The U.S. Environmental Protection Agency estimates that approximately 10 percent (over a billion cubic yards) of the sediment underlying our nation's surface water is sufficiently contaminated with pollutants to pose potential risks to fish and to humans and wildlife that eat fish. Based on current average costs for managing contaminated sediments, this volume of material could cost several trillion dollars to dredge. Methods to assess the potential effect of sediment contamination on human or ecological health are historically based on total contaminant concentrations in the bulk sediment. However, research conducted over the past fifteen years has shown that the bioavailability of many of these contaminants to receptors is much less than the total amount of contaminant in the sediment. "Bioavailability processes," as defined by the National Research Council, are the "individual physical, chemical, and biological interactions that determine the exposure of plants and animals to chemicals associated with soils and sediments." Only the bioavailable fraction of an environmental contaminant may be taken up and subsequently result in an effect on an organism. Incorporating bioavailability considerations in the calculation of risk can optimize the extent of cleanup required to be protective, improve site decision-making, and can be an important factor in balancing the risks caused by remedial action with the risks addressed by remedial action.
ITRC's web-based Technical and Regulatory Guidance, Incorporating Bioavailability Considerations into the Evaluation of Contaminated Sediment Sites (CS-1, 2011) and associated Internet-based training are intended to assist state regulators and practitioners with understanding and incorporating fundamental concepts of bioavailability in contaminated sediment management practices. This guidance and training describe how bioavailability considerations can be used to evaluate exposure at contaminated sediment sites, the mechanisms affecting contaminant bioavailability, available tools used to assess bioavailability, the proper application of those tools, and how bioavailability information can be incorporated into risk-management decisions. This guidance and training also contain summaries of case studies where bioavailability has been assessed and considered in the contaminated sediment remedial decision making process. This guidance and training provide insight on how bioavailability assessments can be used to understand, mitigate, and manage risk at a contaminated sediment site, often at a reduced overall project cost.
The intended users of this guidance and training participants are individuals who have a working knowledge of contaminated sediment management but seek additional information about bioavailability. Prior to the training class, participants are encouraged to review the following documents: