Recommendations to improve wildlife exposure estimation for development of soil screening and cleanup values

An integral component in the development of media-specific values for the ecological risk assessment of chemicals is the derivation of safe levels of exposure for wildlife. Although the derivation and subsequent application of these values can be used for screening purposes, there is a need to identify the threshold for effects when making remedial decisions during site-specific assessments. Methods for evaluation of wildlife exposure are included in the US Environmental Protection Agency (USEPA) ecological soil screening levels (Eco-SSLs), registration, evaluation, authorization, and restriction of chemicals (REACH), and other risk-based soil assessment approaches. The goal of these approaches is to ensure that soil-associated contaminants do not pose a risk to wildlife that directly ingest soil, or to species that may be exposed to contaminants that persist in the food chain. These approaches incorporate broad assumptions in the exposure and effects assessments and in the risk characterization process. Consequently, thresholds for concluding risk are frequently very low with conclusions of risk possible when soil metal concentrations fall in the range of natural background. A workshop held in September, 2012 evaluated existing methods and explored recent science about factors to consider when establishing appropriate remedial goals for concentrations of metals in soils. A Foodweb Exposure Workgroup was organized to evaluate methods for quantifying exposure of wildlife to soil-associated metals through soil and food consumption and to provide recommendations for the development of ecological soil cleanup values (Eco-SCVs) that are both practical and scientifically defensible. The specific goals of this article are to review the current practices for quantifying exposure of wildlife to soil-associated contaminants via bioaccumulation and trophic transfer, to identify potential opportunities for refining and improving these exposure estimates, and finally, to make recommendations for application of these improved models to the development of site-specific remedial goals protective of wildlife. Although the focus is on metals contamination, many of the methods and tools discussed are also applicable to organic contaminants. The conclusion of this workgroup was that existing exposure estimation models are generally appropriate when fully expanded and that methods are generally available to develop more robust site-specific exposure estimates. Improved realism in site-specific wildlife Eco-SCVs could be achieved by obtaining more realistic estimates for diet composition, bioaccumulation, bioavailability and/or bioaccessibility, soil ingestion, spatial aspects of exposure, and target organ exposure. These components of wildlife exposure estimation should be developed on a site-, species-, and analyte-specific basis to the extent that the expense for their derivation is justified by the value they add to Eco-SCV development

A microcosm study to support aquatic risk assessment of nickel : community-level effects and comparison with bioavailability-normalized species sensitivity distributions

The aquatic risk assessment for nickel (Ni) in the European Union is based on chronic species sensitivity distributions and the use of bioavailability models. To test whether a bioavailability-based safe threshold of Ni (the hazardous concentration for 5% of species [HC5]) is protective for aquatic communities, microcosms were exposed to 5 stable Ni treatments (6-96 mu g/L) and a control for 4mo to assess bioaccumulation and effects on phytoplankton, periphyton, zooplankton, and snails. Concentrations of Ni in the periphyton, macrophytes, and snails measured at the end of the exposure period increased in a dose-dependent manner but did not indicate biomagnification. Abundance of phytoplankton and snails decreased in 48 mu g Ni/L and 96 mu g Ni/L treatments, which may have indirectly affected the abundance of zooplankton and periphyton. Exposure up to 24 mu g Ni/L had no adverse effects on algae and zooplankton, whereas the rate of population decline of the snails at 24 mu g Ni/L was significantly higher than in the controls. Therefore, the study-specific overall no-observed-adverse-effect concentration (NOAEC) is 12 mu g Ni/L. This NOAEC is approximately twice the HC5 derived from a chronic species sensitivity distribution considering the specific water chemistry of the microcosm by means of bioavailability models. Thus, the present study provides support to the protectiveness of the bioavailability-normalized HC5 for freshwater communities

Field measurement of nickel sediment toxicity: role of acid volatile sulfide

A field experiment was performed in four freshwater systems to assess the effects of Ni on the benthic macroinvertebrate communities Sediments were collected from the sites (in Belgium Germany and Italy) spiked with Ni and returned to the respective field sites The colonization process of the benthic communities was monitored during a nine month period Nickel effect on the benthos was also assessed in the context of equilibrium partitioning model based on acid volatile sulfides (AVS) and simultaneously extracted metals (SEM) Benthic communities were not affected at (SEM AVS) 2 mu mol/g, (SEM AVS)/f(OC) > 700 mu mol/g OC resulted in clear adverse effects Uncertainty about the presence and absence of Ni toxicity occurred at (SEM AVS) and (SEM AVS)/f(OC) between 04 to 2 mu mol/g and 21 to 700 mu mol/g OC respectively The results of our study also indicate that when applying the SEM AVS concept for predicting metal toxicity in the field study stressors other than sediment characteristics (e g sorption capacity) such as environmental disturbances, should be considered and the results should be carefully interpreted

A Mystery Tale: Nickel Is Fickle When Snails Fail—Investigating the Variability in Ni Toxicity to the Great Pond Snail

ABSTRACT Dissolved Ni concentrations inhibiting the growth of juvenile great pond snails (Lymnaea stagnalis) have been documented to vary from about 1 to 200 µg L−1 Ni. This variability makes L. stagnalis either a moderately sensitive or the most sensitive freshwater species to chronic Ni exposure tested to date. Given the role of sensitive species in environmental risk assessment frameworks, it is particularly important to understand this variability, i.e., to characterize the factors that modulate Ni toxicity and that may confound toxicity test outcomes when uncontrolled. In the present study, we tested if this variability was due to analytical (growth calculation: biomass versus growth rate), environmental (water quality), lab‐specific practices, and/or snail population differences among earlier studies. Specifically, we reanalyzed previously published Ni toxicity data and conducted additional measurements of Ni aqueous speciation, short‐term Ni uptake, and chronic Ni toxicity with test waters and snail cultures used in previous studies. Corrections for Ni bioavailability and growth calculations explained a large degree of variability in the published literature. However, a residual 16‐fold difference remained puzzling between 2 studies: Niyogi et al. (2014) (low ECxs) and Crémazy et al. (2018) (high ECxs). Indeed, differences in metal bioavailability due to water chemistry, lab‐specific practices, and snail population sensitivity could not explain the large variation in Ni toxicity in these 2 very similar studies. Other potentially important toxicity‐modifying factors were not directly evaluated in the present work: test duration, diet, snail holding conditions, and snail age at onset of testing. The present analysis highlights the need for further studies to elucidate 1) the mechanisms of growth inhibition in Ni‐exposed L. stagnalis and 2) the important abiotic and biotic factors affecting this biological response. Until these processes are understood, substantial uncertainties will remain about inclusion of this species in Ni environmental risk assessment. Integr Environ Assess Manag 2020;16:983–997. © 2020 SETAC KEY POINTS Nickel concentrations inhibiting the growth of Lymnaea stagnalis vary by 2 orders of magnitude (1–200 µg L−1) in the literature. The interstudy variability on EC20s was decreased by using specific growth rate instead of biomass as the response variable (by a factor of 5‐fold) and by bioavailability correction with the BLM (by a factor of 3‐fold). A remaining 7‐fold variation in reported EC20s could not be explained by differences in test waters, snail populations, and lab‐specific practices. Other potentially important toxicity‐modifying factors remain to be studied (e.g., test duration and snail age and diet)