Study: Intersex Fish Found in Delaware River Basin

Fish exhibiting intersex characteristics — caused by endocrine-disrupting chemicals — were found in Pennsylvania’s three major river basins.

Scientists are searching for the source of chemical contamination after a study found evidence of intersex fish in the basins of Pennsylvania’s major rivers, including the Delaware. The intersex fish were also found in the Susquehanna and Ohio river basins. The Susquehanna is the most contaminated of the three, while the Delaware is second-most.

Per the study, conducted by the United States Geological Survey and published in Environmental Monitoring and Assessment, smallmouth bass and white sucker with intersex characteristics were found in all three rivers. It’s a sign of exposure to reproductive endocrine-disrupting chemicals.




“The prevalence and severity of the immature eggs in smallmouth bass corresponded with the percent of agricultural land use in the watershed above the collection sites,” said Vicki Blazer, a research fish biologist and lead author of the study, said in a release. “Chemical compounds associated with estrogenic endocrine disruption, in particular estrone, a natural estrogen, were also associated with the extent and severity of these effects in bass.”

The severity of intersex characteristics increased downstream from waste water treatment plants. “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 waste water treatment plant effluent and other sewage discharges,” Blazer said in the release. Further study is ongoing.

Blazer told KYW 1060 the study is cause for concern over chemical usage: “I think that’s where people need to be concerned and think about the chemicals that they are using, particularly when they have children.”

[The Study | USGS Release | KYW 1060]

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