Modesto voters Tuesday overwhelmingly rejected a ballot measure to fluoridate the city’s water supply.

City voters approved advisory measures that could lead to annexation of 480 mostly vacant acres in the northeast and two unincorporated neighborhoods in west Modesto.

With all precincts reporting at 10 p.m., 60.6 percent of voters opposed the fluoridation proposal, Measure M, while 39.3 percent favored it. The city growth measures, N and O, both got support from 54 percent of the voters.

Measure M asked voters whether the city should fluoridate the water supply, with supporters saying the additive would improve dental health. Opponents call fluoride a health danger.

Fluoridated water would have gone to an estimated 200,000 people, including about 35,000 people outside the city limit. Residential water rates would have increased $7 to $8 a year.

Fluoridation opponents said Tuesday’s vote vindicated their efforts.

“Most of the people that I have seen in the last few weeks have told me they’re opposed to it,” said Frank Cousineau, a leader of the anti-Measure M campaign. “We were cautiously optimistic.”

Dr. John Padmos, a Modesto dentist, said months of debating fluoridation’s merits likely contributed to Measure M’s defeat.

“We’re disappointed,” he said. “I think people are just afraid of making the move. (Opponents) had a lot of air time on cable and at council meetings. There was a lot of time when they could spread their fear.”

Tuesday’s vote was a significant blow to fluoridation advocates in the state. California, and much of the western United States, lags behind the rest of the country in fluoridation rates.

A statewide fluoridation group made Modesto a priority because of its high rate of dental disease.

From January through Oct. 20, the pro-fluoridation Citizens for a Healthier Modesto raised almost $68,000 and spent $37,000. Opponents raised about $4,500 and spent $3,500 during the same period.

Tuesday’s outcome marks the second time in 42 years that Modesto voters have rejected fluoridation.

In 1999, Fluoridation 2000, a statewide group, offered Modesto a $1 million grant to cover the cost of fluoridation equipment.

Supporters contend fluoridation is a cheap, safe way to prevent dental decay, while critics attack it as a denial of personal choice and potentially dangerous.

The council at first rejected the idea of a voter referendum on fluoridation. In May 2000, council members voted 4-3 to fluoridate the city’s water supply.

A year later, however, a member of the pro-fluoridation majority changed his mind. Councilman Mike Serpa joined Mayor Carmen Sabatino and Councilmen Bill Conrad and Bruce Frohman in voting to put the issue before the public as an advisory ballot measure.

A month later, fluoridation supporters called for the vote to be binding. The council agreed, setting up Tuesday’s referendum.

Also on the ballot were two growth-related measures.

Measure N asked whether the council should extend a sewer trunk line to the northeast area. Measure O asked the same about the west Modesto neighborhoods.

The votes are a required step before annexation is considered, but the results are not binding on the council.

The Measure N area, running northeast from the corner of Oakdale Road and Sylvan Avenue, could have an estimated 2,448 homes if it is annexed and developed.

One of Measure O’s unincorporated neighborhoods is just east of the intersection of Elm and Emerald avenues and has about 420 residents. The other, just south of Mellis Park, has about 100 residents.