Are man-made chemicals in the environment – chemicals like those linked to changes in the sexual development of fish in streams across the country – causing birth defects in children?
Louis J. Guillette Jr., a reproductive biologist widely known for his studies of sexually stunted alligators in Florida lakes polluted by agricultural pesticides, thinks environmental contaminants almost certainly are producing human birth defects.
Guillette, who recently left the University of Florida after 25 years to become a professor of obstetrics and gynecology at the Medical
University of South Carolina, will deliver the third in a series of lectures sponsored by the Freshwater Society and the University of Minnesota’s College of Biological Sciences.
In addition to his position at the medical university, Guillette has an endowed professorship in marine genomics at the Hollings Marine Laboratory in Charleston, S.C. And he is a professor at the Howard Hughes Medical Institute in Chevy Chase, MD.
The lecture will be at 7 p.m. Tuesday, Sept. 14, in the Student Center theater on the University of Minnesota’s St. Paul Campus. The lecture series, funded by an endowment honoring the late Malcolm Moos, a former University of Minnesota president, is part of the Freshwater Society’s 2010 – The Year of Water.
Guillette’s lecture, which will be aimed at a general audience, is titled “Contaminants, Water and Health: New Lessons from Wildlife.” The lecture is free and open to the public, but seating is limited and pre-registration is required. To register, go to www.freshwater.org.
In an interview with the Freshwater Society, Guillette talked about his research. The transcript of the interview, edited for clarity and brevity, follows:
How do you describe the environmental contaminants you have spent your career researching?
I define them as inducers of birth defects. I’m primarily interested in how environmental contaminants actually alter developing embryos.
What’s the connection between these contaminants and water?
Many of the chemicals that we use, whether it be in agriculture or on our lawns, or even in our everyday lives, all end up in the water. We put them on the land and rain comes along and washes them off, or we put them in the toilet or pour them down the sink.
Theo Colborn wrote in Our Stolen Future about you finding alligators at Lake Apopka with smaller-than-normal penises. Talk about what you found.
Initially, what we found was hatch rates that were very low. Fifty percent of the eggs being laid were dying, and even after many of the baby alligators hatched they would die. I’m a reproductive biologist, so I mostly focus on the reproductive system. We found abnormal development of the ovary, we found abnormal development of the testes, we found altered hormone levels. For example, little males with elevated levels of estrogens and depressed levels of testosterone. Little females actually had elevated levels of estrogen, abnormally high.
Did you at that time form a hypothesis about what was causing the abnormalities?
Our initial observations were not linked to chemicals. We thought it had something to do with extremes in temperature in the nest, or changes in the gas environment of the nest. We even went on to study if it was nutrition. It wasn’t for a number of years that we started to realize there was a strong correlation; that is, the abnormalities we were seeing in alligators were coming primarily from those living in contaminated environments, mostly lakes contaminated with agricultural chemicals.
Pesticides or herbicides?
Mostly pesticides. The main ones we worked on, of course, were some of the legacy ones, the very persistent ones — things like DDT and its metabolites, chlorodane and its metabolites, toxiphene and its metabolites.
And then what sort of experiments did you do in the lab?
The power of studying wildlife is that you can go beyond just associations or correlations. We found there were lots of contaminants and found there were problems, which was suggestive. But we didn’t say that one caused the other. The advantage was that we could follow that up in the laboratory. What we were able to do was to take alligator eggs early in development, actually treat them specifically with various kinds of chemicals that we think are causal agents, then we incubate those eggs and then look at the offspring or even at the embryo. We can take biopsies, we can look at gene expression — we’ve done that.
We can actually cause these young to have altered penis development, altered ovarian development. We’ve been able to start to put together the genetic pathways that lead to these abnormalities. Many of those genetic abnormalities are very similar to genetic abnormalities we see in humans or in laboratory rodents that are exposed to contaminants.
Do you believe you have established a convincing link between environmental contaminants and birth defects in alligators or other species?
Yes, I think we actually have a convincing link between contaminants and various birth defects. The important part beyond that is that we’ve established that concentrations of contaminants that are ecologically relevant can cause abnormalities. That is, we don’t have to give monstrous doses to get those effects. So, do we actually have populations that are being affected? Yes. Have we started to develop that causal link? The answer is, yes.
Have you or anyone else established a link between environmental contaminants and human birth defects? Can that link ever be proven?
That’s a good but difficult question. In order to use the word “causation” you have to do an experiment. So, we actually have to treat an individual with a chemical and show that we created a birth defect. But that’s ethically unacceptable in humans. So there are lots of people who play with these words, and they’ll say to you there’s no causation between contaminant exposure and, for example, birth defects in children, unless it’s from an industrial accident or a pharmaceutical agent where moms were given drugs like diethylstilbestrol (DES), or thalidomide.
Is there enough evidence out there from both laboratory animals and wildlife to show causation between contaminant exposure and birth defects? Yes. Does it also suggest that it happens in humans? Yes. If we can show causation in wildlife, then it’s highly likely the same thing is happening in humans. That’s a long answer but I think people have to understand that there are semantics being played here.
The U.S. Geological Survey recently released a summary of research on fish at sites across the country. The report said one-third of all the male smallmouth bass examined carried immature eggs, a sign of “intersex.” At Lake City on the Mississippi River, 73 percent of the males tested had those eggs. Should we be wary of swimming in the Mississippi or drinking its water?
I don’t think there’s a big problem with swimming, unless you’re swimming directly below sewage treatment facilities or outflows from chemical plants. As far as eating fish, certainly fish are good for you, but it comes down to moderation. If you’re an adult, you need to think about how much fish you eat. And especially if you have children you have to think about what they’re eating. My mantra is moderation.
What about drinking the water?
Public water treatment is pretty effective for removing some things, but not very effective for removing other things. We still don’t know which things are most important. It sounds like I’m waffling here, and I am in some ways. Something we haven’t talked about is nitrate, which is fertilizer. We’re starting to show that nitrate is a pretty effective endocrine disruptor, even at what are approved drinking water limits.
What do you personally do to lower the risk you and your loved ones face from environmental contaminants?
This goes back to my mantra of moderation. We eat moderate amounts of fish and moderate amounts of meat. We try to eat organic vegetables when we can. We don’t microwave in plastic or cook in plastic. We do have filtered drinking water and that’s what we use for tea and coffee. We don’t use a lot of stuff that comes in plastic. It’s not that I exclude any of those kinds of things completely from my life, because I have to live a normal life or at least try to. The big question is whether we can limit our exposure. I think we can do that through being educated and being smart about what you do in everyday life.