SOUTH YARMOUTH — Two years ago the Yarmouth Board of Health bowed to public pressure and voted not to recommend fluoridation of the town’s water supply.

Now the debate is on again and last night at a hearing on the topic the pressure in the room was palpable.

“Why with anything so questionable, so possibly damaging to the rest of the population, would you even think about such a thing?” Barbara Gould of South Yarmouth asked the beleaguered board.

They were instructed by Selectman William Marasco to take up the topic again, said the board’s chairman, Benjamin Gordon.

That wasn’t good enough for some in the crowd, who shouted for an immediate vote by the board not to fluoridate. Others called for a class-action lawsuit if the town chooses to go forward with fluoridation.

Having heard from fluoridation proponents previously, the board last night heard from an opponent; Paul Connett, a professor emeritus of chemistry at St. Lawrence University in New York and executive director of the Fluoride Action Network, an anti-fluoridation organization.

Connett spent a half-hour outlining the various ailments and maladies he said may be related to fluoridation, citing article after article in a whirlwind of data points and studies from countries like China and India.

“Most countries don’t fluoridate their water,” Connett said.

Fluoridation is unethical, dangerous and unnecessary, Connett said. The one part-per-million concentration recommended by the Centers for Disease Control and Prevention and supported by the American Dental Association may be too much, he said.

And a recent study by the National Research Council suggested the Environmental Protection Agency re-evaluate its toxicity standard for fluoride, Connett said. “I urge Yarmouth to wait until the EPA water division has determined a new” maximum contaminant level goal.

That statement was an example of how Connett and people like him are misleading the public, said Myron Allukian Jr., past president of the American Public Health Association and the former dental director of the city of Boston.

Allukian, who spoke in favor of fluoridation before the Yarmouth Board of Selectmen in January, said the National Research Council report had nothing to do with fluoride added to drinking water supplies.

“For anyone to wait until that report to come out is just ridiculous,” Allukian said when reached by telephone last night.

Allukian said Connett’s contentions were based on “junk science” and that hundreds of studies have shown no relationship between fluoridation and various diseases Connett attributed to it.

Connett said there was no scientific evidence that eliminated fluoride as the cause of diseases such as osteosarcoma, a bone cancer that affects young men.

Allukian questioned why the American Cancer Society and the National Cancer Institute would support fluoridation if there were a connection between cancer and adding fluoride to public water supplies.

Should the board of health choose to recommend fluoridation, the action must be advertised, followed by a 90-day waiting period, Gordon said.

If a petition is signed by 10 percent or more of the town’s population during that time, a referendum must be held.

There will be another public hearing on fluoridation in two weeks, Gordon said.

In the United States 170 million people drink fluoridated water in 10,000 communities. Statewide, 139 communities fluoridate their water.