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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
Online NewsHour links
December 23, 1996
Fred de Sam Lazaro looks at Minnesota's mutant frogs.
January 1, 1997
Paul Solman reviews the year in genetics.
Browse the Online NewsHour's science coverage.
The Online NewsHour's editors asks: In simple terms, what is the biochemistry behind synergy?
Dr. Lynn Goldman of the EPA responds:
In the simplest of terms, synergy is defined as a situation where the combined effect of two or more chemicals is much greater than the sum of the effect of each chemical alone. Some pesticide researchers only consider synergy to be significant when it exceeds l00 fold. There are many possible biochemical mechanisms for synergy like that seen in the Tulane study. One chemical may alter transport of another through the yeast cell wall, in effect raising the intracellular levels of a weak estrogen to a physiologically significant level. Alternately, one chemical might bind directly to estrogen receptor binding site, while another activates the receptor through a secondary pathway such as phosphorylation. In general, many different biochemical mechanisms could be affected by different chemicals in mixtures resulting in synergy. However, synergy resulting from different biochemical acting through the same mechanisms unlikely.
Prof. Porter of the University of Wisconsin responds:
We don't know.
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