The Queenstown Lakes District Council has been given a strong signal it may be required to fluoridate up to eight drinking water supplies, at a potential cost extending to millions of dollars.
The council has until February 2 to respond to a letter from director-general of health Dr Diana Sarfati, who is "actively considering" directing the council to fluoridate the Queenstown, Wanaka, Arrowtown, Hawea, Lake Hayes, Arthurs Point, Glenorchy and Luggate supplies.
Dr Sarfati said each supply would be considered separately.
Queenstown Lakes is one of 27 councils that received a "notification of active consideration" from the director-general in November last year.
The Dunedin City Council, which adds fluoride to the vast majority of its network, was advised it could be required to add Waikouaiti and Outram to the list.
Fourteen councils, including the Waitaki district, were already told in July they would need to fluoridate some or all of their drinking water supplies.
Dr Sarfati said she would take into account oral health, population size, estimated costs of fluoridation and whether its benefits outweighed costs.
The Queenstown Lakes district has previously estimated it would cost about $4.1 million to install fluoride dosing at all of its water treatment plants.
The council noted each supply would be considered separately.
Any new requirement to fluoridate water would apply after July 2024.
When the directive to the 14 councils was issued in July last year, then director-general of health Dr Ashley Bloomfield said fluoridation was a safe, affordable and effective method of preventing tooth decay.
Councils cam apply for funding from an $11.3 million fund to help set up the necessary systems.
Several councils have since highlighted increasing costs.
The Ministry of Health estimated the July directives would increase the number of New Zealanders getting fluoridated water from 51% to 60%.
Implementing all of the directives being considered from November would push that up to 68%, the ministry said.
The Dunedin City Council estimated adding fluoride to the Waikouaiti and Outram supplies would cost about $150,000 each.
"These are early, broad estimates, and costs will be refined, if required, as part of any detailed design work that follows," Three Waters group manager David Ward said.
The council already plans to upgrade the Waikouaiti water treatment plant.
"We can accommodate any requirement to fluoridate as part of our planned upgrade," Mr Ward said.
