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A Novel Multi-Species Physiologically-Based Toxicokinetic Modelling Approach in Support of Chemicals Risk Assessment
Contemporary PBTK models for the prediction of bioaccumulation potential of chemicals in fish are based on single-species approaches. These approaches fail to include naturally occurring physiological variability between different species and among individuals of the same species. To overcome this limitation a novel multi-species approach is introduced in this study. By including inter- and intra-species variability of model input parameters through (i) the available physiological data of nonmodel species, and (ii) the incorporation of these data and their statistical distributions rather than as single values, this study developed a new and powerful multi-species PBTK modelling approach. In an extensive literature search, 2,815 single values were revealed, representing 71.9 % of families of freshwater fishes occurring in Canada. Model validation showed that bioaccumulation potential of 82 % of the modeled neutral organic chemicals were predicted within a 10-fold change respective to the corresponding measured data from the literature. This is in reasonable agreement with previously published single-species models while at the same time significantly improving the level of species diversity. As such, this model will potentially enable more environmentally relevant predictions using already existing data and could ultimately lead toward more sustainable use of existing data for risk assessment of chemicals.
Fresh diluted bitumen and a shoreline oil cleaner impair water striders under environmentally realistic conditions
Shoreline cleaners have been proposed as a tool to address oil spills from accidental pipeline breaches in boreal aquatic ecosystems. Littoral zones and the communities that reside in them can be particularly vulnerable from oil fouling and subsequent clean-up. Water strider (Family: Gerridae) communities rely on intact riparian environments for shelter and food and represent a case study for investigating possible impacts from shoreline cleaners. To investigate this, diluted bitumen volumes ranging from 0 μL/m2 to 205 μL/m2 were applied to land based test tanks containing 20 striders each (Metrobates sp.) with and without COREXIT EC9580A, a hydrocarbon-based shoreline cleaner. Oil-only impacts were observed at volumes of 7.5 μL/m2 and up, with greater than 50% immobility observed within 8 hours. Effects were greater when EC9580A was applied, with 100% immobility observed immediately upon application at 2.5 μL/m2 of dilbit and up. Our work reveals a sensitivity to this mixture by surface dwelling insects that warrants further investigation to inform Net Environmental Benefit Analyses (NEBAs). EC9580A and other shoreline cleaners should undergo more stringent regulation to limit impacts to freshwater organisms considering the greater impacts of the cleaner with oil relative to the independent effects of the oil.
Arctic Ecotoxicology: A Critical Review to Break the Ice
There has been a growing focus to quantify the impact of anthropogenic activities on Arctic ecosystems; however, most regulatory guidelines and risk assessments are built primarily around temperate species. This may result in an underestimation of harm to Arctic organisms. To help address this concern, a critical review to assess reported effects for these species in relation to current regulatory guidelines, quantify knowledge and methodological gaps, and identify future research needs for laboratory testing was performed. To accomplish this, an objective evaluation of the literature was employed to quantify the strengths and relevance of published studies to determine the utility of the data. We developed uniform criteria to score each study, allowing an objective comparison across experiments. Data from all publicly available toxicity tests performed on aquatic Arctic algae (n = 22 distinct experiments), invertebrates (n = 167), vertebrates (n = 149) and microbial consortiums (n = 1) were included. These data encompassed a total of 44 published studies, 48 tested compounds, and 74 unique Arctic test species. Our preliminary analysis shows that of 339 test substance and species combinations scored, 273(81%) failed to meet at least one critical study criterion that contributes to data reliability for use in risk assessment. Future Arctic ecotoxicology research should work to ensure test concentrations can be analytically confirmed, include environmentally realistic exposure scenarios, and report test methods more thoroughly. By working to address these identified gaps, future ecotoxicological risk assessments for Arctic regions should be more robust and effective.