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bisphenol a

Science Suppressed:
How America became obsessed with BPA

 

 

Why was the route of exposure to BPA ignored?
One explanation for how this came about is that many journalists turned to a biologist at the University of Missouri, Frederick vom Saal, as the leading authority on BPA. For example, the Milwaukee Journal Sentinel claimed on April 16, 2008 that he is “one of the nation’s leading experts on BPA;” and the Orange County Register described him as “the nation's leading BPA researcher” on August 9, 2008.

Vom Saal appears to have encouraged this view of his work: “What the hell is the FDA doing ignoring the world’s leading experts on the subject?” he said of the FDA’s failure to pay attention to his research, according to a report published on  September 12, 2008, on NewsInferno.

But this designation is perplexing given that his expertise and his research on BPA has failed – and failed rather spectacularly – to influence the numerous risk assessments of BPA around the world. It is more apt to say he has led the charges that BPA is dangerous in this debate for over a decade, but that his contribution has been and remains highly controversial.

Vom Saal had argued, back in February 1998 on PBS Frontline, that the entire field of toxicology needed to realize there was a paradigm change afoot in the way it assessed the risk from chemicals – a change necessitated by his research on BPA.

The stimulus for this paradigm change came from his research on the hormone estradiol. Mice exposed to extremely small amounts of estradiol– much smaller than previously thought – could have significant consequences for reproductive development. Vom Saal then told Frontline that the same thing was happening with BPA:

Vom Saal: We've been working with a chemical, bisphenol-A. It's what polycarbonate plastic, hard plastics, are made out of: CD's, the plastic in your glasses' lens, milk containers, baby bottles. It's the chemical that they use to line cans with, it's the chemical they put on your teeth as a sealant and it is a very potent estrogen. It mimics the hormone that women produce in their ovaries, and it mimics this hormone estradiol that is actually being produced in fetuses and during pregnancy that is a major coordinator [transcript is garbled]

Estradiol plays a critical role in development and then normal functioning of the body for the rest of an individual's life. The amount of estradiol you're exposed to throughout your life is also the best predictor of breast cancer. This chemical mimics that hormone. The body can't tell the difference between bisphenol-A and estradiol. In other words, it sees this chemical and it thinks it's getting exposed to its natural hormone.

Frontline: So you're saying that the hormone that has the clearest link to breast cancer, the hormone that is responsible for sexual development in any animal or human, is found in plastics?

Vom Saal: Absolutely. The plastic materials, if they are polycarbonates, are made with this chemical bisphenol-A. And you can think of polycarbonate as a house made of bricks. Essentially you take this brick, this building block, which is bisphenol-A, and you link it together with other bisphenol-A molecules. That's a polymerization reaction. The bisphenol-A is the monomer used to construct these plastic materials. When it's attached to another one, that forms a polymer. And unfortunately in the process of making these plastics not all of the bisphenol-A gets linked together. So you put your food or other material in the plastic and it absorbs the unreacted bisphenol-A into it. And now in your food is a sex hormone.

Frontline: And what are you finding to be the effect?

Vom Saal: Okay, the chemical bisphenol-A passes out of the plastic or out of the dental sealant that's put on your child's teeth or out of the lining of cans, into the food or liquid that's in contact with the plastic. Now the important point about detection by instrumentation of the bisphenol-A is that, based on our research, the ability of the current instruments used to monitor for bisphenol-A in food is a much lower level of detection than what our animals are able to detect. It's a huge difference as a matter of fact. So that you can put food that you have in contact with plastic into a chemical analysis and say there is no plastic material there. We extract from that same food, put it into animals and we get a big effect. The animals are more sensitive to the chemicals than the machinery. So detection limits, where people say our machine didn't detect this, doesn't mean it's not there and doesn't mean that it won't damage your baby. We have shown that in our experiments.

Frontline: So the plastics we use in daily life, the baby bottles, the food containers, leach chemicals into the food at levels that cause effects in lab animals?

Vom Saal: One of the things that we started doing a number of years ago is we started looking at the effects of the materials that plastics are made out of in cell culture. We used human cells to see how responsive these cells were to these chemicals, and at what doses the chemicals could influence human cells to start growing and doing things differently. So, in other words, we're getting biological responses out of the cells and we were astonished at the incredibly small amounts of these chemicals that were actually able to alter human cell function.

So what we did in mice was based on the studies using human cells. We know that mouse cells are essentially identical to human cells in the way that they respond to these hormones. That's been known actually for quite a long time. So we used our information from human cells to then start treating animals with these very, very low doses of estrogenic chemicals found in plastics. So we had mechanistic information that really directed us towards very low doses.

Now one of the surprising things is that when we started looking into the literature concerning the amounts of these chemicals that were being released into food from plastic containers, and we compared that to the doses active in our cell culture studies, they were the same doses. But they were also doses that the toxicological community was saying were absolutely safe.”

But in the decade that followed, vom Saal’s paradigm change didn’t quite happen. First, there were significant objections to his argument and his research reporting changes in the reproductive tract of mice fed BPA (Vom Saal 1998). John Ashby, a toxicologist with AstraZeneca Central Toxicology Laboratory in Britain, tried to replicate vom Saal’s original studies and those of another research group that had found similar results (Nagel et al 1997).

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