Tuesday, July 30, 2013

In Defense of Fluoride

Recently, the #yegvote twitter feed has been occupied with a lot of discussion about water fluoridation, particularly from and against 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,
  • about 5% of the world's population has fluoride added to the water supply at low concentrations (including Edmonton), and
  • 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, with the first argument referencing the Material Safety Data Sheet for the chemical that's being used in Edmonton, hydrofluosilicic acid. His claim appears to be that since 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 in and ofitself. 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 term "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 was0.45 points lower than reference children.
What constituted "high exposure"? Turns out it ranged from about 3-12 mg/L for most studies. 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 timesmore 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?
While this is mostly a matter of personal opinion, it is interesting to consider the city’s role and responsibilities in providing water to the public. There is a very defined cost vs. benefit analysis to be made when treating water. No treatment and you'll kill people, add some filters and you'll kill a bunch less - but after a certain point there are massively diminishing returns with regards to how expensive it will be to make water just a little bit safer to drink, with the extreme end being an economically devastating plan to provide everyone with pure distilled water (which, actually, maybe isn't all that ideal after all).
If the factors behind water treatment were only economical in nature, then the benefits of saving families hundreds of dollars a year for dental work far outweigh the cost of fluoride at less thana dollar per personFluoridation provides a blanket benefit to everyone who drinks tap water, providing unique aid to those who cannot afford regular dental work or perhaps even other sources of fluoride like toothpaste.
Water fluoridation has been included with vaccinations and family planning as among the ten greatest public health achievements by the Centers for Disease Control and Prevention, and is supported by major health and dental organizationsAs mentioned before, the up to 40% decrease in cavities from fluoridated water is in addition to any benefit already achieved from brushing your teeth. Any policy that so easily and effectively provides this much assistance against such a preventable condition as cavities is surely worth keeping around.
As long as the fluoride program that Edmonton currently uses continues to be beneficial, and the low concentrations that are used continue to not be dangerous, the program should not be stopped.