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News — Pharmaceutical contaminants found in tissues of fish caught downstream from urban areas in a north Texas river could cause behavioral changes in fish that impact their ability to survive, according to research by a Baylor University toxicologist.

Dr. Bryan Brooks, an assistant professor of environmental studies at Baylor's Center for Reservoir and Aquatic Systems Research, has measured fluoxetine, an ingredient in antidepressants, in fish from Pecan Creek, north of Dallas. Fluoxetine is not controlled by EPA regulations for treated wastewater.

Antidepressant accumulation in the fish can cause behavioral changes, which impact aggression, mating and other behaviors necessary for fish survival.

Although treated Texas waters may meet current federal standards, Brooks said no guidelines or federal testing standards exist for pharmaceuticals because their effects in surface waters are not well understood.

The flow of the Trinity River south of Dallas and Fort Worth is greater than 90 percent dominated by wastewater releases. Wastewater refers to water that has been treated and released downstream from urban areas.

In lab and artificial stream studies, Brooks has observed the effects on fish and invertebrates of another class of pharmaceuticals, the active ingredients in birth control medications. Male fish exposed to estrogen have been shown to develop female physical characteristics and lose the ability to reproduce.

"At critical exposure levels, some fish can't reproduce at all, and some have both male and female sexual characteristics," Brooks said.

Another concern Brooks expressed is how the substances may affect humans who eat the fish. "If substances accumulate in fish tissue, and humans ingest them through fish, we don't know if they'll be affected," Brooks said. He added that exposure appears to be below therapeutic levels, but the issue calls for more research to understand the responses of aquatic organisms to pharmaceutical exposures.

Brooks will present his findings at the annual meetings of the Society of Environmental Toxicology and Chemistry (SETAC) in Austin and the Geological Society of America (GSA) in Seattle in November.

Chemosphere, 52: 135-142; Toxicological Sciences, 72: 77-83; Archives of Environmental Contamination and Toxicology, In Press; Bulletin of Environmental Contamination and Toxicology, 71: 504-511.