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STAFF REPORT

Scientists at a Swedish university are publishing a study in Science magazine that maintains exposing perch to traces of the anti-anxiety drug benzodiazepine had an observable effect on the fish. The drug levels mimicked those found in downstream from a wastewater treatment plant.

“What we found was very surprising,” ecologist Jonatan Klaminder told NPR’s All Things Considered in a piece that aired Feb. 13. “Individuals exposed to dilute concentration of this drug became more antisocial, they became more active, and they were actually more effective in eating.”

Endocrine disruptors — trace amounts of pharmaceuticals and household products that end up in waterways — are still a relatively new field of environmental study. Klaminder conceded that the experiment does not establish whether perch in the wild are likewise affected by discharge of the pharmaceutical, which has been used for decades in Sweden.

In 2006 and 2007, a Texas State University aquatic biology graduate student collected samples of water up- and downstream of where treated effluent is released into the San Marcos below Thompson’s Islands. The student discovered 12 chemicals found in common consumer products from plastics to perfume to prescription drugs, albeit often in relatively tiny amounts, in water taken downstream of the discharge point.

“That is not to say that we have concentrations in our water supply or river that are at the level where we know them to be harmful. A lot of people think about environmental contaminants in terms of individual exposure to one of them. The bigger problem is the combined effect of all the different exposures,” Glenn Longley, Texas State’s Edwards Aquifer Research & Data Center, told the San Marcos City Council at the time.

RICHARD HARRIS reports for National Public Radio’s All Things Considered, where this story was originally aired. It is made available here through a news partnership between KUT News and the San Marcos Mercury.