Annotated reference compilation: Conducting qualitative and quantitative ecological risk assessments at hazardous waste sites

As the field of ecological risk assessment (ERA) broadens, scientists from various disciplines are called upon to become assessors at hazardous waste sites. Although a United States Environmental Protection Agency (USEPA) Framework for ERAs exists, the guidance is unlike the detailed USEPA guidance available for human risk assessments. Currently, the quality of an ERA is dependent upon the assessor's scientific acumen, professional experience, and recognized reference documents. This annotated reference compilation encompasses published documents which have provided useful and important information for qualitative and quantitative ERAs.     

Framework for Human Health Risk Assessment

The views expressed in this paper are those of the authors and do not necessarily reflect the views or policies of the USEPA. The U.S. Government has the right to retain a nonexclusive royalty-free license in and to any copyright covering this article. The U.S. Environmental Protection Agency has recognized the need to develop a framework for human health risk assessment that puts a perspective on the approaches in practice throughout the Agency. In response, the USEPA's Risk Assessment Forum has begun the process of developing a framework for human health risk assessment. This paper provides some additional background to the previous review of the framework efforts and notes the Agency's extramural efforts to begin the process of integrating and harmonizing risk assessment approaches for all human health endpoints.     

Bioavailability of Soil-borne Chemicals: A Regulatory Perspective

U.S. Environmental Protection Agency (USEPA) risk assessment guidance documents dating back to 1989 have articulated the principles for incorporating information on bioavailability into the risk assessment process. However, in the interim period both the methods for obtaining media or route specific measures of bioavailability and the corresponding guidance to incorporate these data have languished. Presently, USEPA is developing guidance to address both of these concerns. This article outlines the broad framework for systematically evaluating the role of bioavailability in site-specific risk assessment from a regulatory perspective. At the same time, in appreciation of the vast horizon of uncharted territory ahead, the focus of USEPA's draft guidance, and consequently this report, is on bioavailability adjustments for soil-borne metals. The article describes a two-stage process. The first stage outlines a paradigm for screening sites to determine if generating site-specific data on the bioavailability of a metal in soil is of technical utility and economically justifiable. The second stage focuses on the collection, analysis, and incorporation of these data into the risk assessment for decision-making purposes.     

Regulatory Perspectives on the Significance of Ecological Changes as Reported in Ecological Risk Assessments

A broad range of perspectives exists regarding the interpretation of potentially adverse ecological changes in ecological risk assessments conducted under Superfund and RCRA. While USEPA's Proposed Guidelines for Ecological Risk Assessment recommend determining whether predicted changes are adverse based on the nature of effects, intensity of effects, spatial scale, temporal scale, and potential for recovery, the guidelines do not provide specific stan dards for judging adversity. Hence, implementation of the proposed guide lines varies with each risk manager's subjective judgments regarding the relative importance of each of these five criteria. In an effort to increase consistency in the scientific interpretation of ecological risk assessments, the following practices are recommended. First, measures of effects should focus on levels of ecological organization that are more complex than the individual organ ism. Second, multiple lines of evidence should be evaluated for each assessment endpoint. Third, bioequivalence testing should be used in place of traditional statistical testing (e.g., Student t-test) because the goal of bioequivalence testing is to answer the biologically relevant question of whether measurements differ by, at most, a biologically small amount. Fourth, in defining biologically small differences, site-specific and species specific conditions should be considered to the greatest extent possible. Fifth, where the outcomes of multiple lines of evidence contradict one another, the risk assessor should employ a quantitative approach to weighing the evidence based on the scientific defensibility of each measure of effect.     

Application of an Ecological Risk Assessment for Evaluation of Alternatives Considered for Restoration of Oysters in Chesapeake Bay: Background and Approach

Oyster populations in Chesapeake Bay, USA, declined precipitously over the past three decades, and on-going efforts to restore the native oysters to former abundance were considered to be ineffective. Maryland and Virginia natural resource agencies proposed the introduction of a non-native Asian oyster (Crassostrea ariakensis) that is resistant to diseases affecting the native oyster and well adapted to the Chesapeake Bay environment. Numerous stakeholders raised concerns about potential adverse consequences of an introduction of a non-native species into a new environment. In response, state and federal agencies determined that an Environmental Impact Statement (EIS) should be prepared to address the environmental consequences of such an introduction as well as of seven other oyster restoration alternatives, including several involving only the native oyster. Preparation of an Ecological Risk Assessment (ERA) of the proposed action as well as all alternatives was an integral element of EIS preparation. This series of articles describes several different analyses that contributed to and collectively comprised the ERA conducted as input to the EIS. The final article of this series in HERA describes how the ERA and EIS findings were taken into account in the final decision on the preferred restoration alternative by state and federal agencies.     

Risk Assessment and Life-Cycle Impact Assessment (LCIA) for Human Health Cancerous and Noncancerous Emissions: Integrated and Complementary with Consistency within the USEPA

The historical parallels, complementary roles, and potential for integration of human health risk assessment (RA) and Life-Cycle Impact Assessment (LCIA) are explored. Previous authors have considered the comparison of LCA and risk assessment recognizing the inherent differences in LCA and risk assessment (e.g., LCA's focus on the functional unit, and the differences in perspective of LCA and risk assessment), and also the commonalities (e.g., the basis for the modeling). Until this time, however, no one has proposed a coordinated approach for conducting LCA and risk assessment using models consistent with the U.S. Environmental Protection Agency's (USEPA's) handbooks, policies, and guidelines. The current status of LCIA methodology development can be compared to the early days of human health RA when practitioners were overwhelmed with the model choices, assumptions, lack of data, and poor data quality. Although methodology developers can build on the shoulders of the giant, LCIA requires more innovation to deal with more impact categories, more life-cycle stages, and less data for a greater number of stressors. For certain impact categories, LCIA can use many of the guidelines, methodologies, and default parameters that have been developed for human health RA, in conjunction with sensitivity and uncertainty analysis to determine the level of detail necessary for various applications. LCIA can then identify “hot spots” that require the additional detail and level of certainty provided by RA. A comparison of the USEPA's Tool for the Reduction and Assessment of Chemical and other environmental Impacts (TRACI) and the USEPA's Risk-Screening Environmental Indicators (RSEI) will be explored.     

Public Health Perspectives on Dioxin Risks: Two Decades of Evaluations

The paper provides an overview of approaches to dioxin risk assessment employed by different agencies worldwide over the past 20 years. Our insights regarding understanding of the toxicity of dioxins have advanced tremendously in recent years; however, important data gaps still exist. More information on topics such as mechanism of interaction, effects at low levels of exposure, interspecies differences, and sensitive populations is needed. Some differences exist between USEPA's approach to dioxin assessment and that of other health organizations around the world. The authors conclude that USEPA's reassessment of dioxin and related compounds may place too much confidence in the ability to accurately predict cancer risks at low doses. Further, it is important to derive health-based guidance values for noncancer end points especially in accordance with emerging reports that reproductive and developmental end points are very sensitive to dioxins. A worldwide convergence on the health assessment value being around 1 to 4?pg/kg/day is noted.     

Some Comments on the Selection of Human Intraspecies Uncertainty Factors

The Reference Dose (RfD) is used in the risk assessment of non-carcinogenic chemicals. It is derived by dividing a point of departure by the product of the uncertainty (UFs) and modifying factors (MFs). Separate UFs are used for different variables, e.g., intraspecies variation and, in general, each UF is an order of magnitude (10-fold). On the other hand, the MF is usually based on some known variable such as differences in absorption of a chemical from food and water and its default value is one. The USEPA's Integrated Risk Information System (IRIS) has 14 chemicals that have RfDs based on human studies. We examined those IRIS files to determine the rationale for setting human intraspecies uncertainty factors (UF_H). The first consideration was that the chemical had an adequate peer-reviewed human database. Without such, it would not be possible to derive an RfD based on human data. Ten of the 14 chemicals had an UF_H of 1 or 3; four of these were essential trace elements (ETEs). The rationales for using less than a 10-fold UF_H for the ETEs included; 1) nutritional data, 2) large human exposure groups, 3) minimal effect levels and/or 4) several studies with similar effect levels. For the other compounds, reasons included; 1) large human exposure groups, 2) a critical effect that was not adverse (cosmetic), 3) the most sensitive population was exposed, 4) the compound was on the FDA's “generally regarded as safe” (GRAS) list, 5) database uncertainties and 6) less-than-lifetime exposure adjusted for 70 years exposure. It is important to understand the reasons for selecting a UF_H of 1, or 3 as they will apply to future chemicals considered by the USEPA and other agencies.     

Primed for Change: Developing Ecological Restoration for the 21st Century

Restoration is a young and swiftly developing field. It has been almost a decade since the inception of one of the field's foundational documents—the Society for Ecological Restoration International Primer on Ecological Restoration (Primer). Through a series of organized discussions, we assessed the Primer for its currency and relevance in the modern field of ecological restoration. We focused our assessment on the section entitled “The Nine Attributes of a Restored Ecosystem” and grouped each of the attributes into one of four categories: species composition, ecosystem function, ecosystem stability, and landscape context. We found that in the decade since the document's inception, the concepts, methods, goals, and thinking of ecological restoration have shifted significantly. We discuss each of the four categories in this light with the aim of offering comments and suggestions on options for updating the Primer. We also include a fifth category that we believe is increasingly acknowledged in ecological restoration: the human element. The Primer is an important document guiding the practice of restoration. We hope that this critical assessment contributes to its ongoing development and relevance and more generally to the development of restoration ecology, particularly in our current era of rapid environmental change.     

Cancer and Non-Cancer Risk Assessment from Exposure to Arsenic,Copper, and Cadmium in Borehole,Tap, and Surface Water in the Obuasi Municipality,Ghana

Cancer and non-cancer risk assessment from exposure to As, Cd, and Cu by resident adults and children from different water sources in Obuasi Municipality, Ghana, were measured in this study in accordance with the U.S. Environmental Protection Agency's (USEPA's) Human Health Risk Assessment guidelines. The results of cancer health risk for resident adults in Obuasi exposed to As in their tap water for both Central Tendency Exposure (CTE) and Reasonable Maximum Exposure (RME) parameters, respectively, are 6.6 × 10^?4 and 5.5 × 10^?6. For resident children in Odumasi, we obtained 4.7 × 10^?1 (CTE) and 6.7 × 10^?1 (RME). The results of the study obtained in most cases were found to exceed the USEPA's acceptable cancer risk range of 1 × 10^?6 to 1 × 10^?4 (i.e., 1 case of cancer out of 1,000,000 people to 1 case of cancer out of 10,000 people). Similarly, the results of the non-cancer human health risk for both resident adults and children were also found in most cases to be greater than the USEPA's acceptable non-cancer human health hazard index of 1.     

Genomics: Applications,Challenges, and Opportunities for the U.S. Environmental Protection Agency

Genomics information has great potential to enhance assessment of risks to human health and the environment. Although understanding genomic responses with respect to adverse ecological and human health outcomes is not, as yet, established, it is important to consider the likely future impacts of genomics technologies on risk assessment and decision-making. Four areas are identified as those likely to be influenced by the generation of genomics information within, and the submission of such information to, the U.S. Environmental Protection Agency (USEPA): risk assessment, prioritization of contaminants and contaminated sites, monitoring, and reporting provisions. For each of these risk assessment and regulatory applications, representative activities are presented to illustrate the application. Three major challenges for the USEPA associated with genomics are also identified in the areas of research, technical development, and capacity. The USEPA's initial activities to address these challenges are discussed. The Agency recognizes it must be prepared to use genomics information, and that many scientific, policy, ethical, and legal concerns will need to be addressed. The USEPA also recognizes it is essential to continue to collaborate with other federal agencies, academia, the regulated community, and other stakeholders in order to benefit from ongoing advances in genomics in the wider scientific and regulatory communities.     

Indicators for Human and Ecological Risk Assessment: A U.S. Environmental Protection Agency Perspective

Assessment of risk to public health or environmental resources requires competent characterization of stressors and corresponding effects. Because of the complexity of most stressor-response relationships, it is impossible to completely characterize all the variables, so a select set of measurements is made to reflect the most critical components. Such measurements, or indicators, are included in monitoring programs to estimate trend, stressor source, or magnitude of effects and lead to thresholds for management action or restoration. Although a wide variety of programs and program objectives exists, there are some common challenges for indicator development, including a strong link to management actions. Indicator measurements used in U.S. Environmental Protection Agency (USEPA) risk assessment activities must stem from collaboration among managers, risk assessors, scientists and stakeholders. The primary objective of the USEPA's Fifth Symposium of the National Health and Ecological Effects Research Laboratory was to improve health and ecological risk assessment through dedicated sessions that maximized interaction and discussion among these groups. Existing measurements were challenged for appropriateness, efficiency and scientific validity. Emerging science was explored for greater understanding, better interpretation, and improved methodology. A secondary objective was to uncover and exploit common indicators and supporting data for human health and ecological models.     

Quandaries and complexities of ecological risk assessment: Viable options to reduce humanistic arrogance

Ecological risk assessment has been used to support decisions regarding human‐generated actions which affect natural “resources”; and indigenous ecosystems. Often, the logical and scientific input serve as rationalization to legitimize the process. Though widely accepted as the realistic and sole paradigm, Ecological Risk Assessments do not address the complexities of the natural world, are humanistically arrogant, and disregard or do not consider alternatives which offer imagination and realistic attempts to reduce human impact to the land.

Ecological Alternatives Assessment practices would place the highest priority on: (a) continued temporal and spatial evolution of existing complex ecological relationships, (b) acknowledgment of the inherent rights of all species, and (c) examination of alternatives to reduce effects of anthropogenic actions. These steps, as discussed, are not impossible to accomplish and are necessary for favorable short‐term (50–500 years) anthropocentric alternatives and maintenance of long‐term (+1,000 years) biodiversity of species and ecosystems.     

“Words matter.” A Response to Jørgensen's Treatment of Historic Range and Definitions of Reintroduction

According to Jørgensen, the definition of reintroductions is crucial to their proper implementation and she highlights a number of ambiguities in existing definitions, particularly associated with the concept of historic range. We could not agree more and have incorporated her suggested term of “indigenous range” rather than “historic range” into the current revision of the InternationalUnion for the Conservation of Nature (IUCN) Guidelines for Reintroductions and other Conservation Translocations (in preparation by IUCN Species Survival Commission Reintroduction and Invasive Species Specialist Groups). We also agree with Jørgensen's interpretation that reintroductions are not always necessitated by humans causing the extirpation of species. However, we disagree with other aspects of Jørgensen's argument such as the critique of Seddon, the interpretation of previous IUCN guidance documents, and the recommendation that the conservation community “rethink the basic definition of reintroduction” rather than moving toward other translocation‐based interventions. With regard to the latter point, we emphasize that reintroductions are part of a spectrum of translocations and to focus on reintroductions alone would overlook the fact that introductions beyond a species' indigenous range are being attempted. The new revision of the IUCN guidelines incorporates the whole conservation translocation spectrum and aims to avoid the ambiguities of previous definitions highlighted by Jørgensen.     

International principles and standards for native seeds in ecological restoration

The growing demand for native seeds in ecological restoration and rehabilitation, whether for mining, forest, or ecosystem restoration, has resulted in a major global industry in the sourcing, supply, and sale of native seeds. However, there are no international guidance documents for ensuring that native seeds have the same standards of quality assurance that are regular practice in the crop and horticultural industries. Using the International Principles and Standards for the Practice of Ecological Restoration as a foundation document, we provide for the first time a synthesis of general practices in the native seed supply chain to derive the Principles and Standards for Native Seeds in Ecological Restoration (“Standards”). These practices and the underpinning science provide the basis for developing quality measures and guidance statements that are adaptable at the local, biome, or national scale. Importantly, these Standards define what is considered native seed in ecological restoration and highlight the differences between native seeds versus seeds of improved genetics. Seed testing approaches are provided within a logical framework that outline the many different dormancy states in native seed that can confound restoration outcomes. A “pro‐forma” template for a production label is included as a practical tool that can be customized for local needs and to standardize reporting to end‐users on the level of seed quality and germinability to be expected in a native seed batch. These Standards are not intended to be mandatory; however, the guidance statements provide the foundation upon which regulatory approaches can be developed by constituencies and jurisdictions.     

An Overview of the Development,Status, and Application of Equilibrium Partitioning Sediment Benchmarks for PAH Mixtures

This article provides an overview of the development, theoretical basis, regulatory status, and application of the U.S. Environmental Protection Agency's (USEPA's) Equilibrium Partitioning Sediment Benchmarks (ESBs) for PAH mixtures. ESBs are compared to other sediment quality guidelines (SQGs) for PAHs. Data that examine the ability of the ESB approach to predict toxic effects to invertebrates are discussed. A USEPA draft methodology for the development of site-specific ESBs that takes into account the limited bioavailability of PAHs at certain sites is discussed. Research is presented that compares the ability of ESBs and site-specific ESBs to predict the toxicity of sediments collected from manufactured gas plants (MGPs). Site-specific ESBs that accounted for adsorption of PAHs onto black carbon were better predictors of the toxicity of sediments from MGP sites than ESBs that did not account for adsorption to black carbon.     

An Ecological Risk Assessment Methodology for Screening Discharge Alternatives of Produced Water

Previous studies on Ecological Risk Assessment (ERA) of produced water relied on the use of deterministic hydrodynamic models. The assessment was usually carried out in the North Sea context using a model such as the Chemical Hazard Assessment and Risk Management (CHARM), or in the North American context based on the output of a hydrodynamic model such as the Cornell Mixing Zone Expert System (CORMIX). In both these cases, however, probabilistic analysis has not been employed, particularly, to account for uncertainty associated with hydrodynamic models in the ERA study. In fact, it is the hydrodynamic model that has a direct linkage to the selection of the discharge alternatives. Apart from the monitoring purposes, in this article, it is suggested that criteria for evaluating discharge alternatives of produced water in a marine environment might incorporate an awareness of ecological risks by incorporating engineering and toxicological aspects. An ERA methodology consisting of problem formulation, analysis, and risk characterization is discussed in light of evaluating the discharge alternatives. A probabilistic analysis using Latin Hypercube Sampling (LHS)–based Monte Carlo (MC) simulations was employed. A depiction of associated risks for an area comparable to a regulatory mixing zone of typical effluent discharges is presented.     

What about cultural ecosystems? Opportunities for cultural considerations in the “International Standards for the Practice of Ecological Restoration”

The Society for Ecological Restoration's 2016 (SER) “International Standards for the Practice of Ecological Restoration” is a living document intended to guide restoration projects “anywhere in the world.” Given its intended global scope and in hopes of informing future editions, this document is critically assessed in light of the role people have played in ecosystems around the world. We argue that the Standards has an underlying nature–culture dichotomization that limits its applicability; in qualifying what it calls “cultural ecosystems” for rehabilitation, rather than restoration, the Standards privileges colonial visions of ecological restoration. We also discuss the Standards' representation of the ecological impacts and practices of indigenous groups. Whereas the Standards claims that preindustrial cultural ecosystems exist in states similar to unmodified areas, many historians, anthropologists, and paleoecologists would point out that preindustrial people sometimes had massive environmental impacts through agriculture, hydrological engineering, over‐hunting, living in dense urban environments, transporting species, burning on a scale capable of changing the climate, and other practices. Furthermore, the Standards does not discuss how the cultural goals of indigenous groups fit into the overall picture of ecological restoration. Future drafts of the Standards should more accurately frame the diverse roles people play in nature, and create global standards that account for the validity of cultural goals for ecological restoration.     

Sensitivity Analysis of U.S. EPA's Estimates of Skin Cancer Risk from Inorganic Arsenic in Drinking Water

The current U.S. Environmental Protection Agency's (USEPA's) risk analysis on the Integrated Risk Information System (IRIS) for arsenic in drinking water is based on an epidemiological study of skin cancer in Taiwan. Assumptions used in the USEPA application of the multistage-Weibull model for risk estimation were varied to assess the effect on predicted risk of skin cancer to the U.S. population at arsenic concentrations of 1 to 50?µg/L in drinking water. Among the assumptions tested, the only notable change in risk estimates was a reduction when the arsenic concentration used as representative for Taiwan villages in the low range (<300?µg/L) was increased to the 75th percentile (245?µg/L) in place of the mean used in the USEPA analysis (170?µg/L), but the representative value for Taiwan villages in the high range (≥600?µg/L) was not increased simultaneously to the 75th percentile. Additionally, a simulation study was conducted using records of arsenic measurements in wells from the same period and region of Taiwan as the original study. The exposure-response curve estimated from 60 villages (60 data points) differed only marginally from the outcome when data were summarized into four data points (as in the USEPA skin cancer analysis). Briefly discussed are differences between the study area of Taiwan and the U.S. in nutritional status and consumption of inorganic arsenic in food that might bias predicted U.S. skin cancer risks.     

Assessing Children's Exposures and Risks to Drinking Water Contaminants: A Manganese Case Study

Background: Compared to adults, children maybe more highly exposed to toxic substances in drinking water because they consume more water per unit of body weight. The U.S. Environmental Protection Agency (USEPA) has developed new guidance for selecting age groups and age-specific exposure factors for assessing children's exposures and risks to environmental contaminants. Research Aim: To demonstrate the application and importance of applying age-specific drinking water intake rates, health reference values, and exposure scenarios when assessing drinking water exposures because these approaches illustrate the potential for greater potential for adverse health effects among children. Methods: manganese, an essential nutrient and neurotoxicant, was selected as a case study and chemical of potential concern for children's health. A screening-level risk assessment was performed using age-specific drinking water intake rates and manganese concentrations from U.S. public drinking water systems. Results: When age-specific drinking water intake rates are used to calculate dose, formula-fed infants receive the highest dose of manganese from drinking water compared to all other age groups. Estimated hazard quotients suggest adverse health effects are possible. Use of USEPA's standardized childhood age groups and childhood exposure factors significantly improves the understanding of childhood exposure and risks.