Grantee Research Project Results

1997 Progress Report: Bioavailability & Risk Assessment of Complex Mixtures

EPA Grant Number: R825408
Title: Bioavailability & Risk Assessment of Complex Mixtures
Investigators: Donnelly, Kirby C.
Current Investigators: Donnelly, Kirby C. , Safe, Stephen H. , Autenrieth, R. L. , McDonald, T. J. , Reeves, William , Huebner, Henry J.
Institution: Texas A & M University
EPA Project Officer: Hahn, Intaek
Project Period: November 15, 1996 through November 14, 1999 (Extended to April 15, 2000)
Project Period Covered by this Report: November 15, 1996 through November 14, 1997
Project Amount: $443,997
RFA: Environmental Fate and Treatment of Toxics and Hazardous Wastes (1996) RFA Text |  Recipients Lists
Research Category: Hazardous Waste/Remediation , Safer Chemicals , Land and Waste Management

Objective:

The proposed research is designed to develop an accurate methodology for estimating risk and bioaccessability of complex mixtures at uncontrolled hazardous waste sites. The research has three major objectives: (1) to develop a protocol for preparation of a water soluble fraction (WSF) as a method for estimating residual contaminant concentrations that are protective of human health and the environment; (2) to develop a quantitative toxicokinetic model using genotoxicity and enzyme induction assays to interpret the interactions of complex mixtures of PAHs and HAHs; and, (3) to validate the WSF protocol by analysis and risk assessment of soils from four Superfund sites before and after site remediation.

Progress Summary:

Initial extraction and analysis of a wood-preserving (WPW) and coal tar (CTW) waste have been completed. The initial data have been used to characterize the major components of each waste, although analytical difficulties prevented complete quantification of alkyl-PAHs and many of the high molecular weight PAHs. Fractionation and isolation studies are underway to aid in the characterization of these compounds. A Weswood silt loam soil has been spiked with model compounds (phenanthrene, chrysene, anthracene and pyrene) and/or a complex mixture (WPW or CTW) for use in the bioavailability studies. Spiked and aged soils will be used to evaluate a kinetics based model for bioaccessability which examines the time-dependent desorption of both model PAHs and components of the complex mixtures. The kinetics experiments will serve to identify the labile and refractory components of the spiked chemicals. Using this data, we will then compare several different extraction methods with respect to their abilities to liberate the labile and refractory portions. Extraction solutions to be evaluated include a simulated stomach solution (pH 2), a simulated intestinal solution, both of the former in series, distilled water, phosphate buffered water at pH 7, and a 1:1 methanol:water solution. For the kinetics experiments, desorption is monitored using Tenax polymer beads. Briefly, the Tenax beads are placed along with 1g of spiked soil and 20ml of distilled water into a 50ml glass vial and shaken at 200 rpm for 9 days. The beads are removed and replaced at 0.5hr, 1hr, 3hr, 5hr, 1 day, 3 days, 5 days, 7 days, and 9 days. Previously these beads have been shown to provide the equivalent of an infinite dilution by other researchers studying desorption. In terms of bioaccessability, this study will act as a method of comparison for various methods to solubilize portions of labile and refractory contaminants. Simple desorption data from shake-flask experiments may elucidate the most stringent extraction methods but they shed no light on whether the contaminants in solution are part of the loosely bound or a more resistant fraction.

A new method for fractionation of PAH is being evaluated. As an initial step, fractions were isolated based on functional groups from crude coal tar using an alumina column (appendix 4). Fractions one and two contained nearly all of the PAH from the coal tar and will be used for further fractionation using an aminosilane column. Preliminary studies indicate that this column will provide more complete separation of chemicals by ring number. This segment of the study will begin at the analytical scale and progress towards an eventual increase to a preparative size.

Accomplishments and Research Results:

Initial studies with soil spiked with benzo(a)pyrene, pentachlorophenol and trinitrotoluene (TNT) found that TNT recovery in a methanol:water fraction was reduced within 21 days of spiking the soil; while there was no significant difference in the concentration of PAH that was recovered. For TNT, 31% of the spike was recovered with pH 7 water on day 0 and 61% recovered with a 1:1 methanol:water solution; whereas on day 21 only 17% of the spike was recovered using pH 7 water and 28% was recovered with the methanol:water solution.

Using an alumina column, five fractions were isolated from a coal tar sample. Fraction 1 contained the majority of the naphthalenes through phenanthrenes (2 and 3 ring compounds), while fraction 2 contained most of the methyl pyrenes through benzo(a)pyrenes (4 and 5-ring compounds). The concentration of C1-naphthalene in fraction 1 was 28 g/g, while fraction 2 contained 0.10 g/g; and, the benzo(a)pyrene concentration of fraction 1 was 0.002 g/g and the concentration in fraction 2 was 4.88 g/g.

Future Activities:

A series of soils have been spiked with model chemicals and complex mixtures. Data will be obtained from these aged soils throughout the next 18 months. A preparatory scale column will be used with an HPLC-PDA detector to further isolate components of a CTW and WPW mixture. These isolates will be tested in a battery of biological tests including enzyme induction assays and microbial genotoxicity assays. During the next year, existing sites will be identified where soil can be collected before and after remediation to evaluate the utility of the bioaccessability method. Selected soils will also be used in an animal feeding study to measure uptake and elimination.

Journal Articles:

No journal articles submitted with this report: View all 8 publications for this project

Supplemental Keywords:

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

Progress and Final Reports:

Original Abstract

1998 Progress Report

1999 Progress Report

Final Report