Flouride in our water

What is Flouride

Fluoride is a mineral (ionic form of fluorine) that occurs naturally and is released from rocks into the soil, water, and air. It is the thirteenth most abundant element in the earth’s crust.

Almost all water contains Fluoride; however, the concentration will vary between locations. New Zealand ranges between 0.1 and 0.3 mg per litre. Water is a major fluoride intake for most people; however, it must be noted that tea, coffee, beer, bread, and carbonated drinks also contain fluoride, with fluoride toothpaste having a direct impact.

Dietary fluoride is absorbed rapidly in the stomach and small intestine. One-quarter to one-third of the absorbed fluoride is taken into calcified tissues, whereas the rest is lost in the urine. In bone and teeth, fluoride can displace hydroxyl ions from hydroxyapatite to produce fluorapatite or fluorohydroxyapatite.

About 99% of total body fluoride is contained in bones and teeth, steadily increasing during life. Recommended daily amounts are unknown as of 2022; however, an adequate intake is recommended at a lower amount and raising until 25 years old.

Toddlers 0.7 mg daily
Adult Females 3.0 mg daily
Adult Males 4.0mg daily

It remains unclear whether fluoride is essential, although it may have some beneficial effects. Fluoride has been suggested as a therapy for osteoporosis since the 1960s, but despite producing denser bone, fracture risk is not reduced. Indeed, there is some evidence that nonvertebral fractures may be increased. The only known association with low fluoride intake is the risk of dental caries (damage to the teeth). The consensus from the dental community is that fluoride is a good thing to prevent missing teeth and/or cavities.

Water Fluoridation

The first ‘artificial’ water fluoridation for caries control was introduced in 1945 and 1946 in the United States and Canada, respectively. It was expected that caries prevalence would be reduced by as much as 50%. The success of water fluoridation in preventing and controlling dental caries led to the development of several fluoride-containing products, including toothpaste, mouth rinse, dietary supplements, and professionally applied or prescribed gel, foam, or varnish.

Most research on the effectiveness of water fluoridation was conducted before the 1980s, when oral healthcare was much worse. Over the last 80 years, the tests have led to accepted levels added to the water supply and have been debated in many countries.

Water fluoridation was said to be one of the best public health measures due to its simple yet effective results It was recommended by the World Health Organisation (WHO) as the best method to improve oral care.

Large populations in developed countries suffer from fluorosis due to the fluoridation of drinking water and dental products. Between 1999 and 2004, the prevalence of dental fluorosis was 41% in American adolescents aged 12~15. To minimize fluoride toxicity, fluoride concentration in drinking water has been controlled to attain the recommended level of 0.8~1.0 ppm.

Northland DHB analyzed the cost of water fluoridation at $42 per person. Which would be around 2 million for Whanganui. With an average saving per person of $372 in dental costs (around 16m in a net benefit to Whanganui)

The ministry of health reviewed and released figures on 27 May 2016 as the following impact:

  • children and adolescents: 40% lower lifetime incidence of dental decay on average
  • up to 4 years: 48% reduction in hospital admissions for treatment of tooth decay
  • 18 to 44 years: 21% reduction in dental decay
  • 45 years and over: 30% reduction in dental decay.

There are some concerns about water fluoridation that need to be raised:

  • Once water is fluoridated, it isn’t easy to control excessive fluoride intake, as people drink different amounts of water. For instance, manual labourers, patients (i.e., diabetics), athletes, and so forth need and may consume more water than others. For example, children receive the same amount of fluoride as adults, and some patients (i.e., patients with kidney disease) are receiving the same dose as healthy people. We must also remember that the amount of fluoride added to water (1 ppm) is 200 times higher than that in breast milk (0.005~0.01 ppm).
  • In addition, several animal and human studies on fluoride show some neurotoxic and nephrotoxic effects. Other negative effects of fluoride, even when administered in small doses (starting at 0.3 ppm), occur on the levels of the thyroid function, the skeletal system, and the reproductive system.
  • Another major concern caused by excessive fluoride intake is dental fluorosis, which can range from mild to severe, as proved by the 2010 CDC report on fluorosis among children. Still, the 2009 New Zealand Oral Health Survey found similar cases of fluorosis in both fluoridated and non-fluoridated countries.
  • In 2022, people will receive fluoride from many sources other than fluoridated water. These sources include ingested products such as mechanically deboned meat, tea, pesticide residues on food, and non-ingested products like fluoridated dental products.
  • The fluoride benefit is topical rather than systemic, hence, it is better to deliver the fluoride directly to the tooth using toothpaste instead of ingesting it
  • It is important to note that there are no randomized controlled trials to validate the effectiveness of fluoridation. In 2000, none of the studies on fluoridation received a Grade A classification by the British Government’s “York Review”. Correspondingly, fluoride is classified as an “unapproved new drug” by the US Food and Drug Administration.

The Data

Water fluoridation for the prevention of dental caries

The authors of this meta-analysis reviewed 20 studies on the effects of fluoridated water on tooth decay and 135 studies on dental fluorosis. The evidence is up to date on 19 February 2015.

Key results

1. Our review found that water fluoridation is effective at reducing levels of tooth decay among children. The introduction of water fluoridation resulted in children having 35% fewer decayed, missing and filled baby teeth and 26% fewer decayed, missing and filled permanent teeth. We also found that fluoridation led to a 15% increase in children with no decay in their baby teeth and a 14% increase in children with no decay in their permanent teeth. These results are based predominantly on old studies and may not be applicable today.

2. Within the ‘before and after’ studies we were looking for, we did not find any on the benefits of fluoridated water for adults.

3. We found insufficient information about the effects of stopping water fluoridation.

4. We found insufficient information to determine whether fluoridation reduces differences in tooth decay levels between children from poorer and more affluent backgrounds.

5. Overall, the results of the studies reviewed suggest that, where the fluoride level in water is 0.7 ppm, there is a chance of around 12% of people having dental fluorosis that may cause concern about how their teeth look.


Studies like the above have been found over the last thirty years; however, side-by-side analysis has never been complete, and this is why there are no gold-standard studies on water fluoridation.

The pro-water fluoridation argument has moved from helping everyone to helping our children. The reasoning has been threefold documented in a report from The Office of the Prime Minister’s Chief Science Advisor.

1. Acknowledgment that fluoride absorption reduces as people get older

2. Water fluoridation only helps those that drink water and for the duration that the water is in contact with the teeth

3. More appropriate solutions for fluoride have been used i.e toothpaste and diet

The key reasons from The Office of the Prime Minister’s Chief Science Advisor published review stated that, on average, children living in non-fluoridated areas have 1.7 times as many decayed, missing or filled teeth as those in fluoridated areas.

Figure 5 The adjusted ratio of means of decayed, missing or filled teeth per person, among children (aged 2-17 years old), by fluoridation status (adjusted by age, sex, ethnic group, and index of deprivation) data from the Ministry of Health.[1]

[1] Moore et al., “The Costs and Benefits of Water Fluoridation in Nz,” BMC Oral Health 17, no. 1 (2017)

Based on the recommended stable level of fluoride added to the local water supply to keep a continuous 0.7-1 mg it is doubtful that any adverse reactions would occur. At a lower level, a newborn baby must consume 140 to 896 glasses of water for toxic levels.

However, the amount of water required to meet the daily need of adults is outside the recommended eight glasses a day for an adult. This may also be the reason why water fluoridation does not help adults.

There is 0.25 mg of fluoride in a standard 250ml glass of water.
There is 0.25 mg of fluoride in two slices of bread.
There is 0.25 mg of fluoride in a serving of rice.

Nationwide data from DHBs 2020

In 2020 the DHBs provided data on children up to the age of five, including the percentage of children that had decayed, missing, or filled teeth. It separated those by ethnicity, location, and water fluoridation at the time data.

Data can be found here: https://figure.nz/chart/1rhxZjQPA1DlryUd

This provided data that the national average for carries

free was 57.09% of children aged 5. Split by regions that were non-fluoridated vs fluoridated shows surprisingly that non-fluoridated regions had fewer cases of carriers than fluoridated.

For the Whanganui district to decide where they may stand, I have filtered the results for children aged 5 to segment MidCentral. Mid-central has both fluoridation and non-fluoridation. Lastly, they show differences between ethnicities.

Yet again, we see non-fluoridation showing higher rates of children without carries with larger variances between Maori, Pacific peoples, and others (which include Asian and European descent).

Due to this surprising data, the author has confirmed the definition of carries free:

caries-free children, which means that they did not have any decayed, missing, or filled primary teeth

Also, the author has sourced the data directly from the ministry of health HERE and has confirmed it to be accurate.

It must be noted that correlation does not equal causation. However, throughout our country, there is a correlation between areas with fluoridation and a minor amount of carriers. Good oral hygiene is still the key method to prohibit carries, with a reduction in sugar being more important.

Since the data is quite compelling that fluoride should have a positive impact, we can only assume that other factors have a far greater impact on dental healthcare. Diet, sugar content, fluoride toothpaste, time of eating vs brushing and water intake.

To confirm this, this author evaluates another UK report evaluating middle to higher-income children who use fluoride toothpaste, which is more in line with New Zealand. We find a 57% decrease in carries; our data tends to go against this data and, therefore, must be due to previously stated factors.

Results: Of the 574 studies retrieved, 16 and 10 were included in the qualitative and quantitative analysis, respectively. Fluoridated areas exhibited lower mean dmft/DMFT than non-fluoridated areas did. The mean difference in the dmft between non-fluoridated and fluoridated areas was -2.28 (95% CI -3.26; -1.30) for children aged 5-8 years and -1.12 (95% CI -1.93; -0.32) for those aged 3-12 years; the mean difference in the DMFT was -0.61 (95% CI -0.80; -0.42) for the children aged between 7 and 12 years. The caries prevalence was 1.4 times and 57% lower, respectively, at primary and permanent dentition in fluoridated areas. Heterogeneity was observed in all age groups, ranging from 77.6% to 98.2%.

Conclusion: Community water fluoridation remains effective in preventing dental caries in children younger than 13 years, even with the widespread use of fluoridated toothpaste.


We have looked at what fluoride is and how it can be used to help oral health. The water fluoridation hypothesis holds true in older studies for children between 5 and 12 years old, who maintain fluoride toothpaste and reduce the sugar they consume.

However, the data is inconclusive within New Zealand. Without separating eating habits and splitting between rural and city areas, the number of children with carries will likely be more to do with lifestyle than if they consumed fluoridated water.

The ministry of health stipulated that the cost of $42 per person would reduce dental costs by $372 can not be proven by the ministry of health data. It is in line with global WHO figures, and this author can only assume it was WHO data used in their recommendation. The data does not show a reduction in cost for dentists for two reasons.

1. Water intake is lower with the segments of the population that are at most risk

2. Dental costs are always increasing

When we add the moral dilemma, a cost of around $2 million for Whanganui to add fluoride to the wai, without consent and data backing up the added benefits. This author believes it should not be supported as the economic and social metrics do not show they outweigh the human right to clean and accessible wai.