More than 60% of Americans drink fluoridated water, according to the CDC. Residents in all 50 states are getting tap water that either has fluoride added or is naturally occurring in the water source.
But a new federal study and subsequent ruling is calling into question whether fluoride in drinking water is safe, a practice that's been around for more than 70 years but has been dismissed as a tin-foil hat conspiracy as recently as 10 years ago.
"It's historic, and it affects most people in the United States," Dr. Ashley Malin said.
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Malin carried out a smaller study in Los Angeles that examined if there is a link between fluoride exposure to pregnant women and neurobehavioral problems among children.
"I think there's enough evidence now where we can say that it's probably advisable for pregnant women to take steps and precautions to reduce their fluoride intake and continue to be vigilant about their baby's fluoride intake as well," she said.
In Food & Water Watch v. the EPA, a federal judge ruled the current system of fluoridation "presents an unreasonable risk" and that the EPA must further regulate fluoride in drinking water.
And while the judge says there are "uncertainties" around how much fluoride poses a risk, the judge also said "scientific literature in the record provides a high level of certainty that a hazard is present."
That said, many in the science and dentist communities call this all an overreaction.
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Jess Steier, the founder of Unbiased Science, tried to level set in an op-ed that says the National Toxicology Program report should mean "very little" to most people.
"We have to come back down to earth here. 'Facts, not fear' I like to say," Steier said. "Fewer than 1% of Americans are exposed to the levels that that this NTP report studied; 0.6% of Americans are exposed to fluoride in water levels 1.5 milligrams per liter or higher."
The American Dental Association also criticized the report saying the federal agency used "unorthodox research methods" and "flawed analyses."
"We implemented fluoride in 1945, and we saw over time, an increase in other outcomes," Steier said. "That does not mean that this caused this, right, that fluoride caused those outcomes."
Notably the National Toxicology Program report based its conclusion on studies that took place outside the U.S. and involved fluoride levels at about twice the recommended limit for drinking water.
