Air Date: Week of March 11, 2011
Chemical structure of bisphenol A. (Wikipedia Creative Commons)
Forty-five million different chemicals are commercially available around the world — and many of these chemicals go untested. Host Bruce Gellerman talks with Professor Patricia Hunt from Washington State University who wrote a letter in the journal Science, calling for more stringent review of chemicals. Her letter was co-signed by scientific societies representing 40,000 researchers and clinicians.
GELLERMAN: It's Living on Earth, I'm Bruce Gellerman. The American Chemical Society registers twelve thousand new substances every day. And according to their records, there are nearly 45 million different commercially available chemicals sold worldwide. But data on the potential hazards these chemicals pose is available for only a very small percentage.
That's why Professor Patricia Hunt has sounded a call for swifter and sounder testing of chemicals. She's a reproductive biologist at The Washington State University School of Molecular Biosciences and author of a letter that appears in the current issue of the journal Science. In it, Professor Hunt writes about the need for new ways to safeguard chemicals. The letter is signed by scientific organizations representing 40,000 researchers and clinicians. And Professor Hunt, welcome to Living on Earth.
HUNT: Thank you, it's nice to be here.
GELLERMAN: Did I get that right - there are actually 12,000 new substances registered daily?
HUNT: Yeah, that's correct. It doesn't mean that all of those chemicals go into production and enter our lives. And what we're really concerned about is those that act like hormones in our body. And, of course, the ones that are also of most concern are the ones that are high-volume chemicals, the ones that are produced and are in our lives on a daily basis.
GELLERMAN: But they're currently being tested, right?
HUNT: If they are added to our food, or to the drugs that we take, the pharmaceutical drugs, we test the living daylights out of them.
GELLERMAN: That would be the EPA, the FDA.
HUNT: Right. But much less testing is done of those chemicals that are used for other purposes, and so a lot of those get into our lives and we learn later that they perhaps are not so safe.
GELLERMAN: Well don't these agencies test for these possible hormonal properties?
HUNT: Therein lies a problem: because traditionally, the way toxicologists have test - to gauge the toxicity of a chemical - is a standard set of guidelines for testing. And those guidelines, it turns out, don't work very well for chemicals that mimic the actions of hormones.
These chemicals sort of defy the standard toxicology thought process, which is: the dose makes the poison. In other words, if a little bit of a chemical is harmful to you, more should be even worse, and even more should elicit an even stronger effect. And these chemicals that act like hormones or interfere with hormones don't quite behave like that.
So they pose a real problem, and the federal regulatory agencies have realized that it's a problem and that we need new testing guidelines, but getting these new guidelines is a slow process.
GELLERMAN: So, how do these agencies review chemicals now?
HUNT: They put together review panels to look at specific chemicals. The one on most people's minds right now is bisphenol A, or BPA, because it's received so much attention in the press. And what they'll do is review all of the research that's been published and decide whether or not our current estimates of safe levels of human exposure are adequate, or whether they should be readdressed.
GELLERMAN: So what are you proposing?
HUNT: The field of toxicology testing has actually moved beyond toxicologists and we need a broader expertise. What we're offering is the expertise of different scientific societies: reproductive biologists, developmental biologists, endocrinologists - people who actually work on hormones - and geneticists. And we've asked that these regulatory agencies seek the advice or the council of these societies when they constitute panels to review chemicals.
GELLERMAN: Do we have the ability to test
differently? Not the expertise, but the science?
HUNT: Okay, now you're getting at what, to me, is the heart of the problem. Right now, when these panels sit down to review a chemical like bisphenol A, they're faced with a really daunting task. There are hundreds of studies looking at the effects of bisphenol A - most of them using experimental animals. And when the regulatory panels sit down and look at them, quite frankly, they don't know what to do with a lot of the research.
The studies that have been done using the standard toxicology testing guidelines are easy - they know how to deal with those, so those studies are always included. A lot of the academic studies, like some of the work that we've done in our laboratory, are a bit more puzzling, and frequently those studies just get set aside.
And this is where a wider expertise on some of these panels would be helpful, because some of these studies use very sensitive end points, newer technology, and really give us a very good look at exactly what these chemicals can do in bodies. Even though they're rat bodies or mouse bodies, they're actually very good model systems for what they would do in the human body.
GELLERMAN: So are there human studies that have found these effects, or all they all laboratory studies?
HUNT: It's really hard to study humans directly. There have been some human studies asking things like: are bisphenol A levels correlated with miscarriages? But that's a really difficult study to do because these are looking at correlations and trying to make conclusions. You know, it's hard to establish cause and effect in humans.
I mean, we know this from smoking. We had a lot of data from animals, but actually establishing cause and effect in humans took many, many years. And the problem with these chemicals is, there are so many of them and some of them are present in our daily lives at pretty significant levels. And so, if these are having effects, and if they're having effects on our developing babies and infants, it may take us a couple of generations to actually get that proof - that definitive proof - in humans.
GELLERMAN: So, in effect, we are actually doing these human tests - we're doing them on us!
HUNT: Yeah, that's one way to look at it isn't it? (Laughs). And you know, in the case of something like bisphenol A, we have essentially run this experiment in humans before, because the whole diethylstilbestrol, or DES exposure, was exactly that - an experiment in humans.
It was given to women in the hope that it would prevent miscarriage. And as a result, there are thousands of DES-exposed sons and daughters. And we can in fact see some of these changes. There are some fertility effects, some increased cancer rates, some behavioral changes in these humans that were exposed to DES. And so we have every reason to suspect that some of these same effects would be seen from chemicals like bispehnol A, the phthalates, other endocrine disrupting chemicals.
GELLERMAN: And we'll only see those generations later.
HUNT: Exactly. So that makes us dependent on those rodent studies. And in fact, in the case of DES, those rodent studies were terrific. They came after the human studies, and it turned out that human was a really good model for the mouse.
GELLERMAN: You know the government has big-time budget problems. Where would you get the expertise to satisfy the requirement here?
HUNT: Well I think what we're asking for is a very subtle change, and one that I don't think is going to cost any additional money, or going to be very difficult to accomplish, because the panels are already being convened to assess chemicals - there are already new guidelines being developed. All we're asking for is to take into account some of the expertise that it's now become clear we need to assess some of these chemicals.
GELLERMAN: Well Professor Hunt, thank you so very much, appreciate it.
HUNT: Thank you.
GELLERMAN: Patricia Hunt is a reproductive biologist at the Washington State University School of Molecular Biosciences.
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