Bioavailability & Risk Assessment of Complex Mixtures

EPA Grant Number: R825408
Title: Bioavailability & Risk Assessment of Complex Mixtures
Investigators: Donnelly, Kirby C. , Autenrieth, R. L. , McDonald, T. J. , Reeves, William , Safe, Stephen H.
Current Investigators: Donnelly, Kirby C. , Autenrieth, R. L. , Huebner, Henry J. , McDonald, T. J. , Reeves, William , Safe, Stephen H.
Institution: Texas A & M University
EPA Project Officer: Chung, Serena
Project Period: November 15, 1996 through November 14, 1999 (Extended to April 15, 2000)
Project Amount: $443,997
RFA: Environmental Fate and Treatment of Toxics and Hazardous Wastes (1996) RFA Text |  Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management , Safer Chemicals


There is an urgent need to develop an accurate method to assess the risk associated with contaminated soils and complex mixtures. Perhaps more importantly, this method should provide a means of defining acceptable residue levels to allow a more cost-effective approach to site remediation. Contaminated media at Superfund sites typically consist of complex mixtures of organic and inorganic chemicals. Especially difficult to characterize are the complex mixtures of polycyclic aromatic hydrocarbons (PAHs) and halogenated aromatic hydrocarbons (HAHs) which are often found at wood preserving, coal gasification, and refinery sites. This research program proposes to develop a methodology for estimating bioavailability, to utilize this procedure to assess the risk of complex mixtures, and to validate the method using treated and untreated residues from a variety of Superfund sites. A protocol for obtaining a water soluble fraction (WSF) will be evaluated using water (pH7 and pH9), a simulated gastric fluid (pH2), and a solution of methanol:water (1:1). The WSF protocol will be evaluated using an aged soil contaminated with two complex mixtures (a coal tar and a wood preserving waste). Spiked and unspiked soils will be prepared and extracted using the various solutions at several time points during the research. These mixtures will also be used to validate the Toxic Equivalency Factor (TEF) approach to risk assessment. Complex mixture risk assessment will be developed using a "top-down" and "bottom-up" approach for integration. Each mixture will first be tested in its original state, and then extracted with hexane:acetone (producing a crude extract). The crude extract will then be separated into PAH and HAH fractions. The PAH fraction will be separated into 2-, 3-, 4, 5 and >5-ring fractions, while the HAHs will be separated into chlorophenol and chlorinated dibenzo-p-dioxin and dibenzofuran fractions. Each fraction will be analyzed using bioassays to measure genotoxicity and enzyme induction. For the top-down analysis, biological tests (to define genotoxicity and potential immunotoxicity) will be used to characterize the crude extract and all subsequent fractions. For the bottom-up analysis, selected fractions will be subjected to a GC/MS analysis to identify major constituents, and individual compounds as well as reconstituted mixtures tested in the biological tests. Testing the crude extract and various fractions will delineate interactions of the components. Testing the individual and reconstituted mixtures will be used to validate a TEF approach for risk assessment and to aid in the identification of the more toxic components of the complex mixtures. In the final two years of the study, the WSF procedure will be calibrated using soil:waste mixtures collected from a minimum of four Superfund sites prior to and after remediation. The data from these analyses will be used to prepare a human health risk assessment for each site. The final product of the research will be a better methodology for assessing the risk of complex mixtures in contaminated soils and other solid matrices in the vadose zone.

Publications and Presentations:

Publications have been submitted on this project: View all 8 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 4 journal articles for this project

Supplemental Keywords:

RFA, Health, Scientific Discipline, Toxics, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Bioavailability, Contaminated Sediments, Remediation, Geochemistry, Environmental Chemistry, Health Risk Assessment, pesticides, Chemistry, Risk Assessments, chemical mixtures, Fate & Transport, complex mixtures, risk assessment, fate and transport, cumulative risk, fate, coal gasification sites, Superfund sites, effects assessment, risk assessment techniques, contaminant transport, soil sediment, acceptable residue levels, contaminated sediment, complex mitures, sediment transport, transport contaminants, geotoxicity, PAH metal mixtures, adverse human health affects, chemical contaminants, soils, contaminated soil, PAH, human exposure, toxicity, characterizing chemical mixtures, environmental transport and fate, public health, furans, environmental toxicant, Toxic Equivalency Factor, hazardous materials exposure, assessment methods, refinery sites, vadose zone, hazardous waste sites, dioxins, exposure assessment, environmental chemicals, toxicokinetics

Progress and Final Reports:

  • 1997 Progress Report
  • 1998 Progress Report
  • 1999 Progress Report
  • Final Report