When taking pharmaceuticals, we’re not just self-medicating. Traces of the drugs we consume to regulate hormones, lift our moods or decrease anxiety often make their way into aquatic ecosystems through wastewater. Many of these drugs remain biochemically active, but how they may impact the animals that come into contact with them is little understood.
A new paper in Science tackles this research question in a case study of the psychiatric drug oxazepam’s affect on wild European perch in Swedish rivers.
“Previously, pharmaceuticals have mostly been tested for their toxic effects,” says Micael Jonsson, an ecologist at Umea University in Sweden, and one of the paper’s co-authors. He tells TakePart, “Here, we combined environmental chemistry, or ecotoxicology, with behavioral ecology, which is one new aspect of this study.”
Jonsson says his team meshed these two fields to investigate how fish react behaviorally to elevated levels of oxazepam in their environment. Oxazepam is a type of psychotherapeutic medication prescribed to alleviate anxiety. The drug, which medicates as soon as it enters the body and then is quickly flushed out, is quite resistant to degradation and lasts in aquatic systems for some time, though researchers are not sure exactly how long; wastewater continuously replenishes new loads of drug-laden water into global aquatic systems.
“We think this should be a global phenomena because these pharmaceuticals are so widely used and there’s not—as far as we know—any good way of cleaning them out of water at wastewater plants,” Jonsson says.
The researchers caught juvenile perch from streams in the wild lacking any traces of the drug. In the lab, they divided the fish into three groups. They subjected one group to water containing 1.8 micrograms per liter of oxazepam, an amount comparable to that found in contaminated environments. The second group received a much higher dose, at 910 micrograms per liter, and the final group served as a control.
After seven days of exposure, they found the fish exposed to the low drug dose had accumulated oxazepam in their muscle tissues equivalent to that of fish exposed to the pharmaceutical in the wild. To investigate how the drug affected behavior, they studied the fish for boldness (or a fish’s tendency to enter a new area), sociality (how often it came in contact with others) and activity (the number of times it swam around) before and after treatment. Such “personality traits” can affect how individual animals respond to changes in their environment, and over time can influence a species’ evolution.
Oxazepam did indeed impact the animals’ behavior. Those exposed to the low concentrations became more active and less social than the control group. The high exposure group became even more active and antisocial, and also bolder.
These changes were reflected in the animals’ eating habits. Before exposure, all of the fish fed on zooplankton, or tiny organisms that live in water, at the same rate. After treatment, fish on high doses of drugs experienced a strong case of the munchies, eating earlier and faster than the other two groups. The fish in the middle group likewise became more ravenous than the control group. Since this latter group had the same drug concentration as fish exposed in the wild, the researchers concluded that wild fish probably experience the same behavioral changes as the ones tested in the lab.
“This study shows that, in one sense, fish actually did better than before,” Jonsson said. “So we don’t see any toxicity from this pharmaceutical, but nevertheless it probably will have ecological effects if these same changes occur in natural systems.”
Jonsson and his colleagues can only guess what these changes may look like. The hungry fish could gobble up all the zooplankton, for example, and since zooplankton eat algae, the environment could become overrun with those aquatic plants.
On the other hand, the animals’ increased activity may make them easier targets for predators, which would likely cause a host of other changes. Moreover, many other species possess the same brain receptors the drugs target, including birds and amphibians. Until more studies are done, however, overall ecosystem impacts remain a matter of speculation.
The researchers remind readers that oxazepam is only one of a cocktail of drugs that wind up polluting watery environments. No one knows how multiple pharmaceuticals may interact with one another once inside an animal’s system.
“This is just one drug and one species, and there are so many species and so many drugs,” Jonsson says. “But at the same time, we also want to stress that this drug is important for many people, and it’s not an option to stop using the drug, so there has to be another solution.”
Developing a better way to clean the water of these drugs may be the most feasible option, Jonsson thinks, though this would require time and money.
Pharmaceutical use is projected to only increase in upcoming years, so the authors hope their paper inspires others to take up similar research topics in the hopes of better understanding the full environmental impact of drug residues. “We still know way too little,” Jonsson says. “Hopefully this is just one of many studies that will give us clarity, eventually.”
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