Analysis of Hexafluorosilicic Acid

An analysis of Hexa (Hydro) fluorosilicic acid below was performed in 2000 in Dublin.   The Irish Republic has traditionally used Hexa(Hydro)fluorosilicic Acid as their fluoridating agent.  The chemical parameters which are  part of the originating feedstock - fluorapatite/cryolite ore - and the contaminants in the scrubber water vary in concentration according to where in the open cast mines the ore was excavated and according to other processes going on in the facility which produces phosphate fertiliser.

The laboratory did not analyse the concentration of fluoride, hydrofluoric acid and silicate/silicon. 

Fluoride:   The fluoridating acid is approximately a 20% solution of fluoride.  The British Standard 12175:2013 instructs water companies to add 6.3 mg fluoride to every litre of treated water in order to achieve a concentration of 1 mg fluoride/litre.

Hydrofluoric Acid:  BSEN 12175:2013 (p.7) states that Hydrofluoric Acid (HF) is present in Hexafluorosilicic Acid at 1.5%.  1.5% of 6.3 mg is 0.0945 mg HF/litre.  HF is a contaminant.  It is not a legally permitted compound of fluoride (Water Industry Act 1991, s.87) for the fluoridation of drinking water.

Because of strict copyright law, we cannot reproduce the text of the British Standard on this website.  It is possible to purchase a copy but it is costly to do so and that's why this information has remained hidden for so long.  According to a reply to a Freedom of information Request this autumn, even the DHSC/OHID does not possess a copy. 

The British Standard lists the following "chemical parameters as being present in Hexafluorosilicic acid: Antimony, Arsenic, Cadmium, Chromium, Lead, Mercury, Nickel and Selenium.  So, in order to add fluoride to drinking water, all these heavy metals are also added.  Arsenic should be of great concern to everyone: in drinking water is should be as low as reasonably practicable - the ALARP Principle.  Even though it is never more than the maximum allowable (10 micrograms/litre), there is no excuse to add it because it is a CARCINOGEN.  It should be removed, not added. In reality, no amount of arsenic is safe to swallow and the 10 micrograms/litre is a compromise, made in the realisation that water companies cannot completely remove arsenic from raw water.

Silica: "Like fluorine, silicon is always found in nature compounded with other elements as a silicate.  Silicon is not toxic in itself but it is known to cause irritations in soft tissue, which can lead to the formation of cancers in the same way as asbestos fibres do.  The Merck Index, an encyclopaedia of chemicals, drugs and biological agents, lists the amount of silica in H2SiF6 as 19.49 per cent.

Most silicon compounds that occur in nature are considered harmless, because silicon compounds are poorly absorbed.  Nevertheless, silica derived from reacting fluorosilicic acid with lime is used to induce cancers in laboratory animals.  While the silica itself is harmless, microscopic crystalline silica particles act as "seeds" around which precancerous material forms.

The most damaging forms of silica - silicon halides and hydrides - are extremely toxic by either inhalation or ingestion.  The most-used fluoridation agent both in Britain, Ireland and the US is hexafluorosilicic acid which, as chance would have it, is the most easily metabolised silicon halide.  Thus, everyone who drinks artificially fluoridated drinking water is exposed to this silicon halide.  Each milligram (mg) of hexafluorosilicic acid that is put into drinking water releases millions of molecular fluorosilicate ions.  Even if the fluorosilicate ion dissociates, millions of silicon dioxide molecules remain as suspended solids.  These sub-microscopic silica molecules can be metabolised and circulated through soft tissues in the body."  (B. Groves., Fluoride: Drinking Ourselves to Death, pp. 198-99, Dublin: Newleaf, 2001. )  

Each tanker-load of the acid delivered to water treatment works is accompanied with a Certificate of Conformity.  Water Companies and the Drinking Water Inspectorate do not have to analyse the acid for the concentration of chemical parameters and contaminants.  We have no way of knowing if the producers apply British Standard 12175:2013  before they ship the acid to Ireland and the UK but the Certificate of Conformity seems to confirm that some analysis is performed.

However, in the absence of an analysis being performed in this country, we have to assume that all the chemical parameters are present at their maximum permissible values.  The producers of this hazardous waste acid are unlikely to spend more money refining the acid when they don't have to.