A majority of Massachusetts residents receive tap water that includes a chemical additive — either sodium fluoride, sodium fluorosilicate, or fluorosilicic acid — to help stave off tooth decay. Over the past 60 years, nearly 20 area communities elected to add fluoride to their water, but now a handful of those communities, including Cohasset, Duxbury, Hingham, and Hull, are reexamining the practice.

A primary concern is the risk of mild dental fluorosis, which leaves white markings on tooth enamel. Critics say fluoridation is an unnecessary hazard, particularly for children.

A group called Duxbury Fluoride Choice, founded by residents Peter Capraro and Dianne Siro­onian, recently earned a unanimous vote by the town’s selectmen in support of its article on the March Town Meeting warrant. The petition article seeks a townwide referendum on fluoridation, with its aim to convince the Board of Health, which has final authority over the water supply, that the community wants to end the practice.

“I am happy we are getting a lot of support in town. This is an important public health issue,” said Capraro, a parent of three school-age boys.

Meanwhile, health officials in Cohasset, Hingham, and Hull are working with the Aquarion  Water Co., a private operation that supplies water to those towns, to possibly reduce fluoride levels from 1.0 milligrams per liter to the federal government’s recommended amount of 0.7 milligrams.

Bruce Capman, executive health officer for Hingham, said the matter “is up for discussion right now.”

The health boards in Hingham and Hull have voted to lower the fluoride level to 0.7 milligrams, citing the federal recommendation, the increase in other fluoride sources in the environment, and the case of a Hull mother who said her child’s developing teeth were spotted by water she used in baby formula, said Capman.

However, Felix Zemel, Cohasset’s health administrator, said it will be several months before his town’s board is prepared to vote on the issue. “We are currently reviewing the science behind it,” he said.

While the Massachusetts Dental Society is a vocal advocate of fluoridation, few communities have elected to start up the practice in recent years. In 2007, the eastern portion of Freetown was among the latest in the state to begin receiving fluoridated water; the change came after citizens of New Bedford, which supplies some of Freetown’s water, decided in favor of fluoridation after three years of heated debate.

The American Dental Association says fluoridation is scientifically proven to be beneficial, particularly for children without access to regular dental care. In 1999, the federal Centers for Disease Control and Prevention cited community water fluoridation as one of the 10 great public health achievements of the 20th century.

Yet fluoridation remains a volatile issue for some.

In January 2011, the US Department of Health and Human Services recommended that fluoride levels in drinking water be capped at 0.7 milligrams per liter, to reduce the risk of mild dental fluorosis.

About 70 percent of Massachusetts residents receive fluoridated water, with levels ranging from 0.7 to 1.2 milligrams per liter. The state Department of Public Health has said the federal recommendation was made because other sources of fluoride, including toothpastes and mouthwashes, have increased since the 1960s, and the state levels remain safe.

In an announcement posted on its website, the department said, “There is no public safety concern about fluoridation in Massachusetts at the recommended level. The Department of Public Health continues to support the benefits of community water fluoridation for dental health.”

Zemel said Cohasset health officials have asked graduate students from the Boston University School of Public Health to develop a report on the health impact of fluoridation, comparing current levels, at 0.7 milligrams per liter, and after complete removal of fluoride from the water supply.

John Walsh, vice president of operations at Aquarion Water, said the company would be willing to reduce the fluoride concentration after the three towns produce an official request, and the state health agency is properly informed.

In Duxbury, Capraro said he is fine with the family’s dentist treating his children with topical fluoride, but he considers having the chemical distributed in the public supply excessive and a breach of autonomy.

“We want to uphold the right to choose. People interested in using fluoride can go to the dentist and get pills, but right now the only way to avoid ingesting it is to buy bottled water,” he said. “The only way to remove the fluoride at home is with an expensive reverse-osmosis filter, so my family has to drink it because we cannot opt out.”

No longer pouring sodium fluoride into the water would not only restore free choice but also save Duxbury more than $20,000 a year, he said.

David Pellegrini, a dentist who has practiced in Duxbury for 25 years, said fluoridation remains a safe, effective, and, above all, inexpensive way to prevent tooth decay. “I think these groups are overreacting,” he said of the opponents.

People in relatively affluent Duxbury can afford fluoride pills, he said, but not all children have access to dentistry.

“Who is going to pay for the fluoride if children in a less-advantaged inner-city neighborhood need to get tablets? Either the taxpayer will pay for it, or the kids will not get it,” he said.

Pellegrini said it would be disappointing to see children denied the means to prevent tooth decay because a few individuals are worried about drinking water with fluoride in it. “Fluoridated water has never been shown to be harmful to anyone, but it has been proven time and again to dramatically improve the health of our children’s teeth,” he said.

More than 70 percent of Americans with public water receive it fluoridated, according to 2010 statistics from the Centers for Disease Control. Twelve states require fluoride be added to public water, and 42 of the 50 largest cities in the United States have fluoridated water, according to the Massachusetts Dental Society.

In 15 states, fluoridated water is received by more than 90 percent of residents, with Kentucky topping the list.

On the other end of the spectrum, fluoride is added to the water systems for about 10 percent of residents in Hawaii.

19 south suburbs fluoridate their water

Nineteen area communities have fluoride added to their water, with the first starting in 1953.