Effective and safe

Over 60 years of international and New Zealand research tells us that water fluoridation is effective and safe in reducing tooth decay.

The Office of the Prime Minister’s Chief Science Advisor has examined new evidence on water fluoridation. You can read about this on the Prime Minister's Chief Science Advisor website.

After considering new research on fluoridation and comprehensive reviews published since 2014, they found that the conclusions of the Royal Society Te Apārangi remain appropriate.

You can read this review below, along with an evaluation of the efficacy and cost benefit of water fluoridation. 

  1. Health Effects of Water Fluoridation: a Review of the Scientific Evidence (Royal Society of New Zealand and Office of the Prime Minister’s Chief Science Advisor, 2014)
    In 2014, the Prime Minister’s Chief Science Advisor and the Royal Society of New Zealand reviewed the substantial body of scientific evidence on the efficacy and safety of fluoridation of public water supplies.
  2. Review of the benefits and costs of water fluoridation in New Zealand (Sapere Research Group, 2015)
    The Ministry of Health commissioned the Sapere Research Group to provide an updated evaluation of the benefits and cost of water fluoridation in the New Zealand setting – they took an economists’s perspective and looked at the national cost-effectiveness and cost-benefit of fluoridation. In doing so, they also looked at the evidence for the efficacy and safety of water fluoridation.

Both papers were very clear in their conclusions that water fluoridation has a significant benefit to the reduction of tooth decay across the population, and that there is no evidence of any health issues arising from water fluoridation at the levels currently used in New Zealand.

For more information and to hear more from a range of New Zealand experts on the effectiveness and safety of water fluoridation, visit the Fluoride Facts section.

Evidence: effectiveness of water fluoridation

The most recent New Zealand Oral Health Survey (2009) shows that children and adolescents have 40 percent less tooth decay in areas which have fluoridated water supplies. The Sapere Research Group study highlighted that, while there is variability in individual studies, findings from meta-analysis consistently show significantly less tooth decay in areas with fluoridated water around the world.

Graph showing the findings of several reports and studies that confirm that there is significantly less tooth decay in areas with fluoridated water: the York report from 2000 reported 38 percent, Rugg-Gunn and Do in 2012 showed 30 to 59 percent, the Cochrane review in 2015 showed 35 percent, New Zealand Oral Health Survey in 2009 shows 40 percent less tooth decay for children, and the Australian National Oral Health Survey in 2013 between 20 to 30 percent less decay for adults.

In their review, the Prime Minister’s Chief Science Advisor and the Royal Society of New Zealand concluded that:

“A large body of epidemiological evidence over 60 years, including thorough systematic reviews, confirms water fluoridation prevents and reduces dental decay across the lifespan.“

“There is compelling evidence that fluoridation of water at the established and recommended levels produces broad benefits for the dental health of New Zealanders.”

“Our assessment suggests that it is appropriate, from the scientific perspective, that fluoridation be expanded to assist those New Zealand communities that currently do not benefit from this public health measure – particularly those with a high prevalence of dental caries.”

Evidence: safety of water fluoridation

Many parts of the world have had naturally fluoridated water for thousands of years. Large human populations have been using water fluoridation to ‘top up’ fluoride to optimal levels for more than 60 years. While there is a large body of evidence of its significant benefits to oral health, there is no evidence linking optimal fluoridation with any adverse health effects.

In their 2014 review, the Prime Minister’s Chief Science Advisor and the Royal Society of New Zealand were very clear in their conclusions:

“The only side-effect of fluoridation at levels used in New Zealand 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.”

“We conclude that the scientific issues raised by those opposed to fluoridation are not supported by the evidence.”

Myths about water fluoridation

Claims have been made that fluoridation causes or contributes to a number of conditions such as cancer, skeletal fluorosis, Down’s syndrome, renal disease, allergic conditions and fluoride hypersensitivities, repetition strain injury, and mutations, and that it causes interference with enzyme function. These claims have not been substantiated by experimental studies or epidemiological analyses.

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.

The Prime Minister’s Chief Science Advisor and Royal Society of New Zealand concluded in their 2015 report that:

“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.”

Monitoring water fluoridation levels in New Zealand

The Ministry of Health has responsibility for setting standards and monitoring drinking water in New Zealand. The Code of practice for fluoridation of drinking-water supplies in New Zealand (pdf, 621 KB) specifies good practice for the design and operation of water fluoridation plants to ensure the safe and effective addition of fluoride to drinking-water supplies.

The Ministry of Health commissions and monitors ongoing New Zealand research into the amount of fluoride in New Zealand diets and testing of infant formulas, as well as monitoring tooth enamel defects and the levels of dental decay.

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