American Dental Association (ADA) spins false narrative about National Academies (NASEM) review of NTP monograph

Before diving into the National Academies of Science, Engineering and Medicine’s (NASEM) review and what it really says, for those interested in the lawsuit FAN is currently trying to determine the genesis and legal status of a short unsigned statement purportedly from the National Toxicology Program (NTP) about its monograph which appeared in an Environmental Protection Agency (EPA) submission in the TSCA trial on Feb 22. We will give updates when we can.

The ADA’s false claims about the NASEM review

On February 11, the American Dental Association (ADA) gave its response to the 2^nd NASEM review. The ADA’s response is typical of the way the ADA has responded to any evidence of harm from water fluoridation for over 50 years. They simply state that “white is black.”

The ADA claimed that the NASEM report mirrored its own claims that there have been few studies of fluoride neurotoxicity and those studies are “unreliable”, “conflicting”, and “subject to widespread interpretation” (ADA News, Feb 11, 2021).

This ADA claim is the exact opposite of what both NASEM and the NTP have concluded. NTP found almost 500 studies of neurotoxicity, over 150 of which were in humans. NASEM urged NTP to highlight the fact that 44 out of 46 human IQ studies showed “marked consistency” in finding adverse effects. The NTP rated 29 of the human studies high quality. NASEM quibbled about the quality ratings of a few of them, but never said the studies were “unreliable” or “conflicting”. The NTP clearly stated that there were a great number of studies, including higher quality studies, and that the studies’ “consistency” and “robustness” were the reasons NTP reached a conclusion rating of presumed hazard. Here is how NTP explained their conclusion:

“The NTP conclusion that fluoride is presumed to be a cognitive neurodevelopmental hazard to humans is supported by the extent, consistency, and robustness of the effect in the available data in children. Seventeen of the 19 lower risk-of-bias studies reported an association between higher fluoride exposure and lower IQ scores in children across multiple populations. Meta-analyses conducted at the recommendation of NASEM based on their review of the September 6, 2019 draft monograph provide further support for the hazard conclusion of presumed (NASEM 2020).” [emphasis in original; revised NTP monograph 2020, p 71]

What the NASEM review actually said about the NTP monograph’s conclusion

Most importantly, the NASEM review did not challenge the scientific basis of the NTP’s presumed hazard conclusion. The NASEM committee’s recommendations on specific issues, when considered altogether, would not lead to any change in the presumed hazard conclusion, and if anything, they would strengthen it rather than weaken it. The NAS review even suggested ways the evidence could be used to more strongly support its conclusion, and urged NTP to be as clear as possible about why it had reached its conclusion.

Here is an example of how NASEM applauded the NTP’s meta-analyses and emphasized how they support a conclusion of presumed hazard:

Evaluation of the Meta-Analysis

“The committee found the meta-analysis to be a valuable addition to the monograph and acknowledges the tremendous amount of work that was required. The meta-analysis applied standard, broadly accepted methods, and the data shown in Figure A5-1 and the related evaluations are especially informative (NTP 2020, p. 235). As noted in the revised monograph, 44 of the 46 studies represented in that figure had effect estimates to the left of zero—results that indicate an association between higher fluoride exposures and lower IQ. Those results highlight the marked consistency in the current epidemiological literature on fluoride and childhood IQ. The subgroup analyses also add considerable strength to the monograph.” [emphasis added; NASEM 2021, p 11]

NASEM did, however, strongly castigate NTP for continuing to include claims that the evidence at exposures below 1.5 mg/L were “inconsistent” and “unclear”. NASEM said that NTP had not done any rigorous dose-response analyses so should not offer any conclusions about what dose may or may not be low enough to avoid neurotoxic harm:

“Drawing conclusions about the effects of low fluoride exposures (less than 1.5 mg/L) would require a full dose–response assessment, which would include at a minimum more detailed analyses of dose–response patterns, … [and numerous other analyses] … Those analyses fall outside the scope of the NTP monograph, which focuses on hazard identification and not dose–response assessment. Given the substantial concern regarding health implications of various fluoride exposures, comments or inferences that are not based on rigorous analyses should be avoided.” [emphasis in original; NASEM 2021, p 14]

FAN agrees with NASEM that the NTP should not be making pronouncements about the impacts of low levels of fluoride without a formal risk assessment based on a dose-response analysis. If NTP had followed this NASEM suggestion they would have eliminated a key weakness of both drafts of the NTP’s monograph: the flawed notion that there is a threshold in the quality of evidence at 1.5 ppm. Such a threshold does not exist.

Indeed, FAN used the data gathered by NTP from dozens of higher quality human studies and applied the types of rigorous dose-response analysis methods cited by NASEM and commonly used by EPA. FAN found that the evidence for loss of IQ at exposures below 1.5 mg/L is at least as strong as that for the studies above 1.5 mg/L. FAN’s dose-response analysis also found the highest quality studies showed IQ loss from exposures at and below 0.7 mg/L, the current level for artificial water fluoridation in the USA. Other dose-response assessments have also found a substantial risk of IQ loss from exposures at or below 0.7 mg/L (Hirzy et al 2016; Grandjean et al 2020, preprint).

Another example of the ADA’s deceptive descriptions of the NTP systematic review arises in a wildly out-of-context quote they use that describes an NTP 2016 report on just animal studies, rather than the much more comprehensive NTP 2020 report that found the human evidence was much stronger than the animal evidence. The ADA quotes a reference to the 2016 animal review finding a “low-to-moderate level of evidence” in animal studies, and misapplies that to the large body of human evidence that is the foundation of the current NTP review. Furthermore, even if there were only “low-to-moderate” animal study evidence and no human studies existed, with other chemicals the NTP has often considered such evidence sufficient to conclude they pose a presumed hazard.

Paul Connett, PhD
Director
Fluoride Action Network

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