Short-term exposure to estrogen cuts fish...( After 28 days a measurable decrease i...)

After 28 days, a measurable decrease in fertilization was observed in the treated trout compared with a control group. In some experiments, a 50 percent decrease in sperm fertilization capacity was noted in semen collected from the trout exposed to 10 nanograms of ethynylestradiol per liter. For example, in an experiment using 50,000 sperm for one egg, the exposed fish had 22 percent fertilization compared with 45 percent fertilization of control fish.

That impact is important, say researchers, because 10 nanograms per liter is a level found in some surface water samples. Schultz and his colleagues, including co-author Jim Nagler of the University of Idaho, studied the possible mechanisms for reduced fertility, specifically sperm motility and decreased hormone levels. While they were able to rule out sperm motility as the mechanism, their research revealed increased -- not decreased -- hormone levels in the blood plasma of fish exposed to 10 nanograms per liter of ethynylestradiol. But hormone levels did decrease in fish exposed to the larger concentration of 100 nanograms of ethynylestradiol.

"While other research has shown the visible change that can take place when young male fish are exposed to high levels of estrogen, we're suggesting that low and short-term exposure can have just as significant -- but not physically observable -- effects," Schultz said.

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Contact: Staci Maloof
staci.maloof@pnl.gov
509-372-6313
DOE/Pacific Northwest National Laboratory
3-Jun-2003

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