Undeserved Reputations - Fluoride
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This graphic is the first in a series I’m hoping to make on chemicals with potentially undeserved reputations. In it, I’ll look at the evidence and research on each, and try to come to some kind of rational conclusion as to whether or not their bad reputation amongst the general public is deserved. I thought I’d kick things off with one of the most controversial topics, particularly over in the USA: the fluoridation of water supplies.

The reason for wanting a fluoridated water supply in the first place is the first thing we should consider, and it’s based on the chemical structure of your teeth. The enamel that coats your teeth is made up primarily of the compound hydroxyapatite. This ionic compound consists of calcium ions, phosphate ions and hydroxide ions, and is also a major component of your bones. Enamel is well known for being pretty strong, but it can be slowly broken down and lose ions from its structure under acidic conditions. This is known as demineralisation. Our body has a built-in countermeasure for this, and can replace the ions lost with ions from our saliva, in a process known as remineralisation. However, sometimes the rate at which this replacement occurs is below that at which the ions are being lost. When this happens the pores in the tooth can become enlarged, and cavities and tooth decay can result.

Fluoride ions can help arrest this process. They can be incorporated into the hydroxyapatite structure, replacing the hydroxide ions and forming fluorapatite. Fluorapatite is stronger than hydroxyapatite, and is also more resistant to acidic conditions. This means it can greatly delay the onset of cavities and tooth decay, and this is the reason why there’s a clamour to add it to water supplies. The World Health Organisation, based on research, have set an optimal amount of fluoride in water supplies of around 1 part per million (ppm). To give this some perspective, 1 ppm is equivalent to one minute in two years; it’s 1 milligram of fluoride per litre of water. Studies have suggested that this level of fluoridation could reduce tooth decay by as much as 29%. It’s been hailed as ‘the most cost effective and practical way to provide protection from tooth decay’.

Hydroxyapatite (left) and fluorapatite (right) (created using Atomsmith Apps for chemistry education (http://www.bitwixt.com/jsite/atomsmithmoleculelab))
Hydroxyapatite (left) and fluorapatite (right) (created using Atomsmith Apps for chemistry education (http://www.bitwixt.com/jsite/atomsmithmoleculelab))

Artificial fluoridation of water is carried out in around 35 countries worldwide, including the USA, Australia, Spain, several countries in South America, and parts of the UK and Ireland (not including Northern Ireland). This artificial fluoridation is usually achieved by adding small amounts of fluorosilicic acid to the water, but sodium fluoride and sodium fluorosilicate can also be used. Fluoride also occurs naturally in the majority of natural water supplies; often, this is at a lower concentration than that recommended, but in a select few places it can be much higher. For example, in some lakes in Ethiopa, levels of over 260mg/L have been recorded.

So, if fluoride is so beneficial for the health of our teeth, why the controversy? This stems in part from legitimate studies on the effects of higher fluoride concentrations. An oft-quoted study by the National Research Council in 2006 found that fluoride can have a range of harmful effects – but they were discussing concentrations several times higher than those used in artificially fluoridated supplies. Another frequently mentioned study is one carried out in China and published in 2012, which found that high levels of fluoride in childhood were associated with a reduction in IQ. In this case, the authors of a review including the study noted that their findings weren’t applicable to artificially fluoridated supplies, as the concentrations they were examining were many times higher. They also commented on the poor design of the study. A recent New Zealand study, published this year, found no link between fluoride exposure and IQ or neurotoxicity over a 38 year period at more normal levels of fluoride consumption. Reviews on studies linking fluoride at the levels found in drinking water to cancer and other conditions such as Downs Syndrome have commonly found them to be poorly designed, and those studies that were well designed showed no statistically significant link.

Despite these misinterpretations, it’s not the case that fluoride is completely benign. An accepted adverse effect of fluoridation is dental fluorosis. This can cause streaks or specks in tooth enamel, and discolouration and brown markings in its most severe form. However, it’s estimated that, in the majority of cases, only mild dental fluorosis will be observed in 1 out of 6 people living in artificially fluoridated areas. Mild fluorosis doesn’t cause pain, or affect the health or function of the teeth, and can usually only be spotted by a dentist. Fluorosis of ‘aesthetic concern’ can affect 1 in 22; this is still considered by dentists to be purely aesthetic in its impact, but may be marginally more noticeable.

Generally, the risk of dental fluorosis is a concern for children, especially because at a young age they can have a tendency to swallow toothpaste. This is one reason why child toothpaste with lower fluoride levels are sold. Additionally, if using infant formula instead of breast-feeding, it’s recommended that distilled water is used rather than fluoridated tap water, to ensure that the child isn’t exposed to too much fluoride.

Another form of fluorosis is often cited when discussing fluoridated water – skeletal fluorosis. This occurs when fluoride is ingested, and passes through the body, reacting with hydroxyapatite in the bones to form calcium fluoride. This removes calcium from the bones, which results in increased density but decreased bone strength. Luckily, the levels of fluoride in artificially fluoridated areas are nowhere near high enough to cause skeletal fluorosis.

The World Health Organisation states that skeletal fluorosis can occur in those who’ve ingested 10-20mg of fluoride every day for 20 years. Artificially fluoridated water supplies typically contain 1mg of fluoride per litre; considering that it’s recommended you drink 3 litres of water a day, this would put you on 3mg. Toothpaste also contains fluoride, and even though you don’t eat it, a small amount will still end up being ingested (estimates state around 20% of the fluoride content). This accounts for around an extra 0.4mg per day, assuming you brush your teeth twice. If we’re going to cover all bases, tea and some foods also contain fluoride; in fact, black tea can contain more than any artificially fluoridated water supply, and can be up to 2mg per litre. But even if you binge on tea all day, you’re unlikely to reach the lower bound of the 10-20mg per day figure. Skeletal fluorosis is a problem in some countries, but this tends to be in those where the natural water fluoride concentration is at dangerous levels, rather than as a result of any fluoride added.

It’s often stated, incorrectly, that the vast majority of European countries have rejected fluoridation. Aside from those that do practise some degree of artificial fluoridation, such as Spain, the UK, and Ireland, many other countries fluoridate their salt instead. Germany, Switzerland and France all do this, whilst in some countries in Eastern Europe, milk is fluoridated instead. Some countries don’t fluoridate their water supplies because the natural fluoride levels are already close to the recommended level. Bottled water also frequently contains fluoride.

Another argument commonly put forward is that, with toothpastes commonly being fluoridated, there isn’t any need for water supplies to be fluoridated too. However, a range of studies have shown that, comparing fluoridated water areas with non-fluoridated areas, there was a much lower rate of tooth decay. This was despite the fact that 94% of children living in the non-fluoridated areas were using fluoride toothpaste.

To conclude, it’s not incorrect to say that fluoride can have some unpleasant consequences – at high concentrations. At the concentration at which it’s introduced into water supplies, however, it’s been proven by numerous studies to be both safe, and to have a beneficial effect on tooth health. Despite the allegations of links with cancer and mental health conditions, reviews of the currently available research have found no statistically significant links between these and fluoride at the concentrations commonly found in water supplies.

In summation, we can say that fluoridation of drinking water probably has the right to feel unfairly maligned. Unless we can come up with a more effective and cheaper method, it remains an inexpensive, effective, and safe way of improving our dental health, as long as the concentrations in water are carefully controlled. If you don’t want to just take my word for it, I’d encourage you to take a look at some of the links below, from which I pieced together the graphic in this article.



The graphic in this article is licensed under a  Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. See the site’s content usage guidelines.

References & Further Reading

26 CommentsClose Comments


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  • nyscof
    Posted July 25, 2014 at 2:22 am 0Likes

    Instead of spreading less tooth decay across the land, fluoridation spread dental fluorosis (fluoride-discolored
    teeth) into every nook and cranny of America. Even though the CDC reports up to 60% of adolescents are afflicted with dental fluorosis, 51% of them have cavities.

    Opposite to predictions, since fluoridation began in 1945:

    1) Tooth decay crises occur in all fluoridated cities. http://www.fluoridenews.blogspot.com

    2) New dental professionals were created, e.g. dental therapists.

    3) New dental schools opened.

    4) Dental expenditures went up substantially, higher than the inflation rate.

    5) Poor children’s cavities are more prevalent, severe, occur earlier and more likely to be untreated.

    6) Despite dental spending growth, 42% percent of adults and 4 million children with dental
    problems could not afford dental care.

    7) More states had the need to hire Dental Directors

    8) Since the Surgeon General announced a silent epidemic of tooth decay in 2000, scores of
    government, dental and oral health groups formed having countless meetings,
    symposiums, webinars and conventions including one focused on the growing tooth
    decay rates in toddlers because 1/3 of 3-year-olds now have cavities.

    9) Because the CDC’s oral health group can’t prove fluoridation is safe for everyone, the CDC hired public relations
    firms to spin data to make fluoridation more attractive than science and government reports show it is

    10) 52% of new recruits have oral health problems needing urgent attention that would delay overseas

    US Senator Bernie Sanders, in his 2012 report, “Dental Crisis in America,” says that 9,500 new
    dental providers are needed to meet the country’s current oral health needs and that tooth
    decay is the leading cause of school absenteeism

    • Compound Interest
      Posted July 25, 2014 at 6:21 pm 0Likes

      Do you have a reference for the 51% of the 60% of adolescents afflicted with fluorosis having cavities, or is this just a mashing together of two different statistics to produce a misleading statement?

      With regards to the points you made:

      1) Fluoridation delays tooth decay. It’s not the only factor, and a diet high in sugar will inevitably lead to tooth decay with or without fluoridation of the water supply. Also, a link to an anti-fluoride website (and by the looks of it, your own site) doesn’t really cut the mustard as a reference.

      2) New professions in dentistry being created has nothing to do with fluoridation. This is a fallacy.

      3) New dental schools being opened has nothing to do with fluoridation. This is a fallacy.

      4) Dental expenditures rising could be due to any number of factors, for example rising populations, expense of new technologies and changing diets. This is a fallacy, as it cannot be directly linked to fluoridation.

      5) The cavities of poor children increasing can be due to differences or deficiencies in diet, and these factors have been thoroughly explored in a range of studies. This doesn’t even seem to be a direct argument against fluoridation – surely the problem would be even worse without fluoridated toothpastes and water supplies!

      6) Patients being unable to afford dental care has nothing to do with fluoridation. This is a fallacy.

      7) More states hiring dental directors has nothing to do with fluoridation. This is a fallacy.

      I do happen to believe that, if you don’t wish your water supply to be fluoridated, that’s your decision. However, flipping the argument, why should the unsupported concerns of a minority prevent the majority from benefitting from fluoridation, which research has proven to be beneficial?

  • Lerkero
    Posted July 27, 2014 at 3:10 am 0Likes

    The dose makes the poison. Anything at a high enough concentration can be harmful.

    I would prefer to listen to dentists, biologists, doctors, chemists, and other knowledgeable people rather than someone who has no credible evidence of a conspiracy.

    • Ima Skeptic
      Posted August 2, 2014 at 10:56 pm 0Likes

      Fluoride’s effects depend on the TOTAL daily intake of fluoride from ALL sources. Not just the amount maintained in tap water. About 70–90% of ingested fluoride is absorbed into the blood, where it distributes throughout the body. In infants 80–90% of absorbed fluoride is RETAINED, with the rest excreted, mostly via urine; in adults about 60% is RETAINED. About 99% of retained fluoride is stored in bone, teeth, and other calcium-rich areas, where excess quantities can cause fluorosis (i.e. dental DAMAGE).

      **Fawell J, Bailey K, Chilton J, Dahi E, Fewtrell L, Magara Y. Fluoride in Drinking-water [PDF]. World Health Organization; 2006. ISBN 92-4-156319-2. Human health effects. p. 29–36.

      Dr. P.H. Phillips, biochemist, University of Wisconsin stated,
      “Fluoride is an accumulative poison which accumulates in the skeletal structures, including the teeth, when the body is exposed to small daily intakes of this element. …it is like lead accumulation in the bone until saturation occurs and then lead poisoning sets in.”

  • Ima Skeptic
    Posted August 2, 2014 at 7:42 pm 0Likes

    Fluoride is a bio accumulative rat poison. Even Harold Hodge knew they were using a rat poison.

    “Appointed initially in biochemistry, Hodge pursued dental research including the toxicity of fluoride, as there was a huge stigma against using fluoride for the public health. (It was, after all, a RAT POISON.)”

    And we allow our children to bathe, shower, and swim in this stuff? AND brush their teeth with it? Just inches from their brain?

    If anyone feels deprived of fluoride ions, all they have to do is brush their teeth with a fluoridated toothpaste. Or use a fluoridated mouthwash. Fluoride gets absorbed sublingually. You don’t have to drink it to ingest it. Sodium fluoride dissolves easily in both saliva and water. Almost any form of substance may be amenable to sublingual administration if it dissolves easily in saliva.

    Adding it to everyone’s tap water is senseless. Unless you are in the business of peddling it for profit.

    • Compound Interest
      Posted August 2, 2014 at 9:46 pm 0Likes

      Firstly, got to say that’s some top class selective quoting from the first study. Literally the next sentence after that which you quoted states ‘Today, of course, we fully recognise the benefits of adding fluoride to drinking water.’ Cherry-picking quotes to support your standpoint is bad science.

      I don’t know if you read it thoroughly, but I made the point in the article that concentration is hugely important when discussing the toxicity of chemicals. It’s a naive view to think of chemicals in black and white terms as toxic and non-toxic. Even water is toxic to humans if ingested in large enough quantities. Fluoride at high concentrations is certainly toxic, but at low concentrations it’s been proven to be beneficial for dental health. In fact, there are even some studies which suggest that a deficiency of fluoride could actually be detrimental to dental health, and that optimum levels of fluoride can actually decrease incidence of rickets (http://link.springer.com/article/10.1007/s12665-011-1065-1).

      Incidentally, obvious a statement though it may be, literally everything you eat enters the body inches from your brain, but it doesn’t all magically pass straight from your mouth into your brain! Fluoride can dissolve in the saliva (this is important as it enables it to remain in the vicinity of your teeth for longer and provide beneficial effects), but the blood brain barrier has actually been shown to have some degree of impermeability to fluoride (http://books.google.co.uk/books?id=NAB43R0rTV4C&pg=PA91&lpg=PA91&dq=fluoride+blood+brain+barrier&source=bl&ots=0mx0MfvktM&sig=9rHHGN4LHM6JuFIg10D9hR59a7s&hl=en&sa=X&ei=M0ndU7T6B4WI7Abx_IGwCA&ved=0CDoQ6AEwAzgU#v=onepage&q=fluoride%20blood%20brain%20barrier&f=false).

      Adding it to tap water has been proven by the studies mentioned in the article to have beneficial effects. Whilst you can argue about the magnitude of these beneficial effects, you certainly can’t dispute their existence based on the evidence. Also, I’m a chemistry teacher – I have literally no links with the chemical industry, or anyone with a vested interest in fluoridation. I have nothing to gain from ‘peddling’ fluoridation – just the satisfaction of trying to get the public to better understand the science behind it.

      Incidentally, I’ve already read your comments on the SciBlogs post about this article, and have to back Ken Perrott’s points in that debate. Similarly, I’ve no desire to become embroiled in a non-evidence based debate on fluoride – happy to debate properly referenced evidence, minus the sensationalism and deliberate cherry-picked quoting, however.

      • Ima Skeptic
        Posted August 2, 2014 at 10:39 pm 0Likes

        It is top class PROOF it’s a RAT POISON. That was all it was meant to be. Proof. You think everyone should be dosed with bio accumulative rat poison I suppose? Harold Hodge was a top class act himself. He also enjoyed secretly injecting patients with plutonium and uranium. The US government settled with the victims’ families, paying $400,000 per family. You might have liked him.

        • Compound Interest
          Posted August 2, 2014 at 10:56 pm 0Likes

          It seems you and me define proof very differently. That’s a statement in a profile of Harold Hodge, not a referenced statement in the article you linked in. It’s not even a main point in the article, just a throwaway comment.

          As I said, happy to engage in a discussion on properly referenced evidence. However, if you’re going to trumpet the same poorly referenced points as you did in the other comment thread, relying on fallacies and personal insults to make your points, then I really don’t see any purpose in continuing this discussion, especially if you’re just going to point blank ignore the points I’m making.

          • Ima Skeptic
            Posted August 2, 2014 at 10:59 pm 0Likes

            Chronic exposure to fluoride can also cause a loss of adult teeth and premature aging. Good stuff.
            See PubMed:
            U.S. National Library of Medicine – National Institute of Health
            “[Fluorine as a factor in premature aging].”

            “Dental fluorosis during tooth growth and loss of dentition (TOOTH LOSS) in adulthood are two consequences of chronic intoxication with fluorine compounds.”

            So why do dentists recommend a substance that has the potential to destroy teeth to protect teeth? Seems a little irrational to me.

          • Lerkero
            Posted August 2, 2014 at 11:04 pm 0Likes

            You throw around quotes and references as if people have teeth falling out of their mouths due to fluorine. There are other minerals in tap water too, do you think those are harmful?

            I am glad that I can supplement flossing and brushing with clean fluoridated water. I haven’t been to the dentist in years and my teeth are fine. What exactly are you trying to say fluorine does? All of your sources don’t seem to have any relevance to what is actually happening.

          • Ima Skeptic
            Posted August 2, 2014 at 11:10 pm 0Likes

            America has been fluoridating water for 60 or 70 years. Roughly 75% of the USA now receives fluoridated water and dental fluorosis is increasing among teenagers. Dental veneers and dental implants have also become a lucrative business. The dentists couldn’t care less about this increase of dental fluorosis (dental DAMAGE). They make a living repairing this damage. Dental fluorosis due to chronic fluoride exposure seems to be a little more than just cosmetic as well. See “Comparative Toxicity of Fluorine Compounds”.

            “Mottled teeth are not only disfiguring in appearance but are so defective in structure and strength that they often have to be replaced by false teeth at an early age.”

            When did this FACT change? This was known as far back as the 1930’s. Why would a dentist recommend a substance KNOWN to damage teeth to protect teeth? Sound logical? Are they using lab work on their patients to determine the fluoride levels in their body? Using the scientific method? Lab work has been available for decades.

          • Compound Interest
            Posted August 2, 2014 at 11:20 pm 0Likes

            Again, in this case you need to read the study you’re referencing. They are talking about a level of 5ppm fluioride, much higher than the recommended level of 1ppm the WHO advocates.

          • Ima Skeptic
            Posted August 2, 2014 at 11:29 pm 0Likes

            You have to realize that all the studies are flawed. Fluoride doesn’t just occur in tap water. It’s cumulative from ALL sources. Not just the amount contained in tap water (Unless you’re relying on pseudoscience). The most significant flaw in fluoride research is the failure to account for the inhalation, mucosal, and dermal exposure to fluoride compounds. It invalidates all dosage conclusions based solely on ingestion. Do you have lab work showing the levels of fluoride in any given population? Lab work would actually be considered science as opposed to the pseudoscience of cavity counting. Lab work has been available for decades. Why isn’t it used?

            Here is the “York Report”- the largest systematic, quantitative meta-analysis of water fluoridation ever conducted. Their conclusion? That water fluoridation is not proven effective by the standards of evidence-based medicine (i.e. the effect is not statistically significant).

            Water fluoridation has never been tested in a randomized controlled trial. All water fluoridation trials have been NON-blinded. This is enormously problematic because cavity identification is highly subjective. Every single water fluoridation trial therefore has big problems with observation bias.

            The science of water fluoridation efficacy SUCKS. It is not even close to being proven effective by the standards of evidence-based medicine.

          • Lerkero
            Posted August 2, 2014 at 11:57 pm 0Likes

            Where are you getting all this fluoride from?

            From your source:

            There is a dose-response relationship between water fluoride
            level and the prevalence of fluorosis. Fluorosis appears to occur frequently (predicted 48%, 95% CI
            40 to 57) at fluoride levels typically used in artificial fluoridation schemes (1 ppm). The proportion of
            fluorosis that is aesthetically concerning is lower (predicted 12.5%, 95% CI 7.0 to 21.5). Although 88
            studies of fluorosis were included, they were of low quality (level C). The best available evidence on
            the association of water fluoridation and bone fractures (27 of 29 studies evidence level C) show no
            association. Similarly, the best available evidence on the association of water fluoridation and cancers
            (21 of 26 studies evidence level C) show no association. The miscellaneous other adverse effects
            studied did not provide enough good quality evidence on any particular outcome to reach conclusions.
            The outcomes related to infant mortality, congenital defects and IQ indicate a need for further high
            quality research, using appropriate analytical methods to control for confounding factors. While
            fluorosis can occur within a few years of exposure during tooth development, other potential adverse
            effects may require long-term exposure to occur. It is possible that this long-term exposure has not
            been captured by these studies.

            The source itself admits that the reviewed studies were low quality and finds no significant dangerous impact. If fluorosis was easy to affect people, many more children would be getting it in their young age. That is not happening. You can debate whether fluoridated water is necessary considering how easy it is to add to toothpaste or other supplements, but calling the current level of fluoridated water dangerous is not a sound conclusion.

          • Ima Skeptic
            Posted August 3, 2014 at 12:09 am 0Likes

            They aren’t relying on lab work, are they? Just guesses. Lab work (i.e. urine, blood, or hair analysis) could determine fluoride overexposure before dental fluorosis (dental DAMAGE) ever occurred. But this isn’t done. Why?

            If anyone feels deprived of fluoride ions, all they have to do is brush their teeth with a fluoridated toothpaste. Or use a fluoridated mouthwash. Fluoride gets absorbed sublingually. Sodium fluoride dissolves easily in saliva. Almost any form of substance may be amenable to sublingual administration if it dissolves easily in saliva.

            Adding it to everyone’s tap water is senseless. Unless you are in the business of peddling it for profit.
            Prescription strength or high fluoride toothpaste has a high concentration of sodium fluoride (NaF) and ranges from above 1,500 parts per million (ppm) to 5,000 ppm which is the maximum concentration available. But of course a dentist wouldn’t think twice about prescribing it to use every day, if not multiple times a day.

            If anyone wants the systemic affects of fluoride, all they have to do is brush their teeth with a fluoridated toothpaste. You don’t even have to drink it to get the “systemic effects”. Fluoridation should have ended when fluoridated toothpaste and fluoridated mouthwash came on the market.

          • Compound Interest
            Posted August 3, 2014 at 12:21 am 0Likes

            At this stage, where you’re repeating yourself ad-infinitum, I think it’s a good point to close the comments on this article. Myself, and other, don’t have the time to waste convincing someone who doesn’t want to be convinced, so this conversation serves little purpose.

            As Lerkero has very rightly stated, whilst you can argue that topical fluoride is more effective than water fluoridation, that in no way means that fluoridation of water poses a threat to the population. The systematic review of fluoridation for the Australian Government (included in the references in the article) found that there was no evidence of fluoridation of the water supply causing any risk to the health and well-being of the population. They also debate other sources of fluoride, which somewhat debunks your claim that no-one has ever considered this.

          • Compound Interest
            Posted August 2, 2014 at 11:16 pm 0Likes

            The very study you linked explains that it’s discussing excessive fluoride concentrations – I appreciate that you’re referencing your points rather than just making them, but it’s also important that you understand the research you’re referencing and when and where it applies.

            I’m in no way claiming that excessive fluoride doesn’t cause unpleasant side effects and fluorosis, but this is the exact reason why limits on the concentrations of fluoride in water and toothpaste exist. Within these limits, fluoride has a delaying effect on dental caries, as outline in the article above.

  • Ima Skeptic
    Posted August 2, 2014 at 10:51 pm 0Likes

    You don’t even need fluoride in tap water to have healthy teeth.
    On PubMed.gov
    U.S. National Library of Medicine – National Institute of Health
    “The fluoride content of drinking water and caries experience in 15-19 year old school children in Ibadan, Nigeria”

    “Nine hundred fifty-five students aged 15-19 years randomly selected from eleven secondary schools in Ibadan metropolis were examined for dental caries. The fluoride level of the different water sources was between 0.02 and 0.03 ppm. [only] Forty-four (4.6%) of the children had dental caries. In conclusion, both the fluoride level and caries prevalence were low.”

    Now compare the above with Singapore which has been 100% fluoridated (w/water fluoridation) since 1958. Currently 40% of their preschoolers are suffering with SEVERE dental caries. Does this sound like a success story to you?

    Singapore is a great study case because they have been 100% fluoridated for so long. And I don’t believe the population of Ibadan, Nigeria even uses fluoridated toothpaste. But I couldn’t find a study case with a lower amount of fluoride in their water. It will be impossible to find people who haven’t been exposed to fluoride at all. Fluoride is even inhaled from air pollution. The most significant flaw in fluoride research is the failure to account for the inhalation, mucosal, and dermal exposure to fluoride compounds. It invalidates all dosage conclusions based solely on ingestion.

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