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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 2021-2026

Microplastics in the Aquatic Environment: An Issue for the St. Lawrence?

The accumulation of microplastics in the marine environment is a known phenomenon and has been studied for several decades. Microplastics are particles smaller than 5 mm. Common sources of microplastics are the microbeads found in certain personal care products (whose sale in Canada is now prohibited) and the synthetic fibres shed from clothes during washing. However, a large proportion of microplastics, called secondary microplastics, results from the fragmentation and degradation of larger plastics from consumer products, such as containers, packaging and other single-use products.

Microplastics are found in the surface waters and sediments of the St. Lawrence and Ottawa Rivers.

This St. Lawrence Action Plan project aims to:
1) establish robust, standardized analytical methods for microplastics, with a view to environmental monitoring; and

2) assess sources of microplastics in the St. Lawrence and their bioavailability. Ultimately, the project's objective is to assess the risk of microplastics to the health of aquatic organisms in a context of cumulative effects.

Study the effect of ozonation of Montreal wastewater on aquatic organisms

The City of Montreal alone accounts for 50% of Quebec’s wastewater discharges. Many contaminants, such as drug residues, flame retardants and personal care products, end up in the St. Lawrence River. Montreal’s wastewater also contains pathogenic microorganisms. The municipality decided to use ozonation to eliminate them. Once in the water, ozone is transformed into oxygen, which does not in itself create pollution. However, ozone is also a very powerful oxidizing agent that can transform some contaminants into even more toxic by-products. In addition, aquatic life may suffer as a result of the excess oxygen conditions created by ozonated water.
For this project, our scientists are studying how ozonation affects aquatic organisms. In addition, they are inventorying the substances at risk and verifying how they are transformed and accumulate in aquatic fish and wildlife throughout the food chain.

Study the presence and effects of cancer drugs in the St. Lawrence

Over the past few decades, numerous studies have reported the presence of pharmaceuticals in the environment. Anti-inflammatory drugs, antibiotics and antidepressants are among the substances discharged from municipal wastewater treatment plants. The effects of these substances in the environment are also being studied for their toxicity to aquatic organisms.

In contrast, few studies have been conducted on cytostatics, a class of drugs used to rapidly destroy cancer cells. However, the increasing use of these substances in the treatment of cancer is a cause for concern. Although cytostatics are mainly administered in hospitals, a growing number of patients continue their treatment at home and these pharmaceutical compounds eventually end up in municipal wastewater. Several studies confirm the poor degradation of cytostatics in conventional water treatment plants. The study of the effects of the cytostatics in the environment, including their toxicity on aquatic organisms in surface waters receiving effluents, i.e. those downstream of the Montreal region, initiated between 2016 and 2021, will continue in this 2021-2026 phase of the St. Lawrence Action Plan.

Sharing scientific knowledge on emerging contaminants of interest

Over the last century, several factors have contributed to the transformation of the St. Lawrence including riverbed reshaping, extensive shoreline hardening, increased erosion of the fluvial islands, and significant high inputs of contaminants such as mercury, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) from numerous industrial and municipal sources.

Today, new issues related to aquatic biodiversity are emerging with the proliferation of contaminants of emerging concern (CECs), such as flame retardants, perfluorinated substances (PFAS) and nanoparticles, to name a few. 

Scientists still know very little about the biological effects of nonpoint source pollution or of the synergistic effects of CECs and their transfer to the food chain. While discussions and knowledge sharing are still ongoing about this, they have produced a fact sheet to provide an initial portrait of substances of emerging interest in sediments and suspended sediments. 

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

Few studies have been conducting on the effects of cancer drugs on aquatic organisms. Although cancer drugs are generally present at low concentrations in municipal effluents, they are believed to be toxic to aquatic organisms and to cause mutations and cancers in them. Recent studies have raised questions about the genotoxicity of these drugs in municipal wastewater. Since these drugs are not well broken down in conventional wastewater treatment plants, they are likely to be detected in the aquatic environment when excreted by patients.

It is therefore important to acquire knowledge of the hazard potential associated with these substances in order to be able to determine the risks they pose to the aquatic environment. Scientists are developing methods to analyze these contaminants in the river. They are monitoring their presence in the river near Montreal and studying their effects on invertebrates and fish.

The data produced for this study are used to determine the extent of the problem associated with the presence of cancer drugs in the St. Lawrence. These results are used to define the needs for further knowledge acquisition on these substances.

Share scientific knowledge on contaminants of emerging concern

With the banning of many organic substances, effective environmental monitoring, wastewater treatment and public awareness, water and sediment contamination in the St. Lawrence River has been significantly reduced over the past 40 years. Despite these efforts, new contaminants are being detected in the environment, such as siloxanes, phthalates, flame retardants and nanoparticles. 

This project aims to create a meeting platform where scientists can share their knowledge and establish a common strategy for the study of contaminants present in the river ecosystem. Such exchanges are essential because of the complexity of the St. Lawrence ecosystem. Indeed, changes in currents and water levels, as well as the presence of different water masses, are likely to influence the dispersion of contaminants and their effects on aquatic fauna.

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.