Intersex fish have been found in three Pennsylvania rivers, leading Department of Environmental Protection to begin searching for chemical pollutants.
Male fish carrying eggs were found in the Delaware, Ohio and Susquehanna river basins, according to research released by the U.S. Geological Survey Monday.
Researchers found intersex smallmouth bass and white sucker fish, which must have been exposed to endocrine-disrupting and estrogen-mimicking chemicals to cause the male fish to produce eggs, the Los Angeles Times reported.
A DEP spokeswoman, Amanda Witman, says the agency is sampling and testing water from two tributaries feeding into the Susquenhanna: Swatara Creek and Juniata River.
"The sources of estrogenic chemicals are most likely complex mixtures from both agricultural sources, such as animal wastes, pesticides and herbicides, and human sources from wastewater treatment plant effluent and other sewage discharges," said Vicki Blazer, a fish biologist and lead author of the USGS study.
Fish collected downstream from wastewater treatment plants were generally in worse condition.
"We weren't expecting the issue to be as widespread as it was," Blazer said. "The number of fish affected and the severity was surprising."
Researchers found some brand new compounds and contaminants in the water and had to develop a new testing process to measure them.
"The results will provide a much better understanding of the kinds, distribution and concentrations of these compounds," Whitman said.
"DEP's plan is to continue the sampling until it has an understanding of how these compounds may or may not impact the aquatic life in all streams and rivers, not just the Susquehanna," she said.