Should Canadian communities continue to fluoridate water?

Water fluoridation has been hailed as one of the top ten great public health achievements of the 20th century by the U.S. Centers for Disease Control. Yet, in the past five years, dozens of Canadian communities have stopped adding fluoride to the municipal water supply, including Calgary, Waterloo, Windsor and Saint John.

Inspired by online campaigns like Canadians Opposed to Fluoridation, vocal community groups say new science shows fluoride isn’t as effective as previously thought, and that fluoride causes harms.

Health Canada reported in 2010 that around 45% of Canadians lived in a community with fluoridated water. The federal agency hasn’t updated this number since then, according to spokesperson Sean Upton, but one anti-fluoride group claims that in 2015, only around 30% of Canadians are exposed to fluoridated water.

“We’re hearing that it’s poison and people are saying ‘We’re being medicated and we’re not being given a choice,’” says Dennis Radbourne, a councillor in Fairview, Alberta, where the council has scheduled a plebiscite on the issue this fall.

Dick Ito, a professor of community dentistry at the University of Toronto, takes issue with that line of argument. “Fluoride is natural. It’s in all waters,” he explains. “What we’re doing is optimizing the level to a level where it can prevent caries [tooth decay]….we don’t think it’s any different from fortifying salt with iodine or cereals with folate to prevent other diseases.”

Ito is not alone. More than 90 major organizations support adding fluoride to water to reduce the incidence of cavities, including Health Canada, the Canadian Dental Association, the Canadian Medical Association and the Canadian Association of Public Health Dentistry.

Why is water fluoridated?

Water fluoridation has a long history. In the early 1900s, a young dentist moved to Colorado and was perplexed by the prominent brown stains on many of his patients’ teeth. Patients with the condition almost never had cavities. Though it took decades to discover, high levels of naturally occurring fluoride in the water was eventually found to be behind the brown stains, and the cavity-free teeth.

Fluoride is a mineral that binds to the enamel of teeth, thereby strengthening the enamel and preventing bacteria from decaying it. In high concentrations, fluoride can cause noticeable dental fluorosis – the brown staining first reported in Colorado, which, though harmless, may be a cosmetic issue.

In 1945, Brantford, Ontario became the first community in Canada to fluoridate its water. A study that followed cavity rates over the next 11 years found that children in Brantford had 35% fewer cavities when compared to Sarnia, Ontario, which didn’t have fluoridated water. Numerous studies and reviews conducted since then have found that the addition of fluoride to water decreases the prevalence of tooth decay. The most recent review – just published last month by the Cochrane Oral Health Group – concluded that water fluoridation results, on average, in a 35% reduction in decayed, missing or filled baby teeth and a 26% reduction in these same indicators for permanent teeth. However, the reviewers pointed out that because few high quality studies have been published since 1975, “the applicability of the results to current lifestyles is unclear.”

“If we are able to minimize caries, people can keep their teeth for life,” says Richard Musto, the medical officer of health for the Calgary Zone in Alberta. “For older folks who have lost their teeth, nutrition becomes a real challenge. Dental caries are painful. They’re the number one cause for elective general anesthetic surgery in pediatric hospitals.”

Fluoridation is a highly cost-effective intervention, public health experts argue. According to Radbourne, the biggest cost of fluoridation is the testing of fluoride levels, which amounts to $8,000 a year for his community of Fairview. The cost to individuals and the public health system of filling cavities and extracting teeth are well beyond the cost of fluoridating water. One analysis looking at costs of tooth decay in Quebec found that even if water fluoridation only reduces tooth decay by 1%, it’s still cost-effective –the cost of fluoridating the water is much less than the cost of treating 1% more cavities.

Because low-income children and adults have higher incidences of cavities, water fluoridation is also seen as a way to reduce health disparities. “It benefits everybody who drinks the water, regardless if they have access to dental care or a healthy diet,” explains Musto.

Benefits of fluoridated water may be much smaller today compared to the past

Those who oppose the addition of fluoride in water argue that the impact of fluoride on cavities is not as great as it once was. Access to fluoride-containing toothpaste, free dental care for people in need and the promotion of tooth brushing and flossing in schools have all contributed to improved dental health – thus fluoridated water is no longer required, the argument goes.

The argument is not without merit. The rate of tooth decay has been declining dramatically, both in countries that have high levels of water fluoridation and those that do not.

One way to understand the benefit of fluoride today is to look at what happens in communities that have recently ended water fluoridation programs. The evidence here doesn’t tell us much. The Cochrane review only found one study on fluoride cessation that met its quality standards, and that study didn’t show that the removal of fluoride increased cavities in children. The results of the other studies not included in the Cochrane review vary, with some finding that cavities continue to drop after the removal of fluoride, some finding cavity rates remain the same and others concluding cavity rates go up.

Musto explains that removing fluoride doesn’t lead to overall decreases in oral health in places where other interventions to increase dental health are in place and awareness of dental health measures are high. But, he says, alternatives to water fluoridation – like programs that promote routine brushing with fluoridated toothpaste – “are more expensive” and may not reach the most marginalized groups in a society.

A study examining the effects of the end of fluoridation in Calgary is currently underway but results aren’t expected until later this year.

Are there any harms to fluoridated water?

Just as studies have examined the effectiveness of fluoride to prevent tooth decay, so too have many researchers looked at whether the low levels of fluoride naturally present in or added to drinking water cause any harms. (Health Canada recommends that fluoride be added to water at a concentration of 0.7 parts per million.) Many reviews have concluded that there is no evidence to show that the recommended levels of fluoride pose any harm.

The only proven undesirable side effect of optimally fluoridated water is dental fluorosis, which poses no health threat, only an aesthetic concern. (Exposure to fluoride in toothpaste can also cause fluorosis.) According to Health Canada, rates of moderate or severe dental fluorosis are too low to measure in this country. Mild dental fluorosis is found in about 16% of children. In most cases, this mild fluorosis is not even noticed, says Ito. “It requires someone who is trained to even see it. It’s not an aesthetic concern,” he says.

Those who advocate against fluoride point to one-off studies that show people who live in fluoridated water communities may have an elevated risk of everything from cancer to a lowered IQ. But, says Musto, studies that have found links to potential harms “just aren’t replicated.”

For example, while three human studies have found an “association” between rates of osteosarcoma (a very rare type of bone cancer) and fluoridation exposures, the majority of studies haven’t found a link.

Associations are highly problematic, explains Dr. Victor Kutcher, president of the Ontario Dental Association. Elevated rates of a poor health outcome in a community with fluoridated water doesn’t mean that fluoride is the cause, he says. “Malaria is prevalent in countries where many children don’t wear shoes,” he explains, but that doesn’t mean going bare foot increases one’s risk of malaria.

Robert Dickson, a physician in Calgary opposed to fluoridated water, agrees that “undisputed and undeniable evidence” that fluoridated water causes harm doesn’t exist. He argues, however, that not enough high-quality studies have been conducted on the safety of fluoride, and therefore the mineral shouldn’t be added to water.

Who should decide whether fluoride is added to water?

One of the key arguments made by people who don’t want fluoride in the water is that they should be able to choose, as individuals, if they want to consume fluoride or not.

As Marilyn Hafichuk, a spokesperson for the anti-fluoride group Fluoride Free Lethbridge, explains, “if fluoride is in the water you have no choice but to take it.”

Hardy Limeback, former head of the Department of Preventive Dentistry for the University of Toronto is another rare voice of dissent within a health care community that overwhelmingly supports water fluoridation. Since the benefit of fluoride is largely from the fluoride touching the teeth (not so much from swallowing it), he explains that if fluoride is removed from water, those who want fluoride can still access it in toothpaste, while those who don’t feel they need fluoride can choose to avoid it.

In a report on the ethics of water fluoridation, the Nuffield Council on Bioethics tackled this question of consent. It concluded that the addition of fluoride to water with the aim of improving public health is ethical so long as the decision is made through “democratic decision-making procedures.”

Indeed, across the country, public consultations on the addition of fluoride to the water continue. Elected councillors listen to the arguments of community members and provincial and regional public health experts. Councillors then vote for or against water fluoridation and may invite residents to vote as well.

But some health experts question whether municipal councillors and members of the public are informed enough to make decisions about fluoride. Kutcher points out that most people aren’t able to recognize the flaws in studies that have found potential problems with fluoride.

Another problem that Kutcher sees with fluoridated water decisions being made at the community level is that those opposed to fluoride are vocal about it, while those who agree with fluoride are not as passionate. “Politicians listen to the squeaky wheel,” he says.

As Radbourne says, when it comes to fluoride in the water, “the silent majority remains silent.”

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