Fluoride Action Network

The National Toxicology Program

This section is dedicated to the National Toxicology Program’s (NTP) long involvement with the issue of fluoride's toxicity. The NTP is the scientific research arm for U.S. regulatory agencies. It comes under the aegis of the National Institute of Environmental Health Sciences (NIEHS). The NIEHS, in turn, comes under the umbrella of the National Institutes of Health (NIH). -Updated May 2, 2023 (EC).

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The National Toxicology Program (NTP), established in 1978, is the research arm of U.S. regulatory agencies and is best known for its Reports on Carcinogens. The NTP comes under the aegis of the National Institute of Environmental Health Sciences (NIEHS), an agency that has been able to perform good science amidst a battlefield of conflicting inter-agency interests. However, time will tell whether the good reputation of the NIEHS and NTP will survive the battle on fluoride’s neurotoxicity. The NIEHS comes under the umbrella of the National Institutes of Health (NIH).

In 1990 the NTP’s reputation was battered after chaos erupted over its report on fluoride’s carcinogenicity when William Marcus, chief toxicologist at the Environmental Protection Agency (EPA), expressed concerns over the “systematic downgrading” of cancers in the study.

The 1990 study included the finding of a dose-dependent increase of a rare liver cancer (hepatocholangiocarcinoma) in male and female mice and a small but statistically significant dose-related increase in osteosarcomas in male rats but not in the female rats.

Melvin Reuber M.D., a board certified pathologist, was the first scientist to describe hepatocholangiocarcinoma. Reuber reviewed the pathology slides from the NTP study and said that the diagnosis was correct. However, this rare liver cancer was reclassified by a government review panel as a non-cancer and one of the osteosarcomas was downgraded leading to the classification of “equivocal evidence of cancer”.

In 1990, the American Council on Science and Health, the most industry-friendly non-profit in the U.S., said “that it will seek to restrain any federal agency from banning or seeking to reclassify fluoride from a non-carcinogen to a probable carcinogen.”

The background to the chaos that ensued after NTP released its cancer study in 1990 is similar to what is happening today with the publication of groundbreaking studies on fluoride’s neurotoxicity and the efforts underway to minimize their importance. With attribution to Mark Twain, History doesn’t repeat itself, but it sure does rhyme.

Concurrent with the NTP’s systematic review of fluoride’s neurotoxicity, a Citizen’s Petition, under Section 21 of the Toxic Substances Control Act (TCSA), was delivered to EPA in 2016 requesting that they prohibit fluoridation chemicals from entering drinking water because of fluoride’s neurotoxicity at the levels used in community fluoridation programs. This issue is now in federal court. The EPA used Exponent, an industry-friendly consulting firm, as their experts in the TSCA trial held in June 2020.

The TSCA trial continues as the Court has requested the NTP’s report on fluoride’s neurotoxicity before it makes its ruling. However, on February 9, 2021, the NTP stated in a private statement only available to the EPA, that it would not complete this review, but would instead write “a state of the science” document without any conclusions. The public only learned of this after EPA’s lawyers submitted NTP’s statement into the trial record.

NTP has spent four years and millions of dollars to produce two draft systematic reviews on fluoride’s neurotoxicity. Both draft reviews stated,

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

To read more, see Cowed by dental interests? by the Fluoride Action Network, April 19, 2021.

Linda Birnbaum was the director of the NIEHS and NTP from 2009 to 2019. Under her leadership several landmark studies on fluoride’s neurotoxicity were funded, such as

These studies revealed that in fluoridated communities the fetus and the formula-fed infant are the most vulnerable to fluoride’s neurotoxicity. Certain high levels of fluoride in the pregnant women’s urine were found to significantly impact the IQ, or neurodevelopment, of the offspring. These high urinary fluoride levels are found in pregnant women living in fluoridated areas as well as in naturally-occurring high fluoride areas.

Grandjean et al., used these studies in a benchmark dose analysis, published June 8, 2021. The analysis found that a maternal urine fluoride concentration of 0.2mg/L was enough to lower IQ by 1 point.  This level is exceeded 4 to 5 times in pregnant women living in fluoridated communities. Reference: A Benchmark Dose Analysis for Maternal Pregnancy Urine-Fluoride and IQ in Children.

• See the March 15, 2023, documents released by the NTP for the ongoing TSCA lawsuit against the EPA on fluoride’s neurotoxicity.

• See update on NTP’s website dated April 22, 2022:” Fluoride: Potential Developmental Neurotoxicity”

See the list of all U.S. government-funded fluoride studies here

The Index to this dedicated section on the National Toxicology Program


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