In a blow to the anti-fluoridation lobby, the Aspen City Council opted Monday to continue adding fluoride to the municipal water supply, albeit at a lower concentration.

Discussion during Monday night’s regular council meeting on options to ban the practice or continue it were somewhat limited, with council members saying they had spent enough hours researching the pros and cons of fluoridation, the focus of a lengthy September work session. Mayor Mick Ireland, a tax lawyer, even joked that since so many people inundated him with information on the topic, he would return the favor by emailing sections of the tax code.

“I appreciate all of the information people gave us,” Ireland said. “I know a lot more about fluoride than I had before — perhaps more than I want — and I felt like at some point I should send chunks of tax code back to make it even. But it is educational.”

A resolution to continue adding the controversial substance to city water passed unanimously. However, at the beginning of Monday’s discussion, Councilman Torre said he had been persuaded by arguments against adding fluoride to the water, even at the reduced amount recommended by the city’s Environmental Health Department and the federal Environmental Protection Agency.

“To me, this is medicating nine out of 10 people because one out of 10 people might need that medication,” Torre said.

But Torre added that minimizing the amount of the additive is “a good first step” and ended up going along with the staff recommendation after he could not find support from two other councilmen to get a majority to move for a ban on the practice of adding fluoride.

“I’ve given this a lot of consideration,” Councilman Derek Johnson said. “The most compelling argument for me was (from a local dentist) who said Basalt and Carbondale don’t have fluoride and their kids had many, many more cavities.”

A staff memorandum points out that fluoride reduces the risk of cavities, especially in children. But too much of it can increase the risk of dental fluorosis — various degrees of tooth discoloration — and bone fractures.

In addition, various studies and claims have raised the possibility that excess fluoride might increase the risk of rare bone cancers and can even lead to a lower IQ, “but there is no support for these effects based on existing science,” wrote Environmental Health Director C.J. Oliver.

In January 2011, the EPA and the U.S. Department of Health and Human Services proposed a recommendation that water districts decrease the amount of fluoride to the lowest amount expected to help reduce cavities, or 0.7 milligrams of fluoride per liter of water. Currently, the city adds fluoride to the natural amount that already exists in the water supply to achieve a level of 1 to 1.1 milligrams of fluoride per liter.

According to the federal Centers for Disease Control and Prevention, 515 water systems in Colorado are classified as nonfluoridated, while 196 systems are listed as fluoridated through natural means. Fifty systems, such as those in Aspen and Snowmass Village, have natural fluoride in their water supplies but adjust the levels with additives to meet a certain standard.

The council’s action lowers the amount of fluoride that will be added to city water to whatever is needed to reach the 0.7 milligram standard.

Ireland said the council will review the fluoridation issue annually and asked the city’s Water Department to test the substance in the bag, before it’s added, on a regular basis. Fluoride is not manufactured in the United States — China is a leading producer — and part of the council discussion centered on ensuring its quality so that there is no outside health risk to the public.