When a person takes a pharmaceutical, the entire dose doesn’t get absorbed by the body: A good-sized portion of the drug gets excreted along with its metabolites. It can then swirl down drains, evade filters in wastewater treatment facilities, and merge with the water supply.
According to a new report, a member of the commonly used antianxiety drug family called benzodiazepines significantly affects the behavior of fish exposed to it even at low levels (Science, DOI: 10.1126/science.1226850).
These behavioral changes could have negative consequences for the ecosystem, say the researchers from Sweden’s Umeå University who published the report.
Previous studies have demonstrated that pharmaceuticals typically found in the water supply can alter a fish’s behavior as well as its ability to reproduce. This new investigation is one of the first to study the environmental impact of a benzodiazepine, says Jerker Fick, a member of the research team. It’s also one of the first to demonstrate behavioral changes in aquatic creatures from concentrations of pharmaceuticals close to those found in nature, Fick adds.
To carry out the experiment, the researchers collected wild European perch—fish that are normally timid and stick together in schools—from a pristine lake in Sweden. They exposed one group of perch to 1.8 µg/L of a benzodiazepine, oxazepam, for seven days. According to the researchers, this level of drug resulted in the fish having a muscle tissue concentration of oxazepam similar to that found in perch living in a river fed by Swedish wastewater treatment facilities.
They then monitored all the experimental fish with video surveillance. The researchers found that perch that swam in water laced with oxazepam became more active and less interested in spending time with one another. The perch also ate at a significantly faster rate.
These results are interesting, says Bryan W. Brooks, an environmental scientist at Baylor University, “but it remains necessary to relate such laboratory observations of pharmaceutical effects on fish to ecological consequences in the field.”