PORTLAND, Ore. – Early returns Tuesday night showed voters rejecting fluoridating Portland’s water 60 percent to 40 percent.

And just before 9 p.m., the pro-fluoride group Healthy Kids, Healthy Portland conceded it would not win its battle to get fluoride added to the city’s water.

But the campaign declared the fight is not over.

“We will not rest until this passes,” said Alejandro Queral of the Northwest Health Foundation during the campaign’s concession speech.

Tuesday night’s vote was the first time in 30 years that Portland voters decided whether to add fluoride to their drinking water.

It was the fifth time they have voted on the issue. The last time was in 1980 when voters repealed a 1978 voter-approved decision to add fluoride to the water. Fluoride was never added to the water in the interim, however.

This time around the City Council voted to fluoridate the water last September but those opposed to it quickly organized and successfully gathered enough signatures to get the issue on the ballot.

Elections officials expect turnout to top 40 percent in this election, which higher than usual for special elections.

The issue has drawn strong emotion and reaction from Portlanders, making it a hotly debated topic with both sides charging sign vandalism and theft.

And a last-minute controversy erupted last week after The Oregonian reported that Oregon Health Authority emails suggested a pro-fluoride group worked to pressure a state official to present a dental report to its advantage.

Mel Rader, co-director of Upstream Public Health, denied his group was trying to pressure Oregon’s oral health program manager Shanie Mason in any way.

Proponents of fluoridation say it will help prevent tooth decay, especially among low-income children. Opponents fear adding fluoride will erode the purity of Portland’s water by adding contaminants such as lead and arsenic.

The pro-fluoride side has most of the medical community behind it but the anti-fluoride side questions whether fluoridation really works. And others don’t like the idea of having their choice of whether they want fluoride in their water ripped away from them.

This story will be updated with KATU Problem Solver Shellie Bailey-Shah and reporter Dan Cassuto contributing.