The U.S. Geological Survey has reported startlingly high numbers of fish with intersex traits in Pennsylvania waterways.
USGS fish pathologist Vicki Blazer looked at several species of fish at 16 sites across Pennsylvania. She found that a high number of male smallmouth bass and sucker fish were feminized, and had started to produce an egg yolk protein.
“Normally, males don’t have that in their bloodstream,” she said. “But when males are exposed to estrogenic compounds, that gene is turned on in the liver.”
The smallmouth bass also had immature eggs growing within their testes.
Blazer said the chemicals, which are known as endocrine disruptors and are currently unregulated, come from a variety of sources, including human waste and agricultural sources.
“When you have large accumulations of animals — whether they’re cattle or chickens or pigs — and then you’re spreading that manure on the fields often,” she said, “you have runoff events that can add that natural estrogens to the water system.”
That may help explain why the Susquehanna River, more than the Ohio or Delaware rivers, had the highest number and most extreme cases of feminization.
Blazer said the results are worrisome not only for the reproductive health of the fish, but also for people.
“The endocrine system, which we have as well as fish have, really regulates a huge amount of both our behavior as well as our physiology,” she said.
The Pennsylvania Department of Environmental Protection collaborated on the effort, which was published in the journal of Environmental Monitoring and Assessment.
Department spokeswoman Amanda Witman said the state is paying more attention to these chemicals in rivers as it works on another study, begun in 2012.
“We test for 180 different compounds, which include things like PCBs, hormones, wastewater compounds, pesticides, and other types of emerging contaminants,” she said.
Witman said they have found estrogens in all sampled areas, but no particular patterns have emerged.