Environmentalists are going bonkers over bisphenol-a (BPA) a chemical component of polycarbonate plastic bottles. A new report by a coalition of environmental groups, The Work Group for Safe Markets, calls for a moratorium on the use of the chemical.
STATS gets a lot of stick for challenging these kinds of reports, along the lines of “we must be taking money from the plastics industry or, as a recent post on treehugger claims, beholden to some ultra-conservative, pro-industry ideology.
We’re not – on either count. And we aren’t making up the science; we’re just pointing out what the science actually says – or rather, that there’s a whole lot of science ignored by the environmental activists, and that their claims about impending doom never address, on a methodological level, why this rival science is inferior).
In the case of BPA that would include a massive risk assessment by Europe’s Food Safety Authority, which was conducted by independent scientists. Basically, they junked all the science marshaled by the environmental groups as being either badly done (statistically underpowered or didn’t follow accepted international protocols) or not relevant to determining reproductive risks in humans.
Take the common claim, repeated by treehugger, that BPA is a gender-bending chemical. BPA is weakly estrogenic. So, in theory, it could have an effect on the endocrine system. But what happens when BPA is ingested by humans? It’s worked on by enzymes, gains a sugar molecule, loses all estrogenic power and is rapidly excreted in urine.
But this is not what happens when BPA is administered to rats and mice either orally or intravenously. In each case the metabolic pathways are different and there is more free BPA and/or other metabolites swimming around. This is, at a highly simplified level, why independent European, Japanese and American risk assessments rejected the studies cited by environmentalists. (For more, see Should You Be Worried About Toxic Baby Bottles?)
The European Union sets a specific migration limit (SML) rate of 600 parts per billion per day for children when it comes to BPA migrating from plastic contact to food. As the European Food Safety Agency recently raised the Tolerable Daily Intake (TDI) of BPA by a factor of five, this SML is now effectively 3000 parts per billion. The plastic bottles in the The Work Group for Safe Markets required 24 hours at 176 degrees Fahrenheit to produce a migration level of 5 to 7 parts per billion.
Leaving aside whether this method of extraction models a likely exposure route in the real world, there is the question of whether, even if such tiny amounts of BPA are ingested, they could have any damaging effect once processed in the intestines and liver. The very latest research – and one of the most rigorous studies to date – does not suggest so, even for infants. It examined whether gestational and lactational exposure to BPA and the oral contraceptive Ethinyl Estradiol (EE) would damage male reproductive systems and alter hormone levels at very low doses in rats. EE did; BPA didn’t. In fact, the researchers found no significant effects for BPA at all. And bear in mind that rats are more susceptible to BPA than humans.
If environmentalists want to be credible in their demands for moratoriums, bans and so forth, they must account for why their science is superior to the research that challenges their hypotheses. Anything else is propaganda.