The taste and smell won’t change, but starting on Monday something was different about Calgary’s water supply — fluoride is back in the taps across the city in Western Canada.
Fluoride, a mineral found in water, has widely established dental benefits shown to strengthen the tooth surface, or enamel, and help prevent decay.
Calgary stopped adding fluoride to its water supply in 2011, deciding that the cost to treat its system with the mineral outweighed the benefits.
But a push by city residents coupled by worsening oral health among children has led Calgary officials to reverse course.
“There’s no question that it reduces cavities, which is not just a cosmetic issue, because poor dental health is associated with poor body health,” said Joe Schwarcz, a chemistry professor at McGill University in Montreal and director of a university office focused on debunking misinformation in science.
Fluoridation is largely viewed as one of the most significant and cost effective public health innovations of the last century. But fluoride has long been regarded with suspicion in some quarters and has been the target of conspiracy theories. In the 1950s critics of Communism in the United States claimed it was a mind-control tool to poison Americans.
Robert F. Kennedy Jr., the U.S. health secretary, has called for states to ban fluoride, pointing to contested studies that have linked lower I.Q. among children born to mothers who had a high exposure to fluoride during pregnancy. Those studies were based in countries that use higher levels of fluoride than the United States.
“I don’t have faith that enough was studied and researched,” said Cat Hackman, an interior designer in Calgary, who opposes adding fluoride back to the water.
Health Canada, a federal agency, is among the global health authorities to recommend fluoridation, but the decision is largely up to local governments.
Both in Canada and the United States, experts say, water fluoridation reduces dental decay by at least 25 percent in children and adults. In the United States, about 75 percent of Americans are served by fluoridated water systems, according to the latest data.
In Canada, roughly 39 percent of Canadians have access to fluoridated water, a government report says, and availability varies greatly across provinces. Less than 2 percent of the population in Quebec and British Columbia, the second- and third-largest provinces in Canada after Ontario, fluoridate their water.
In Calgary, a city of about 1.8 million people in Alberta, the City Council voted to remove fluoride from its drinking water in 2011, two decades after it was introduced in 1991. The water treatment infrastructure to process the fluoride was at the end of its life cycle and councilors did not believe that the cost to replace it outweighed the existing science around the health value.
Gian-Carlo Carra, a councilor who initially voted to not continue adding fluoride, said his decision at the time came after “a thoughtful conversation” about whether it was a municipal responsibility or something to be decided and paid for at higher levels of government.
He has since changed his mind and believes the discussion about the claimed risks of fluoridation have taken on an increasingly polarizing tone.
“Over the last 10 years when it was not in our water supply, it was alarming to see the fringe conversations that were anti-fluoride take center stage,” Mr. Carra said.
In 2021, the city held a nonbinding plebiscite, the equivalent of a referendum, on whether to restore fluoride to the water system and 62 percent of voters supported doing so.
The effects before and after fluoridation were most apparent in children, researchers in Calgary found.
The Alberta Children’s Hospital saw a stark increase in the number of children from Calgary who needed antibiotics to treat dental infections after fluoride was removed from the drinking water.
A study in 2021 from the University of Calgary compared the dental health of about 2,600 children with a similar group in Alberta’s capital, Edmonton, where the water remained fluoridated. In the Calgary group, about 65 percent of the children developed one or more cavities, while in Edmonton, that number was about 55 percent.
The research, led by Lindsay McLaren, a professor of community health sciences at the university, mirrored findings in studies she conducted about three years after fluoride was removed from Calgary’s water.
“The use of public policy to provide the conditions to be well is under siege,” Dr. McLaren said. “I applaud our municipal government for doing this against what is likely a great deal of hostility.”
The fluoridation was supposed to begin in 2023, but was delayed several times pending upgrades to two water treatment plants, which cost about 28 million Canadian dollars, or $20 million.
Water flowing from the Canadian Rockies to the Bow River and Elbow River, two waterways that meet in southern Alberta, will be treated with fluoride to reach levels that both Canada’s health agency and the U.S. Public Health Service say are optimal to fight tooth decay.
Vjosa Isai is a reporter and researcher for The Times based in Toronto, where she covers news from across Canada.
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