Boiling tap water causes fluoride in the water to be “more toxic.”

A video shared on Facebook claimed that “the worst thing you can do” to improve “bad” tap water is to boil it.

Boiling changes fluoride into fluorine, which “is more deadly for the human body,” the narrator said.

The post was flagged as part of Facebook’s efforts to combat false news and misinformation on its News Feed. (Read more about our partnership with Meta, which owns Facebook and Instagram.)

Experts said boiling tap water does not change fluoride into fluorine and does not make the water toxic.

“The video is complete nonsense,” said chemistry professor Timothy Schmidt of the University of New South Wales in Australia.

The safety of fluoride is a subject of misinformation we’ve tackled several times over the years.

Fluorine is an element, and fluoride is a variation of it. Fluoride occurs naturally in rivers, lakes, oceans, rocks and soil. The types of fluoride added to the drinking water supply typically are extracted from phosphate rock.

Adding fluoride to the U.S. water supply began in 1945 to combat tooth decay, particularly in children. It’s considered a safe, cost-effective way to prevent cavities. 

Fluoride can be toxic in very large amounts, but the amount added to drinking water is not toxic.

Schmidt and Chris Cappa, a civil and environmental engineering professor at the University of California, Davis, said boiling water does not turn fluoride into fluorine.

Dr. Steven Slott, a North Carolina dentist and spokesperson for the American Fluoridation Society, said fluoride “is a negatively charged atom of the naturally occurring element fluorine. Fluoride can therefore not be turned into fluorine as it is already a component of that element.”

At the level fluoride is present in tap water, “there is no credible evidence of (it) being, in any manner, toxic to anyone.”

As for health effects of boiling water, it “can be a great way to kill potential disease-causing germs, such as microbes, viruses or bacteria,” Cappa said. 

Fluoridation expert Howard Pollick, a dentistry professor at the University of California, San Francisco, said water companies sometimes recommend boiling when the water supply is contaminated. 

Lilly D’Angelo, president and founder of Global Food and Beverage Technology Associates consulting company, said “there is no downside to boiling water other than it takes a little more energy and time.”

The claim that boiling water makes it toxic is false and ridiculous — Pants on Fire!

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