Furthering the derivation of predictive wildlife toxicity reference values for use in soil cleanup decisions

Abstract

The development of media-specific ecological values for risk assessment includes the derivation of acceptable levels of exposure for terrestrial wildlife (e.g., birds, mammals, reptiles, and amphibians). Although the derivation and subsequent application of these values can be used for screening purposes, there is a need to identify toxicological effects thresholds specifically for making remedial decisions at individual contaminated sites. A workshop was held in the fall of 2012 to evaluate existing methods and recent scientific developments for refining ecological soil screening levels (Eco-SSLs) and improving the derivation of site-specific ecological soil clean-up values for metals (Eco-SCVs). This included a focused session on the development and derivation of toxicity reference values (TRVs) for terrestrial wildlife. Topics that were examined included: methods for toxicological endpoint selection, techniques for dose-response assessment, approaches for cross-species extrapolation, and tools to incorporate environmental factors (e.g., metal bioavailability and chemistry) into a reference value. The workgroup also made recommendations to risk assessors and regulators on how to incorporate site-specific wildlife life history and toxicity information into the derivation of TRVs to be used in the further development of soil cleanup levels.

Benchmark dose analysis framework for developing wildlife toxicity reference values

“…Considerable scientific debate has occurred in recent years regarding the use of NOAELs and LOAELs in ERAs, and recommendations for alternative metrics have been advanced (Chapman et al 1996;Crane and Newman 2000;Allard et al 2010;Landis and Chapman 2011;van Dam et al 2012;Mayfield et al 2014). As noted by previous authors, NOAELs/ LOAELs have shortcomings because of limitations in study design or sample size and lack of attention to the full doseresponse curve or treatment group variability.…”

“…As noted by previous authors, NOAELs/ LOAELs have shortcomings because of limitations in study design or sample size and lack of attention to the full doseresponse curve or treatment group variability. Furthermore, in certain circumstances, the use of NOAELs/LOAELs may lead to inconsistent, problematic, or inappropriate TRVs to characterize risks (Allard et al 2010;Mayfield and Fairbrother 2013;Mayfield et al 2014;Sample et al 2014aSample et al , 2014b. Thus, performing dose-response analyses, when data are sufficient, is frequently recommended to reduce uncertainty in detailed (postscreening) risk assessments (US Environmental Protection Agency 1997, 1998Allard et al 2010;Landis and Chapman 2011;Mayfield et al 2014).…”

Sensitivity of ecological soil‐screening levels for metals to exposure model parameterization and toxicity reference values

“…Although no clear guidance for selecting TRVs suitable for developing soil cleanup values is available from regulatory agencies , multiple viable options for data based, site‐specific selections have been made in the present study and elsewhere []. Although several of the approaches necessitate time‐consuming literature searches and data retrieval, the number of species and feeding guilds for which TRVs are required for site cleanup is less than that for initial screening.…”

Methods for Derivation of Wildlife Toxicity Values for Use in Ecological Risk Assessments

“…Current practices for making site-specific clean-up decisions can be found elsewhere [7]. The TRV report provides the method used, the number and magnitude of uncertainty factors used, and the logic for the exclusion of any other pertinent information, if necessary.…”