If approved by a majority of voters, Measure N would prohibit adding fluoride or anything else to the city's water system in the name of promoting public health. In other words, a yes vote means no to fluoride.

``I want to be able to control how much fluoride goes into my body, and I want others to have that same choice,'' said Jeffrey Levine, a Santa Cruz chiropractor backing the measure. Dentists who have lined up against the measure are flabbergasted at the lingering controversy surrounding a practice widely embraced by health officials for half a century.

``I was a teenager here in the 1950s when this issue came up before, and back then, they were claiming it was a communist plot,'' said Bruce Donald, a local dentist fighting Measure N. ``I was hoping we'd evolve into just having fluoride like so many other communities. Many people are really surprised that we're having this debate.''

Measure N supporters have raised only $1,500 compared with more than $7,000 amassed by the dentists and doctors who oppose it.

Fluoride is a natural element found at trace levels in air, soil and water. The discovery that communities with elevated fluoride levels in their water had fewer cases of tooth decay led to adoption of fluoridation after World War II.

Fluoridation boosts the fluoride in water to about one part per million, a level considered optimal in fighting tooth decay. Health officials say fluoridation can reduce tooth decay as much as 60 percent in children and 35 percent in adults.

Today, 145 million Americans drink fluoridated water, including nine in 10 San Francisco Bay Area residents. Nearly two-thirds of all U.S. communities and 70 percent of major cities have fluoridated water.

Still, only 17 percent of California communities are fluoridated. That led the state in 1995 to adopt a law requiring municipal water systems serving 10,000 or more customers to fluoridate when funding is provided to do so.

Many communities, including Sacramento, Los Angeles and Mountain View, which voted overwhelmingly in favor of fluoridation last November, have since jumped on the fluoride bandwagon. Santa Cruz has long been among the holdouts. In 1952, when conservatives ran the town, voters rejected fluoridation as a form of socialized medicine.

Today, much of Santa Cruz's liberal citizenry views fluoride with the same suspicion it holds for irradiated produce. Residents cheered as the city council voted 6-1 last year to prohibit fluoridation without a public vote.

Measure N, dubbed the ``Safe Drinking Water Initiative,'' was put on the ballot by fluoride foes who feared a new city council majority could reverse its earlier vote. If approved, it will replace the council's earlier action.

Measure backers are hoping to make Santa Cruz a test case in a legal battle against the state fluoride mandate. State officials maintain that even if the measure is approved, it is superseded by the state's fluoridation mandate.

Although the state has mandated fluoridation, funds have yet to be allocated. When money is set aside for the project, it is uncertain that Santa Cruz, though high on the list of 167 water districts that do not use fluoride, would be among the first to get funding.

Fluoride critics cite reports from a handful of researchers alleging possible links to cancer, Alzheimer's disease and bone fractures. They point ominously at the new ``poison'' warnings on fluoride toothpastes.

Others argue on more practical grounds that the treated water would largely be wasted on lawns and laundry and that the state shouldn't force its will on local communities.

Measure N critics say proof of fluoridation's safety and effectiveness can be seen in its endorsement by virtually every credible health agency. Those include the Centers for Disease Control and Prevention, World Health Organization, American Medical Association, American Dental Association, National Cancer Institute and National Academy of Sciences.

Because of the timing of its submission, the measure requires a special election in which it is the only item on the ballot. The election will cost the city more than $100,000, county elections manager Gail Pellerin said.

Not everyone who drinks city water gets to vote on the measure. Santa Cruz's water system serves 88,000 customers, 34,000 of whom are outside the city limits.

``I've had a lot of people call me about that,'' said City Attorney John Barisone. ``They're real upset.''