She is the Associate Director for Health of the National Health and Environmental Effects Research Laboratory of U.S. EPA. Approximately 40 scientists at Birnbaum's EPA laboratory in North Carolina are studying endocrine disruption. She has long been interested in chemicals that affect hormone systems. Her expertise is in studying dioxin and PCBs, both very potent at disrupting hormones. Interview conducted by Doug Hamilton, producer of FRONTLINE's "Fooling With Nature."

DH: The issue of endocrine disruption has become polarized. You're in the middle.

LB: It's actually fairly uncomfortable because people that I respect have taken very strong positions on either extreme. And it makes scientific discourse much more difficult when people are not listening to each other because of their views.

DH: Why aren't they listening to each other?

LB: I don't really know the answer. The issue arose from good, solid, scientific hypotheses and I think what's happened is the fact that these things that are just ideas -- they're suggestions, they're maybes -- have been transported into fact.

DH: Where are we in this issue -- the continuum of proof on this.

But when it comes to people, are there endocrine effects going on from environmental levels of chemicals in people -- I really don't think we know the answer.

We absolutely do know that chemicals can affect hormone systems of people. That's not a question. We make drugs to do that all the time. That's the purpose of certain drugs.

So, people are certainly susceptible to having hormone systems altered or modulated or disrupted. But whether the low levels of chemicals that are present in the environment are affecting people in an adverse way is really not clear at all.

DH: Because of the difficulty of testing on people, or the subtlety of the effects?

LB: It's probably, it's probably both. When we look for effects on people, we tend to look for "either/or", or "yes or no". And what we maybe should be considering is, are people more at risk? Have we slightly altered their ability to respond to another stress?

It's really a population phenomenon more than an individual phenomenon. When we're looking at the problems that have happened in fish and birds, we're not looking at what happens to a single fish or a single bird. We're looking at what has happened to this whole population of fish and birds.

When we look at people, we tend to look at you or me. It's an individual thing. And what we really need to be thinking about is what's happening to the population as a whole.

I really think the best analogy for the possibility of hormone disruption is the lead story. You can't look at little Joey and say, "Little Joey, if you had ten points lower blood lead, you'd be five points smarter on your IQ scale." But you can look at a population of children and say, "Oh, these children who have lower blood lead tend to have higher IQs."

DH: Saying we could be affecting the intellectual or reproductive development of certain populations is a frightening thought.

LB: It is. I absolutely agree. It is cause for concern. Because there's that hypothesis, and because there is scientific support for those hypotheses from studies with fish and wildlife, from studies with laboratory animals. That's why we have to be investigating it now in the human population.

I've been interested in chemicals that affect hormone systems for more years than I care to count. But my expertise has to do with the dioxins and the PCBs, which are very, very potent at altering hormonal systems.

I usually talk about dioxin as, you know, I usually say I don't know a hormone system that dioxin doesn't like to disrupt. And that has lead me into this larger area of other chemicals that can alter hormone systems. I think it's really important to remember that there are many different kinds of hormone systems, not just estrogens, not just androgens and even not just thyroid systems.

But the focus in the debate that's going on now, in the very loud debate, is on effects on estrogens and androgens.

DH: Why is that?

I think that people are very concerned about developmental effects, or reproductive and developmental effects. I think one of the things that has driven the emphasis on estrogens is the DES story. DES is a very powerful drug. It is not an environmental chemical. It was made as a potential -- it's an estrogenic chemical and it was used to treat women who were in danger of miscarriage. To our horror, it turned out that this chemical was associated with an increased risk of vaginal cancer in young girls whose mothers had taken this hormone.

But I think the study of DES, which is an estrogenic compound, and our understanding of how this can perturb the reproductive development has spilled over into hypotheses about other chemicals which might have some estrogenic-like activity.

Back in the mid-80s, when we were just beginning to understand how DES causes these terrible problems which could be replicated in animal studies as well as in human studies, we began to say, well, are there environmental chemicals that can do the same kind of thing?

Now, we've known that there are naturally occurring plant estrogens that, in fact, can impact reproduction. They can impact development. Farmers have known for years that you don't yet let the sheep into the clover because it can be a real problem with their ability to reproduce.

So there, we understood how DES was doing these things, we understood how high levels of natural estrogens could cause problems, so we began to say, are there environmental chemicals that can do the same kind of thing?

DH: Synthetic chemicals?

LB: Synthetic chemicals? That's a very interesting issue because there is nothing inherently different about synthetic chemicals from natural chemicals.

What may make them different or may make their response, the response to these chemicals, different is how long they stay in the body. Some of the synthetic chemicals can do the same kind of thing as the natural chemicals, but they don't go away.

What we saw with DES in the human population was this induction of a very rare form of cancer in girls who had been prenatally exposed. There are other effects that we're also seeing in this group of young women, in addition to cancer: effects on their fertility, effects on the development of their reproductive tract, and there also appear to be some effects on the DES sons.

Are we seeing those same kinds of effects in the general population? I don't think we know. We're not seeing vaginal cancer in the general population. But remember that was a very high pharmacological kind of exposure, not a low kind of exposure.

I think some people are concerned that environmental estrogens might lead to the same spectrum of responses that we're seeing with DES. So far, there's no evidence for that kind of response. The doses that were used in DES led to very, very high levels of estrogen-like activity in the women. Much higher, orders of magnitude higher, than what we're considering when we talk about environmental chemicals.

DH: Why do I keep hearing about cancers that may be related to endocrine disruption?

LB: The endocrine system is intimately involved in some of the major human cancers. We know that one of the greatest risk factors for breast cancer is the woman's total lifetime exposure to estrogens. We know that the male hormones, that androgens, are critical to the development of prostate cancer. We know that if you alter thyroid hormone levels, it can be associated with an increase in thyroid cancer. Those are just some examples.

So, altering the levels of hormones clearly can play a role with cancer. Some of the push for studying endocrine disruption came about because people were concerned that non-cancer effects were not being sufficiently considered in the risk assessment process. And I think there's a history to this.

The way that EPA regulated cancer was based on a linear model -- that is, the dose of the chemical was proportional to the amount of cancer that you got. And you could extrapolate this all the way back to zero. So at infinitesimally low levels of chemical, there was still some probability that you could get a cancer response.

This kind of an approach is extremely sensitive. And, in fact, in most cases, if a chemical was regulated on the basis of its cancer-causing properties, that would also be protective of its neurological properties, or its liver effects, or its developmental toxicity or almost any other effect.

What we began to realize towards the late 80s is there may be some exceptions to this case. There might be some chemicals that were not very active as carcinogens, but, in fact, had effects on other systems. And we were concerned that not enough attention was being paid to adverse effects on other systems.

DH: And now?

LB: I think there's growing attention to these effects. How you regulated something that was a carcinogen led to the perception that if something wasn't a carcinogen, there wasn't a concern.

We often talk about people looking for their keys under the lamppost. And what some of the emphasis on endocrine disruption has done, is it's forced people to look farther from the lamp post.

DH: Is that a good thing?

LB: I think it absolutely is. I think that we are beginning to uncover issues that we didn't know were there previously.

DH: Is this change part of a need to better understand human biology?

LB: Well, I do think we need to understand human biology. But I think we need a new paradigm to understand human biology. I think the way we've tended to study things has been with a very linear approach. Chemical A causes affect B in species C. And we leave it at that.

In fact, when we're dealing with endocrine systems, if you perturb or you modulate the level of one hormone, you're going to affect multiple tissues in multiple organs.

DH: So this might make people worried, that we don't really know what we're doing to ourselves.

LB: We don't. We don't know what we're doing to ourselves. But I don't think that we necessarily should be terribly frightened. I think that what we are moving to try to do is identify the chemicals that have the most biological activity. I think the point is that a chemical which is biologically active for one kind of response is likely to have the potential, in at least some situations, to have that activity in multiple scenarios.

Personally, I will look at a chemical which causes multiple effects, in multiple tissues, of both sexes, of several species, as being of much greater concern to me personally and to other people than a compound where you have to really look hard to find any kind of response in one tissue, or one sex, or one organism.

DH: Is looking for those subtle effects splitting hairs?

LB: I think we have to be very careful when we look at the wildlife examples -- although I do think that there are clear evidences of endocrine effects in wildlife species. Many of the things that are happening with our wildlife have nothing to do with endocrine effects, but have to do with change in water temperature, altered habitat, habitat destruction, changes in the food chain. Not things that can be tied to perturbation of their endocrine systems.

DH: Is there clear evidence that their endocrine systems have been affected?

LB: There is clear evidence in certain populations of certain species out there in the wild that their hormone systems have been messed up. Absolutely. But I don't think that we should jump to the conclusion that every time we hear about an endangered species, that the reason it's endangered is because they, some, some chemical has monkeyed around with their hormones.

I think that there has been so much hype about endocrine disruption that it makes it difficult to carry on a reasonable scientific discourse on the topic. The level of politics that has entered the discussion has made it very hard to discuss the science.

Because it's difficult sometimes to discuss the science because views are so polarized.

One of the important things about hormone systems, or really almost any biological system, is that we have tremendous ability to repair damage and we have a lot of buffering capacity. So the issue with hormones is, or hormone disruption is, are we exceeding that ability to be buffered?

And with many of the chemicals, on an individual basis, it's unlikely that we're doing that. The real question, to me, with endocrine disruption is, are we taking so many multiple hits that we're beginning to exceed that buffering capacity that's built into all biological systems?

DH: How do you begin to study that?

We live in a soup. Nobody's exposed to a single chemical or at a single instant in time. It's continuous and it's multiple chemicals.

And when we talk about hormone systems, it's not as simple as a single hormone which binds to a single receptor, the lock and the key analogy. The interaction with a receptor involves multiple proteins in order to bring about a response.

But the hormone has to get to the receptor to begin with. They're carried around in the blood on specific proteins. You can affect how they get carried. And that can modulate your hormone action.

And before the hormones ever get to the carrier proteins, they have to be made. So there are many ways that you can alter hormone action in addition to the single issue that many people have looked at, which is binding of this one hormone to one receptor.

DH: Do you as a mother look at this differently as you as a scientist do?

LB: I think I do a little bit. I think, I think any scientist who tells you that they have a complete congruity between their scientific life and their personal life is probably stretching the truth a little bit. When I look at this as a scientist, I see an interesting hypothesis and that there's some data to support the hypothesis.

As a wife and mother when I look at this issue, I get a little bit nervous. I think, do I want to take the risk that I might be doing something that will affect my children and their children in the future?

DH: Is there the possibility that your children could be affected?

LB: Rationally, I think it's very unlikely. But emotionally, I can't help being concerned. I will say that I think, I think the things that I read, the things that I hear from the schools, from the teachers, are that they're having a harder time with their children in classes today than they did ten or twenty years ago. There appear to be more children with learning disabilities, more children with attention deficit disorder and that kind of thing.

But whether this is due to problems with parenting or whether this is due to exposure that the children had before they were born, or any kind of exposure, I don't think we really know.

But you have this nagging concern that maybe these things could be due to developmental exposures that occurred either before the child was born or after birth.

DH: Makes you think we should be doing a lot more.

LB: Well, I think we are doing quite a bit. We have been looking for chemicals that perturb hormone action for years. For a toxic chemical or pesticide to be registered, you have to demonstrate that it doesn't cause effects on reproduction and development.

We look for things like alterations in certain kinds of hormone levels. The real problem is that there are maybe 70,000 chemicals out there in commerce and we know very little about many of those chemicals. So, we know a lot about a small number. And I think we are adequately protected against the chemicals that we've studied. But there are so many chemicals that we know very, very little about.

DH: Only the newer ones have really been studied?

LB: I think more of the newer ones have been adequately studied than some of the chemicals that have been around for a long time.

To test all those chemicals adequately is probably not feasible. We have to begin to think smarter. We have to develop ways to test these chemicals in a broader sense. And our approach to this -- we're beginning to try to look for markers of biological activity. What is there about a chemical, what is there about the structure of a chemical, the molecular structure of a chemical, that we can study that will tell us that this chemical is likely to behave like another chemical? We have to begin to look for relationships between chemicals and not take chemicals one at a time.

We have to look for classes of chemicals, groups of chemicals. And, again, I would urge that we need to try to understand which chemicals have the most biological activity. If a chemical has a structure that says this chemical is going to cause a mutation, then this chemical has a red flag and we need to study this further before we go ahead and use it.

I think some of the concern with endocrine disruption definitely plays into chemophobia. Absolutely. I think we need to sit back and look at a population and accept the fact that people are living longer and healthier than we've ever lived before. That doesn't mean that there may not be chemicals out there that are affecting some of us maybe in a bad way. But as a whole, the population is living longer and healthier than we've ever done before.

DH: Who is the group of scientists putting forward this hypothesis of endocrine disruption?

LB: I think there are many legitimate scientists that have real concerns about endocrine disruption. I think there are people who have looked at the data and believe that this is a valid hypothesis. I think there are some people who take that valid hypothesis and are going beyond the data as far as saying that there are adverse effects due to alterations of endocrine systems in people.

I think the majority of the people who are in this are respected scientists ranging from biologists, to environmental scientists, to toxicologists, to physicians. This is not a single group of scientists.

And I think it's unfortunate when people tend to try to disparage another group's views because they disagree.

On the other hand, I think some of the scientists who tend to downplay the issue of environmental endocrine disruption also tend to be legitimate scientists. And two equally respected scientists can look at the same data and draw different conclusions, and neither one of them is necessarily wrong.

DH: What do you do when scientists disagree?

LB: You continue. If you don't have a clear-cut answer, you have to design the appropriate experiments to try to get you to the answer. And I think we have to be smarter to try to get to the answer. We have to design experiments which will enable us to draw consensus conclusions.

DH: Where are we in that process with endocrine disruption?

LB: I don't think we're asking the right questions in endocrine disruption. I think, due to the polarization, we have people in one camp saying let's screen every chemical out there to see whether it binds to an estrogen receptor or an androgen receptor or a thyroid receptor, and if it does, it's an endocrine disrupter and we should ban it.

And on the other side, you have people saying none of these chemicals mean anything.

That kind of polarization isn't going to get us to the answers. Some of the new approaches that scientists need to begin to be thinking of are the networking kinds of approaches.

I think if we want to move forward in the endocrine disruption area, we're going to have to involve some more sophisticated ways of asking the questions because a one-chemical, one-effect way is not going to get us to the answer either yes or no.

DH: Why has this issue gotten so much attention?

LB: I think endocrine disruption gets attention because it scares people. I think that's the basis for it. When you talk about teeny weenies in alligators or you talk about increased breast cancer in people or you talk about male fish that are making female proteins or you talk about birds where there aren't any male birds or the male birds are acting like females, that concerns people.

DH: Makes me worry!

LB: They make me worry too. But then I have to say, how widespread are they? Do we really understand what's causing them? Do we think that these kinds of effects are happening in the general population?

We should be looking at issues of when little girls go into puberty or when women go into menopause. Are those times changing? Now, we might find that they are changing. We know that girls go into puberty earlier than they used to. And until now, most of that has been associated with the fact that nutrition is better. But is that the only reason?

We have to be looking, I think, at these kinds of gradual changes or shifts as opposed to looking for really strict defects or crashes happening in the human population.

One of the problems with endocrine disruption is we frequently don't know what chemicals we're talking about.

But all these chemicals aren't ubiquitous. There are populations that tend to be more highly exposed to some chemicals than others. The problem is finding the appropriate populations and making sure that you can control for the differences.

DH: What are the trends with children?

LB: Well, this is the emotional part of me and I think everybody has their rational and their emotional parts. But, it does seem to me that there are more children who are having organic kinds of behavior problems -- not just because mommy and daddy fight all the time or not just because there are economic issues or there's not enough structure in the life they lead.

But it does seem that there are more children who, who have learning problems or have attention problems. And we know that in experimental animals we can model those kinds of behavior if we've had exposure, pre-natal exposure, to some of those kinds of chemicals. So it does make me wonder at times whether there might be something in our environment which is associated with what appears to be an increase in these kinds of problems.

DH: How difficult would it be to solve these problems? Can science do that?

LB: Science is a process of discovery. It's very hard at the beginning of your trek to know how quickly you're going to get to the end. The potential, or the possibility, of endocrine disruption is just one of the issues that we deal with when we are concerned with environmental effects on human health. We know that air pollution can affect our health. We know that certain chemicals in our water supply can affect our health. We know that certain herbicides and pesticides can affect our health. We don't know whether some of these chemicals may also be affecting our hormonal system.

So we've embarked on a research program to try to get to those answers. But it's going to take time. And if we try to rush it, we're going to end up without any answers at all and just more confusion.

DH: Making this a top priority -- is that what's called for?

LB: Congress was absolutely appropriate in the Safe Drinking Water Act of '96, and in the Food Quality Protection Act, saying that we need to determine whether endocrine disruption is a problem. However, Congress was not very helpful to scientists when Congress told us how to do it. Because there's no way that we can develop a rapid screen in two years and have it be scientifically valid.

DH: Are you frustrated about just studying it more?

LB: I would say we need to study it smarter. Screening tens of thousands of chemicals to find out whether or not they bind to a specific hormone receptor is not going to tell us whether these compounds in the environment are going to disturb our endocrine systems.

DH: What is the most convincing data that says the sky isn't falling here?

LB: It would be easier to answer the converse: what's the most convincing data to suggest that there could be some problems happening?

There's fairly good agreement that, in quite a number of countries, testicular cancer has increased. There is growing evidence that there is an increase in hypospadias. I think the jury is not in yet on whether or not there is a decrease in sperm count. However, this does make me wonder whether or not something might not be happening.

DH: With sperm counts, it's not clear.

LB: I think it's absolutely unclear whether or not sperm counts are declining over time in different populations.

I think this is a very complex issue. Just measuring sperm counts is not as simple as it sounds. A decrease in sperm counts can be due to lots of different things. Not just estrogens. Tight jockey shorts can cause a decrease in sperm counts, or too long in the hot tub could decrease sperm counts.

It's probably rather naive of us to think that if there's a drop in sperm count, it's due to a single kind of chemical exposure.

DH: And there are conflicting studies.

LB: When I see conflicting data, it usually means to me that the jury's not in. We just don't have all the information yet. So until we have more information, and that may mean more studies, better studies, larger studies, I think we're still going to be in the situation that maybe there's a problem, maybe not.

Sometimes it can get more confusing. But some of that confusion really is going to help us ask more questions, eventually, to make sense of the entire package. So when we look at the whole sperm count debate, we have some studies that show a 50 percent decrease. Other studies that say absolutely no decrease. But we're beginning to try to look at the studies in total, look at the whole weight of evidence of all the studies, look more carefully at the individual studies and try to pull it all together to make a coherent whole.

DH: Should industry be making more out of this?

LB: I think industry is very legitimately involved in trying to determine how valid the hypothesis of endocrine disruption is. They are, industry is the source of many of our chemicals in commerce today and they are concerned that many chemicals which have important commercial and industrial uses might become suspect. And they are really interested in trying to determine which of their chemicals, in fact, might be a problem because the people in industry are people just like you and I and they don't want their children or their grandchildren to be impacted by something which may turn out to be a bad actor.

I think at this point industry is really reserving judgment and trying to understand are there really chemicals out there that are perturbing hormone systems in people.

My impression is that industry scientists have been actively involved in trying to develop, say, some of the relatively short-term screens to identify chemicals that might have the potential to disrupt hormone systems. I think industry is concerned. I think many people in industry do not think that this is a major environmental problem. But I think that they feel they need to determine and prove whether it is or it isn't.

DH: Why would they feel it's not a potential problem?

LB: Well, I don't know whether hormone disruption is a major environmental hazard to people or not. I know there's a potential that it could be. I know chemicals can disrupt endocrine systems in people. That's unequivocal. But whether the levels of environmental chemicals to which you and I are exposed could be associated with any kind of adversity in the general population at this point is a question I don't think we have the answer to.

DH: What is the role of the fear of breast cancer in this debate?

LB: Breast cancer is one of the cancers that we know has a strong hormonal component. We know that one of the major risk factors for breast cancer is sort of the total amount of estrogen that a woman has seen in her lifetime. So that women who have more children tend to have less breast cancer. Women who enter puberty later and menopause earlier tend to have lower levels of breast cancer. We know that prophylactically, if you reduce estrogen levels in a woman, you may reduce the risk. Or, in the case of a breast cancer that was already there, the recurrence of breast cancer. So we know that this is a cancer that has an endocrine component.

Over the past maybe, I'm not sure if it's 20 or 40 years, we've seen a fairly dramatic increase in the level of breast cancer in our population. And we don't have a clear-cut answer to what the basis for this increase is. We know it's not just better detection. Although, that may be responsible for part of the increase.

So, since we know that chemicals that act like estrogens can enhance the growth of breast cancers, it's a reasonable hypothesis that maybe there are environmental chemicals out there that are associated with the increased risk of this endocrine sensitive tumor.

DH: Some say research does not show a correlation between manmade chemicals and breast cancer.

LB: I'm not sure that we really know. And clearly people haven't looked at all potential chemicals that might have estrogen-like activity.

If we want to prove a hypothesis or even test a hypothesis, we'd be much better off looking at people who have much higher exposure as compared to people who are just slightly more highly exposed.

So, at this point, I don't think that we have a final answer on whether or not these kinds of chemicals might or might not be associated with the increase in breast cancer in our population.

DH: This is an emotionally powerful issue. Is it fair to include the issue of breast cancer in the debate?

LB: Well, I, actually, you're asking me this personally. And I personally think it's important to include it because endocrine disruption is more than just effects on reproduction and development.

In fact, cancer is a result of altered endocrine status. Or altered endocrine responsiveness. And, so, I think it's appropriate to include it.

I think science and scientific discovery is a process. It's not an all or nothing thing. As we learn more, as we learn about something, that prompts us to ask additional questions and then we learn more. And then that forces more questions and our knowledge base increases and eventually we develop an understanding based upon all the available information and everything we've learned, not based upon a single piece of information.

Scientific discovery is rarely a straight line. It's usually a winding road. And it's very hard when you embark at the beginning, or even jump in at the middle, to know where it's going to lead you in the end.

At best, we're in the middle. I personally think we're still pretty much at the beginning and I think this road has some fairly, is going to require some pretty new engineering technology to get us across some of the bridges.

DH: Given our experience with DES, what are the worries for children?

LB: I think as parents, we all worry about our children. But I think we have to look at the world that our children are living in and realize that they have tremendous access to food, to education, to all the necessities of life plus much more. That their life span is likely to be greater than ours is, which is certainly greater than our parents' was and much greater than our grandparents' or great-grandparents'.

So, while we may have concerns, and I'm not discounting that there may be real concerns, I don't think that we should be paralyzed by them or overly worried about what chemicals may be doing to future generations.

So, EDSTAC has been given a nearly impossible task. It involves all the stakeholders -- so it involves people from environmental action groups, it involves industrial representatives, it involves government people, it involves academic people. And they have been charged, within a very short period of time, to develop a rapid and sensitive screen to identify endocrine disrupters.

There is no way that that can be done in the time frame which has been asked. They are focusing on three types of hormone systems. Estrogens, androgens, and thyroid hormones. The charge is to develop a sensitive and rapid screen.

They've done an excellent job trying to meet that charge. But it was probably not the right charge to begin with. And, even if they can develop a rapid and sensitive screen which will pick up some kinds of endocrine activity, it is unlikely to pick up all kinds of estrogenic, androgenic, or thyroidal endocrine activity. And it may not even begin to address all the other hormone systems that we have in our bodies.

DH: Theo Colborn suggests that we need a Manhattan-like project to address the issue.

LB: I think this issue could use to have the whole level of discourse lowered so that we can begin to really say what is the question, where is the data to address the question, and what, what do we need to do to get the answer.

I think there are a lot of people sort of playing on the periphery of the question and not getting to the heart of the issue. So I think that some quiet discourse, involving all the stakeholders, where we really begin to say what is the real question that we're trying to address -- is the real question subtle changes in people which are, for example, causing more children to have behavioral problems? Is that the question we're trying to address? If that's the question, how do we go about getting the answer?

If the question is the increase in breast cancer associated with chemicals in our environment that are causing breast cancer by a hormonal interference, how do we go about addressing that question?

I think there's a lot of science which is being done where people haven't really stepped back and said, is this science going to answer the question I really want to ask?

DH: Is there enough evidence to act with precaution?

LB: I think caution is always appropriate, but not when that becomes paralysis. I think that we need to look at areas where there may be chemicals that may have some hormonal activity, and ask the question, do we need these chemicals? I think there should be some kind of issue of need.

If there's a chemical for which there is no use or there's an alternative which can do the job just as well, and the first chemical we know can, say, bind tightly to the estrogen receptor and cause estrogen like effects, maybe we should say we don't need this chemical because we have an alternative.

Or, if there's a chemical that's out there as an unwanted contaminate or byproduct of an industrial process and we know how to run an industrial process without the contaminate, well, let's do it.

But in many cases, we're dealing with chemicals that have real benefits. Chemicals that are important to how we live our life. And to say that we should just eliminate those chemicals may not be the most reasonable approach.

DH: Even given potential health effects?

LB: I think we have to step back and look at the whole plate. If you eliminate chemical X, do you now bring in chemical Y. Maybe we don't know anything about chemical Y. Ok, we know that chemical X might have some potential to disrupt hormone systems, but if we know nothing about chemical Y, maybe that's going to be much worse.

I think we have to be careful not to jump from frying pans into fires before we totally evaluate all the issues.

DH: Reasonable thing to do. Some people say they can't wait.

LB: For example, in Theo Colborn's book, she suggests that you don't microwave in plastic because maybe there's a potential for some chemicals that are present in plastic to leach into your food.

Well, I've stopped microwaving in plastic, not because I'm convinced that this is a real hazard, but because it's something I didn't have to do anyway. It's just as easy for me to microwave my food, you know, in glass and that means that there's less plastic going into the environment which has other problems.

So, I think we can look at what makes sense from multiple perspectives, and maybe it makes sense that we try to use less plastic. Maybe it makes sense that we use less disposables. And maybe as a side benefit from using less of those, maybe there'll be less potential -- and I stress potential -- for endocrine effects. But there clearly would be fewer disposal issues for all this plastic.

We're clearly concerned about tremendous amounts of waste. We talk about the "3 Rs" in the environment: reduce, reuse and recycle. So that it makes sense that we try to apply those principles across the board, and if by doing those principals, maybe we also help ourselves by less exposure to certain kinds of chemicals -- two benefits.

DH: What do you think of the Jacobsons' work on the effects of these contaminants in children?

LB: I think the Jacobsons' work is an example of work which is being done by a number of investigators who are trying to associate chemical exposure -- usually pre-natal chemical exposure or maybe early infantile exposure -- with adverse effects on neurodevelopment.

We know that some of these neurodevelopmental changes can be caused by alterations in the endocrine system. We know that some of these chemicals can cause those kinds of alterations in the endocrine system. So, we're beginning to build the bridge: chemical can alter endocrine system, altered endocrine system can cause this effect. Therefore, chemical can cause this effect.

That's the bridge that's being built in a number of different kinds of studies. But I don't think that we've completed the span.

DH: How concerned are you about health effects?

I think endocrine disruption may be occurring in segments of our population who are more heavily exposed to endocrine disrupting chemicals, or are at increased susceptibility either because of their age or their genetics or some other condition.

I am personally most concerned about the persistent chemicals that we have more difficulty in controlling, since once you get them into your body they tend to last a long time. Or once they enter the environment, they're there a long time.

I think for the chemicals that are not environmentally persistent or not biologically persistent, we really need to understand how high are the doses that are associated with adverse affects.

The real question in all of this is, if we are getting multiple hits, are these multiple hits enough to bring about adverse affects? And I think we're just at the beginning of trying to understand the issues of mixtures of chemicals that may be able to impact our endocrine systems in different ways. The question is, will the multiple hits be enough to knock us down?