Sunday, March 27, 2016

The BPA scare again

This has been rumbling on for decades now.  It's part of the aversion some people have for "chemicals".  That all foods are full of chemicals just cannot get into certain heads.  BPA is used to make sturdy, clear plastic, as in babies' bottles.  It is very weakly soluble in water and has estrogen-like effects in the human body.  So you can imagine all the twitching over that.

What the twitchy ones are probably incapable of recognizing is the old truth that the toxicity is in the dose.  Depending on the amount absorbed, a thing can be good for you, bad for you or neither.  Even drinking too much water can kill you, for instance.  It can bring on hyponatremia. And the low levels (typically only a few molecules) of BPA found in food and drink kept in BPA containers has repeatedly been found by all sorts of research and official enquiries to be harmless

But every now and again you get some finding that gives encouragement to the paranoid ones.  One such is below

The original acdemic journal article is "High bisphenol A (BPA) concentration in the maternal, but not fetal, compartment increases the risk of spontaneous preterm delivery".  So just from the title we know that BPA had no effect on the baby. And from the Results section we learn that three quarters of the women showed no effects from the BPA in their blood. It was only women with very high levls of BPA who were slightly more likely to deliver pre-term.

And given those very marginal findings, we may well be looking here at one of the many unreplicable findings that infest the social and biological research literature.  Such weak effects are exactly those which do normally fail to replicate.  And an unreplicable finding is a non-finding

A chemical commonly found in plastic wrapping is linked to preterm births, scientists have warned. Preterm birth occurs when an infant is born before 37 weeks of pregnancy.

It is the greatest contributor to infant death – and one of the leading causes of long-term neurological disabilities in children, according to the Centers for Disease Control and Prevention.

Pregnant women with high concentrations of the chemical Bisphenol A – or BPA – are more likely to deliver their babies early, revealed experts from The University of Texas Medical Branch at Galveston.

Study author Dr Ramkumar Menon said: ‘Women are continuously exposed to BPA because it's used in the construction and coatings of food containers and its release into food is increased by microwave or other heat sources.  ‘In fact, BPA is so widely used that nearly all women have some level of exposure.’

For the study, Texas scientists analysed blood samples from pregnant women admitted to the hospital for labor and delivery.

They also tested the amniotic fluid of the fetus collected during labor. They found that pregnant women with higher levels of BPA in their blood had a higher chance of delivering a baby preterm.

The samples were obtained by the Nashville Birth Cohort Biobank, according to the study, which was published in The Journal of Maternal-Fetal & Neonatal Medicine.

BPA is structurally similar to the female hormone estrogen. The chemical binds estrogen receptors within the body – including those responsible for inflammation.

The study was the first to investigate the role of BPA levels on preterm birth.


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