Around one in four Montrealers take some kind of anti-depressant, and according to new research, the drugs are passing into the waterways and affecting fish. The findings are internationally significant as the city’s sewage treatment system is similar to that in use in other major cities, and moreover, it is reputed to be the third largest treatment system in the world. Lead by Dr. Sébastien Sauvé at the University of Montreal’s Department of Chemistry and André Lajeunesse, a PhD candidate, the research team found that the drugs accumulate in fish tissues and are affecting the fish’s brain activity.

The Saint Lawrence is a major international waterway that connects the Atlantic Ocean to the Great Lakes, and it surrounds the island of Montreal. Sauvé has been looking at the chemical pollution of the water system for years. ‘Montreal has a very basic sewage system – the city basically only removes solids, there’s no disinfecting of the water,’ he explained. ‘In any case, the chemical structure of anti-depressants makes them extremely difficult to remove from sewage, even with the most sophisticated systems available.’

‘We know that antidepressants have negative side effects on human beings,’ Sauvé said, ‘but we don’t know how exactly how these […]