Human and Ecological Risk Assessment - Earthjustice

Appendix HEcological BenchmarksRisk Analysis for Fossil Fuel Combustion Phase 2 (FFC2) (U.S. EPA, 1998). The receptors andendpoints selected for the 1998 analysis were evaluated and considered appropriate for the goalsof this risk assessment. The benchmarks were derived for each chemical and receptor to theextent that supporting data were available.As in 1998, the lowest (most sensitive) benchmark for each chemical in each mediumwas selected to calculate HQs in the CCW risk assessment. For example, several receptors(aquatic invertebrates, mammals, and birds) may be exposed to constituents in surface water. Thesurface water HQ for a given chemical was calculated using whichever benchmark was lowestand would thus give the highest (most protective) HQ.H.1.1Direct Contact ExposureEcological receptors that live in close contact with contaminated media are considered tobe potentially at risk. These receptors are exposed through direct contact with contaminants insurface water and sediment. The receptors selected to assess the direct contact exposure route foreach medium are summarized in Table H-1. The benchmarks for receptor communities are nottruly community-level concentration limits in that they do not consider predator-prey interactions.Rather, they are based on the theory that protection of 95 percent of the species in the communitywill provide a sufficient level of protection for the community (see, for example, Stephan et al.,1985, for additional detail). The following sections summarize the benchmark derivationmethods for each receptor assessed for the direct contact route of exposure.Aquatic Community BenchmarksThe aquatic community receptor comprises fish and aquatic invertebrates exposedthrough direct contact with constituents in surface water. For the aquatic community, the finalchronic value (FCV), developed either for the Great Lakes Water Quality Initiative (U.S. EPA,1993) or the National Ambient Water Quality Criteria (NAWQC) (U.S. EPA, 1995a,b), was thepreferred source for the benchmark. If an FCV was unavailable and could not be calculated fromavailable data, a secondary chronic value (SCV) was estimated using methods developed forwildlife criteria for the Great Lakes Initiative (e.g., 58 FR 20802; U.S. EPA, 1993). The SCVmethodology is based on the original species data set established for the NAWQC; however, itrequires fewer data points and includes statistically derived adjustment factors. For benchmarkderivation, the minimum data set required at least one data point.Amphibian BenchmarksFor amphibian populations, data availability severely limited benchmark development. Areview of several compendia presenting amphibian ecotoxicity data (e.g., U.S. EPA, 1996;Power et al., 1989), as well as primary literature sources, found a lack of standard methods onendpoints, species, and test durations necessary to derive a chronic benchmark for amphibians.Consequently, an acute benchmark was derived for aqueous exposures in amphibians by taking ageometric mean of LC 50 (i.e., concentration lethal to 50 percent of test subjects) data identified instudies with exposure durations less than 8 days. Although the use of acute effects levelsproduced a benchmark that was not consistent with the other (chronic) ecological benchmarks,the sensitivity of these receptors warranted the use of acute effects levels in the absence ofchronic concentration limits. Recent studies (Hopkins and Rowe, 2004; Hopkins et al., 2006)April 2010–Draft EPA document. H-2