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The Dose Transcript for November 28, 2024

Host: Dr. Brian Goldman

BRIAN GOLDMAN: Hi, I'm Dr. Brian Goldman. Welcome to The Dose. There is a lot of talk in the United States these days about removing fluoride from community water supplies. Well, it's also happening in Canada. Recently, officials decided to end water fluoridation on the island of Montreal. While there's strong research supporting the fluoridation of water, there's lots of public debate over safety and health concerns. So this week we're asking: What should I know about fluoridated drinking water? Hi Gerry, welcome to The Dose.

GERRY USWAK: Thank you for having me.

BRIAN GOLDMAN: Is the water fluoridated in your community?

GERRY USWAK: It is. There's no debate. But I live in La Ronge, which is a small northern Saskatchewan town. So there's not a lot of water fluoridation debate here.

BRIAN GOLDMAN: There's a lot of controversy about this and certainly a lot of discussion coming from the United States, which is why we wanted to talk to you. But before we begin, can you give us a hi, my name is? Tell us what you do and where you do it.

GERRY USWAK: Hi, my name is Dr. Gerry Uswak. I am a dental public health dentist and I'm director of the Bachelor of Science program in Dental Therapy at the University of Saskatchewan College of Dentistry.

BRIAN GOLDMAN: Explain what fluoride is and what it does to teeth.

GERRY USWAK: Fluoride is a naturally occurring mineral, right. It's found in nature, it's found in water, it's found in the soil. It prevents dental decay. It does three things. The cavity process is, when we eat sugars and other fermentable carbohydrates, the bacteria in our mouths, some of them love the sugar as much as we do, and when they metabolize it, they produce acid. And that acid is what dissolves the mineral, the enamel of the tooth, and that is, you know, a bacterially mediated cavity process. So what fluoride does is in the presence of acid demineralization, so calcium and phosphate are being dissolved and going from the enamel into saliva solution, it stops that. It actually drives calcium and phosphate back into the tooth, stopping the demineralization. So it's promoting remineralization. And not only does calcium and phosphate get redeposited back into the enamel, fluoride ion is incorporated into the enamel, making fluorapatite, which is more acid resistant and a stronger form of the enamel.

BRIAN GOLDMAN: Are the effects of fluoride in the mouth confined to the teeth or does it do anything else to the oral cavity?

GERRY USWAK: No, it affects its actions at the tooth plaque biofilm interface. So when bacteria are congregated on your teeth processing sugars, fluoride is in saliva. That is the body's reservoir for fluoride. And then it is expressed and it remineralizes the tooth right there. It's a topical effect and it's not a systemic effect.

BRIAN GOLDMAN: What is the history of how the water supply in Canada and elsewhere got fluoridated?

GERRY USWAK: Back in 1901, a dentist in Colorado discovered two things about his patients. One, they didn't have the same level of decay that the rest of the population had, and they had this strange brown stain on their teeth. And then over 30 years, it was eventually discovered that the lack of decay was due to fluoride, and so was the staining. So that 30-year period was the initial research into the effects of fluoride. And then the U.S. Public Health Service did a fluoridation survey of naturally fluoridated water supplies to find out the ambient sort of average levels, and that's where we got the one part per million that historically has been utilized. That's where the U.S. Public Health Service found the best bang for the buck in preventing decay with minimal aesthetic problems from, from the fluoride. So what happened in 1945, because of the 30 years of seeing the benefits in reducing decay of fluoride, it was decided to do community-based trials. So Kingston, Newburgh, New York in 1945, and Brantford, Ontario was included in there. So technically we started fluoridating at the same time the U.S. did. And then over time, because this is a municipal decision, different cities come online at different times. Like originally, I'm from Winnipeg, so they started fluoridating in 1956.

BRIAN GOLDMAN: So today, how widespread is the fluoridation of water currently in Canada?

GERRY USWAK: I mean, we're pushing 40%. It's kind of the opposite of what's happening in America, where over 70% of municipal water systems are fluoridated. Here in Canada, because we don't have the similar population and we have reduced scale of major centres, so we're about 40%.

BRIAN GOLDMAN: Is that because the drinking water is more naturally fluoridated in many parts of Canada?

GERRY USWAK: No. We don't have very many spots. So there...Around the world there are fluoride belts below what we fluoridate at and then others at five parts per million and higher. There are other places that are up to all 15 parts per million. But in Canada, there are some-- there are places that have a higher fluoride concentration naturally than what we fluoridate at [at] .7 parts per million. But the vast majority of the population of Canada is not getting fluoride higher than what we fluoridate at.

BRIAN GOLDMAN: Is bottled water fluoridated?

GERRY USWAK: It depends. They will list fluoride on the ingredients, so it all depends on what is the source of that water.

BRIAN GOLDMAN: So if the bottled water comes from a fluoridated water source, then the bottled water is fluoridated. And if not, then it isn't.

GERRY USWAK: Right. And then there's other waters that are filtered or, heh, re-bottled tap water.

BRIAN GOLDMAN: Is there an obligation to put the fluoride level contained in the bottled water on the label?

GERRY USWAK: It is, there, along with the other trace minerals, yes.

BRIAN GOLDMAN: Okay, let's start to talk about some of the benefits. I've got a disclaimer. I'm old enough... you're not going to like this. When I went to the dentist for the first time, I had a mouth full of cavities. So clearly, I predated fluoridated water. I also know that as soon as the water supply where I live was fluoridated, kids simply stopped getting cavities, like to a large extent. So what do we know about the research benefits of fluoridating community water supplies?

GERRY USWAK: When cavities were endemic, right, when we were suffering before fluoridation, once patients were followed... I mean, that's where we get the 60% decrease in decay because that's where, through these trials, we saw the mega reduction in decay rates, especially when children grew up in fully fluoridated settings from when the teeth are developing.

BRIAN GOLDMAN: You're a dentist, you're a dental epidemiologist. There's no question the fluoridation of water changed the practice of dentistry, didn't it?

GERRY USWAK: Yeah, absolutely. Not only does the fluoride reduce the development of decay, it also reduces the extent and severity of that decay. The cavities are not as spread throughout the tooth. The fluoride confines the decay, it prevents a significant amount of decay. It also minimizes the destruction from that decay.

BRIAN GOLDMAN: Now, I may be wrong about the timing, but, you know, I've been following this for a long time. My sense is that around 10 or 15 years ago, we started getting stories in the media about too much fluoride being bad for you. So what is the harm?

GERRY USWAK: I go back even further than that, 30-40 years ago when... the minute I started doing my specialty training. Part of it is the politics of community water fluoridation, and, and the various claims made over history. And in a lot of ways, those claims were Chicken Little or the sky is falling or crying wolf, later to be disproved. Like a number of studies found an association between hip fracture and fluoride. And they just do this at a geographic level. Take community A, community B, or whatever series, look at the number of hip fractures in each place and say, Well, it's higher in fluoride. But that's an association, and it's never been taken further to find causation. And that's, and that's part of what we're talking about here is causation. You know, there is no evidence that fluoride causes any of these systemic diseases or conditions. And the same thing can be said for reduction in intellectual output, is that, well, that's an association if fluoride is found there. But even the authors say there needs to be more research to find if there is a causative relationship here.

BRIAN GOLDMAN: Those are false claims. We also know too much fluoride can do things to teeth and to skeletal bones. What can you tell us about that?

GERRY USWAK: If we have water fluoridation, say, at around 12 parts per million, you can get deformation bones. And that's what skeletal fluorosis is. It's from natural groundwater or contaminated groundwater from industry. You know, regardless what the source is, but at that 12 parts per million, you start to see deformation of bone. We fluoridate at .7 parts per million. It's not extensive. We're not seeing skeletal fluorosis in Canada and the United States, so that-- This occurs in the fluoride belts throughout the world, where there's a higher ambient natural fluoride level than elsewhere.

BRIAN GOLDMAN: What about dental fluorosis?

GERRY USWAK: Dental fluorosis exists, and it's an aesthetic problem. If we put things into context, very mild/mild/approaching moderate, typically looks like little white spots, lines on your chewing teeth, like your molars. It's like a snow cap on a mountain on the cusp. It's an aesthetic problem. It is a sign that that individual is getting too much fluoride, but it's not causing a deleterious effect. So we're paying attention. And if we look at the Canadian Health Measures Survey that was done on the health of Canadians coast to coast, [it] included a dental examination, and they could not find enough moderate level fluorosis to even be statistically significant in the CHMS. So I'm not saying that it's not a problem, but the advanced forms of fluorosis is not significant based on the CHMS findings.

BRIAN GOLDMAN: What's the CHMS?

GERRY USWAK: Oh, the Canadian Health Measures Survey that was done 2007 to 2009. It included health questionnaires as well as examinations. So it was a physical exam to get a sense of the health of Canadians. And it was redone last year. There will be a, you know, the second generation of stats are going to be assessed. Prior to 2007, 2009 when the CHMS was conducted, the last grand scale epidemiologic study of the oral health of Canadians was probably a generation 30 years prior. And what we found was, is again, that the prevalence of decay hasn't changed. So, you know, Canadians 19 years and older, about 95% of them have had experience with at least one cavity in their permanent tooth. That's pretty much the same as it was 30 years ago. And as I said before, the significant difference is the extent and severity of that decay, right. The number of surfaces, tooth surfaces involved is far less than it was 30 years ago.

BRIAN GOLDMAN: Is it biologically plausible that fluoridating water, exposure to fluoridated water at some level might cause intellectual deficits?

GERRY USWAK: Yeah, sure. I'm not going to discount that. Whilst I'm here suggesting that community water fluoridation still is a valuable preventive endeavor, I'm also not going to say we're going to ignore the science. I think some of these papers have been called to task for not very robust scientific designs. So I'm all for, you know, replicating these studies or taking them to the next level to try and find if there is a causal relationship here or if it just is an association.

BRIAN GOLDMAN: What about the risk of a particular kind of bone cancer called osteosarcoma in boys?

GERRY USWAK: Yep. That happened, right? Because there was a blip in osteosarcoma prevalence as they compared decades. Couldn't be explained. And then there was the Harvard, part one of the Harvard research that found that there was a statistically significant increase in osteosarcoma in young men above the normal rates. But again, that was for fluoridation at two parts per million and higher. And the researchers said, we can't infer anything but an association here and more research needs to be done. And then subsequently, part two of that study did not find any causation. So no one's going to ignore that. But it's a matter of doing more research to see. You know, when you control for a variety of things, does that controlling of variables still show that there's an association? Does it show that -- can we show that there's causation or was it just spurious?

BRIAN GOLDMAN: Communities like Calgary have actually removed fluoride from their water supply. We've heard the same proposal on the island of Montreal. What does the research show about how oral health, for instance, has changed in places like Calgary?

GERRY USWAK: If we do look, and there is research being done by researchers at University of Alberta and University of Calgary, looking at the difference in decay rates between Edmonton being fluoridated and Calgary being non-fluoridated, and the series of publications that resulted from that, show statistically significant differences that people who live in Edmonton with fluoridated water have better oral health, lower decay. Ultimately, it's a municipal decision. It's going to come down to mayor and council wherever this is being debated. Are we putting fluoride in for the first time? Are we starting it back up? Are we taking it out? And ultimately, we have to respect the democratic process for when a municipality chooses to fluoridate or not to fluoridate.

BRIAN GOLDMAN: So how do people who live in rural and remote communities and who rely on non-fluoridated water get their supply of fluoride?

GERRY USWAK: Hopefully they brush their teeth with a fluoridated toothpaste, and hopefully they see their oral health-care provider once or twice a year, depending on what sort of risk for disease has been established. And they can get topical fluoride applications once or twice a year and then brush their teeth with fluoride toothpaste. But there's no guarantee that that alone is going to provide enough fluoride to reduce the development of new decay or reduce the extent and severity. It may or it may not. There's a huge socioeconomic status gradient with respect to community water fluoridation and the use of topical fluorides.

BRIAN GOLDMAN: Can you say more about that?

GERRY USWAK: We have acknowledged over time that we're not seeing 60% reduction in decay, as happened in the fluoride trials in 1945. You know, we have settled on about 25% reduction in decay, all things considered equal across populations. However, those people in the population that face access to care barriers, they're the ones that experience the bulk of the disease. So they are reaping a higher benefit from community water fluoridation versus 25% across the population, all things considered equal. So, you know, we have to decide, is government benevolent enough to maintain community water fluoridation, right, to have a bigger impact on those who suffer the majority of disease, and to have a smaller impact [indistinct] historically across the general population.

BRIAN GOLDMAN: There are people who are going to be listening to this podcast, listening to you, who live in communities where a decision will be made by the municipal government to remove fluoride from the community water supply. Is there a surefire way for people who live in those communities to find a substitute supply of fluoride that will be effective in reducing tooth decay in young kids that is commensurate or equivalent somehow to community fluoridation of water?

GERRY USWAK: Not equivalent, no. Because everything else requires compliance, right. The beauty of water fluoridation is all you have to do is drink it.

BRIAN GOLDMAN: All you have to do is drink the water.

GERRY USWAK: That's right. That's-- Drink the water to reap the benefits. Everything else requires participation. Either you need to go to a professional to have it applied, or a parent has to be trained. I mean, this is all eminently doable, but in the grand scheme of things, it's not going to have a similar effect. And it's not going to have a replacement effect necessarily if we take fluoride out of the water.

BRIAN GOLDMAN: Speaking as somebody whose early childhood predated the fluoridation of water where I was living at the time, I can tell you I would much rather have not had a mouth full of dental caries. So perhaps I'm showing my bias there. But if the U.S. federal government takes steps to reduce or hold sway over the fluoridation of water in communities in the United States, it will be interesting as a natural experiment to see what happens to levels of tooth decay in the United States versus a country like Canada. And Gerry, I want to thank you for coming on The Dose to talk about these issues.

GERRY USWAK: Absolutely. My pleasure.

BRIAN GOLDMAN: Dr. Gerry Uswak is associate professor and director of the Bachelor of Science degree in Dental Therapy program at the University of Saskatchewan. Here's your dose of smart advice. Fluoride binds to the outer enamel of your teeth. It works by making teeth stronger and more resistant to decay. The U.S. Centers for Disease Control considers fluoridating the water supply in the U.S. as one of the ten greatest public health achievements of the 20th century. Fluoridated water and fluoride toothpaste, or fluoride topical applications by your dental provider, work in tandem to prevent cavities. The big advantage of community fluoridated water is that you don't have to do anything other than consume tap water to get the benefit. Too much fluoride while teeth are growing can cause dental fluorosis, which causes the outer enamel layer to have white flecks, spots or lines. In general, this only happens in young kids as their permanent teeth come in. Older children, teens and adults do not get dental fluorosis. Excess consumption of fluoride can also cause skeletal fluorosis or abnormal hardening of bones, as well as calcification of tendons and ligaments, and bone deformities. The World Health Organization says the prevalence of dental and skeletal fluorosis is not entirely clear, but it adds that excessive fluoride concentrations in drinking water have caused tens of millions of dental and skeletal fluorosis cases worldwide over a range of years. Some studies have suggested a possible association between high levels of fluoride in drinking water and osteosarcoma, a rare type of bone cancer in boys under the age of 19. But no clear association has been established, and the evidence for a causal link has not been confirmed. The Canadian Cancer Society believes that adding fluoride to water is unlikely to increase the risk of cancer in humans. The International Agency for Research on Cancer has concluded that there is no evidence of a link between cancer rates and fluoridated water. There is an association between fluoride and lower IQ, but studies have not demonstrated a cause-and-effect link. The Public Health Agency of Canada says that as of 2022, roughly 14.4 million Canadians, just under 40% of the population, live in communities with fluoridated water. In Canada, the optimal level of fluoride in the water is 0.7 parts per million. That level assumes that people also get fluoride from toothpaste or mouth rinse. Bottled water may or may not contain fluoride depending on the source. Bottled water labelled as deionized, purified, demineralized or distilled contains, at most, trace amounts of fluoride, unless listed on the label as an added ingredient. Ready-to-feed infant formula contains little fluoride and does not cause dental fluorosis. Powdered or liquid concentrated formula preparations that are mixed with fluoridated water, may increase the chance of dental fluorosis. Compared to community fluoridated water, water from a private well may have more or less fluoride. If you want to know how much, check with your local drinking water authorities about getting it tested. If you have topics you'd like discussed or questions answered, our email address is thedose@cbc.ca. If you liked this episode, please give us a rating and review wherever you get your podcasts. This edition of The Dose was produced by Sameer Chhabra. Our senior producer is Colleen Ross. The Dose wants you to be better informed about your health. If you're looking for medical advice, see your health-care provider. I'm Dr. Brian Goldman. Until your next dose.

What should I know about fluoridated drinking water? - Transcript

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