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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
Appendix C: Site-Specific PAH Methodology, Foster AFB
Acronyms
Glossary
Acknowledgments
Team Contacts
Document Feedback

 

Bioavailability of Contaminants in Soil
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11 Case Studies

The case studies describe how bioavailability values have been used in decision making at specific sites. Examples include results for lead, arsenic, and PAHs in soil. These case studies illustrate the type of work that might be undertaken in site-specific bioavailability assessment or in support of a new program on bioavailability. The studies outline the site-specific analyses that were conducted to support alternative (not default) inputs for bioavailability in the human health evaluation or remedy selection for the site. In some instances, the analyses were relatively straightforward and based on in vitro extraction data for soils from the site. In other instances, the effort entailed new research or the development of new research methods.

ITRC continues to collect case studies that illustrate the use of technologies for which it publishes guidance; contact team leaders to share a case study.

The case studies presented are summarized in Table 11-1.

Table 11‑1. BCS Case Studies

Case study Contaminants Soil Type Source Type State
Empire Mine State Historic Park, CA Arsenic High Iron Mining California
Road 1815, Cattle Dip Vat Site, Ozark National Forest, AR Arsenic Sandy loam with gravel and cobbles Pesticide, pre-1950 Arkansas
Hill Air Force Base, UT Arsenic Red-stained surface soil at former groundwater seeps on a hillside Naturally occurring arsenic mobilized by reduced groundwater conditions and historical wastes Utah
Resolution Copper West Plant Site, AZ Arsenic Not available Smelter Arizona
Red Rock Road, Douglas County, OR Arsenic Well-graded gravel with some fines. High in Iron oxides Mining of mercury ore Oregon
Confidential Site, Midwest, U.S. Lead Not available Industrial Midwest, U.S.
Former Foster Air Force Base, Victoria, TX PAH Clay, silt, sand with localized gravel and caliche Skeet target fragments Texas
Bingham-Magna Ditch, Salt Lake Valley, UT Arsenic Arsenic occurs predominantly in association with iron oxyhydroxides Tailings water from copper precipitation plants, copper ore Utah
Over the Horizon Backscatter (OTHB) Receiver site, CA Arsenic Red soils, high in iron oxides CCA wood preservative California
Former MGP site, MI Arsenic Fill, fine to medium grained sand MGP coal ash Michigan
Barker, Hughesville Mining District, MT Lead Not available Mining Montana
Silver Bow Creek/Butte Area Superfund Site, Butte, MT Lead Alluvial deposits, sandy clay to sand and gravel Mining Montana
Midvale Slag NPL Site, Midvale UT Lead Soil and slag Former smelter Utah

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