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

Do Pesticides Alter Hormones?

Air Date: Week of

New studies on children and mice suggest a link between pesticide exposure and hormonal disruption, leading to learning disabilities and changes in aggressive behavior. Steve Curwood talks with Los Angeles Times environment reporter Marla Cone, who has been following the research.


CURWOOD: This is Living on Earth. I'm Steve Curwood. A growing body of research on pesticides suggests they may be permanently damaging the developing brains of mammals, including humans. One study, done in Mexico, showed children with high pesticide exposures were more likely to have personality and motor-skill difficulties. Another, more recent study, published in the journal Toxicology and Industrial Health, found that mice fed small doses of insecticide, herbicide, and fertilizer, changed their aggressive behavior and became more violent sometimes and unusually placid at other times. Marla Cone, an environmental reporter for the Los Angeles Times, has been following this research.

CONE: Well, these mice were fed a mix of insecticide and herbicide and fertilizer, a very common mix that's found in the drinking water in many farming communities. And what they found is that it altered the thyroid hormones of these young mice, and it also changed their aggressiveness. And they measured that by attacks on other mice. And it suppressed their immune systems.

CURWOOD: Do thyroid hormones affect aggressiveness?

CONE: Yes. The thyroid hormones are what affect a variety of behaviors, because it affects your nervous system.

CURWOOD: Now, how similar are mice and people when it comes to thyroid hormones and aggressiveness? I mean, are researchers suggesting that a similar mechanism could affect children who are exposed to pesticides and herbicides and fertilizer?

CONE: Yes. The endocrine systems, which produce the hormones, are the same in virtually all mammals. So people now speculate that what might affect a young mouse is also affecting a young child.

CURWOOD: Now, there's another study that was published recently, and this one compared 2 groups of children living in Mexico: those living in an agricultural area, where there's heavy pesticide use, versus those living in the nearby foothills. You've looked at that research, haven't you? What did they find?

CONE: Oh, this was a fascinating study and an unprecedented one as far as I could tell. What they found with these children is -- and they tested 4 and 5 year olds -- the differences were just so dramatic. When they asked the 4 and 5 year olds from the farm valley to draw a human being, their figures were a bunch of squiggly lines that didn't even have any body parts, whereas they asked the 4 and 5 year olds living in the area where no pesticides were used, and they had a head and eyes and arms and all kinds of body parts And what scientists believe that is showing is that there is a problem with their fine motor skills. They can see a human being, they know a human being has all these body parts, but their brain cannot command their muscles to actually draw these body parts. In addition to their problems with drawing stick figures, they also had problems catching balls, and they seem to be less social. They played by themselves, and they had more levels of aggression with their family and their siblings.

CURWOOD: Now, there's been some skepticism about this study, hasn't there? Can you tell us a bit about that?

CONE: Yes. There are some toxicologists, and certainly the manufacturers of pesticides, that really doubt that you can find these types of neurological effects in children at the everyday levels of pesticides that we're seeing today. They're skeptical of the Mexico study. And I think a lot of scientists would be, because they're asking these children to draw pictures and to throw a ball, and they're watching their social behavior. This is a very subjective form of science.

CURWOOD: What about here in the United States? Are there studies showing that children here in the US are being affected by pesticide use?

CONE: Yes. There have been studies in many areas, especially in the Midwest, that link pesticide use with birth defects. And what they find is that birth defects in an area of rural Minnesota go up when these babies are conceived in the spring season, when pesticides are used the most.

CURWOOD: Are there also changes in aggression in US kids who have been exposed to pesticides?

CONE: Well, there are some thoughts that there might be that happening. There hasn't been that much research. The study out of Mexico was pretty much a landmark study.

CURWOOD: Marla, right now the EPA tests chemicals, pesticides, one at a time. But the effects you're talking about come in combinations. Is there any way to test the more common pesticide combinations? Should the EPA be doing that?

CONE: Well, the scientist who did this study with these young mice believes that the EPA should be testing some commonly-found mixes of pesticides at the very least, because he believes the EPA tests as they are now generate a great deal of false confidence in the public in the safety of pesticides.

CURWOOD: Marla Cone covers the environment for the Los Angeles Times. Thanks, Marla.

CONE: Thank you.



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