Newly released review of fluoride’s toxicity
- highlights NTP scientist’s battle to follow the science
Newly released documents reveal how scientists at the U.S. National Toxicology Program fought to preserve their conclusion that fluoride can reduce IQ in children.
On Wednesday the U.S. National Toxicology Program released a previously suppressed report which concluded that high exposure to fluoride can reduce IQ for children. The NTP’s drafts from May and September 2022 both concluded that, “higher fluoride exposure is consistently associated with lower IQ in children. More studies are needed to fully understand the potential for lower fluoride exposure to affect children’s IQ.”.
The NTP review was made public on Wednesday per an agreement between the U.S. Environmental Protection Agency (EPA) and the Fluoride Action Network (FAN), as part of an ongoing lawsuit under the Toxic Substances Control Act. The FAN and plaintiffs are attempting to prove that fluoride is a neurotoxin and should be regulated or banned under the Toxic Substances Control Act.
In addition to the NTP draft monograph on fluoride’s impact on IQ in children, several other documents were included in the release. One of these documents was a July 2022 meta analysis, titled Association between fluoride exposure and children’s intelligence: A systematic review and meta-analysis. The scientists behind this meta analysis drew similar conclusions as the monograph, writing:
“This meta-analysis confirms results of previous meta-analyses and extends them by including newer, more precise studies with individual-level exposure measures. The consistency of the data supports an inverse association between fluoride exposure and children’s IQ.”
Other documents include several sections with comments from external reviewers and responses from the scientists within the NTP. Over and over again these comments illustrate that the NTP believed they had adequately addressed previous concerns from reviewers, and that their review was complete. Some of the back and forth centers around the reviewer’s desire to have the NTP insert statements noting that the majority of the studies being reviewed involved exposure to fluoride at levels above the U.S. government’s recommended dose for water fluoridation.
The NTP scientists repeatedly assert their view that adding such a statement is unnecessary because water fluoridation is not the only exposure an individual faces. “As we discuss in the monograph, fluoride is found in water, certain foods, dental products, some pharmaceuticals, etc., and individual behaviors are likely to be an important determinant of actual total fluoride exposures,” the NTP writes.
In another response the scientists reiterate their reasoning, stating “It is true that our stated confidence assessment is based primarily on studies with total exposures higher than those generally associated with consumption of optimally fluoridated water in the United States. However, the confidence assessment also includes findings from studies with fluoride exposures that are similar to, or lower than, those associated with optimally fluoridated water supplies in the United States.”
Another comment from the NTP 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 comments from NTP experts offer further confirmation that the NTP believed their monograph on fluoride was ready for public release. The Last American Vagabond has previously reported that emails obtained by attorneys for the Fluoride Action Network highlighted how NTP scientists repeatedly said the monograph was complete.
In one email on April 28, 2022, Dr. Mary Wolfe, the Director of NTP’s Office of Policy, Review and Outreach, told Casey Hannan, the Director of CDC’s Division of Oral Health, that the NTP’s “analysis and conclusions are set”. Dr. Wolfe also let Hannan know that the NTP had reviewed the CDC’s submitted comments, but still planned to release the review “mid/late May” 2022.
The NTP monograph and the meta-analysis offer damning conclusions for the proponents of water fluoridation, including the EPA, the Centers for Disease Control and Prevention, and the Food and Drug Administration. These reports are likely to factor into any decisions made by Judge Edward Chen at the next scheduled hearing on April 11th.
The Studies Behind the NTP Monograph
The description for the September and May 2022 draft monographs note that “NTP monographs serve as an environmental health resource to provide information that can be used to make informed decisions about whether exposure to a substance may be of concern for human health.
The abstract for the NTP monograph describes the history which preceded the monograph, noting that in 2006 the National Research Council “found support for an association between consumption of high levels of naturally occurring fluoride in drinking water and adverse neurological effects in humans and recommended further investigation”.
The NTP acknowledges that in the years since the NRC evaluation “the number and location of studies examining cognitive and neurobehavioral effects of fluoride in humans have grown considerably, including several recent North American prospective cohort studies evaluating prenatal fluoride exposure”.
The NTP describes how they searched numerous scientific databases for studies relating to fluoride. Out of more than 25,000 references the researchers narrowed their focus to 547 studies, including 167 human studies, 339 non-human mammal studies, and 60 in vitro/mechanistic studies. In the end, the NTP would choose only studies that were viewed as high quality and a low risk-of-bias.
When it came to studying the impact of fluoride on children, 72 epidemiological studies were identified that evaluated the association between fluoride exposure and children’s IQ. Nineteen of the 72 IQ studies were determined to have low potential for bias. These studies were based in China, Canada, Mexico, India, and Iran. The NTP concluded that,
“the results from 18 of the 19 low risk-of-bias studies that evaluated IQ in children provide consistent evidence that higher fluoride exposure is associated with lower IQ scores”.
The NTP monograph also looked at studies which might show a connection between fluoride exposure and cognitive neurodevelopmental effects beyond lower IQ. The researchers concluded that the high-quality studies show evidence of “an association between fluoride exposure and other cognitive neurodevelopmental effects”, including lower neurobehavioral scores in infants, increased “attention-related disorders including ADHD in children”.
The researchers do note that because of “limitations in the data set” they have “low confidence” that fluoride exposure is associated with “other cognitive neurodevelopmental effects in children”. However, despite the caveat about the limitations of the studies examined for effects other than IQ, the researchers conclude by stating, “although there are limitations in the body of evidence, the low risk-of-bias studies demonstrate a relationship between higher fluoride exposure and neurodevelopmental effects, even in very young children, which supports the consistency in evidence shown in children’s IQ studies of an association between fluoride exposure and adverse effects on cognitive neurodevelopment.”
The Last American Vagabond will continue to report on the findings contained within the 1500 pages of documents released by the NTP and the upcoming hearing on April 11th.