Tag Archives: Fluorine

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.

Is fluoride an essential dietary mineral?


Source: Dietary Minerals, Wikipedia

Anti-fluoridation activists often assure us that fluorine (F) is not an essential element. But what does that mean? Literally I guess it means that there are no identified biological pathways essential to human life involving F. So anti-fluoridation activists often claim the only safe level of flourine in the human diet is zero!

But whether an element is essential or not is often unclear or undecided. Some sources claim about 16 elements seem to be essential to maintain life. Others claim over 20 elements are essential.

Fluorine is rather debatable, as the above Periodic Table of the elements suggests. The Wikipedia entry on Dietary Minerals does say, however:

“Fluorine (as Fluoride) is not generally considered an essential mineral element because humans do not require it for growth or to sustain life. However, if one considers the prevention of dental cavities an important criterion in determining essentiality, then fluoride might well be considered an essential trace element.”

So F may well be considered an essential trace element, or a beneficial element. By the way, we should not let the fact that F is known to have harmful effects when in excess lead us to deny its beneficial effects. Probably all essential or beneficial elements and trace elements do.

Essential and beneficial elements usually display a “beneficial window” of  intake. This can be shown by a U shaped  graph when we plot the incidence of negative effects against intake (see figure below).


Source:  Howd & Fan, 2007 –  Risk Assessment for Chemicals in Drinking Water page 202.

So we expect to see that sort of relationship with F intake if the element is essential, or even just beneficial. If there are no benefits from F we would expect only an increasing incidence of negative effects when the intake increases from zero. Of course we also see that for essential or beneficial elements if we restrict our data to only high levels of intake.

Does F have benefits besides dental ones?

Do the benefits of F extend more widely than the prevention of dental cavities? I have often thought they do because F has a clear effect on the structure and solubility of hydroxyapatites – an important and major componet of bones. A small amount  of substitution of F for OH in the hydroxyapatite structure can strengthen such minerals and lower their solubility. Bioapatites are a major component of our skeletons, and play a role in many of our organs. This chemical substitution may actually have positive effects on bone health, and the properties of other bioapatites. Of course excessive substitution, or differentiation into different chemical crystalline phases, may also have negative effects when there is excessive intake.

By the way, F is not the only elements that substitutes at trace levels in bioapatites. There are many more and they can each influence the properties of the bioapatite.

Another way of looking at this is that pure chemically defined compounds rarely exist in the real world. Other minor elements are often incorporated into the crystal structure, or be present in a closely associated crystal phase.  These “impurities” or substituted elements usually impart features to the natural material which are greater or lesser than, or perhaps not even seen, in the pure compound. These features can be important to the biological role of crystals in nature and life.

Because biological systems are always exposed to a whole range of chemical elements at varying concentrations there will be no such thing as zero F intake. Nobody’s body is “fluoride free.”

Beneficial effects of F on human bones?

I recently checked out a paper which shows beneficial effects  of F on human bones along the lines I have suggested.  The paper is Yiming Li et al., (2001): Effect of Long-Term Exposure to Fluoride in Drinking Water on Risks of Bone Fractures. The authors are a group of researchers from the US and China. You can download the PDF here and check out methodology and other details.

Here’s one of the figures from their paper summarising the relationship of overall bone fractures to F content of the water supply used.


Effectively, this displays the U-shaped curve mentioned for essential elements in Risk Assessment for Chemicals in Drinking Water.

Or, perhaps more importantly – statistically significant increases in numbers of bone fractures occur at both low levels of fluoride in drinking water (<0.3 ppm) and at high levels (>4 ppm).

The authors express it this way:

“The data appear to suggest that there may be a “beneficial window” of fluoride intake for bone health, because an increased risk of overall bone fractures was detected in both the populations with deficient and excessive fluoride in drinking water.”

Not surprisingly this window corresponds approximately to current New Zealand advice for oral health  – concentrations of fluoride in the water supply in the range 0.7 to 1.0 ppm are beneficial.

So perhaps we should consider F as an essential, or at least, beneficial trace element as Wikipedia suggests. And perhaps health authorities in New Zealand should include bone health, together with oral health, in their advice on fluoridation.

The quality of research studies is critical

Other groups have produced similar conclusions to that of Yiming Li et al. – particularly that the incidence of bone fractures are reduced by fluoride doses in the beneficial range of F intake. But, these sort of investigations are very complex so it’s possible to find other studies which don’t show this result, or show only the effects of high fluoride intake. This raises the question of the quality of such investigations and the need for readers and reviewers to be particularly informed about such issues.

Many of these sorts of studies produce results of questionable quality because they ignore the role of other factors besides F in the water supply. For example, in many developed countries, and many developing ones, dietary intake of fluoride also comes from toothpaste, mouthrinses and dietary supplements. The high mobility of modern populations also makes it difficult to relate clinical effects to simple factors in the current environment of the individuals. It’s no wonder that attempts to relate health effects to fluoride concentrations in the public water supply produces controversial findings.

Mind you, that’s a great gift to the unscrupulous cherry-picking, uncritical reviewer with an ideological or activist axe to grind. If you are selecting studies to support a preconceived viewpoint the influence of other factors is not important – you just choose what suits your argument and ignore the quality. But if you are trying to establish a reliable picture of what is actually happening, as we hope our health professionals and scientists are, it’s important to consider the quality, and reliability, of each study.

My impression is that this particular study is considered of high quality because it used populations with a defined history of fluoride exposure. The authors say:

“In contrast to the U.S. population, residents of rural China rarely change residences, and most have been using the same water supply throughout their life. Because of its unique environmental and cultural conditions, such as virtually no residential mobility and a relatively consistent lifestyle, rural China has been considered a perfect “living laboratory” for studying the relationship between various factors and diseases. The survey results of our study sites and data from individual subjects show that fluoride exposure in rural Chinese communities is still limited to water and diet.”

And in their methodology:

“The residency of each subject was determined by the following three measures: (1) objective assessment by checking the Family Registry Book, an official document issued by the government; (2) a subject survey questionnaire; and (3) confirmation by village officials who were familiar with the subject.”

This sort of reliability of information is just not available for modern populations in most countries, making these sort of studies unreliable.

The lesson here is that there must employ intelligent and expert consideration when reading or reviewing research in this sort of area. People consulting such studies and reviews should also be aware of the dangers. When public debates, like that over fluoridation, occur we need to be aware of the way activists may draw unreliable conclusions from the literature and promote those unreliable conclusions to the public.

As an aside – this study also considered possible effects of factors like gender, smoking and alcohol – not surprisingly bone fracture were higher for men, and for those consuming alcohol!


So, is fluoride an essential element? I don’t know and I am hardly the person to decide. But clearly it is possible to argue the case that it may be, or that it is at least a beneficial element, provided dietary intake is neither too low or too high. It’s a complex area – just beware of activists with an axe to grind and a simple picture to support their claims.

See also:
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

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