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Examination of the Toxicity of Diluted Bitumen on Freshwater Fish


Much remains to be understood about the toxicity of diluted bitumen to aquatic species. Bitumen is a black, viscous mixture of hydrocarbons that is commonly used as a binder in asphalt. Diluted bitumen (dilbit) is bitumen blended with one or more lighter petroleum products (diluent) to reduce its viscosity to make it easier to transport by pipeline, for example. Building on previous research, this study will analyze the toxicity of dilbit to three fish species found in Canada—two cold-water (Rainbow Trout and Atlantic Salmon) and one warm-water (Fathead Minnow)—using standard tests under conditions that are representative of a spill in a freshwater system.

Phase one of the research will establish acute toxicity thresholds, while phase two will analyze chronic toxicity to assess the non-lethal impacts, including the effects of dilbit on the growth, condition and malformations of early-stage fish. Phase three, which will be carried out concurrently with the first two phases, will measure several biomarkers of exposure and effects (e.g. oxidative stress and resulting damage to DNA and lipids, endocrine disruption) to learn more about the cellular and molecular impacts of dilbit exposure. The findings of this research, and other concurrent studies, will provide a greater understanding of dilbit toxicity and the risks that potential spills pose to freshwater fish. This knowledge will inform the establishment of water contamination thresholds to protect the early life stage of three Canadian fish species, and inform decision-making and the prioritization of spill response measures.

Program Name

National Contaminants Advisory Group (NCAG)


2017 - 2020



Principal Investigator(s)

Dr. Patrice Couture
INRS-ETE (Institut national de la recherche scientifique)
Centre Eau Terre Environnement

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