In the 1940’s, as municipalities around the country began putting fluoride into their water, opponents spoke darkly of Communists and said fluoridation was nothing less than a plot to control America through its faucets. The arguing died down in most places as studies began to show that fluoride did fight childrens’ tooth decay, and today, 130 million Americans live in areas with fluoridated water.

But in Suffolk County, where many residents have a deeply rooted sense of independence and a visceral mistrust of a government they feel is far too intrusive, the debate goes on.

Next month, the Department of Health Services is to vote on a resolution that would urge the county’s water suppliers, particularly those in low-income areas where childrens’ dental problems are the worst, to begin adding fluoride to water.The County Health Commissioner, Dr. David Harris, supports fluoridation. But the proposal brought out longtime opponents, and some new ones, to a Board of Health meeting here today to talk about fluoride’s possible links to cancer, about the large expense of putting it into the water, and about its potential effects on the underground water system.

To a person, they said that enforced ingestion of fluoride had no place in a country whose population was already overburdened with chemicals.

“It’s another chemical that we can control that should not be in our drinking water,” said Carol Kopf, whose efforts eight years ago helped end fluoridation in Levittown.

Yvonne Langer, of Fort Salonga, said she does not give fluoride to her children, even in toothpaste. “I regard fluoridation as enforced medication,” she said.

Though they follow a long line of fluoride opponents who, years ago, were led by the ultraconservative John Birch Society, today’s opponents of fluoridation present themselves as informed citizens whose position is bolstered by scientific evidence. Led by a group called the New York State Coalition Opposed to Fluoridation Inc., they say that putting fluoride in the water brings health risks that have only begun to be studied.

Among the studies they cite most often is one released last year by the National Toxicology Program, the Federal Government’s top agency for evaluating chemical risks, that suggested that high doses of fluoride may cause cancer in male laboratory rats. But a more recent study by the Department of Health and Human Services, released several weeks ago, said there was no evidence linking fluoride to cancer in humans.

They cite other evidence in the toxicology report, that too much fluoride can weaken bones in elderly people and that, in excessive doses, it can even cause dental problems.

Elsa Ford, chairwoman of the environmental committee of the New York State Congress of Parents and Teachers, said that with many children already receiving fluoride from dentists, from toothpaste and from fluoride programs in schools, it was impossible to tell how much was too much. “We must regard the total effect,” she said. “We should not foist it on people who do not want to take the risk.”

“There is enough scientific evidence right now, including government studies, that proves fluoridation is extremely harmful to human health,” said Paul S. Beeber, a Hicksville lawyer who is president of the anti-fluoridation group.

Supporters of fluoridation say that the risks are negligible and point out that 70 percent of the public water supply in New York State contains fluoride, with no obvious ill effects.

“I think it is unfair and discriminatory to the children of Suffolk County to deprive them of the beneficial effects of fluoride,” said Dr. William Steibel, director of the County Health Department’s Division of Patient Care Services. Studies have shown, he told the health board, that children and teen-agers who drank fluoridated water had up to 70 percent less tooth decay than those in non-fluoridated areas.

Most major cities, including New York, fluoridate their water. Nassau County’s water is non-fluoridated except in several small areas. The county’s Health Commissioner supports countywide fluoridation, though the County Executive, Thomas S. Gulotta, opposes it.

Fluoridating Suffolk County’s water would be a 10-year, $32 million project that could raise residents’ water bills as much as 20 percent, said Michael A. LoGrande, chairman of the Suffolk County Water Authority, which supplies almost a million residents.

The county has 74 other community water suppliers, all much smaller, and has nearly 250 community wells, Mr. LoGrande said. Unlike New York City, where the fluoride is introduced to the water at a handful of spots, each of Suffolk’s individual wells would need its own new valve system, he explained.

“I’m not so sure that in the end it isn’t easier just to give fluoride treatments to our families that need them,” Mr. LoGrande said. “We spend an awful lot of time at the water authority keeping things out of the water. It seems silly to have to put something else in.”

Photo: Elsa Ford of the New York State Congress of Parents and Teachers questioned the effects of fluoridation at a hearing in Hauppauge, L.I. Dr. David Harris, right, Suffolk County Health Commissioner, supports fluoridation. (Photographs by Michael Shavel for The New York Times)