Recently, the #yegvote twitter feed has been occupied with a lot of discussion about water fluoridation, particularly from mayoral candidate Curtis Penner (including him tweeting a bibliography of 70 consecutive journal articles early Thursday morning). As has been pointed out, a lot of the twitter debate has devolved into personal attacks on both sides, but the question of water fluoridation is important and worth discussing on its merits alone.
First of all, some fun fluoridation facts!
- Low concentrations of fluoride in your mouth reduces the rate at which your enamel breaks down.
- Fluoride is often naturally present in water all over the world in different concentrations, and about 5% of the world has fluoride added to the water supply at low concentrations (including Edmonton).
- Different studies have shown that the presence of fluoride in water can reduce cavities by between 27 and 40% relative to regular brushing.
The ideal concentration for fluoride in water appears to be somewhere between 0.5-1.0 milligrams per liter. This is lower than the natural levels found in lots of communities, and in many parts of the world fluoride concentrations are reduced or even eliminated before being pumped into municipal water supplies.
Mr. Penner’s platform for mayor includes a lengthy paragraph against water fluoridation. The first argument references the Material Safety Data Sheet (MSDS) for the chemical that’s being used in Edmonton to add fluoride to the water, hydrofluosilicic acid. His claim appears to be that as this chemical is listed as corrosive and dangerously reactive, we shouldn’t have anything to do with it. This is at best a red herring, and not an argument at all—at the high concentrations that the chemical is stored, very nearly anything is poisonous. We add chlorine to our water supply explicitly to kill living organisms, and its MSDS warnings are even more severe than fluoride. This isn’t to say that the concentrated version of the chemical is ok to drink, but the final product in our taps is millions of times less concentrated than the solution the data sheet refers to.
Dropping evil-sounding chemical names and referring to alarming MSDS data sheets can’t form an argument alone. People regularly consume citric acid and acetic acid, whose MSDS data sheets name them as flammable and corrosive and include pages of toxicity warnings, but we enjoy them as orange juice and vinegar. The fact of the matter is that data sheets have to cover all possibilities and naturally make anything sound evil – even the data sheet for plain old boring water has lethal dosage information.
Mr. Penner then goes on to reference this Harvard meta-analysis on the effects of fluoride on children. His claim is that the study indicates that “children who do not drink fluoride have a 20% better chance of having high intelligence, whereas those who do drink fluoride have a 9% better chance of developing mental retardation.” Oddly enough, the words “mental retardation” and the figure “20%” don’t show up in the journal article at all. In fact, they write instead that their “results support the possibility of adverse effects of fluoride exposures on children’s neurodevelopment.” Their major finding, actually, is that children who had “high exposure” to fluoride had an IQ that was 0.45 points lower than reference children.
What constituted “high exposure” in the Harvard study? High concentrations ranged from about 3-12 mg/L. Their reference points—the points the study considered not exposed to fluoride—were between 0.34-2.35 mg/L. In fact, some of the reference healthy populations were drinking water that was two to three times more fluoridated than what would ever be allowed in Edmonton’s water. An overwhelming majority of the over 70 studies tweeted by Mr. Penner that supposedly support his position deal with high concentrations of naturally-occurring fluoride in India or China, not low concentrations carefully monitored in Canada. So while it most likely is true that high concentrations of fluoride can cause adverse effects, it is far more likely that increasing your intake of any substance by a factor of 5 to 10 over what scientists recommend would be similarly poisonous.
It has also been pointed out that Calgary stopped water fluoridation in 2011. This is true – and already has dentists raising alarms about increases in cavities (and don’t forget, dentists get less work if people have fewer cavities. They must be really concerned…).
With studies showing the positive effects of low concentrations of fluoride, and other studies showing adverse effects only at levels significantly higher than Edmonton’s, the scientific argument for those opposing the current fluoride program doesn’t seem that strong. The remaining argument is one of policy – is it morally acceptable to add a substance to the water with the goal of treating an entire population?