Claim: Fluoride is a poison (HHS Secretary RFK Jr.)

[joel_yancey]

Source: https://youtu.be/S9aOnc76gTA?si=Pxii7ksOmv2lWD2p

In the above September 2024 interview with The New York Sun, RFK Jr. states "I think fluoride is a poison" and describes it as "toxic". Not withstanding the old adage that everything is toxic in large enough amounts (there was a well-known tragedy around where I grew up of a person who died as a result of water intoxication while competing in a contest held by a popular radio station)—is this fluoride claim pure quackery or is there even a kernel of truth to it?

Study: Developmental fluoride neurotoxicity: an updated review (2019)

A 2019 meta-analysis of 14 studies published in Environmental Health drew the following conclusion:

Article:

The recent epidemiological results support the notion that elevated fluoride intake during early development can result in IQ deficits that may be considerable. Recognition of neurotoxic risks is necessary when determining the safety of fluoride-contaminated drinking water and fluoride uses for preventive dentistry purposes.

Source: https://ehjournal.biomedcentral.com/articles/10.1186/s12940-019-0551-x

Study: Fluoride exposure and cognitive neurodevelopment: Systematic review and dose-response meta-analysis (2023)

A 2023 meta-analysis of 30 studies published in Environmental Research makes a crucial comment in its abstract that although a negative correlation between fluoride and IQ seems evident in the data, the vast majority of studies on this topic have high likelihood of bias. Conversely, just one study with low likelihood of bias had been published at the time of writing, and the data did not bear out any correlation:

Article:

The inverse association between fluoride exposure and IQ was particularly strong in the studies at high risk of bias, while no adverse effect emerged in the only study judged at low risk of bias. Overall, most studies suggested an adverse effect of fluoride exposure on children's IQ, starting at low levels of exposure. However, a major role of residual confounding could not be ruled out, thus indicating the need of additional prospective studies at low risk of bias to conclusively assess the relation between fluoride exposure and cognitive neurodevelopment.

Source: https://www.sciencedirect.com/science/article/pii/S0013935123000312?via%3Dihub

Pro-fluoride position

For matters of public health, it is important to weigh forseeable harm/risk against practical benefits. Since I do not believe it is disputed (and at the risk of putting myself asleep), for now suffice it to say the scientific literature proving the major benefits of fluoride on oral health outcomes is beyond reproach. Notwithstanding, as the World Health Organization notes, "Oral diseases are among the most common noncommunicable diseases worldwide, affecting an estimated 3.5 billion people" (https://www.who.int/health-topics/oral-health#tab=tab_1)

How RFK Jr.'s bunk sausage gets made

When properly performed and peer-reviewed, longitudinal studies are powerful investigative tools. However, as every clinical researcher knows, this type of study is notoriously challenging to conduct and requires many years to conduct. And even then, parsing correlation from causation is difficult, and so large sample sizes are necessary to achieve high statistical power (which in turn has knock-on effects on monetary cost). But crucially, only a longitudinal study is capable of definitively ruling out pesky "unknown unknowns" that may lurk. I posit that perhaps the long time-horizon and low-availability of longitudinal studies are also the qualities which make them excellent vehicles for smuggling bunk. Many of RFK Jr.'s psuedoscientific beliefs follow the same pattern: it's something in the environment, or something in the food supply, or the water supply, or is the vaccines from your childhood, which is have had a cumulative negative effects over long periods of time. In every case these claims are difficult to disprove, and it can always be be argued to a credulous or uninformed person that the jury is still out. RFK Jr. has litigated this argument to his great-benefit in the form of lucrative settlements. Evidently this is how RFK Jr.'s bunk sausage gets made.

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Editor's note 1: This is my second new thread post, so please if there are any mistakes in format, style, or content, please constructively inform me so that I may improve the quality of future posts.

Editor's note 2: I will briefly mention my background so that I will not need to repeat it in future posts. I earned a BS degree in Neuroscience from UCLA, minored in Bioinformatics, and have worked in research laboatories (not clinical) for at least 6 years so I am on the lesser end of qualified to muse on topics like these, but more qualified than RFK Jr. so that will be sufficient for purposes of this post. I am certified as a UNIX & Linux System Administrator through UCSD Extension and worked for >4 years as a systems administrator (later scientific programmer) to the Computational Neurobiology Laboratory at the Salk Institute for Biological Studies (named after Jonas Salk of polio vaccine fame). Currently I work as a web and software developer.

 

[Mendel]

Article:

Toxic doses and toxicity classes

Toxic doses are often given as LD50 values in mg/kg body weight. The LD50 is the median lethal dose meaning the dose at which 50% of test subjects die upon exposure to a compound.

Toxicity classes are defined according to the globally harmonized system of classification of labelling of chemicals (GHS). LD50 values are given in [mg/kg]:
Class I: fatal if swallowed (LD50 ≤ 5)
Class II: fatal if swallowed (5 < LD50 ≤ 50)
Class III: toxic if swallowed (50 < LD50 ≤ 300)
Class IV: harmful if swallowed (300 < LD50 ≤ 2000)
Class V: may be harmful if swallowed (2000 < LD50 ≤ 5000)
Class VI: non-toxic (LD50 > 5000)

Source: https://tox.charite.de/protox3/

Article:

The generally accepted "certainly lethal dose" range for 70 kg adults, i.e., from 5 to 10 g of sodium fluoride or from 32 to 64 mg fluoride/kg, is discussed.

Source: https://pubmed.ncbi.nlm.nih.gov/3301934/

Article:

The oral LD50 of sodium fluoride is 44 mg/kg in mice and 31 mg/kg in rats. The oral LD50 of sodium fluoride in rabbits is 200 mg/kg.

Source: https://go.drugbank.com/drugs/DB09325

It follows that fluoride is correctly labeled as "toxic if swallowed", if not stronger.

The paper I cited argues that toxicity in small children might begin at 5 mg/kg.

Notwithstanding the debate on how much of a dose of fluoride is safe, and for whom, labeling fluoride as "toxic" seems to be technically correct (the best kind of correct).

The point is that small amounts of fluoride are beneficial for dental health, so there's a trade-off to be made in terms of benefits and risks from a public health standpoint. Any discussion of the public health aspects of fluoride use should present both the benefits and the risks.

 

[joel_yancey]

Thank you @Mendel, your additional data is very useful in evaluating this claim.

@Mendel As you cite, technically correct in one context. But the proposed analysis of 'this number of molecules per unit mass of body weight corresponds to GHS classification of toxicity' does not seem directly relevant to validating RFK Jr.'s claim. The GHS Level classification is more useful in the context of Safety Data Sheets (SDSs) which accompany all chemicals in all laboratories so that lab workers can handle them safely. RFK Jr. contends that citizens are actually suffering the affects of fluoride toxicity, irl. So we need to consider the context of our objective exposure (or the exposure level of the most affected people) and then assess its harm.

You just cited some key data so let's try out these the numbers...

• Average newborn baby weight in kg ~= 3.5kg
• The EPA sets a Maximum Contaminant Level (MCL) of 4.0 mg/L fluoride
• The half life of fluroide when ingested has been estimated at ~5 hours (need double to reach threshold within half life time window)
• To reach class III LD50 toxicity according to the GHS toxicity scale, a newborn baby would need to have consumed 50mg/kg * 3.5kg * 2 half lifes = 350mg ; to 300mg * 3.5 kg * 2 half lifes = 2100mg of fluoride
• 350mg ÷ 4.0mg/L = 87.5L ; to 2100mg ÷ 4.0mg/L = 525L of water
• Therefore a newborn baby would need to ingest 87.5 to 525 liters of water contaminated by Maximum Contaminant Level of 4.0 mg/L fluoride, in a 5hr time window without excreting to have a 50% chance of death
• Alternatively, to use your number of 5mg/kg where toxicity has been estimated to occur in children, 5mg/kg * 3.5kg * 2 half lifes = 35mg of fluoride
• 35mg ÷ 4.0mg/L = 8.75L of water
• Therefore a newborn baby would need to ingest 8.75L liters of water contaminated by Maximum Contaminant Level of 4.0 mg/L fluoride, in a 5hr time window without excreting in order to be affected by fluoride toxicity

Even using conservative numbers, to me this does not seem in support of RFK Jr.'s claim. Not at all. The volume of water required in a 5 hour time window to reach your cited level for toxic-to-children becomes even more unrealistic once you start adding more body mass to the equation. Based on this analysis, I contend that a child would die from water intoxication long before experiencing fluoride toxicity. As mentioned in my previous post, there was a well-known tragedy near the area where I grew up of a young person whose cause of death was water intoxication. The incident took place while this person was competing in a contest for a popular radio station (the radio station was 107.9 The End in Sacramento if anyone cares to look this up). If memory serves, the contest was who could drink the most water.

Any discussion of the public health aspects of fluoride use should present both the benefits and the risks.

I agree completely.

 

[Mendel]

The half life of fluroide when ingested has been estimated at ~5 hours (need double to reach threshold within half life time window)

I don't follow that.

If a baby gets hold of a tube of toothpaste and sucks on it, the ingestion is what it is: 50mg/kg per 3.5kg body weight means 175mg fluoride, and it's a coin flip on whether that baby ends up dead. Symptoms of poisoning (as described on the drugbank page I linked) would occur at much lower doses, such as 5mg/kg.

The half life is important when it comes to exposure over time: if you drink 10 mg of fluoride, after 5 hours your exposure isn't 10 mg, but 5mg, because half of the original fluoride is gone or converted to something non-toxic. After 10 hours, it'd be 2.5mg, and so on.
But if you kept this up and ingested 10 mg of fluoride every 5 hours, you'd eventually end up with 20mg of fluoride in your body as enduring exposure. These kinds of calculations are generally more important when the exposure is continuos as well, e.g. via the air.

 

[joel_yancey]

If a baby gets hold of a tube of toothpaste and sucks on it,

RFK Jr.'s claim in the video at the top of the post is that the fluoride concentration in our water supply is poisoning us.

The half life is important when it comes to exposure over time

I agree. Ingestion is a form of exposure.

The half life is important when it comes to exposure over time: if you drink 10 mg of fluoride, after 5 hours your exposure isn't 10 mg, but 5mg, because half of the original fluoride is gone or converted to something non-toxic

I agree. That is why I multiplied by two. If it takes 5 hours to lose half, then we can double the total amount ingested such that we will reach the target concentration after 1 half life of time.

 

[Mendel]

Article:

The recent epidemiological results support the notion that elevated fluoride intake during early development can result in IQ deficits that may be considerable. Recognition of neurotoxic risks is necessary when determining the safety of fluoride-contaminated drinking water and fluoride uses for preventive dentistry purposes.

Source: https://ehjournal.biomedcentral.com/articles/10.1186/s12940-019-0551-x

This is really the crux of the claim.

First, it pertains to both drinking water and "preventative dentistry" such as mouthwash and toothpaste. (Teach your kids to always spit those out, even if it tastes good!) A person's exposure to fluoride would be a combination of these sources, not just one source alone.

Secondly, the argument being made here is that there's a long-term exposure effect that previous studies have failed to detect, and that this effect can be seen at dosages that are conventionally considered safe.

Not having read either paper, I have some questions that someone with a background in neuroscience can perhaps answer.

1) Are there other substances where long-term exposure is neurotoxic?

2) How is neurotoxicity commonly determined?

3) Are IQ tests a suitable tool to assess neurotoxicity?

4) Are the studies that have examined fluoride neurotoxicity methodologically sound? Are there pre-registered studies among them? How many participants?

5) How did the 2023 meta-analysis determine "risk of bias"?

 

[Mendel]

RFK Jr.'s claim in the video at the top of the post is that the fluoride concentration in our water supply is poisoning us.

That's not evident from your post, because you did not transcribe it (ideally with the time in the video).

I agree. That is why I multiplied by two. If it takes 5 hours to lose half, then we can double the total amount ingested such that we will reach the target concentration after 1 half life of time.

If you double the amount, you have double the target concentration at the time of ingestion. The fact that you'll be somewhat less poisoned after 5 hours is of little comfort.

 

[joel_yancey]

That's not evident from your post, because you did not transcribe it (ideally with the time in the video).

Thank you, you are right. I will be sure to fix this tomorrow.

If you double the amount, you have double the target concentration at the time of ingestion. The fact that you'll be somewhat less poisoned after 5 hours is of little comfort.

I see your point, but my point is that it is impossible to instantly ingest such a large volume of water. You must factor in some time, which is possible to do if the half life is known (amount of time before half leaves your system).

 

[Bob Jase]

Dear Rest of the World, please give up on the USA - it ain't worth saving.

 

[JMartJr]

That's a "politely disagree", @Bob Jase ! ^_^ I think we are worth saving. Some days, I even remain hopeful that we can save ourselves...

 

[Ann K]

Dear Rest of the World, please give up on the USA - it ain't worth saving.

They already have given up on a country that used to lead but is now an untrustworthy nation. I hope it's temporary, but at my age I despair of living long enough to see the return of sanity.

 

[joel_yancey]

A person's exposure to fluoride would be a combination of these sources, not just one source alone.

Fair enough, I concede that. But RFK Jr. thinks boogymen are poisoning our water supply. That is the specific claim I am trying to address.

Secondly, the argument being made here is that there's a long-term exposure effect that previous studies have failed to detect, and that this effect can be seen at dosages that are conventionally considered safe.

I agree with your framing. I also want to point I am not glued to one side on this issue. Even a quack can be right, if only by accident. Whether or not RFK Jr. is a quack will be more of a challenge to persuade me otherwise, because this is a pattern with him. But the purpose of this thread is to investigate one specific claim honestly and with an open mind.

1) Are there other substances where long-term exposure is neurotoxic?

Many substances in high enough dose. Anything that get into your blood stream and permeate your blood-brain barrier (BBB). These are often small like fluoride ions and/or fat-soluble molecules. It seems the mechanism by which Flouride ions cross the BBB is not fuly understood.

2) How is neurotoxicity commonly determined?

You would have to ask a clinical neuroscientist or medical doctor. I was never a pre-med student, have never worked in a hospital, and didn't take those electives. But I suspect there is no simple answer. It's funny, I used to raise that exact question when I was in college with my girlfriend at the time (who was also neuroscience but pre-med)... what even is neurotoxicity I would ask in a snarky tone. I never got an answer lol.

3) Are IQ tests a suitable tool to assess neurotoxicity?

In my view, IQ tests are bunk. I don't think they are a good way to measure intelligence. I even take it a step further, because I am of the belief that "intelligence" as a concept is not very useful. Humans are too complicated to slap a numeric value on their forehead. And I am not going to look for it now, but I heard there were studies proving that IQ tests can be trained for. Basically if you practice, you can improve your score over time. If those studies do exist, that really undermines the notion of IQ.

4) Are the studies that have examined fluoride neurotoxicity methodologically sound? Are there pre-registered studies among them? How many participants?

I will get back to you on this. I am still investigating and there is a lot of literature on this topic.

5) How did the 2023 meta-analysis determine "risk of bias"?

I will get back to you on this. I am still investigating and there is a lot of literature on this topic.

 

[FatPhil]

That's not evident from your post, because you did not transcribe it (ideally with the time in the video).

If you double the amount, you have double the target concentration at the time of ingestion. The fact that you'll be somewhat less poisoned after 5 hours is of little comfort.

Nah. *At the time of ingestion* you basically have *zero* concentration in both cases. It takes time to get in. How quickly gets in might be limited by some physical process that depends on some substance that is limited in availability, likewise sites for ingestion may be limited, so you can't even say that after ingestion the concentration in the double-dose case will be twice the concentration in the single case dose.

If you stuff yourself on sausages and potato salad, you'll be precisely as drunk the instant after chugging two small beers as you would after chugging one, namely not at all. It's just PDEs.

 

[joel_yancey]

Interestingly, Head Start, a program run by the United States Department of Health and Human Services (HHS), repeatedly contradicts RFK's claims about flouride (for now!). It will be interesting to check up on these .gov web resources periodically.

Currently the main resource page on flouride reads:

Tips to Help Parents Prevent Tooth Decay with Fluoride

• Reassure parents that fluoride is safe. Fluoride is a mineral that is found naturally in water, soil, plants, and rocks. There is strong scientific evidence to show that fluoride does not cause health problems in children or adults. Common Questions about Fluoride: A Resource for Parents and Caregivers can help answer any questions parents have about fluoride. Healthy Habits for Happy Smiles: Getting Fluoride for Your Child also provides information that can be shared with parents. Post the I Like My Teeth posters to start a conversation about the importance of fluoride.
• Urge parents to serve fluoridated water to their children. Whenever possible, encourage parents to serve their children water from the tap. Healthy Habits for Happy Smiles: Encouraging Your Child to Drink Water offers tips on making water appealing to children. If parents prefer to serve bottled water, show them how to find out if the water has fluoride. Often, bottled water does not have fluoride.
• Encourage parents to brush their child's teeth with fluoride toothpaste twice a day. The best times to brush are in the morning and at bedtime. Parents should put a rice-size amount on the toothbrushes of children under age 3 and a pea-size amount on the brushes of children ages 3 and older. Children can spit out any remaining toothpaste but should not rinse after brushing. Healthy Habits for Happy Smiles: Brushing Your Child's Teeth provides additional tips and photos of toothpaste amounts that can be shared with parents.
• Remind parents to ask their child's dentist or doctor about fluoride varnish. Fluoride varnish can be painted onto a child's teeth in their dental or medical office. Varnish can be applied up to four times a year. It strengthens enamel, making teeth less likely to develop tooth decay. Fluoride varnish should be used in addition to fluoridated water and fluoride toothpaste.

Last Updated: November 16, 2022

https://headstart.gov/oral-health/b...how-fluoride-helps-prevent-repair-tooth-decay

Also,

A child's body needs water to be healthy and active. Many communities have tap (faucet) water with fluoride. Giving children water with fluoride is one of the best ways to keep their teeth healthy. When children drink water with fluoride throughout the day, their teeth are bathed in low levels of fluoride, which helps to keep teeth strong.

Tips for encouraging your child to drink water:

• Make drinking water fun for your child. Use bendy, silly, or colored straws. Or let your child choose their favorite cups or water bottles.
• Use water bottles that can be carried anywhere. Refill them with tap water. Most bottled water does not have fluoride.
• Add a lemon, lime, or orange slice or fresh mint leaves to the water. Or add fruit like blueberries, raspberries, or strawberries.
• Give your child water with ice cubes or crushed ice. Look for ice cube trays in fun shapes like dinosaurs, letters, or animals.
• Be a good role model for your child. Drink water instead of drinks that have sugar, like juice, fruit drinks, soda (pop), or sports drinks.
• Set up a station where your child can get a drink of water when they are thirsty. Keep a nonbreakable water pitcher or thermos on a low stool or a chair where your child can reach it.
• Read books or show your child videos about drinking water, for example Potter the Otter: A Tale About Water and Potter the Otter Loves to Drink Water.

Last Updated: November 9, 2022

https://headstart.gov/publication/encouraging-your-child-drink-water

Also,

2. Is fluoridated water safe for me and my children to drink?

Yes. Decades of research and practical experience have confirmed the safety of fluoride. Based on what has been learned from both science and our years of experience, the world's leading health, dental, and medical organizations recognize water fluoridation as an effective way to reduce tooth decay for everyone – children and adults alike.

7. Are the fluoride additives used to fluoridate drinking water safe?

Yes. The fluoride that is added to public water supplies conforms to stringent safety standards and results in water that complies with the Safe Drinking Water Act. The quality and safety of fluoride additives are ensured by Standard 60, a program that was commissioned by the U.S. Environmental Protection Agency (EPA). This program is monitored by an independent committee of experts, including the Association of State Health Officials and other key organizations

9. I have heard fluoride can cause all kinds of things, from lower IQ to cancer. Can that be true?

No. There is no credible scientific evidence that water fluoridated at the levels used in the United States contributes to or causes disease or poor health. The only proven risk associated with fluoride intake from any source is dental fluorosis which can be lowered with proper use of fluoridated products like toothpaste and mouth rinse.

https://ilikemyteeth.org/wp-content/uploads/2014/02/CommonQuestionsAboutFluorde.pdf
(this document was linked to but is hosted on an external website)

And finally (the wording of this cracks me up),

Fluoride in Water

• Since most water doesn't have enough natural fluoride to prevent tooth decay, many communities add fluoride to their water supply (tap water) used for drinking and cooking.
• Give your child tap water with fluoride. If you are not sure if your water has enough fluoride, ask your child's dental clinic for help in finding out.
• Some bottled waters contain fluoride, and some do not. Check with the bottled water's manufacturer to ask about the fluoride content of a particular brand.
• If your tap water does not have enough fluoride, ask your dental or medical clinic if your child needs fluoride drops or tablets

https://headstart.gov/sites/default/files/pdf/encourage-child-drink-water.pdf

Attached for preservation:

• a static copy of https://headstart.gov/oral-health/b...how-fluoride-helps-prevent-repair-tooth-decay as it looks today March 12, 2025 (.tar.gz)
• a static copy of https://headstart.gov/publication/encouraging-your-child-drink-water as it looks today March 12, 2025 (.tar.gz)
• a document hosted on headstart.gov titled Understanding How Fluoride Helps Prevent and Repair Tooth Decay (.pdf)
• a document linked to on headstart.gov titled COMMON QUESTIONS ABOUT FLUORIDE:A Resource for Parents and Caregivers (.pdf)
• a document hosted on headstart.gov titled Getting Fluoride for Your Child (.pdf)

 

[Gary C]

Some areas do have naturally fluoridated drinking water and a few sites in the US have higher levels of fluoride in their ground water than recommended by ADA. Are there any studies documenting higher rates of child development issues in these areas? Since they predate the fluoridated water policies in the US, they should provide epidemiological evidence for or against RFK's claim.

A study would still have to control for socio-economic factors and other contaminants such as arsenic so a simple mapping of developmental problems vs fluoride levels is not likely to be informative.

 

[Ann K]

And I am not going to look for it now, but I heard there were studies proving that IQ tests can be trained for. Basically if you practice, you can improve your score over time. If those studies do exist, that really undermines the notion of IQ.

IQ tests are not often given to adults, I believe. They're used most frequently to assess children. My best memory is that I had ONE in about the sixth grade, and that's all, so "practicing" doesn't really enter into it. Cognitive tests may be given to senior citizens who show signs of senility, but that's another thing altogether.

Edit to add: thanks for linking to those sites. It'll be interesting (or terrifying) to see if they're all removed or replaced with pages that support RFK jr in the future.

 

[SuppaCoup]

The evidence of bad oral health having negative effects on the brain is much stronger than any of the claims towards flouride:
https://www.sciencealert.com/expert-reveals-a-surprising-link-between-oral-health-and-your-brain

A new study in Japan has once again raised questions about the relationship between oral health and brain health; which most experts agree are surprisingly interconnected.

It investigated whether problems in the mouth like periodontitis (gum disease) and tooth loss can increase the risk of neurodegenerative disorders like stroke, Alzheimer's, and other forms of dementia.


The results were clear: both issues are associated with a faster rate of atrophy in the hippocampus – the part of the brain that governs memory, learning, and emotion. This is a significant result, however it is not the first time such a link has been made.


In March, a US study of more than 40,000 adults enrolled in the UK Biobank research project found that poor oral health appears to be a key risk factor for stroke and dementia.


In a 2019 literature review, another set of researchers concluded that "collectively, experimental findings indicate that the connection between oral health and cognition cannot be underestimated".

 

[joel_yancey]

5) How did the 2023 meta-analysis determine "risk of bias"?

Thank you @Mendel for asking a really good question and the same one I had. Here is what I learned about how one research team does it (Taylor, Bucher et. al)...

Risk of Bias Assessment
Performed using HAWC (don't look up the acronym it will not help)

• white paper: https://ehp.niehs.nih.gov/doi/10.1289/EHP4224
• a collaborative software tool by the National Toxicology Program (NTP) designed to facilitate environmental human health assessments of available scientific literature (ie. Risk of Bias assessment for fluoride studies conducted across many countries, notably China where many of the studies on flouride toxicology are conducted)
• it basically organizes the workflow of loading, extracting, visualizing, categorizing, and ultimately assessing the data from many studies
• not a fully automated pipeline. They don't advertise this anti-feature and I found it difficult to confirm, but alas it seems a huge team of very bored zombies (reviewers) is necessary for a Risk of Bias assessment. HAWC just makes everything methodical and scientific.
• It has a Python API (which now I want to play with)
• when a study is entered into the HAWC database for use in an assessment, risk of bias metrics can be entered for a metric of bias for each study.
• Screenshots of HAWC:

Fluoride Risk of Bias Assessment

• The exact protocol when assessing a study for Risk of Bias differs for each of 3 possible study type categories:
  • Bioassay
  • Epidemiology
  • In Vitro
• assessment protocol outlines for each study type can be found here: https://hawcproject.org/rob/assessment/405/

Source: https://hawcproject.org/rob/assessment/405/
​

This is just how one team of investigators performed their Risk of Bias analysis, but I would imagine it usually goes something like this. It would be pretty hard to completely automate such an analysis even with modern technology. So the tl;dr answer @Mendel is human reviewers do it manually with an esoteric scoring rubric. I decided to look more closely at this group's methods because I am putting together a comprehensive post outlining the best evidence in support of flouride as a neurotoxin. I feel like that is necessary to stay objective. I was unaware just how many research groups and meta-analyses actually conclude there could be a link (or may support a link). Impossible not to deep dive on this one study in particular, and I will have more to say about it soon. It is hot off the press, brand spankin new 2025 meta-analysis of 74 separate studies by an American team at the National Institute of Environmental Health Sciences. Suffice it to say they went pretty big with their conclusions. It also published in a very high impact journal (~24.7). One interesting methodological choice that warrants scrutiny is they included zero USA studies in their analysis. Moreover, most of the studys they looked at (45 out of 74) are from China. This goes back to that whole Risk of Bias thing, and why this side quest into HAWC was necessary. Stay tuned, or dive in if you are so inclined. This investigation is getting salty...

The full PDF can be download here (let's get some more eyeballs on this):
https://jamanetwork.com/journals/jamapediatrics/fullarticle/2828425

 

[joel_yancey]

The evidence of bad oral health having negative effects on the brain is much stronger than any of the claims towards flouride:

Correlation/causation issues abound. When I heard this I assumed it's probably some sort of correlation thing. Like you start forgetting to brush your teeth when you start getting dementia. Or if it is causation then it starts with dementia, because it wouldn't be surprising if that led to worse oral hygiene, I would actually expect that. I haven't looked into it, these were just my inital thoughts when I first heard this. That sure would be strange if there if dementia was starting in the mouth and the causality was in that direction... causation going the other way is expected. I worked in a lab that studied Alzheimer's for 18 months, but it was so long ago. I am so not up to speed with the latest in neurodegeneration research.

Now I am curious but I can't handle more than one investigation right now lol thanks @SuppaCoup

 

[joel_yancey]

As a corollary to my previous post...

I don't mean to sound heartless but... would anyone be surprised if kids who swallowed more toothpaste performed worse on IQ tests?

Lead author of the study talking to NBC News:

For every small increase of fluoride found in kids' urine, Taylor wrote, "there is a decrease of 1.63 IQ points in children."

Source: https://www.nbcnews.com/health/heal...-research-possible-children-brains-rcna185788

Conclusions and Relevance This systematic review and meta-analysis found inverse associations and a dose-response association between fluoride measurements in urine and drinking water and children's IQ across the large multicountry epidemiological literature. There were limited data and uncertainty in the dose-response association between fluoride exposure and children's IQ when fluoride exposure was estimated by drinking water alone at concentrations less than 1.5 mg/L. These findings may inform future comprehensive public health risk-benefit assessments of fluoride exposures.

Source: https://jamanetwork.com/journals/jamapediatrics/fullarticle/2828425

Food for thought.

 

[Mendel]

That sure would be strange if there if dementia was starting in the mouth and the causality was in that direction... causation going the other way is expected.

having a chronic inflammation in the mouth, close to the brain, with a quick pathway to the blood for irritants entering the mouth, sure seems like a plausible risk to me.

but we're at the "needs further investigation" stage until the causal link has been established, which I imagine is quite challenging.

 

[Mendel]

There were limited data and uncertainty in the dose-response association between fluoride exposure and children's IQ when fluoride exposure was estimated by drinking water alone at concentrations less than 1.5 mg/L.

Source: https://jamanetwork.com/journals/jamapediatrics/fullarticle/2828425

This supports the idea that under 1.5mg/L fluoride in drinking water is "safe", and that higher concentrations may not be.

There's a short older thread at https://www.metabunk.org/threads/fl...isk-to-merit-new-epa-action-judge-says.13670/ (thank you, @Gary C ) that explains the established limits:

Edit: the US recommended level is 0.7 mg/L , and the study considered a fluoride intake exceeding 1.5 mg/L , the WHO limit.The EPA limit is 4 mg/L .

From the same thread:

The report said that about 0.6% of the U.S. population — about 1.9 million people — are on water systems with naturally occurring fluoride levels of 1.5 milligrams or higher.

If RFK Jr. pushed the EPA to lower the limit from 4mg/l to 1.5mg/l, that might be a benefit to those people, with no health drawbacks.

 

[joel_yancey]

If RFK Jr. pushed the EPA to lower the limit from 4mg/l to 1.5mg/l, that might be a benefit to those people, with no health drawbacks.

He wants it removed. Please don't be an apologist for this quack @Mendel. You're my first friend on this site. I want to keep this thread focused on the claim, not hypotheticals. He doesn't mince words.

https://x.com/RobertKennedyJr/status/1852812012478398923

And by the way, water is also an industrial waste. That doesn't make it harmful. He is intentionally trying to elicit a visceral response from people by calling it "industrial waste". Okay tactic for an ambulance-chasing attorney, not for the top public health official of the United States. Moreover, I could equally point out that fluoride is a naturally occurring mineral in groundwater, and has been there since long before the industrial age. But I am not looking to score cheap rhetorical points. I would never make the faulty argument that because it is natural, therefore it is safe. And don't even get me started on GMO hysteria, they play the same games.

 

[Ann K]

Please don't be an apologist for this quack

The highly contagious disease-we-thought-we-had-eliminated, measles, is making a comeback, and RFK jr has ducked his department's responsibility by telling parents "It's up to you to decide whether to vaccinate", and has recommended cod liver oil and "measles parties" so all the kids can get sick and thus be immunized. In other words, they should get sick to prevent them from getting sick? His "advice" has previously led to many deaths:

Robert F. Kennedy Jr. was asked about the deadly measles outbreak that occurred in Samoa in 2019 and claimed the lives of 83 people, mostly children. Kennedy, a leading anti-vaxxer who had visited the Pacific island nation a few months before the outbreak, replied, "I'm aware there was a measles outbreak…I had nothing to do with people not vaccinating in Samoa. I never told anybody not to vaccinate. I didn't go there with any reason to do with that."

Kennedy was being disingenuous, sidestepping his connection to that tragedy. Children's Health Defense, the nonprofit anti-vax outfit he led until becoming a presidential candidate, had helped spread misinformation that contributed to the decline in measles vaccination that preceded the lethal eruption. And during his trip to Samoa, Kennedy had publicly supported leading vaccination opponents there, lending credibility to anti-vaxxers who were succeeding in increasing vaccine hesitation among Samoans.

https://www.motherjones.com/politic...ection-to-a-deadly-measles-outbreak-in-samoa/

 

[JMartJr]

If this thread is going to go on much longer, I'm going to need an "enraged" emoji. Mr. Kennedy's nonsense is infuriating.

 

[joel_yancey]

As a corollary to my previous post...

I don't mean to sound heartless but... would anyone be surprised if kids who swallowed more toothpaste performed worse on IQ tests?

Lead author of the study talking to NBC News:

For every small increase of fluoride found in kids' urine, Taylor wrote, "there is a decrease of 1.63 IQ points in children."

Source: https://www.nbcnews.com/health/heal...-research-possible-children-brains-rcna185788

Conclusions and Relevance This systematic review and meta-analysis found inverse associations and a dose-response association between fluoride measurements in urine and drinking water and children's IQ across the large multicountry epidemiological literature. There were limited data and uncertainty in the dose-response association between fluoride exposure and children's IQ when fluoride exposure was estimated by drinking water alone at concentrations less than 1.5 mg/L. These findings may inform future comprehensive public health risk-benefit assessments of fluoride exposures.

Source: https://jamanetwork.com/journals/jamapediatrics/fullarticle/2828425

Food for thought.

Re-post. Just to put this thread back on topic. I would like for people to seriously think about this. I can't stop thinking about it.

1) Would anyone be surprised if many children in this study brushed their teeth at some point in their life?

2) Would anyone be surprised if kids who swallowed more toothpaste performed worse on IQ tests?

3) Would anyone be surprised if fluoride concentration in urine, as a proxy for fluoride exposure in water supply, was primary evidence in a peer-reviewed study published in a high impact journal in 2025?

I wouldn't be too surprised, except for a little surprise on the last one. However, if you think obvious explanations can't fly under the radar of government researchers, look no further than AATIP (it's not the best comparison since AATIP never published a peer-reviewed study as far as I know). I do not mean to sound like a deep-state fear-mongerer, because I love love love big government. But the fact that this 2025 fluoride meta-analysis is a government study may have had something to do with it's acceptance into a high-impact journal. Btw, when I say this was a government study, I do not mean indirectly funded via NIH, NSF grants, etc even I have helped fill out those grant applications. Those grants are the means through which most of the biomedical research in this country gets funded, for example universities and non-profit research institutes like Salk Institute where I used to work... I mean this study was actually conducted by a government agency called the National Institute of Environmental Health Sciences (which coincidentally is a subdivision of HHS), and is under the umbrella of the National Toxicology Program (or something like that, I may have got it backwards). The ONLY reason I bring up that government conducted this study is because I am trying to rationalize how it was accepted into such a high-impact journal.

One more note. "Peer-reviewed" means 3 people looked at it and approved of it. It's not a be-all-end-all of truth. Sometimes I think lay persons or non-scientists hear "peer-reviewed" and think "community-reviewed". But it just means 3 senior researchers in the same field, selected by the journal and anonymous to the authors, have read it and approve.

 

[Ann K]

In what world
(other than an absolute swamp in which unqualified people get positions of power for kissing DJT butt)
is a quack like this put in charge of Americans' health?!?

Not really an exception to your parenthetical expression, but remember that Florida elevated Ladapo to a similar position.

 

[tinkertailor]

IQ tests are not often given to adults, I believe. They're used most frequently to assess children. My best memory is that I had ONE in about the sixth grade, and that's all, so "practicing" doesn't really enter into it. Cognitive tests may be given to senior citizens who show signs of senility, but that's another thing altogether.

Edit to add: thanks for linking to those sites. It'll be interesting (or terrifying) to see if they're all removed or replaced with pages that support RFK jr in the future.

IQ tests show a great deal of cultural bias: some states mandate that you cannot use tests based in IQ with children of certain cultural backgrounds. I know in CA we cannot use them to determine eligibility for special ed with Black children due to the "Larry P" ruling:

The Larry P. v. Riles (Larry P.) case was filed in 1971 when five African-American children who had been placed in special education classes for the "educable mentally retarded" (EMR) in the San Francisco Unified School District filed suit in the Federal District Court of Northern California claiming that they had been wrongly placed in the EMR classes based on their performance on intelligence tests that were racially biased and discriminatory. [Larry P. v. Riles, 495 F. Supp. 926 (N.D. Cal. 1979).] The suit also claimed that a disproportionate total number of African-American students were placed in EMR classes compared to the number of African-American students in the school system.

I doubt studies on flouride impacting IQ scores are considering this.


More subjectively as a person who has assessed a fair few kids at this point, I know that many tests require compliance. Some kids are just not gonna do what you tell them to, so they fail the test even though we know they can do it.

I've given cognitive tests to kids and adults at this point and I think they're useless for kids. Utterly useless.

 

[joel_yancey]

Excellent point @tinkertailor thank you for your input! I am going to go out on a limb and argue that you have identified how the other half of this bunk sausage was made. Let me cite the study's conclusions here again as a reminder. Remember there were two parts to this study:

Conclusions and Relevance This systematic review and meta-analysis found inverse associations and a dose-response association between fluoride measurements in urine and drinking water and children's IQ across the large multicountry epidemiological literature. There were limited data and uncertainty in the dose-response association between fluoride exposure and children's IQ when fluoride exposure was estimated by drinking water alone at concentrations less than 1.5 mg/L. These findings may inform future comprehensive public health risk-benefit assessments of fluoride exposures.

Source: https://jamanetwork.com/journals/jamapediatrics/fullarticle/2828425

The study draws its conclusions based on two different but related lines of evidence. The second major aim of this study not yet discussed in this thread, was to associate drinking water fluoride concentration by region, to IQ scores of children in those regions. As @tinkertailor brilliantly points out, there may be cultural/regional bias in IQ scores. Well, it is known that China has unusually high concentrations of fluoride (and other contaminants) in its drinking water supplies which varies wildly by region. This is why they do so much research on flouride intoxication in China, it's not regulated and controlled the same way it is here. Also bear in mind that the second most represented country in this meta-analysis was India (I believe 11 of the 74 studies were from India).

We now have a much simpler explanation to the second finding in this study. I've outlined this argument in 3 suppositions again:

1) Would anyone be surprised if IQ scores were culturally/ethnically/socioeconomically biased?

2) Would anyone be surprised if the amount of contamination in a region's drinking water was biased by the socioeconomic/ethnic/cultural makeup of that region? Bear in mind that most of the children in this study were from China and India, which may not regulate their water supply as successfully as USA and also which may have greater cultural divides and socioeconomic disparity than USA.

3) Would anyone be surprised if a correlation between regional fluoride concentration and IQ was primary evidence in a peer-reviewed study published in a high impact journal in 2025?

@tinkertailor Thanks again for providing the great insight!

---

I am starting to come to the view that the whole idea of having special-interest government research programs is inherently flawed. Government is obviously necessary to fund research that private companies are unwilling to do or is unprofitable. Buuuuut does the government need to be the one doing the research? And if government does do the research, what kind of incentive structure does that create? What is the argument for special-interest government agencies like AATIP and NIEHS (National Institute of Environmental Health Sciences), the government agency that conducted this questionable, eyebrow-raising 2025 fluoride-in-drinking-water meta-analysis. The argument in either case simply cannot be that if the government didn't do it then who would. It's not that if the government doesn't do the research then no one will; it's that if the government doesn't pay for the research then no one will. Hundreds of elite research laboratories all across the country would line up and be clambering just for a chance to apply for such grants. If government does do the research, what incentive structure does that create when it comes to job security? When the COVID crisis struck, we didn't establish a National Institute of Vaccine Research; rather, we farmed out the work to hundreds of the nation's top universities and non-profit research institutes. I realize that I am totally contradicting my earlier statement that I love big government, well what can I say; I am a flawed person changing my mind in real-time... Grant-based research funding, the way the vast majority of biomedical research is funded in this country, is so successful precisely because it is a cut-throat, competitive process to get awarded grant funding by NIH or NSF (often >95% chance of rejection). The grant-based system for funding essential research is competitive in the best possible way. It forces innovation and makes waste impossible. NIH and NSF are overwhelmingly successful precisely because they don't do research. They direct (or "referee") it. And that's the way it should be. So, I will resolve my internal conflict about big government as follows: I like a big dynamic government. Thanks for hearing me out everyone.

I am becoming anxious to start on the next RFK Jr claim. WiFi causes cancer looks fun. Feel free to beat me to it! Or any of them!

 

[FatPhil]

I am becoming anxious to start on the next RFK Jr claim. WiFi causes cancer looks fun. Feel free to beat me to it! Or any of them!

Fluoride's not dead yet! Have you sat through this video? (linked to from RJK's tweet)

EXPERT ATTORNEY EXPOSES DECADES OF FLUORIDE HARMS

Fresh off a historic win against the EPA over the use of fluoride in drinking water, lead attorney for the plaintiffs, Michael Connett, Esq., discusses the decades-long concealment of the significant harms fluoride poses to human health and its implications for the future of water fluoridation.
AIRDATE: October 31, 2024

-- https://thehighwire.com/ark-videos/expert-attorney-exposes-decades-of-fluoride-harms/
video link: https://static.arkengine.com/video/cm2z1180e0047jp01okht4rw7/file/mp4/CONNETT INTV_EP_396.mp4

The download looked big, so I backed out. It's very much not my field, so all I could perform is the shallowest of sniff tests anyway. Volunteering someone else to do the hard work is more my thing

 

[Mendel]

3) Would anyone be surprised if fluoride concentration in urine, as a proxy for fluoride exposure in water supply, was primary evidence in a peer-reviewed study published in a high impact journal in 2025?

You quoted this earlier:

Article:

Conclusions and Relevance
This systematic review and meta-analysis found inverse associations and a dose-response association between fluoride measurements in urine and drinking water and children's IQ across the large multicountry epidemiological literature. There were limited data and uncertainty in the dose-response association between fluoride exposure and children's IQ when fluoride exposure was estimated by drinking water alone at concentrations less than 1.5 mg/L. These findings may inform future comprehensive public health risk-benefit assessments of fluoride exposures.

Source: https://jamanetwork.com/journals/jamapediatrics/fullarticle/2828425

Not having read the study, I understood this to mean that
• fluoride concentration in urine is a proxy for fluoride intake from all sources, it varies individually¹
• fluoride concentration in water varies geographically

I understood the conclusion to say
• IQ varies (statistically) with urine concentration, i.e. total fluoride intake seems to affect IQ
• IQ varies (statistically) with water concentration, but only above 1.5mg/l, i.e. fluoride intake via tap water seems to affect IQ if it is above 1.5 mg/l ²

1.5 mg/l is, coincidentally, the WHO limit, so it supports that.

The US would have to upgrade less than 2% of its water systems to achieve this limit. (Given how hard this was in Flint with actual lead in the water, this may be more difficult than it sounds.)

Now the question that was before the court is, do the uncertainties associated with this result justify delaying regulatory action?

---

¹ "Unlike drinking water levels, individual-level urinary fluoride concentrations include all ingested fluoride and are considered a valid estimate of total fluoride exposure."
² However: "In analyses restricted to low risk-of-bias studies, the association remained inverse when exposure was restricted to less than 4 mg/L, less than 2 mg/L, and less than 1.5 mg/L fluoride in drinking water."

[Edit: added footnotes]

 

[Mendel]

I am starting to come to the view that the whole idea of having special-interest government research programs is inherently flawed. Government is obviously necessary to fund research that private companies are unwilling to do or is unprofitable. Buuuuut does the government need to be the one doing the research? And if government does do the research, what kind of incentive structure does that create? What is the argument for special-interest government agencies like AATIP and NIEHS (National Institute of Environmental Health Sciences), the government agency that conducted this questionable, eyebrow-raising 2025 fluoride-in-drinking-water meta-analysis. The argument in either case simply cannot be that if the government didn't do it then who would.

You started this thread with a meta-study that claimed most of the rearch on this issue is biased.

On issues that the government regulates, it is important that the knowledge underpinning these regulations is not biased. Thus, the rationale for having "our people" look at the existing research and sort it out is there. (And that's exactly what a meta-review does.)

When the COVID crisis struck, we didn't establish a National Vaccine Agency; rather, we farmed out the work to hundreds of the nation's top universities and non-profit research institutes.

WHO, for example, had a group of experts who sifted through all of that independent research that came flooding in to ensure they had an accurate picture of what was known, and how well supported it was. They did that because they bore the responsibility to inform the Covid response for many countries, most of them too small to do this work themselves.

I do not think it'd be a good idea for government to not have health experts whose knowledge informs health regulations. Goverment needs to be accountable for its decisions, they can't just point to some private researcher and blame them.

 

[Mendel]

What is the argument for special-interest government agencies like AATIP

AATIP is not (and was not) a government agency, and it's about UFOs, not health. I suggest taking this topic to DMs, or elsewhere, at any rate.

 

[joel_yancey]

@Mendel If the argument was bubblegum exposure leads to IQ loss in children, it wouldn't prove anything to check if they're chewing bubble gum when they take the IQ test. Also the possibility that it could be a temporary effect caused by recent acute exposure was controlled for by giving them regimes of water at various flouride concentrations for some time, and then re-testing IQ (it remained the same)

 

[Mendel]

Buuuuut does the government need to be the one doing the research?

Nobody else does.

Article:

To our knowledge, no studies of fluoride exposure and children's IQ have been performed in the United States, and no nationally representative urinary fluoride levels are available, hindering application of these findings to the US population.

Source: https://jamanetwork.com/journals/jamapediatrics/fullarticle/2828425

 

[Mendel]

@Mendel If the argument was bubblegum exposure leads to IQ loss in children, it wouldn't prove anything to check if they're chewing bubble gum when they take the IQ test.

That's not what they did, especially when the water concentration is the exposure measurement:

Article:

Among the low risk-of-bias cross-sectional studies, most provided information to establish that exposure likely preceded the outcome (eg, only including children who had lived in a community since birth or children who had dental fluorosis).

Source: https://jamanetwork.com/journals/jamapediatrics/fullarticle/2828425

and

An analysis stratified by prenatal or postnatal exposure was suggested post hoc.

---

Also the possibility that it could be a temporary effect caused by recent acute exposure was controlled for by giving them regimes of water at various flouride concentrations for some time, and then re-testing IQ (it remained the same)

I didn't see that in the JAMA paper. Could you please provide a source quote for that paraphrase?

 

[Bob Jase]

They already have given up on a country that used to lead but is now an untrustworthy nation. I hope it's temporary, but at my age I despair of living long enough to see the return of sanity.

Yeah, after watching half a century of deterioration I don't have hope any more. And, thanks to the cost of living adjustment my social security is being cut by about%150 a month, thanks Elon.

 

[deirdre]

1) Would anyone be surprised if IQ scores were culturally/ethnically/socioeconomically biased?

i'd be surprised if China and India were using 'white people' iq tests.

socioeconomics is certainly a thing to watch out for. you'd have to dig into the nitty gritty of the individual studies to determine that.

 

[Mendel]

@Mendel You're spamming this thread. If you haven't read the study

well, an hour later I had, as you can see by the quotes I made, including the footnotes I added to the earlier post.

why tell me I am wrong. You are looking for disagreement rather than understanding.

I told you exactly why you are wrong, and how you misunderstood the "conclusions" section.

You are especially wrong when you claim that the JAMA paper uses "fluoride concentration in urine as a proxy for fluoride exposure in water supply".

 

[JMartJr]

You're spamming this thread. If you haven't read the study why tell me I am wrong. You are looking for disagreement rather than understanding.

Be cautious, please, in assuming motivations. Unless you are one of them mind readers!