STUART — Martin County commissioners voted 3-2 this afternoon against adding fluoride to the water the utility department serves to more than 20,000 customers.

The majority agreed with a large group of activists who questioned the safety of using the chemical, as well as its usefulness.

Commissioners had decided to reconsider their earlier approval of putting fluoride in the water after residents began an active campaign against the idea, claiming that the chemical can cause problems with teeth, bones and thyroid gland.

The utility department was prepared to begin fluoridating the water early next year until today’s vote put a stop to those plans.

More than two dozen opponents – including leaders of other political groups fighting airport expansion, river pollution and urban development – showed up today wearing blue T-shirts as a sign of their camaraderie.

Activist Pat Arena complained that a recent study found that fluoride can damage bones and teeth.

“I am appalled at the prospect of using water as a vehicle for drugs,” said Lynne Pine of Stuart. “In today’s world, mass medication through water is not a good idea. It’s about more than teeth.”

The opponents, who came from Martin and Palm Beach counties, claimed fluoride causes diseases ranging from cancer to mental illnesses and has been used in the past to mentally subdue and control people.

“I don’t want fluoride in my water,” said Glenn Burdge. “If you want fluoride, go get drops from your dentist and then drink it. Leave us to our choices,”

Commissioners Lee Weberman and Sarah Heard voted against it because studies on the issue raise too many questions about negative impacts, and they said they weren’t convinced there was a demonstrated oral health problem in the county.

Commissioner Doug Smith and Chairman Michael DiTerlizzi voted to stick with the plan to fluoridate the water.

“This will be an enormous letdown for a community that deserves better,” Smith said.

Michael Easley, dental coordinator for the state Department of Health, said fluoridating water was not dangerous in controlled amounts and was not medicating the public.

“It’s not a prescription medicine,” he said. “It’s a nutritional supplement.”