Fentanyl Traces Found in Ontario Fish
- Researchers found trace amounts of fentanyl and other drugs in fish sampled from Ontario waters, including near Waterloo Region. - Study lead Cárdenas‑Soracá highlighted detections occurred despite water treatment, emphasizing persistent contamination concerns. - Researchers say further monitoring is needed to assess ecological and human health risks (globalnews.ca).
A University of Waterloo study found fentanyl and other neuroactive drugs in wild freshwater fish living downstream of treated urban wastewater in southern Ontario. (uwaterloo.ca) The team reported the findings on April 16, 2026, after testing small-bodied fish from rivers that receive wastewater effluent, including sites in the Waterloo Region. The study was published in *Environmental Pollution*. (uwaterloo.ca) Researchers screened for 26 compounds and consistently detected four in all species collected: fentanyl, methadone, venlafaxine, and O-desmethylvenlafaxine, a breakdown product of the antidepressant venlafaxine. (pubmed.ncbi.nlm.nih.gov) Wastewater plants clean water before it is released, but they were not built to strip out every pharmaceutical molecule. Mark Servos, a biology professor at Waterloo, said those chemicals are “very diverse” and can pass through treatment at low concentrations. (globalnews.ca) The fish in this study were darters, small bottom-dwelling fish that scientists use like sentinels because they stay close to one stretch of river. In the downstream samples, concentrations were higher than at the upstream location. (pubmed.ncbi.nlm.nih.gov) The paper says this is the first documentation of these substances in wild fish in Canada. Earlier research had already linked similar neuroactive chemicals to changes in fish behaviour, development, and reproduction. (uwaterloo.ca) The researchers also found sex-based differences: male fish accumulated higher concentrations of some substances than females. The authors said physiology and metabolism may help explain that gap. (uwaterloo.ca) Diana Cárdenas-Soracá, the Waterloo postdoctoral fellow who led the work, said the detections do not mean treatment plants are failing. She said the plants have improved their methods, but “very small amounts can pass” even after treatment. (globalnews.ca) Servos told Global News the trace levels found in fish do not appear to pose a direct risk to people or drinking water. He said the larger concern is chronic exposure for fish that “breathe it continuously” in rivers receiving wastewater. (globalnews.ca) The next step is not a fish consumption warning but more monitoring. Cárdenas-Soracá said the new testing method should help researchers track emerging contaminants and study possible effects on fish brains, behaviour, and reproduction. (uwaterloo.ca)
