Skip common site navigation and headers
United States Environmental Protection Agency
Exposure Research
Begin Hierarchical Links EPA Home > Research & Development > Exposure Research > Publications/Presentations > End Hierarchical Links

 

Bioavailability of Metals in Contaminated Soil and Dust

spacer
spacer
Abstract: Due to widespread metal contamination, it is necessary to characterize soils suspected of metal contamination and determine if the metal levels in these soils pose a hazard. Metal toxicity is often not directly related to the total concentration of metals present due to a number of modifying factors that depend, in part, on soil physicochemical properties. Soil organic matter, pH, and clay content are a few of the soil physicochemical properties that influence metal toxicity and bioavailability. Current routine practices of investigating the nature and extent of contamination at metal-contaminated sites involve determining total metal content in media, such as soil and dust. Approximately 60-80% of household dust is tracked-in soil. The quantity of toxic element to be used as exposure concentrations in the risk calculation is an assumed percentage of the total content, which may be the bioavailable concentration. Often, very high percentages (near 100%) of total metals are assumed bioavailable. While this assumption is conservative in terms of being protective of human health and the environment, it may not be a reasonable estimate of site conditions because the actual bioavailability of metals has not been assessed. The resulting risk calculations may overestimate the true risk of exposure to site media. Use of the bioavailability approach in conjunction with the total concentration analysis will reduce uncertainty in the risk assessment, thus avoiding unnecessary risk-reduction expenses.

The data from research showing the effect of soil properties on the bioavailability and toxicity of metals in 21 contaminated soils with a wide range of physicochemical properties (pH, % organic carbon, % clay, and amorphous iron and aluminum oxides) will be presented. The combined relationship between biological endpoints (lettuce and earthworms) and soil properties were examined using multiple regression and structural equation modeling (path analysis). Structural equation models proved useful for providing a quantitative causal influence of soil properties on metal bioavailability and toxicity.

In addition, an overview of on-going research projects within the National Exposure Research Laboratory (NERL), Human Exposure and Atmospheric Sciences Division (HEASD) will be presented. These projects include investigating the bioavailability of arsenic from select soil samples contaminated with chromated copper arsenate (CCA) in a controlled field study as well as a sub-set of soils and house dusts collected in the U.S. Department of Housing and Urban Development's (HUD) nationwide "American Healthy Homes Survey". Both projects will produce data under varying environmental conditions to help establish relationships between total concentrations and bioavailable concentrations to yield a better understanding of the absorbed dose of toxic elements.

Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.
spacer
Citation:Bradham, K., S. L. Harper, and E. A. Coppedge. Bioavailability of Metals in Contaminated Soil and Dust. Presented at 19th Annual Regional Risk Assessors Meeting, Boston, MA, May 3-7, 2004.
spacer
spacer
Contact: Liz Hope - (919) 541-2785 or hope.elizabeth@epa.gov
spacer
Division: Human Exposure & Atmospheric Sciences Division
spacer
Branch: Methods Development & Application Branch
spacer
Product Type: Abstrct/Oral
spacer
Presented: 05/05/2004
spacer
Related Entries:
spacer
Bullet Item Toxic Elements: Development/Improvement of Traditional and Bioavailability Methods to Characterize Human and Ecological Exposure
spacer Relationship Reason:   A Project of the Product
spacer
spacer
spacer

 

ORD Home | Search EPA | Search NERL | Search EIMS | Contacts | Help

 
Begin Site Footer

EPA Home | Privacy and Security Notice | Contact Us

Last Updated on Monday, October 22, 2007
URL: http://cfpub.epa.gov