About 100 supporters and opponents gave the San Francisco Public Utilities Commission an earful last night during a special hearing on adding fluoride to the water of 460,000 Bay Area customers.

At issue is a proposal from the commission’s staff that a new water fluoridation station be built in the East Bay as part of a water disinfectant program.

The SFPUC — which provides drinking water to about 2.4 million people in San Francisco and portions of Alameda, Santa Clara and San Mateo counties — took no action last night and will consider the matter again Friday at 10 a.m.

Among the communities that would have fluoride added to their water are Belmont, East Palo Alto, Menlo Park, Milpitas, Mountain View, Redwood City, San Jose, Santa Clara and Sunnyvale. San Francisco has had fluoridated water since 1952.

The proposed East Bay fluoridation station was included in a feasibility study that was initiated in April last year.

Another option outlined in the study is building a new fluoridation station at the existing Polhemus site in San Mateo. The study concluded that this option would cost nearly $2 million more over a 30-year period and would not be as efficient as the East Bay option.

While organizations ranging from the American Dental Association and the National Academy of Sciences back the proposal, many at the hearing voiced concerns about fluoridation.

Fluoride opponents suspect that the additive causes medical problems including bone decay, cancer and brain damage and low IQ in children.

Some speakers last night viewed the proposal as a direct assault on their freedom of choice, while others said fluoride failed to prevent cavities. There is already too much fluoride in things such as toothpaste, fruit juice and produce grown with pesticides, some critics added.

“People have never voted on a plan to add substances to their water that cannot be filtered out,” said Patricia Gray, a Burlingame resident. “I do not want my water fluoridated.”

Representatives from Bay Area Action, an environmental group, and Citizens for Safe Drinking Water also voiced their concerns.

Others at the City Hall meeting voiced support, saying fluoridation reduces tooth decay by as much as 40 percent.

Dan Gustavson, a Glen Park dentist, said his patients that moved to San Francisco from nonfluoridated areas had poor dental health as opposed to those who had lived in the city. He urged the SFPUC to go ahead with fluoridation.

The controversy over the use of fluoride in drinking water goes back decades. During the Cold War era, some people argued that fluoridation was part of a Communist plot. More recently, opponents have condemned it as forced medication.

The U.S. Environmental Protection Agency endorses fluoridation, as long as it is kept to four milligrams per liter of water. The federal Centers for Disease Control and Prevention, the National Cancer Institute, the Food and Drug Administration and the World Health Organization also endorse fluoridated water.