Short-term estrogen exposure cuts fish fertility

A new study by Pacific Northwest National Laboratory and the University of Idaho shows that exposure to estrogen affects adult fish as they swim through rivers, lakes and streams to spawn. The study suggests that when adult male fish are exposed to short-term and low concentrations of synthetic estrogen, their fertility can drop by as much as 50 percent.

Previous research reported that high concentrations of estrogen could change sex organs, causing juvenile male fish to develop female organs. Estrogen is an active ingredient in most oral contraceptives and often travels to surface waters through sewer systems. The PNNL study looked at the impact of a synthetic estrogen called ethynylestradiol, which is the chemical in oral contraceptives.

Irvin Schultz, the PNNL toxicologist who led the study, said the research reinforces that impacts aren't limited to juvenile fish.

"We can see that adult fish aren't immune to the effects of estrogen in waterways. Even short-term exposure to low levels of synthetic estrogen can impact fertility," Schultz said. He noted that results indicate fertility in a healthy male trout that has developed normally can be affected if that exposure takes place during a critical sexual maturation stage before spawning.

The experiment took place at PNNL's Marine Sciences Laboratory. Adult male rainbow trout were exposed for 62 days to three different concentrations of the chemical. The sperm of exposed fish were harvested, then used to fertilize eggs from a healthy female rainbow trout. A measurable decrease in fertilization was observed in the treated trout, compared with a control group. For more information see http://www.pnl.gov/news/2003/03-20.htm.