Medicinal drugs pollute the St. Lawrence River

(Image: Pixabay CC0) The 3,000-km artery contains a large quantity and variety of pharmaceutical compounds, some of which could be harmful to ecosystems and human health. A new study shows troubling levels of pharmaceutical pollution in the St. Lawrence River and its largest tributaries, especially near and downstream of urban areas. Some of the compounds detected even pose a moderate-to-high risk to aquatic organisms when there's chronic exposure. Université de Montréal doctoral candidate Marc-Antoine Vaudreuil did the study under the supervision of Sébastien Sauvé, an environmental chemist and professor in the Department of Chemistry. From 2017 to 2021, Vaudreuil took part in a five-year field research program, collecting surface water samples along a 700-kilometre stretch of the 3,000-kilometre river. The results show that despite the St. Lawrence waters' significant dilution effect, concentrations of four compounds-caffeine, carbamazepine, diclofenac and ibuprofen-are high enough to negatively impact growth and reproduction in aquatic fauna. "Some concentrations exceeded toxicity thresholds for long-term exposure in aquatic life, but for most pharmaceutical compounds, there are currently no Canadian environmental standards," said Vaudreuil.