NC Health News sat down with Linda Birnbaum, head of the National Institute of Environmental Health Sciences last week before the FDA came out with their determination about bisphenol A (BPA).
Birnbaum is a toxicologist who has published widely on environmental toxicants, in particular substances that humans are exposed to at very low doses, such as dioxin.
You can also read our accompanying story on local scientists’ work on BPA.
NCHN: Does NIEHS have an official ‘conclusion’ that you’ve reached about BPA at present?
Birnbaum: No. if we had a conclusion, we wouldn’t be spending $30 million on research.
Under the stimulus package, we funded about $14.5 million on BPA, and now we have funded a consortium of grantees from across the country who are working with the National Toxicology Program (NTP) and the FDA to address some specific questions. Our intramural program also has some research going on looking at some of the human health effects.
We think that there are still scientific questions that need to be addressed.
NCHN: Can you talk about some of the things that your researchers have concern about in regards to BPA?
Birnbaum: We know BPA’s present in cans, and some of it in the epoxy lining of cans does get into food. We funded a study that came out last summer, from some of our grantees at Harvard. They measured people’s BPA level, and then had them eat ate a bowl of soup, and then they measured their BPA levels shortly after they had the soup and they went right up and by 12 hours later, they were way down, showing that was a major source.
We now know also that thermal papers (used in receipts), many of them use BPA and so people are getting it on their hands, and not only is that a potential for skin absorption but certainly… anything you get in your hands, you get in your mouth.
NCHN: What are studies that are coming up at the National Toxicology Program?
Birnbaum: We are conducting two effects of human studies where we’re actually recruiting cashiers, pre- and post-shift to measure their BPA levels before they work for 8 hours and after they work for 8 hours, which I think will give us an indication of how much exposure they get from thermal papers.
Then we’re doing a another study where we’ll actually be recruiting into our clinic on campus as many as 50 healthy adult volunteers where we’re actually going to give them a very, very low dose of BPA in a cookie, early in the morning We’ll be following that very completely with multiple blood samples very shortly after exposure, up to more than 5 days.
NCHN: But like, with cashiers, is the actual dose as important if people are being exposed constantly?
Birnbaum: We now know its not only the ‘dose that makes the poison,’ it’s timing, it’s inherent susceptibility, and we know that different things happen at different doses. We’re often looking for different kinds of effects than we might have been looking for in the past.
If you have ongoing exposure, if there’s exposure to something that is essentially ubiquitous, and it may have a very short half-life, that sounds like a hormone.
Many of our hormones have very, very short half-lives, right? But they’re constantly being secreted. We’re being exposed to these in a more pulsitile fashion, so you have peaks and valleys but you have lots of exposure. if something has a short half life, you may have ongoing exposure because you’re constantly getting it from external sources, but the levels will not build up.
NCHN: What are the effects of most concern for people at NIEHS and NTP, that you folks think are most related to BPA exposure?
Birnbaum: We know that the developing embryo, fetus and the developing infant are extremely susceptible to any kind of perturbation. There are some now epidemiological studies where we’re seeing some of the things that the animal studies might have predicted.
The epidemiological studies in many cases still are small, they need to be repeated. But there are a couple of longitudinal studies that are coming out looking at the neurobehavioral changes in little girls associated with their mother’s in utero exposure. Some of the other effects that are being reported in adults in cross sectional studies are associations with diabetes, obesity, heart disease, and all of those kinds of things are also being reported in the animal models.
NCHN: What happens if FDA rules in a way that you at NIEHS conclude allows for too much exposure. Where do you go then?
Birnbaum: Our role is to do the research. Our role is not to set the regulations. FDA and EPA are the ones who are responsible for that. We provide the scientific information upon which others are going to base decisions.
Note: The FDA ruled in April 2012 to reject a ban on BPA in plastics, saying they planned to study the issue further.
NCHN: In that interaction between the market and the science, often the market seems to be stronger… leading the science.
Birnbaum: I think we all know that the market has spoken and that BPA has now been removed from, for example, baby bottles or sippy cups. They’re not using BPA in the hard polycarbonate plastics. if you go and buy a plastic drinking cup, it’s not going to have BPA in it any more.
Campbell’s soups announced a week or two ago that they were going to be taking BPA out of their cans. And again, they’re doing that because consumers are expressing concern.
NCHN: One of issues that have been raised by BPA is that now, instead of, in testing paradigms focusing mainly, for example, on cancer or overt birth defects, we’re focusing on functional, and subtle kinds of changes that are more difficult to get a handle on.
Birnbaum: The kinds of things that we’re trying to look at today are things that are difficult to detect in an individual. You can really only detect some when you look in populations.
I often use the example of lead. You can’t look at somebody and say, “Well, Johnny, if you had a little less blood lead, you could have a few more IQ points.” But you can look at the whole population, and see the shift in the population distribution. And that’s the importance of doing some of the epidemiology studies, where you can look for effects on the population that would be very difficult to define in the individual.
NCHN: But with epidemiological research you always get the guy who says, “My grandfather ate stuff out of BPA lined cans for all his life and he lived to be 90 and he was fine.” The things you find are not bright line effects, with clear relationships between exposure and someone’s health problem.
Birnbaum: Well, that was the approach used for 50 years by the tobacco companies to block regulation of cigarettes. where they would have someone say, “I smoked for 50 years and I’m perfectly fine” and it’s true because only 11 percent of smokers ever get lung cancer.
That doesn’t mean that smoking doesn’t cause lung cancer. It means that… everything is really an interaction between your genes and your environment and your history.
By history, I mean, what were you exposed to in the past? What is your level of stress? Are you eating a high fat or a low fat diet? Do you happen to be fighting a bacterial infection right now? what drugs are you taking? All those things are going to impact your response.
NCHN: Isn’t it frustrating that the US ends up in this cycle of introducing a chemical, someone finds there’s harm, we spend money on testing, we eventually reduce the use… but it’s always after the fact.
Birnbaum: It would be nice if chemicals were tested for safety before they went on the market.
NCHN: Is there any movement towards that, or is that a total non-starter?
Birnbaum: The Toxic Substances Control Act has been around for over 30 years and it has not be terribly effective. And there are bills that have been proposed in Congress to modify that law. I think there’s recognition across the spectrum from industry to public interest groups that TSCA needs an update. Sometimes the marketplace talks and we remove chemicals, but I think that sometimes, we know almost nothing about the alternatives, and sometimes the alternatives can be worse!
NCHN: Is this experience of doing research into BPA and other low dose chemicals going to result in new testing paradigms for things that are effective at very low doses?
Birnbaum: I think we’ve already started to move into that. For example, NTP a couple of years ago, switched from doing their long term rat studies from only dealing with adults, starting to expose the animals in utero. That’s really important, because, guess what? That’s when you’re really susceptible.
This is why we’re moving towards the use of ‘predictive toxicology.’ You have a chemical that runs through hundreds of assays and it’s activating reactions in a large number of cells, to me that would be red warning flag. And if something is not doing anything in a whole number of assays, then maybe that’s a chemical that may not be a problem.