Tag Archives: Water supply

Fluoride sensitivity – all in the mind?

anecI have had a few letters from anti-fluoridation activists lately assuring me they have symptoms of fluoride sensitivity, or hypersensitivity. The local campaigners have even produced a video of one of their members discussing his own symptoms (see Gus Hastie on fluoride hypersensitivity).

Now, I never want to be in the position of ignoring people’s symptoms, but really – self-diagnosis is always dangerous. What they attribute to fluoride sensitivity may turn out to be something far more serious. People should always check out their health problems with a qualified professional.

Like all claims based on anecdotal evidence fluoride sensitivity and hypersensitivity could be nothing more than an attempt to produce damning evidence against fluoridation – without actually having any evidence. I have had an upset stomach and headaches for a few months – ever since fluoridation was stopped! I would be a fool to just assume this was due to lack of fluoride, wouldn’t I?

Perhaps health authorities could have taken advantage of the Hamilton City Council’s decision to stop fluoridation to carry out a social experiment – to check if people’s claimed symptoms of fluoride sensitivity actually coincided with fluoridation, or its absence.

The Finnish experiment

Well, I found out recently the experiment has already been done. Fluoridation was stopped in the Finnish town of Kuopio at the end of 1992. (see Lamberg et al. Symptoms experienced during periods of actual and supposed water fluoridation.)

The public had been well informed of the change, but what they did not know is that fluoridation was actually stopped a month earlier than planned. The public were surveyed about their symptoms using questionnaires in the month of November (when water was till fluoridated and citizens believed it was), December (when water was no longer fluoridated but citizens believed it was) and March (when the water was no longer fluoridated and citizens knew that it wasn’t).

The graph below shows the percentage of respondents to the surveys reporting symptoms at the three times. Data is the average of the 5 most often reported symptoms (joint and muscular pain, headaches, skin itching and skin dryness).


These results do suggest that the prevalence of symptoms is more connected with the psychological and not the actual physical effects of exposure to fluoridated water.

Not surprisingly the mean number of symptoms reported was lower among those who supported fluoridation than among those who opposed it. A similar relationship occurred with people reporting that they could taste the fluoride in the water – both in November (when the water was fluoridated) and in December (when it wasn’t). The numbers reporting the taste dropped to nearly zero in March when they knew fluoridation had stopped.

One should always be suspicious of anecdotal evidence – no matter how passionately advocates of a particular cause use it.

Thanks to Ian at Making Sense of Fluoride for drawing my attention to this research.

See also:

New Zealanders for Fluoridation

Other articles on fluoridation

Water treatment chemicals – why pick on fluoride?

Almost every person arguing against fluoridation makes the claim that the fluoridation chemicals used are toxic and corrosive. They also claim they contain toxic heavy metals which contaminate our drinking water.

But this is simply fear mongering – relying on chemophobia, because most concentrated chemicals are toxic and often corrosive. And such claims could also be made of the other chemicals used in drinking water treatment. But the anti-fluoridation activists don’t – why pick on fluoride?

Actually, the fluoridation chemicals used are not the main source of possible toxic contamination of our water supply – yet these other chemicals are ignored by anti-fluoridationists. When we consider fluoridation in the context of the water treatment process and analytical data for the chemicals used we find the anti-fluoridation arguments baseless.

The water treatment process

The figure below provides a context for considering the chemicals used in public drinking water treatment and the stages where they are added. It’s a diagrammatic outline of Hamilton City’s water treatment plant (it still include fluoride addition – I guess they are holding off changing the diagram until after the referendum). You can see further details in  A Guide to Hamilton’s Water Supply : River to the Tap.


This is only a typical example. Different treatment plants use different chemicals depending on the plant size, the water source and the availability and cost of chemicals. I consider just a few  representative chemicals below with information on their safety, corrosive nature and chemical contaminants.

Information sources used

The safety information is from safety data sheets produced by the manufacturer or seller. Many of these are in the Orica Chemicals SDS database.

Information on contaminating heavy elements and other contaminants is from Brown et al. (2004). Trace contaminants in water treatment chemicals: sources and fate, American Water Works Association, Journal. 96: 12, 111-125.

Extra information on contaminants in fluoridation chemicals is from the NSF Fact Sheet on Fluoridation Products (2013) and the  NZ Water and Wastes Association Standard for “Water Treatment Grade” fluoride, 1997.

miscellaneous chemicals

A number of chemicals like lime, soda ash, carbon dioxide, potassium permanganate and other acids and alkalis are used, sometimes or commonly. This could be for initial treatment to remove biological matter and in pH control and sedimentation. Adjustment of pH is also necessary to prevent corrosion of pipes.

Coagulation and sedimentation

Aluminium sulphate or alum, is a common coagulant.  Its Safety Data sheet does not classify it as dangerous for transport but does classify it as hazardous – subclasses 6.1 – 9.3.

Under disposal methods it says:  “Refer to local government authority for disposal recommendations. Dispose of contents/container in accordance with local/regional/national/international regulations.”

Possible contaminants (Brown, Cornwall & McPhee, 2004): Coagulant chemicals are the main source of trace metal contamination in water treatment.” However, these together with contaminant trace metals in the source water are generally transferred to the residue stream during sedimentation and filtering so there is little transfer to the finished water.

Soda ash is used for pH control. Its Safety sheet does not classify it as dangerous for transport but does classify it as hazardous – subclasses 6.1 – 6.4.

Under disposal methods it says:  Refer to local government authority for disposal recommendations. Dispose of material through a licensed waste contractor.”


Chlorine is commonly used. Its Safety data Sheet classifies it as a class S7 dangerous poison which “must be stored, maintained and used in accordance with the relevant regulations.”

Under disposal methods it says: “Refer to Waste Management Authority. Dispose of material through a licensed waste contractor. Contact supplier for advice.”

Possible contaminants (Brown, Cornwall & McPhee, 2004)Carbon tetrachloride (used to clean storage containers)


Fluorosilicic acid is the most common fluoridating chemical. Its Safety data sheet describes it as a class S7 dangerous poison.

Under disposal methods it says: “Refer to Waste Management Authority. Dispose of  material through a licensed waste contractor. Decontamination and destruction of containers should be considered.”

Possible contaminants (Brown, Cornwall & McPhee, 2004): Arsenic was the only trace metal contaminant found above detection levels in just a few samples, and then in small amounts.

This year’s NSF Fact sheet on fluoridation  also confirmed this picture. saying:

“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.”

(NSF International is a global independent public health and environmental organization that provides standards development, product certification, testing, auditing, education and risk management services for public health and the environment.)

The  NZ Water and Wastes Association Standard for “Water Treatment Grade” fluoride, 1997 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.”

I discussed the question of the level of toxic metal contamination in fluorosilicic acid in my article Fluoridation – are we dumping toxic metals into our water supplies? This mentions the requirement of suppliers to provide certificates of analysis to make sure their product is suitable for water treatment. A number of certificates of analysis for fluorosilicic acid are available on line which confirm the very low levels of contaminant heavy metals. For typical fluorosilicic acid certificates see Incitec 09, Incitec 08 and Hamilton City.

The table below also shows typical analytical results for fluorosilicic acid.

General conclusions

According to Brown, Cornwall & McPhee, 2004:

“Except for occasional contamination from bromate in sodium hypochlorite and carbon tetrachloride in chlorine., drinking water treatment chemicals were not typically shown to be significant sources of most contaminants of regulatory concern (including lead, copper, arsenic, and other trace metals) in finished water. This was becausc of the low occurrence of contaminants in drinking water treatment chemicals and the partitioning of most contaminants into the residuals streams when they were present in raw water or treatment chemicals.”

The recovery of sediment and sludge after coagulant treatment removes most of the toxic contaminants coming from the source water and the treatment chemicals (mainly the coagulant). No significant contamination comes from the chlorine or fluoridation chemicals added towards the end of the treatment. The table below confirms this.

The real amounts of contaminant toxic metals in fluorsilicic acid are far lower than the amounts allowed by the water treatment standards.  The regulated impurity levels are calculated from the maximum acceptable values of an impurity (taken from the Drinking Water Standards for New Zealand 1995) and the dilution when the material is added to drinking water to achieve a concentration of 0.7 – 1.0 ppm F. It incorporates a safety factor of 10. The data for the fluorosilicic acid is from my research but confirms figures in certificates of analysis. And the last column shows that there is no detectable contamination of toxic heavy metals in the final drinking water

Final drinking water quality

Toxic Element Impurity limits FSA Drinking water
As (ppm) 132 2 <0.002
Cd (ppm) 40 <1 <0.001
Cr (ppm) 660 5 <0.001
Hg (ppm) 26 < 0.1 <0.001
Ni (ppm) 264 < 1 <0.001
Pb (ppm) 132 0.3 <0.001
Cu (ppm)   < 0.2 <0.013
Zn (ppm)   2.1 <0.013

Impurity limits – calculated from maximum acceptable values in drinking water and a safety factor of 10. See NZ Water and Wastes Association Standard for “Water Treatment Grade” fluoride, 1997.
FSA – typical analytical data for fluorosilicic acid used in fluoridating New Zealand water supplies.
Drinking water – actual levels of toxic elements in your drinking water (Wellington region) – all below the limit of detection of the standard analytical procedure.

The “proof of the pudding is in the drinking” – one could say. The antifluoridation activists have been simply scare mongering with their claims that fluoridation amounts to putting toxic elements into our drinking water. The fluoridation chemicals are not even the main possible source of such contaminants.

See also
Fluoride in our water facebook page
Debunking the anti-fluoridation myths
From Australia – debunking anti-fluoridation arguments

For other articles on fluoridation see Fluoridation page.

Fluoridation – it does reduce tooth decay

In the current fluoridation debate anti-fluoridation activists will often claim fluoridation of public water supplies actually doesn’t reduce tooth decay. This conflicts directly with the advice of our health authorities – so what is the truth?

The claim

Again I will directly consider the claim of the Fluoridation Action Network of NZ (FAANZ). It’s summarised in the first objection to fluoridation (1. New science proves there is no benefit from swallowing fluoride ):

There are numerous modern studies to show that there is no difference in dental decay rates between fluoridated and non-fluoridated areas. The most recent, large-scale one was conducted in Australia (Armfield & Spencer, 2004 Community Dental Oral Epidemiology. 32:283-96).

When you observe the statistics of the world they clearly show tooth decay has declined in both fluoridated and non-fluoridated areas alike. This is a trend that is demonstrated when viewing the statistics across the States in America and in the smaller counties. See the charts and findings by Dr. Bill Osmunson in the above video by Professional Perspectives.

In New Zealand there have been two recent studies that showed there was no difference in dental decay for permanent teeth. One was the Southland Study in 2005 and the other was the Auckland study in 2008. These, among many other studies, have proven water fluoridation to be ineffective.

(This objection goes on to discuss topical vs systemic intake of F which I won’t discuss here)

But, health authorities in New Zealand disagree – and they have the data to support their case. So how credible is the FANNZ claim?

The citation.

Again, another citation, unlinked, so I had to go to the trouble of hunting it down to read what it actually does say – which turns out to be the exact opposite of FANNZ claim! Same problems I met when I looked at their claim about toxic elements in fluoridating agents (see ).

The Australian study (Armfield& Spencer, 2004 Community Dental Oral Epidemiology. 32:283-96) investigated concerns about the high use of bottled and rainwater. Several social, economic and dietary factors were considered but the major significant effect was that of fluoride. Children consuming tank and bottled water had much higher carries than those consuming water from fluoridated public water supplies. This was found for deciduous teeth, but not for permanent teeth and the authors speculated on the dietary and other reasons for this. They concluded:

“This study demonstrates the continued community effectiveness of water fluoridation and provides support for the extension of this important oral health intervention to populations currently without access to fluoridated water.”

The authors considered lack of fluoride is an important problem for tank water use saying:

“Efforts could be directed at either reducing the use of tank water for domestic drinking water consumption or further encouraging the appropriate use of fluoride to compensate for the lack of fluoride in the drinking water.”

About bottled water they say:

“consumers currently have little choice in Australia and the imminent introduction of fluoride-containing bottled water does not look likely.”


“It is also time that bottled water manufacturers in Australia began marketing fluoridated water. In the US more than 20 companies produce water with optimum fluoride concentrations.”

They finish their paper with this:

“Bottled water is promoted as a healthy, chemical-free alternative. There is a need for bottled water manufacturers to take a stand on the issue of the benefits of appropriately fluoridated water and provide consumers with choice.”

So another example of FANNZ using a citation inappropriately – to support a claim the exact opposite to the study’s results.

The New Zealand data.

The Ministry of Health (MOH) keeps records on the oral health of New Zealand children – and anyone can download that data from their website. There is data for age 5 and year 8 children over the time period 1990 to 2011. I’ll have a detailed look at the data for 2002 – 2011 (earlier data doesn’t include the ethnic breakdown which is very relevant). But first a few comments about the way many of the anti-fluoridation activists are cherry picking this and similar data to support their arguments.

Recently I received two specific claims made about this data:

  1. The oral health of Christchurch people is better than for New Zeland as a whole. The don’t have access to fluoridated water therefore this proves fluoridation doesn’t work.
  2. In 2011 the mean number of decayed, missing and filled teeth in 5 year old Waikato children was greater for children drinking fluoridated water than for those drinking unfluoridated water. This proves fluoridation doesn’t work.

In both claims data was carefully selected to “prove” fluoridation doesn’t work. One can’t directly compare Christchurch data with that for the whole of New Zealand as that ignores the influence of ethnic, social and other factors. And selection of one small piece (Waikato in 2011) of the total picture cannot give you any idea of that total picture. The data includes all sorts of variation over time and region and these cherry-pickers are make cynical use of this.

I have summarised the MOH data in this table as the changes for the percentage of carries free teeth, and mdmf – the mean number decayed, missing and filled teeth per child per year. The data are for 2 age groups and are averages, over the period 2002 to 2011, of annual data . The totals and the separate data for Maori give some idea of differences which are probably largely a result of the well established social and economic disadvantage of Maori.

Effect of fluoridation of % carries free and mdmf

Year 8

Total Maori
Carries free (%) 8.86 10.42
MDMF* -0.48 -0.81

5 years

Total Maori
Carries free (%) 8.05 12.46
MDMF* -0.63 -1.38

*MDMF = Mean decayed, missing and filled teeth

I think that shows fluoridation is associated with a clear increase in numbers of carries free teeth, and a clear decrease in the mean decayed, missing and filled teeth.

So much for FANN’s claim “that there is no difference in dental decay rates between fluoridated and non-fluoridated areas.”

The figures below show the data graphically to enable readers to get a better understanding.

First a comparison of average annual % carries free teeth and mdmf in the period 2002 -2011 for the two age groups.

% carries free


Mean decayed, missing and filled teeth


Plots of the data below give and idea of variability and trends. They also show the influence of social and economic deprivation is long-term.

% carries free




A comment in trends

Some anti-fluoridationists are making an issue of the apparent improvement in oral health for people consuming unfluoridated as well as fluoridated water. For example, the claim above asserts:

“When you observe the statistics of the world they clearly show tooth decay has declined in both fluoridated and non-fluoridated areas alike.”

Perhaps they think that this somehow covers up the fact that despite the trends oral health it is still better for the fluoridated groups.

Mind you, another reason is that many of the statistics they refer to are presented only graphically. For example this figure from Fluoride Alert (an anti-fluoridation group) actually does not correspond to the data it refers to.


It seems the figure was constructed using only 2 data points of each line – 1 very old and 1 recent. This means that all sorts of factors, (such as changes in criteria and attitude of dentists towards saving teeth) could be involved – quite apart from fluoridation.

The data I have plotted above the New Zealand in the period 2002 – 2011 does not show the declines that the anti-fluoridationists claim.

Another example of cherry-picking to mislead.

See also:

Getting a grip on the science behind claims about fluoridation
Is fluoride an essential dietary mineral?
Fluoridation – are we dumping toxic metals into our water supplies?
Tactics and common arguments of the anti-fluoridationists
Hamilton City Council reverses referendum fluoridation decision
Scientists, political activism and the scientific ethos

Similar articles

Will Hamiltonians finally get a voice on fluoridation?

Well, I am not surprised this has happened but am surprised it’s happened so quickly.

Disaffection with the Hamilton City Council decision to stop fluoridation has resulted in an attempt by at least one councillor to get the decision reversed and submitted to a referendum. The Waikato Times is reporting:

The notice of motion from Mr Wilson being circulated today among city councillors today would force the council to debate when it meets in three weeks whether it should hold a referendum.

Mr Wilson said the controversial decision had been hijacked by the anti-fluoride lobby and was not what the majority of Hamiltonians wanted.

“The anti-fluoride position are mostly well-meaning individuals that have misinterpreted the science. And then there’s a group of nutters who are convinced this is mass-medication. There is considerable good science that shows fluoridation is a good base for public health. I believe the majority of people in Hamilton want fluoridation, and they should have the final say.”

Seems to me this would be the best outcome. Hamiltonians have shown in the previous referendum and recent polls they support fluoridation and there has been a lot of criticism of the Council’s recent decision.

Mind you, the anti-fluoridationists are not happy:

the co-ordinator of Fluoride Free Hamilton, Pat McNair, said a referendum was not necessary.

“A tribunal is a robust process where reasoned evidence from both sides can be given. A referendum is just peoples’ opinion in the street.

“The others [Councillors who voted against water Fluoridation] in their summary gave very good reasons why a referendum would not work.”

Ms McNair said she would only accept a referendum if lobbies from both sides of the argument had equal amount of money to campaign with, as education costs “hundreds of thousands of dollars.”

Ms McNair really seems to not like a democratic and full discussion. She preferred a almost behind-doors tribunal dominated by 90% anti-fluoridation submission when the city itself had voted 70% support for fluoridation. The real problem is not money to campaign with – but the presence of activist groups to do the campaigning. She had everything her own way with the tribunal, no wonder she doesn’t want a referendum and the associated public discussion

A referendum will give opportunities for supporters of fluoridation to organise and get their case across. Hopefully they will do so. If not they will only have themselves to blame.

See  Hamilton City Council | Referendum On Fluoride |… | Stuff.co.nz.

See also: Fluoridation

Hamilton City Council reverses referendum fluoridation decision

Well, this morning’s news was a shock. The local council (Hamilton City Council) has decided to stop fluoridating our water supply (see Fluoride to be removed from Hamilton’s water supply).

(Note: If you are sufficiently interested that Waikato Times article has an attached poll where you can express your view. Early votes ran against the council decision, but subsequently the anti-fluoridators seem to have organised to fix that).

Yes, I know. I should have paid attention. But I am probably pretty typical in my apathy about local body politics.

I did know something was afoot – after all an old friend of mine had told me months ago he was part of a campaign to stop fluoridation. But as we had been through all that 7 years ago I thought the format would be the same.

In 2006 a citizen referendum decisively supported continuation of fluoridation in Hamilton’s water supply. That referendum was preceded by much public debate in which supporters and opponents actively presented their arguments.

So, I think I (and other Hamiltonians) can be excused for thinking we were running up to similar referendum held alongside the next local body elections. But we were mistaken. The Waikato Times tells us how it was done:

“The decision, just reached after less than an hours’ debate, followed a lengthy tribunal which heard the weight of public submissions, many from outside the city, argue for the removal of hydrofluorosilicic acid from the water supply.”

Well, I guess that is the price of apathy. But, given the history, I can’t help feeling rather duped. In my mind there are two issues:


This time the issue seems to have taken place behind closed doors – at least figuratively. Apparently submissions are on the City Council web site (and I will certainly be perusing those as the Times article implies they were one-sided). But the public discussion has been pretty minimal – it certainly didn’t register with me. And as a chemist, with some background in researching carbonate apatites (and the role of fluoride in them) I should normally have noticed.

The vote seems rather funny – 7 to 1 to stop fluoridation. With five councillors withdrawing from the vote – 3 councillors “removed themselves after declaring a conflict with their district health board roles.” Bloody hell, one might have expected these three councillors to have a better understanding than the others.

And the question of understanding also raises issues. How informed were the 7 councillors who voted to stop fluoridation? How representative were the submissions they presumably took note of? And, considering the importance of health issues like this, shouldn’t they have done more to get advice from reliable professionals?

In fact, I really wonder if a local council is the right sort of body to consider such important health issues.


In public discussion of these issues the science is often problematic. Both sides on the fluoridation issue will present sciency sounding arguments and these are often difficult for the layperson to consider objectively. Just like the climate change issue. However, given the importance of the fluoridation issue and the fact that a representative body is charged with making the decision it is important for public discussion to at least have the opportunity to be informed scientifically.

In this case I don’t believe the public was adequately informed – and I suspect that neither were the council members. (I really must check out the submissions they received).

The other aspect of these sort of public issues is the way that scientific knowledge gets used. Often pseudo scientific arguments are used. Strongly motivated people will cherry pick, search for information, misrepresent information, to support their firmly held views. Yes, I know – this is only human – we are all prone to confirmation bias. But that is why it is important to make sure there is adequate representation of views. And to make sure professional experts make submissions and give their comments on the submissions of others.

Finally, this is a health issue – and like most health issues it is the most vulnerable who have the most at stake, but usually have the least opportunity to take part in decisions. It will be the children of the economically most disadvantaged families who suffer the decline in dental health. Not only because of weakened dental enamel but also because they are also the people less likely to be receiving adequate dental care as they grow.

See also:

Water Fluoridation – the emotional tail wags the dog in Hamilton
Waikato DHB ‘very disappointed’ with fluoride decision