Friday, January 16, 2015


As much as I would like to brag, or say "I told you so", I really don't feel that I'm prescient in the least. Any scientist with a little appreciation for their field would instantly recognize that when somebody says "Chemical X is poisonous! We need to stop using it!", the immediate follow-up questions should be:
  • OK, so what should we replace it with?
  • Why do you think the replacement is any better?
And yet that is what we face with the chemical bisphenol A, also known as BPA. It is the condensation product of 2 moles of phenol (hence the bisphenol) and 1 mole of acetone (hence the A). It is used to make the polycarbonate that is used for making Blu-ray/DVD/CD discs (other polycarbonate do exist as well). It is also used for making epoxies, some of which are used as adhesives, but others of which are used for lining steel cans to prevent their rusting.

Once the BPA has reacted and formed the polymer, there is very little reason to be concerned about it. The polymer is good and stable. The concern over BPA arises from unreacted BPA in the polymer, not from the reacted BPA (although chemophobes will try and convince you otherwise). As much as the FDA and regulatory bodies around the world have looked at the available data and said that there is no reason for concern (see the link above), some people are concerned and want to avoid any contact with BPA.

One popular suggestion as an alternative is BPS, made by reacting two moles of phenol with one mole of sulfuric acid (hence the "S"). (If you are curious, there is a whole alphabet of bisphenols out there, even a BPZ.) But now we have a report that in zebrafish embryos, BPS appears to causing at least as much hormonal damage as BPA. While I don't ever want to create problems for any animal, let alone zebrafish, for us humans, well, we have to wait and see if the effects of BPS are the same in humans.

While the biological aspects of the research are beyond my understanding, the interpretation and conclusions are not. The researchers contradict themselves and don't even see it. Near the end of the article they state
"...manufacturers have turned to BPS with little proper toxicology testing to produce the “BPA-free” products demanded by society..."
and yet the authors have no problem with proposing their own open-ended experiment:
"These a societal push to remove all structurally similar bisphenol analogues..."
And the alternative compounds (that of course have been "properly" tested) are...?

That last statement quoted above is shockingly overreaching just by itself. So because BPS didn't work out in one (unreplicated) study on fish (and not humans), we need to toss out all bisphenol compounds, even the ones that are safe (such as BPA)? Wow. What an overstatement. Could the researchers take themselves and their results even more seriously? It's only January 16th, but I'm ready to predict that this quote will easily win the "Overstatement of the Year 2015 " Award.

Previous Years

January 16, 2014 - Recycling Plastics for the Do-It-Yourselfer

January 16, 2013 - Does Going Public Kill Innovation?

January 16, 2012 - Flying Cupcake Update

January 16, 2009 - The Pitch Drop Experiment

1 comment:

Anonymous said...

If the amount of leached monomer is negligible, then I guess the ethics of deceptively switching to BPS is a moot point. That being said, there's many studies on the structure–property relationship of bisphenol compounds in regards to their estrogenic and antiandrogenic effects. From what I remember, adding halogens ortho to the phenol or hydrophilic groups at the methylene position made the bisphenols safer. I'm sure there is a better alternative to BPA or BPS.