Using emerging science to inform risk characterizations for wildlife within current regulatory frameworks.

Many jurisdictions have regulatory frameworks that seek to reduce the effects of environmental exposures of anthropogenic chemicals on terrestrial wildlife (i.e., mammals, birds, reptiles, and amphibians). The frameworks apply for new and existing chemicals, including pesticides (prospective assessments), and to environmental contamination from releases (retrospective risk assessments). Relatively recently, there have been many scientific advances that could improve risk estimates for wildlife. Here, we briefly describe current regulations from North America (United States and Canada) and from Europe that include risk assessments for wildlife to ascertain whether they are conducive to the use of emerging science and new methods. We also provide examples where new and emerging science may be used to improve wildlife risk characterization and identify areas in need of future research. Integr Environ Assess Manag 2024;20:765-779. © 2024 His Majesty the King in Right of Canada and The Authors. Integrated Environmental Assessment and Management © 2024 Society of Environmental Toxicology & Chemistry (SETAC). Reproduced with the permission of the Minister of Environment and Climate Change Canada. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

In situ sediment treatment using activated carbon: a demonstrated sediment cleanup technology.

This paper reviews general approaches for applying activated carbon (AC) amendments as an in situ sediment treatment remedy. In situ sediment treatment involves targeted placement of amendments using installation options that fall into two general approaches: 1) directly applying a thin layer of amendments (which potentially incorporates weighting or binding materials) to surface sediment, with or without initial mixing; and 2) incorporating amendments into a premixed, blended cover material of clean sand or sediment, which is also applied to the sediment surface. Over the past decade, pilot- or full-scale field sediment treatment projects using AC-globally recognized as one of the most effective sorbents for organic contaminants-were completed or were underway at more than 25 field sites in the United States, Norway, and the Netherlands. Collectively, these field projects (along with numerous laboratory experiments) have demonstrated the efficacy of AC for in situ treatment in a range of contaminated sediment conditions. Results from experimental studies and field applications indicate that in situ sequestration and immobilization treatment of hydrophobic organic compounds using either installation approach can reduce porewater concentrations and biouptake significantly, often becoming more effective over time due to progressive mass transfer. Certain conditions, such as use in unstable sediment environments, should be taken into account to maximize AC effectiveness over long time periods. In situ treatment is generally less disruptive and less expensive than traditional sediment cleanup technologies such as dredging or isolation capping. Proper site-specific balancing of the potential benefits, risks, ecological effects, and costs of in situ treatment technologies (in this case, AC) relative to other sediment cleanup technologies is important to successful full-scale field application. Extensive experimental studies and field trials have shown that when applied correctly, in situ treatment via contaminant sequestration and immobilization using a sorbent material such as AC has progressed from an innovative sediment remediation approach to a proven, reliable technology.

Passive sampling methods for contaminated sediments: risk assessment and management.

This paper details how activity-based passive sampling methods (PSMs), which provide information on bioavailability in terms of freely dissolved contaminant concentrations (Cfree ), can be used to better inform risk management decision making at multiple points in the process of assessing and managing contaminated sediment sites. PSMs can increase certainty in site investigation and management, because Cfree is a better predictor of bioavailability than total bulk sediment concentration (Ctotal ) for 4 key endpoints included in conceptual site models (benthic organism toxicity, bioaccumulation, sediment flux, and water column exposures). The use of passive sampling devices (PSDs) presents challenges with respect to representative sampling for estimating average concentrations and other metrics relevant for exposure and risk assessment. These challenges can be addressed by designing studies that account for sources of variation associated with PSMs and considering appropriate spatial scales to meet study objectives. Possible applications of PSMs include: quantifying spatial and temporal trends in bioavailable contaminants, identifying and evaluating contaminant source contributions, calibrating site-specific models, and, improving weight-of-evidence based decision frameworks. PSM data can be used to assist in delineating sediment management zones based on likelihood of exposure effects, monitor remedy effectiveness, and, evaluate risk reduction after sediment treatment, disposal, or beneficial reuse after management actions. Examples are provided illustrating why PSMs and freely dissolved contaminant concentrations (Cfree ) should be incorporated into contaminated sediment investigations and study designs to better focus on and understand contaminant bioavailability, more accurately estimate exposure to sediment-associated contaminants, and better inform risk management decisions. Research and communication needs for encouraging broader use are discussed.

Regulatory considerations for the potential development and application of metal cleanup values.

This article addresses the regulatory issues associated with the application of recent data to support Registration, Evaluation, Authorisation and Restriction of Chemical substances (REACH) requirements in Europe and the use of metal-specific parameters by other countries to generate remediation values for metals in soil. The purposes of this article are to: 1) present approaches and advances developed over the last decade in Europe for the REACH regulation and proposed in Australia by the National Environment Protection Council, 2) review current US and Canadian regulatory practices on ecological soil cleanup values, and 3) evaluate the application of new scientific approaches, methods, and soil criteria development processes used in other countries.

A sediment ecotoxicity assessment platform for in situ measures of chemistry, bioaccumulation and toxicity. Part 1: System description and proof of concept.

In situ-based testing using aquatic organisms has been widely reported, but is often limited in scope and practical usefulness in making decisions on ecological risk and remediation. To provide this capability, an integrated deployment system, the Sediment Ecotoxicity Assessment (SEA) Ring was developed, which incorporates rapid in situ hydrological, chemical, bioaccumulation, and toxicological Lines-of-Evidence (LoE) for assessing sediment and overlying water contamination. The SEA Ring system allows for diver-assisted, or diverless, deployment of multiple species of ecologically relevant and indigenous organisms in three different exposures (overlying water, sediment-water interface, and bulk sediment) for periods ranging from two days to three weeks, in a range of water systems. Measured endpoints were both sublethal and lethal effects as well as bioaccumulation. In addition, integrated passive sampling devices for detecting nonpolar organics (solid phase micro-extraction fibers) and metals (diffusive gradients in thin films) provided gradient measures in overlying waters and surficial sediments.

A sediment ecotoxicity assessment platform for in situ measures of chemistry, bioaccumulation and toxicity. Part 2: Integrated application to a shallow estuary.

A comprehensive, weight-of-evidence based ecological risk assessment approach integrating laboratory and in situ bioaccumulation and toxicity testing, passive sampler devices, hydrological characterization tools, continuous water quality sensing, and multi-phase chemical analyses was evaluated. The test site used to demonstrate the approach was a shallow estuarine wetland where groundwater seepage and elevated organic and inorganic contaminants were of potential concern. Although groundwater was discharging into the surficial sediments, little to no chemical contamination was associated with the infiltrating groundwater. Results from bulk chemistry analysis, toxicity testing, and bioaccumulation, however, suggested possible PAH toxicity at one station, which might have been enhanced by UV photoactivation, explaining the differences between in situ and laboratory amphipod survival. Concurrently deployed PAH bioaccumulation on solid-phase micro-extraction fibers positively correlated (r(2) ≥ 0.977) with in situ PAH bioaccumulation in amphipods, attesting to their utility as biomimetics, and contributing to the overall improved linkage between exposure and effects demonstrated by this approach.

Spatially explicit ecological exposure models: a rationale for and path toward their increased acceptance and use.

Spatially explicit wildlife exposure models have been developed to integrate chemical concentrations dispersed in space and time, heterogeneous habitats of varying qualities, and foraging behaviors of wildlife to give more realistic wildlife exposure estimates for ecological risk assessments. These models not only improve the realism of wildlife exposure estimates, but also increase the efficiency of remedial planning. However, despite being widely available, these models are rarely used in baseline (definitive) ecological risk assessments. A lack of precedent for their use, misperceptions about models in general and spatial models in particular, non-specific or no enabling regulations, poor communication, and uncertainties regarding inputs are all impediments to greater use of such models. An expert workshop was convened as part of an Environmental Security Technology Certification Program Project to evaluate current applications for spatially explicit models and consider ways such models could bring increased realism to ecological exposure assessments. Specific actions (e.g., greater accessibility and innovation in model design, increased communication with and training opportunities for decision makers and regulators, explicit consideration during assessment planning and problem formulation) were discussed as mechanisms to increase the use of these valuable and innovative modeling tools. The intent of this workshop synopsis is to highlight for the ecological risk assessment community both the value and availability of a wide range of spatial models and to recommend specific actions that may help to increase their acceptance and use by ecological risk assessment practitioners.

Review of aquatic in situ approaches for stressor and effect diagnosis.

Field-based (in situ) approaches are used increasingly for measuring biological effects and for stressor diagnoses in aquatic systems because these assessment tools provide realistic exposure environments that are rarely replicated in laboratory toxicity tests. Providing realistic exposure scenarios is important because environmental conditions can alter toxicity through complex exposure dynamics (e.g., multiple stressor interactions). In this critical review, we explore the information provided by aquatic in situ exposure and monitoring methods when compared with more traditional approaches and discuss the associated strengths and limitations of these techniques. In situ approaches can, under some circumstances, provide more valuable information to a decision maker than information from surveys of resident biota, laboratory toxicity tests, or chemical analyses alone. A decision tree is provided to assist decision makers in determining when in situ approaches can add value.

Case study of contaminated groundwater discharge: how in situ tools link an evolving conceptual site model with management decisions.

In this paper, we show how simple in situ tools provide key insights into groundwater transport and exposure pathways. We illustrate how integration between managers, hydrogeologists, and ecologists, through the use of an evolving conceptual site model, helps direct management decisions. An initial conceptual site model was used to guide a preliminary investigation to determine the extent to which contaminant exposure from discharging groundwater occurs in a waterway. Regulatory agency managers, informed by phased input of data, supported extending the site investigation subtidally to identify the nature and extent of waterway contamination and to provide the basis for developing remedial alternatives. Approaches and tools used in this reconnaissance investigation included monitoring ambient surface water for groundwater signatures, installing minipiezometers within the sediment, and installing diffusion samplers and seepage meters. Despite high concentrations of contaminants in nearby piezometer samples, the diffusion sampler array indicated few locations with contaminant accumulation in the top 20 cm of the sediment. At the location where deployed, seepage meters demonstrated a high degree of connectivity and the potential for mass loading in the waterway. In the collective experience of the authors, this is one of the 1st sites where this comprehensive suite of tools has been applied in a regulatory setting to evaluate the movement of industrial contaminants beneath and into a waterway. This approach was effective because of integration of disciplines, unification of previously separate groundwater and sediment investigations, and collaboration across separate agencies and programs. In large part because of the results, the facility and agency managers agreed, and have begun a comprehensive subtidal investigation, to characterize the distribution of sediment and groundwater contamination and to quantify the groundwater flux to the surface water.

Desorption kinetics of fluoranthene and trifluralin from Lake Huron and Lake Erie, USA, sediments.

Desorption kinetics were determined for fluoranthene (FLU) and trifluralin (TF) spiked onto Lake Erie and Lake Huron, USA, sediments at three concentrations (10, 40, 100 mg/kg dry wt). Following four months of equilibration, desorption was measured by extraction with Tenax and the data were fit to a first-order three-compartment kinetic model. The rate constants of the rapidly (k(rap)), slowly (k(slow)), and very slowly (k(vs)) desorbing fractions were on the order of 10(-1)/h, 10(-2-3)/h, and 10(-4)/h, respectively. The t99.9 (time required for 99.9% of the FLU and TF to desorb from each pool value) for each compartment indicated that FLU and TF desorption from rapid, slow, and very slow compartments were on the order of hours, days, and years, respectively. Higher rates of desorption were observed for FLU and TF from the Lake Huron sediments and this was not apparently related to the total organic carbon (TOC), particle size distribution, or polarity (carbon-to-nitrogen ratio) of the sediments. In general, the total fraction of the initial contaminant amounts that desorbed over the time course was directly related to concentration, which we hypothesized was due to the combined effects of saturation of high-energy (slow and very slow) binding sites in the organic carbon matrix and hysteresis. In extrapolations to field conditions, FLU and TF were predicted to persist in the sediments for years due to the very slow desorption of an estimated 31 to 53% of the bulk concentrations. Based on the rapidly desorbing fractions, the bioavailable amounts of the contaminants were predicted to be between 31 to 55% of bulk sediment concentrations.

In situ exposures using caged organisms: a multi-compartment approach to detect aquatic toxicity and bioaccumulation.

An in situ toxicity and bioaccumulation assessment approach is described to assess stressor exposure and effects in surface waters (low and high flow), the sediment-water interface, surficial sediments and pore waters (including groundwater upwellings). This approach can be used for exposing species, representing major functional and taxonomic groups. Pimephales promelas, Daphnia magna, Ceriodaphnia dubia, Hyalella azteca, Hyalella sp., Chironomus tentans, Lumbriculus variegatus, Hydra attenuatta, Hexagenia sp. and Baetis tibialis were successfully used to measure effects on survival, growth, feeding, and/or uptake. Stressors identified included chemical toxicants, suspended solids, photo-induced toxicity, indigenous predators, and flow. Responses varied between laboratory and in situ exposures in many cases and were attributed to differing exposure dynamics and sample-processing artifacts. These in situ exposure approaches provide unique assessment information that is complementary to traditional laboratory-based toxicity and bioaccumulation testing and reduce the uncertainties of extrapolating from the laboratory to field responses.

Investigating the role of desorption on the bioavailability of sediment-associated 3,4,3',4'-tetrachlorobiphenyl in benthic invertebrates.

Only a fraction of all sediment-associated hydrophobic organic contaminants are bioavailable, and a simple Tenax extraction procedure may estimate this fraction. Bioavailability is assumed to coincide with the rapidly and, possibly, slowly desorbing sediment-associated contaminant. River sediment was spiked with radiolabeled (14C) and nonradiolabeled (12C) 3,4,3',4'-tetrachlorobiphenyl (TCBP), and desorption kinetics using Tenax extraction were obtained at 10 degrees C and 22 degrees C. Bioaccumulation was measured in Lumbriculus variegatus, Chironomus tentans, and Hyalella azteca. Desorption of TCBP was triphasic at 22 degrees C and slowed at 10 degrees C to show only biphasic kinetics. The rapidly desorbing fractions decreased with increasing TCBP sediment concentration. The biota sediment accumulation factors, biota accumulation factors, and sediment clearance coefficients (ks) also decreased with increasing sediment TCBP concentration. The rapidly plus slowly desorbing fractions and the total TCBP desorbed when 99.9% of the rapidly desorbing fraction had desorbed were used to estimate bioavailable TCBP. These Tenax-based fractions did not explain the decreasing bioavailability with increasing TCBP load. Several factors, such as animal behavior and TCBP water solubility limitations, were evaluated to explain the concentration effect, but the most likely cause was severe diffusion limitations in whole sediment that were not predicted by the fully mixed Tenax extraction. Therefore, desorbing fractions determined by Tenax extraction overestimated the bioavailable fractions in sediments.

Optimizing interpretation of in situ effects of riverine pollutants: impact of upwelling and downwelling.

In situ toxicity and bioaccumulation tests with Ceriodaphnia dubia (48 h), Chironomus tentans (96 h), Hyalella azteca (96 h), and Lumbriculus variegatus (96 h) were conducted at three stations on a river that was contaminated primarily with chlorobenzenes (CBs), and results were compared to a nearby reference site. Exposures were characterized by using minipiezometers for contaminant profiling and determination of hydraulic heads and vertical flow direction within the sediments and measuring contaminants in sediment, surface water, and exposure chamber water samples. Localized zones of upwelling and downwelling existed in the exposure areas at contaminated sites 5 and 18, while site 23 was downwelling at all measurement positions. Pore-water samples from minipiezometers contained CBs at the three contaminated sites that were highest at site 23. However, sediment and water samples from exposure chambers at site 23 contained the lowest levels of CBs among the contaminated sites. The CBs were not detected at the reference site, but other organic contaminants and metals were detected at all sites, with the highest concentrations occurring at sites 5 and 18. In water column exposures, no significant (p > 0.05) differences were observed in species survival between the contaminated sites and the reference. Mean percentage survival of H. azteca, C. dubia, and C. tentans exposed to surficial sediments (SS) at sites 5 and 18 was significantly (p < 0.05) reduced compared to the reference, whereas only C. tentans survival was significantly reduced at site 23. Body residues of total CB congeners in L. variegatus exposed to SS were highest at site 18 (618 micromol/kg lipid) and lowest at site 23 (21 micromol/kg lipid). The data suggest that downwelling reduced the bioavailability of CBs in surficial sediments, most likely by mobilizing the freely dissolved and colloid-bound fractions to deeper sediments. Overall, downwelling conditions reduced the in situ exposure of organisms in surficial sediments and hence the toxicity and bioaccumulation of CBs. Hydrologic and chemistry data from nested minipiezometers improved the interpretation of exposure-effects relationships.