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Toxic substances

The growing presence of emerging contaminants related to wastewater discharge as well as urban and agricultural streaming waters still has unknown effects on the environment and on human health. The future of these toxic substances and of their degradation products in the River is still unknown and the complexity of the interactions between these substances and the bacteriological load associated with these rejections raises several questions regarding the risks of toxicity in aquatic ecosystems.

Projects 2016-2021

Study the effect of Montreal wastewater ozonation on aquatic organisms

On its own, the City of Montreal dumps 50% of Quebec’s wastewater. Several contaminants, such as medication residue, flame retardants or health care products are found in the river. Montreal’s wastewater also contains pathogenic organisms. The municipality therefore decided to use an ozonation technique to eliminate the pathogens. Once in the water, the ozone transforms into oxygen, which in itself does not create pollution. However, the ozone is also a very powerful oxidizing agent that can transform some of the river’s contaminants into even more toxic by-products. Furthermore, aquatic life can suffer from an excess of oxygen carried by the wastewater treated by ozonation.

The researchers in this project study the ways in which ozonation affects the aquatic organisms. Additionally, they identify the risk substances and verify how they transform and accumulate in aquatic wildlife throughout the food chain.

Study the presence of cancer medications in the St. Lawrence and their associated effects

There are few studies on the effects of cancer medications on aquatic organisms. Although they are present in weak concentrations in municipal effluents, we suspect them to be toxic to cells and to aquatic organisms' DNA, and to also cause mutations and cancer.  However, since they do not degrade much in the traditional wastewater treatment plants, these medications, excreted by the patients, may be detected in aquatic environments.

It is therefore important to build knowledge on the potential dangers associated with these substances to determine the risks they present for the aquatic environment. Researchers update the methods to analyze these river contaminants. They monitor their presence in the river waters near Montreal and in Lake Saint-Pierre. Finally, they study the effects these medications have on invertebrates and fish. 

The data obtained from this study determine the extent of the problems associated with the presence of cancer medications in the St. Lawrence River. These results are used to identify the additional knowledge requirements for these substances. 

Share the scientific knowledge on organic contaminants, including emerging contaminants of concern

Sediment contamination in the river’s water has greatly reduced over the last 40 years with the ban on using several organic substances, effective environmental monitoring, wastewater remediation and public awareness. Despite these efforts, new contaminants continue to be found, such as siloxanes, phthalates, polybrominated diphenyl ether (PBDE) and nanoparticles.  
This new project aims to create a platform for meetings where researchers can share their knowledge and develop common strategies for studying the contaminants present in the river ecosystem. Such exchanges are essential given the complexity of the river. Indeed, changes in current and water levels, the presence of different bodies of water that may influence the dispersion of contaminants and their effects on endangered aquatic wildlife.

Projects 2011-2016

Document the presence of pharmaceutical products in municipal effluents in the Montréal region and assess their effects on aquatic fauna

Urban effluents are a major pollution source, and 50% of all wastewater in Quebec is discharged into the St. Lawrence. These effluents contain various forms of pharmaceutical products.

The purpose of this project is to assess:

  • the transport and bioaccumulation potential of the pharmaceutical products present in the dispersion plume of the major effluent of the city of Montréal;
  • the effects of wastewater treatment and disinfection processes on the chemical forms and toxic potential of pharmaceutical products;
  • the exposure and trophic transfer of pharmaceutical products in the aquatic and terrestrial (riverine) environments;
  • the ecotoxicological effects of exposure to pharmaceutical products.

This initiative will help to shed light on the impact of discharging pharmaceutical products on the environment and human health.

Read the backgrounder for this project.

Document the presence of pharmaceutical and personal care products in the St. Lawrence and selected tributaries

Over the last several years, some participants in the St. Lawrence Action Plan have been collecting data on pharmaceutical and personal care products detected in the St. Lawrence. In doing so, they seek to jointly interpret the resulting data and disseminate this information.

Read the backgrounder for this project.

Assess the environmental and human health risks of urban effluents in the Quebec City region

Municipal effluents are discharged into the St. Lawrence in the Quebec City area primarily by Quebec City and Lévis. Since the St. Lawrence also serves in this region as a drinking water source and site of recreational activities, it is important to characterize the nature, load and dispersion of contaminants coming from upstream and being discharged locally.

This project involves forming a team in order to evaluate the risks that these effluents represent for the ecosystem and for human health. First, we will create this team of experts representing the various authorities involved, and we will develop the project while taking into account all the important aspects, including financial structuring.

Read the backgrounder for this project.

Combine tools for numerical environmental prediction and state of the St. Lawrence monitoring and apply them to mapping the water quality of Lake Saint-Pierre

The objective of this project is to leverage the synergy among the Numerical Environmental Prediction and State of the St. Lawrence Monitoring groups to generate information (data, maps, indicators, etc.) regarding the status of pesticide contamination in Lake Saint-Pierre. This information can be used to identify the areas most affected by water contamination in Lake Saint-Pierre and support a review of the location of sampling sites in Lake Saint-Pierre and adjustment of the sampling plan where necessary.

Read the backgrounder for this project.

Assess sediment dynamics and contamination levels in the wetlands of Lake Saint-Pierre

Indicators are to be measured for each historical stratum of sediment. These parameters will be used to evaluate the impact of certain human activities on the wetlands of Lake Saint-Pierre, including the influence of municipal and industrial wastewater, agricultural inputs, water level variations, dredging and climate change. This project will assist in better understanding the temporal and spatial dynamics of certain habitats deemed essential for the St. Lawrence ecosystem.

Read the backgrounder for this project.

Assess the ecotoxicological risk of the round goby in the St.Lawrence River in terms of the impact of invasive species on the trophic transfer of contaminants

In recent years, the St. Lawrence ecosystem has been disrupted by the introduction of invasive exotic species. One of these, the round goby, is a highly competitive species that has profoundly modified the trophic dynamics of the St. Lawrence River. A recent study by researchers with Quebec's Ministère des Ressources naturelles et de la Faune (MRNF) also demonstrated that the goby has now become the main prey of numerous predatory fish. A benthic, weakly mobile species, the round goby may also receive significant exposure to domestic household contaminants that have accumulated in sediment. Before the introduction of the round goby, these contaminants were confined to zebra mussels, a prey species known to build up concentrations of the contaminants present in its environment, making them unavailable to the majority of other fish species. Predation of the zebra mussel by the round goby creates a new pathway for the transfer of contaminants to fish and fish-consuming birds. Determining the ecotoxicological risk created by the round goby and assessing its role in the food chain and the transfer of legacy and emerging contaminants to sport fish and fish-consuming birds will enable an assessment of the risk of contamination of predators and the risks to human health.

Read the backgrounder for this project.

Form a knowledge exchange group on substances of emerging concern

Scientists possess little information about the biological effects of the relationship between nonpoint source pollution, synergy among contaminants in the environment and the transfer of these contaminants to the food chain. The formation of a working group bringing together a range of professionals conducting research and monitoring activities in the St. Lawrence River will make it possible to increase knowledge about substances of emerging concern and other persistent, bioaccumulative toxic substances and develop further projects in this area.

Read the backgrounder for this project.

Set up a scientific knowledge exchange group on Lake Saint-Pierre

Lake Saint-Pierre is a fluvial lake of the St. Lawrence that supports significant economic activity. Its rich biodiversity makes it a site of international importance. However, many stakeholders are concerned about the degradation of its water quality, habitats and biodiversity. The purpose of this project is therefore to set up a scientific knowledge exchange group on the ecosystem integrity of Lake Saint-Pierre. This group will bring together researchers and experts to examine the possible causes of the deterioration and determine the restoration and research work that should be carried out as part of the St. Lawrence Action Plan.

Read the backgrounder for this project.