As parliament considers a bill to put decision-making about community water fluoridation in the hands of district health boards, fluoridation is likely to remain a polarising issue for some communities.
The SMC asked New Zealand and international experts to discuss what the science says about the benefits of fluoridation and where the objections stem from. Feel free to use these comments in your reporting.
– Dr Robin Whyman, Hawke’s Bay District Health Board
– Associate Professor Jonathan Broadbent, University of Otago
– The United States Centre for Disease Control and Prevention
EXPERT Q&A: Dr Robin Whyman
Dr Robin Whyman
Clinical Director Oral Health, Hawke’s Bay District Health Board
NZ’s fluoridation is decided on a region-by-region basis – is there any evidence for differences between health outcomes in fluoridated vs non-fluoridated regions?
“A number of studies have examined the differences in dental caries (dental decay) between children living in fluoridated and non-fluoridated area of New Zealand.
“A study published in 2004 reported the severity of dental decay of children aged 5 years and 12 years in Wellington (fluoridated) and Canterbury (non-fluoridated). In 5-year-old children dental decay severity was 30% lower, and in 12-year-old children 40% lower, in fluoridated Wellington than in non-fluoridated Canterbury children, after controlling for confounding factors.
“In 2005 a study of Southland children living in Invercargill, Gore, Winton and Queenstown reported that children aged 9 and 10 years living in fluoridated areas had half the severity of dental decay of those living in non-fluoridated areas, again after controlling for confounding factors.
“In 2009 an Auckland study of 9-year-old children found those living all of their lives in fluoridated areas were under half as likely to have dental caries as those living none of their lives in fluoridated areas.
“In 2009 New Zealand conducted a national oral health survey of children and adolescents and reported that those living in areas with fluoridated water had a 40% lower incidence of dental decay.
“The evidence regarding the effect of fluoridation on oral health for children and adolescents in NZ is summarised in a report for the NZ Ministry of Health by the Sapere Research Group entitled Review of the benefits and costs of fluoridation in New Zealand and published in 2015.”
Globally, what is the current evidence for fluoridation?
“The Sapere Report (2015) summarises three key multi-study analysis reports on the effectiveness of community water fluoridation for children. It reports that the benefit was a 38% reduction in dental decay in the York Report (2000), 35% in a 2015 Cochrane review and 30-59% reduction in primary teeth and 50-59% reduction in children’s permanent teeth in a 2012 meta-analysis of available studies (Rugg-Gunn and Do 2012).
“The Sapere report also summarises the results of studies of adult oral health. The 2013 Australian adult oral health survey found the impact of community water fluoridation was 10% fewer decayed missing and filled teeth in adults aged 15-44 years and 11% fewer decayed missing and filled teeth in adults 45 years and over.
“The study reported a greater impact on the numbers of decayed and filled tooth surfaces, rather than just counting total teeth. The study controlled strongly for the many confounding factors that affect decay levels between adults groups, including the length of time people had lived in a fluoridated area. The only group to have statistically significantly lower levels of dental decay were those who had lived more than or equal to 75% of their lives in a fluoridated area.
“Similarly the recent Cochrane review published in 2015 reported that a meta-analysis of 10 before-and-after fluoridation studies for adults, reported a 26% reduction in the level of dental decay.”
“A 2017 statement from the Australian National Health and Medical Research Centre (NHMRC), based on a comprehensive review of the evidence published by the NHMRC in 2016, reported that community water fluoridation reduces tooth decay in children and adolescents 26% – 44% and in adults by 27%”
Fluoridation has become a highly-charged debate, where does this opposition stem from?
“Opposition to fluoridation focuses on a lack of acceptance of the science. Opponents question the benefits to oral health, and frequently do not accept that science does not support purported health risks.
“Opposition also focuses on the question of the legalities of fluoridation and suggests that community water fluoridation is unethical because it is suggested to constitute a form of mass medication.”
What are the main arguments against fluoridation and where does the evidence stand on these points?
“The evidence of a documented benefit to oral health from community water fluoridation has been discussed in questions 1 and 2.
“In 2014 the Royal Society of New Zealand published a report entitled Health effects of water fluoridation: A review of the scientific evidence. The report was commissioned by Sir Peter Gluckman (Prime Minister’s Chief Science Advisor) and Sir David Skegg (then-President of the Royal Society of New Zealand). It was undertaken by an expert panel, and then reviewed by international peer reviewers.
“The report’s summary finding, in terms of health effects from community water fluoridation, is:
“Given the caveat that science can never be absolute, the panel is unanimous in its conclusion that there are no adverse effects of fluoride of any significance arising from fluoridation at the levels used in New Zealand. In particular, 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.
“All of the panel members and ourselves conclude that the efficacy and safety of fluoridation of public water supplies, within the range of concentrations currently recommended by the Ministry of Health, is assured. We conclude that the scientific issues raised by those opposed to fluoridation are not supported by the evidence.”
“The 2017 NHMRC statement discussed in the previous question regarding current evidence for fluoridation summarized their 2016 comprehensive review of the evidence on effects on human health by stating “There is no reliable evidence of an association between community water fluoridation at current Australian levels and any health problems”. Levels of fluoride used for community water fluoridation in Australia and New Zealand are very similar.
“In recent years a group opposed to fluoridation has tested the legality of fluoridation in New Zealand and suggested that fluoridation is a breach of s11 of the NZ Bill of Rights Act (1990) (New Health New Zealand v Sth Taranaki District Council) which covers the right refuse medical treatment.
“The case was initially heard in the High Court by Justice Hansen. He found that the fluoridation of community water supplies is lawful and rejected the suggestion that it breaches s11 of the NZ Bill of Rights Act (1990) (NZBORA).
“He went further to state that while fluoride has a therapeutic purpose, it does not constitute medical treatment, and even if it did, s5 of the NZBORA applies, that is that fluoridation is a justified curtailment of the right to refuse medical treatment.
“These rulings were appealed to Court of Appeal, and upheld in 2016.”
How should DHBs or local government balance the public health benefits of fluoridation against the perceived issues raised by opponents?
“District Health Boards (DHBs) or local government should seek the advice of the scientists, medical and dental professionals with expertise in public health issues and fluoridation.
“DHBs and local governments should weigh statements against fluoridation with the information about the benefits to oral health for communities, especially children and people who are at greatest risk of dental decay.
“A public health approach to considering these issues requires careful consideration of the benefits to people who are the most vulnerable, or unable to express strong opinions themselves.”
Fluoridating a community’s water supply holds significant infrastructure costs – how do these costs compare to savings in public health costs?
“The Sapere Report 2015 has stated that:
‘We estimate that adding fluoride to New Zealand’s water treatment plants classified as medium (i.e. those supplying populations over 5,000), is cost-saving; and for those plants classified as minor (i.e. those supplying populations over 500) it is likely to be cost-saving.
‘We estimate the net discounted saving over 20 years for minor and above plants to be $1,401 million, made up of a cost of fluoridation of $177 million and cost offsets of $1,578 million from reduced dental decay. We estimate the 20-year discounted net saving of water fluoridation to be $334 per person, made up of $42 for the cost of fluoridation and $376 savings in reduced dental care.
‘In short, there is a 9 times payoff; adjusting the discount rate from 3.5 percent to 8 percent results in a 7 times payoff. The costs of fluoridating water treatment plants fall to district councils. The benefits accrue to the health system in a small way and largely to individuals.’”
What would you say to people who are confused or concerned by the debate around community water fluoridation?
“Community water fluoridation has a history in New Zealand of over 60 years, and a similar history in other countries such as the US and Australia.
“Community water fluoridation remains a safe and effective contribution to reducing the burden of dental decay for both children and adults with natural teeth. Ongoing research to test the effectiveness continues to show benefits, even though other measures such as fluoridated toothpastes are also now available.
“Repeated review reports, such as that by the Royal Society of New Zealand, conclude that adverse effects, other than minimal levels of very mild dental fluorosis, do not occur when water supplies are fluoridated at levels optimal to reduce tooth decay.”
EXPERT Q&A with A/Prof Jonathan Broadbent
Associate Professor Jonathan Broadbent
Associate Professor in Preventive & Restorative Dentistry, University of Otago
Globally, what is the current evidence for fluoridation?
“Dental health can vary between regions due to a range of reasons, such as deprivation and fluoridation. The evidence on this comes from epidemiological studies from New Zealand and overseas. Studies such as the most recent New Zealand National Dental Survey found differences in tooth decay between those living in fluoridated vs non-fluoridated regions.
“Appropriate levels of fluoride in water are beneficial for the teeth and this has been known for well over 50 years. The studies of fluoride in water are epidemiological in nature. The concentrations used are low and dental problems can take a long time to develop, so long-term studies are best for investigating this.”
What are the main arguments against fluoridation and where does the evidence stand on these points?
“Epidemiological research can’t absolutely prove that there is no possibility of harm from something like fluoridation. Epidemiological research can give us good confidence that it does not cause harm, but not with 100% certainty.
“The precautionary principle suggests that we don’t do something ‘just in case it causes harm’. However, applying this inappropriately can be counter-productive. I would argue that the known benefits of fluoridation in reducing the impact of such a prevalent disease as tooth decay, outweighs the hypothetical harms.”
How should DHBs or local government balance the public health benefits of fluoridation against the perceived issues raised by opponents?
“They should balance the known benefits of fluoridation against the known costs and harms of fluoridation.
“There are no known harms at the levels of fluoride used for fluoridation. The known costs are for things like infrastructure and ongoing costs of water treatment chemicals as well as staffing and monitoring.”
Fluoridating a community’s water supply holds significant infrastructure costs – how do these costs compare to savings in public health costs?
“The Ministry of Health has put out a valuable analysis of the cost vs effectiveness of fluoridation.
“In it, the Ministry of Health uses two competing analyses, which use different calculations, and yet come to the same basic conclusions. Dentistry is expensive, fluoridation is not, and it results in considerable cost saving.”
What would you say to people who are confused or concerned by the debate around community water fluoridation?
“Fluoride is in water anyway – all that is done in fluoridation is an adjustment of the levels. In New Zealand, the naturally-occurring fluoride levels are low, in other countries they are too high. It is important that fluoride levels be controlled so that they are ‘just right’.
“Fluoridation has been around for a long time. Fluoride toothpaste and fluoridated water are an important part of the reason that young New Zealander’s teeth are now much better than they were in previous generations.
“Fluoride is only part of the equation for improving dental health – we need to keep the pressure on for control of added sugars in foods and drinks. We also need to find ways to make dental care more accessible to people, as so many New Zealanders find dental care to be unaffordable.”
EXPERT Q&A: United States Centers for Disease Control and Prevention (CDC)
Representatives from The US Centers for Disease Control and Prevention (CDC)
Globally, what is the current evidence for fluoridation?
“The safety and benefits of fluoride are well documented and have been reviewed comprehensively by several scientific and public health organizations. The U.S. Public Health Service; the United Kingdom’s National Institute for Health Research, Centre for Reviews and Dissemination, at the University of York; and the National Health and Medical Research Council, Australia have all conducted scientific reviews by expert panels and concluded that community water fluoridation is a safe and effective way to promote good oral health and prevent cavities (tooth decay).”
The majority of US citizens drink fluoridated water – is there any evidence of differences in health outcomes between fluoridated and non-fluoridated regions?
“Evidence from the Guide to Community Preventative Services shows that water fluoridation prevents tooth decay by providing frequent and consistent contact with low levels of fluoride, ultimately reducing tooth decay by 25% in children and adults.
“Additional evidence shows that schoolchildren living in communities where water is fluoridated have, on average, 2.25 fewer decayed teeth compared to similar children not living in fluoridated communities.”
Fluoridation has become a highly-charged debate, where does this opposition stem from? AND what are the main arguments against fluoridation and where does the evidence stand on these points?
“Even though we have more than 70 years of experience and research to show that water fluoridation is safe and effective in promoting good oral health, many myths and misperceptions persist.
“In 2015, the U.S. Public Health Service reviewed the scientific information when they published the final recommendation for optimal level of fluoride (0.7mg/L) in drinking water.
“In 2006, the National Research Council (NRC) conducted an extensive, multi-year review of fluoride in drinking water. This report provides the most comprehensive summary of unwanted health effects. The NRC review focused on potential adverse effects of naturally occurring fluoride at 2-4 mg/L – a level notably higher than that recommended for community water fluoridation (0.7 mg/L).
“At levels below 4.0 mg/L, the only documented risk was dental fluorosis, a change in the appearance of the tooth enamel. Most dental fluorosis in the United States is very mild to mild. There have been no reported cases of severe dental fluorosis.
“The American Dental Association developed a comprehensive encyclopedia of fluoridation facts from over 350 scientific references, titled Fluoridation Facts.”
How should governments balance the public health benefits of fluoridation against the perceived issues raised by opponents?
“Each community should weigh the costs and benefits when deciding whether to begin fluoridation. Expert panels consisting of scientists from the United States and other countries, with expertise in various health and scientific disciplines, have considered the available evidence in peer-reviewed literature and have not found convincing scientific evidence linking community water fluoridation with any potential adverse health effects or systemic disorders such as an increased risk for cancer, Down syndrome, heart disease, osteoporosis and bone fracture, immune disorders, low intelligence, renal disorders, Alzheimer disease, or allergic reactions.”
What would you say to people who are confused or concerned by the debate around community water fluoridation?
“Community water fluoridation is one of the most practical, cost-effective, equitable and safe measures communities can take to prevent tooth decay and improve their oral health.
“Water fluoridation benefits people of all ages and socioeconomic groups, including those difficult to reach through traditional public health programs and private dental care. In fact, each generation born since the implementation of water fluoridation has enjoyed better dental health than the generation that preceded it.
“In addition, community water fluoridation saves communities money by avoiding the cost of dental treatment by protecting teeth. Communities of all sizes that support water fluoridation see a positive return on investment (ROI) by avoiding costs of dental treatment.”