Siska Salmon and Human Health Project – Effects of Environmental Contaminants in Upriver Migration in the Fraser and Thompson River Basins: Toxicity and Exposure Levels

The Siska Traditions Society in Lytton, British Columbia (BC) was concerned about the quality of salmon they consumed due to its possible exposure to contaminants within the Fraser and Thompson River basins. Over the last forty years, they witnessed a reduction in the number of salmon returning to their spawning grounds and changes to the physical characteristics of the salmon. They had also been concerned with rising water temperatures, and changes to the size and characteristics of the rivers. The objectives of this study included assessing the extent and possible health impacts of contaminant exposure from salmon. The study also aimed to assist in the development of risk assessment studies and traditional knowledge indicators of contaminant exposure.

The project team collected samples of raw and cooked salmon and roe, and analyzed them for heavy metals, PCBs (polychlorinated biphenyls), dioxins/furans (PCDD/Fs) and pesticides. Both spring salmon and sockeye salmon were tested.

The project team found spring salmon and sockeye salmon varied in levels of contaminants. The team also found variations in the levels of contaminants in salmon flesh and eggs. Although dioxin levels in salmon were well below the tolerable daily intake for humans, the team considered the levels high enough to potentially affect egg survival.  The study found the levels of contaminants in salmon were similar to or less than levels in common store-bought foods. The cooking methods resulted in a slight increase in contamination due to water evaporation in the cooking process.

Community members expressed great interest in the results and the project team undertook several knowledge translation activities including workshops, videos, and pamphlets.