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| Toxic Cocktail? Is a toxic mix more deadly than its parts? March 22, 1997 |
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Questions asked
in this forum:
Where do estrogenic toxins come from? How could combinations of estrogenic toxins be more harmful than its parts? What could be causing the discrepency between the synergy studies? Could a better cellular test be developed to look for synergy? If the Tulane study proves correct, should the EPA lower its acceptable levels for estrogenic toxins by a factor of 1600? If synergy is proven to exist, how should EPA testing of toxins be changed? Additional comments
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Any good barfly knows that a cocktail's punch is much more potent than its individual parts. Unfortunately, the same may be true for toxins. A team of researchers at Tulane University in New Orleans believe that a mixture of estrogenic toxins -- chemicals that act like the natural hormone estrogen and found in groundwater, food and soil -- can be more harmful than had been previously thought if mixed together. For example, the Tulane researchers found one mixture of estrogenic toxins to be 160 to 1600 times more toxic than chemicals that made up the mixture.
The effect is called endocrine disruptor synergy, but not everybody believes the Tulane data proves its existence. Two groups -- one from Texas A&M University, the other from the Environmental Protection Agency's National Health and Environmental Effects Research Laboratory (NHEERL) -- presented data at a toxicologist meeting in March that showed no synergy between estrogenic toxins.
"Basically we haven't found synergy ... but my view is that it's always possible," Thomas Wiese, a University of North Carolina post-doc researcher currently working at the NHEERL, told an Online NewsHour editor.
But the real story in this controversy may be its effect on how it could change the way EPA measures toxicity of chemicals. The government's environmental watchdog current tests doesn't examine how a chemcial interacts with other toxins that it could come in contact with once its released into the environment.
Also, simply exposing a colony of cells to a toxin may not be the best way to test for toxicity, says Prof. Warren Porter, a University of Wisconsin zoologist, who is also a guest for this forum. The contradictory data regarding synergy may be due to the limits of using only cellular tests, Porter says, and animal tests may be needed to clear up the confusion.
Our forum asks: What could be causing the synergy? Could other chemicals act in a similar fashion? Should the EPA change it testing practices to account for synergy and other effects?
Your questions are answered by Prof. Warren Porter, chair of the University of Wisconsin's zoology department, and Dr. Lynn Goldman, the EPA's assistant administrator for prevention, pesticides and toxic substances.
Questions asked in this forum:
Where do estrogenic toxins come from? How could combinations of estrogenic toxins be more harmful than its parts? What could be causing the discrepency between the synergy studies? Could a better cellular test be developed to look for synergy? If the Tulane study proves correct, should the EPA lower its acceptable levels for estrogenic toxins by a factor of 1600? If synergy is proven to exist, how should EPA testing of toxins be changed? Additional comments
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