Risk-based cleanup goals are often calculated assuming that chemicals present in soil are absorbed by humans as efficiently as the chemicals dosed during the toxicity tests used to determine regulatory toxicity values (such as the Reference Dose or Cancer Slope Factor). This assumption can result in inaccurate exposure estimates and associated risks for some contaminated sites because the amount of a chemical absorbed (the chemical’s bioavailability) from contaminated soil can be a fraction of the total amount present. Properly accounting for soil-chemical interactions on the bioavailability of chemicals from soil can lead to more accurate estimates of exposures to soil contaminants and improve risk assessments by decreasing uncertainty.
The basis for this training course is the ITRC guidance: Bioavailability of Contaminants in Soil: Considerations for Human Health Risk Assessment (BCS-1). This guidance describes the general concepts of the bioavailability of contaminants in soil, reviews the state of the science, and discusses how to incorporate bioavailability into the human health risk assessment process. This guidance addresses lead, arsenic, and polycyclic aromatic hydrocarbons (PAHs) because evaluating bioavailability is better understood for these chemicals than for others, particularly for the incidental ingestion of soil.
The target audience for this guidance and training course are:
- Project managers interested in decreasing uncertainty in the risk assessment which may lead to reduced remedial action costs.
- Risk assessors new to bioavailability or those who want additional confidence and training in the current methods and common practices for using bioavailability assessment to more accurately determine human health risk at a contaminated site.
- Value the ITRC document as a “go-to” resource for soil bioavailability
- Apply the decision process to determine when a site-specific bioavailability assessment may be appropriate
- Use the ITRC Review Checklist to develop or review a risk assessment that includes soil bioavailability
- Consider factors that affect arsenic, lead and PAH bioavailability
- Select appropriate methods to evaluate soil bioavailability
- Use tools to develop site-specific soil bioavailability estimates and incorporate them into human health risk assessment