MSU Superfund Projects and Cores:

Project 1: Characterization of the Pathways Linking Ah Receptor Activation with Altered B Cell Differentiation Using an Integrated Experimental and Computational Modeling Approach

Project 2: Dissecting the Signaling Network for Ah Receptor-mediated Bcell Toxicity

Project 3: Non-Additive Ah Receptor Ligand Interactions

Project 4: Influence of Ah Receptor Ligands on Inflammatory Responses: Consequences for Tissue Injury and Gene Expression

Project 5: A Proteomic Analysis of the AHR signaling Network

Project 6: Molecular Insight into Polyaromatic Toxicant Degradation by Microbial Communities

Project 7: Geochemical Controls on the Adsorption, Bioavailability, and Long-term Environmental Fate of Dioxins, PCBs, and PAHs

Core A: Administration

Core B: Research Translation

Core C: Computational Modeling of Mammalian Biomolecular Response

Core D: Biomedical Informatics

Core E: Environmental Molecular Analysis

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Link to the NIEHS SBRP site

Superfund Project 7

Geochemical Controls on the Adsorption, Bioavailability,
and Long-term Environmental Fate of Dioxins, PCBs, and PAHs

This project's objectives are to characterize poorly understood mechanistic processes that control sorption of Ah-receptor ligands (AhRLs) to mineral surfaces, and then use these well-defined systems to probe the bioavailability of sorbed AhRLs to bacteria and mammals. Since AhRLs tend to have exceptionally low water solubilities, these highly toxic compounds exist in the environment predominantly as sorbed species. We argue that clay minerals are a major, largely unrecognized sink for AhRLs in the environment. Our preliminary studies and the literature suggest that clays may play a nearly equal or even dominant role to that of organic matter in the immobilization of dioxins in soils. 

The figure below illustrates that compounds with strong affinities for the Ah-receptor include 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD, left), 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF, center), and 3,3’,4,4’,5-pentachloro-biphenyl (PCB 126, right). We propose to study sorption of these compounds, among others, to minerals.

Our research has four specific aims:

1. To measure sorption and sequestration of key AhRLs to clay minerals and to characterize the geochemical controls on that sorption,
2. To determine the molecular mechanisms of such sorption through integrating bulk results with spectroscopy and molecular simulation studies, thereby promoting more rational long-term Superfund site stewardship,
3. To identify microbial genetic and functional responses to minerals themselves and to mineral-adsorbed AhRLs in order to elucidate key mechanisms of microbial interaction with these adsorbed compounds, and
4. To quantify the microbial functionality enabling bioavailability and biodegradation of mineral-sorbed AhRLs by using fluorescent markers that are expressed with key microbial responses. 

Thus our proposal supports the mission of the Superfund Basic Research and Training Program because in Objective 1 we will work to “identify and quantify chemical forms of the contaminants,” in Objectives 1-2 we will assess “the physical, chemical and biological processes affecting chemicals in environmental media,” and in Objectives 3-4 we will link this work directly to bioavailability of Superfund chemicals to bacteria (in conjunction with parallel Project 6) and to mammals (in Projects 1, 4, and 5).

Relevance of this research to public health: Many toxic organic contaminants are so insoluble in water that the main route of human exposure is through ingestion of adsorbed contaminants. We propose to characterize adsorption of dioxins and related compounds to clay minerals, and then use both bulk and molecular methods to understand the effects of adsorption on the toxicity of the compound (to mice) and the biodegradation of the compound (by soil bacteria), which is needed in remediation and risk assessment.

Stephen A. Boyd, Ph.D.
Project Leader
Michigan State University

Cliff T. Johnston, Ph.D.
Co-Investigator
Purdue University

Hui Li, Ph.D.
Co-Investigator
Michigan State University

Thomas J. Pinnavaia, Ph.D.
Co-Investigator
Michigan State University

Brian J. Teppen, Ph.D.
Co-Investigator
Michigan State University