Tag Archives: Hexafluorosilicic acid

Anti-fluoridation study flawed – petition rejected

A recent research paper claiming a signficant cost/benefit advantage in banning the use of fluorosilicic acid as a fluoridating agent in public water treatment, and replacing it with sodium fluoride, has been found flawed. This was revealed as a result of the rejection by the US Environmental protection Agency (EPA) of a petition by the author


Dr William Hirzy testifies for an anti-fluoridation group

The original paper by Hirzy et al. (2013) is on-line – full details are Hirzy, J.W., Carton, R.J., Bonanni, C.D., Montanero, C.M., Nagle, M.F. (2013) Comparison of hydrofluorosilicic acid and pharmaceutical sodium fluoride as fluoridating agents—A cost–benefit analysis  J Environmental Science and Policy Volume 29, May 2013, Pages 81–86.

Briefly the authors had used data (arsenic (As) concentrations in a number of samples of fluorosilicic acid and sodium fluoride) and a model for the predicted incidence of cancers resulting from As contamination in water supplies. Their cost/benefit analysis claimed “the U.S. could save $1 billion to more than $5 billion/year” by using pharmaceutical grade sodium fluoride instead of fluorosilicic acid.

Consequently Hirzy petitioned the EPA to ban use of fluorosilicic acid, using his study as supporting evidence. The EPA responded officially on August 6 and, despite some of the legalese, their notice is worth reading for anyone interested in the fluoridation controversy.

A calculation error for arsenic

When I first read Hirzy’s paper I was concerned that the quoted values for As in the fluorosilicic acid samples he considered were higher than found in New Zealand. (As concentrations in local fluorosilicic acid for water treatment are about the same as for the pharmaceutical garde sodium fluoride he used). I wondered if his data was out of date, or he had used commercial grade samples and not water treatment samples. However, the EPA found a more basic fault – Hirzy’s calculations were wrong! They had “failed to convert their estimates of lifetime cancer risk to estimates of annual cancer risk for the purpose of calculating annual net benefits.” When corrected the cost benefit analysis favoured fluorosilicic acid “(-$81M/year to -$8M/year, respectively) rather than pharmaceutical grade NaF over HFSA:”

1. Arsenic. EPA evaluated the cost-benefit analysis submitted by the petitioners and determined that the petitioners miscalculated net benefits for pharmaceutical grade NaF compared to HFSA. Specifically, it appears that the petitioners failed to convert their estimates of lifetime cancer risk to estimates of annual cancer risk for the purpose of calculating annual net benefits. This error alone results in a 70-fold overestimation of the number of annual cancer cases due to arsenic. That is, for the analysis in which the petitioners evaluate arsenic concentrations of 0.078 parts per billion (ppb) due to HFSA and 0.00084 ppb due to pharmaceutical grade NaF, the estimated numbers of cancer cases, when corrected, decrease from 320 to 4.6 per year for HFSA and from 3.4 to 0.05 per year for pharmaceutical grade NaF (Refs. 2 and 9). Similarly, for the analysis in which the petitioners evaluate an arsenic concentration of 0.43 ppb due to HFSA and 0.00084 due to pharmaceutical grade NaF, the estimated numbers of cancer cases,  when 8 corrected, decrease from 1,800 to 25 per year for HFSA and from 3.4 to 0.05 per year for pharmaceutical grade NaF (Refs. 2 and 9). After making the correction (i.e., annualizing the lifetime cancer risk), and retaining all other assumptions of the petitioners analysis, the analysis actually indicates that the cost-benefit ratio is in favor of using HFSA over pharmaceutical grade NaF (-$81M/year to -$8M/year, respectively) rather than pharmaceutical grade NaF over HFSA (Ref. 9). As a result, the information submitted by petitioners does not support the petitioners’ claim that there are net benefits in switching from HFSA to pharmaceutical grade NaF. Given that the petition is based upon the premise that the benefits of using pharmaceutical grade NaF as a fluoridation agent significantly exceed the costs relative to the use of HFSA as a fluoridation agent, EPA concludes that petitioners have not set forth sufficient facts to establish that HFSA presents or will present an unreasonable risk of injury to health or the environment with respect to arsenic or that it is necessary to initiate a TSCA section 6(a) rulemaking to protect adequately against such risk.

Lead risk not proved

The EPA similarly found that Hirzy’s claim that fluorosilicic acid caused leaching of lead from pipes in the water supply system was similarly unproved”

2. Lead. Petitioners assert that HFSA contains lead but provided no data to support this assertion. Petitioners also assert that the use of HFSA in lead-containing water piping systems results in leaching of lead from lead-containing water piping systems into water (Ref. 5), and that when chloramine is used in conjunction with silicofluorides greatly enhanced leaching of lead into water occurs (Ref. 3). . . . .  Based on the available evidence, EPA cannot conclude that the use of HFSA, with or without the presence of chloramine, results in enhanced leaching of lead.

Radioactive contaminants

Again the EPA found that Hirzy’s claims about radionuclide contamination were not supported:

4. Radionuclides. Although the petitioners mention “concern” about radionuclides, the petitioners present limited information to support a claim that HFSA presents or will present and unreasonable risk with respect to radionuclides. NSF compiled data from initial and annual monitoring tests for fluoridation products that NSF certified to NSF/ANSI 60 between 2007 and 2011 (216 samples) and between 2000 and 2006 (245 samples). Alpha emitters (type of radioactive decay in which an atomic nucleus emits an alpha particle) were detected in less than 1% of the 216 samples analyzed between 2007 and 2011. The mean (non-detects were estimated at ½ the detection limit) and maximum values were less than the MCL of 15 picoCuries per liter (pCi/L) and were less than the NSF/ANSI 60 SPAC of 1.5 pCi/L (Ref. 15). Beta photon emitters (another type of radioactive decay in which an atomic nucleus emits a beta particle) also were detected in less than 1% of the 216 samples analyzed between 2007 and 2011. The mean (non-detects were estimated at ½ the detection limit) and maximum values were less than the MCL of 4 millirems per year (mrem/y) and were less than the NSF/ANSI 60 SPAC of 0.4 mrem/y (Ref. 15). Radionuclides (alpha or beta) were not detected in any (0%) of the 245 samples analyzed between 2000 and 2006 (Ref. 11). The concentrations reported represent contaminant levels expected when the fluoridation products are dosed into water at the allowable maximum use levels for NSF/ANSI 60- 2012 (see Refs. 14 and 15). NSF notes that lower product use levels would produce proportionately lower contaminant concentrations. Thus, the petition has failed to present facts that establish that HFSA presents or will present an unreasonable risk of injury to health or the environment with respect to radionuclides, or that it is necessary to issue a TSCA section 6 rulemaking to protect health and the environment from such risk.

So, it would be nice if anti-fluoridationists would stop using Hirzy’s paper to “prove” that use of fluorosilicic acid causes cancer when used as a fluoridating agent. Or better still, stop promoting the lie that such fluoridating agents contaminate our drinking water with toxic heavy metals and radioactive elements.

But, going by past practice I am not going to hold my breath.

Similar articles on fluoride and fluoridation

Hamilton – the water is the problem, not the fluoride!

Saw this on Facebook the other night – together with the comment:

“If Hamilton don’t want fluoride in the water, how about we replace the water”


Yes, that would be convenient, wouldn’t it. Instead of Hot and Cold taps, why not Red and White?

However, there is an element of truth in the joke. To some extent, the Waikato water is the problem, rather than fluoride added during fluoridation. Anti-fluoridationists are concentrating on the “evils” of the fluoridation agent, fluorosilicic acid, without realising that the source for our water supply in Hamilton introduces more contamination than the fluoridation chemicals.

Have a look at this graphic showing the levels of arsenic (As) in the Waikato River. Through almost the entire length of the river As levels are several times higher than the recommended maximum concentration for human consumption which is 0.01 parts per million (ppm).

The source water for the Hamilton water treatment plant is 2 or 3 times that recommended maximum As concentration.

Fortunately the treatment process remove about 80% of the As.

Let’s compare that with the contamination introduced by fluoridation chemicals.

A typical concentration of As in fluorosilicic acid is 2 ppm (see Fluoridation – are we dumping toxic metals into our water supplies?  and Water treatment chemicals – why pick on fluoride?). There is a large amount of dilution of the fluorosilicic acid when added to water at the recommended dose (0.7 – 1.0 ppm). The final concentration in our drinking water is 0.0001 ppm As. Several orders of magnitude lower than the maximum recommended concentration for human consumption.

In reality, even after removal of 80% of As from the source water the major contribution to any As contamination in Hamilton’s public water supply is the Waikato River itself – not the fluoridation chemicals. By several orders of magnitude.

  Original Arsenic (ppm As) Dilution Contribution to finished water (ppm)
Recommended maximum As (ppm)     0.01
Waikato River water ~0.025 None ~0.005
Fluorosilicic acid 2* ~200,000 ~0.0001

* see Fluoridation – are we dumping toxic metals into our water supplies?  and Water treatment chemicals – why pick on fluoride?

Haven’t the Hamilton anti-fluoridation campaigners got their priorities wrong when they complain about contamination of the fluoridation chemicals used?

See also:

Making sense of fluoride Facebook page
Other Fluoridation articles

Fluoridation – are we dumping toxic metals into our water supplies?

Opponents of fluoridation usually use a raft of arguments – this sometimes make discussions difficult because it leads to Gish Galloping which prevents proper discussion of any one issue. So in this blog post I want to restrict myself to just one of the anti-fluoridationist claims – one I have always been cynical about.

This is the assertion that the fluorides used for fluoridation of public water supplies is contaminated with toxic elements – heavy metals and radioactive elements.

Problem is – about 10 years ago I was using a commercial batch of hydrofluorosilicic acid – FSA (the chemical used for fluoridating Hamilton’s water supply) for our research. We analysed our material – and the results show definitely that it was not contaminated with toxic elements. The amounts present were extremely low

As (ppm) Cd (ppm) Cr (ppm) Hg (ppm) Ni (ppm) Pb (ppm) Cu (ppm) Zn (ppm)
2 <1 5 < 0.1 < 1 0.3 < 0.2 2.1

So what’s going on? Is my data (admittedly anecdotal evidence for one batch) an outlier? Or is somebody telling porkies?

The claim

Here I quote from the 7 objections to fluoridation listed by the Fluoride Action Network – FANNZ (the activist group leading the current activist mobilisation against fluoridation). See Our objections to fluoridation.

6. Fluoride used in fluoridation is contaminated with heavy metals including lead

Fluoridation was originally a corporate promoted solution for the aluminium industry to sell their toxic waste product for profit. Today fluoride for drinking water comes from the chimneys of the phosphate fertilizer industry. The fluoride used is contaminated with heavy metals (including lead a known neuro toxin) and sometimes radioactive material, posing added health risks (NZ Water and Wastes Association Standard for “Water Treatment Grade” fluoride, 1997). The phosphate industry use “scrubbers” to capture fluoride gases produced in the production of commercial fertilizer. This is because if they allowed too much of it to escape into the atmosphere they would be liable for being major polluters. If the fluoride acid was placed in a barrel with holes in it, and dumped in our rivers they would face heavy fines and criminal prosecution.

However a solution has been found whereby the fluoride acid (hydrofluorosilicic acid), a classified hazardous waste, is barrelled up and sold, unrefined, to communities across the world for the purpose of adding it to public water supply to mass medicate populations to prevent tooth decay in forming teeth. Mysteriously the substance becomes safe for the environment and humans once it’s sold in this regard. Even if you don’t live in a community where fluoride is added to water, you’ll still be getting a dose of it through cereal, soda, juice, beer and any other processed food and drink manufactured with fluoridated water. If it is illegal for these corporations to dump the waste in our rivers it certainly should be illegal for them to sell fluoride for the purpose of adding it to our drinking water.

Of course, this sort of claim gets copied and pasted when activists make submissions  to local bodies on the fluoridation issues. Here’s one made to a Palmerston North hearing by “a concerned citizen and grandmother” who is “appalled at the documented adverse health effects associated with water fluoridation. . . . .  After much research on the subject” she “discovered some sobering and disturbing facts (and I emphasise that these are facts and not just my opinion).” 


Notice the claims, and the confidence with which they are made. Also notice  how a citation to NZ Water and Wastes Association Standards is used to give the claims an air of “sciency” authority.

The citation.

Unfortunately no link to the actual publication was provided by FANNZ – perhaps because it doesn’t actually say what they claim it does. I’ll give the link here – NZ Water and Wastes Association Standard for “Water Treatment Grade” fluoride, 1997.  Download the pdf and read it for your self. Check it out.

Here’s a comparision of the anti-fluoridationist claim with what the document says about the fluoridation chemicals used for public water treament in New Zealand.



The fluoride used is contaminated with heavy metals (including lead a known neuro toxin) and sometimes radioactive material, posing added health risks (NZ Water and Wastes Association Standard for “Water Treatment Grade” fluoride, 1997). Commercially available hydrofluosilicic acid, sodium fluoride and sodium silicofluoride are not known to contribute significant quantities of contaminants that adversely affect the potability of drinking water.

The claim is completely wrong and is not supported by the citation.

That is the only comment the document mnakes about actual levels of contaminants in the  commercial chemicals on the market. Why should such a publication go into further details?  The standards are aimed at protecting the health of the people. Preventing chemicals from being used if they are contaminated by toxic elements, for example. It’s not their job to go into the history, manufacture and composition of commercial chemicals – only to consider these issues when they come to select material for use.

The publication describes, for example, standard for maximum levels of heavy metals in fluoridation agents:

“ Hydrofluosilicic acid shall not contain more than 0.02% w/w heavy metals expressed as lead (Pb).”

It describes standard procedures for handling the chemicals used. (Yes, many chemicals in their concentrated forms a dangerous and must be handled correctly, even though they are harmless when diluted to the concentration they are used. Just think about chlorine – really dangerous in the form purchased commercially – but no one is complaining about the levels in our water supply).

The publication describes requirements for chemical analysis of supplied materials, and the responsibility of the supplier to provide materials which comply with the standards and certificates guaranteeing compliance.

So FANZZ is being rather disingenuous using this publication to support their erroneous claim. If anything the publication shows that authorities have a regime in place to make sure the material they use is not contaminated.

What are the concentrations in our drinking water?

The Greater Wellington Region uses Hydrofluorosilicic acid (HFA) at their Gear Island treatment plant. Their web site say that “the HFA we use is tested to ensure that any other chemical elements of health significance that it contains are at safe levels in relation to the Drinking Water Standards for New Zealand.” And they provide a chemical analsis of the water supplied to their citizens. Here are some typical results:

As (ppm) Cd (ppm) Cr (ppm) Hg (ppm) Ni (ppm) Pb (ppm) Cu (ppm) Zn (ppm)
<0.002 <0.001 <0.001 <0.001 <0.001 <0.001 <0.013 <0.013

The Fluoridation Action Network (FANZZ) is simply fear mongering with this claim. They are capitalising on a naive fear of “chemicals.” They are making false claims about contamination of the fluoridating agents used. And they are using a citation dishonestly – to support a claim the publication does not support.

Similar articles

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