Thursday 1 May 2014


Those TLAs (three letter aconyms) are so important for writing science efficiently.  But it's curious that many of them are culture dependent.
"Polls claim that people believe that BNP more than BPA infiltrates every corner of our society"
means something different in England to what
"Sondages affirment que les gens croient que BNP plus de BPA infiltre tous les coins de notre société."
implies in France.  Regardless what anyone prefers, in both countries  BPA (Bisphenol A) has inveigled itself into the fabric of our daily lives more than either the British National Party or the Banque National de Paris. It's the subject of a piece-to-camera by Josie Glausiusz in a recent Nature, because it is an essential ingredient in pretty much all hard polycarbonate plastics.  Until recently it was in all those robust plastic babies bottles despite an increasing flap about its effects on our infants' health.  Only in 2011 was it legislated out of baby products by the EU and the following year by the FDA.
The flap hinged on the fact that the BPA molecule looks a bit like estradiol to the proteins that act as estrogen receptors.  It would be entirely naive of you to call estrogen the 'female' hormone or, indeed, testosterone the 'male' counter part.  Both men and women produce and respond to both hormones and its clear that at least some of the responses are nothing to do with sexual differentiation or sexual behaviour.  You'll have to take my human physiology course next year to get more details.  On your left are three steroid hormones with BPA down the bottom.  By any objective assessment the testosterone (on top . . . as always) is more similar to the estrogens estriol and estradiol immediately below it, than they are to BPA .  But in the molecular world the case is altered and BPA can act, in a variety of assays, as a potent hormone analogue.  In other words it triggers the same response as estradiol or more often it overloads the system so that it can promote cell death when it is tested in conditions with BPA and estrodiol both present.

And it's not just babies bottles, it is lavishly used in food tins and cans to keep the, often acidic, food product separate from the metal of the container. Before they add the beans or tin toms they lacquer the inside of the tin with BPA, which is quite chemically inert even at the high temperature required to sterilise the food, so that it will keep for 2 years or more.  So clearly the chemical has its uses.  The controversy is about whether BPA monomer (shown in the picture) will leach out of the plastic at sufficiently high rates at sufficiently normal temperature and pressure and chemical conditions to trigger an estrogen receptor in a real cell in a living human.
The response to the compulsory removalof BPA was to replace it with  . . . BPS, which looks remarkably similar to BPA, no?  And it is known to be at least as potent as BPA as an estrogen analogue!  So when you read the advertisement in big letters saying Avent BPA free bottle, you might take care to read the small BPS print.  The hyphen nazi's among us would also prefer "BPA-free bottles" unless they're giving away condemned stock.

But I think the scientific thing is not to hear one fact and go squawking and flapping and changing your lifestyle: breast-feeding your babies and only eating beans that you buy in a sack and soak yourself.  By carefully evaluating the evidence (ooops hard work, more than a soundbyte to utter or a tweet to read) you may be confident that the BPA in the products you actually consume, will have {a/no} real effect on your or your family.  The fact that large quantities of the chemical in a wholly artificial construct like cultured rat pituitary cells have a measurable estrogen-ish-like effect is only indicative of its effect in your boy-child. And you really want to watch out for the uncultured rat pituitary cells - they're real yobs.

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