Toxic Contamination of Freshwater Fish

3rd edition

Printable version (PDF)

Current status: Moderate

For the years 2010-2014, only Northern Pike from Lac Saint-Louis had mercury concentrations that exceeded the Canadian standard, and only Walleye near Montréal and in Lac Saint-Pierre exceeded the European Union standard for PCBs.

Change since 1976: There has been a sharp downward trend in mercury and PCB contamination since the 1970s.

               2010-2014

 

Classes for judging the state of fish contamination

Good: all concentrations measured in fish flesh are below the standard – not a concern

Moderate: the concentrations measured in fish flesh are near the standard, but one species may exceed it on the local level – to be monitored

Poor: several species show above-standard concentrations in fish flesh or a single species presents above-standard concentrations throughout the fluvial corridor – of concern

The Canadian standard for the marketing of fish products is 0.5 mg/kg of flesh for mercury. The European Union standard is 125 µg/kg of flesh for polychlorinated biphenyls (PCBs) (the Canadian standard of 2,000 µg/kg is under review). There is no standard for polybrominated diphenyl ethers (PBDEs). For dioxins and furans, the European standard is 3.5 ng/kg of flesh.

 

Overview of the Situation

Various contaminants, including mercury and other metals, polychlorinated biphenyls (PCB), polybrominated diphenyl ethers (PBDE), and dioxins and furans have been detected in the flesh of fish from the St. Lawrence. Only mercury is present in concentrations that sometimes exceed the consumption guidelines, primarily in older specimens. Concentrations of other contaminants in fish flesh are often low.

There has been a sharp downward trend in contamination since the 1970s, especially for mercury and PCBs. As a result, fish from the St. Lawrence River can be consumed without risk, so long as the recommendations issued by the Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques1 and the Ministère de la Santé et des Services sociaux2 are followed.

The species studied to determine the contaminant concentrations in fish flesh include the Walleye, the Northern Pike and the Yellow Perch, which are sport fish species. Whole white sucker was also analysed to obtain estimates on the exposure to contaminants of fish-eating terrestrial wildlife who consume whole fish.

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[1] Québec Ministry of sustainable development, the environment and climate change
[2] Québec Ministry of health and social services

 

Figure 1 Location of fish sampling stations in the St. Lawrence River

Long description

Map showing the location of fish sampling stations in the St Lawrence River and designating these stations by numbers 1 to 20. Stations 1 to 3 are found at Lac Saint-François, stations 5 to 7 are located at Lac Saint-Louis, stations 4, 8 and 9 do not appear on the map (owing to insufficient numbers of fish for the study), stations 10 and 11 are located near Montréal, stations 12 to 15 are found at Lac Saint-Pierre, stations 17 and 18 are located near Bécancour and Neuville respectively, and stations 19 and 20 are situated respectively upstream and downstream from Québec City.

 

Mercury

When we compare the values observed in 1976 and for the period 1983 1997 to the data for the period 2010-2014, it is apparent that the efforts invested in reducing mercury contamination in the river have yielded positive results since, generally speaking, mercury concentrations in fish have fallen (figure 2). Average mercury concentrations in the flesh of Walleye (425 mm), Northern Pike (600 mm) and Yellow Perch (215 mm) were below the Canadian fish marketing standard (0.5 mg/kg) (figure 2). Average values that exceeded the Canadian standard, however, were observed in Northern Pike (0.72 mg/kg and 0.97 mg/kg) from Lac Saint-Louis in the Îles de la Paix sector (stations 5 and 6). It appears that the local contamination from past industrial activities is persisting in this area and continuing to influence the levels of mercury contamination in fish. In 2006, sediments contaminated with mercury were removed near the outlet of the Saint-Louis River.

Average mercury concentrations for the three species exceed the criterion of 0.057 mg/kg for fish-eating terrestrial wildlife at all sites. This exceedance is not exceptional, however, as this criterion is exceeded by the majority of fish in the province of Québec owing to the atmospheric transport of mercury.


Figure 2  Changes in average mercury concentrations in Walleye, Nothern Pike and Yellow Perch in the St. Lawrence River over the period 1976-2014

Long description

Graphic using vertical bars in three different colours representing mercury concentrations in Walleye, Northern Pike and Yellow Perch for the periods 1976, 1983-1997 and 2010-2014. The stations are grouped together in six sectors: Lac Saint-François, Lac Saint-Louis, downstream from Lac Saint-Louis, Lac Saint-Pierre, Gentilly and Québec City. A broken horizontal line traverses the diagram to indicate the position of the Canadian standard of 0.5 mg/kg established for the marketing of fish products.

Overall, mercury concentrations in the three fish species fell between 1976 and 2010-2014.

At Lac Saint-François (stations 1, 2 and 3), the average mercury concentrations measured in Walleye ranged from 0.54 to 0.63 mg/kg in 1976, from 0.30 to 0.41 mg/kg in 1983-1997 and from 0.21 to 0.43 mg/kg in 2010-2014. In Northern Pike, the average concentrations varied from 0.61 to 0.71 mg/kg in 1976, from 0.47 to 0.57 mg/kg in 1983-1997 and from 0.26 to 0.49 mg/kg in 2010-2014. In Yellow Perch, they varied from 0.16 to 0.21 mg/kg in 1976, from 0.22 to 0.31 mg/kg in 1983-1997 and from 0.15 to 0.25 mg/kg in 2010-2014.

At Lac Saint-Louis (stations 5, 6 and 7), the average mercury concentrations measured in Walleye ranged from 0.53 to 0.96 mg/kg in 1976, from 0.47 to 0.51 mg/kg in 1983-1997 and from 0.29 to 0.36 mg/kg in 2010-2014. In Northern Pike, average concentrations varied from 0.41 to 1.12 mg/kg in 1976, from 0.39 to 1.36 mg/kg in 1983-1997 and from 0.32 to 0.97 mg/kg in 2010-2014. In Yellow Perch, they ranged from 0.25 to 0.54 mg/kg in 1976, from 0.22 to 0.62 mg/kg in 1983-1997 and from 0.15 to 0.23 mg/kg in 2010-2014.

Downstream from Lac Saint-Louis (stations 10 and 11), average concentrations in mercury measured in Walleye were 0.63 mg/kg in 1983-1997 and 0.26 mg/kg in 2010-2014. In Northern Pike, average concentrations were 0.54 mg/kg in 1983-1997 and ranged from 0.29 to 0.46 mg/kg in 2010-2014. In Yellow Perch, they were 0.22 mg/kg in 1983-1997 and varied from 0.15 to 0.16 mg/kg in 2010-2014. No measurements were taken in this sector in 1976.

In Lac Saint-Pierre (stations 12, 13, 14, 15 and 16), average mercury concentrations measured in Walleye were 0.55 mg/kg in 1976 and varied from 0.22 to 0.43 mg/kg in 1983-1997 and from 0.25 to 0.31 mg/kg in 2010-2014. In Northern Pike, average concentrations were 0.59 mg/kg in 1976 and varied from 0.32 to 0.45 mg/kg in 1983-1997 and from 0.28 to 0.50 mg/kg in 2010-2014. In Yellow Perch, they were 0.27 mg/kg in 1976 and ranged between 0.14 and 0.19 mg/kg in 1983-1997 and between 0.16 and 0.18 mg/kg in 2010-2014.

In the sectors of Gentilly and Québec City (stations 17, 18, 19 and 20), average mercury concentrations measured in Walleye were 0.52 mg/kg in 1976 and varied from 0.41 to 0.63 mg/kg in 1983-1997 and from 0.23 to 0.35 mg/kg in 2010-2014. In Northern Pike, average concentrations were 0.42 mg/kg in 1976, 0.19 mg/kg in 1983-1997 and 0.17 mg/kg in 2010-2014. In Yellow Perch, they were 0.18 mg/kg in 1976 and ranged from 0.15 to 0.23 mg/kg in 1983-1997 and from 0.08 to 0.18 mg/kg in 2010-2014.

 

Polychlorinated biphenyls PCB

Major reductions in PCB concentrations from the values observed in 1976 and over the period 1983 1997 were observed during the period 2010 2013. The most important reductions were observed between 1976 and 1983 1997. These reductions demonstrate that the banning of PCBs and the efforts to recover and destroy them have led to major reductions in the contamination of the St. Lawrence. In fact, over the period 2010 2013, average PCB concentrations in the flesh of Walleye, Northern Pike and Yellow Perch in the St. Lawrence River were below the Canadian standard of 2,000 µg/kg (under review) for the marketing of fish products (figure 3). These values are also generally below the European Union standard of 125 µg/kg for the marketing of fish products. Only two sites show PCB concentrations above 125 µg/kg. These concentrations (130 µg/kg) were observed only in Walleye near Montréal (station 10) and in Lac Saint-Pierre (station 13).

The average PCB concentrations measured in these three species during the period 2010 2013 remain below the criterion for the protection of fish-eating terrestrial wildlife (160 µg/kg). However, the concentrations reported here, since they derive from measurements of the flesh rather than of the fish as a whole, constitute a less than ideal indicator for assessing the potential risk to protected fish-eating terrestrial wildlife. It is a fact that PCB concentrations in the flesh are lower than in the fish as a whole since these contaminants tend to accumulate much more in the fatty tissues than in the flesh. It is worth noting that concentrations close to the criterion likely indicate a potential risk to this wildlife and the food chain as a whole, since these species represent part of the diet of numerous wildlife species. Note as well that PCB concentrations measured in the whole white sucker (unrepresented on figure 3) during the period 2010 2013 exceeded the criterion of 160 µg/kg at several sites located near Montréal (stations 10 et 11) and in Lac Saint-Pierre, with concentrations frequently hovering between 160 and 450 µg/kg.

Figure 3 Changes in average PCB concentrations in Walleye, Northern Pike and Yellow Perch in the St Lawrence River over the period 1976-2013

Long description

Graphic using vertical bars in three different colours representing PCB concentrations for the periods 1976, 1983-1997 and 2010-2013 in Walleye, Northern Pike and Yellow Perch. The stations are grouped together in six sectors: Lac Saint-François, Lac Saint-Louis, downstream from Lac Saint-Louis, Lac Saint-Pierre, Gentilly and Québec City. A broken horizontal line traverses the diagram to indicate the position of the European Union standard (125 µg/kg) established for the marketing of fish products.

PCB concentrations in the three fish species fell significantly between 1976 and the period 2010-2014.

At Lac Saint-François (stations 1, 2 and 3), average PCB concentrations measured in Walleye ranged between 2,609 and 3,529 µg/kg in 1976, between 180 and 353 µg/kg in 1983-1997 and between 49 and 110 µg/kg in 2010-2013. In Northern Pike, average concentrations ranged between 579 and 599 µg/kg in 1976, between 26 and 128 µg/kg in 1983-1997 and between 11 and 23 µg/kg in 2010-2013. In Yellow Perch, they varied from 218 to 594 µg/kg in 1976, from 5 to 68 µg/kg in 1983-1997 and from 7 to 21 µg/kg in 2010-2013.

At Lac Saint-Louis (stations 5, 6 and 7), average PCB concentrations measured in Walleye varied from 449 to 1002 µg/kg in 1976, from 94 to 127 µg/kg in 1983-1997 and from 34 to 48 µg/kg in 2010-2013. In Northern Pike, average concentrations varied from 154 to 614 µg/kg in 1976, from 32 to 99 µg/kg in 1983-1997 and from 13 to 69 µg/kg in 2010-2013. In Yellow Perch, they were 368 µg/kg in 1976 and ranged from 30 to 42 µg/kg in 1983-1997 and from 11 to 14 µg/kg in 2010-2013.

Downstream from Lac Saint-Louis (stations 10 and 11), average PCB concentrations measured in Walleye were 163 µg/kg in 1983-1997 and ranged from 44 to 130 µg/kg in 2010-2013. In Northern Pike, average concentrations were 76 µg/kg in 1983-1997. In Yellow Perch, they were 40 µg/kg in 1983-1997. In this sector, no PCB measurements were taken in 1976, and no PCB measurements were taken in Northern Pike and Yellow Perch in 2010-2013.

At Lac Saint-Pierre (stations 12, 13, 14, 15 and 16), average PCB concentrations measured in Walleye were 2,178 µg/kg in 1976 and ranged from 41 to 100 µg/kg in 1983-1997 and from 34 to 130 µg/kg in 2010-2013. In Northern Pike, average concentrations were 205 µg/kg in 1976 and varied from 17 to 108 µg/kg in 1983-1997 and from 17 to 30 µg/kg in 2010-2013. In Yellow Perch, they were 430 µg/kg in 1976 and ranged from 8 to 40 µg/kg in 1983-1997 and from 3 to 8 µg/kg in 2010-2013.

In the Gentilly and Québec City sectors (stations 17, 18, 19 and 20), average PCB concentrations measured in Walleye were 440 µg/kg in 1976 and ranged between 14 and 130 µg/kg in 1983-1997 and 14 and 49 µg/kg in 2010-2013. In Northern Pike, average concentrations were 867 µg/kg in 1976 and varied from 20 to 37 µg/kg in 1983-1997 and 20 µg/kg in 2010-2013. In Yellow Perch, they ranged from 3 to 32 µg/kg in 1983-1997 and from 3 to 5 µg/kg in 2010-2013. In this sector, no PCB measurements were taken in Yellow Perch in 1976.

 

Polybrominated diphenyl ethers PBDE

Analyses of PBDE in the flesh of fish from the St. Lawrence River began in 2002. PBDE concentrations remained relatively stable during the studied period of 2002 2013.

There is no standard governing the quantity of PBDEs in fish flesh deemed acceptable for human consumption. The concentrations normally measured are not deemed to pose a significant risk to human health.

Environment Canada has established criteria, however, for different congener groups of PBDEs in order to protect fish-eating wildlife and birds. For the three main congener groups normally detected in fish, ie, the  tetra BDE, penta BDE and hexa BDE, the criteria are 44 µg/kg, 3 µg/kg and 4 µg/kg respectively. All average tetra BDE and hexa BDE concentrations in Walleye, Northern Pike and Yellow Perch are below the established criteria (44 µg/kg and 4 µg/kg respectively). With respect to the penta BDE, criterion of 3 µg/kg is exceeded in the Walleye and Northern Pike at Boucherville (station 10), Lac Saint-Pierre and Québec City, with concentrations ranging from 3.86 µg/kg to 14.1 µg/kg.


Port of Québec
Photo : Paul Grant © Le monde en images

As with PCBs, however, PBDE concentrations measured in whole white suckers over the period 2002 2013 exceeded the criteria at several sites. At the sites near Montréal (station 11), they reached values of 303 µg/kg for tetra BDEs, 46.8 µg/kg for penta BDEs and 15.5 µg/kgs for hexa BDEs. Similarly, the concentrations measured at Lac Saint-Pierre (station 13) reached values of 84 µg/kg for tetra BDEs, 14.7 µg/kg for penta BDEs and 5.9 µg/kg for hexa BDEs and posed a potential risk to fish-eating terrestrial wildlife and birds.

Dioxins and furans

Analyses of dioxins and furans in the flesh of fish in the St. Lawrence River were initiated in 1991 with some exploratory sampling. Given the relatively low concentrations measured, the analyses were subsequently limited to a few species, generally the largest fish.

From 2001 to 2013, dioxin and furan concentrations remained low and relatively similar. The Canadian standard of 20 ng/kg for 2,3,7,8 TCDD is under review. The European Union standard for the marketing of fish products is 3.5 ng/kg. All the 2,3,7,8 TCDD toxic equivalence concentrations measured in the flesh of Walleye, Northern Pike and Yellow Perch from the St.Lawrence River were below the European Union standard and are not deemed to pose a major risk to human health.


St. Lawrence River at Repentigny
Photo : Naomie Proulx © Le monde en images

In whole white suckers, the 2,3,7,8 TCDD toxic equivalence concentrations occasionally exceed the criterion of 0.66 ng/kg for the protection of fish-eating wildlife and birds. Most of the values that exceed the criterion are less than twice the criterion value and do not pose a major risk given the limited number of measurements that exceed the criterion. Most of the highest concentrations were measured in 2001 and 2002 near Montréal and in the Boucherville and Repentigny areas (stations 10 et 11); the concentrations exceeding the criterion ranged from 0.732 to 1.546 ng/kg.

 

Port of Montréal
Photo : Denis Chabot © Le monde en images

Perspectives

Thanks to stronger regulations and several government programs, we have seen significant reductions in the release of contaminants into the Great Lakes – St. Lawrence system.  Current levels of toxic contamination are low enough to allow the public to resume its traditional usage of the river, ie, fishing and fish consumption. The available data indicate that the presence of toxins does not preclude the enjoyment, at this time, of eating fish from the river and reaping the health benefits associated with such a diet. These contaminants will likely still be present, but in decreasing quantities, for decades to come in the water, the sediments and the biological communities of the St. Lawrence.

 

St. Lawrence River at Sorel-Tracy
Photo : Robert Desjardins © Le monde en images

To learn more

Guide de consommation du poisson de pêche sportive en eau douce, Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques and Ministère de la Santé et des Services sociaux, Québec. www.mddelcc.gouv.qc.ca/eau/guide/index.htm.

LALIBERTÉ, D. 2011. Teneurs en polybromodiphényléthers (PBDE) dans les poissons du fleuve Saint-Laurent et des lacs et rivières du Québec3  (2002-2008). Québec, Ministère du Développement durable, de l’Environnement et des Parcs, Direction du suivi de l’état de l’environnement, ISBN 978-2-550-60987-2 (PDF), 48 p.

State of the St. Lawrence Monitoring Program

Five government partners—Environment and Climate Change Canada, Fisheries and Oceans Canada, Parks Canada, the Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques du Québec and the Ministère des Forêts, de la Faune et des Parcs du Québec—and Stratégies Saint-Laurent, a non-governmental organization that works actively with riverside communities, are pooling their expertise and efforts to provide Canadians with information on the state of the St. Lawrence and long-term water-quality changes.

 

Source of data and writing :

Denis Laliberté
Direction générale du suivi de l’état de l’environnement4
Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques

ISBN 978-2-550-75680-4 (PDF)

© Her Majesty the Queen in Right of Canada, represented by the Minister of Environment and Climate Change, 2016

Published with the authorization of the Ministre du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques

© Gouvernement du Québec, 2016

Aussi disponible en français sous le titre: La contamination des poissons d’eau douce par les toxiques – 3e édition

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[3] Polybrominated diphenyl ether (PBDE) concentrations in fish in the St. Lawrence River and lakes and rivers in the province of Québec

[4] Environmental monitoring branch

 

St. Lawrence River at Berthierville
Photo : Denis Chabot © Le monde en images