Portland may be the country’s last large city to fill its cup with fluoridated water, but it’s not the first to draw the angst of residents fearful of the now common practice.

The debate between dental health advocates trying to decrease tooth decay and residents leery of exposure to fluoride keeps surfacing, as cities join the fluoridation trend that started more than 60 years ago.

As Portlanders take to the streets, gathering signatures for a petition against the City Council’s decision last week to add fluoride to the drinking water, they join a national debate that fluoride advocates appear to be winning.

Portland residents who oppose fluoridation say they don’t want a substance added to their drinking water and fear it could have harmful health effects from discolored teeth to a lower IQ in children.

The group, led by Clean Water Portland, a political action committee formed to fight the fluoridation of Portland’s water, has less than 30 days to collect 20,000 signatures for a referendum that would effectively stall the project, which would cost water ratepayers $5 million.

Kimberly Kaminski, director of Cleanwater Portland, argues fluoridation is not the answer to dental health issues.

“It is the cheapest, most ineffective Band-Aid that we have instead of addressing the real issue, with which is access to dental care,” she said

In addition to the potential health hazards of fluoride, opponents in Portland are up in arms over the City Council’s decision — prompted by a push from dental and other health advocates — to move forward without a public vote.

But despite the opposition and residents packing the council chambers for hours, Portland commissioners unanimously voted in favor of fluoridation, hailing it as a public health priority.

Since Grand Rapids, Mich., became the first community more than 60 years ago to add fluoride to the public’s drinking water, the trend has spread nationwide. Nearly 74 percent of Americans, who get their water from municipal systems, now drink fluoridated water, according to the American Dental Association.

Portland’s opposition movement is not unlike that in other major cities recently considering fluoridation, including San Jose, Calif., which is implementing fluoridation and Wichita, Kan., where voters will decide the issue in November. And, Kaminski argues, though it’s widespread in the United States, fluoride is not used everywhere.

“Most large cities in the world don’t fluoridate. It’s something that’s fairly unique to this country,” she said. ”I think the argument that everybody else is doing it is not a good argument.”

The World Health Organization acknowledges the risks and benefits of fluoridation in water.

In addition to Portland, Tuscon, Ariz., and Fresno, Calif., are the only other large-cities that have not added fluoride to their water, U.S. Centers for Disease Control and Prevention spokeswoman Brittany Raines said in an email. Albuquerque, N.M., doesn’t add fluoride, but its natural levels are close to those recommended, she added.

Cleanwater Portland must collect 20,000 signatures — it is shooting for 27,000 to be safe — for a referendum that would halt the city’s fluoridation project, scheduled to be up and running by March 2014.

“People are coming out of the woodwork. People are very passionate about this issue,” Kaminski said.

Cleanwater Portland and other volunteers announced shortly after the City Council’s decision Wednesday that they would start collecting signatures for a referendum. She said they have hundreds of volunteers and are trying to raise money for this grassroots effort.

Opponents are up in arms over the council’s unanimous decision that was pushed by Commissioner Randy Leonard. Kaminski and others feel their voices weren’t heard and it should have gone to a public vote.

“That is not a democracy,” she said. “That is a blatant violation of due process.”

Portland residents have voted down fluoridation three times in the past, and it had not been considered for 30 years, until the Everybody Deserves Healthy Teeth Coalition, a group of health and educational organizations, and Upstream Public Health, a nonprofit that advocates for policy solutions to public health problems, pushed for the fluoridation of Portland’s water.

The Healthy Teeth Coalition wants to decrease the rate of tooth decay in Oregon and believes fluoridating the water is the most effective way to do it. “We can’t start soon enough. I see significant differences in the teeth of the children from fluoridated Vancouver and Beaverton and children from non-fluoridated Portland,” Dr. Jim Smith, a dentist at Kaiser Permanente, said in a news release from the coalition.

Upstream could not be reached for comment.

Supporters of fluoridated water, including the ADA and CDC, say it prevents dental decay, rates of which have dropped since fluoridation started 67 years ago. Opponents argue drinking the fluoride poses risks from tooth discoloration to bone disease to a lowered IQ in children.

Leonard’s policy adviser Stu Oishi said the commissioner pushed fluoridation after seeing data provided by fluoride proponents that showed a dental hygiene crisis in Portland. According to the Healthy Teeth group, one-third of children suffer from untreated dental decay.

“It’s upsetting to see how many folks out there suffer from just bad dental health hygiene,” he said.

In Oregon, 835,834 residents drink fluoridated water. If Portland’s fluoridation system is built, that will add about 932,000 more.

The upfront construction cost for the project is $5 million and will take more than $500,000 a year to operate and maintain. Water rates are expected to increase by 0.3 percent to 0.4 percent or 8 to 11 cents a month for the average customer that pays $26.64 a month. That rate increase would cover the capital cost, but it would take more to operate the system. The details are still being worked out, according to the Portland Water Bureau.

If Clean Water Portland can get enough signatures, the issue would go to the ballot in May 2014 and would stall the project.

“Who knows how long it takes to construct this,” Oishi said. Plans for construction of a fluoridation plant still have to go before City Council.