• Skip to main content
itrc_logo

Bioavailability of Contaminants in Soil: Considerations for Human Health Risk Assessment

Navigating this Website
1 Introduction
1 Introduction Overview
1.1 Using Bioavailability Information
1.2 Background
1.3 Definition of Terms
2 Regulatory Background
2 Regulatory Background Overview
2.1 Current Practices: Survey of State Regulators
3 Technical Background
3 Technical Background Overview
3.1 Soil Mineral Phases
3.2 Soil pH, Organic Matter, and Reactive Clay Minerals
3.3 Soil Particle Size
4 Decision Process
4 Decision Process Overview
4.1 Decision Process Flowchart
4.2 Is there a Method Available?
4.3 Could Bioavailability Assessment Affect the Remedial Decisions?
4.4 Do the Benefits of Bioavailability Assessment Justify the Costs?
4.5 Further Considerations
5 Methodology
5 Methodology for Evaluating Contaminant Oral Bioavailability Overview
5.1 In Vivo Approach
5.2 In Vitro Approach
6 Lead
6 Lead Overview
6.1 Fate and Transport
6.2 Toxicology and Exposure
6.3 Methodology for Quantifying RBA of Lead in Soil
6.4 When Does a Bioavailability Study Make Sense?
6.5 Case Studies
6.6 Using Bioavailability Methods to Evaluate Remedies (Bioavailability-Based Remediation)
7 Arsenic
7 Arsenic Overview
7.1 Fate and Transport
7.2 Toxicology and Exposure
7.3 Methodology for Evaluating Arsenic Bioavailability
7.4 When Does It Make Sense to Use Bioavailability?
7.5 Case Studies
7.6 Using Bioavailability Methods to Evaluate Remedies (Bioavailability Based Remediation)
8 PAHs
8 Polycyclic Aromatic Hydrocarbons (PAHs) Overview
8.1 PAH Sources and Exposure
8.2 General Toxicity of PAHs
8.3 Influences of Soil on Bioavailability of PAH
8.4 Methodology for Evaluating PAH Bioavailability
8.5 Dermal Absorption
8.6 Amendment Strategies and Permanence of Bioavailability
8.7 Case Study
9 Risk Assessment
9 Using Bioavailability Information in Risk Assessment Overview
9.1 Risk Calculations
9.2 Other Considerations and Limitations
10 Stakeholder Perspectives
10 Stakeholder Perspectives Overview
10.1 Stakeholder Concerns
10.2 Specific Tribal Stakeholder Concerns
10.3 Stakeholder Engagement
11 Case Studies
11 Case Studies Overview
11.1 Arsenic, Mining, CA
11.2 Arsenic, Pesticide, AR
11.3 Arsenic, Naturally occurring, UT
11.4 Arsenic, Smelter, AZ
11.5 Arsenic-contaminated tailings, OR
11.6 Lead, Industrial, Midwest US
11.7 PAH, Skeet targets, TX
11.8 Arsenic, Copper precipitation, UT
11.9 Arsenic, CCA wood preservative, CA
11.10 Arsenic, MGP coal ash, MI
11.11 Lead, Mining MT
11.12 Lead, Mining, MT
11.13 Lead, Smelter, UT
Additional Information
Review Checklist
Appendix A: Detailed Survey Responses
Appendix B: Chemical Reactions of Metals
Acronyms
Glossary
Acknowledgments
Team Contacts
Document Feedback

 

Bioavailability of Contaminants in Soil
HOME

1 Introduction

Contaminants in soil may not be as available as the forms used in the toxicity tests used to develop risk-based criteria (such as the Reference Dose or Cancer Slope Factor). However, cleanup goals are often calculated assuming that the uptake of contaminants from soil is the same as when the chemicals are dosed in water or feed. 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 relatively small fraction of the total amount present. Properly accounting for the impacts of 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.

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. This guidance will help regulators, practitioners, and stakeholders with the following tasks:

  • Understand the tools available to develop site-specific bioavailability values in human health risk assessment, including the pros and cons of different in vivo methods and in vitro methods.
  • Identify methods most appropriate for site conditions without compromising human health protection.
  • Apply these tools and methods in different scenarios.

Techniques for evaluating the bioavailability of lead, arsenic, and PAHs in soil are better developed than for other chemicals. While the risk assessment section discusses other contaminants, the information currently available is not sufficient to develop detailed guidance for those contaminants. The information presented in this guidance may be useful, however, when considering and planning site-specific studies for other contaminants.

This guidance includes information about the dermal exposure pathway for PAHs. Dermal PAH exposure from soil can be significant under standard default exposure calculations. While the bioavailability of chemicals from other media, to other receptors, or by other exposure pathways may be important considerations in the risk assessment process, those considerations are not addressed here.

image_pdfPrint this page/section



BCS

web document
glossaryBCS Glossary
referencesBCS References
acronymsBCS Acronyms
ITRC
Contact Us
About ITRC
Visit ITRC
social media iconsClick here to visit ITRC on FacebookClick here to visit ITRC on TwitterClick here to visit ITRC on LinkedInITRC on Social Media
about_itrc
Permission is granted to refer to or quote from this publication with the customary acknowledgment of the source (see suggested citation and disclaimer). This web site is owned by ITRC • 1250 H Street, NW • Suite 850 • Washington, DC 20005 • (202) 266-4933 • Email: [email protected] • Terms of Service, Privacy Policy, and Usage Policy ITRC is sponsored by the Environmental Council of the States.