Human and Ecological Risk Assessment - Earthjustice

Section 3.0Analysis• The analysis considered exposures for three child receptor cohorts and one adult receptorcohort; exposure for these cohorts was assumed to start at ages 3, 8, 15, and 20,respectively• Chemical properties (bio-uptake and bioaccumulation factors) were collected from bestavailable literature values (see Appendix J)• Human exposure factors (e.g., body weight, exposure duration, exposure frequency,consumption rates) were set at central tendency values.Appendix I describes the methodology used to develop the CCW HBNs and provides theHBNs used in the screening analysis.3.2.3.2 CSCL CalculationsThe CCW ecological screening analysis paralleled the human health screening analysisand addressed two routes of exposure for ecological receptors: direct contact with contaminatedmedia and ingestion of contaminated food items. Ecological exposure scenarios occurring nearCCW landfills or surface impoundments and addressing these exposure routes included thefollowing:• Direct contact with surface water contaminated by CCW leachate through thegroundwater-to-surface-water pathway• Ingestion of aquatic organisms in streams and lakes contaminated by CCW leachatethrough the groundwater-to-surface-water pathway.CSCLs for the contaminated media in each of these exposure scenarios were calculatedas described in Section 3.1.2 and Appendix H (the same CSCLs were used for both screeningand the full-scale analysis). As with the HBNs, CSCLs were compared directly to concentrationsof constituents found in CCW and CCW leachate and porewater, or to protective offsite mediaconcentrations to estimate risk for screening.3.2.4 Screening ResultsThe screening analysis conducted in 2002 (U.S. EPA, 2002a) was used in this riskassessment to help narrow the list of constituents to be addressed in the full scale analysis for thegroundwater-to-drinking-water and groundwater-to-surface-water pathways. Detailed human andecological screening results for these pathways are provided in Appendix K. The groundwaterto-drinking-waterand groundwater-to-surface-water pathways (human fish consumption andecological risks) did show risks above the screening criteria for several CCW constituents in thescreening analysis. Table 3-5 lists the 21 constituents that had 90th percentile screening analysisgroundwater pathway risks greater than a cancer risk of 1 in 100,000 or a noncancer risk with anHQ greater than 1 for human health and 10 for ecological risk. 99 An HQ of 10 was used for screening ecological risks to account for conservatism of ecological benchmarks andexposure estimates used in the screening analysis (see Section 4.4.3.4).April 2010–Draft EPA document. 3-11