John Wiley & Sons, Ltd.

Sensitivity of Ecological Soil screening levels for metals to exposure model parameterization and toxicity reference values

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Ecological soil‐screening levels (Eco‐SSLs) were developed by the USEPA (United States Environmental Protection Agency) for purposes of setting conservative soil screening values that can be used to eliminate the need for further ecological assessment for specific analytes at a given site. Eco‐SSLs for wildlife represent a simplified dietary exposure model solved in terms of soil concentrations to produce exposure equal to a no observed adverse effect toxicity reference value (TRV). Sensitivity analyses were performed for six avian and mammalian model species, and 16 metals/metalloids for which Eco‐SSLs have been developed. The relative influence of model parameters was expressed as the absolute value of the range of variation observed in the resulting soil concentration when exposure is equal to the TRV. Rank Analysis of Variance was used to identify parameters with greatest influence on model output. For both birds and mammals, soil ingestion displayed the broadest overall range (variability), although TRVs consistently had the greatest influence on calculated soil concentrations; bioavailability in food was consistently the least influential parameter, although an important site specific variable. Relative importance of parameters differed by trophic group. Soil ingestion ranked second for carnivores and herbivores, but was fourth for invertivores. Different patterns were exhibited depending upon which parameter, trophic group, and analyte combination was considered. The approach for TRV selection was also examined in detail, with copper as the representative analyte. The underlying assumption that generic body‐weight‐normalized TRVs can be used to derive protective levels for any species is not supported by the data. Whereas the use of site‐, species‐, and analyte‐specific exposure parameters is recommended to reduce variation in exposure estimates (soil protection level), improvement of TRVs is more problematic. Environ Toxicol Chem © 2014 SETAC

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