Tag Archives: calcium fluoride

Scaremongering and chemophobia

This poster/internet meme is making the rounds at the moment. A “true believer” asked for my comments on it as he seemed to think its arguments amounted to “gospel truth.”

misleading poster

So here are some comments:

“Natural” vs “man-made”

They are comparing  crystals found in nature with a processed chemical here. But if CaF2 (the ore fluorite) was meant be used for water treatment it would have to be processed to remove impurities (the natural ore is far from pure). The most effective way of removing contaminants is conversion to hydrofluoric acid and precipitation of calcium fluoride (CaF2). Ending up with a “man-made” product!

Some anti-fluoride campaigners seem to argue that fluoridation would be OK if the fluoridating agent used was CaF2. The contaminants present and need for purification are only two of the flaws in their argument. The low solubility of CaF2 is another flaw.

Incidentally, fluorosilicic acid is effectively purified in its manufacture because of the differing melting and boiling points of heavy metal fluorides and silicon tetrafluoride.

“Safe to hold” vs corrosive

True, concentrated fluorosilicic acid is much more corrosive than CaF2. But so what – this is an issue for those manufacturing, transporting and handling the source material. It is not an issue for consumers as drinking water does not contain either CaF2 or fluorosilicic acid.

By the way, the material safety data sheet for CaF2 says this:

“Potential Acute Health Effects: Hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. Corrosive to eyes and skin. The amount of tissue damage depends on length of contact. Eye contact can result in corneal damage or blindness. Skin contact can produce inflammation and blistering. Inhalation of dust will produce irritation to gastro-intestinal or respiratory tract, characterized by burning, sneezing and coughing. Severe over-exposure can produce lung damage, choking, unconsciousness or death.”


“Precautions: Keep locked up.. Keep container dry. Do not ingest. Do not breathe dust. Never add water to this product. Wear suitable protective clothing. In case of insufficient ventilation, wear suitable respiratory equipment. If ingested, seek medical advice immediately and show the container or the label. Avoid contact with skin and eyes.”

So the advice to those manufacturing, handling and transporting CaF2 is that it is not safe to hold  with bare hands!

Sparingly soluble in water

This is one of the disadvantages of CaF2 as a fluoridating agent as a saturated solution has a fluoride concentration of about 7.5 ppm. Just imagine the size of the container required to hold the quantities of CaF2 solution required for addition to a reservoir!

The high concentration of fluoride in liquid fluorosilicic acid (and the fact that it rapidly decomposes to produce the hydrated fluoride anion on dilution with water) provides a big advantage to it as a fluoridating agent.

Fluoride toxicity reduced by calcium

Yes, high concentrations of fluoride are toxic – although the concentration in community fluoridated water (CWF) (0.7 ppm) is quite safe. The toxicity of ingested fluoride at high concentrations can be reduced by the presence of calcium – because of the low solubility of CaF2.

But let’s be realistic, in the absence of other factors the addition of the appropriate amount of calcium would reduce the fluoride concentration to about 8 ppm. Far higher than the regulated maximum for CWF.

As for some other speculated protective action the calcium in CaF2 could provide – the calcium concentration in a saturated CaF2 solution is only about 7.5 ppm – and at the fluoride concentration used for fluoridated water CaF2 would support a calcium concentration of about 0.8 ppm. Any calcium from added calcium fluoride would be irrelevant compared with the natural calcium concentrations in drinking water. The graph compares these figures for several treatment stations in New Zealand –  see Calcium fluoride and the “soft” water anti-fluoridation myth for further information.

“Man-made waste product”

I have discussed the “man-made” fallacy above. Anti-fluoride campaigners love to describe fluorosilicic acid as a “waste product.”  But Wikipedia defines a waste product as:

“unwanted or unusable materials. Waste is any substance which is discarded after primary use, or it is worthless, defective and of no use”

By definition, then, the fluorosilicic acid used in CWF is not a waste product. It would be if it were disposed of without use – then so is food.

Anti-fluoride campaigners also seem to think that a by-product is somehow evil. This is because most fluorosilicic acid is produced as a by-product of phosphate ore processing. But, come on. Surely production and use of by-products is a desirable feature in judging the conservation aspects of a manufacturing process. And would phosphate chemicals be somehow evil if they were produced as a by-product of fluoride chemical manufacturer from phosphate ores?

Toxicity of “co-contaminants”

I discussed the problem of contaminants in “natural” CaF2 above and added that contaminants in the fluorosilicic acid used for CWF are very low.

But don’t take my word for it. Water treatment chemicals are regulated and the fluorosilicic acid used for CWF must pass rigid tests for the presence of contaminants. The regulations provide for maximum concentrations of contaminants and where a certificate of analysis shows these are exceeded the material is rejected by water treatment plants.

I discussed this in my article Fluoridation – are we dumping toxic metals into our water supplies? where I debunked this claim made by Fluoride Free NZ. I also provided some data on the chemical analysis of fluorosilicic acid samples. In the article Fluoridation: emotionally misrepresenting contamination I compare the real concentration of contaminants recorded in certificates of analysis with the regulated limits. It turns out that the fluorosilicic acid manufactured in Australia and New Zealand is very low in such contaminants – see figure below.

Of course – some opponents like to claim that any amount of contaminants is too much, despite the regulations. Well, if they want to pursue that argument then they must look at all sources of contamination. In many cases, they will find that there is a larger amount of contamination coming from the original water source, natural contamination, than from the water treatment chemicals

I showed this in the article Fluoridation: putting chemical contamination in context where I compared the amount of arsenic from different sources  in the Hamilton City water supply. The figure below from that article shows that natural levels of arsenic in the water source (the Waikato River) are much higher than the recommended levels for drinking water. Even after treatment (which reduces the arsenic levels to below the recommended maximum) the contribution of arsenic from this natural source is still much greater than the calculated contribution from the fluoridating agent used.


This bit of anti-fluoride propaganda is just another example of scaremongering relying on chemophobia and lack of information, even ignorance.

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Calcium fluoride and the “soft” water anti-fluoridation myth

hogwash1Concepts of “natural” and “unnatural” or “artificial” ( or even “industrial”) fluoride often come up in the fluoride debates. Some fluoridation opponents claim “natural” calcium fluoride is quite safe, maybe even necessary for the body, but “artificial fluorides” are toxic. For example, a recent commenter stated:

“I understand that the addition of calcium fluoride to our water supply could be a safe alternative as its use in the small quantities needed would not be harmful. It is not very reactive, but has the desired effect on teeth.”

One of the arguments used is that the presence of calcium is what makes calcium fluoride (CaF2) good, whereas its supposed absence with “artificial” or “industrial” fluorides makes these bad. Anti-fluoride campaigner Eron Brokovich put it this way in here recent “open letter” to the US Institute of Medicine / National Academy of Sciences:

“The 2013 study of chemist Dr. Richard Sauerheber examined the differences between aturally occurring Calcium Fluoride and the highly toxic Industrial Fluoride used in water supplies. Dr. Sauerheber confirmed that the calcium in CaF(sic) makes the fluoride much less absorbable by the human body and therefore less toxic when ingested in that form, whereas the industrial fluoride is . . .  highly absorbable . . .”

Sauerheber’s paper (which Brockovich relies on as “evidence”) is a meandering and naive anti-fluoridation rant, published in a shonky journal. But anti-fluoridation propagandists treat “peer-reviewed friendly papers like this as pure gold, so they do tend to rely on them. But don’t take my word for this – here is the citation for anyone wanting to check out the paper

Sauerheber, R. (2013). Physiologic conditions affect toxicity of ingested industrial fluoride. Journal of Environmental and Public Health, 2013,

Sauerheber’s (and therefore Brockovich’s) argument is that calcium in CaF2 reduces assimilation of fluoride into the body and, therefore, renders it non-toxic. He says, for example:

“Natural mineral fluorides are not absorbed well when ingested because of the natural metal cations that accompany fluoride. Having no biologic similarity at all with natural fluoride  minerals, industrial manufactured fluoride compounds have cations that replaced those in the natural mineral. . . . . Free fluoride ion in some water supplies as a contaminant is naturally present
from natural fluoride minerals that exhibit low solubility. The equilibrium double-arrow natural partial dissolution of the insoluble solid into some waters is given by:

CaF2(s) ↔ Ca2+(aq) + 2F(aq).

Industrial fluorides stripped of natural mineral cations lack antidote calcium and are fully assimilated from artificially treated water with insufficient calcium.”


“Fluoride minerals are not neurotoxins, because fluoride is not absorbed from ingested minerals. Free fluoride ion in drinking water can be so classified, but industrial fluoride sources are assimilated more readily than fluoride from hard water or from natural calcium fluoride.”

So, “natural” fluoride, CaF2, is good because the calcium present stops it getting into your blood stream. But “industrial” fluoride is bad because it has no calcium present to inhibit assimilation.

True, the most commonly used fluoridating chemicals are fluorosilicic acid, sodium fluosilicate or sodium fluoride. These do not contain calcium. But wait a minute! These chemicals are drastically diluted in the water supply which already contains calcium from natural sources, and sometimes from water treatment chemicals like lime.

Sauerheber sort of hints at this in his reference to “hard water.” Water “hardness” refers to its mineral content and is usually expressed as the calcium, or calcium carbonate, concentration. It is a common measure of water quality so data is readily available from water treatment plants. In the graph below I compare the calcium concentration from some typical New Zealand water treatment plants with the calcium concentration of a saturated CaF2 solution and the theoretical calcium concentration of “pure” water fluoridated with CaF2 to produce a fluoride concentration of 0.75 ppm (mg/L).



  • The majority of NZ waters are considered “soft” with a hardness of 30 ppm (expressed as Ca) or less. I have used this for the NZ maximum.
  • The Te Marua, Wainuiomata and Waterloo treatment plants are in the Wellington region. The Hamilton treatment plant is in Hamilton city.
  • CaF2 is only slightly soluble so a saturated solution  contains approximately 7.5 ppm Ca and 7.5 ppm F, depending on pH and temperature.


All this talk about “natural” CaF2 somehow being “safe” because it contains calcium, whereas the fluoridation chemicals used do not contain calcium, is hogwash There is plenty of calcium even in “soft” drinking water – far more calcium that could be derived from “natural” CaF2 if it were used to produce the optimum concntration fo fluoride used in community water fluoridation.

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