Monday 12 May 2014


Triclosan? Ever heard of it? No, me neither until three nights ago ploughing through the backlog of unread Natures.
I've had a rant about fluoride which is added willy-nilly, without much contemporary evidence for any benefit, to our water supply. And I've had a go at BPA (left) which comes into contact with our industrialised commodified food-supply despite at least some evidence that it is harmful.  We have in The West signed up to this mantra that The Market decides what is good for us all, but we have also drawn some lines in the food and medical sandpits to save us consumers from our own folly and from market forces.  Thus I cannot buy methylated spirits from a pharmacy in Ireland without signing my name and address into the poisons book.  The woman in the chemist was also required to ask me what I intended to use the meths for.  "Cleaning", I said.  "They all say that", she replied.  Sherlock Holmes was able to buy cocaine over the counter but since 1916 it has been medical prescription-only or banned absolutely.

But some products and ingredients seem to slip through the net of regulation when it is probably a good idea not to have them in free circulation.  One such product is triclosan (right). Which looks superficially rather similar to BPA but we don't want to make too much of that because BPA seems to look rather like certain steroid hormones to the molecular machinery of our cells; and steroids don't look a bit similar cartooned on a page.
Indeed triclosan looks to me a lot like DDT (left) and dozens of other compounds in which a pair of  'aromatic' rings are joined together by a variety of different links and decorated with a variety of additional groups. You need a chemical degree to sort out when similar structure is likely to mean similar function.  Mais revenons nous a now triclosans!
Trioclosan isn't allowed to be added to food but it can be added to toothpaste  (!) as a bacteriocide and antifungal agent.  There is another related product triclocarban which you also want to look out for on the table of contents. There is evidence that both these additives act as hormone analogues in a way similar to BPA.  And also after we've gobbed the toothpaste down the plug-hole into the wastewater, it gets degraded and converted by UV light to dioxins, some of which are known to be potent carcinogens.  But whether the amount of converted material is enough to cause us, or the fish in the rivers downstream, concern - that's another matter that will require work, time and energy to determine.

There are lots of hazards out there and the bad-hats tend to surface as much through advocacy as through an objective comparison of relative risk.  Just on The Blob, we've seen this through thalidomide, fluoride, cytokines, chromium, tobacco, tea, So it makes me wonder whether we're shearing away from a trivial 'hazard' and tumbling into the clutches of one much more significant.  In Nature on 24/04/14, which I've just gotten round to reading, there's a snippet which suggests that Staphylcoccus aureus is much more common up the noses of people who have ingested lots of triclosan - it is absorbed from soap through the skin as well swallowed from toothpaste.  It seems that triclosan has a significant effect on the adherence of Staph A to glass, plastic and human proteins like collagen and keratin. That includes MRSA which scythes through hip-replacees and other sick people in our hospitals.  From teaching immunology to Pharm Techies, I know that adherence is an essential prerequisite for the process of microbial infection.  The whole range of effects of these additives needs to be thought through and investigated but science has a strong tendency to reductionism whereby we create a simple experiment so structured that the answer is clearly apparent.  But that simple experiment may have little or nothing to say about the real complex world to which our nifty new product will be exposed.

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