Be it nerves or a desired effect, Williams’s words reverberate through the boardroom with sibilance and crackly feedback: “Highly corrosive. Highly poisonous.”

Williams was one of thirteen people who stood before the Orange Water and Sewer Authority Thursday night to speak against adding fluoride to the water supply—in some ways a lost cause, given that the board made its decision on the matter more than six months ago. No one spoke for fluoridation, although the board has received comments touting the practice as a low-cost, low-risk way to prevent tooth decay among the masses.

And that’s generally the position of the board. OWASA water has been fluoride-free since February, when the authority shut down its water plant after too much fluoride was pumped in and the system unrelatedly experienced a major water main break. In March, the board (with one nay vote from Yinka Ayankoya) decided to resume fluoridation once improvements were made at the plant. Last Thursday, chairman Robert Morgan said that work would likely be complete in the next week or so. (An announcement will be made before fluoridation resumes.)

In the interest of public input, the board’s October 26 meeting will include a discussion of how OWASA should continue to review whether fluoridation is the right choice, but it’s unlikely to cause any changes.

“We don’t expect to revisit the decision in the near future,” Morgan said.

The February 2 fluoride overfeed has revived an unsuccessful 2012 attempt to remove fluoride from OWASA’s water, drawing new members now united under the banner Fluoride Free Chapel Hill/Carrboro. Then, like now, the board didn’t see compelling evidence to overturn a practice that has been in place in Chapel Hill and Carrboro since 1964 and in America since 1945.

About 75 percent of the American population is served by a fluoridated water supply. As of 2015, that included 88 percent of North Carolinians. But the last time many Americans gave much thought to fluoride was probably while sitting at a dentist’s office with a foamy tray of it shoved in their mouths, trying not to drool.

The Centers for Disease Control and Prevention considers fluoridation one “of 10 great public health achievements of the 20th century.” The EPA has denied several activist petitions seeking an end to the practice, citing a lack of evidence that fluoride is harmful to health. Fluoridation has the backing of the U.S. Public Health Service, the American Dental Association, and the American Medical Association.

OWASA says it fluoridates its water to the level of 0.7 parts per million, the same amount the U.S. Public Health Service recommends for community water systems. The federal limit is four parts per million. Children exposed to too much fluoride may see enamel damage known as dental fluorosis.

According to its website, OWASA uses a compound called hydrofluorosilicic acid that it buys from the Unimin Corp. in Bakersville, North Carolina, for about $25,000 per year and dilutes.

Critics are unconvinced that fluoride is really so beneficial to teeth or even necessary given the prevalence of fluoride today in everything from toothpaste to soda. Instead, they are concerned fluoride exposure can cause a variety of adverse effects, including lower IQs and thyroid problems. Studies have linked fluoride exposure to these ailments, but they’ve generally been limited or based on fluoride levels much higher than American drinking water.

“Common sense told me if you’re not supposed to swallow it in your toothpaste, then you shouldn’t be drinking it in some unknown quantity,” says Daria Barazandeh, who has been trying since 2012 to get OWASA to stop fluoridating its water.

Barazandeh, like other fluoride opponents, says support for fluoride use is being perpetuated by “endorsements” from the CDC and entrenched financial interests. She realizes this may get her labeled as a conspiracy theorist or a “crazy hippie,” she says.

Indeed, opposing fluoridation requires not only rejecting a practice that has been passively accepted in America for seven decades, but also institutions that are supposed to be our safeguards and our sources of neutral, vetted information. In its most extreme forms, fluoride opposition has involved theories about the practice being used by Nazis, communists, fascists, and the Illuminati to subdue the masses.

“I have some sympathy for the people who are pro-fluoride,” Sharon Reese told the OWASA board last week, “because they’ve been in a situation where they believed something to be correct for a long time. They might be in their fifties or sixties and have believed this their whole lives, and it’s really very difficult to change your mind.”

Barazandeh says she just wants OWASA officials to look at science themselves and to consult experts other than dentists. Last week, she handed them a packet of studies.

“What I was asking of OWASA back then, and what I’m asking now, is for them to have a fair look at this without prejudice,” she says.

Perhaps the group’s most compelling point is that the fluoridation debate is a matter of informed consent. It’s an argument that taps into a basic desire for personal liberty and can circumvent dissections of which study says what. Speakers last week lined up to tell OWASA officials they did not have their permission to medicate them.

Last month, Carrboro alderman Sammy Slade introduced a resolution stating that OWASA is medicating the town’s water with fluoride, and that neither the town board nor its appointees to the OWASA board “can ethically provide consent on behalf of individual Carrboro citizens.” Ultimately, the resolution was not voted on by the town board.

“That is the foundation upon which most communities have been able to stop fluoride going in their water,” Barazandeh says. “How can OWASA decide what’s best for me medically?”