Antidepressant drugs detected at potentially harmful levels in waterways

Depression, anxiety and sleep disorders are among the conditions often treated with antidepressant drugs. Yet, up to 90% of these drugs pass through the body into wastewater. They're also difficult to remove during water treatment, presenting a possible risk of environmental contamination and threats to ecological and human health. Now, researchers reporting in ACS' Environmental Science & Technology found some antidepressant drugs at levels that could be harmful to aquatic wildlife in North Carolina waterways. 

"Findings from this study, along with others, reveal that pharmaceuticals are increasingly detected in waterways across the globe, especially near wastewater treatment plant discharge sites, posing a mounting environmental concern," says Erin Baker, the corresponding author of the study. 

To determine the scale of the problem, Emily Vincent from Baker's research group at the University of North Carolina at Chapel Hill and colleagues determined the levels of antidepressant drugs in four rivers near outflows from wastewater treatment plants and an isolated lake in North Carolina. They assessed samples collected in December 2024 for 34 compounds in major antidepressant medication categories, including selective serotonin reuptake inhibitors (SSRIs), selective norepinephrine reuptake inhibitors (SNRIs) and norepinephrine-dopamine reuptake inhibitors (NDRIs). 

Water sampled downstream of the treatment facilities contained 17 drugs or metabolites (substances created as the body breaks down the drugs), whereas samples taken upstream or in the lake were drug-free, except for one site. Furthermore, the concentrations of some contaminants well exceeded levels known to cause behavioral abnormalities and other toxicities in aquatic wildlife (e.g., minnows and small crustaceans). The researchers noted that previous animal studies only examined short-term exposure to single drugs, so further studies of chronic and combined exposures are needed to understand the ecological risks. 

The team says that these results also have potential implications for human health because many of the waterways that were tested provide drinking water and are used for agriculture and recreation. 

"Future research should prioritize broadening sampling efforts across global waterways to fully capture the scope of the issue," Baker adds. "In addition, studies on effective remediation strategies for these pharmaceuticals are urgently needed to eliminate them from wastewater and mitigate this escalating challenge."