Superfund Research Program

Lead Exposure and Accumulation in Bone in Adolescents

Project Leader: P. Barry Ryan (Emory University School of Public Health)
Grant Number: P42ES005947
Funding Period: 1995 - 2000

Project-Specific Links

Final Progress Reports

Year:   1999 

This project has focused on the determination of the bioaccessibility of organic species in model solids and soils. Researchers have completed comparison work on the extraction efficiencies of Soxhlet extractions, microwave-assisted extractions, and water-based microwave extractions. Results suggest that microwave-assisted techniques work as efficiently as Soxhlet extractions in determining total pesticide concentrations in soil, and that both techniques are superior to water-based microwave extractions in recovering spiked model solids and soil samples. A manuscript on this work is currently in preparation. In addition to this completed data collection effort, project investigators are finalizing data collection on two related avenues of investigation. The first of these is a comparison of various extraction procedures in model solids with respect to a physiologically based extraction technique designed to mimic the human digestion system. Results suggest that the water-based microwave extraction discussed above most closely resembles the extraction efficiency of the physiologically based system suggesting that bioaccessibility is best represented by analytical techniques that extract only a small percentage of organic contaminants from soil. Finally, in a related study, the “aging” phenomenon of these materials in model solids and soils has been investigated. This effort is designed to assess the changes in bioaccessibility of these materials associated with long-term contact with soil.

Additionally, the researchers are performing arsenic speciation work. The first matrix being completed is food. Using 71 duplicate diet samples collected in another investigation, total arsenic has been determined by ICP-MS, and inorganic arsenic using a wet chemical analytical work-up followed by GF-AAS analysis. A second determination of total arsenic used GF-AAS. Results suggest significant variability in inorganic arsenic as a fraction of total arsenic with concomitant implications for arsenic toxicity in food.