Management of polychlorinated biphenyl (PCB)-contaminated sediments is a difficult challenge that has been evolving for decades. In this report, the National Research Council’s Committee on the Remediation of PCB-Contaminated Sediments reviews the nature of the challenge; provides an overview of current knowledge about the inputs, fates, and effects of PCBs; recommends a risk-based framework for assessing remediation technologies and risk-management strategies; elaborates on this framework as it applies to PCB-contaminated sediments specifically; and provides recommendations for research that should enhance the nation’s ability to manage PCB-contaminated sediments effectively.
This chapter briefly reviews why PCBs in sediments are of environmental concern, states the tasks addressed by the committee, sets forth the committee’s activities and deliberative process in developing the report, and explains the organization of the report.
OVERVIEW OF PCBs IN SEDIMENTS
PCBs are a contaminant of the nation’s waterways as a result of both deliberate and inadvertent releases to the environment, primarily during the 1950s and 1960s when their production and use were greatest. Although PCBs are distributed globally to waters, soils, and sediments by a combination of
atmospheric and aquatic transport processes, they are found typically in the greatest concentrations in marine and freshwater sediments near the sources of their environmental release. Most PCBs do not degrade easily in the environment and may persist for years in sediments. Furthermore, PCBs are bioaccumulated by aquatic and terrestrial organisms and thus can enter the food web. Humans and wildlife that consume contaminated organisms, such as fish, can accumulate PCBs in their tissues. Such accumulations are of concern, because they may lead to body burdens of PCBs that could have adverse health effects in humans and wildlife. PCBs can affect not only individual organisms but ultimately whole ecosystems.
The presence of PCBs in sediments might trigger several regulatory actions, such as designation of part of a water body as a hazardous waste site, possible inclusion on the U.S. Environmental Protection Agency’s (EPA’s) National Priorities List (NPL), issuance of a fish consumption advisory for some or all fish species in a water body, and restrictions on permits for navigational dredging of the sediments, among others. Of the 1,230 sites on the NPL, 535 contain PCBs, of which 122 sites have contaminated sediments. As of 1998, there were 679 fish consumption advisories for PCBs in the United States (J.Bigler, EPA, personal commun., October 12, 2000). Many NPL sites are quite large and have “hot spots” where PCB concentrations are considerably higher than those in other parts of the site. Such sites include the upper Hudson River, Commencement Bay in Washington, and New Bedford Harbor in Massachusetts.
Legitimate concerns over the potential health, environmental, economic, and social impacts of the various strategies for managing PCB-contaminated sediments have led to extensive debate among industry, regulators, communities, and other interested or affected parties on the best course of action for dealing with these sediments. The debate often focuses on certain questions: What are the immediate and the long-term (decades) human health and ecological risks associated with PCB concentrations found in various parts of a specific ecosystem? If PCB concentrations must be reduced, how much reduction is needed, and what is the best approach to achieve the reduction? What are the immediate and the long-term human health and ecological risks associated with the various processes to reduce PCB concentrations both locally and for a wider geographic area? What are the economic and social costs of various options?
THE COMMITTEE’S TASK
The challenges of managing PCB-contaminated sediments have drawn the attention of the U.S. Congress. In 1998, the U.S. House of Representatives
Report 105–107 to accompany H.R. 2158, Department of Veterans Affairs and Housing and Urban Development, and Independent Agencies Appropriations Bill, 1998, called for the EPA to enter into an agreement with the National Academy of Sciences to conduct a study that evaluates the risks, availability, effectiveness, costs, and effects of technologies for the management of sediments contaminated with PCBs, including dredging and disposal.
In response to this request, the National Research Council (NRC) convened the Committee on Remediation of PCB-Contaminated Sediments. The committee was given the following charge:
This NRC study will provide a scientific risk-based framework for evaluating different approaches for remediating PCB-contaminated, submerged sediments in terms of the efficacy and human and ecological risks associated with each approach. In developing a scientific framework, the committee will evaluate data from specific sites with PCB contamination such as the Hudson River, New Bedford Harbor, etc. Remediation approaches to be assessed and compared include natural recovery, source control, dredging, capping, and contaminated-sediment disposal.
This report responds to the EPA request and to the scientific and technical issues associated with the congressional concerns.
To accomplish its charge, the committee undertook the following tasks:
Select, refine, and apply a risk-based framework for assessing the remediation alternatives for exposure of humans and other biota to PCBs in contaminated sediments.
Evaluate the likelihood that the specified remediation technologies will achieve their remedial objectives, considering different site-specific conditions, and water and sediment dynamics.
For a few selected sites and using the framework, estimate human and ecological risks associated with each of the specified remediation approaches for contaminated sediments containing PCBs in light of the availability, costs, and effectiveness of the various approaches.
Where applicable, recommend areas for future research.
The committee determined that differences in environmental dynamics and toxicity of various PCB congeners were to be taken into consideration with respect to the above tasks. In addition, the committee considered PCBs in combination with other contaminants that might be present in sediment.
THE COMMITTEE’S APPROACH
To accomplish its task, the committee convened a series of seven meetings between June 1999 and December 2000. At the initial meeting, the committee decided to visit several PCB-contaminated sites to hear the perspectives and experiences of federal, state, and local government officials; industry representatives; environmental and community groups; and local citizens and to view first-hand the terrain and waterways in areas affected by PCB-contaminated sediments.
At three of the six committee meetings (Washington, DC; Green Bay, Wisconsin; and Albany, New York), public sessions were held where committee members heard from regulators, industry groups, environmental organizations, local citizens, researchers, and legislators, about the risks posed by the sediments and possible management options. At two of the meetings (Green Bay and Albany), committee members toured nearby PCB-contaminated sites, i.e., the Fox River and Hudson River, respectively. (Appendix B contains a list of speakers at the public meetings.)
At the public sessions, the committee devoted substantial time to listening to a variety of interested organizations and individuals. The committee emphasized, however, that its purpose in visiting the contaminated sites was not to solve or recommend any solutions for any specific site, but to obtain information that would be valuable for addressing the management of PCB-contaminated sites nationwide. The committee also reviewed written materials submitted by EPA; state and local government agencies; affected industries, such as the Fox River Group and General Electric Corporation; environmental groups, such as the Scenic Hudson and Sierra Club; numerous business and community groups; American Indian organizations; and many concerned and knowledgeable individuals. A complete list of written materials provided to the committee is given in Appendix C.
On the basis of the information provided to the committee and its own expertise, the committee determined that, although there are many concerns that are applicable to PCBs in general, management strategies to address the risks posed by PCB-contaminated sediments and any selection of management options must be developed on a site-by-site basis. The committee also found that a framework for assessing risks associated with the remediation technologies and developing a risk-management strategy was imperative. Such a framework should be flexible, inclusive of all affected parties, comprehensive, transparent, and applicable to a variety of sites and situations. It should provide a consistent approach that would be of use to all parties in the risk-management process. The committee adopted and refined the framework set forth by the Presidential/Congressional Commission on Risk Assessment and
Risk Management (PCCRARM 1997) for application to water bodies with PCB-contaminated sediments.
After considerable deliberation, the committee concludes that it is impossible to state unequivocally whether dredging, capping, monitored natural attenuation, or any particular risk-management option is applicable in general to PCB-contaminated sediment sites. Because each PCB-contaminated site is unique, the selection of management options and a risk-management strategy must be based on site-specific factors and risks. Therefore, the committee finds that it is inappropriate to make generalizations about the effectiveness of an option for a particular site without detailed knowledge of that site.
The committee is aware that many readers expect this report to recommend risk-management options that are most suitable for reducing the risks associated with PCB-contaminated sediments or that would be most applicable to specific sites. However, the committee strongly believes that making such recommendations is not appropriate, because selection of management options must be based on numerous site-specific factors that require evaluation by all affected parties, including local communities and federal and state regulatory agencies. In the committee’s view, the adequacy of the site-specific decisions depends upon the extent to which they are consistent with the risk-management process that the committee recommends.
Chapter 2 provides a brief review of the nature of PCBs, their inputs, fates, and effects in the environment, striking a balance between providing an exhaustive literature review and highlighting significant aspects of the environmental chemistry and ecological and human health effects of PCBs. Further information on the toxicity of PCBs to humans and wildlife may be found in Appendix G. Chapter 3 explains the risk-based framework recommended by the committee and provides a brief review of other frameworks considered by the committee. Chapter 4 addresses the importance of community involvement in dealing with PCB-contaminated sediments, drawing on concerns raised at public meetings held by the committee. Chapter 5 presents the first stage of the risk-based framework, defining the problem of PCB-contaminated sediments and setting risk-management goals. This chapter provides an approach for identifying the affected parties, defining the problems associated with the contaminated sediments, determining the extent of the contamination and its sources, and setting management goals. Chapter 6 addresses the issue of characterizing existing and potential risks at PCB-contaminated sediment sites and provides an overview of the environmental risk-
assessment process, including the use and limitations of scientific information in this process. Chapter 7 describes the options available to achieve risk-management goals at a contaminated site and analyzes their benefits, effectiveness, costs, and feasibility. Chapter 8 discusses the issues that must be considered when choosing among the various risk-management options and making a decision that is most likely to achieve the management goals established in the first stage of the framework. Chapter 9 discusses the factors that must be considered when implementing the risk-management strategy. Chapter 10 addresses the need for evaluation in assessing the efficacy of risk-management projects and reviews recent evaluations that have been conducted on selected contaminated sites.
PCCRARM (Presidential/Congressional Commission on Risk Assessment and Risk Management). 1997. Framework for Environmental Health Risk Management: Final Report. Washington, DC: The Commission.