(CBS/AP) Portland's City Council approved a plan Wednesday to add fluoride to the city's water supply, meaning Oregon's biggest city is no longer the largest holdout in the United States.
The ordinance approved Wednesday morning calls for the city water to be fluoridated by March 2014.
Health experts say fluoride is effective against decay by providing teeth with frequent contact with low levels of fluoride throughout each day. The Centers for Disease Control and Prevention cite studies that show water fluoridation reduces tooth decay nearly 25 percent over a person's lifetime. The agency also said its been studied for more than 65 years and has shown strong evidence of its safety and efficacy.
Opponents of public fluoridation say it's unsafe and violates an individual's right to consent to medication. They also add that council members rushed into action without a public vote, and they plan to collect signatures to force a referendum in May 2014.
Voters in Portland twice rejected fluoridation before approving it in 1978. But that plan was overturned before any fluoride was ever added to the water.
Portland's drinking water already contains naturally occurring fluoride, though not at levels considered to be effective at fighting cavities.
Portland City Commissioner Nick Fish, who co-sponsored the plan, has said more than 200 million Americans drink water with added fluoride, and it doesn't appear to have caused great harm. Most mainstream health organizations, such as the American Medical Association and American Dental Association, endorse it as safe.
Public fluoridation came up this week in Phoenix when a public stir prompted re-examination of a policy in place since 1989. After a contentious hearing Tuesday, council members voted to continue adding fluoride to the water in the nation's sixth-largest city.
Grand Rapids, Michigan became the world's first city to fluoridate its water supply on January 25, 1945, according to the American Dental Association.
The CDC says more than 204 million Americans are served by community water supplies that contain enough fluoride to protect dental health - about 74 percent of the country. For its Healthy People campaign, the agency hopes to boost that level to about 80 percent of Americans by 2020.