Human and Ecological Risk Assessment - Earthjustice

Section 3.0AnalysisFor surface water and sediments, the ingestion route of exposure addresses the exposureof terrestrial mammals and birds through ingestion of aquatic plants and prey. Thus, thebenchmarks for ingestion exposure represent media concentrations that, based on certainassumptions about receptor diet and foraging behavior, are expected to be protective ofpopulations of mammals and birds feeding and foraging in contaminated areas.For birds and mammals, the derivation of ingestion benchmarks required the selection ofappropriate ecotoxicological data based on a hierarchy of sources. The assessment endpointchosen for birds and mammals was population viability and therefore, the ingestion benchmarkswere based on study data for physiological effects that are relevant to populations. These dataincluded measures of reproductive fitness, developmental success, survival, and othertoxicological effects that could have an impact on the population rather than just the health of anindividual animal. Choosing these measures of effect provided the basis to evaluate the potentialfor adverse effects at the population level by inference; this analysis did not evaluate the effectson population dynamics in the sense that a reduction in the population was predicted over time inresponse to exposure to constituents released from CCW. Population-level modeling was beyondthe scope of this risk assessment.Once an appropriate ingestion exposure study was identified, a benchmark wascalculated. Appendix H describes the basic technical approach used to convert avian ormammalian benchmarks (in daily doses) to the CSCLs (in units of concentration) used to assessecological risks for contaminated surface water and sediment. The methods reflect exposurethrough the ingestion of contaminated plants, prey, and various media, and include parameterson accumulation (e.g., BCFs), uptake (e.g., consumption rates), and dietary preferences.Where multiple ecological benchmarks were available for a pathway of interest, thebenchmark that produced the lowest (most sensitive) CSCL for each chemical in each mediumwas used. For example, several types of receptors (the aquatic community, amphibians, aquaticplants, mammals, birds) can be exposed to contaminants in surface water. The surface watercriterion for a given constituent represents the lowest CSCL for these receptors, and thus givesthe highest (most protective) HQ. The CSCLs used to assess ecological endpoints in the fullscaleanalysis and the associated receptor are summarized in Table 3-3. Additional details on theCCW ecological benchmarks and CSCLs and their development can be found in Appendix Hand in U.S. EPA (1998a).Table 3-3. Ecological Risk Criteria Used for Surface Water and SedimentConstituent Medium a Exposure Route CSCL Units ReceptorAluminum Surface Water Direct contact 0.09 mg/L Aquatic biotaArsenic total Sediment Ingestion 0.51 mg/kg Spotted sandpiperArsenic III Surface Water Direct contact 0.15 mg/L Aquatic biotaArsenic IV Surface Water Direct contact 8.10E-03 mg/L Aquatic biotaBarium Sediment Ingestion 190 mg/kg Spotted sandpiperSurface Water Direct contact 4.00E-03 mg/L Aquatic biotaBoron Surface Water Direct contact 1.60E-03 mg/L Aquatic biota(continued)April 2010–Draft EPA document. 3-7