Fluorine is one of the most chemically reactive elements in nature. As a consequence, it is always found in combination with other elements. CAS number 16984-48-8 relates to the fluoride ion. Fluoride compounds have different CAS numbers, e.g.16961-83-4 for Hydrofluosilicic Acid (HFSA), which is used for water fluoridation. The fluoride currently used for water fluoridation is sourced as a primary product. It is mined directly from a raw material source, the mineral fluorospar as calcium fluoride (CaF2). It then goes through a purification process to conform to tightly controlled specifications under the requirements of CEN Standard I.S.EN 12175:2001 to produce HFSA. It should also be noted that there are fluoridated public water supplies where there are existing background levels of naturally occurring fluoride and these levels are augmented using HFSA to the prescribed optimal level.
The principles for approval of use of HFSA in treatment of water intended for human consumption are no different to those relating to other chemicals used in drinking water treatment, such as disinfectants and coagulants. No water treatment chemical is intended for direct human consumption. The level of fluoride in drinking water in Ireland has been set at between 0.6-0.8 parts per million. This level of fluoride is deemed optimal for protecting the oral health of all age groups.