Conspiracy theorists have railed for seven decades against fluoride, suggesting that water fluoridation was a government mind-control trick or communist plot.
Now, an August study published by a well-regarded medical journal, JAMA Pediatrics, has reignited debate about fluoride, both from harsh critics of fluoridation and harsh critics of the study. The authors observed a link between fluoride, pregnant women, and the IQ of their children. It stopped short of recommending canceling fluoridation programs, but did warn expecting mothers to watch how much fluoride they consumed while the link was checked out.
“Maternal exposure to higher levels of fluoride during pregnancy was associated with lower IQ scores in children aged 3 to 4 years,” concluded the study.
The study authors and independent experts told BuzzFeed News that the finding raises questions about unknown effects that fluoride could have on vulnerable people, such as extremely young kids and expecting mothers. However, they also braced themselves for their concerns to be co-opted by the anti-fluoride camp.
“I think that it is highly likely that it will stoke conspiracy theories, even though it is not merited at this point,” Adam Spanier, professor of pediatrics at the University of Maryland School of Medicine, told BuzzFeed News by email ahead of the study’s launch. Tracey Woodruff, a professor of reproductive health at the University of California, San Francisco, who was not involved with the study, told BuzzFeed News that publishing on fluoride “is like touching a third rail in public health,” anticipating that the paper would stir controversy. “I think this message could be easily misconstrued as us saying don’t drink fluoridated water — we’re not saying that,” study author Christine Till, professor of psychology at York University in Toronto, told BuzzFeed News.
Sure enough, the Fluoride Action Network (FAN), a noted anti-fluoride group, posted links to more than a dozen media reports of the study on its website. And it issued its own press release two days after the study ran, claiming that “pro-fluoridation” critiques of the study were “unfounded.” On Facebook, the group has posted nearly daily about the study since Aug. 19, the day it was published online. “To ignore brain health and continue fluoridation in name of dental health is a huge disservice to the children of this country,” the group wrote on Twitter.
When environmental lawyer and anti-vaccine proponent Robert Kennedy Jr. tweeted a CNN story covering the paper, someone tweeted back: “Fluoride is a byproduct of aluminum and a smart con man convinced people to put in the water many years ago. And we have been drinking that poison for years,” echoing an anti-fluoride theory famously satirized in the 1964 flick Dr. Strangelove. On Infowars, right-wing conspiracy theorist Alex Jones devoted a segment to the news, wrongly claiming that fluoride “brain-damages babies, lowers IQ,” and then plugged water filters sold on his website.
Public health groups meanwhile pushed back hard against the study’s results: The UK’s National Health Service wrote that there was “No proof that a mother’s intake of fluoride in pregnancy affects their child’s IQ,” and framed it as a takedown of a Daily Mail story describing the study results. The American Dental Association said it was “committed to fluoridation of public water supplies as the single most effective public health measure to help prevent tooth decay,” in a statement. “We welcome this and further scientific study of the issue to see if the findings can be replicated with methods that demonstrate more conclusive evidence.” The pro-industry nonprofit the American Council on Science and Health asked, “Are study’s conclusions true?” And concluded: “It’s doubtful.”
Amid the fisticuffs, researchers say the tenor of the public debate over fluoride has chilled necessary work into a health program that affects millions of Americans. Also, they say, fluoride ideas have been fiercely divisive even among academic groups.
“‘Anti-fluoride’ seems to mean that you’re an evil human being that doesn’t think,” Pamela Den Besten, a professor at the UCSF School of Dentistry, told BuzzFeed News. “It’s like having a scarlet ‘AF’ letter on you, and it really impacts careers.”
Den Besten said she describes the schism in science on fluoride thinking “more like religion than science,” and as a dental expert studying fluoride’s effects on cells in teeth, she has found it to be at times a difficult field to work in.
It’s been an uphill battle to find funding for this research, Till, who led the new study, told BuzzFeed News. The idea that IQ in kids and fluoride consumption were linked was not a new one — environmental health journals have been publishing such studies since about 2012. But Till wanted doctors, and ultimately the patients they saw, to get the message.
“The medical journals where we felt we had to get the dialogue going were a bit more skeptical of the research,” she said. “I was close to giving up on the medical establishment when we were trying to publish.” Grants and study manuscripts would get opposite reviews from different reviewers: “Someone loves it, someone hates it.”
The study itself included 512 mothers and their children from six cities in Canada. The researchers measured how much fluoride the mothers consumed by testing their urine for traces of it each trimester. Also, they calculated how much fluoride 400 women drank — black and green tea are known to contain fluoride, for example, and some women lived in cities that are known to add fluoride to the water.
Spanier, of the University of Maryland, told BuzzFeed News that the methods were more powerful than studies that came before it. “The study suggests that pregnant women expecting a boy might want to be cautious about their fluoride intake if they are in the demographic presented — wealthy, white, married, educated,” Spanier said. He repeated also Till’s message that the study included all kinds of fluoride intake, and did not link the children’s IQ to fluoride from drinking water specifically. He added the unified demographics of the group limited how broadly it could be interpreted.
In an editorial that ran with Till’s study, David Bellinger, a professor of neurology at Harvard Medical School and Boston Children’s Hospital, wrote that “the hypothesis that fluoride is a neurodevelopmental toxicant must now be given serious consideration.” He told NPR: “It’s actually very similar to the effect size that’s seen with childhood exposure to lead.”
An editorial note accompanying the study acknowledged the controversy it might trigger within the academic community. “This decision to publish this article was not easy,” JAMA Pediatrics editor and University of Washington pediatrics professor Dimitri Christakis wrote, adding that the piece had undergone “additional scrutiny” of its methods and results.
The CDC has listed water fluoridation, which began in the US in 1945, as one of the top public health wins of the 20th century, alongside car safety, vaccinations, and the acknowledgement that tobacco is a health hazard. The stuff occurs naturally in some water systems, but when added to municipal water, it inexpensively prevented tooth decay in kids and tooth loss in adults, the CDC wrote. The additive has also been previously found to be harmful in excess: After studies showed how fluoride consumed in very high levels could damage the bones and teeth, in 2015, the US Public Health Service recommended fluoridating at about 0.7 milligrams per liter of water, and the EPA limited how much of the substance was allowed in the drinking water. In the last few years, some communities have stopped fluoridating their water after residents questioned the practice and complained to remove it.
“There’s something very personal about water. People take the sanctity of their water very, very seriously,” Catherine Carstairs, a history professor at the University of Guelph who has written about the past decades of fluoride fights, told BuzzFeed News. She said that most people who worry about fluoridation aren’t conspiracy theory converts — they’re just concerned about something they see as a chemical in the water supply. “It’s certainly time for a much more nuanced and complex debate,” Carstairs said.
As a next step, Till is looking to study fluoride levels in baby teeth to more clearly link children’s fluoride exposure during their early childhood to their IQ.
“We have our work cut out for the rest of my career at least,” Till said.
Tracey Woodruff is a professor at the University of California, San Francisco. Her affiliation was misstated in earlier version of this post.