EXPLAINER: The Government will amend a long-dormant bill to shift control of water fluoridation discussions from local authorities to Director-General of Health, Dr Ashley Bloomfield. Hannah Martin looks at what fluoridation is, how it works, and what it means.

The decision whether to fluoridate water supply is in the hands of individual councils, leading to varying uptake across the country. A proposed change would see the buck stop with Dr Ashley Bloomfield.

Currently, close to 60 per cent of New Zealand’s population on reticulated water supplies – the piped water network – receive fluoridated water, approximately 2.5 million people.

Associate Health Minister Dr Ayesha Verrall announced the move on decision-making on Thursday, saying it will result in a nationally-consistent approach based on evidence.

The move has been hailed by health experts as a “victory for science”, one which will have “significant” health and cost-saving benefits and “hugely reduce suffering” linked to tooth decay.

What is fluoride?

Fluoride is a mineral found in your bones and teeth.

It also naturally exists in water, soil, plants, rocks, air and lots of foods, including spinach, grapes, potatoes and tea.

Fluoride makes teeth more resistant to decay by strengthening the tooth surface. It also interferes with the growth of cavity-causing bacteria, and helps repair the early stages of tooth decay.

Fluoride is also used in medical imaging scans, such as PET scans, as a cleaning agent, in pesticides and to make Teflon, steel, and aluminium products.

It is ubiquitous in the environment, so every human who has ever lived has had at least some exposure to fluoride.

What is water fluoridation?

Water fluoridation is the process of adjusting the natural level of fluoride in drinking water supply to between 0.7 ppm (parts-per-million) and 1.0 ppm.

The Ministry of Health says this is the optimal amount that provides protection against tooth decay, as recommended by the World Health Organisation.

The current level of fluoride found in untreated water supplies is not effective enough to be of benefit in helping prevent tooth decay, so ‘topping up’ the fluoride levels in water supplies has been done in many regions over several decades.

The amount added is monitored to make sure that the levels stay within that range.

Along with brushing twice a day, eating healthy foods and regular dental check-ups, water fluoridation is the “most effective” public health measure to prevent tooth decay – backed by the World Health Organisation and the Centers for Disease Control and Prevention (CDC).

The most recent New Zealand Oral Health Survey (2009) found that children and adolescents have 40 percent less tooth decay in areas with fluoridated water supplies.

Water fluoridation is not new in New Zealand, and has been occurring in some parts of the country since 1955.

How does water fluoridation work?

Fluoride is usually added during the final stages of water treatment, according to Water New Zealand.

There are three chemicals used for the fluoridation of drinking water:

• Fluorosilicic acid (FSA) – formerly called Hydrofluorosilicic acid (HFA)
• Sodium fluoride
• Sodium fluorosilicate (SFS) – also known as sodium silicofluoride.

Sodium fluoride and SFS are supplied as powders that are dissolved in water to make a solution that is then added to the water supply, while FSA is supplied as a liquid.

Fluoride is added to the water at a controlled rate, relative to the flow through the treatment plant to achieve a target concentration.

There are currently 50 treatment plants supplying more than 2.5 million people with fluoridated water across 137 drinking-water zones, according to the Institute of Environmental Science and Research (ESR).

Water New Zealand said while all three chemicals are used in Aotearoa, FSA (fluorosilicic acid) predominates.

Fluoride dosing at treatment plants is the responsibility of the water supply owner.

Public health officials say adding fluoride to the water system doesn’t change the taste or smell of the water itself.

What has been done until now, and what does the change mean?

At present, individual councils have had the final say on whether to fluoridate its water supply.

This week, Verrall made the change by picking up a dormant bill from the last National government that would shift the power to the country’s 20 District Health Boards instead.

She is amending the Health (Fluoridation of Drinking Water) Amendment Bill so the power goes directly to Bloomfield, as director-general of health.

The proposed change will be made by a Supplementary Order Paper.

Professor Barry Borman?, director of Environment Health Indicators NZ, of Massey University said it “was about time” the change was made.

“This should have been done years ago,” he said, stating the issue was “far too important for there to not be national approach”.

However, National’s health spokesman Dr Shane Reti? has expressed concern in the move, calling it an “over-reach” by Government.

“At first blush it looks like an over-reach by Government with quite a dramatic change.”

Reti said he supported the science behind fluoridation absolutely, but was worried the centralisation of power would stir up more resentment by those who are against fluoridation.

Many people have lobbied councils – sometimes successfully – against fluoridating water.

NZ First blocked the fluoridation bill from being progressed during the last term.

Which areas do and don’t fluoridate their water?

Currently, only about a third of the country’s councils provide fluoridated water, according to a list compiled by an anti-fluoride lobby group.

All Auckland homes on the reticulated network – barring Onehunga and Huia – receive fluoridated water.

None of Northland’s three councils provide water fluoridation.

About half of Waikato councils fluoridate their water, while the majority of those in the Bay of Plenty do not – except for Taup? and Whak?tane district councils.

No Hawke’s Bay councils provide fluoridation at present, but Hastings District Council – which stopped adding fluoride to drinking water after the 2016 gastro outbreak – plans to resume this in 2021.

The majority of greater Wellington’s eight city councils provide fluoridation, except Carterton and South Wairarapa city councils. Petone, under Hutt City Council, does not receive fluoridated water.

Most Manawatu-Wanganui councils do not fluoridate their water, but Palmerston North and Feilding (under Manawatu District Council) do, the lobby group states.

Tasman, Nelson, Marlborough, and the three West Coast councils do not have fluoridated water, and neither do all nine councils in Canterbury – save for Methven, under Ashburton District Council.

Dunedin, Clutha – set to resume fluoridation from June – and Invercargill are the only councils in Otago and Southland to fluoridate their water supply.

Verrall has said the intended move is for a more aligned approach.

“The proposed change, which will be made by a Supplementary Order Paper, simplifies the decision making and means we are taking a nationally consistent approach that’s based on evidence,” Verrall said.

What are people’s concerns?

Claims have been made that fluoridation causes or contributes to a number of health conditions such as cancer, skeletal fluorosis, Down’s syndrome, renal disease, allergic conditions, repetition strain injury, and that it causes interference with enzyme function.

These claims have not been substantiated by experimental studies or epidemiological analyses, the Ministry of Health states.

With hundreds of millions of people continuing to receive the benefits of fluoride in drinking water, the absence of documented adverse health effects is particularly convincing.

In 2015, the Prime Minister’s Chief Science Advisor and Royal Society of New Zealand concluded: “No effects on brain development, cancer risk or cardiovascular or metabolic risk have been substantiated, and the safety margins are such that no subset of the population is at risk because of fluoridation.”

“There is no evidence to support these claims. And we don’t see a difference in fluoridated and non-fluoridated areas in New Zealand.”

Who foots the bill?

Experts say there is “strong evidence” community water fluoridation is cost-effective, saving much more in dental costs for individuals than it costs to run the programmes.

A 2015 Sapere Research Group study put the cost of fluoridation at approximately $2.60 per person, per year, versus the average cost of a single filling for an adult: $250.

Sapere stated that for every dollar spent on water fluoridation, $9 is saved in dental care costs.

Some of these savings are seen by the health system, but it was largely individuals who benefit, it said.

Local authorities are responsible for the direct operating and capital costs of fluoridating drinking.

There will be funding available to support meeting the costs of fluoridation-related capital works for those councils that are not currently fluoridating, a ministry spokesperson told Stuff.

Is it safe?

“Overwhelming” evidence from decades of community water fluoridation is that it is safe, the Ministry of Health states.

Professor Peter Gluckman?, the Prime Minister’s Chief Science Advisor from 2009-2018, previously said: “It is absolutely clear that at doses used in New Zealand to adjust the natural level to one that is consistent with beneficial effects… there is no risk from fluoride in the water”.

While there is a large body of evidence of its “significant benefits” to oral health, there is no evidence linking fluoridation with any adverse health effects, health officials said.

While fluoride can be toxic in large amounts, the ministry has said a person would need to drink thousands of glasses of water in a single sitting to obtain anything near a lethal dose.

*Original article online at https://www.stuff.co.nz/national/health/300256240/what-is-water-fluoridation-and-how-does-it-work

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