just as common in children who had received fluoridated water as non-fluoridated water and the level of these defects had decreased about three fold from about 15 percent of children in the mid-1980s.

FANNZ version

The quote here is from the FANNZ website page Dental health.

Fluoridation causes dental fluorosis

Dental fluorosis is the outward sign that has a child has consumed too much fluoride – it is a bio-marker of over-exposure.  In New Zealand, dental fluorosis statistics are lacking, even though the Ministry of Health acknowledges this condition to be an undisputed side effect of fluoridation.

Very mild fluorosis
 Moderate fluorosis
Severe fluorosis
Severe fluorosis

According to the Ministry of Health*, “The most recent New Zealand information indicates that about 29 percent of 9-year-old children in Southland who had always received fluoridated water had these changes to the tooth enamel. This level had not changed since several earlier studies undertaken in the 1980s.” (Bold my stress).

* Note this link goes only to the MoH front page – not the page from which the quote was taken and which contains the photographs. Now, I wonder why the link isn’t direct?

So a blatant example of misrepresentation. Conscious misrepresentation at that because it involved substitution of the official photos by others. The intention was clearly to make the MoH seem to state that fluoridation causes severe fluorosis when the MoH clearly did not state that.

I really wonder how these people sleep straight in their bed at night.

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Fluoride debate Part 1: Perrott

This is Ken Perrott’s response to Paul Connett’s first article – Fluoride debate Part 1: Connett.

Paul’s first article appears to be a general overview and not detailed consideration of the ten points he makes. I will be similarly brief in my response to each point. Paul may wish to go deeper into specific issues in later contributions and I will respond in more detail then.

 The medical argument

Paul’s first 3 arguments rely on defining fluoridation as a medical treatment. This is a common anti-fluoridationist approach. I have no wish to argue about that definition as it is really just a matter of semantics. You could use a weak definition of “medicine” which can include practically anything in your diet the body uses and may tolerate over a wide range of intake without harm. Or a tighter definition implying a drug with some sort of marked effect in the body and requiring relatively careful control of intake. But whatever definition is used should be openly declared and applied consistently.

Opponents of fluoridation usually apply their definitions of “medicine” inconsistently and the argument becomes a classic bait and switch tactic. It uses a weak definition of “medicine” to capture fluoride and then switches to a tight definition to argue that use of fluoride requires rigid controls. This presents them with a number of problems because a weak definition of “medicine” must also include “natural” as well as “artificial” fluoride at natural levels in water a food. (A weak definition may also include many other elements – perhaps even water itself). There is no such thing as a “fluoride-free” water supply. If we exclude natural levels of fluoride (and most other elements) from our definition of “medicine” then why should we treat levels for artificially fluoridated water any differently?

Connett’s point 1: Why should we not be concerned about controlling the dose of natural levels of fluoride (or many of the other elements we consume) while only be concerned about the fluoride added as a “top up?” The are no differences between the “artificial” and “natural” fluoride anions in drinking water. In reality most elements like this have a sufficiently wide range of concentrations and intakes for efficacy that it is just ridiculous to treat them like powerful drugs which need accurate dosage.

Connett’s point 2: Similarly why make charges of indiscriminate intake only for artificially added F and not for natural levels of F and other elements? The small number of people, if any, who may have problems with fluoridation levels of F will also have the same problems with natural levels of F. Such people, if they real exist, will need individual responses to either natural or artificial levels of F and possibly other elements. These people will need individual responses whether their water supply is artificially fluoridated or not.

Connett’s point 3: Why demand “informed consent” for situations where natural levels of fluoride have been “topped up” and not require it for natural levels of fluoride – which in some situations may actually be higher than for fluoridated water supplies.

 Is fluoride a nutrient?

 Connett’s point 4: This also reduces to semantics – how should “nutrient” be defined? Paul restricts his definition only to elements involved in “biochemical processes” – a definition confidently excluding the role of F in bioapatites – bones and teeth. Yet bones and teeth are important to organisms – so the strengthening of bioapatites, and the reduction of their solubility, by incorporation of fluoride is important.

Perhaps we can agree that F is at least a beneficial element, even if we can’t reach agreement on the use of terms like “nutrient” and “essential.”

 Biochemical processes and fluoride

 Connet’s point 5: It is easy to cite literature references showing negative effects of fluoride but we should not ignore the conditions used. Most such studies refer to much higher concentrations than used in water fluoridation and this is also true for the review by Barbier et al, 2010 Connett cites.

Let’s not forget that community water fluoridation describes “topping up” fluoride concentrations to about 0.7 ppm F. Yet reviews of negative effects on biochemical process will quote studies which have used 50 ppm, 100 ppm or even greater concentration of F in drinking water. Opponents of fluoridation often seem completely oblivious of these huge differences in concentration when they present a long list of claims about the ill effects of fluoridation.

Another confusion readers often have with such reviews is the use of different units. The sensible reader must often apply a few conversion factors when checking the fluoride concentrations used in the reviewed studies. 1 mM = 19 ppm (or mg/L) for fluoride.

It is possible to find similar evidence of harmful effects of essential elements when present in high concentrations. Selenium is an example of such an essential element. This graph illustrates the situation for fluoride and is common to many elements.

Diagram from Ethan Seigel’s blog Starts with a Bang (see Weekend Diversion: Fluoridated Water: Science, Scams and Society).

I am not denying the usefulness of these studies of negative effects of fluoride. Researchers and policy makers should continuously assess research findings for their relevance to the fluoridation issue and guidelines used in regulations. But this assessment must be critical and intelligent – not simply a search to confirm biases.

Health authorities should not be swayed by populist naive interpretations of research.

 Naturalistic fallacies

 Connett’s point 6: Sure, organisms evolve to fit the parameters of their environment. But to say “it is more likely that nature knows more about what the baby needs  than a bunch of dentists  from Chicago or public health officials in Washington, DC” is really not a good way of deciding this issue. Do we really want to argue that the situations in which marine animals evolved are the best to aim for in a society which has undergone so much cultural and intellectual evolution? Are we to reject the idea that society should task experts to consider possible approaches for our future by the argument that “nature knows best” and give up all rights for humanity to improve its condition? Do we really think that the environment that ancestral species experienced millions of years ago are necessarily the best for us today?

Modern humans live in environments offering a range of natural dietary fluoride intakes. We know that very low or very high intakes present problems for our bones and teeth. We should not avoid the problems this presents by saying “nature knows best.”

The very low levels of F in breast milk may have more to do the with inorganic role of F in animal bodies than any wisdom that “nature” has.


Proponents of fluoridation do acknowledge dental fluorosis in a negative, although minor, aspect of fluoridation.

 Connett’s point 7: Opponents of fluoridation will often quote high values of the incidence of fluorosis which ignore the fact that much of it is “questionable” and/or “very mild.” These grades are really only cosmetic and usually can only be detected by a professional. Opponents may also hide the fact that the incidence of fluorosis for children living in fluoridated may often be the same as, or only slightly greater than, the incidence for children living in non-fluoridated areas.

The graphs below shows the situation reported for New Zealand in the 2009 New Zealand Oral health Survey (see Our Oral Health).


See Wikipedia for a  brief description of Dean’s Fluorosis Index.

Health experts have generally concluded that the apparent rise in the incidence of fluorosis is caused by increases in other forms of fluoride intake, such as from eating toothpaste, and not from fluoridated water.

Fluorosis could well have been a normal feature of teeth and bones for a very long time. Remember many areas of the world are high in natural forms of fluoride and the body does not seem to have a process for fine regulation of blood and plasma fluoride concentrations. Perhaps we should consider very mild and questionable levels of fluoride as cosmetically perfectly acceptable. Considering the natural variation in fluoride intakes some people might argue that “nature knows best.”

Nature of fluoridating chemicals

Connett’s point 8: Anti-fluoridationists make wild claims about fluoridation chemicals. “They are industrial waste products, loaded with heavy metals and fluorosilicates are toxic and/or untested for toxicity!”

Claims of contamination with toxic elements are easily, and often, made but are never justified with any evidence. So lets look at the reality.

By-products that are used are not waste products – and surely we should aim for the efficient use of natural resources. The purchaser of any product will sensibly make sure it is suitable for their requirements – and these are rigidly defined for water treatment chemicals.

Suppliers are required to provide certificates of analysis and maximum values for contaminants in chemicals used for water treatment. Those regulations are determined from the maximum concentrations of contaminants allowed in the finished water for human consumption. Safety factors are also involved as well as allowance for contribution from other sources.

The table below contains analytical data for contaminants taken from certificate of analysis for the last batch of fluorosilicic acid used in the Hamilton, New Zealand, water treatment plant (see FSA column). I compare the data with the maximum allowed impurity levels of fluorosilicic acid defined in the regulations (Impurity limits column) and with an example of the contaminant concentrations in finished water (Drinking water column).

Toxic Element Impurity limits* FSA** Drinking water**
Sb (ppm) 40 <0.09
As (ppm) 132 0.4 <0.002
Cd (ppm) 40 0.11 <0.001
Cr (ppm) 660 0.8 <0.001
Hg (ppm) 26 < 0.05 <0.001
Ni (ppm) 264 < 1 <0.001
Pb (ppm) 132 0.8 <0.001

* Maximum acceptable contamination.
** From Certificate of Analysis
***For Gear Island Treatment Plant, Greater Wellington region.

There are several points to make.

1: These concentrations are extremely low, meaning that the final concentrations in the finished water are insignificant.

2: For comparison, column one provides the maximum permissible concentrations allowed for fluorosilicic acid used for water treatment ( NZ Water and Wastes Association Standard for “Water Treatment Grade” fluoride, 1997. ).

3: The NSF,which regularly monitors contaminants in water treatment chemicals says in this year’s NSF Fact sheet on fluoridation: 

“In summary, the majority of fluoridation products as a class, based on NSF test results, do not contribute measurable amounts of arsenic, lead, other heavy metals, radionuclides, to the drinking water.”

And the NZ Waste Water Association’s report says:

“Commercially available hydrofluorosilicic acid, sodium fluoride and sodium silicofluoride are not known to contribute significant quantities of contaminants that adversely affect the potability of drinking water.”

Brown, Cornwall & McPhee, 2004 say in their review paper, Trace contaminants in water treatment chemicals: sources and fate:

“ Coagulant chemicals are the main source of trace metal contamination in water treatment.”

4: Some people seem to think that simply quoting concentration  of contaminant species is proof of contamination – irrespective of the actual magnitudes. I have seen speakers flash up a slide listing heavy metal contents without bringing notice to the actual concentrations. That is silly. Our environment, no matter how “natural,”  will always contain some amount of contaminant chemicals – it is the actual amount that is important – not that it can be, or is, measured.

Arsenic in community water supplies

Paul raises the problem of arsenic and this provides an opportunity to put the contaminants in fluorosilicic acid into context. The table shows that As levels are typically very low in fluorosilicic acid used for water treatment (0.4 ppm As). In my article Hamilton – the water is the problem, not the fluoride! “ I show that in the local Hamilton, New Zealand, situation the source water from the Waikato River is the major source of As in the finished water – several orders of magnitude greater than for than from treatment chemicals.

Anti-fluoridationists often rely on a recent paper by  Hirzy et al. (2013) for their claims about As in fluoroslicic acid and it’s effect on the incidence of cancer. Hirzy has since acknowledged errors in his calculations and described himself as embarrassed by them and his mistake about cancers. A petition to the EPA which used his data to  argue against use of fluorosilicic acid in water treatment was rejected partly because of these errors (see Anti-fluoridation study flawed – petition rejected).

Fluoridation data around the world

Connett’s point 9: Yes, a few countries do not fluoridate their water community supplies for political reasons, but decisions against water fluoridation can depend on a range of factors including size and centrality of water treatment plants, widespread use of bottled water, naturally sufficient water fluoride concentrations, etc.

Paul refers to a plot used by Cheng et al (2007) – which is similar to this one:

This and similar plots are much beloved but anti-fluoridation propagandists. But while the plots do show improvements in oral health for countries irrespective of fluoridation they say nothing about the effect of fluoride. Simple comparison of countries obscures all sorts of effects such as differences in culture, history, social and political policies, etc. Such plots are also influenced by changes and differences in dental treatment and measurement techniques.

However, there are some within country data within the WHO data set Cheng et al used which can give a better idea of the beneficial effects of fluoridation. This plot shows the results for the WHO data for Ireland. A clear sign that fluoridation has played a beneficial role.


Political and scientific arenas.

Connett’s point 10: The debates around fluoridation involve both scientific and political issues. Inevitably this leads to the separate issues being mixed. I find, for example, that attempts to discuss the ethical aspects always get diverted into differences in understanding of the science. For example the paper Ethics of Artificial Water Fluoridation in Australia by Niyi Awofeso is meant to be a description of the ethical issues. However, it assumes mistaken ideas about the science – that fluorosilicate species are present in fluoridated drinking water. Without the correct science it is so easy to end up with invalid ethics.

Appeal to authority is also a problem. Connett does this, for example, in his reference to Prof. James Summer, Nobel prize winner. Similarly wild claims are often made about Nobel prize winners and “top scientists” opposing community water fluoridation  – these are really not valid arguments.

I feel that opponents of fluoridation commonly rely more on confirmation bias than critical and objective assessment when referring to the scientific literature.

There is also a reliance on conspiracy theories and poisoning of the well. We have seen personal attacks on scientists and health authorities in New Zealand when they have spoken up to defend the science. Childish name calling, accusations of being paid to make incorrect claims, charges of being “shills” for industry, etc. This is simply “playing the man and not the ball” and makes good faith discussion of the science impossible.

This even gets into peer-reviewed scientific literature. The authors of the paper Connett refers to, Cheng et al 2007, do this when they accused one side, that of health authorities, of “questionable objectivity.” Pots and kettles?

All of these problems are probably inevitable for an issue like this where political and ideological interests operate. But they are an anathema to proper scientific consideration.

Professor Gluckman, the NZ Prime Ministers Chief advisor on Science commented that fluoridation controversies were an example of science being a proxy for values/political issues. This leads to misrepresentation of the science, cherry picking of data, and relying on confirmation bias and google for literature searches. Ideology and values are the motivating factors but a caricature of science is used in the debate.

Good faith discussion of the scientific issue around fluoridation requires much more objectivity than  is usually demonstrated by the opponents of fluoridation.

Anyone wanting to follow the debate and/or check back over previous articles in the debate can find the list of articles at Fluoride Debate.

See also:

Similar articles on fluoridation
Making sense of fluoride Facebook page

Fluoride debate Part 1: Connett

Ken Perrott’s response to this article is at Fluoride debate Part 1: Perrott

Connett versus Perrott Internet Debate on Fluoridation.

This is part 1 of a five-part series of internet exchanges on the fluoridation debate between Paul Connett (USA) and Ken Perrott (NZ).

1. Fluoridation is a poor medical practice.

2. The evidence that swallowing fluoride reduces tooth decay is very weak. Better alternatives for fighting tooth decay

3. The large database that indicates that fluoride can impact the brain of animals and humans.

4. Other health concerns and the lack of an adequate margin of safety to protect everyone drinking fluoridated water.

5. Key moments since 1990 that should have forced an end to fluoridation.

Paul Connett is co-author of The Case Against Fluoride (Chelsea Green, 2010) and executive director of the Fluoride Action Network ( www.FluorideALERT.org ) Paul’s cv and list of publications is attached.

Part 1. Fluoridation is a poor medical practice


Introduction. Using the public water supply to deliver medical treatment is a very unusual practice. In fact it has only been done only once before and that was a short trial in which iodine was added to the drinking water to help fight hypothyroidism. However this was quickly abandoned when it was found that some people were being over-exposed to iodine. Since then fluoridation has been the only example. The reasons for not using the water to deliver medical treatment are fairly obvious.

1) It is impossible to control the dose people get. Once a chemical is added to the water to treat people (as opposed to treating the water to make it safe or palatable to drink) it is impossible to control the dose people get. People drink very different amounts of water. In short, engineers at the water works can control the concentration added to the water (mg/liter) but no one can control the total dose (mg/day) individuals receive.

2) It is totally indiscriminate. It goes to everyone regardless of age, regardless of health or nutritional status. Of particular concern is that it goes to people with poor kidney function who are unable to clear the fluoride from their bodies via the kidneys as effectively as others. It thus accumulates in their bones more rapidly. It also goes to people with low or borderline iodine intake, which makes them more vulnerable to fluoride’s impact on the thyroid gland. In general, according to studies done in India, people with poor diet (low protein, low calcium and low vitamin intake) are more vulnerable to fluoride’s toxic effects.

3) It violates the individual’s right to informed consent to medical treatment. This is a very important medical ethic which is fully described on the website of the American Medical Association (www.AMA.org). It is very surprising that so many medical doctors standby while the community does to everyone what they are not allowed to do to a single patient.

The above arguments would apply to any medicine added to the drinking water but there are other aspects to the fluoride ion, which makes it particularly unsuitable for addition to the drinking water.

 4) Fluoride is NOT a nutrient. There is not one single biochemical process in the body that has been shown to require fluoride for normal function (we will see later that fluoride’s predominant action on teeth is topical not systemic). However,

5) There are many biochemical processes that are harmed by fluoride (given a sufficient dose). These include the inhibition of many enzymes. This is the reason that some of the earliest opponents of fluoridation were biochemists like Professor James Sumner from Cornell University, who won the Nobel Prize for his work on enzyme chemistry. More recently fluoride has been shown to activate G-proteins and interfere with the cell’s messaging systems. It can also cause oxidative stress. An excellent summary of fluoride’s biochemistry can be found in the article “Molecular Mechanisms of Fluoride Toxicity” by Barbier et al, 2010.

6) The levels of fluoride in mothers’ milk is extremely low. This level, on average for a woman in a non-fluoridated community, is 0.004 ppm (NRC, 2006, p.40). This means that a bottle-fed baby in a fluoridated community (at 1 ppm) will get about 250 times more fluoride than a breast fed baby in a non-fluoridated community. Bearing in mind the fact that life emerged from the sea where the average level of fluoride is about 1.4 ppm, and thus there was no impediment for nature to use fluoride when developing human metabolism, her verdict appears to be that the baby a) does not need fluoride and b) that it may be harmed by fluoride. In my view, it is more likely that nature knows more about what the baby needs than a bunch of dentists from Chicago or public health officials in Washington, DC.

7) Fluoridation has always been a trade-off between lowered tooth decay and dental fluorosis but a key question was never satisfactorily answered. When the fluoridation trials began in 1945 it was known that the trade off was that approximately 10% of the children would develop dental fluorosis in its mildest form (this was a mottling or discoloration of the tooth enamel). While the mechanism whereby fluoride caused this effect was not known it was known to be a systemic effect. In other words it was caused by fluoride interfering with biochemistry during the development of the tooth cells. The question that was not answered before the US Public Health Service endorsed fluoridation in 1950, was: “What other tissues in the body may be interfered with at the same time that fluoride was interfering with the laying down of the tooth enamel?” Were the baby’s bone cells also being impacted? How about brain cells? How about the cells of the glands in the endocrine system? Sadly, very little has been done in fluoridated countries to answer these questions since fluoridated was started. However, proponents do acknowledge that the appearance of dental fluorosis means that a child was over-exposed to fluoride before the permanent teeth have erupted. Meanwhile, in 2010 the CDC reported that 41% of American children aged 12-15 have dental fluorosis, with 8.6% having the mild form (with up to 50% of the enamel impacted) and 3.6% with moderate or severe dental fluorosis (100% of the enamel impacted).  In later arguments in this debate I will be presenting evidence that fluoride is capable of harming other developing tissues.

 8) The fluoridating chemicals used to fluoridate the water supply are not the pharmaceutical grade chemicals as used in dental products. Most of the chemicals used are obtained from the phosphate fertilizer industry’s wet scrubbing systems (see Chapter 3, The Case Against Fluoride). One of the problems with this source is that it is contaminated with a number of other toxic chemicals including arsenic. Arsenic is a known human carcinogen and as such for the US Environmental Protection Agency (EPA) there is no safe level. The EPA’s maximum contaminant level goal (MCLG) for drinking water is thus set at zero. Proponents will argue that after the dilution of these bulk chemicals by about 180,000 to 1, the level of arsenic is negligible. However it is not zero and thus this practice will inevitably increase cancer rates in the population. As there are other delivery systems which are cost-effective and do not involve the use of these industrial grade chemicals, increasing the cancer rate even by a small amount is not acceptable.

9) Worldwide fluoridation is not a common practice. Proponents will often imply that fluoridating the drinking water is a common practice. It is not. Most countries do not fluoridate their water. 97% of the European population is not forced to drink fluoridated water. Four European countries have salt fluoridation (Germany, France, Switzerland and Austria), but the majority of European countries have neither fluoridated water nor fluoridated salt, yet according to World Health Organization (WHO) data available online (measured as DMFT in 12-year-olds) tooth decay rates in 12-year-olds have declined as rapidly over the period 1960 to the present in non-fluoridated countries as fluoridated ones and there is little difference in tooth decay rates today (see Cheng et al, 2007). The reasons that European spokespersons have given for not fluoridating their water are usually twofold: a) they do not want to force fluoride on people who don’t want it and b) there are still many unresolved health issues (see a list of statements by country at http://fluoridealert.org/studies/caries01 ).

10) Typically fluoridation is promoted via endorsements not via sound science. When the US Public Health Service (PHS) endorsed fluoridation in 1950, before a single trial had been completed and before any meaningful health studies had been published, it clearly was not the result of solid scientific research. However the PHS endorsement set off a flood of endorsements from other health agencies and professional bodies (see Chapters 9 and 10 in The Case Against Fluoride). Most of these came between 1950 and 1952. These endorsements were not scientific but simply reflected a subservience of public policy to the US government.  However, promoters of fluoridation for over 60 years have used these endorsements very effectively with the general public as if they were coming from scientific bodies reflecting thorough and comprehensive scientific research. Very seldom is this the case.  Hopefully, in these exchanges with Ken Perrott we will both focus on what the primary science actually says and not what some “authority” has to say about the matter.


Barbier et al., 2010. Molecular Mechanisms of Fluoride Toxicity. Chem Biol Interact. 188(2):319-33 http://www.ncbi.nlm.nih.gov/pubmed/20650267

CDC, 2010.  Beltrán-Aguilar,Prevalence and Severity of Dental Fluorosis in the United States http://www.cdc.gov/nchs/data/databriefs/db53.htm

Cheng et al. 2007.  Adding fluoride to water supplies. BMJ 335:699


Connett, P., Beck, J and Micklem HS. The Case Against Fluoride. Chelsea Green, White River Junction, Vermont,  2010.

NRC, 2006. Fluoride in Drinking Water: A Scientific Review of EPA’s Standards (2006) http://www.nap.edu/catalog.php?record_id=11571

Anyone wanting to follow the debate and/or check back over previous articles in the debate can find the list of articles at Fluoride Debate.

See also:

Similar articles on fluoridation
Making sense of fluoride Facebook page