The US National Toxicology Program (NTP) Review of Fluoride Neurotoxicity: Presumed Hazard to Humans

The US National Toxicology Program (NTP) Review of Fluoride Neurotoxicity: Presumed Hazard to Humans

The National Toxicology Program is an inter-agency program headquartered at the National Institute of Environmental Health Sciences (NIEHS). The NTP provides toxicological evaluations on substances of public health concern.

On October 22, the DRAFT NTP Monograph on the Systematic Review of Fluoride Exposure and Neurodevelopmental and Cognitive Health Effects, was released and stated:

“NTP concludes that fluoride is presumed to be a cognitive neurodevelopmental hazard to

humans. This conclusion is based on a consistent pattern of findings in human studies across several different populations showing that higher fluoride exposure is associated with decreased IQ or other cognitive impairments in children…”

On November 6, the National Academy of Sciences (NAS) held a public meeting to share the findings of the NTP report, and to start their review of the report. Chris Neurath, FAN’s Science Director, and Bill Hirzy PhD (FAN Board Member) attended this meeting. Read Chris’ review here.

FAN nominated fluoride for review by NTP back in 2015 and NTP accepted.  They systematically reviewed all the available evidence of fluoride neurotoxicity up through August 2019.  This cut-off date means the three most recent high-quality studies were not included (Green 2019: Riddell 2019: Till 2020 (published ahead of print in Nov 2019).

The report identified 149 published human neurotoxicity studies, and 339 animal experiment studies deemed relevant. Their consistency in finding neurotoxic harm, especially lowered IQ in the human studies, was striking. The NTP review recognized 18 of the human neurobehavioral studies in children as being relatively high quality.  Every one of the 18 found statistically significant neurobehavioral harm.  Not a single study rated high quality failed to find a neurotoxic effect from fluoride.

This finding undermines fluoridation defenders frequently citing the Broadbent 2015 study, which found no effect, to claim there is no clear evidence of fluoride neurotoxicity.  The NTP rated Broadbent 2015 as relatively low quality and high risk of bias so gave it little weight compared to the numerous higher quality studies.

The review noted, “Many of the studies (n = 49) included in the entire human body of evidence were initially published in a foreign language (mainly Chinese) and translated by the Fluoride Action Network.” These translations were expensive, but necessary. FAN was able to do this because of the donations from those who put their trust in us over many years.

The NTP review does have a serious problem, however, in what appears to be a last-ditch effort to buy time for fluoridation.  Without any reasonable justification, the NTP review claims the evidence for neurotoxicity at exposure levels similar to those in the USA from fluoridated water is “inconsistent”.  The review therefore suggests that no conclusion can be made about whether fluoride is causing any neurotoxic harm at levels experienced by people with fluoridated water.  Even before consideration of the three most recent studies done in Canada and the USA, which are clearly at levels relevant to fluoridation, this argument “holds no water”.   Of the 18 high quality studies in children, 9 were at exposure levels equivalent to those experienced by at least some people in the USA with fluoridated water.  Every single one of these 9 studies found a statistically significant lowering of IQ, increase of ADHD, or other adverse effect.  The Green 2019 study was one of the 9, and it indisputably found lowered IQ from artificially fluoridated water at the same levels as in the USA.

The unfounded NTP claim that the evidence is “inconsistent” at levels of fluoride exposure in the USA is further debunked by a comprehensive independent review of fluoride neurotoxicity published just yesterday [Grandjean 2019].  Dr. Philippe Grandjean is one of the world’s leading experts in developmental neurotoxicity.  Using methods sanctioned by the National Academies of Sciences and EPA, he estimated the level of fluoride that would cause a harmful loss of IQ based on the recent highest quality studies.  The levels were well below 0.7 mg/L fluoride in drinking water or its equivalent in urine fluoride, even before any safety factors were applied.  Grandjean’s conclusion is clear: “… there is little doubt that developmental neurotoxicity is a serious risk associated with elevated fluoride exposure … due to community water fluoridation….”

In his full conclusions, he further explains the strength of the evidence and suggests the neurotoxic harms from existing studies may be, if anything, underestimates of the harm.

Previous assessment of neurotoxicity risks associated with elevated fluoride intake relied on cross-sectional and ecological epidemiology studies and findings from experimental studies of elevated exposures. The evidence base has greatly expanded in recent years, with 14 cross-sectional studies since 2012, and now also three prospective studies of high quality and documentation of individual exposure levels. Thus, there is little doubt that developmental neurotoxicity is a serious risk associated with elevated fluoride exposure, whether due to community water fluoridation, natural fluoride release from soil minerals, or tea consumption, especially when the exposure occurs during early development. Even the most informative epidemiological studies involve some uncertainties, but imprecision of the exposure assessment most likely results in an underestimation of the risk. [Grandjean 2019]

The NTP review of fluoride neurotoxicity comes from the most authoritative US government source.  It found extensive, consistent, and clear evidence that fluoride harms the developing brains of children.  However, in its discussion of the relevance to artificial water fluoridation it strays from objective analysis.  Grandjean’s careful review corrects this problem.

FAN will be bringing Grandjean’s review and our own comments to the NAS committee that is peer-reviewing the NTP report.  We believe an honest and responsible assessment of the scientific evidence would conclude that artificial water fluoridation is currently causing loss of IQ and other neurotoxic harm in the USA and wherever fluoridation is practiced.

Thank you,

Chris Neurath
Research Director