This is the second of a two-part review of the current state-of-the-science pertaining to the assessment and management of contaminated sediments. The goal of this review is to introduce some of the major technical and policy issues stemming from the assessment and management of contaminated sediments, highlight a number of aspects of contaminated sediment assessment and management found to be successful, and, when appropriate, address the barriers that still exist for improving contaminated sediment management. In Part I (Apitz et al. 2005), the key elements of an effective investigation and risk evaluation strategy were reviewed, beginning with the development of a conceptual site model (CSM) and including a discussion of some of the key factors influencing the design of sediment investigations and ecological risk assessment of sediment-bound chemicals on aquatic biota. In this paper, Part II, various approaches are reviewed for evaluating sediment risk and monitoring sediment remedy effectiveness. While many of the technical and policy issues described in this review are relevant to dredged material management, the focus of this paper is on sediment assessment for environmental management.

This is the first of a two-part review of the current state-of-the-science pertaining to the assessment and management of contaminated sediments. The goal of this review is to introduce some of the major technical and policy issues stemming from the assessment and management of contaminated sediments, highlight a number of aspects of contaminated sediment assessment and management found to be successful, and, when appropriate, address the barriers that still exist for improving contaminated sediment management. In this paper, Part I, the many key elements of an effective investigation and risk evaluation strategy are reviewed, beginning with the development of a conceptual site model (CSM) and including a discussion of some of the key factors influencing the design of sediment investigations and ecological risk assessment of sediment-bound chemicals on aquatic biota. In Part II of this paper (Apitz et al. 2005), various approaches are reviewed for evaluating sediment risk and monitoring sediment remedy effectiveness. While many of the technical and policy issues described in this review are relevant to dredged material management, the focus of this paper is on sediment assessment for environmental management.

Standard toxicity tests assess the physiological responses of individual organisms to exposure to toxic substances under controlled conditions. Time and space restrictions often prohibit the assessment of population-level responses to a toxic substance. Compounds affecting various toxicity endpoints, such as growth, fecundity, behavior, or immune function, alter different demographic traits and produce different impacts on the population. Chronic effects of immune suppression, reproductive impairment, and growth reduction were examined using life history models for Chinook salmon (Oncorhynchus tshawytscha). Modeled immune suppression acted through reductions in age-specific survival, with first- and second-year survival producing the greatest changes in the population growth rate (λ). A 10% reduction in various reproductive parameters all produced a similar λ, but different sensitivity and stable age distributions. Growth reduction models incorporated effects to both survival and reproduction and produced additive effects. Overall, model output indicated that for Chinook salmon, alteration of first-year survival has the greatest relative impact on λ. Results support the importance of linking toxicity endpoints to the demographic traits that they influence and help generate toxicity tests that are more relevant for the species. Life history modeling provides a useful tool to develop testable hypotheses regarding specific and comparative population-level impacts.

Polycyclic aromatic hydrocarbons (PAHs) are nearly ubiquitous contaminants of freshwater and marine sediments. Sediment PAHs are derived from combustion of organic matter, fossil fuels, and biosynthesis by microbes. Pyrogenic PAHs, particularly those associated with combustion particles (soot), have a low accessibility and bioavailability in sediments. Polycyclic aromatic hydrocarbons associated with petroleum, creosote, or coal tar in sediments may have a moderate accessibility/bioavailability, particularly if the PAHs are part of a nonaqueous phase liquid (NAPL) phase that is in contact with sediment pore water. We present a method for estimating the hazard of complex PAH assemblage in sediments to benthic organisms. Concentrations of all PAHs in sediment pore water are estimated by an equilibrium partitioning model relative to concentrations in bulk sediment. Predicted log K_oc values can be used for predicting sediment/water partitioning of petrogenic PAH, but empirically derived log K_d values are needed to predict partitioning of pyrogenic PAH. A hazard quotient (HQ) for each PAH is calculated as the ratio of the estimated concentration in pore water to the chronic toxicity of the PAH determined by a log K_ow/toxicity model. Hazard quotients for all PAH in a sample are summed to produce a hazard index (HI), which is a measure of the worst-case estimated hazard of the sediment PAH to benthic organisms. The results of this study show that the integration of HI results with PAH source data provides insights into the causes of sediment toxicity that are useful in an ecological risk assessment.

During the past three decades, significant advances have been made in understanding how environmental factors modify the bioavailability and the toxicity of metals such as copper in aquatic environments. Several of these advances have led to the development of guidelines to indirectly account for modifying factors, adjustment of criteria on a site-specific basis, and direct changes to the U.S. Environmental Protection Agency (U.S. EPA) freshwater quality criteria. To date, most of this effort has focused on freshwater systems, although similar modifying factors exist in marine environments as well. This paper focuses on one such modifying factor, dissolved organic carbon (DOC), and describes a method to aid in risk assessments or to refine the saltwater copper criteria on a site-specific basis. The relationship between DOC and toxicity of copper to the most sensitive saltwater genus in the U.S. EPA criteria database, Mytilus, is extensively analyzed. Dissolved copper 50% effective concentrations (EC50s) are highly correlated (r² = 0.71, n = 54, p < 0.001) across a wide range of sample DOC concentrations (0.3–10 mg carbon [C]/L) and are explained by the equation EC50 = 11.53DOC^0.54. Two equations based on DOC are proposed for consideration as a means for deriving site-specific final chronic criteria (FCC) and final acute criteria (FAC) for copper in marine and estuarine environments (Copper FCC_DOC = 3.71DOC^0.54 and Copper FAC_DOC = 5.843DOC^0.54).

A biologically based risk-assessment model of arsenic (As) exposure evaluated farmed tilapia (Orechromis mossambicus) and human health during tilapia consumption in an area of southwestern Taiwan where blackfoot disease (BFD) occurs. The risk assessment addressed exposures to city residents who lived in Taipei, Taichung, and Kaohsiung, as well as subsistence fishers living in the BFD area who consumed tilapia. The models implemented included a physiologically based toxicokinetic and toxicodynamic (PBTK/TD) model to account for As exposure and dose-response profiles in tilapia and a human health exposure/risk model that accounts for target lifetime risk (TR) and hazard quotient (HQ) for humans consuming farmed tilapia. Results demonstrated that 90th percentiles of TR ranged from 1.53 × 10⁻⁸ to 1.62 × 10⁻⁶ for city residents with farmed tilapia consumption rates of 0.41 to 1.37 g/d. The 90th percentiles ranged from 2.07 × 10⁻⁶ to 7.89 × 10⁻⁵ for subsistence fishers in the BFD area with farmed tilapia consumption rates of 16.80 to 59.15 g/d. All predicted 90th percentiles of HQ were less than 1 for city residents and subsistence fishers in the BFD area, indicating small contributions from farmed tilapia consumption. Critical variables included whole-fish body weight, water As content, and As level in tilapia muscle. Although bioaccumulation of As seems unlikely to result in toxicity to farmed tilapia and humans consuming tilapia, the theoretical human health risks in the BFD area are alarming, using a probabilistic risk-assessment model based on conservative assumptions.

Encroachment of residential development on agricultural lands in the United States where arsenical pesticides were extensively used prior to the 1990s has increased the potential for human exposure to arsenic (As), a group A carcinogen. Soil ingestion by children is a critical issue in assessing health risks from exposure to As-enriched soils. In the absence of a universal “soil model” on As bioavailability, many baseline risk assessment studies use the assumption that all (100%) As present in soil is bioavailable. However, As exists in many geochemical forms as dictated by soil chemical properties. Because As bioavailability is a function of soil speciation, using total soil arsenic values potentially overestimates human health risk, thereby increasing site cleanup expenses. A laboratory incubation study was conducted to estimate in vitro As bioavailability as a function of soil properties in four chemically variant soil types contaminated with sodium arsenite pesticide. Results demonstrate that As speciation in certain soils translates to significant lowering of As bioavailability and hence potential cancer risk.

On 24 September 2003, life cycle assessment (LCA) practitioners and decision makers gathered at the InLCA/LCM Conference in Seattle, Washington, USA (see  http://www.lcacenter.org/InLCA-LCM03/index.html) to discuss the role of LCA in management, product design, process development, and regulatory/policy development decisions and to compare life cycle–based methods and tools with traditional product evaluation methods and tools. This article is a summary of that meeting and was prepared by the organizers as an overview of the many different technical, regulatory policy, and decision-making policy perspectives presented to an international gathering of participants representing academia and the industrial and regulatory communities.

A frank assessment of present-day ecological risk assessments (ERA) for managed contaminated sites reveals that fundamental concepts regarding the receptors that are considered and the chemical exposures they experience are commonly misapplied. As a consequence, environmental managers are not being supplied with the information needed for proper decision making. The stepwise review of ecological risk issues provided here suggests that the ERA process needs to be severely revamped. Further, what is likely hindering the development of a refined ecological assessment process that is better suited to environmental problem solving and land management is the unwillingness of stakeholders to agree that much of the current ERA practice and convention is flawed.

Recently, the U.S. Environmental Protection Agency examined its current risk-assessment principles and practices. As part of the examination, aspects of ecological risk-assessment practices were reviewed. Several issues related to ecological risk assessment were identified, including the use of organism-level versus population-level attributes to characterize risk, the possible opportunities associated with the increased use of probabilistic approaches for ecological risk assessment, and the notion of conservatism in estimating risks. The agency examination provides an understanding of current practices and is intended to begin a dialogue in which the risk assessment community can engage in addressing the identified issues to improve and enhance ecological risk assessment.

As part of an agency evaluation of the development of risk assessment tools, the U.S. Environmental Protection Agency (U.S. EPA) issued a staff paper in March 2004 describing the current state of practices and policies regarding risk assessment from the agency's perspective. The staff paper provided a rationale for the agency's positions regarding technical topics frequently the subject of comments or complaints. Considerations relevant to ecological risk assessment were included, primarily in a single chapter focused on this topic. This commentary highlights four technical issues important to the advancement of ecological risk assessment practice and discusses how some of the points raised by the U.S. EPA in the staff paper have significance to ecological risk assessors. Discussion regarding incorporating population- and community-level analysis into risk assessments and the apparent reluctance of the U.S. EPA to adopt advances in this area is provided. Also, continuing inconsistencies in the body weight scaling of toxicity values between human health and ecological risk assessment practices are discussed. Ideas for refining the calculation of exposure point concentrations for ecological receptors and the progression between screening steps and comprehensive risk assessment are also discussed.

In March 2004, the U.S. Environmental Protection Agency (U.S. EPA) published a review of its risk assessment principles and practices. In examining this review, we find a broad, but not particularly deep, review by the authors and areas where the U.S. EPA should strive to further improve the risk assessment process. Recommended areas of improvement include the use of less conservative default assumptions, calculating risk based on populations instead of individuals, and fostering research on multiple stressors and their impacts on estimating risks to ecological receptors.