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Toxicity of diluted bitumen to Canadian marine and freshwater fish species


Proposals to transport diluted bitumen (Dilbit) from Alberta to coastal terminals on both the Pacific and Atlantic coasts have raised concerns among Canadians about the potential impacts of spills in marine and freshwater ecosystems. Although toxicity of other crude and refined oils has been tested extensively, toxicity of Dilbit and its components (i.e., bitumen and oil-gas condensates) is less well known. In general, the potential impacts of crude and refined oils on fish populations have been associated with toxicity to developing embryos, a life stage that cannot actively avoid exposure to spilled oil, but is uniquely sensitive by virtue of embryogenesis. Embryo toxicity would be expressed as recruitment failure and a deficit in fish abundance. The species most at risk would be those that spawn in coastal ecosystems, or in rivers or lakes along the route of pipelines or railways, where exposure following an accidental spill would be most severe.

The toxicity of Dilbit is likely quite variable, in part due to differences in sensitivity of the species that might be exposed, and in part due to the variations in chemical composition of the oil-gas condensates used as diluents, and in the bitumen generated by different extraction processes. Toxicity will also vary according to the nature of the exposure, i.e., whether it is dispersed into small droplets, coats surfaces underwater, or simply floats on the surface of water.

This research project will study the biological effects of different Dilbit formulations and physical status (i.e., weathered and non-weathered) along with their diluents in several Canadian fish species from coastal marine and freshwater ecosystems.

Program Name

National Contaminants Advisory Group (NCAG)


2014 - 2017



Principal Investigator(s)

Valérie Langlois
School of Environmental Studies
Queen’s University, Kingston, Ontario

Peter Hodson
School of Environmental Studies
Queen’s University, Kingston, Ontario

Team Member(s)

Barry Madison, Queen’s University, School of Environmental Studies

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