Thursday, 27 February 2014

Fluoridation follies

There is a long standing campaign in the US to stop fluoridation of drinking water, due to concerns about the dangers of sodium fluoride. (Most of the UK doesn't do this, though around 10 per cent of us get fluoridated water, and most of our toothpastes contain sodium fluoride.)

I have no particular axe to grind on this, though I would be rather surprised if there is a significant health risk with this particular salt - NHS England says 'Reviews of the risks have found no evidence to support these concerns and the general consensus is that water containing the correct amount of fluoride and fluoride toothpaste have a significant benefit in reducing tooth decay.'

What I do object to, though, is when people use scaremongering tactics - specifically making statements that are irrelevant or unsubstantiated.

The other day, as you do, I got one of those graphics sent to me on Facebook, which I have attached here. And it's hard to imagine a better example of naughtiness in misleading statements. Let's take those facts:

  • Waste product of the fertiliser and aluminium industry - it may be, I don't know. But so what? Many dangerous production processes have water as a waste product. Does that mean water is the 'silent killer'? (It's certainly true that water has killed far more people than sodium fluoride.)
  • Basic ingredient of Sarin and PROZAC - Certainly both contain fluorine, though I don't know if sodium fluoride is used in the manufacture. But even more so, so what? That's like saying 'Ricin is the most poisonous substance known to man. Carbon is its main ingredient. So don't consume carbon. It must be bad for you.' It makes no sense at all.
  • Used in Nazi prison camps - I can find no evidence that sodium fluoride acts as a sedative, and it's a very unlikely salt to do so. Nor can I find any evidence that the Nazis made any use of it - this seems to have emerged as a construct in some anti-fluoridation literature. If in doubt, bring the Nazis in.
  • Used as an insecticide - no it isn't. The only recently-used fluorine containing inorganic insecticide was sulfuryl fluoride, though that has now been discontinued. Having said that, sodium fluoride was once used as an insecticide. In sufficient quantities (which isn't much for an insect), sodium fluoride is poisonous, but as with all poisons (water is poisonous if you drink too much at once, as is eating too much chocolate), it is the dose that is all-important, and at the levels in drinking water or toothpaste, sodium fluoride is not toxic to humans.
  • All the 'Linked tos' - only in anti-fluoridation literature. At the levels in water/toothpaste no good trial has shown any of these. The trouble with this sort of claim is that it can be true but irrelevant. For instance, practically everything we eat can be 'linked to cancer' in that if you feed enough of it a rat it may well develop a cancer. Again it's all about quantities and risk. Eating celery, for instance, has a small cancer risk. But it's so small it isn't worth worrying about.
So there you have it. I have no objection to proper arguments being put forward against fluoridation, but using 'facts' of this kind is not the way to go about it.

[UPDATE 9:51 27/2/14]

Thanks to Anthony Morris for providing a link to this review - it doesn't in any way make the misleading and untrue statements in the graphic okay, but it appears to be interesting evidence in terms of impact on one of the 'linked to's - children's IQ.

I would point out, though, that this is for high levels of fluoridation (specifically it provides 'Sensitivity analyses of pooled random-effects standardized weighted mean difference (SMD) estimates of child’s intelligence score with high exposure of fluoride.') And my other concern with it is that I couldn't find any absolute figures for the reported IQs, only a weighted mean difference of -0.45, which is pretty negligable unless I misunderstand it.

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