Apocalyptic visions and global conspiracies were the mainstay of Cold War tensions, fostering fears of nuclear annihilation, sudden invasions and dark deeds by spies who might live just next door. Books and movies captured the temper of this era in excruciating detail; among the most revealing — and entertaining — of these artifacts is director Stanley Kubrick’s 1964 comic masterpiece Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb. The story revolves around a general who launches a bombing strike against the Soviet Union in order to initiate a Third World War. When asked why he did it, the officer responds with a question: “Have you ever heard of a thing called fluoridation, fluoridation of water?” he asks. “Do you realize that fluoridation is the most monstrously conceived and dangerous Communist plot we have ever had to face?”

Today talk of Communist plots has faded but fluoridation continues to spark lively public debate. Across North America, councillors in dozens of communities large and small have rejected this measure in recent years. In the past year alone three Ontario communities: Cornwall, Parry Sound and Kingsville, took this step. An even more dramatic rejection came in 2011, when Calgary removed fluoride from drinking water it provides to more than a million residents.     

The roots of controversy were sown in the 1800s as scientists first began unravelling the properties of fluorine, which is the most reactive non-metal element. Difficult to isolate and highly corrosive, fluorine rushes to bond with nearby neighbours. It commonly appears in apatite, a calcium-phosphate mineral that readily welcomes fluoride into its lattice to become a variety known as fluorapatite. 

Bones and teeth, the toughest structures of our own physiology, likewise contain forms of apatite that are equally eager to incorporate fluorine into their makeup.  Too much of this can be a bad thing: early investigators were drawn into the study of diseases afflicting populations where the local drinking water naturally contained high levels of this element. The effects included serious skeletal deformities and blackened, mottled teeth, symptoms that can still be found in many parts of the developing world.

Yet these same affected populations also showed far lower levels of tooth decay, the breakdown of tooth enamel. This possible link between fluoride and the apatite in the enamel quickly spawned speculation that this agent could protect teeth from this growing health problem. A widespread scourge of dental caries — the painful divots known as cavities — heralded the arrival of the Industrial Revolution in the early 1800s. Today this trend is credited to the rising proportion of sugar in people’s diets, which promoted the growth of bacteria that consume enamel. In the 1870s, however, popular magazines in Europe were discussing the prospect that the cause was a lack of fluorine, which might be overcome by ingesting a powder made up of the mineral fluorspar. 

At the time the concept of public health was in its infancy and it would be decades before cities mounted formal strategies to fight disease on a large scale. The most successful of these measures was undoubtedly the chemical treatment of urban water supplies with antiseptic agents like chlorine, which almost immediately improved the quality of life for millions of people. Montreal, which prior to the First World War had rates of cholera and typhoid on the same scale as the slums of Calcutta, stopped these blights in their tracks with the opening of its first water treatment plant in 1918. 

The notion that fluoride could have a similarly dramatic impact on dental health began to take hold in the 1930s. The challenge revolved around arriving at the right amount to include in the water supply, since it was already well known that too high a level would be detrimental. Studies in a variety of communities with naturally fluoridated drinking water pointed to a sweet spot at around one part per million of dissolved fluoride: high enough to significantly reduce the prevalence of tooth decay in the population but low enough to avoid generating abnormalities such as blackened teeth.  

Since the first steps in water fluoridation were taken by pioneering municipal officials in Grand Rapids, Michigan and Brantford, Ont. in 1945, this figure of one parts per million has remained the gold standard for the procedure. These first steps were carefully conducted in concert with local dentists, who provided detailed reports on how their patients’ teeth were faring; the findings confirmed a decline in the number of cavities being found, a result that was persuasive enough to entice municipalities across North America to embrace fluoridation in the 1950s. 
Then things got interesting. Dental agencies championed fluoridation while others were offended by it.  Books with titles such as The Drama of Fluorine: Arch Enemy of Mankind fuelled popular protests that gave political leaders pause when it came to voting on water treatment. Scientific assurances were regularly drowned out by accusations — largely undocumented — linking fluoridation to everything from heart disease and cancer to mental disorders, crime and mind control. The full sweep of this story has been captured in unrivalled detail by Allan Freeze, an emeritus engineering professor from the University of British Columbia and Jay Lehr, chief scientist of EarthWater Global, a New York-based groundwater management firm. Together they wrote a book, The Fluoride Wars, published in 2009, which reads like a multi-generational political thriller, outlining the good, the bad and the downright ugly in the decades-long struggle to determine what fluoride can do for or to human health.

Fluoride ions (F–) replace hydroxyl groups (OH–) in hydroxyapatite to form fluorapatite in the tooth enamel. A portion of the apatite crystal lattice is depicted showing the replacement of hydroxide for fluoride.

Fluoride ions (F–) replace hydroxyl groups (OH–) in hydroxyapatite to form fluorapatite in the tooth enamel. A portion of the apatite crystal lattice is depicted showing the replacement of hydroxide for fluoride.

Advocates celebrate the decline in the prevalence of cavities in teeth from 1950 to 2000, which dropped to a fraction of what they had been at the beginning of the century. Nevertheless, opponents of fluoridation pointed out that this decline happened everywhere in the developed world, whether local water was fluoridated or not. No one, it appears, could find any definite cause for this trend.  

That stalemate persists to this day. Extensive websites now challenge the scientific community, who for their part are continuing to pin down the chemical mechanisms that enable fluoride to protect teeth. Given that many of us might not even know if our own tap water is fluoridated, this lingering dispute may come as a surprise, especially since definitive bodies such as the Canadian Dental Association officially assert the safety and effectiveness of this public health measure. 

Even more surprising, then, may be the disparity within Canada when it comes to fluoridation. According to a 2009 overview in the Journal of the Canadian Dental Association, only about 45 percent of Canadians have access to fluoridated water. More specifically, in Ontario that figure is 75 percent, while in Quebec it is just over six percent and in British Columbia less than four percent. Since Canadians as a whole generally enjoy some of the best oral health on the planet, critics maintain that fluoridated water cannot take the credit. This argument suggests that most of us get fluoride from toothpaste or applied directly to our teeth by a dentist, so that anything found in our water is superfluous or perhaps even increasing our exposure to dangerous levels. 

Tim Caulfield is all too familiar with this line of reasoning. The University of Alberta law professor has spent much of his career dissecting the way in which popular opinion can shape the perception of science and the way science interacts with society. Most recently he has focused on the inordinate influence of celebrity culture in spreading outright misperceptions that are championed by prominent personalities. He took on this mechanism for the spread of pseudoscience in a 2015 book, Is Gwyneth Paltrow Wrong About Everything?, which won the Science in Society Book Award from the Canadian Science Writers’ Association. “There’s always a little bit of a scientific discussion to be had,” he says about the debate over fluoridation. “One of the problems for the scientific community is that they can’t use definitive language, because that’s the way science is. ” 

Caulfield adds that the scientific community does not do itself any favours when it withdraws from such conflict, however uncomfortable it might be for members to wade into such strident disagreements. “We need to not shy away from calling things unscientific,” he says. “We don’t do it in physics or engineering but we seem to be very cautious when we’re talking about different perspectives in the realm of health. We need to be more forthright and honest about what the science really says and when something’s bunk we need to call it bunk.” 
Unfortunately, researchers do appear to have shied away and the formal literature on fluoridation is less comprehensive than even its advocates would prefer. In a 1999 review of the benefits and risks of fluoridation conducted for the Ontario Ministry of Health, University of Toronto dentistry researcher David Locker noted the limited volume of evidence on both sides of this question. “The main limitations of current research on the effectiveness of water fluoridation are its exclusion of adults and elderly and failure to consider quality of life outcomes,” he wrote. “Since water fluoridation is a total population strategy, its benefits to the population as a whole need to be documented.” 

There is a lack of information on what happens to children’s teeth when water fluoridation is banned.

There is a lack of information on what happens to children’s teeth when water fluoridation is banned. 

Opponents of fluoridation have taken advantage of the absence of such information but it can be exceedingly difficult to gather and there are few researchers doing so. Lindsay McLaren finds herself in just that position at the University of Calgary, where the Canadian Institutes of Health Research, the Public Health Agency of Canada and Alberta Innovates-Health Solutions have sponsored her in an Applied Public Health Chair devoted to studying the cessation of fluoridation in Canada.

“I was actually surprised at how limited the research was on what happens when you stop fluoridation,” McLaren says, pointing to her own opportunity to contribute by following up on the City of Calgary’s 2011 decision to stop fluoridating its water supply. She was able to take advantage of two sets of data collected on caries in elementary school children in Edmonton and Calgary. One survey was from 2004-05 and the other was in 2013-14, so the information straddles Calgary’s move on fluoridation. The results were published earlier this year in Community Dentistry and Oral Epidemiology. “We found that dental decay increased over that time in both cities but it increased to a greater extent in Calgary — where fluoridation was stopped — than Edmonton, where fluoridation remains in place,” says McLaren. A great deal of popular media attention pounced on the idea that Calgary’s municipal council had been putting that city’s kids’ teeth at risk since 2011, but she is quick to point out that such a sweeping observation is hard to extract from the available figures. “We were not able to answer the question, ‘what has happened since cessation?’ We were able to answer the question, ‘what has happened between 2004-05 and 2013-14?’ when cessation happened in one community and not the other.”

Such crucial distinctions are essential to moving toward the deeper understanding requested by Locker but McLaren has found few good examples of such research. “There’s just really limited information on what happens to kids’ teeth when cessation occurs,” she says. 
Nor is there much information on the curious observation that more cavities were also being reported in a city that still fluoridates its water, which raises questions about whether other factors in our 21st century lifestyle — including dietary changes and the inability of many individuals to afford regular dental care — might be eclipsing the century of gains that have been attributed to fluoridation. So long as those questions are not approached in a rigorous way, says Caulfield, they will remain a playground for speculation by anyone who wants to piece together a story about chemicals in our environment. “The scientific community needs to be more engaged, they need to become part of the conversation,” he says. “I don’t think it’s going to change people’s minds.” tomorrow but I do think over the long term science wins.”