The New Zealand Ministry of Health defines water fluoridation as:
"The process of adjusting the natural level of fluoride in the water supply to between 0.7 ppm and 1.0 ppm. This is the optimal amount that provides protection against tooth decay. The amount added is monitored to make sure that the levels stay within that range."
The Ministry of Health website also points out that, in June 2018, the New Zealand Supreme Court issued a judgment confirming that local authorities have the legal authority to fluoridate water supplies. The judgment also notes that “in doing this, local authorities are not breaching people’s individual rights to refuse to undergo medical treatment”.
The Ministry of Health reports that tooth decay is “the single most common chronic disease for New Zealanders” and that water fluoridation provides benefits “over and above brushing twice daily with fluoride toothpaste and eating a healthy diet”.
Fluoride Free NZ is an organisation whose purpose is to end water fluoridation in New Zealand. It argues that water fluoridation doesn’t work, is not safe and robs people of choice. Its website also says that “the overwhelming body of scientific and statistical evidence does not support fluoridation”.
Review of international evidence
The Royal Society of New Zealand and the Office of the Prime Minister’s Chief Science Advisor were commissioned to review the scientific evidence relating to water fluoridation. Their conclusions (2014) include these statements:
"The only side effect of fluoridation at levels used in NZ is minimal fluorosis, and this is not of major cosmetic significance. There are no reported cases of disfiguring fluorosis associated with levels used for fluoridating water supplies in New Zealand.
"There is no evidence that typical fluoride intakes from formula feeding, using optimally fluoridated water for reconstitution, has any adverse effects on infant health or child development aside from a possible greater risk of mild dental fluorosis.
"We conclude that the scientific issues raised by those opposed to fluoridation are not supported by the evidence."
The important point is that the scientific studies that anti-fluoride campaigners use tend not to be directly relevant to the issue of water fluoridation at the levels that are used in New Zealand.
Fluoridation – a question of science or a question of societal values?
Sir Peter Gluckman, former Chief Science Advisor, writes that there are two issues on which the public debate is often centred, and both of these involve values.
The first issue is how to balance the common good of a population-based intervention with individual rights. He says that this is primarily a question of societal values – not science – similar to regulations that require us to wear seatbelts.
The second issue also involves values – should food be used as a medium for delivering a public health intervention? He points out that we already do this by adding iodine to salt. Too little iodine leads to neck swelling, weight changes, tiredness, hair loss, flaky skin, changes in the body’s ability to control its temperature, changes in heart rate and difficulties in learning and remembering and may stunt the development of an unborn baby.
Using scientific evidence inappropriately
There are genuine concerns regarding fluorine poisoning in areas overseas where extremely high concentrations of fluoride naturally occur in the water or in the diet, but the science is clear that there is no risk of such disorders at the doses of fluoride added to local New Zealand water supplies. So why do these concerns continue? The misuse or inappropriate and alarmist use of science is a classic example of science being a proxy for values debates.
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.Sir Peter Gluckman
A socio-scientific issue is an issue that draws on both scientific and social or values-based arguments. Because of this, people hold different viewpoints about how it might be addressed. Students should have access to a wide range of sources while developing their own personal viewpoint on any one issue. The skills they will develop include:
- critiquing sources of information
- analysing the relevant scientific evidence
- identifying the potential social implications and multiple perspectives about these issues
- articulating and justifying their own positions.
Being able to form and justify a personal position is a critical skill in the scientific community as well as in everyday life.
The fluoride debate in New Zealand has been well documented. The article Hamilton’s fluoride debate chronicles the Hamilton City Council’s decision to stop and then restart fluoridating the city’s water supplies.
Below are a selection of links that students can use to read about scientific reviews, critiques and responses both for and against the issue. What constitutes evidence and the use of emotive language are two interesting aspects to explore.
Other food interventions
Fluoride is just one of many treatments used in New Zealand to protect human health. Others to consider are:
- the mandatory addition of iodised salt to bread
- the voluntary addition of folic acid to bread
- the chlorination of water supplies
- the pasteurisation of milk to eliminate health risks such as tuberculosis, brucellosis, E. coli and Campylobacter.
Students may wish to explore public attitudes to these treatments and what alternatives are available for people who oppose the treatments.
Nature of science
Socio-scientific issues are an engaging and relevant way to develop students’ scientific literacy. Being able to understand and evaluate scientific evidence helps students to recognise the misuse or inappropriate use of science in values debates.
The Hub has other articles on socio-scientific issues, ethics and pedagogy.
Explore the use of fluoridation from different ethical perspectives using the Ethics thinking toolkit.
How much is 1 ppm? The activity Exploring small doses provides the opportunity to make a liquid measure of one part per million.
New Zealand scientist Muriel Bell was instrumental in having iodine added to salt (to prevent the swelling of the thyroid gland called goitre) and fluoride to water (to reduce tooth decay). This timeline outlines her research and fluoridation in New Zealand.
The following links will give students a range of perspectives regarding water fluoridation – not all of which are scientifically robust. This will be useful for students to develop skills to critically analyse sources of information.
The Open Parachute website has articles and comments from Ken Perrott who is pro-fluoride and Paul Connett who is anti-fluoride.
The Supreme Court’s 2018 decision and media release regarding local authorities’ legal authority to fluoridate water supplies.
Fluoride Free NZ’s media release regarding the Supreme Court’s 2018 decision.
A Royal Society Te Apārangi expert panel unanimously concludes that the benefits of mandatory fortification of packaged bread with folic acid outweigh possible but unproven adverse effects.