The St. Lawrence River Heavily Polluted By Pharmaceutical Products

A recent study reveals that a large amount of pharmaceutical pollutants are found in the water of the St. Lawrence River and could pose intermediate to high risks to aquatic organisms.

This study is at the heart of the doctoral thesis of Marc-Antoine Vaudreuil, student supervised by Sébastien Sauvé, researcher in environmental chemistry and professor in the Department of Chemistry at the University of Montreal. The doctoral student participated in taking surface water samples for five years (2017-2021) on a 700 km stretch along the river.

Despite the significant dilution effect of the river, the results indicate that four compounds (caffeine, carbamazepine, diclofenac and ibuprofen) could have deleterious effects on the growth and reproduction of aquatic fauna.

“Certain concentrations exceed thresholds in terms of long-term exposure, although to date there are no Canadian environmental standards for most pharmaceutical residues,” explains Sébastien Sauvé.

He continues: “The consequences would therefore not be immediate, if we consider that most molecules degrade quite quickly, with the exception of carbamazepine. Chronic exposure would also likely be accompanied by greater toxicity for organisms in the early stages of growth, such as fry.”

The researcher notes that contamination of water resources with pharmaceuticals may also indirectly contribute to antibiotic resistance, a significant threat to global health.

Marc-Antoine Vaudreuil also emphasizes that certain rivers tributary to the river located in densely populated regions are also strongly affected by pharmaceutical contaminants.

The case of Montreal
According to the study, the body of water in the St. Lawrence River after the Montreal effluent is considerably more contaminated than other bodies of water. This contamination is visible up to 70 km downstream, up to Lake Saint-Pierre.

“It’s surprising to see that the trace extends so far,” notes Sébastien Sauvé. On the other hand, the contamination of the metropolitan region was predictable given the fact that two million people live on the island of Montreal and that there is a single wastewater treatment plant that treats approximately 900 billion liters of water each year. .”

Currently, the city's wastewater treatment facilities are not designed to specifically eliminate pharmaceuticals. The effectiveness of elimination processes is therefore sometimes low or non-existent for these pollutants.

Fortunately, Sébastien Sauvé indicates that an ozonation project is underway in Montreal to clean up wastewater. This technique would destroy 80% of drug molecules.

“It’s a double-edged sword. The system must be well done, since ozone transforms pharmaceutical residues into even more toxic molecules. We therefore need enough ozone to also eliminate these new molecules,” he argues.

Solutions?
From a structural point of view, the implementation of advanced wastewater treatments that would reduce chemical loads could help improve the water quality of the St. Lawrence River which, remember, is also a source of potable water.

Sébastien Sauvé also proposes precisely targeting wastewater discharges from places more likely to produce a large quantity of pharmaceutical waste, such as hospitals or residences for the elderly.

On a smaller scale, the professor encourages the efforts of the pharmaceutical industries and the general population to properly dispose of expired medications, for example.

“Let's keep in mind that the release of pharmaceutical compounds into urban wastewater comes from the medications that everyone consumes, so it is important to make appropriate use of them,” he concludes.