Silicon Valley’s largest drinking water provider took the first steps Tuesday toward adding fluoride to the drinking water in most of Santa Clara County, including San Jose, the largest city in the nation without the cavity-battling additive.

After a lively 90-minute debate at a packed meeting, the board of the Santa Clara Valley Water District voted 7-0 to put the district on record supporting fluoridation.

During the meeting, critics told the board that fluoride has no health benefits, is costly and can lead to problems such as fluorosis — a pitting of the teeth. But supporters outnumbered them, with dentists and public health officials calling fluoride a key step in reducing tooth decay for children, particularly low-income children without access to regular dental care.

“I know for some this is a very emotional issue,” board member Linda LeZotte said. “But I hope we can agree to disagree. For me the science is more in favor of the benefits than any perceived harm.”

Only 21 percent of residents in Santa Clara County — most in areas such as Palo Alto, which receives water from San Francisco’s Hetch Hetchy system — have fluoridated water, compared with 72 percent of U.S. residents.

“I’m elated,” Santa Clara County Health Officer Dr. Marty Fenstersheib said after the vote. “It has been my hope that this would happen. It’s taken a very concerted effort over many years.”

Tuesday’s vote does not mean the district’s drinking water will be immediately fluoridated, however. It will take at least a year before funding can be located to pay for it. The board voted to work with community groups on a partnership to find funding. The district estimates the cost at $4.4 million to $9.5 million, with annual operating expenses at $836,000.

“We need to get into the details,” board Chairman Don Gage said. “The devil is in the details.”

Board members also voted to delete language in the original staff recommendation that would have put the district on record supporting fluoridation only if an outside group — such as a private foundation or state or federal agencies — paid all startup and annual costs.

“When you start putting all these different conditions on it, that becomes an excuse for not doing it,” said board member Tony Estremera, whose wife is a nurse.

Under the proposed plan, the water district, a government agency and water wholesaler based in San Jose, would add fluoride at its three drinking water treatment plants and a well field in Campbell. There are seven retail customers who buy treated drinking water from the district, including the San Jose Water Co., along with cities such as Santa Clara and Milpitas.

The district provides treated drinking water to cities that are home to 1.5 million people, including San Jose, Sunnyvale, Santa Clara, Campbell, Cupertino, Los Altos, Milpitas and Mountain View.

Some of those areas, such as Mountain View and Sunnyvale, also receive drinking water from San Francisco’s Hetch Hetchy system, which is fluoridated, as is the water in San Francisco, Oakland, San Diego, Los Angeles and other major California cities. San Jose has been slow because of the complex water system in the area — a mix of different providers, wells and treated water — and because the largest retail water provider, San Jose Water Co., is a for-profit company that has not pursued fluoridation.

Some communities served by the Santa Clara Valley Water District receive water from multiple providers. Roughly 12 percent of San Jose’s population — those located in Evergreen, Alviso and North San Jose, for example — is served by San Jose’s municipal water system, which already contains fluoride. Other neighborhoods, including Santa Teresa and Almaden Valley, are served by the Great Oaks Water Co., a private company with unfluoridated well water.

Other parts of the county, such as Gilroy and Morgan Hill, rely entirely on city-owned well water, which would not be fluoridated under Tuesday’s policy.

Critics said Tuesday that fluoride is too costly, can cause medical problems and can harm people with thyroid conditions. They said high rates of cavities and root canals that low-income children in and around San Jose suffer are unrelated to fluoride.

“The parents are uneducated,” said Maureen Jones, with Citizens for Safe Drinking Water, in San Jose. “They are bedding down children with bottles of fruit juice and soda. That’s an educational issue. It has nothing to do with fluoride.”

Supporters at the meeting included representatives from the California Dental Association, Silicon Valley Leadership Group and the Lucile Packard Children’s Hospital. They noted the California Environmental Protection Agency recently concluded that fluoride is not linked to cancer and that the amount being considered by the water district — less than .7 parts per million — has not been linked to serious cases of fluorosis.

“When you fluoridate the water, childhood tooth decay drops 40 percent and among the elderly, tooth loss and decay drops 70 percent,” said Dr. Donald Lyman, of the state Department of Public Health. “It’s a twofer.”

One of the main organizations advocating for fluoride, The Health Trust, a nonprofit based in Campbell that runs two dental clinics, said it will help find funding.

“It’s time to do the right thing by our kids,” said Fred Ferrer, CEO of The Health Trust.