Contaminants of concern are found in the St. Lawrence
Ultraviolet (UV) absorbers and industrial antioxidants are contaminants found in the products we use every day. What happens to them in the St. Lawrence River near Montreal? Here is an analysis by three university researchers from the University of Quebec at Rimouski (UQAR) and the University of Quebec at Montreal (UQAM).
ANALYSIS – Ultraviolet (UV) absorbers and industrial antioxidants are contaminants that are attracting more and more interest since they are found in a variety of products that are used daily. These products include sunscreens, anti-aging creams and shampoos, but also materials such as plastics and textiles, domestic or industrial. They are mainly used to protect our skin and consumer goods from UV radiation from the sun or from oxidizing agents naturally present in the air.
Given their great versatility, there are several entry points for these contaminants in aquatic environments. The vectors commonly targeted are the effluents of municipal wastewater treatment plants, since they collect water from common domestic uses as well as industrial water.
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To improve the state of knowledge about the situation in Quebec, during my master's project, I became interested in the future of these contaminants into the St. Lawrence River near Montreal. With my colleagues, we present here the conclusions of this study.
From showers and garbage cans… to fish from the St. Lawrence River
When you take your stump, the water used for rinsing contains residue from sunscreen, shampoo or other personal care products used and it will be sent to a wastewater treatment plant. Similarly, swimming in more touristy places can lead to contamination directly in the waterways.
Another source is linked to plastic pollution, which ends up in aquatic environments, in particular through direct discharge into the environment, for example when people leave debris on beaches. There may also be an indirect release of plastics, through their presence in the effluents of domestic wastewater treatment plants. During the degradation of plastics, which occurs among other things following exposure to the sun, water salinity or prolonged contact with waves, the compounds they contain (such as UV absorbers and industrial antioxidants) can migrate to the environment.
As soon as they enter the environment, these contaminants can disperse in sediments, water, and even in aquatic organisms, and thus harm biodiversity and the health of ecosystems. Indeed, some of these compounds are suspected of causing harmful effects, including disruption of the hormonal system in exposed aquatic organisms or even promoting coral bleaching.
However, it is important to better understand their distribution and fate in aquatic environments in order to be able to assess the risk currently incurred by species exposed to these contaminants.
Contaminants present in the river
To promote understanding of the fate of pollutants of interest in the St. Lawrence ecosystem, several types of samples were studied from upstream and downstream of the Montreal wastewater treatment center. We collected water, suspended matter (which are insoluble particles visible in water), sediments and tissues of two species of fish, northern pike and lake sturgeon.
The results of the analyzes detected several contaminants, confirming their presence in the St. Lawrence ecosystem. In addition, a certain affinity for suspended matter was observed, with higher concentrations for certain contaminants, which indicates the importance of a better understanding of the risks associated with the ingestion of suspended matter. Indeed, the latter can be an important route of accumulation for organisms.
By comparing the dominant contaminants in the two fish studied, we observed an important distinction between lake sturgeon and northern pike. This difference can be induced by different factors, such as a difference in the diet of the two organisms. Northern pike are opportunistic carnivores that feed on what is easily accessible. Its main diet consists of yellow perch, suckers, sunfish and others.
In comparison, lake sturgeon are bottom predators that feed on small organisms such as larvae, crayfish and small molluscs. This distinction between lifestyles creates a difference in the way organisms will be exposed to pollution and therefore the extent of contamination by certain pollutants. For example, if a contaminant has a greater affinity for sediments, organisms that live near the bottom are more likely to be impacted by it.
Some contaminants are more of a concern than others
The results also show that BHT, an industrial antioxidant, and its degradation product, BHTQ, are the only compounds that have been found in the brain of northern pike. The effects of these contaminants on the nervous system of aquatic organisms are not well known at this time. A previous study, however, demonstrated that BHT can build up in rat brains and can lead to an increase in the number of dead cells. To our knowledge, this is the first observation of these toxic compounds in the St. Lawrence.
UV328, which is found mainly in plastics and paints, is a molecule of international interest followed by the Stockholm Convention for its damaging effects on the liver and for its potential for hormonal disruption. Its presence has been detected mainly in lake sturgeon, water, suspended matter and river sediments.
Encore gaps to fill
The study carried out made it possible to highlight the presence of contaminants of interest in the St. Lawrence River and to target some of them, such as UV328 and BHT, as being of greater concern. On the other hand, there is still a lack of knowledge to be filled in order to be able to understand the impact of these contaminants on the various organisms that inhabit the St. Lawrence, particularly in terms of the effects of longer-term exposure.
< p>In addition, it is important to remember that aquatic organisms are subject to a mixture of several pollutants and that it is therefore essential to have a better understanding of the consequences of the interactions between these contaminants on the health of the organisms.
Zhe Lu, Professor, University of Quebec at Rimouski (UQAR); Abigaëlle Dalpé-Castilloux, M Sc Oceanography (marine ecotoxicology laboratory, environmental analytical chemistry), University of Quebec at Rimouski (UQAR), and Magali Houde, Research Scientist, University of Quebec at Montreal (UQAM)
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