Sensitivity of ecological soil-screening levels for metals to exposure model parameterization and toxicity reference...

Area of Science:

• Environmental Science
• Ecotoxicology
• Risk Assessment

Background:

• Ecological soil-screening levels (Eco-SSLs) are used by the US Environmental Protection Agency (USEPA) to set soil screening values.
• These values help eliminate the need for further ecological assessment at contaminated sites.
• Eco-SSLs for wildlife utilize a simplified dietary exposure model.

Purpose of the Study:

• To conduct sensitivity analyses on ecological soil-screening levels (Eco-SSLs) for wildlife.
• To determine the influence of various model parameters on calculated soil concentrations.
• To evaluate the appropriateness of generic toxicity reference values (TRVs) for different species.

Main Methods:

• Performed sensitivity analyses on Eco-SSLs for 6 avian and mammalian species and 16 metals/metalloids.
• Utilized rank analysis of variance to identify influential model parameters.
• Examined the approach for selecting TRVs using copper (Cu) as a representative analyte.

Main Results:

• Soil ingestion showed the broadest variability, while TRVs had the greatest influence on soil concentrations.
• Bioavailability in food was the least influential parameter but remains a key site-specific variable.
• Parameter importance varied by trophic group (carnivore, herbivore, invertivore).

Conclusions:

• Generic, body-weight-normalized TRVs are not universally protective across all species.
• Site-, species-, and analyte-specific exposure parameters can reduce variation in soil protection levels.
• Improving TRVs presents a significant challenge for refining Eco-SSLs.