Step 1 – Production of SiF4 The superphosphate production process results in the evolution of carbon dioxide, steam and SiF4. This SiF4 is an environmental pollutant and so is removed from the gas stream and used to produce fluorosilicic acid.
Step 2 – Hydrolysis of SiF4 The SiF4 is removed from the gas stream by contacting the gas with water droplets. This water hydrolyses the SiF4 as follows: 3SiF4 + 2H2O → 2H2SiF6 + SiO2 The resultant hydrofluorosilicic acid (H2SiF6) is used for fluoridating drinking water

TV advert aired on TV3 IN 2014. This advert explains where the fluoridation chemicals come from. Complaints were made by the public to the Advertising Standards Authority claiming this couldn’t be true, but the complaints were not upheld. See Supporting Evidence.

A report by RNZ in January 2023 explains:

“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.”

https://www.rnz.co.nz/news/environment/483279/northland-s-first-major-fluoride-treated-drinking-water-likely-next-year

A report by Water New Zealand explains:

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.

Water New Zealand – Supply of Fluoride for Use in Water Treatment 2014

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”. See to Leslie A Russell 30 March 1983

Ballance Agri-Nutrients Limited (Ballance), charged with discharging a contaminant (namely sulphur dioxide and/or fluoride) from an industrial or trade premises into air, contrary to s15(1)(c) and 338(1)(a) of the Resource Management Act 1991 on 22 May 2017.

The maximum penalty for such an offence under s 339 of the Act is a fine not exceeding $600,000.

Ballance pleaded guilty to the charge and were ordered to pay a fine of $82,500, less 10% payable to the Crown, paid to the Bay of Plenty Regional Council.

Ruling BAY OF PLENTY REGIONAL COUNCIL vs BALLANCE AGRI-NUTRIENTS LIMITED