Hamilton’s fluoride debate

In June 2013, Hamilton’s city councillors voted to stop adding fluoride, used to protect teeth from tooth decay, to Hamilton’s drinking water. National public reaction and the debate that followed highlight both the need to source quality research-based advice and the importance of scientific literacy when making policy decisions.

Background to the 2013 Hamilton decision

Public consultation on the issue ran for a month, with a total of 1,557 submissions received. The majority (1,385) of submissions wanted the council to stop adding fluoride to the city water supply, with 170 submissions supporting the continuation of fluoride. After 4 days of hearings, the council voted 7–1 to stop the fluoridation when stocks run out.

Key reasons for stopping fluoridation

The key reasons submitters wanted the council to stop fluoridation were individuals having the right to choose what they ingest (994), the links between fluoride and a number of illnesses and risks (807) and that fluoride is considered ineffective in preventing tooth decay (741).

In the first area of objection, the view was that water fluoridation uses the public water supply to deliver a drug to a person who has not given their consent for this.

In the second case, submitters argued that fluoridation of the water is linked to a number of illnesses and risks, including bone cancer, arthritis, thyroid dysfunction, kidney disease, dental fluorosis, negative effects on brain development (particularly in infants and young children) and negative effects on the pineal gland (resulting in the earlier onset of puberty).

In the third area of objection, submitters drew on information by the Fluoride Action Network (FANNZ), which opposes fluoridation. This information summarised the latest New Zealand studies on dental health, finding that there was no significant difference in tooth decay rates in fluoridated areas compared to non-fluoridated areas.

Reactions from scientists

The decision infuriated experts, dentists and scientists throughout the country, who labelled the anti-fluoride campaign as inaccurate scaremongering. The Chief Science Advisor to the Prime Minister at the time, Sir Peter Gluckman, commented that the fluoride debate was a classic example of “science being a proxy for values debates”. In other words, he argued that people were using values rather than science to form their views.

In an interview with the Science Media Centre, Dr Jonathan Broadbent, Senior Lecturer in Preventive and Restorative Dentistry, University of Otago, said the decision undermines public health in New Zealand.

"The World Health Organisation, the World Dental Federation and the International Association for Dental Research have all stated that ‘universal access to fluoride for dental health is part of the basic human right to health’. In New Zealand, a central part of the universal right to fluoride is community water fluoridation. The New Zealand Ministry of Health Guidelines and Statements (2010) on fluoridation are clear: community water fluoridation is effective and safe, and community water supplies in New Zealand should be fluoridated at 0.7–1.0 parts per million (ppm) wherever feasible. The 7 Councillors who voted against this in Hamilton were either unaware of this, or disregarded it (as well as disregarding the opinion of their own citizens from a 2006 referendum).

"Those who are unwilling to drink fluoridated water should not be permitted to impose the risks, damage and costs of failure to fluoridate on others. The ethics and science in support of fluoridation are clear, but antifluoridation arguments often present a highly misleading picture of water fluoridation."

Dr Broadbent said a recent New Zealand Oral Health Survey found much less tooth decay in fluoridated than non-fluoridated areas. “There is generally 0.3 ppm background fluoride in New Zealand (although it varies), and adjusting that to Ministry of Health-recommended levels has a significant effect of reducing tooth decay among people of all ages.”

It is clear that there is no risk of such disorders at the doses of fluoride being used and extensive epidemiological surveys have repeatedly confirmed this to be the case. So why does this concern continue? The misuse or inappropriate and alarmist use of science is a classic example of science being a proxy for values debates.

Sir Peter Gluckman

A New Zealand Herald editorial stated: “Given the abundance of research confirming the benefits of fluoridation, it seems bizarre that its use is even being discussed. Yet the number of councils bowing to the scaremongering of a vocal minority is increasing.”

What the debate is really about

Sir Peter Gluckman wrote in his statement on 12 June 2013 that we need to examine what the debate is really about.

"There is no doubt that the presence of low amounts of fluoride in water (either naturally occurring or adjusted to between 0.7 and 1 ppm) reduces the incidence of dental caries and this is even in advanced economies where dental hygiene has been much improved and where fluoride toothpastes are available. In some countries, fluoride need not be added to the water supply because their geology naturally provides water with fluoride in at least these concentrations. But for some decades, in countries such as New Zealand, where fluoride levels are very low in natural water, fluoride has been added to the water supply.

"Notably, both the very young and the old benefit from fluoride in the water supply. They develop fewer dental caries and thus have a significant reduction in the downstream effects such as the need for invasive dental surgery associated with problematic dental status. As in all populations the burden of poor dental health is considerably greater for those in less advantaged socioeconomic conditions and it is this population that benefits most from water fluoridation.

"Like any agent, including salt, sugar and water itself, if you eat or drink enough, it can become toxic. At the doses used in New Zealand water, however, one would in all likelihood become very ill or succumb to water intoxication before any toxic effect of fluoride was discernible."

Common good versus individual rights

Sir Peter writes there are at least two primary questions on which public debate seems to be hinged. The first is how to balance the common good of a population-based intervention with individual rights.

"This is primarily a question of societal values not science. Indeed, the balance between doing good (reducing caries) and not doing significant harm (minimal dental mottling) is scientifically clear. Thus in some ways any remaining debate has analogies to the immunization situation and to the imposition of regulations such as those requiring the wearing of seat belts. [The issue is not whether fluoride at the recommended dose works but] whether to apply the science-based knowledge in this equation is a question of public health ethics and societal values."

The second issue is a related values debate. Should food be used as a medium for delivering a public health intervention?

"Is it OK for public water to be manipulated for an additional health benefit or for a potentially medicinal purpose? As it happens we already do so with iodine – our salt is iodised to prevent the developmental delay (cretinism) and goiters (big thyroid glands) associated with iodine deficiency and which was so common in New Zealand 100 years ago. There is no scientific issue here – it is purely an issue of values.

"It is often easier for those seeking to advance values-based concerns to make the science sound scary or more uncertain than it really is. Indeed, it becomes a tactic amongst those who become passionate about their cause. Because biology and medicine are complex, studies can be difficult to put in perspective and odd results can be given undue weight."

Development of good evidence-based policy requires scientific input, particularly when turning research findings into policy.

Dr Jonathan Broadbent, Senior Lecturer in Preventive and Restorative Dentistry, University of Otago

Inappropriate interpretations of scientific studies

The fluoride debate is based in no small part on numerous examples of inappropriate extrapolation from what happens at hugely higher doses of fluoridation.

With regard to fluoride, concerns have been raised regarding risks of bone disease, thyroid disease, brain disease and cancer. While these claims are not supported by scientific evidence, they continue to be emphasised by those who oppose fluoride. Some of this continued emphasis is based on inappropriate interpretations of studies in rats or from humans who have fluoride poisoning or live in areas where there are extremely high concentrations of fluoride naturally occurring in the water or diet. It is clear that there is no risk of such disorders at the doses of fluoride being added to drinking water, and extensive epidemiological surveys have repeatedly confirmed this to be the case.

So why does debate about fluoride in water continue? Rather than discussing the values involved, which would be appropriate, the debate can be hijacked by a misinterpretation (and sometimes deliberate misuse) of science.

Values debates are critical for a healthy democracy, but they cannot proceed usefully if the debate is shifted inappropriately to another domain. On the other hand, scientists do not have a privileged position within a values debate beyond clarifying when science is being misused.

The outcome for Hamilton city residents

Within a month of the Hamilton City Council decision, Hamilton residents presented a petition calling for a referendum on fluoridation. The non-binding referendum was held during the October 2013 local government elections. The votes were 70% in favour of resuming fluoridation to the city’s water supply. In March 2014, the council voted 9-1 to recommence fluoridation. In April 2016, the council provided two taps that supply unfluoridated water for those who wish to collect water from them.

National decision

In June 2018, a Supreme Court judgment confirmed that local authorities have the legal authority to fluoridate water supplies.