U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division


Risk Assessment

Contaminated sediments present short and long-term toxic risks to human health and wildlife. Sediment contaminants include persistent organic pollutants, such as the polychlorinated dibenzo-p-dioxins and furans (PCDDs and PCDFs), polychlorinated biphenyls (PCBs), and chlorinated pesticides. Recognized adverse impacts of long-term exposure of both human and wildlife receptors to PCDDs, PCDFs, and the dioxin-like PCBs include impairment of the immune, neurological, and reproductive systems, impaired development of the young, and an increased risk of cancer. Polycyclic aromatic hydrocarbons (PAHs), present in fuel spills, coal tars, creosotes, and urban runoff, are frequent sediment contaminants and are known human and animal carcinogens. The chlorinated pesticides can impair the central nervous system and disrupt the endocrine systems of human and wildlife receptors. Contamination of sediment with heavy metals, such as cadmium, lead, arsenic, and mercury, can lead to kidney and nervous system damage and impaired development in ecological and human receptors.

The adverse effects of contaminated sediment on the structure and function of the benthic community can result in a loss of population for the wildlife communities that depend on them as their primary food source. Ecosystem processes that naturally purify water, such as the decomposition of organic matter and water filtration, can also be lost, resulting in environmental degradation.

The nature and magnitude of current and potential threats to human health and ecological receptors posed by contaminated sediment are characterized by the baseline risk assessment (BRA). A Superfund BRA is usually performed as part of the Remedial Investigation/Feasibility Study (RI/FS) phase of a response action.

Risk assessment supports risk management in the adoption of a management strategy for remediating contaminated sediment. Management strategies encompass a wide variety of actions, from intrusive remedies, such as dredging, removal, and treatment of contaminated sediment, to monitored natural recovery (MNR), or to a "no action" alternative. Each action has its own economic cost, engineering limitations and benefits, risks during implementation, and residual long-term risks to human and ecological receptors. Risk assessment provides a framework for identifying and ranking the risks associated with each alternative (US EPA 2005).

Baseline Ecological Risk Assessment of the Calcasieu Estuary, Louisiana
D.D. MacDonald, et al.
Archives of Environmental Contamination and Toxicology 61(1):1-58(2011)

As part of the RI/FS for this site, a baseline ecological risk assessment was conducted. Details of this work have been published in three consecutive papers in the July 2011 issue of Archives of Environmental Contamination and Toxicology. These papers describe the environmental setting and site history; identify the chemicals of potential concern (metals, PCBs, PAHs, PCDD/Fs, chlorinated benzenes, TCE, pesticides); present the exposure scenarios and conceptual model for the site; summarize the assessment and measurement endpoints used in the investigation; describe the results of an evaluation of effects-based sediment-quality guidelines; and present an assessment of risks to benthic invertebrates associated with exposure to contaminated sediment. Background information is summarized in an EPA document, Calcasieu Estuary Remedial Investigation/Feasibility Study (RI/FS): Baseline Ecological Risk Assessment WorkshopAdobe PDF Logo (2000). Link to abstracts

Adobe PDF LogoContaminated Sediment Remediation Guidance for Hazardous Waste Sites
USEPA OSWER December 2005

Adobe PDF LogoFramework for Metals Risk Assessment
EPA, Office of Science Adviser, EPA 120/R-07/001, 172 pp, 2007

This document covers both human health and ecological risk assessment for metals.

Adobe PDF LogoHudson River Natural Resources Damage Assessment Plan
Hudson River Trustee Council, 81 pp, 2002

This document describes the wide-ranging economic, cultural, and ecotoxicological impacts of PCB contamination on the Hudson River.

Adobe PDF LogoImplementation of Dredging Risk Assessment Modeling Applications for Evaluation of the No-Action Scenario and Dredging Impacts
U. S. Army Corps off Engineers (USACE), ERDC TN-DOER-R2, 14 pp, 2001

Importance of Implementation and Residual Risk Analyses in Sediment Remediation
Wenning, R.J., S. Sorenson, and V.S. Magar.
Integrated Environmental Assessment and Management, Vol 2, No 1, Jan 2006

This review links risk assessment to cost/benefit analysis and discusses two types of risk—biological and engineering—that deserve consideration when evaluating sediment remedy alternatives.

Adobe PDF LogoRapid Sediment Characterization (RSC) Tools for Ecological Risk Assessment
SPAWAR Systems Center Pacific, 21 pp, June 2011

RSC technologies are field-transportable screening tools that provide measurements of chemical, biological or physical parameters on a real-time or near real-time basis. These tools can streamline many aspects of the ecological risk assessment (ERA) process when used to delineate areas of concern, fill in information gaps, and assure that expensive, certified analyses have the greatest possible impact. X-ray fluorescence for metals, UV fluorescence for PAHs, QwikSed bioassay for assessing toxicity, and several other techniques are discussed for their use at marine sediment sites, and examples are provided.

Adobe PDF LogoRisk Characterization Handbook
USEPA, Science Policy Council, EPA 100/B-00/002, 189 pp, 2000

The Risk Characterization Guide is designed to provide risk assessors, risk managers, and other decision-makers an understanding of the goals and principles of risk characterization, the importance of planning and scoping for a risk assessment, the essential elements to address in a risk characterization, the factors that are considered in decision making by risk managers, and the forms the risk characterization takes for different audiences. A discussion of the various administrative details regarding risk characterization completes the guide.

A Risk Management Strategy for PCB Contaminated Sediments
National Academy of Sciences, 452 pp, 2001

The summary of this document presents the 11 major conclusions and recommendations concerning the risks presented by PCB contaminated sediments and management options.

Sediment Toxicology
USGS Columbia Missouri Office

This Web page contains numerous primarily USGS produced documents and studies concerning toxicity assessments of sediment.

Toxicity of Sediments
Burton, G.A. and P.F. Landrum.
In the Encyclopedia of Sediments and Sedimentary Rocks, Kluwer Academic Publishers, Dordrecht, p 748-751, 2003

This chapter includes a brief introduction to the subject of sediment toxicity.

Toxicological Profiles
Agency for Toxic Substances and Disease Registry (ATSDR)

ATSDR publishes toxicological profiles for organic and inorganic chemicals, some of which may be found in sediment. Each profile lists the chemical�s health effects by route of exposure (oral, dermal, and inhalation); its toxicokinetics, chemical, and physical information; its potential for human exposure, including its environmental fate and transport; and methods of chemical analysis.