An overflow crowd seeking to remove fluoride from the county’s water supply was told by Marin Municipal Water District officials that their hands are tied by state law at a meeting Wednesday night.

“You are in the wrong place, you need to talk to the state,” board member Jack Gibson told fluoridation opponents at the meeting in Corte Madera. “We are not allowed to make a decision.”

That’s not what the crowd wanted to hear.

“Fluoride is a toxic that causes disease,” said Dawna Gallagher-Stroeh, director of Clean Water Sonoma-Marin.

She was one of more than a dozen speakers who asked the board to halt fluoridation at the sometimes testy meeting which saw the presence of a Central Marin Police Authority officer stationed in the back of the room.

Beginning early this year a group of Marin residents has been asking the water district to remove fluoride from drinking water saying it presents health risks. Opponents say the mandatory use of the compound can cause thyroid issues and can cause fluorosis, which shows itself in tiny white specks or streaks on a tooth. The latter is a cosmetic condition.

But the U.S. Centers for Disease Control and Prevention says water fluoridation “has been a safe and healthy way to effectively prevent tooth decay.” The organization has recognized water fluoridation as one of the “10 great public health achievements of the 20th century.” Two dentists at the meeting testified fluoride does protect teeth from decay.

But fluoride opponents were hoping to get the water board to begin to take steps to remove the substance from water supplies. But at every turn, board members and district attorneys said the agency is required to fluoridate.

“This district is not in a position to say, ‘we will not follow state law,’ ” said special counsel Tom Berliner.

In 1995 Assembly Bill 733 was passed into law. The law requires public water systems that have more than 10,000 connections to provide fluoridated water as long as they don’t use ratepayer dollars. The district receives about $1 million annually in rental income and uses $140,000 of that for fluoridation.

Fluoridation at Marin Municipal began in December 1973 after voters gave approval in November 1972 with 57 percent approval. Opponents failed to block it in court action and through an appeal to the state Department of Health.

It was taken up again by voters in 1978 after water to five West Marin communities was overdosed accidentally with up to eight times the accepted level of fluoride for about two weeks in late 1977. In that vote, 53 percent of voters gave approval to continue fluoridation.

While board member Liza Crosse said she questioned adding anything to water, she did agree the board had little leeway on the issue.

The water district is one of 18,400 U.S. water systems that fluoridate water. In 2010 about 66 percent of residents in the United States received fluoridated water.

The Marin Municipal Water District serves about 190,000 people between Sausalito and San Rafael. The North Marin Water District, which provides water to Novato and West Marin, doesn’t fluoridate its water and the issue has never come to a public vote.