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How pure are the chemicals used?

POSTED 10 July 2018

It may come as a surprise to many people that the chemicals used to fluoridate drinking water in New Zealand are not pharmaceutical grade, meaning that they are not of the same purity used in dental products. Instead, the bulk of the chemicals used come from the wet-scrubbing systems of the phosphate fertiliser industry.

The Phosphate Fertiliser Industry

Wet scrubbers were introduced into he phosphate manufacturing process to remove two highly toxic gases: hydrogen fluoride (HF) and silicon tetrafluoride (SiF4). For many years these gases had damaged vegetation in the vicinity of phosphate plants, as well as crippling cattle on local farms. Fortunately, a spray of water is able to capture the gases and convert them to a solution of hexafluorosilicic acid (H2SiF6). When this resulting solution has reached a concentration of about 23 percent, it is shipped untreated in large tanker trucks to chemical companies that then send it around the country to be used as a fluoridating agent.

These chemicals cannot be dumped onto the land, into the sea or rivers by law and it would be costly for industry to dispose of this hazardous product.

New Zealand councils

Of the 23 councils that fluoridate their water, all use the acid form normally referred to as hydrofluorosilicic acid. Only in Lower Hutt’s Waterloo pumping station is it added as a dry powder of this same chemical, sodiumsilicofluoride. Most of the chemical is sourced in New Zealand although Invercargill buys their fluoridation chemical from China.

Environmental Impact

The Water NZ Good Practice Guide confirms HFA is a “co product” from manufacture of phosphate fertilisers. “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.. This byproduct has other uses - solar panel fabrication, computer chip fabrication, chemical stock, glass etching. This is not something that we want added to the water supply. The US Environmental Protection Agency (EPA) has described the use of HFA “as an ideal environmental solution long standing problem.” 

In May 2018, Balance Agri-nutrients was fined for toxic fluoride gas being emitted into the environment. These fluoride gases should be caught in the wet scrubber chimneys to protect the surrounding environment.  In October 2015, Mosaic Fertilizer, a phosphate mining and fertilizer company agreed to a settlement of over $1 billion with the US EPA. The EPA accused Mosaic of improper storage and disposal of waste from the production of phosphoric and sulfuric acids. “Fluoride compounds are toxic and should be handled with care. Suppliers of fluoride compounds must comply with the relevant regulations for classification, marking, packaging, labelling and transporting of material, currently including the Hazardous Substances and New Organisms Act 1996 and Regulations and their amendments, Land Transport Rule 45001/1 and NZS 5433.1&2: 2012, Transport of Dangerous Goods on Land.

In 2016 and 2017, Fluoride Free NZ aired a TV advertisement (see below) which clearly explains the source of fluoride chemicals used to fluoridate. Complaints against the advertisement were “not upheld” because the advertisement was truthful.

The Ministry of Health doesn’t specifically mention the source of Fluoride. They state, “Water fluoridation is the process of adjusting the natural level of fluoride in the water supply” . IXOM, largest supplier of HFA in NZ, do not disclose the source of fluoridation chemicals used other than referring to the Water NZ Good Practice Guide and state that HFA is “sourced from reputable specialist manufacturers” .

The use of the hazardous chemicals used to fluoridate have begun to receive increased exposure from high profile environmental activists like Erin Brockovich. “My career has been about making people aware of harmful exposures and the deception that often accompanies those exposures. Drinking water fluoridation is harmful, we’ve been deceived to believe it is safe, and with new found knowledge we must all act now to stop it.” 


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