MAIN FINDINGS:

• “High-quality studies of fluoride neurotoxicity are remarkably consistent in finding statistically significant adverse effects at exposure levels of artificial fluoridation.” 
• “Dose-response analyses show adverse effects likely at exposures as low as 0.3 mg/L or lower.”

Last month, FAN’s Research Director, Chris Neurath, gave an invited presentation on fluoride neurotoxicity at the 2022 Conference of the International Society for Fluoride Research (ISFR), which was held in Harbin, China.  Activists are urged to watch Neurath’s presentation on A Dose-Response Assessment of Fluoride Developmental Neurotoxicity Studies, a 5-minute video:

Dose-response assessment is central to the current debate about the strength of scientific evidence on fluoride’s neurotoxicity at exposure levels relevant to water fluoridation. The National Toxicology Program’s (NTP) ongoing review of fluoride neurotoxicity has equivocated on this question, and while concluding that “fluoride is presumed to be a cognitive neurodevelopmental hazard to humans,” they also suggested that the evidence for fluoride’s neurotoxicity is less clear at exposures below 1.5 mg/L than above [NTP 2019, 2020].  Yet NTP never conducted any formal dose-response assessments and does not offer cogent justification for their claim that the evidence is less clear in studies with lower doses. The National Academies (NASEM) peer-review committee severely criticized NTP for making claims about evidence at different dose levels without having conducted a formal dose-response assessment [NASEM 2020 1^st report, NASEM 2021 2^nd report].

To fill the void in rigorous dose-response analyses, Neurath used both standard EPA methods and more advanced methods, summarizing the results at the ISFR Conference. His dose-response assessment was previously submitted to NTP [Neurath 2020].  He found that the evidence was as clear or clearer at exposures below 1.5 mg/L than above, confirming that the NTP’s own data contradicts their claims of inconsistent data at lower exposure levels.

His analysis began with tallying the number of studies finding adverse effects (mostly loss of IQ) at exposures below 1.5 mg/L compared to the number of studies finding adverse effects above 1.5 mg/L.

He found that: “Of the 27 fluoride neurotoxicity studies considered high quality by NTP, 25 showed statistically significant adverse effects such as lowered IQ.  The other 2 found no significant effect.”

“Of those 25 studies finding an adverse effect, 15 were at exposures below 1.5 mg/L and 10 at exposures above 1.5 mg/L.”

Neurath then looked at the studies finding effects below 0.7 mg/L to zero in on those at the lowest doses and found more studies with statistically significant adverse effects below 0.7 mg/L (11 studies) than in the ranges 0.7-1.5 (4 studies) or 1.5+ mg/L (10 studies).

“The undeniable conclusion is that amongst these higher quality studies, there is clearer evidence of neurotoxicity at exposures below 1.5 mg/L and even below 0.7 mg/L, than above 1.5 mg/L.  The NTP’s opposite conclusion is contradicted by the data that NTP itself has extracted and posted on its data repository.”

Neurath’s dose-response assessment report also used two more formal statistical methods for assessing the strength of evidence that fluoride reduces IQ in children even at low exposure levels.

He focused on the highest quality studies, which were the 14 with individual-level data and conducted statistical analyses known as meta-analysis and meta-regression. Meta-analysis pools results from multiple studies to get a more reliable and precise estimate of the true effect. Neurath divided the studies into those with a mean exposure above 1.5 mg/L and those with mean exposure equal or below 1.5 mg/L.  There were 7 studies in each exposure category, and the pooled estimate for the loss of IQ per 1 mg/L increase in fluoride, was greater in the studies with the lowest dose ranges.  Such a situation is also found with neurotoxicity from childhood lead exposure, where the greatest loss of IQ per unit of lead exposure occurs at lower exposure ranges, and then tends toward a plateau as the exposure gets very high [Lanphear 2005, Little Things Matter video].

In the meta-regression each of the 14 high-quality studies was considered a single data point and the dose-response relationship for all of them was calculated.  The result was a highly significant negative association with 3 IQ points lost for every 1 mg/L increase in fluoride.  Furthermore, the relationship held with no threshold down to the studies with the lowest exposures well below 0.7 mg/L.  The meta-regression, pooling the results from all the studies, predicts that an exposure of 0.3 mg/L will produce an average loss of 1 IQ point amongst children, so for water fluoridation at 0.7 mg/L the average predicted loss is 2.3 IQ points.  While that may not sound like a large effect, the EPA has previously concluded an average loss of even 1 IQ point was unacceptable in the general population.  That’s because economists estimate that each person will have their lifetime earnings reduced by $20,000 per 1 IQ point lost  [Schwartz 1994, Gould 2009, Lanphear 2020].  Furthermore, if the average loss is 2.3 IQ points in a population, there will be some subset of children whose IQ and subsequent earnings will be reduced much more because of genetic susceptibility to fluoride, or higher-than-average exposure, or other reasons.  Genetic susceptibility has been found in several recent studies [Wang 2021, Zhao 2021, Cui 2018, Zhang 2015].  Those studies found that normal variation in genes amongst several percent of the population could result in IQ losses 5-times greater than average, or on the order of 10 or more IQ points.

The video of Neurath’s presentation gives strong evidence supporting a conclusion that water fluoridation is likely causing unacceptable lowered IQ.

There should be little surprise that experts in child development who have objectively looked at the evidence have said the loss of IQ from fluoride is “on par with that from lead” [FAN 2019].

Water fluoridation is like the Flint, Michigan, fiasco with lead in drinking water, but much more widespread, because instead of one city, 2/3rds of America’s cities and towns are intentionally fluoridated.