Human and Ecological Risk Assessment - Earthjustice

Section 2.0Problem FormulationGroundwater model results were passed to the multimedia modeling system to estimatesurface water and sediment concentrations and to calculate human and ecological exposure andrisk. Additional inputs sent to the model at this stage included• Site-based surface waterbody type, dimensions, flows, pH, and total suspended solids(TSS) concentration• Chemical-specific fish bioconcentration factors (BCFs)• Human exposure factors (from national distributions)• Human and ecological health benchmarks.For human health, the multimedia modeling system calculated risk from drinking wateringestion and fish consumption for each realization. For ecological risk, the model used surfacewater and sediment concentrations along with ecological benchmarks to estimate the risks toecological receptors.2.4.3 Exposure AssessmentTable 2-4 lists the human and ecological receptors considered in the CCW riskassessment, along with the specific exposure pathways that apply to each receptor. All of thereceptors that EPA considered were assumed to live offsite, at a location near the WMU.Table 2-4. Receptors and Exposure Pathways Addressed in theFull-Scale CCW AssessmentReceptorHuman ReceptorsIngestionof DrinkingWaterAdult resident Child resident FishConsumptionAdult recreational fisher Child recreational fisher Ecological ReceptorsDirect Contactwith SurfaceWater andSedimentAquatic and sediment organisms Mammals and birdsIngestion ofAquaticOrganismsFor human receptors, the exposure assessment estimated the dose to an individualreceptor by combining modeled CCW constituent concentrations in drinking water or fish withintake rates for adult and child receptors. The full-scale CCW risk assessment consideredexposures due to chemicals leaching from WMUs and contaminating groundwater. Thegroundwater exposures include drinking water ingestion and consumption of recreationallycaught contaminated fish from surface waterbodies affected by contaminated groundwater. Forthe groundwater-to-drinking-water pathway, it was assumed that well water was the only sourceApril 2010–Draft EPA document. 2-15