No harm from silica and other trace elements in the fluoride compounds added to water
The Water Research Council’s 2002 report Chemistry and Bioavailability Aspects of Fluoride In Drinking Water explains that, when hexafluorosilicic acid is added to water, it dissociates to form fluoride ion (F–) and silicic acid (Si(OH). Click here for copy of full report.
The silicic acid (Si(OH)4) will itself dissociate into silica (silicon dioxide) and water: Si(OH)4 D SiO2 + 2H2O. The familiar forms of silica are quartz or sand, which are usually considered inert.
There are no health, or other adverse implications, for the consumer of the “residual” silica in fluoridated water since the silica is both indigestible and biologically inactive. Indeed, silica is frequently used as a food additive, primarily as a flow agent in powdered foods or to absorb water.
Other trace elements
Opponents of fluoridation argue that fluoridated water contains silicates and trace elements – for example, arsenic – that would not normally be present in non-fluoridated water. They are wrong; the trace elements in question are found in all water, whether fluoridated or not. Indeed, they are often present in higher concentrations in non-fluoridated water supplies than in fluoridated ones.
Fluorosilicic acid is derived from a fluoride-bearing mineral in the ground – commonly apatite – which contains a number of naturally occurring trace elements.
In its 2011 report on fluoride in drinking water, the European Commission’s Scientific Committee on Health and Environmental Risks (SCHER) concluded that the calculated concentrations of trace metals in fluoride compounds used in the fluoridation process “are at least two orders of magnitude below drinking water guideline values for these metals established by WHO and other organisations, and therefore are not regarded as an additional health risk”.
Water companies in the UK are required to monitor the microbiological, chemical and aesthetic qualities of drinking water and to ensure that trace elements do not exceed maximum permitted levels.
The companies routinely publish the results of their monitoring. These give the minimum, mean and maximum levels found in analysed samples of water taken over a specific period.
Tables 1 and 2 record the maximum permitted concentrations – together with the mean and maximum actual concentrations found in water samples taken – of fluoride and a number of trace elements. All of these substances occur in water naturally and in the fluorosilicic acid compounds used in the water fluoridation process.
The tables give the concentrations found in two fluoridated water supplies (Solihull and Birmingham) and four non-fluoridated supplies (Bolton, Leeds, London and Croydon).
Overall, they show that whilst the fluoridation process does raise the level of fluoride present (as it is intended to do), fluoridated water may contain lower levels of the trace elements than non-fluoridated water, and that in neither case do the trace elements come anywhere near to the maximum permitted concentrations.
When hexafluorosilicic acid is added to water, it dissociates to form fluoride ions and silicic acid. The fluoride ions are identical to those which are present in water naturally.
Residual silica has no health implications
There are no health, or other adverse implications, for the consumer of the “residual” silica in fluoridated water since the silica is both indigestible and biologically inactive.
Trace metals at least two orders of magnitude below WHO guidelines
Concentrations of trace metals in fluoride compounds used in the fluoridation process are at least two orders of magnitude below drinking water guideline values for these metals established by WHO and other organisations.
Trace metal concentrations may be higher in non-fluoridated water
Trace metal concentrations found in non-fluoridated water in England are often higher than those found in fluoridated water.