Bisphenol A
Our inquiry into Bisphenol A starts at the end of the Duckering Building – just down the hallway from my office. There for $1.25 you can buy a bottle of coke. I can remember buying cokes for $0.10. They came in heavy glass bottles and only had about half the fluid as today’s soda. The glass bottles were refillable and there was a deposit on them - an honor system to put the empties back near the machine. The bottoms were heavy glass too and thus a kid with thick glasses was accused of wearing “coke bottle bottoms.” Over the years as the price increased, the containers morphed to a thinner glass that did not have a deposit, to cans, and now to plastic bottles. You can still get cans and you would need to do a detailed economic calculation to decide between a 12 oz can and a 16 oz plastic bottle. Besides coke, you can have diet coke, which I will drink, and caffeine-free diet coke, which I will not. Of course you can buy water too, but I am conditioned to drink the university’s water, which sometimes has a head on it, but is free. Dilbert’s Boss has pondered that issue:
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The plastic that forms the bottle is polycarbonate. Polycarbonates are organic polymers that are made of many small molecules called monomers linked together. [See wiki for some more technical info on polycarbonates, but you don’t need to. http://en.wikipedia.org/wiki/Polycarbonate or polymers http://en.wikipedia.org/wiki/Polymer ] The basic polymer is the same monomer linked together over and over. However many other chemical are added, varying the properties of the basic polymer, for example cross linking strands of the polymer, etc. While the basic polymer remains unchanged over time, it can release some of the original monomers or one of the additives, either because some of them were not chemically attached to the polymer in the first place, or the polymer was degraded by sunlight or other chemicals. Thus some of the monomer may leach from the plastic into the environment, or into the substance the polymer was holding, like the water Dilbert’s boss drinks. Polymers are usually not toxic, since they are very large inert molecules and unlikely to be absorbed. Some of the monomers and additives may be toxic.
Bisphenol A is a monomer common in polycarbonate plastics and thus may be found as a contaminant of the coke or whatever in contained in the plastic. Is Bisphenol A toxic? Like most chemicals, both naturally occurring and industrial, it is harmful at high doses. So by now you know the next question is, what is the dose? And are we talking about acute toxicity or chronic toxicity, etc. Rather then try to settle the science, which by now you realize we probably can’t do – let examine this from the public’s perspective. We’ll look at the information that might get to public and contrast it.
First read this site, from a green group that sells air purifiers:
http://www.home-air-purifier-expert.com/bisphenol-a.html
Or this from an activist group:
http://www.ourstolenfuture.org/NewScience/oncompounds/bisphenola/2002-0515wetherill.htm
They see BPA as a terrible danger that needs to be controlled pronto.
Now glance this site from a “hired gun” group that defends industry:
http://www.bisphenol-a.org/human/herEndocrineEffects.html
They are confident everything is OK as is.
Finally, Wikipedia’s take on the health effects is quite balanced:
http://en.wikipedia.org/wiki/Bisphenol_A#Health_effects
One of the issues with Wikipedia is that you don’t know who wrote the article or if it was reviewed. However this brief articles seem to sum up the issues.
Lastly, here is the National Toxicology Program report that most of the above use. NTP report
So what do I think? I think the low dose effects in animals are uncertain, but there are some plausible bad effects. Because BPA is ubiquitous, it makes sense to do thorough lab testing of low does effects now. Of course those will only lead to a description of the effects in lab animals, and extrapolation to humans will add some uncertainty, but would be a step in the right direction. Meanwhile, I will continue to use plastic bottles, but would not heat my baby's bottle in the microwave.