Since then, the conspiracy theories have evolved from fears of a communist plot to other worries about purported dangers of fluoride — an abundant element that occurs naturally in water, even when it’s not added by the government.

“Now, you have this weird backlash where people think that anything that is a chemical is bad, even though everything is a chemical,” said University of Miami associate professor Joseph Uscinski, co-author of the book “American Conspiracy Theories.” “There are groups of people who think that if something isn’t natural, it is somehow impure or bad, and it grosses them out.”

To experts, objecting to fluoride is nonsensical. The compound, consumed in water or applied topically through toothpaste or mouthwash, prevents cavities by replacing weakened structures in the teeth, said Dr. Kerry Maguire, associate clinical investigator of Forsyth, an independent research institute specializing in oral health.

It’s true that too much fluoride can be dangerous — one complication is skeletal fluorosis, which causes stiffening and pain of the joints and bones or abdominal pain, nausea and vomiting — but those effects only occur with prolonged exposure to a far higher level of fluoride than is found in public water systems in the U.S., experts say. In this country, the only common side effect of fluoridation is fluorosis of the teeth — minor staining that is often only visible to a dentist.


Today, nearly 75 percent of the U.S. receives fluoridated water from community water systems.

That’s a number that Paul Connett, a chemistry professor emeritus at St. Lawrence University in Canton, New York, hopes to get down to zero.

“There’s umpteen ways that fluoride can cause damage,” said Connett, executive director of the nonprofit Fluoride Action Network, which aims to end fluoridation worldwide.

Connett was initially skeptical of concerns about fluoride when his wife asked him two decades ago about its health effects.

“The prevailing attitude is that people who are opposed to fluoride are crazy, so I didn’t want to be stigmatized in that way,” Connett said.