NORTH COUNTY —- The city of Escondido will not have to change the way it adds fluoride to the water supply, according to a state Supreme Court decision Wednesday.

The state’s highest court declined to review a 4-year-old lawsuit in which a group of Escondido residents alleged that the way the city fluoridates the water violates their constitutional rights and state law.

The decision from the state’s highest court leaves in place an August state appeals court ruling that rejected the residents’ arguments. The appeals court upheld a Superior Court judge’s decision to dismiss the residents lawsuit.

“They’ve spoken,” the residents’ attorney, Norman Blumenthal, said Wednesday of the Supreme Court. “We have to respect their decision and move on.”

The residents could ask the U.S. Supreme Court to consider the case, but have not decided whether to do so, Blumenthal said.

Assistant City Attorney Jennifer McCain, who represented the city, could not be reached Wednesday for comment.

The Statewide Fluoridation Act requires public water systems throughout California with more than 10,000 water-service connections to fluoridate their water to promote dental health. Escondido has 25,000 service connections that serve about 130,000 people, the appeals court opinion stated.

The Escondido City Council voted 3-2 in June 2001 to lift a 1999 city ban against putting certain chemicals in city water so that it could begin the process of adding fluoride to the drinking water. A group of residents filed a lawsuit in September 2001 that challenged the city’s planned water fluoridation.

A trial of the lawsuit was scheduled for Oct. 12, 2004, but on that day, Superior Court Judge Jacqueline Stern made her decision to throw out the lawsuit, saying the residents had failed to provide a legal reason why Escondido’s water fluoridation violated their rights.

Blumenthal has argued that the substance the city is using to fluoridate the water —- hydrofluorosilic acid —- contains lead and arsenic at levels that will cause cancer, and that the city is “mass medicating the entire community.”

Attorneys for the city and the state, which also was a defendant in the lawsuit, have argued that Escondido’s water is safe, that the city is complying with state law, and that hydrofluorosilic acid is used elsewhere in California and across the country to fluoridate water supplies.

The appeals court opinion stated that laws and regulations allow “fluoridating agents” such as hydrofluorosilic acid to contain contaminants like lead and arsenic as long as they comply with maximum contaminant levels and detection levels.

McCain said in August that the city has had no problems with its detection levels and that “everything is safe.”