“If fluoridation goes ahead, councils will be using New Zealand-made industrial fluoride in the form of fluosilicic acid, also known as hydrofluosilicic acid. Hydrofluosilicic acid is produced during the manufacture of superphosphate fertiliser. It is the form of fluoride most widely used by New Zealand councils, added into drinking water as a liquid.”
Hydrofluosilicic acid is produced as a co-product in the manufacture of phosphate fertilisers. Phosphate rock, which contains fluoride and silica, is treated with sulphuric acid. This produces two gases: silicon tetrafluoride and hydrogen fluoride. These gases are passed through scrubbers where they react with water to form hydrofluosilicic acid.
In 1983, Rebecca Hamner, Deputy Assistant Administrator For Water, US EPA stated:
“In regard to the use of fluosilicic acid as a source of fluoride for fluoridation, this agency regards such use as an ideal environmental solution to a long-standing problem. By recovering by-product fluosilicic acid from fertilizer manufacturing, water and air pollution are minimised”.