Both prescription and illegal drugs that are abused have been found in Canadian surface waters. New research shows that wastewater discharges flowing downstream have the potential to contaminate sources of drinking water with these drugs at relatively low concentrations.

The concentrations of cocaine, morphine, and oxycodone did not decline with distance downstream from the wastewater treatment plant discharge, and many of the drugs were not removed effectively by drinking water treatment plants.

The research is part of a special section on pharmaceuticals in the journal Environmental Toxicology & Chemistry.

"These results demonstrated a link between wastewater discharges and quality of potable water sources and emphasized the importance of evidencing that improvements to wastewater treatment protect sources of drinking water--a project we have embarked on since the publication of these results," said lead author Dr. Viviane Yargeau.