Scientists research effects of pesticides
Subject: Scientists research effects of pesticides
Date: Tue, 8 Jan 2002 11:00:17 -0500
From: Stephen Tvedten <steve@getipm.com>
Organization: Get Set Inc. (www.getipm.com)
To: Paul Helliker <phelliker@cdpr.ca.gov>
Director, State of
California, Department of Pesticide Regulation
cc: Christine Whitman whitman.christine@epa.gov
Dear Mr. Helliker, I thought you might like to read an article that was published 1/7/2002, entitled: Scientists research effects of pesticides in the Tri-City Herald (Kennewick, Pasco and Richland, Wash.) By Annette Cary, Herald staff writer.
The statistics cited by the Environmental Protection Agency on children and pesticides are frightening.
Somewhat controversial research has found that children develop leukemia three to nine times more often when pesticides are used around their homes. Other cancers, including brain tumors, also have been linked to exposures to insecticides.
But the amount of scientific information is limited on how harmful exposures to small amounts of pesticides are. That includes pesticides children may be exposed to from sources such as flea collars on pets, spider sprays and residues on food.
At Pacific Northwest National Laboratory in Richland, scientist Charles Timchalk is leading a team hoping to get a better idea of how different quantities of pesticides may affect children with a $750,000 grant from the EPA. A second grant for the same amount from the U.S. Centers for Disease Control will be used to look at how exposures to multiple pesticides may affect farm workers.
For both studies, he's exposing rats to pesticides, then using the lab's sophisticated computing systems to build computer models estimating the effects of pesticide exposure based on the physiology of rats and humans.
He's focusing on organophosphates, a commonly used type of pesticide. They work by targeting and disrupting the nervous systems of insects.
"The (human) nervous system is not much different than insects," Timchalk said. "We have the same target."
Organophosphate pesticides inhibit the enzyme acetylcholensterase, which is found at many nerve endings and is necessary for nerves to function correctly. Interfering with the enzyme from high doses of pesticides can cause vomiting, profuse sweating and muscle twitching, according to the EPA. Repeated exposure may damage the nervous system.
Greater doses can paralyze the chest and cause breathing difficulties or death, which can occur in those who use pesticides to commit suicide.
In Timchalk's research for the EPA, he's exposing both newly born and adult rats to small amounts of pesticides, then comparing the effects for different doses. He'll look at how the chemical is absorbed and metabolized and he'll also measure the inhibition of neurological enzymes.
"The trick is to make extrapolations of the data to humans," he said.
The information will be used to build a mathematical model fitting the rat data to existing data for humans to predict the effect of pesticides on children.
There is some data on how adults metabolize and eliminate toxins, including chemical company tests of very small amounts of pesticides on adult volunteers and studies of people, such as suicide victims, who consumed large quantities of pesticides.
But "children are just not small adults," Timchalk said. "You can't treat them the same."
First, their behavior is different. They may spend more time on the ground or floor, where pesticides may have been tracked or settled out of the air. They also are more likely to put their hands or other objects that may be contaminated with small amounts of pesticide in their mouths.
Second, their bodies are still developing and immature systems may not handle toxins as effectively as adult systems.
"We're interested in how they metabolize and eliminate the toxins," Timchalk said.
He already knows baby rats are more sensitive to pesticides than adults. The EPA fears that greater sensitivity could translate to problems with brain or other nervous system development in humans.
The study will look at exposure through the skin and ingestion of the chemical, such as in the residues on food, and also see what repeated exposure does.
Now the EPA sets standards on how much residue is safe, based on amounts with no observed effects on animals. Those amounts are then reduced multiple times to take into account uncertainty and other factors.
"The question is 'Is that good enough?' " Timchalk said. "There is uncertainty in the process. There is not a lot of science."
Timchalk's model should give the EPA a physiological model to help base limits more on science.
"I think we are going to find they are overly conservative," he said. "I think it will make us feel very comfortable there is not any effect on children" from residue levels allowed now.
Timchalk's second study is intended to help the federal government understand whether the limits it sets on individual pesticides may be insufficient if people are exposed to multiple pesticides. That will primarily affect farm workers, who may work with more than one chemical at once or over the course of a week or two.
By testing rats, he and other scientists will learn more about the metabolism of various pesticides and develop computer models of the merged effects of the chemicals.
Timchalk is hoping the project will have applications for another lab project, development of a saliva monitor that uses a few drops of saliva to quickly and inexpensively check for harmful chemicals in the body.
With more information available on the cumulative and combined effects of pesticides, the monitor could be useful for quick tests to show when farm workers may need medical care or should not work around chemicals for periods of time.
Source url: http://www.tri-cityherald.com/news/2002/0107/story2.html
Well Mr. Helliker, even when scientific research clearly proves your "registered" POISONS are injuring and/or killing innocent people; your continuing demand that only these dangerous "registered" POISONS can be "legally" used/misused to "control" pest problems, will continue to create more and more innocent POISONING victims.
Respectfullly, Stephen L. Tvedten
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