"Out of sight, out of mind" is how we often treat what is flushed down our toilets. But the drugs we take, from anxiety medications to antibiotics, don't simply vanish after leaving our bodies.

Many are not fully removed by wastewater treatment systems and end up in rivers, lakes and streams, where they can linger and affect wildlife in unexpected ways.

In our new study, we investigated how a sedative called clobazam, commonly prescribed for sleep and anxiety disorders, influences the migration of juvenile Atlantic salmon (Salmo salar) from the River Dal in central Sweden to the Baltic Sea.

Our findings suggest that even tiny traces of drugs in the environment can alter animal behaviour in ways that may shape their survival and success in the wild.

A recent global survey of the world's rivers found drugs were contaminating waterways on every continent – even Antarctica. These substances enter aquatic ecosystems not only through our everyday use, as active compounds pass through our bodies and into sewage systems, but also due to improper disposal and industrial effluents.

To date, almost 1,000 different active pharmaceutical substances have been detected in environments worldwide.

Particularly worrying is the fact that the biological targets of many of these drugs, such as receptors in the human brain, are also present in a wide variety of other species. That means animals in the wild can also be affected.

In fact, research over the last several decades has demonstrated that pharmaceutical pollutants can disrupt a wide range of traits in animals, including their physiology, development and reproduction.

Pharmaceutical pollution in the wild

The behavioural effects of pharmaceutical pollutants have received relatively less attention, but laboratory studies show that a variety of these contaminants can change brain function and behaviour in fish and other animals.

This is a major cause for concern, given that actions critical to survival, including avoiding predators, foraging for food and social interaction, can all be disrupted.

Lab-based research has provided useful insights, but experimental conditions rarely reflect the complexity of nature. Environments are dynamic and difficult to predict, and animals often behave differently than they do in controlled settings. That's why we set out to test the effects of pharmaceutical exposure in the wild.

As part of a large field study in central Sweden, we attached implants that slowly released clobazam (a common pharmaceutical pollutant) and also miniature tracking transmitters to juvenile Atlantic salmon on their seaward migration through the Dal.

【打印本页】【关闭窗口】