Portland’s plan to add fluoride to a water supply serving more than 900,000 Oregonian’s has rankled some suburban city leaders who were left out.

Gresham Mayor Shane Bemis and Tualatin Mayor Lou Ogden have written letters to Portland criticizing the City Council for deciding to fluoridate water without first consulting wholesale customers.

Beyond serving city residents, Portland provides water to 19 cities or water districts beyond city limits. Those jurisdictions accout for about 40 percent of the demand for water from Portland’s Bull Run. The Portland City Council will hold a hearing Thursday and vote next Wednesday to add fluoride.

Bemis wrote to Portland Mayor Sam Adams Aug. 24 saying he is “very disappointed” that Gresham was not consulted about fluoride, adding that he learned about the issue through media reports.

“In this case, fluoridation is clearly an elective expense as opposed to a necessary expense,” Bemis wrote. “Especially given the lack of voice given to the wholesale customers on this issue, I trust that we will not be billed for any expenses associated with this change.”

Ogden wrote to the City Council Aug. 29, saying leaders had “proposed an aggressive timeline for implementing this proposal with little to no public input.” Ogden added that Portland’s decision-making is disconcerting for wholesale customers who weren’t consulted, and that the region deserved a “true public process” but instead it “feels like it happened behind closed doors with very little input.”

The city of Tigard, another wholesale customer, has yet to submit its letter. But officials there also share concerns over poor process, said Dennis Koellermeier, Tigard’s public works director.

None of the cities took a stance on fluoridation itself.