News and Events

Alligators: Canaries in a Pesticide Coal Mine?

Chemicals that cause reproductive problems in gators pose similar risk to humans says CLAS zoologist Lou Guillette

This article was originally published in the May 1999 issue of CLASnotes.

Lou GuilletteLou Guillette began conducting field research on Florida alligators in 1986. By the early 1990s he knew something was wrong. In collaborative efforts with the Game and Fish Commission and the US Fish and Wildlife Service, the CLAS zoologist had documented surprisingly low egg hatching rates and an unusually high incidence of birth defects. He'd found abnormal testosterone levels in male alligators and elevated estrogen levels and ovarian abnormalities, including growths called polyovular follicles, in females. The symptoms clearly indicated that Florida alligators were suffering from reproductive/endocrine disturbances, but why?

The pieces of the puzzle began to fit together during a 1991 visit from Guillette's "academic grandfather," Howard Bern (UC Berkeley). While at UF, Bern gave a talk on his work with a reproductive syndrome in humans called DES Daughters. The syndrome is caused by the synthetic estrogen DES, which, erroneously thought to prevent miscarriage, was prescribed to pregnant women from the 1950s to the early 1970s. Interestingly, expectant mothers who took the drug developed no complications, but their female children exposed to DES in utero all later experienced altered fertility including increased spontaneous miscarriage and symptoms of polyovular follicles. "When [Bern] started showing various slides supporting his findings," says Guillette, "I realized that this was identical to what we were seeing in the alligators....So the question became 'Where in the world are alligators getting estrogens from?' And that's when we got on the trail that maybe these pesticides [that had run off or been spilled into Florida lakes] were estrogenic."

They were right. Like DDT, many of the most commonly used agricultural pesticides act as hormones, such as synthetic estrogen, and can therefore adversely affect the endocrine and reproductive systems of living things exposed to them.

Taking a closer look at the effects of estrogenic pesticides made sense, since the lowest hatching rates (25% at that time) and highest incidence of birth defects were found in Lake Apopka, which, after years of agricultural run-off and a massive 1980 pesticide spill was (and still is) one of the most polluted lakes in the state. Conversely, hatching rates are nearer to 80% in Lake Woodruff, located in a wildlife reserve near DeLand.

Once they'd made the pesticide connection, it was time to rule out other causal agents. Guillette and his team brought uncontaminated eggs from the wildlife refuge into the laboratory and treated these eggs with the same pesticides they found in eggs from Lake Apopka. "The disturbing thing is that we've been able to recreate many of these problems [birth defects, low hatching rates, endocrine and reproductive dysfunction] in the lab using chemical concentrations equal or lower than concentrations found in Apopka eggs," says Guillette. "In fact, the EPA, the CDC and others have now taken note because the blood levels of pesticides that have caused abnormalities in alligators are similar to levels seen in the blood of many humans. We're talking about quite low concentrations."

Guillette admits that many are unwilling to accept the idea that his alligator data is relevant to human health. But the UF zoologist maintains that his primary research question, "How do man-made chemicals affect embryonic development?" has implications beyond wildlife. "People are shocked when I tell them that humans and alligators have the same hormones," he says. "We're not as different or unique as we like to think."

If alligators and other wildlife are the canaries in the pesticide coal mine, research like Guillette's may dramatically transform public policy. Guillette currently sits on three policy panels, one for the European Community, one for the Japanese Government, and one here in the US for the National Academy. "We are trying to understand where current policy fails in its understanding of the biological risk or significance of using these types of compounds," he explains. Panel members reevaluate why and how we use chemicals and what appropriate endpoints should be when calculating the risks associated with these chemicals. "Traditionally we've used things like cancer and death or major birth defects (arms and legs in the right place and the right number of eyes) to determine problems," says Guillette. "Those are still perfectly good endpoints because none of us wants those things to happen, but the question we're now asking is, are there subtler effects (subtle only in their ability to be detected, not subtle in how they might influence the organism) that we need to recognize as important endpoints in gauging the safety of these chemicals. For example, what happens if your immune system is suppressed by 15% or 20% your whole life? You have 15-20% more colds and flu and your chance of developing cancer increases by 15-20%. What happens if your child's intelligence is lowered by 10 IQ points? Is that considered detrimental? Or let's say it doesn't alter IQ but your attention span or your memory, or your ability to interact with others so that socially you have difficulty relating with colleagues and friends...if you can even make friends at all."

It's not that we should ban all chemicals, stresses Guillette. But if we do choose to use chemicals in our society we need to know what the real costs are. At present, he maintains, chemical companies only tell the public how much is going to come out of their pocketbooks at the cash register. They don't discuss what the ecological or public health costs are. "Flip over a bag of lawn chemicals and read the warning signs: 'Don't use in house,' 'Don't use on lawn next to water or lake,' 'Toxic to fish' or 'Toxic to wildlife,'" he says. "Do we think that somehow humans are exempt? What's the difference between a bird or fish cell and yours? There is none. We don't understand the implications these chemicals have for developing embryos—whether developing fish, frogs, or human beings."

Convincing the public of potential risks, however, can be difficult. "We all take drugs for headaches or other problems," points out Guillette. "These drugs were tested in some kind of animal model before they ever got to us. So on the one hand, we believe that animal reactions to pharmaceutical chemicals can give us valuable public safety information, but if you try to do the exact same thing with pesticides or environmental chemicals the argument you get back is 'Oh, I'm sorry that's animal data. You can't say that would happen in humans.' It's a real Catch-22."

Nevertheless, the Florida scientist feels it's part of his job as a state educator to try to help society understand what the implications of his research are. "Many university professors and researchers are doing this," he says. "We are public servants. We're paid by the state, and it's important for us to speak out when we see something that constitutes either a good or a bad for society." Accordingly, Guillette gives up to 50 talks around the world each year, writes articles for both academic and lay publications, does interviews and TV segments for national media, sits on environmental policy panels and works locally in the public school system.

Despite these sweeping efforts, Guillette's goals are modest: "My major goal as a scientist is to leave a legacy of people. I have no idea what the significance of my own work will be five or 10 or 50 years from now—or whether my work will even end up being significant. But I think that my legacy to science will be the students and the people I help to become scientists themselves."

And of course he also hopes that work like his will eventually make a lasting impression on lawmakers. "If we can argue in Washington that public health is equal to economic health, then I'll be really happy," he says. "Look at the epidemics in this country. The ones we don't speak about: endometriosis, fibroids, prostate disease, breast cancer. They are all diseases of hormones. The question is what's happened to our endocrine systems? Look at attention deficit disorder in children or abnormalities in growth in wildlife. When you start adding these things up, you realize there are some major concerns and problems here. One of the arguments that I've made for years in Washington is a lack of data does not mean a lack of effect. A lack of data just means we don't know. And the more we admit we don't know, the more people like me will be stimulated to find the answers."

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