Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 1/10)
Character Range: 1440976–1444099

5                   Appendices

5.1              Appendix A: Review and comparison of frameworks for deriving soil quality guidelines in other countries

5.1.1         A1: USA
The US EPA has developed a series of Eco-SSLs (www.epa.gov/ecotox/ecossl/) to protect terrestrial organisms from soil contamination.

Eco-SSLs apply to sites where terrestrial organisms may be exposed directly or indirectly to contaminated soil. Eco-SSLs were developed to support risk management decisions for Superfund sites (orphaned contaminated sites identified as having significant contamination potentially present for many years or even decades). This was undertaken to avoid repetitious risk assessment and literature reviews of toxicity data for the same contaminants at each contaminated site, and to allow risk assessors to focus their efforts on the main contaminants of concern.

Seven types of receptors were initially considered in the development of the Eco-SSLs (mammals, birds, reptiles, amphibians, soil invertebrates, plants, and soil microbes and their processes) but final SSLs were produced without consideration of amphibians and reptiles due to insufficient data being available, in the view of the US EPA, to derive screening levels. Soil microorganisms and microbial processes were also not included in the derivation of Eco-SSLs but the rationale for this was over the variability of the data and their ecological significance.

For plants and invertebrates, the methodology used to develop Eco-SSLs was to review the relevant toxicity literature for each contaminant, screen the data for quality, and only use toxicity data representing high bioavailability conditions in upland aerobic soils (that is, avoiding consideration of flooded soil conditions). Because of the different behaviour of many contaminants in soils, high bioavailability was defined for three broad groups of contaminants—cationic metals, anionic metals and non-ionising organic contaminants. For example, high bioavailability for cationic metals was defined as low soil pH and organic matter content. Where literature data did not exist for a contaminant, this was developed by experimentation.

The Eco-SSL for a contaminant was calculated as the geometric mean of all the toxicity values at the highest relative bioavailability score for which sufficient data existed (that is,  ≥3 data points). If less than three data values were available at the highest relative bioavailability level, data from the next highest bioavailability score was included in that Eco-SSL data set. This process proceeded until a combined data set of three or more data values was identified for calculating the Eco-SSL. If there were less than three acceptable studies, an Eco-SSL was not calculated.

For wildlife Eco-SSLs, three avian and three mammalian species were chosen to represent some of the most highly exposed species at contaminated sites (meadow vole, short-tailed shrew, long-tailed weasel, mourning dove, American woodcock and red-tailed hawk). Wildlife Eco-SSLs were developed by back-calculating from a hazard quotient (HQ) of 1.0, calculated by