Potential Effects of Contaminants on Fraser River Sockeye Salmon

were used in the effects and exposure assessments (i.e., the maximum concentrationmeasured for each habitat type in each Area <strong>of</strong> Interest was selected as the exposure pointconcentration for each chemical <strong>of</strong> potential concern; estimates <strong>of</strong> no-effect concentrationsfor aquatic organisms were selected as the toxicity screening values). Chemicals for whichall measured concentrations were below the corresponding no-effect concentrations wereconsidered to be unlikely to cause adverse effects on sockeye salmon or other aquaticorganisms within the Fraser River Basin and were not considered further in theinvestigation. Chemicals for which one or more measured concentrations exceeded theselected toxicity screening value were identified as contaminants <strong>of</strong> concern and subjectedto further evaluation (see Chapter 5 for additional information). Chemicals for whichinsufficient information was available to complete the assessment were identified asuncertain contaminants <strong>of</strong> concern and were evaluated using qualitative analyses (seeChapter 6 for more information). Each <strong>of</strong> these steps in the preliminary evaluation <strong>of</strong>chemicals <strong>of</strong> potential concern is described in the following sections <strong>of</strong> this Chapter. Inaddition, the results <strong>of</strong> these analyses are presented herein.4.2 Identification <strong>of</strong> <strong>Potential</strong>ly-Complete Exposure PathwaysBased on the results <strong>of</strong> the evaluation conducted in Chapter 3, it is apparent that land andwater use activities in the study area and in areas spatially removed from the watershedhave resulted or are likely to have resulted in the release <strong>of</strong> 200 or more chemicalsubstances into aquatic habitats within the Fraser River Basin. Each <strong>of</strong> these contaminantspartition into water, sediment, and/or biological tissues in accordance with their physicalchemicalproperties and the conditions within the receiving water system. Suchpartitioning and other environmental fate processes determine which media (i.e., water,sediment, and/or biota) become contaminated and, thereby, represent potentially-completeexposure pathways to sockeye salmon in the study area. For an exposure pathway to becomplete, a contaminant must be able to travel from the source to the ecological receptorunder consideration and must be taken up by that ecological receptor via one or moreexposure routes.There are a number <strong>of</strong> pathways through which Fraser River sockeye salmon can beexposed to the substances identified in the Aquatic <strong>Contaminants</strong> Inventory (Table 3.28).For the substances that partition into water, direct exposure to contaminated waterrepresents the most important exposure pathway for sockeye salmon (i.e., uptake throughthe gills and/or through the skin). For substances that partition into sediments, directexposure to contaminants in sediment and/or pore water during incubation and46