Honest Universe

Superstition, pseudoscience, and scepticism

Fluoride in Onehunga

with 14 comments

In last month’s issue of my local community newsletter, Onehunga Community News, an article was published about water fluoridation. For those of you who are non-locals, Onehunga is a suburb of Auckland, and in general drinking water in Auckland is fluoridated.

Click to view the full image and read the article

Click to view the full image and read the article.

The article mentioned some of the recent national news about fluoridation, which I won’t get into here, and used it to bring up the fact that much of Onehunga’s water is not fluoridated. It gave links to the Ministry of Health for pro-fluoridation information and Fluoride Action Network New Zealand (FANNZ) for anti-fluoridation information, and it called for readers to send in their thoughts.

I decided to send in a message in response to the article. The May edition of this newsletter has just been released, and as part of it several responses, including a small part of mine, have been published:

Click to view the full image and read the article.

Click to view the full image and read the article.

I was happy to see that most of the responses were sensible, although there was still one talking about such rubbish as “chemicals” being synonymous with “poisons”. As only a small section of my message was published, I’ve decided to publish the entire message here. Here is the full message I sent in to Onehunga Community News:

To whom it may concern,

I was rather disappointed to see the article “To fluoridate or not to fluoridate…” mention the anti-fluoride group “Fluoride Action Network New Zealand” as though it were a reputable source of information on fluoride. This group relies largely on scare-tactics and misinformation, driven by ideology rather than evidence. In comparison, the Ministry of Health is driven by the available to evidence to find the best conclusion, which it believes is that fluoridating the public water supply is an effective, safe, and cost-effective way of improving dental health.

The Ministry of Health website has a page listing a number of websites that provide accurate information on water fluoridation. The FANNZ site is not on this list. That is not simply because FANNZ disagrees with the Ministry of Health on this issue, it is because FANNZ is not a reliable or trustworthy science-based source of unbiased information on this issue.

When I first discovered that Onehunga is not fluoridated I admit I was very disappointed. I had thought that all public water supplies in Auckland were fluoridated, and was sad to hear that I lived in one of the few areas in which this is not the case. I would be ecstatic to see the public water supply in Onehunga go through a process of fluoridation.

It is worth noting that the process of fluoridation is not necessarily as simple as adding fluoride to the water – it is ensuring that the levels fall within a particular range. As some locations have high natural levels of fluoride, this process can involve the lowering of fluoride levels in order to ensure it is maintained at a concentration that is safe and effective.

According to data from the New Zealand Institute of Chemistry (the data are from 1995, but I’m not aware of any more recent data. I have no particular reason to expect a large change since that date though) the level of fluoride in Onehunga drinking water is around 0.15-0.16 mg/L. In comparison, the fluoride level in Ardmore drinking water was increased from 0.04 mg/L to 0.86 mg/L. Onehunga water did have substantially higher natural levels of fluoride than that of the other Auckland areas sampled, but the final level after treatment was also significantly lower than those areas in which the water was fluoridated.

Water fluoridation to prevent dental caries is akin to the fortification of bread with folic acid to prevent neural tube defects in children, or iodine in table salt to prevent iodine deficiency. These are all safe and effective science-based preventive methods that improve public health.

I understand the journalistic urge to provide balance on all issues, but it is important not to establish a false balance such as this. This is a topic on which it is important to listen to the experts.

Mark Hanna

The editor responded to defend their approach to pursue balance by saying that they shouldn’t only provide government resources. I didn’t find it convincing, but I do understand somewhat the urge for journalists to provide both sides of every story. There is some merit in that but, as I said in my message quoted above, it is possible to take it too far.

It feels relevant to note that, since I sent this message, 3 separate ASA complaints have been upheld against FANNZ on the basis that they failed to adequately distinguish opinion from fact. I wouldn’t be surprised to see a couple more in the future either.

When it comes to the fluoride debate there is a lot of misinformation out there, so you have to be extra careful that you’re getting yours from a reliable source. FANNZ is not a reliable source of information. The Ministry of Health is, and if you want a non-governmental source then you might want to check out Making Sense of Fluoride.

For the sake of full disclosure, I’m Facebook friends with some of the people in charge of Making Sense of Fluoride, and gave some advice on the ASA complaints submitted against FANNZ when they were being written.

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Written by Mark Hanna

2014/05/05 at 5:27 pm

14 Responses

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  1. Folic acid and iodine are added to foods because they are nutrients required by the body. Fluoride is a deadly poison which is not a nutrient. There are no conditions in the body which is fluoride deficient. It cures nothing or heals nothing. Exactly why would someone want to consume it in every glass of water every day of their life.
    No doctor or dentist has ever prescribed it to an ADULT. It is not included in any ADULT multi-vitamin.

    It is illegal for a doctor or a dentist to force anyone to take a drug or a chemical.
    It should be illegal for the government as well. Fluoride should not be added to drinking water, which forces everyone to consume it against their will.


    2014/05/05 at 6:56 pm

    • Hi jwillie6, thanks for your comment. I’m afraid I think what you’ve said is a bit of an oversimplification. You’ve used words like “nutrient” and “poison” as though they’re much more precise and well-defined than they are.

      I can understand the temptation to oversimplify matters like this. I see it all the time when dealing with alternative medicine; if the cause or cure of disease were simple then that would make medicine so much easier. Unfortunately, however, biology is complicated. Horrendously complicated. Because of this, in order to understand how a particular substance affects people thorough testing needs to be undertaken.

      When undertaking such tests, one of the most important considerations is the dose. For example, if you look at the fact sheet for a substance, such as this Material Safety Data Sheet for folic acid, you will see the term “LD50″ under the toxicology information. This refers to the dose that is lethal 50% of the time (LD50; Lethal Dose 50%), i.e. when a substance is administered at that dose, 50% of the subjects given that dose will die. Of course, such tests are not carried out in humans, we usually use a rat or mouse “model” (this means a rat or mouse is used as a “model” or stand-in for a human) instead.

      In this example, the LD50 for an oral dose of folic acid in a mouse is 10,000 mg/kg. That means if, for every kg of mouse 10,000 mg of folic acid is administered orally, there is a 50% chance the mouse will be killed by it. Substances with a lower LD50 are more toxic, whereas those with a higher LD50 are less so. As you can see, there is no clear line between “poison” and “not poison”; everything is poisonous at a certain level. The Wikipedia page has a table containing various examples, such as sucrose (29,700 mg/kg given orally to rats, so not very toxic).

      You characterising substances as “nutrients” is a similar oversimplification, although it can often be a useful one. Basically what you have to look at is, again at a particular dose, how is the body affected by a substance? If the body use the substance for something useful, such as iron being used for the formation of haemoglobin, then that sounds pretty much like a nutrient. Fluoride ions interact with the hydroxyapatite enamel of your teeth to form fluorohydroxyapatite, which is more resistant to decay. That sounds pretty useful to me.

      So the question becomes “is way to administer fluoride in a particular way and at a particular dose that we can benefit from it without any harmful effects?”. And, like biology, the answer is complex. The best way to do this that we know of is via topical application, mainly through fluoride-containing toothpastes. However, fluoridating drinking water, which involves treating the water to ensure that the fluoride concentration is with a certain narrow band.

      Fluoridating the community water supply benefits everyone who drinks it. Although I’ve heard many argue that those who want to consume fluoride in this way should buy fluoride supplements of some sort, that argument misses the point that unfluoridated water disproportionately affects those who cannot afford such luxuries, and members of lower socioeconomic groups may also miss out on other sources of fluoride such as fluoride-containing toothpaste.

      If you’re interested in learning about the legality of community water fluoridation, a decision was recently made in the High Court of New Zealand that it is legal in New Zealand. The entire decision is freely available if you’d like to read it: New Health New Zealand vs. South Taranaki District Council.

      Mark Hanna

      2014/05/05 at 8:40 pm

      • Hello Mr. Hanna:
        You present some well thoughtout comments. You are correct that my comment is over simlified. It is impossible to offer more in a few sentences. However, there are many studies done by research scientists which indicate a variety of health dangers associated with water fluoridation. Many of them are presented at the site below. It begins with a statement from Dr. Phyllis Mullenix, PhD in pharmacology:

        “fluoride exposures today are out of control,” and “.. there are no advantages to water fluoridation. The risks today far exceed the hoped for benefit.” Dr. Mullenix cites data from 18 clinical studies in her analysis.

        The list presented at this site is supported by over 40 scientific references. I urge everyone to visit this site to investigate the evidence which is counter to your presentation. Then they can make up their minds.



        2014/05/06 at 8:38 am

      • Remember, as I stated in my previous comment, the process of water fluoridation involves limiting the concentration of fluoride to be within a narrow band. In areas with a high concentration of fluoride prior to processing, this involves removing some of it. The statement “fluoride exposures today are out of control” would make considerably more sense in an unfluoridated context.

        As I stated previously, the most important factor to consider is dose. The effects of a substance and their strength, whether helpful or harmful, are dependent entirely on dose. I’m aware, for example, that there are studies linking the consumption of fluoride through drinking water to lowered IQ but this effect is not observed at the levels of fluoride occurring in regularly fluoridated drinking water.

        Unfortunately, the list you’ve linked to doesn’t contain any links to any of the studies, and I’m not particularly interested in finding all 40+ studies manually and reading through them (assuming they’re freely available to the public) in order to see if they live up to the claims made about them.

        If you have a specific criticism regarding the effects of water fluoridation, then please provide it along with a reference and we’ll be able to have a discussion about it.

        Mark Hanna

        2014/05/06 at 2:17 pm

      • Mr. Hanna:
        I tried to reply to your interesting comments, but my response was not accepted. Too bad, because we are all searching for the truth.


        2014/05/06 at 8:41 am

      • Hmm, I’m not sure what might have happened there. I haven’t had a comment come into the moderation queue, I’ll have a look and see if it might have been caught by the automatic spam filter.

        Mark Hanna

        2014/05/06 at 10:37 am

      • Yeah, it looks like your comment was caught in the spam filter. I’ve let it through now, but I’m afraid I won’t have time to read it through or reply for a while yet.

        Mark Hanna

        2014/05/06 at 10:40 am

    • “Fluoride is a deadly poison which is not a nutrient.”


      Mike Drake

      2014/05/06 at 1:43 am

      • jwillie6 re Mullenix,
        Big problem with using this paper as “evidence” is that her study exposed rats to drinking water concentrations of 0, 75, 100, or 125 ppm! Behavioural effects were observed at the high concentrations. But community drinking water is fluoridated to only about 0.7 ppm F!


        2014/05/07 at 8:36 pm

    • It’s not true that no dentist has ever proscribed fluoride to an adult. I was recently proscribed PreviDent (http://www.colgateprofessional.com/products/Colgate-PreviDent-5000-Plus-Rx-only/details), a prescription toothpaste designed to provide fluoride.


      2014/05/06 at 6:21 am

      • Anon:
        What is wrong with you? Prevent is a tooth paste. A treatment applied to the outside of the tooth might help, but no one should swallow fluoride.


        2014/05/06 at 6:33 am

      • jwillie6, please keep your comments civil. Anon’s response to your comment was directly relevant to your claim that “No doctor or dentist has ever prescribed [fluoride] to an ADULT”.

        If you want to point out the distinction between a topical application and an oral dose then feel free to do so, but we can do without insults thank you very much.

        Mark Hanna

        2014/05/06 at 2:15 pm

  2. What Jwillie6 was saying is that fluoride is not required by the body. Consuming a fluoride-free diet does not cause tooth decay. Fluoride is a choice and a drug with side effects. In the US, the Food and Drug Administration regulates fluoride in toothpaste for topical application; but it has never tested fluoride for safety or efficacy when ingesting it. The FDA calls fluoride an unapproved drug. Since fluoride changes body parts in ways nature didn’t intend, it is a drug. Like all drugs, fluoride has side effects – some of them quite nasty. It’s foolhardy at least and hazardous at most to add fluoride drugs into the human digestive system via the water supply without regard for an indivdual’s age, weight, height, health or need. The level of fluoride in water supplies does not equate to an individual’s dose. Fluoridation delivers fluoride doses based on thirst – which makes no sense.


    2014/05/06 at 9:04 am

    • Hi nyscof, thanks for your comment. Like jwillie6’s first comment, I’m afraid you’ve oversimplified matters.

      I’m sure you realise that nature doesn’t actually have intentions, and no such concept is used in the definition of what is or is not a drug. With regard to the FDA, they have issued a health claim notification stating that, from October 14 2006, they have approved the following claim for use:

      “Drinking fluoridated water may reduce the risk of [dental caries or tooth decay].”

      To state that “fluoride changes body parts in ways nature didn’t intend” honestly seems like a rather disingenuous oversimplification to me. Surely either nature’s intention is a metaphor for the laws of physics and anything that happens as a result, such as the biological effects of fluoride, qualify as “intended by nature”, or nature similarly didn’t intend other useful technologies such as vaccines or antibiotics, in which case we would do well to ignore nature’s intentions as they are obviously not in out best interests. The only other option I can think of is that the effects of fluoride are somehow miraculous, and I’m certain that’s not what you mean.

      The fact is that fluoride, like any substance, has certain effects on the human body. These effects are determined by the dose and method of administration. The goal of community water fluoridation is to elicit the beneficial effects that fluoride has with regard to reducing the incidence of dental caries without also seeing any negative effects.

      You are correct in that the dose of fluoride delivered by community water fluoridation depends on thirst, but thirst is self-limiting (and related to the size of a person) and the level of fluoride in fluoridated water is low enough that it would be difficult to consume enough fluoride to see negative effects through the consumption of fluoridated water alone. It’s not a consideration that is ignored in the determination of the upper limit of fluoride concentration to be allowed in a water supply.

      Mark Hanna

      2014/05/06 at 2:13 pm

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