Anxiety Drug in Waterways May Drastically Affect Fish Behavior

Careful what you drink. An anti-anxiety medication has been found in local waterways and is altering fish behavior, according to a new study.

The medication, known as oxazepam, is released into wastewater after patients pass it into their urine. It belongs to a class of drugs called benzodiazepines, the most widely prescribed anti-anxiety drugs. Thought to be highly stable in aquatic environments, it enhances neuron signals and helps patients relax.

Yet this drug isn't alone. It's just part of a list of pharmaceutical products that escape wastewater treatment facilities unscathed into the surrounding environment. It can drastically affect freshwater communities that include fish and other organisms. Other studies have found that chemicals found in contraceptive pills and other drugs have also altered fish behavior.

The researchers, including Tomas Brodin of Umea University of Sweden and colleagues, measured the drug's concentration in the Fyris River in Sweden. They found that the perch that inhabited the river, Perca fluviatilis, accumulated the drug in their muscles in concentrations more than six times higher than those found in the water. The reason for this was probably bioaccumulation--a process where pollutants can accumulate at higher concentrations the higher up the food chain you go; the same problem can be found with mercury in the world's oceans.

In order to further test how the drug affected the perch, the researchers exposed juvenile perch to two concentrations of oxazepam. One was roughly twice the concentration found in the Fyris River while the other was nearly 1,000 times higher. The scientists found that, surprisingly, even the lower concentration affected the fish's behavior. While non-medicated perch are timid and prefer to stick to familiar territory, the medicated fish were more aggressive, more anti-social toward fish of the same species and were quicker to eat the zooplankton in their tanks.

So why did an anti-anxiety medication cause fish to be bolder? The scientists speculated that the drug caused the fish to be less inhibited by fear.

These findings have major implications for freshwater ecosystems. Since treatment plants don't always effectively remove chemicals associated with drugs, they could be dumping them into the surrounding ecosystem. The altered fish behavior could cause species to be less successful at surviving in the wild or could affect the balance of the environment. For example, since medicated fish eat more zooplankton and zooplankton eat algae, more medicated fish could mean more algal blooms.

Unfortunately, it doesn't look like the problem of wastewater containing drugs will be fixed any time soon. Removing or treating the chemicals is a costly business, and is unlikely to receive support.