City Council members face renewed pressure from a small group of activists who want the Water Management Department to stop adding fluoride to Durham’s drinking water.

The council deflected similar entreaties in 2011, but the issue landed back on its agenda recently after the Durham County Board of Health, at Mayor Bill Bell’s request, studied fluoridation and weighed in with a recommendation.

Its members urge continuing the practice, agreeing that it’s a cost-effective preventive measure against tooth decay that has no major drawbacks from a health standpoint.

That’s in line with medical consensus from the 1950s through to today, but critics on Thursday told council members that the health board and Water Management are trying to prop up “a failed public health nightmare.”

They claim studies show that fluoride in effect causes brain damage, lowering IQ in children. The leader of the activists, Jordan High School graduate Corey Sturmer, called it “a neurotoxic poison.”

Bell alone on the council appeared to give some weight to the complaints, telling administrators that he’d like to see why other major cities have decided against the use of fluoride as a water-treatment additive.

He didn’t name any specifically, but a pro-fluoridation referendum failed in Portland, Ore., in May. That city has never fluoridated its water.

Other council members were dubious.

“I just found the whole conversation interesting about lack of facts,” Councilwoman Diane Cattoti, in private life a health-policy consultant, said at the end of Thursday’s meeting. “The presentation from our health board had a lot of research in it – and I didn’t see any research presented by the opponents.”

The health board in fact compiled a report that, with attachments, ran to over 200 pages. The meat of it, however, covered 22 pages and rejected what members saw as the main contentions of the critics.

That included the IQ allegation, which was anchored mainly on a 2012 report from a team that included researchers from Harvard and schools in Denmark and China.

It said “very little is known” about fluoride’s effects on childhood neurological development and tried to remedy that by collating the results from 27 epidemiological studies other researchers had done in areas of China and Iran with high, naturally occurring fluoride concentrations in water.

It found “the possibility of an adverse effect” and called for additional research in the field.

But experts questioned by the health board noted that many of the studies used as their control group – the one high-fluoride groups were being compared to – populations exposed to levels of fluoride more typical of what would be seen in the United States.

Durham treats its water to include 0.73 milligrams per liter or parts per million of fluoride. The control groups in the study generally had concentrations ranging from 0.18 milligrams per liter up to around 1.1 milligrams per liter.

Depending on the study, the original papers deemed anything from 0.57 to 11.5 milligrams a high level of fluoride.

The 2012 team acknowledged that the methods of the original researchers had varied so much that it was impossible to draw conclusions about an exposure limit, not least “because the actual exposures of the individual children are not known.”

State health officials found the 2012 study unconvincing.

It “is not relevant to community water fluoridation as practiced in the U.S.” given the low concentrations used here and the lack of consideration in the Chinese and Iranian research for other risk factors like lead, Jean Spratt, a dentist in the N.C. Division of Health’s oral health section, told the Durham health board.

Sturmer and his fellow activists have also pushed for the elimination of fluoridation in neighboring southern Orange County.

But directors of the Orange Water and Sewer Authority in June said they would continue using the chemical.