At noon today the NZ Herald had an on-line forum around fluoridation. Aside from engendering a bit of frustration (it took ages for comments to get past moderation), following the chat was an interesting experience. It also left me with questions/comments that weren't addressed in the relatively short time available. (The forum included Dr Jonathan Broadbent, who provided the Science Media Centre with expert commentary following Hamilton City Council's decision to stop fluoridation of the municipal water supply, and Mary Byrne, from the Fluoride Action Network.)
One questioner asked if any animals ingest fluoride. Jonathan noted that "the ocean contains 1.3ppm fluoride, and the fish are very happy", and went on to point out that this particular element is pretty much ubiquitous in food and drink. Mary's response was that
there's very good reasons why sea water is not suitable for human consumption. One of them, being there is too much fluoride.
Actually, the reason we shouldn't drink seawater is that our kidneys can't cope: in attempting to remove the excess salt, they end up producing an excessive amount of urine, so too much seawater will lead to dehydration.
But I wanted to ask: Mary, you've indicated here (& in other comments) that fluoride in any quantity is bad for you. So, would you advocate against eating fish and drinking tea (1-9 mg/L)? After all, both have higher levels of fluoride than our tap water does (or will up until June 21, anyway), we're advised to eat several serves of fish each week, and a lot of Kiwis drink a lot of tea (57-64% were regular drinkers, in a 1999 survey).
There was also the comment that
The evidence that fluoride impacts on other bodily systems is obvious just by using common sense.
The problem here is that common sense is often wrong. That's why decisions like this really should be based on good scientific evidence, and not on common sense. From a piece on Psychology Today:
...common sense isn't real sense, if we define sense as being sound judgement, because relying on experience alone doesn't usually offer enough information to draw reliable conclusions... Real sense can rarely be derived from experience alone because most people's experiences are limited.
Maybe that's why (as a species) we're not very good at handling risk assessment - because we place too much emphasis on common sense?
And an aside to our Mayor: if you believe such decisions are best left to central government, then why on earth did you table the motion to change the status quo, and then vote for it? (Not to mention, deciding to overturn the 2006 binding referendum on this very issue?)