The problem is that it looks a little like estrogen:
(Both pictures from the Wikipedia entries for the respective molecules)
Bisphenol A is used to make plastics, like baby bottles, Nalgene bottles, etc. The two OH groups on the end are useful little groups that can do some reactions and make the plastic work right. And if it's used in a baby bottle, and the baby's estrogen receptors react with the bisphenol A ... then strange, bad things could happen in the body. I know some of that plastic gets into the kids' systems: for my boys, sippy cups might as well be chewable rawhide bones from the way they gnawed on them. All those strings of plastic sure look toxic hanging off the end of the spout. But then again, my kids would (and probably do) chew the lawn when I'm not looking, so I'm not going to worry too much about milligram amounts of anything.
The real question is, does the body get confused? Does bisphenol A look enough like estrogen to cause a problem?
You know, it's not out of the question that it could happen in some cases. There are about 10 papers of studies with mice that suggest something could happen (although different stuff seems to happen in each study). And so, if Nalgene wants to stop using bisphenol A, then fine, and if we want to do more studies, we should. The evidence for a wide-scale out-and-out ban, or what Canada is considering, is simply not there.
I'm echoing the recent judgment of a panel convened to look into this is as follows, for current exposure levels to bisphenol A:
Neurological damage to children or infants --> "some concern"
Bad effects on pregnant women, fetuses or adults --> "negligible chance"I actually have been most concerned about the pregnant woman thing, but the studies so far don't support that concern. I just don't see how bisphenol A looks enough like estrogen to confuse the body's receptors. Remember that there's tons of hormones, include testosterone, that look even more like estrogen but bind different receptors and act differently. Bisphenol A is very different from any of those hormones.
The evidence is not enough for me to suggest a wide-scale ban. Let the plastic bottle-makers make bottles and label them "NOW with NO BPA!" and let the parents buy those if they're worried. But 10 somewhat touch-and-go studies on mammals isn't enough evidence to overturn an industry. Not to mention my own eyes tell me they're not really all that similar. Now, I could be wrong -- sometimes more dissimilar things do interfere -- but I'm going to demand proof before I go against what I can see with my own two eyes.
Here's a link to the American Chemical Society article on the panel's findings: