March 21st, 2023 | Fluoride Action Network
After a 6-year long systematic review of fluoride’s impact on the developing brain, a court order has led to the National Toxicology Program (NTP) making public their finalized report that was blocked by US Department of Health and Human Services (HHS) leadership and concealed from the public for the past 10 months. The NTP reported 52 of 55 studies found decreases in child IQ associated with increase in fluoride, a remarkable 95% consistency. The NTP’s report says:
“Our meta-analysis confirms results of previous meta-analyses and extends them by including newer, more precise studies with individual-level exposure measures. The data support a consistent inverse association between fluoride exposure and children’s IQ.”
A meta-analysis is when information from all the relevant studies are combined to get a fuller and unbiased overall picture, rather than just looking at individual studies in isolation.
The NTP’s meta-analysis also put the magnitude of harm into perspective:
“[R]esearch on other neurotoxicants has shown that subtle shifts in IQ at the population level can have a profound impact on the number of people who fall within the high and low ranges of the population’s IQ distribution. For example, a 5-point decrease in a population’s IQ would nearly double the number of people classified as intellectually disabled.”
So, while an average drop of 5 IQ points in a population might sound small it is huge from a public health perspective. Furthermore, the NTP acknowledged there was the potential for some people to be more susceptible than average, so those people could lose much more than 5 IQ points. Those susceptible individuals could lose 10, 15, 20 or more IQ points which would likely cause profound lifetime negative consequences.
The five independent peer-reviewers of the NTP report all voted to accept the review’s main conclusion and lauded the report. Their comments include: “what you have done is state-of-the-art”; “the analysis itself is excellent, and you thoroughly addressed comments”; “Well done!”; “Findings… were interpreted objectively”.
The newly released documents include comments from the NTP’s own experts confirming that the report’s conclusion that fluoride can lower IQ does apply to communities with water fluoridation programs. NTP report says the evidence is not just in those who drink water with higher fluoride concentrations exceeding the World Health Organization (WHO) recommended maximum level of 1.5 mg/L. Furthermore, the WHO guideline was set in 1984 to protect against more severe forms of dental fluorosis and neurotoxicity was never considered. Few neurotoxicity studies even existed in 1984.
In numerous responses to comments by reviewers of the report, the NTP made clear that they had found evidence that exposures of at least some people in areas with fluoridated water at 0.7 mg/L were associated with lower child IQ.
For example, when an unnamed government fluoridation proponent claimed:
“The data do not support the assertion of an effect below 1.5 mg/L…all conclusory statements in this document should be explicit that any findings from the included studies only apply to water fluoride concentrations above 1.5 mg/L.”
The NTP responded:
“We do not agree with this comment…our assessment considers fluoride exposures from all sources, not just water…because fluoride is also found in certain foods, dental products, some pharmaceuticals, and other sources… Even in the optimally fluoridated cities…individual exposure levels…suggest widely varying total exposures from water combined with fluoride from other sources.”
Additional NTP responses about the review’s relevance to water fluoridation programs:
“We have no basis on which to state that our findings are not relevant to some children or pregnant people in the United States.”
“Several of the highest quality studies showing lower IQs in children were done in optimally fluoridated (0.7 mg/L) areas…many urinary fluoride measurements exceed those that would be expected from consuming water that contains fluoride at 1.5 mg/L.”
The NTP also responded to commenters asking whether their meta-analysis had identified any safe exposure threshold, below which there would be no loss of IQ.
The NTP responded that they found “no obvious threshold” for either total fluoride exposure or water fluoride exposure, referring to a graph in the meta-analysis (NTP’s eFigure 17 reproduced below) showing that as water fluoride concentration increased from 0.0 to 1.5 mg/L there was a steep drop in IQ of about 7 points (expressed as “standardized mean difference” units in the graphs). An external peer-reviewer commented on the size of the IQ loss:
“Wow … that is substantial … That’s a big deal.” {p 1060}
The graph uses standardized mean difference (SMD) units where each -1.0 SMD is equivalent to about -15 IQ points.
In the left-hand graph each circle represents a study. Several have mean water fluoride below 1.5 mg/L. The right-hand graph shows the relationship between fluoride concentration and loss of IQ when all the studies are pooled. This analysis, based on many studies, is strong evidence that fluoride is associated with a substantial loss of IQ at levels of exposure common in people drinking artificially fluoridated water, and there is no observable threshold indicating a “safe” dose.
The NTP’s experts further stated that the science showing neurotoxic harm “is a large, consistent and growing database.”
Overall, the report provides strong evidence that fluoride is associated with a substantial loss of IQ at levels of exposure common in people drinking fluoridated water.