Drinking water supplies across the country are set to be fluoridated after an amendment bill passed five years after it was first proposed.

Associate Health Minister Dr Ayesha Verrall ?said she was proud of the bill, which would reduce pain and suffering from dental decay and provide a nationally consistent approach to fluoridation.

After a chorus of support for the bill from MPs of almost every political stripe, the bill passed its third and final reading on Tuesday evening. Initial funding of $8.3 million, plus another $3m per year, will be available to contribute towards local authorities’ fluoridation-related capital works.

Currently, territorial authorities have responsibility for decisions on fluoridating drinking water supplies and about half of the population live in areas with fluoridation.

In 2016, the National government, submitted a bill to transfer responsibility for fluoridation from local councils to district health boards.

In March this year, Verrall announced an amendment to the proposed bill, giving Director-General of Health Dr Ashley Bloomfield control of water fluoridation.

Christchurch is the only major centre in New Zealand without a fluoridated water supply.

A 2020 study by public dental health researchers said the poor oral health of Canterbury children was an “ongoing paediatric health crisis”. Their data showed nearly 20 per cent of Canterbury’s 5-year-olds had tooth decay.

Water fluoridation is the process of adjusting the natural level of fluoride in drinking water supply to between 0.7ppm (parts-per-million) and 1.0ppm – the optimal amount for protection against tooth decay, as recommended by the World Health Organisation.

Verrall said the Government anticipated 80 per cent of the population would have access to fluoridated water as a result of the legislation.

She said there was “unequivocal evidence” in support of fluoridation, with the science supporting it established in the 1950s.

“It has been recommended for a long time by the Ministry of Health and the prime minister’s chief science adviser,” Verrall said.

“This bill will create a consistent national decision-maker and end a patchwork of different approaches across the country.”

Verrall said under the legislation “local factors will be taken into account and the feasibility of implementation at each location” by the director-general of health. Private water supplies will not be required to be fluoridated.

But she said the science of fluoridation would not be “re-litigated”.

“The science of fluoridation is settled, like that of seat belts and vaccination.”

Dr Shane Reti? said National supported the bill and the science behind fluoridation.

As a Northland health board member, he successfully advocated for the Far North’s water supplies to be fluoridated in 2007.

Reti said if the bill had not been amended, some health boards would likely have voted against fluoridation.

Green Party MP Elizabeth Kerekere? said the party supported the bill but asked for non-fluoridated drinking water access to continue, to provide an opt-out option.

ACT’s Brook van Velden? said the party supported the law “on balance” despite reservations about giving one person significant power “over local communities”.

MPs Sarah Pallett? (Labour), Kerekere?, and Chris Luxon? (National) acknowledged the issue of fluoridation had been plagued by misinformation, with most submissions on the bill containing incorrect information.

Christchurch specialist paediatric dentist and president of the New Zealand branch of the Australia-New Zealand Society of Paediatric Dentistry Arun Natarajan? said tooth decay was the most common reason for hospitalisation of children.

He said fluoridation was not a “magic bullet” but was one of the “key tools we have in fighting tooth decay”.

About 7000 children were referred for treatment requiring a general anaesthetic for severe tooth decay each year with hospital waiting lists growing year by year.