ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Friday, June 7, 1996 TAG: 9606070075
SECTION: NATIONAL/INTERNATIONAL PAGE: A-4 EDITION: METRO
SOURCE: Los Angeles Times
RESEARCHERS suggest that government screening of chemicals may not be adequately protecting the public from reproductive ailments and declining fertility.
Expanding on the evidence that environmental chemicals could be altering sex hormones, scientists have discovered that some pesticides with weak potential to imitate estrogen on their own become hundreds of times more potent when two are combined.
The findings suggest that exposure to mixes of chemicals routinely found in the environment could be posing a much greater risk than suspected, and that government screening of pesticides may be inadequately protecting the public from reproductive ailments and declining fertility.
Reporting today in the journal Science, Tulane University scientists used a novel system to test four pesticides by genetically engineering yeast cells to add human proteins that send signals to produce estrogen. All four chemicals were weakly estrogenic alone. But when two - especially endosulfan and dieldrin - were paired, the potency rose by 160 to 1,600 times, a huge leap that stunned the researchers.
``The thing that was most compelling was the dramatic synergy between two unlike chemicals,'' said endocrinologist John A. McLachlan, who led the Tulane University team. ``Instead of one plus one equaling two, we found that one plus one equals a thousand-fold. We expected interactions, but we were surprised they were so strong.''
Endosulfan is one of the most widely used insecticides in the United States, where about 2 million pounds are applied annually on fruit, vegetables and other crops. The other three compounds - toxaphene, dieldrin and chlordane - were banned by the Environmental Protection Agency in the 1980s but still contaminate many areas.
The pesticides were chosen because they commonly combine in many environmental settings, including Florida's Lake Apopka, where alligators with feminized hormones and half-male, half-female genitals have been discovered.
National Institutes of Health hormone expert S. Stoney Simons Jr. called the results remarkable, but said in an editorial in Science that ``as is often the case with significant new discoveries, this paper ... poses more questions than it answers.'' Key among the uncertainties is whether the effects on cells are comparable to real-life impacts on human beings or other animals.
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