Comment by jandrewrogers | Hacker News Reader

Comment by jandrewrogers | Hacker News Reader

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The underlying study makes a much weaker claim than the people who are using it to campaign against fluoridation.

A big issue in this discourse is that for the strong claims to be true, it would essentially require existing science around fluoride toxicity and the related mechanisms of action to be materially incorrect, contrary to all historical evidence. Fluoride poisoning is a thing that happens and has straightforward interventions. Are we supposed to pretend this science doesn't exist? I actually worked in fluoride chemistry, it is difficult to square this circle.

In addition to the "plausible mechanism of action" question, there is the inconvenient observation that exposure to fluoride from natural dietary sources is far higher today than from municipal water. Why the obsession with municipal water augmentation in historically low-fluoride environs? Most people eat far more fluoride than what their water exposes them to.

I find this particular social contagion deeply weird. You see the same persistent misrepresentation on social media as climate science, but in the case of climate science the effects on people is obviously consequential so the motivated reasoning is more understandable. The fluoride thing is trying to invent an issue around a topic that is inconsequential by all evidence and science.

Who benefits by encouraging people to tilt at this windmill?

Do you have a reference for the claim that exposure to fluoride from natural dietary sources is far higher than what occurs from fluoridated water?

An EPA review on fluoride exposure that I found (https://www.epa.gov/sites/default/files/2019-03/documents/fl...) puts most estimates of the "natural" dietary fluoride intake at 0.9mg per day. This is in contrast to the estimated 0.7 * 2 = 1.4mg of fluoride a person will ingest from consuming fluoridated water (with a fair number of water systems fluoridated at levels greater than 0.7mg/L).

Another study I found from the EFSA estimates fluoride intake from non-supplemented food at 0.120mg per day for adults compared to 0.500mg per day from water fluoridated at (1.0mg/L) (https://efsa.onlinelibrary.wiley.com/doi/epdf/10.2903/j.efsa...). Admittedly, in countries where salt is fluoridated, this will constitute the majority of fluoride ingested (especially given most of them don't fluoridate their water :P). But I don't think anti-fluoride advocates would support this either.

I also don't understand what you mean by the "strong claim" and "weak claim" of the NTP monograph. You seem to have doubts that the claims of the NTP monograph are true, based off of the known mechanisms of fluoride toxicity?

My best guess for why the rational anti-fluoride advocates are so stirred up over water fluoridation is that it is a policy proposed without currently a rigorous scientific backing. Per the recent Cochrane review, there is evidence that fluoridation mildly benefits children's teeth, and a lack of high-quality evidence that fluoridation presently benefits adults teeth. There also isn't good evidence that fluoride consumption isn't harmful at present levels (fluorosis is known to occur, and studies evaluated by the NTP point to neurodevelopmental harms, albeit with the conclusion for higher concentrations of fluoride); nor is there strong evidence that systemic fluoride ingestion has any benefits. They might therefore be angry at a somewhat political policy of forced medication that isn't well backed.

Both, the EPA and the EFSA estimates, are incorrect. One standard cup of Asian organic green tea (6 oz - 177 ml) may contain 1.20 mg of fluoride.

https://poisonfluoride.com/phpBB3/viewtopic.php?f=11&t=5677

The NTP monograph is a very flawed document, as the review failed to consider a crucial confounder/modifier - iodine/thyroid status. Fluoride toxicity is directly dependent on the individual's thyroid/iodine status. If iodine-deficient, even miniscule amounts of fluoride may affect you. If iodine intake is excessive, then iodine toxicity may be pre-dominant - this has been known since the 1930s.

See https://pfpc.substack.com/p/pfpc-letter-to-richard-woychik-d...

Are you sure the estimates of the fluoride intake and fluoride consumed respectively are wildly incorrect in light of this? This isn't the best source of information but using data from here (https://www.teausa.com/teausa/images/Tea_Fact_2021.pdf) you can put the estimate at the number of cups of green tea consumed by the average US citizen at 0.1 per day. This is definitely concerning for someone drinking lots of green tea but I don't think it invalidates the statistics. The EPA study also does account for tea consumption, stating in some contexts it forms the highest component of fluoride intake from beverages.

For the second article, this is interesting information and I can see causes for concern in the study (there were multiple hick-ups in the peer review process), and ideally high-quality randomised control trials would form the basis for a conclusion. But what is your opinion on policies of water fluoridation in light of this (I know you are a different commenter than who I was replying to, and don't expect your opinion to be the same)? Is it that people should be focussing on studying its (potentially harmful) effects in light of iodine exposure within regions? The link you posted, written by members of Parents of Fluoride-Poisoned Children, states that:

> As fluoride toxicity is directly related to iodine status - and iodine toxicity to fluoride status -, both mass-supplementation programs require urgent reassessment on a global scale.

and also asks:

> Furthermore, we call for the proper evaluation of the toxicity of fluoride on neurodevelopment based on the extensive body of evidence that addresses the impact on iodine and thyroid hormone metabolism.

They (Andreas Schuld) also state in a later article (https://substack.com/home/post/p-139843513) that: > We also learned that most of the research linking fluoride to thyroid dysfunction had been actively suppressed by public health agencies worldwide, including the World Health Organization (WHO), the European Scientific Committee on Health and Environmental Risks (SCHER), as well as the U.S. CDC, the Agency for Toxic Substances and Disease Registry (ATSDR), the NTP, and the EPA.

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