Ecological Evaluation Technical Guidance - State of New Jersey

applied (USEPA, 1989b, 1989c, and 1999a). Quantitative uncertainty analyses provideobjective measures of the relative confidence in the conclusions that have been drawn inan evaluation.Uncertainty surrounding risk assessment conclusions has important implications for riskmanagement (USEPA, 1988, 1998a). However, uncertainty is not a single, generallyapplicable parameter. Uncertainty surrounding a risk estimate or application has anumber of components, including parameter variability, calculation error andsimplification, and the underlying reality of exposure assumptions and pathways(USEPA, 1988). Uncertainty includes both real variation (reflecting actual, mechanisticbiological response ranges and variability in ecosystem conditions) and error (USEPA,1997a).Because biological systems are inherently uncertain and variable, some component ofvariability in risk estimation is due to a realistic expression of ecological conditions,while another component is due to error or uncertainty introduced by the overallanalytical process. Error is the component to be minimized because error encompassesundesirable uncertainty that has been introduced by the assessment process. However, itis critically important to understand ecosystem variability because this represents animportant component of the ecosystem within which RMDs will be made. Substantialdifferences exist between observations and conclusions made at the individual,population, and community levels of biological organization. For example, effects notmanifested at the population or community levels (e.g., mortality of only a fewindividuals) may not be observable with the type of studies implemented. Theramifications of this also include an understanding that, because the assessment levelendpoints are protective of populations and communities and not individuals, theprojected loss of a few individuals may not cause impacts that are important at the levelsof assessment at which RMDs are made.Because of the many potential receptor species and general lack of knowledge regardingtheir life cycles, feeding habits, nutritional requirements (e.g., essential elements such asarsenic, trivalent chromium, selenium, and zinc), and relative toxicological sensitivity,the uncertainty surrounding estimates of ecological risks may be substantially greaterthan those associated with human health risk assessment. The generic screening andregulatory criteria and TRVs used in this assessment are intended to provide conservativebenchmarks, but it is important to note that no one approach to criterion or TRVderivation is adequate for all sites and all COPECs. The criteria or TRVs used in thisassessment are all chemical-specific and as such, cannot address the additive,antagonistic, or synergistic effects of the chemical mixtures typically found in theenvironment. Further, these criteria or TRVs do not take into account the structure anddynamics of the ecosystem present at the site, site-specific conditions regulating chemicalcontact and bioavailability, the potential toxicity of other constituents that were notquantified, or the pervasive influence of physical stressors associated with the disruptionby human activities that is characteristic of an area that may have an industrial history.The uncertainty evaluations should be performed within a range of conditions defined bycharacteristics of the environment at the time field data were gathered. As such, dataobtained and conclusions drawn represent a series of snapshots of site conditions and,while they can be extrapolated to a broad range of conditions, they are most accurateEcological Evaluation Technical Guidance Document 83Version 1.2 8/29/12