The editorial in the Watsonville Register-Pajaronian offered local voters some blunt advice: “Shield your eyes,” it said, “because the City Council is preparing to spit in your face.”

That was this month, as the council inched toward finally fluoridating the city’s water — a state-mandated action that has been bitterly debated since city residents narrowly voted to block it in 2002. At a council meeting in January, an anti-fluoridation activist held up a sign alluding to Nazis. When speakers threatened to boycott local businesses if fluoridation goes through, a council member told them to jump off the parking-garage roof.

Although the argument in the Santa Cruz County agricultural town of 50,000 has raged for years, people on both sides see a resolution as urgent.

Health officials say that Watsonville, with a large population of migrant workers, is in the throes of a dental-decay epidemic. One study of local students found an average of two dental abscesses in every classroom, not to mention an outsize number of cavities.

Still, one of the biggest employers in town — the Martinelli beverage company, famous for its sparkling apple cider — said it would rather move a planned expansion elsewhere than use fluoridated water in a new line of juices.

“We believe fluoride is bad for your body so, morally and ethically, we simply cannot put that water in our products,” said John Martinelli, president of S. Martinelli & Co., his family’s business for 142 years. “If half the people in this town don’t want to be mass-medicated, then we shouldn’t be.”

Although water supplies across the U.S. have been fluoridated for decades and the Centers for Disease Control and Prevention has called the process “one of the 10 great public health achievements of the 20th Century,” California has been late to embrace it. Opponents link it to bone cancer, thyroid problems, kidney malfunction, fetal damage and a host of other conditions. Their critics, including most mainstream medical and dental organizations, accuse them of distorting scientific studies.

Suspicion of fluoridation comes from the right and the left. Some see it as a dangerous erosion of liberty. Others believe it’s an underhanded way for businesses to get rid of industrial waste.