Public Opinion on Water Fluoridation Is Changing, Expert Says

Kathy Thiessen, Ph.D., a leading fluoride expert, joined “The Defender In-Depth” this week to discuss the latest science on water fluoridation.

by Michael Nevradakis, Ph.D.

Kathy Thiessen, Ph.D., a leading fluoride expert, joined “The Defender In-Depth” this week to discuss a meta-analysis published last week by the National Toxicology Program (NTP) concluding that that “fluoride is a neurotoxicant in humans.”

Thiessen, president and senior scientist at the Oak Ridge Center for Risk Analysis, testified last year in a lawsuit against the U.S. Environmental Protection Agency (EPA). A September 2024 federal court ruling in the case found that water fluoridation at current U.S. levels poses an “unreasonable risk” of reduced IQ in children.

The ruling requires the EPA to take regulatory action to address the risks of water fluoridation. The agency, which has until Jan. 20 to appeal, has not yet taken action.

Thiessen co-authored a 2006 National Research Council report that addressed the toxic effects of fluoride and called for more research into its effects.

Thiessen said the new meta-analysis and a previous NTP report show that “fluoride is a neurotoxicant in humans and as fluoride exposure is increased, the likelihood of reduced IQ and some other cognitive deficits … increases.”

According to Thiessen, exposure to fluoride during pregnancy harms the fetus. “Fluoride crosses the placenta, so whatever the mother’s fluoride exposure is, the baby’s going to be exposed to that.”

And those risks continue after birth. “If the [infant] formula is made up with fluoridated tap water, those babies get the largest dose per body weight of anybody in the population at an age when they’re still developing,” Thiessen said.

‘Consistent body of literature’ shows ‘fluoride is neurotoxic during development’

The NTP’s latest meta-analysis reviewed 74 epidemiological studies examining the link between children’s IQ and fluoride exposure. Thiessen said the number and quality of such studies has increased substantially in recent years.

“When we wrote the [2006 report], there were just a few studies of fluoride exposure and cognitive deficits,” Thiessen said. “Many of the … most recent ones have been funded by our National Institutes of Health. They are high-quality studies.”

Thiessen said the studies together form “a very consistent body of literature showing that the fluoride is neurotoxic during development.” In the case of the NTP report and meta-analysis, however, there were repeated efforts to block or delay their publication.

Thiessen said the lawsuit against the EPA, filed by the Fluoride Action Network, Moms Against Fluoridation and Food & Water Watch, along with individual parents and children in 2017 was instrumental in the public release of the NTP report and meta-analysis.

“My best guess is that, if possible, they would’ve suppressed them totally,” Thiessen said. “But … because they were important to the court case, the judge required them to be made public. And we have that to be thankful for there.”

Efforts to block or delay publication of the NTP’s reports are part of “a very long history of suppression” and “of adverse information about fluoridation,” Thiessen said.

Scientists raised concerns about water fluoridation as early as the 1940s when it first started, Thiessen said. “From the 1940s on, there have been vested interests of several sorts that have pushed for water fluoridation.”

The EPA has ignored evidence of fluoride’s risks, Thiessen said. “I have said on record in the fluoride trial that if EPA had done its job responsibly, even back in the 1980s, we would not be having that case,” Thiessen added.

‘There should simply be a national end to water fluoridation’

Thiessen responded to claims that fluoridation protects oral health and that it was one of the 10 great public health achievements of tkskdldgklgklhe 20th century. She said, “The real evidence shows that it’s probably one of the 10 leading contributors to poor health in this country.”

Thiessen referred to a 2024 Cochrane report finding that water fluoridation confers minimal benefits to public health. She suggested that diet and other lifestyle factors are more significant determinants of oral health than fluoridation or lack of it.

“There are studies showing that children in areas where it’s a subsistence existence … These kids have great teeth. You have poor kids in this country whose diet is mostly sugar and no, they’re not going to have good teeth … It’s much more a matter of access to care, and access to good nutrition,” Thiessen said.

Thiessen suggested children in poorer and rural populations “are most likely to be adversely affected” by fluoridation, as their parents are more likely to bottle-feed babies with baby formula mixed with tap water.

Thiessen said public attitudes toward water fluoridation are changing. “The tide has been turning slowly for 20-something years, but we’re seeing a lot more of that now.”

She said many communities will be using the court ruling to justify stopping fluoridation.

“Hopefully, this will happen at the state level in those states that mandate it. I’d like to see it at the national level that we just don’t do this anymore,” Thiessen said. “There should simply be a national end to water fluoridation.”

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