Human and Ecological Risk Assessment - Earthjustice

Appendix HEcological BenchmarksAppendix H. Ecological BenchmarksBoth the screening and full-scale CCW assessments included an ecological riskassessment that paralleled the human health risk assessment. The ecological risk assessmentaddressed two routes of exposure for ecological receptors: direct contact with contaminatedmedia and ingestion of contaminated food items. For each CCW chemical for which ecologicaleffect data were available, hazard quotients (HQs) were calculated using chemical-specific mediaconcentrations assumed to be protective of ecological receptors of concern.This appendix provides the ecological benchmarks used in both the CCW screening andfull-scale risk assessment. Section H.1 describes the data sources and methods used to developthese benchmarks. Additional details can be found in U.S. EPA (1998). Section H.2 provides thebenchmarks.H.1 Data Sources and MethodologyTo calculate ecological HQs, the concentration-based ecological benchmarks (also knownas chemical stressor concentration limits, or CSCLs) were divided by the estimatedconcentrations of constituents in environmental media contaminated by CCW. The CSCLs areenvironmental quality criteria intended to represent a protective threshold value for adverseeffects to various ecological receptors in aquatic ecosystems (surface water and sediment). AnHQ greater than target of 1 indicates that the predicted concentration will be above the CSCLand, therefore, the potential for adverse ecological effects exists. In this regard, the use of CSCLsto calculate an ecological HQ is analogous to the use of the reference concentration (RfC) forhuman health where the air concentration is compared to the health-based concentration (theRfC), and an HQ greater than the target value of 1 is considered to indicate the potential foradverse health effects. Table H-1 shows the receptor types assessed for each exposure route ineach environmental medium addressed by the CCW risk assessment.Table H-1. Ecological Receptors Assessed by Medium Impacted by CCWReceptor Type Surface Water SedimentDirect Contact ExposureAquatic Community Sediment CommunityAmphibians Aquatic Plants and Algae Ingestion ExposureMammals Birds Ecological benchmarks for the CCW risk assessment were taken directly from the 1998fossil fuel combustion risk analysis, Non-Groundwater Pathways, Human Health and EcologicalApril 2010–Draft EPA document. H-1