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

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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
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7.6 Using Bioavailability Methods to Evaluate Remedies (Bioavailability-Based Remediation)

Excavating and replacing contaminated soil is expensive and may be ecologically destructive. Therefore, an alternative remedial option that can be considered for sites is an in situ soil amendment that reduces contaminant bioavailability. This bioavailability-based remediation does not remove the soil contaminant, but instead reduces its bioavailability and potential exposure and risk. Extensive research has shown a variety of soil amendments can successfully reduce lead bioavailability (Chaney and Mahoney 2014; Scheckel et al. 2013; Hettiarachchi and Pierzynski 2004). However, phosphate-based treatments that reduce lead bioaccessibility increase arsenic bioaccessibility (Henry et al. 2015; Scheckel et al. 2013).

Compared to the available literature on lead, studies on the use of soil amendments to reduce arsenic bioavailability or bioaccessibility are limited. Although iron absorption of As(V) from water is well known, limited research is available on the on the ability of iron and other soil amendments to reduce bioavailable or bioaccessible arsenic in soil, especially over time. In the research available, Ferric chloride plus lime treatment of arsenic-contaminated soil reduces IVBA As 30 to 41% (Cutler et al. 2014). Using iron sulfate to treat soils contaminated with arsenical pesticides reduces arsenic bioaccessibility as much as 81% (Redwine et al. 2010). The measured reduction in arsenic bioaccessibility ranged from 20% to 81%, depending on the bioaccessibility method. Soil treatment with iron salts is inexpensive and shows potential for in situ remediation of arsenic contaminated soil (Redwine et al. 2010). Strong specific adsorption onto Fe oxides is the mechanism for the decreased bioaccessibility (Beak et al. 2006a).

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