It was an all too familiar scene. In late January, city councillors in Windsor, Ont., gathered to vote on whether or not to remove fluoride from the municipal water system. Health experts, including Canada’s chief dental officer, Peter Cooney, had descended on the town with stacks of evidence about the benefits of fluoridation as a harmless, cost-effective way to prevent tooth decay. Meanwhile a much more vocal, angrier crowd of activists railed against the decades-old health policy as paternalistic and dangerous. The debate raged into the night, but for those who have followed the mounting backlash against fluoride in Canada in recent years, the ending was all but guaranteed. And like that, Windsor’s local politicians became the latest to bow to pressure from the anti-fluoride lobby, voting to scrap the practice starting in April.

For scientists and health officials, the decision was a blow. “We’re not talking about a new subject here, this is a well-accepted public health intervention,” says Allen Heimann, the medical officer for Windsor-Essex County. But it could hardly have been unexpected. Since 2005, more than 30 communities have voted to do away with fluoridation, including Calgary, Waterloo, Ont., Slave Lake, Alta., and Quebec City. During this same period, the share of the Canadian population with access to fluoridated water has fallen to 32.5 per cent, down from 43 per cent, according to the Ontario-based Environmental Training Institute, which trains municipal waterworks operators across Canada.

Those in Windsor who opposed fluoride rehashed many of the same arguments put forth in other cities—that the additive is harmful to the teeth and bones of children, citing studies that link fluoride to kidney disease and lowered IQs. These claims have been dismissed by the Canadian Dental Association, the World Health Organization and Health Canada. The U.S. Centers for Disease Control hails water fluoridation as one of the 10 great public health achievements of the 20th century.

Yet in the face of such a complex issue, municipal governments have tended to side not with the experts being helicoptered in for council hearings, but with motivated local voters who inundate them with phone calls, petitions and their own stacks of evidence sourced from the Internet.