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Public Radio's Environmental News Magazine (follow us on Google News)


Air Date: Week of

Recent research into the combined effects of various chemicals shows some deleterious health effects. Of special concern is the substance Atrazine when it comes into contact with other pesticides and herbicides. Robin Finesmith of Living on Earth's Midwest Bureau in Cleveland reports.


CURWOOD: This is Living on Earth. I'm Steve Curwood. This year has not been a good one for those concerned about the quality of drinking water. Study after study has found substantial levels of pesticides and other farm chemicals in the water supply of many communities. Some of these chemicals are known to cause cancer. But cancer may not be the biggest worry. Many of these substances are also known to be disrupters of human and animal hormone systems. That means that they can wreak havoc with our reproductive and immune functioning, as well as our ability to think and perform other neurological tasks. Some say these chemicals are only harmful in high doses, and that current Federal health standards more than ensure public safety. But those claims are based on government regulations that test each chemical separately. Recent research suggests that mixtures of these chemicals can be harmful at low levels commonly found in the environment. From the Midwest Bureau of Living on Earth at WCPN in Cleveland, Robin Finesmith reports.

FINESMITH: If we lived in a world where there was only one environmental pollutant, life would be fairly simple. We'd have to worry about how much of that pollutant we came in contact with, and how often, but not much else. Of course, life isn't like that; there are thousands of potentially dangerous substances around us. But EPA regulations don't usually take that into account. The Agency screens chemicals one by one and sets safe exposure levels based only on contact with that one substance. But what happens when we're exposed to several of these at the same time? Say, for instance, a number of common pesticides?

PORTER: Atrazine by itself looks very clean. But when we begin to put in other compounds, like nitrates or other insecticides or herbicides, then things start popping up that didn't show up before.

FINESMITH: Dr. Warren Porter is a Professor of Zoology at the University of Wisconsin at Madison, who has been looking at the interactions of various pollutants commonly found together in the environment. The findings of his current research involving the herbicide atrazine haven't yet been published, so he's not talking about the specific results yet. But in another study published in 1993, he and 3 Wisconsin colleagues found some startling hormonal and neurological effects in laboratory rats exposed to combinations of 3 other pesticides, including a close relative of atrazine.

PORTER: We are seeing an elevation of thyroid levels. We are seeing a suppression of learning abilities and spatial discrimination capabilities. A suppression of speed of learning. And correlated with that, we have seen changes in certain nerve transmitters. Chemicals that the nerve endings release in the brain. Particularly, these changes have been concentrated in the memory and the motor coordination centers of the brain.

FINESMITH: This type of research is fairly new to science and challenges established toxicological and epidemiological practices, which generally look for health effects following a single substance line of inquiry. But proponents say it's vital if we're to understand how industrial and other chemicals actually affect us and the environment. Dr. Ana Soto is a professor of cellular biology at Tufts University.

SOTO: One of the things that concerned people working on the Great Lakes area, in special, was that wildlife was contaminated. Specimens were contaminated with a lot of different chemicals. And the problem was to discern whether the effects that are being manifested, like if, for example, if these animals cannot reproduce, is it due to one of those compounds? Or to the combined effect of all of them, or a few of them?

FINESMITH: Dr. Soto and her colleagues have tested the effects of mixtures of a number of commonly used chemicals on human cells in her lab. they combine things like pesticides, plasticizers, and food preservatives.

SOTO: Now, our experiments have shown that minute quantities of these chemicals, that if found singly, will not be a problem. When they are found together with other chemicals at those low doses, could be a problem because they can produce an effect.

FINESMITH: But Dr. John McCarthy, Vice President of the American Crop Protection Association, is skeptical. He doubts that otherwise safe amounts of industrial chemicals can combine together to cause problems in the real world outside of a laboratory. And McCarthy thinks it's virtually impossible to test for such real life effects in any credible way.

McCARTHY: It's kind of like a never ending game of trying to figure out what kind of mixtures. You not only have manmade chemicals, you have naturally occurring chemicals that might have the same thing. You know, what are the combinations and permutations of all this? So that it becomes almost a mind boggling exercise to figure out what kind of a potion do you put together to figure this out?

FINESMITH: Mind boggling or not, it's an exercise the EPA is starting to tackle. Mixtures are a part of the EPA's new research into endocrine disrupting chemicals, and they're also part of the Agency's review of atrazine and related pesticides. Dr. Penelope Fenner-Crisp is the Deputy Director of the EPA's Office of Pesticide Programs.

FENNER-CRISP: We may not know fully how to do it, but how will you learn if you don't try? And so you start step by step; you don't try to figure out how a thousand things in your life may affect you all at once. You start small.

FINESMITH: Still, there remains considerable debate within the EPA and elsewhere as to how much emphasis should be put on research into the combined effects of chemicals, especially in light of other pressing research needs and shrinking Federal dollars. For Living on Earth, I'm Robin Finesmith in Cleveland.



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