THEO COLBORN: There were a lot of bits of information. One of the most obvious was that wildlife biologists had not found a single top predator fish in the Great Lakes that didn't have an enlarged, odd looking thyroid. And the same was true of the birds.
Environment Canada for years has been using herring gulls to monitor contaminate loadings in the Great Lakes. They can actually plot contamination around the lake by using "thyroid indices," which are a measure of the abnormalities of the thyroids of the herring gulls.
A second indicator was the behavior of the animals. There was the female/female pairing syndrome that everyone's heard about, where two females share a nest. The males are away, showing little interest in breeding, territoriality, or protecting the nests. There's an elegant study that shows one population of Forster's Terns, which experienced a tremendous loss of chicks; some of that loss is attributed to lack of parental care. In colonies where these problems prevailed, the young males were actually developing what are called "ovo-testes."
Other animals showed less ability to recover from immune challenges, to fight off infection. Another very common problem was "wasting"; the embryos of birds, fish, and reptiles were unable to convert the yolk sac into energy.
In every one of these instances, the animals that were troubled were dependent upon the Great Lakes for their food.
SARAH: What made you think these problems were a result of chemicals in the lakes?
THEO: I put all these bits of information into a spreadsheet to see if I could see what it all meant. What was really startling was the pattern of eggs not hatching and youngsters not being born. Among those that did make it, there was often something obviously wrong. Many of those that looked OK as youngsters didn't make it to sexual maturity and couldn't reproduce.
I looked into the chemicals associated with these ailments and came across a suite of organochlorine chemicals, including PCBs, DDT, Dieldrin. These are persistent chemicals that build up in fatty tissue.
Although every animal has these chemicals in them now, when you move inland, you don't see the high concentrations associated with shoreline exposure - nor do you see these problems. The more highly contaminated animals were showing the most severe effects. In some areas, the contamination was so great that whole populations had crashed.
The government only required industry to test these chemicals for their cancer-producing effects, and there was very little evidence that they indeed caused cancer. But the peer-reviewed literature makes clear that these chemicals are capable of causing developmental effects in the offspring through disruption of the hormonal system - that is, the endocrine system.
SARAH: We've been talking about wildlife so far. How did this concern get connected to humans?
THEO: Dr. Wayland Swain, who was director of the EPA laboratory on the Great Lakes during the 1970s, saw what was happening with wildlife in the Great Lakes area and wondered whether similar things might be happening to our children. At his suggestion, a team of psychologists studied children whose mothers ate fish from Lake Michigan two to three times per month at least six years prior to their pregnancies, and compared them with controls (children whose mothers did not eat Great Lakes fish).
They found measurable neurological deficits in these infants at birth. At age 4, these children had obvious short-term memory problems. At age 11, the average I.Q. deficit in these children was 6.2. In some children, it was much greater. These children were two years behind their peers in school.
Then Dr. Helen Daly replicated the study on Lake Ontario, and she got the same results. She also found that the children with these neurological deficits had differences in their temperaments as well. They didn't laugh and smile as much. They expressed more fear, and they were very difficult to calm down under stressful situations.
One of the more disturbing things that has come out of the study is that some of these parents who did not eat fish out of the lake had as much of the PCBs in their bodies as the women who ate fish. And their children were affected as well. So fish eating is not the sole source for this problem.
SARAH: So they found a significant shift both in I.Q. and in temperament among these kids?
THEO: It seems so. If you go back to when they first started the Lake Michigan study, you'll see that at age 4, there were 17 children who would not take the test. They were intractable. So they were removed from the study. They later found out that they were the 17 children of the mothers who had the highest PCB concentrations in their bodies during gestation.
Then at the end of the study, they removed another child from the study because he slipped below an I.Q. of 70, which put that child in the retarded class. So they took the outliers out of the study, and they still had a highly significant result. A sizeable proportion of the children in the study were affected.
Also, I guess you've read recently about the increases in what are called hypospadias. Boys with hypospadias are born with a urethra that doesn't come out of the end of the penis. Now the penis and the urogenital tract have to start growing at the same time. Hormones have to be really right in tune. This kind of a problem has more than doubled in the US, between 1970 and 1993. And that's about one in 100 boys on the average. Some places, the incidence is as high as one in 50 boys.
I've had physicians and nurses tell me that this is a highly unreported event. If this gets onto a child's health record, the insurance companies will be reluctant to insure them, because these boys have a much greater risk of developing testicular cancer and a greater likelihood of fertility problems. For the same reason, doctors often neglect to report undescended testicles because the odds of developing testicular cancer increase.
SARAH: How is it that small amounts of these chemicals can have such significant effects on behavior, metabolism, and the reproductive systems in some people, but seemingly have no effect in others?
THEO: From the day of conception until an individual is born or hatched, the development of each stage of life is fully under the control of hormones. The endocrine system controls neurological development - the brain and intelligence.
It also controls the development of the reproductive system. From conception through the 15th day in mice, and the 56th day in humans, you can't tell whether an embryo is female or male. The same tissue that would become a testicle in a male becomes the ovary in a female. On a certain day during embryonic development, hormones kick in that tell certain tissues to die back and other tissues to start growing in one way for males and in another way for females.
So the development of neurological, reproductive, and metabolic systems can be disrupted by very small quantities of chemicals that either mimic hormones or prevent them from binding to hormone receptors. A lot depends on the timing of the exposure.
SARAH: What is the connection, do you think, between testicular and breast cancer and these chemicals?
THEO: It appears now that exposure to certain chemicals during early prenatal development can increase the risk of cancers of the sex organs. With the current state of knowledge, there's a much more powerful trail from prenatal disturbances to testicular cancer than there is to breast cancer in women.
SARAH: Let's talk about that for a minute. Breast cancer risk has been associated with the length of time a woman is exposed to high levels of estrogen. Those who reach puberty early, have few or no children, and don't breast feed are thought to be at a higher risk for breast cancer. Despite that, are you saying that we still don't know if estrogen-mimicking chemicals are putting women at a higher risk of breast cancer?
THEO: That's right. The research doesn't address this. In the laboratory, very little work on these chemicals has been done with female rats and mice because their hormonal cycles make them difficult to work with. It's much easier to work with male mice.
Male mice and rats exposed to elevated levels of estradiol, the natural female hormone, or diethylstilbestrol, or to bisphenol-A, which is a very commonly-used plastics component, or to methoxychlor, a commonly used pesticide - those male mice are born with heavier prostates because the prostates have more hormonal responsive tissue in them.
Now, we have no way of knowing whether boys are born with larger prostrates, but we sure know that one of the costliest health problems in the country today is benign, enlarged prostates in men. And also, prostate cancer is killing more men than it ever did before.
So, this gives us a clue. What's happening in the breast tissue in females before they're born? Do they have a greater number of estrogen receptors, which could increase a woman's risk of breast cancer when she is exposed to chemicals that mimic estrogen? This is a field of research that is wide open and needs to be addressed. Pharmaceutical companies are making money treating problems, but you can't make money selling prevention. The research emphasis has been in the wrong place.
SARAH: The long time between exposure and evidence of illness or defect also makes it particularly difficult to link cause and effect.
THEO: We'll never have a true cause-and-effect link. This is what industry's calling for, but we never will have it. We're never going to feed substances to pregnant women and watch to see what happens to their children. Basically, we're doing that kind of experiment on a giant scale right now with everyone, but we have no control group.
SARAH: I understand another one of the challenges is that the amount of exposure can be very small and still have an effect.
THEO: Extremely small. All it took was a tenth of a trillionth of a gram of free estradiol increase to cause male mice to develop the heavier prostates. Dr. Fred vom Saal and his team at the University of Missouri found that that is the range of free hormone exposure in which the human embryo develops as well. Remember, the developing embryo takes its signal from hormones.
So now we know that the way we've been testing chemicals has been all wrong. High-dose testing that checks for gross and obvious birth defects and for cancer and mutations just hasn't worked for chemicals of this nature.
SARAH: We've talked about very low doses and the problem with making a clear case for a cause-and-effect link. There is also the question of synergistic effects, in which a combination of chemicals can have an impact many times greater than the sum of the parts.
THEO: There are about 82,000 industrial chemicals in use. Pesticides have about 875 active ingredients along with 1,800 inert ingredients, some of which are not really inert. There are about 21,000 formulations of pesticides that include various combinations of chemicals.
There are so many different chemicals out there that we know nothing about, especially when you start getting into the plastics, the plastic polymers, and additives to plastics. The biggest part of our manufacturing system in this country today uses plastics, which are used in construction materials, telephones, airplanes, packaging, etc.
Packaging is a tremendous problem, because we now know that some of these chemicals are leaching out of packaging into food.
So industry is concerned.
SARAH: And wondering if they'll get sued if these effects can be traced back to their products?
THEO: You're right. I didn't want to say that, but that's what industrialists are thinking.
We didn't know before five or six years ago that plastics were a problem. There are a lot of companies that are really concerned, particularly those producing products from materials they thought were safe. They're the ones who are going to be held liable, because they produce the products that you put in your home.
SARAH: Are some companies taking a precautionary approach and moving away from using these chemicals?
THEO: Many of them are trying to find alternative materials. They want to be able to assure their customers that people can use these products without harm to themselves or their children. But we know the continued use of these plastics increases what leaches out of them.
SARAH: How cautious do people need to be about these chemicals once they're past childbearing age?
THEO: Well, that's an interesting question. If you were sensitized in the womb, it would appear that then you need to try to avoid exposure to these chemicals later on in life.
I'm one of the fortunate ones. I was born in 1927, so I do not have to worry about prenatal sensitization. But I do worry about my children, who were born in the 1950s. They were the first guinea pigs. My body was full of these chemicals by the time I gave birth. I was a pharmacist; I thought DDT was the best thing since sliced bread. My husband came home with the first pest strips. We filled our house with pest strips. I regret how I exposed my children.
In an adult, it seems you can reverse these effects. If you feed estrogen to a man, he'll start growing breasts, but if you take that estrogen away, the breasts will disappear. But changes that happen during development are far less reversible; you can't go back and rewire the brain. The brain has to be programmed and develop correctly during specific stages of development.
We don't want to have to put pregnant women into isolation. I really think we need to get certain chemicals out of our lives, for example, the organochlorine chemicals, DDT, PCBs, dioxin, hexachlorobenzene; these are in all of our bodies, in the Arctic, in our food web - in beef, lamb, chicken. As a matter of fact, it looks like beef may have more persistent organochlorine chemicals like PCBs than ocean-caught fish.
We can't do anything about the chemicals that have been released and are out in the environment. But we could at least not make any more, and we could try to contain those that are now in use.
SARAH: Which brings up the question of the precautionary principle. Barry Commoner has said that we should avoid any substances that were not part of the evolutionary soup from which we evolved.
THEO: It's beginning to look more and more like that is a profound statement. But, you see, we're hooked into petroleum. Some of the by-products of producing gasoline are pretty nasty, and industry uses those nasty things to make plastics. This makes plastics cheap, and it gets the gasoline producers off the hook, since they're not blowing those nasties into the air or putting them into our water. They're putting them into products that are generally thought of as safe, because they're solid and long-lived.
SARAH: When you work with something that's this pervasive and so seemingly intractable, what is your source of hope?
THEO: My source of hope is that every day, we're learning more and more.
Scientists are now looking at the effects of exposure across generations. They're thinking not only in terms of damage to genes but in terms of the ways the genetic messages get expressed, since genes are turned on and off by chemical messengers at very low doses. They're researching low doses, thinking about what happens when you tweak a system that's up and running and what happens when you change the message.
Also, people are beginning to look at the question of what this can do to a society. A groups of scientists meeting in 1995 in Erice, Sicily, observed that these chemicals can not only destabilize wildlife populations, they can change the character of human societies.
Theo Colborn is coauthor of Our Stolen Future: A Scientific Detective Story - Are We Threatening our Fertility, Intelligence, and Survival?, She is also a senior scientist at the World Wildlife Fund in Washington, DC. She has raised four children and worked as a pharmacist and a sheep rancher before going back to school to get her doctorate in zoology at age 58.