Embarrassing knock-back of second draft review of possible cognitive health effects of fluoride

We have come to expect exaggeration of scientific findings in media reports and institutional press releases. But it can also be a problem is original scientific publications where findings are reported in an unqualified or exaggerated way. Image Credit: Curbing exaggerated reporting

This is rather embarrassing for a US group attempting to get the science right about possible toxic effects of fluoride. It’s also embarrassing for the anti-fluoride activists who have “jumped the gun” and been citing the group’s draft review as if it was reliable when it is not.

The US National Academies of Sciences, Engineering, and Medicine (NAS) have released their peer-review of the revised US National Toxicity Program (NTP) draft on possible neurodevelopmental effects of fluoride (see Review of the Revised NTP Monograph on the Systematic Review of Fluoride Exposure and Neurodevelopmental and Cognitive Health Effects).

This is the second attempt by the NTP reviewers to get acceptance of their draft and it has now been knocked back by the NAS peer reviewers for a second time.

Diplomatic but damning peer-review

Of course, the NAS peer reviewers use diplomatic language but the peer review is quite damning. It criticises the NTP for ignoring some of the important recommendations in the first peer review. One which is quite critical was the lack of response to the request that NTP explains how the monograph can be used (or not) to inform water fluoridation concentrations. The second NAS peer review firmly states that the NTP:

“should make it clear that the monograph cannot be used to draw any conclusions regarding low fluoride exposure concentrations, including those typically associated with drinking-water fluoridation.”


“Given the substantial concern regarding health implications of various fluoride exposures, comments or inferences that are not based on rigorous analyses It seems to me that there is soime internal politicsshould be avoided.”

It seems to me there is some internal politics involved and some of the NTP authors may be promoting their own, possibly anti-fluoride, agenda. Certainly, the revised NTP draft monograph continues to obfuscate this issue. It continues to state that “fluoride is presumed to be a cognitive neurodevelopmental hazard to humans” – a clause which anti-fluoride campaigner consistently quote out of context. Yes, it does state that this is based on findings demonstrating “that higher fluoride exposure (e.g., >1.5 mg/L in drinking water) is associated with lower IQ and other cognitive effects in children.” But this is separated from the other fact that the findings on cognitive neurodevelopment for “exposures in ranges typically found in drinking water in the United States (0.7 mg/L for optimally fluoridated community water systems)” are “are inconsistent, and therefore unclear.”

Monograph exaggerates by enabling unfair cherry-picking

So, you see the problem. The draft NTP monograph correctly refers to IQ and other cognitive effects in children exposed to excessive levels of fluoride. The draft also correctly refers to that lack of evidence for such effects at lower fluoride exposure levels typical of community water fluoridation. But in different places in the document.

The enables activist cherry-picking to support an anti-fluoride agenda and that is a fault of the document itself. It should clearly state that the monograph should not be used to draw any conclusion at these low exposure levels. This is strongly expressed in the peer-reviewers’ comments.

I find the blanket “presumed to be a hazard for humans” quite misleading. For example, no one says that calcium is “presumed to be a cardiovascular hazard to humans.” Or that selenium is “presumed to be a cardiovascular or neurological hazard to humans.” Or what about magnesium – would you accept that it is a “presumed neurological hazard to humans?” Would you accept that iron is a “presumed cardiovascular, cancer, kidney or erectile dysfunction hazard to humans?” Yet all those problems have been reported for humans at high intake levels of these elements.

No, we sensibly accept that various elements and microelements have beneficial, or essential benefits, to humans at reasonable intake levels., Then we sensibly warn that these same elements can be harmful at excessive intake. To proclaim that any of these elements are “presumed” to be hazardous – without clearly saying at excessive intake levels, is simply distorting or exaggerating the data.

What does “presumed” mean?

A lot of readers find the use of “presumed” strange. But it’s meaning is related to the levels of evidence found by reviewers.

No, don’t believe those anti-fluoride activists who falsely claim that “presumed” is the highest level of evidence and that the finding should be treated as factual. They are simply wrong.

Some idea of the word’s use is presented in this diagram from the NTP revised draft monograph.

So “presumed” means that the evidence for the effect is moderate. That the effect is not factual or known. But as further evidence comes in the ranking of fluoride as a hazard may increase, or decline.

As the monograph bases this “presumed” rating solely on evidence from areas of endemic fluorosis where fluoride intake levels are high it is correct to avoid stating the effects as factual. For example, consider these images from areas of endemic fluorosis in China (taken from a slide presentation by Xiang 2014):

Clearly, people in these areas suffer a range of health effects related to the high fluoride intake. The cognitive effects like IQ loss from these areas could result from these other health effects, not directly from fluoride (although excessive fluoride intake leads to the health effects).

So we can “presume” that fluoride (in areas of endemic fluorosis where fluoride intake is excessive) is a “cognitive neurodevelopmental hazard for humans” but we can not factually state that the neurodevelopment effects are directly caused by fluoride. That would require further scientific work to elucidate the specific mechanisms involved in creating that effect.

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