In the June 7 1996 issue of Science, Tulane University researchers studying the potential estrogenic effects of pesticides claimed combinations of pesticides act synergistically. In other words, compared to individual pesticides, combinations of pesticides may be anywhere from 150 times to 1,500 times more potent in binding to estrogen receptors and in an estrogen response-assay in yeast.
Just before this research was published, we had just weathered the unfortunate appearance of Theo Colburn's Our Stolen Future, a book claiming manmade chemicals are harming people by interfering with normal hormonal processes (so called "environmental estrogens" or "endocrine disrupters"). Even the reliably gullible mainstream press (e.g., The New York Times, The Washington Post and NBC Nightly News) seemed skeptical of such claims!
But the Tulane research added quite a bit of fuel to the Our Stolen Future fire. By the end of last summer, Congress enacted the Food Quality Protection Act of 1996, a law requiring the EPA to develop a screening program for pesticides that might exhibit estrogenic characteristics..
At the time, I criticized the Tulane research because the work focuses on the effect of pesticide "cocktails" on yeast. If people think mouse-to-human extrapolations are guesswork, imagine how "iffy" yeast-to-human extrapolations are. After all, at least mice and humans are both in the animal kingdom. Yeast, as you will recall, are fungi.
Now, researchers from Texas A&M, Duke, the Chemical Industry Institute of Technology and EVEN THE U.S. National Institute of Environmental Health Sciences report in technical comments to Science that efforts to duplicate the Tulane research have fallen flat. No synergistic activity was observed for any pesticide combination! Combinations of pesticides were observed to act only in an additive fashion (as would be expected to occur normally).
In their response, Tulane's Green Wave (pun intended?) researchers stated that the new work
while appearing to be similar to our, was in each case different. The differences, however, have been instructive in helping us frame some of the parameters that may be important in determining the synergistic action of weakly estrogenic chemicals.
TRANSLATION: OOPS! BACK TO THE DRAWING BOARD!
Unfortunately for the Tulane researchers, (good) science is capable of being replicated. That's a basic principle of the scientific method. If the Tulane results can't be replicated by other labs, then perhaps some larger questions need to be answered.
************************** Sidebar: Was Science justified in heavily promoting the Tulane results? They certainly don't merit the hype but have, in effect, been enacted as federal law. Shouldn't Science have been a little more cautious in its promotion of the findings?
As punishment, maybe the editors should atone for their sins by calling their next edition, say,
(Junk) Science?
Click here to e-mail the editors of Science with your own thoughts about the Tulane research, and Science's own penance and redemption. Tell'em the Junkman sends his regards!
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