Study finds fish near wastewater plants have opioids and antidepressants in their systems

Researchers said substances that affect the central nervous system — including fentanyl, methadone and venlafaxine — were detected in small fish living in rivers that receive urban wastewater. (Source: University of Waterloo)

A new study from University of Waterloo has found that fish living downstream of wastewater treatment plants are accumulating drugs such as antidepressants and opioids in their bodies.

Researchers said substances that affect the central nervous system — including fentanyl, methadone and venlafaxine — were detected in small fish living in rivers that receive urban wastewater.

The study used a new testing method developed by the research team, allowing them to detect very small amounts of these substances in wild fish.

“This research shows that fish are exposed to and can accumulate these novel drugs when exposed to even well-treated wastewater,” Dr. Mark Servos, a professor in the department of biology and a researcher at the Water Institute, said in a media release. “Because wastewater treatment plants are not designed to remove pharmaceuticals, aquatic organisms are likely exposed to these chemicals downstream of most communities where these drugs are prescribed or used illicitly.”

Previous studies have suggested these substances could affect fish behaviour, development and reproduction. Researchers said this is the first time their presence has been documented in wild fish in Canada.

The study also found male fish had higher concentrations of some substances compared to females, which researchers believe could be linked to biological differences such as metabolism.

“This research demonstrates the importance of developing sensitive analytical methods for monitoring emerging contaminants and improving our ability to assess their potential for impacts on aquatic ecosystems,” Dr. Diana Cárdenas-Soracá, a postdoctoral fellow in the department of biology said in the release. “Hopefully this work will highlight the need to continue to characterize the diversity of new chemicals potentially entering the environment.”

Researchers said future work will focus on how these substances affect fish health, including potential impacts on behaviour, brain function and reproduction.

They said the findings raise concerns about the long-term effects of pharmaceuticals entering freshwater ecosystems.