Last February, the City of Calgary made it onto Jimmy Kimmel’s roster of topics on his late-night television show, Jimmy Kimmel Live! – but not for a reason you might think. 

In 2021, the City of Calgary voted 62 per cent in favour of community water fluoridation (CWF) a decade after it was stopped because the infrastructure had reached the end of its lifecycle. After some delays, reintroduction is expected in summer 2025. The reason Kimmel mentioned Calgary was because Utah is setting up to be the first U.S. state to ban CWF, despite opposition from U.S. health and dental authorities. 

Just a few years ago, in 1999, the U.S. Centers for Disease Control (CDC) named drinking water fluoridation one of 10 great public health interventions of the 20th century because of the dramatic decline in dental cavities. However, that all may change now that Robert F. Kennedy Jr. is the U.S. federal health secretary. In an X post in November 2024, Kennedy said he intends to order fluoride removed from all U.S. water systems, calling it “an industrial waste associated with arthritis, bone fractures, bone cancer, IQ loss, neurodevelopmental disorders, and thyroid disease.” 

In Canada, debates about CWF have been taking place at a municipal level since it was introduced in Brantford, Ont., in 1945. Other Canadian municipalities held votes and many followed suit. According to a 2022 report, 38.7 per cent of Canadians have access to fluoridated water. CWF continues to be fully supported by Health Canada, Canadian Dental Association, Canadian Public Health Association, and provincial health and dental associations, as well as internationally by World Health Organization and, for now anyway, the American Dental Association and CDC. The chief reason for support is that fluoride has been proven to prevent tooth decay, and tooth decay is a serious health issue. In addition to pain, suffering, and expense, tooth decay is caused by a bacteria that can enter the bloodstream and cause potentially life-threatening health issues. 

James A. Dickinson, PhD, a professor of medicine at the University of Calgary, says that in the eight years after CWF ended in Calgary, the need for intravenous antibiotic therapy at Alberta Children’s Hospital doubled from 22 per 100,000 in 2010–11 to 45 per 100,000 in 2018–19. Meanwhile in Edmonton, where CWF continued during the same period, rates for intravenous antibiotic therapy stayed the same. Dickinson led an article that provides an in-depth look at the issues from the perspective of family physicians. Furthermore, treating children with antibiotics and anesthetic comes with its own risks.

“Sadly, in the U.S., the same people who are causing harm to children by their anti-vaccine views are also pushing anti-fluoride views,” says Dickinson. “It is tragedy in the making: that people, but especially children who have no opportunity for choice, are having these harms pushed on them. It will take a long time for the outcomes to show, by which time, the perpetrators will be gone, leaving others to clean up their mess.” 

Like Calgary, Halifax Water’s CWF has been offline since April 2020 due to infrastructure issues. More alum has been needed in the water to counter the effects of climate change and achieve treatment objectives, which led to a storage issue and fluoride was cut. An additional problem is that Halifax Water neglected to tell Nova Scotia’s chief medical officer of health or the utility’s customers about the interruption. It might take years to get it back online.

Meanwhile, other communities in Canada have been discussing the pros and cons of CWF. In Regina, CWF was set to start in early 2026 but now a city councillor wants to revisit it. That prompted a recent <i>CBC Morning Edition</i> interview with Gerry Uswak, an associate professor at the University of Saskatchewan’s college of dentistry to explain the science and benefits of CWF. In Kingston, the CWF plan has been paused to consider “emerging evidence,” a reprieve some believe indicates changing attitudes. And in Montreal, after years of debate, those opposed have succeeded in shutting down CWF to the West Island.

Why is there opposition to CWF?

The list of points against CWF is long and includes protests that it a poison on par with lead, mass medication, and even a communist plot. A common objection is cost, which is generally under $1 per person per year. In a city the size of Toronto, where CWF costs $0.77 per person, that equals an estimated $1.9 million per year.

All sides agree that too much fluoride carries the risk of dental fluorosis, which can cause discolouration of tooth enamel in younger children. To prevent that, fluoride levels in Canada are highly monitored to maintain an optimal, safe level of 0.7 parts per million (0.7 milligrams per litre). 

However, a growing concern is the potential for neurocognitive effects, especially on the IQ of children. One of the key studies on this was led by Christine Till, PhD, a professor at York University’s Faculty of Health. 

“While health effects of low-level exposure to fluoride may not be definitive, the current evidence is sufficient to shift the burden of proof to showing that it is safe,” says Till. “We now have a compelling body of evidence suggesting health risks of total fluoride intake, particularly for vulnerable groups like pregnant women and young children.”

She refers to a recent meta-analysis conducted by the U.S. National Toxicology Program that examined 74 cross-sectional and prospective cohort studies. Results showed significant inverse associations between fluoride exposure and children’s IQ scores. 

“The evidence for these associations was strongest when considering fluoride exposure from drinking water at levels of 1.5 mg/L or higher, which is about twice the recommended level of 0.7 mg/L,” says Till. “This is not an adequate margin of safety. We know some people are exposed to fluoride at higher levels when you factor in all sources of fluoride intake.”

Till and colleagues expected their study would reignite the fluoride controversy because their findings went against widespread beliefs that fluoride is safe. 

“We waded into a no-go zone concerning health effects of water fluoridation, an idea long associated with conspiracy theorists and science skeptics,” says Till, adding that there are passionate views held by health professionals on both sides of the fluoride debate. “The dental community promotes water fluoridation as an effective way to reduce dental caries. You can’t blame them because it’s their job to care about teeth. On the other side, you have non-dental public health professionals concerned about fluoride’s impact on the brain. While both groups are trying to promote optimal child health, they are differentially weighing the health risks and benefits of fluoride.”

In addition to recommending that pregnant women should try to limit their fluoride intake, Till would also like to see warnings in areas with high fluoride concentrations and health promotion strategies aimed at reducing sugar consumption, reducing disparities in oral health, promoting the safe use of topical fluorides, and even providing free dental care to children. 

On the other side of the argument, an assessment of evidence claiming that CWF is associated with harm to foetal and infant cognitive development concludes: “The MIREC fluoride-IQ articles’ results should be considered unacceptable for legal and policy purposes; other water fluoridation studies and systematic reviews show no effect of fluoridation on cognition.” 

Ultimately, as Till says, public health officials need to weigh the costs and benefits of fluoride exposure, with a commitment to the best available science and consideration of vulnerable groups. 

In 2023, Health Canada asked an expert panel to provide recommendations on fluoride exposure, dental fluorosis, neurocognitive effects, and derivation of the health-based value. The panel’s final report indicates that neurocognitive effects and dental fluorosis are “the most sensitive endpoints of concern for updating the Health Canada guideline technical document on fluoride in drinking water.” The report also states that “there is not a sufficient basis at this time to recommend a specific point of departure and health-based value for neurocognitive effects.” The report concludes that: “Given the uncertainty about possible neurocognitive effects at low levels of exposure, the panel recommended the use of an uncertainty factor for database deficiency for deriving the health-based value but was unable to recommend a specific numeric uncertainty factor, leaving this decision to Health Canada.” 

What about groundwater? 

The fluoride controversy is mainly focused on treated municipal pipeline water. However, as Trish Luty, general manager of the Ontario Ground Water Association, points out, fluoride is naturally occurring in some groundwater sources in Ontario, primarily due to the dissolution of fluoride-bearing minerals in bedrock aquifers.

“While elevated levels are not widespread, certain regions with specific geological formations may have concentrations exceeding Health Canada’s guideline of 1.5 mg/L for drinking water,” says Luty. 

Heather Murphy, PhD, an associate professor at the Morwick G360 Groundwater Research Institute at the University of Guelph, agrees that harmful levels of fluoride are possible in groundwater.

“To my knowledge, it seems to be less common to find it at levels above the guideline values in Canada, but all homeowners on a private well are recommended to test for it at least once to see if it is present in elevated levels – those recommended by Health Canada and provincial health units – and then every two years after that is prudent,” says Murphy. “If (a well) is close to the guideline level, then it should be tested for more frequently, i.e., annually.”

A well should also be tested every two years if it is located in area known for fluoride contamination reported by a public health unit. To demonstrate, Murphy references the Provincial Groundwater Monitoring Network website to search and view chemistry data. 

“If testing is negative or stable after repeat testing, testing can be reduced to every five years,” says Murphy. “Fluoride levels shouldn’t fluctuate much in groundwater if naturally occurring. It would likely only change if there was a new contaminant source. It would also be prudent to test for fluoride if new mining or industrial activities were occurring nearby a homeowner’s well.”

Luty says fluoride is not included in public health testing and must be tested through a private, accredited laboratory. Private water testing can include a range of parameters based on local conditions or specific concerns, such as fluoride, nitrate and nitrite, hardness (calcium and magnesium), sodium, iron and manganese, chloride and sulfate, pH and alkalinity, arsenic, lead, and other metals. 

“While high fluoride concentrations are not common, they can be a concern in certain areas,” says Luty. “Well owners, groundwater professionals, and hydrogeologists often assess water quality and recommend treatment options if fluoride levels exceed recommended guidelines.”

For example, if your well water has levels of fluoride above 2.4 mg/L, the Eastern Ontario Health Unit suggests either installing a filter or treatment system to remove fluoride or using another source of water for drinking and preparing food. 

How much the current discussions in the fluoride debate affect the groundwater industry, if at all, remains to be seen. But the increased attention on fluoride may generate some questions from customers about their well water.