If you live in the reticulated parts of Lower Hutt, Porirua, Upper Hutt or Wellington, then you almost certainly receive fluoridated water. Petone and Korokoro - supplied from Hutt City Council's Rahui reservoir - are the only areas within the four cities that receive unfluoridated water. This is because they have historically had an unfluoridated water supply and Hutt City Council asked that we continue that arrangement following a public survey in 2000.
The natural level of fluoride in Wellington’s water is around 0.1 milligrams per litre or parts per million (ppm). The Ministry of Health recommends that water suppliers should adjust the amount of fluoride in drinking water to between 0.7 and 1.0 ppm, as this is considered the optimal level for good dental health. Our policy is to adjust the fluoride content of the water we supply in line with the Ministry's recommendation. Our customers, the region’s four city councils, support this policy.
There has been much debate about the merits of adding fluoride to water supplies. The current advice and information that we have from the Ministry of Health is that there are no significant health concerns associated with water fluoridation at the optimal level for dental health: 0.7 to 1.0ppm.
Sodium silicofluoride (SSF), a powder, is used at our Te Marua, Wainuiomata and Waterloo treatment plants. The SSF we use has a minimum purity of 98.5% and is regularly tested to ensure that the minute quantities of other chemical elements, such as metals, that it contains are well within the maximum safe limits described in the Drinking Water Standards for New Zealand.
Hydrofluorosilicic acid (HFA), a liquid, is used at our Gear Island treatment plant. HFA has a fluoride content of not less than 15% and is typically around 18%. As for SSF, the HFA we use is tested to ensure that any other chemical elements of health significance that it contains are at safe levels in relation to the Drinking Water Standards for New Zealand.
The total annual cost of fluoridating the water that we supply is approximately $220,000 or around 55 cents per head of population supplied.